Sharing direct fiber channels between protection and enterprise applications using wavelength division multiplexing

Protection system communications are increasing in importance because they enable optimal operation of power systems. Because of the high cost of communications systems in the past, protection systems had to be optimized to use minimum bandwidth and were often forced to rely on a single bit of information. A synchronous 64 kbps channel reserved exclusively for the most critical transmission lines was seen as the best-case scenario. Communications system developments over the last three decades have opened a deluge of information, with a single optical fiber now capable of carrying multiple terabits of data simultaneously. Modern protection systems face a totally different problem. Communications bandwidth is almost unlimited, but the channel must be shared with other users and may present multiple challenges, such as channel asymmetry, variable latency, path reconfiguration due to automated failure recovery, packet-based transport, and the need for system-wide time synchronization. This paper reports on an experimental investigation that uses coarse or dense wavelength division multiplexing (CWDM, DWDM) for applications in high-speed traveling-wave protection. The investigation was performed using the latest generation of carrier-grade optical transport network (OTN) equipment. The paper documents the performance, opportunities, and pitfalls associated with this application and outlines practical strategies for the seamless integration of protection systems with the latest generation of OTN technologies.