A high speed TFBG-SPR sensing demodulation system based on microwave photonics interrogation is proposed theoretically. The wavelength shifting of the SPR envelope in optical domain is converted to the microwave pulse shifting in time domain. The RI resolution is improved by one order of magnitude compared with wavelength demodulation, and the sensing speed is as high as 40 KHz.
An incoherent microwave photonic filter (MPF), based on multiwavelength phase modulation (PM) and a WaveShaper, is proposed and investigated. The multiwavelength erbium-doped fiber laser provides multiple taps, while the WaveShaper and a dispersive device perform PM to amplitude modulation (AM) conversion. The WaveShaper can also induce both spectral shaping effect for the taps and a different phase for radio-frequency signal during the PM-to-AM conversion. Principle analysis of MPF based on PM-to-AM conversion is discussed. Simulation is carried out to investigate the influence of WaveShaper parameters on the frequency response of the MPF. Through adjustment of the WaveShaper, MPFs with positive, negative, or complex coefficients are also obtained in the experiment. Experimental observations agree well with the simulation results and discussions are given.