Energy Conservation in Optical Fibers with Distributed Brick-Walls Filters

TL;DR

This paper introduces a novel band-pass filtering scheme with distributed brick-wall filters in fiber optics, aimed at conserving energy and improving spectral efficiency by mitigating nonlinear effects and channel coupling.

Contribution

It models a modified NLS equation with brick-wall filters, demonstrating energy conservation and deriving conditions for optimal channel spacing and spectral efficiency using Sidon sequences.

Findings

Brick-wall filters conserve total in-band energy.

Derived conditions for energy conservation per channel.

Maximum spectral efficiency achieved with Sidon sequences.

Abstract

A band-pass filtering scheme is proposed to mitigate spectral broadening and channel coupling in the Nonlinear Schr\"odinger (NLS) fiber optic channel. The scheme is modeled by modifying the NLS Equation to include an attenuation profile with multiple brick-wall filters centered at different frequencies. It is shown that this brick-walls profile conserves the total in-band energy of the launch signal. Furthermore, energy fluctuations between the filtered channels are characterized, and conditions on the channel spacings are derived that ensure energy conservation in each channel. The maximum spectral efficiency of such a system is derived, and a constructive rule for achieving it using Sidon sequences is provided.