Methods for monitoring optical path characteristics in an optical communication system
First Claim
1. A method of operating a digital communication network comprising a first optical communication station having an optical transmitter and a signal monitoring device, a second optical communication station having a signal receiving device, and a communication path coupling the first optical communication station to the second optical communication station, the method comprising:
- launching a signal having at least two different levels into the communication path from the first communication station to the second optical communication station, said signal comprising at least one first signal portion having an amplitude that exceeds a predetermined amplitude threshold and at least one second signal portion having an amplitude between the amplitude of the first signal portion and the predetermined amplitude threshold;
returning a portion of the signal to the first optical communication station via the communication path; and
evaluating at the signal monitoring device the returned signal for a presence of said second signal portion, the amplitude of the second signal portion selected so that said second signal portion will not be reliably detected when a power margin of the path is below a minimum acceptable threshold;
wherein the first and the second signal portions occupy sequential and non-overlapping time slots of the optical signal.
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Accused Products
Abstract
An optical distribution network using optical fibers connects a central office terminal to a number of optical network units which service respective subscribers. In order to monitor the onset and pace of signal degradation in the individual fibers of the network, an optical carrier signal is modulated with an amplitude-varied signal including at least two different amplitude levels that are above a selected amplitude threshold. At least one of the amplitude levels is chosen so that a portion of the signal having the chosen amplitude will not be reliably detected when a fiber in the path between the central office terminal and a destination optical network unit fails to meet a specified threshold power margin. Specifically, the amplitude-varied optical signal is transmitted from the central office terminal to each optical network unit, and a version or replica of the signal is returned by each optical network unit to the central office terminal, where a monitoring device attempts to detect the signal portions in the returned replica signals having the chosen amplitude. Non-detection of some or all of the signal portions having the chosen amplitude indicates that the power margin of a fiber link has fallen below the threshold.
31 Citations
29 Claims
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1. A method of operating a digital communication network comprising a first optical communication station having an optical transmitter and a signal monitoring device, a second optical communication station having a signal receiving device, and a communication path coupling the first optical communication station to the second optical communication station, the method comprising:
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launching a signal having at least two different levels into the communication path from the first communication station to the second optical communication station, said signal comprising at least one first signal portion having an amplitude that exceeds a predetermined amplitude threshold and at least one second signal portion having an amplitude between the amplitude of the first signal portion and the predetermined amplitude threshold; returning a portion of the signal to the first optical communication station via the communication path; and evaluating at the signal monitoring device the returned signal for a presence of said second signal portion, the amplitude of the second signal portion selected so that said second signal portion will not be reliably detected when a power margin of the path is below a minimum acceptable threshold; wherein the first and the second signal portions occupy sequential and non-overlapping time slots of the optical signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 24, 25, 26)
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12. A method of monitoring a power margin of an optical path in an optical communication network, wherein the optical path is coupled to a first optical communication station having an optical transmitter and a signal monitoring device and a second optical communication station having a receiving device, the method comprising:
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launching an amplitude-varying optical signal into the optical path from the first optical communication station to the second optical communication station, said signal comprising at least one first signal portion having an amplitude that exceeds a predetermined amplitude threshold and at least one second signal portion having an amplitude between the amplitude of the first signal portion and the predetermined amplitude threshold; receiving said optical signal at the second optical communication station; returning said optical signal to the first optical communication station via the optical path; and the signal monitoring device evaluating the returned optical signal at the first optical communication station with the signal monitoring device for a presence of said second signal portion, the amplitude of the second signal portion selected so that the second signal portion will not be reliably detected at the first optical communication station when the power margin of the optical path is below a minimum acceptable threshold; wherein the first and the second signal portions occupy sequential and non-overlapping time slots of the optical signal. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 27, 28, 29)
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21. A method of monitoring performance of a digital transmission system in which digital data pulses are transmitted from a transmitter of a first digital transmission system to a receiver of a second digital transmission system via a communication channel extending between the first and second digital transmission systems, said method comprising:
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sending evaluation pulses, that are modulated with the digital data pulses, from the transmitter to the receiver, each evaluation pulse having a selected level such that that evaluation pulse will not be reliably detected at the receiver when a power margin of the communication channel is below a minimum acceptable threshold; and measuring a number of the evaluation pulses successfully transmitted to the receiver. - View Dependent Claims (22, 23)
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Specification