Optical fiber cable with tampering detecting means

DETAILED DESCRIPTION I claim: 1.
An optical fiber cable comprising at least one optical fiber extending lengthwise of said cable, a first substantially gas impermeable layer encircling said optical fiber and a second substantially gas impermeable layer encircling said first substantially gas impermeable layer, a viscous filler filling any otherwise empty spaces within said first layer and said second layer having at least a portion of its inner surface spaced from the outer surface of said first layer to provide at least one gas receiving duct intermediate said first layer and said second layer which extends lengthwise of said cable.
2.
An optical fiber cable as set forth in claim 1 wherein said optical fiber is loosely received within a buffer tube of plastic material having any otherwise empty spaces therein filled with a viscous filler and wherein said second layer is a layer of plastic material encircling said buffer tube.
3.
An optical fiber cable as set forth in claim 1 wherein there are a plurality of optical fibers and a plurality of buffer tubes of plastic material disposed around the least one optical fiber loosely received therein and having any otherwise empty spaces therein filled with a filler and wherein said first layer is a layer of plastic material encircling said plurality of buffer tubes.
4.
An optical fiber cable as set forth in claim 3 wherein one of said first layer and said second layer has a plurality of ribs extending therefrom and from said one layer toward the other said layer to provide a plurality of longitudinally extending gas receiving ducts intermediate said first layer and said second layer.
5.
An optical fiber cable as set forth in claim 4 wherein said second layer is a layer of plastic material and further comprising a layer of metal armor encircling said first layer and intermediate said first layer and said second layer.
6.
An optical fiber cable as set forth in claim 5 further comprising a central longitudinally extending strength member disposed at said axis of said cable, each of said plurality of buffer tubes being disposed adjacent to other buffer tubes and said plurality of buffer tubes being disposed around said central strength member