JPS60175008A - Variable optical attenuator for optical fiber - Google Patents

Abstract

PURPOSE:To set exactly the rate of light attenuation to an assigned value by turning a turning member to move a moving acceptor in the optical axis direction thereby changing the space of an optical fiber on a moving side with respect to an optical fiber on a stationary side. CONSTITUTION:A variable optical attenuator for optical fibers is so constituted that an optical fiber 11' on a moving side is linearly moved in an optical axis direction by a moving acceptor 14 when a turning member 15 is turned. Both fibers 11 and 11' can be positioned apart at some space 19 from each other or can be brought into direct contact with each other by such movement, by which the light attenuation is induced between the two fibers 11 and 11'. The extent of the movement of the fiber 11' is finely adjustable by turning of the member 15. If, for example, a stationary adapter 13 is preliminarily graduated, the exact setting of the rate of light attenuation to an assigned value is made possible by reading the extent of the movement.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a variable optical attenuator for an optical fiber suitable for use in optical communication using an optical fiber.

[Prior art]

In conventional optical variable range detectors, optical attenuation is performed by making the amount of optical attenuation variable by passing the optical signal through an attenuation filter such as a metal vapor deposited film. Figure 1 shows a typical example. In the optical attenuator shown in Fig. 1, light emitted from an optical fiber 1 or 1' is converted into parallel light by a microlens 2 or 2', and the parallel light is transmitted through a filter 3 coated with metal vapor deposition. Light attenuation is performed, and the amount of light attenuation is adjusted by rotating the filter 3 along a rotation axis 4. Note that 5 and 5 are optical fibers 1
and 1' are connectors for connecting them to the optical attenuator body, respectively. In this method, it is necessary to use expensive parts such as the microlens 2, 2' and the optical attenuation filter 3, which increases the price. Moreover, since the structure is complicated, there is a limit to miniaturization below a certain size.Furthermore, looking at the characteristics, the transmitted light is transmitted through the microlenses 2, 2' and the light attenuation filter 3. For example, in the case of optical data links, the attenuation range is 10 to 30 dB, and it is difficult to create a minimum attenuation close to 0 dBK. Level difference is about 10-30 tiB, 0-20 dB
Since the majority of requests are for optical attenuation between To provide a small, lightweight, and low-cost variable optical attenuator for optical fiber, which can bring the minimum attenuation close to O dB and has improved reproducibility of the optical attenuation.

[Structure of the invention]

In order to achieve this object, the present invention provides a space between the optical fibers and shifts one of the optical fibers in the optical axis direction to reduce the amount of transmitted light. The end faces of the optical fibers are brought into contact with each other or via an intermediate transmission medium. That is, one optical fiber is attached to a fixed adapter, the other optical fiber is attached to a moving acceptor that moves in the optical axis direction by rotating a rotating body, and both optical fibers are attached based on the linear movement of this moving acceptor with respect to the fixed adapter. By changing the distance between the optical fibers in the optical axis direction, the transmitted light of the optical fibers can be arbitrarily attenuated, thereby making it possible to bring the minimum attenuation amount close to 0 dBK.

In a first aspect of the present invention, a fixed adapter having a through hole and a guide groove, a fixed optical fiber fixed to the through hole of the fixed adapter, and a fixed optical fiber screwed to the fixed adapter,
As the fixed adapter rotates, the rotating member is engaged with and cooperates with the rotating member movable in the direction of the optical axis of the optical fiber, and the guiding groove is guided through the through hole of the fixed adapter. a movable acceptor movable along the movable acceptor, and a movable optical fiber fixed in the movable acceptor so as to face the fixed optical fiber with their optical axes aligned; A second embodiment of the present invention is characterized in that the moving acceptor is moved in the optical axis direction by rotation K, thereby changing the distance between the moving side optical fiber and the fixed side optical fiber. Here, a fixed adapter having an intermediate transmission medium and a guide groove, a fixed side optical fiber fixed to the intermediate transmission medium of the fixed adapter, and a fixed side optical fiber fixed to the intermediate transmission medium of the fixed adapter are screwed to the fixed adapter, and the intermediate transmission is caused by rotation of the fixed adapter. A rotating member movable in the optical axis direction of the medium, a movable acceptor that is engaged with and cooperates with the rotating member and movable along the guide groove Ki of the fixed adapter, and the intermediate transmission. The moving acceptor is moved in the optical axis direction by rotating the rotating member, and pressure is applied to change the distance between the moving optical fiber and the intermediate transmission medium. [Example] Hereinafter, the present invention will be described in detail based on an example with reference to the drawings.

An example of the optical attenuator of the present invention is shown in FIG. Here, 11 and 11' are optical fibers, respectively. 12 is a connector for one of the optical fibers 11, and the optical fiber 11 is inserted into the hole drilled in the central rod 12A, and the end surface of the optical fiber 11 and the end surface of the rod 12A are aligned flush.012B surrounds the rod 12A. This is a hollow cylindrical portion formed of a hollow cylindrical portion, and a screw is formed inside the hollow cylindrical portion to be screwed into the screw carved in the connector acceptor end portion 13A of the fixed adapter 13. The fixed adapter 13 has a through hole 13B.
& Insert the central rod 12A of the connector 12 into this hole 13B, and screw the screw of the cylindrical part 12B to the screw of the end part 13A. A circular hole 130 with a large inner diameter is made concentrically with the through hole 13B, and the cylindrical portion 14A of the movable acceptor 14 is inserted into this hole 13G.
can be answered. The fixed adapter 13 has a cylindrical shape,
A screw 13D is carved into the cylindrical surface. This screw 13D connects the moving acceptor 14 to the optical fiber 11.11.
The rotary member 15 is engaged with a screw formed inside the hollow cylindrical portion 15A of the rotary member 15 for moving the rotary member 15 in the optical axis direction.

A hole is formed in the cylindrical portion 14A of the movable acceptor 14, and the connector 1 for the other optical fiber 11' is inserted into this hole.
6 central rod 16A is inserted. A screw 140 is formed in a portion of the cylindrical portion 14A outward from the collar 14B, so that it can be screwed into a screw formed in a hollow cylindrical portion 16B surrounding the rod 16A of the connector 16. The -yt: fiber 11' is inserted into the central rod 16A of the connector 16. Here, the central rod 16A of the connector 16 fits into the hole 13B described above and is made to protrude beyond the hole of the cylindrical portion 14A.
One optical fiber 1 is connected through the uneven holes of B and 130.
It can be joined to the center rod 12A of the connector 12 on the first side.

A rib 14B is formed in the center of the cylindrical portion 14A of the movable acceptor 14, and the barb 14B is fixed to the end portion 15B of the rotating member 15. For this purpose, a threaded ring 17 is screwed onto the inner thread of the cylindrical portion 15A of the rotating member 15, and the boxwood 14B is pressed against and fixed to the end portion 15B by the ring 17. Further, a guide plate 18 is provided on the cylindrical portion 14A of the moving acceptor 140, and
The groove 13K for guiding this guide plate 18 is fixed by the adapter 13.
In this way, in this example, by rotating the rotating part $15, the movable optical fiber 11' is linearly moved in the optical axis direction by the movable acceptor 14. Both party fiber 11
and 11' are spaced apart from each other by a space 19 as shown in FIG. cause attenuation.

In this example, the fixed adapter 13 is provided with a groove 13K, and the guide plate 18 provided on the movable acceptor 14 prevents the movable acceptor 140 from rotating, thereby preventing the optical fiber 11' from twisting. ing. The amount of movement of the optical fiber 11' can be finely adjusted by rotating the rotating member 150. For example, by attaching a scale to the fixed adapter 13, the amount of movement can be read to accurately set the value that specifies the amount of optical attenuation. Can be set.

According to the structure of this example, it is extremely easy to make the variable attenuator smaller and lighter, and since there is no need to use particularly expensive optical components, the cost of the device can be reduced.

FIG. 3 shows the characteristics of the variable optical attenuator based on this embodiment when a plastic optical fiber with a core diameter of 0.5 mm and a numerical aperture of 0.55 is used. Here, the horizontal axis represents the amount of movement of the moving acceptor 14 in the optical axis direction, and the vertical axis represents the amount of optical attenuation. In this example, the minimum attenuation j is 0.5 dB
, the maximum attenuation was 15 dB. Maximum travel distance is 5M
Therefore, the error in the motion transmission from the rotating portion shrine 15 to the moving acceptor 14 was approximately 50 μm. Therefore, in this example, the error in the reproducibility of the optical attenuation amount was within 0.15 dB.

In this way, in this example, the minimum optical attenuation is as small as 0.5 dB, and the error in the reproducibility of the optical attenuation is 0.15 dB.
It is clear that the optical attenuator is approximately B, which is significantly better than conventional optical attenuators.

Next, a second embodiment of the present invention is shown in FIG. In this example,
Use a general-purpose connector instead of a dedicated connector like the one above. That is, in the fourth part, the optical fibers 11 and 11' are inserted into the connector 21 having the same structure. The connector 21 has a central rod 21A with a hole into which the optical fibers 11 and 11' are inserted, and a hollow cylindrical portion 21B formed around the rod 21A. Threads are formed to engage with screws 22A and 23A formed on each of the acceptor 22 and the movable acceptor 23. Holes 22B and 23B for receiving the central rod 21A of the connector 21 are formed in the centers of these acceptors 22 and 23, respectively.The flange 22c of the fixed acceptor 22 is fixed to one end of the intermediate member 24 for supporting the intermediate transmission medium. do.

This intermediate member 24 has a rod 24A through which a plastic optical fiber of the same or different type or a rod lens is inserted as an intermediate transmission medium 25, and a hollow cylindrical portion 24B surrounding the rod 24A. Cylindrical part 2
A thread is carved on the outer periphery of 4B, and this thread K is screwed into a thread provided inside the hollow cylindrical portion 26A of the rotating member 26. The rotary member 26 is provided with a stepped portion 26B that is connected to the cylindrical portion 26A, and this portion accommodates the shoulder 230 formed on the pressure and movement acceptor 23, and further outside the hollow cylindrical portion 26A.
A screw is carved on the inside of 60, and the boxwood 23C is attached to the uneven part 2.
6B. Tighten the ring 27 formed with a screw to fix it to the screw 23 to the flat collar 230.
It has a hollow cylindrical part 23E extending on the side opposite to A, and the rod 24A of the intermediate member 24 can be inserted into the cylindrical part 23E, and a guide groove 2 is provided inside the cylindrical part 23.
A guide plate 24 provided on the rod 24A with a 3F formed in advance.
0 can move along this groove 23F, so that
When the movable acceptor 23 moves in the optical axis direction in response to the rotation of the rotating member 26, the optical fiber 11' moves straight in the optical axis direction without being twisted. In this way, in this embodiment, it is possible to use a general-purpose connector without using a dedicated connector, and it is possible to use a general-purpose connector on both the fixed side and the moving side (the end faces of 11 and 11'). The amount of movement of the optical fiber 11', which is connected via the intermediate transmission medium 25 without direct contact, can be finely adjusted by rotating the rotating member 26, and furthermore, the intermediate member 24 is provided with a scale. By reading the amount of movement of the rotating member 26, the amount of movement of the moving acceptor 23 can be known, and from this, the amount of optical attenuation can be set accurately.

FIG. 5 shows that using a plastic optical fiber with a core of 5 φ and an aperture of 0.55, the optical attenuation in this example is as small as 1.5 dB, and the maximum optical attenuation is 15 dB (mobile adapter 2
The amount of movement of 3 was 5 as ). When reading the movement amount, the minimum scale was 10 μm, and the inaccuracy in the transmission of the movement amount between the zero-movement adapter 23 and the old rotating part 26 was about 50 μm. As a result, the setting error of the optical attenuation amount is approximately 0.
15 (IB), making it possible to achieve optical attenuation with very high precision and good reproducibility. 0 In this way, in this example, the minimum attenuation amount is as small as 1.5 dB, and even though it is small, optical attenuation is possible. The setting error of the amount was 0.15 dB, which was very high precision.0 [Effect] As explained above, the present invention has a simple optical attenuation principle, so the structure can be simplified and the optical attenuator can be easily used. It is small, lightweight, and can be configured at low cost.Moreover, in terms of characteristics, it has the advantage that the minimum optical attenuation P can be reduced and the reproducibility of the amount of optical attenuation can be improved. The present invention is suitable as a variable optical attenuator for a large diameter plastic optical fiber.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a conventional variable optical attenuator, FIG. 2 is a sectional view showing the configuration of an embodiment of the present invention, FIG. 3 is a diagram of the optical attenuation characteristic curve of this embodiment, and FIG. The figure is a sectional view 1 showing the structure of another embodiment of the present invention. FIG. 5 is a diagram of the optical attenuation characteristic curve of this embodiment. 1.1'...optical fiber, 2, 2'11. Microlens, 3... Optical attenuation filter, 4... Optical attenuation filter rotation axis, 5.5'... Connector, 11... Fixed side optical fiber, 11'... Moving side optical fiber, 12... Connector, 12A... Central rod, 12B... Hollow cylindrical portion, 13... Fixed adapter, 13A... Connector acceptor end, 13B... Through hole, 13G... Circular hole, 13D...Screw, 13K...Groove, 14...Moving acceptor, 14A...Cylindrical portion, 14B...Brim, 140...Screw, 15...Rotating member, 15A... Cylindrical portion, 15B... End portion, 16... Connector, 16A... Center rod, 16B... Hollow cylindrical portion, 17... Ring, 18... Guide plate, 19... Space, 21... Connector, 21A... Central rod, 21B... Hollow cylindrical portion, 22... Fixed acceptor, 22A... Screw, 22B... Hole, 220... Flange rib 23... Movement acceptor, 23A...screw, 23B...hole, 230...flange, 23E...hollow cylindrical portion, 23F...guide groove, 24...intermediate member, 24A...rod, 24B ...Hollow circular surface part, 240... Guide plate, 25... Intermediate transmission medium, 26... Rotating member, 26A... Hollow cylindrical part, 26B... Different level part, 260... Hollow Cylindrical part, 27...Ring 0 Fig. 1 Fig. 3 Amount of movement of the 7th puff [mml] Fig. 5 Amount of movement of the I-assistant pig [mm]

Claims (1)

[Scope of Claims] 1) A fixed adapter having a through hole and a guide groove; a fixed optical fiber fixed to the through hole of the fixed adapter; A rotation member movable in the optical axis direction of the optical fiber; and a rotation member that is engaged with and cooperates with the rotation member and is movable within the through hole of the fixed adapter along the guide groove. a movable acceptor, and a movable optical fiber fixed in the movable acceptor so as to face the fixed optical fiber with their optical axes aligned, and rotate the rotating member. Therefore, the variable optical attenuator for an optical fiber is characterized in that the movable acceptor is moved in the optical axis direction to change the distance between the movable optical fiber and the fixed optical fiber. 2) a fixed adapter having an intermediate transmission medium and a guide groove; a fixed optical fiber fixed to the intermediate transmission medium of the fixed adapter; a rotating member movable in the optical axis direction of the intermediate transmission medium; a movable acceptor that is engaged with and cooperates with the rotating member and movable along the guide groove of the fixed adapter; a movable side optical fiber fixed in the movable acceptor so that it faces the medium with its optical axis aligned; and by rotating the rotating member, the movable acceptor is moved in the optical axis direction. A variable optical attenuator for an optical fiber, characterized in that the distance between the moving side optical fiber and the intermediate transmission medium is changed by moving the optical fiber.