Computer control of fiber Bragg grating spectral characteristics using a thermal head

We present a new technique for arbitrarily controlling the temperature distribution in fiber Bragg gratings (FBG's) to control their spectral characteristics. A thermal head consisting of a microheater array, driven with computer control signals is used as a controlling device. Various spectral characteristics including a chirped grating and a transmission filter are demonstrated using a single unchirped grating. An effective improvement in response time constant of thermal control was observed on bonding of the fiber grating to thermal head (18 ms), in comparison to that without bonding (40 ms). The measured results did not show any hysterisis. Reliability studies of this technique are also reported. The same technique is further used for the dual wavelength operation of an Er-doped fiber laser.