Using and OMA to Optimize QAM Optical Transceivers

Using an Optical Modulation Analyzerto Optimize 16QAM Optical Transceivers

1

Your Presenters:Dr Alan Blankman, Teledyne LeCroyDr Sung-Hoon Im, Coherent Solutions

2

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

Dr Alan Blankman

4


Experimental Setup

5


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

6


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

7


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

8


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:

9


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

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 outputsto oscilloscope

11


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

12


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

13


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

14

PAM4 Signal Optimization

Dr Alan Blankman

15


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

25

Optical Transmitter Optimization Using an OMA

Dr Sung-Hoon Im

26


Optical signal generation and characterization

Optical signal generationIQTransmitter

Optical signal characterizationIQScope-RT

27


Optical signal generation

OMA

4Ch PPG

PAM4

28


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

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

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

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

32


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

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

36


IQ Optical phase offset bias optimization

37


IQ Optical phase offset bias optimization

38


I bias optimization

39


I bias optimization

40


Q bias optimization

41


Q bias optimization

42


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

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

1.0VAHigh

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

50


Experimental Setup

51



52



53



54


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

55

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

56

http://lcry.us/1pd6O6c

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

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

57

Using and OMA to Optimize QAM Optical Transceivers

Technology

Transcript of Using and OMA to Optimize QAM Optical Transceivers