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WO1992017007A1 - Method and control circuit for controlling a laser diode transmitter - Google Patents

Method and control circuit for controlling a laser diode transmitter Download PDF

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Publication number
WO1992017007A1
WO1992017007A1 PCT/FI1992/000079 FI9200079W WO9217007A1 WO 1992017007 A1 WO1992017007 A1 WO 1992017007A1 FI 9200079 W FI9200079 W FI 9200079W WO 9217007 A1 WO9217007 A1 WO 9217007A1
Authority
WO
WIPO (PCT)
Prior art keywords
laser diode
signal
level
optical output
controlling
Prior art date
Application number
PCT/FI1992/000079
Other languages
French (fr)
Inventor
Denis O'shea
Original Assignee
Telenokia Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telenokia Oy filed Critical Telenokia Oy
Priority to GB9319225A priority Critical patent/GB2269932B/en
Priority to DE4290770T priority patent/DE4290770T1/en
Publication of WO1992017007A1 publication Critical patent/WO1992017007A1/en
Priority to FI934114A priority patent/FI106677B/en
Priority to SE9303077A priority patent/SE516099C2/en

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/564—Power control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/501—Structural aspects
    • H04B10/503—Laser transmitters
    • H04B10/504—Laser transmitters using direct modulation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/068—Stabilisation of laser output parameters
    • H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
    • H01S5/06832—Stabilising during amplitude modulation

Definitions

  • the invention relates to a method of controlling the optical output level of a laser diode transmitter, comprising detecting a portion of an optical output signal of the laser diode transmitter, generating a monitor signal representing said optical output signal and controlling the mean level of the optical output of the laser diode transmitter on the basis of said monitor signal and a data signal to be transmitted.
  • the inven ⁇ tion relates further to a control circuit embodying the method.
  • a typical problem encountered in laser diodes is that the optical output power of the laser diode varies with temperature and time. More specifically, the effect of aging and increasing temperature on the laser diode is to increase the threshold current and decrease the slope efficiency thereof. Conventionally, this problem has been solved to a certain extent by the use of a Peltier cooler to eliminate temperature changes and a mean level feedback loop to compensate for the aging.
  • the object of the invention is to obtain a new method for controlling the optical output level of a laser diode transmitter, to be used in a telecommunica ⁇ tions network where a lifetime of 20 years is expected.
  • Extinction ratio is defined by the ratio of the optical "1" level to the "0" level.
  • the "0" level is very small in comparison to the "1" level. Therefore, even a slight disturbance or offset in the control loop can cause a considerable change in the "0" level and consequently in the extinction ratio.
  • the control loop must be insensitive to temperature changes, power supply changes, input signal changes and component tolerances. This means that when for example the temperature changes, the loop should act to compensate for the va ⁇ riation in laser efficiency, and not for the offsets and drift in the loop itself.
  • control signal for the control loop is derived from a balanced modulator or mixer.
  • the output of the balanced modulator or mixer depends directly upon the amplitude of the input sig ⁇ nals.
  • data signal itself or the data signal after some logical operation is used as the re ⁇ ference signal.
  • the data signal is said to be a digital signal, hence derived from a logic gate. It is well known that the output levels from any logic gate vary in amplitude with tem-perature changes. Hence the re- ference signal to the balanced modulator or mixer will change with tempera- ture. This will cause an erronious change in the output of the multiplier which in turn affects the extinction ratio.
  • the balanced modulator or mixer itself is composed of transistors or diodes whose base-emitter voltages changes with temperature. Again this causes the output to be unnecessarily adjusted.
  • control signal is derived from a com ⁇ bination of a positive peak detected signal and the average signal level. Again internal temperature compen ⁇ sation is not included and no provision is made for the signal duty cycle. In fact if transmission is interrup ⁇ ted during operation, the loop will act to increase the modulation current infinitely, and so damage or destroy the laser.
  • the objects of the present invention are achieved by a method according to the invention, in which the peak level of the optical output of the laser diode transmitter is controlled on the basis of the difference between the peak levels of said monitor signal and the data signal to be transmitted.
  • the method according to the invention is based on the principle that the monitor signal and the data sig ⁇ nal are generated by the same mechanism. Hence any changes which occur in the system will appear symmet- rically in both signals so that the output remains the same. Due to this principle, the circuit is internally temperature compensated and immune to power supply and input signal variations.
  • both the peak level and the mean level of the optical output of the laser diode are si ⁇ multaneously monitored and controlled by using the data signal to be transmitted as a reference signal. Due to the use of the data signal as a reference signal, even during a long sequence of data bits without transitions, the operation will not be disrupted or the laser power falsely adjusted.
  • the invention relates further to a control circuit for controlling an optical output level of a laser diode transmitter, comprising a monitoring photo diode means for detecting a portion of an optical output signal of the laser diode transmitter, a preamplifier generating a monitor signal representing said optical output sig ⁇ nal, and first control means for controlling the mean level of the output of the laser diode transmitter on the basis of said monitor signal and the data signal to be transmitted.
  • the control circuit comprises peak level detector means for de ⁇ tecting the peak level of the monitor signal and the peak level of a data signal to be transmitted; and sec ⁇ ond control means for controlling the peak level of the optical output of the laser diode transmitter on the basis of a difference between said peak levels detected by the peak level detector means.
  • Figure 1 is a block diagram of a control circuit according to the invention.
  • Slope efficiency refers to the ability of a laser to convert electrical current to light, i.e. a laser with good efficiency will need little current variation to produce a large deviation in the output light level, whereas an inefficient laser will require more current variation for the same change in light output.
  • Slope variations refers to changes in the effi ⁇ ciency on the laser over time and temperature. Typical ⁇ ly, as the laser ages and the operating temperature rises, the efficiency decreases, hence requiring increased drive current.
  • Figure 1 shows an optical transmitter comprising a laser diode LD, a laser diode driver 1, a modulation current source 2 and a bias current source 3.
  • the laser diode LD is forward biased by a bias current I Bia ⁇ l from the bias current source 3 in a conventional manner.
  • the modulation current source 2 generates a modulation cur ⁇ rent I Hod on the basis of an incoming data signal in ⁇ putted to the source 2.
  • the modulation current l Hod is fed to the laser diode driver 1 to modulate the laser diode LD so that an optical signal which corresponds to the incoming data is transmitted by the laser diode LD to an optical transmission medium, such as an optical fiber 11.
  • a portion of the optical output power of the laser diode LD is led to and detected by a monitoring photo- diode PD in order to monitor the output level of the laser diode LD.
  • the photodiode PD is connected to a high-bandwidth preamplifier 4, which outputs an electrical signal 4a representing the optical output of the laser diode LD.
  • the preamplifier 4 is realized for example as a wideband transimpedance preamplifier so that the amplitude of its output voltage is independent of temperature changes.
  • the output signal 4a is applied to a peak level detector 6, which determines the peak value of the signal 4a and outputs the result as an output signal 6a.
  • Incoming data which is to be transmitted, is applied to a limiting amplifier 12 which amplifies and limits the data signal so that the 1-level of its output re ⁇ mains constant at all temperatures.
  • the preamplifier 4 and the limiting amplifier 12 have both the same supply voltage V cc , and so variations in V cc , caused by e.g. temperature changes, affect both signals in the same way.
  • the signal from the limiting amplifier 12 is ap ⁇ plied to another peak level detector 7, which determines the peak value of the incoming data and outputs the result as an output signal 7a.
  • the time constants of the peak level detectors 6 and 7 should be the same.
  • the peak level detectors are preferably realized by using transistors or other circuit means integrated on the same chip so that they are constantly at the same tem ⁇ perature with respect to each other, and no error caused by a temperature difference occurs at their outputs as compared with each other.
  • the output signals from the detectors 6 and 7 are inputted to a comparator means 9, such as a differential amplifier, which forms a single- ended difference signal 9a, representing the difference between the signals 6a and 7a.
  • the peak level detectors 6 and 7 have both the same reference voltage V ⁇ so that variations in V ⁇ , caused by e.g. temperature changes, affect the output signals of both said detectors in the same manner.
  • the difference signal 9a is applied to the modulation current source 2 as a negative feedback signal to maintain zero error signal within the closed loop by adjusting the modulation current I ⁇ and thereby the peak level of the optical output signal of the laser diode LD.
  • the output signal 4a is also applied to a mean level detector 5, which determines the mean level of the signal 4a and outputs the result as an output signal 5a.
  • Incoming data which is to be transmitted, is applied to another mean level detector 8, which determines the mean level of the incoming data and outputs the result as an output signal 8a.
  • the time constants of the mean level detectors 5 and 8 should be the same.
  • the output signals from the detectors 5 and 8 are inputted to a comparator means 10, such as a differential amplifier, which forms a single-ended difference signal 10a repre ⁇ senting the difference between the signals 5a and 8a.
  • the differential amplifier 10 is preferably an integrat- ing amplifier in order that the dependence on the phase of the detector output signals 5a and 8a should be eliminated.
  • the difference signal 10a is applied to the bias current source 3 as a negative feedback signal to maintain zero error signal within the closed loop by ad- justing the bias current I Bia8 and thereby the mean level of the optical output signal of the laser diode
  • the bias control loop should preferably be faster than the peak control loop.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Optics & Photonics (AREA)
  • Semiconductor Lasers (AREA)
  • Optical Communication System (AREA)

Abstract

The invention relates to a control method and a control circuit for a laser diode transmitter. The control circuit comprises a monitoring photo diode means (PD) for detecting a portion of an optical output signal of the laser diode transmitter (LD) and generating a monitor signal (4a) representing said optical output signal. In the invention, the control circuit further comprises a peak level detector means (6, 7) for detecting the peak level of the monitor signal (4a) and the peak level of a data signal to be transmitted, first control means (2, 9) for controlling the peak level of the optical output of the laser diode transmitter (LD) on the basis of a difference between said peak levels detected by the peak level detector means (6, 7), mean level detector means (5, 8) for detecting the mean level of the monitor signal (4a) and the mean level of the data signal to be transmitted, and second control means (3, 10) for controlling the mean level of the output of the laser diode transmitter (LD) on the basis of a difference between said mean levels detected by the mean level detector means (5, 8).

Description

Method and control circuit for controlling a laser diode transmitter
The invention relates to a method of controlling the optical output level of a laser diode transmitter, comprising detecting a portion of an optical output signal of the laser diode transmitter, generating a monitor signal representing said optical output signal and controlling the mean level of the optical output of the laser diode transmitter on the basis of said monitor signal and a data signal to be transmitted. The inven¬ tion relates further to a control circuit embodying the method.
A typical problem encountered in laser diodes is that the optical output power of the laser diode varies with temperature and time. More specifically, the effect of aging and increasing temperature on the laser diode is to increase the threshold current and decrease the slope efficiency thereof. Conventionally, this problem has been solved to a certain extent by the use of a Peltier cooler to eliminate temperature changes and a mean level feedback loop to compensate for the aging.
Several methods of controlling the optical output level without a cooler have also been tried, but no co - pletely satisfactory system is known. Most of the meth¬ ods known are either too complex or error susceptible to be used under dynamic operating conditions, or to be assembled on a production line.
The object of the invention is to obtain a new method for controlling the optical output level of a laser diode transmitter, to be used in a telecommunica¬ tions network where a lifetime of 20 years is expected. Especially the specifications for extinction ratio are tight so the control circuit needs to be accurate. Extinction ratio is defined by the ratio of the optical "1" level to the "0" level. For a large extinction ratio the "0" level is very small in comparison to the "1" level. Therefore, even a slight disturbance or offset in the control loop can cause a considerable change in the "0" level and consequently in the extinction ratio. To avoid this happening, the control loop must be insensitive to temperature changes, power supply changes, input signal changes and component tolerances. This means that when for example the temperature changes, the loop should act to compensate for the va¬ riation in laser efficiency, and not for the offsets and drift in the loop itself.
The system known from EP-patent application 218 449 does not fulfil the above-mentioned objects for several reasons. In this system the control signal for the control loop is derived from a balanced modulator or mixer. The output of the balanced modulator or mixer depends directly upon the amplitude of the input sig¬ nals. In the system the data signal itself or the data signal after some logical operation is used as the re¬ ference signal. The data signal is said to be a digital signal, hence derived from a logic gate. It is well known that the output levels from any logic gate vary in amplitude with tem-perature changes. Hence the re- ference signal to the balanced modulator or mixer will change with tempera- ture. This will cause an erronious change in the output of the multiplier which in turn affects the extinction ratio.
The balanced modulator or mixer itself is composed of transistors or diodes whose base-emitter voltages changes with temperature. Again this causes the output to be unnecessarily adjusted.
In this known system the phases of the recovered signal and the reference signal need to be aligned. This method is not suitable at high bit rates where the pulse width is comparable to the phase shift caused by the parasitic capacitances in the circuit. This requirement for individual adjustment of each circuit is a major disadvantage in volume production. In one embodiment according to the EP Patent Ap¬ plication No. 218 449 the positive and negative peaks of the signal are detected. As the negative peak corre¬ sponds to the "0" level which is a small amount, a slight offset or drift, will cause a large error. In a control circuit according to U.S. patent No. 4 277 846 the control signal is derived from a negative peak detector and a fixed reference signal. The circuit is not internally temperature compensated and hence changes in the base-emitter voltage of the peak detector will be strongly reflected as errors in the modulation current.
In a control circuit according to JP publication No. 55-83280 the control signal is derived from a com¬ bination of a positive peak detected signal and the average signal level. Again internal temperature compen¬ sation is not included and no provision is made for the signal duty cycle. In fact if transmission is interrup¬ ted during operation, the loop will act to increase the modulation current infinitely, and so damage or destroy the laser.
The objects of the present invention are achieved by a method according to the invention, in which the peak level of the optical output of the laser diode transmitter is controlled on the basis of the difference between the peak levels of said monitor signal and the data signal to be transmitted.
The method according to the invention is based on the principle that the monitor signal and the data sig¬ nal are generated by the same mechanism. Hence any changes which occur in the system will appear symmet- rically in both signals so that the output remains the same. Due to this principle, the circuit is internally temperature compensated and immune to power supply and input signal variations. In the invention both the peak level and the mean level of the optical output of the laser diode are si¬ multaneously monitored and controlled by using the data signal to be transmitted as a reference signal. Due to the use of the data signal as a reference signal, even during a long sequence of data bits without transitions, the operation will not be disrupted or the laser power falsely adjusted. By means of the invention the level and the extinction ratio can therefore be maintained constant in spite of changing input signal conditions. The invention relates further to a control circuit for controlling an optical output level of a laser diode transmitter, comprising a monitoring photo diode means for detecting a portion of an optical output signal of the laser diode transmitter, a preamplifier generating a monitor signal representing said optical output sig¬ nal, and first control means for controlling the mean level of the output of the laser diode transmitter on the basis of said monitor signal and the data signal to be transmitted. The control circuit according to the invention comprises peak level detector means for de¬ tecting the peak level of the monitor signal and the peak level of a data signal to be transmitted; and sec¬ ond control means for controlling the peak level of the optical output of the laser diode transmitter on the basis of a difference between said peak levels detected by the peak level detector means.
In the following the invention will be described in greater detail by means of an exemplifying embodiment with reference to the attached drawings, in which Figure 1 is a block diagram of a control circuit according to the invention.
Some technical terms used here will be now explained.
Slope efficiency refers to the ability of a laser to convert electrical current to light, i.e. a laser with good efficiency will need little current variation to produce a large deviation in the output light level, whereas an inefficient laser will require more current variation for the same change in light output. Slope variations refers to changes in the effi¬ ciency on the laser over time and temperature. Typical¬ ly, as the laser ages and the operating temperature rises, the efficiency decreases, hence requiring increased drive current. Figure 1 shows an optical transmitter comprising a laser diode LD, a laser diode driver 1, a modulation current source 2 and a bias current source 3. The laser diode LD is forward biased by a bias current IBiaιl from the bias current source 3 in a conventional manner. The modulation current source 2 generates a modulation cur¬ rent IHod on the basis of an incoming data signal in¬ putted to the source 2. The modulation current lHod is fed to the laser diode driver 1 to modulate the laser diode LD so that an optical signal which corresponds to the incoming data is transmitted by the laser diode LD to an optical transmission medium, such as an optical fiber 11.
A portion of the optical output power of the laser diode LD is led to and detected by a monitoring photo- diode PD in order to monitor the output level of the laser diode LD. The photodiode PD is connected to a high-bandwidth preamplifier 4, which outputs an electrical signal 4a representing the optical output of the laser diode LD. The preamplifier 4 is realized for example as a wideband transimpedance preamplifier so that the amplitude of its output voltage is independent of temperature changes.
The output signal 4a is applied to a peak level detector 6, which determines the peak value of the signal 4a and outputs the result as an output signal 6a. Incoming data, which is to be transmitted, is applied to a limiting amplifier 12 which amplifies and limits the data signal so that the 1-level of its output re¬ mains constant at all temperatures. The preamplifier 4 and the limiting amplifier 12 have both the same supply voltage Vcc, and so variations in Vcc, caused by e.g. temperature changes, affect both signals in the same way. The signal from the limiting amplifier 12 is ap¬ plied to another peak level detector 7, which determines the peak value of the incoming data and outputs the result as an output signal 7a. The time constants of the peak level detectors 6 and 7 should be the same. The peak level detectors are preferably realized by using transistors or other circuit means integrated on the same chip so that they are constantly at the same tem¬ perature with respect to each other, and no error caused by a temperature difference occurs at their outputs as compared with each other. The output signals from the detectors 6 and 7 are inputted to a comparator means 9, such as a differential amplifier, which forms a single- ended difference signal 9a, representing the difference between the signals 6a and 7a. The peak level detectors 6 and 7 have both the same reference voltage Vββ so that variations in Vββ, caused by e.g. temperature changes, affect the output signals of both said detectors in the same manner. The difference signal 9a is applied to the modulation current source 2 as a negative feedback signal to maintain zero error signal within the closed loop by adjusting the modulation current I^ and thereby the peak level of the optical output signal of the laser diode LD.
The output signal 4a is also applied to a mean level detector 5, which determines the mean level of the signal 4a and outputs the result as an output signal 5a. Incoming data, which is to be transmitted, is applied to another mean level detector 8, which determines the mean level of the incoming data and outputs the result as an output signal 8a. The time constants of the mean level detectors 5 and 8 should be the same. The output signals from the detectors 5 and 8 are inputted to a comparator means 10, such as a differential amplifier, which forms a single-ended difference signal 10a repre¬ senting the difference between the signals 5a and 8a. The differential amplifier 10 is preferably an integrat- ing amplifier in order that the dependence on the phase of the detector output signals 5a and 8a should be eliminated. The difference signal 10a is applied to the bias current source 3 as a negative feedback signal to maintain zero error signal within the closed loop by ad- justing the bias current IBia8 and thereby the mean level of the optical output signal of the laser diode LD.
In order to control the action and interaction of the two parallel feedback loops, the bias control loop should preferably be faster than the peak control loop. The figure and the specification relating thereto are only intended to clarify the invention. As to the details, the method and control circuit according to the invention can vary within the scope of the enclosed claims.

Claims

Claims
1. A method of controlling the optical output level of a laser diode transmitter, comprising detecting a portion of an optical output signal of the laser diode transmitter, generating a monitor signal representing said optical output signal, and controlling the mean level of the optical output of the laser diode transmit¬ ter on the basis of said monitor signal and a data signal to be transmitted, c h a r a c t e r i z e d by controlling the peak level of the optical output of the laser diode transmitter on the basis of the dif¬ ference between the peak levels of said monitor signal and the data signal to be transmitted.
2. A method according to claim 1, c h a r a c ¬ t e r i z e d in that the controlling the peak level of the optical output comprises controlling a modulation current of the laser diode transmitter so that said difference is maintained zero.
3. A method according to claim 1 or 2, c h a r ¬ a c t e r i z e d in that controlling the mean level of the optical output comprises controlling a bias cur¬ rent of the laser diode transmitter on the basis of a difference between the mean levels of said monitor sig¬ nal and the data signal to be transmitted so that said difference is maintained zero.
4. A method according to claim 1, 2 or 3, c h a r¬ a c t e r i z e d in that the mean level control is faster than the peak level control.
5. A control circuit for controlling an optical output level of a laser diode transmitter, comprising a monitoring photo diode means (PD) for detecting a por¬ tion of an optical output signalsof the laser diode transmitter (LD), a preamplifier (4) generating a moni- tor signal (4a) representing said optical output signal, and first control means (3,10) for controlling the mean level of the output of the laser diode transmitter (LD) on the basis of said monitor signal and the data signal to be transmitted, c h a r a c t e r i z e d in that said control circuit comprises peak level detector means (6,7) for detecting the peak level of the monitor signal (4a) and the peak level of a data signal to be transmitted, and second control means (2,9) for controlling the peak level of the optical output of the laser diode transmitter (LD) on the basis of a difference between said peak levels detected by the peak level detector means (6,7).
6. A control circuit according to claim 5, c h a r a c t e r i z e d in that it further comprises a limiting amplifier (12) connected in front of the peak level detector (7) for the data signal for rendering the "1" level of the data signal temperature independent.
7. A control circuit according to claim 5 or 6, c h a r a c t e r i z e d in that the preamplifier is a wideband transimpedance preamplifier (4).
8. A control circuit according to claim 5, 6 or 7, c h a r a c t e r i z e d in that the peak level detectors (6, 7) for the data signal and the monitor signal are by construction and in operation identical.
9. A control circuit according to claim 5, c h a r a c t e r i z e d in that said second control means (2,9) controls a modulation current of the laser diode transmitter (LD), and said first control means (3,10) controls a bias current of the laser diode trans¬ mitter (LD) on the basis of a difference between mean levels of the monitor signal and the data signal to be transmitted as detected by mean level detector means (5,8) for detecting the mean level of the monitor signal (4a) and the mean level of the data signal to be trans¬ mitted.
10. A control circuit according to claim 5 or 7, c h a r a c t e r i z e d in that the mean level con- trol is faster than the peak level control.
AMENDED CLAIMS
[received by the International Bureau on 14 August 1992 (14.08.92); original claims 1 and 4 replaced by new claim 1; claims 5, 6 and 10 replaced by new claim 4; claims 2 and 3 unchanged; claims 5,7, 8 and 9 unchanged but renumbered as claims 4-7 (2 pages)]
1. A method of controlling the optical output le- vel of a laser diode transmitter, comprising detecting a portion of an optical output signal of the laser diode transmitter, generating a monitor signal representing said op¬ tical output signal, controlling the mean level of the optical output of the laser diode transmitter on the basis of said moni¬ tor signal and a data signal to be transmitted, and controlling the peak level of the optical output of the laser diode transmitter on the basis of the dif- ference between the peak levels of said monitor signal and the data signal to be transmitted, c h a r a c ¬ t e r i z e d in that the mean level control is faster than the peak level control.
2. A method according to claim 1, c h a r a c - t e r i z e d in that the controlling the peak level of the optical output comprises controlling a modulation current of the laser diode transmitter so that said dif¬ ference in maintained zero.
3. A method according to claim l or 2 , c h a - a c t e r i z e d in that controlling the mean level of the optical output comprises controlling a bias current of the laser diode transmitter on the basis of a differ¬ ence between the mean levels of said monitor signal and the data signal to be transmitted so that said difference is maintained zero.
4. A control circuit for controlling a optical output level of a laser diode transmitter, comprising a monitoring photo diode means (PD) for detecting a portion of an optical output signal of the laser diode transmitter (LD) , a preamplifier (4) generating a monitor signal (4a) representing said optical output signal, first control means (3, 10) for controlling the mean level of the output of the laser diode transmitter (LD) on the basis of said monitor signal and the data signal to be transmitted, peak level detector means (6, 7) for detecting the peak level of the monitor signal (4a) and the peak level of a data signal to be transmitted, and second control means (2, 9) for controlling the peak level of the optical output of the laser diode transmitter (LD) on the basis of a difference between said peaks levels detected by the peak level detector means (6, 7), c h a r a c t e r i z e d in that the con¬ trol circuit further comprises a limiting amplifier (12) connected in front of the peak level detector (7) for the data signal for rendering the "1" level of the data sig¬ nal temperature independent, and that the mean level con¬ trol is faster than the peak level control.
5. A control circuit according to claim 4, c h a r a c t e r i z e d in that the preamplifier is a wideband transimpedance preamplifier (4) .
6. A control circuit according to claim 4 or 5, c h a r a c t e r i z e d in that the peak level detect¬ ors (6, 7) for the data signal and the monitor signal are by construction an in operation identical.
7. A control circuit according to claim 4, c h a r a c t e r i z e d in that said second control means (2, 9) controls a modulation current of the laser diode transmitter (LD) , and said first control means (3, 10) controls a bias current of the laser diode transmit¬ ter (LD) on the basis of a difference between mean levels of the monitor signal and the data signal to be transmit¬ ted as detected by mean level detector means (5, 8) for detecting the mean level of the monitor signal (4a) and the mean level of the data signal to be transmitted.
PCT/FI1992/000079 1991-03-21 1992-03-20 Method and control circuit for controlling a laser diode transmitter WO1992017007A1 (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
GB9319225A GB2269932B (en) 1991-03-21 1992-03-20 Method and control circuit for controlling a laser diode transmitter
DE4290770T DE4290770T1 (en) 1992-03-20 1992-03-20 Method and control circuit for controlling a laser diode transmitter
FI934114A FI106677B (en) 1991-03-21 1993-09-20 Control procedure and control circuit for a laser diode transmitter
SE9303077A SE516099C2 (en) 1991-03-21 1993-09-21 Method and control circuit for controlling the optical output level of a laser diode transmitter

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI911382A FI911382A0 (en) 1991-03-21 1991-03-21 REGLERINGSFOERFARANDE OCH REGLERINGSKRETS FOER EN LASERDIODSAENDARE.
FI911382 1991-03-21

Publications (1)

Publication Number Publication Date
WO1992017007A1 true WO1992017007A1 (en) 1992-10-01

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PCT/FI1992/000079 WO1992017007A1 (en) 1991-03-21 1992-03-20 Method and control circuit for controlling a laser diode transmitter

Country Status (4)

Country Link
FI (1) FI911382A0 (en)
GB (1) GB2269932B (en)
SE (1) SE516099C2 (en)
WO (1) WO1992017007A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0913961A1 (en) * 1997-10-28 1999-05-06 Koninklijke Philips Electronics N.V. Optical transmitter for reducing impulse noise in a fiber optic link
WO2021051676A1 (en) * 2019-09-20 2021-03-25 武汉光迅科技股份有限公司 Drive circuit for direct modulated laser, and direct modulated optical transmitter

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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EP0218449A2 (en) * 1985-09-30 1987-04-15 Kabushiki Kaisha Toshiba Apparatus for stabilizing the optical output power of a semiconductor laser

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JPS6190487A (en) * 1984-10-11 1986-05-08 Nippon Telegr & Teleph Corp <Ntt> Semiconductor laser drive circuit
EP0218449A2 (en) * 1985-09-30 1987-04-15 Kabushiki Kaisha Toshiba Apparatus for stabilizing the optical output power of a semiconductor laser

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Cited By (3)

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Publication number Priority date Publication date Assignee Title
EP0913961A1 (en) * 1997-10-28 1999-05-06 Koninklijke Philips Electronics N.V. Optical transmitter for reducing impulse noise in a fiber optic link
WO2021051676A1 (en) * 2019-09-20 2021-03-25 武汉光迅科技股份有限公司 Drive circuit for direct modulated laser, and direct modulated optical transmitter
US12334708B2 (en) 2019-09-20 2025-06-17 Accelink Technologies Co., Ltd. Drive circuit for direct modulated laser, and direct modulated optical transmitter

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SE9303077D0 (en) 1993-09-21
SE516099C2 (en) 2001-11-19
SE9303077L (en) 1993-11-11
GB9319225D0 (en) 1993-12-15
FI911382A0 (en) 1991-03-21
GB2269932B (en) 1995-02-15
GB2269932A (en) 1994-02-23

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