Optimal Design of Short Fiber Bragg Grating Using Bat Algorithm With Adaptive Position Update

We propose a new method to optimally design short triangular-spectrum fiber Bragg gratings (TS-FBGs), using the metaheuristic bat algorithm (BA). In addition, we propose a novel modification, i.e., adaptive position update (APU), to optimize the index modulation within a predetermined range. The discrete layer-peeling algorithm is used to efficiently initialize BA. The APU improves the search performance and accuracy of the BA algorithm in fiber Bragg grating (FBG) design application. Using the proposed method, a 0.2-nm-bandwidth TS-FBG, operating in the C-band, is designed. The short-length FBG with chirp-free structure prevents complex phase modulation for practical considerations. In addition, a dual-wavelength TS-FBG of 0.75-nm bandwidth operating in the eye-safe region has been designed and provided the most accurate optimum design length. The latter is well suited for FBGs inscribed in high-birefringent fibers, which are utilized in multiwavelength fiber laser systems. For both cases, the accuracy and search performance of APU-BA are shown to be better than those of previously reported algorithms in the literature.