JP2007057591A - Optical transmission system for optical spatial communication, light receiving system, and optical waveguide processing method for optical spatial communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve miniaturization of each of optical transmitting and receiving systems and flexibility of laying out by separating a light emitting element or a light receiving element from start and terminal points of optical spatial communication. <P>SOLUTION: Only the light emitting element 111 and its drive circuit 112 are incorporated in an optical transmission part 11, and signal light emitted from the light emitting element 111 is guided to a prescribed position by an optical waveguide 12 to discharge the signal light L with a prescribed spot size to a space by a transmission lens 13. A receiving lens 21 is arranged at an opposite receiving position, the signal light transmitted spatially from the transmission lens 13 is condensed, guided to a light receiving part 23 by an optical waveguide 22 and the signal light from the optical waveguide 22 is received with the light receiving element 231, and the received signal is demodulated to obtain the original transmission signal. In the configuration, only lens parts at the transmission side and the receiving side may be accurately aligned while facing, and arrangement/size or the like of the optical transmission part 11 and the optical receiving part 23 are not restricted. In addition, a power supply facility in the vicinity of the lenses is not needed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical transmission device and an optical reception device used in an optical space communication device for transmitting and receiving an optical signal through a space.

  2. Description of the Related Art Conventionally, an optical transmission device and an optical reception device constituting an optical space communication device are manufactured by integrating an optical lens and a light emitting device or a light receiving device in such a manner that the light emitting device or the light receiving device is disposed at the focal position of the optical lens. (See Non-Patent Documents 1 and 2, for example). However, the conventional integrated structure of the optical lens and the light emitting element or the light receiving element as described above has a limit in reducing the size of each device, and there is a problem that the installation space for the device must be secured accordingly. there were. Further, in order to adjust with high accuracy so that the optical axes of the transmission / reception optical systems coincide with each other, the optical transmission device and the optical reception device have to be accurately opposed to each other.

  Furthermore, it is necessary to supply power to each of the optical transmitter and the optical receiver, and in the case of outdoor installation, it is necessary to provide facilities that are not originally related to communication, such as wiring for power supply and battery installation.

H. Willebrand, B. S. Ghuman: “Free-space optics”, Sams Publishing (2002).

H. Hemmati el al.: “Approachs for efficient coupling of lasers to telescopes with secondary mirror and buffle obsuration”, Proc. SPIE Vol.4635, pp.288-297 (2002).

  As described above, the conventional optical space communication device uses the optical transmission device and the optical reception device having an integrated structure of the optical lens and the light emitting element or the light receiving element, and thus cannot meet the demand for downsizing of each device. It is coming. Further, in order to adjust with high accuracy so that the optical axes of the transmission / reception optical systems coincide with each other, the optical transmission device and the optical reception device need to be accurately opposed to each other, and power supply equipment is required for each device.

  The present invention has been made in view of the above circumstances, and solves the limitation of the integrated optical design of the optical lens and the light emitting element or the light receiving element, and separates the light emitting element or the light receiving element from the start and end points of the optical space communication to reduce the size of the apparatus It is an object of the present invention to provide an optical transmission device for optical space communication, an optical reception device, and an optical waveguide processing method for optical space communication, which realize flexibility in use and handling.

  An optical transmission device for optical space communication according to the present invention includes a light emitting element that generates signal light, and transmits signal light generated by the light emitting element from one end to an arbitrary position, and transmits the other end. And an optical waveguide that irradiates the space toward the space, thereby solving the restrictions on the integrated optical design of the optical lens and the light emitting element.

  In addition, the optical receiver for optical space communication according to the present invention includes an optical waveguide that takes in signal light emitted toward the space from the optical transmitter and transmits the signal light to an arbitrary place, and the optical waveguide. It comprises a light receiving element that receives signal light derived from the other end and converts it into an electrical signal, thereby unrestricting the integrated optical design of the optical lens and light receiving element.

  Further, the optical waveguide processing method for optical space communication according to the present invention, after inserting the optical fiber of the optical waveguide into the quartz tube in order to enter or output the signal light at the optical waveguide tip surface for optical space communication, The optical waveguide is stretched and processed into a taper shape to enlarge the cross-sectional area of the tip surface of the optical waveguide. Alternatively, a plurality of optical waveguides having different diameters are connected to the end portion of the optical waveguide so as to spread toward the distal end portion, and are processed into a taper shape to enlarge the sectional area of the distal end surface of the optical waveguide.

  In the present invention, the optical lens is separated from the light emitting element or the light receiving element by transmitting the signal light through the optical waveguide, and the lens is unnecessary by processing the optical waveguide itself. In this case, it is only necessary to arrange the optical lens or the optical waveguide tip at the start and end of the optical space communication, and it is possible to substantially reduce the size of the apparatus and to easily handle the optical axis adjustment. Further, it is possible to cope with the problem by simply processing the tip of the optical waveguide into a tapered shape and enlarging the sectional area of the tip surface of the optical waveguide. Therefore, according to the present invention, the limitation of the integrated optical design of the lens and the light emitting element or the light receiving element is solved, and the light emitting element or the light receiving element is separated from the start and end points of the optical space communication, thereby reducing the size of the apparatus and the flexibility of the apparatus It is possible to provide an optical transmission device for optical space communication, an optical reception device, and an optical waveguide processing method for optical space communication that realize the optical characteristics.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a conceptual diagram showing a configuration of a unidirectional communication system as a first embodiment of an optical space communication apparatus according to the present invention. In FIG. 1, a light emitting element 111 and its drive circuit 112 are incorporated in the optical transmitter 11. The light emitting element 111 is a light source that is driven by a driving circuit 112 and modulates and outputs light having a predetermined wavelength by a transmission signal. The signal light emitted by the light emitting element 111 is guided to an arbitrary light emitting position, for example, to a predetermined position by the optical waveguide 12 using an optical fiber cable. The optical waveguide 12 may be either quartz or plastic. A transmission lens 13 is attached to the tip of the optical waveguide 12. The transmission lens 13 emits the signal light L transmitted through the optical waveguide 12 into the space with a predetermined spot size.

  A receiving lens 21 is disposed at the opposite receiving position. The receiving lens 21 condenses the signal light spatially transmitted from the transmitting lens 13 and guides it to the optical waveguide 22 using, for example, an optical fiber cable. The other end of the optical waveguide 22 is connected to the optical receiving unit 23. Connected. The light receiving unit 23 includes a light receiving element 231 and a reception signal processing circuit 232 thereof. The light receiving element 231 receives the signal light from the optical waveguide 22 and converts it into an electric signal (reception signal), and demodulates the reception signal. The original transmission signal is obtained.

In the configuration according to the present embodiment, it is only necessary to oppose the lens 13 and 21 accurately on both the transmission side and the reception side, and there is no restriction on the arrangement / size of the optical transmission unit 11 and the optical reception unit 23. Further, no power supply equipment in the vicinity of the lens is required.
FIG. 2 shows a second embodiment of the optical space communication apparatus according to the present invention, in which the optical transmission / reception part of the first embodiment is improved, and the tips of the optical waveguides 12 and 22 are processed into a tapered shape. It is a conceptual diagram which shows the structure in the case of transmitting / receiving signal light without a lens by enlarging a surface cross-sectional area. Reference numeral 14 denotes a transmitter taper, and 24 denotes a receiver taper. FIG. 3 shows a state where a taper is formed at the tip of the optical waveguide 12 or 22. In FIG. 3, when an optical fiber is processed, A1 represents a core and A2 represents a clad.

  That is, when there is no lens, the light receiving area depends on the core diameter of the optical waveguide. For example, when the optical waveguide is a single mode fiber, since the core diameter is 10 μm, it is difficult to hit the signal light with this accuracy from a long distance. Further, it is difficult to reduce the signal light to 10 μm. Here, the received light intensity is the ratio of the spot area of the signal light to the area of the optical waveguide core. For example, even if the signal light is reduced to a diameter of 1 mm, the area ratio is 1/10000, and the received light intensity is attenuated to 1/10000. On the other hand, if the tip of the waveguide is processed into a tapered shape, it is possible to prevent a decrease in received light intensity.

  FIG. 4 shows a third embodiment of the space optical communication apparatus according to the present invention, in which the transmission lens 13 and the reception lens 21 used in the first embodiment are applied to the optical waveguide tapers 14 and 24 of the second embodiment. It is a conceptual diagram which shows the structure at the time of attaching. According to this configuration, even when the diameter of the signal light to be received is larger than the tapered optical waveguide, a wide range of signals can be collected and reception loss can be suppressed. Regarding light emission, optically accurate signal light can be emitted.

  FIG. 5 is a conceptual diagram showing an example of creating a taper described in the second embodiment. First, as shown in FIG. 5A, a large-diameter fiber B1 used for an optical waveguide for optical space communication is inserted into a quartz tube B2, and then stretched and tapered as shown in FIG. 5B. To increase the cross-sectional area of the end face of the optical waveguide. For example, if a large diameter fiber having a core diameter of 1 mm is used and drawn to the core diameter (10 μm) of a single mode fiber, a taper with an area ratio of 10,000 times can be created.

The above is the description of the basic structure of the space optical communication apparatus according to the present invention, but it is effective to combine the following structures.
First, in the taper structure shown in FIG. 3, if the tip surface of the optical waveguide is processed into a spherical shape as shown in FIG. 6, the lens effect prevents the emitted light from diverging, and the incident light is efficiently collected. Effect.

  Further, as shown in FIG. 7, by processing the tapered end face so as to give an inclination angle θ with respect to the optical axis, an effect of suppressing reflection of signal light on the end face can be obtained. This leads to the effect of preventing crosstalk due to reflection, particularly during bidirectional communication. The angle θ of the inclined surface is preferably several degrees or more, which is generally used in optical fiber communication (reference: Suzuki / Fujiwara, examination of optical connector Fresnel reflection countermeasures, IEICE Technical Report, OQE 82-15 (1982-05)).

  As a taper forming method, as shown in FIG. 8, optical waveguides C1, C2, and C3 having a small diameter, a medium diameter, and a large diameter are connected so as to spread toward the distal end portion of the optical waveguide, and are melted at respective joint portions. There is also a method for achieving optical coupling by performing a landing connection or the like. Even with the taper formed by this, the same effect as that of the second embodiment can be obtained.

  Although the unidirectional communication system has been described in the above embodiment, bidirectional communication can also be realized by using an optical branching device. FIG. 9 is a conceptual diagram showing a configuration when the unidirectional communication system shown in FIG. 2 is changed to a bidirectional communication system. In this system, the first optical transmitter 11A and the first optical receiver 23A are arranged on the transmission side shown in FIG. 2 and are optically connected to the optical waveguide 12 via the optical branching device 15, respectively. In this case, the end of the waveguide 12 functions as a taper 16 used for both optical transmission and reception. On the other hand, the second optical transmitter 11B and the second optical receiver 23B are arranged on the receiving side shown in FIG. 2, and are optically connected to the optical waveguide 22 via the optical branching device 25, respectively. In this case, the end of the waveguide 22 functions as a taper 26 used for both optical transmission and reception.

  According to the above configuration, the signal light transmitted from the first optical transmitter 11 </ b> A is emitted to the space from the optical transmission / reception shared taper 16 via the optical branching device 15. The signal received by the opposing optical transmission / reception shared taper 26 passes through the optical waveguide 22 and is received by the second optical receiver 23B via the optical branching device 25. The same applies to the reverse direction, and the signal light transmitted from the second optical transmission unit 11B is emitted into the space from the optical transmission / reception taper 26 via the optical branching device 25. The signal received by the opposing optical transmission / reception shared taper 16 passes through the optical waveguide 12 and is received by the first optical receiver 23A via the optical branching device 15.

In addition, although the embodiment of the bidirectional communication has been described as an application example of the unidirectional communication shown in FIG. 2, bidirectional communication can be similarly realized in other embodiments.
In addition, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a conceptual diagram showing a configuration of a unidirectional communication system as a first embodiment of an optical space communication apparatus according to the present invention. The conceptual diagram which shows the structure in the case of transmitting / receiving signal light without a lens as 2nd Embodiment of the optical space communication apparatus which concerns on this invention. The figure which shows the Example which formed the taper in the front-end | tip part of the optical waveguide in embodiment shown in FIG. The conceptual diagram which shows the structure at the time of attaching a lens to the front-end | tip part of an optical waveguide as 3rd Embodiment of the optical space communication apparatus which concerns on this invention. The conceptual diagram which shows the creation example of the taper demonstrated in 2nd Embodiment. The figure which shows the Example which processed the optical waveguide front end surface into the spherical shape in the taper structure shown in FIG. The figure which shows the Example which processed the front-end surface of the optical waveguide in the taper structure shown in FIG. The figure which shows the Example which couple | bonded the optical waveguide from which a diameter differs in series in the taper structure shown in FIG. The conceptual diagram which shows the Example which comprises a bidirectional | two-way communication system based on the unidirectional communication system shown in FIG.

Explanation of symbols

11, 11A, 11B: Optical transmitter 111: Light emitting element 112: Drive circuit 12: Optical waveguide 13: Transmission lens 14: Transmitter taper 15: Optical branching device 16: Optical transmission / reception shared taper 21: Reception lens 22: Optical Waveguides 23, 23A, 23B: optical receiver 231: light receiving element 232: received signal processing circuit 24: receiver taper 25: optical branching device 26: optical transmission / reception shared taper

Claims (12)

A light emitting element for generating signal light;
An optical waveguide that takes in the signal light generated by the light emitting element from one end and transmits it to an arbitrary location, and irradiates the space from the other end to the space;
An optical transmission device for optical space communication.   2. The optical transmission device for optical space communication according to claim 1, further comprising an optical lens arranged on the signal light irradiation optical axis at the other end of the optical waveguide and shaping the shape of the irradiation light.   2. The optical transmission device for optical space communication according to claim 1, wherein the other end of the optical waveguide that irradiates the signal light is processed into a tapered shape. 3.   4. The optical transmission device for optical space communication according to claim 3, wherein the end face on the taper processing side of the optical waveguide is spherical.   4. The optical transmission device for optical space communication according to claim 3, wherein the end face on the taper processing side of the optical waveguide has an inclination with respect to the irradiation optical axis of the signal light. An optical waveguide that takes in signal light emitted toward the space from the optical transmitter from one end and transmits it to an arbitrary location;
A light receiving element that receives signal light derived from the other end of the optical waveguide and converts it into an electrical signal;
A receiver for optical space communication, comprising:   7. The optical receiver for optical space communication according to claim 6, further comprising an optical lens arranged on the signal light irradiation optical axis at the other end of the optical waveguide and shaping the shape of the irradiation light.   7. The optical receiving device for optical space communication according to claim 6, wherein one end of the optical waveguide that receives the signal light is processed into a tapered shape.   9. The optical receiver for optical space communication according to claim 8, wherein the end face on the taper processing side of the optical waveguide is spherical.   9. The optical receiving device for optical space communication according to claim 8, wherein an end face of the optical waveguide has an inclination with respect to an incident optical axis of the signal light.   In order to input or output signal light at the front end surface of the optical waveguide for optical space communication, the optical fiber of the optical waveguide is inserted into a quartz tube, and then stretched and processed into a tapered shape to obtain a sectional area of the front end surface of the optical waveguide. An optical waveguide processing method for optical space communication, characterized by enlarging the size of the optical waveguide.   In order to input or output signal light at the front end surface of the optical waveguide for optical space communication, a plurality of optical waveguides having different diameters are connected to the end of the optical waveguide so as to spread toward the end, and processed into a tapered shape. An optical waveguide processing method for optical space communication characterized by enlarging the cross-sectional area of the tip surface of the optical waveguide.

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