Strained distributed optical fiber communication system

Claim 1

A subscriber telephone system for interconnecting a plurality of subscriber telephones and at least one telephone central office or remote extension thereof for communicating information therebetween, comprising: a plurality of subscriber telephones; means for interconnecting the telephones and the telephone central office or remote extension thereof, the interconnecting means including at least one optical fiber comprising a glass core surrounded by a glass cladding surrounding by a protective coating in contact with the cladding, the coating being substantially transparent to light guided by the core used to represent the information and having an index of refraction throughout its thickness which is greater than that of the cladding, the fiber having a predetermined proof stress strength; a plurality of optical taps serially disposed on the optical fiber and in communication with the plurality of telephones, each tap including bending means for maintaining a bend in the fiber of a radius sufficiently small so as to enable either light injection into or light withdrawal from the core of the optical fiber by passing the light being injected or detected through a side of the fiber cladding and coating at an unbroken intermittent section of the fiber, each fiber bend having a maximum radius of curvature sufficiently small so as to impose a maximum static stress on the fiber glass in excess of one-half the fiber proof stress, the bending means maintaining the maximum stress on the fiber whenever light is being transmitted on the fiber regardless of whether one or more telephones associated with the tap is in operation or is operational; a plurality of means for enclosing various ones of the plurality of taps and bends associated therewith so as to provide a water-tight seal for the various ones of the taps capable of keeping water located outside the enclosing means from entering an interior thereof and contacting the fiber taps and associated bends.