JP2769752B2 - Optical fiber multi-core connector plug - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-core connector plug for simultaneously connecting a plurality of optical fibers, and more particularly to a multi-core connector plug having high operability and high performance.

[0002]

2. Description of the Related Art When connecting optical fiber connector plugs, if a gap exists between the optical fiber connection end faces, light that propagates in the optical fiber due to this gap causes Fresnel reflection, and the light source side. To cause the phenomenon that the light emission characteristics of the light source are deteriorated and the connection loss is increased due to Fresnel reflection. Various studies have hitherto been made to solve this problem.

As a first conventional example, FIG. 8 shows a longitudinal sectional view of a butt connection portion between single-core connector plugs 3 and 3 'having a convex spherical end face shape. The connection end of the single-core connector plug 3 has a cylindrical shape, and the optical fiber 2 in the optical fiber 1 is fixed to the axis of the plug 3.
The connection end face 4 of the plug 3 has a convex spherical surface with a plane orthogonal to the plug axis as a reference plane. The connection end face 4 is formed by polishing the plug end face at right angles, and then performing spherical polishing using the right angle polishing as a reference plane. As a constituent material of the plug 3, a ceramic material is widely used. The same applies to the other plug 3 '.

The connection between the plugs 3 and 3 'is made by inserting each plug from both ends of the guide sleeve 5, applying pressure in the axial direction with a spring or the like, and abutting the connection end surfaces 4 and 4' of each plug. Done. At this time, the connection end faces 4, 4 '
Are in contact with each other and a circular contact surface is formed around the plug axis.

[0005] The diameter of the osculating circle is determined by the Young's modulus of the plug material, the radius of curvature of the spherical surface, and the axial load. When alumina ceramic (Young's modulus is 370 GPa) which is a typical material of a single-core connector plug is used, the radius of curvature of the spherical surface is 60 mm, and the load in the axial direction is 1 kgf, the diameter of the contact surface is calculated from the Hertz equation. , Its diameter is about 0.2 mm. When this contact circle is formed, the contact end faces of the optical fibers located at the axis of the plug are brought into a connected state in which they are in direct contact with each other, thereby making it possible to eliminate Fresnel reflection caused by the air gap.

FIGS. 9 and 10 show a second conventional example.
The perspective view of the optical fiber multi-core connector plug,
And a longitudinal sectional view of a butt connection portion thereof. In the multi-core connector plug 8, a plurality of optical fibers 7 in the optical fiber tape 6 are arranged and fixed between a pair of guide pin insertion holes 9, and the connection side end face 10 surrounds the plurality of optical fibers. A protrusion 11 is provided, and an end surface 12 of the protrusion 11 is provided.
Has a surface perpendicular to the optical fiber axis by perpendicular polishing. A plastic material is used as a plug constituent material.

The connection between plugs 8 and 8 'is shown in FIG.
As shown in the figure, a pair of guide pins 13 are used as positioning guides, and are pressed in the axial direction by a spring or the like, so that the plug 8
And 8 '. The plug material is made of an elastic plastic material, and furthermore, a protruding portion 11 is provided on the plug end surface to reduce the connection end surface, so that the connection end surfaces of the multi-core optical fibers are brought into contact at the time of connection, and Fresnel reflection caused by the air gap is reduced. It is possible to remove.

Next, as a third conventional example, FIG. 11 shows a longitudinal sectional view of a single-core connector plug having an inclined end face shape and a butt connection portion thereof. Single core connector flag 1
The connection terminal portion 4 has a cylindrical shape, and the optical fiber 2 in the optical fiber 1 is fixed to the axis of the plug 14. The connection end face 15 of the plug 14 has an inclined surface having an angle θ larger than a critical angle of total reflection of light propagating in the optical fiber with respect to a plane orthogonal to the axis of the plug. This inclined surface is formed by polishing the plug end surface in advance. A ceramic material is used as a plug constituent material. The mutual connection of the plugs 14 and 14 'is performed by butting each plug with the guide sleeve 16 as a positioning guide. At this time, the connection end faces of the optical fiber are connected to each other at an angle θ, but there is a gap between the connection end faces.

The first cause of the void is that the ceramic material has a small elastic deformation, so that the angle error generated at the time of oblique polishing is not absorbed at the time of connection, and secondly, the connection of the circular plugs is relative to the rotational direction. Third, the ceramic material is harder than quartz, which is the optical fiber material, and the optical fiber is quickly cut off during oblique polishing.
The optical fiber connection end face has a concave shape.

Due to the connection between the inclined surfaces having the angle θ, the reflected light caused by the gap and the high-refractive-index work-strained layer generated at the time of polishing is reflected light from the inclined surface having the angle θ, and is reflected with respect to the optical fiber axis. Since it has an angle larger than the critical angle for total reflection, it does not propagate to the light source side, and low-loss characteristics of -50 dB or less are realized.

Next, as a fourth conventional example, FIGS.
1 shows a perspective view of a multi-core connector plug having an inclined surface, and a longitudinal sectional view of a butt connection portion. In the multi-core connector plug 17, a plurality of optical fibers 7 in the optical fiber tape 6 are arranged and fixed between two V-grooved silicon substrates, and an inclined surface having an angle θ is formed on the plug connection end surface 18. Have been. As shown in FIG. 13, the connection between the plugs 17 and 17 'is made by abutting the plugs 17 and 17' with the arcuate spring 20 arranged in the rectangular sleeve 19 as a positioning guide.

The connection end faces of the optical fiber are connected to each other at an angle θ. However, since the silicon material has a small elastic deformation, the angle error of the plug end face generated during the oblique polishing is not absorbed at the time of connection. Is harder than the optical fiber, and the optical fiber is sharpened earlier during the oblique polishing, so that the optical fiber connection end face becomes concave, so that a gap is generated between the connection end faces.

[0013]

However, when the contact end faces of the single-fiber connector plugs 3 and 3 'of the first conventional example shown in FIG. A processing strain layer having a high refractive index generated during polishing remains. Although studies have been made to remove the work-strained layer, complete removal is practically difficult. For this reason, at the time of connection, light propagating in the optical fiber causes reflection from the processing strained layer having a high refractive index, and this reflected light returns to the light source side, so that the amount of reflection is practically limited to -40 to -35 dB. However, it cannot be applied to an analog optical transmission system or the like that requires a low reflection characteristic of -50 dB or less.

Further, since the diameter of the contact circle formed at the time of connection between the plugs is small and it is technically difficult to accurately position the multi-core optical fiber with respect to the circular plug, the single-core connector plug is difficult. The technology of bringing multi-core optical fibers into contact all at once has not been realized by the extension technology of the above.

9 and FIG. 10, when viewed microscopically, similarly to the first conventional example, a high refractive index processing strain remaining on the surface of the optical fiber connection end face. Since reflection from the layer occurs, the reflection amount is -40 to -35 dB.
Will be restricted. In the plug connection state, the end faces of the protruding portions 11 are in contact with each other.
Since the plug end surfaces around 1 are not in contact with each other and have a large space therebetween, when an external force is applied in the thickness direction and the width direction of the plug, the end of the right-angled surface of the protrusion is used as a fulcrum.
An angle shift occurs between the plugs. For this reason, there is a problem that the direct contact state of the optical fiber connection end face is destroyed by an external force applied at the time of plug attachment / detachment or after connection, and a gap is easily generated, and stable reflection characteristics and connection loss cannot be obtained.

The third conventional example shown in FIG. 11 also has a problem that the presence of the air gap causes an increase in connection loss due to Fresnel reflection. Further, similarly to the first conventional example, since it is technically difficult to accurately position the multi-core optical fiber with respect to the circular plug, a multi-core connector by the extension technology of the single-core connector has not been realized.

Further, in the fourth conventional example shown in FIGS. 12 and 13, although multi-core optical fibers can be simultaneously connected with low reflection, the connection loss increases due to Fresnel reflection as in the third conventional example. There was a problem that would occur.

In addition to these methods, a method of removing Fresnel reflection by interposing a refractive index matching agent between plug connection end faces has also been used.
It was limited to applications where the number of attachments and detachments was small, and could not be applied to locations where attachments and detachments were common, such as connection to equipment.

An object of the present invention is to provide a multi-core connector plug which can improve the detachability by eliminating the need for a refractive index matching agent, and can realize low reflection and low loss characteristics.

[0020]

According to the present invention, there is provided a multi-core connector plug in which a plurality of optical fibers are arranged and fixed between a pair of guide pin insertion holes, wherein the plug has a Young's modulus of 30.
It is composed of an elastic material having GPa or less, and the connection end face of the plug is an inclined plane having an angle larger than a critical angle of total reflection of light propagating in the optical fiber with respect to a plane orthogonal to the optical fiber axis as a reference plane. The shape of the convex ellipsoid surface is such that the radius of curvature of the convex ellipsoid surface on the center of the plug axis is maximum in the arrangement direction of the optical fibers and minimum in the direction orthogonal to the arrangement direction of the optical fibers.

[0021]

According to the present invention, at the time of connection between plugs, the contact portion between the plug connection end surfaces is formed into an elliptical shape having an inclined surface and a long diameter in the optical fiber arrangement direction, thereby providing a connection end surface of the multi-core optical fiber. By bringing them into oblique and direct contact with each other to eliminate Fresnel reflection caused by voids and reflection caused by a high-refractive-index processed strained layer, low-reflection and low-loss connection characteristics can be realized without a refractive index matching agent.

[0022]

Embodiments of the present invention will be described below. 1 to 5 are views showing a multi-core connector plug according to the first embodiment. FIG. 1 is a perspective view, FIG. 2 is a cross-sectional view as viewed from a side, FIG. 6 is a cross-sectional view of the plug butt connection portion as viewed from the side, FIG. 5 and a cross-sectional view as viewed from above. 6, 6 'are optical fiber tapes, 7, 7' are multi-core optical fibers, 21, 21 'are multi-core connector plugs,
2 is a pair of guide pin insertion holes, 23 is a connection end face of the plug 21, and 24 is a pair of guide pins.

The plug 21 is made of an elastic material having a Young's modulus of 30 GPa or less. In this plug 21, a plurality of optical fibers 7 in the optical fiber tape 6 are arranged and fixed between a pair of guide pin insertion holes 22, and the connection end face 23 of the plug 21 is optically connected to a plane orthogonal to the optical fiber axis. It has a shape of a convex ellipsoid with an inclined surface having an angle θ larger than the critical angle of total reflection of the propagation light in the fiber as a reference surface. The radius of curvature of the convex ellipsoidal surface has a maximum value R1 in the optical fiber arrangement direction and a minimum value R2 in the direction orthogonal to the optical fiber arrangement direction on the plug axis.

In order to obtain the connection end face 23 of the plug 21, first, an inclined face having an angle θ is formed by obliquely polishing the end face of the plug 21, and then the convex ellipse is formed by buffing the inclined face. This is done by forming a body surface. The convex ellipsoid surface is formed by utilizing the following phenomenon. That is, when a polishing pressure in the axial direction is applied to a plug having a rectangular end surface and buff polishing is performed using free abrasive grains on a plastic sheet polishing machine that rotates the plug end surface, the peripheral portion of the plug end surface is larger than the central portion. Because of the polishing pressure, it is polished faster. As a result, the shape of the convex ellipsoidal surface having the maximum radius of curvature R1 in the long side direction and the minimum radius of curvature R2 in the short side direction at the center of the end surface is formed on the end face of the plug after polishing.

Here, the maximum and minimum radii of curvature R1, R
Step 2 can be controlled by selecting the rectangular dimensions of the plug end surface before buffing and the conditions of buffing (polishing pressure, polishing rate, material of polishing board / abrasive grains, polishing time). Therefore, by arranging the optical fibers in the long side direction of the rectangular plug end surface before buffing, the plug end surface after buffing has an inclined surface having an angle θ as a reference plane, and is located on the plug axis. A convex ellipsoidal surface having a maximum radius of curvature in the direction in which the optical fibers are arranged and a minimum in a direction perpendicular to the radius of curvature can be formed.

As shown in FIGS. 4 and 5, the plugs 21 and 21 'are connected to each other by using a pair of guide pins 24 as positioning guides and applying pressure in the axial direction with a spring or the like.
This is done by matching 1 and 21 '. At the time of butt connection, the plug connection end surfaces are formed on a slope having an angle θ as a reference surface, and a convex ellipse having a maximum radius R1 in the optical fiber arrangement direction at a contact point of the plug axis and a minimum radius R2 in a direction orthogonal thereto. The body surfaces come into contact with each other, and the contact surface has an elliptical shape. The dimensions of this elliptical contact surface can be calculated as follows.

That is, assuming that a load applied in the axial direction by a spring or the like at the time of connection is F, a force Fn (= Fcos θ) perpendicular to this surface and a force Ft (Ft ( = Fsinθ) acts. Ft is a force for sliding the plug end face, and this force balances with the frictional force. It can be approximated that the contact between the plug end faces is caused by the elastic deformation of the plug due to the load Fn. He
From the equation of rtz, the major axis C, the minor axis D, and the amount of elastic deformation W in the load direction of the elliptical contact surface formed by the contact between the ellipsoidal surfaces.
Is given by the following equation. C = 1.11α [(Fn / E ) · R1 · R2 / (R1 + R2)] 1/3 ··· (1) D = 1.11β [(Fn / E) · R1 · R2 / (R1 + R2)] 1/3 ··· (2) W = 0.308 λ [(Fn 2 / E 2) · (R1 + R2) / (R1 · R2)] 1/3 ··· (3) where, E is Young's modulus of the plug material, α , Β, λ are R1
/ R2 is a parameter determined by, for example,
When R1 / R2 = 1, α = β = 1 and λ = 2, and the expressions (1) to (3) match the case of contact between spheres, and R1
When / R2 = 10, α = 2.40, β = 0.530,
λ = 1.55.

For example, the plug material is an epoxy resin containing quartz powder of plastic material (E = 15 GPa), the load is Fn = 1 kgf, and the maximum radius R1 at the contact point is 1000 m.
m, and a minimum radius R2 = 100 mm, Equations (1) to
From (3), 2C = 2.1 mm, 2D = 0.46 mm,
W = 0.8 × 10 ⁻³ mm.

This is about 2 mm in the optical fiber arrangement direction,
This indicates that an elliptical contact surface having a size of about 0.5 mm can be obtained in a direction orthogonal to this. When the optical fiber arrangement interval of the multi-core optical fiber is 0.25 mm, the length in the arrangement direction including the eight-core optical fiber is about 1.9 mm. It is possible.

On the other hand, when the plug material is a silicon material or a ceramic material, its Young's modulus is 170 to 370 GPa.
And the size of the contact surface is about one order of magnitude larger than that of the plastic material.
D is less than 1/2 and W is less than 1/5. For this reason,
It can be said that it is difficult to bring the multi-core optical fiber into contact at once with a plug made of a silicon material or a ceramic material.

According to the present invention, the plug material has a Young's modulus (30 GPa) which is approximately one digit smaller than that of a silicon material or a ceramic material.
An elastic material having the following shape is used, and a convex ellipsoidal surface having the maximum radius in the optical fiber arrangement direction is formed at the plug end surface with the inclined surface as a reference surface. It is possible to make contact at once on the surface.

Here, the air gap at the time of connection caused by the angle error of the plug end face generated at the time of the oblique polishing is absorbed by the compression elastic deformation of the plug and is not generated because the plug is made of an elastic material. In addition, since the optical fiber material is harder than the plug material, the optical fiber connection end face is not formed in a concave shape by polishing, so that the optical fiber connection end face such as that seen with a plug using a silicon material or a ceramic material is not formed. There is no void due to the concave shape. Therefore, in the plug connection state, Fresnel reflection due to the void does not occur, and reflection due to the high-refractive-index work-strained layer during polishing does not propagate to the light source side because it is reflection from the inclined surface. As a result, low-reflection and low-loss connection characteristics can be realized when connecting a multi-core optical fiber without using a refractive index matching agent.

FIGS. 6 and 7 show a multi-core connector plug according to a second embodiment. FIG. 6 is a perspective view thereof, and FIG. 7 is a longitudinal sectional view. 25 is a multi-core connector plug, 26 is a pair of guide pin insertion holes, and 27 is a connection end face of the plug 25. This multi-core connector plug 25 has the same basic structure as that of the first embodiment, and is different from the first embodiment in that the optical fiber connection end face slightly protrudes from the plug connection end face and is fixed. different. It is sufficient that the protrusion amount ΔL is about 1% of the outer diameter of the optical fiber. The protrusion can be formed by utilizing a phenomenon that the optical fiber material is harder than the plug material and the plug material is cut faster as the buffing time is extended. By providing the protrusions of the optical fiber connection end faces in this way, it is possible to more reliably realize multi-core optical fiber collective contact when plugs are connected.

The experimental results are shown below. The optical fiber tape used in the experiment is a four-core optical fiber containing a 1.3 μm band single mode fiber. The optical fiber arrangement interval in the tape is 0.25 mm. Optical fiber outer diameter is 125
A plug component having a mode field diameter of 9.5 μm and a plug part having a mode field diameter of 9.5 μm is formed by molding a silica powder-containing epoxy (Young's modulus: 15 GPa), and the optical fiber is adhesively fixed in the optical fiber insertion hole. Polished diagonally,
Further, buffing was performed on a plastic polishing machine using free abrasive grains. The conditions of the buff polishing are as follows: the radius of curvature of the convex ellipsoidal surface on the axis of the plug is a maximum of about 1000 mm in the optical fiber arrangement direction, and a minimum of 100 to 2 in the direction orthogonal thereto.
00 mm, and the amount of protrusion of the optical fiber was set to about 1% of the outer diameter of the optical fiber. The cross-sectional dimension of the plug is 7
× 3 mm.

The plurality of plugs manufactured as described above are
A plug selected as a standard was connected without a refractive index matching agent, and the amount of reflection and connection loss were measured. The axial load at the time of plug connection was about 1 kgf. As a result, the reflection amount is -59 dB on average and -55 dB at maximum with respect to 32 connection cores,
The connection characteristics of the connection loss were 0.2 dB on average and 0.6 dB at maximum. Further, the characteristics with the refractive index matching agent were measured and compared with the characteristics without the refractive index matching agent. As a result, the difference between the individual reflection amounts with respect to the number of connection cores 32 was 1 dB or less, and the difference between the individual connection losses. Was 0.1 dB or less, no significant difference was observed between the presence and absence of the refractive index matching agent, and it was confirmed that the optical fiber connection end faces could be connected together in a state of direct contact.

Further, the amount of change in the connection loss after 100 times of plug connection / disconnection was 0.1 dB or less, and damage to the optical fiber connection end face after connection / disconnection was not observed. Furthermore, a vibration test (frequency: 10 to 55 Hz, total amplitude: 1.5
mm, vibration direction: orthogonal 3 axis directions, load time: 2 hours in each direction), and impact test (acceleration: 100 G, load time: 6 ms, load direction: orthogonal 3 axis directions, number of loads:
(3 times in each direction) As a result, the connection loss fluctuation amount during the test is 0.03 dB or less at maximum and within the range of the measurement error, and the direct connection state between the plug connection end faces can be maintained even with an external force applied to the connection portion. It was confirmed. From the above results, it has been confirmed that low-loss and low-reflection characteristics can be obtained for the connection of multi-core optical fibers without a refractive index matching agent.

[0037]

As described above, according to the multi-core connector plug of the present invention, the plaque constituent material has a Young's modulus of 30 GPa.
The following elastic material is used to form a convex ellipsoidal surface on the plug connection end surface with an inclined surface having an angle larger than the critical angle for total reflection of light propagating in the optical fiber as a reference surface. Since the connection end faces of the optical fibers are directly contacted collectively on an inclined surface, the connection between the multi-core optical fibers can be performed with low reflection and low loss without using a refractive index matching agent. There are benefits that can be achieved. This advantage is more advantageously exerted in the field of optical fiber connection for optical subscriber systems and optical premises systems where the density and the number of optical fiber cables are increasing.

[Brief description of the drawings]

FIG. 1 is a perspective view of a multicore connector plug according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the plug of FIG. 1 as viewed from a side.

FIG. 3 is a cross-sectional view of the plug of FIG. 1 as viewed from above.

FIG. 4 is a cross-sectional view as viewed from a side surface of a butt connection portion of two plugs in FIG. 1;

FIG. 5 is a cross-sectional view of the two butt connection portions of the plug of FIG. 1 as viewed from above.

FIG. 6 is a perspective view of a multicore connector plug according to a second embodiment.

FIG. 7 is a cross-sectional view of the plug of FIG. 6 as viewed from the side.

FIG. 8 is a longitudinal sectional view of a butt connection portion of a single-core connector plug of the first conventional example.

FIG. 9 is a perspective view of a second conventional multi-core connector plug.

FIG. 10 is a longitudinal sectional view of a butt connection portion of two plugs in FIG. 9;

FIG. 11 is a longitudinal sectional view of a butt connection portion of a multi-core connector plug of a third conventional example.

FIG. 12 is a perspective view of a fourth conventional multi-core connector plug.

FIG. 13 is a longitudinal sectional view of a butt connection part of two plugs of FIG. 12;

[Explanation of symbols]

1, 1 ': optical fiber core, 2, 2': optical fiber,
3, 3 ': first conventional single-core connector plug, 4,
4 ': Connection end faces of plugs 3, 3', 5: Guide sleeve, 6, 6 ': Optical fiber tape, 7, 7': Plural optical fibers, 8, 8 ': Multicore of second conventional example Connector plug, 9: One pair of guide pin insertion holes, 10: Connection-side end face of plug 8, 11: Projection, 12: End face of protrusion 11, 13: 1 pair of guide pins, 14, 14 ': Third Of the conventional single-core connector plug, 15, 15 ': plug 1
4, 14 'connection end face, 16: guide sleeve, 17,
17 ': Fourth conventional multi-core connector plug, 18, 1
8 ': Connection end face of plug 17, 17', 19: Square sleeve, 20: Arc spring, 21, 21 ': Multi-core connector plug of the first embodiment, 22: 1 pair of guide pin insertion holes, 23: Connection end face of plug 21, 24: one pair of guide pins, 25: multi-core connector plug of the second embodiment, 2
6: One pair of guide pin insertion holes, 27: Connection end face of plug 25.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02B 6/32 G02B 6/10 G02B 6/36 G02B 6/40

Claims (2)

(57) [Claims] An optical fiber multi-core connector plug in which a plurality of optical fibers are arranged and fixed between a pair of guide pin insertion holes, wherein the plug is made of an elastic material having a Young's modulus of 30 GPa or less. The connection end face of the plug has a shape of a convex ellipsoid with an inclined plane having a larger angle than the critical angle of total reflection of light propagating in the optical fiber with respect to a plane orthogonal to the optical fiber axis as a reference plane. An optical fiber multi-core connector plug characterized in that the radius of curvature on the axis of the plug is maximized in the direction in which the optical fibers are arranged and minimized in the direction orthogonal to the direction in which the optical fibers are arranged. 2. The optical fiber multi-fiber connector plug according to claim 1, wherein connection end faces of the plurality of optical fibers are slightly protruded from the plug connection end face having the shape of the convex ellipsoid and fixed.