Experimental fabrication of add/drop filters using a Bragg grating-assisted mismatched coupler

All-fiber add/drop filter is a key component in the optical fiber communication system.Add/drop filters using a Bragg grating-assisted mismatched coupler were fabricated and tested in the laboratory.The filter was based on 248 nm ultraviolet-written Bragg grating in 2×2 coupler fused with a standard single mode fiber and a high germanium doped photosensitive fiber fabricated by our own laboratory.The insertion loss and the return loss of the device were 6.74 dB and -18.84 dB,respectively.The performance of the device is tested at 10 Gbps networks.The eye diagram of the input signal and the eye diagram of the signal from the drop port of the device are obtained.The signal-to-noise ratio of the signal from the drop port declines from 10.04 dB to 9.27 dB,and the extinction-ratio of the signal from the drop port declines from 8.89 dB to 4.68 dB.