Patent US3840741A successfully refreshed from Google Patents.
US3840741A
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Semiconductor delay line detector for equalization of optical fiber dispersion
Assignee: AT&T Inc
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Filing: 1973-09-18
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Granted: 1974-10-08
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Expires: 1993-09-18
Abstract
Abstract The propagation in an optical fiber of an incoherent optical signal pulse containing a moderate spread of optical wavelength carrier components, such as supplied to the optical fiber by a light emitting diode (LED) source, results in a broadening (distortion) of the optical output signal emerging from the fiber. This distortion is caused by the fact that different optical wavelengths propagate at different velocities through the fiber material, that is, by the dependence of refractive index upon wavelength (material dispersion); and also by the fact that different optical modes propagate at different velocities (mode dispersion). In order to compensate for such distortions, a semiconductor charge carrier drift delay line is located in the path of the optical radiation emanating from the fiber. Advantageously, this semiconductor delay line is depleted of bulk majority charge carriers by means of a reverse voltage bias and is terminated by a charge carrier detector having an inherent gain (such as an avalanche diode or a transistor). The delay line is arranged such that the time delays of different wavelengths or modes in the fiber are compensated by the different drift time delays of the charge carriers generated by the different wavelengths or modes absorbed at different locations in the semiconductor delay line. In the case of mode dispersion compensation, the s
Inventors
- 👤 H Melchior
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 12:32
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/25; H04B10/2507; H04B10/2513; H04B10/25133; G; G02; G02B; G02B6/00; G02B6/10; G02B6/12; G02B6/12007; G02B6/24; G02B6/26; G02B6/28; G02B6/293; G02B6/29379; G02B6/29392; G02B6/29394; G02B6/42; G02B6/4201; G02B6/4204; G02B6/4215; H04B2210/00; H04B2210/25; H04B2210/252
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
97 words
A photodetection apparatus for equalization of optical fiber dispersion which comprises a depleted semiconductor body portion of a semiconductor body located such that said optical radiation after emerging from the fiber is incident upon said portion, said depleted portion terminated in said body by detection means characterized by charge carrier gain, said portion being located with respect to the fiber such that the components which are more delayed in the fiber are incident on the depleted semiconductor body portion at positions less remote from the detection means than other components which are less delayed in the fiber.
Claim 2
Dependent Claim
97 words
A photodetection apparatus for equalization of optical fiber dispersion which comprises a depleted semiconductor body portion of a semiconductor body located such that said optical radiation after emerging from the fiber is incident upon said portion, said depleted portion terminated in said body by detection means characterized by charge carrier gain, said portion being located with respect to the fiber such that the components which are more delayed in the fiber are incident on the depleted semiconductor body portion at positions less remote from the detection means than other components which are less delayed in the fiber.
Claim 3
Dependent Claim
14 words
Apparatus recited in claim 1 in which the detection means include an avalanche diode.
Claim 4
Dependent Claim
62 words
Apparatus recited in claim 2 in which the said diode comprises a relatively low resistivity first semiconductive localized surface zone located in a relatively high resistivity semiconductor layer, said high resistivity layer being located on a semiconductive substrate of opposite conductivity type from that of said low resistivity first zone, and said depleted semiconductor portion being provided by said high resistivity layer.
Claim 5
Dependent Claim
47 words
Apparatus according to claim 3 which further includes circuit means for applying a voltage bias to the low resistivity zone relative to the substrate which is sufficient for producing a nonself-sustaining avalanche in response to charge carriers in the high resistivity layer drifting to said first zone.
Claim 6
Dependent Claim
101 words
Apparatus according to claim 3 which further comprises a second relatively low resistivity semiconductor zone of the same conductivity type as said first zone and circuit means for applying a voltage bias across said first and second zones sufficient to produce a drift electric field between said first and second zones which is directed so that a first type of charge carrier drift times of photo-excited charge carriers, which are generated in the said high resistivity layer and which drift to the detection means, tend to compensate for the optical delay times in the fiber corresponding to the different wavelength components.
Claim 7
Dependent Claim
13 words
Apparatus according to claim 1 in which the detection means include a transistor.
Claim 8
Dependent Claim
70 words
Apparatus according to claim 6 in which the said transistor comprises a relatively low resistivity first semiconductive surface zone in a relatively high resistivity semiconductor layer, said layer located on a semiconductive substrate of opposite conductivity type from that of said low resistivity first zone, said first zone serving as a base zone of the transistor during operation and said depleted semiconductor portion being provided by said high resistivity layer.
Claim 9
Dependent Claim
38 words
Apparatus according to claim 3 which further includes circuit means for applying a voltage to a second surface zone in said layer spaced apart from said first zone and of the same conductivity type as said first zone.
Claim 10
Dependent Claim
81 words
Apparatus according to claim 8 which further comprises circuit means for applying a voltage bias across said first and second zones sufficient to produce a drift electric field between said first and second zones which is directed so that the charge carrier drift times of photo-excited charge carriers, which are generated in the said high resistivity layer and which drift to the detection means, tend to compensate for the optical delay times in the fiber corresponding to the different wavelength components.
Claim 11
Dependent Claim
38 words
Apparatus for equalization of fiber mode dispersion according to claim 1 in which said depleted body portion is located in the far optical radiation field region of the exit port of the fiber, for fiber mode dispersion compensation.
Claim 12
Dependent Claim
53 words
Apparatus for equalization of fiber material dispersion according to claim 1 which further includes an optical deflection means, located at the exit port of the fiber between said port and the depleted body portion, For angularly separating different wavelength components in the optical radiation exiting at said port in accordance with the wavelength.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-10-07 | 1978-04-08 | 1978-10-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-10-07 | 1982-04-08 | 1982-10-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-10-07 | 1986-04-08 | 1986-10-08 | $7700.00 | Window Closed / Lapsed |