Distributed Coherent Optical Computing via Injection-Locked Photonic Networks

TL;DR

This paper introduces a novel approach for distributed coherent optical computing using injection locking of lasers, enabling real-time processing without optical-electrical conversions, and explores the operational conditions for stability and accuracy.

Contribution

It proposes a new strategy leveraging optical injection locking for distributed, real-time coherent optical processing, avoiding traditional conversion limitations.

Findings

Higher injection powers broaden locking margins but increase amplitude-phase mixing.

Lower injection powers provide a more predictable and stable operating window.

Reducing injection ratio improves computational accuracy by suppressing residual modulation.

Abstract

Coherent photonic computing uses both the phase and amplitude of light to implement linear operations such as dot products and matrix multiplication but requires phase stability between the interfering paths. This poses a challenge for such strategies when optical data is generated at a remote source due to environmental phase variations in fiber. Conventional approaches to distributed computing rely on optical-to-electrical conversion and buffering, limiting truly real-time and distributed computation. Here, we propose a new strategy via optical injection locking to enable distributed, real-time coherent optical processing without unnecessary conversions in the optical-to-electrical or analog-to-digital domains. Using a semiconductor laser rate-equation model, we explore the conditions required for stable operation by sweeping the power injection ratio, frequency detuning, and modulation conditions of the remote and injected lasers. Our results indicate that higher injection powers broaden the locking margin but more readily exhibit frequency-selective features associated with relaxation oscillations and increased amplitude-phase mixing, whereas lower injection powers yield a narrower, but more predictable operating window which remains stable under large modulation depth. End-to-end symbol-sequence simulations with balanced detection and temporal integration further confirm that reducing the injection ratio suppresses residual remote-modulation components in the injected laser output and improves computational accuracy. Overall, our study provides guidance and design trade-offs for remote coherent detection and distributed coherent photonic computing enabled by injection locking.