WO2020008566A1 - Laser diode drive device and optical transmitter - Google Patents

Laser diode drive device and optical transmitter Download PDF

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Publication number
WO2020008566A1
WO2020008566A1 PCT/JP2018/025371 JP2018025371W WO2020008566A1 WO 2020008566 A1 WO2020008566 A1 WO 2020008566A1 JP 2018025371 W JP2018025371 W JP 2018025371W WO 2020008566 A1 WO2020008566 A1 WO 2020008566A1
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Prior art keywords
temperature
current
laser diode
tracking error
bias current
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PCT/JP2018/025371
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French (fr)
Japanese (ja)
Inventor
菜々子 洞山
聡 吉間
啓祐 江草
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三菱電機株式会社
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Priority to PCT/JP2018/025371 priority Critical patent/WO2020008566A1/en
Publication of WO2020008566A1 publication Critical patent/WO2020008566A1/en

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    • 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

Definitions

  • the present invention relates to a laser diode driving device and an optical transmitter.
  • a laser diode (LD: Laser Diode) that generates an optical signal is driven by a drive current that is the sum of a bias current and a modulation current.
  • the power that is, the intensity of the optical signal is determined by the bias current, and the optical signal is extinguished by the modulation current.
  • the ratio is determined.
  • the drive current is adjusted based on the result of monitoring the temperature. (For example, Patent Document 1).
  • the present invention has been made in view of the above, and provides a laser diode driving device capable of maintaining the power and the extinction ratio of an optical signal emitted by an LD at target values even when the temperature of the LD changes.
  • the purpose is to gain.
  • a temperature sensor for detecting a temperature of the laser diode and an intensity of an optical signal output from the laser diode are predetermined.
  • An optical output control unit that generates a bias current to be supplied to the laser diode so as to have a first value; and a laser so that the extinction ratio of the optical signal has a predetermined second value when there is no tracking error.
  • a modulation current generator that generates a modulation current to be supplied to the diode based on the temperature detected by the temperature sensor.
  • the driving device of the laser diode is based on the temperature detected by the temperature sensor and the output characteristic data indicating the correspondence between the value of the driving current, which is the current supplied to the laser diode, and the intensity of the optical signal.
  • a tracking error compensator for calculating a bias current correction amount used for bias current correction performed for compensating for a tracking error, and correcting a modulation current for compensating for a tracking error, and a bias based on the correction amount.
  • a bias current control unit for correcting the current.
  • the laser diode driving device has an effect that the power and the extinction ratio of the optical signal emitted from the laser diode can be maintained at target values even when the temperature of the laser diode changes.
  • FIG. 1 is a diagram illustrating a configuration example of an optical transmitter according to an embodiment of the present invention.
  • FIG. 2 is a diagram showing an example of current-light output characteristics (PI characteristics) of the laser diode shown in FIG.
  • FIG. 2 is a diagram illustrating an example of a PI characteristic indicated by data held in an output characteristic data storage unit illustrated in FIG.
  • FIG. 4 is a diagram showing an image of an Imod correction value calculation performed by the TE compensator shown in FIG. 1.
  • FIG. 2 is a diagram illustrating a configuration example of hardware for realizing the laser diode driving device
  • FIG. 1 is a diagram illustrating a configuration example of an optical transmitter according to an embodiment of the present invention.
  • the optical transmitter 100 includes a laser diode (LD) 1 that outputs an optical signal, and a laser diode driving device 20 that generates a drive current for the LD 1.
  • LD laser diode
  • the laser diode driving device 20 is referred to as an LD driving device 20.
  • the LD drive device 20 includes a photodiode (PD) 2, a temperature sensor 3, a tracking error (TE: tracking error) compensator 4, a current adjustment value calculator 5, a bias current controller 6, and a modulation current controller. It includes a unit 7, an optical output control unit 8, an output characteristic data storage unit 9, a modulation characteristic data storage unit 10, and a compensation data storage unit 11.
  • the LD 1 is driven by a driving current supplied from the LD driving device 20 and emits light.
  • the drive current supplied to the LD 1 is the sum of the current output from the bias current control unit 6 and the current output from the modulation current control unit 7.
  • the current output from the bias current control unit 6 is the bias current supplied to the LD1
  • the current output from the modulation current control unit 7 is the modulation current supplied to the LD1.
  • the LD driving device 20 causes the LD 1 to generate an optical signal by changing the modulation current supplied from the modulation current control unit 7 to the LD 1 and changing the intensity of light emitted by the LD 1 according to the value of the modulation current.
  • the LD 1 outputs light having a power corresponding to the value of the drive current from each of the front surface and the rear surface.
  • light output from the front surface of the LD 1 is referred to as front light
  • light output from the rear surface is referred to as back light.
  • the PD2 is installed at a position capable of receiving the light emitted from the LD1, converts the light received from the LD1 into a current, and outputs the current.
  • the current output from PD2 is referred to as a monitor PD current. Further, in the present embodiment, it is assumed that PD2 is installed at a position where the back light of LD1 can be received.
  • the temperature sensor 3 is installed inside the optical transmitter 100 and detects the temperature of the LD 1 in the optical transmitter 100. This is because the LD 1 has a temperature characteristic (hereinafter, referred to as PI characteristic) in which the light emission amount changes depending on the temperature. The PI characteristics of LD1 will be described later. Therefore, the temperature sensor 3 is provided for the purpose of grasping the temperature of the LD 1 in the optical transmitter 100.
  • the installation position of the temperature sensor 3 may be a position for detecting the temperature around the LD 1.
  • the TE compensator 4 holds temperature information obtained from the temperature sensor 3, a bias current adjustment value and a modulation current adjustment value, which will be described later, obtained from the current adjustment value calculator 5, and a compensation data storage unit 11.
  • the bias current correction amount and the modulation current correction value are calculated using a temperature function described later.
  • the bias current correction amount is a correction amount of the bias current in a correction process performed to compensate for TE.
  • the modulation current correction value is a modulation current after performing correction for compensating for TE.
  • the calculation method of the bias current correction amount and the modulation current correction value will be described later.
  • the bias current adjustment value is called an Ibias adjustment value
  • the modulation current adjustment value is called an Imod adjustment value.
  • the current adjustment value calculator 5 derives Ibias (T) and Imod (T), which are temperature functions representing modulation characteristics corresponding to the temperature T detected by the temperature sensor 3.
  • the temperature function Ibias (T) is a function for obtaining a bias current from the temperature of the LD1
  • the temperature function Imod (T) is a function for obtaining a modulation current from the temperature of the LD1.
  • the current adjustment value calculation unit 5 uses the derived Ibias (T) and Imod (T) to calculate the Ibias adjustment value corresponding to the temperature T, which satisfies the target optical output power in the absence of TE, If not, an Imod adjustment value corresponding to the temperature T that satisfies the target extinction ratio is calculated.
  • a method for deriving Ibias (T) and Imod (T) and a method for calculating the Ibias adjustment value and the Imod adjustment value will be described later.
  • the bias current control unit 6 adds an Ibias correction amount, which is a bias current correction amount output by the TE compensation unit 4, to a bias current Ibias, which is a bias current before correction output by an optical output control unit 8 described later. To correct the bias current.
  • the bias current control unit 6 outputs a bias current correction value (Ibias correction value), which is the corrected bias current, to the LD 1.
  • the modulation current control unit 7 receives the corrected modulation current, which is the Imod correction value output from the TE compensation unit 4, and outputs it to the LD 1.
  • the optical output control unit 8 is an APC circuit that performs an APC operation for maintaining the optical output power of the LD 1 at a target value that is a predetermined first value, and outputs a bias current Ibias output to the bias current control unit 6. Generate. Specifically, the light output control unit 8 adjusts Ibias based on the monitor PD current output from the PD2 and indicating the light output power of the LD1, such that the monitor PD current value becomes a predetermined value. That is, the light output control unit 8 generates Ibias to be output to the bias current control unit 6 based on the power of the light output from the LD 1.
  • the output characteristic data storage unit 9 stores the data indicating the PI characteristic of the LD 1 acquired when the temperature T detected by the temperature sensor 3 is the normal temperature, that is, the first temperature, and the temperature T detected by the temperature sensor 3 is the first temperature. Data indicating the PI characteristic of the LD 1 acquired when the temperature is the second temperature higher than the temperature is held.
  • the data indicating the PI characteristics obtained at room temperature is data indicating the PI characteristics when the LD 1 is at room temperature
  • the data indicating the PI characteristics obtained at a high temperature is data indicating the PI characteristics when the LD 1 is at a high temperature.
  • “normal temperature” is a reference temperature for controlling the bias current and the modulation current of the LD 1 and is a predetermined temperature.
  • the data indicating the PI characteristic held by the output characteristic data storage unit 9 is output characteristic data indicating the relationship between the value of the current supplied to the LD 1 and the optical output power of the LD 1.
  • the modulation characteristic data storage unit 10 holds data indicating the modulation characteristic when the temperature T detected by the temperature sensor 3 is at room temperature, and data indicating the modulation characteristic when the temperature T detected by the temperature sensor 3 is high. .
  • the data indicating the modulation characteristic is data indicating an Ibias value and an Imod value such that a target optical output power and an extinction ratio are obtained at each temperature.
  • the Ibias value and Imod value at normal temperature and the Ibias value and Imod value at high temperature held by the modulation characteristic data storage unit 10 are obtained by actually operating the optical transmitter 100 at normal temperature and at high temperature, respectively. This is the actual measurement value.
  • the compensation data storage unit 11 holds a temperature function of the TE amount used when the TE compensating unit 4 calculates the TE amount at each temperature.
  • the temperature function of the TE amount may be described as ⁇ Pmon (T).
  • the PD 2 receives the back light of the LD 1, converts the received light power into a monitor PD current, and outputs it to the optical output control unit 8.
  • the light output controller 8 controls the bias current Ibias output to the bias current controller 6 so that the monitor PD current input from the PD 2 has a predetermined value.
  • the bias current control unit 6 adds a bias current correction amount (Ibias correction amount) for TE compensation calculated by the TE compensation unit 4 to the bias current Ibias input from the optical output control unit 8. Is supplied to the LD 1 as a bias current correction value.
  • the LD driving device 20 controls the bias current supplied to the LD 1 so as to obtain the target optical output power.
  • the TE compensator 4 calculates the Ibias correction amount using the temperature information from the temperature sensor 3 and the temperature function of the TE amount stored in the compensation data storage unit 11.
  • the current adjustment value calculation unit 5 outputs the modulation current supplied to the LD 1 to the LD 1 so that the extinction ratio of the optical signal generated by the LD 1 becomes a target value that is a predetermined second value when there is no TE.
  • This is a modulation current generator that generates based on temperature.
  • the current adjustment value calculation unit 5 calculates a modulation current adjustment value that satisfies the target extinction ratio in the absence of TE by using the temperature information detected by the temperature sensor 3 and the output characteristic data storage unit 9. The calculation is performed based on the held data indicating the PI characteristic and the data indicating the modulation characteristic held in the modulation characteristic data storage unit 10.
  • the current adjustment value calculation unit 5 When calculating the modulation current adjustment value when there is no TE, the current adjustment value calculation unit 5 outputs this to the TE compensation unit 4. Similarly to the bias current correction amount, the TE compensation unit 4 calculates the modulation current correction amount for TE compensation for the modulation current, and applies the calculated correction amount to the modulation current adjustment value input from the current adjustment value calculation unit 5. The modulation current correction value is calculated by adding to the value. Then, the TE compensating unit 4 outputs the calculated modulation current correction value to the modulation current control unit 7, and the modulation current control unit 7 supplies a modulation current corresponding to the modulation current correction value to the LD 1, thereby setting the target extinction ratio. Control to obtain
  • the LD driving device 20 performs correction for TE compensation on each of the bias current and the modulation current. Thereby, the LD drive device 20 can control the drive current supplied to the LD 1 so as to obtain the target extinction ratio while securing the target light output power.
  • the output characteristic data storage unit 9 is a memory in which data indicating PI characteristics acquired in advance at two temperatures (normal temperature and high temperature) is stored. As described above, the data indicating the PI characteristic indicates the relationship between the drive current of the LD 1 and the optical output power, and indicates the amount of the optical output power when the drive current is supplied to the LD 1. In the following description, the light output power may be referred to as the monitor PD light receiving power.
  • FIG. 2 is a diagram showing an example of a current-light output characteristic (PI characteristic) of the LD 1 shown in FIG. 2, the horizontal axis indicates the LD drive current I, and the vertical axis indicates the monitor PD light receiving power P.
  • the modulation current is the difference between the LD drive current Iop (1) at P (1) and the LD drive current Iop (0) at P (0), and the light intensity ratio between P (1) and P (0). Is determined.
  • FIG. 3 is a diagram illustrating an example of a PI characteristic indicated by data held in the output characteristic data storage unit 9 illustrated in FIG. 3, the horizontal axis represents the LD drive current I, and the vertical axis represents the monitor PD light receiving power P.
  • the luminous efficiency of the laser diode decreases as the temperature increases, and the LD 1 has the same characteristics. Therefore, when the LD 1 emits light at the same optical power at high temperature and at room temperature, the LD 1 has a temperature characteristic that a larger drive current is required at high temperature than at room temperature. Therefore, the PI characteristics differ depending on the temperature as shown in FIG.
  • the modulation characteristic data storage unit 10 is a memory that stores data indicating modulation characteristics at two temperatures (normal temperature and high temperature).
  • the current adjustment value calculation unit 5 calculates the Ibias adjustment value and the Imod adjustment value corresponding to each temperature T that satisfy the target optical output power and the extinction ratio when there is no TE.
  • the current adjustment value calculator 5 uses the temperature functions Ibias (T) and Imod (T), which are the temperature functions representing the modulation characteristics corresponding to each temperature T, in the calculation process of the Ibias adjustment value and the Imod adjustment value. It is assumed that the current adjustment value calculation unit 5 holds temperature functions Ibias (T) and Imod (T) derived in advance by the following method.
  • a method for deriving the temperature functions Ibias (T) and Imod (T) will be described in detail.
  • the description will be given assuming that the current adjustment value calculation unit 5 derives each temperature function, but other than the current adjustment value calculation unit 5 may derive. If one temperature function is derived from the data at two temperatures, that is, normal temperature and high temperature, the error on the low temperature side may increase because the data on the low temperature side lower than the normal temperature is not used. Therefore, different temperature functions are derived and used on the high temperature side and the low temperature side higher than the normal temperature.
  • the current adjustment value calculation unit 5 first determines the LD threshold current Ith1 at normal temperature and the LD threshold current at high temperature in the two-temperature (normal temperature, high temperature) PI characteristics stored in the output characteristic data storage unit 9.
  • the temperature function Ith (T) of the LD threshold current is calculated by exponential function approximation using the two data of the threshold current Ith2.
  • the LD threshold current Ith1 is a driving current at which the LD1 starts emitting light at normal temperature
  • the LD threshold current Ith2 is a driving current at which the LD1 starts emitting light at high temperature.
  • the current adjustment value calculation unit 5 determines the luminous efficiency ⁇ 1 at normal temperature and the luminous efficiency ⁇ 2 at high temperature, indicating the slope of the PI characteristic, the LD threshold current Ith1 at normal temperature, and the LD at high temperature. Using the threshold current Ith2, constants ⁇ and ⁇ required for deriving the temperature functions Ibias (T) and Imod (T) are obtained according to the equations (1) and (2). Further, the current adjustment value calculation unit 5 obtains the temperature function ⁇ (T) of the luminous efficiency in the PI characteristic according to the equation (3).
  • the current adjustment value calculation unit 5 uses the constants ⁇ and ⁇ , Imods shown in Expression (4), and K shown in Expression (5), and obtains Ibias at normal temperature according to Expression (6). A calculated value is obtained, and an Imod calculated value at normal temperature is obtained according to the equation (7).
  • ER is the extinction ratio
  • Pmon is the monitor PD received power. ER and Pmon are provisional values and set appropriately.
  • Imods ⁇ 2 ⁇ Pmon ⁇ (ER ⁇ 1) ⁇ ⁇ / (ER + 1)
  • K ⁇ 2 ⁇ Pmon ⁇ (ER ⁇ 1) ⁇ ⁇ / (ER + 1)
  • Imod calculated value at normal temperature Imods + K ⁇ Ith1 (7)
  • the current adjustment value calculation unit 5 minimizes the error between the Ibias calculated value obtained in the procedure # 3 and the Ibias value at normal temperature stored in the modulation characteristic data storage unit 10,
  • the monitor PD received light power Pmon 'and the extinction ratio ER' are set so that the error between the Imod calculated value obtained in step # 3 and the Imod value at normal temperature stored in the modulation characteristic data storage unit 10 is minimized. Is calculated by the least squares method.
  • the current adjustment value calculation unit 5 updates the values of Imods and K by substituting the Pmon ′ and ER ′ obtained in the procedure # 4 into the above equations (4) and (5). I do.
  • the updated values are Imods 'and K', respectively.
  • the current adjustment value calculator 5 derives the temperature function Ibias (T) according to the equation (8) using the Imods ′ and K ′ obtained in the procedure # 5, and also obtains the equation (9) ) To derive a temperature function Imod (T).
  • Ibias (T) Ith (T) + Pmon '/ ⁇ (T) (8)
  • Imod (T) Imods '+ K' ⁇ Ith (T) (9)
  • the current adjustment value calculation unit 5 uses the data of two points of the Ibias actual measurement value at normal temperature and the Ibias actual measurement value at high temperature held in the modulation characteristic data storage unit 10 to calculate the temperature function on the high temperature side by exponential function approximation. Derive Ibias (T). Similarly, the current adjustment value calculation unit 5 performs exponential function approximation using data of two points of the Imod actual measurement value at normal temperature and the Imod actual measurement value at high temperature held in the modulation characteristic data storage unit 10, Is derived from the temperature function Imod (T).
  • FIG. 4 is a diagram showing an example of the temperature function Ibias (T) on the high temperature side
  • FIG. 5 is a diagram showing an example of the temperature function Imod (T) on the high temperature side.
  • the temperature function Ibias (T) shown in FIG. 4 is a measured value of the bias current (Ibias) supplied to the LD1 when the temperature of the LD1 is room temperature (T1), and the temperature function Ibias (T) when the temperature of the LD1 is high temperature (T2). It is derived using the measured value of the bias current supplied to the LD 1.
  • Ibias (T) A ⁇ Exp (B ⁇ T) (10)
  • Imod (T) C ⁇ Exp (D ⁇ T) (11)
  • the current adjustment value calculation unit 5 adjusts the adjustment value of the bias current and the modulation current using the acquired temperature information and the temperature functions Ibias (T) and Imod (T). Calculate the value.
  • the current adjustment value calculation unit 5 uses the temperature functions Ibias (T) and Imod (T) on the low temperature side to obtain the acquired temperature information. Is higher than the normal temperature, that is, the temperature functions Ibias (T) and Imod (T) on the high temperature side are used.
  • the compensation data storage unit 11 is a memory that holds a temperature function ⁇ Pmon (T) of the TE amount for the TE compensation unit 4 to calculate the TE amount at each temperature.
  • the temperature function ⁇ Pmon (T) of the TE amount indicates the correspondence between the temperature of the LD 1 and the TE amount.
  • the temperature function ⁇ Pmon (T) of the TE amount is an upwardly convex quadratic function representing the TE amount, which is derived from the TE amount data at two temperatures of low temperature and high temperature when the TE amount is set to 0 at normal temperature. .
  • the bias current and the modulation current are adjusted so that the target optical power and the target extinction ratio are obtained and the TE amount becomes 0 while the LD 1 is at room temperature. adjust.
  • the temperature of the LD 1 is changed to a low temperature side (a temperature lower than the normal temperature) and a high temperature side (a temperature higher than the normal temperature) to change the TE amount at the low temperature and the TE amount at the high temperature.
  • a temperature function ⁇ Pmon (T) of the TE amount is derived using the TE amount at a low temperature and the TE amount at a high temperature.
  • the temperature function ⁇ Pmon (T) of the TE amount can be expressed by Expression (12), and is a function indicating the relationship between the temperature of the LD 1 and the TE amount as shown in FIG.
  • a, b, and c are coefficients
  • T is temperature.
  • FIG. 6 is a diagram showing an example of the temperature function ⁇ Pmon (T) held by the compensation data storage unit 11 shown in FIG.
  • the TE compensator 4 derives the temperature function ⁇ Pmon (T) of the TE amount, for example. It may be derived by means other than the TE compensator 4.
  • ⁇ Pmon (T) a ⁇ T ⁇ 2 + b ⁇ T + c (12)
  • the TE compensator 4 calculates a correction amount of the current adjustment value for TE compensation.
  • the TE compensator 4 calculates a correction amount used in correcting the bias current for the bias current, and calculates an Imod correction value in which the correction amount is reflected on the Imod adjustment value for the modulation current.
  • the bias current is corrected by the bias current control unit 6.
  • the TE compensating unit 4 holds the temperature information obtained from the temperature sensor 3, the bias current adjustment value and the modulation current adjustment value calculated by the current adjustment value calculation unit 5, and the compensation data storage unit 11.
  • the correction amount of the bias current and the Imod correction value are calculated using the temperature function ⁇ Pmon (T) of the TE amount.
  • T temperature function
  • the TE compensating unit 4 firstly converts the TE amount corresponding to the temperature indicated by the temperature information acquired from the temperature sensor 3 into a temperature function ⁇ Pmon (T ).
  • T the temperature indicated by the temperature information acquired by the TE compensator 4 from the temperature sensor 3
  • Tx the temperature indicated by the temperature information acquired by the TE compensator 4 from the temperature sensor 3
  • Tx the TE amount obtained by the TE compensator 4
  • the TE compensator 4 uses the TE amount ⁇ Pmon (Tx) obtained in Procedure # 1 and the temperature function ⁇ (T) of the luminous efficiency in the PI characteristic to perform TE compensation.
  • the correction amount ⁇ Ibias (Tx) of the bias current is calculated according to equation (13).
  • the temperature function ⁇ (T) of the luminous efficiency in the PI characteristic is a function represented by the above equation (3).
  • the TE compensating unit 4 previously derives and holds the temperature function ⁇ (T) in the same manner as the case where the current adjustment value calculating unit 5 derives the temperature functions Ibias (T) and Imod (T) on the low temperature side. deep.
  • the TE compensator 4 may receive the temperature function ⁇ (T) derived by the current adjustment value calculator 5 from the current adjustment value calculator 5 and hold the temperature function ⁇ (T).
  • the TE compensating unit 4 may obtain the luminous efficiency value ⁇ (Tx) calculated using the temperature function ⁇ (T) when the temperature is Tx from the current adjustment value calculating unit 5.
  • the TE compensator 4 outputs the obtained correction amount ⁇ Ibias (Tx) to the bias current controller 6.
  • ⁇ Ibias (Tx) ⁇ Pmon (Tx) / ⁇ (Tx) (13)
  • FIG. 7 is a diagram showing an image of an Imod correction value calculation performed by the TE compensating unit 4 shown in FIG.
  • the Imod correction value at the temperature Tx is obtained by adding the Imod correction amount at the temperature Tx to the Imod adjustment value at the temperature Tx.
  • the TE compensator 4 outputs the obtained Imod correction value to the modulation current controller 7.
  • Imod correction value (Tx) Imod (Tx) + ⁇ Imod (Tx) (15)
  • the TE compensator 4 calculates the correction amount of the bias current for TE compensation based on the temperature of the LD 1 indicated by the temperature information obtained from the temperature sensor 3 and the luminous efficiency of the LD 1, and , A correction amount for the TE compensation of the modulation current Imod is calculated based on the bias current correction amount for the TE compensation, and the modulation current is corrected to compensate for the TE.
  • the bias current controller 6 outputs the generated Ibias correction value (T) to the LD 1. Thereby, control of the bias current that satisfies the target optical output power can be realized.
  • the modulation current control unit 7 outputs an Imod correction value (T), which is a correction value of the modulation current for TE compensation obtained from the TE compensation unit 4, to the LD 1. Thereby, control of the modulation current that satisfies the target extinction ratio can be realized.
  • T an Imod correction value
  • the output characteristic data storage unit 9, the modulation characteristic data storage unit 10, and the compensation data storage unit 11 of the LD driving device 20 are realized by a memory.
  • the TE compensating unit 4, the current adjustment value calculating unit 5, the bias current control unit 6, and the modulation current control unit 7 of the LD driving device 20 are configured by processing circuits that realize the functions of these units.
  • the processing circuit is, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a dedicated combination of these. It may be hardware or a processor 201 and a memory 202 as shown in FIG.
  • the processor 201 shown in FIG. 8 is a CPU (Central Processing Unit), a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a DSP (Digital Signal Processor), or the like.
  • the memory 202 is a non-volatile or volatile semiconductor memory such as a random access memory (RAM), a read only memory (ROM), and a flash memory.
  • the TE compensating unit 4, the current adjustment value calculating unit 5, the bias current control unit 6, and the modulation current control unit 7 of the LD driving device 20 store programs for operating as these units in the memory 202, and Is read out from the memory 202 by the processor 201 and executed.
  • a part of the TE compensator 4, the current adjustment value calculator 5, the bias current controller 6, and the modulation current controller 7 of the LD driving device 20 is realized by the processor 201 and the memory 202, and the rest is realized by dedicated hardware. You may.
  • the current adjustment value calculator 5, the bias current controller 6, and the modulation current controller 7 of the LD driving device 20 are realized by the processor 201 and the memory 202 shown in FIG.
  • the characteristic data storage unit 9, the modulation characteristic data storage unit 10, and the compensation data storage unit 11 may be realized by the memory 202.
  • the light output control unit 8 generates the bias current at which the power of the light output from the LD 1 becomes the target value.
  • the current adjustment value calculation unit 5 generates a modulation current based on the temperature of the LD 1 so as to obtain a target extinction ratio when there is no tracking error.
  • the TE compensator 4 calculates a tracking error generation amount based on the temperature of the LD 1 and the luminous efficiency when the LD 1 is at room temperature and high temperature, and calculates a bias current correction amount based on the calculated tracking error generation amount. In addition to the calculation, a correction for compensating for the tracking error is performed on the modulation current.
  • the bias current control unit 6 performs correction for compensating for a tracking error on the bias current based on the correction amount of the bias current, and supplies the corrected bias current to the LD 1.
  • the modulation current controller 7 supplies the corrected modulation current output from the TE compensator 4 to the LD 1.
  • the LD driving device 20 can set the power and the extinction ratio of the optical signal generated by the LD 1 to target values even when the temperature of the LD 1 changes. That is, the optical transmitter 100 according to the present embodiment can generate an optical signal having the target power and the extinction ratio even when the temperature of the LD 1 changes.

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Abstract

A laser diode drive device (20), comprising: a temperature sensor (3) for detecting the temperature of a laser diode (1); an optical output control unit (8) for generating a bias current fed to the laser diode so that the intensity of an optical signal outputted by the laser diode assumes a first value defined in advance; a current adjustment value computation unit (5) for generating, on the basis of the detected temperature, a modulation current to be fed to the laser diode, so that the extinction ratio of the optical signal when no tracking error is present assumes a second value defined in advance; a tracking error compensation unit (4) for calculating a correction amount used in correction of the bias current, which is performed in order to compensate for tracking error, on the basis of the detected temperature and output characteristic data indicating the correlation between the intensity of the optical signal and the value of a drive current, which is a current fed to the laser diode, and for correcting the modulation current to compensate for the tracking error; and a bias current control unit (6) for correcting the bias current.

Description

レーザダイオードの駆動装置および光送信器Drive device for laser diode and optical transmitter
　本発明は、レーザダイオードの駆動装置および光送信器に関する。 The present invention relates to a laser diode driving device and an optical transmitter.
　光信号を生成するレーザダイオード（ＬＤ：Laser　Diode）は、バイアス電流と変調電流の和からなる駆動電流により駆動され、バイアス電流によって光信号のパワーすなわち強度が決定し、変調電流によって光信号の消光比が決定する。また、ＬＤに供給される駆動電流とＬＤが出力する光信号の強度との対応関係を示す電流―光出力特性は温度に依存して変化するため、温度のモニタ結果に基づいて駆動電流を調整する制御が行われている（例えば、特許文献１）。 A laser diode (LD: Laser Diode) that generates an optical signal is driven by a drive current that is the sum of a bias current and a modulation current. The power, that is, the intensity of the optical signal is determined by the bias current, and the optical signal is extinguished by the modulation current. The ratio is determined. In addition, since the current-optical output characteristic indicating the correspondence between the drive current supplied to the LD and the intensity of the optical signal output from the LD changes depending on the temperature, the drive current is adjusted based on the result of monitoring the temperature. (For example, Patent Document 1).
　特許文献１に記載の半導体レーザの駆動方法では、ＬＤが発する光信号を受光するフォトダイオード（ＰＤ：Photodiode）から出力されるモニタ電流を一定にするＡＰＣ（Automatic　Power　Control：自動パワー制御）を行うことにより、ＬＤが発する光信号の強度を一定に保持し、環境温度のモニタ値に基づいて変調電流を調整することにより、光信号の消光比が所望の値となるようにしている。 In the method of driving a semiconductor laser described in Patent Literature 1, APC (Automatic Power Control) that makes a monitor current output from a photodiode (PD) receiving an optical signal emitted from an LD constant is performed. Thus, the intensity of the optical signal emitted from the LD is kept constant, and the modulation current is adjusted based on the monitored value of the environmental temperature, so that the extinction ratio of the optical signal becomes a desired value.
特開２０１３－８８４３号公報JP 2013-8843 A
　特許文献１に記載の発明では、環境温度に基づいて変調電流を調整するため、環境温度が変化した場合でも所望の消光比を維持できる。しかしながら、光信号の強度である光出力パワーを制御するＡＰＣでは環境温度を考慮しないため、特許文献１に記載の発明では、環境温度が変化した場合、バイアス電流が適切な値からずれてしまい、ＬＤが発する光信号の光出力パワーが変動する現象であるトラッキングエラーが発生する、という問題があった。 In the invention described in Patent Document 1, since the modulation current is adjusted based on the environmental temperature, a desired extinction ratio can be maintained even when the environmental temperature changes. However, since the APC that controls the optical output power, which is the intensity of the optical signal, does not consider the environmental temperature, in the invention described in Patent Document 1, when the environmental temperature changes, the bias current deviates from an appropriate value, There has been a problem that a tracking error, which is a phenomenon in which the optical output power of the optical signal emitted by the LD fluctuates, occurs.
　本発明は、上記に鑑みてなされたものであって、ＬＤの温度が変化した場合でもＬＤが発する光信号のパワーおよび消光比を目標の値に維持することが可能なレーザダイオードの駆動装置を得ることを目的とする。 The present invention has been made in view of the above, and provides a laser diode driving device capable of maintaining the power and the extinction ratio of an optical signal emitted by an LD at target values even when the temperature of the LD changes. The purpose is to gain.
　上述した課題を解決し、目的を達成するために、本発明にかかるレーザダイオードの駆動装置は、レーザダイオードの温度を検出する温度センサと、レーザダイオードが出力する光信号の強度が予め定められた第１の値となるよう、レーザダイオードに供給するバイアス電流を生成する光出力制御部と、トラッキングエラーが無い状態の時に光信号の消光比が予め定められた第２の値となるよう、レーザダイオードに供給する変調電流を温度センサで検出された温度に基づいて生成する変調電流生成部と、を備える。また、レーザダイオードの駆動装置は、温度センサで検出された温度と、レーザダイオードに供給される電流である駆動電流の値と光信号の強度との対応関係を示す出力特性データと、に基づいて、トラッキングエラーを補償するために行うバイアス電流の補正で使用するバイアス電流の補正量を算出するとともに、トラッキングエラーを補償するために変調電流を補正するトラッキングエラー補償部と、補正量に基づいてバイアス電流を補正するバイアス電流制御部と、を備える。 In order to solve the above-described problems and achieve the object, in a laser diode driving device according to the present invention, a temperature sensor for detecting a temperature of the laser diode and an intensity of an optical signal output from the laser diode are predetermined. An optical output control unit that generates a bias current to be supplied to the laser diode so as to have a first value; and a laser so that the extinction ratio of the optical signal has a predetermined second value when there is no tracking error. A modulation current generator that generates a modulation current to be supplied to the diode based on the temperature detected by the temperature sensor. Further, the driving device of the laser diode is based on the temperature detected by the temperature sensor and the output characteristic data indicating the correspondence between the value of the driving current, which is the current supplied to the laser diode, and the intensity of the optical signal. A tracking error compensator for calculating a bias current correction amount used for bias current correction performed for compensating for a tracking error, and correcting a modulation current for compensating for a tracking error, and a bias based on the correction amount. A bias current control unit for correcting the current.
　本発明にかかるレーザダイオードの駆動装置は、レーザダイオードの温度が変化した場合でも、レーザダイオードが発する光信号のパワーおよび消光比を目標の値に維持することができる、という効果を奏する。 The laser diode driving device according to the present invention has an effect that the power and the extinction ratio of the optical signal emitted from the laser diode can be maintained at target values even when the temperature of the laser diode changes.
本発明の実施の形態にかかる光送信器の構成例を示す図FIG. 1 is a diagram illustrating a configuration example of an optical transmitter according to an embodiment of the present invention. 図１に示すレーザダイオードの電流―光出力特性（ＰＩ特性）の一例を示す図FIG. 2 is a diagram showing an example of current-light output characteristics (PI characteristics) of the laser diode shown in FIG. 図１に示す出力特性データ記憶部が保持しているデータが示すＰＩ特性の一例を示す図FIG. 2 is a diagram illustrating an example of a PI characteristic indicated by data held in an output characteristic data storage unit illustrated in FIG. 図１に示す電流調整値演算部が使用する高温側の温度関数Ｉｂｉａｓ（Ｔ）の一例を示す図The figure which shows an example of the temperature function Ibias (T) of the high temperature side used by the current adjustment value calculation part shown in FIG. 図１に示す電流調整値演算部が使用する高温側の温度関数Ｉｍｏｄ（Ｔ）の一例を示す図The figure which shows an example of the temperature function Imod (T) of the high temperature side used by the current adjustment value calculation part shown in FIG. 図１に示す補償用データ記憶部が保持する温度関数ΔＰｍｏｎ（Ｔ）の一例を示す図The figure which shows an example of the temperature function (DELTA) Pmon (T) which the compensation data storage part shown in FIG. 1 hold | maintains. 図１に示すＴＥ補償部が行うＩｍｏｄ補正値計算のイメージを示す図FIG. 4 is a diagram showing an image of an Imod correction value calculation performed by the TE compensator shown in FIG. 1. 図１に示すレーザダイオードの駆動装置を実現するハードウェアの構成例を示す図FIG. 2 is a diagram illustrating a configuration example of hardware for realizing the laser diode driving device illustrated in FIG. 1.
　以下に、本発明の実施の形態にかかるレーザダイオードの駆動装置および光送信器を図面に基づいて詳細に説明する。なお、この実施の形態によりこの発明が限定されるものではない。 Hereinafter, a laser diode driving device and an optical transmitter according to an embodiment of the present invention will be described in detail with reference to the drawings. It should be noted that the present invention is not limited by the embodiment.
実施の形態．
　図１は、本発明の実施の形態にかかる光送信器の構成例を示す図である。光送信器１００は、光信号を出力するレーザダイオード（ＬＤ）１と、ＬＤ１の駆動電流を生成するレーザダイオードの駆動装置２０とを備える。以下、レーザダイオードの駆動装置２０をＬＤ駆動装置２０と記載する。 Embodiment.
FIG. 1 is a diagram illustrating a configuration example of an optical transmitter according to an embodiment of the present invention. The optical transmitter 100 includes a laser diode (LD) 1 that outputs an optical signal, and a laser diode driving device 20 that generates a drive current for the LD 1. Hereinafter, the laser diode driving device 20 is referred to as an LD driving device 20.
　ＬＤ駆動装置２０は、フォトダイオード（ＰＤ）２と、温度センサ３と、トラッキングエラー（ＴＥ：Tracking　Error）補償部４と、電流調整値演算部５と、バイアス電流制御部６と、変調電流制御部７と、光出力制御部８と、出力特性データ記憶部９と、変調特性データ記憶部１０と、補償用データ記憶部１１と、を備える。 The LD drive device 20 includes a photodiode (PD) 2, a temperature sensor 3, a tracking error (TE: tracking error) compensator 4, a current adjustment value calculator 5, a bias current controller 6, and a modulation current controller. It includes a unit 7, an optical output control unit 8, an output characteristic data storage unit 9, a modulation characteristic data storage unit 10, and a compensation data storage unit 11.
　ＬＤ１は、ＬＤ駆動装置２０から供給される駆動電流により駆動され、発光する。ＬＤ１に供給される駆動電流は、バイアス電流制御部６から出力される電流と、変調電流制御部７から出力される電流との和である。バイアス電流制御部６から出力される電流がＬＤ１に供給されるバイアス電流、変調電流制御部７から出力される電流がＬＤ１に供給される変調電流である。ＬＤ駆動装置２０は、変調電流制御部７からＬＤ１に供給される変調電流を変化させ、ＬＤ１が発する光の強度を変調電流の値に応じて変化させることにより、ＬＤ１で光信号を生成させる。ＬＤ１は、前面および背面のそれぞれから、駆動電流の値に対応するパワーの光を出力する。以下、ＬＤ１の前面から出力される光を前面光と称し、背面から出力される光を背面光と称する。 The LD 1 is driven by a driving current supplied from the LD driving device 20 and emits light. The drive current supplied to the LD 1 is the sum of the current output from the bias current control unit 6 and the current output from the modulation current control unit 7. The current output from the bias current control unit 6 is the bias current supplied to the LD1, and the current output from the modulation current control unit 7 is the modulation current supplied to the LD1. The LD driving device 20 causes the LD 1 to generate an optical signal by changing the modulation current supplied from the modulation current control unit 7 to the LD 1 and changing the intensity of light emitted by the LD 1 according to the value of the modulation current. The LD 1 outputs light having a power corresponding to the value of the drive current from each of the front surface and the rear surface. Hereinafter, light output from the front surface of the LD 1 is referred to as front light, and light output from the rear surface is referred to as back light.
　ＰＤ２は、ＬＤ１が発した光を受光可能な位置に設置され、ＬＤ１から受光した光を電流に変換して出力する。これ以降の説明では、ＰＤ２が出力する電流をモニタＰＤ電流と称する。また、本実施の形態では、ＰＤ２がＬＤ１の背面光を受光可能な位置に設置されているとする。 The PD2 is installed at a position capable of receiving the light emitted from the LD1, converts the light received from the LD1 into a current, and outputs the current. In the following description, the current output from PD2 is referred to as a monitor PD current. Further, in the present embodiment, it is assumed that PD2 is installed at a position where the back light of LD1 can be received.
　温度センサ３は、光送信器１００の内部に設置され、光送信器１００内のＬＤ１の温度を検知する。これは、ＬＤ１が温度に依存して発光量が変化する温度特性（以下、ＰＩ特性とする）を持つためである。ＬＤ１のＰＩ特性については後述する。そのため、光送信器１００内のＬＤ１の温度を把握する目的として温度センサ３は設置される。温度センサ３の設置位置は、ＬＤ１の周囲の温度を検出する位置であってもよい。 The temperature sensor 3 is installed inside the optical transmitter 100 and detects the temperature of the LD 1 in the optical transmitter 100. This is because the LD 1 has a temperature characteristic (hereinafter, referred to as PI characteristic) in which the light emission amount changes depending on the temperature. The PI characteristics of LD1 will be described later. Therefore, the temperature sensor 3 is provided for the purpose of grasping the temperature of the LD 1 in the optical transmitter 100. The installation position of the temperature sensor 3 may be a position for detecting the temperature around the LD 1.
　ＴＥ補償部４は、温度センサ３から得られる温度情報と、電流調整値演算部５から得られる、後述するバイアス電流調整値および変調電流調整値と、補償用データ記憶部１１が保持している、後述する温度関数とを使用して、バイアス電流補正量および変調電流補正値を計算する。バイアス電流補正量はＴＥを補償するために行う補正処理におけるバイアス電流の補正量である。変調電流補正値は、ＴＥを補償するための補正を行った後の変調電流である。バイアス電流補正量および変調電流補正値の計算方法については後述する。これ以降の説明では、バイアス電流調整値をＩｂｉａｓ調整値と称し、変調電流調整値をＩｍｏｄ調整値と称する。 The TE compensator 4 holds temperature information obtained from the temperature sensor 3, a bias current adjustment value and a modulation current adjustment value, which will be described later, obtained from the current adjustment value calculator 5, and a compensation data storage unit 11. The bias current correction amount and the modulation current correction value are calculated using a temperature function described later. The bias current correction amount is a correction amount of the bias current in a correction process performed to compensate for TE. The modulation current correction value is a modulation current after performing correction for compensating for TE. The calculation method of the bias current correction amount and the modulation current correction value will be described later. In the following description, the bias current adjustment value is called an Ibias adjustment value, and the modulation current adjustment value is called an Imod adjustment value.
　電流調整値演算部５は、温度センサ３で検出される温度Ｔに対応する変調特性を表す温度関数であるＩｂｉａｓ（Ｔ）およびＩｍｏｄ（Ｔ）を導出する。温度関数Ｉｂｉａｓ（Ｔ）は、ＬＤ１の温度からバイアス電流を求めるための関数であり、温度関数Ｉｍｏｄ（Ｔ）は、ＬＤ１の温度から変調電流を求めるための関数である。また、電流調整値演算部５は、導出したＩｂｉａｓ（Ｔ）およびＩｍｏｄ（Ｔ）を用いて、ＴＥがない場合に目標の光出力パワーを満たす、温度Ｔに対応するＩｂｉａｓ調整値と、ＴＥがない場合に目標の消光比を満たす、温度Ｔに対応するＩｍｏｄ調整値を算出する。Ｉｂｉａｓ（Ｔ）およびＩｍｏｄ（Ｔ）の導出方法、Ｉｂｉａｓ調整値およびＩｍｏｄ調整値の計算方法については後述する。 The current adjustment value calculator 5 derives Ibias (T) and Imod (T), which are temperature functions representing modulation characteristics corresponding to the temperature T detected by the temperature sensor 3. The temperature function Ibias (T) is a function for obtaining a bias current from the temperature of the LD1, and the temperature function Imod (T) is a function for obtaining a modulation current from the temperature of the LD1. Further, the current adjustment value calculation unit 5 uses the derived Ibias (T) and Imod (T) to calculate the Ibias adjustment value corresponding to the temperature T, which satisfies the target optical output power in the absence of TE, If not, an Imod adjustment value corresponding to the temperature T that satisfies the target extinction ratio is calculated. A method for deriving Ibias (T) and Imod (T) and a method for calculating the Ibias adjustment value and the Imod adjustment value will be described later.
　バイアス電流制御部６は、後述する光出力制御部８が出力する補正前のバイアス電流であるバイアス電流Ｉｂｉａｓに対して、ＴＥ補償部４が出力するバイアス電流補正量であるＩｂｉａｓ補正量を加算してバイアス電流を補正する。バイアス電流制御部６は、補正後のバイアス電流であるバイアス電流補正値（Ｉｂｉａｓ補正値）をＬＤ１に出力する。 The bias current control unit 6 adds an Ibias correction amount, which is a bias current correction amount output by the TE compensation unit 4, to a bias current Ibias, which is a bias current before correction output by an optical output control unit 8 described later. To correct the bias current. The bias current control unit 6 outputs a bias current correction value (Ibias correction value), which is the corrected bias current, to the LD 1.
　変調電流制御部７は、ＴＥ補償部４が出力するＩｍｏｄ補正値である補正後の変調電流を受け取り、ＬＤ１に出力する。 The modulation current control unit 7 receives the corrected modulation current, which is the Imod correction value output from the TE compensation unit 4, and outputs it to the LD 1.
　光出力制御部８は、ＬＤ１の光出力パワーを予め定められた第１の値である目標値に保つためのＡＰＣ動作を行うＡＰＣ回路であり、バイアス電流制御部６に出力するバイアス電流Ｉｂｉａｓを生成する。具体的には、光出力制御部８は、ＰＤ２が出力する、ＬＤ１の光出力パワーを示すモニタＰＤ電流に基づいて、モニタＰＤ電流値が予め定められた値となるようにＩｂｉａｓを調整する。すなわち、光出力制御部８は、ＬＤ１が出力する光のパワーに基づいて、バイアス電流制御部６に出力するＩｂｉａｓを生成する。 The optical output control unit 8 is an APC circuit that performs an APC operation for maintaining the optical output power of the LD 1 at a target value that is a predetermined first value, and outputs a bias current Ibias output to the bias current control unit 6. Generate. Specifically, the light output control unit 8 adjusts Ibias based on the monitor PD current output from the PD2 and indicating the light output power of the LD1, such that the monitor PD current value becomes a predetermined value. That is, the light output control unit 8 generates Ibias to be output to the bias current control unit 6 based on the power of the light output from the LD 1.
　出力特性データ記憶部９は、温度センサ３が検知する温度Ｔが第１の温度である常温のときに取得したＬＤ１のＰＩ特性を示すデータと、温度センサ３が検知する温度Ｔが第１の温度よりも高い第２の温度である高温のときに取得したＬＤ１のＰＩ特性を示すデータとを保持する。常温のときに取得したＰＩ特性を示すデータはＬＤ１が常温のときのＰＩ特性を示すデータ、高温のときに取得したＰＩ特性を示すデータはＬＤ１が高温のときのＰＩ特性を示すデータである。本実施の形態において「常温」とは、ＬＤ１のバイアス電流および変調電流を制御する際の基準温度であり、予め定められた温度とする。出力特性データ記憶部９が保持するＰＩ特性を示すデータは、ＬＤ１に供給される電流の値とＬＤ１の光出力パワーとの関係を示す出力特性データである。 The output characteristic data storage unit 9 stores the data indicating the PI characteristic of the LD 1 acquired when the temperature T detected by the temperature sensor 3 is the normal temperature, that is, the first temperature, and the temperature T detected by the temperature sensor 3 is the first temperature. Data indicating the PI characteristic of the LD 1 acquired when the temperature is the second temperature higher than the temperature is held. The data indicating the PI characteristics obtained at room temperature is data indicating the PI characteristics when the LD 1 is at room temperature, and the data indicating the PI characteristics obtained at a high temperature is data indicating the PI characteristics when the LD 1 is at a high temperature. In the present embodiment, “normal temperature” is a reference temperature for controlling the bias current and the modulation current of the LD 1 and is a predetermined temperature. The data indicating the PI characteristic held by the output characteristic data storage unit 9 is output characteristic data indicating the relationship between the value of the current supplied to the LD 1 and the optical output power of the LD 1.
　変調特性データ記憶部１０は、温度センサ３が検知する温度Ｔが常温のときの変調特性を示すデータと、温度センサ３が検知する温度Ｔが高温のときの変調特性を示すデータとを保持する。変調特性を示すデータとは、各温度のときに目標の光出力パワーおよび消光比となるようなＩｂｉａｓ値およびＩｍｏｄ値を示すデータである。変調特性データ記憶部１０が保持する常温時のＩｂｉａｓ値およびＩｍｏｄ値、高温時のＩｂｉａｓ値およびＩｍｏｄ値は、常温時および高温時のそれぞれにおいて光送信器１００を実際に動作させるなどして取得しておく実測値である。 The modulation characteristic data storage unit 10 holds data indicating the modulation characteristic when the temperature T detected by the temperature sensor 3 is at room temperature, and data indicating the modulation characteristic when the temperature T detected by the temperature sensor 3 is high. . The data indicating the modulation characteristic is data indicating an Ibias value and an Imod value such that a target optical output power and an extinction ratio are obtained at each temperature. The Ibias value and Imod value at normal temperature and the Ibias value and Imod value at high temperature held by the modulation characteristic data storage unit 10 are obtained by actually operating the optical transmitter 100 at normal temperature and at high temperature, respectively. This is the actual measurement value.
　補償用データ記憶部１１は、ＴＥ補償部４が各温度でのＴＥ量を計算する際に使用するＴＥ量の温度関数を保持する。なお、これ以降の説明では、ＴＥ量の温度関数をΔＰｍｏｎ（Ｔ）と記載する場合がある。 The compensation data storage unit 11 holds a temperature function of the TE amount used when the TE compensating unit 4 calculates the TE amount at each temperature. In the following description, the temperature function of the TE amount may be described as ΔPmon (T).
　次に、図１に示したＬＤ駆動装置２０の動作概要について説明する。 Next, an outline of the operation of the LD driving device 20 shown in FIG. 1 will be described.
　まず、バイアス電流の制御動作の概要について説明する。ＰＤ２は、ＬＤ１の背面光を受け、受光パワーをモニタＰＤ電流に変換して光出力制御部８へ出力する。光出力制御部８は、ＰＤ２から入力されるモニタＰＤ電流が予め定められた値となるように、バイアス電流制御部６へ出力するバイアス電流Ｉｂｉａｓを制御する。バイアス電流制御部６は、光出力制御部８から入力されるバイアス電流Ｉｂｉａｓに対して、ＴＥ補償部４にて算出される、ＴＥ補償のためのバイアス電流補正量（Ｉｂｉａｓ補正量）を加算し、バイアス電流補正値としてＬＤ１に供給する。このようにして、ＬＤ駆動装置２０は、目標の光出力パワーを得られるようにＬＤ１に供給するバイアス電流を制御する。ＴＥ補償部４は、温度センサ３からの温度情報と、補償用データ記憶部１１に保存されているＴＥ量の温度関数とを使用してＩｂｉａｓ補正量を算出する。 First, the outline of the bias current control operation will be described. The PD 2 receives the back light of the LD 1, converts the received light power into a monitor PD current, and outputs it to the optical output control unit 8. The light output controller 8 controls the bias current Ibias output to the bias current controller 6 so that the monitor PD current input from the PD 2 has a predetermined value. The bias current control unit 6 adds a bias current correction amount (Ibias correction amount) for TE compensation calculated by the TE compensation unit 4 to the bias current Ibias input from the optical output control unit 8. Is supplied to the LD 1 as a bias current correction value. In this way, the LD driving device 20 controls the bias current supplied to the LD 1 so as to obtain the target optical output power. The TE compensator 4 calculates the Ibias correction amount using the temperature information from the temperature sensor 3 and the temperature function of the TE amount stored in the compensation data storage unit 11.
　次に、変調電流の制御動作の概要について説明する。電流調整値演算部５は、ＴＥがない状態の時に、ＬＤ１が生成する光信号の消光比が予め定められた第２の値である目標値となるよう、ＬＤ１に供給する変調電流をＬＤ１の温度に基づいて生成する変調電流生成部である。具体的には、電流調整値演算部５は、ＴＥがない場合に目標の消光比を満たすような変調電流調整値を、温度センサ３で検知される温度情報と、出力特性データ記憶部９で保持されているＰＩ特性を示すデータと、変調特性データ記憶部１０で保持されている変調特性を示すデータとに基づいて演算する。電流調整値演算部５は、ＴＥがない場合の変調電流調整値を求めると、これをＴＥ補償部４に出力する。ＴＥ補償部４は、バイアス電流補正量と同様に、変調電流についてもＴＥ補償のための変調電流の補正量を計算し、計算した補正量を電流調整値演算部５から入力される変調電流調整値に加算して変調電流補正値を算出する。そして、ＴＥ補償部４は、算出した変調電流補正値を変調電流制御部７に出力し、変調電流制御部７が変調電流補正値に対応する変調電流をＬＤ１へ供給することで目標の消光比を得られるように制御する。 Next, the outline of the modulation current control operation will be described. The current adjustment value calculation unit 5 outputs the modulation current supplied to the LD 1 to the LD 1 so that the extinction ratio of the optical signal generated by the LD 1 becomes a target value that is a predetermined second value when there is no TE. This is a modulation current generator that generates based on temperature. Specifically, the current adjustment value calculation unit 5 calculates a modulation current adjustment value that satisfies the target extinction ratio in the absence of TE by using the temperature information detected by the temperature sensor 3 and the output characteristic data storage unit 9. The calculation is performed based on the held data indicating the PI characteristic and the data indicating the modulation characteristic held in the modulation characteristic data storage unit 10. When calculating the modulation current adjustment value when there is no TE, the current adjustment value calculation unit 5 outputs this to the TE compensation unit 4. Similarly to the bias current correction amount, the TE compensation unit 4 calculates the modulation current correction amount for TE compensation for the modulation current, and applies the calculated correction amount to the modulation current adjustment value input from the current adjustment value calculation unit 5. The modulation current correction value is calculated by adding to the value. Then, the TE compensating unit 4 outputs the calculated modulation current correction value to the modulation current control unit 7, and the modulation current control unit 7 supplies a modulation current corresponding to the modulation current correction value to the LD 1, thereby setting the target extinction ratio. Control to obtain
　このように、ＬＤ駆動装置２０は、バイアス電流および変調電流それぞれに対してＴＥ補償のための補正をかける。これにより、ＬＤ駆動装置２０は、目標の光出力パワーを担保しつつ目標の消光比を得られるようにＬＤ１に供給する駆動電流を制御することができる。 As described above, the LD driving device 20 performs correction for TE compensation on each of the bias current and the modulation current. Thereby, the LD drive device 20 can control the drive current supplied to the LD 1 so as to obtain the target extinction ratio while securing the target light output power.
　次に、ＬＤ駆動装置２０の各部の動作の詳細について説明する。 Next, the operation of each part of the LD driving device 20 will be described in detail.
　出力特性データ記憶部９は、二温度（常温、高温）にて予め取得したＰＩ特性を示すデータが格納してあるメモリである。上述したように、ＰＩ特性を示すデータは、ＬＤ１の駆動電流と光出力パワーとの関係を示し、ＬＤ１にどれくらいの駆動電流が供給されたときにどれくらいの光出力パワーとなるのかを表す。なお、これ以降の説明では、光出力パワーをモニタＰＤ受光パワーと称する場合がある。 The output characteristic data storage unit 9 is a memory in which data indicating PI characteristics acquired in advance at two temperatures (normal temperature and high temperature) is stored. As described above, the data indicating the PI characteristic indicates the relationship between the drive current of the LD 1 and the optical output power, and indicates the amount of the optical output power when the drive current is supplied to the LD 1. In the following description, the light output power may be referred to as the monitor PD light receiving power.
　図２は、図１に示すＬＤ１の電流―光出力特性（ＰＩ特性）の一例を示す図である。図２において、横軸はＬＤ駆動電流Ｉを示し、縦軸はモニタＰＤ受光パワーＰを示す。図２に示すように、バイアス電流Ｉｂｉａｓは、光のパワーレベルが１すなわちＰ（１）であるときと、光のパワーレベルが０すなわちＰ（０）であるときとの平均光パワー（＝Ｐａｖｅ）におけるＬＤ駆動電流であり、ＬＤ１からの光出力パワーを決定するものである。一方、変調電流はＰ（１）におけるＬＤ駆動電流Ｉｏｐ（１）とＰ（０）におけるＬＤ駆動電流Ｉｏｐ（０）との差分であり、Ｐ（１）とＰ（０）との光強度比である消光比を決定するものである。なお、図２に示したＩｂｉａｓは光出力制御部８が出力するバイアス電流ではなく、ＬＤ１に実際に供給されるバイアス電流である。また、図３は、図１に示す出力特性データ記憶部９が保持しているデータが示すＰＩ特性の一例を示す図である。図３において、横軸はＬＤ駆動電流Ｉを示し、縦軸はモニタＰＤ受光パワーＰを示す。一般的に、レーザダイオードは温度が高くなるにつれて発光効率が下がり、ＬＤ１も同様の特性を有する。よって、ＬＤ１は、高温時と常温時とで同等の光パワーで発光する場合、高温時に常温時よりも駆動電流がより多く必要になるという温度特性を持つ。そのため、図３に示すように温度によってＰＩ特性が異なる。 FIG. 2 is a diagram showing an example of a current-light output characteristic (PI characteristic) of the LD 1 shown in FIG. 2, the horizontal axis indicates the LD drive current I, and the vertical axis indicates the monitor PD light receiving power P. As shown in FIG. 2, the bias current Ibias is an average optical power (= Pave) between when the light power level is 1, ie, P (1), and when the light power level is 0, ie, P (0). ) Determines the optical output power from the LD 1. On the other hand, the modulation current is the difference between the LD drive current Iop (1) at P (1) and the LD drive current Iop (0) at P (0), and the light intensity ratio between P (1) and P (0). Is determined. It should be noted that Ibias shown in FIG. 2 is not a bias current output from the optical output control unit 8, but a bias current actually supplied to the LD1. FIG. 3 is a diagram illustrating an example of a PI characteristic indicated by data held in the output characteristic data storage unit 9 illustrated in FIG. 3, the horizontal axis represents the LD drive current I, and the vertical axis represents the monitor PD light receiving power P. Generally, the luminous efficiency of the laser diode decreases as the temperature increases, and the LD 1 has the same characteristics. Therefore, when the LD 1 emits light at the same optical power at high temperature and at room temperature, the LD 1 has a temperature characteristic that a larger drive current is required at high temperature than at room temperature. Therefore, the PI characteristics differ depending on the temperature as shown in FIG.
　変調特性データ記憶部１０は、二温度（常温、高温）における変調特性を示すデータが保存されているメモリである。 The modulation characteristic data storage unit 10 is a memory that stores data indicating modulation characteristics at two temperatures (normal temperature and high temperature).
　電流調整値演算部５は、ＴＥがない場合に目標の光出力パワーおよび消光比を満たすような各温度Ｔに対応するＩｂｉａｓ調整値およびＩｍｏｄ調整値を演算により求める。電流調整値演算部５は、Ｉｂｉａｓ調整値およびＩｍｏｄ調整値の算出処理において、各温度Ｔに対応する変調特性を表す温度関数であるＩｂｉａｓ（Ｔ）およびＩｍｏｄ（Ｔ）をそれぞれ使用する。電流調整値演算部５は、以下に示す方法で予め導出された温度関数Ｉｂｉａｓ（Ｔ）およびＩｍｏｄ（Ｔ）を保持しているものとする。 (4) The current adjustment value calculation unit 5 calculates the Ibias adjustment value and the Imod adjustment value corresponding to each temperature T that satisfy the target optical output power and the extinction ratio when there is no TE. The current adjustment value calculator 5 uses the temperature functions Ibias (T) and Imod (T), which are the temperature functions representing the modulation characteristics corresponding to each temperature T, in the calculation process of the Ibias adjustment value and the Imod adjustment value. It is assumed that the current adjustment value calculation unit 5 holds temperature functions Ibias (T) and Imod (T) derived in advance by the following method.
　温度関数Ｉｂｉａｓ（Ｔ）およびＩｍｏｄ（Ｔ）の導出方法の詳細について説明する。ここでは、電流調整値演算部５が各温度関数を導出するものとして説明を行うが、電流調整値演算部５以外が導出を行ってもよい。なお、常温および高温の二温度におけるデータからひとつの温度関数を導いてしまうと、常温よりも低い低温側のデータは使用していないため低温側で誤差が大きくなってしまう可能性が考えられる。そのため、常温よりも高い高温側と低温側とで異なる温度関数を導出し使用するものとしている。 A method for deriving the temperature functions Ibias (T) and Imod (T) will be described in detail. Here, the description will be given assuming that the current adjustment value calculation unit 5 derives each temperature function, but other than the current adjustment value calculation unit 5 may derive. If one temperature function is derived from the data at two temperatures, that is, normal temperature and high temperature, the error on the low temperature side may increase because the data on the low temperature side lower than the normal temperature is not used. Therefore, different temperature functions are derived and used on the high temperature side and the low temperature side higher than the normal temperature.
［低温側の温度関数Ｉｂｉａｓ（Ｔ）およびＩｍｏｄ（Ｔ）の導出方法］
（手順＃１）電流調整値演算部５は、まず、出力特性データ記憶部９に保存されている二温度（常温、高温）のＰＩ特性における、常温でのＬＤ閾値電流Ｉｔｈ１および高温でのＬＤ閾値電流Ｉｔｈ２の２つのデータを用いて、指数関数近似によりＬＤ閾値電流の温度関数Ｉｔｈ（Ｔ）を算出する。ＬＤ閾値電流Ｉｔｈ１は、図３に示したように、常温時にＬＤ１が発光を開始する駆動電流であり、ＬＤ閾値電流Ｉｔｈ２は、高温時にＬＤ１が発光を開始する駆動電流である。 [Method of Deriving Temperature Functions Ibias (T) and Imod (T) on Low Temperature Side]
(Procedure # 1) First, the current adjustment value calculation unit 5 first determines the LD threshold current Ith1 at normal temperature and the LD threshold current at high temperature in the two-temperature (normal temperature, high temperature) PI characteristics stored in the output characteristic data storage unit 9. The temperature function Ith (T) of the LD threshold current is calculated by exponential function approximation using the two data of the threshold current Ith2. As shown in FIG. 3, the LD threshold current Ith1 is a driving current at which the LD1 starts emitting light at normal temperature, and the LD threshold current Ith2 is a driving current at which the LD1 starts emitting light at high temperature.
（手順＃２）電流調整値演算部５は、次に、ＰＩ特性における傾きを表す、常温での発光効率ρ１および高温での発光効率ρ２と、常温でのＬＤ閾値電流Ｉｔｈ１および高温でのＬＤ閾値電流Ｉｔｈ２とを用い、式（１）および式（２）に従って、温度関数Ｉｂｉａｓ（Ｔ）およびＩｍｏｄ（Ｔ）の導出で必要な定数αおよびβを求める。また、電流調整値演算部５は、式（３）に従い、ＰＩ特性における発光効率の温度関数ρ（Ｔ）を求める。
　　α　＝　（１／ρ１－１／ρ２）／（Ｉｔｈ１－Ｉｔｈ２）　…（１）
　　β　＝　１／ρ１－（α×Ｉｔｈ１）　　　　　　　　　　　…（２）
　　ρ（Ｔ）　＝　１／｛α＋β×Ｉｔｈ（Ｔ）｝　　　　　　　…（３） (Procedure # 2) Next, the current adjustment value calculation unit 5 determines the luminous efficiency ρ1 at normal temperature and the luminous efficiency ρ2 at high temperature, indicating the slope of the PI characteristic, the LD threshold current Ith1 at normal temperature, and the LD at high temperature. Using the threshold current Ith2, constants α and β required for deriving the temperature functions Ibias (T) and Imod (T) are obtained according to the equations (1) and (2). Further, the current adjustment value calculation unit 5 obtains the temperature function ρ (T) of the luminous efficiency in the PI characteristic according to the equation (3).
α = (1 / ρ1-1 / ρ2) / (Ith1-Ith2) (1)
β = 1 / ρ1- (α × Ith1) (2)
ρ (T) = 1 / {α + β × Ith (T)} (3)
（手順＃３）電流調整値演算部５は、次に、定数α，βと、式（４）に示すＩｍｏｄｓと、式（５）に示すＫとを用い、式（６）に従って常温におけるＩｂｉａｓ計算値を求めるとともに、式（７）に従って常温におけるＩｍｏｄ計算値を求める。式（４）および式（５）において、ＥＲは消光比、ＰｍｏｎはモニタＰＤ受光パワーである。ＥＲおよびＰｍｏｎは仮値とし、適当に設定する。
　　Ｉｍｏｄｓ　＝　｛２×Ｐｍｏｎ×（ＥＲ－１）×β｝／（ＥＲ＋１）　…（４）
　　Ｋ　＝　｛２×Ｐｍｏｎ×（ＥＲ－１）×α｝／（ＥＲ＋１）　　　　　…（５）
　　常温におけるＩｂｉａｓ計算値　＝　Ｉｔｈ１＋Ｐｍｏｎ／ρ１　　　　…（６）
　　常温におけるＩｍｏｄ計算値　＝　Ｉｍｏｄｓ＋Ｋ×Ｉｔｈ１　　　　　…（７） (Procedure # 3) Next, the current adjustment value calculation unit 5 uses the constants α and β, Imods shown in Expression (4), and K shown in Expression (5), and obtains Ibias at normal temperature according to Expression (6). A calculated value is obtained, and an Imod calculated value at normal temperature is obtained according to the equation (7). In equations (4) and (5), ER is the extinction ratio, and Pmon is the monitor PD received power. ER and Pmon are provisional values and set appropriately.
Imods = {2 × Pmon × (ER−1) × β} / (ER + 1) (4)
K = {2 × Pmon × (ER−1) × α} / (ER + 1) (5)
Calculated value of Ibias at normal temperature = Ith1 + Pmon / ρ1 (6)
Imod calculated value at normal temperature = Imods + K × Ith1 (7)
（手順＃４）電流調整値演算部５は、次に、手順＃３で求めたＩｂｉａｓ計算値と、変調特性データ記憶部１０で保持されている常温時のＩｂｉａｓ値との誤差が最小となり、かつ、手順＃３で求めたＩｍｏｄ計算値と、変調特性データ記憶部１０で保持されている常温時のＩｍｏｄ値との誤差が最小となるように、モニタＰＤ受光パワーＰｍｏｎ’および消光比ＥＲ’を最小二乗法により計算する。 (Procedure # 4) Next, the current adjustment value calculation unit 5 minimizes the error between the Ibias calculated value obtained in the procedure # 3 and the Ibias value at normal temperature stored in the modulation characteristic data storage unit 10, In addition, the monitor PD received light power Pmon 'and the extinction ratio ER' are set so that the error between the Imod calculated value obtained in step # 3 and the Imod value at normal temperature stored in the modulation characteristic data storage unit 10 is minimized. Is calculated by the least squares method.
（手順＃５）電流調整値演算部５は、次に、手順＃４で求めたＰｍｏｎ’およびＥＲ’を上記の式（４）および式（５）に代入してＩｍｏｄｓおよびＫの値を更新する。更新後の値をそれぞれＩｍｏｄｓ’およびＫ’とする。 (Procedure # 5) Next, the current adjustment value calculation unit 5 updates the values of Imods and K by substituting the Pmon ′ and ER ′ obtained in the procedure # 4 into the above equations (4) and (5). I do. The updated values are Imods 'and K', respectively.
（手順＃６）電流調整値演算部５は、次に、手順＃５で求めたＩｍｏｄｓ’およびＫ’を使用し、式（８）に従って温度関数Ｉｂｉａｓ（Ｔ）を導出するとともに、式（９）に従って温度関数Ｉｍｏｄ（Ｔ）を導出する。
　　Ｉｂｉａｓ（Ｔ）　＝　Ｉｔｈ（Ｔ）＋Ｐｍｏｎ’／ρ（Ｔ）　　　…（８）
　　Ｉｍｏｄ（Ｔ）　＝　Ｉｍｏｄｓ’＋Ｋ’×Ｉｔｈ（Ｔ）　　　　　…（９） (Procedure # 6) Next, the current adjustment value calculator 5 derives the temperature function Ibias (T) according to the equation (8) using the Imods ′ and K ′ obtained in the procedure # 5, and also obtains the equation (9) ) To derive a temperature function Imod (T).
Ibias (T) = Ith (T) + Pmon '/ ρ (T) (8)
Imod (T) = Imods '+ K' × Ith (T) (9)
［高温側の温度関数Ｉｂｉａｓ（Ｔ）およびＩｍｏｄ（Ｔ）の導出方法］
　電流調整値演算部５は、変調特性データ記憶部１０で保持されている常温時のＩｂｉａｓ実測値および高温時のＩｂｉａｓ実測値の２点のデータを用いて、指数関数近似により高温側の温度関数Ｉｂｉａｓ（Ｔ）を導出する。同様に、電流調整値演算部５は、変調特性データ記憶部１０で保持されている常温時のＩｍｏｄ実測値および高温時のＩｍｏｄ実測値の２点のデータを用いて、指数関数近似により高温側の温度関数Ｉｍｏｄ（Ｔ）を導出する。 [Method of Deriving Temperature Functions Ibias (T) and Imod (T) on High Temperature Side]
The current adjustment value calculation unit 5 uses the data of two points of the Ibias actual measurement value at normal temperature and the Ibias actual measurement value at high temperature held in the modulation characteristic data storage unit 10 to calculate the temperature function on the high temperature side by exponential function approximation. Derive Ibias (T). Similarly, the current adjustment value calculation unit 5 performs exponential function approximation using data of two points of the Imod actual measurement value at normal temperature and the Imod actual measurement value at high temperature held in the modulation characteristic data storage unit 10, Is derived from the temperature function Imod (T).
　図４は、高温側の温度関数Ｉｂｉａｓ（Ｔ）の一例を示す図、図５は、高温側の温度関数Ｉｍｏｄ（Ｔ）の一例を示す図である。図４に示した温度関数Ｉｂｉａｓ（Ｔ）は、ＬＤ１の温度が常温（Ｔ１）のときにＬＤ１に供給されるバイアス電流（Ｉｂｉａｓ）の実測値と、ＬＤ１の温度が高温（Ｔ２）のときにＬＤ１に供給されるバイアス電流の実測値とを使用して導出される。同様に、図５に示した温度関数Ｉｍｏｄ（Ｔ）は、ＬＤ１の温度が常温（Ｔ１）のときにＬＤ１に供給される変調電流（Ｉｍｏｄ）の実測値と、ＬＤ１の温度が高温（Ｔ２）のときにＬＤ１に供給される変調電流の実測値とを使用して導出される。高温側の温度関数Ｉｂｉａｓ（Ｔ）およびＩｍｏｄ（Ｔ）は、式（１０）および式（１１）で表される。式（１０）および式（１１）において、Ａ，Ｂ，Ｃ，Ｄは係数、Ｔは温度である。
　　Ｉｂｉａｓ（Ｔ）　＝　Ａ×Ｅｘｐ（Ｂ×Ｔ）　　　…（１０）
　　Ｉｍｏｄ（Ｔ）　＝　Ｃ×Ｅｘｐ（Ｄ×Ｔ）　　　　…（１１） FIG. 4 is a diagram showing an example of the temperature function Ibias (T) on the high temperature side, and FIG. 5 is a diagram showing an example of the temperature function Imod (T) on the high temperature side. The temperature function Ibias (T) shown in FIG. 4 is a measured value of the bias current (Ibias) supplied to the LD1 when the temperature of the LD1 is room temperature (T1), and the temperature function Ibias (T) when the temperature of the LD1 is high temperature (T2). It is derived using the measured value of the bias current supplied to the LD 1. Similarly, the temperature function Imod (T) shown in FIG. 5 includes the actual measurement value of the modulation current (Imod) supplied to the LD1 when the temperature of the LD1 is normal temperature (T1) and the temperature function Imod (T) when the temperature of the LD1 is high (T2). And the actual value of the modulation current supplied to the LD 1 at the time. The temperature functions Ibias (T) and Imod (T) on the high temperature side are represented by Expressions (10) and (11). In equations (10) and (11), A, B, C, and D are coefficients, and T is temperature.
Ibias (T) = A × Exp (B × T) (10)
Imod (T) = C × Exp (D × T) (11)
　電流調整値演算部５は、温度センサ３から温度情報を取得すると、取得した温度情報と、温度関数Ｉｂｉａｓ（Ｔ），Ｉｍｏｄ（Ｔ）とを用いて、バイアス電流の調整値および変調電流の調整値を算出する。このとき、電流調整値演算部５は、取得した温度情報が低温側すなわち常温よりも低い温度を示す場合は低温側の温度関数Ｉｂｉａｓ（Ｔ），Ｉｍｏｄ（Ｔ）を使用し、取得した温度情報が示す温度Ｔが高温側すなわち常温よりも高い場合は高温側の温度関数Ｉｂｉａｓ（Ｔ），Ｉｍｏｄ（Ｔ）を使用する。 When acquiring the temperature information from the temperature sensor 3, the current adjustment value calculation unit 5 adjusts the adjustment value of the bias current and the modulation current using the acquired temperature information and the temperature functions Ibias (T) and Imod (T). Calculate the value. At this time, if the acquired temperature information indicates a low temperature side, that is, a temperature lower than room temperature, the current adjustment value calculation unit 5 uses the temperature functions Ibias (T) and Imod (T) on the low temperature side to obtain the acquired temperature information. Is higher than the normal temperature, that is, the temperature functions Ibias (T) and Imod (T) on the high temperature side are used.
　補償用データ記憶部１１は、ＴＥ補償部４にて各温度でのＴＥ量を計算するためのＴＥ量の温度関数ΔＰｍｏｎ（Ｔ）を保持するメモリである。ＴＥ量の温度関数ΔＰｍｏｎ（Ｔ）は、ＬＤ１の温度とＴＥ量との対応関係を示す。ＴＥ量の温度関数ΔＰｍｏｎ（Ｔ）は、常温でＴＥ量を０とした際の低温および高温の２温度でのＴＥ量データから導出される、ＴＥ量を表す上に凸の２次関数である。温度関数ΔＰｍｏｎ（Ｔ）を導出する処理では、まず、ＬＤ１を常温とした状態で、目標の光パワーおよび目標の消光比が得られ、かつＴＥ量が０となるようにバイアス電流および変調電流を調整する。次に、バイアス電流および変調電流を変化させずに、ＬＤ１の温度を低温側（常温よりも低い温度）および高温側（常温よりも高い温度）に変化させて低温時のＴＥ量および高温時のＴＥ量を求める。次に、低温時のＴＥ量および高温時のＴＥ量を用いてＴＥ量の温度関数ΔＰｍｏｎ（Ｔ）を導出する。ＴＥ量の温度関数ΔＰｍｏｎ（Ｔ）は、式（１２）で表すことができ、図６に示すような、ＬＤ１の温度とＴＥ量との関係を表す関数である。式（１２）において、ａ，ｂ，ｃは係数、Ｔは温度である。図６は、図１に示す補償用データ記憶部１１が保持する温度関数ΔＰｍｏｎ（Ｔ）の一例を示す図である。ＴＥ量の温度関数ΔＰｍｏｎ（Ｔ）は、例えばＴＥ補償部４が導出する。ＴＥ補償部４以外で導出するようにしてもよい。
　　ΔＰｍｏｎ（Ｔ）　＝　ａ×Ｔ＾２＋ｂ×Ｔ＋ｃ　　…（１２） The compensation data storage unit 11 is a memory that holds a temperature function ΔPmon (T) of the TE amount for the TE compensation unit 4 to calculate the TE amount at each temperature. The temperature function ΔPmon (T) of the TE amount indicates the correspondence between the temperature of the LD 1 and the TE amount. The temperature function ΔPmon (T) of the TE amount is an upwardly convex quadratic function representing the TE amount, which is derived from the TE amount data at two temperatures of low temperature and high temperature when the TE amount is set to 0 at normal temperature. . In the process of deriving the temperature function ΔPmon (T), first, the bias current and the modulation current are adjusted so that the target optical power and the target extinction ratio are obtained and the TE amount becomes 0 while the LD 1 is at room temperature. adjust. Next, without changing the bias current and the modulation current, the temperature of the LD 1 is changed to a low temperature side (a temperature lower than the normal temperature) and a high temperature side (a temperature higher than the normal temperature) to change the TE amount at the low temperature and the TE amount at the high temperature. Find the TE amount. Next, a temperature function ΔPmon (T) of the TE amount is derived using the TE amount at a low temperature and the TE amount at a high temperature. The temperature function ΔPmon (T) of the TE amount can be expressed by Expression (12), and is a function indicating the relationship between the temperature of the LD 1 and the TE amount as shown in FIG. In equation (12), a, b, and c are coefficients, and T is temperature. FIG. 6 is a diagram showing an example of the temperature function ΔPmon (T) held by the compensation data storage unit 11 shown in FIG. The TE compensator 4 derives the temperature function ΔPmon (T) of the TE amount, for example. It may be derived by means other than the TE compensator 4.
ΔPmon (T) = a × T ＾ 2 + b × T + c (12)
　ＴＥ補償部４は、ＴＥ補償のための電流調整値の補正量を計算する。ＴＥ補償部４は、バイアス電流についてはバイアス電流の補正で使用する補正量を計算し、変調電流についてはＩｍｏｄ調整値に補正量を反映したＩｍｏｄ補正値を計算する。なお、バイアス電流の補正はバイアス電流制御部６が行う。ＴＥ補償部４は、温度センサ３から得られる温度情報と、電流調整値演算部５で算出されるバイアス電流の調整値および変調電流の調整値と、補償用データ記憶部１１で保持されているＴＥ量の温度関数ΔＰｍｏｎ（Ｔ）とを使用して、バイアス電流の補正量およびＩｍｏｄ補正値を算出する。ＴＥ補償部４の動作の詳細について、以下に説明する。 The TE compensator 4 calculates a correction amount of the current adjustment value for TE compensation. The TE compensator 4 calculates a correction amount used in correcting the bias current for the bias current, and calculates an Imod correction value in which the correction amount is reflected on the Imod adjustment value for the modulation current. The bias current is corrected by the bias current control unit 6. The TE compensating unit 4 holds the temperature information obtained from the temperature sensor 3, the bias current adjustment value and the modulation current adjustment value calculated by the current adjustment value calculation unit 5, and the compensation data storage unit 11. The correction amount of the bias current and the Imod correction value are calculated using the temperature function ΔPmon (T) of the TE amount. The operation of the TE compensator 4 will be described in detail below.
（手順＃１）ＴＥ補償部４は、まず、温度センサ３より取得した温度情報が示す温度に対応するＴＥ量を、補償用データ記憶部１１で保持されているＴＥ量の温度関数ΔＰｍｏｎ（Ｔ）を用いて求める。ここでは、ＴＥ補償部４が温度センサ３より取得した温度情報が示す温度をＴｘとし、ＴＥ補償部４が求めるＴＥ量をΔＰｍｏｎ（Ｔｘ）とする。 (Procedure # 1) The TE compensating unit 4 firstly converts the TE amount corresponding to the temperature indicated by the temperature information acquired from the temperature sensor 3 into a temperature function ΔPmon (T ). Here, the temperature indicated by the temperature information acquired by the TE compensator 4 from the temperature sensor 3 is Tx, and the TE amount obtained by the TE compensator 4 is ΔPmon (Tx).
（手順＃２）ＴＥ補償部４は、次に、手順＃１で求めたＴＥ量ΔＰｍｏｎ（Ｔｘ）と、ＰＩ特性における発光効率の温度関数ρ（Ｔ）とを用いて、ＴＥ補償のためのバイアス電流の補正量ΔＩｂｉａｓ（Ｔｘ）を式（１３）に従って計算する。なお、ＰＩ特性における発光効率の温度関数ρ（Ｔ）は、上記の式（３）で表される関数である。ＴＥ補償部４は、電流調整値演算部５が低温側の温度関数Ｉｂｉａｓ（Ｔ）およびＩｍｏｄ（Ｔ）を導出する場合と同様の方法で温度関数ρ（Ｔ）を予め導出して保持しておく。ＴＥ補償部４は、電流調整値演算部５で導出された温度関数ρ（Ｔ）を電流調整値演算部５から受け取って保持しておいてもよい。ＴＥ補償部４は、温度がＴｘのときに温度関数ρ（Ｔ）を用いて算出される発光効率の値ρ（Ｔｘ）を電流調整値演算部５から取得するようにしてもよい。ＴＥ補償部４は、求めた補正量ΔＩｂｉａｓ（Ｔｘ）をバイアス電流制御部６へ出力する。
　　ΔＩｂｉａｓ（Ｔｘ）　＝　ΔＰｍｏｎ（Ｔｘ）／ρ（Ｔｘ）　　　…（１３） (Procedure # 2) Next, the TE compensator 4 uses the TE amount ΔPmon (Tx) obtained in Procedure # 1 and the temperature function ρ (T) of the luminous efficiency in the PI characteristic to perform TE compensation. The correction amount ΔIbias (Tx) of the bias current is calculated according to equation (13). The temperature function ρ (T) of the luminous efficiency in the PI characteristic is a function represented by the above equation (3). The TE compensating unit 4 previously derives and holds the temperature function ρ (T) in the same manner as the case where the current adjustment value calculating unit 5 derives the temperature functions Ibias (T) and Imod (T) on the low temperature side. deep. The TE compensator 4 may receive the temperature function ρ (T) derived by the current adjustment value calculator 5 from the current adjustment value calculator 5 and hold the temperature function ρ (T). The TE compensating unit 4 may obtain the luminous efficiency value ρ (Tx) calculated using the temperature function ρ (T) when the temperature is Tx from the current adjustment value calculating unit 5. The TE compensator 4 outputs the obtained correction amount ΔIbias (Tx) to the bias current controller 6.
ΔIbias (Tx) = ΔPmon (Tx) / ρ (Tx) (13)
（手順＃３）ＴＥ補償部４は、次に、手順＃２で求めた補正量ΔＩｂｉａｓ（Ｔｘ）を用いて、ＴＥ補償のためのＩｍｏｄ調整値の補正量ΔＩｍｏｄ（Ｔｘ）を式（１４）に従って計算する。
　　ΔＩｍｏｄ（Ｔｘ）　＝　ΔＩｂｉａｓ（Ｔｘ）×２　　　…（１４） (Procedure # 3) Next, the TE compensating unit 4 calculates the correction amount ΔImod (Tx) of the Imod adjustment value for TE compensation by using the correction amount ΔIbias (Tx) obtained in Step # 2 according to Expression (14). Calculate according to
ΔImod (Tx) = ΔIbias (Tx) × 2 (14)
（手順＃４）ＴＥ補償部４は、次に、手順＃３で求めた補正量ΔＩｍｏｄ（Ｔｘ）を用いて、Ｉｍｏｄ補正値を式（１５）に従って計算する。図７は、図１に示すＴＥ補償部４が行うＩｍｏｄ補正値計算のイメージを示す図である。温度ＴｘにおけるＩｍｏｄ補正値は、温度ＴｘにおけるＩｍｏｄ調整値に温度ＴｘにおけるＩｍｏｄの補正量を加算することで得られる。ＴＥ補償部４は、求めたＩｍｏｄ補正値を変調電流制御部７へ出力する。
　　Ｉｍｏｄ補正値（Ｔｘ）　＝　Ｉｍｏｄ（Ｔｘ）＋ΔＩｍｏｄ（Ｔｘ）…（１５） (Procedure # 4) Next, the TE compensator 4 calculates an Imod correction value according to the equation (15) using the correction amount ΔImod (Tx) obtained in the procedure # 3. FIG. 7 is a diagram showing an image of an Imod correction value calculation performed by the TE compensating unit 4 shown in FIG. The Imod correction value at the temperature Tx is obtained by adding the Imod correction amount at the temperature Tx to the Imod adjustment value at the temperature Tx. The TE compensator 4 outputs the obtained Imod correction value to the modulation current controller 7.
Imod correction value (Tx) = Imod (Tx) + ΔImod (Tx) (15)
　以上のように、ＴＥ補償部４は、温度センサ３から得られる温度情報が示すＬＤ１の温度と、ＬＤ１の発光効率とに基づいて、ＴＥ補償のためのバイアス電流の補正量を算出し、さらに、ＴＥ補償のためのバイアス電流の補正量に基づいて、変調電流であるＩｍｏｄのＴＥ補償のための補正量を算出し、変調電流を補正してＴＥを補償する。 As described above, the TE compensator 4 calculates the correction amount of the bias current for TE compensation based on the temperature of the LD 1 indicated by the temperature information obtained from the temperature sensor 3 and the luminous efficiency of the LD 1, and , A correction amount for the TE compensation of the modulation current Imod is calculated based on the bias current correction amount for the TE compensation, and the modulation current is corrected to compensate for the TE.
　バイアス電流制御部６は、式（１６）に示したように、光出力制御部８から得られるバイアス電流Ｉｂｉａｓに対して、ＴＥ補償部４から得られるＴＥ補償のためのバイアス電流の補正量ΔＩｂｉａｓ（Ｔ）を加算することでＩｂｉａｓ補正値（Ｔ）を生成する。
　　Ｉｂｉａｓ補正値（Ｔ）　＝　Ｉｂｉａｓ＋ΔＩｂｉａｓ（Ｔ）　　…（１６） The bias current controller 6 corrects the bias current Ibias obtained from the optical output controller 8 with respect to the bias current Ibias obtained from the TE compensator 4 for the TE current compensation amount ΔIbias for TE compensation, as shown in Expression (16). By adding (T), an Ibias correction value (T) is generated.
Ibias correction value (T) = Ibias + ΔIbias (T) (16)
　バイアス電流制御部６は、生成したＩｂｉａｓ補正値（Ｔ）をＬＤ１に出力する。これにより、目標の光出力パワーを満足するバイアス電流の制御を実現できる。 The bias current controller 6 outputs the generated Ibias correction value (T) to the LD 1. Thereby, control of the bias current that satisfies the target optical output power can be realized.
　変調電流制御部７は、ＴＥ補償部４から得られるＴＥ補償のための変調電流の補正値であるＩｍｏｄ補正値（Ｔ）をＬＤ１に出力する。これにより、目標の消光比を満足する変調電流の制御を実現できる。 (4) The modulation current control unit 7 outputs an Imod correction value (T), which is a correction value of the modulation current for TE compensation obtained from the TE compensation unit 4, to the LD 1. Thereby, control of the modulation current that satisfies the target extinction ratio can be realized.
　次に、本実施の形態にかかるＬＤ駆動装置２０のハードウェア構成について説明する。ＬＤ駆動装置２０の出力特性データ記憶部９、変調特性データ記憶部１０および補償用データ記憶部１１は、上述したように、メモリによって実現される。ＬＤ駆動装置２０のＴＥ補償部４、電流調整値演算部５、バイアス電流制御部６および変調電流制御部７は、これら各部の機能を実現する処理回路で構成される。ここで、処理回路は、例えば、単一回路、複合回路、プログラム化したプロセッサ、並列プログラム化したプロセッサ、ＡＳＩＣ（Application　Specific　Integrated　Circuit）、ＦＰＧＡ（Field-Programmable　Gate　Array）またはこれらを組み合わせた専用のハードウェアであってもよいし、図８に示したようなプロセッサ２０１およびメモリ２０２であってもよい。 Next, a hardware configuration of the LD driving device 20 according to the present embodiment will be described. As described above, the output characteristic data storage unit 9, the modulation characteristic data storage unit 10, and the compensation data storage unit 11 of the LD driving device 20 are realized by a memory. The TE compensating unit 4, the current adjustment value calculating unit 5, the bias current control unit 6, and the modulation current control unit 7 of the LD driving device 20 are configured by processing circuits that realize the functions of these units. Here, the processing circuit is, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a dedicated combination of these. It may be hardware or a processor 201 and a memory 202 as shown in FIG.
　図８に示したプロセッサ２０１は、ＣＰＵ（Central　Processing　Unit、中央処理装置、処理装置、演算装置、マイクロプロセッサ、マイクロコンピュータ、ＤＳＰ（Digital　Signal　Processor）ともいう）などである。メモリ２０２は、ＲＡＭ（Random　Access　Memory）、ＲＯＭ（Read　Only　Memory）、フラッシュメモリ等の、不揮発性または揮発性の半導体メモリなどである。ＬＤ駆動装置２０のＴＥ補償部４、電流調整値演算部５、バイアス電流制御部６および変調電流制御部７は、これらの各部として動作するためのプログラムをメモリ２０２に格納しておき、このプログラムをプロセッサ２０１がメモリ２０２から読み出して実行することにより実現される。ＬＤ駆動装置２０のＴＥ補償部４、電流調整値演算部５、バイアス電流制御部６および変調電流制御部７の一部をプロセッサ２０１およびメモリ２０２で実現し、残りを専用のハードウェアで実現してもよい。ＬＤ駆動装置２０のＴＥ補償部４、電流調整値演算部５、バイアス電流制御部６および変調電流制御部７を図８に示したプロセッサ２０１およびメモリ２０２で実現する場合、ＬＤ駆動装置２０の出力特性データ記憶部９、変調特性データ記憶部１０および補償用データ記憶部１１はメモリ２０２で実現されてもよい。 The processor 201 shown in FIG. 8 is a CPU (Central Processing Unit), a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a DSP (Digital Signal Processor), or the like. The memory 202 is a non-volatile or volatile semiconductor memory such as a random access memory (RAM), a read only memory (ROM), and a flash memory. The TE compensating unit 4, the current adjustment value calculating unit 5, the bias current control unit 6, and the modulation current control unit 7 of the LD driving device 20 store programs for operating as these units in the memory 202, and Is read out from the memory 202 by the processor 201 and executed. A part of the TE compensator 4, the current adjustment value calculator 5, the bias current controller 6, and the modulation current controller 7 of the LD driving device 20 is realized by the processor 201 and the memory 202, and the rest is realized by dedicated hardware. You may. When the TE compensator 4, the current adjustment value calculator 5, the bias current controller 6, and the modulation current controller 7 of the LD driving device 20 are realized by the processor 201 and the memory 202 shown in FIG. The characteristic data storage unit 9, the modulation characteristic data storage unit 10, and the compensation data storage unit 11 may be realized by the memory 202.
　以上のように、本実施の形態にかかるＬＤ駆動装置２０において、光出力制御部８は、ＬＤ１が出力する光のパワーが目標値となるバイアス電流を生成する。電流調整値演算部５は、ＬＤ１の温度に基づいて、トラッキングエラーが無い状態のときに目標の消光比が得られる変調電流を生成する。ＴＥ補償部４は、ＬＤ１の温度とＬＤ１が常温および高温のときの発光効率とに基づいてトラッキングエラーの発生量を算出し、算出したトラッキングエラーの発生量に基づいて、バイアス電流の補正量を算出するとともに、トラッキングエラーを補償するための補正を変調電流に対して行う。バイアス電流制御部６は、バイアス電流の補正量に基づいて、トラッキングエラーを補償するための補正をバイアス電流に対して行い、補正後のバイアス電流をＬＤ１に供給する。変調電流制御部７は、ＴＥ補償部４から出力される補正後の変調電流をＬＤ１に供給する。これにより、ＬＤ駆動装置２０は、ＬＤ１の温度が変化した場合でも、ＬＤ１が生成する光信号のパワーおよび消光比を目標の値とすることができる。すなわち、本実施の形態にかかる光送信器１００は、ＬＤ１の温度が変化した場合でも、目標のパワーおよび消光比の光信号を生成することができる。 As described above, in the LD driving device 20 according to the present embodiment, the light output control unit 8 generates the bias current at which the power of the light output from the LD 1 becomes the target value. The current adjustment value calculation unit 5 generates a modulation current based on the temperature of the LD 1 so as to obtain a target extinction ratio when there is no tracking error. The TE compensator 4 calculates a tracking error generation amount based on the temperature of the LD 1 and the luminous efficiency when the LD 1 is at room temperature and high temperature, and calculates a bias current correction amount based on the calculated tracking error generation amount. In addition to the calculation, a correction for compensating for the tracking error is performed on the modulation current. The bias current control unit 6 performs correction for compensating for a tracking error on the bias current based on the correction amount of the bias current, and supplies the corrected bias current to the LD 1. The modulation current controller 7 supplies the corrected modulation current output from the TE compensator 4 to the LD 1. Thereby, the LD driving device 20 can set the power and the extinction ratio of the optical signal generated by the LD 1 to target values even when the temperature of the LD 1 changes. That is, the optical transmitter 100 according to the present embodiment can generate an optical signal having the target power and the extinction ratio even when the temperature of the LD 1 changes.
　以上の実施の形態に示した構成は、本発明の内容の一例を示すものであり、別の公知の技術と組み合わせることも可能であるし、本発明の要旨を逸脱しない範囲で、構成の一部を省略、変更することも可能である。 The configurations described in the above embodiments are merely examples of the contents of the present invention, and can be combined with other known technologies, and can be combined with other known technologies without departing from the gist of the present invention. Parts can be omitted or changed.
　１　レーザダイオード、２　フォトダイオード、３　温度センサ、４　トラッキングエラー補償部、５　電流調整値演算部、６　バイアス電流制御部、７　変調電流制御部、８　光出力制御部、９　出力特性データ記憶部、１０　変調特性データ記憶部、１１　補償用データ記憶部、２０　レーザダイオードの駆動装置、１００　光送信器。 1 laser diode, 2 photodiode, 3 temperature sensor, 4 tracking error compensation unit, 5 current adjustment value calculation unit, 6 bias current control unit, 7 modulation current control unit, 8 optical output control unit, 9 output characteristic data storage unit, 10 modulation characteristic data storage unit, 11 compensation data storage unit, 20 laser diode driving device, 100 optical transmitter.

Claims (4)

  1. 　レーザダイオードの温度を検出する温度センサと、
    　前記レーザダイオードが出力する光信号の強度が予め定められた第１の値となるよう、前記レーザダイオードに供給するバイアス電流を生成する光出力制御部と、
    　トラッキングエラーが無い状態の時に前記光信号の消光比が予め定められた第２の値となるよう、前記レーザダイオードに供給する変調電流を前記温度センサで検出された温度に基づいて生成する変調電流生成部と、
    　前記温度センサで検出された温度と、前記レーザダイオードに供給される電流である駆動電流の値と前記光信号の強度との対応関係を示す出力特性データと、に基づいて、トラッキングエラーを補償するために行う前記バイアス電流の補正で使用する前記バイアス電流の補正量を算出するとともに、前記トラッキングエラーを補償するために前記変調電流を補正するトラッキングエラー補償部と、
    　前記補正量に基づいて前記バイアス電流を補正するバイアス電流制御部と、
    　を備えることを特徴とするレーザダイオードの駆動装置。     A temperature sensor for detecting the temperature of the laser diode,
    An optical output control unit that generates a bias current to be supplied to the laser diode, such that the intensity of the optical signal output by the laser diode is a predetermined first value;
    A modulation current for generating a modulation current to be supplied to the laser diode based on a temperature detected by the temperature sensor so that an extinction ratio of the optical signal becomes a second predetermined value when there is no tracking error. A generation unit;
    Compensating for a tracking error based on a temperature detected by the temperature sensor and output characteristic data indicating a correspondence between a drive current value, which is a current supplied to the laser diode, and the intensity of the optical signal. Calculating a correction amount of the bias current to be used in the correction of the bias current to be performed, and a tracking error compensating unit that corrects the modulation current to compensate for the tracking error;
    A bias current control unit that corrects the bias current based on the correction amount,
    A driving device for a laser diode, comprising:
  2. 　前記変調電流生成部は、トラッキングエラーが無い状態かつ前記レーザダイオードが第１の温度のときの前記駆動電流と前記強度の対応関係を示す第１の出力特性データと、トラッキングエラーが無い状態かつ前記レーザダイオードが第２の温度のときの前記駆動電流と前記強度の対応関係を示す第２の出力特性データとに基づいて、トラッキングエラーが無い状態における、前記レーザダイオードの温度と、前記光信号の消光比を前記第２の値とする変調電流との関係を示す関数を導出して保持しておき、前記温度センサから前記レーザダイオードの温度の検出結果を取得すると、取得した前記検出結果と保持している前記関数とを使用して前記レーザダイオードに供給する変調電流を生成する、
    　ことを特徴とする請求項１に記載のレーザダイオードの駆動装置。     The modulation current generation unit includes a first output characteristic data indicating a correspondence relationship between the drive current and the intensity when the tracking error is not present and the laser diode is at a first temperature, Based on the drive current when the laser diode is at a second temperature and second output characteristic data indicating the correspondence between the intensities, the temperature of the laser diode in a state where there is no tracking error and the optical signal Deriving a function indicating a relationship with the modulation current having the extinction ratio as the second value and holding it, and obtaining a detection result of the temperature of the laser diode from the temperature sensor, holding the obtained detection result and the holding Generating a modulation current to supply to the laser diode using the function
    The driving device for a laser diode according to claim 1, wherein:
  3. 　前記トラッキングエラー補償部は、トラッキングエラーが無い状態で前記強度が前記第１の値となり、かつ前記消光比が前記第２の値となるよう、前記バイアス電流および前記変調電流を調整した状態を基準状態とし、前記基準状態から前記レーザダイオードの温度が低温側に変化した場合に発生するトラッキングエラーの量と、前記基準状態から前記レーザダイオードの温度が高温側に変化した場合に発生するトラッキングエラーの量とに基づいて導出された、前記レーザダイオードの温度とトラッキングエラーの量との対応関係を示す関数、を使用して、前記温度センサで検出された温度に対応するトラッキングエラーの量を算出し、算出した前記トラッキングエラーの量に基づいて前記補正量を算出し、算出した前記補正量に基づいて前記変調電流を補正する、
    　ことを特徴とする請求項１または２に記載のレーザダイオードの駆動装置。     The tracking error compensator is based on a state in which the bias current and the modulation current are adjusted such that the intensity becomes the first value and the extinction ratio becomes the second value in the absence of a tracking error. State, the amount of tracking error that occurs when the temperature of the laser diode changes from the reference state to a lower temperature, and the amount of tracking error that occurs when the temperature of the laser diode changes from the reference state to a higher temperature. Using a function derived based on the amount and a function indicating the correspondence between the temperature of the laser diode and the amount of tracking error, the amount of tracking error corresponding to the temperature detected by the temperature sensor is calculated. Calculating the correction amount based on the calculated tracking error amount, and calculating the correction amount based on the calculated correction amount. To correct the serial modulation current,
    3. The driving device for a laser diode according to claim 1, wherein
  4. 　請求項１から３のいずれか一つに記載のレーザダイオードの駆動装置と、
    　前記レーザダイオードの駆動装置により駆動されるレーザダイオードと、
    　を備えることを特徴とする光送信器。     A laser diode driving device according to any one of claims 1 to 3,
    A laser diode driven by the laser diode driving device,
    An optical transmitter, comprising:
PCT/JP2018/025371 2018-07-04 2018-07-04 Laser diode drive device and optical transmitter WO2020008566A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007103398A (en) * 2005-09-30 2007-04-19 Fujitsu Ltd Extinction ratio controller, extinction ratio control method and extinction ratio control program
JP2009070879A (en) * 2007-09-11 2009-04-02 Nec Corp Laser diode drive circuit and drive method
JP2013008843A (en) * 2011-06-24 2013-01-10 Sumitomo Electric Device Innovations Inc Method of driving semiconductor laser

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007103398A (en) * 2005-09-30 2007-04-19 Fujitsu Ltd Extinction ratio controller, extinction ratio control method and extinction ratio control program
JP2009070879A (en) * 2007-09-11 2009-04-02 Nec Corp Laser diode drive circuit and drive method
JP2013008843A (en) * 2011-06-24 2013-01-10 Sumitomo Electric Device Innovations Inc Method of driving semiconductor laser

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