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US 5,117,196 AGranted
Optical amplifier gain control
AssigneeStc PLC
InventorsRichard E. Epworth, Kevin C. Byron, Robert A. Baker, Nigel Taylor
Life of this patent
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AssigneeStc PLC
InventorsRichard E. Epworth, Kevin C. Byron, Robert A. Baker, Nigel Taylor
Estimating the term…
The gain of an optical amplifier is maintained constant by employing a portion of the amplified optical signal in a feedback loop. In one arrangement this is used to control the output of a pump signal source accordingly. The portion of the said signal corresponds to spontaneous emission (ASE) at a control wavelength or band of wavelengths different to the wavelength of the optical signal output. In the case of an erbium, for example, optical fibre amplifier the portion is preferably ASE at 980 nm, the amplified signal being at 1.535 .mu.m, i.e. completely different transitions in the amplifying medium are used for gain and ASE feedback in order to lessen requirements on the filter used to extract the portion for the feedback loop.
An optical amplifier with automatic gain control including an input port for an optical signal to be amplified, means for achieving amplification of the optical signal, means for extracting a portion of the amplified signal, an output port for the remainder of the amplified optical signal, and feedback loop means for employing the extracted portion whereby to maintain the output amplified optical signal constant, the extracted portion comprising spontaneous emission at a control wavelength, or band of wavelengths, different to the wavelength, or band of wavelengths, of the output amplified optical signal.
A method of controlling the gain of an optical amplifier including the steps of amplifying an optical signal to be amplified, extracting a portion of the amplified optical signal and employing it in a feedback loop such as to maintain the gain of the amplified optical signal at a constant value, the extracted portion comprising spontaneous emission at a control wavelength, or band of wavelengths, different to the wavelength, or band of wavelengths, of the amplified optical signal.
Dependencies are inferred from the claim text.