“…As the Bragg wavelength changes in response to variations in surrounding conditions, such as temperature or strain, FBGs have been shown to be very useful as optical fiber sensors. Likewise, by modifying external parameters in a controlled manner one can design a tunable, or programmable, wavelength response with useful applications in, e.g., optical sensing [3][4][5], tunable laser sources [6,7,8] or spectroscopic analysis [9]. For many applications, a wide tunability, while maintaining the bandwidth of the grating wavelength is preferred.…”