InP-based monolithic optical frequency discriminator module for WDM systems

We have developed an InP-based monolithic optical frequency discriminator c onsisting of a temperature-insensitive optical filter and dual photodiodes. This integrated device detects the optical frequency deviation of the inpu t light as differential photocurrent from the dual photodiodes, and the pho tocurrent is fedback to the light source for frequency stabilization throug h a differential amplifier. The FSR and extinction ratio of the filter are 50 GHz, and 20 dB. The total opto-electronic conversion efficiency is 40%. In a frequency stabilization experiment using the developed discriminator, the frequency fluctuation of a DFB laser was reduced to less than 10 MHz.