Widely tunable optical filters based on fiber Bragg gratings

The authors design and demonstrate a widely tunable wavelength filter, which is realized by lateral bending of a fiber Bragg grating mounted on a substrate. The 40-nm tunable range of the device covers the entire C-band of erbium-doped fiber amplifiers with very small changes in a spectral width and a reflectivity across the operation bandwidth. Furthermore, employment of a hybrid material as a substrate alleviates the stringent requirement for the bending radius. With this hybrid substrate structure, a tuning range as wide as 50 nm is achieved.