Phase noise analysis of the optically generated and distributed millimeter wave signal using an external optical modulator

We recently proposed a method to generate a millimeter-wave signal using a laser, an intensity modulator and a fiber Bragg grating filter. Using this approach, we have shown that it is possible to optically generate a microwave carrier that is oscillating at four times the frequency of the electrical signal used to drive the intensity modulator. In this paper, we investigate the phase noise in our signal generation scheme. We show that the spectral quality of the microwave carrier, generated by photo-detection at the end of a fiber span, is affected by phase noise in the modulator drive electrical signal and the optical carrier, and dispersion in the optical fiber. Expressions for the power spectral density of the generated electrical carrier, before and after propagation, are obtained. Outcomes from the analysis are compared with experimental results.