A novel design for wavelength tuning of fiber Bragg gratings to restrain bandwidth broadening

Under the structure of the wavelength tuning of fiber Bragg gratings by bending strain due to an axial compressive load, we design a beam with a new shape called the uniform-strain-beam, whose axial strain is uniform when it is bent, in order to eliminate additional chirps produced by nonuniform strains when a uniform-cross-section-beam is bent. Furthermore, by employing an improved design called the almost-uniform-strain-beam, a wavelength tuning process is demonstrated, in which a tuning range of 48 nm with 3-dB bandwidth varying less than 0.1 nm over the full tuning range is achieved. This design scheme has not been reported.