FBG-Based Matched Filters for Optical Processing of RF Signals

We demonstrate the detection of RF pulses using complex matched filters implemented in photonics. The optical receiver consists of an intensity Mach-Zehnder modulator (MZM) for electrical-to-optical conversion as well as precisely tailored fiber Bragg grating (FBG) filters performing as matched filters. We examine the performance of the receiver under two bias conditions of the MZM, namely, quadrature and minimum transmission. We design the corresponding matched filters for both cases by optimizing the impulse response of linearly chirped FBGs. We fabricate the FBGs by achieving the required apodization profiles through a multiple-scan writing procedure. We discuss the relative performance of the two solutions.