In this paper, we present experimental results for monitoring long distance WDM communication links using a line monitoring system suitable for legacy optically amplified long-haul undersea systems. This monitoring system is based on setting up a simple, passive, low cost high-loss optical loopback circuit at each repeater that provides a connection between the existing anti-directional undersea fibres, and can be used to define fault location. Fault location is achieved by transmitting a short pulse supervisory signal along with the WDM data signals where a portion of the overall signal is attenuated and returned to the transmit terminal by the loopback circuit. A special receiver is used at the terminal to extract the weakly returned supervisory signal where each supervisory signal is received at different times corresponding to different optical repeaters. Therefore, the degradation in any repeater appears on its corresponding supervisory signal level. We use a recirculating loop to simulate a 4600 km fibre link, on which a high-loss loopback supervisory system is implemented. Successful monitoring is accomplished through the production of an appropriate supervisory signal at the terminal that is detected and identified in a satisfactory time period after passing through up to 45 dB attenuation in the loopback circuit.
Bibliographical noteNOTICE: this is the author’s version of a work that was accepted for publication in Optics Communications. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Nahas, M & Blow, K, 'Monitoring long distance WDM communication lines using a high-loss loopback supervisory system', Optics communications, vol 285, no. 10-11 (2012) DOI http://dx.doi.org/10.1016/j.optcom.2012.02.004
Nahas, M. M., & Blow, K. J. (2012). Monitoring long distance WDM communication lines using a high-loss loopback supervisory system. Optics Communications, 285(10-11), 2620-2626. https://doi.org/10.1016/j.optcom.2012.02.004