Real-time monitoring and fault locating using amplified spontaneous emission noise reflection for tree-structured Ethernet passive optical networks

Nowadays, optical networks are becoming dense while detecting faulty branches in the tree-structured networks has become problematic. Conventional methods are inconvenient as they require an engineer to visit the failure site to check the optical fiber using an optical time-domain reflectometer. An innovative monitoring technique for tree-structured network topology in Ethernet passive optical networks (EPONs) by using the erbium-doped fiber amplifier to amplify the traffic signal is demonstrated, and in the meantime, a residual amplified spontaneous emission spectrum is used as the input signal to monitor the optical cable from the central office. Fiber Bragg gratings with distinct center wavelengths are employed to reflect the monitoring signals. Faulty branches of the tree-structured EPONs can be identified using a simple and low-cost receiver. We will show that this technique is capable of providing monitoring range up to 32 optical network units using a power meter with a sensitivity of −65 dBm while maintaining the bit error rate of 10 −13. 1 Introduction The passive optical network (PON) is renowned as the best architecture for employing fiber-to-the-home (FTTH) system due to the passive components implementation in the transmission line and optimal fiber infrastructure. By considering the types of multiplexing, PON can be divided into two classes: time division multiplexing (TDM) and wavelength division multiplexing. For PON, there are only passive components between the optical line terminal placed at the central office and the optical network unit (ONU) located on the customer premises. In TDM-PON, a single optical fiber carries all traffic channels to a remote node, where all the channels will be split by a passive optical power splitter into different fibers connected to the ONU. This architecture, which has no electronic components with a tendency to breakdown, is estimated to reduce the operation-and-maintenance expenses (OPEX). Operators do not need to provide and monitor electrical power or maintain extra batteries in this area.