JPH0894843A - Optical variable attenuator - Google Patents

Abstract

PURPOSE: To make it possible to lessen the reflection at the air boundary of connecting ends by building two kinds of ferrules into an optical variable attenuator, to decrease the reflection attenuation quantity in a gap as the moving ferrules having a terminating angle are formed and to easily mount the attenuator in a small space by integrating the structure as a plug and jack type and PJ type to a small size. CONSTITUTION: This optical variable attenuator 100 holds the first optical fiber ferrule 40 on one end side and holds the second optical fiber ferrule 80 on the other side. The ends 42, 82 on one side of the first optical fiber ferrule 40 and the second optical fiber ferrule 80 are so subjected to a termination treatment as to have the angle to terminate the Fresnel reflection at the air boundary and the ends 41, 81 on the other side thereof are subjected to a spherical surface treatment to suppress the reflection in the coupling part. The first optical fiber ferrule 40 and the second optical fiber ferrule 80 are made relatively movable with each other along the optical axis in the state that their ends on one side are disposed opposite to each other on the optical axis, by which the width of the gap 91 applied between the ends on one side is made variable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical variable attenuator used for adjusting the amount of transmitted light in an optical fiber communication circuit or the like.

[0002]

2. Description of the Related Art Various types of optical attenuators, including variable type, have been proposed and used as optical attenuators used for adjusting the amount of light attenuation in optical fiber communication circuits.

In particular, as an optical attenuator using an optical fiber ferrule, the end face of the optical fiber ferrule is provided with a specific inclination angle to prevent the reflected light from returning and to appropriately control the interval between the optical fiber ferrules. By doing so, a controllable attenuation amount has been developed. An example of such an optical attenuator is disclosed in Japanese Utility Model Laid-Open No. 56-170406. A schematic configuration of such a conventional optical attenuator is shown in FIG. 1 of the accompanying drawings.

The structure of this conventional optical attenuator will be briefly described with reference to FIG. 1. The first optical fiber ferrule 1 and the second optical fiber ferrule 2 are aligned on the optical axis L. They are arranged so as to sandwich a gap having a predetermined width W. The first optical fire ferrule 1 has an optical fiber core 3 and an optical fiber clad 4 in its center hole.
And the second optical fiber ferrule 2 also has an optical fiber composed of an optical fiber core 3 and an optical fiber clad 4 in its center hole. Optical fiber core 3 of the first optical fiber ferrule 1
And the optical fiber core 3 of the second optical fiber ferrule 2 are aligned on the optical axis L with a gap therebetween. The end faces of the optical fiber ferrules 1 and 2 which are opposed to each other with a gap therebetween are terminated so as to be inclined by an angle θ with respect to a plane perpendicular to the optical axis L, as shown in FIG.

According to such a conventional optical attenuator, it is possible to reduce the reflection return light loss in the void portion and obtain the optical attenuation amount according to the width W of the void, and also to obtain the width of the void. The light attenuation amount can be made variable by changing W.

As another type of variable optical attenuator, as shown in FIG. 6 of Japanese Patent Laid-Open No. 3-210504,
It has been proposed to use a glass plate whose transmittance changes continuously.

Further, as another type of variable optical attenuator, the attenuation amount is continuously changed by adjusting the distance between the end faces of the ferrule member as disclosed in Japanese Patent Laid-Open No. 63-273812. The thing which made it do is proposed.

Another type of variable optical attenuator is a plug having a ferrule end face inclined with respect to the optical axis, as shown in FIGS. 1 and 2 of Japanese Patent Laid-Open No. 3-210504. There has been proposed a ferrule that uses a rotatable adapter.

[0009]

However, in the structure of the conventional optical attenuator as described with reference to FIG. 1, the multiple reflections occurring between the end faces of the optical fiber ferrules 1 and 2 facing each other with the air gap therebetween are sufficient. However, there is a problem that third-order distortion occurs when a plurality of waves of light modulation signals are incident, and the same problem remains as it is even with a variable type.

Further, in the variable optical attenuator as shown in FIG. 6 of Japanese Patent Laid-Open No. 3-210504, reflection occurs at the air interface of a glass plate or the like, and so-called reflected return light loss increases, which causes a light source. There was a problem that it was returned to and affected the light source. Moreover, in such a device, there is a problem that the transmittance of the glass plate changes with time and the attenuation becomes unstable.

Further, the variable optical attenuator disclosed in Japanese Patent Laid-Open No. 63-273812 has a problem that the device structure is complicated and the adjusting operation is very complicated. In addition, the reflected return light loss at the air interface is also large, and for this reason, it cannot be used for long-distance large-capacity communication or video communication.

Furthermore, the variable optical attenuator as shown in FIGS. 1 and 2 of Japanese Patent Laid-Open No. 3-210504 requires a special plug and adapter, so that a standard adapter and a standard spherical surface treatment are required. There was a problem that it could not be directly connected to the plug. In addition, there is a problem that it is difficult to confirm the attenuation amount because there is no attenuation amount display.

An object of the present invention is to provide an optical variable attenuator capable of solving the problems of the prior art.

[0014]

An optical variable attenuator according to the present invention comprises a first optical fiber ferrule held at one end and a second optical fiber ferrule held at the other end. , The first optical fiber ferrule and the second optical fiber ferrule are terminated so that one end has an angle that terminates Fresnel reflection at an air interface, and the other end is a coupling portion. Are subjected to a spherical surface treatment to suppress the reflection of the first optical fiber ferrule and the second optical fiber ferrule in a state where the one end portions of the first optical fiber ferrule and the second optical fiber ferrule are arranged to face each other on the optical axis. It is characterized in that it is movable relative to each other along the optical axis, and the width of the gap provided between the one end portions is variable.

According to a preferred embodiment of the present invention, at least one of the first optical fiber ferrule and the second optical fiber ferrule is provided with the air gap provided between the one end portions. Has another void that is inclined in the opposite direction to the plane perpendicular to the optical axis.

According to a preferred embodiment of the present invention, the first optical fiber ferrule is fixedly held with respect to a plug type part fitted to one mating coupling part, and the second optical fiber ferrule is fixed to the plug type part.
Optical fiber ferrule is fixedly held with respect to a jack type part fitted to the other mating coupling part, and the jack type part has a second optical fiber in order to make the width of the gap variable. With the ferrule fixedly held, it is movable along the optical axis with respect to the plug-shaped portion.

According to a preferred embodiment of the present invention,
The jack type portion is formed by rotating a variable dial screw-engaged with the plug type portion.

Further, according to a preferred embodiment of the present invention, the jack type portion is provided with a marker indicating a reference point, the variable dial is provided with an attenuation amount display, and the marker is provided. By setting the attenuation amount display, the set attenuation amount can be designated.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in more detail with reference to the accompanying drawings, and in particular with reference to FIGS.

FIG. 2 is a schematic diagram for explaining an example of a configuration which can be applied to the optical variable attenuator of the present invention to perform effective optical attenuation. As shown in FIG. 2, the configuration for this optical attenuation is the same as the configuration of the conventional optical attenuator described above with reference to FIG. The second optical fiber ferrule 2 and the second optical fiber ferrule 2 are arranged so as to sandwich a gap having a predetermined width W. Further, the first optical fire ferrule 1 has an optical fiber composed of an optical fiber core 3 and an optical fiber clad 4 arranged in its center hole, and the second optical fiber ferrule 2 also has an optical fiber arranged in its center hole. An optical fiber including a fiber core 3 and an optical fiber clad 4 is arranged. The optical fiber core 3 of the first optical fiber ferrule 1 and the optical fiber core 3 of the second optical fiber ferrule 2 are aligned on the optical axis L with a gap therebetween. As shown in FIG. 2, the end faces of the optical fiber ferrules 1 and 2 which are opposed to each other with a gap therebetween are aligned with the optical axis L by an angle θ terminating Fresnel reflection at the air interface, for example, an angle of 8 degrees or more. It is terminated to be inclined with respect to the vertical plane.

Further, a slit 5 is formed in the first optical fiber ferrule 1. As shown in FIG. 2, this slit 5 is provided in the first optical fiber ferrule 1
Is inclined in the opposite direction to the inclination of the slit 6 having the above-described gap width W provided between the end surface of the first optical fiber ferrule 2 and the end surface of the second optical fiber ferrule 2. That is,
The slit 5 is inclined with respect to a plane perpendicular to the optical axis L by an angle θ in a direction opposite to the inclination direction of the slit 6 and has a gap of a predetermined width W ′ along the optical axis L. It is supposed to be created. In this way, the optical fiber ferrule of this optical attenuation structure is formed at a predetermined position along the optical axis so as to have a V shape, and the pair of slits 5 is formed.
And 6 are provided.

As described above, the pair of slits (voids) 5 and 6 inclined in opposite directions are provided at predetermined positions separated from each other along the optical axis of the optical fiber ferrule having the optical attenuation structure, whereby the first slit is formed. It was experimentally confirmed that the multiple reflections that could not be removed by 5 can be removed by the second slit 6 and the third-order distortion can be reduced. Further, in the structure example of FIG. 2, only one C-shaped slit pair is provided. However, by providing a plurality of such slit pairs at positions separated along the optical axis, multiple pairs can be provided. It was also experimentally confirmed that the effect of removing reflection can be improved and the effect of reducing third-order distortion can be enhanced.

Next, an optical variable attenuator as an embodiment of the present invention will be described. FIG. 3 is a plan view schematically showing the appearance of the variable optical attenuator, and FIG. 4 is a schematic sectional view of the variable optical attenuator. As shown in FIGS. 3 and 4, the variable optical attenuator 100 of this embodiment is grouped as a plug jack type (PJ type), and has a cylindrical body shell 10 as a whole and the body shell 10. 10
A plug frame 20 attached to one end of the main body shell 10, a plug coupling nut 30 attached to the periphery of the plug frame 20, and an adapter shell 50 attached to the other end of the main body shell 10 are mainly provided. Since the detailed structure of each of these members may be one that is usually adopted in an optical connector, such ordinary parts will not be described in detail here.

According to the present invention, the first optical fiber ferrule 40 is fixedly mounted via the mounting member 21 so as to extend along the central axis of the plug frame 20. On the other hand, a sleeve 90 is fixedly attached to the central portion of the adapter shell 50 via a mounting member 51, and the sleeve 90 is extended in the sleeve 90 along the central axis of the adapter shell 50. Second
The optical fiber ferrule 80 is mounted and fixed.

The adapter shell 50 is attached to the body shell 10 so as to be movable in the direction of the central axis thereof. As shown in FIG. 4, the tip end of the adapter shell 50 is an annular portion 54, and a deviation spring 56 is attached in the annular portion 54. The deviation spring 56 is formed on the inner peripheral wall of the main body shell 10 and the shoulder portion 13 and the annular portion 5 of the adapter shell 50.
Between the shoulder 55 formed on the inner peripheral wall of the main body 4, the adapter shell 50 always exerts a shift force that shifts the adapter shell 50 in the backward direction along the central axis of the main body shell 10. .

An outer peripheral shoulder portion 52 and an outer peripheral protruding portion 53 are formed on the outer periphery of the adapter shell 50. Outer peripheral projection 53
Is brought into contact with the rear end 14 of the main body shell 10 so that the adapter shell 50 is no longer attached.
Make sure you can't move towards zero. Also, the body shell 1
A variable dial 70 is provided around 0 and the adapter shell 50. On the inner circumference of this variable dial 70,
The threaded portion 71 is formed so that it can be engaged with the threaded portion 11 formed on the outer peripheral portion of the main body shell 10. An annular protrusion 73 is formed on the inner periphery of the rear end of the variable dial 70, and the annular protrusion 73 is adapted to abut on the outer peripheral shoulder 52 of the outer periphery of the adapter shell 50. On the other hand, a lock nut 60 is screwed onto the outer periphery of the rear portion of the adapter shell 50. The variable dial 70 can rotate around the main body shell 10 and the adapter shell 50 in a state where the annular protrusion 73 is sandwiched between the outer peripheral shoulder portion 52 of the adapter shell 50 and the lock nut 60. ing.

With such a structure, the variable dial 70 is rotated around the body shell 10 with the lock nut 60 slightly loosened, so that the screw portion 71 engages with the screw portion 71. Because of the matching, the variable dial 70 is moved back and forth along the central axis of the body shell 10 by an amount corresponding to the pitch of the screw. For example, when the variable dial 70 is moved clockwise when the variable dial 70 is rotated clockwise, the annular protrusion 73 of the variable dial 70 is moved to the front direction toward the plug frame 20. To move the adapter shell 50 in the forward direction against the displacement force of the displacement spring 56. FIG. 4 shows a state where the adapter shell 50 has been moved to the frontmost position in this way. On the contrary, when rotating the variable dial 70 in the counterclockwise direction, the variable dial 70 is moved in the rearward direction away from the plug frame 20, and the adapter shell 50 is also moved in the rearward direction by the displacement force of the displacement spring 56. To be After the variable dial 70 is thus rotated, the lock nut 60 is completely tightened, so that the annular protrusion 73 of the variable dial 70 is firmly held between the outer peripheral shoulder portion 52 and the lock nut 60. Therefore, the variable dial 70 is fixedly locked in that state, and the plug frame 20 of the adapter shell 50 is
The position with respect to will be fixed.

Next, the first optical fiber ferrule 40 fixedly held by the plug frame 20 and the second optical fiber ferrule 8 fixedly held by the adapter shell 50.
The structure of 0 will be described in detail below. First, in the first optical fiber ferrule 10, the front end 41 is subjected to spherical treatment (PC polishing) while suppressing reflection at the coupling portion, and the rear end 42 has an angle θ at which Fresnel reflection at the air interface is terminated, for example, , Is terminated so that it has an angle of 8 degrees or more with respect to a plane perpendicular to the ray axis. Further, in this embodiment, a slit 43 is formed in the middle portion of the first optical fiber ferrule 10. The slit 43 has the same configuration as the slit 5 in the example of the light attenuation structure described above with reference to FIG. 2 and achieves the same effect, and therefore the details thereof will not be repeated here.

The rear end 81 of the second optical fiber ferrule 80 is spherically treated (PC polishing) to suppress reflection at the coupling portion, and the front end 82 has an angle θ at which Fresnel reflection at the air interface ends, For example, 8 for a plane perpendicular to the ray axis
It is terminated so that it has an angle of more than degrees.
The front end 82 of the second fiber optic ferrule 80 opposes the rear end 42 of the first fiber optic ferrule 40 entering through the front end of the sleeve 90 when the adapter shell 50 is mated to the body shell 10. hand,
A slit 91 is formed between them. The slit 91 has the same configuration as the slit 6 in the example of the light attenuation structure described above with reference to FIG. 2 and achieves the same effect, and therefore the details thereof will not be repeated here.

Next, the overall operation of the optical variable attenuator 100 of this embodiment will be described. For example, in the state shown in FIG. 4, the lock nut 60 is loosened and the variable dial 70 is rotated counterclockwise. When this is done, the variable dial 70 is retracted by an amount corresponding to its rotation amount, and therefore,
The displacement force of the displacement spring 56 also retracts the adapter shell 50 by the same amount. This allows the adapter shell 5
The second optical fiber ferrule 80 fixed to the sleeve 90 fixed to 0 is also retracted together with the sleeve 90. As a result, the rear end 42 of the first optical fiber ferrule 40 and the second optical fiber ferrule 8
Slit (gap) 91 formed between the front end 82
The width of is increased by that amount, and the amount of light attenuation is also increased by that amount. At the position where the desired light attenuation is obtained,
By re-tightening the lock nut 60, the lock nut 60 can be fixedly held in that state.

As well shown in the plan view of FIG. 3, by attaching the marker 12 to the outer periphery of the main body shell 10 and attaching the attenuation amount display (dB) 72 to the outer periphery of the variable dial 70, The set light attenuation amount can be easily read. Also, by varying the screw pitch of the screw portion 71 of the variable dial 70, the attenuation amount range can be adjusted variously.

Next, an application example of the variable optical attenuator 100 having such a structure and function will be described with reference to FIG. FIG. 5 schematically shows a spherically coupled first plug 200 and second plug 300, which are coupled to each other via an adapter 400, in a separated state. The detailed structure of the adapter 400 and the plugs 200 and 300 is as follows.
Since it is normally used in optical connectors,
It will not be detailed here. The first plug 200 has an optical fiber ferrule 210, and a front end surface 211 of this optical fiber ferrule 210 is subjected to a spherical surface treatment (PC polishing) that suppresses reflection at a coupling portion. Similarly, the second plug 300 has an optical fiber ferrule 310, and the front end face 311 of the optical fiber ferrule 310.
Is subjected to a spherical surface treatment (PC polishing) to suppress reflection at the joint.

For example, the variable optical attenuator 100 of the present invention is
In FIG. 5, it is used by being attached between the adapter 400 and the first plug 200. The variable optical attenuator 100 is
One end is connected to the adapter 400 side by the plug coupling nut 30. First optical fiber ferrule 40
The spherical end 41 is aligned with the spherical end 311 of the optical fiber ferrule 310 of the second plug 300, which is coupled to the opposite side of the adapter 400, by the sleeve inside the adapter 400 to make a spherical connection. Also, the jack part is the first
Of the second optical fiber ferrule 80, which is coupled to the adapter shell 50 by the coupling nut of the plug 200 of FIG.
The spherical end 81 of the optical fiber ferrule 210 of the first plug 200 is aligned with the spherical end of the optical fiber ferrule 210 by the sleeve 90 to make a spherical connection. As a result, the first plug 200
The variable optical attenuator 100 can be mounted between the adapter and the adapter 400.

In this state, the variable dial 70 is rotated to rotate the first optical fiber ferrule 40.
The rear end 42 and the front end 8 of the second optical fiber ferrule 80.
The gap width between the slit 91 and the slit 91 can be changed, and the light attenuation amount can be set to a desired value. At this time, the spherical end 311 of the optical fiber ferrule 310 of the second plug 300 is
And the spherical end 41 of the first optical fiber ferrule 40 of the first variable optical attenuator 100 are maintained as they are, and the optical end of the optical fiber ferrule 210 of the first plug 200 and the spherical end 211 of the variable optical attenuator are maintained. The spherical connection with the spherical end 81 of the second optical fiber ferrule 80 of the attenuator 100 is also maintained.

After adjusting the attenuation amount display 72 of the variable dial 70 to the marker (reference point) 12 of the main body shell 10 and adjusting the gap width of the slit 91 to set the attenuation amount to a desired value, the lock nut 60 is set. It can be fixed in that state by re-tightening.

The optical variable attenuator 100 according to this embodiment has a first
Since the slit 43 is formed in the optical fiber ferrule 40, the optical attenuation can be made variable by changing the gap width of the slit 91, and the multiple reflection in the gap can be canceled out, and the third-order distortion can be eliminated. Can be reduced.

[0037]

Since two types of ferrules are incorporated inside, reflection at the air interface at the connecting end can be reduced.

Since the movable ferrule has the terminating angle, it is possible to obtain the effect of reducing the return loss in the air gap.

The structure is the so-called plug jack type, PJ
Since it can be compactly assembled as a mold, it can be easily installed in a small space.

The movable part can be used for dial adjustment,
In this case, by changing the dial pitch, it is possible to obtain an effect that various attenuation amount ranges can be set.

By forming another space in the ferrule, which has a V-shape, with respect to the inclined space between the first optical fiber ferrule and the second optical fiber ferrule, the amount of optical attenuation can be reduced. Not only can it be made variable, but multiple reflection at the void can be removed, and third-order distortion that occurs when a plurality of waves of optical modulation signals are incident can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a conventional optical attenuator.

FIG. 2 is a schematic diagram showing a structural example for optical attenuation effective when applied to the variable optical attenuator of the present invention.

FIG. 3 is a plan view schematically showing the appearance of an optical variable attenuator as an embodiment of the present invention.

FIG. 4 is a schematic sectional view of the variable optical attenuator of FIG.

FIG. 5 is a schematic diagram for explaining an application example of the optical attenuator of the present invention.

[Explanation of symbols]

 1 1st optical fiber ferrule 2 2nd optical fiber ferrule 3 Optical fiber core 4 Optical fiber clad 5 1st slit 6 2nd slit 10 Main body shell 11 Screw part 20 Plug frame 30 Plug coupling nut 40 1st Optical fiber ferrule 41 Spherical processing end 42 Inclination processing end 43 Slit 50 Adapter shell 56 Deflection spring 60 Lock nut 70 Variable dial 71 Screw part 72 Attenuation display 80 Second optical fiber ferrule 81 Spherical processing end 82 Inclination processing end 90 Sleeve 91 slit 100 variable optical attenuator 200 first plug 300 second plug 400 adapter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hironori Sakamoto 5-1-1 Shimorenjaku, Mitaka-shi, Tokyo Within Japan Radio Co., Ltd. (72) 5-1-1 1-1 Shimorenjaku, Mitaka-shi, Tokyo Japan Wireless Co., Ltd.

Claims (5)

[Claims] 1. A first optical fiber ferrule held at one end side, and a second optical fiber ferrule held at the other end side, wherein the first optical fiber ferrule and the second light are provided. The fiber ferrule is terminated so that one end has an angle that terminates Fresnel reflection at the air interface, and the other end is spherically treated to suppress reflection at the coupling part, The first optical fiber ferrule and the second optical fiber ferrule are relatively arranged with respect to each other along the optical axis in a state where the one end portions are arranged to face each other on the optical axis. An optical variable attenuator which is movable and in which a width of an air gap provided between the one ends is variable. 2. The air gap provided between the one end portions of at least one of the first optical fiber ferrule and the second optical fiber ferrule is perpendicular to the optical axis. The variable optical attenuator according to claim 1, wherein another air gap is formed which is inclined in a direction opposite to the plane. 3. The first optical fiber ferrule is fixedly held with respect to a plug-shaped portion fitted in one mating coupling portion, and the second optical fiber ferrule is held in the other mating coupling portion. The jack mold part is fixed and held to the mating jack mold part, and the jack mold part holds the second optical fiber ferrule fixedly in order to make the width of the gap variable. 3. The variable optical attenuator according to claim 1, wherein the variable attenuator is movable along the optical axis with respect to the section. 4. The variable optical attenuator according to claim 3, wherein the jack type portion is formed by rotating a variable dial screw-engaged with the plug type portion. 5. The jack type portion is provided with a marker indicating a reference point, the variable dial is provided with an attenuation amount display, and by setting the attenuation amount display on the marker, the set attenuation is set. The variable optical attenuator according to claim 4, wherein the variable amount can be indicated.