Detector noise model verification for undersea free space optical data links

The need for midrange, high throughput data networks in the undersea environment is evident for a variety of applications, including sensor networks and remote control and telemetry for unmanned underwater vehicles. While research continues into undersea acoustic and radio frequency networks, results show that these suffer from low data rates (in the case of the former) or severe range limitations (in the case of the latter) [1]. Free space optical technology provides a good balance between data throughput and potential distance between communicating nodes; given the cost of deploying and testing these types of networks, however, it is necessary to develop accurate models that allow us to simulate digital communication between nodes, facilitating the development of optimal protocols at low cost. One important component of such a system is an accurate model for the noise in the detector output signal. This paper evaluates one such model [2] for its suitability in predicting shot noise (the random variation in the detector output signal that is caused by the random arrival times of the photons at the detector photocathode) and the noise introduced by a Photomultiplier Tube (PMT) detector.