Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Patent
1995-10-27
1998-08-04
Bacares, Rafael
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
359110, 359137, H04B 1012
Patent
active
057902933
ABSTRACT:
An optical distribution network connects a downstream central office terminal to a number of upstream optical network units which service respective subscribers. Transmit and receive feeder fibers branch out to the optical network units. An optical carrier is modulated with an amplitude-varied signal including at least two different amplitude levels above a selected amplitude threshold, with at least one of the amplitude levels being selected so that it will not be reliably detected at the upstream end when a fiber in the path between the central office terminal and a destination optical network unit fails to meet a threshold power margin. The amplitude-varied optical signal is transmitted upstream to each destination optical network unit during, for example, a corresponding time slot. The portion of the signal containing the lower amplitude portions has no significance to the optical network units and is ignored. A version or replica of this signal, however, is returned by each optical network unit to the central office terminal. A monitoring device at the downstream end attempts to detect the low amplitude level signal portions that are expected from each optical network unit, over a detection interval corresponding to that unit.
In accordance with an illustrative embodiment of the present invention, the amplitude-varied signal may be in the form of a sequence of pulses having the appropriate amplitude levels, with pulses of at least one of the amplitude levels being representative of digitally transmitted data. Alternatively, the amplitude-varied signal may be an analog signal modulated in accordance with conventional analog transmission techniques. The inventive arrangement monitors the onset and pace of signal degradation in the individual fibers of the network. When the power margin of a fiber link falls below a predefined threshold, as indicated by non-detection of some or all of the second signal portions, maintenance personnel are prompted to investigate or service the affected optical links before an unacceptably high error rate or system failure is experienced.
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Bacares Rafael
Dinicola Brian K.
Lucent Technologies - Inc.
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