Secure Splice Closures for Optical Fiber Systems

The problems of splice closure are discussed briefly and the options available for optical fiber cable systems are reviewed. It is concluded that for long-haul point-to-point cables, absolute security is paramount, and that for these, welded splice closures should be used. For optical fiber cables in local distribution networks, however, closures which can easily be reentered are needed. This requirement can only be met with some kind of mechanical closure. The security of these is considered inadequate for nonpressurized optical fiber networks. It is concluded that the use of mechanical closures must be supported by a satisfactory test method to confirm that they are sealed after each reentry. Conventional pressure testing of complete closures is considered to be too unreliable and slow for the purpose. A new double-seal closure system is described which allows the integrity of closures to be tested in seconds using a purpose-designed test device. The double-seal system is being used for the optical fiber distribution system being installed in the city of London by Mercury Communications Ltd.