JP5419141B2 - Light intensity controller - Google Patents

Description

    The present invention relates to a light intensity controller.

  In a subscriber optical network, Passive Optical Network (PON) is widely adopted. In PON, a single optical fiber connected to a distribution station called Optical Line Terminal (OLT) is branched by a splitter and connected to many subscribers, so that the optical fiber is shared by many subscribers. The cost per hit is reduced. In general, since the subscriber does not always transmit a signal, the signal transmitted from the subscriber is an intermittent signal (burst signal) in which bit signals are bundled as shown in FIG.

  The burst signal transmitted from the subscriber is coupled to one fiber by the splitter and sent to the OLT. However, the intensity of each burst signal sent to the OLT varies due to differences in the distance from each subscriber to the splitter, individual differences in each subscriber's equipment, variations in excess loss due to differences in connection status, and the like.

  On the other hand, demands for increasing transmission capacity in subscribers are increasing year by year, and the transmission bit rate from subscribers is also increasing. When the bit rate increases, the optical signal receiver on the OLT side needs to receive at a high speed, but the dynamic range of the intensity of the optical signal that can be received by the increase in speed decreases. As described above, when the intensity of the burst signal sent to the OLT varies, it becomes difficult to receive a signal having a high bit rate.

  Therefore, an apparatus that outputs light intensity at a constant intensity by automatic control, called an automatic light intensity controller, is arranged at the front stage of receiving an optical signal in the OLT so that it can be received even if the dynamic range of the optical receiver is small. Become. That is, a signal with a high bit rate can be received.

  As shown in FIG. 3, the automatic light intensity controller includes a variable optical attenuator and an optical branching element disposed in a subsequent stage, and a monitor that converts an optical signal branched by the optical branching element into an electrical signal, Non-Patent Document 1 discloses an apparatus that performs control for driving a variable optical attenuator according to light intensity information obtained by the monitor.

  In Non-Patent Document 1, a constant intensity is provided by a feedback control system that is arranged at the subsequent stage of the variable optical attenuator and drives the variable optical attenuator according to light intensity information obtained by a monitor that converts an optical signal into an electrical signal. The method of outputting the optical signal is used.

  "Development of a high-speed optical auto-level controller using electro-optic variable optical attenuator" 2006 IEICE Electronics Society Conference (C-3-24)

Problems to be solved by the present invention

  When burst signals from a large number of subscribers are coupled to one optical fiber by a splitter, burst signals of various strengths as shown in FIG. 4 are input to the OLT one after another. Each burst signal is separated by a time when there is no signal called a guard time, but it is preferable to shorten the guard time without a signal as much as possible in order to increase the capacity. However, the method of Non-Patent Document 1 uses a feedback control method, and requires a control time of 10 times or more the response time of the variable optical attenuator that is the controlled object. It was difficult to control the intensity fluctuation instantly.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is a main object of the present invention to provide a light intensity controller that instantly outputs a burst signal automatically controlled to a constant intensity even when a burst signal of various intensity is input. And

Means for solving the problem

  An optical intensity controller according to claim 1 of the present invention includes an optical signal branching unit that branches a part of an input optical signal, an optical intensity monitor that monitors the intensity of the optical signal branched by the optical signal branching unit, and A variable optical attenuator capable of attenuating the optical signal and varying the amount of attenuation by a drive signal; an optical signal delaying unit disposed between the optical signal branching unit and the variable optical attenuator; and the optical intensity And a control means for driving the variable optical attenuator so as to have an output signal intensity corresponding to the intensity monitored by the monitor.

  Here, the “light intensity monitor for monitoring the intensity of the optical signal” means a monitoring means for converting the optical signal into a form of an electric signal such as voltage, current, and power. The “variable optical attenuator” means a means that attenuates an input optical signal, and the amount of attenuation can be varied by a control signal to be given. Since a high-speed drive type with a response time of 1 microsecond or less is preferable, examples of variable attenuating elements include, but are not limited to, elements capable of high-speed response such as electro-optic materials, electroabsorption materials, semiconductor materials, and acousto-optic materials. . The drive signal applied to the variable optical attenuator may be voltage, current, power, or light. Further, the “optical signal delay means” means means for giving a time delay of at least 20 nanoseconds or more while an optical signal travels from the optical signal branching means to the variable optical attenuator. In addition, “control means for driving the variable optical attenuator so that the intensity of the output signal according to the intensity monitored by the light intensity monitor” is to drive the variable optical attenuator according to the input signal intensity. Means feedforward control means. As a control signal generating means for driving the variable optical attenuator according to the input signal strength, the relationship between the electric signal input and attenuation amount of the variable optical attenuator obtained in advance by preliminary measurement or the like is obtained from an analog circuit or a digital circuit. A method realized by a configured arithmetic circuit, or the relationship between the electrical signal input and attenuation of the variable optical attenuator obtained in advance by preliminary measurement or the like is stored in the memory as table information, and the table information is extracted as necessary. A method is mentioned.

  The light intensity controller according to claim 2 of the present invention is the light intensity controller according to claim 1, wherein the input optical signal is a burst optical signal.

  Here, the “burst optical signal” means a bundle of bit signals sandwiched between guard times that do not include a signal, as shown in FIG.

  The light intensity controller according to claim 3 of the present invention is characterized in that the control means includes detection means for detecting rising of the burst optical signal or falling of the burst optical signal. Item 3. The light intensity controller according to Item 2.

  Here, the “rising of the burst optical signal” means a state from when the burst optical signal exceeds 10% of the predetermined intensity until the burst optical signal exceeds 90% of the predetermined intensity. The “falling edge” means a state from when the burst optical signal becomes 90% or less of the predetermined intensity to when the burst optical signal becomes 10% or less of the predetermined intensity.

The optical intensity controller according to claim 4 of the present invention is the optical signal delay unit, wherein the detection unit causes the burst optical signal to be higher than a timing at which the rising edge of the burst optical signal is input to the variable optical attenuator. The optical signal delay amount is set so that the timing at which the response of the previous variable optical attenuator to the drive signal output from the control means to the variable optical attenuator is completed is earlier. The light intensity controller according to claim 1.

  The light intensity controller according to claim 5 of the present invention is the light intensity controller according to any one of claims 1 to 4, wherein the optical delay means is an optical fiber of 10 m or more.

  The light intensity controller according to claim 6 of the present invention includes delay means for delaying output of a drive signal to the variable optical attenuator in the control means. The light intensity controller according to claim 1.

  The light intensity controller according to claim 7 of the present invention is such that, in the delay means, the detection means causes the detection of the burst optical signal to be less than the timing at which the falling edge of the burst optical signal is input to the variable optical attenuator. The delay amount is set so that the timing at which the response of the previous variable optical attenuator to the drive signal output from the control means to the variable optical attenuator is detected is delayed. The light intensity controller according to any one of claims 1 to 6.

  As an example, a configuration as shown in FIG. 1 is shown. The input optical signal 201 is separated into the main signal 22 and the monitor signal 211 by the optical signal branching means 111, and the monitor signal 211 is converted from the optical signal to the electric signal 231 by the intensity monitor 131 and is driven through the control means 14. The signal 25 is supplied to the variable optical attenuator 10. On the other hand, since the main signal 22 is delayed by the optical signal delay means 12, the monitor signal 211 is converted into the drive signal 25 before the main signal 22 arrives at the variable optical attenuator. The delay time by the optical signal delay means 12 is set so that the response up to the response of the variable optical attenuator is completed.

  Furthermore, the control means 14 is configured as shown in FIG. The electric signal 231 input to the control means 14 is converted into a digital signal 232 by the A / D converter 16 and input to the digital control circuit 18 to determine the delay time and output intensity. The output digital signal 232 that has passed through the digital control circuit 18 is converted into an analog signal by the D / A converter 17, and a drive signal 25 that drives the variable optical attenuator 10 is generated by the driver 15.

  Further, the digital control circuit 18 discriminates the rise and fall of the burst signal, gives a delay according to the discrimination result to the signal, and further drives the variable optical attenuator so as to obtain a predetermined optical signal output. Output a signal.

  An optical intensity controller according to an eighth aspect of the present invention is the optical intensity controller according to any one of the first to seventh aspects, wherein the first optical signal branching branches a part of the input optical signal. Means, a first optical intensity monitor for monitoring the intensity of the optical signal branched by the first optical signal branching means, and a variable optical attenuator capable of attenuating the optical signal and varying the amount of attenuation by the drive signal And an optical signal delay unit installed between the optical signal branching unit and the variable optical attenuator, and an output signal intensity corresponding to the intensity monitored by the first optical intensity monitor. Control means for driving the variable optical attenuator, and branching by the second optical signal branching means for branching a part of the output optical signal output from the variable optical attenuator, and the second optical signal branching means Second strength to monitor the transmitted optical signal A monitor value, an output optical signal intensity setting value and a difference by the second intensity monitor, and an intensity of an output signal corresponding to a sum of drive signals output from the control means to the variable optical attenuator. The light intensity controller is characterized in that the variable optical attenuator is driven.

  As an example, a configuration as shown in FIG. 6 is shown. A second intensity monitor 132 is provided, and feedback control is performed by the output light intensity monitor.

  A light intensity controller according to claim 9 of the present invention is characterized in that an optical amplifier with an automatic gain control function is arranged in front of the optical device according to any one of claims 1 to 8. It is a controller.

  Here, “optical amplifier with automatic gain control function” means an optical amplifier that performs automatic gain control using amplification means that can amplify an optical signal as it is, and an optical fiber amplifier or a semiconductor optical amplifier can be used as the optical amplifier. An amplifier may be used.

    As an example, a configuration as shown in FIG. 7 is shown.

Effect of the invention

    As described above, according to the present invention, it is possible to output burst optical signals having various intensities as burst optical signals having a constant intensity.

Configuration example of the present invention Example of burst optical signal Configuration of conventional light intensity controller Burst optical signal input to the light intensity controller of the present invention Configuration example of control means in light intensity controller of the present invention Second configuration example of the present invention Third configuration example of the present invention First embodiment of the present invention Control block configuration diagram in the first embodiment of the present invention Example of characteristics of variable optical attenuator used in the present invention Timing chart of the first embodiment of the present invention Second embodiment of the present invention Control block configuration diagram in the second embodiment of the present invention Timing chart of the second embodiment of the present invention Control block configuration diagram in the third embodiment of the present invention Fourth embodiment of the present invention Control block configuration diagram in the fourth embodiment of the present invention Fifth embodiment of the present invention

    Hereinafter, embodiments of the present invention will be described with reference to the drawings.

    A first embodiment is shown in FIG. The light intensity controller includes an input optical signal coupler 1110, an input optical signal photodiode 1310, a transimpedance type electric amplifier circuit (TIA) 30, an A / D converter 16, a control block 14, a D / A converter 17, and a variable optical attenuator driver. 15, an optical signal delay optical fiber 120, and a variable optical attenuator 10. Further, as shown in FIG. 9, the control block 14 includes functional blocks of a register 141, a table 142, and an output unit 143. The control block is preferably composed of a high-speed device such as a dedicated LSI, a field programmable gate array (FPGA), or a digital signal processor (DSP).

    Next, a method for constant control of the burst optical signal intensity using the first embodiment when a burst optical signal having various intensities is input will be described in detail.

    The burst optical signal input to the optical intensity controller is a signal sequence sandwiched between guard times as shown in FIG. 1, and the average value of the burst optical signal intensity has a dynamic range of 20 dB or more.

      An optical signal 201 input to the light intensity controller is separated into a main signal 22 and a monitor signal 211 by an input optical signal coupler 1110, and the monitor signal 211 is converted from an optical signal to an electrical signal 231 by an input optical signal photodiode 1310. The digital signal is input to the control block 140 through the TIA 30 and the A / D converter 16. In the control block 140, digital signals that are sequentially input are written to the register 141, the data written to the register 141 is input to the table 142, an output value corresponding to the input value is selected from the table, and an output 143 is selected. Output outside the control block. Thereafter, a drive signal is output to the variable optical attenuator via the D / A converter 17 and the variable optical attenuator driver 15. In the table 142, the drive signal value of the variable optical attenuator measured in advance and the corresponding output value are written.

    Thus, high-speed control of the variable optical attenuator is realized by feedforward control by the input optical signal monitor.

    On the other hand, the main signal 22 separated by the input optical signal coupler 1110 is input to the variable optical attenuator 10 through the optical signal delay optical fiber 120. The delay time by the optical signal delay optical fiber 120 is inputted as the drive signal 25 to the variable optical attenuator 10 through the control block 140 after the monitor signal 211 is separated by the input optical signal coupler 1110, and the variable optical attenuator. It is set larger than the time until 10 responses are completed. In this embodiment, an acousto-optic variable optical attenuator is used as the variable optical attenuator 10, and an example of response characteristics is shown in FIG. The response time from 10% attenuation to 90% attenuation is about 40 nanoseconds.

    In the first embodiment, the time from when the monitor signal 211 is separated by the input optical signal coupler 1110 until it is input as the drive signal 25 to the variable optical attenuator 10 through the control block 140 is about 40 nanometers. Therefore, when the delay time by the optical signal delay optical fiber 120 is set to 80 nanoseconds, the variable optical attenuator 10 driven by the monitor signal 211 before the main signal 22 reaches the variable optical attenuator 10 is set. Is complete. FIG. 11 shows a timing chart of the main signal input to the variable optical attenuator at this time, the attenuation amount of the variable optical attenuator, and the main signal output from the variable optical attenuator. If the guard time is 80 nanoseconds or more, the response of the variable optical attenuator at the rising edge of the burst optical signal starts and ends within the guard time, and the intensity fluctuation of the burst optical signal does not occur.

    However, when the variable optical attenuator 10 starts to respond by 80 nanoseconds at the rising edge of the burst optical signal, the variable optical attenuator starts to respond by 80 nanoseconds at the falling edge of the burst optical signal. Intensity fluctuation occurs in a part of the signal.

  Next, a second embodiment is shown in FIG. The light intensity controller includes an input optical signal coupler 1110, an input optical signal photodiode 1310, a transimpedance type electric amplifier circuit (TIA) 30, an A / D converter 16, a control block 140, a D / A converter 17, and a variable optical attenuator driver. 15, an optical signal delay optical fiber 120, and a variable optical attenuator 10. Further, as shown in FIG. 13, the control block 140 includes functional blocks of a register 141, a rising / falling determination unit 144, a delay determination unit 145, a table 142, and an output unit 143.

    Next, a method for constant control of the burst optical signal intensity using the second embodiment when a burst optical signal having various intensities is input will be described in detail.

    As in the first embodiment, the optical signal 201 input to the light intensity controller is separated into the main signal 22 and the monitor signal 211 by the input optical signal coupler 1110, and the monitor signal 211 is output by the input optical signal photodiode 131. The signal is converted into an electric signal 231, which is input to the control block 140 as a digital signal via the TIA 30 and the A / D converter 16. In the control block 140, the digital signal that is sequentially input is written in the register 141, and whether the rising or falling edge of the burst signal is input in the rising / falling determination unit 144 based on the information written in the register 141. Determine. The delay determination unit 145 determines the delay time with the input determination of the rising or falling edge of the burst signal as a trigger. Data is picked up from the register 141 in consideration of the delay time. The picked-up data is input to the table 142, an output value corresponding to the input value is selected from the table, and output from the output 143 to the outside of the control block. Thereafter, a drive signal is output to the variable optical attenuator via the D / A converter 17 and the variable optical attenuator driver 15. In the table 142, the drive signal value of the variable optical attenuator measured in advance and the corresponding output value are written.

    As in the first embodiment, an acousto-optic variable optical attenuator is used as the variable optical attenuator 10, and the response time from the attenuation of 10% to the attenuation of 90% is about 40 nanoseconds. It is. When no intentional delay is given in the control block 140, the monitor signal 211 is separated by the input optical signal coupler 1110 and then input as a drive signal to the variable optical attenuator 10 via the control block 140. The time until is about 40 nanoseconds. For example, when the delay time due to the optical signal delay optical fiber OO is set to 80 nanoseconds, the response of the variable optical attenuator 10 driven by the monitor signal 211 is changed before the main signal 22 reaches the variable optical attenuator 10. It will be completed. Furthermore, by controlling the delay amount in the control block 140 using the falling edge of the burst optical signal as a trigger, the response of the possible guard can be obtained without changing the intensity of the burst optical signal as shown in the timing chart of FIG. It starts and ends within the guard time, and the intensity fluctuation of the burst optical signal does not occur.

    As a third embodiment, as shown in FIG. 15, there is a method in which a comparison calculation unit 146 is set in the control block 140 and a table is not used.

  As shown in FIG. 16, the light intensity controller as the fourth embodiment includes an input optical signal coupler 1110, an output optical signal coupler 1120, an input optical signal photodiode 1310, an output optical signal photodiode 1320, and a transimpedance type electric amplifier. The circuit (TIA) 30, the A / D converter 16, the control block 140, the D / A converter 17, the variable optical attenuator driver 15, the optical signal delay optical fiber 120, and the variable optical attenuator 10 are configured. As shown in FIG. 17, the control block 140 includes functional blocks of a register 141, a rising / falling determination unit 144, a delay determination unit 145, a table 142, a comparison operation unit 146, an addition unit 147, and an output unit 143. It is configured.

    A method for constant control of the burst optical signal intensity using the fourth embodiment will be described in detail.

    The optical output signal output from the variable optical attenuator 10 is compared with the output set value by the comparison calculation unit 146, and the difference is sent to the addition unit 147. The digital signal output from the output unit 143 of the control block 140 is also sent to the adding unit and added to the optical output signal. That is, feedback control and feedforward control are used in combination, and high-speed and stable control is realized.

    As a fifth embodiment, as shown in FIG. 18, a light intensity controller with an optical amplification function in which an optical amplifier is connected to the input part of the light intensity controller as one of the first to fourth embodiments. is there. By connecting and using an apparatus that was originally a separate function, cost benefits such as omission of a delay optical fiber (also used as an amplification optical fiber) can be expected. Further, as an advantage of the present embodiment, there is an advantage that a slight transient response in the optical amplifier is controlled constant by the subsequent light intensity controller, so that it is not necessary to strictly control the transient response of the optical amplifier. As the optical amplifier, either an optical fiber amplifier or a semiconductor optical amplifier may be used.

    Note that the present invention is not limited to the above-described embodiments, and can be implemented by modifications without departing from the spirit of the invention.

    According to the present invention, since a light intensity controller capable of high-speed response can be realized, it can be used as an optical communication device.

DESCRIPTION OF SYMBOLS 10 Variable optical attenuator 111 Input optical signal branch means 112 Output optical signal branch means 1110 Input optical signal coupler 1120 Output optical signal coupler 12 Optical signal delay means 120 Optical signal delay optical fiber 131 Input intensity monitor 132 Output intensity monitor 1310 Input optical signal Photodiode 1320 Output optical signal photodiode 14 Control means 140 Control block 141 Register 142 Table 143 Output unit 144 Rising / falling judgment unit 145 Delay judgment unit 146 Comparison operation unit 147 Addition unit 15 Variable optical attenuator driver 16 A / D converter 17 D / A converter 18 Digital control circuit 19 Optical amplifier 201 Input optical signal 202 Output optical signal 203 Variable optical attenuator attenuation 211 Input monitor light 212 Output monitor light 22 Main signal 231 Electrical signal 232 Digital signal 24 control signals 25 drive signal 30 TIA
400 burst optical signal time 401 guard time

Claims (9)

  An optical signal branching unit for branching a part of the input optical signal, an optical intensity monitor for monitoring the intensity of the optical signal branched by the optical signal branching unit, the optical signal is attenuated, and the attenuation amount is determined as a drive signal. A variable optical attenuator that can be varied by the optical signal branching means, an optical signal delaying means installed between the optical signal branching means and the variable optical attenuator, and an intensity of the output signal according to the intensity monitored by the optical intensity monitor And a control means for driving the variable optical attenuator.   The light intensity controller according to claim 1, wherein the input optical signal is a burst optical signal.   3. The light intensity controller according to claim 1, wherein the control means includes detection means for detecting a rising edge of the burst optical signal or a falling edge of the burst optical signal. 4. In the optical signal delay means, the detection means detects the rising edge of the burst optical signal from the timing when the rising edge of the burst optical signal is input to the variable optical attenuator, and the variable optical attenuator is detected from the control means. 4. The optical signal delay amount is set so that a timing at which the response of the variable optical attenuator with respect to the drive signal output to is completed is earlier. 5. Light intensity controller.   5. The light intensity controller according to claim 1, wherein the optical delay means is an optical fiber having a length of 10 m or more.   6. The light intensity controller according to claim 1, wherein the control means includes delay means for delaying output of a drive signal to the variable optical attenuator. In the delay means, the timing at which the falling edge of the burst optical signal is input to the variable optical attenuator,
The detection means detects the falling edge of the burst optical signal and delays the timing at which the response of the variable optical attenuator to the drive signal output from the control means to the variable optical attenuator is delayed. The light intensity controller according to claim 1, wherein an amount is set.   8. The light intensity controller according to claim 1, wherein the light intensity controller is branched by a first optical signal branching unit that branches a part of an input optical signal and the first optical signal branching unit. A first optical intensity monitor for monitoring the intensity of the optical signal; a variable optical attenuator capable of attenuating the optical signal and varying the amount of attenuation by a drive signal; the optical signal branching means; and the variable optical attenuator. Optical signal delay means installed between, and a control means for driving the variable optical attenuator so as to be the intensity of the output signal according to the intensity monitored by the first light intensity monitor, A second optical signal branching unit for branching a part of the output optical signal output from the variable optical attenuator; and a second intensity monitor for monitoring the optical signal branched by the second optical signal branching unit. Including the second intensity monitor. Driving the variable optical attenuator so that the intensity of the output signal corresponds to the sum of the output value, the output optical signal intensity setting value, the difference, and the drive signal output from the control means to the variable optical attenuator. Light intensity controller featuring.   An optical amplifier with an automatic gain control function is disposed in front of the optical intensity controller according to any one of claims 1 to 8.

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