All-fiber birefringent filter with fine tunability and changeable spacing

A novel all-fiber birefringent filter has been proposed and demonstrated. Simulation results show that the birefringence fiber filter with one section of polarization-maintenance fiber (PMF) can be finely tuned with its free spectrum range, and the filter with two sections of PMFs can generate changeable wave-length spacing. Experiment agrees well with simulation. This filter has potential applications for flexible multiwavelength fiber laser.