METHOD AND APPARATUS FOR REGULATING ELECTROABSORPTION MODULATORS

摘要

An electroabsorption modulator (EAM) is regulated by obtaining a first signal representing the optical output power of the EAM (P, Do) and a second signal representing its photocurrent (Ip); combining the first and second signals to obtain a control function that has an identifiable value at the half-power point; and adjusting the bias value to bring the function to that identifiable value. The control function may be obtained by multiplying the first and second signals, in which case the bias voltage will be adjusted to maximise it; or, provided the signals are in such proportion to the variables they represent that their sum is substantially independent of the bias voltage, by computing the difference between the first and second signals, and adjusting the bias voltage until the difference is substantially zero. The second signal represents 1-x, where x is the optical output (P), and a correction factor varying with the bias voltage can be used to improve the accuracy with which it does so.