Polarization-independent all-fiber flat-top comb filter

A novel polarization-independent all-fiber flat-top comb filter based on high birefringent (Hi–Bi) fiber Sagnac interferometer is proposed for the first time to our knowledge. The numerical simulation results show that the proposed device exhibits flat-top and the extinction ratio reads about 30 dB. A good agreement between the numerical simulations and the experimental results is achieved.