Using and OMA to Optimize QAM Optical Transceivers

Using an Optical Modulation Analyzerto Optimize 16QAM Optical Transceivers

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Your Presenters:Dr Alan Blankman, Teledyne LeCroyDr Sung-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

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System Setup

Dr Alan Blankman

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Experimental Setup

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Block Diagram for OMA Test Setup

1. PAM4 Signal Generator

2. DP-16QAMGenerator

3. Coherent Receiver

4. Oscilloscope(Acquisition)

5. Oscilloscope(Analysis)

Anritsu MP1800A

Coherent SolutionsIQTransmitter

Coherent SolutionsIQScope-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 PPGMP1800A Mainframe

MZ1834A 4PAM Converter

to optical IQ TransmitterPAM4 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 & Bhigh set for ~2 V PPG ALow & BLow set for ~1 V

Summing AHigh + ALow PAM4 signal with levels 0, 1, 2, 3. Example bitstream for I or Q:

11 01 10 00 11 11 01 00 10 01

3 1 2 0 3 3 1 0 2 1PAM4 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 laser power Control of modulator bias

points: I, Q, Quadrature Single & Dual-Pol outputs

Electrical PAM4 signals fromMP1800A Generatorto RF I&Qinputs

PMF LO out-in

PMF 1-pol-outto 2-pol in

SMF carrying DP-16QAMto coherent optical receiver

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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 outputsto 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 Tx and Rx. Modulator bias points: I – 282, Q – 122, Quad – 172

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PAM4 Signal Optimization

Dr Alan 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.

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Experimental Setup

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Coherent Solutions | Teledyne LeCroy 18


Oscilloscope Acquisition

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Eye Diagrams of PAM4 Signals

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PAM4 Eye Showing Skew Between High and Low

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Adjusting Skew

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Adjusting Skew

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Skew Adjusted.

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Non-equally Spaced Levels

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Optical Transmitter Optimization Using an OMA

Dr Sung-Hoon Im

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Optical signal generation and characterization

Optical signal generationIQTransmitter

Optical signal characterizationIQScope-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 MixerX - I

X - Q

BPD

BPD

Y - I

Y - Q

Modulated Signal

Reference LO

PBS

IQScope-RT HardwareGold Standard Coherent Receiver- High bandwidth components- Low Noise- Calibrated

ADC + DSP

LabMasterOscilloscope

+IQScope-RT

Software

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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

Freq offset compensation

- Automatic- Custom

Carrier Phase estimation

- Viterbi & Viterbi- Decision directed- Custom- None

Raw signal treatments

- Spectral filtering- Interpolation- Resampling

Input

Xi, Xq, Yi, Yq

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DSP selection

Dispersion Compensation

Pol Demux &Equilizer

Carrier Recovery

- Frequency domain

- FIR

- CMA

- MMA

- Max Ratio

- Viterbi & Viterbi

- Decision directed

Best Algorithms for QPSK

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DSP selection

Dispersion Compensation

Pol Demux &Equilizer

Carrier Recovery

- Frequency domain

- FIR

- CMA

- MMA

- Max Ratio

- Viterbi & Viterbi

- Decision directed

Best Algorithms for 16QAMNote: Need to use smaller MMA gradient and larger number of symbols for 16QAM

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Modulator Optimization

Modulator optimization in QPSK mode Turn off A_low and B_low to get A_high and B_high channels generating

QPSK

AHigh

Off

PAM4 Generator

AHigh

10dB ATTN

10dB ATTN

10dB ATTN

10dB ATTN



BHigh

Off

BHigh

QPSK

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Modulator Optimization

Modulator bias point optimization IQ optical phase offset bias I bias Q bias

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Experimental Setup

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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

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Q bias optimization

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Q bias optimization

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Transmitter skew correction

Add a delay to B_high and B_low PPG 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

+100mUIIQTransmitter

I

Q

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Experimental Setup

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Transmitter RF skew optimization

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Transmitter RF skew optimization

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Transmitter RF skew optimization - LSB

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Transmitter RF skew optimization - LSB

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Level spacing optimization

Optical modulator response

Even optical amplitude levels

Uneven electrical drive voltage levels

Optical output amplitude

Drive voltage

LEGEND

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PPG level adjustments

1.0VAHigh

0.5VALow

1.0VAHigh 0.5V

ALow

Even level spacing

0.9VAHigh

0.6VALow

0.9VAHigh

0.6VALow

Uneven level spacing

0

1

2

3

0

1

2

3

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Experimental Setup

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Summary

Check out the Lightwave webcast 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 LabMaster oscilloscope

Optimization of 16QAM optical signals using an IQScope-RT OMA

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https://event.webcasts.com/starthere.jsp?ei=1038346


Want to know more?

Ask us for a product demonstration

Email us for the latest IQScope-RT, IQTransmitter, LabMaster datasheets

Optical-LinQ stand-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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http://lcry.us/1pd6O6c

Thank You for Participating!Please contact us to schedule a demonstration or evaluation:

Alan Blankman: [email protected] Im: [email protected]

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Using and OMA to Optimize QAM Optical Transceivers

Technology

coherent solutions2

coherent receiver4

teledyne lecroydrsung

teledyne lecroy labmaster

optical signalagenda

optical signalbuilt

alowpam4 signal

diff pam4 signal generation8