Using and OMA to Optimize QAM Optical Transceivers

Using an Optical Modulation Analyzerto Optimize 16QAM Optical Transceivers
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Your Presenters: DrAlan Blankman, Teledyne LeCroyDrSung-Hoon Im, Coherent Solutions
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Coherent Solutions | Teledyne LeCroy
In this Webinar…

We will show a live demo of acquisition and analysis of a 28GBaud DP-16QAM modulated optical signal

Agenda:

Review the system setup

Live Demo: View and tune the PAM4 electrical signals that will be modulated

Review of coherent optical transmitter and receiver

Review of DSP for optical modulation analysis

Live Demo: Tuning up the DP-16QAM optical transmitter
3

System Setup
DrAlan Blankman
4

Experimental Setup
5

Block Diagram for OMA Test Setup
1. PAM4 Signal
Generator
2. DP-16QAM
Generator
3. Coherent Receiver
4. Oscilloscope
(Acquisition)
5. Oscilloscope
(Analysis)
Anritsu MP1800A
Coherent Solutions
IQTransmitter
Coherent Solutions
IQScope-RT
Teledyne LeCroyLabMaster 10 Zi
Teledyne LeCroy / Coherent SolutionsOMA software
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PAM4 Signal Generator: Anritsu MP1800A Series SQA
MU183020A Dual Channel 32Gbit/s PPG
MP1800AMainframe
MZ1834A4PAMConverter
to optical IQ Transmitter
PAM4 Electrical
Equipment Courtesy of Anritsu
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Anritsu MZ1834A 4PAM Converter
AHigh
ALow
PAM4 Generator
PAM4-A I
10dB ATTN
10dB ATTN
10dB ATTN
10dB ATTN
Power Divider (Combiner)
BHigh
BLow
PAM4-B Q

Creates 2 PAM4 signals from 4 NRZ signals, to be used as I and Q
Uses power dividers to add the NRZ signals
Small box -can mount onto PPG for diff PAM4 signal generation
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Electrical PAM4 Signal Generation

Example config:

PPG AHigh& Bhighset for ~2 V

PPG ALow& BLowset for ~1 V

Summing AHigh+ ALowPAM4 signal with levels 0, 1, 2, 3.

Example bitstreamfor I or Q:
11 01 10 00 11 11 01 00 10 01
3 1 2 0 3 3 1 0 2 1
PAM4 stream:
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16QAM Optical Signal Generation: Coherent Solutions IQTransmitter

Receives RF I & Q signals

Built-in laser for LO

Control of laser wavelength,

Control of laserpower

Control of modulator bias points: I, Q, Quadrature

Single & Dual-Pol outputs
Electrical PAM4 signals from
MP1800A Generator
to RF I&Qinputs
PMF LO out-in
PMF 1-pol-out
to 2-pol in
SMF carrying DP-16QAM
to coherent optical receiver
10

Coherent Optical Receiver: Coherent Solutions IQScope-RT
SMF DP-16-QAM
From Optical IQ Transmitter
Coherently demodulate IQ- modulated optical signal
Built-in laser for LO
Control of laser wavelength
Control of laser power
4 electrical outputs: I & Q, X & Y polarizations
PMF LO out-in
I & Q electrical outputs
to oscilloscope
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Signal Acquisition: Teledyne LeCroy LabMaster 10 Zi

Real-time digital oscilloscope

36 GHz analog bandwidth

160 GS/s sample rate

130 fs channel-channel jitter

Modular system: expandable to up to 80 channels

Using 36 GHz for this webinar, 65 GHz model available
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Signal Analysis: Teledyne LeCroy/Coherent Solutions OMA software

OMA analysis SW:

Receives I & Q signals

Performs DSP:

Dispersion comp

Polarization demux

Carrier recovery

Return measurements

EVM, IQBias, etc

Displays visualizations

Constellation

Trajectory

Eye diagrams
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Summary of System Configuration

PPG bit rate: 28 GB/s

MSB Steam: (A_high, B_high)

Voltage levels: 0.9V, Delays: 180mUI, 220 mUI

LSB Stream:

Voltage levels: 0.5V, Delays: 0 mUI, 100 mUI

LO Laser Frequency: 191.5 THz

Wavelength = 1565.5 nm

LO Laser Power: 16dBm for both Txand Rx.

Modulator bias points: I –282, Q –122, Quad –172
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PAM4 Signal Optimization
DrAlan Blankman
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Steps to Checkout PAM4 Electrical Signals

Acquire signals on the scope

View the PAM4 Eye diagrams

Configure voltages and delays for each NRZ tributary

Considerations for optimization: Aim to maximize signal integrity

Avoid losses due to impedance mismatches

Poor cables/connectors will cause losses, reflections

Depending on your setup, phase-matched cables may be required.

Let’s acquire the PAM4 signals and modify the delays/levels.
16

Experimental Setup
17

Coherent Solutions | Teledyne LeCroy 18

Oscilloscope Acquisition
19

Eye Diagrams of PAM4 Signals
20

PAM4 Eye Showing Skew Between High and Low 21

Adjusting Skew
22

Adjusting Skew
23

Skew Adjusted.
24

Non-equally Spaced Levels
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Optical Transmitter Optimization Using an OMA
DrSung-Hoon Im
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Optical signal generation and characterization
Optical signal generation
IQTransmitter
Optical signal characterization
IQScope-RT
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Optical signal generation
OMA
4Ch PPG
PAM4
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Polarization Diverse Coherent Optical Receiver
BPD
BPD
90°Hybrid Mixer
X -I
X -Q
BPD
BPD
Y -I
Y -Q
Modulated Signal
Reference LO
PBS
IQScope-RT Hardware
Gold Standard Coherent Receiver
-High bandwidth components
-Low Noise
-Calibrated
ADC + DSP
LabMasterOscilloscope
+
IQScope-RT Software
29

Digital Signal Processing
Hardware calibration
-
Coherent receiver channel skew
-
Coherent receiver frequency response
-
I Q imbalance
-
I Q phase error
CD compensation
-
Frequency domain
-
FIR
-
Custom
-
None
Pol demuxequalizer
-
CMA
-
MMA
-
Max ratio
-
Custom
-
None
Freqoffset compensation
-
Automatic
-
Custom
Carrier Phase estimation
-
Viterbi & Viterbi
-
Decision directed
-
Custom
-
None
Raw signal treatments
-
Spectral filtering
-
Interpolation
-
Resampling
Input
Xi, Xq, Yi, Yq
30

DSP selection
Dispersion
Compensation
Pol Demux&
Equilizer
Carrier Recovery
-Frequency domain
-FIR
-CMA
-MMA
-Max Ratio
-Viterbi & Viterbi
-Decision directed
Best Algorithms for QPSK
31

DSP selection
Dispersion
Compensation
Pol Demux&
Equilizer
Carrier Recovery
-Frequency domain
-FIR
-CMA
-MMA
-Max Ratio
-Viterbi & Viterbi
-Decision directed
Best Algorithms for 16QAM
Note: Need to use smaller MMA gradient and larger number of symbols for 16QAM
32

Modulator Optimization

Modulator optimization in QPSK mode

Turn off A_lowand B_lowto get A_highand B_highchannels generating QPSK
AHigh
Off
PAM4 Generator
AHigh
10dB ATTN
10dB ATTN
10dB ATTN
10dB ATTN
BHigh
Off
BHigh
QPSK
33

Modulator Optimization

Modulator bias point optimization

IQ optical phase offset bias

I bias

Q bias
34

Experimental Setup
35

Modulator optimization in QPSK mode
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IQ Optical phase offset bias optimization
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IQ Optical phase offset bias optimization
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I bias optimization
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I bias optimization
40

Q bias optimization
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Q bias optimization
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Transmitter skew correction

Add a delay to B_highand B_lowPPG channels to compensate for phase mismatch between PAM4-A and PAM4-B
AHigh
ALow
PAM4 Generator
PAM4-A
10dB ATTN
10dB ATTN
10dB ATTN
10dB ATTN
BHigh
BLow
PAM4-B
+100mUI
+100mUI
+100mUI
IQTransmitter
I
Q
43

Experimental Setup
44

Transmitter RF skew optimization
45

Transmitter RF skew optimization
46

Transmitter RF skew optimization -LSB
47

Transmitter RF skew optimization -LSB
48

Level spacing optimization
Optical modulator response
Even optical amplitude levels
Uneven electrical drive voltage levels
Optical output amplitude
Drive voltage
LEGEND
49

PPG level adjustments
1.0V
AHigh
0.5VALow
1.0VAHigh
0.5VALow
Even level spacing
0.9VAHigh
0.6VALow
0.9VAHigh
0.6VALow
Uneven level spacing
0
1
2
3
0
1
2
3
50

Experimental Setup
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Summary

Check out the Lightwavewebcast from July 2014: ‘Generation, Acquisition and Analysis of PAM4 and 16QAM Signals’
https://event.webcasts.com/starthere.jsp?ei=1038346

Demonstration of 16QAM generation using voltage combined PAM4 signals.

Optimization of RF PAM4 signals using a LabMasteroscilloscope

Optimization of 16QAM optical signals using an IQScope-RT OMA
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Want to know more?

Ask us for a product demonstration

Email us for the latest IQScope-RT, IQTransmitter, LabMasterdatasheets

Optical-LinQstand-alone OMA software now available

Seminar tomorrow 10AM (5 September 2014) in Santa Clara, USA. Register Now! http://lcry.us/1pd6O6c

Visit us at ECOC booth 212 in Cannes, France, 22 –24 September 2014
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Thank You for Participating!
Please contact us to schedule a demonstration or evaluation:
Alan Blankman:alan.blankman@teledynelecroy.com
SungHoonIm:s.im@coherent-solutions.com
57

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