Coding for the Optical Channel: the Ghost-Pulse Constraint

TL;DR

This paper introduces constrained coding techniques to prevent ghost pulses in optical fiber channels, aiming to reduce nonlinear effects and improve data integrity.

Contribution

It proposes new coding schemes using binary and ternary sequences that avoid patterns leading to ghost pulses, along with encoder and decoder designs.

Findings

Coding schemes effectively mitigate ghost pulse formation.

Analysis shows improved error resilience in optical channels.

Designs are practical for implementation in optical communication systems.

Abstract

We consider a number of constrained coding techniques that can be used to mitigate a nonlinear effect in the optical fiber channel that causes the formation of spurious pulses, called ``ghost pulses.'' Specifically, if $b_1 b_2 ... b_{n}$ is a sequence of bits sent across an optical channel, such that $b_k=b_l=b_m=1$ for some $k,l,m$ (not necessarily all distinct) but $b_{k+l-m} = 0$, then the ghost-pulse effect causes $b_{k+l-m}$ to change to 1, thereby creating an error. We design and analyze several coding schemes using binary and ternary sequences constrained so as to avoid patterns that give rise to ghost pulses. We also discuss the design of encoders and decoders for these coding schemes.