JP2005302874A - Optical signal controller and its regulating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical signal controller capable of controlling the frontward emission light of a light source fixedly. <P>SOLUTION: The optical signal controller comprises a light source 32 for emitting a frontward emission light L as an optical signal frontward, a rearward emission light monitoring means 33 for monitoring a rearward emission light Lb to be leaked rearward of the light source 32, a control means 2 for controlling the frontward emission light L depending on a signal monitored by the rearward emission light monitoring means 33, a storing means 4 for in advance storing the temperature characteristic table of the rearward emission light monitoring means 33, and a temperature sensor 3 for detecting a peripheral temperature of the light source 32. The control means 2 recognizes the peripheral temperature by the temperature sensor 3 to control to correct the frontward emission light L referring to the temperature characteristic table. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical signal control device that controls the light emitted from a light source at a constant level and an adjustment method thereof.

  A conventional optical signal control device 31 as shown in FIG. 3 includes a semiconductor laser module (LD module) that includes a semiconductor laser (LD) 32 and a monitor photodiode (monitor PD) 33 that monitors the backward emission light Lb of the LD 32. ) 34, an APC control circuit 35 that is connected to the LD module 34 and performs APC control (Automatic Power Control) of the LD 32, and is connected between the LD 32 and the APC control circuit 35 to control a bias current for driving the LD 32. A transistor (for example, a bipolar transistor or a MOS-FET) 36.

  The backward emitted light Lb is light with respect to forward emitted light (output light) emitted forward by the LD 32 as an optical signal, and refers to minute light that leaks behind the LD 32 due to the structure of the LD 32.

  The optical signal control device 31 is mainly used as an optical transmitter. In this case, the optical output, waveform, extinction ratio, and the like are determined by the specifications of optical communication. For this reason, the optical signal control device 31 performs APC control of the LD 32 by the APC control circuit 35, that is, monitors the rearward emitted light Lb of the LD 32 with the monitor PD 33, and keeps the monitor current flowing through the monitor PD 33 constant. In addition, by performing feedback control of the bias current flowing through the LD 32, the light emitted forward from the LD 32 is kept constant.

  APC control is performed on the assumption that the temperature characteristics of the monitor PD 33 are ideally constant. That is, in the optical signal control device 31, for example, as indicated by the temperature characteristic line 42 in FIG. 4B, if the intensity (power) of the backward emission light Lb is constant, the ambient temperature T (° C.) of the LD 32 is reached. Regardless, it is assumed that the monitor current Ip is constant.

  The prior art document information related to the invention of this application includes the following.

Japanese Patent Laid-Open No. 2002-204022

  However, since the actual monitor PD 33 has temperature characteristics caused by the element itself and temperature characteristics due to structural distortion of the LD module 34, even if the power of the rear emission light Lb is constant, it depends on the ambient temperature T. The monitor current Ip changes.

  That is, the actual monitor PD 33 does not follow the constant temperature characteristic line 42 regardless of the ambient temperature T as shown in FIG. 4B, but, for example, at the ambient temperature T as shown in FIG. It has a characteristic according to a temperature characteristic curve 41 that changes depending on the characteristic. In this case, the monitor current Ip obtained from the monitor PD 33 increases at the ambient temperature t1 and decreases at the ambient temperature t2 (> t1) even if the power of the backward emission light Lb is constant.

  That is, in the conventional optical signal control device 31, the LD 32 is APC controlled assuming the temperature characteristic line 42, but the monitor PD 33 actually follows the temperature characteristic curve 41, so the ambient temperature has changed from t 1 to t 2. Sometimes an error Δ occurs in the monitor current Ip. In this way, errors and deviations from actual values in elements used for control and adjustment are called tracking errors.

  Therefore, in the optical signal control device 31, if a tracking error occurs, the bias current flowing through the LD 32 is deviated from an appropriate value even if the APC control of the LD 32 is performed. is there. As a result, optical communication specifications are not satisfied.

  In addition to the fact that the monitor PD 33 has temperature characteristics (including those caused by changes in the LD 32), the cause of the tracking error is 1) LD 32 due to individual variations, characteristics of the element itself, or ambient temperature. The ratio of the front outgoing light to the rear outgoing light changes, 2) the ambient temperature causes an axial misalignment between the output port of the optical signal control device 31 and the optical fiber, and 3) 2). The point that the beam shape of the light emitted from the front of the LD 32 changes. 4) Various causes such as mechanical expansion and contraction of the substrate on which the LD 32 and the monitor PD 33 are mounted or the housing of the optical signal control device depending on the ambient temperature. There is.

  The optical signal control device 31 has a problem that it cannot cope with not only the tracking error due to the temperature characteristic of the monitor PD 33 but also the tracking error due to the causes 1) to 4) described above.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical signal control device that can control the forward emission light of a light source to be constant no matter what causes a tracking error.

  The present invention has been devised to achieve the above object, and the invention of claim 1 monitors a light source that emits forward emitted light that is an optical signal in front and a backward emitted light that leaks behind the light source. A rear emission light monitoring means, a control means for controlling the front emission light based on a signal monitored by the rear emission light monitoring means, and a memory in which a temperature characteristic table of the rear emission light monitoring means is stored in advance. And a temperature sensor for detecting the ambient temperature of the light source, wherein the control means recognizes the ambient temperature by the temperature sensor and refers to the temperature characteristic table to correct and control the forward emitted light. It is a control device.

  A second aspect of the present invention is the optical signal control apparatus according to the first aspect, wherein the control means is a microcontroller unit, a sequencer, or a reconfigurable LSI or IC.

  According to a third aspect of the present invention, the temperature characteristic table comprises an address corresponding to the ambient temperature and a temperature characteristic of the backward emission light monitoring means stored at the address. It is.

  According to a fourth aspect of the present invention, the temperature characteristic table includes an address corresponding to each order of the temperature characteristic function approximated to the temperature characteristic of the backward emission light monitoring means, and each order of the temperature characteristic function stored at the address. 3. The optical signal control device according to claim 1, comprising a coefficient.

According to a fifth aspect of the present invention, the temperature characteristic function is the following equation f (x) = A _n x ⁿ + A _n-1 x ^n-1 +... + A ₁ x + A ₀
5. The optical signal control device according to claim 4, wherein x is approximated by an input variable comprising a temperature detection amount of the temperature sensor.

  According to a sixth aspect of the present invention, the temperature characteristic table processes the forward emitted light monitoring means for monitoring the forward emitted light, the information from the forward emitted light monitor means, and the information used for control from the control means. The optical signal control device according to claim 1, wherein the optical signal control device is obtained using a means and a temperature control means capable of controlling the ambient temperature constantly and arbitrarily.

  The invention according to claim 7 is an adjustment method for an optical signal control device that monitors backward emitted light leaking behind the light source and controls the forward emitted light, which is an optical signal of the light source, to be constant based on information stored in advance. Then, after assembling the optical signal control device, the temperature of the rear outgoing light monitoring means for monitoring the rear outgoing light by monitoring the front outgoing light while changing the ambient temperature of the light source for each predetermined temperature step. This is a method of adjusting an optical signal control device that measures characteristics, creates a temperature characteristic table of the rear emission light monitoring means from the temperature characteristics, and stores the created temperature characteristic table in advance.

  The invention according to claim 8 is the optical signal control device according to claim 7, wherein the temperature characteristic table is created by associating an address with the ambient temperature and storing the temperature characteristic of the rear emission light monitoring means at the address. This is the adjustment method.

  According to a ninth aspect of the present invention, the temperature characteristic table associates an address for each degree of the temperature characteristic function approximated to the temperature characteristic of the rear light monitoring means, and a coefficient of each order of the temperature characteristic function is stored at the address. 8. An adjustment method for an optical signal control device according to claim 7, wherein the adjustment is made.

  According to the present invention, an excellent effect that the forward emission light of the light source can be controlled to be constant is exhibited.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings.

  FIG. 1 is a block diagram of an optical signal control apparatus showing a preferred embodiment of the present invention.

  As shown in FIG. 1, an optical signal control device 1 according to the present embodiment is mainly used as an optical transmitter, and an LD 32 as a light source that emits forward emitted light (output light) that is an optical signal forward. The LD module 34 having a built-in monitor PD 33 as a rear emitted light monitoring means for monitoring the backward emitted light Lb leaking behind the LD 32, and the LD 32 and the monitor PD 33 are connected to the LD 32 and the monitor PD 33, respectively. A microcontroller unit (MCU) 2 as a control means for APC control, a temperature sensor 3 such as a thermistor for detecting the ambient temperature of the LD 32, and an LD 32 and the MCU 2 for driving the LD 32 Transistor that controls the bias current (eg, bipolar transistor) Jistor or MOS-FET) 36.

  In the present embodiment, an example in which the MCU 2 composed of software and hardware is used as the control means will be described. However, since a series of processing in the MCU 2 can be performed only by hardware, for example, a sequencer, Alternatively, a reconfigurable (so-called programmable) LSI or IC may be used.

  The ambient temperature of the LD 32 includes the environmental temperature where the optical signal control device 1 is placed, the temperature of the LD 32 itself, the temperature of the case of the optical signal control device 1, and the like. The temperature sensor is attached to an appropriate location of the optical signal control device 1 according to these various cases.

  The LD 32, the monitor PD 33, and the temperature sensor 3 are connected to the MCU 2, respectively. An optical fiber 6 connected to the transmission path is connected to the output port 5 of the optical signal control device 1 that transmits the forward emission light L.

  APC control is to control the forward emitted light L of the LD 32 to be constant by performing feedback control of the current (bias current) IL flowing to the LD 32 so as to keep the current (monitor current) Ip flowing to the monitor PD 33 constant. Say.

  The MCU 2 incorporates a control / calculation program for correcting and controlling the APC control with reference to a temperature characteristic table described later with reference to FIG. In addition, the storage unit 4 is built in the MCU 2. The storage means 4 is composed of a semiconductor memory element such as a nonvolatile ROM that can store data without a power source.

  The storage unit 4 stores a temperature characteristic table of the monitor PD 33 in advance. As will be described later, the temperature characteristic table is easily obtained from the actual temperature characteristic curve 21 of the monitor PD 33 with the horizontal axis being the ambient temperature T (° C.) of the LD 32 and the vertical axis being the monitor current Ip, as shown in FIG. can get. This temperature characteristic curve 21 reflects not only all causes of tracking errors, that is, the temperature characteristics of the monitor PD 33 itself (including those due to changes in the LD 32), but also the causes 1) to 4) described above. It is a thing.

  The temperature characteristic table 22 includes a plurality of addresses 0x0000 to 0x00005... Corresponding to the ambient temperature of the LD 32 and temperature characteristic data a0 to a5... Is used. Each temperature characteristic data a0 to a5... Is a measured value of the monitor current Ip at each ambient temperature of the temperature characteristic curve 21 in FIG.

  In the temperature characteristic table 22, the number of addresses is the total number of temperature steps to be described later, and when the address increases or decreases by 1 (from one address to the next address), the ambient temperature of the LD 32 increases or decreases by one step by a predetermined temperature. Corresponding to the monitor current Ip.

Further, as the temperature characteristic table, each order of the temperature characteristic function stored in each address 0x0000 to 0x0004... Corresponding to each order of the temperature characteristic function approximated to the temperature characteristic of the monitor PD 32 and each address 0x0000 to 0x0004. You may use the temperature characteristic table 23 which consists of coefficient data b0-b4 .... This temperature characteristic function is obtained by converting the temperature characteristic curve 21 shown in FIG. 2 into the following formula f (x) = A _n x ⁿ + A _n-1 x ^n-1 +... + A ₁ x + A ₀
Is an approximation.

x is an input variable consisting of the temperature detection electricity quantity of the temperature sensor 3 of FIG. A _{n to} A ₁ are coefficients of the respective orders of the function f (x), A ₀ is a constant of the function f (x), and these A _{n to} A ₁ and A ₀ are stored in the respective addresses 0x0000 to 0x0004. The In the temperature characteristic table 23 in the present embodiment, the coefficient data b0 corresponds to a constant A _0, the coefficient data b1.about.b4 ... corresponds to the coefficient A ₁ to A _n, respectively.

The calculation result of the function f (x) is an approximated monitor current Ip. The function f (x) itself excluding the coefficients A _{n to} A ₁ and the constant A ₀ is stored in the MCU 2 of FIG. 1 and a control / arithmetic program incorporated in the processing means described later.

  As the temperature characteristic function, for example, it is sufficient to use a third-order polynomial function, but if a third-order or higher polynomial function is used, the temperature characteristic function can be made closer to the temperature characteristic curve 21 of FIG.

  Since the temperature characteristic table 23 can reduce the amount of data compared to the temperature characteristic table 22, if the temperature characteristic table 23 is used instead of the temperature characteristic table 22, a storage unit 4 having a small capacity can be used. .

  Next, a method for adjusting the optical signal control device 1, that is, a method for creating the temperature characteristic tables 22 and 23 will be described.

  In order to create the temperature characteristic table, as shown in FIG. 1, a constant temperature bath 11 as a temperature control means capable of controlling the ambient temperature of the LD 32 to be constant and arbitrary, and a forward emission light monitor for monitoring the front emission light L of the LD 32 A power monitor 12 as a means, information from the power monitor 12 (front emission light power PL), and information used for control from the MCU 2 (ambient temperature T of the LD 32, bias current IL, monitor current Ip) are processed, and the temperature An adjustment device 14 comprising a computer 13 as processing means for creating a characteristic table is used. The power monitor 12 converts the forward emitted light L inputted thereto into an electric signal corresponding to the power, and further A / D converts the electric signal and outputs the electric signal.

  After assembling the optical signal control device 1, the power monitor 12 is connected to the other end of the optical fiber 6 whose one end is connected to the output port 5, and the computer 13 is connected between the power monitor 12 and the MCU 2 via a signal line. Then, the optical signal control device 1 is placed in the constant temperature bath 11.

  In this state, the optical signal control device 1 is operated to transmit the test front emission light L from the output port 5. At this time, the MCU 2 performs APC control of the LD 32. The front emission light L is received by the power monitor 12 and input to the computer 13 as information on the front emission light power PL. The computer 13 accesses the MCU 2 and includes the temperature T of the thermostatic chamber 11 detected by the temperature sensor 3 (ambient temperature of the LD 32) T, the bias current IL flowing through the LD 32, and the monitor current Ip flowing through the monitor PD 33. Receive information from MCU2.

  Thereafter, the above operation is performed while changing the temperature of the thermostatic chamber 11 for each appropriate temperature step over a wide temperature range. In this example, the temperature range was set to −10 to 80 ° C., and the temperature steps were set every 2 ° C. (total number of temperature steps 46).

  The computer 13 processes four pieces of information including each ambient temperature T, monitor current Ip, bias current IL, and forward emission light power PL. More specifically, the computer 13 monitors the forward emitted light power PL so as to be a desired constant value defined in the optical communication specifications regardless of the ambient temperature T, and the forward emitted light power PL is a constant value. Is exceeded, the MCU 2 is instructed to decrease the bias current IL, and when the forward emission light power PL is less than a certain value, the MCU 2 is instructed to increase the bias current IL. At this time, the computer 13 stores each ambient temperature T and the monitor current Ip at each ambient temperature T. As a result, the computer 13 obtains the temperature characteristic curve 21 of FIG. 2 reflecting all the causes of the tracking error.

  When the computer 13 obtains the temperature characteristic curve 21, the computer 13 accesses the storage means 4 of the MCU 2, associates each temperature with an address, and stores the monitor current Ip at each temperature of the temperature characteristic curve 21 at each address. Thus, the temperature characteristic table 22 of FIG. 2 is created by writing data in the storage means 4.

  On the other hand, when obtaining the temperature characteristic curve 21, the computer 13 refers to the temperature characteristic function excluding the coefficient and constant incorporated in the control / calculation program, determines the coefficient and constant, and approximates the temperature characteristic curve 21. Get the characteristic function. When the computer 13 obtains the temperature characteristic function, it accesses the storage means 4 of the MCU 2 and writes data in the storage means 4 so that the coefficient and constant of the temperature characteristic function are stored in each address. 2 temperature characteristic table 23 is created.

  The above-described temperature characteristic table is created individually for each optical signal control device 1 according to the present invention. In the optical signal control device 1 in which the temperature characteristic table is stored in the storage unit 4, the adjustment device 14 is removed, the adjustment before product shipment is completed, and then the product is shipped as a product.

  Next, the operation of the optical signal control device 1 will be described.

  First, it is assumed that the optical signal control device 1 is placed at the ambient temperature T2. At the ambient temperature T2, the monitor current value of the temperature characteristic curve 21 in FIG. 2 and the monitor current value of the temperature characteristic line 42 in FIG. 4 are the same.

  When the bias current IL is supplied to the LD 32 by the MCU 2, the LD 32 emits light, and the forward emission light L is transmitted from the output port 5 through the optical fiber 6. The backward emitted light Lb leaks from the LD 32, and the backward emitted light Lb is received by the monitor PD33. If the ambient temperature remains at T2, the MCU 2 performs APC control of the LD 32 based on the current value Ip2 of the temperature characteristic curve 21 in FIG. 2, and controls the forward emitted light L of the LD 32 to be constant.

  When the ambient temperature falls from T2 to T1, the MCU 2 recognizes that the ambient temperature has fallen from T2 to T1 by a signal from the temperature sensor 3. At this time, as shown by the temperature characteristic curve 21 in FIG. 2, the monitor current Ip rises from the current value Ip2 at the temperature T2 to the current value Ip1, so that if the LD 32 is APC-controlled based on the current value Ip2, the error ΔI (Ip1-Ip2) is generated. That is, a tracking error occurs in the optical signal control device 1.

When the temperature characteristic table 22 of FIG. 2 is stored in the storage means 4;
When the MCU 2 recognizes that the ambient temperature has dropped from T2 to T1, the MCU 2 refers to the temperature characteristic table 22 and obtains the current value Ip1 stored at the address corresponding to the ambient temperature T1. Based on this current value Ip1, the MCU 2 controls the APC control so as to eliminate the error ΔI (so that the current value Ip is constant), thereby controlling the forward emission light L of the LD 32 to be constant. Thereby, the tracking error which generate | occur | produced in the optical signal control apparatus 1 is eliminated.

When the temperature characteristic table 23 of FIG. 2 is stored in the storage means 4;
When the MCU 2 recognizes that the ambient temperature has decreased from T2 to T1, the MCU 2 determines the order of the temperature characteristic function that approximates the temperature characteristic curve 21 of FIG. 2, and then refers to the temperature characteristic table 23 to correspond to the determined order. The coefficient and constant of the temperature characteristic function stored at the address to be obtained are obtained, and the temperature characteristic function approximated to the temperature characteristic curve 21 of FIG. 2 is obtained. The MCU 2 obtains an approximate current value Ip1 by substituting an input variable consisting of the temperature detection electric quantity of the temperature sensor 3 at the ambient temperature T2 into this temperature characteristic function. The MCU 2 controls the forward emission light L of the LD 32 to be constant by correcting and controlling the APC control based on the approximated current value Ip1. Thereby, the tracking error which generate | occur | produced in the optical signal control apparatus 1 is eliminated.

  Thus, in the optical signal control apparatus 1 according to the present invention, the MCU 2 performs APC control of the LD 32 and corrects the APC control with reference to the temperature characteristic table 22 (or 23) stored in advance in the storage unit 4 of the MCU 2. Since the control is performed, the front emission light L of the LD 32 can always be controlled with high accuracy and constant even if a tracking error occurs due to any cause.

1 is a block diagram of an optical signal control device showing a preferred embodiment of the present invention. It is a figure which shows an example of the actual temperature characteristic of monitor PD, and an example of a temperature characteristic table. It is the schematic explaining operation | movement of the conventional optical signal control apparatus. FIG. 4A is a diagram showing actual temperature characteristics of the monitor PD, and FIG. 4B is a diagram showing ideal temperature characteristics of the monitor PD.

Explanation of symbols

1 Optical signal control device 2 MCU (control means)
3 Temperature sensor 4 Storage means 11 Constant temperature bath 12 Power monitor (front emission light monitoring means)
13 Computer (Processing means)
32 LD (light source)
33 Monitor PD (Backward outgoing light monitoring means)
L Front outgoing light Lb Back outgoing light

Claims (9)

  A light source that emits forward emitted light that is an optical signal forward, a rear emitted light monitoring means that monitors backward emitted light that leaks behind the light source, and a signal that is monitored by the backward emitted light monitor means, Control means for controlling the emitted light constant; storage means for preliminarily storing a temperature characteristic table of the rear emission light monitoring means; and a temperature sensor for detecting an ambient temperature of the light source, wherein the control means includes the temperature sensor. The optical signal control device is characterized in that the ambient temperature is recognized by the above and the forward emission light is corrected and controlled with reference to the temperature characteristic table.   2. The optical signal control apparatus according to claim 1, wherein the control means is a microcontroller unit, a sequencer, or a reconfigurable LSI or IC.   3. The optical signal control device according to claim 1, wherein the temperature characteristic table includes an address corresponding to the ambient temperature and a temperature characteristic of the backward emission light monitoring means stored at the address.   2. The temperature characteristic table comprises an address corresponding to each order of a temperature characteristic function approximated to the temperature characteristic of the rearward emitted light monitoring means, and a coefficient of each order of the temperature characteristic function stored at the address. Or the optical signal control apparatus of 2. The temperature characteristic function is expressed as follows: f (x) = A _n x ⁿ + A _n-1 x ^n-1 +... + A ₁ x + A ₀
5. The optical signal control device according to claim 4, wherein x is approximated by an input variable comprising a temperature detection amount of the temperature sensor.   The temperature characteristic table includes a front emission light monitoring unit that monitors the front emission light, a processing unit that processes information from the front emission light monitoring unit and information used for control from the control unit, and the ambient temperature. 6. The optical signal control device according to claim 1, wherein the optical signal control device is obtained by using temperature control means that can be controlled in a constant and arbitrary manner.   A method of adjusting an optical signal control device that monitors backward outgoing light leaking behind a light source and controls the forward outgoing light, which is an optical signal of the light source, to be constant based on information stored in advance. After assembling the apparatus, the ambient temperature of the light source is changed for each predetermined temperature step, while monitoring the forward emitted light and measuring the temperature characteristic of the backward emitted light monitoring means for monitoring the backward emitted light, and the temperature A method of adjusting an optical signal control device, comprising: creating a temperature characteristic table of the rear emission light monitoring means from the characteristics, and storing the created temperature characteristic table in advance.   8. The method of adjusting an optical signal control device according to claim 7, wherein the temperature characteristic table is created by associating an address with the ambient temperature and storing the temperature characteristic of the rear emission light monitoring means at the address. The temperature characteristic table is created by associating an address for each degree of the temperature characteristic function approximated to the temperature characteristic of the rear light monitoring means and storing a coefficient of each order of the temperature characteristic function at the address. 8. A method for adjusting an optical signal control device according to item 7.

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