Effects of polarization modulation induced by electro-optic modulators in fiber-based setups

TL;DR

This paper analyzes how electro-optic modulators induce polarization modulation in fiber setups, affecting measurement sensitivity through residual amplitude modulation and signal distortion, with theoretical modeling of these effects.

Contribution

It provides a theoretical framework for understanding polarization modulation effects caused by electro-optic modulators in fiber-based systems.

Findings

Polarization modulation leads to residual amplitude modulation in PDL components.

Signal distortion occurs at the output of fiber cavities due to polarization effects.

Theoretical expressions quantify the impact of polarization modulation on detected signals.

Abstract

Using the Jones formalism, it is shown that electro-optic modulators used for phase modulation generate a modulation of the output polarization induced by the difference of phase modulation depth along the crystallographic axes of the modulator. We study two consequences of this polarization modulation in the fiber setups, limiting the performance of high sensitivity measurement devices. The first one is its partial conversion into a residual amplitude modulation (RAM) within any component presenting polarization dependent losses (PDL). The second one is a new effect that consists of the distortion of the signal detected at the output of a fiber cavity. The theoretical expressions of the detected signals are computed in each case.