WO1993013577A1 - Appareil et procede de regulation du rapport d'extinction d'une diode laser en fonction de la temperature - Google Patents

Appareil et procede de regulation du rapport d'extinction d'une diode laser en fonction de la temperature Download PDF

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Publication number
WO1993013577A1
WO1993013577A1 PCT/US1992/011157 US9211157W WO9313577A1 WO 1993013577 A1 WO1993013577 A1 WO 1993013577A1 US 9211157 W US9211157 W US 9211157W WO 9313577 A1 WO9313577 A1 WO 9313577A1
Authority
WO
WIPO (PCT)
Prior art keywords
voltage
laser
light source
magnitude
logical
Prior art date
Application number
PCT/US1992/011157
Other languages
English (en)
Inventor
William L. Geller
Original Assignee
Raynet Corporation
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 Raynet Corporation filed Critical Raynet Corporation
Priority to AU34186/93A priority Critical patent/AU672188B2/en
Priority to KR1019940702062A priority patent/KR940704073A/ko
Priority to JP5511863A priority patent/JPH07502627A/ja
Priority to PCT/US1992/011157 priority patent/WO1993013577A1/fr
Priority to DE69224534T priority patent/DE69224534T2/de
Priority to EP93902712A priority patent/EP0617852B1/fr
Priority to US08/244,983 priority patent/US5502298A/en
Publication of WO1993013577A1 publication Critical patent/WO1993013577A1/fr

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
    • 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
    • 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
    • H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
    • H01S5/042—Electrical excitation ; Circuits therefor
    • 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
    • H01S5/06835—Stabilising during pulse modulation or generation

Definitions

  • the present invention relates to an apparatus for controlling an output of a laser diode over temperature so as to control and optimally maintain constant its extinction ratio, and a method for initially setting HIGH and LOW outputs of the laser diode so as to have a desired extinction ratio.
  • FIG 1 illustrates various characteristic curves for a laser diode whereby current I versus power P is graphed, the three curves illustrating data for a laser diode at three distinct temperatures.
  • a pedestal bias current 4 of the laser diode increases with temperature.
  • One method of controlling an output of a laser diode is to incorporate a thermoelectric cooler into a laser package so as to keep the diode at a constant temperature so that its pedestal bias current remains constant.
  • thermoelectric cooler designs tend to increase the laser cost, and decreases reliability of the laser diode since any failure in the thermoelectric cooler device or its circuitry will result in the applied bias current being inappropriate as the temperature of the laser diode varies.
  • first means for comparing the first voltage magnitude to a first preset voltage value representative of a preset desired modulation current while the light source is transmitting the continuous logical 1 and then adjusting the modulation current of the light source in response to the first means comparison to maintain the first voltage magnitude in close proximity to the first preset value;
  • second means for comparing the second voltage magnitude to a second preset voltage value representative of a preset desired bias current while the light source is transmitting the continuous logical 0 and then adjusting the bias current of the light source in response to this second means comparison to maintain the second voltage magnitude in close proximity to the second preset value;
  • the first and second detecting means detecting the first and second voltage magnitudes and the first and second comparing means adjusting the modulation and bias currents respectively over time at a frequency which is sufficiently large so as to maintain an extinction ratio of the light source relatively constant as an efficiency of the light source varies over time.
  • a method for optimally initially setting the HIGH and LOW levels of a laser diode preferably comprising the steps of:
  • FIG I illustrates several current versus power characteristic curves of a laser at various temperatures and shows bias and modulation current values
  • FIG 2 illustrates a preferred frame preamble and clock times for se with the present invention
  • FIG 3 illustrates a schematic of one embodiment of the invention or maintaining an extinction ratio of a laser constant
  • FIG 4 illustrates a switch modulator shown in FIG 3
  • FIGs 5A and 5B together illustrate a preferred circuit implementation of the schematic illustrated in FIG 3;
  • FIG 6 illustrates a plurality of optical network units connected to a host digital terminal which includes a laser controlled according to the invention.
  • a circuit for independently monitoring a pedestal bias output power Pi (FIG 1) of a laser periodically over time, independently monitoring a HIGH power output P1+P2 of the laser over time, and independently increasing or decreasing these powers over time so that an extinction ratio of the laser is maintained constant and the laser LOW power is kept at its pedestal point.
  • a pedestal bias output power Pi FOG 1
  • the extinction ratio N is defined as the HIGH laser output power P1+P2 divided by the LOW laser output power Pi. For N greater than 10, the extinction ratio is approximated by P2/P 1 .
  • a control circuit is proposed for use for information frames 61 which preferably include training pulses 62, 63, the training pulses comprising several successive binary LOWs followed by several successive binary HIGHs, preferably the successive LOWs and HIGHs each comprising a byte or more of bandwidth (typically 8 bits, or 10 bits for 4B5B coding of 8 bit bytes).
  • this LOW-HIGH training pulse is transmitted once per frame.
  • the laser power output is strobed by clock CLl and measured and compared to a preset dynamic LOW power reference value. If the measured LOW power is below the preset dynamic LOW power reference value, a bias current I ⁇ to the laser is incrementally increased.
  • the pedestal bias current is incrementally decreased. It is readily evident that if this done repetitively, the bias current supplied to the laser can be readily adjusted so as to keep the bias current at the laser pedestal threshold regardless of the speed with which the pedestal may move as induced by laser aging or more commonly due to temperature variations. According to a preferred embodiment, as indicated, this measurement and comparison is done once per frame, and at a frame rate of 8 KHz, 8,000 bias current adjustments per second are achievable. Accordingly, the bias current will toggle about the LOW power reference value.
  • the laser power is again strobed by clock CL2, measured, and compared to another preset dynamic HIGH power reference value and when the strobed and measured power is below the preset HIGH reference value a modulation current IM to the laser is increased and whenever it is above the preset HIGH reference value the modulation current IM is decreased.
  • the modulation current will also toggle about a desired level.
  • both the HIGH power output and LOW power output are independently measured and compared repetitively over time keeping these values relatively constant so as to maintain the laser extinction ratio constant.
  • FIG 3 illustrates a schematic illustration of one preferred embodiment of the invention.
  • laser diode LASC to be controlled has its anode connected to junction A which in turn is connected in parallel to -first and second current sources IM and I ⁇ .
  • the laser diode anode is connected to the current source IM through a switch MOD having a data input TxD which completes a path between the anode and the current source IM only during HIGH output frame periods of the laser.
  • Light emitted by the laser diode is monitored, preferably via a back facet of the laser diode, by a monitor diode connected to a bias voltage 8.
  • a current output of an anode B of the monitor diode is converted to a voltage by a transimpedance amplifier 9 which is connected to first and second control circuits 32, 31.
  • Each control circuit includes a comparator 12, 14, a flip-flop 16, 18, having clock inputs CL2 and CLl respectively, and a current integrator 20, 22.
  • the control loop 31 is connected to the constant current source I ⁇ , and the control loop 32 is connected to the other constant current source I .
  • switch MOD In operation, during the LOW training pulse, switch MOD is open so anode A is connected to only the pedestal current source I ⁇ . Current from the laser output anode B is converted to a voltage by the amplifier 9 and presented to the comparator 14. Upon being strobed by CLl by the flip-flop 18, the comparator puts out a HIGH or LOW pulse depending on whether or not the amplifier voltage is above or below the threshold VR/N. This pulse is utilize by the integrator 22 to either decrease or increase a value of I ⁇ so as to maintain the LOW power output of the laser constant and toggling about the dynamic reference established by VR/N.
  • switch MOD is closed so that the laser LASC anode A is connected to both the current source IM and I ⁇ .
  • An output of the laser LASC is monitored by the monitor diode, and a current from its anode B is again converted to a voltage by the amplifier 9 and presented to the comparators 12, 14.
  • the flip-flop 16 Upon being strobed by CL2, the flip-flop 16 causes the voltage at comparator 12 to be compared to the predetermined HIGH reference voltage VR, and the resultant comparison is inputted to the integrator 20 to adjust IM up or down to keep the HIGH laser output toggling about its reference value.
  • the reference voltages VR and VR N of the comparators 12, 14 readily result in a laser extinction ratio which is approximately equal to N.
  • the laser control circuit of the present invention is very easy to optimize and set prior to being used for transmitting information.
  • the reference voltages V r and V r /N are maintained in a fixed ratio by being connected to a voltage divider network, i.e. a pair of resistors in series, as is well understood in the art, and accordingly by simply adjusting an input voltage to the voltage divider network one can easily adjust both the LOW power output and the HIGH power output of the laser simultaneously without varying the laser extinction ratio.
  • the laser output can be optimized so as to achieve the desired extinction ratio N.
  • Prior art lasers typically require multiple adjustments for setting a bias power and a HIGH power.
  • An example of a preferred voltage divider network is illustrated in FIG 5B by resistors R96, R97 which form a voltage divider network for reference voltages inputted to comparators 12, 14.
  • FIG 4 shows one preferred embodiment of the switch MOD, the switch comprising first and second transistors 40, 41, a current source IM being connected to their common anodes, and their cathodes being connected to the laser LASC being modulated, as shown.
  • transistor 41 is enabled so that the laser LASC is biased by the threshold current I ⁇ and the modulation current IM, and when a LOW pulse is to be generated by the laser LASC the transistor 41 is disabled so that the anode A of the laser is only connected to the pedestal current I ⁇ .
  • FIGs 5A and 5B illustrate a detailed preferred electrical schematic of a circuit according to the invention.
  • elements in FIG 5A and 5B which perform the functions referred to in FIG 3 are identified by identical reference symbols in each of these figures.
  • a voltage converter 50 is provided for converting the TxD voltages from +5V and 0V to 0V and -5V respectively. These converted voltages are then inputted to the switch MOD which selectively connects the laser anode with the constant current IM as described during HIGH periods.
  • An output B of the monitor laser is connected to the transimpedance amplifier 9 which is then connected to first and second feedback paths 32, 31 each having a comparator, flip-flop, and integrator, as previously described.
  • Feedback loop 31 which includes the comparator 14, flip-flop 18, and integrator 22, controls the pedestal current I ⁇ , and the comparator 12, flip-flop 16, and integrator 20 of the feedback loop 32 control the modulation current IM- AS is evident by examining FIG 5B, N equals the resistance of R96 divided by the resistance of R97.
  • FIG 6 illustrates a preferred use for the invention, this figure showing a host digital terminal 71 connected to a plurality of optical network units 72 via at least one optical fiber 73 which preferably transports bidirectional traffic.
  • a splitter/combiner 74 splits a signal originating from the host digital terminal from the fiber 73 to a plurality of additional fibers 75 for transmission to each optical network unit, and conversely signals from each optical network unit 72 are combined at the point 74 so as to be transported to the host digital terminal via the fiber 73.
  • high receiver sensitivity for each optical network unit is enhanced by maintaining an extinction ratio of a laser transmitting from the host digital terminal at a relatively high level, preferably above 10.

Abstract

Un circuit de régulation du rapport d'extinction d'un laser dont la température peut changer dans le temps comprend des première et seconde boucles de retour contrôlant une puissance de sortie BASSE du laser pendant une première impulsion de formation de séquence, et une puissance de sortie de laser HAUTE pendant une seconde impulsion de formation de séquence. La sortie de puissance BASSE est comparée à une référence de puissance BASSE dynamique prédéterminée, et un courant de polarisation BASSE appliqué au laser est augmenté ou diminué de façon incrémentielle afin de maintenir cette sortie de puissance BASSE autour de cette référence BASSE. De même, la sortie de puissance HAUTE est comparée à une référence de puissance HAUTE, et un courant de modulation destiné au laser est augmenté ou diminué de façon incrémentielle afin de maintenir la puissance de sortie du laser HAUTE autour de cette référence HAUTE. L'impulsion de formation est de préférence transmise une fois par séquence, permettant ainsi aux deux sorties de puissance du laser BASSE et HAUTE d'être maintenues constantes indépendamment des changements possibles des variables dynamiques dans le temps, maintenant ainsi constant le rapport d'extinction du laser.
PCT/US1992/011157 1991-12-20 1992-12-21 Appareil et procede de regulation du rapport d'extinction d'une diode laser en fonction de la temperature WO1993013577A1 (fr)

Priority Applications (7)

Application Number Priority Date Filing Date Title
AU34186/93A AU672188B2 (en) 1991-12-20 1992-12-21 Apparatus and method for controlling an extinction ratio of a laser diode over temperature
KR1019940702062A KR940704073A (ko) 1991-12-20 1992-12-21 온도에 대한 레이저 다이오드의 소광비를 제어하기 위한 장치 및 방법(apparatus and method for controlling an extinction ratio of a laser diode over temperature)
JP5511863A JPH07502627A (ja) 1991-12-20 1992-12-21 半導体レーザの吸光比を時間に対して制御する装置と方法
PCT/US1992/011157 WO1993013577A1 (fr) 1991-12-20 1992-12-21 Appareil et procede de regulation du rapport d'extinction d'une diode laser en fonction de la temperature
DE69224534T DE69224534T2 (de) 1991-12-20 1992-12-21 Vorrichtung und verfahren zur steuerung der temperaturabhängigkeit des ein/aus-verhältnisses einer laserdiode
EP93902712A EP0617852B1 (fr) 1991-12-20 1992-12-21 Appareil et procede de regulation du rapport d'extinction d'une diode laser en fonction de la temperature
US08/244,983 US5502298A (en) 1992-12-21 1992-12-21 Apparatus and method for controlling an extinction ratio of a laser diode over temperature

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US81119791A 1991-12-20 1991-12-20
US07/811,197 1991-12-20
PCT/US1992/011157 WO1993013577A1 (fr) 1991-12-20 1992-12-21 Appareil et procede de regulation du rapport d'extinction d'une diode laser en fonction de la temperature

Publications (1)

Publication Number Publication Date
WO1993013577A1 true WO1993013577A1 (fr) 1993-07-08

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000004655A1 (fr) * 1998-07-15 2000-01-27 Maxim Integrated Products, Inc. Controle local pour emetteurs optiques en mode rafale
GB2397689B (en) * 2003-01-10 2007-02-28 Agilent Technologies Inc Calibration of laser systems
WO2007059258A1 (fr) * 2005-11-21 2007-05-24 Intel, Corporation Régulation de la puissance optique et du rapport d'extinction d'un laser a semi-conducteur
US7400662B2 (en) 2005-01-26 2008-07-15 Avago Technologies Fiber Ip Pte Ltd Calibration of laser systems
US7869478B2 (en) 2005-12-12 2011-01-11 Electronics And Telecommunications Research Institute Apparatus and method for maintaining constant extinction ratio of laser diode
GB2541291A (en) * 2016-07-08 2017-02-15 Hilight Semiconductor Ltd Laser power controller
US10749605B2 (en) 2016-07-08 2020-08-18 Hilight Semiconductor Limited Laser power controller

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US4985896A (en) * 1985-03-29 1991-01-15 Canon Kabushiki Kaisha Laser driving device
US4995105A (en) * 1989-09-18 1991-02-19 Xerox Corporation Adaptive laser diode driver circuit for laser scanners
EP0428016A2 (fr) * 1989-11-13 1991-05-22 Siemens Aktiengesellschaft Commande de courant de modulation pour diodes laser
US5036189A (en) * 1990-04-03 1991-07-30 Raynet Corporation Thermal control for laser diode used in outside plant communications terminal

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4985896A (en) * 1985-03-29 1991-01-15 Canon Kabushiki Kaisha Laser driving device
US4995105A (en) * 1989-09-18 1991-02-19 Xerox Corporation Adaptive laser diode driver circuit for laser scanners
EP0428016A2 (fr) * 1989-11-13 1991-05-22 Siemens Aktiengesellschaft Commande de courant de modulation pour diodes laser
US5036189A (en) * 1990-04-03 1991-07-30 Raynet Corporation Thermal control for laser diode used in outside plant communications terminal

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Title
PATENT ABSTRACTS OF JAPAN vol. 1, no. 213 (E-422)25 July 1986 & JP,A,61 052 042 ( HITACHI LTD ) *
PATENT ABSTRACTS OF JAPAN vol. 13, no. 109 (E-727)15 March 1989 & JP,A,63 280 482 ( NEC CORP ) *
PATENT ABSTRACTS OF JAPAN vol. 8, no. 167 (E-258)2 August 1984 & JP,A,59 063 787 ( FUJITSU KK ) *

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000004655A1 (fr) * 1998-07-15 2000-01-27 Maxim Integrated Products, Inc. Controle local pour emetteurs optiques en mode rafale
US6188498B1 (en) * 1998-07-15 2001-02-13 Maxim Integrated Products, Inc. Local control for burst mode optical transmitters
GB2397689B (en) * 2003-01-10 2007-02-28 Agilent Technologies Inc Calibration of laser systems
US7400662B2 (en) 2005-01-26 2008-07-15 Avago Technologies Fiber Ip Pte Ltd Calibration of laser systems
WO2007059258A1 (fr) * 2005-11-21 2007-05-24 Intel, Corporation Régulation de la puissance optique et du rapport d'extinction d'un laser a semi-conducteur
GB2445513A (en) * 2005-11-21 2008-07-09 Intel Corp Controlling optical power and extincation ratio of a semiconductor laser
US7869478B2 (en) 2005-12-12 2011-01-11 Electronics And Telecommunications Research Institute Apparatus and method for maintaining constant extinction ratio of laser diode
GB2541291A (en) * 2016-07-08 2017-02-15 Hilight Semiconductor Ltd Laser power controller
GB2541291B (en) * 2016-07-08 2018-06-20 Hilight Semiconductor Ltd Laser power controller
US10205532B2 (en) 2016-07-08 2019-02-12 Hilight Semiconductor Limited Laser power controller
US10749605B2 (en) 2016-07-08 2020-08-18 Hilight Semiconductor Limited Laser power controller

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