Improved Expression for Intensity Noise in Multimedia over Fiber Networks

The relative intensity noise (RIN) plays an important role in multimedia over fiber (MOF) networks. The RIN is conventionally considered to be proportional to the square of the mean optical power. This is true under small signal, single channel conditions. Nevertheless, experiments have shown that the RIN also increases with the modulation index m that reflects the power of the stochastic modulating signal s(t). Winston Way observed this dependency and mentioned a dynamic RIN under direct modulation conditions. Accurate characterization of the RIN is important especially in MOF systems that support multiple radio channels in subcarrier multiplexed manner in addition to digital data. Modern MOF links tend to have large carrier to sideband ratio that enhances RIN. In this paper, a mathematical expression for the RIN is derived from fundamental principles that shows the dependency of RIN on modulation index m and modulating multimedia signal power E[s²(t)]. The new expression better explains the excess increment of noise power in MOF systems observed many authors