Patent US3158771A successfully refreshed from Google Patents.
EP0218449A2
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Apparatus for stabilizing the optical output power of a semiconductor laser
Assignee: Toshiba Corp
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Filing: 1986-09-30
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Granted: —
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Expires: 2006-09-30
Abstract
Abstract A drive circuit (20) supplies a semiconductor laser (l0) with current pulses corresponding to an input pulse signal (l6). A current supply (22) feeds a d.c. bias current to the laser (l0). A monitoring photodiode (l2) produces a light detection signal indicative of the actual laser output level. The detection signal is supplied to a subtraction device (28), to which the pulse signal (l6) is also supplied via a low-pass filter (32). The subtraction device (28) detects the difference between the two signals to produce an error signal. Integration devices (36, 48) produce average value signals (38, 50), which are compared by comparators (40, 52) with reference voltages (Vrl, Vr2) to obtain control signals (24, 54). The current supply and the current drive circuit are responsive to these control signals to independently modulate the d.c. bias current and the amplitude of the drive pulses applied to the laser (l0), whereby the laser output level can be stabilized to remain at a constant level.
Inventors
- 👤 Taro Patent Division Shibagaki
- 👤 Osamu Patent Division Kinoshita
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 11:53
CPC Classifications
H; H01; H01S; H01S5/00; H01S5/06; H01S5/068; H01S5/0683; H01S5/06835
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
216 words
An apparatus for stabilizing an optical output level of an electro-optical converter (l0, 202), having modulator means (20, 22; 200) for supplying the converter (l0, 202) with drive pulses corresponding to an electrical input pulse signal and a d.c. bias current, and light sensitive means (l2, 2l0) for producing a first electrical signal indicative of the actual optical output level of said converter, characterized in that said apparatus comprises: signal processing means (32, l02, DLl, DL2) for receiving the pulse signal to produce a second electrical signal indicative of an ideal optical output level of said converter; subtraction means (28; 106, l08; 224, 226) for detecting a difference between integration values of the first and second signals to produce as an error signal a third electrical signal indicative of a change in the actual optical output level of said converter; and temperature-compensation means (36, 40, 42, 48, 52; 106, l08, ll0, ll2, ll2, ll6; 232, 234) for producing first and second feedback signals based on the third signal to feed these feedback signals to said modulator means, said modulator means being responsive to the first and second feedback signals to independently modulate the d.c. bias current and the amplitude of the drive pulses applied to said converter, whereby the actual optical output level remains substantially constant.
Claim 2
Independent Claim
216 words
An apparatus for stabilizing an optical output level of an electro-optical converter (l0, 202), having modulator means (20, 22; 200) for supplying the converter (l0, 202) with drive pulses corresponding to an electrical input pulse signal and a d.c. bias current, and light sensitive means (l2, 2l0) for producing a first electrical signal indicative of the actual optical output level of said converter, characterized in that said apparatus comprises: signal processing means (32, l02, DLl, DL2) for receiving the pulse signal to produce a second electrical signal indicative of an ideal optical output level of said converter; subtraction means (28; 106, l08; 224, 226) for detecting a difference between integration values of the first and second signals to produce as an error signal a third electrical signal indicative of a change in the actual optical output level of said converter; and temperature-compensation means (36, 40, 42, 48, 52; 106, l08, ll0, ll2, ll2, ll6; 232, 234) for producing first and second feedback signals based on the third signal to feed these feedback signals to said modulator means, said modulator means being responsive to the first and second feedback signals to independently modulate the d.c. bias current and the amplitude of the drive pulses applied to said converter, whereby the actual optical output level remains substantially constant.
Claim 3
Independent Claim
92 words
The apparatus according to claim l, characterized in that said temperature-compensation means comprises: integration means for integrating said error signal to generate first and second mean value signals, which are compared with first and second reference voltages and fed back to said current supply means (22) and said drive means (20l); and multiplying means connected to said integration means, for applying a multiplication operation to said electrical signal and said third signal to extract a pulse component from said third signal, and for supplying a wave-shaped error signal to said integration means.
Claim 4
Independent Claim
117 words
The apparatus according to claim l, characterized in that said temperature-compensation means comprises: integration means (36, 48) for integrating said third signal to generate first and second mean value signals (36, 48); and comparing means (40, 52) for receiving first and second reference voltages respectively defining said d.c. bias current necessary for said electro-optical converter to keep a predetermoned laser output power level, and a reference level of said drive pulse width, and for comparing said first and second mean value signals with said first and second reference voltages to generate first and second difference signals, said first and second difference signals being fed back to said modulator means (20, 22), as first and second feedback signals.
Claim 5
Dependent Claim
74 words
The apparatus according to claim 3, characterized in that said temperature compensation means further comprises multiplying means (42) having a first input connected to said third error signal, a second input connected to said electrical pulse, and an output connected to said integration means, said multiplying means extracting a pulse wave component from said third signal on the basis of said electrical pulse signal, and supplying a wave-shaped error signal to said integration means.
Claim 6
Dependent Claim
41 words
The apparatus according to claim 4, characterized in that delay circuit means (44) is connected to said multiplying means, for delaying said electrical pulse signal to make a phase of said electrical pulse signal coincident with that of said third signal.
Claim 7
Dependent Claim
40 words
The apparatus according to claim 5, characterized in that said integration means has first and second integration circuits with different time constants, whereby a temperature compensation for said bias current is performed prior to that for said drive pulse amplitude.
Claim 8
Independent Claim
132 words
The apparatus according to claim l, characterized in that said temperature-compensation means comprises: subtractor means (l06, l08) for receiving first and second reference voltages (Vr3, Vr4) defining the peak and minimum levels of the laser power output of said electro-optical converting means, for detecting differences between said third signal and said first reference voltage, and between said third signal and said second reference voltage, and for detecting differences between the first and second difference signals and said first and second reference voltages, thereby to generate first and second difference signals; and integration means (ll4, ll6) connected to said subtractor means (l06, l08), for integrating said first and second difference signals to generate first and second means value signals, said first and second mean value signals being fed back to said modulator means.
Claim 9
Dependent Claim
68 words
The apparatus according to claim 7, characterized in that said temperature-compensate means further comprises multiplier means (ll0, ll2) connected between subtractor means and said integration means, for receiving said electrical pulse signal to extract a pulse-wave component from said first and second difference signals on the basis of said received electrical pulse signal, and for supplying said first and second difference signals thus wave-shaped to said integration means.
Claim 10
Dependent Claim
46 words
The apparatus according to claim 8, characterized in that said apparatus further comprises delay means (l22) connected to said mutiplier means, for delaying said electrical signal to make a phase of said electrical pulse signal coincident with the phases of said first and second difference signals.
Claim 11
Dependent Claim
42 words
l0. The apparatus according to claim 9, characterized in that said integration means includes first and second integration circuits (ll4, ll6) with different time constants, whereby the temperature-compensation for said bias current is performed prior to that for said drive pulse amplitude.
Claim 12
Independent Claim
63 words
The apparatus according to claim l, characterized in that said apparatus further comprises first detection means (2l2, 2l4) connected to said light sensitive means (2l0), for receiving said first signal to generate a fourth electrical signal including a signal component during the logic "high" level period of said first signal and a fifth electrical signal including a signal component during logic "low" level.
Claim 13
Independent Claim
64 words
The apparatus according to claim ll, characterized in that said subtractor means includes a subtractor device (224, 226) for detecting differences between said fourth and fifth signals and second signal, to generate, as error signals, a sixth electrical signal representing an error component contained in said logic "high level, and a seventh electrical signal representing an error component contained in said logical "low" level.
Claim 14
Independent Claim
62 words
The apparatus according to claim l2, characterized in that said temperature-compensation means comprises second detection means (232, 234) for generating first and second means value signals representing a mean value of said sixth and seventh electrical signals, said first and second means value signals being inverted and fed back as said first and second feed back signals to said modulation means (200).
Claim 15
Independent Claim
19 words
The apparatus according to claim l, characterized in that said electro-optical converting element includes a semiconductor laser (l0, 202).
Claim 16
Independent Claim
42 words
The apparatus according to claim l4, characterized in that said modulator means comprises: current supply means (22) for supplying said d.c. pulse current to said laser; and current drive means (20) for supplying current pulses corresponding to drive pulse to said laser.
Claim 17
Independent Claim
18 words
The apparatus according to claim l5, characterized in that said light sensitive means is a photodiode (l2, 2l0).
References Cited (Backward Citations)
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