Patent ID: 6700654
Filing Date: 2004-03-02
Classification: H04B

Abstract:
A monitoring system receiving a first optical signal tapped from an optical communication channel, comprising:an optical coupler combining said first optical signal received on a first input and a second optical signal received on a second input and producing an incident combined optical signal; a photodiode detecting said incident combined optical signal and outputting a first electrical signal; an analog-to-digital converter receiving said first electrical signal and sampling it to produce a multi-bit second electrical signal; an electrical signal generator producing a third electrical signal that is repetitive and has a predetermined harmonic characteristic; a light emitting electrical device receiving said third electrical signal and outputting said second optical signal to said second input in an optical band in which said photodiode is responsive; an isolator coupled to the first input of the optical coupler for preventing said first optical signal and said second optical signal from propagating back onto said optical communication channel; and a signal processor receiving said second electrical signal and capable of distinguishing a portion of said second electrical signal according to said predetermined harmonic characteristic, wherein said electrical signal generator is a digital electrical generator controlled by said signal processor; and a selective optical absorber having input and output sides and receiving said first optical signal on said input side, connected to said first input on said output side, and controlled by said signal processor to variably attenuate said first optical signal.