| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical fiber constructed to prevent theft of an optical signal. SOLUTION: One constitution is designed to block the access of a fiber core to the 'writing' radiation necessary to form a grating tap. In a variation of this embodiment, optical fiber cladding is provided with highly absorbing UV layer. In the variation of this embodiment, one or more additional optical paths are provided in the optical fiber to accommodate a monitoring signal. The additional optical paths enable the monitoring signal to be transmitted in the optical fiber, separate from an information signal, to signal an attempt to breach the outer coating or the cladding of the optical fiber. A second case of intrusion is addressed by increasing the sensitivity of the fiber to microbending loss to the extent that bends in the fiber cause such high attenuation of the signal that the bends do not go undetected at a receiving station. |
