JPH03210504A - Variable type optical attenuator - Google Patents

Abstract

PURPOSE:To easily attenuate the quantity of light only by an optional value by constituting a pair of ferules so that their end faces are inclined from the optical axis at a fixed angle, one of them is fixed and the other is rotated to adjust the distance between respective optical fibers. CONSTITUTION:The variable type optical attenuator has the 1st ferule member 41 inclined from the optical axis at the fixed angle and the 2nd ferule member 42 having the practically same inclination as the 1st member 41. One optical fiber 33 is connected to a light source and the other optical fiber 34 is connected to an optical power meter. The member 41 is stuck and fixed to a holder member 51 and the member 42 is rotated within the 180 deg. range while holding the outer end part 42c of the member 42 and reading out an attenuation value. On the rotational angle position at which the attenuation value reaches a necessary value, a rapid curing bonding agent is injected between the member 42 and a holder member 52 to fix the member 42. After fixing the member 42, the 2nd coupling nut 58 is loosened and an adjusting side optical connector plug 31 is detached, so that even if attachment/detachment is repeated, the set attenuation value is not changed.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a variable optical attenuator used for continuous attenuation adjustment of the amount of transmitted light in optical fiber communication circuits, etc. High-performance variable light range that minimizes loss of reflected return light! ! Concerning vessels.

(Problem B to be Solved by the Prior Art and the Invention) Various systems have been proposed and put into practical use as variable optical attenuators used to adjust the attenuation of the amount of light in optical fiber communication circuits.

FIG. 6 is a schematic diagram for explaining the operation of a conventional variable optical attenuator using a glass plate whose transmittance changes continuously.

Two Rondo lenses j arranged in the transmission optical path 4.

A glass plate 3 coated with a metal thin film is arranged so that the concentration changes continuously between 2 and 3.

This glass plate 3 is moved in a direction perpendicular to the optical axis (indicated by an arrow) using an adjustment device (not shown), and an arbitrary portion of the glass plate 3 is made to correspond to the optical axis, thereby adjusting the amount of light in the optical path 4.

Reflection occurs at the end face (air interface) of the Rondo lens 1.2 and at the air interface of the vapor-deposited glass plate 3.

The so-called reflected return light loss increases and is returned to the light source, affecting the light source.

Further, in this device, the transmittance of the glass plate 3 changes over time,
The amount of attenuation becomes unstable.

Unlike the method described above, it is known that the amount of attenuation of light can be changed by adjusting the distance between the connecting end surfaces of opposing optical connectors.

FIG. 7 is a sectional view illustrating an attenuator that continuously changes the amount of attenuation by adjusting the distance between the end faces of the ferrule members.

The illustrated connector structure for adjusting the distance between the connecting end faces of the optical lid is based on a proposal by the inventor of the present invention.

The alignment adapter member 5 is a cylindrical member made of metal, and a through hole 20 for receiving the ferrule members 14 and 15 is provided in the center.

A threaded portion 22 that engages with an adjusting screw nut 21 is provided on the inner periphery of one end of the alignment adapter member 5 .

Threaded portions 12.13 are provided at both ends of the outer diameter portion of the alignment adapter member 5 to engage with threaded portions 10.1) of the coupling nuts 8, 9 of the optical connector plug 6.7.

The threaded portion 12.13 also has an optical connector plug 6.
A key groove 18.19 is provided in which a locking key 16.17 provided on the outer diameter of the ferrule portion 14.15 of No. 7 is fitted.

A biasing compression spring 22 is inserted between the coupling nut 8 and the ferrule member 14, and another compression spring 23 is inserted between the coupling nut 9 and the ferrule member 15 to align the ferrule members 14 and 15 toward the center of the adapter member 5. is energized.

Retaining rings 24,25 are each attached to ferrule member 14.
It is fitted into the grooves 26 and 27 of No. 15.

An appropriate groove 28 for turning is provided on one end surface of the adjustment screw Nand 210.

The adjustment of the amount of attenuation of this variable optical attenuator will be briefly explained.

First, the optical connector plug 6.7 and the adjustment screw nut 21
is attached to the adapter member 5 as shown.

The optical fiber 29 is connected to a light source (not shown), and the optical fiber 3o is similarly connected to an optical power meter (not shown) to read the attenuation value of the amount of light.

The operation of attaching and detaching the optical connector plug 7 and adjusting the screwing amount of the adjusting screw nut 21 until the desired attenuation value is obtained (
Adjustment of interval S) is repeated many times.

As mentioned above, this device requires very complicated adjustment operations.

Furthermore, similar to the above-described device, the loss of reflected return light at the air interface is as large as about 10 to 12 dB on average.

Therefore, this attenuator cannot be used for long-distance, high-capacity communications, video communications, or the like.

The main object of the present invention is to provide a novel variable optical attenuator that has less loss of reflected return light and that allows easy setting and coupling of arbitrary attenuation amounts.

(Means for Solving the Problems) In order to achieve the above object, a variable optical attenuator according to the present invention has a pair of ferrules each having an optical fiber attached to its center hole, with the end faces of the pair being aligned with respect to a plane perpendicular to the optical axis. Using ferrules that have been obliquely polished to an inclination angle of 7 to 20 degrees, the end faces of each ferrule are pressed against each other, and one of the ferrules is fixed while the other is rotated within a range of 0 to 180 degrees. The distance between the optical fibers is adjusted by adjusting the distance between the optical fibers.

Thereby, the amount of light transmitted from one optical fiber to the other optical fiber can be attenuated by an arbitrary amount without attaching or detaching each ferrule from the adapter member.

That is, the variable optical attenuator according to the present invention is a variable optical attenuator that transmits light incident from one optical fiber to the other optical fiber coupled to the optical fiber after attenuating the light by an arbitrary amount. , an alignment adapter member, a first ferrule member in which a transmission terminal surface that exposes an optical fiber end has a certain inclination with respect to the optical axis together with the optical fiber end surface, and the first ferrule member is attached to the alignment adapter member. a first fixing means for supporting the optical fiber with limited rotation; and a second fixing means, the transmission terminal surface of which the optical fiber end is exposed having substantially the same inclination as the first ferrule member with respect to the optical axis together with the optical fiber end surface. combining a ferrule member with the alignment adapter member, constantly urging the second ferrule member in the direction of the first ferrule member;
The optical fiber connector member is supported concentrically with respect to the first ferrule member so as to be rotatable over a certain angle, and is fixed to the alignment adapter member at any angular position within the range.

The alignment adapter member has an alignment sleeve hole that precisely fits the outer diameters of the first and second ferrule members to rotatably support at least the second ferrule member.

The pair of ferrule end faces can be formed by oblique polishing so that they have the same inclination angle of 7 degrees or more and 20 degrees or less with respect to a plane perpendicular to the optical axis of the optical fiber.

The optical fiber connector member rotatably supports the second ferrule member while restricting movement in the axial direction, and includes a holder member that is linearly guided in the optical axis direction with respect to the alignment adapter member, and a bottom penetrating member. a coupling nut that receives and supports the holder member in the hole and is screwed to the alignment adapter member at the opening; and a coupling nut that is inserted between the coupling nut and the holder member to allow the second ferrule member to pass through the holder member. It can be constituted by a spring means that is always biased in the direction of the first ferrule member.

The first fixing means for supporting the first ferrule member on the alignment adapter member with limited rotation may be an optical fiber connector member having the same structure as the optical fiber connector member.

By rotating the second ferrule member within 180 degrees with respect to the alignment adapter member, the slope of each ferrule changes from a minimum attenuation state where the end faces are in close contact, where the distance between the optical fibers is minimum, to a maximum angle. It can be continuously varied up to the maximum attenuation position.

The ferrule member of %2 is rotated to a position where necessary attenuation is obtained relative to the first ferrule member, and the rotational positions of the holder member and the ferrule member are fixed to obtain a constant amount of attenuation. be able to.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings and the like.

FIG. 1 is a partially cutaway view of an embodiment of a variable optical attenuator according to the present invention, showing a state in which the amount of attenuation is adjusted to the minimum.

FIG. 2 is a partially cutaway view showing an embodiment of the variable optical attenuator according to the present invention in a state where the amount of attenuation is adjusted to the maximum.

FIG. 3 is a cross-sectional view of an embodiment of the variable optical attenuator according to the present invention, taken along the line X--X in FIG. 2.

FIG. 4 is a graph showing the operating characteristics of the variable optical attenuator according to the present invention.

FIG. 5 is a histogram showing the results of actually measuring the reflection return loss of a large number of variable optical attenuators according to the present invention manufactured.

The variable optical attenuator according to this embodiment attenuates the light incident from one optical fiber 33 by an arbitrary amount and transmits it to the other optical fiber 34 coupled to the optical fiber, and vice versa. This is a variable optical attenuator that can also be used.

This variable optical attenuator basically consists of a first optical connector plug 31 shown on the left side in FIG. 1, an alignment adapter member 59, and a second optical connector plug 32 shown on the right side thereof. It is configured.

The alignment adapter member 59 has a through hole 64 in the center and threaded portions 60, 61 at both ends.

This threaded portion 60.61 is provided with a keyway 62.63.

The first ferrule member 41 is composed of a small diameter portion 41a that is fitted into the alignment adapter member 59, a larger diameter portion 41b that is fitted into the holder member 51, and a knob portion 41c, and a groove 41d on the outer periphery of the 41b portion. is provided.

Similarly, the second ferrule member 42 also has a small diameter portion 42a.
, a larger diameter portion 42b and a knob portion 42C, and a groove 42d is provided on the outer periphery of the portion 42b.

The first ferrule member 4 is attached to the first holder member 51.
A through hole 47 is provided to rotatably receive the portion 41b of 1. A groove 49 is provided on the inner periphery of this through hole at a position corresponding to the groove 41d of the first ferrule member 41, and a retaining ring 37 is inserted between these grooves.

As a result, the first ferrule member 41 is rotatably supported by the first holder member 51, although its axial movement is restricted.

Further, a flange 43 is provided on the outer periphery of the right end of this holder member 51, and this flange 43 has a detent key 4.
5 is provided and is coupled by this key 45 to the keyway 62 of the alignment adapter member.

The second holder member 52 has the second ferrule member 4
A through hole 48 is provided to rotatably receive the portion 42b of No. 2. A groove 50 is formed on the inner periphery of the through hole 48 at a position corresponding to the groove 42d of the second ferrule member 42.
are provided, and a retaining ring 38 is inserted between these grooves.

Further, a flange 44 is provided on the outer periphery of the left end of this holder member 52, and this flange 44 has a detent key 4.
6 is provided and is coupled by this key 46 to the keyway 63 of the alignment adapter member.

The first coblin beech throat 57 is in the shape of a looped nut, loosely receives the holder member 51 in a through hole at the bottom, has a screw 55 on the inner periphery of the opening, and is coupled to the threaded portion 60 of the alignment adapter member 59. I'm forced to.

The flange portion 43 of the first holder member 51 and the pre-glycoside 1
A coil spring 53 is inserted between the coupling nuts 57, and this spring 53 constantly urges the first ferrule member 41 through the first holder member 51 toward the alignment adapter member 59.

A second coupling nut 58 also loosely receives the holder member 52 in its bottom through hole and is connected by a screw 56 to the threaded portion 61 of the alignment adapter member 59.

Similarly to the above, a coil spring 54 is also provided between the flange portion 44 of the second holder member 52 and the second coupling nut 58.
is inserted, and constantly biases the second ferrule member 42 in the direction of the alignment adapter member 59.

Next, the adjustment for obtaining a desired amount of attenuation will be briefly explained.

Assemble each part as shown in Figure 1, and connect one optical fiber 33
is connected to a light source (not shown), and the optical fiber 34 is connected to an optical power meter (not shown).

Note that the optical connector plug 31 on the fixed side does not require adjustment.
The ferrule member 41 and the holder member 51 are adhesively fixed from the beginning.

Holding the outer end 42c of one ferrule member 42, rotate the ferrule member 42 within a range of 180 degrees while reading the attenuation value.

At the rotation angle position where the damping value reaches a required value, a fast-curing adhesive is injected into the gap between the ferrule member 42 and the holder member 52 and fixed.

After this fixation, loosen the second coupling nut 58,
Even if the optical connector plug 31 on the adjustment side is removed and repeatedly connected and disconnected, the relative angle of the second ferrule member 42 with respect to the first ferrule member 41 and the distance between the fibers are accurately restored, so that the set attenuation amount can be maintained. No fluctuations occur.

FIG. 4 is a graph showing the operating characteristics of the variable optical attenuator according to the present invention.

This graph shows the amount of optical attenuation when the distance aS between the optical fibers is changed in a pair of ferrules in which the angle θ of the end face of the ferrule member with respect to the plane perpendicular to the optical axis is 12 degrees in the variable optical attenuator. It is a graph.

Note that in the above-described structure, the distance between the optical fibers can be continuously changed by rotating one of the ferrule members.

FIG. 2 shows a state in which the second ferrule member 42 is rotated 180 degrees with respect to the first ferrule member 41 to maximize the distance S between the optical fibers.

For reference, the attenuation characteristics are also shown when θ is 0 degrees. It should be understood that this was measured using the structure shown in FIG.

As can be understood from this graph, the amount of attenuation increases as θ and S increase.

Using this graph, the angle θ of oblique polishing can be determined from the required attenuation range.

FIG. 5 is a histogram showing the results of actually measuring the reflection return loss of a large number of variable optical attenuators according to the present invention manufactured.

5M-10/125 as an optical fiber (single mode optical fiber with core diameter of 10 μm and clad diameter of 125
μm) was used. This figure shows the results of actually measuring the loss of reflected return light using 150 variable optical attenuators having the above structure using members whose ferrules have an inclination angle θ=12°. A laser diode with a wavelength (λ=13 μm) was used as a measurement light source.

The average value of the reflected return light loss is -67.9 dB.

The standard deviation is 1.6 dB, which is a good result with extremely little variation. Note that the loss of reflected return light does not change depending on the rotation angle of the ferrule.

(Effects of the Invention) As explained above, the variable optical attenuator according to the present invention has the following features:
The structure of the optical connector can be used almost as is.

Polish the tip of the ferrule diagonally within the range of 7 to 20 degrees depending on the required optical attenuation, insert and fix one side of the optical connector plug into the alignment adapter, and align the ferrule part of the other optical connector plug with the angle between 0 and 20 degrees. Since the amount of optical attenuation can be varied by a simple operation of turning within a range of 180 degrees, there is no need to adjust the attenuation amount by repeatedly attaching and detaching as in the conventional case, and the adjustment is easy.

Furthermore, by obliquely polishing the ferrule tip surface to an angle of 7 to 8 degrees, reflection return loss can be significantly reduced.

It is known that this can reduce the return due to surface reflection, but in the present invention as well, by constructing an optical attenuator using a ferrule that is diagonally polished in the range of 7 to 20 degrees, the distance between the optical fiber end face can be reduced. Regardless of this, a variable optical attenuator with excellent reflected light loss characteristics as shown in the histogram of reflected return light loss in FIG. 5 can be mass-produced.

As described above, the variable optical attenuator according to the present invention has a simple structural principle, ease of adjustment, and excellent loss characteristics for reflected return light, so it is not only low-priced but also different from conventional variable optical attenuators of various types. There are no restrictions on usage like type optical attenuators,
It is highly effective and can be used for all sorts of purposes.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway view of an embodiment of a variable optical attenuator according to the present invention, showing a state in which the amount of attenuation is adjusted to the minimum. FIG. 2 is a partially cutaway view showing an embodiment of the variable optical attenuator according to the present invention in a state where the amount of attenuation is adjusted to the maximum. FIG. 3 is a cross-sectional view of an embodiment of the variable optical attenuator according to the present invention, taken along the line X--X in FIG. 2. FIG. 4 is a graph showing the operating characteristics of the variable optical attenuator according to the present invention. FIG. 5 is a histogram showing the results of actually measuring the reflection return loss of a large number of variable optical attenuators according to the present invention manufactured. FIG. 6 is a schematic diagram for explaining the operation of a conventional variable optical attenuator using a glass plate whose transmittance changes continuously. FIG. 7 is a sectional view illustrating an attenuator that continuously changes the amount of attenuation by adjusting the distance between the end faces of the ferrule members. 31.32... Optical connector plug 51.52... Holder member 3.54-... Compression spring for ferrule biasing 5.56...
・Threaded part of the coupling nut 7.58...Coupling nut 3.44...Flange 5.46...Stop key 7.48...Through hole 9.50...Groove 9...Alignment Adapter member 0.61...Threaded part 2.63...Keyway 4...Through hole

Claims (7)

[Claims] (1) A variable optical attenuator that transmits light incident from one optical fiber to the other optical fiber coupled to the optical fiber after attenuating the light by an arbitrary amount, comprising: an alignment adapter member; and an optical fiber end. The first transmission terminal surface that exposes the optical fiber has a certain inclination with respect to the optical axis together with the optical fiber end surface.
a ferrule member, a first fixing means for supporting the first ferrule member on the alignment adapter member with limited rotation, and a transmission terminal surface exposing the optical fiber end with respect to the optical axis together with the optical fiber end surface. a second ferrule member having substantially the same inclination as the first ferrule member; coupled with the alignment adapter member to constantly bias the second ferrule member in the direction of the first ferrule member; A variable optical attenuator comprising an optical fiber connector member that is supported concentrically with respect to a first ferrule member so as to be rotatable over a certain angle, and that is fixed to the alignment adapter member at any angular position within the range. (2) The alignment adapter member has an alignment sleeve hole that precisely fits the outer diameter portions of the first and second ferrule members, and can rotatably support at least the second ferrule member. The variable optical attenuator according to claim 1. (3) The variable type according to claim 1, wherein the end faces of the pair of ferrules are obliquely polished so that they have the same inclination angle of 7 degrees to 20 degrees with respect to a plane perpendicular to the optical axis of the optical fiber. optical attenuator. (4) the optical fiber connector member rotatably supports the second ferrule member while restricting movement in the axial direction, and is guided linearly in the optical axis direction with respect to the alignment adapter member; a coupling nut that receives and supports the holder member in a through hole at the bottom and is screwed to the alignment adapter member through an opening; 2. The variable optical attenuator according to claim 1, further comprising a spring means which is always biased toward said first ferrule member through said first ferrule member. (5) The variable variable according to claim 4, wherein the first fixing means for supporting the first ferrule member on the alignment adapter member with limited rotation is an optical fiber connector member having the same structure as the optical fiber connector member. type optical attenuator. (6) By rotating the second ferrule member within 180 degrees with respect to the alignment adapter member, the slope of each ferrule changes from the minimum attenuation state where the end faces are in close contact, where the distance between the optical fibers is the minimum, to the maximum attenuation. 2. The variable optical attenuator according to claim 1, wherein the variable optical attenuator can be continuously varied up to a maximum attenuation position at an angle of . (7) Rotate the second ferrule member relative to the first ferrule member to a position where the necessary attenuation is obtained, and fix the rotational positions of the holder member and the ferrule member to obtain a constant amount of attenuation. 5. The variable optical attenuator according to claim 4, wherein the variable optical attenuator is configured as follows.