Patent ID: 8224188

Claim:
A method for producing an output RF signal free from second-order harmonic distortion in an analog optical fiber link, comprising: receiving, at a dual-output Mach-Zehnder modulator, a first analog optical signal having a first wavelength λ 1 and a second analog optical signal having a second wavelength λ 2 ; applying, at the Mach-Zehnder modulator, an input RF signal and a bias voltage to the first and second analog optical signals, wherein λ 1 is high-biased and λ 2 is simultaneously low-biased at a first output arm of the Mach-Zehnder modulator, and λ 1 is low-biased and λ 2 is simultaneously high-biased at a second output arm of the Mach-Zehnder modulator, receiving, at a multiplexer operatively connected to the Mach-Zehnder modulator, the output from the first and second output arms of the Mach-Zehnder modulator; filtering, at the multiplexer, the output from the first and second output arms and outputting, from the multiplexer, a multiplexed signal consisting of biased λ 1 and biased λ 2 wherein both biased λ 1 and biased λ 2 have the same bias; receiving biased λ 1 at a first one PD 1 of a pair of photodiodes operatively connected to the demultiplexer and receiving biased λ 2 at a corresponding second one PD 2 of the pair of photodiodes, each of PD 1 and PD 2 outputting a corresponding photocurrent I PD1 and I PD2 based on its respective input λ 1 and λ 2 ; and differencing the photocurrents I PD1 and I PD2 to produce the output RF signal; wherein the even-order harmonics are cancelled in the output RF signal.