JP2009069525A - Optical power control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical power control circuit capable of preventing cost from increasing, a noise from being mixed and control time from increasing. <P>SOLUTION: A control device 11 controls optical powers of light signals in response to control voltages Va-Vd (control parameters). A photo-electric conversion circuit 12 converts optical output signals from the control device 11 into electric signals. An amplifier 13 having a log characteristic amplifies the output signals from the photo-electric conversion circuit 12. Partial differentiation circuits 14a-14d partially differentiate output signals from the amplifier 13, respectively, by the control voltages Va-Vd. Parameter generation circuits 15a-15d computation-process, respectively, outputs from the partial differentiation circuits 14a-14d to generate respectively the control voltages Va-Vd. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical power control circuit that controls an optical power of an optical output signal to a maximum value, and relates to an optical power control circuit that can prevent an increase in cost, mixing of noise, and an increase in control time. is there.

  An optical power control circuit that controls the optical power of the optical output signal so as to become the maximum value is used. However, when the optical power of the optical input signal varies, the optical power of the optical output signal is also affected, so that the maximum value cannot be detected correctly. Therefore, in the first prior art, the optical power of the optical input signal is monitored, and control is performed so that the numerical value obtained by normalizing the optical power of the optical output signal with the optical power of the optical input signal takes the maximum value. In the second prior art, control is performed by superimposing a small amplitude modulation signal and detecting its phase (see, for example, Patent Document 1).

Japanese Patent No. 2642499

  However, in the first prior art, in order to monitor the optical power of the optical input signal, an element that performs optical branching and photoelectric conversion is further required. In the second prior art, an analog circuit for demodulating the modulation signal is further required. Thus, there is a problem that expensive optical parts need to be added and the cost increases. There is also a problem that noise is mixed in the optical signal. Further, when there are a plurality of control parameters for controlling the optical power, it is necessary to perform peak search by changing the control parameters one by one, and the control time is increased by the number of control parameters.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain an optical power control circuit that can prevent an increase in cost, noise, and an increase in control time. .

  An optical power control circuit according to the present invention includes a control device that controls the optical power of an optical signal in accordance with at least one control parameter, a photoelectric conversion circuit that converts an optical output signal of the control device into an electrical signal, An amplifier having a log characteristic for amplifying the output signal of the conversion circuit, at least one partial differentiation circuit for partial differentiation of the output signal of the amplifier with at least one control parameter, and an output signal of at least one partial differentiation circuit, respectively And at least one parameter generation circuit that generates at least one control parameter by processing. Other features of the present invention will become apparent below.

  According to the present invention, it is possible to prevent an increase in cost, mixing of noise, and an increase in control time.

  FIG. 1 is a block diagram showing an optical power control circuit according to an embodiment of the present invention. The control device 11 inputs an optical input signal and controls the optical power of the optical signal according to the control voltages Va to Vd (control parameters). The photoelectric conversion circuit 12 converts the optical output signal of the control device 11 into an electrical signal.

  The amplifier 13 having log characteristics amplifies the output signal of the photoelectric conversion circuit 12. The partial differentiation circuits 14a to 14d partially differentiate the output signals of the amplifier 13 with the control voltages Va to Vd, respectively. The parameter generation circuits 15a to 15d calculate the output signals of the partial differentiation circuits 14a to 14d, respectively, generate control voltages Va to Vd, and input them to the terminals 16a to 16d of the control device 11, respectively.

  FIG. 2 is a schematic diagram showing a control device according to the embodiment of the present invention. The control device 11 can be configured by a MEMS (Micro Electro Mechanical Systems) device, an LN (Lithium Niobate) modulator, or the like. Here, a case where the control device 11 is configured by a MEMS device will be described. Electrodes 18 a to 18 d are arranged around the MEMS mirror 17. The optical input signal introduced from the optical fiber 19 is reflected by the MEMS mirror 17 and input to the optical fiber 20 to be output as an optical output signal. Here, when the control voltages Va to Vd input from the terminals 16a to 16d are respectively applied to the electrodes 18a to 18d, the angle of the MEMS mirror 17 is changed by the electrostatic force. Thereby, since the condensing state to the optical fiber 20 changes, the optical power of an optical output signal can be adjusted.

  Here, the optical input signal is expressed by a function IN (t) of time t. The characteristics of the control device 11 are represented by a function D (Va, Vb, Vc, Vd) of the control voltages Va to Vd. Therefore, the optical output signal is expressed by a function OUT (t, Va, Vb, Vc, Vd) of time and control voltage. Since the control parameters of the optical output signal are related to each other, the optical output signal of the control device 11 is OUT (t, Va, Vb, Vc, Vd) = OUTA (t) × OUTA (Va) × OUTA It is expressed as (Vb) × OUTA (Vc) × OUTA (Vd). Therefore, the output signal of the amplifier 13 having the log characteristic is OUTL = log (OUTA (t)) + log (OUTA (Va)) + log (OUTA (Vb)) + log (OUTA (Vc)) + log (OUTA (Vd)).

  As described above, since the output signal of the amplifier 13 is an addition of a function for each parameter, the fluctuation of the optical power of the optical input signal can be removed by partial differentiation of the output signal of the amplifier 13. Therefore, it is not necessary to add an expensive optical component, and an increase in cost can be prevented. And mixing of noise can be prevented.

  Further, even when there are a plurality of control parameters such as a MEMS device, the output signal of the amplifier 13 having a log characteristic is partially differentiated simultaneously with each control parameter, so that the change in optical power due to each control parameter can be reduced. Can be extracted. Therefore, even when there are a plurality of control parameters, an increase in control time can be prevented.

FIG. 3 is a diagram showing the characteristics of the optical power of the optical output signal. The optical power of the optical output signal has one pole with respect to the control voltage. Therefore, the maximum value of the optical power of the optical output signal can be obtained by controlling the control voltage so that the partial differential of the optical power of the optical output signal becomes zero. For example, consider the case where the optical power characteristic of the optical output signal is expressed as Y = aX ² + bX + c, where Y is the optical power of the optical output signal and X is the control voltage. If Y is partially differentiated, dY / dX = 2aX + b. Therefore, if X is controlled so that dY / dX = 0, the maximum value of the optical power of the optical output signal can be obtained. Therefore, the parameter generation circuits 15a to 15d automatically increase or decrease the control voltages Va to Vd so that the output signals of the partial differentiation circuits 14a to 14d approach 0, respectively. Control converges when the output signals of the partial differential circuits 14a to 14d become zero. Thereby, the maximum value of the optical power of the optical output signal can be obtained.

  The parameter generation circuits 15a to 15d perform PID control for proportionally, integrating, or differentiating the output signals of the partial differentiation circuits 14a to 14d, respectively. Here, PID control is a kind of feedback control. Feedback control is a control parameter that monitors the optical power of the optical output signal and, if there is a difference between the optical power of the optical output signal and the desired target value, the optical power of the optical output signal is as expected. This is a control method that automatically increases or decreases. For example, in the case of P (proportional) processing, the difference between the target value and the monitor value is added to the control parameter as it is. However, since the difference between the target value and the monitor value does not become zero in the P process, it is used in combination with the I (integration) process. In order to improve high-speed response, D (differentiation) processing may be combined. Generally, it is determined whether proportional, integral or differential processing is selected according to the control target.

  In the present embodiment, the case where the number of control parameters, the number of partial differentiation circuits, and the number of parameter generation circuits are four has been described. However, the present invention is not limited to this, and the present invention can be applied to the case where the number of control parameters, the number of partial differentiation circuits, and the number of parameter generation circuits are each at least one.

  The partial differentiation circuits 14a to 14d and the parameter generation circuits 15a to 15d can be configured by an FPGA (Field Programmable Gate Array) or a CPU (Central Processing Unit).

It is a block diagram which shows the optical power control circuit which concerns on embodiment of this invention. It is the schematic which shows the control device which concerns on embodiment of this invention. It is a figure which shows the characteristic of the optical power of an optical output signal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Control device 12 Photoelectric conversion circuit 13 Amplifier 14a-14d Partial differentiation circuit 15a-15d Parameter generation circuit Va, Vb, Vc, Vd Control voltage (control parameter)

Claims (3)

A control device for controlling the optical power of the optical signal according to at least one control parameter;
A photoelectric conversion circuit that converts an optical output signal of the control device into an electrical signal;
An amplifier having log characteristics for amplifying an output signal of the photoelectric conversion circuit;
At least one partial differentiation circuit for partial differentiation of the output signal of the amplifier with the at least one control parameter;
An optical power control circuit comprising: at least one parameter generation circuit that respectively performs an arithmetic processing on an output signal of the at least one partial differentiation circuit to generate the at least one control parameter.   2. The optical power according to claim 1, wherein the at least one parameter generation circuit increases or decreases the at least one control parameter so that an output signal of the at least one partial differentiation circuit approaches 0, respectively. Control circuit.   3. The optical power control circuit according to claim 1, wherein the at least one parameter generation circuit performs PID control for proportionally, integrating, or differentiating an output signal of the at least one partial differentiation circuit, respectively. 4.

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