Signal level control circuitry for a fiber communications system
AssigneeScientific-Atlanta, Inc.
InventorsFrank R. Little, John G. Megna, Heather H. Rand, Frederick T. Zendt
Life of this patent
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Abstract
A system for signal level control in AM fiber systems is provided. The system provides level controls at both transmitter and receiver ends of the fiber transmission system, utilizing compensation and control techniques at each end to maintain and optimize the performance of the system. The transmitter includes two stage level control based on a composite power level of a detected RF signal. The receiver includes two stage level control based on a pilot channel filtered from the channels transmitted to the receiver.
Claims28
A transmitter for use in a fiber communications system, comprising:
- an input terminal for receiving a composite electrical signal;
- a first level setting circuit for variably setting a level of the composite electrical signal supplied to said input terminal;
- a second level setting circuit for variably setting a level of a composite electrical signal output by said first level setting circuit;
- a laser responsive to a composite electrical signal output by said second level setting circuit for outputting a modulated optical signal corresponding to the composite electrical signal supplied to said input terminal;
- detecting means for detecting the composite electrical signal output by said second level setting circuit and outputting a control signal based on a composite level of the detected electrical signal;
- and
- adjusting means responsive to the control signal for adjusting said first and second level setting circuits.
A receiver for use in a fiber communications system, comprising:
- a photodetector for converting a received optical signal to a composite electrical signal;
- a variable gain amplifier for variably amplifying the composite electrical signal output by said photodetector;
- a level setting circuit for variably setting a level of a composite electrical signal output by said variable gain amplifier;
- an output terminal for outputting a composite electrical signal output by said level setting circuit as an output composite electrical signal corresponding to the received optical signal;
- detecting means for detecting the composite electrical signal output by said level sitting circuit and outputting a control signal based on a level of a pilot portion of the detected electrical signal;
- and
- adjusting means responsive to the control signal for adjusting said variable gain amplifier and said level setting circuit.
A receiver for a fiber communications system comprising first and second receiving units for receiving respective optical signals and outputting respective composite electrical signals and a combiner for combining the outputs of said first and second receiving units into a single output composite electrical signal, each of said first and second receiving units comprising a photodetector for converting a received optical signal to a composite electrical signal, a variable gain amplifier for variably amplifying the composite electrical signal output by said photodetector, a level setting circuit for variably setting a level of a composite electrical signal output by said variable gain amplifier, detecting means for detecting the composite electrical signal output by said level setting circuit and outputting a control signal based on a level of a pilot portion of the detected electrical signal, and adjusting means responsive to the control signal for adjusting said variable gain amplifier and said level setting circuit.
A fiber optics communications system, comprising:
- a transmitter for transmitting an optical signal, said transmitter comprising:
- an input terminal for receiving a composite electrical signal;
- level setting circuitry for variably setting a level of the composite electrical signal supplied to said input terminal;
- a laser responsive to a composite electrical signal output by said level setting circuitry for outputting a modulated optical signal corresponding to the composite electrical signal supplied to said input terminal;
- detecting means for detecting the composite electrical signal output by said level setting circuitry and outputting a control signal based on a composite level of the detected electrical signal;
- and
- adjusting means responsive to the control signal for adjusting said level setting circuitry;
- and
- a receiver for receiving the optical signal transmitted by said transmitter, said receiver comprising:
- a photodetector for converting the received optical signal to a composite electrical signal;
- level setting circuitry for variably setting a level of a composite electrical signal output by said photodetector;
- an output terminal for outputting a composite electrical signal output by said level setting circuitry as an output composite electrical signal corresponding to the received optical signal;
- detecting means for detecting the composite electrical signal output by said level setting circuitry and outputting a control signal based on a level of a pilot portion of the detected electrical signal;
- and
- adjusting means responsive to the control signal for adjusting said level setting circuitry.
A transmitter for use in a fiber communications system, comprising:
- an input terminal for receiving a composite electrical signal;
- a first level setting circuit for variably setting a level of the composite electrical signal supplied to said input terminal;
- a first amplifier for amplifying an output signal of said first level setting circuit;
- a second level setting circuit for variably setting a level of an output signal of said first amplifier;
- a second amplifier for amplifying an output signal of said second level setting circuit;
- a laser responsive to a signal output by said second amplifier for outputting a modulated optical signal corresponding to the received composite electrical signal;
- detecting means for detecting the signal output by said second amplifier and outputting a control signal based on a level of the detected signal;
- and
- adjusting means responsive to the control signal for adjusting said first and second level setting circuits.
A receiver for use in a fiber communications system, comprising:
- a photodetector for converting a received optical signal to a composite electrical signal;
- a first variable gain amplifier for amplifying the composite electrical signal output by said photodetector;
- a level setting circuit for setting a level of an output signal of said variable gain amplifier;
- a second amplifier for amplifying an output signal of said level setting circuit;
- an output terminal for outputting a signal output by said second amplifier;
- detecting means for detecting the signal output by said second amplifier and outputting a control signal based on a level of a pilot portion of the detected signal;
- and
- adjusting means responsive to the control signal for adjusting said variable gain amplifier and said level setting circuit.
Dependencies are inferred from the claim text.