Novel all-fiber variable optical attenuator based on high birefringence fiber loop mirror

In this paper, we propose a novel all-fiber variable optical attenuator based on high birefringence fiber loop mirror. Part of the birefringence fiber was pasted onto an equivalent-strength beam and by applying a strain with a high precision screw thruster on the free end of the beam, we observed that the transmission spectrum of the fiber loop mirror shifted with nearly unaltered shape. The attenuation at 1551nm is more than 30dB with about 6dB insertion loss. By tuning the angle between the fast or slow axes of input and output planes of the birefringence fiber, the insertion loss of this VOA can be minimized to no more than 1.5dB. The wavelength shift of this VOA varies linearly (the linear correlation coefficient reaches 0.9979) with the deflection of the beam and it turns out good attenuation characteristics.