Suppression of intermodulation distortion in phase-modulated analog photonic links

We describe and experimentally demonstrate a technique to suppress the dominant in-band analog distortion in an RF photonic link. The anisotropic electrooptic coefficient of Lithium Niobate is exploited to modulate orthogonally polarized fields. These fields are then combined to null the third-order distortion. This technique uses a single phase modulator, requiring no external bias or control, for a highly linear photonic microwave relay. The link is limited by fifth-order intermodulation distortion (IMD) instead of third-order IMD. For many scenarios the added complexity of heterodyne optical detection may be an appropriate cost to gain simplicity at the remote end.