Broadband photonic radio frequency (RF) channelization based on coherent optical frequency combs and polarization I/Q demodulation

In this work, we analyze and demonstrate a novel photonic-assisted broadband and high-resolution radio frequency (RF) channelization scheme based on dual coherent optical frequency combs (OFCs), regular optical de-muxes, and polarization I/Q demodulators in theory and experiment. The use of two coherent combs avoids precise optical alignment, and a numerical filter in digital signal processor (DSP) enables an ideal rectangular frequency response in each channel without any ultra-narrow optical filters. Besides, due to the use of polarization I/Q demodulation, ambiguous frequency estimate in direct detection can be avoided and the amplitude, phase mismatch in traditional I/Q demodulation can be mitigated. In experiment, we use two coherent OFCs with the free spectrum range (FSR) of about 40 GHz to demonstrate the channelization scheme with seven channels, 500 MHz channel spacing and frequency coverage from 3.75 GHz to 7.25 GHz. The input RF tones are accurately down-converted to an intermediate frequency (IF) with a maximum frequency error of 110 kHz. Meanwhile, crosstalk and spurious free dynamic range (SFDR) of the scheme are also discussed.