A microwave photonic phase-tunable mixer with local oscillator frequency doubling

A microwave photonic phase-tunable mixer with a doubled local oscillator (LO) frequency is presented based on an integrated dual-polarization dual-parallel Mach-Zehnder modulator (DP-DPMZM). A radio frequency (RF) signal is sent to one of the sub-DPMZMs via an electrical 90 degrees hybrid coupler, and the carrier-suppressed single-sideband (CS-SSB) modulation is output. Another sub-DPMZM is modulated by a LO signal, and the 2nd-order carrier-suppressed double-sideband (CS-DSB) modulation is produced by combining a fiber Bragg grating (FBG). A single bias voltage of the modulator can change the phase shift linearly. The mixing signal with double LO frequency and phase shift can be acquired after the photodetector. Experimental setup is implemented, and the results indicate that the spur suppression ratios of the up/down-converted signals are 22.5 dB and 25.2 dB. The spurious-free dynamic range (SFDR) values are 102.97 dB.Hz(2/3) in the down-conversion mode and 100.81 dB.Hz(2/3) in the up-conversion mode. The phase shift can be varied continuously in the range of 360 degrees. The proposed compact link is characterized by function multiplexing, half reduction of the LO frequency and high electrical purity.