Photonic Generation of Microwave Signals

This chapter reviews different techniques proposed and demonstrated in the last few decades for the generation of microwave signals based on photonics. Numerous techniques have been proposed and demonstrated to generate low‐phase‐noise microwave signals with the phase terms of the two optical waves being locked. These techniques can be generally classified into five categories: optical injection locking, optical phase‐locked loop, microwave generation using external modulation, dual‐wavelength laser source, and optoelectronic oscillator. The chapter discusses the performance in terms of the frequency, frequency tunability, frequency stability, and system complexity of all the methods. The phase noise performance of a photonically generated microwave signal can be improved by tens of dBc/Hz using a technique called photonic microwave frequency division. The key advantage of using photonics for microwave generation is the low phase noise.