Photonic-assisted approach for instantaneous microwave frequency measurement with tunable range by using Mach-Zehnder interferometers

A novel photonic-assisted approach to microwave frequency measurement is proposed and experimentally demonstrated. The proposed scheme is based on the frequency-to-power mapping with different transmis- sion responses. A polarizer is used in one output branch of a phase modulator to simultaneously implement phase modulation and intensity modulation. Owing to the complementary nature of the transmission re- sponses and the Mach-Zehnder interferometers （MZIs）, this scheme theoretically provides high resolution and tunable measurement range. The measurement errors in the experimental results can be kept within 0.2 GHz over a freauencv ranee from 0.1 to 5.3 GHz.

A microwave photonic filter based on multi-wavelength fiber laser and infinite impulse response

A microwave photonic filter(MPF) based on multi-wavelength fiber laser and infinite impulse response(IIR) is proposed. The filter uses a multi-wavelength fiber laser as the light source, two sections of polarization maintaining fiber(PMF) and three polarization controllers(PCs) as the laser frequency selection device. By adjusting the PC to change the effective length of the PMF, the laser can obtain three wavelength spacings, which are 0.44 nm, 0.78 nm and 1.08 nm, respectively. And the corresponding free spectral ranges(FSRs) are 8.46 GHz, 4.66 GHz and 3.44 GHz, respectively. Thus changing the wavelength spacing of the laser can make the FSR variable. An IIR filter is introduced based on a finite impulse response(FIR) filter. Then the 3-d B bandwidth of the MPF is reduced, and the main side-lobe suppression ratio(MSSR) is increased. By adjusting the gain of the radio frequency(RF) signal amplifier, the frequency response of the filter can be enhanced.