JP2013247282A - Light-emitting element driving device, optical communication device, light-emitting element driving device control method, and light-emitting element driving device control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting element driving device that allows appropriate inspection to be easily executed.SOLUTION: A laser driving circuit 200 capable of selecting a normal operation mode and an adjustment inspection mode comprises: an input terminal I for inputting a transmission electric signal; a modulation current control unit 212 for controlling current flowing to a laser diode LD; and a test signal output circuit 208 for outputting a plurality of types of test signals respectively having different mark rates. The modulation current control unit 212 controls, in the normal operation mode, current flowing to the laser diode LD on the basis of the transmission electric signal input from the input terminal I, and controls, in the adjustment inspection mode, current flowing to the laser diode LD on the basis of the plurality of types of test signals respectively having different mark rates output by the test signal output circuit 208.

Description

  The present invention relates to a light emitting element driving device, an optical communication device, a method for controlling the light emitting element driving device, and a control program for the light emitting element driving device, for example, a light emitting element driving device that can be used in a PON (Passive Optical Network) system, and the like. The present invention relates to a device, a control method for a light emitting element driving device, and a control program for the light emitting element driving device.

  As a communication technology using optical broadband, for example, a PON system is known. In the PON system, a station-side terminal device (hereinafter referred to as “OLT” (Optical Line Terminal)) and a plurality of user-side terminal devices (hereinafter referred to as “ONU” (Optical Network Unit)) are an optical splitter. Optically connected with an optical fiber.

  The ONU includes an optical transceiver. The optical transceiver has a semiconductor laser element (an example of a light emitting element). When transmitting an optical signal from the ONU to the OLT, each of the plurality of ONUs transmits an optical burst signal during the timing when transmission permission is obtained. That is, each of the plurality of ONUs transmits an upstream burst signal in a time division manner by an intermittent signal (modulation current) that is intermittently supplied to the semiconductor laser element.

  The optical transceiver is manufactured as a separate component from the ONU board and mounted on the ONU board. Before the optical transceiver is attached to the ONU substrate, a pulse pattern generator (PPG) is connected to the optical transceiver. A pulse pattern is applied to the optical transceiver, and the light emission intensity is inspected and adjusted by an optical power meter and an oscilloscope. The optical transceiver after inspection / adjustment is attached to the substrate of the ONU. As a method of attaching the optical transceiver to the ONU board, there are a method of attaching directly (directly) and a method of attaching via a connector.

  The following Patent Document 1 discloses an optical transceiver inspection system. In this inspection system, a pulse pattern generator generates an electrical signal for inspection. The electrical signal for inspection is input to the light emitting element of the optical transceiver. The light emitting element converts an electrical signal for inspection into an optical signal. The optical signal is input to an oscilloscope or an optical power meter via an optical switch. A PC (personal computer) reads light intensity data from an optical power meter and also reads waveform data of an optical signal from an oscilloscope. The PC obtains the transmission characteristics of the optical transceiver at the current temperature by determining the light intensity, extinction ratio, and eye pattern of the optical signal. Based on the characteristics, the bias current and modulation current of the optical transceiver light emitting element are adjusted.

  The following Patent Document 2 discloses an extinction ratio measuring apparatus that measures an extinction ratio of an optical switch used for optical communication, an optical pulse tester, and the like.

JP 2011-53114 A JP-A-7-322010

  However, the inspection method described in Patent Document 1 requires equipment such as a pulse pattern generator (PPG), an optical power meter, and an oscilloscope in order to test drive the optical transceiver. Therefore, in the inspection at the field (ONU installation location), it is necessary to carry these equipments into the field. In the field inspection, it is necessary to remove the already connected optical fiber and reconnect it after the inspection. For this reason, there exists a problem that inspection and adjustment require time and cost.

  Furthermore, in the prior art, since the labor and cost are high, the inspection and adjustment of the optical transceiver cannot be frequently performed. For this reason, there is a possibility that a period during which the optical transceiver does not operate with an appropriate light emission amount due to a change over time may occur.

  Further, in the conventional optical transceiver, since it is necessary to perform the inspection with the optical transceiver removed from the ONU board (the optical circuit of the optical transceiver is disconnected from the ONU), the optical transceiver and the ONU board are removed. In order to be possible, both had to be manufactured as separate bodies. For this reason, there was a limit in reducing the manufacturing cost of ONU.

  Neither of the above-mentioned Patent Documents 1 and 2 discloses a solution to the above problem.

  The present invention has been made to solve the above-described problems, and a light emitting element driving device, an optical communication device, a light emitting element driving device control method, and a light emitting element driving device capable of easily performing an appropriate inspection. The purpose is to provide a control program.

  In order to achieve the above object, according to one aspect of the present invention, a light emitting element driving apparatus capable of selecting a normal operation mode and an adjustment inspection mode includes an input unit for inputting a transmission electric signal, and a current flowing through the light emitting element. A current control unit for controlling the output and an output unit for outputting a plurality of types of inspection signals having different mark rates, and the current control unit emits light based on a transmission electrical signal input from the input unit in the normal operation mode. In the adjustment inspection mode, the current flowing through the element is controlled based on a plurality of types of inspection signals output from the output unit and having different mark ratios.

  According to the light emitting element driving apparatus configured as described above, the normal operation mode and the adjustment inspection mode can be selected. In the adjustment inspection mode, the current flowing through the light emitting element can be controlled based on a plurality of types of inspection signals output from the output unit and having different mark rates. Thereby, the light emitting element drive device which can perform an appropriate test | inspection easily can be provided.

  Preferably, the plurality of types of inspection signals include at least an inspection signal with a mark ratio of 0% and an inspection signal with a mark ratio of 100%.

  As described above, more accurate inspection can be performed by controlling the current flowing through the light emitting element based on at least the inspection signal with a mark ratio of 0% and the inspection signal with a mark ratio of 100%.

  Preferably, the light emitting element driving device is a selection unit that can select a transmission electric signal and an inspection signal input from the input unit as signals to be sent to the current control unit, and electrically connect the output unit and the input unit. It further includes a selection unit having a function of blocking.

  By providing the selection unit as described above, the transmission electrical signal and the inspection signal input from the input unit can be selected as signals to be sent to the current control unit. In addition, since the selection unit has a function of cutting off the electrical connection between the output unit and the input unit, the quality of the transmission electrical signal input from the input unit and the inspection signal output from the output unit can be maintained.

  Preferably, the input unit and the current control unit are electrically connected, and the output unit further includes a voltage control unit that controls a voltage at a connection portion between the input unit and the current control unit, and the voltage control unit includes: In the adjustment inspection mode, by controlling the voltage at the connection portion between the input unit and the current control unit, a plurality of types of inspection signals having different mark rates are applied to the current control unit.

  As described above, in the adjustment inspection mode, the voltage at the connection portion between the input unit and the current control unit is controlled, and a plurality of types of inspection signals having different mark rates are provided to the current control unit, thereby emitting light. The circuit configuration of the element driving device can be simplified.

  Preferably, an element for blocking an AC signal is provided on a line for the voltage control unit to control a voltage at a connection portion between the input unit and the current control unit.

  As described above, in the line for controlling the voltage at the connection portion between the input unit and the current control unit, the quality of the transmission electric signal input from the input unit can be maintained by providing an element that blocks the AC signal. it can.

  Preferably, the current control unit and the light emitting element are connected by DC coupling.

  As described above, by connecting the current control unit and the light emitting element by DC coupling, the light emitting element can be driven even by a low frequency (for example, direct current) signal.

  Preferably, the light emitting element driving device further includes a detection unit that detects light output from the light emitting element and an adjustment unit that adjusts a current flowing through the light emitting element based on a detection result of the detection unit in the adjustment inspection mode.

  As described above, it is possible to perform inspection and adjustment more easily by adjusting the current flowing through the light emitting element by the detection unit and the adjustment unit.

  Preferably, the light emitting element driving device further includes a temperature monitor circuit for detecting a temperature in the apparatus, and based on the output of the temperature monitor circuit, the magnitude of the bias current flowing through the light emitting element and the magnitude of the modulation current flowing through the light emitting element are determined. Control.

  As described above, by controlling the magnitude of the bias current flowing through the light emitting element and the magnitude of the modulation current flowing through the light emitting element based on the output of the temperature monitor circuit, the driving and adjustment inspection of the light emitting element according to the temperature can be performed. It becomes possible.

  According to another aspect of the present invention, an optical communication device including a communication control unit includes a light emitting element driving device described in any of the above, and an optical transmitter including a light emitting element driven by the light emitting element driving device. And an optical receiver that receives an optical signal from the outside, the components that constitute the communication control unit, the components that constitute the optical transmitter, and the components that constitute the optical receiver are mounted on a single substrate. Is done.

  As described above, the components of the optical communication device, the components constituting the optical transmitter, the components constituting the optical transmitter, and the components constituting the optical receiver are mounted on a single substrate, thereby configuring the optical communication device. Can be simplified.

  According to still another aspect of the present invention, in the control method of the light emitting element driving apparatus capable of selecting the normal operation mode and the adjustment inspection mode, the light emitting element driving apparatus includes: an input unit that inputs a transmission electric signal; A current control unit that controls a current flowing through the light emitting element, and an output unit that outputs a plurality of types of inspection signals having different mark rates, and the control method is a transmission electrical signal input from the input unit in the normal operation mode In the adjustment control mode, the first control step for controlling the current flowing through the light emitting element based on the output current, the current flowing through the light emitting element based on a plurality of types of inspection signals having different mark ratios output from the output unit. And a second control step for controlling.

  According to the control method of the light emitting element driving apparatus configured as described above, it is possible to select the normal operation mode and the adjustment inspection mode. In the adjustment inspection mode, the current flowing through the light emitting element can be controlled based on a plurality of types of inspection signals output from the output unit and having different mark rates. Thereby, the control method of the light emitting element drive device which can perform an appropriate test | inspection easily can be provided.

  According to still another aspect of the present invention, in a control program for a light emitting element driving apparatus capable of selecting a normal operation mode and an adjustment inspection mode, the light emitting element driving apparatus includes an input unit that inputs a transmission electric signal, A current control unit that controls a current flowing through the light emitting element, and an output unit that outputs an inspection signal having a predetermined mark ratio, and the control program is based on a transmission electrical signal input from the input unit in the normal operation mode. In the first control step for controlling the current flowing through the light emitting element and the adjustment inspection mode, a plurality of types of inspection signals having different mark ratios are output to the output unit, and a plurality of types of inspection signals having different mark ratios are output. Based on this, the computer is caused to execute a second control step for controlling the current flowing through the light emitting element.

  According to the control program of the light emitting element driving apparatus configured as described above, it is possible to select the normal operation mode and the adjustment inspection mode. In the adjustment inspection mode, it is possible to output a plurality of types of inspection signals having different mark ratios to the output unit, and to control the current flowing through the light emitting element based on the plurality of types of inspection signals having different mark ratios. Become. Thereby, it is possible to provide a control program for the light-emitting element driving device that can easily perform an appropriate inspection.

  According to the present invention, since the light emitting element can be driven based on the inspection signal having a different mark ratio in the adjustment inspection mode, separately from the operation in the normal operation mode, the light emitting element capable of easily performing an appropriate inspection The driving device, the optical communication device, the control method for the light emitting element driving device, and the control program for the light emitting element driving device can be provided.

It is a block diagram which shows the structure of ONU in the 1st Embodiment of this invention. FIG. 2 is a block diagram illustrating a configuration of an optical transmitter 110 in FIG. 1. FIG. 2 is a more specific circuit diagram of the optical transmitter 110 in FIG. 1. 6 is a diagram illustrating a specific example of a table recorded in a recording unit 206. FIG. It is a figure which shows the relationship between the electric current value which permeate | transmits laser diode LD, and the optical power which laser diode LD outputs. It is a figure which shows the relationship between the mark rate of the signal which drives laser diode LD, and average optical power. It is a figure for demonstrating the content of adjustment in adjustment inspection mode. It is a flowchart which shows the process which the control part (CPU) 202 of ONU100 in 1st Embodiment performs in adjustment inspection mode. It is a block diagram which shows the structure of optical transmitter 110 'used for ONU100 in 2nd Embodiment. FIG. 10 is a more specific circuit diagram of the optical transmitter 110 ′ of FIG. 9. It is a flowchart which shows the process which the control part (CPU) 202 of ONU100 in 2nd Embodiment performs in adjustment test | inspection mode. It is a flowchart which shows the process which the control part (CPU) 202 of ONU100 in 1st or 2nd embodiment performs in a normal operation mode.

[First Embodiment]
FIG. 1 is a block diagram showing a configuration of an ONU in the first embodiment of the present invention.

  Referring to the figure, ONU 100 (a specific example of an optical communication device) includes a communication control unit 104 connected to a LAN (router or the like) or an optical telephone, and an optical transceiver 106 connected to the communication control unit 104. . The communication control unit 104 includes a MAC_LSI (Media Access Control Large Scale Integration). The optical transceiver 106 is optically connected to the OLT by a single optical fiber 114 via an optical coupler (passive optical branching node) (not shown).

  The optical transceiver 106 includes an optical receiver 108, an optical transmitter 110, and an optical multiplexer / demultiplexer 112. The optical receiver 108 is a device that converts an optical signal (downlink frame) received from the optical fiber 114 via the optical multiplexer / demultiplexer 112 into an electrical signal and transmits the electrical signal to the communication control unit 104. The optical transmitter 110 is a device that converts the electrical signal received from the communication control unit 104 into an optical signal (upstream frame) and sends the optical signal to the optical fiber 114 via the optical multiplexer / demultiplexer 112. The optical transmitter 110 receives an electrical signal from the communication control unit 104 via the input terminal I (an example of an input unit), and outputs the optical signal to the optical multiplexer / demultiplexer 112.

  A plurality of electronic components constituting the communication control unit 104 and a plurality of electronic components constituting the optical transceiver 106 are mounted on one common substrate 102. That is, in the present embodiment, the optical transceiver 106 is not packaged, and the optical transceiver 106 and the communication control unit 104 cannot be easily attached and detached. By operating the optical transceiver 106 in the adjustment inspection mode on the substrate 102, a preferable modulation current Imod and bias current Ibias for driving the laser diode at a certain temperature are calculated. The calculated preferable modulation current Imod and bias current Ibias are set in the optical transceiver 106 (adjustment of the optical transceiver 106 is performed).

  Conventionally, the communication control unit 104 and the optical transceiver 106 are manufactured as separate parts, and the communication control unit 104 and the optical transceiver 106 are connected after adjusting the optical transceiver 106. In this embodiment, due to the presence of the adjustment inspection mode, the optical transceiver 106 can be adjusted even if a circuit board in which the communication control unit 104 and the optical transceiver 106 are integrated is employed. For this reason, the number of parts constituting the ONU 100 can be reduced, and the cost of the ONU 100 can be reduced.

  FIG. 2 is a block diagram showing a configuration of the optical transmitter 110 of FIG.

  Referring to the drawing, the optical transmitter 110 includes a laser driving circuit 200 (an example of a light emitting element driving device) and a TOSA (Transmitter Optical Subsembly) 250.

  The TOSA 250 includes a laser diode LD (an example of a light emitting element) and a photodiode PD (an example of a detection unit). The photodiode PD is a diode for monitoring light output from the laser diode LD. In the case of a semiconductor laser, the light generated from the PN junction and output from a certain direction of the laser diode LD is sent to the optical multiplexer / demultiplexer 112 (FIG. 1) through the lens. Light output from the other direction of the laser diode is input to the photodiode PD, and the emission intensity and emission characteristics are monitored.

  An optical multiplexer / demultiplexer 112 (FIG. 1) is provided between the laser diode LD and the optical fiber 114. The optical fiber 114 and the optical transmitter 110, and the optical fiber 114 and the optical receiver 108 are optically connected via the optical multiplexer / demultiplexer 112, respectively.

  The laser driving circuit 200 includes a control unit (CPU) 202 that controls the laser driving circuit 200, a temperature monitoring circuit 204 (including a thermistor), a recording unit 206 including an EEPROM and the like, and test signals having different mark rates. From a test signal output circuit 208 (an example of an output unit) capable of outputting (an example of a test signal), a transmission electric signal from the communication control unit 104 input from the input terminal I, or a test signal output circuit 208 A selection unit (selector) 210 that selects and outputs one of the test signals, and a modulation current control unit 212 (current) that controls a modulation current for driving the laser diode LD based on the output of the selection unit 210 An example of a control unit), an LD bias control unit 214 that controls a bias current for driving the laser diode LD, It monitors the electrical signals from the diode PD, and an LD light output power monitor 216 to send the amount of light received by the photodiode PD to the control section 202 (., Including a current-voltage conversion circuit).

  In the laser drive circuit 200, a transmission electrical signal is input from the input terminal I. Further, the detection signal of the photodiode PD is input from the input terminal I3. A modulation current is output from the output terminal O1 to the laser diode LD, and a bias current is output from the output terminal O2 to the laser diode LD. The sum of the modulation current and the bias current becomes the drive current for the laser diode LD.

  When the current mode of the laser drive circuit 200 is the normal operation mode, the control unit 202 sends a control signal to the selection unit 210 so that a transmission electric signal is output from the selection unit 210. On the other hand, when the current mode of the laser driving circuit 200 is the adjustment inspection mode, the control unit 202 sends a control signal to the selection unit 210 so that a test signal is output from the selection unit 210. In addition, when the current mode of the laser driving circuit 200 is the adjustment inspection mode, the control unit 202 sends a signal for designating the mark ratio of the test signal to the test signal output circuit 208. The test signal output circuit 208 outputs a signal having a designated mark ratio.

  Here, the mark rate refers to the proportion of the time occupied by the digital signal “1” within a certain time. When “0” is always transmitted during a certain time, the mark rate is 0 (0%). When “1” is always transmitted during a certain time, the mark rate is 1 (100%). If the frequency at which “1” and “0” are transmitted within a certain time is the same, the mark rate is 0.5 (50%).

  More specifically, in the adjustment inspection mode, the control unit 202 requests the test signal output circuit 208 to output a signal having the first mark ratio, and the test signal output circuit 208 responds to the request by the test signal output circuit 208. Output rate signal. Thereafter, the control unit 202 requests the test signal output circuit 208 to output a signal with the second mark rate, and the test signal output circuit 208 outputs a signal with the second mark rate in response to this ( Thereafter, the control unit 202 may make a request to the test signal output circuit 208 to output a signal of the third and subsequent mark ratios).

  Alternatively, the test signal output circuit 208 may autonomously output a plurality of types of test signals each indicating a different mark rate. That is, the test signal output circuit 208 outputs the first mark ratio signal and the second mark ratio signal (and thereafter the third and subsequent mark ratio signals) regardless of the instruction of the control unit 202. Also good.

  In order to maintain the quality of the transmission electrical signal and the test signal, the selection unit 210 is preferably configured so that the output line of the test signal output circuit 208 and the line from the input terminal I are not electrically connected. . When the normal operation mode is selected, the line from the input terminal I and the input line of the modulation current control unit 212 are electrically connected, and the output line of the test signal output circuit 208 is connected to the modulation current control unit. It is desirable to configure the circuit of the selection unit 210 so as not to be electrically connected to the input line 212. Similarly, when the adjustment inspection mode is selected, the output line of the test signal output circuit 208 and the input line of the modulation current control unit 212 are electrically connected, and the line from the input terminal I is modulated current control. It is desirable to configure the circuit of the selection unit 210 so that it is not electrically connected to the input line of the unit 212. With such a configuration, it is possible to prevent deterioration of the quality of the transmission electric signal due to the provision of the test signal output circuit 208. In the adjustment inspection mode, the communication control unit 104 (FIG. 1) and the optical transmitter 110 can be electrically disconnected, so that the quality of the test signal can be maintained. In the normal operation mode, the test signal output circuit 208 and the line through which the transmission electric signal flows can be electrically disconnected, so that the quality of the transmission electric signal can be maintained.

  At the start of the adjustment inspection mode or in the normal operation mode, the control unit 202 records the temperature information in the optical transmitter 110 (or the temperature information of the laser diode LD or the vicinity thereof) output from the temperature monitoring circuit 204 in the recording unit 206. Are converted into the value of the bias current Ibias and the value of the modulation current Imod based on the table (or conversion formula) recorded in the table. The LD bias control unit 214 and the modulation current control unit 212 drive the laser diode LD based on the value of the bias current Ibias output from the control unit 202 and the value of the modulation current Imod.

  The controller 202 analyzes the current emission characteristics of the laser diode LD based on the signal from the LD light output power monitor 216 during the operation in the adjustment inspection mode. Based on the analysis result, the preferred bias current Ibias value of the laser diode LD and the modulation current Imod at the temperature in the optical transmitter 110 grasped from the temperature monitor circuit 204 (or the temperature at or near the laser diode LD) X ° C. Value. The table or conversion formula of the recording unit 206 is updated (overwritten) by the obtained value of the bias current Ibias and the value of the modulation current Imod. Subsequent control of the laser diode LD is performed using the updated table or conversion formula.

  For example, when the table is recorded in the recording unit 206, only the part corresponding to the temperature X ° C. in the table may be rewritten in the update. Alternatively, the control unit 202 determines a temperature other than X ° C. from the analysis result of the light emission characteristic at the temperature X ° C. and the temperature characteristic of the laser diode LD stored in the recording unit 206 (this may be a table or a calculation formula). The value of the preferred bias current Ibias and the value of the modulation current Imod of the laser diode LD at the temperature is calculated, and thereby the value of the bias current Ibias corresponding to a temperature other than X ° C. in the table recorded in the recording unit 206 is calculated. The value of the modulation current Imod may also be updated.

  When recording the conversion formula in the recording unit 206, variables (parameters, etc.) of the conversion formula are updated based on the preferable bias current Ibias value and the modulation current Imod value of the laser diode LD at the current temperature X ° C. The

  In this way, even if the characteristics of the laser diode LD change due to aging, the data in the recording unit 206 can be updated and optimized.

  FIG. 3 is a more specific circuit diagram of the optical transmitter 110 of FIG.

  In the actual laser driving circuit 200, the transmission electrical signal from the communication control unit 104 is sent by two lines that transmit a differential signal. That is, when one of the two lines is HIGH level, the other is LOW level, and when one is LOW level, the other is HIGH level. By transmitting the transmission electric signal as a differential signal, the resistance of the transmission electric signal to noise can be increased. Transmission electric signals from the two lines are input to the laser drive circuit 200 from the input terminals I1 and I2 (in FIG. 1 and FIG. 2, they are collectively referred to as the input terminal I). Transmission electric signals from the input terminals I 1 and I 2 are input to the selection unit 210. A power source VT is connected to each of the two lines connecting the input terminals I1 and I2 to the selection unit 210 via impedance matching resistors R1 and R2.

  Similarly to the input terminals I1 and I2, the test signal output circuit 208 also outputs a differential signal to the selection unit 210 through two lines.

  The modulation current control unit 212 includes two buffer circuits 226 (here, a voltage follower circuit having an amplification degree of “1”) connected to the two differential output lines of the selection unit 210 and two buffer circuits 226. Transistors Tr1 and Tr2 to which the respective base electrodes are connected, and resistors R3 and R4 whose one ends are connected to the collector electrodes of the transistors Tr1 and Tr2 and whose other ends are connected to the power source Vcc, One end of the transistors Tr1 and Tr2 is connected to the emitter electrode, and the other end is connected to the ground potential.

  The transistors Tr1 and Tr2, resistors R3 and R4, and the modulation current source 222 constitute a differential amplifier circuit that outputs a signal proportional to the difference between the differential signals sent from the previous stage. The output terminals of the differential amplifier circuit are a node N1 on a line connecting the resistor R3 and the transistor Tr1, and a node N2 on a line connecting the resistor R4 and the transistor Tr2. The node N1 and the node N2 correspond to the output terminal O1 of the modulation current control unit 212 illustrated in FIG.

  The modulation current source 222 determines the total current flowing through the transistors Tr1 and Tr2. The output of the differential amplifier circuit is determined by the balance of the current flowing through the transistors Tr1 and Tr2 (and the current flowing through the modulation current source 222). The control unit (CPU) 202 controls the modulation current source 222 to determine the modulation current Imod of the laser diode LD.

  Two lines connecting the nodes N1 and N2, the LD bias control unit 214, and the laser diode LD are lines for controlling the current flowing through the laser diode LD. These two lines are constituted by lines for DC-coupling each component. As a result, even a DC signal with a mark rate of 0% and 100% or an AC signal with a mark rate of 50% can be transmitted from the modulation current control unit 212 to the laser diode LD.

  LD bias controller 214 includes nodes N3 and N4 that are DC-coupled to nodes N1 and N2, respectively, and ferrite bead (or coil) FB1 having one end connected to node N3 and the other end connected to power supply Vcc, A bias current source 224 having one end connected to a node N4 via a ferrite bead (or coil) FB2 is provided. The other end of the bias current source 224 is connected to the ground potential. Laser diode LD is connected between nodes N3 and N4.

  The control unit (CPU) 202 controls the bias current source 224, whereby the bias current Ibias of the laser diode LD is determined.

  The buffer circuit 226 is used for stabilizing the laser driving circuit 200 and can be omitted.

  In the circuit of FIG. 3, for example, VT = 2.25V, R1 = R2 = 50Ω, and R3 = R4 = 25Ω.

  The circuit described above operates as follows.

  The selection unit 210 outputs the differential signals from the input terminals I1 and I2 to the gate electrodes of the subsequent transistors Tr1 and Tr2 (via the buffer circuit 226) or from the two lines of the test signal output circuit 208, respectively. Is determined based on the output of the control unit (CPU) 202 as to whether or not to output the differential signal of (1) via the buffer circuit 226 to the gate electrodes of the subsequent transistors Tr1 and Tr2. In the normal operation mode, the control unit 202 sends a control signal to the selection unit 210 so that signals from the input terminals I 1 and I 2 are output to the buffer circuit 226.

  In the normal operation mode, when the input terminal I1 is at the HIGH level and the input terminal I2 is at the LOW level, the transistor Tr1 is turned on and the transistor Tr2 is turned off. As a result, only the bias current Ibias flows through the laser diode LD, and the laser diode LD outputs only weak light. This state is a state in which the laser diode LD is transmitting a LOW level signal (the optical power of the laser diode LD is “P0”).

  In the normal operation mode, when the input terminal I1 is at the LOW level and the input terminal I2 is at the HIGH level, the transistor Tr1 is turned off and the transistor Tr2 is turned on. As a result, a bias current Ibias + modulation current Imod flows through the laser diode LD, and the laser diode LD outputs strong light. This state is a state in which the laser diode LD transmits a HIGH level signal (the optical power of the laser diode LD is “P1” (where P1> P0)).

  Further, for example, when a signal with a mark ratio of 50% is input to the modulation current control unit 212, a current of the bias current Ibias + (modulation current Imod / 2) flows through the laser diode LD on average over time. . The average optical power of the laser diode LD averaged over time is (P0 + P1) / 2.

  In the adjustment inspection mode, the control unit 202 sends a control signal to the selection unit 210, so that the signal from the test signal output circuit 208 is output to the buffer circuit 226. The control unit 202 also outputs a signal for selecting the mark ratio of the test signal to be output to the test signal output circuit 208. Accordingly, in the adjustment inspection mode, a differential signal similar to the transmission electrical signal is output from the test signal output circuit 208 via two lines.

  The output of the test signal output circuit 208 in the adjustment inspection mode is as follows.

  When the mark rate selection signal from the control unit 202 indicates a mark rate of 0%, the positive output line of the test signal output circuit 208 is fixed to + 2.3V, and the negative line is fixed to 0V. As a result, the transistor Tr1 is turned on and the transistor Tr2 is turned off. As a result, only the bias current Ibias flows through the laser diode LD, and the laser diode LD outputs only weak light.

  When the mark ratio selection signal from the control unit 202 indicates a mark ratio of 100%, the positive output line of the test signal output circuit 208 is fixed to 0V, and the negative line is fixed to + 2.3V. As a result, the transistor Tr1 is turned off and the transistor Tr2 is turned on. As a result, a bias current Ibias + modulation current Imod flows through the laser diode LD, and the laser diode LD outputs strong light.

  When the mark rate selection signal from the control unit 202 indicates a mark rate of 50%, a 2.3 V AC signal (for example, a 10 Gbps signal) is output from the plus side output line and the minus side output line of the test signal output circuit 208. Is output. Thereby, the transistor Tr1 and the transistor Tr2 are alternately turned on and off. When averaged over time, a current of bias current Ibias + (modulation current Imod / 2) flows through the laser diode LD.

  FIG. 4 is a diagram illustrating a specific example of a table recorded in the recording unit 206.

  Here, the temperature is converted into the value of the bias current Ibias (the magnitude of the bias current Ibias) and the value of the modulation current Imod (the magnitude of the modulation current Imod) using a table. That is, the value of the bias current Ibias to be set and the modulation current Imod are recorded in association with each of the predetermined temperatures within the temperature of 0 ° C. to 70 ° C. Since the laser diode LD tends to have a weak emission intensity as the temperature increases, the table is set so that the value of the bias current Ibias and the value of the modulation current Imod increase as the temperature increases.

  FIG. 5 is a diagram showing the relationship between the current value transmitted through the laser diode LD and the optical power output from the laser diode LD.

  In the graph of the figure, the horizontal axis represents the current value that passes through the laser diode LD, and the vertical axis represents the optical power output from the laser diode LD. As shown in the figure, when the current passing through the laser diode LD is within a certain range from “0”, there is a region (inactive region) where the output optical power does not change much even if the current is changed. . When the current exceeds a certain threshold value, a region where stimulated emission starts (linear operation region) is formed, and in this region, the optical power greatly changes in accordance with the change of the current. A bias current Ibias is applied to the laser diode LD so that the laser diode LD operates in the linear operation region in both the normal operation mode and the adjustment inspection mode. When the modulation current Imod does not flow, the current flowing through the laser diode LD is Ibias, and the optical power at that time is P0. When the modulation current Imod flows, the current flowing through the laser diode LD is Ibias + Imod, and the optical power at that time is P1. Depending on the difference between the optical power P0 and the optical power P1, a digital signal of “0” or “1” is transmitted.

  FIG. 6 is a diagram showing the relationship between the mark ratio of the signal for driving the laser diode LD and the average optical power.

  Referring to FIG. 6, when the mark ratio is 0, the optical power of the laser diode LD is always P0 (FIG. 5), so the average optical power is also P0. When the mark ratio is 1 (100%), the optical power of the laser diode LD is always P1 (FIG. 5), so the average optical power is also P1. When the mark rate is 0.5 (50%), the optical power of the laser diode LD is half in the period P0 and half in the period P1, so the average optical power is (P0 + P1) / 2. The extinction ratio of the laser diode LD is represented by P1 / P0.

  FIG. 7 is a diagram for explaining the adjustment contents in the adjustment inspection mode.

  In the figure, the horizontal axis indicates the transmission current of the laser diode LD, and the vertical axis indicates the average optical power of the laser diode LD.

  Assume that the bias current value and the modulation current value recorded at the recording unit 206 when the ONU 100 is introduced are Ibias (before adjustment) and Imod (before adjustment), respectively. This is because the characteristics when the laser diode LD is introduced are shown in FIG. That is, Ibias (before adjustment) and Imod (before adjustment) are set in order to cause the laser diode LD to emit light at a temperature T in the range of the average optical power from PL to PH. For example, when a signal with a mark ratio of 50% is output, the current applied to the laser diode LD is Ibias (before adjustment) + (Imod (before adjustment) / 2) in terms of time average. The average optical power at this time is PM.

  It is assumed that the characteristics of the laser diode LD at the temperature T change from A to B in FIG. That is, it is assumed that the light emission intensity of the laser diode LD is lowered due to the change over time.

  When the characteristics of the laser diode LD change from A to B in FIG. 7, when currents Ibias (before adjustment) and Imod (before adjustment) are applied to the laser diode LD according to the recording unit 206, the average optical power of the laser diode LD is It is in the range from PL ′ to PH ′, and changes compared to the time of introduction. Further, the average optical power when the mark ratio is 50% also changes from PM to PM '. The extinction ratio has also changed.

  In the adjustment inspection mode, the currents Ibias and Imod are corrected in order to correct such a characteristic change of the laser diode LD. More specifically, when the temperature is T, the laser diode LD is driven according to the values of Ibias (before adjustment) and Imod (before adjustment) recorded in the recording unit 206. Test signals with mark rates of 0%, 50%, and 100% are applied to the laser diode LD, and the average optical power of the laser diode LD is measured by the photodiode PD. Here, they are PL ′, PM ′, and PH ′, respectively.

  The current characteristic B of the laser diode LD can be obtained from the values of PL ′, PM ′, PH ′ and the values of Ibias (before adjustment) and Imod (before adjustment). Based on the characteristic B of the laser diode LD, Ibias '(after adjustment) and Imod' (after adjustment) for causing the laser diode LD to emit light in the range of the average optical power PL to PH can be obtained. The recording data of the recording unit 206 is updated based on the values of Ibias '(after adjustment) and Imod' (after adjustment), and the adjusted recording data is used in the next drive of the laser diode LD.

  FIG. 8 is a flowchart illustrating processing executed in the adjustment inspection mode by the control unit (CPU) 202 of the ONU 100 according to the first embodiment.

  The control unit (CPU) 202 operates according to a program that executes the processing of the flowchart of FIG. When the ONU 100 shifts to the adjustment inspection mode, the control unit 202 sends a control signal to the selection unit 210 in step S101 so that the signal from the test signal output circuit 208 is output to the modulation current control unit 212. In step S <b> 103, the control unit 202 measures the current temperature T in the ONU 100 based on the output of the temperature monitor circuit 204. In step S105, the control unit 202 acquires the table (FIG. 4) in the recording unit 206, and converts the measured temperature T into Ibias and Imod values based on the table. The control unit 202 sends control signals to the modulation current source 222 and the bias current source 224 so that the currents of the modulation current source 222 and the bias current source 224 become Ibias and Imod.

  In step S107, the control unit 202 sends a control signal to the test signal output circuit 208 so as to output a test signal with a mark rate of 0%. The control unit 202 measures and stores the average optical power output from the laser diode LD based on the signal from the LD light output power monitor 216.

  In step S109, the control unit 202 sends a control signal to the test signal output circuit 208 so as to output a test signal with a mark rate of 50%. The control unit 202 measures and stores the average optical power output from the laser diode LD based on the signal from the LD light output power monitor 216.

  In step S111, the control unit 202 sends a control signal to the test signal output circuit 208 so as to output a test signal having a mark rate of 100%. The control unit 202 measures and stores the average optical power output from the laser diode LD based on the signal from the LD light output power monitor 216.

  In step S113, the control unit 202 obtains the characteristics and extinction ratio of the laser diode LD at the current temperature T shown in FIG. 7 based on the measurement results in steps S107 to S111. In step S115, the control unit 202 determines Ibias ′ (after adjustment) such that the maximum and minimum values of the average optical power become PH and PL in accordance with the characteristics of the current laser diode LD obtained in step S113. ), Imod ′ (after adjustment) is obtained. The control unit 202 obtains Ibias '(after adjustment) and Imod' (after adjustment) at a temperature other than the temperature T based on the temperature characteristics of the laser diode LD stored in the recording unit 206.

  In step S117, the control unit 202 overwrites the recording unit 206 with Ibias '(after adjustment) and Imod' (after adjustment) at each temperature obtained in step S115.

  Steps S101 and S107 to S111 constitute a control step for controlling the current flowing through the laser diode LD based on a plurality of types of inspection signals having different mark rates in the adjustment inspection mode.

[Second Embodiment]
Hereinafter, the difference between the ONU 100 according to the second embodiment of the present invention and the ONU 100 according to the first embodiment will be described.

  FIG. 9 is a block diagram illustrating a configuration of an optical transmitter 110 ′ used in the ONU 100 according to the second embodiment.

  Compared with the optical transmitter 110 of FIG. 2, the optical transmitter 110 ′ of FIG. 9 is not provided with the selection unit 210 and the test signal output circuit 208, but is provided with a voltage control unit 302 instead. Yes. The transmission electrical signal input from the input terminal I is input to the voltage control unit 302. The output of the voltage control unit 302 is input to the modulation current control unit 212.

  FIG. 10 is a more specific circuit diagram of the optical transmitter 110 ′ of FIG. 9.

  Compared with the optical transmitter 110 in FIG. 3, in the optical transmitter 110 ′ in FIG. 10, the input terminals I <b> 1 and I <b> 2 are electrically connected to the buffer circuit 226, respectively.

  The control unit (CPU) 202 is connected to a line connecting the input terminal I1 and the buffer circuit 226 via the resistor R5 and the ferrite bead FB3. The control unit 202 is connected to a line connecting the input terminal I2 and the buffer circuit 226 via the resistor R6 and the ferrite bead FB4. This is a configuration for controlling the voltage of a line connecting the input terminals I1 and I2 and the buffer circuit 226 by the voltage control lines VDAC1 and VDAC2 of the control unit 202 (corresponding to the voltage control unit 302 of FIG. 9).

  Ferrite beads FB3 and FB4 have the property of blocking (blocking) high-frequency signals and allowing low-frequency signals to pass. This prevents transmission electrical signals (high-frequency signals, AC components) input from the input terminals I1 and I2 from flowing to the control unit 202 side. As a result, deterioration of a transmission electric signal (for example, a 10 Gbps signal) from the communication control unit 104 is prevented.

  In the adjustment inspection mode, the control unit 202 can input a LOW level signal or a HIGH level test signal to the input terminal of the buffer circuit 226 via the voltage control lines VDAC1 and VDAC2. That is, in the second embodiment, the control unit 202 assumes the function of the test signal output circuit 208 described in the first embodiment. Since the ferrite beads FB3 and FB4 are provided, the test signal that can be input to the buffer circuit 226 is a DC signal. For this reason, the mark rate of the test signal in the ONU 100 of the second embodiment is set to 0% or 100%.

  In the circuit of FIG. 10, for example, VT = 2.25V, R1 = R2 = 50Ω, R3 = R4 = 25Ω, and R5 = R6 = 10Ω.

  When the inspection is performed at the mark rate of 0% in the adjustment inspection mode, the voltage of the line connecting the input terminal I1 and the buffer circuit 226 is fixed to + 2.3V by the voltage control line VDAC1, and the input terminal I2 is fixed by the voltage control line VDAC2. And the voltage of the line connecting the buffer circuit 226 is fixed to 0V. As a result, the transistor Tr1 is turned on and the transistor Tr2 is turned off. Only the current Ibias flows through the laser diode LD.

  When the inspection is performed at the mark rate of 100% in the adjustment inspection mode, the voltage of the line connecting the input terminal I1 and the buffer circuit 226 is fixed to 0 V by the voltage control line VDAC1, and the input terminal I2 and the buffer are fixed by the voltage control line VDAC2. The voltage of the line connecting the circuit 226 is fixed to + 2.3V. As a result, the transistor Tr1 is turned off and the transistor Tr2 is turned on. A current of Ibias + Imod flows through the laser diode LD.

  FIG. 11 is a flowchart illustrating processing executed in the adjustment inspection mode by the control unit (CPU) 202 of the ONU 100 according to the second embodiment.

  In the flowchart of FIG. 11 including steps S203 to S217, processes corresponding to step S101 (switching process of the selection unit 210) and step S109 (output of a test signal with a mark rate of 50%, optical power acquisition process) of FIG. It is omitted. In the adjustment of the ONU 100 according to the second embodiment, the average optical power when the mark rate is 0% (average optical power when Ibias (before adjustment) in FIG. 7 flows) and the average when the mark rate is 100% are obtained. The optical power (the average optical power when Ibias (before adjustment) + Imod (before adjustment) in FIG. 7 flows) is measured (steps S203 to S211), and the measured value of the laser diode LD after time at temperature T is measured. Characteristics are obtained (step S213). Based on the characteristics of the laser diode LD after the lapse of time, Ibias '(after adjustment) and Imod' (after adjustment) for achieving the average optical powers PH and PL are obtained (step S215), and the adjustment of the optical transmitter 110 is performed. Is performed (step S217).

  In the second embodiment, an AC signal may be input from the control unit 202 to the buffer circuit 226 by not providing the ferrite beads FB3 and FB4. By doing in this way, adjustment inspection can be performed with a mark rate other than 0% and 100% (for example, 50%).

  Further, a capacitor (DC blocking capacitor) is connected to each of the connection line between the input terminal I1 and the communication control unit 104 and the connection line between the input terminal I2 and the communication control unit 104, and the input terminal I1 and It is desirable to configure the circuit so that the communication control unit 104 and each of the input terminal I2 and the communication control unit 104 are AC coupled. This prevents a test signal (DC signal) with a mark rate of 0% and 100% from flowing to the communication control unit 104 side.

[Processing in normal operation mode]
FIG. 12 is a flowchart showing processing executed in the normal operation mode by the control unit (CPU) 202 of the ONU 100 according to the first or second embodiment.

  Referring to the figure, control unit (CPU) 202 operates according to a program that executes the processing of the flowchart of FIG.

  When the ONU 100 shifts to the normal operation mode, the control unit 202 sends a control signal to the selection unit 210 in step S301 so that the signal from the input terminal I is output to the modulation current control unit 212 (first embodiment). Only for form). In step S <b> 303, the control unit 202 measures the current temperature T in the ONU 100 based on the output of the temperature monitor circuit 204. In step S305, the control unit 202 acquires a table (FIG. 4) in the recording unit 206, and converts the measured temperature T into values of Ibias and Imod based on the table. The control unit 202 sends control signals to the modulation current source 222 and the bias current source 224 so that the currents of the modulation current source 222 and the bias current source 224 become Ibias and Imod.

  In step S307, the ONU 100 drives the laser diode LD based on the transmission electrical signal input from the input terminal I.

  Steps S301 and S307 constitute a control step for controlling the current flowing through the laser diode LD based on the transmission electric signal input from the input terminal I in the normal operation mode.

[Effects of the embodiment]
According to the optical transmitter 110 configured as described above, and the optical transceiver 106 and the ONU 100 using the optical transmitter 110, test signals having different mark rates such as 0%, 50%, and 100% are generated in the optical transmitter 110. It can be used for adjustment inspection of the laser diode LD. Accordingly, the adjustment inspection can be easily performed without connecting a device for adjustment inspection separately.

  When the apparatus enters the adjustment inspection mode, inspection using test signals with different mark ratios is automatically performed, and the contents of the recording unit 206 are automatically updated. As a result, there is an advantage that even a user who does not have a skilled technique can perform an accurate adjustment inspection.

  In the first embodiment, the selection unit 210 is used to cut the electrical connection between the communication control unit 104 and the optical transmitter 110 and then adjust the optical transceiver 106 by the test signal output circuit 208. Inspection can be performed. As a result, the optical transceiver 106 does not have to be removed from the communication control unit 104 in order to perform the adjustment inspection of the optical transceiver 106 as in the related art. That is, even if the electronic components constituting the communication control unit 104 and the electronic components constituting the optical transceiver 106 are mounted on one common substrate 102, the adjustment inspection of the optical transceiver 106 can be performed. Further, by mounting the electronic components constituting the communication control unit 104 and the electronic components constituting the optical transceiver 106 on one common board 102, the number of components of the ONU 100 can be reduced.

  In the second embodiment, since it is not necessary to provide the selection unit 210 as in the first embodiment, the scale of the laser drive circuit can be reduced. In the second embodiment, since the signal from the communication control unit 104 can be blocked by the ferrite beads FB3 and FB4, the quality of the transmission electric signal can be maintained.

[Modification of Embodiment]
In the above-described embodiment, the example in which the light-emitting element driving device of the present invention is used for the optical transceiver 106 and the ONU 100 incorporating the optical transceiver 106 is shown, but the present invention is not limited to this, Can be applied to any device.

  Further, the laser diode LD is taken as an example of the light emitting element, but the present invention can be applied to other light emitting elements.

  In the first embodiment, examples of different mark rates are 0%, 50%, and 100% (in the second embodiment, 0% and 100%). However, the present invention is not limited to this. It may be adopted. However, the characteristics of the laser diode LD can be grasped more accurately by performing the adjustment inspection with the mark rates of 0% and 100%.

  Switching (selection) between the normal operation mode and the adjustment inspection mode may be performed by the user operating a switch (not shown). If the normal operation mode is executed for a predetermined time, the adjustment inspection mode is automatically performed. The operation in may be executed once. Further, the control unit 202 may switch between the normal operation mode and the adjustment inspection mode in accordance with an instruction from the OLT. Furthermore, in addition to the normal operation mode and the adjustment inspection mode, the light emitting element driving apparatus may be able to select another mode (third mode).

  In the measurement processing of PH, PL, and PM in FIG. 7, it is desirable to use an average value after performing measurement several times in consideration of measurement errors and the like.

  A computer control program for operating the control unit (CPU) 202 may be recorded in the control unit (CPU) 202 or may be recorded in the recording unit 206. The program may be recorded on an external recording medium and installed in the ONU 100 from an input terminal (not shown). Alternatively, the program may be installed in the ONU 100 through the Internet line. The computer operates by being recorded in some storage unit and read and executed by the computer.

  The above-described embodiment is to be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

100 ONU (an example of an optical communication device)
DESCRIPTION OF SYMBOLS 102 1 board | substrate 104 Communication control part 106 Optical transceiver 108 Optical receiver 110 Optical transmitter 112 Optical multiplexer / demultiplexer 114 Optical fiber 200 Laser drive circuit (an example of a light emitting element drive device)
202 Control unit (CPU)
204 Temperature monitor circuit 206 Recording unit 208 Test signal output circuit (an example of an output unit)
210 Selector (Selector)
212 Modulation current control unit (an example of a current control unit)
214 LD bias control unit 216 LD optical output power monitor 222 Modulation current source 224 Bias current source 226 Buffer circuit 302 Voltage control unit LD Laser diode (an example of a light emitting element)
PD photodiode (example of detector)
I, I1-I3 input terminals (an example of an input unit)
FB1 to FB4 Ferrite beads VDAC1, VDAC2 Voltage control line

Claims (11)

A light emitting element driving apparatus capable of selecting a normal operation mode and an adjustment inspection mode,
An input unit for inputting a transmission electric signal;
A current control unit for controlling a current flowing in the light emitting element;
An output unit that outputs a plurality of types of inspection signals each having a different mark rate,
The current controller is
In the normal operation mode, the current flowing through the light emitting element is controlled based on the transmission electrical signal input from the input unit,
In the adjustment inspection mode, a light-emitting element driving device that controls a current flowing through the light-emitting element based on a plurality of types of inspection signals output from the output unit and having different mark ratios.   The light emitting element driving device according to claim 1, wherein the plurality of types of inspection signals include at least an inspection signal having a mark ratio of 0% and an inspection signal having a mark ratio of 100%.   A selection unit capable of selecting a transmission electrical signal and the inspection signal input from the input unit as a signal to be sent to the current control unit, and a function of cutting off an electrical connection between the output unit and the input unit The light-emitting element driving device according to claim 1, further comprising a selection unit having the following. The input unit and the current control unit are electrically connected,
The output unit further includes a voltage control unit that controls a voltage at a connection portion between the input unit and the current control unit,
In the adjustment inspection mode, the voltage control unit applies a plurality of types of inspection signals having different mark ratios to the current control unit by controlling a voltage at a connection portion between the input unit and the current control unit. The light emitting element drive device according to claim 1 or 2.   The light emitting element drive device according to claim 4, wherein an element that blocks an AC signal is provided on a line for the voltage control unit to control a voltage at a connection portion between the input unit and the current control unit. .   The light emitting element driving device according to claim 1, wherein the current control unit and the light emitting element are connected by DC coupling. In the adjustment inspection mode, a detection unit that detects light output from the light emitting element;
The light emitting element drive device according to claim 1, further comprising an adjusting unit that adjusts a current flowing through the light emitting element based on a detection result of the detection unit. A temperature monitor circuit for detecting the temperature in the apparatus;
The magnitude of a bias current flowing through the light emitting element and a magnitude of a modulation current flowing through the light emitting element are controlled based on an output of the temperature monitor circuit. Light emitting element driving device. An optical communication device provided with a communication control unit,
A light-emitting element driving device according to any one of claims 1 to 8, and an optical transmitter including a light-emitting element driven by the light-emitting element driving device;
An optical receiver for receiving an optical signal from the outside,
An optical communication device in which a part constituting the communication control unit, a part constituting the optical transmitter, and a part constituting the optical receiver are mounted on a single substrate. A method of controlling a light emitting element driving apparatus capable of selecting a normal operation mode and an adjustment inspection mode,
The light emitting element driving device includes:
An input unit for inputting a transmission electric signal;
A current control unit for controlling a current flowing in the light emitting element;
An output unit that outputs a plurality of types of inspection signals each having a different mark rate,
The control method is:
A first control step for controlling a current flowing through the light emitting element based on a transmission electrical signal input from the input unit in the normal operation mode;
A light emitting element driving device comprising: a second control step for controlling a current flowing through the light emitting element based on a plurality of types of inspection signals output from the output unit and having different mark rates in the adjustment inspection mode; Control method. A control program for a light emitting element driving apparatus capable of selecting a normal operation mode and an adjustment inspection mode,
The light emitting element driving device includes:
An input unit for inputting a transmission electric signal;
A current control unit for controlling a current flowing in the light emitting element;
An output unit that outputs an inspection signal having a predetermined mark ratio,
The control program is
A first control step for controlling a current flowing through the light emitting element based on a transmission electrical signal input from the input unit in the normal operation mode;
In the adjustment inspection mode, a plurality of types of inspection signals having different mark rates are output to the output unit, and a current flowing through the light emitting element is controlled based on the plurality of types of inspection signals having different mark rates. A control program for a light emitting element driving apparatus, causing a computer to execute the second control step.

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