IN-SERVICE MONITORING OF A FIBEROPTIC NETWORK

摘要

An optical fiber breakage point may be located by coupling to the optical fiber an out-of-band optical test signal modulated at a periodic modulation pattern. A distance to the breakage point may be determined from a difference between modulation patterns of transmitted and received test signals.

主权项

1. A system for in-service monitoring of a fiberoptic network comprising a first fiberoptic link spanning between a test location and a first remote location, wherein the first fiberoptic link carries a first information signal at a first wavelength between the test location and the first remote location, the system comprising:
a transmitter comprising a light source for generating an optical test signal at a test wavelength different from the first wavelength, wherein the optical test signal is modulated at a modulation frequency periodically swept at a sweep period from a first modulation frequency to a second modulation frequency; a first test channel comprising:
a first coupler for optically coupling the light source to the first fiberoptic link at the test location, for causing the optical test signal to propagate along the first fiberoptic link towards the first remote location;a first wavelength-selective reflector for optically coupling into the fiberoptic link at the first remote location, for redirecting the optical test signal at the test wavelength to propagate back towards the test location, while propagating therethrough the first information signal at the first wavelength;a first signal photodetector optically coupled to the first coupler, for detecting a first returning optical test signal at the test wavelength propagating in a direction from the first remote location towards the first coupler; and a controller operationally coupled to the first signal photodetector and operable to:
determine a magnitude of the first returning optical test signal;determine a modulation frequency offset of the first returning optical test signal relative to a current value of the periodically swept modulation frequency; anddetect a fault in the first fiberoptic link based on at least one of:
a comparison between the determined magnitude of the first returning optical test signal and a reference magnitude of the optical test signal redirected by the first wavelength-selective reflector; anda comparison between the determined modulation frequency offset of the first returning optical test signal to a reference modulation frequency offset of the optical test signal redirected by the first wavelength-selective reflector.