SC460 - Digital Coherent Optical System Performance Basics

Sunday, 06 March
09:00 - 12:00

Short Course Level: Beginner and Advanced Beginner


Maurice O'Sullivan, Ciena, Canada
John Cartledge, Queen’s University, Kingston, Ontario, Canada

Short Course Description:

Coherent optical fiber transmission is a commercial solution which supports capacity growth in reconfigurable WDM networks at bit rates of 40 Gb/s and higher. Its implementation follows on available CMOS technology that is capable of digital signal processing (DSP) capacities of multiple terabits per second and co-integration with analog-to-digital (ADC) and digital-to-analog (DAC) conversion, as well as forward error correction (FEC) coding. This course is designed to equip participants with an understanding of the metrics used to assess the performance of coherent optical fiber transmission systems, and the ability to estimate and compare link performance in practical coherent transmission applications including nonlinear WDM propagation. Where possible, analytic approximations are used to estimate transceiver performance.

Topics addressed:

  • Brief review of DSP assisted electric field modulation and coherent detection
  • Metrics for characterizing transceiver performance:

             -optical and electrical signal-to-noise ratios 

             -pre FEC bit error ratio (pre-FEC-BER) and post-FEC-BER,

             -Q-factor corresponding to pre-FEC-BER, 

             -minimum distance Q-factor corresponding to pre-FEC-BER,

            - mutual information and generalized mutual information

  • Contributions to the link SNR: ASE noise, nonlinear interference noise, and transceiver noise
  • SNR budget approximations 
  • Maximum SNR, maximum net system margin, provisioned power, reach and capacity trade-offs


Short Course Benefits:

This course should enable you to:

  • Understand basic coherent systems and standard implementations of electric field transmitters and coherent receivers
  • Understand the different metrics for characterizing transceiver performance
  • Estimate transceiver performance for basic modulation formats
  • Determine approximate trade-offs between spectral efficiency, baud, reach and transceiver throughput
  • Perform link design and budgeting for WDM systems based on approximate mathematical descriptions 
Short Course Audience:

This course is intended for those familiar with optical fiber transmission, including optical modulation and detection, who are interested in the workings and estimates of performance of commercial multi-rate coherent solutions in multi-span amplified WDM systems.

Instructor Biography:

For more than 25 years Maurice O'Sullivan has contributed to the design and manufacture of optical fiber and, mostly, the highest capacity long line transmission equipment of its day with emphasis on layer 0. He holds a PhD in Physics from the University of Toronto.

For more than 35 years John Cartledge has conducted research on optical fiber communication systems. He holds a PhD in Applied Mathematics from Queen’s University.