Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Patent
1997-05-20
1999-09-28
Negash, Kinfe-Michael
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
359128, 385 24, H04J 1400
Patent
active
059597496
ABSTRACT:
An add/drop multiplexer/demultiplexer (ADM) for switching, modulating and attenuating optical signals in a fiber optic network employing wavelength division multiplexing (WDM) is disclosed. The ADM is equipped an optical multiplexer for splitting an input WDM signal into individual optical signals, leading to respective 2.times.2 switches. Each switch has another input originating from a plurality of "add lines", and selects one of its inputs to be dropped and the other to continue along a main signal path. The retained signals may be modulated and attenuated prior to being tapped and finally multiplexed together by a WDM multiplexer. The tapped signals are optoelectronically converted and fed back to a controller, preferably a digital signal processor running a software algorithm, which controls the switching, modulation and attenuation. This permits remote control of the ADM functions by encoding instructions for the controller into a low-frequency dither signal that is embedded within the individual optical signals. The ADM can accordingly be instructed to reroute traffic, dynamically equalize or otherwise change optical channel power levels, and add or remove dither, all in real time. A specific optical channel may be reserved for control purposes, allowing a network administrator to "log in" to the ADM to override the controller software algorithm. Optionally, the optical signals can be tapped upon entry to the ADM. A bidirectional ADM can be constructed from two unidirectional ADMs, and may share the same controller. Also, a single, general multi-input multi-output switch can be used to provide an arbitrary mapping between individual input and output optical signals.
REFERENCES:
patent: 5612805 (1997-03-01), Fevrier et al.
patent: 5717795 (1998-02-01), Sharma et al.
Baker Nigel
Bordogna Giuseppe
Danagher David John
Forbes Duncan John
Habel Richard A.
Negash Kinfe-Michael
Nortel Networks Corporation
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