Injection Locking of Optoelectronic Oscillators with Large Delay

TL;DR

This paper develops a new theoretical framework for injection locking in large delay optoelectronic oscillators, accurately predicting their dynamics, sidemode suppression, and phase noise, validated by experimental results.

Contribution

It introduces a comprehensive model that accounts for large delays and removes simplifying assumptions, improving understanding of injection locking in optoelectronic oscillators.

Findings

New formulation accurately predicts locking range and sidemode suppression.

Experimental validation confirms theoretical predictions.

Enhanced understanding of phase noise behavior in large delay oscillators.

Abstract

The optoelectronic oscillator is a delay line oscillator that leverages optical fiber technology to realize the large delay required for low phase noise systems. Spurious sidemodes are an artifact of the delay line oscillator, yet treatments of injection locking of optoelectronic oscillators have relied on the application of classical injection locking theory valid only for single mode oscillators. The large delay contributed by the optical fiber delay line is accounted for by classical theory only in part through the quality factor Q that captures the round-trip group delay in a neighborhood of the oscillation frequency. This paper presents a new formulation of time delay oscillators subject to injection that describes all the essential features of their dynamics and phase noise. The common assumptions of a single mode oscillator and weak injection are removed. This is important to correctly predict the locking range, the suppression of sidemodes and the phase noise spectrum. The findings of the analysis are validated by experimental measurements provided by an optoelectronic oscillator under injection by an external source.