# Capacity-Achieving Input Distribution in Per-Sample Zero-Dispersion Model of Optical Fiber

## TL;DR

This paper characterizes the capacity-achieving input distribution for the per-sample zero-dispersion optical fiber model, showing it has uniform phase and discrete amplitude, under various input constraints.

## Contribution

It proves the unique capacity-achieving distribution structure for this optical fiber model with general input constraints.

## Key findings

- Capacity is achieved by a distribution with uniform phase and discrete amplitude.
- The result holds under peak and joint average-peak amplitude constraints.
- The distribution takes finitely many amplitude values.

## Abstract

The per-sample zero-dispersion channel model of the optical fiber is considered. It is shown that capacity is uniquely achieved by an input probability distribution that has continuous uniform phase and discrete amplitude that takes on finitely many values. This result holds when the channel is subject to general input cost constraints, that include a peak amplitude constraint and a joint average and peak amplitude constraint.