Multicarrier Light Source With Flattened Spectrum Using Phase Modulators and Dispersion Medium

This paper describes a phase-locked multicarrier light source that employs a continuous wave (CW) light source, two phase modulators, and a dispersion medium. A sinusoidal phase modulation (PM) with a modulation index of ??/4 and a group velocity dispersion of ??1/(4??fm ²), where fm is the modulation frequency, are applied to a CW light followed by a large sinusoidal PM. This configuration provides a multicarrier light with a flattened optical power spectrum for any modulation index of the second PM. By adopting a chirped fiber Bragg grating (FBG) as a dispersion medium instead of a long normal dispersion fiber, we can increase the stability of the optical output spectrum and reduce the size of the multicarrier light generator. We have built a prototype with this configuration that generates a 61-carrier light with a 25 GHz interval and a power deviation of less than 8 dB.