Theoretical Study of the Spurious-Free Dynamic Range of a Tunable Delay Line based on Slow Light in SOA

TL;DR

This paper presents a theoretical model for analyzing the spurious-free dynamic range of a tunable delay line based on slow light effects in semiconductor optical amplifiers, relevant for radar frequencies.

Contribution

It introduces a comprehensive predictive model that accounts for gain oscillations and saturation variations, providing new insights into SFDR optimization in CPO-based delay lines.

Findings

SFDR can be optimized over a wide frequency range (40kHz to 30GHz).

High order distortions significantly impact the microwave spectrum.

CPO effects improve SFDR in Mach-Zehnder modulators.

Abstract

We developed a predictive model describing harmonic generation and intermodulation distortions in semiconductor optical amplifiers (SOAs). This model takes into account the variations of the saturation parameters along the propagation axis inside the SOA, and uses a rigorous expression of the gain oscillations harmonics. We derived the spurious-free dynamic range (SFDR) of a slow light delay line based on coherent population oscillation (CPO) effects, in a frequency range covering radar applications (from 40kHz up to 30GHz), and for a large range of injected currents. The influence of the high order distortions in the input microwave spectrum is discussed, and in particular, an interpretation of the SFDR improvement of a Mach-Zehnder modulator by CPOs effects in a SOA is given.