Abstract image of a woman sitting on books and studying on a laptop

Troubleshooting Coherent Optical Communication Systems

CPqD, profile picture
CPqD

1) The document discusses troubleshooting of coherent optical communication systems. It covers topics such as market trends driving higher data rates, challenges in coherent measurements, and typical tests and impairments in coherent transmission systems. 2) The document outlines techniques used to maximize transmission capacity within the physical layer, including higher order modulation formats, time-domain pulse shaping, and polarization division multiplexing. It also discusses requirements for test instruments to test these advanced modulation schemes. 3) The presentation provides an overview of using arbitrary waveform generators to emulate optical distortions in the electrical domain, allowing for deterministic and precise testing with complex impairments like phase noise and polarization mode dispersion.

Technology
1 of 65
Downloaded 157 times
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
Troubleshooting Coherent Optical Communication Systems Created by: Michael Koenigsmann Application Specialist Digital & Photonic Test Division May 18th 2015 © 2015 Keysight Technologies Presented by: Rodrigo Vicentini Applications Engineering Manager Latin America Region
Agenda • Market and Technology Trends • Coherent Measurement Challenges • Typical Tests in Coherent Transmission Systems • Typical Impairment Emulation in the electrical Domain • Tools to generate signals for Coherent Optical Applications • References
Market and Technology Trends Drivers for higher Datarates
Page 4 Troubleshooting Coherent Optical Comms Systems Market and Technology Trends Big Data Demand drives Technology Changes Challenges: • Transmission demand exceeds system capacity • Cost-effective increase of capacity • Pressure to release new technology on time To maximize transmission within Phy layer, combine & optimize all dimensions for efficiency, cost, power, reach, reliabiliy etc. • Mobile apps and services, • high resolution devices, • Internet of Things drive high speed I/O, network and data center traffic Modulation SymbolRate Multi level signaling in digital links, e.g. C-Phy, PAMx Parallel lines, subcarrier density Polarization Mux, OFDM, DMT Amplitude & Phase modulation in optical links e.g. QPSK, QAMx Maximize Bits per Symbol Increase Symbol Rate 32 GBd and beyond Nyquist fs > 2 x fmax Rule of thumb: sampling rate = 2.5x Signal BW Maximize # of carriers By 2020 there will be around 20 Billion devices connected to the Internet © 2015 Keysight Technologies
Page Maximize Transmission within Physical Layer Troubleshooting Coherent Optical Comms Systems Different techniques… Motivation Higher Order Modulation Formats  OFDM From OOK to Coherent Detection Time-Domain Pulse Shaping Polarization Division Multiplex 4 © 2015 Keysight Technologies
Page Application Requirements Troubleshooting Coherent Optical Comms Systems 6 Coherent Optical Communication • Requirements for a test instrument: • Flexibilty to address different modulation schemes • Clean signal to test your device and not your instrument • Bandwidth at least 20 GHz • 4 sychronized channels to support dual polarization (= 2 pairs of I/Q signal) QPSK QAM128 OFDM Need higher data throughput: 100 G  400 G  1 Tbit/s © 2015 Keysight Technologies
Page Emulate Optical Distortions in the Electrical Space 7 Pattern Gen RefTx or golden Line Card Error Detector Network or Test Bed DUT (100/400G Rx) AWG DUT (DSP) ADC ADC ADC ADC Digital Coherent Receiver DSP Test Error Detector DUT (100/400G Tx) AWG - or - Traditional setup Test setup with AWG Deterministic and precise testing with complex impairments e.g. Phase Noise, OSNR, Polarization, PMD Troubleshooting Coherent Optical Comms Systems OSNR Gen. DUT (100/400G Rx) AWG Error Detector E/O - or - © 2015 Keysight Technologies
Page AWG’s in Coherent Optical Applications – Endless modulation formats for higher data throughput – Generates clean signals at 32 GBd and beyond – Provides 4 independent analog outputs for dual-polarization optical applications • Uses out of the box and in-situ calibration to achieve a clean signal at the device under test • Emulate optical distortions in the electrical space 8 Cost-effective increase in capacity 16 QAM at 32 GBd with < 4% EVM QPSK Signal with added phase noise; emulating a 2 MHz laser line width Troubleshooting Coherent Optical Comms Systems Optical Modulation Generator TooI © 2015 Keysight Technologies
Coherent Measurement Challenges • Clean Signal generation (electrical & optical) • Clean Signal at defined test points • High datarates 32 GBd and beyond • Accurate and Repeatable Test Signals • Distortion Emulation • Flexible Modulation Formats
Page Accurate and Repeatable Test Results Out-of-the-box calibration ensures clean signal at the frontpanel connector In-situ calibration – extend clean signal to the receiver test point • S-Parameters of channel are embedded or de-embedded • Frequency/Phase response is measured in-system and then de-embedded 11 QPSK, 32 GBd PRBS 6 Gbit/s Without correction With correction Without correction With correction Troubleshooting Coherent Optical Comms Systems © 2015 Keysight Technologies
Page Out-of-the Box Calibration & In-situ calibration Pre-distortion techniques for frequency and phase response compensation 12 AWG Optionally: optimize the second I/Q pair at the same time Troubleshooting Coherent Optical Comms Systems or iqtools Optical Modulation SW phase and frequency response data I/Q I/Q Vector Signal Analysis (VSA) software to determine frequency and phase response Infiniium Series Oscilloscope © 2015 Keysight Technologies
Page In-situ-calibration 13 End-to-end equalization Measure frequency/phase response as determined by the coherent receiver  End-to-end calibration of the whole transmission system  This includes the characteristic of the receiver as well ! Troubleshooting Coherent Optical Comms Systems M8195A I Y-Polarization Q I Q X-Polarization π/2 π/2 Tunable Laser N4391A or N4392A AWG MZMAmplifiers Coherent Receiver Optional Fiber & Optical Amplifiers Optical Modulation Generator Tool phase and frequency response data © 2015 Keysight Technologies
Typical Tests in Coherent Transmissions © 2015 Keysight Technologies
Page 15 Test application: system and link stress test TX electronic IQ Mod. Carrier Laser ROADM WSS Optical Coherent IQ det. RX Signal Processing LO Laser Typical test requirements:  BER (EVM) vs. Power or OSNR  Spectral behavior over 1-2 neighbor channels  Signal integrity along the link (time domain modulation analysis)  Nonlinear characteristics (PMD, PDL, CD,…) N4391A or N4392A Troubleshooting Coherent Optical Comms Systems 15 ROADM – Reconfigurable Optical Add-Drop Multiplexer WSS - Wavelength Selective Switching © 2015 Keysight Technologies
Page 16 Test application: Rx stress test (optical) Multi-format Reference Transmitter or optical AWG with or without stress generation M8195A + OMFT + Tunable Laser + Optical Modulation Gen. Tool Optical Coherent IQ det. RX Signal Processing LO Laser Stress generation on Optical Signal - Loss - Polarization - PMD - OSNR - Non-Linearities Troubleshooting Coherent Optical Comms Systems 16 © 2015 Keysight Technologies Typical requirements:  Availability of numerous modulation formats for research and development  High quality PAMx, (D)QPSK and QAMx signal for manufacturing  Arbitrary constellations for advanced research required (arbitrary stress)  BER vs various stress parameters  Some customers need RZ DQPSK  Support of up to 56 GBd rates for >> 100G research  PRBS test pattern, Pre-defined or User-defined  Test of receiver algorithm robustness with distorted signals
Page 17 Test application: Rx stress test (electrical) Typical requirements:  Availability of numerous modulation formats for research and development  High quality PAMx, (D)QPSK and QAMx signal for manufacturing  Arbitrary constellations for advanced research required (arbitrary stress)  BER vs various stress parameters  Some customers need RZ DQPSK  Support of up to 56 GBd rates for >> 100G research  PRBS test pattern, Pre-defined or User-defined  Test of receiver algorithm robustness with distorted signals Multi-format Reference Transmitter or optical AWG with or without stress generation M8195A + OMFT + Tunable Laser + Optical Modulation Gen. Tool Optical Coherent IQ det. RX Signal Processing LO Laser Stress generation on Optical Signal - Loss - Polarization - PMD - OSNR - Non-Linearities Stress generation on Electrical Signal - Loss - Polarization - PMD - OSNR - Non-Linearities Troubleshooting Coherent Optical Comms Systems 17 M8195A + Optical Modulation Gen. Tool © 2015 Keysight Technologies
Page 18 Test application: IQ modulator Typical test requirements:  Cut-off frequency for each path  In-application test to specify best EVM and other measures  Polarization behavior  Phase Response, Skew  Modulator Bias Control Multiformat TX DAC electrical output ! Analysis of modulation quality and polarization behaviour Frequency response of modulator TX electronic IQ Mod. Carrier Laser I Y-Polarization Q I Q X-Polarization π/2 π/2 Tunable Laser M8195A + Tunable Laser + Optical Modulation Gen. Tool LCA N4391A or N4392A Troubleshooting Coherent Optical Comms Systems 18 © 2015 Keysight Technologies
Page Troubleshooting Coherent Optical Comms Systems 19 Typical Measures Indication EVM & Q-Factor General figure of merit for Signal Quality EVM percentile Signal Quality w/o the effect of IQ Gain Imbalance and Quadrature Error IQ Gain Imbalance Different amplitudes for I- and Q-Signal IQ Skew Timing skews between I- & Q-Signal IQ Offset Wrong bias setting or DC offset at modulator Quadrature Error IQ phase shifter, wrong bias point of 90 º phase shifter Frequency Error Carrier Frequency Offset between Tx & Rx, EVM Symbol Rate Error, V-shape in ErrorVector vs Time Mismatch in Symbol Rate between Tx and Rx Dual Pol: IQ Skews, X-Y Skew & X-Y Imbalance Skew & Gain differences between Polarizations Bit Error Results Indentify Bit Errors per Polarization or across Polarization Missing Transitions in Constellation De-correlation issue between I- & Q-Signal Coherent testing Typical Measures © 2015 Keysight Technologies
Page EVM & Q-Factor 20 Troubleshooting Coherent Optical Comms Systems Error Vector connects the measured Vector and the expected vector, Error Vector Magnitude or EVM is magnitude of this vector EVM Q-factor 1% ~ 100 2% ~ 50 5% ~ 20 10% ~ 10 The Q-Factor describes the signal-to-noise ratio at the decision points. It is calculated from the EVM. The formula is proportional to 1/EVMa and the result is converted into dB. It is calculated from the Eye-Diagram aEVM 1 Q  © 2015 Keysight Technologies
Page EVM percentile 21 Troubleshooting Coherent Optical Comms Systems EVM_pctl EVM_pctl defines the radius of a circle around a group of measured constellation points centered at the reference constellation point. In contrast to EVM_pctl, the classical EVM value from the VSA software includes I-Q Imbalance and Quadrature Error and is a RMS averaged value. The “Hit Ratio” multiplied with the number of points is equal to the number of points outside the circle. For Gaussian Noise dominated impairments, the classical EVM and the EVM_pctl are equal if a “Hit Ratio” of 0.3173 is selected. The "Hit Ratio" can be set in the EVM_percentile algorithm of the OMA Software. © 2015 Keysight Technologies Constellation Reference EVM_pctl
Page IQ Gain Imbalance 22 Troubleshooting Coherent Optical Comms Systems IQ Gain Imbalance compares the amplitude of the I signal with the amplitude of the Q signal and shows the difference in dB. The effects of IQ gain imbalance are best viewed in constellation diagrams where the width of the constellation diagram is different than its height.  Rectangular shape of constellation, different amplitudes in I- and Q-Eye © 2015 Keysight Technologies
Page IQ Skew 23 Troubleshooting Coherent Optical Comms Systems IQ Skew Timing skew between I- and Q-signals  distorted IQ Plot, Eye- Diagrams are shifted with respect to each other  45° transitions open up  Increased EVM © 2015 Keysight Technologies
Page IQ Offset 24 Troubleshooting Coherent Optical Comms Systems IQ Offset DC offsets at the I- or the Q-Signals cause I/Q or origin offsets as shown. I/Q offsets can also result in carrier feedthrough. It is a measure for the shift between the origin of the measured constellation with regard to the origin of the reference constellation (yellow). Without DC offsets, the carrier feed through as well as the IQ offset becomes zero (-infinity dB).  Vertically shifted Eye- Diagram traces  Carrier Feedthrough  EVM carrier feed through Individual I- and Q- Imbalance available © 2015 Keysight Technologies
Page Quadrature Error 25 Troubleshooting Coherent Optical Comms Systems Quadrature Error indicates the orthogonal error between the I and Q Quadrature-Phase. Ideally, I and Q should be orthogonal (90 degrees apart). In the screenshot to the right a quadrature error of 22.91 degrees means I and Q are 67,09 degrees apart instead of 90 degrees. This could result from wrong bias point setting for the 90° phase shifter in the Mach-Zehnder-Modulator  distorted IQ Plot, distorted Eye-diagrams  EVM π/2 I Q © 2015 Keysight Technologies
Page Frequency Error 26 Troubleshooting Coherent Optical Comms Systems Frequency Error shows the carrier's frequency error relative to the VSA's center frequency displayed in Hertz. It is the amount of frequency shift from the VSA's center frequency that the VSA must perform to achieve carrier lock. The maximum allowable Frequency Error depends on the Modulation Format used. Here’s a list of formats: 2 GHz Modulation Format Maximum frequency offset QPSK 9.6% symbol rate 16-QAM 4.8% symbol rate 32-QAM 3.15% symbol rate 64-QAM 4.65% symbol rate 128-QAM 0.3% symbol rate 256-QAM 0.3% symbol rate 512-QAM 0.15% symbol rate 1024-QAM 0.15% symbol rate 2048-QAM 0.1% symbol rate* 4096-QAM 0.1% symbol rate* © 2015 Keysight Technologies
Page Symbol Rate Error 27 Troubleshooting Coherent Optical Comms Systems Symbol Rate Error If the Digital Demodulator is only able to recover the clock phase but not the clock rate, a wrong symbol rate shows up as typical „V“ shape when looking at EVM vs time plot.  Symbols start to spread all over the constellation  High EVM Measured SymbolRate ≠ SymbolRate setting © 2015 Keysight Technologies
Page Dual Pol: IQ Skews, XY Skew and XY Imbalance 28 Troubleshooting Coherent Optical Comms Systems Optical Signal Summary Screen Display of - Timing skew between I- and Q-Signals for X- and Y-Polarization - Timing skew between X- and Y-Polarization. - Gain Imbalance between X and Y Polarization - Symbol Rate Display - Frequency Error between Tx and Rx (in this case OMA) - EVM and Q-Factor © 2015 Keysight Technologies
Page Bit Error Results 29 Troubleshooting Coherent Optical Comms Systems Bit Error Result Screen - Actual BER - Cumulated BER - BER (EVM) - Bit & Error Counts - Delay between X & Y - PRBS generation details © 2015 Keysight Technologies
Page PRBS Pattern Sources 30 Troubleshooting Coherent Optical Comms Systems Effects of IQ PRBS Delay in bit (PRBS length 215-1) 0 bit 2 bit 4 bit 1 bit 3 bit 5 bit Effects of Delay issues between I- & Q-Data Source Effect of PRBS delay Using the same PRBS sequence for I and Q and decorrelating it with a too small delay might lead to missing transitions and asymetric spectral content ! Screenshots were taken based on a PRBS 215-1 with different delays between I and Q showing result in the corresponding constellation and spectrum. © 2015 Keysight Technologies
Typical Impairment Emulation in the electrical Domain
Page Example Impairment Troubleshooting Coherent Optical Comms Systems 32 Phase Noise in Optical Modulation Generator Tool © 2015 Keysight Technologies
Page Carrier Phase Noise 33 Troubleshooting Coherent Optical Comms Systems Analysis of Carrier PhaseNoise PhaseNoise Analysis of modulated signals. Display of Carrier Phase, Lorentzian Linewidth, Flicker & Random Noise. Graphical result of Phase Spectrum and corresponding Phase Spectrum Model Upper Constellation shows performance without PhaseTracker. Lower Constellation shows result after PhaseTracking Algorithm using Kalman Filters. 500kHz Linewidth 2MHz Linewidth 5MHz Linewidth © 2015 Keysight Technologies
Page Emulation of PolController 34 Troubleshooting Coherent Optical Comms Systems Polarization Pattern: Great Circle © 2015 Keysight Technologies
Page Emulation of PolController 35 Troubleshooting Coherent Optical Comms Systems Polarization Pattern: Slicer © 2015 Keysight Technologies
Page Stokes Space Analysis in OMA: Great Circle & Slicer 36 Troubleshooting Coherent Optical Comms Systems Analysis of Stokes Space Trajectory The OMA allows to analyze polarization changes. Two patterns „Great Circle“ and „Slicer“ are generated with the AWG electrically. This electrical signal can be used for receiver stress testing. Here the electrical signal is directly connected to the OMA inputs. Great Circle Slicer © 2015 Keysight Technologies
Page 37 35ps PMD, 991ps^2 SOPMD Troubleshooting Coherent Optical Comms Systems Example Impairment: PMD (1st and 2nd order) PMD in Optical Modulation Generator Tool © 2015 Keysight Technologies
Page Example Impairment: PMD (1st and 2nd order) 38 Troubleshooting Coherent Optical Comms Systems PMD Analysis in OMA The OMA allows to compensate and analyze the PMD. An electrical signal is generated with the AWG and analyzed by the OMA. This signal could be used for receiver stress testing. © 2015 Keysight Technologies
Tools to generate signals for Coherent Optical Applications © 2015 Keysight Technologies
Page Go Where you Have Never Been Able to Test Before – Sample rate up to 65 GSa/s per channel – 20 GHz analog bandwidth – 1, 2 or 4 differential channels per 1-slot AXIe module – In Speed, in Bandwidth and in Channel Density Explore your possibilities New M8195A 65 GSa/s AWG – Up to 16 GSa of waveform memory per module (*) – Amplitude up to 1 Vpp(se) (2 Vpp(diff.)), voltage window -1.0 … +3.3V – Ultra low intrinsic jitter (RJrms < 200 fs @ 32 Gb/s PRBS 211-1) – 16-tap FIR filter in hardware for frequency response compensation (*) – Multi-module synchronization up to 16 channels per 5-slot AXIe chassis (*) (*) rev 2 40 Troubleshooting Coherent Optical Comms Systems © 2015 Keysight Technologies
How about Optical IQ Modulator ? I Y-polarization Q I Q X-polarization π/2 π/2 © 2015 Keysight Technologies
Page Optical IQ Modulator: Troubleshooting Coherent Optical Comms Systems 42 Optical Multiformat Transmitter: OMFT by IDPhotonics / HHI • Symbol rate  46 GBd for binary formats such as BPSK, QPSK  34 GBd: for multi-level formats such as 16QAM • typically >23 GHz BW  Dual polarization I-Q modulator with typically 28 GHz bandwidth  40 GHz linear RF amplifiers • C+L band • Manual as well as automatic bias setting (automatic for QPSK and 16- QAM only) • In combination with DAC/AWG: pre-distortion to compensate for nonlinearities of amplifiers and modulator • 19“ form factor OMFT frequency response (S-parameters) and RF cables de-embedded in AWG In combination with M8195A AWG © 2015 Keysight Technologies OMFT performance verified in combination with M8195A AWG
Page Optical Modulation Generator Tool with E/O Troubleshooting Coherent Optical Comms Systems 43 E/O Modulator pre-distortion E/O converter in Optical Mod. Gen Tool • Apply pre-distortion to compensate modulator non-linearities • Includes settings to compensate for amplifier gain and Vp • Provides compensation of E/O modulator frequency response (S-parameters) © 2015 Keysight Technologies
Page AWG software tools for optical applications 44 Troubleshooting Coherent Optical Comms Systems Optical Modulation Generator Tool * • Dedicated for optical applications • Generates 2 x I/Q simultaneously • Optical impairments in electrical domain • Signal Path De-Embedding using S- Parameters, VSA Equalizer and factory cal * based on MATLAB Optical Modulation Generator Tool (1) © 2015 Keysight Technologies Waveform Input page Basic Setup Amplitude Pulse Shaping
Page AWG software tools for optical applications 45 Troubleshooting Coherent Optical Comms Systems Optical Modulation Generator Tool * • Dedicated for optical applications • Generates 2 x I/Q simultaneously • Optical impairments in electrical domain • Signal Path De-Embedding using S- Parameters, VSA Equalizer and factory cal * based on MATLAB Optical Modulation Generator Tool (1) Compensation of Cable Skews & S-Parameters © 2015 Keysight Technologies
Page AWG software tools for optical applications 46 Troubleshooting Coherent Optical Comms Systems * based on MATLAB Optical Modulation Generator Tool (2) Optical Modulation Generator Tool * Electrical Emulation of Optical Signal Properties in Real Time (1): - Phase Noise & Laser Linewidth - Polarization Rotation - 1st & 2nd order PMD (1) with Rev 2 of AWG in Oct 2015 © 2015 Keysight Technologies Polarization Phase Noise PMD
Tools for Coherent Signal Analysis
Page N439xA Optical Modulation Analyzer Family N4391A Optical Modulation Analyzer • 4 x 33 GHz in a single scope • 4 x 63 GHz as dual instrument setup special (call factory) • 4 x 80 GSa/s sampling rate (160 Gsa/s for 63 GHz) • Up to 2 GSa/Ch memory • Lowest noise floor (typ. 1.5% EVMrms) Troubleshooting Coherent Optical Comms Systems 48 For coherent transmission research & Mfg N4392A integrated Optical Mod. Analyzer • Compact, fully integrated, no external cabling • 4 x 23 GHz in a single instrument for dual polarization optical analysis • 4 x 23 GHz electrical inputs for dual polarization ICR testing • 4 x 63 GSa/s sampling rate • 16 kSa/Ch memory • Noise floor (typ. 2 % EVMrms) © 2015 Keysight Technologies
Page Smart Setup in OMA Software Troubleshooting Coherent Optical Comms Systems 49 „Smart setup“ - the easiest way to setup an OMA 0 Enter carrier wavelength or frequency Enter symbol rate Check modulation format Select between back to back and link measurement -> done 1 2 3 4 1 2 3 4 © 2015 Keysight Technologies
Page Tabular Measurement results, well structured Troubleshooting Coherent Optical Comms Systems 50 Per Polarization results Cross Channel results X-Polarization Y-Polarization © 2015 Keysight Technologies
Page Widest Selection of Modulation Formats Troubleshooting Coherent Optical Comms Systems 51 No limits … Custom APSK & OFDM It‘s your choice: • 39 pre-defined modulation formats or • Custom APSK demodulation o Up to 8 amplitude levels o In up to 256 constellation points o More to come, stay tuned ... • Custom OFDM demodulation For now and the future ! © 2015 Keysight Technologies Custom APSK Custom OFDM
Page Summary Optical Communication Solutions 52 Keysight’s Offering Wideband AWG Tools for Coherent Signal Generation Accurate and Repeatable Impairments Tools for Coherent Signal Analysis Troubleshooting Coherent Optical Comms Systems N4391A OMA M8195A AWG Opt. Mod. Gen. Tool © 2015 Keysight Technologies
Page Further References 53 Troubleshooting Coherent Optical Comms Systems Publication title Publication No. N4391A Optical Modulation Analyzer – Data Sheet 5990-3509EN N4392A Integrated Optical Modulation Analyzer – Data Sheet 5990-9863EN Infiniium Z-Series Oscilloscopes - Data Sheet 5991-3868EN M8195A 65 GSa/s Arbitrary Waveform Generator 5992-0014EN Metrology of Advanced Optical Modulation Formats - White Paper 5990-3748EN Kalman Filter Based Estimation and Demodulation of Complex Signals – White paper 5990-6409EN Vector Signal Analysis Basics - Application Note 5989-1121EN Digital Modulation in Communications Systems - An Introduction – Application Note 5965-7160E Essentials of Coherent Optical Data Transmission - Application Note 5991-1809EN Contact: michael_koenigsmann@keysight.com More Information is available from these Jumpstations: Arbitrary Waveform Generator M8195A and Optical Modulation Generator Software: www.keysight.com/find/M8195A Optical Modulation Analyzer: www.keysight.com/find/OMA Lightwave Component Analyzer: www.keysight.com/find/LCA © 2015 Keysight Technologies
Questions? Comments? 54 Troubleshooting Coherent Optical Comms Systems
Page Troubleshooting Coherent Optical Comms Systems 55
Backup
Page Overview: AWG Software tools for coherent optical applications Soft Front Panel Optical Modulation Software IQTools Availability Comes with M8195A Firmware Purchased separately Available free of charge Requires - MATLAB runtime Modulation Formats QPSK, QAMx and many more QPSK, QAMx QPSK, QAMx, OFDM Dual I/Q Yes Yes No Built-in Cal Yes Yes Yes In-system Cal Manual Automatic 1, 2 Automatic 1, 2, 3 I/Q Skew Manual Manual Automatic Optical impairments (incl. support for real- time DSP) No Yes No 1 Keysight Infiniium Series Scope needed 2 using VSA Equalizer 3 using own cal routine MATLAB Troubleshooting Coherent Optical Comms Systems 57 © 2015 Keysight Technologies
Page N4391A & N4392A core specification comparison Troubleshooting Coherent Optical Comms Systems 58 Parameter N4391A N4392A Analog Bandwidth 4x 33 GHz 4x 23 GHz EVM noise floor typ. 1) < 1.5 % rms < 2 % rms Sample rate 4x 80 GSa/s 4x 63 GSa/s Max. BaudRate 63 GBd 46 GBd Sensitivity -20 dBm -22 dBm Sample Memory Up to 4x 2 GSa 4x 16 kSa Software platform VSA/OMA 4.x Wavelength accuracy +/- 5 pm +/- 2 pm Weight ~ 48 kg (106 lbs) 13 kg (28.7 lbs) Portability no yes 1) @ reference conditions © 2015 Keysight Technologies
Page  Debug your Tx by identifiying the path of each data stream  Full flexibility to setup the link from pattern source to tributary  Select Pre-defined or User PRBS files  Easy intuitive setup Individual BER Test on each Tributary Troubleshooting Coherent Optical Comms Systems 59 Debug your transmitter faster © 2015 Keysight Technologies
Page New Measurements and Result Tables Troubleshooting Coherent Optical Comms Systems 60  7 new measurement traces and tables related to each polarization plane  4 new measurement traces and tables for cross-channel measurement results  Get new measurement results in the same way as you are used to. © 2015 Keysight Technologies
Page Improved Training Tools Troubleshooting Coherent Optical Comms Systems 61 12 Demo traces in VSA demo environment for self paced learning  32 GBd demo files measured at 5 power levels  Selection of 5 generic files with various modulation formats  Selection of PAM 4 recordings  New help system  Dynamic Help  Demo Video © 2015 Keysight Technologies
Page OMA Software 4.1 (1) Get deeper insight  to behavior of your carrier laser relative to used local oscillator  by seeing IQ offset resolved in I and Q part to speed up transmitter alignment  by analyzing X-Y imbalance to see imbalances in power between polarization planes Carrier phase display – Residual carrier phase calculated from Kalman phase tracking Troubleshooting Coherent Optical Comms Systems 62 I - Q resolved IQ offset – Offset of I component of the modulator – Offset of Q component of the modulator X - Y Imbalance – Basic test for PDL analysis by analyzing X-Y imbalance over time © 2015 Keysight Technologies
Page OMA Software 4.1 (2) Get deeper insight  In long term signal distribution by percentile EVM analysis  By requesting more analysis points for your own algorithm  Adding software Brick Wall Filter  Plotting a scalar value over number of screen updates to analyze long term effects EVM percentile – Calculate the percentile of a selectable hit ratio – Resolved to polarization plane or full signal Troubleshooting Coherent Optical Comms Systems 63 More Algorithms – Brick Wall Filter – Request more points Value over time – Plot any scalar measured value over selectable number of frames © 2015 Keysight Technologies
Page 64 Optical Coherent Rx RX Signal Processing LO Laser Typical Tests in Complex Transmissions Loss, PDL CD, PMD TX electronic IQ Mod. Carrier Laser Carrier Laser  Line-width  Phase Noise Transmitter  Signal Quality (EVM, Skews…) Received Signal  Signal Quality (EVM, BER,…)  Distortion caused by link impairments Carrier Laser  Line-width  Phase Noise Coherent Rx assembly  Phase Angle vs l  Skew  Relative gain  Polarization  S-parameter  CMRR Modulator  S-parameter  S21, Bandwidth  El. ReturnLoss  Skews, Crosstalk Substitute TX Electronic  Multiformat AWG M8195A  Optical Impairment Emulation  Clean Signal  Wide Bandwidth Substitute Tx with “Golden Tx” based on AWG M8195A and Reference Modulator N4391A / N4392A N4391A / N4392A N4391A / N4392A N4392A M8195A + OMFT M8195A LCA LCA 64 © 2015 Keysight Technologies
Page 65 Typical AWG requirement (electrical) 65 Company Confidential Troubleshooting Coherent Optical Comms Systems © 2015 Keysight Technologies 32 GBd, 16QAM  EVM ~ 3%rms 32 GBd, 16QAM  EVM ~ 3%rms
Page 66 … up to the high end you can achieve Troubleshooting Coherent Optical Comms Systems 66 32 GBd, 64 QAM = 192 Gb/s 56 GBd, QPSK = 112 Gb/s © 2015 Keysight Technologies

More Related Content

PDF
Etching
sangeetkhule
 
PPTX
Colonizing Mars
Shammas bilal
 
PDF
Lect 30- traffic signal i
HamidullahFarhang
 
PDF
National Highway Alignment from Namakkal to Erode Using GIS
IJERA Editor
 
PDF
The Dawn of Industry 4.0
CPqD
 
PDF
Cognitive Technique for Software Defined Optical Network (SDON)
CPqD
 
PDF
Embedded Electronics for Telecom DSP
CPqD
 
PDF
Brazilian Semiconductor Scenario and Opportuni3es
CPqD
 
Etching
sangeetkhule
 
Colonizing Mars
Shammas bilal
 
Lect 30- traffic signal i
HamidullahFarhang
 
National Highway Alignment from Namakkal to Erode Using GIS
IJERA Editor
 
The Dawn of Industry 4.0
CPqD
 
Cognitive Technique for Software Defined Optical Network (SDON)
CPqD
 
Embedded Electronics for Telecom DSP
CPqD
 
Brazilian Semiconductor Scenario and Opportuni3es
CPqD
 

Similar to Troubleshooting Coherent Optical Communication Systems (20)

PPTX
P9 addressing signal_integrity_ in_ew_2015_final
Aamir Habib
 
PDF
Ds2460q datasheet
Camilo Andres Restrepo Ospina
 
PDF
STS RF IC Test System
Hank Lydick
 
PDF
MaxEye DVB Test and Measurement Solutions Overview
MaxEye Technologies Private Limited
 
PPTX
Optical Modulation Analysis (OMA) Present and Future
CPqD
 
PPT
Broadcast day-2007-advantech
SSPI Brasil
 
PDF
Micro e systems_data_sheet-veratus_series_preliminary
Electromate
 
PDF
GTG 2015 General Test Presentation V2.0
Muthu Babu
 
PDF
Anywave Technical Seminar July 2016 OFDM ISDB-T2
Frank Massa
 
PDF
A to D Convertors
sangeetkhule
 
PPTX
MaxEye SDR System Level Testing
MaxEye Technologies Private Limited
 
PDF
Digital modulation basics(nnm)
nnmaurya
 
PPS
QST-88b
Yuriy Umanskiy
 
PDF
Resume_Karthik_Koneru_Analog_and_Mixed Signal
Arizona State University
 
PDF
Resume_Karthik_Koneru_Analog_and_Mixed Signal
Arizona State University
 
DOCX
Link adaptation
DILSHAD AHMAD
 
PDF
High Performance Network Infrastructure for Future Internet - Julio Oliveira
CPqD
 
PPTX
Pin pointpresentation
Levan Huan
 
PPTX
Advanced Electrical Asset Monitoring T501 - Rugged Monitoring.pptx
Rugged Monitoring
 
PDF
RS_insert
Sarah Wehrle
 
P9 addressing signal_integrity_ in_ew_2015_final
Aamir Habib
 
Ds2460q datasheet
Camilo Andres Restrepo Ospina
 
STS RF IC Test System
Hank Lydick
 
MaxEye DVB Test and Measurement Solutions Overview
MaxEye Technologies Private Limited
 
Optical Modulation Analysis (OMA) Present and Future
CPqD
 
Broadcast day-2007-advantech
SSPI Brasil
 
Micro e systems_data_sheet-veratus_series_preliminary
Electromate
 
GTG 2015 General Test Presentation V2.0
Muthu Babu
 
Anywave Technical Seminar July 2016 OFDM ISDB-T2
Frank Massa
 
A to D Convertors
sangeetkhule
 
MaxEye SDR System Level Testing
MaxEye Technologies Private Limited
 
Digital modulation basics(nnm)
nnmaurya
 
QST-88b
Yuriy Umanskiy
 
Resume_Karthik_Koneru_Analog_and_Mixed Signal
Arizona State University
 
Resume_Karthik_Koneru_Analog_and_Mixed Signal
Arizona State University
 
Link adaptation
DILSHAD AHMAD
 
High Performance Network Infrastructure for Future Internet - Julio Oliveira
CPqD
 
Pin pointpresentation
Levan Huan
 
Advanced Electrical Asset Monitoring T501 - Rugged Monitoring.pptx
Rugged Monitoring
 
RS_insert
Sarah Wehrle
 
Ad

More from CPqD (20)

PDF
Control Plane for High Capacity Networks Public
CPqD
 
PDF
OPTICAL COMMUNICATIONS APPLICATIONS
CPqD
 
PDF
Integrated Photonics Advances in Optical Transmission: An Industry View
CPqD
 
PDF
Novo modelo de apoio à inovação
CPqD
 
PDF
CPqD at Optical Communication Ecosystem - Last/Next 10 years and R&D&I opport...
CPqD
 
PDF
Flexible Optical Transmission
CPqD
 
PDF
High Capacity Optical Access Networks
CPqD
 
PDF
BNDES: Instrumentos de Apoio à Inovação
CPqD
 
PDF
Câmara de Gestão M2M/IoT
CPqD
 
PDF
Mesa Redonda: Fomento Governamental para o Setor
CPqD
 
PDF
Creating Business Value By Enabling the Internet of Things
CPqD
 
PDF
RFID and NFC Providing the last yards for IoT
CPqD
 
PDF
Apresentação Paulo Curado (CPqD) - RFID Journal Live! Brasil 2015
CPqD
 
PDF
Fiber Technology Trends for Next Generation Networks
CPqD
 
PPTX
Emerging Trends and Applications for Cost Effective ROADMs
CPqD
 
PPTX
Optics for 100G and beyond
CPqD
 
PPTX
Optical Signal Property Synthesis at Runtime – An new approach for coherent t...
CPqD
 
PPTX
The ACTION Project: Applications Coordinate with Transport, IP and Optical Ne...
CPqD
 
PPT
Development through Innovation
CPqD
 
PPTX
Ministry of Communication - Research & Development in Telecommunications
CPqD
 
Control Plane for High Capacity Networks Public
CPqD
 
OPTICAL COMMUNICATIONS APPLICATIONS
CPqD
 
Integrated Photonics Advances in Optical Transmission: An Industry View
CPqD
 
Novo modelo de apoio à inovação
CPqD
 
CPqD at Optical Communication Ecosystem - Last/Next 10 years and R&D&I opport...
CPqD
 
Flexible Optical Transmission
CPqD
 
High Capacity Optical Access Networks
CPqD
 
BNDES: Instrumentos de Apoio à Inovação
CPqD
 
Câmara de Gestão M2M/IoT
CPqD
 
Mesa Redonda: Fomento Governamental para o Setor
CPqD
 
Creating Business Value By Enabling the Internet of Things
CPqD
 
RFID and NFC Providing the last yards for IoT
CPqD
 
Apresentação Paulo Curado (CPqD) - RFID Journal Live! Brasil 2015
CPqD
 
Fiber Technology Trends for Next Generation Networks
CPqD
 
Emerging Trends and Applications for Cost Effective ROADMs
CPqD
 
Optics for 100G and beyond
CPqD
 
Optical Signal Property Synthesis at Runtime – An new approach for coherent t...
CPqD
 
The ACTION Project: Applications Coordinate with Transport, IP and Optical Ne...
CPqD
 
Development through Innovation
CPqD
 
Ministry of Communication - Research & Development in Telecommunications
CPqD
 
Ad

Recently uploaded (20)

PDF
Taming the Chaos: How to Turn Unstructured Data into Decisions
Safe Software
 
PDF
A proposed approach for plagiarism detection in Myanmar Unicode text
IAESIJAI
 
PDF
Getting started with AI Agents and Multi-Agent Systems
Maxim Salnikov
 
PPTX
The various Industrial Revolutions .pptx
bandileshozi3
 
PPTX
TEXTILE technology diploma scope and career opportunities
kriti38
 
DOCX
Basics of Cloud Computing - Cloud Ecosystem
suthak11
 
PPTX
AI IN MARKETING- PRESENTED BY ANWAR KABIR 1st June 2025.pptx
HiraJay1
 
PPTX
Benefits of Physical activity for teenagers.pptx
Nokwanda Thabethe
 
PPTX
Microsoft Excel 365/2024 Beginner's training
frank yeboah
 
PDF
A contest of sentiment analysis: k-nearest neighbor versus neural network
IAESIJAI
 
PDF
Accessing-Finance-in-Jordan-MENA 2024 2025.pdf
Mustafa Kuğu
 
PDF
Developing a website for English-speaking practice to English as a foreign la...
IAESIJAI
 
PDF
UiPath Agentic Automation session 1: RPA to Agents
suhanisingh58689
 
PDF
How ambidextrous entrepreneurial leaders react to the artificial intelligence...
IAESIJAI
 
PDF
Improvisation in detection of pomegranate leaf disease using transfer learni...
IAESIJAI
 
PPTX
Build Your First AI Agent with UiPath.pptx
suhanisingh58689
 
PDF
“A New Era of 3D Sensing: Transforming Industries and Creating Opportunities,...
Edge AI and Vision Alliance
 
PDF
Flame analysis and combustion estimation using large language and vision assi...
IAESIJAI
 
PDF
Comparative analysis of machine learning models for fake news detection in so...
IAESIJAI
 
PDF
A review of recent deep learning applications in wood surface defect identifi...
IAESIJAI
 
Taming the Chaos: How to Turn Unstructured Data into Decisions
Safe Software
 
A proposed approach for plagiarism detection in Myanmar Unicode text
IAESIJAI
 
Getting started with AI Agents and Multi-Agent Systems
Maxim Salnikov
 
The various Industrial Revolutions .pptx
bandileshozi3
 
TEXTILE technology diploma scope and career opportunities
kriti38
 
Basics of Cloud Computing - Cloud Ecosystem
suthak11
 
AI IN MARKETING- PRESENTED BY ANWAR KABIR 1st June 2025.pptx
HiraJay1
 
Benefits of Physical activity for teenagers.pptx
Nokwanda Thabethe
 
Microsoft Excel 365/2024 Beginner's training
frank yeboah
 
A contest of sentiment analysis: k-nearest neighbor versus neural network
IAESIJAI
 
Accessing-Finance-in-Jordan-MENA 2024 2025.pdf
Mustafa Kuğu
 
Developing a website for English-speaking practice to English as a foreign la...
IAESIJAI
 
UiPath Agentic Automation session 1: RPA to Agents
suhanisingh58689
 
How ambidextrous entrepreneurial leaders react to the artificial intelligence...
IAESIJAI
 
Improvisation in detection of pomegranate leaf disease using transfer learni...
IAESIJAI
 
Build Your First AI Agent with UiPath.pptx
suhanisingh58689
 
“A New Era of 3D Sensing: Transforming Industries and Creating Opportunities,...
Edge AI and Vision Alliance
 
Flame analysis and combustion estimation using large language and vision assi...
IAESIJAI
 
Comparative analysis of machine learning models for fake news detection in so...
IAESIJAI
 
A review of recent deep learning applications in wood surface defect identifi...
IAESIJAI
 

Troubleshooting Coherent Optical Communication Systems

  • 1. Troubleshooting Coherent Optical Communication Systems Created by: Michael Koenigsmann Application Specialist Digital & Photonic Test Division May 18th 2015 © 2015 Keysight Technologies Presented by: Rodrigo Vicentini Applications Engineering Manager Latin America Region
  • 2. Agenda • Market and Technology Trends • Coherent Measurement Challenges • Typical Tests in Coherent Transmission Systems • Typical Impairment Emulation in the electrical Domain • Tools to generate signals for Coherent Optical Applications • References
  • 3. Market and Technology Trends Drivers for higher Datarates
  • 4. Page 4 Troubleshooting Coherent Optical Comms Systems Market and Technology Trends Big Data Demand drives Technology Changes Challenges: • Transmission demand exceeds system capacity • Cost-effective increase of capacity • Pressure to release new technology on time To maximize transmission within Phy layer, combine & optimize all dimensions for efficiency, cost, power, reach, reliabiliy etc. • Mobile apps and services, • high resolution devices, • Internet of Things drive high speed I/O, network and data center traffic Modulation SymbolRate Multi level signaling in digital links, e.g. C-Phy, PAMx Parallel lines, subcarrier density Polarization Mux, OFDM, DMT Amplitude & Phase modulation in optical links e.g. QPSK, QAMx Maximize Bits per Symbol Increase Symbol Rate 32 GBd and beyond Nyquist fs > 2 x fmax Rule of thumb: sampling rate = 2.5x Signal BW Maximize # of carriers By 2020 there will be around 20 Billion devices connected to the Internet © 2015 Keysight Technologies
  • 5. Page Maximize Transmission within Physical Layer Troubleshooting Coherent Optical Comms Systems Different techniques… Motivation Higher Order Modulation Formats  OFDM From OOK to Coherent Detection Time-Domain Pulse Shaping Polarization Division Multiplex 4 © 2015 Keysight Technologies
  • 6. Page Application Requirements Troubleshooting Coherent Optical Comms Systems 6 Coherent Optical Communication • Requirements for a test instrument: • Flexibilty to address different modulation schemes • Clean signal to test your device and not your instrument • Bandwidth at least 20 GHz • 4 sychronized channels to support dual polarization (= 2 pairs of I/Q signal) QPSK QAM128 OFDM Need higher data throughput: 100 G  400 G  1 Tbit/s © 2015 Keysight Technologies
  • 7. Page Emulate Optical Distortions in the Electrical Space 7 Pattern Gen RefTx or golden Line Card Error Detector Network or Test Bed DUT (100/400G Rx) AWG DUT (DSP) ADC ADC ADC ADC Digital Coherent Receiver DSP Test Error Detector DUT (100/400G Tx) AWG - or - Traditional setup Test setup with AWG Deterministic and precise testing with complex impairments e.g. Phase Noise, OSNR, Polarization, PMD Troubleshooting Coherent Optical Comms Systems OSNR Gen. DUT (100/400G Rx) AWG Error Detector E/O - or - © 2015 Keysight Technologies
  • 8. Page AWG’s in Coherent Optical Applications – Endless modulation formats for higher data throughput – Generates clean signals at 32 GBd and beyond – Provides 4 independent analog outputs for dual-polarization optical applications • Uses out of the box and in-situ calibration to achieve a clean signal at the device under test • Emulate optical distortions in the electrical space 8 Cost-effective increase in capacity 16 QAM at 32 GBd with < 4% EVM QPSK Signal with added phase noise; emulating a 2 MHz laser line width Troubleshooting Coherent Optical Comms Systems Optical Modulation Generator TooI © 2015 Keysight Technologies
  • 9. Coherent Measurement Challenges • Clean Signal generation (electrical & optical) • Clean Signal at defined test points • High datarates 32 GBd and beyond • Accurate and Repeatable Test Signals • Distortion Emulation • Flexible Modulation Formats
  • 10. Page Accurate and Repeatable Test Results Out-of-the-box calibration ensures clean signal at the frontpanel connector In-situ calibration – extend clean signal to the receiver test point • S-Parameters of channel are embedded or de-embedded • Frequency/Phase response is measured in-system and then de-embedded 11 QPSK, 32 GBd PRBS 6 Gbit/s Without correction With correction Without correction With correction Troubleshooting Coherent Optical Comms Systems © 2015 Keysight Technologies
  • 11. Page Out-of-the Box Calibration & In-situ calibration Pre-distortion techniques for frequency and phase response compensation 12 AWG Optionally: optimize the second I/Q pair at the same time Troubleshooting Coherent Optical Comms Systems or iqtools Optical Modulation SW phase and frequency response data I/Q I/Q Vector Signal Analysis (VSA) software to determine frequency and phase response Infiniium Series Oscilloscope © 2015 Keysight Technologies
  • 12. Page In-situ-calibration 13 End-to-end equalization Measure frequency/phase response as determined by the coherent receiver  End-to-end calibration of the whole transmission system  This includes the characteristic of the receiver as well ! Troubleshooting Coherent Optical Comms Systems M8195A I Y-Polarization Q I Q X-Polarization π/2 π/2 Tunable Laser N4391A or N4392A AWG MZMAmplifiers Coherent Receiver Optional Fiber & Optical Amplifiers Optical Modulation Generator Tool phase and frequency response data © 2015 Keysight Technologies
  • 13. Typical Tests in Coherent Transmissions © 2015 Keysight Technologies
  • 14. Page 15 Test application: system and link stress test TX electronic IQ Mod. Carrier Laser ROADM WSS Optical Coherent IQ det. RX Signal Processing LO Laser Typical test requirements:  BER (EVM) vs. Power or OSNR  Spectral behavior over 1-2 neighbor channels  Signal integrity along the link (time domain modulation analysis)  Nonlinear characteristics (PMD, PDL, CD,…) N4391A or N4392A Troubleshooting Coherent Optical Comms Systems 15 ROADM – Reconfigurable Optical Add-Drop Multiplexer WSS - Wavelength Selective Switching © 2015 Keysight Technologies
  • 15. Page 16 Test application: Rx stress test (optical) Multi-format Reference Transmitter or optical AWG with or without stress generation M8195A + OMFT + Tunable Laser + Optical Modulation Gen. Tool Optical Coherent IQ det. RX Signal Processing LO Laser Stress generation on Optical Signal - Loss - Polarization - PMD - OSNR - Non-Linearities Troubleshooting Coherent Optical Comms Systems 16 © 2015 Keysight Technologies Typical requirements:  Availability of numerous modulation formats for research and development  High quality PAMx, (D)QPSK and QAMx signal for manufacturing  Arbitrary constellations for advanced research required (arbitrary stress)  BER vs various stress parameters  Some customers need RZ DQPSK  Support of up to 56 GBd rates for >> 100G research  PRBS test pattern, Pre-defined or User-defined  Test of receiver algorithm robustness with distorted signals
  • 16. Page 17 Test application: Rx stress test (electrical) Typical requirements:  Availability of numerous modulation formats for research and development  High quality PAMx, (D)QPSK and QAMx signal for manufacturing  Arbitrary constellations for advanced research required (arbitrary stress)  BER vs various stress parameters  Some customers need RZ DQPSK  Support of up to 56 GBd rates for >> 100G research  PRBS test pattern, Pre-defined or User-defined  Test of receiver algorithm robustness with distorted signals Multi-format Reference Transmitter or optical AWG with or without stress generation M8195A + OMFT + Tunable Laser + Optical Modulation Gen. Tool Optical Coherent IQ det. RX Signal Processing LO Laser Stress generation on Optical Signal - Loss - Polarization - PMD - OSNR - Non-Linearities Stress generation on Electrical Signal - Loss - Polarization - PMD - OSNR - Non-Linearities Troubleshooting Coherent Optical Comms Systems 17 M8195A + Optical Modulation Gen. Tool © 2015 Keysight Technologies
  • 17. Page 18 Test application: IQ modulator Typical test requirements:  Cut-off frequency for each path  In-application test to specify best EVM and other measures  Polarization behavior  Phase Response, Skew  Modulator Bias Control Multiformat TX DAC electrical output ! Analysis of modulation quality and polarization behaviour Frequency response of modulator TX electronic IQ Mod. Carrier Laser I Y-Polarization Q I Q X-Polarization π/2 π/2 Tunable Laser M8195A + Tunable Laser + Optical Modulation Gen. Tool LCA N4391A or N4392A Troubleshooting Coherent Optical Comms Systems 18 © 2015 Keysight Technologies
  • 18. Page Troubleshooting Coherent Optical Comms Systems 19 Typical Measures Indication EVM & Q-Factor General figure of merit for Signal Quality EVM percentile Signal Quality w/o the effect of IQ Gain Imbalance and Quadrature Error IQ Gain Imbalance Different amplitudes for I- and Q-Signal IQ Skew Timing skews between I- & Q-Signal IQ Offset Wrong bias setting or DC offset at modulator Quadrature Error IQ phase shifter, wrong bias point of 90 º phase shifter Frequency Error Carrier Frequency Offset between Tx & Rx, EVM Symbol Rate Error, V-shape in ErrorVector vs Time Mismatch in Symbol Rate between Tx and Rx Dual Pol: IQ Skews, X-Y Skew & X-Y Imbalance Skew & Gain differences between Polarizations Bit Error Results Indentify Bit Errors per Polarization or across Polarization Missing Transitions in Constellation De-correlation issue between I- & Q-Signal Coherent testing Typical Measures © 2015 Keysight Technologies
  • 19. Page EVM & Q-Factor 20 Troubleshooting Coherent Optical Comms Systems Error Vector connects the measured Vector and the expected vector, Error Vector Magnitude or EVM is magnitude of this vector EVM Q-factor 1% ~ 100 2% ~ 50 5% ~ 20 10% ~ 10 The Q-Factor describes the signal-to-noise ratio at the decision points. It is calculated from the EVM. The formula is proportional to 1/EVMa and the result is converted into dB. It is calculated from the Eye-Diagram aEVM 1 Q  © 2015 Keysight Technologies
  • 20. Page EVM percentile 21 Troubleshooting Coherent Optical Comms Systems EVM_pctl EVM_pctl defines the radius of a circle around a group of measured constellation points centered at the reference constellation point. In contrast to EVM_pctl, the classical EVM value from the VSA software includes I-Q Imbalance and Quadrature Error and is a RMS averaged value. The “Hit Ratio” multiplied with the number of points is equal to the number of points outside the circle. For Gaussian Noise dominated impairments, the classical EVM and the EVM_pctl are equal if a “Hit Ratio” of 0.3173 is selected. The "Hit Ratio" can be set in the EVM_percentile algorithm of the OMA Software. © 2015 Keysight Technologies Constellation Reference EVM_pctl
  • 21. Page IQ Gain Imbalance 22 Troubleshooting Coherent Optical Comms Systems IQ Gain Imbalance compares the amplitude of the I signal with the amplitude of the Q signal and shows the difference in dB. The effects of IQ gain imbalance are best viewed in constellation diagrams where the width of the constellation diagram is different than its height.  Rectangular shape of constellation, different amplitudes in I- and Q-Eye © 2015 Keysight Technologies
  • 22. Page IQ Skew 23 Troubleshooting Coherent Optical Comms Systems IQ Skew Timing skew between I- and Q-signals  distorted IQ Plot, Eye- Diagrams are shifted with respect to each other  45° transitions open up  Increased EVM © 2015 Keysight Technologies
  • 23. Page IQ Offset 24 Troubleshooting Coherent Optical Comms Systems IQ Offset DC offsets at the I- or the Q-Signals cause I/Q or origin offsets as shown. I/Q offsets can also result in carrier feedthrough. It is a measure for the shift between the origin of the measured constellation with regard to the origin of the reference constellation (yellow). Without DC offsets, the carrier feed through as well as the IQ offset becomes zero (-infinity dB).  Vertically shifted Eye- Diagram traces  Carrier Feedthrough  EVM carrier feed through Individual I- and Q- Imbalance available © 2015 Keysight Technologies
  • 24. Page Quadrature Error 25 Troubleshooting Coherent Optical Comms Systems Quadrature Error indicates the orthogonal error between the I and Q Quadrature-Phase. Ideally, I and Q should be orthogonal (90 degrees apart). In the screenshot to the right a quadrature error of 22.91 degrees means I and Q are 67,09 degrees apart instead of 90 degrees. This could result from wrong bias point setting for the 90° phase shifter in the Mach-Zehnder-Modulator  distorted IQ Plot, distorted Eye-diagrams  EVM π/2 I Q © 2015 Keysight Technologies
  • 25. Page Frequency Error 26 Troubleshooting Coherent Optical Comms Systems Frequency Error shows the carrier's frequency error relative to the VSA's center frequency displayed in Hertz. It is the amount of frequency shift from the VSA's center frequency that the VSA must perform to achieve carrier lock. The maximum allowable Frequency Error depends on the Modulation Format used. Here’s a list of formats: 2 GHz Modulation Format Maximum frequency offset QPSK 9.6% symbol rate 16-QAM 4.8% symbol rate 32-QAM 3.15% symbol rate 64-QAM 4.65% symbol rate 128-QAM 0.3% symbol rate 256-QAM 0.3% symbol rate 512-QAM 0.15% symbol rate 1024-QAM 0.15% symbol rate 2048-QAM 0.1% symbol rate* 4096-QAM 0.1% symbol rate* © 2015 Keysight Technologies
  • 26. Page Symbol Rate Error 27 Troubleshooting Coherent Optical Comms Systems Symbol Rate Error If the Digital Demodulator is only able to recover the clock phase but not the clock rate, a wrong symbol rate shows up as typical „V“ shape when looking at EVM vs time plot.  Symbols start to spread all over the constellation  High EVM Measured SymbolRate ≠ SymbolRate setting © 2015 Keysight Technologies
  • 27. Page Dual Pol: IQ Skews, XY Skew and XY Imbalance 28 Troubleshooting Coherent Optical Comms Systems Optical Signal Summary Screen Display of - Timing skew between I- and Q-Signals for X- and Y-Polarization - Timing skew between X- and Y-Polarization. - Gain Imbalance between X and Y Polarization - Symbol Rate Display - Frequency Error between Tx and Rx (in this case OMA) - EVM and Q-Factor © 2015 Keysight Technologies
  • 28. Page Bit Error Results 29 Troubleshooting Coherent Optical Comms Systems Bit Error Result Screen - Actual BER - Cumulated BER - BER (EVM) - Bit & Error Counts - Delay between X & Y - PRBS generation details © 2015 Keysight Technologies
  • 29. Page PRBS Pattern Sources 30 Troubleshooting Coherent Optical Comms Systems Effects of IQ PRBS Delay in bit (PRBS length 215-1) 0 bit 2 bit 4 bit 1 bit 3 bit 5 bit Effects of Delay issues between I- & Q-Data Source Effect of PRBS delay Using the same PRBS sequence for I and Q and decorrelating it with a too small delay might lead to missing transitions and asymetric spectral content ! Screenshots were taken based on a PRBS 215-1 with different delays between I and Q showing result in the corresponding constellation and spectrum. © 2015 Keysight Technologies
  • 30. Typical Impairment Emulation in the electrical Domain
  • 31. Page Example Impairment Troubleshooting Coherent Optical Comms Systems 32 Phase Noise in Optical Modulation Generator Tool © 2015 Keysight Technologies
  • 32. Page Carrier Phase Noise 33 Troubleshooting Coherent Optical Comms Systems Analysis of Carrier PhaseNoise PhaseNoise Analysis of modulated signals. Display of Carrier Phase, Lorentzian Linewidth, Flicker & Random Noise. Graphical result of Phase Spectrum and corresponding Phase Spectrum Model Upper Constellation shows performance without PhaseTracker. Lower Constellation shows result after PhaseTracking Algorithm using Kalman Filters. 500kHz Linewidth 2MHz Linewidth 5MHz Linewidth © 2015 Keysight Technologies
  • 33. Page Emulation of PolController 34 Troubleshooting Coherent Optical Comms Systems Polarization Pattern: Great Circle © 2015 Keysight Technologies
  • 34. Page Emulation of PolController 35 Troubleshooting Coherent Optical Comms Systems Polarization Pattern: Slicer © 2015 Keysight Technologies
  • 35. Page Stokes Space Analysis in OMA: Great Circle & Slicer 36 Troubleshooting Coherent Optical Comms Systems Analysis of Stokes Space Trajectory The OMA allows to analyze polarization changes. Two patterns „Great Circle“ and „Slicer“ are generated with the AWG electrically. This electrical signal can be used for receiver stress testing. Here the electrical signal is directly connected to the OMA inputs. Great Circle Slicer © 2015 Keysight Technologies
  • 36. Page 37 35ps PMD, 991ps^2 SOPMD Troubleshooting Coherent Optical Comms Systems Example Impairment: PMD (1st and 2nd order) PMD in Optical Modulation Generator Tool © 2015 Keysight Technologies
  • 37. Page Example Impairment: PMD (1st and 2nd order) 38 Troubleshooting Coherent Optical Comms Systems PMD Analysis in OMA The OMA allows to compensate and analyze the PMD. An electrical signal is generated with the AWG and analyzed by the OMA. This signal could be used for receiver stress testing. © 2015 Keysight Technologies
  • 38. Tools to generate signals for Coherent Optical Applications © 2015 Keysight Technologies
  • 39. Page Go Where you Have Never Been Able to Test Before – Sample rate up to 65 GSa/s per channel – 20 GHz analog bandwidth – 1, 2 or 4 differential channels per 1-slot AXIe module – In Speed, in Bandwidth and in Channel Density Explore your possibilities New M8195A 65 GSa/s AWG – Up to 16 GSa of waveform memory per module (*) – Amplitude up to 1 Vpp(se) (2 Vpp(diff.)), voltage window -1.0 … +3.3V – Ultra low intrinsic jitter (RJrms < 200 fs @ 32 Gb/s PRBS 211-1) – 16-tap FIR filter in hardware for frequency response compensation (*) – Multi-module synchronization up to 16 channels per 5-slot AXIe chassis (*) (*) rev 2 40 Troubleshooting Coherent Optical Comms Systems © 2015 Keysight Technologies
  • 40. How about Optical IQ Modulator ? I Y-polarization Q I Q X-polarization π/2 π/2 © 2015 Keysight Technologies
  • 41. Page Optical IQ Modulator: Troubleshooting Coherent Optical Comms Systems 42 Optical Multiformat Transmitter: OMFT by IDPhotonics / HHI • Symbol rate  46 GBd for binary formats such as BPSK, QPSK  34 GBd: for multi-level formats such as 16QAM • typically >23 GHz BW  Dual polarization I-Q modulator with typically 28 GHz bandwidth  40 GHz linear RF amplifiers • C+L band • Manual as well as automatic bias setting (automatic for QPSK and 16- QAM only) • In combination with DAC/AWG: pre-distortion to compensate for nonlinearities of amplifiers and modulator • 19“ form factor OMFT frequency response (S-parameters) and RF cables de-embedded in AWG In combination with M8195A AWG © 2015 Keysight Technologies OMFT performance verified in combination with M8195A AWG
  • 42. Page Optical Modulation Generator Tool with E/O Troubleshooting Coherent Optical Comms Systems 43 E/O Modulator pre-distortion E/O converter in Optical Mod. Gen Tool • Apply pre-distortion to compensate modulator non-linearities • Includes settings to compensate for amplifier gain and Vp • Provides compensation of E/O modulator frequency response (S-parameters) © 2015 Keysight Technologies
  • 43. Page AWG software tools for optical applications 44 Troubleshooting Coherent Optical Comms Systems Optical Modulation Generator Tool * • Dedicated for optical applications • Generates 2 x I/Q simultaneously • Optical impairments in electrical domain • Signal Path De-Embedding using S- Parameters, VSA Equalizer and factory cal * based on MATLAB Optical Modulation Generator Tool (1) © 2015 Keysight Technologies Waveform Input page Basic Setup Amplitude Pulse Shaping
  • 44. Page AWG software tools for optical applications 45 Troubleshooting Coherent Optical Comms Systems Optical Modulation Generator Tool * • Dedicated for optical applications • Generates 2 x I/Q simultaneously • Optical impairments in electrical domain • Signal Path De-Embedding using S- Parameters, VSA Equalizer and factory cal * based on MATLAB Optical Modulation Generator Tool (1) Compensation of Cable Skews & S-Parameters © 2015 Keysight Technologies
  • 45. Page AWG software tools for optical applications 46 Troubleshooting Coherent Optical Comms Systems * based on MATLAB Optical Modulation Generator Tool (2) Optical Modulation Generator Tool * Electrical Emulation of Optical Signal Properties in Real Time (1): - Phase Noise & Laser Linewidth - Polarization Rotation - 1st & 2nd order PMD (1) with Rev 2 of AWG in Oct 2015 © 2015 Keysight Technologies Polarization Phase Noise PMD
  • 46. Tools for Coherent Signal Analysis
  • 47. Page N439xA Optical Modulation Analyzer Family N4391A Optical Modulation Analyzer • 4 x 33 GHz in a single scope • 4 x 63 GHz as dual instrument setup special (call factory) • 4 x 80 GSa/s sampling rate (160 Gsa/s for 63 GHz) • Up to 2 GSa/Ch memory • Lowest noise floor (typ. 1.5% EVMrms) Troubleshooting Coherent Optical Comms Systems 48 For coherent transmission research & Mfg N4392A integrated Optical Mod. Analyzer • Compact, fully integrated, no external cabling • 4 x 23 GHz in a single instrument for dual polarization optical analysis • 4 x 23 GHz electrical inputs for dual polarization ICR testing • 4 x 63 GSa/s sampling rate • 16 kSa/Ch memory • Noise floor (typ. 2 % EVMrms) © 2015 Keysight Technologies
  • 48. Page Smart Setup in OMA Software Troubleshooting Coherent Optical Comms Systems 49 „Smart setup“ - the easiest way to setup an OMA 0 Enter carrier wavelength or frequency Enter symbol rate Check modulation format Select between back to back and link measurement -> done 1 2 3 4 1 2 3 4 © 2015 Keysight Technologies
  • 49. Page Tabular Measurement results, well structured Troubleshooting Coherent Optical Comms Systems 50 Per Polarization results Cross Channel results X-Polarization Y-Polarization © 2015 Keysight Technologies
  • 50. Page Widest Selection of Modulation Formats Troubleshooting Coherent Optical Comms Systems 51 No limits … Custom APSK & OFDM It‘s your choice: • 39 pre-defined modulation formats or • Custom APSK demodulation o Up to 8 amplitude levels o In up to 256 constellation points o More to come, stay tuned ... • Custom OFDM demodulation For now and the future ! © 2015 Keysight Technologies Custom APSK Custom OFDM
  • 51. Page Summary Optical Communication Solutions 52 Keysight’s Offering Wideband AWG Tools for Coherent Signal Generation Accurate and Repeatable Impairments Tools for Coherent Signal Analysis Troubleshooting Coherent Optical Comms Systems N4391A OMA M8195A AWG Opt. Mod. Gen. Tool © 2015 Keysight Technologies
  • 52. Page Further References 53 Troubleshooting Coherent Optical Comms Systems Publication title Publication No. N4391A Optical Modulation Analyzer – Data Sheet 5990-3509EN N4392A Integrated Optical Modulation Analyzer – Data Sheet 5990-9863EN Infiniium Z-Series Oscilloscopes - Data Sheet 5991-3868EN M8195A 65 GSa/s Arbitrary Waveform Generator 5992-0014EN Metrology of Advanced Optical Modulation Formats - White Paper 5990-3748EN Kalman Filter Based Estimation and Demodulation of Complex Signals – White paper 5990-6409EN Vector Signal Analysis Basics - Application Note 5989-1121EN Digital Modulation in Communications Systems - An Introduction – Application Note 5965-7160E Essentials of Coherent Optical Data Transmission - Application Note 5991-1809EN Contact: [email protected] More Information is available from these Jumpstations: Arbitrary Waveform Generator M8195A and Optical Modulation Generator Software: www.keysight.com/find/M8195A Optical Modulation Analyzer: www.keysight.com/find/OMA Lightwave Component Analyzer: www.keysight.com/find/LCA © 2015 Keysight Technologies
  • 56. Page Overview: AWG Software tools for coherent optical applications Soft Front Panel Optical Modulation Software IQTools Availability Comes with M8195A Firmware Purchased separately Available free of charge Requires - MATLAB runtime Modulation Formats QPSK, QAMx and many more QPSK, QAMx QPSK, QAMx, OFDM Dual I/Q Yes Yes No Built-in Cal Yes Yes Yes In-system Cal Manual Automatic 1, 2 Automatic 1, 2, 3 I/Q Skew Manual Manual Automatic Optical impairments (incl. support for real- time DSP) No Yes No 1 Keysight Infiniium Series Scope needed 2 using VSA Equalizer 3 using own cal routine MATLAB Troubleshooting Coherent Optical Comms Systems 57 © 2015 Keysight Technologies
  • 57. Page N4391A & N4392A core specification comparison Troubleshooting Coherent Optical Comms Systems 58 Parameter N4391A N4392A Analog Bandwidth 4x 33 GHz 4x 23 GHz EVM noise floor typ. 1) < 1.5 % rms < 2 % rms Sample rate 4x 80 GSa/s 4x 63 GSa/s Max. BaudRate 63 GBd 46 GBd Sensitivity -20 dBm -22 dBm Sample Memory Up to 4x 2 GSa 4x 16 kSa Software platform VSA/OMA 4.x Wavelength accuracy +/- 5 pm +/- 2 pm Weight ~ 48 kg (106 lbs) 13 kg (28.7 lbs) Portability no yes 1) @ reference conditions © 2015 Keysight Technologies
  • 58. Page  Debug your Tx by identifiying the path of each data stream  Full flexibility to setup the link from pattern source to tributary  Select Pre-defined or User PRBS files  Easy intuitive setup Individual BER Test on each Tributary Troubleshooting Coherent Optical Comms Systems 59 Debug your transmitter faster © 2015 Keysight Technologies
  • 59. Page New Measurements and Result Tables Troubleshooting Coherent Optical Comms Systems 60  7 new measurement traces and tables related to each polarization plane  4 new measurement traces and tables for cross-channel measurement results  Get new measurement results in the same way as you are used to. © 2015 Keysight Technologies
  • 60. Page Improved Training Tools Troubleshooting Coherent Optical Comms Systems 61 12 Demo traces in VSA demo environment for self paced learning  32 GBd demo files measured at 5 power levels  Selection of 5 generic files with various modulation formats  Selection of PAM 4 recordings  New help system  Dynamic Help  Demo Video © 2015 Keysight Technologies
  • 61. Page OMA Software 4.1 (1) Get deeper insight  to behavior of your carrier laser relative to used local oscillator  by seeing IQ offset resolved in I and Q part to speed up transmitter alignment  by analyzing X-Y imbalance to see imbalances in power between polarization planes Carrier phase display – Residual carrier phase calculated from Kalman phase tracking Troubleshooting Coherent Optical Comms Systems 62 I - Q resolved IQ offset – Offset of I component of the modulator – Offset of Q component of the modulator X - Y Imbalance – Basic test for PDL analysis by analyzing X-Y imbalance over time © 2015 Keysight Technologies
  • 62. Page OMA Software 4.1 (2) Get deeper insight  In long term signal distribution by percentile EVM analysis  By requesting more analysis points for your own algorithm  Adding software Brick Wall Filter  Plotting a scalar value over number of screen updates to analyze long term effects EVM percentile – Calculate the percentile of a selectable hit ratio – Resolved to polarization plane or full signal Troubleshooting Coherent Optical Comms Systems 63 More Algorithms – Brick Wall Filter – Request more points Value over time – Plot any scalar measured value over selectable number of frames © 2015 Keysight Technologies
  • 63. Page 64 Optical Coherent Rx RX Signal Processing LO Laser Typical Tests in Complex Transmissions Loss, PDL CD, PMD TX electronic IQ Mod. Carrier Laser Carrier Laser  Line-width  Phase Noise Transmitter  Signal Quality (EVM, Skews…) Received Signal  Signal Quality (EVM, BER,…)  Distortion caused by link impairments Carrier Laser  Line-width  Phase Noise Coherent Rx assembly  Phase Angle vs l  Skew  Relative gain  Polarization  S-parameter  CMRR Modulator  S-parameter  S21, Bandwidth  El. ReturnLoss  Skews, Crosstalk Substitute TX Electronic  Multiformat AWG M8195A  Optical Impairment Emulation  Clean Signal  Wide Bandwidth Substitute Tx with “Golden Tx” based on AWG M8195A and Reference Modulator N4391A / N4392A N4391A / N4392A N4391A / N4392A N4392A M8195A + OMFT M8195A LCA LCA 64 © 2015 Keysight Technologies
  • 64. Page 65 Typical AWG requirement (electrical) 65 Company Confidential Troubleshooting Coherent Optical Comms Systems © 2015 Keysight Technologies 32 GBd, 16QAM  EVM ~ 3%rms 32 GBd, 16QAM  EVM ~ 3%rms
  • 65. Page 66 … up to the high end you can achieve Troubleshooting Coherent Optical Comms Systems 66 32 GBd, 64 QAM = 192 Gb/s 56 GBd, QPSK = 112 Gb/s © 2015 Keysight Technologies