Modelling of sub-shot noise optocouplers using relative noise difference

From sub-shot noise photonic measurements in optocouplers we obtain the frequency characteristics of quantum noise reduction using the relative noise difference (RND) method. We have shown that the RND method enables us to remove the dependence of noise measurements on the noise and frequency response of the instrumentation amplifier. We have also attempted to derive the same frequency characteristics using a circuit-based model incorporating photonic noise sources. There is good agreement between measurement and modelling, hence lending experimental support to the use of the photonic noise model to other sub-shot noise optocoupler structures