JP2006080362A - Optical transmitting/receiving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmitting/receiving device having high receiving sensitivity without restricting the diameter of an optical fiber for connection thereof. <P>SOLUTION: A vertical resonance type surface emitting laser diode 18 for transmitting an optical signal, a light receiving element 20 for monitoring light quantity, a laser beam for transmission, a beam splitter 22, and a light receiving element 24 for a received signal are provided on a base 12. A first laser beam L1 emitted upwardly from the vertical resonance type surface emitting laser diode 18 is transmitted through the beam splitter 22 and converged by a ball lens 34 to irradiate the end surface of the optical fiber 32. Further, the first laser beam L1 is reflected by the beam splitter 22 rightward in the figure and incident on the light receiving element 20 for monitoring light quantity. On the other hand, a second laser beam L2 emitted from the communication partner is emitted from the end surface of the optical fiber 32. The second laser beam L2 emitted from the end surface of the optical fiber 32 is transmitted through the ball lens 34, and then reflected leftward by the beam splitter 22 and incident on the light receiving element 24 for the received signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical transceiver, and more particularly to an optical transceiver with high reception sensitivity.

  Conventionally, as a so-called single-fiber bidirectional optical transmission / reception module that transmits a bidirectional optical signal to a single optical fiber, the transmission light and the reception light are guided in a predetermined direction using a half mirror as in Patent Document 1. The method is known.

  However, in this method, since the transmission light and the reception light are halved by the half mirror, the amount of light guided to the light receiving element is reduced by 3 dB or more, and the reception sensitivity is deteriorated.

  As a method for solving this, there is known a method of efficiently separating light using a wavelength filter by changing the wavelengths of transmission light and reception light as disclosed in Patent Document 2 and the like.

  However, this method has a problem that the partner of transmission and reception is limited and expensive.

  As another solution, there is a method of efficiently guiding the received light to the light receiving element by spatially separating a region through which the transmitted light and the received light pass, as in Patent Document 3 and the like.

However, since this method requires a large space in the module, it is difficult to adjust the position, and there is a problem that it can only be applied practically to a large-diameter optical fiber.
JP-A-10-39180 Japanese Patent Laid-Open No. 2003-29093 Japanese Patent Laid-Open No. 2002-124687

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an optical transmission / reception apparatus having high reception sensitivity without limiting the diameter of an optical fiber to be connected.

  According to a first aspect of the present invention, a light emitting element that emits first light, a light receiving element that receives second light, and light that emits the first light and enters the second light. An optical transmission / reception apparatus used for single-core bidirectional optical communication, comprising: an input / output unit; and an optical distribution unit that distributes incident light into transmitted light and reflected light, wherein the optical distribution unit The reflectance is set higher than 50%, and a part of the incident first light is reflected so as to limit the amount of light reaching the light input / output part.

  Next, the operation of the optical transceiver according to claim 1 will be described.

  When transmitting and receiving optical signals, two optical transmission / reception devices are used, and both light incident / exit portions are connected by, for example, an optical fiber.

  When the second light (an optical signal from the other side) is incident on the light incident / exiting portion, a part of the light is reflected by the light distribution means and reaches the light receiving element.

  On the other hand, when the first light emitted from the light emitting element (an optical signal to be sent to the other side) is incident on the light incident / exiting part, a part of the light is transmitted through the light incident / exiting part and reaches the light emitting part.

  Here, the light reflectance of the light distribution means is set to be higher than 50%, in other words, the light transmittance is lower than at least 50%. This is a substitute for a filter for suppressing the amount of light, and the amount of light reaching the light incident / exit section can be limited without increasing the number of components, and the amount of laser light incident on the light receiving element can be secured to increase the reception sensitivity.

  Further, since a large space for securing an optical path in the apparatus is not required, the apparatus can be reduced in size. Furthermore, since the light is distributed by the light distribution means, it is possible to connect with no problem even with a small-diameter optical fiber or a large-diameter optical fiber.

  According to a second aspect of the present invention, in the optical transmission / reception apparatus according to the first aspect, the optical distribution means has a reflectance set to 70% or more and 95% or less.

  Next, the operation of the optical transceiver according to claim 2 will be described.

  By setting the reflectance of the light distribution means to 70% or more and 95% or less, a high effect as a filter can be obtained, the amount of laser light incident on the light receiving element can be increased, and reception sensitivity can be increased. If the reflectance exceeds 95%, the amount of first light transmitted, that is, the amount of laser light output outside the apparatus is insufficient.

  According to a third aspect of the present invention, in the optical transmission / reception apparatus according to the first or second aspect, the light distribution means is a beam splitter made of a metal thin film.

  Next, the operation of the optical transceiver according to claim 3 will be described.

  By using a beam splitter made of a metal thin film as the light distribution means, the apparatus cost can be reduced.

  According to a fourth aspect of the present invention, in the optical transmission / reception apparatus according to the first or second aspect, the light distribution means is a beam splitter made of a dielectric multilayer film.

  Next, the operation of the optical transceiver according to claim 4 will be described.

  By using a beam splitter made of a dielectric multilayer film as the light distribution means, there is no light absorption and the reflectance can be increased efficiently.

  According to a fifth aspect of the present invention, in the optical transmission / reception device according to any one of the first to fourth aspects, the light emitting element is a vertical cavity surface emitting laser.

  Next, the operation of the optical transceiver according to claim 5 will be described.

  Considering the balance between keeping the amount of light emitted outside the device within the laser safety standards and increasing the receiving sensitivity, use a vertical cavity surface emitting laser as the light emitting element, which has higher emission efficiency than the edge emitting laser. Is preferred.

  As a vertical cavity surface emitting laser, there is a VCSEL manufactured by Fuji Xerox Co., Ltd.

  According to a sixth aspect of the present invention, in the optical transmission / reception apparatus according to any one of the first to fifth aspects, the first light reflected by the light distribution unit is placed on the optical path of the first light. An antireflection means for preventing light reflection is provided.

  Next, the operation of the optical transceiver according to claim 6 will be described.

  By providing an antireflection means for preventing the reflection of the first light on the optical path of the first light reflected by the light distribution means, the return light to the light emitting element and the stray light to the light receiving element are reduced, and oscillation occurs. Becomes stable and crosstalk during transmission and reception is reduced.

  According to a seventh aspect of the present invention, in the optical transmission / reception device according to any one of the first to sixth aspects, a light receiving element for monitoring is provided to receive the first light reflected by the light distributing means. It is characterized by that.

  Next, the operation of the optical transceiver according to claim 7 will be described.

  By receiving the first light reflected by the light distribution means by the light receiving element for monitoring, the output of the light emitting element can be monitored, and the light output of the light emitting element can be controlled.

  According to an eighth aspect of the present invention, in the optical transmitter / receiver according to the seventh aspect, an optical attenuating unit is provided between the optical distributing unit and the monitoring light receiving element.

  Next, the operation of the optical transceiver according to the eighth aspect will be described.

  By providing the light attenuating means between the light distributing means and the light receiving element for monitoring, it is possible to prevent light from entering the light receiving element for monitoring excessively, and stable light output control is possible.

  According to a ninth aspect of the present invention, in the optical transceiver according to any one of the first to eighth aspects, the light receiving surface of the light receiving element and the light emitting surface of the light emitting element are directed in the same direction. It is characterized by that.

  Next, the operation of the optical transceiver according to claim 9 will be described.

  By directing the light receiving surface of the light receiving element and the light emitting surface of the light emitting element in the same direction, the light receiving element and the light emitting element can be mounted on the same surface side of the same substrate, for example, and miniaturization and cost reduction are achieved. I can do it.

  According to a tenth aspect of the present invention, in the optical transmission / reception device according to the seventh or eighth aspect, the light receiving surface of the light receiving element, the light receiving surface of the light receiving element for monitoring, and the light emitting surface of the light emitting element are the same. It is characterized by being oriented in the direction.

  Next, the operation of the optical transceiver according to claim 10 will be described.

  By directing the light receiving surface of the light receiving element, the light receiving surface of the light receiving element for monitoring, and the light emitting surface of the light emitting element in the same direction, the light receiving element, the light receiving element for monitoring, and the light emitting element are arranged on the same surface side of the same substrate, for example. Therefore, it is possible to reduce the size and cost.

  According to an eleventh aspect of the present invention, in the optical transmission / reception device according to the tenth aspect, the light distribution means is coupled to the light receiving element to guide the second light and is coupled to the monitor light receiving element. The light guide means for guiding the first light is integrally provided.

  Next, the operation of the optical transceiver according to claim 11 will be described.

  Connecting the light receiving element to the light guide means facilitates positioning of the light receiving element with respect to the light guide means, and connecting the light emitting elements to the light guide means facilitates positioning of the light emitting elements with respect to the light guide means. Positioning parts are not required, the number of parts is reduced, and the cost can be reduced.

  As described above, according to the optical transmission / reception apparatus of the present invention, there is an excellent effect that the reception sensitivity can be increased.

[First Embodiment]
The first embodiment of the optical signal transmission apparatus of the present invention will be described in detail with reference to FIGS.

  The optical signal transmission device 10 of this embodiment is used for a single-core bidirectional communication line.

  As shown in FIG. 1, the optical signal transmission device 10 of this embodiment includes a package 16 including a pedestal 12 and a cover 14.

  The pedestal 12 is provided with a vertical cavity surface emitting laser diode 18, a light amount monitoring light receiving element 20, a beam splitter 22 as light distribution means, and a received signal light receiving element 24.

  The vertical cavity surface emitting laser diode 18 is attached to the central portion of the upper surface (in FIG. 1) of the base 12.

  The vertical cavity surface emitting laser diode 18 of the present embodiment is configured so that, for example, the first laser light L1 (first light of the present invention) having a wavelength of 850 nm is drawn upward (arrow U direction: first direction of the present invention). Exit toward

  On the upper surface of the pedestal 12, a first block 26 is mounted on the right side of the vertical cavity surface emitting laser diode 18 in the drawing (the direction of the arrow R: the second direction of the present invention). An inclined surface 26A is formed on the first block 26, and the light quantity monitoring light receiving element 20 is attached to the inclined surface 26A.

  A second block 28 is mounted on the upper surface of the pedestal 12 in the left direction of the vertical cavity surface emitting laser diode 18 (arrow L direction: the third direction of the present invention).

  The second block 28 is formed with an inclined surface 28A, and the received light receiving element 24 is attached to the inclined surface 28A.

  As the light receiving element for receiving signal 24 and the light receiving element 20 for monitoring light quantity, a photodiode (PD), for example, a high-speed silicon-based or gallium arsenide-based PIN photodiode, or MSM (Metal-Semiconductor-Metal) is used. A type photodiode can be used, but other elements may be used.

  The beam splitter 22 is disposed on the laser beam emission side (in the direction of arrow U) of the vertical cavity surface emitting laser diode 18 and is attached to a block (not shown) mounted on the pedestal 12.

  The beam splitter 22 of this embodiment is inclined upward at an angle of 45 ° with respect to the upper surface of the base 12.

  Here, the beam splitter 22 needs to set the reflectance higher than 50%, and the reflectance is preferably 70% or more and 95% or less. The reflectivity of the beam splitter 22 of this embodiment is set to 85%.

  As shown in FIG. 1, the cover 14 has a cylindrical shape and is attached to the upper surface of the pedestal 12.

  An optical fiber 32 is inserted and fixed above the through hole 14A of the cover 14, and a ball lens 34 is attached to a substantially middle portion of the through hole 14A.

  In the present embodiment, GI-POF is used as the optical fiber 32.

As shown in FIG. 2, the pedestal 12 is mounted with a drive circuit 38 for the vertical cavity surface emitting laser diode 18 and an amplifier 44 for the received light receiving element 24.
(Function)
Next, the operation of the optical signal transmission device 10 of the present embodiment will be described.

  When transmitting and receiving an optical signal, two optical signal transmission devices 10 are used and both are connected by an optical fiber 32.

  First, transmission of an optical signal will be described.

  Part of the first laser light L1 emitted upward from the vertical cavity surface emitting laser diode 18 passes through the beam splitter 22, is collected by the ball lens 34, and is irradiated onto the end face of the optical fiber 32. As a result, the first laser light L1 can be transmitted to the communication counterpart via the optical fiber 32.

  Further, a part of the first laser beam L1 is reflected by the beam splitter 22 in the right direction in FIG.

  As a result, the transmission state of the first laser light of the vertical cavity surface emitting laser diode 18 can be monitored by the light quantity monitoring light receiving element 20, and the drive of the vertical cavity surface emitting laser diode 18 can be controlled.

  On the other hand, from the end face of the optical fiber 32, the second laser light L2 emitted from the communication partner is emitted.

  The second laser light L2 emitted from the end face of the optical fiber 32 passes through the ball lens 34, is reflected by the beam splitter 22 in the left direction in FIG. 1, and enters the light receiving element 24 for received signals.

  In the present embodiment, since the reflectance of the beam splitter 22 is set to 85%, it serves as a filter for suppressing the amount of the first laser light L1 emitted outside the apparatus within the laser safety standard, and the number of parts is reduced. The amount of light incident on the optical fiber 32 can be limited without being increased, and the amount of the second laser light L2 incident on the light receiving element 24 for received signals can be sufficiently secured, thereby improving the reception sensitivity. I can do it.

  Since the beam splitter 22 reflects and transmits light, the optical signal transmission apparatus 10 does not require a large space for securing an optical path, and can be downsized. Even if the optical fiber 32 has a small diameter, the optical fiber 32 is large. Even if it is a caliber, it can be connected without any problems.

When transmitting and receiving an optical signal, two optical signal transmission apparatuses 10 having exactly the same configuration are used. Therefore, compared with a system in which the wavelength of the laser light of one apparatus is different from the wavelength of the laser light of the other apparatus Since the configuration is simplified by using low-cost parts (an inexpensive beam splitter for an expensive mirror having wavelength selectivity), an apparatus can be provided at a low cost.
[Second Embodiment]
The second embodiment of the optical signal transmission apparatus of the present invention will be described in detail with reference to FIGS. In addition, the same code | symbol is attached | subjected to the same structure as embodiment mentioned above, and the description is abbreviate | omitted.

  As shown in FIG. 3, the receiving signal light receiving element 24 is attached to the pedestal 12 of the optical signal transmission device 10 of the present embodiment via the spacer 50 with the light receiving surface facing upward in the drawing, and the spacer 52 is interposed therebetween. The light receiving element 20 for monitoring the light quantity is attached with the light receiving surface facing upward, and the vertical cavity surface emitting laser diode 18 is directly attached with the light emitting surface facing upward.

  A prism 54 is mounted and adhered to the light emitting surface of the vertical cavity surface emitting laser diode 18 and the light receiving surface of the light quantity monitoring light receiving element 20 so as to straddle both.

  The prism 54 is formed by joining a first prism 54A whose side view shape is a parallelogram and a second prism 54B whose side view shape is a triangle.

  In the present embodiment, the first inclined surface 56 of the first prism 54A and the first inclined surface 58 of the second prism 54B are bonded.

  The first inclined surface 56 of the first prism 54A is provided with mirror coating (not shown) as light distribution means.

  Here, the reflectance of the mirror coating part is set similarly to the beam splitter 22 of the first embodiment.

  The second inclined surface 60 of the second prism 54B and the lower surface 62 to which the light quantity monitoring light receiving element 20 is connected are each provided with an antireflection film (not shown).

As shown in FIG. 4, on the upper surface of the pedestal 12, one side is a ground of the reception signal light receiving element 24 and the other side is a ground of the vertical cavity surface emitting laser diode 18 with a boundary line 64 indicated by a one-dot chain line as a boundary. It is preferable to do.
(Function)
Next, the operation of the optical signal transmission device 10 of the present embodiment will be described.

  A portion of the first laser light L1 emitted upward from the vertical cavity surface emitting laser diode 18 passes through the mirror coating portion, is condensed by the ball lens 34, and is irradiated onto the end face of the optical fiber 32. As a result, the first laser light L1 can be transmitted to the communication counterpart via the optical fiber 32.

  Further, most of the first laser beam L1 is reflected in the right direction in the drawing by the mirror coating portion, and further reflected downward by the second inclined surface 60 and enters the light amount monitoring light receiving element 20.

  As a result, the transmission state of the first laser light of the vertical cavity surface emitting laser diode 18 can be monitored by the light quantity monitoring light receiving element 20, and the drive of the vertical cavity surface emitting laser diode 18 can be controlled.

  On the other hand, from the end face of the optical fiber 32, the second laser light L2 emitted from the communication partner is emitted.

  The second laser light L2 emitted from the end face of the optical fiber 32 is transmitted through the ball lens 34, then reflected to the left in the drawing by the mirror coating portion, and is reflected by the second inclined surface 66 of the first prism 54A. The light is reflected downward and enters the received light receiving element 24.

  In this embodiment, since the reflectance of the mirror coating portion is set to 85%, similarly to the beam splitter 22 of the first embodiment, the light quantity of the first laser light L1 emitted to the outside of the apparatus is changed to laser safety. This is a substitute for a filter for suppressing the amount within the reference, and the amount of light incident on the optical fiber 32 can be limited without increasing the number of components, and the amount of the second laser light L2 incident on the light receiving element 24 for received signals is sufficiently large. And reception sensitivity can be increased.

  Since the antireflection film (not shown) is provided on the second inclined surface 60 of the second prism 54B and the lower surface 62 to which the light quantity monitoring light receiving element 20 is connected, the vertical cavity surface emitting laser diode 18 is provided. Return light to the light source and stray light to the reception signal light receiving element 24 are reduced, the oscillation of the vertical cavity surface emitting laser diode 18 is stabilized, and crosstalk during transmission and reception is reduced.

  Further, in the present embodiment, the light receiving surface of the reception signal light receiving element 24, the light receiving surface of the light amount monitoring light receiving element 20, and the light emitting surface of the vertical cavity surface emitting laser diode 18 are oriented in the same direction, As a result, it was possible to reduce the size and cost.

Further, the light receiving element is connected to the light guide means to facilitate the positioning of the light receiving element with respect to the light guide means, and the light emitting element is connected to the light guide means to facilitate the positioning of the light emitting elements relative to the light guide means. Positioning parts are not required, the number of parts is reduced, and the cost can be reduced.
[Other Embodiments]
When the amount of light incident on the light amount monitoring light receiving element 20 is too large, in the first embodiment, between the beam splitter 22 and the light amount monitoring light receiving element 20, and in the second embodiment, a mirror coating portion and A light attenuating means (filter) may be arranged between the light receiving element 20 for monitoring the light amount. Thereby, stable light output control becomes possible.

  In addition to the light emitting element, the light receiving element, and the beam splitter being mounted in an integrated package as shown in FIGS. 1 and 3, even if each mounted in a separate package is integrally disposed, Naturally good.

  The beam splitter may be a beam splitter made of a metal thin film or a beam splitter made of a dielectric multilayer film.

It is sectional drawing of the optical signal transmission apparatus which concerns on 1st Embodiment. It is a top view of the base of the optical signal transmission apparatus concerning a 1st embodiment. It is sectional drawing of the optical signal transmission apparatus which concerns on 2nd Embodiment. It is a top view of the base of the optical signal transmission apparatus which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical signal transmission apparatus 12 Base 14A Through hole (light incident / exit part)
18 Vertical cavity surface emitting laser diode (light emitting device)
20 Light receiving element for light intensity monitoring 22 Beam splitter 24 Light receiving element for receiving signal (light receiving element)
32 optical fiber 54 prism (light guide means)

Claims (11)

A light emitting element emitting first light;
A light receiving element for receiving the second light;
A light incident / exit section through which the first light is emitted and the second light is incident;
Light distribution means for distributing incident light into transmitted light and reflected light;
An optical transceiver used for single-core bidirectional optical communication comprising:
The light distribution means is characterized in that a light reflectance is set to be higher than 50% and a part of the incident first light is reflected so as to limit a light amount reaching the light input / output section. Optical transmission / reception device. The optical transmission / reception apparatus according to claim 1, wherein the optical distribution unit has a reflectance set to 70% or more and 95% or less. The optical transmission / reception apparatus according to claim 1, wherein the light distribution unit is a beam splitter made of a metal thin film. The optical transmission / reception apparatus according to claim 1, wherein the light distribution unit is a beam splitter made of a dielectric multilayer film. The optical transmission / reception apparatus according to any one of claims 1 to 4, wherein the light emitting element is a vertical cavity surface emitting laser. The antireflection means for preventing the reflection of the first light is provided on the optical path of the first light reflected by the light distribution means. The optical transmission / reception device according to item. The optical transmission / reception apparatus according to claim 1, further comprising: a monitoring light receiving element that receives the first light reflected by the light distribution unit. 8. The optical transmission / reception apparatus according to claim 7, further comprising an optical attenuation unit provided between the optical distribution unit and the light receiving element for monitoring. 9. The optical transceiver according to claim 1, wherein a light receiving surface of the light receiving element and a light emitting surface of the light emitting element are oriented in the same direction. 9. The optical transceiver according to claim 7, wherein the light receiving surface of the light receiving element, the light receiving surface of the monitor light receiving element, and the light emitting surface of the light emitting element are oriented in the same direction. . The light distribution means is integrally provided with a light guide means connected to the light receiving element to guide the second light and connected to the monitor light receiving element to guide the first light. The optical transceiver according to claim 10.

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