Symmetrical Encoder for Surveillance of Ring Optical Networks

Optical coding has been extensively investigated for monitoring fiber-to-the-X point-to-multipoint passive optical networks. In this letter, we propose to extend this type of coding for ring based metropolitan networks. We show that this new application requires a novel design for the optical coding devices, which we call symmetrical encoders. We propose one implementation of this encoder and examine its suitability to monitor faults in each segment of the ring and also to detect faulty nodes. In addition, we evaluate the performance of the system in terms of signal-to-noise ratio and network recovery time.