Physical layer monitoring based on 2D-OCDMA concepts and electronic decoding for high density PON networks

In this paper we propose a two-dimensional (2D) time-wavelength OCDMA physical layer monitoring system for passive optical networks. The proposal employs reflective encoders based on Fiber Bragg Grating serial arrays located at the ONUs and centralised and simplified electronic decoding of M sub-bands after optical filtering on the central office. We present an experimental verification of the concept with M = 5 sub-bands in a passive optical network with 4 closely spaced users (link-length differences small than 2.3 meters) providing a very high user density of d ≈ 1.74 users/meter. Moreover, we provide a theoretical model limited by beating noise and straightforward expressions of user density, false alarm and non-detection of fault probabilities.