For the ultra-long haul optical fiber communication system, the traditional communication mode is to set up a relay station in the line, and then continue transmission after the optical signal is amplified and reshaped at the relay station. However, the route of the industry private network, especially power transmission lines of the power system usually tends to be relatively remote. After passing through harsh areas such as deserts and mountains, there is little room for the selection of optical cable routing, thus it is difficult to conduct the site selection, construction and maintenance of the relay station. The ultra-long haul optical transmission technology is end-to-end direct access, without relay equipment, low cost of operation and maintenance. Using the ultra-long haul optical transmission technology, the optical path subsystem products of Accelink can effectively realize long-distance direct communication, reduce the faults of the relay station, and improve the stability and safety of line operation.