JP2005086569A - Angle adjustment mechanism of optical instrument for optical communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an angle adjustment system which compensates for a variable amount of a luminous parallel degree for directly leading light to a single mode fiber from spatial light with ease, efficiently, at a low cost in optical radio communication within a close range. <P>SOLUTION: An angle adjustment mechanism of an optical receiving fiber collimator is composed of a fixing and supporting portion, a driven supporting portion for supporting a fiber collimator, a fixed supporting axis fixed to at least one fixed part of the fixing and supporting portion and the driven supporting portion, a first elastic member shortening the distance between moving parts of the fixing and supporting portion and the driven supporting portion, a second elastic member elongating the distance between moving bodies of the fixing and supporting body and the driven supporting body, an angle adjusting mechanism driven by an external drive control portion, an optical coupler 42 taking out monitor light from received light, and a control portion controlling the angle adjusting mechanism so that a power measured value of the monitored light becomes the maximum, through the external drive control portion 54. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an angle adjustment mechanism of an optical device for optical communication, and in particular, to adjust the angle of a fiber collimator with respect to the propagation direction of incoming light so that the optical power received by a fiber collimator for receiving light is maximized. It relates to a mechanism and a system.

  Light is a kind of electromagnetic wave, but its frequency is much higher than that of a conventional microwave or the like. Therefore, the amount of information that can be transmitted for communication using light is dramatically higher than that of a conventional method. In recent years, optical communication using laser light has been put into practical use, and satellite-to-satellite, satellite-to-ground or terrestrial optical communication is known. Among these, in a relatively short distance optical communication, a simple device that receives light propagating in space with low loss is desired.

  Reception in optical wireless communication is generally bulk reception in which light is received by a surface such as a semiconductor light receiving element. However, if the received signal light can be guided directly to an optical fiber, particularly a single-mode optical fiber, the spatial portion can be regarded as a part of a simple transparent line, which can be conveniently handled as a part of the fiber system. . A single mode optical fiber is designed to propagate only single mode light with a very small core diameter (or aperture), does not generate mode dispersion, has very small pulse spread, and is suitable for broadband communication. .

  In order to efficiently collect spatial light into the fiber, it is necessary to match the optical constants of the lens and fiber, etc. However, it is very difficult to receive the signal and involves a large light receiving loss.

  Therefore, many systems that realize fiber light reception use multimode optical fibers having a large aperture or core diameter in order to reduce light reception loss. However, in a multimode optical fiber, the propagation speed in the direction of the optical axis differs depending on the mode and mode dispersion occurs, so there is a disadvantage that high-density information cannot be transmitted.

  On the other hand, using a large optical antenna developed for inter-satellite communication in space can realize light reception with a single mode fiber, but the configuration becomes very complicated and expensive.

As a tracking method for maintaining the light reception level, highly sensitive position detection sensors (multi-channel APD, PSD, CCD, etc.) are known in the wavelength range of 0.8 μm, but in the wavelength range of 1.55 μm Therefore, it is necessary to prepare a method (see Non-Patent Document 1) for simultaneously projecting light in the 0.8 μm band as reference light, and a special detection sensor, resulting in high cost.
Lucent Technology WaveSTAR OpticAIR OLS SPIE Conference on Optical Wireless Communications, Nov. 1998, SPIE Vol. 3532 JP-A-8-122705

  Normally, when light is guided into a fiber, light with an angle larger than the NA (Numerical Aperture numerical aperture) of the fiber does not enter. The numerical aperture is defined as NA = sin ψ where ψ is the angle between the critical ray that can enter the fiber and the optical axis of the fiber. In addition, the optical wireless device slightly changes the incident angle of light due to the distortion of the installation point due to temperature changes and the change in refractive index due to the atmospheric temperature gradient. difficult. Therefore, as shown in FIG. 1, it is common to provide the collimator part 4 in the edge part of the single mode fiber 6. As shown in FIG. The collimator unit 4 selects one that is larger than the expected angle variation. The optical signal 1 arriving at the main lens 2 is condensed on the collimating lens 3 by the main lens 2. The collimator lens 3 converts the light into a parallel light beam and guides it to the collimator unit 4. The light beam received by the collimator unit 4 is guided into the single mode fiber 6 with low loss. Usually, the collimator unit is used to collimate the light emitted from the fiber to the outside, but here it is used in reverse to use it to easily guide the parallel light beam into the fiber with low loss. .

  In general, the parallel relationship between the light beam 1 reaching the light receiving device and the main lens 2 of the light receiving device is not always maintained. In many cases, the parallelism fluctuates due to a distortion of the light receiving device due to a temperature change or a refractive index change due to an atmospheric temperature gradient. Considering the application range of this device (for example, the short-range usage range of 1 km or less), the wavefront fluctuation of the light beam propagating in space is small and acceptable, but the parallelism due to mechanical fluctuations such as the ground plane of the light receiving device The inclination of the light beam due to the change in the temperature and the temperature gradient in the atmosphere is relatively large, which makes it difficult to connect the aligned collimating lenses (see FIG. 2).

  Therefore, the present invention has been made in view of the above points, and in parallel optical wireless communication, light flux parallelism for guiding light directly from a spatial light to a single mode fiber in a simple, efficient and inexpensive manner. An object of the present invention is to provide an angle adjustment system that compensates for fluctuations in the angle.

  According to one aspect of the present invention for achieving the above object, an angle adjustment mechanism for adjusting an angle of an optical device for optical communication with respect to a propagation direction of communication light includes a fixed support portion; A fixed support shaft that is fixed to at least one fixed portion of the fixed support portion and the driven support portion and maintains the fixed portion at a fixed distance from the fixed support portion; A first elastic member acting in a direction to reduce the distance between the moving part of the driving support part; a second elasticity acting in a direction to widen the distance between the fixed support part and the moving part of the driven support part And at least one drive shaft that is driven by the external drive control unit and changes the distance between the fixed support part and the moving part of the driven support part.

  The first elastic member can be composed of a leaf spring, and the second elastic member can be composed of a spring. The drive shaft can be composed of a first drive shaft for adjusting the angle of the optical device in the vertical plane and a second drive shaft for adjusting the angle of the optical device in the horizontal plane.

  The optical device for optical communication may be a fiber collimator for receiving light.

  According to another aspect of the present invention, an angle adjustment system for a fiber collimator for receiving light includes an angle adjustment mechanism for adjusting an angle of the fiber collimator with respect to a propagation direction of incoming light; distributing light received by the fiber collimator; An optical coupler that extracts the monitor light; and a control unit that measures the monitor light from the optical coupler and controls the angle adjustment mechanism so that the measured value is maximized.

  According to another aspect of the present invention, an angle adjustment system for a fiber collimator for receiving light is an angle adjustment mechanism for adjusting an angle of a fiber collimator with respect to a propagation direction of incoming light, and includes a fixed support portion and a fiber collimator. A driven support portion for supporting, and a fixed support shaft fixed to at least one fixed portion of the fixed support portion and the driven support portion, and maintaining the fixed portion at a fixed distance from the fixed support portion; The first elastic member acting in the direction of reducing the distance between the fixed support portion and the driven support portion in the direction of movement, and the direction of increasing the distance between the fixed support portion and the movement portion of the driven support portion. Angle adjustment composed of an acting second elastic member and at least one drive shaft that is driven by the external drive control unit and changes the distance between the fixed support part and the moving part of the driven support part. Structure: Optical coupler that distributes the light received by the fiber collimator and extracts the monitor light; and the power of the monitor light from the optical coupler is measured, and the angle is adjusted through the external drive control unit so that the measured value becomes maximum A control unit for controlling the mechanism.

  According to the embodiments of the present invention, in short-distance optical wireless communication, angle adjustment for compensating for fluctuations in the parallelism of light flux for guiding light directly from spatial light to a single mode fiber in a simple, efficient and inexpensive manner. A system is provided.

  In addition, since the force balance is achieved by using both the elastic member that pulls the swinging position of the driven support and the elastic member that pushes out, the position of the driven support is finely adjusted by the drive shaft without backlash. Can be controlled accurately.

  In consideration of short-range communication, the system according to the present invention outputs a light beam 1 having a magnitude that does not deviate from the main lens 2 on the receiving side even if the transmitting side is tilted to some extent. The receiving side has no special sensor system, and the light receiving system always drives the collimator autonomously, scans around the current position, and moves to an angular position where the light receiving level is strong. . One method for controlling the angle is to control the inclination of the collimator by pushing and pulling the support table holding the collimator fiber independently at two points.

  Embodiments of an angle adjusting mechanism for adjusting the angle of an optical communication fiber collimator according to the present invention will be described below with reference to the drawings.

  FIG. 3 is a schematic side view of the angle adjustment mechanism 10 that adjusts the angle of the fiber collimator for optical communication. A fixed support base 14 serving as a fixing instruction unit is fixed to the base 12 of the optical receiver. One fixed support shaft 16 fixed to and extending from the fixed support base 14 fixes one position (this is a fulcrum) of the driven support base 18 as a driven support portion. As shown in FIG. 4, the driven support base 18 can swing (angle fluctuation) around a fulcrum as a fixed part. In the front view of the angle adjustment mechanism 10 shown in FIG. 5, one fixed support shaft 16 is shown. A fiber collimator 20 is attached to the driven support 18 as shown in FIG. 3, and light incident thereon is propagated through the fiber 40.

  By moving the rocking position as the moving part of the driven support base 18 in the front-rear direction with respect to the propagation direction of the incoming light while fixing the fixed position (fulcrum) as the fixed part of the driven support base 18, The angle of the fiber collimator with respect to the incoming light can be adjusted. As shown in FIGS. 3 to 5, between the support base 14 and the swinging position of the driven support base 18, one leaf spring 22 as a first elastic member and a second elastic member as The three springs 24 are provided. In this embodiment, there are three swing positions indicated by 32, 34, and 36 in FIG. 5 (these are reference numerals of the drive shafts, but are also useful for indicating the swing position). . As shown in FIG. 5, the shape of the leaf spring 22 is a U shape that can cope with torsion. The leaf spring 22 applies a tensile force to the swinging positions 32 and 36 of the driven support base 18 in a direction approaching the fixed support base 14. On the other hand, the spring 24 applies a pressing force to the swing positions 32, 34, and 36 of the driven support base 18 in a direction away from the fixed support base 14. The driven support base 18 stops at a position where these two opposite forces are balanced.

  As a preferred example, a leaf spring and a spring are shown, but the elastic member is not limited to these, and any type of elastic member may be used. For example, other shapes of springs and springs, or elastic materials such as rubber and resin can be used.

  Further, an up / down angle drive shaft 32 is attached to one swinging position of the driven support base 18, and the up / down angle drive shaft 32 is axially driven by a linear drive actuator (not shown) as an external drive control unit. Driven. When the vertical drive shaft 32 is driven, the driven support 18 swings as shown in FIG. By this swinging, the optical axis of the fiber collimator 20 attached to the driven support base 18 varies in the vertical direction within the vertical plane.

  A left / right angle drive shaft 34 is attached to the other swing position of the driven support 18, and the left / right angle drive shaft 34 is driven in the axial direction by an external actuator (not shown). When the left / right angle drive shaft 34 is driven, the driven support 18 swings. By this swinging, the optical axis of the fiber collimator 20 attached to the driven support base 18 varies in the horizontal direction in the horizontal plane.

  A free shaft 36 is attached to the third swing position of the driven support base 18 and is slidable with respect to the free shaft when the driven support base 18 swings.

  By driving the two drive shafts 32 and 34 independently, the driven support base 18 and the optical axis of the fiber collimator 20 can be freely displaced vertically and horizontally. It is only necessary to control the two drive shafts. As a result, it is possible to shorten the scanning time, simplify the control algorithm, and reduce the cost.

  Since the force balance is achieved by using both the elastic member for pulling the swinging position of the driven support base 18 and the elastic member for pushing out, the position of the driven support base 18 is backlashed by the drive shafts 32 and 34. It can be controlled finely and accurately.

  In the above embodiment, an example in which light is received has been described. However, the principle of the present invention can also be applied to a case in which light is transmitted. The angle adjusting mechanism as described above can be used to finely control the optical axis of the optical device on the light transmitting side vertically and horizontally.

  FIG. 6 schematically shows an angle adjustment system 60 of a fiber collimator according to an embodiment of the present invention. A single mode fiber 40 extends from a light receiving unit 11 that receives incoming light via a fiber collimator (not shown), and an optical signal received therein is propagated. The angle of the fiber collimator of the light receiving unit is adjusted by the angle adjusting mechanism 10. The light propagating through the single mode fiber 40 is partly distributed in the optical coupler 42 that distributes the optical power and guided to the monitor circuit 48. Most of the optical power is used as the main signal light 44 for original optical communication. As the optical coupler 42, various couplers such as a diffusion type coupler that uses evanescent light, an area division type directional coupler that divides an optical waveguide cross section, and a beam division type coupler that uses partial reflection can be used.

  The monitor circuit 48 measures the power of the received light and outputs the measurement result to the control arithmetic unit 50. The control arithmetic unit 50 includes an A / D conversion unit that converts an analog signal from the monitor circuit 48 into a digital signal, a CPU that executes a control calculation, and a memory unit that stores a driving algorithm, and the amount of monitor light is maximized. Thus, the drive control unit 54 is controlled. The drive control unit 54 drives the drive shafts 32 and 34 in accordance with a command from the control arithmetic unit 50 to adjust the vertical and horizontal angles of the fiber collimator. As the drive control unit 54, various actuators such as an actuator using a servo motor such as a step motor that rotates by a fixed angle by pulse input, a plunger type voice coil actuator, and a piezoelectric type actuator can be used. In this way, it is possible to construct a system that autonomously follows the inclination of incoming light without preparing a special monitor system for control.

  The monitor circuit 48 and the control arithmetic unit 50 correspond to a control unit, and the drive control unit 54 corresponds to an external drive control unit.

  The angle adjustment mechanism according to the present invention can be used in an optical device for optical communication at a relatively short distance, and is used in a technical field that requires adjustment of the fiber collimator angle with respect to the propagation direction of incoming light. be able to.

It is a schematic side view of the light-receiving part in the optical communication for demonstrating the principle of this invention. It is a figure similar to FIG. 1, and is a figure which shows a mode that incoming light inclines slightly upwards. It is a schematic side view of the angle adjustment mechanism which adjusts the angle of the fiber collimator for optical communications according to one Example of this invention. FIG. 4 is a view similar to FIG. 3, showing the swing of the driven support base. It is a schematic front view of the angle adjustment mechanism which adjusts the angle of the fiber collimator for optical communications of FIG. 1 is a schematic view of an angle adjustment system for adjusting the angle of a fiber collimator for optical communication according to an embodiment of the present invention.

Explanation of symbols

10 Angle adjustment mechanism
14 Fixed instruction stand
18 Driven support base
16 Fixed support shaft
32, 34 Drive support shaft
22 leaf spring
24 Spring
60 angle adjustment system
42 Optical coupler
48 Monitor circuit
50 Control arithmetic unit 50
54 Drive controller

Claims (10)

An angle adjustment mechanism for adjusting the angle of an optical device for optical communication with respect to the propagation direction of communication light, comprising:
Fixed support;
A driven support for supporting the optical device;
A fixed support shaft that is fixed to at least one fixed part of the fixed support part and the driven support part, and maintains the fixed part at a fixed distance from the fixed support part;
A first elastic member acting in a direction to reduce the distance between the fixed support part and the driven support part from the moving part;
A second elastic member acting in a direction to increase the distance between the fixed support part and the moving part of the driven support part; and the moving part of the fixed support part and the driven support part driven by an external drive control unit At least one drive shaft that changes the distance between
Angle adjustment mechanism composed of The angle adjusting mechanism according to claim 1, wherein the first elastic member is formed of a leaf spring. The angle adjusting mechanism according to claim 1, wherein the second elastic member includes a spring. The drive shaft includes a first drive shaft for adjusting an angle of the optical device in a vertical plane and a second drive shaft for adjusting an angle of the optical device in a horizontal plane. Item 4. The angle adjustment mechanism according to items 1 to 3. The angle adjustment mechanism according to claim 1, wherein the optical device is a light receiving fiber collimator. An angle adjustment system for a fiber collimator for optical reception:
An angle adjustment mechanism for adjusting the angle of the fiber collimator with respect to the propagation direction of the incoming light;
An optical coupler that distributes light received by the fiber collimator and extracts monitor light; and a controller that measures the monitor light from the optical coupler and controls the angle adjustment mechanism so that the measured value is maximized;
Angle adjustment system composed of. An angle adjustment system for a fiber collimator for optical reception:
It is an angle adjustment mechanism that adjusts the angle of the fiber collimator with respect to the propagation direction of incoming light,
A fixed support;
A driven support for supporting the fiber collimator;
A fixed support shaft fixed to at least one fixed part of the fixed support part and the driven support part, and maintaining the fixed part at a fixed distance from the fixed support part;
A first elastic member that acts in a direction to reduce the distance between the fixed support part and the driven support part among the moving parts;
A second elastic member acting in the direction of increasing the distance between the fixed support part and the moving part of the driven support part;
At least one drive shaft driven by an external drive control unit to change a distance between the fixed support part and the moving part of the driven support part;
An angle adjustment mechanism comprising:
An optical coupler that distributes the light received by the fiber collimator and extracts monitor light; and the power of the monitor light from the optical coupler is measured, and the angle is passed through the external drive controller so that the measured value is maximized. A control unit for controlling the adjusting mechanism;
Angle adjustment system composed of. The angle adjusting mechanism according to claim 7, wherein the first elastic member is configured by a leaf spring. The angle adjusting mechanism according to claim 7 or 8, wherein the second elastic member is formed of a spring. The drive shaft is composed of a first drive shaft for adjusting the angle of the fiber collimator in a vertical plane, and a second drive shaft for adjusting the angle of the fiber collimator in a horizontal plane. The angle adjusting mechanism according to any one of Items 9 to 9.

Images