In-water fiber optic branching unit

Abstract

A high reliability, long life fiber optic branching unit has been successfully installed as part of a 1.2 Gbit/second fiber optic telecommunication system off the coast of California. This branching unit will be used to connect a second offshore site into the existing network at a later date. The installed branching unit allows future expansion to be accomplished without grappling and with a minimum of at-sea time. The design, test, fabrication and installation of the branching unit is discussed. Branching unit applications for telecommunication systems are also discussed. Modern in-water fiber optic cable systems require flexibility in configuration and capabilities. Incorporating a high reliability, long life branching units in the system design allows more options in network configuration when compared to a simple point-to-point cable. This is particularly true of a scalloped or festooned system where a high fiber count trunk cable in conjunction with branching units allows fibers to be split out at different shore landings. The installation method described involves a pre-packaged branch unit included as part of the main cable system. Multiple branch units can be installed serially, allowing multiple branch connections to be installed in one exercise. The branching unit includes a branch cable which can be recovered and deployed as appropriate. The branch cable is terminated in an end housing which is essentially half of a splice box. When needed, the end housing can be recovered, spliced to additional cable if required, and laid to the shore landing site.