An all-fiber optical attenuator based on adjustable coupling angle of microfiber

A tunable all-fiber optical attenuator (AOA) based on microfiber with adjustable coupling angle is reported and demonstrated. The AOA is fabricated of a microfiber probe coupled to a tapered fiber on the waist region through van der Waals and electrostatic forces. The attenuation can be tuned by adjusting the coupling angle of the two microfibers. When the coupling is fabricated of angles adjust from 80o to 10o, the optical attenuation can be tuned in a large range from 5.7 dB to 40.1 dB with low insertion loss. The simulation and experimental show that the coupling length can be changed by increasing the coupling angle, which results in decreasing the attenuation of AOA. The attenuation of AOA is decreased linearly by increasing the coupling angle. It provides a feasible approach to achieve attenuators with miniature volume, low cost, and multiple functions in optical communication and fiber lasers.