Millimetre-wave signal generation by optical filtering of frequency modulated laser spectra

We have demonstrated the generation of a 19.2 GHz signal from a 3.2 GHz drive signal; a multiplication factor of 6. This was limited only by the frequency responses of the available photodiode and spectrum analyser. Signals generated by this approach are inherently narrowband since the sidebands have correlated phase noise. A simple fibre Mach-Zehnder was used. This could be replaced with an integrated optic device with feedback to maintain the correct bias point, resulting in a robust and simple-to-operate unit which would be more compact than the alternative of using fibre dispersion. The scheme described, in common with other multiplicative approaches, results in spurious signals around the desired output frequency. These are separated by multiples of the drive frequency and it is not anticipated that they would present a problem in most applications since they would fall out side the passband of subsequent components