JP2008244391A - Optical module and method of manufacturing the optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-performance optical module in which a receiving function and a light-intensity monitoring function are separated from each other. <P>SOLUTION: The optical module having a light-receiving element 3 and the other light-receiving element 4 further includes an input light splitting means 1 for splitting input light into at least two optical paths. The input light splitting means 1 causes one of the split optical paths to be incident to the light-receiving element 3 and causes the other split path to be incident to the other light-receiving element 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical module and a method for manufacturing the optical module.

  In the field of optical communication or the like, a light receiving element is used as a receiver of an optical signal transmitted from a transmitter using an optical fiber as a medium. As a light receiving element, a pin photodiode (pinPD) (see Non-Patent Document 1 below) and an avalanche photodiode (APD) (see Non-Patent Document 2 below) are generally used. The pin PD has a function of converting an optical signal into an electric signal by converting irradiated photons into an electric current.

  On the other hand, the APD obtains an electric signal larger than that of the pin PD by further multiplying the converted current. In general optical communication, each base is connected with an optical fiber, and a transmitter and a receiver are connected to both ends of these optical fibers to propagate an optical signal.

  By the way, an optical signal propagating through a general optical fiber suffers a loss of about 0.3 dB per 1 km. Since transmitters and receivers are usually of the same type, the communication between bases with a short distance from each other has a small optical fiber loss due to the short optical fiber, and the intensity of the optical signal reaching the receiver is small. In communication between bases that are large and have a long distance from each other, the loss of the intensity of the optical signal is large because the optical fiber is long, and the intensity of the optical signal reaching the receiver is small.

  For example, when the distance between the bases is 10 km, the optical signal undergoes a loss of 0.3 × 10 = 3 dB by propagating through the optical fiber. Since the optical signal intensity from the transmitter is normally about +3 dB, the intensity of the optical signal incident on the receiver is 3-3 = 0 dBm.

  On the other hand, for example, when the distance between the bases is 80 km, the optical signal undergoes a loss of 0.3 × 80 = 24 dB by propagating through the optical fiber. In this case, the intensity of the optical signal incident on the receiver is 3-24 = -21 dBm. A pin PD or APD that receives light in a receiver exhibits a feature in efficiently converting a low-intensity optical signal or converting it into an electrical signal, but conversely, in the case of a strong optical signal, A saturation phenomenon of the electric signal intensity occurs, the signal is distorted, and the pin PD or APD is destroyed by Joule heat generated because the current exceeds the rated value.

In particular, since the rated value of the light receiving intensity of APD is around 0 dBm, it is necessary to attenuate the intensity of the optical signal incident on the receiver in communication between bases having a short propagation distance.
Therefore, in the conventional technique, an optical attenuator is inserted between the optical fiber and the receiver to attenuate the light intensity.

Supervised by Tetsuhiko Ikegami, Haruhiko Tsuchiya, edited by Osamu Mikami, “Semiconductor Photonics Engineering”, first edition, first edition, Corona, Inc., January 10, 1995, p. 363-369 Supervised by Tetsuhiko Ikegami, Haruhiko Tsuchiya, edited by Osamu Mikami, “Semiconductor Photonics Engineering”, first edition, first edition, Corona, Inc., January 10, 1995, p. 372-379

  However, in the conventional optical module as described above, since the light intensity is monitored from the light received by the light receiving element itself that receives the optical signal, the reception circuit becomes complicated or the original reception characteristics deteriorate. There were problems such as.

  In view of the above problems, an object of the present invention is to provide a high-performance optical module in which a reception function and a light intensity monitoring function are separated.

An optical module according to a first invention (corresponding to claim 1) for solving the above problem is
A light receiving element;
In an optical module comprising other light receiving elements,
Input light branching means for branching the input light into at least two optical paths;
The input light branching means is
One of the branched light beams is incident on the one light receiving element,
The other branched light is incident on the other light receiving element.

An optical module according to a second invention (corresponding to claim 2) for solving the above problem is the optical module according to the first invention,
The branching ratio of at least two branched lights branched by the input light branching means is 1: 2 or more.

An optical module according to a third invention (corresponding to claim 3) for solving the above problems is the optical module according to the first invention or the second invention.
An avalanche photodiode is used for the one light receiving element.

An optical module according to a fourth invention (corresponding to claim 4) for solving the above problem is the optical module according to any one of the first invention to the third invention,
A branched light beam having a maximum branching ratio among at least two branched light beams branched by the input light branching unit is incident on the one light receiving element.

An optical module according to a fifth invention (corresponding to claim 5) for solving the above-mentioned problems is an optical module according to any one of the first to fourth inventions,
A variable optical attenuator for attenuating light between the input light branching means and the one light receiving element;
Either one of the branched lights branched by the input light branching unit is incident on the one light receiving element via the variable optical attenuator,
The transmission loss of the variable optical attenuator is changed based on the output of the other light receiving element.

An optical module according to a sixth invention (corresponding to claim 6) for solving the above problem is the optical module according to the fifth invention,
A temperature control element that changes heat generation based on the output of the other light receiving element,
The temperature control element changes the transmission loss of the variable optical attenuator according to a temperature change caused by the heat generation.

An optical module according to a seventh invention (corresponding to claim 7) for solving the above problem is the optical module according to the fifth invention or the sixth invention,
The variable optical attenuator adjusts the amount of light attenuation so that the intensity of the branched light incident on the one light receiving element decreases as the intensity of the branched light received by the other light receiving element increases. To do.

An optical module according to an eighth invention (corresponding to claim 8) for solving the above problem is the optical module according to any one of the first invention to the seventh invention,
The input light branching means adjusts the branching ratio of the input light based on the output of the other light receiving element.

An optical module according to a ninth invention (corresponding to claim 9) for solving the above problem is the optical module according to the eighth invention,
The input light branching unit adjusts the branching ratio so that the intensity of the branched light incident on the one light receiving element decreases as the intensity of the branched light received by the other light receiving element increases. .

An optical module according to a tenth invention (corresponding to claim 10) for solving the above problems is the optical module according to any one of the first invention to the ninth invention,
Gain changing means for changing the gain of the one light receiving element,
The gain changing means adjusts the gain of the one light receiving element based on the output of the other light receiving element.

An optical module according to an eleventh invention (corresponding to claim 11) for solving the above problem is the optical module according to the tenth invention,
The gain changing means reduces the gain by reducing a bias voltage applied to the one light receiving element.

An optical module according to a twelfth invention (corresponding to claim 12) for solving the above problem is the optical module according to any one of the first invention to the eleventh invention.
The input light branching unit, the one light receiving element, and the other light receiving element are integrally formed in an optical module.

A method for manufacturing an optical module according to a thirteenth invention (corresponding to claim 13) for solving the above-described problem is
An input light branching means for branching the input light;
A variable optical attenuator;
A light receiving element;
In a manufacturing method of an optical module comprising other light receiving elements,
The light branching means is composed of a half mirror or an optical filter, and the light receiving area image of the one light receiving element and the light receiving area image of the other light receiving element observed by being transmitted or reflected through the light branching means overlap. And adjusting the position of the optical branching means.

  According to the present invention, a high-performance optical module can be realized by providing different light receiving elements with a receiving function and a light intensity monitoring function.

  The optical module according to the present invention is such that one of incident light branched into at least two or more optical paths by the light branching means is received by a light receiving element for reception and the other is received by a light receiving element for light intensity monitoring. is there. Further, an avalanche photodiode (APD) is used as a light receiving element for reception, and the bias voltage of the APD is adjusted according to the intensity received by the light receiving element for monitoring.

  The light attenuating means is disposed between the light branching means and the receiving light receiving element, and the light attenuation amount of the light attenuating means is adjusted according to the light intensity received by the monitoring light receiving element. Further, the light branching means, the light receiving element for reception, and the light receiving element for monitoring are integrally housed in the same package.

  Further, in the method for manufacturing an optical module according to the present invention, the light branching means is constituted by a half mirror or an optical filter, and the light receiving element for reception that is observed through the half mirror or the optical filter is observed. The position of the half mirror or the optical filter is adjusted so that the area image and the light receiving area image of the light receiving element for monitoring overlap each other.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of an optical module and a method for manufacturing the same according to the present invention will be described with reference to FIGS. 1 is a diagram for explaining a first embodiment of an optical module according to the present invention, FIG. 2 is a diagram for explaining response characteristics of the optical module according to the present invention, and FIG. 3 is used for the optical module according to the present invention. FIG. 4 is a diagram for explaining the transmittance of the light attenuating means according to the present invention, FIG. 5 is a diagram for explaining the transmittance of the etalon filter using the plastic according to the present invention, and FIG. FIG. 7 is a diagram illustrating a second embodiment of an optical module according to the present invention, FIG. 7 is a diagram illustrating an embodiment of a variable optical branching unit of the optical module according to the present invention, and FIG. 8 is a diagram illustrating an optical module according to the present invention. FIG. 9 is a diagram for explaining a fourth embodiment of the optical module according to the present invention, and FIG. 10 is an example of the relationship between the bias voltage and gain of the receiving APD according to the present invention. FIG. 11 shows a conventional optical module. It is a diagram illustrating a response characteristic.

[First Embodiment]
FIG. 1 is a diagram showing a first embodiment of an optical module according to the present invention.
As shown in FIG. 1, in the optical module of this embodiment, one of the optical paths branched into two by the optical branching means 1 passes through the variable optical attenuator 2 and is an APD 3 for reception, and the other is for monitoring. It arrange | positions at each position so that light may be received by pin-PD4. Here, by monitoring the incident light intensity with the monitoring pin-PD 4, it is possible to always measure the incident light intensity with a constant sensitivity or less without changing the receiving sensitivity of the receiving APD 4.

  Thus, in this embodiment, APD is used as a light receiving element. APD is destroyed when the light intensity is too high. As the APD, a structure in which an InGaAsP material having sensitivity to light of 1.3 to 1.6 microns is used as a light receiving layer is used. A general APD operates normally in the range of −30 dBm to +5 dBm, and the maximum rating is +5 dBm.

  In this embodiment, since the optical element (etalon filter) can attenuate light by 3 dB or more, when the light is strong, the light is attenuated by 3 dB, thereby realizing an APD in which incident light operates normally in a range of −30 dBm to +8 dBm. did it.

  As shown in FIG. 11, in the conventional optical module that monitors the incident light based on the light receiving intensity of the receiving APD and adjusts the light attenuation amount of the variable optical attenuator with the monitored light receiving current, the incident light is incident when there is no incident light. Since it is necessary to detect the presence or absence of light with high sensitivity, the light attenuator of the optical attenuator is set to the minimum (ideally 0 dB) and is on standby.

  When signal light is incident on the APD in this state, a large light receiving current is instantaneously generated because the sensitivity of the APD is high. For example, a light receiving current of 20 mA is generated by incident light of +10 dBm. The intensity of the light receiving current of the APD is monitored by an external circuit, and the light attenuation amount of the variable optical attenuator is increased so that the light receiving current does not exceed the maximum rated value of 10 mA.

  However, since the response speed of the external circuit is normally about 1 microsecond, a light receiving current of 20 mA is instantaneously generated between the time when light enters and the variable optical attenuator operates, and the maximum rated light receiving current value of the APD is obtained. If exceeded, the APD will be destroyed.

  On the other hand, as shown in FIG. 2, in the optical module that monitors incident light with the pin-PD 4 which is a light receiving element for monitoring of the present invention and adjusts the light attenuation amount of the optical attenuator with the monitored light receiving current, Using the variable optical attenuator 2 that can adjust the optical attenuation so that a large light receiving current does not occur instantaneously even in the absence of light, and waiting with the optical attenuation of the variable optical attenuator 2 increased. Can do.

  For example, if the optical attenuation of the variable optical attenuator 2 is 20 dB, even if +10 dBm signal light is incident, the incident light to the APD becomes -10 dBm, and the light receiving current generated thereby becomes 0.2 mA. Here, the incident light intensity is measured by the monitoring light receiving element pin-PD4, and the light attenuation amount of the variable optical attenuator 2 is adjusted according to the incident light intensity, so that the APD 3 for reception is instantaneously received. The maximum rated light receiving current value can be prevented from exceeding. For this reason, the receiving APD 3 is not destroyed.

  Here, an etalon filter can be used as the variable optical attenuator 2. As shown in FIG. 3, the etalon filter includes a plastic 31, an incident side reflection film 32, and an emission side reflection film 33. Here, the plastic 31 needs to have a transparency of 90% or more with respect to incident light. For example, ZEONEX (registered trademark) manufactured by Nippon Zeon Co., Ltd. has a permeability of 92%.

In order to configure an etalon filter, the incident side reflection film 32 and the emission side reflection film 33 have the same reflectance. Both reflectivities are about 1 to 10%. The reflective film is produced by laminating TiO ₂ and SiO ₂ by 0.4 microns each with a sputter deposition apparatus.

The thickness of the plastic 31 changes with temperature. The rate of change in thickness per unit temperature K is expressed by an expansion coefficient, and the ZEONEX is about 5 × 10 ⁻⁵ / K. The plastic 31 may have a thermal expansion coefficient of 1 × 10 ⁻⁵ / K to 1 × 10 ⁻⁴ / K. Moreover, when using a semiconductor, the thing from 1 * 10 < ^-6 > / K to 1 * 10 < ^-5 > / K can be used.

As shown in FIG. 4, the etalon filter has a property that the transmittance increases and decreases periodically with respect to the wavelength λ, and the cycle is λ / 2. If the expansion coefficient of the semiconductor constituting the etalon filter is 5 × 10 ⁻⁵ / K as described above, an expansion of 7.5 × 10 ⁻⁴ occurs for a temperature change of 15 K.

For example, when a plastic 31 having a thickness of 1000 μm is used, 7.5 × 10 ⁻⁴ × 1000 μm = 0.75 μm. When the wavelength λ of the incident light is 1.5 μm, the transmittance period of the etalon filter is shifted by one period due to a temperature change of 15K. That is, the transmittance of the etalon filter can be adjusted to an arbitrary value between the maximum value and the minimum value by adjusting the temperature within a temperature change range of 15K.

  As shown in FIG. 5, the transmittance of the etalon filter using the plastic 31 is specifically 80% at a reference temperature of 25 ° C. with respect to 1.55 micron light. Further, the transmittance is 50% at 35 ° C. and 30% at 45 ° C., and the transmittance rises by ½ or less, that is, the transmitted light intensity is attenuated by 3 dB or more by the temperature rise of 20 ° C. The same effect can be obtained at wavelengths other than 1.55 microns, for example, 1.3 microns and 1.6 microns.

In the present embodiment, an example in which the plastic 31 is used as the etalon filter is shown. However, even if a semiconductor is used, a similar effect can be expected by utilizing the fact that the refractive index changes with temperature. When a change in refractive index due to the temperature of the semiconductor is used, a refractive index change from 1 × 10 ⁻⁶ / K to 1 × 10 ⁻⁵ / K can be used. For example, when a compound semiconductor such as GaAs or InP is used as the semiconductor, the refractive index change rate is about 5 × 10 ⁻⁵ / K.

If the change rate of the refractive index of the semiconductor constituting the etalon filter is 5 × 10 ⁻⁵ / K, a change in refractive index of 5 × 10 ⁻⁴ occurs with respect to a temperature change of 10 K. This value corresponds to 5 × 10 ⁻⁴ μm, for example, when the wavelength λ of incident light is 1.5 μm, and the transmission characteristic curve in FIG. 4 is shifted along the 5 × 10 ⁻⁴ μm wavelength axis. become.

  The intensity ratio of the light (signal light) branched by the optical branching means 1 in this embodiment and incident on the variable optical attenuator 2 and the light incident on the monitoring pin-PD 4 is 1: 1, and the variable optical attenuator 2 The light (signal light) incident on is 1/2 of the total light. Here, the intensity ratio of the branched light may not be 1: 1 but may be branched at other ratios. However, if too much light is incident on the monitoring pin-PD 4, the light received by the receiving APD 4 correspondingly. Since (signal light) is reduced, it is desirable that the light incident on the variable optical attenuator 2 is 1/3 or more of the total light.

  In this embodiment, the temperature control element is installed adjacent to or near the etalon filter that is the variable optical attenuator 2. By controlling the temperature control element in accordance with the output of the pin-PD 4 that is a light receiving element for monitoring, the output current (voltage) of the pin-PD 4 changes due to the incident light intensity at the pin-PD 4, and the temperature control element generates heat. Change.

  Since the transmission loss of the etalon filter changes due to the temperature change due to this heat generation, it is possible to control the incident light intensity to the APD 3 that is the receiving light receiving element. As a result, the receiving APD 3 can maintain good characteristics without being deteriorated or destroyed by incident light.

[Second Embodiment]
FIG. 6 is a diagram showing a second embodiment of the optical module according to the present invention.
As shown in FIG. 6, in the optical module of this embodiment, one of the optical paths branched into two by the variable optical branching means 51 is received by the receiving APD 52 and the other is received by the monitoring pin-PD 53. Are arranged at respective positions. Here, by monitoring the incident light intensity with the pin-PD 53, it is not necessary to adjust the branching ratio of the variable light branching means 51 to change the reception sensitivity of the APD 52 for reception, and the incident light intensity is always kept at a constant sensitivity or less. Can be measured.

  In this configuration, the branching ratio of the variable optical branching means 51 to the monitoring pin-PD 53 is maximized, that is, the branching ratio to the receiving APD 52 is minimized so that a large light receiving current does not occur instantaneously even in the absence of incident light. Can wait.

  For example, when the branching ratio of the variable light branching means 51 is 1: 100, even if +10 dBm signal light is incident, the incident light to the receiving APD 52 becomes -10 dBm, and the light receiving current generated thereby becomes 0.2 mA. . Here, by measuring the incident light intensity to the pin-PD 53 which is a light receiving element for monitoring and adjusting the branching ratio of the variable light branching means 51 according to the intensity, the maximum rating of the receiving APD 52 is instantaneously received. It is possible to prevent the light receiving current value from being exceeded. For this reason, the receiving APD 52 is not destroyed.

  As shown in FIG. 7, as the variable light branching means 61, for example, a planar lightwave circuit using a glass material is used. This planar lightwave circuit is composed of a Mach-Zehnder interferometer using the principle of interference between two optical paths. One optical path is used as an optical waveguide, and a heater 63 is formed in the other optical path. By changing the rate, the effective optical path length is changed to change the branching ratio. As the planar lightwave circuit, plastic, polyimide, or semiconductor can be used.

  In the planar lightwave circuit used in this embodiment, the temperature of the heater 63 is increased from room temperature to about 60 ° C. to 70 ° C., and the branching ratio (intensity of light branched to the receiving light receiving element (APD 52): monitoring light receiving element ( The intensity of light splitting into pin-PD53) can be changed from 1: 100 to 100: 1. By controlling the heater 63 of the planar lightwave circuit in accordance with the output of the pin-PD 53 which is a light receiving element for monitoring, the output current (voltage) of the pin-PD 53 is changed by the incident light intensity at the pin-PD 53 and the heater 63 Change the fever.

  Since the branching ratio of the planar lightwave circuit changes due to the temperature change due to this heat generation, the intensity of incident light on the APD 52 that is the light receiving element for reception can be controlled. As a result, the receiving APD 52 can maintain good characteristics without being deteriorated or destroyed by incident light.

[Third Embodiment]
FIG. 8 is a diagram showing a third embodiment of the optical module according to the present invention.
As shown in FIG. 8, the optical module of this embodiment includes the optical branching means 71, variable optical attenuator 72, receiving APD 73, and monitoring pin-PD 74 described in the first embodiment in one housing. It is an optical module mounted on.

  The light branching means 71 is formed of a half mirror, and transmitted light and reflected light are incident on the receiving APD 73 and the monitoring pin-PD 74, respectively, at a desired branching ratio. Here, the branching ratio to the APD 73 for reception is generally set higher. In the assembly of this optical module, the image of the receiving APD 73 transmitted through the half mirror and the image of the monitoring pin-PD 74 reflected from the half mirror are observed simultaneously from the incident side.

  By adjusting the position of each component so that these images overlap, the transmitted light and the reflected light are incident on the receiving APD 73 and the monitoring pin-PD 74, respectively, by a very simple method.

  In this embodiment, the transmitted light and reflected light of the half mirror are respectively incident on the receiving APD 73 and the monitoring pin-PD 74. Conversely, the transmitted light and the reflected light are respectively monitored on the monitoring pin-PD 74. Even if it is arranged so as to be incident on the receiving APD 73, the same effect can be obtained.

  In this embodiment, the temperature control element is installed adjacent to or near the etalon filter that is the variable optical attenuator 72. By controlling the temperature control element in accordance with the output of the pin-PD 4 which is a light receiving element for monitoring, the output current (voltage) of the pin-PD 74 is changed by the incident light intensity at the pin-PD 74 and the temperature control element generates heat. Change.

  The transmission loss of the etalon filter that is the variable optical attenuator 72 changes due to the temperature change due to this heat generation, so that the incident light intensity to the APD 73 that is the receiving light receiving element can be controlled. As a result, the reception APD can maintain good characteristics without being deteriorated or destroyed by incident light.

[Fourth Embodiment]
FIG. 9 is a diagram showing a fourth embodiment of the optical module according to the present invention.
As shown in FIG. 9, in the optical module of this embodiment, one of the optical paths branched into two by the optical branching means 81 is received by the receiving APD 82 and the other is received by the monitoring pin-PD 83. , Are arranged at each position.

  Here, the gain of the APD 82 for reception is adjusted by monitoring the intensity of incident light with the pin-PD 83 so that a photocurrent exceeding the maximum rated light receiving current value does not flow. With this configuration, even when there is no incident light, it is possible to stand by with the gain of the receiving APD 82 minimized so that a large light receiving current is not instantaneously generated.

  FIG. 10 is a diagram for explaining an example of the relationship between the bias voltage and gain of the receiving APD 82 according to the present invention. As shown in FIG. 10, it can be seen that in this example, the gain is 3 at a bias voltage of 20V, the gain is 1 at 10V, and the gain is 10 at 30V. Assuming that the sensitivity at which incident light is converted into electron-hole pairs is Res (unit: A / W), the photoelectric conversion efficiency is Res × 1 for a gain of 1, and Res × for a gain of 10. 10 In general, the sensitivity of the APD is about 1 A / W for an optical signal having a wavelength of 1.5 μm, so that when the gain is 1, the photoelectric conversion efficiency is 1 A / W, and when the gain is 10, the photoelectric conversion efficiency is 10 A. / W.

  In the present embodiment, an optical signal having a light intensity of +10 dBm (= 10 mW) is branched into 9: 1 by the optical branching means 81 and is incident on the receiving APD 82 and the monitoring pin-PD 83, respectively. The light intensity incident on the receiving APD 82 is 9 mw, and the light intensity incident on the monitoring pin-PD 83 is 1 mW.

  Since the monitor pin-PD 83 has a constant gain of 1 in the range of a bias voltage of 1 to 10 V, the photoelectric conversion efficiency is 1 A / W, and the light receiving current is 1 mA. At this time, the bias voltage of the reception APD 82 is set to 10 V in the standby state, and the bias voltage of the reception APD 82 is set so as not to exceed the rated maximum light reception current value based on the light reception current value at the monitor pin-PD 83. The voltage is still 10 V (the photoelectric conversion efficiency is 1 A / W), and the light receiving current value is 9 mA.

  Next, in this embodiment, when an optical signal having a light intensity of −10 dBm (= 0.1 mW) is incident, the light intensity incident on the receiving APD 82 is 0.09 mW, and is incident on the monitoring pin-PD 83. The light intensity is 0.01 mW. The light receiving current of the monitoring pin-PD 83 is 0.01 mA. At this time, if the bias voltage is increased to 30 V from the standby state of the bias voltage 10 V of the receiving APD 82, the photoelectric conversion efficiency is 10 A / W, so the light receiving current value is 0.9 mA, and the reception is highly efficient and sensitive. It becomes possible to do.

  As described above, the intensity of incident light on the receiving APD 82 is measured by the light reception current of the monitoring pin-PD 83 and the bias voltage of the receiving APD 82 is controlled, so that the receiving APD 82 has high intensity light. Therefore, light with low intensity can be received with high efficiency and high sensitivity without being deteriorated or destroyed.

  The optical module and the method for manufacturing the optical module according to the present invention are suitable for application to the optical input part of a receiver for optical communication. It is also possible to adjust the light intensity in the middle of the road and to apply to the light emitting part or the light receiving part of the optical measuring instrument.

It is a figure explaining 1st Embodiment of the optical module which concerns on this invention. It is a figure explaining the response characteristic of the optical module which concerns on this invention. It is a figure explaining the optical attenuation means used for the optical module which concerns on this invention. It is a figure explaining the transmittance | permeability of the light attenuation means which concerns on this invention. It is a figure explaining the transmittance | permeability of the etalon filter using the plastic which concerns on this invention. It is a figure explaining 2nd Embodiment of the optical module which concerns on this invention. It is a figure explaining embodiment of the variable optical branching means of the optical module which concerns on this invention. It is a figure explaining 3rd Embodiment of the optical module which concerns on this invention. It is a figure explaining 4th Embodiment of the optical module which concerns on this invention. It is a figure explaining an example of the relationship between the bias voltage and gain of APD for reception which concerns on this invention. It is a figure explaining the response characteristic of the conventional optical module.

Explanation of symbols

1 Optical branching means 2 Variable optical attenuator 3 APD for reception
4 Pin-PD for monitor
31 Plastic 32 Incident-side reflective film 33 Emission-side reflective film 51 Variable light branching means 52 APD for reception
53 Pin-PD for monitor
61 Variable optical branching means 62 Optical waveguide 63 Heater 71 Optical branching means 72 Variable optical attenuator 73 APD for reception
74 Pin-PD for monitor

Claims (13)

A light receiving element;
In an optical module comprising other light receiving elements,
Input light branching means for branching the input light into at least two optical paths;
The input light branching means is
One of the branched light beams is incident on the one light receiving element,
An optical module, wherein the other branched light is incident on the other light receiving element. The optical module according to claim 1,
An optical module, wherein a branching ratio of at least two branched lights branched by the input light branching means is 1: 2 or more. In the optical module according to claim 1 or 2,
An optical module, wherein an avalanche photodiode is used for the one light receiving element. The optical module according to any one of claims 1 to 3,
An optical module, wherein a branched light beam having a maximum branching ratio among at least two branched light beams branched by the input light branching unit is incident on the one light receiving element. The optical module according to any one of claims 1 to 4,
A variable optical attenuator for attenuating light between the input light branching means and the one light receiving element;
Either one of the branched lights branched by the input light branching unit is incident on the one light receiving element via the variable optical attenuator,
An optical module, wherein a transmission loss of the variable optical attenuator is changed based on an output of the other light receiving element. The optical module according to claim 5,
A temperature control element that changes heat generation based on the output of the other light receiving element,
The optical module, wherein the temperature control element changes a transmission loss of the variable optical attenuator according to a temperature change caused by the heat generation. 7. The optical module according to claim 5, wherein the variable optical attenuator decreases the intensity of the branched light incident on the one light receiving element as the intensity of the branched light received by the other light receiving element increases. An optical module characterized by adjusting the amount of light attenuation so that The optical module according to any one of claims 1 to 7,
The optical module according to claim 1, wherein the input light branching unit adjusts a branching ratio of the input light based on an output of the other light receiving element. The optical module according to claim 8,
The input light branching unit adjusts the branching ratio so that the intensity of the branched light incident on the one light receiving element decreases as the intensity of the branched light received by the other light receiving element increases. Optical module. The optical module according to any one of claims 1 to 9,
Gain changing means for changing the gain of the one light receiving element,
The optical module characterized in that the gain changing means adjusts the gain of the one light receiving element based on the output of the other light receiving element. The optical module according to claim 10,
The optical module characterized in that the gain changing means lowers the gain by lowering a bias voltage applied to the one light receiving element. The optical module according to any one of claims 1 to 11,
The optical module, wherein the input light branching means, the one light receiving element, and the other light receiving element are integrally formed in an optical module. An input light branching means for branching the input light;
A variable optical attenuator;
A light receiving element;
In a manufacturing method of an optical module comprising other light receiving elements,
The light branching means is composed of a half mirror or an optical filter, and the light receiving area image of the one light receiving element and the light receiving area image of the other light receiving element observed by being transmitted or reflected through the light branching means overlap each other. And adjusting the position of the optical branching means.

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