# Time-delay signature suppression in a chaotic semiconductor laser by fiber random grating induced distributed feedback

## TL;DR

This paper shows that using a fiber random grating for distributed feedback in a semiconductor laser effectively suppresses the time-delay signature, resulting in highly complex chaos with minimal delay imprint.

## Contribution

It introduces a novel method of using fiber random gratings for feedback, significantly improving delay signature suppression compared to traditional single reflection feedback.

## Key findings

- Achieved the smallest time delay signature of 0.0088 to date.
- Demonstrated high-dimensional chaos with numerous external cavity modes.
- Validated the theoretical model with experimental results.

## Abstract

We demonstrate that a semiconductor laser perturbed by the distributed feedback from a fiber random grating can emit light chaotically without the time delay signature. A theoretical model is developed based on the Lang-Kobayashi model in order to numerically explore the chaotic dynamics of the laser diode subjected to the random distributed feedback. It is predicted that the random distributed feedback is superior to the single reflection feedback in suppressing the time-delay signature. In experiments, a massive number of feedbacks with randomly varied time delays induced by a fiber random grating introduce large numbers of external cavity modes into the semiconductor laser, leading to the high dimension of chaotic dynamics and thus the concealment of the time delay signature. The obtained time delay signature with the maximum suppression is 0.0088, which is the smallest to date.

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Source: https://tomesphere.com/paper/1703.07444