JP2005135961A - Optical transmission module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmission module where damage to a light emitting element due to the malfunction of an automatic temperature control circuit can be avoided. <P>SOLUTION: The optical transmission module is provided with an automatic light output control circuit 17 controlling the light emitting element in accordance with an output of a light receiving element detecting the output light of the light emitting element, an automatic temperature control circuit 14 controlling the temperature of the light emitting element in accordance with an output of a temperature detector, and a protection circuit 20 stopping the operation of the automatic light output control circuit and the automatic temperature control circuit when it is detected that the temperature of the light emitting element becomes abnormal from the output signal of the temperature detector. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical transmission module, and more specifically, a temperature detection element for detecting the temperature of the light emitting element, and an automatic temperature control circuit for controlling the temperature of the light emitting element in accordance with an output signal of the temperature detection element. The present invention relates to an optical transmission module provided.

  In order to control the output wavelength of the light emitting element, for example, Japanese Patent Application Laid-Open No. 7-95159 (Patent Document 1), Japanese Patent Application Laid-Open No. 8-148763 (Patent Document 2), Japanese Patent Application Laid-Open No. 2002-368893 (Patent Document 3). 2), an automatic temperature control circuit that keeps the output signal of the temperature detector of the optical module constant is known.

  In the optical transmission module, when a malfunction occurs in the automatic temperature control circuit, the light emitting element may be abnormally heated or abnormally cooled. In particular, when the automatic temperature control circuit is converted to a digital circuit in order to reduce the module size, the light emitting element and its peripheral parts are abnormally heated due to, for example, malfunction of the circuit due to the influence of external noise, etc., and the ambient temperature of the light emitting element May be as high as 150 ° C. In this case, even if the operation of the automatic temperature control circuit returns to a normal state, there is a possibility that the light emitting element and peripheral parts on the light transmission module are damaged.

  Patent Documents 1 to 3 described above do not describe a countermeasure when a malfunction occurs in the automatic temperature control circuit. Japanese Patent Laid-Open No. 10-229231 (Patent Document 4) describes that an automatic light output control circuit is operated when an automatic temperature control circuit operates and an output signal of a temperature detector enters a desired range. This patent document also does not describe a countermeasure when the temperature control circuit malfunctions.

JP 7-95159 A

Japanese Patent Laid-Open No. 8-148763 JP 2002-368893 A Japanese Patent Laid-Open No. 10-229231

  In the optical transmission module, it is necessary to prevent abnormal heating and abnormal cooling before the light emitting element and peripheral components are damaged. Since the output light of the light emitting element is controlled by the element temperature and the element driving current, if the element driving current is monitored, the danger of the element can be detected when the driving current becomes an abnormal value. However, even if the drive current value is the same, the amount of light emission changes as the element temperature changes. Therefore, simply monitoring the element drive current can completely prevent damage to the light emitting element and prevent abnormal light emission. It is difficult to guarantee.

An object of the present invention is to provide an optical transmission module capable of avoiding damage to a light emitting element due to a malfunction of a control circuit.
Another object of the present invention is to provide an optical transmission module capable of detecting abnormal heating / cooling of a light emitting element due to a malfunction of an automatic temperature control circuit and avoiding damage to the light emitting element and its peripheral elements.

  In order to achieve the above object, the present invention provides an automatic light output control circuit for controlling an operating current of a light emitting element according to an output signal of a light receiving element that detects output light of the light emitting element, and an output signal of a temperature detector. In an optical transmission module equipped with an automatic temperature control circuit that controls the temperature of the light emitting element in response, the heating / cooling state of the light emitting element is determined from the output signal of the temperature detector, and the light emitting element has an abnormal temperature. And a protection circuit for generating a control signal for stopping the operation of the automatic light output control circuit and the automatic temperature control circuit when detected.

  In one embodiment of the present invention, an optical transmission module includes a modulation element disposed on an output optical path of a light emitting element, and a modulation element driving circuit for controlling the modulation element. In another embodiment of the present invention, the optical transmission module includes a light emission output modulation circuit for modulating the output light of the light emitting element, and the protection circuit is generated when an abnormal temperature of the light emitting element is detected. The operation of the light emission output modulation circuit is also stopped by a control signal.

  According to the present invention, even when an abnormality occurs in the automatic temperature control circuit, abnormal heating / cooling of the light emitting element and its peripheral components can be detected at an early stage, and the abnormal heating / cooling state can be escaped. It is possible to prevent damage to peripheral components. Therefore, when the automatic temperature control circuit returns to the normal state, the optical transmission module can be normally operated.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a functional block diagram of a control system of an optical transmission module according to the present invention.
A light emitting element 11 made of a semiconductor laser, a temperature control element 12 such as a Peltier element, a temperature detecting element 13 and a light receiving element 16 form a laser module indicated by a broken line. The automatic temperature control circuit 14 changes the drive current of the temperature control element 12 according to the output signal (electric signal) S13 from the temperature detection element 13, and controls the temperature of the light emitting element 11 to the target temperature.

  The forward output light generated by the light emitting element 11 is output to the optical transmission line (optical fiber) 10, and the backward output light is detected by the light receiving element 16. The light receiving element 16 generates an electric signal S10 proportional to the output light intensity of the light emitting element 11. The automatic light output control circuit 17 controls the drive current of the light emitting element 11 according to the signal S10 output from the light receiving element 16, and keeps the signal S10 at the target value.

  The feature of the present invention is that the output signal S13 of the temperature detector 13 is inputted to a protection circuit (level conversion circuit) 20 to monitor whether or not the temperature of the light emitting element 11 is in a normal range. When the temperature is out of the normal temperature range, the operation of the automatic temperature control circuit 14 and the automatic light output control circuit 17 is forcibly stopped by the output signals S1 and S2 from the protection circuit 20.

  As the automatic temperature control circuit 14 and the automatic light output control circuit 17, for example, when a circuit configuration having a circuit stop function such as shutdown is adopted, when the light emitting element temperature deviates from the normal range, an output signal from the protection circuit 20 By changing S1 and S2 to low level, the operation of these automatic control circuits can be stopped instantaneously.

  In the present invention, at the initial stage of abnormal heating / cooling when the temperature of the light emitting element deviates from the normal range, the light emitting element is heated excessively to the damage temperature by instantaneously stopping the heating / cooling of the light emitting element. / Prevents cooling. Therefore, according to the present invention, it is possible to restore the function of the optical transmission module without damaging the light emitting element.

FIG. 2 shows a configuration of a level conversion circuit as an embodiment of the protection circuit 20.
An output signal of the temperature detector 13 is input to a window comparator including two open drain type comparators 21 and 22. The comparators 21 and 22 are supplied with a reference voltage Vmax indicating the upper limit of the normal temperature range and a reference voltage Vmin indicating the lower limit from the reference voltage generation circuits 23 and 24, respectively. The open drain type comparators 21 and 22 hold the output level during normal operation at a high level by the pull-up resistor 25 and the power supply voltage 26.

  If the output signal of the temperature detector 13 is between the upper limit reference voltage Vmax and the lower limit reference voltage Vmin, the outputs of the comparators 21 and 22 are both at a high level, so the potential at the window comparator output terminal OUT is at a high level. Is retained. When the output signal of the temperature detector 13 exceeds the upper limit reference voltage Vmax or falls below the lower limit reference voltage Vmin, that is, when the temperature of the light emitting element is out of the normal temperature range, the comparator 21 or 22 Since any of the outputs becomes low level, the potential of the output terminal OUT changes to low level. Signals S1 and S2 in FIG. 1 are output signals from the output terminal OUT. In FIG. 1, the same control signal is displayed as two signals according to the supply destination.

FIG. 3 shows a first embodiment of an optical transmission module according to the present invention.
The optical transmission module of the first embodiment includes an optical transmission module 30 and an optical reception module 40 mounted on the same substrate. The optical transmission module 30 includes the automatic temperature control circuit 14 and the automatic optical output shown in FIG. An operation stop function of the control circuit 17 is provided.

The optical transmission module 30 of the present embodiment includes a modulation element 33 integrated with the light emitting element 11, and a transmission signal output from the signal processing circuit 31 is input to the modulation element drive circuit 32. By controlling the modulation element 33, a transmission optical signal is generated.
On the other hand, the optical receiver module 40 is amplified by the light receiving element 41 for converting the received optical signal into an electric signal, the first amplifier 42 for amplifying the output signal (electric signal) of the light receiving element 41, and the first amplifier. The second amplifier 43 further amplifies the electric signal, and a signal processing circuit 44 that processes the received electric signal output from the second amplifier 43.

  In this embodiment, the output signal of the temperature detector 13 is monitored by a protection circuit (level detection circuit) 20, and when the temperature of the light emitting element 11 is out of the normal temperature range, the operation of the automatic temperature control circuit 14 is stopped. Yes. Therefore, for example, even when the automatic temperature control circuit 14 malfunctions and the light-emitting element 11 is abnormally heated or cooled by the temperature control element 12, the temperature control element 12 performs the initial operation when the element temperature is out of the normal range. The heating / cooling operation stops instantaneously, and it becomes possible to avoid damage to the light emitting element due to excessive abnormal heating / cooling. Further, when the light emitting element temperature is out of the normal temperature range, the automatic light output control circuit 17 is also stopped to prevent abnormal light emission of the light emitting element due to excessive current driving.

FIG. 4 shows a second embodiment of the optical transmission module according to the invention.
The optical transmission module of the second embodiment also includes an optical transmission module 30 and an optical reception module 40. In the optical transmission module 30 of this embodiment, the transmission signal output from the signal processing circuit 31 is input to the light emission output modulation circuit 34, and the light emission output modulation circuit 34 controls the drive current of the light emitting element 11, thereby transmitting light. It is the structure which produces | generates a signal.

  In this embodiment, when the temperature of the light emitting element 11 deviates from the normal temperature range, the operation of the automatic temperature control circuit 14 and the automatic light output control circuit 17 is stopped, and at the same time, the output signal S3 of the protection circuit (level detection circuit) 20 Thus, the operation of the light emission output modulation circuit 34 is also stopped.

  As is apparent from the first and second embodiments described above, according to the present invention, when the temperature of the light emitting element deviates from the normal temperature range, the operation of the automatic temperature control circuit is instantaneously stopped, whereby the temperature control is performed. Since excessive heating / cooling by the element is prevented, the light emitting element 11 and its peripheral elements can be prevented from being damaged. Further, when the light emitting element temperature is out of the normal temperature range, the automatic light output control circuit and the light emission output modulation circuit are stopped instantaneously to prevent abnormal light emission of the light emitting element due to excessive current driving.

  In the embodiment, the application example to the transmission / reception integrated optical transmission module including the optical transmission module 30 and the optical reception module 40 on the same substrate has been described. However, the application target of the present invention is dedicated to optical transmission. The optical transmission module may be used. In the embodiment, the signal processing circuits 31 and 44 are mounted on the substrate of the optical transmission module. However, the application target of the present invention is a circuit configuration for externally connecting these signal processing circuits. It may be.

  Conventionally, when the automatic temperature control circuit malfunctions, the light emitting element is abnormally heated / cooled, the light emitting element temperature exceeds the allowable temperature range, and the light emitting element and its peripheral components may be damaged. According to the transmission module structure, even if the automatic temperature control circuit malfunctions, the light emitting element and its peripheral elements can be prevented from being damaged. Therefore, when the control circuit failure is resolved, normal operation as an optical transmission module can be guaranteed.

The functional block diagram of the control system of the optical transmission module by this invention. The figure which shows one Example of the protection circuit 20 shown in FIG. 1 shows a first embodiment of an optical transmission module according to the present invention; 2 shows a second embodiment of an optical transmission module according to the present invention.

Explanation of symbols

10: optical transmission line, 11: light emitting element, 12: temperature control element, 13: temperature detector,
14: automatic temperature control circuit, 16: light receiving element, 17: automatic light output control circuit,
20: protection circuit (level conversion circuit), 21, 22: comparator, 30: optical transmission module,
31: signal processing circuit, 32: modulation element driving circuit, 33: modulation element,
34: light emission output modulation circuit, 40: light receiving module, 41: light receiving element,
42, 43: amplification circuit, 44: signal processing circuit.

Claims (5)

A light emitting element; a light receiving element that detects output light of the light emitting element; and an automatic light output control circuit that controls an operating current of the light emitting element in accordance with an output signal of the light receiving element;
A temperature detector for detecting the temperature of the light emitting element, a temperature control element for adjusting the temperature of the light emitting element, and an automatic temperature control for controlling the temperature control element in accordance with an output signal of the temperature detector Circuit,
The heating / cooling state of the light emitting element is judged from the output signal of the temperature detector, and the operation of the automatic light output control circuit and the automatic temperature control circuit is stopped when it is detected that the light emitting element has an abnormal temperature. An optical transmission module comprising a protection circuit for generating a control signal for performing on the same substrate.   The light emission output modulation circuit for modulating the output light of the light emitting element is provided, and the operation of the light emission output modulation circuit is stopped by a control signal from the protection circuit when the abnormal temperature is detected. 2. The optical transmission module according to 1.   The optical transmission module according to claim 1, further comprising: a modulation element disposed on an output optical path of the light emitting element; and a modulation element driving circuit for controlling the modulation element.   A signal processing circuit for inputting a transmission signal to the light emission output modulation circuit or the modulation element driving circuit, wherein the light emission output modulation circuit or the modulation element driving circuit responds to the transmission signal from the signal processing circuit; The optical transmission module according to claim 2 or 3, wherein the modulation element is controlled. 2. An optical receiving module comprising a light receiving element for converting a received optical signal into an electrical signal and an amplifier circuit for amplifying an output signal of the light receiving element, on the same substrate. The optical transmission module according to claim 4.

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