Deyuan Chang

LDPC convolutional codes using layered decoding algorithm for high speed coherent optical transmission

We successfully realized layered decoding for LDPC convolutional codes designed for application in high speed optical transmission systems. A relatively short code with 20% redundancy was FPGA-emulated with a Q-factor of 5.7dB at BER of 10-15.

20x224Gbps (56Gbaud) PDM-QPSK Transmission in 50GHz grid over 3040km G.652 fiber and EDFA only link Using Soft Output Faster than Nyquist Technology

We report 20×224Gbps PDM-QPSK in 50GHz grid over G.652 fiber and EDFA-only link. Using Soft Output Faster than Nyquist and 7% SDFEC, 4bit/s/Hz net spectral efficiency transmission over 3040km with 21dB span loss is achieved.

FEC for high speed optical transmission

This paper will at first explain the requirement of high speed optical transport network on forward error correction (FEC) codes in terms of code length, code rate, coding gain, burst error correction capability, error floor, latency, coding/decoding complexity. Then, a few code schemes used in current optical transport systems such as Reed-Solomon codes recommended by ITU-T G.709 and enhanced FECs listed in ITU-T, G.975.1 are introduced. Advanced codes recently developed by vendors used for 100Gbps systems and their performances are summarized. Features and special requirements on soft decoding FEC (SDFEC) especially inter-working between SDFEC and equalizer, with and without deferential coding etc. are analyzed. Some perspectives of future FEC for optical transport are also given.

Implementation of coded modulation and FEC

We discuss implementation aspects of LDPC based soft-decision FEC schemes for high speed optical systems. Several BICM schemes with LDPC convolutional codes are proposed and compared in respects of both performance and implementation complexity.

Reusing Common Uncoded Experimental Data in Performance Estimation of Different FEC Codes

In this letter, we present a method for performance estimation of forward error correction (FEC) codes using off-line data without data encoding. Only a few hundred thousand uncoded symbols are used to accurately evaluate post-FEC bit error rate of soft FEC codes decodable by the sum-product algorithm at very low error rates, e.g., 10-8 which is only limited by computer performance and simulation time. The method is applicable to both single and concatenated codes. The demonstration is carried out in optical 128-Gb/s polarization division multiplexed experiments with differentially encoded data and 20% redundancy quasi cyclic low-density parity check code.

Adaptive joint carrier recovery and turbo decoding for nyquist terabit optical transmission in the presence of phase noise

An adaptive joint carrier recovery and soft LDPC turbo decoding scheme in the presence of nonlinear phase noise is proposed and experimentally verified with 1.9dB coding gain in Nyquist Terabit PDM-DQPSK systems.

Concatenated QC-LDPC and SPC Codes for Turbo Decoding in Differentially Encoded System

A new class of codes is proposed for differentially encoded coherent systems. Regular Quasi Cyclic Low Density Parity Check codes concatenated with two-dimensional single parity check codes improved performance by 0.4 dB without complexity increase.