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US3852591A
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Graded bandgap semiconductor photodetector for equalization of optical fiber material delay distortion
Assignee: AT&T Inc
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Filing: 1973-10-19
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Granted: 1974-12-03
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Expires: 1993-10-19
Abstract
Abstract In optical fiber transmission, one of the causes of signal distortion (pulse broadening) stems from the fact that energy at different optical wavelengths travels at different velocities in the fiber material (material dispersion), and hence these wavelength components undergo different time delays while propagating through the fiber. In order to reduce this optical distortion, a p-n junction photodiode made of a graded bandgap semiconductor material is disclosed as a delay equalizing detector. The gradient of the bandgap is made in such a manner that the different time delays of drifting charge carriers, generated by the absorption of different wavelengths at different depths in the graded bandgap semiconductor, can be made to compensate for the time delays suffered by the optical energy at different wavelengths while propagating through the fiber.
Inventors
- 👤 T Lee
- 👤 T Li
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 18:50
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/25; H04B10/2507; G; G02; G02B; G02B6/00; G02B6/24; G02B6/26; G02B6/28; G02B6/293; G02B6/29379; G02B6/29392; G02B6/29394; G02B6/42; G02B6/4201; G02B6/4204; G02B6/4215; H10; H10F; H10F99/00; Y; Y10; Y10S; Y10S438/00; Y10S438/936
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
151 words
Apparatus for equalizing the delay distortion of optical radiation, which comprises a semiconductor body portion having a graded energy bandgap terminated by a charge carrier collection means, whereby different wavelength components in said radiation incident upon the body are absorbed in the body portion at different average positions according to said wavelength, thereby producing charge carriers which drift within the body porTion having the graded energy bandgap to the charge collection means, said body located in the path of the optical radiation emanating from an optical fiber in which different wavelength components of said radiation undergo different optical time delays in accordance with the material dispersion property of the fiber, said graded energy bandgap being such that the different optical time delays of the different wavelength components in the fiber are substantially compensated by the different delays of the drifting charge carriers in the body portion generated by said wavelength components.
Claim 2
Dependent Claim
151 words
Apparatus for equalizing the delay distortion of optical radiation, which comprises a semiconductor body portion having a graded energy bandgap terminated by a charge carrier collection means, whereby different wavelength components in said radiation incident upon the body are absorbed in the body portion at different average positions according to said wavelength, thereby producing charge carriers which drift within the body porTion having the graded energy bandgap to the charge collection means, said body located in the path of the optical radiation emanating from an optical fiber in which different wavelength components of said radiation undergo different optical time delays in accordance with the material dispersion property of the fiber, said graded energy bandgap being such that the different optical time delays of the different wavelength components in the fiber are substantially compensated by the different delays of the drifting charge carriers in the body portion generated by said wavelength components.
Claim 3
Dependent Claim
59 words
Apparatus according to claim 1 which said body portion is characterized in that at least a subportion thereof has a net significant impurity concentration gradient suitable for producing an electric field, in said subportion when a voltage bias is applied across said body portion, which is a more nearly uniform electric field than in the absence of said gradient.
Claim 4
Dependent Claim
26 words
Apparatus according to claim 2 in which said gradient is substantially exponential in an increasing sense going away from a first location in the body portion.
Claim 5
Dependent Claim
48 words
Apparatus according to claim 3 in which the charge collection means includes a p-n junction at the first location, so that the electric field in the immediate neighborhood of the junction is significantly higher than in the remainder of the subportion when the said voltage bias is applied.
Claim 6
Dependent Claim
38 words
Apparatus according to claim 4 which further comprises circuit means for applying a reverse voltage bias across the p-n junction whereby a substantially uniform electric field is produced in a region of the subportion removed from the junction.
Claim 7
Dependent Claim
34 words
Apparatus according to claim 1 in which the semiconductor portion of graded bandgap is essentially aluminum gallium arsenide having a relative concentration of aluminum which is correspondingly graded to furnish said graded energy bandgap.
Claim 8
Dependent Claim
28 words
Apparatus according to claim 6 in which the relative concentration of aluminum varies linearly with distance from a second location, whereby said bandgap correspondingly varies linearly with distance.
Claim 9
Dependent Claim
43 words
Apparatus according to claim 7 in which at least a subportion of the body portion is characterized by a net significant impurity concentration gradient suitable for producing a substantially uniform electric field in response to a voltage bias applied across said body portion.
Claim 10
Dependent Claim
26 words
Apparatus according to claim 8 in which said gradient is substantially exponential in an increasing sense going away from a first location in the body portion.
Claim 11
Dependent Claim
38 words
Apparatus according to claim 9 in which a p-n junction is located at the first location so that the electric field in the immediate neighborhood of the junction is significantly higher than in the remainder of the subportion.
Claim 12
Dependent Claim
31 words
Apparatus according to claim 10 which further comprises circuit means for applying a reverse voltage bias across the p-n junction whereby the electric field produced in the subportion is substantially uniform.
Claim 13
Dependent Claim
71 words
Apparatus for detecting optical radiation which comprises a semiconductor body portion having a graded energy bandgap terminated by a p-n junction, in which a region of the graded energy gap has a net significant impurity concentration gradient suitable for producing an electric field, in said subportion when a voltage bias is applied across said body portion, which is more nearly a uniform electric field than in the absence of said gradient.
Claim 14
Dependent Claim
71 words
Apparatus for detecting optical radiation which comprises a semiconductor body portion having a graded energy bandgap terminated by a p-n junction, in which a region of the graded energy gap has a net significant impurity concentration gradient suitable for producing an electric field, in said subportion when a voltage bias is applied across said body portion, which is more nearly a uniform electric field than in the absence of said gradient.
Claim 15
Dependent Claim
25 words
Apparatus according to claim 12 in which the net significant concentration gradient is substantially exponential increasing going away from the P-n junction in said region.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-12-02 | 1978-06-03 | 1978-12-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-12-02 | 1982-06-03 | 1982-12-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-12-02 | 1986-06-03 | 1986-12-03 | $7700.00 | Window Closed / Lapsed |