Analysis of polarization-independent tunable optical comb filter by cascading MZI and phase modulating Sagnac loop

A novel scheme of tunable optical comb filter constructed by cascading a polarization-swapping MZI and a phase modulating Sagnac loop is proposed. The key features of this comb filter design are its polarization-independence and high speed in wavelength tuning. The wavelength tunability can be readily achieved by incorporating an electro-optic phase modulator into the Sagnac loop. In addition, the filter can be made amplitude adjustable as well. The filter will be desirable for multi-wavelength fiber lasers, multi-channel optical signal processing and optical WDM systems.

► A polarization-independent ultra-fast tunable optical comb filter is proposed.
► It consists of a polarization-swapping MZI and a phase modulating Sagnac loop.
► The MZI and Sagnac loop combination ensures the filter polarization-independent.
► Introducing a phase modulator to Sagnac loop enables high-speed wavelength tuning.