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 per...