Novel bias control of electroabsorption waveguide modulator

A novel approach is proposed for controlling the bias of an electroabsorption waveguide modulator for maximum radio-frequency (RF) gain in analog fiber-optic links. It is based upon the correlation between the RF gain and the modulator DC photocurrent. It is found that, under various operating conditions, the modulator bias at which the modulator DC photocurrent experiences the largest change with incremental bias, coincides with the bias for the maximum RF gain. This approach eliminates the need for an external tracking photodiode, and can be useful in bias controls of a modulator array.