EP0314373A2
Expired / Lapsed
EP
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Lightwave systems using optical amplifiers
Assignee: AT&T Inc
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Filing: 1988-10-19
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Granted: —
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Expires: 2008-10-19
Abstract
Abstract A single frequency lightwave system employs semiconductor, optical amplifiers arranged in tandem with suitable noise filtering and isolation between amplifier stages. Feedback control maintains overlap between the signal frequency and one of the passbands of the amplifiers. Either direct detection or coherent detection can be used. Also described is a receiver front end which includes such an amplifier between the incoming signal and a photodetector. Both transmission systems and switching systems are described.
Inventors
- 👤 Nils Anders Olsson
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 18:12
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/29; H04B10/291; H04B10/2912; H04B10/2914; H03; H03K; H03K17/00; H03K17/51; H03K17/78; H01; H01S; H01S5/00; H01S5/50; H01S5/5027
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
126 words
In an optical communication system including a transmitter having a single longitudinal mode source for generating an optical radiation signal at a first optical frequency, a receiver of said signal, and a fiber optic communication link for carrying said signal from said transmitter to said receiver, amplification apparatus characterized by a plurality (16,18) of semiconductor optical amplifiers of said signal arranged in tandem within said link, each of said amplifiers having a plurality of passbands at different frequencies and generating spontaneous emission noise within said passbands, said first frequency being located in one of said passbands, and filter means (20) for reducing the amount of said noise, generated in any one of said amplifiers outside said one passband, which is amplified in another of said amplifiers.
Claim 2
Dependent Claim
126 words
In an optical communication system including a transmitter having a single longitudinal mode source for generating an optical radiation signal at a first optical frequency, a receiver of said signal, and a fiber optic communication link for carrying said signal from said transmitter to said receiver, amplification apparatus characterized by a plurality (16,18) of semiconductor optical amplifiers of said signal arranged in tandem within said link, each of said amplifiers having a plurality of passbands at different frequencies and generating spontaneous emission noise within said passbands, said first frequency being located in one of said passbands, and filter means (20) for reducing the amount of said noise, generated in any one of said amplifiers outside said one passband, which is amplified in another of said amplifiers.
Claim 3
Dependent Claim
52 words
The apparatus of claim 1 wherein said filter means comprises at least two adjacent ones of said amplifiers having sufficiently different lengths so as to reduce the amount of said noise, generated in one of said two amplifiers outside said one passband, which is amplified in the other of said two amplifiers.
Claim 4
Independent Claim
33 words
The apparatus of claims 1 or 2 wherein each of said amplifiers has a gain spectrum which exhibits a gain maximum at a frequency f m which is greater than said first frequency.
Claim 5
Independent Claim
49 words
The apparatus of claims 1 or 2 further characterized by feedback means for controlling said amplifiers so that said one passband of each of said amplifiers overlaps said first frequency, and isolation means for preventing any substantial radiation transmitted through one of said amplifiers from re-entering said one amplifier.
Claim 6
Dependent Claim
39 words
The apparatus of claim 4 wherein said transmitter has source means for generating a plurality of optical radiation signals each at a different optical frequency, and the frequencies of all of said signals are located in said one passband.
Claim 7
Dependent Claim
71 words
The apparatus of claim 4 wherein said transmitter has source means for generating a plurality of optical radiation signals each at a different optical frequency, the frequencies of all of said signals are located in different ones of said passbands, and said filter means prevents any substantial amount of said noise generated in one of said amplifiers outside said passbands containing said signals from being amplified in another of said amplifiers.
Claim 8
Dependent Claim
53 words
An amplifier of an optical signal at a first optical frequency comprising a semiconductor gain medium through which said signal propagates, said medium having a gain spectrum characterized by a gain maximum at a frequency f m which is greater than said first frequency, and means for pumping said medium to produce gain.
Claim 9
Dependent Claim
53 words
An amplifier of an optical signal at a first optical frequency comprising a semiconductor gain medium through which said signal propagates, said medium having a gain spectrum characterized by a gain maximum at a frequency f m which is greater than said first frequency, and means for pumping said medium to produce gain.
Claim 10
Dependent Claim
15 words
The amplifier of claim 7 wherein said medium includes a waveguide for guiding said signal.
Claim 11
Dependent Claim
10 words
The amplifier of claim 8 wherein said medium comprises InGaAsP.
Claim 12
Dependent Claim
48 words
The amplifier of claim 7 wherein said medium includes input and output coatings such that the single-pass gain G of the medium and the reflectivity R of the coatings satisfies the inequality 0.3 ≲ GR < 1 and said signal is generated by a single longitudinal mode source.
Claim 13
Dependent Claim
43 words
The amplifier of claim 7 wherein said medium includes input and output coatings such that the gain G of the medium and reflectivity R of the coatings satisfies the inequality GR ≲ 0.06 and said signal is generated by a multi-longitudinal mode source.
References Cited (Backward Citations)
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