Characterization and Compensation of the Residual Chirp in a Mach-Zehnder-Type Electro-Optical Intensity Modulator

TL;DR

This paper characterizes the residual phase modulation (chirp) in a fiber-based Mach-Zehnder electro-optical intensity modulator using multiple techniques, and demonstrates effective compensation with a separate phase modulator.

Contribution

It introduces a comprehensive set of methods to measure the residual chirp and shows how to effectively compensate for it in practical applications.

Findings

Chirp parameter measured by heterodyne technique and sideband ratio are in agreement.

Residual chirp can be largely compensated with a separate phase modulator.

Frequency chirp on nanosecond timescales was successfully characterized.

Abstract

We utilize various techniques to characterize the residual phase modulation of a fiber-based Mach-Zehnder electro-optical intensity modulator. A heterodyne technique is used to directly measure the phase change due to a given change in intensity, thereby determining the chirp parameter of the device. This chirp parameter is also measured by examining the ratio of sidebands for sinusoidal amplitude modulation. Finally, the frequency chirp caused by an intensity pulse on the nanosecond time scale is measured via the heterodyne signal. We show that this chirp can be largely compensated with a separate phase modulator. The various measurements of the chirp parameter are in reasonable agreement.