Accurate bias point control for an electrically isolated, Mach-Zehnder interferometric modulator via an analog optical fiber link

Published

August 2, 2004

Author(s)

John Hamilton, Keith D. Masterson

Abstract

We describe a new method to keep an electrically isolated Mach-Zehnder electro-optic modulator biased in quadrature in spite of changes in temperature and optical coupling efficiency. The modulator is part of a system to measure electromagnetic waves in an outdoor environment. All data and control signals between the modulator and electronics control module are carried by analog optical fiber links and all of the bias signals and control procedures are implemented with an onboard computer and digital signal processing unit. Our method compares the average DC optical power in the complementary outputs of the modulator to adjust the bias point by controlling the optical power to small photocells in the sensor head. A second control loop balances small dither amplitudes and hence the optical losses in each of the complementary outputs by way of an optical variable attenuator. This control system enables us to maintain the bias to within ?2 degrees of the quadrature point. The response time of the control loop is 100 ms.

Proceedings Title

SPIE International Symposium on Optical Science and Technology

Conference Dates

August 2-6, 2004

Conference Location

Denver, CO

Pub Type

Conferences

Keywords

bias control, electro-optic modulator, optical uplink, RF probe

Citation

Hamilton, J. and Masterson, K. (2004), Accurate bias point control for an electrically isolated, Mach-Zehnder interferometric modulator via an analog optical fiber link, SPIE International Symposium on Optical Science and Technology, Denver, CO (Accessed July 20, 2024)