A carrier-suppressed phase-modulated fiber optic link with IF downconversion of 30GHz 64-QAM signals

We develop and demonstrate an efficient, simple fiber optic link for K-band through millimeter-wave signal relay and downconversion. The link uses optical phase modulation to simplify the transmitter and re-modulates the optical carrier with a local oscillator (LO) tone in the receiver, eliminating the need for a second frequency or phase-coherent optical heterodyne source. An optical notch filter in the receiver removes the carrier to allow direct detection of the intermediate frequency (IF). A 30 GHz signal is downconverted to a 140 MHz IF, with a measured noise figure (NF) of 32.5 dB, thirdorder spur-free dynamic range (SFDR) of 112 dB/Hz^2/3, and only 3.5 dB RF conversion loss with 10mA of received DC photocurrent. A 10MBaud 64-QAM signal at 30 GHz is also passed through the link; the IF output has no measureable degradation in error vector magnitude (EVM) from the back-to-back, all-electrical case.