Free Spectral Range Variation of a Broadband, High-Finesse, Multi-Channel Fabry-Perot Filter using Chirped Fiber Bragg Gratings

The free spectral range (FSR) variation of a broadband, high finesse, multi-channel Fabry-Perot (FP) filter using linearly chirped fiber gratings has been studied theoretically. It is found that the FSR variation of the FP filter using linearly chirped fiber gratings was determined by the relationship between the distance between two fiber gratings and the total transmitted phase change. The variation of the FSR of a FP filter using linearly chirped fiber gratings was explained by the equation obtained in this study. This simulation dealt with three types of FP filters using linearly chirped fiber gratings of different grating lengths for 1.3 µ m single mode fibers. These were 4.47 mm, 6.67 mm and 7.50 mm in grating length, which are easily obtainable using recent inscription technologies. The different behaviors of the spectral response of FP filters using fiber gratings and bulk FP etalon were also established.