GRATING-FRUSTRATED COUPLER - A NOVEL CHANNEL-DROPPING FILTER IN SINGLE-MODE OPTICAL-FIBER

A low-insertion-loss, all-single-mode fiber, wavelength-division-multiplexing filter comprising a four-port polished coupler and a strong fiber grating is demonstrated. The device operates in a novel way by a process we can grating-frustrated directional coupling. A fiber grating, present in only one half of the coupler, frustrates the transference of power to the other half within a narrow wavelength range. The performance of a prototype device-a 1535-nm channel-dropping filter with 0.7-nm bandwidth, 70% peak transmission, and 13-dB isolation-shows great promise for wavelength-division-multiplexing and line-filtering applications.