High-dynamic-range analog fiber-optic link using phase modulation and tunable optical filter

摘要

A cw-laser source transmits low-noise, narrow-linewidth optical power via an optical fiber to a bias-free electro-optic phase modulator at a remote site, where an antenna or an RF sensor is located. The RF electrical signal modulates the phase modulator at the remote site, converting an electrical signal into an optical signal. The phase-modulated optical signal is fed back via the optical fiber to an optical filter whose filter transfer characteristics can be tuned and reconfigured to cancel the intermodulation distortion terms, particularly the dominant 3^rd order intermodulation, as well as the 2^nd order. The filtered optical signal is converted to the RF signal at the photodetector. The optical filter is used to effectively “linearize” the signal at the receiver end, rather than at the modulator end.