Method and apparatus for inducing a temporary localized transmission loss in a telecommunications cable

摘要

PCT No. PCT/AU94/00133 Sec. 371 Date Nov. 15, 1995 Sec. 102(e) Date Nov. 15, 1995 PCT Filed Mar. 18, 1994 PCT Pub. No. WO94/22241 PCT Pub. Date Sep. 29, 1994A method and apparatus for inducing a localised optical transmission loss in an optical fiber cable is described, which is particularly well suited for use with optical time-domain reflectometry (OTDR) equipment to aid in locating faults in an optical fiber cable. A small portion of the optical fiber cable is cooled, such as by immersion in a cryogenic liquid like liquid nitrogen, and fibres in the cooled cable portion exhibit localised optical transmission loss which can be detected as a point loss (26) with the OTDR trace (24). The technique of inducing the point loss is non-invasive, and the localised transmission loss disappears when the cable portion returns to the ambient temperature, without damage to the cable.