Dual-wavelength linearization of analog photonic link based on PM–IM conversion

Abstract

A novel method for linearization of phase-modulated analog photonic link is proposed in this paper. Heterodyne carrier source (HCS) is obtained by polarization multiplexing of two different-wavelength optical carriers. A Z-cut phase modulator (PM) which exhibits different electro-optic modulation indexes in orthogonal polarization states is used to modulate radio frequency signal onto the heterodyne optical carriers. Two channels of a WDM are used to filter out the positive or negative optical sidebands respectively and thus implement PM–IM conversion. The third-order intermodulation distortions (IMD3s) of the two different WDM channels are opposite in phase. IMD3 can be suppressed by combining signals from the two different WDM channels and adjusting the power ratio of the two optical carriers. Apart from the obvious improvement of SFDR, no need for bias control and easy adjusting of the power ratio make the method easy to implement. Experimental results show that the spurious free dynamic range (SFDR) of the system is improved by 14.54 dB.