Study of the microwave photonic sensing by utilizing the incoherent light source with the serial fiber Bragg gratings

Microwave photonic filter is one of the key technologies of microwave photonics. Its main purpose is to replace the traditional method to process radio frequency signal, modulate optical carrier by radio frequency signal, and process it directly in the optical domain. The advantage of FIR microwave photonic filter is that it has no system poles and is more stable. It guarantees linear phase, which is very important in signal processing. In this paper, the incoherent microwave photon sensor cascaded by FBG is verified experimentally. In the experiment, three FBG wavelengths are 1530 nm, 1550.12nm and 1539.5nm respectively to form a high-order FIR microwave photon filter, two 3dB couplers and three km fibers to form an unbalanced M-Z interferometer. The incoherent light generated by EDFA is modulated by a filter electro-optic modulator through an optical fiber Bragg grating, demodulated by an M-Z interferometer, and eventually received by a photodetector. In the experiment, 60 MHz near notch is chosen as the modulation frequency, the amplitude of modulation signal is 4 Vpp, the temperature range is 30-40°C with the temperature interval of 1°C. The sensitivities of 0.2219dBm/°Care obtained by processing the average values of 3 points, 5 points, 7 points, 10 points and 15 points.