Optical frequency comb generator based on interference among parallel phase modulators

Abstract

We propose an optical frequency comb (OFC) generator for ultra-flat and multiple frequency-spaced OFC. By appropriately set the amplitude and phase of radio frequency (RF) signals fed to the parallel phase modulators, an ultraflat OFC with multiple frequency spacing can be generated. Since the frequency spacing of the generated OFC can be multiplied, it can be much larger than the typical modulation bandwidth of electro-optic modulators. Previously reported ultra-flat and multiple frequency-spaced OFC generators suffer from complex and invalid configuration since they employed either more than one-stage modulators or single-stage modulators attached with other components such as optical switches, which suffer from light leakage and limited extinction ratio in practice. Compared with previously reported method, Our scheme has much simpler configuration since only single-stage parallel modulators are used. The operating conditions for generation of multiple frequency spacing and spectrum flattening are clarified. The concept is verified in numerical analysis for generation of N×25GHz-spaced OFC. Performance analysis of the proposed scheme is also investigated.