An Improved Expression for Relative Intensity Noise

A directly modulated ROF link is mainly subjected to shot, RIN and thermal noise. The thermal noise is independent of the signal power. The shot noise linearly increases with the mean optical power. However, the relative intensity noise (RIN) needs a special attention. That is the focus of this chapter. The RIN is conventionally considered to be proportional to the square of the mean optical power. Nevertheless, many experiments have shown that the RIN also increases with the modulation index. In this chapter, a mathematical expression for the RIN is derived from fundamental principles which, shows these dependencies.