US4876442A
Expired / Lapsed
US
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Laser control circuit
Assignee: NEC Corp
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Filing: 1988-10-31
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Granted: 1989-10-24
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Expires: 2008-10-31
Abstract
Abstract A laser control circuit is provided in which temperature compensation is achieved by controlling the bias current, thereby preventing intersymbol interference when the temperature of the semiconductor laser rises.
Inventors
- 👤 Masaya Fukushima
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 08:47
CPC Classifications
H; H01; H01S; H01S5/00; H01S5/06; H01S5/068; H01S5/0683; H01S5/06835; H01S5/06804; H01S5/06812
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
152 words
A laser control circuit responsive to an electrical modulating signal, wherein part of the optical output power of a semiconductor laser is detected and converted into an electric signal for controlling a bias current to be supplied to said laser, said laser control circuit comprising: laser driving means for intensity-modulating said laser in response to said electrical modulating signal; a light receiving element for receiving part of the output light of said laser and outputting a current corresponding to the optical power of said output light received; current/voltage converting means for converting said output current from said light receiving element into a voltage at a prescribed current/voltage converting efficiency A(T), said converting efficiency A(T) having a positive temperature coefficient with respect to the temperature in the vicinity of said laser; and control means for so controlling said bias current so as to keep constant said voltage provided by said current/voltage converting means.
Claim 2
Dependent Claim
152 words
A laser control circuit responsive to an electrical modulating signal, wherein part of the optical output power of a semiconductor laser is detected and converted into an electric signal for controlling a bias current to be supplied to said laser, said laser control circuit comprising: laser driving means for intensity-modulating said laser in response to said electrical modulating signal; a light receiving element for receiving part of the output light of said laser and outputting a current corresponding to the optical power of said output light received; current/voltage converting means for converting said output current from said light receiving element into a voltage at a prescribed current/voltage converting efficiency A(T), said converting efficiency A(T) having a positive temperature coefficient with respect to the temperature in the vicinity of said laser; and control means for so controlling said bias current so as to keep constant said voltage provided by said current/voltage converting means.
Claim 3
Dependent Claim
65 words
A laser control circuit, as claimed in claim 1, wherein said control means comprises: means for outputting a first voltage proportional to the difference between the output voltage of said current/voltage converting means and a reference voltage, and means for prebiasing said laser according to the difference between a second voltage, which is a signal extracted from said electrical modulating signal, and said first voltage.
Claim 4
Dependent Claim
69 words
A laser control circuit, as claimed in claim 1, wherein said current/voltage converting efficiency A(T) is set so as to substantially satisfy the condition of A(T)=A(T.sub.0).DQE(T.sub.0)/DQE(T) wherein A(T 0 ) and DQE(T 0 ) are respectively the current/voltage converting efficiency and the differential quantum efficiency of said laser at a standard temperature T 0 , and DQE(T) is the differential quantum efficiency of said laser at a temperature T.
Claim 5
Dependent Claim
64 words
A laser control circuit, as claimed in claim 2, wherein said means for outputting a first voltage proportional to the difference between the output voltage of said current-voltage converting means and a reference voltage includes a thermistor, a first resistor positioned in series with said thermistor, and a second resistor arranged in parallel to the series circuit comprising said thermistor and said first resistor.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-10-23 | 1993-04-24 | 1993-10-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-10-23 | 1997-04-24 | 1997-10-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-10-23 | 2001-04-24 | 2001-10-24 | $7700.00 | Window Closed / Lapsed |