A hybrid method for designing fiber Bragg gratings with right-angled triangular spectrum in sensor applications

Based on the quantum-behaved particle swarm optimization (QPSO) algorithm and the discrete layer peeling (DLP) approach, we propose a scheme to design the right-angled triangular spectrum fiber Bragg gratings (RTS-FBGs). In this method, for a target reflectivity spectrum, the DLP approach is used to generate an appropriate initial guess of the complex coupling coefficients, and the QPSO technique is applied to optimize the initial complex coupling coefficients. For the QPSO method, the whole complex solution space can be searched for the coupling coefficients. Using the proposed method, single- and multi-channel RTS-FBGs are designed. Simulation results demonstrate that the edge of the right-angled triangular spectrums designed by our method is quite linear and the shape of the spectrum is also very consistent with the target spectrum, in contrast to those obtained by existing method. The RTS-FBGs can find potential applications in wavelength interrogation in optical sensor system.