JP6730965B2 - Optical fiber side input/output device - Google Patents

Description

The present disclosure relates to an optical fiber side input/output device that inputs and outputs light from the side of a bent optical fiber.

An optical fiber side input/output device has been proposed which bends an optical fiber with respect to an optical fiber covered with a protective tube (optical fiber with a tube) and inputs/outputs light from a bent portion using a probe (for example, See Patent Document 1.).

FIG. 1 is a diagram illustrating a cross section of an optical fiber 101 with a tube. In the optical fiber 101 with a tube, a core tube 31 composed of a core, a clad, and a sheath is covered with a protective tube 32, and a gap exists between the core wire 31 and the protective tube 32.

When such an optical fiber with a tube is bent, since the protection tube and the optical fiber core wire have different rigidity, the tube is not evenly bent as shown in FIG. 2, and a gap is generated between the optical fiber core wire and the tube. Due to the existence of the air gap, the leaked light from the core of the optical fiber core is reflected at the boundary surface between the coating of the optical fiber core and the air gap, and the intensity of the light leaked to the outside of the optical fiber core is significantly reduced. To do.

Then, in patent document 1, the side input/output device which has the mechanism which crushes a protective tube so that a space|gap may disappear when an optical fiber with a tube is bent is proposed. FIG. 3 is a diagram for explaining the optical fiber side input/output device disclosed in Patent Document 1. In the lateral input/output device of Patent Document 1, an optical fiber with a tube is sandwiched by a jig having a convex curved surface and a jig having a concave curved surface, and the optical fiber with tube is pressed by the convex curved surface to form a guide groove dug into the concave curved surface. This is a structure in which the protective tube is pushed in and crushed over the entire concave curved surface.

JP, 2015-121460, A

T. Uematsu, et. al. , "High-efficiency light injection and extraction using fiber bending", OFC, W2A. 15, Mar. 2017

As shown in FIG. 3, the method of Patent Document 1 has the following problems because the protective tube is crushed over the entire concave curved surface.
(1) Since the protective tube is crushed over the bent portion and the straight portion as a whole, lateral pressure is applied not only to the bent portion but also to the optical fiber core wire in the straight portion, and bending loss increases, which has a great effect on the current communication.
(2) The input/output efficiency increases as the bending is increased to increase the amount of leaked light that can be condensed by the probe, but the input/output efficiency only contributes to the vicinity of the apex of the bent portion. In the conventional method of crushing the protective tube over the entire bent portion and the straight portion, a bending loss other than the bending loss of the bent portion is generated. That is, in the method of Patent Document 1, there is a trade-off relationship between the bending loss and the input/output efficiency, and if the bending of the optical fiber is reduced, the bending loss of the straight portion is reduced, but the bending loss is equivalent to the reduced bending loss. I/O efficiency is reduced.

In order to solve the above-mentioned problems, the present invention reduces bending loss and improves light input/output efficiency when a bend is formed in an optical fiber with a tube and light is input/output from a bent portion using a probe. An object is to provide a compatible optical fiber side input/output device.

In order to achieve the above object, the optical fiber side input/output device according to the present invention is configured to press the optical fiber with a tube only at the apex of bending and limit the amount of crushing the protective tube near the apex. ..

Specifically, the optical fiber side input/output device according to the present invention,
A concave portion curved in the longitudinal direction with respect to the optical fiber with a tube having a structure in which a protective tube covers the optical fiber with a gap interposed therebetween, and light is input and output to and from the optical fiber with the optical fiber with a tube provided with a bend. A first jig having a holding portion for holding the probe optical fiber;
A second jig having a convex portion that comes into contact only with the portion that is the apex of the bend formed in the optical fiber with a tube;
A direction in which the concave portion of the first jig and the convex portion of the second jig approach so that the closest distance S between the concave portion of the first jig and the convex portion of the second jig is S>0. A pressing portion for applying a pressing force to the tube-shaped optical fiber to form the bend,
Equipped with.

The optical fiber lateral input/output device bends the optical fiber core wire by pressing only one point. Therefore, it is not necessary to crush the protective tube over the entire concave curved surface, the lateral pressure to the optical fiber core is only at one location, and the bending loss is small and the influence on the current communication is small. Further, the input/output efficiency can be improved by limiting the amount of crushing the protective tube to the amount of eliminating the gap between the protective tube and the optical fiber core wire.

Therefore, the present invention is an optical fiber side capable of simultaneously reducing bending loss and improving light input/output efficiency when forming a bend in an optical fiber with a tube and inputting/outputting light from a bent portion using a probe. One-way input/output device can be provided.

In the second jig of the optical fiber lateral input/output device according to the present invention, the tip shape of the convex portion is a part of the side surface of the cylinder, and the generatrix of the cylinder is the direction in which the pressing force is applied and the Perpendicular to the longitudinal direction of the optical fiber with a tube,
The radius r of the side surface of the cylinder is r≦R−d−2t
It is preferable to satisfy. Here, d is the diameter of the core wire of the optical fiber with a tube, t is the thickness of the tube, and R is the radius of curvature of the recess of the first jig.

In the optical fiber lateral input/output device according to the present invention, the closest distance S allows the bending loss of the tube-attached optical fiber when the pressing portion forms the bend in the tube-attached optical fiber with a pressing force. Below the value, and with a value designed so that the input efficiency of light from the probe optical fiber to the optical fiber with a tube and the output efficiency of light from the optical fiber with a tube to the probe optical fiber is a specified value or more. It is characterized by

For example, when lateral input/output is performed from an optical fiber with a tube having a tube diameter D of 0.9 mm, a tube thickness t of 0.275 mm, and an optical fiber core diameter d of 0.25 mm, the bending loss is 2 dB or less and the output efficiency is In order to satisfy the requirement of -30 dB or more, the closest distance S should be 0.755 mm or more and 0.84 mm or less.
Further, when lateral input/output is performed from an optical fiber with a tube having a tube diameter D of 0.9 mm, a tube thickness t of 0.2 mm, and an optical fiber core diameter d of 0.25 mm, the bending loss is 2 dB or less and the output efficiency is In order to satisfy the requirement of -30 dB or more, the closest distance S should be 0.63 mm or more and 0.69 mm or less.

The optical fiber side input/output device according to the present invention is characterized by further including an adjusting unit for varying the closest distance S. By providing the adjusting unit, it can be applied to optical fibers with tubes of various sizes.

The probe optical fiber of the optical fiber side input/output device according to the present invention has a structure in which a plurality of optical fibers are arranged in parallel, and the central axis of the optical fiber with a tube and the central axes of all the probe optical fibers are on the same plane. It is characterized by being in. When the tube thickness of the optical fiber with a tube is different, the central axes of leaked light and incident light are different. Therefore, in one probe optical fiber, the input/output efficiency may decrease due to the thickness of the tube of the optical fiber with a tube. In this optical fiber side input/output device, a plurality of probe optical fibers are arranged in advance, and any one of the probe optical fibers is used for input/output to prevent a decrease in input/output efficiency.

The present invention provides an optical fiber side-entry capable of reducing bending loss and improving light input/output efficiency when a bend is formed in an optical fiber with a tube and light is input/output from a bent portion using a probe. An output device can be provided.

It is a figure explaining the cross section of the optical fiber with a tube. It is a figure explaining the subject of the optical fiber with a tube. It is a figure explaining the conventional optical fiber side input/output device. It is a figure explaining the optical fiber side input/output device which concerns on this invention. It is a figure explaining the 2nd jig of the optical fiber side input/output device which concerns on this invention. It is a figure explaining operation|movement of the optical fiber side input/output device which concerns on this invention. It is a figure explaining the design method of the optical fiber side input/output device which concerns on this invention. (A) is a figure explaining the relationship of the bending loss of the optical fiber with a tube with respect to the amount of crushing. (B) is a diagram illustrating the relationship between the crushing amount and the input/output efficiency with the probe optical fiber. It is a figure explaining the design method of the optical fiber side input/output device which concerns on this invention. (A) is a figure explaining the relationship of the bending loss of the optical fiber with a tube with respect to the amount of crushing. (B) is a diagram illustrating the relationship between the crushing amount and the input/output efficiency with the probe optical fiber. It is a figure explaining the optical fiber side input/output device which concerns on this invention.

Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In addition, in the present specification and the drawings, components having the same reference numerals indicate the same components.

(Embodiment 1)
FIG. 4 is a diagram illustrating an outline of the optical fiber side input/output device 301 of the present embodiment. The optical fiber side input/output device 301 is
The protection tube 32 covers the core wire 31 with a gap interposed therebetween, and the concave portion 21 is curved in the longitudinal direction with respect to the optical fiber 101 with tube having a structure in which the optical fiber 101 is bent. A first jig 11 having a holding portion 51 for holding a probe optical fiber 50 for inputting and outputting
A second jig 12 having a convex portion 22 that comes into contact only with the portion that becomes the apex of the bend formed in the optical fiber 101 with a tube;
The concave portion 21 of the first jig 11 and the convex portion 22 of the second jig 12 are such that the closest distance S between the concave portion 21 of the first jig 11 and the convex portion 22 of the second jig 12 is S>0. And a pressing portion (not shown) that applies a pressing force in a direction approaching to form the bend in the optical fiber 101 with a tube,
Equipped with.

FIG. 5 is a diagram illustrating the second jig 12. 5A is a top view, FIG. 5B is a side view, and FIG. 5C is a perspective view. In the second jig 12, the tip shape of the convex portion 22 is a part of the side surface of the cylinder, and the generatrix of the cylinder is the direction in which the pressing force is applied (Z direction) and the longitudinal direction of the optical fiber with a tube ( It is perpendicular to (X direction) and (Y direction).
Here, the radius r of the side surface of the cylinder of the convex portion 22 satisfies r≦R−d−2t. However, d is the diameter of the core wire 31, t is the thickness of the protective tube 32, and R is the radius of curvature of the recess 21 of the first jig 11.

As shown in FIG. 4, when forming a bend in the optical fiber 101 with a tube by the first jig 11 and the second jig 12, only the protective tube 32 near the apex of the bend to be formed is pressed so as to be crushed. FIG. 6 is a cross-sectional view illustrating a state of the optical fiber 101 with a tube near the apex of the bend to be formed. FIG. 6A shows a state before the protective tube 32 is crushed, and FIG. 6B shows a state after the second jig 12 is pushed toward the first jig 11 by the pressing force and the protective tube 32 is crushed. Explaining.

In FIG. 6B, “X” indicates the crushing amount (the pushing amount of the second jig 12), and “S” indicates the first jig 11 and the second jig 12 when the second jig 12 is pushed. It is the closest distance. That is, the optical fiber side input/output device 301 is designed so that a gap of S is formed between the first jig 11 and the second jig 12 even when the second jig 12 is pushed. The closest distance S is set to 0 or more and about d+2t (amount for eliminating the gap of the protective tube 32). The details of the closest distance S and the pushing amount X will be described later.

As shown in FIG. 6B, the optical fiber side input/output device 301 eliminates the gap between the core wire 31 and the protective tube 32 in the vicinity of the apex of bending, thereby reducing the light intensity of leaked light. It can be prevented. Further, in the optical fiber side input/output device 301, the side pressure applied to the core wire 31 due to the pressing force is only in the vicinity of the apex of bending, so that the loss due to the side pressure can be reduced and the influence on the current communication can be reduced.

(Embodiment 2)
In this embodiment, a design procedure of the optical fiber side input/output device 301 will be described.
The design procedure is as follows.
[Step 1]
The radius of curvature R of the recess 21 of the first jig 11 is determined. The bending radius of the central axis of the optical fiber is R-t-d/2.
[Step 2]
The radius of curvature r of the convex portion 22 of the second jig 12 is determined. As described in the first embodiment, r is set to Rd-2t or less.
[Step 3]
The bending loss and the input/output efficiency when the crushing amount X is changed are measured using the first jig 11 and the second jig 12 designed in steps 1 and 2. At this time, it is efficient to change the crushing amount X based on D-2t-d.
[Step 4]
If the condition required for the bending loss is A or less, the condition required for the input efficiency is B or more, and the condition required for the output efficiency is C or more, all of A, B and C are satisfied using the result measured in step 3. Find the crush amount X.
[Step 5]
Since the crush amount X=tube diameter D−closest distance S, the closest distance S is calculated using the crush amount X obtained in step 4.

That is, the closest distance S is such that the bending loss of the optical fiber with a tube 101 is equal to or less than the allowable value when the pressing portion forms the bend in the optical fiber with a tube 101, and the optical fiber with the tube from the probe optical fiber 50. It is a value designed so that the input efficiency of light to the fiber 101 and the output efficiency of light from the optical fiber 101 with a tube to the probe optical fiber 50 are equal to or higher than a specified value.

(Specific example 1)
Experimental verification was performed under the following conditions.
・Tube diameter D: 0.9mm
・Tube thickness t: 0.275 mm
-Diameter d of optical fiber core: 0.25 mm
・Curved radius R of concave surface: 2.125 mm
・Curved radius r of convex surface: 1.0 mm

FIG. 7A is a diagram illustrating the relationship between the crushing amount X and the bending loss of the optical fiber 101 with a tube. Here, the crush amount X is a value obtained by subtracting the closest distance S between the first jig 11 and the second jig 12 from the tube diameter D, that is, X=DS, and the crush amount X in the present embodiment. = 0.9-S. As shown in FIG. 7(A), as the crush amount X increases, the bending loss also increases. Therefore, if the crush amount X is too large, the bending loss increases and the working communication is greatly affected. Therefore, for example, when the bending loss is 2 dB or less, the crushing amount X needs to be 0.145 mm or less.

FIG. 7B is a diagram illustrating the relationship between the crushing amount X and the input/output efficiency with the probe optical fiber 50. The probe optical fiber 50 is a double-clad fiber with a GRIN lens connected to the tip as described in Non-Patent Document 1. Each time the crushing amount X was changed, the probe optical fiber 50 was aligned and arranged so that the input/output efficiency was maximized. In the mark of FIG. 7B, the square points indicate the output efficiency, and the white square points indicate the input efficiency. The white circle points in the mark of FIG. 7B are the normalized leakage light amount P calculated by substituting the bending loss L of FIG. 7A into the following equation, and are leaked from the bent optical fiber core wire. It shows the amount of light.

It can be seen that the input/output efficiency is improved by increasing the crushing amount X from the square points and the white square points in FIG. 7B. Further, it can be seen that when the crushing amount X is 0.1 mm or more, the difference between the input/output efficiency and P becomes smaller. This means that when the crushing amount X is 0.1 mm or more, the voids in the optical fiber with tube 101 are eliminated. In the optical fiber 101 with a tube used in this example, the width of the void is D-2t-d=0.1 mm, which is in agreement with the experimental result.

From the above, in order to suppress bending loss and obtain high input/output efficiency, which is an object of the present invention, it is desirable that the crushing amount X of the tube is 0.1 mm or more and 0.145 mm or less. Further, since a certain amount of input/output efficiency can be obtained without completely removing the void of the optical fiber 101 with a tube, for example, when the output efficiency is -30 dB or more, the crushing amount X is 0.06 mm. And it is sufficient. That is, the closest distance S may be 0.755 mm or more and 0.84 mm or less.

(Specific example 2)
An experiment was conducted by using a protective tube having a size different from that of Example 1 as described below. The conditions other than the tube thickness are the same as in Example 1.
・Tube diameter D: 0.9mm
・Tube thickness t: 0.2 mm
-Diameter d of optical fiber core: 0.25 mm
・Curved radius R of concave surface: 2.125 mm
・Curved radius r of convex surface: 1.0 mm

FIG. 8A is a diagram illustrating the relationship between the crushing amount X and the bending loss of the optical fiber 101 with a tube. FIG. 8B is a diagram illustrating the relationship between the crushing amount X and the input/output efficiency with the probe optical fiber 50. From FIGS. 8A and 8B, it is understood that the bending loss increases and the input/output efficiency also improves as the crushing amount X is increased except for the crushing amount X.

For example, in order to set the bending loss to 2 dB or less, the crushing amount X needs to be 0.27 mm or less. Further, in the tube used in this example, since the void is D-2t-d=0.25 mm, the void disappears when the crushing amount X is 0.25 mm or more, and the difference between the input/output efficiency and P becomes small. ing.

Therefore, in this example as well, in order to obtain high input/output efficiency while suppressing bending loss as in Example 1, it is desirable that the crushing amount X of the tube be 0.25 mm or more and 0.27 mm or less. Further, for example, when the output efficiency is required to be -30 dB or more, the crushing amount X may be 0.21 mm or more. That is, the closest distance S may be 0.63 mm or more and 0.69 mm or less.

(Summary of specific examples of design methods)
The design method of this embodiment will be summarized below for each specific example. Here, as an example, A is 2 dB or less, B is -30 dB or more, and C is -40 dB or more.
(Specific example 1)
[Step 3] Since D-2t-d=0.1 mm, bending loss and input/output efficiency are measured in the vicinity of 0.1 mm as shown in FIGS. 7(A) and 7(B).
[Step 4] In order to satisfy all of A, B and C, it is understood from FIGS. 7A and 7B that the crushing amount X should be 0.06 to 0.145 mm.
[Step 5] Since S=DX and D=0.9 mm, S may be 0.755 to 0.84 mm.
(Specific example 2)
[Step 3] Since D-2t-d=0.2 mm, the bending loss and the input/output efficiency around 0.2 mm are as shown in FIGS. 8A and 8B.
[Step 4] In order to satisfy all of A, B and C, it is clear from FIGS. (A) and (B) that the crushing amount X should be 0.21 to 0.27 mm.
[Step 5] Since S=DX and D=0.9 mm, S may be set to 0.63 to 0.69 mm.

(Embodiment 3)
The optical fiber lateral input/output device of the present embodiment is characterized by further including an adjusting unit (not shown) for varying the closest distance S to the optical fiber lateral input/output device 301 of the first embodiment. To do. In order to deal with the optical fibers with tubes having different dimensions as in the specific example of the second embodiment, it is desirable to provide an adjusting unit for adjusting the crushing amount X according to the dimensions of the optical fibers with tubes.

For example, in the case of the optical fiber with a tube of the specific example 1 of the second embodiment, the adjusting unit adjusts the S to be 0.755 to 0.84 mm, and in the case of the optical fiber with a tube of the specific example 2, S is Is adjusted to 0.63 to 0.69 mm.

Since the size of the optical fiber with a tube can be determined in advance, the operator determines the size and switches S by the adjusting unit of the optical fiber side input/output device. Further, when the tube thickness t of the optical fiber with a tube is different, the hardness of the tube in the side direction is different. By utilizing this, the adjusting unit may measure the difference in hardness of the tubes in advance, determine the difference, and adjust S.

By thus providing the optical fiber side input/output device with the adjusting portion, it is possible to adapt to optical fiber core wires with tubes having different dimensions, and one device can be used as in the specific examples 1 and 2 of the second embodiment. It is possible to realize a lateral input/output device having various characteristics.

(Embodiment 4)
FIG. 9 is a diagram illustrating the optical fiber side input/output device 302 of this embodiment. The optical fiber side input/output device 302 has a structure in which the probe optical fiber 50 arranges a plurality of optical fibers 55 in parallel with the optical fiber side input/output device 301 of the first embodiment, and is the center of the optical fiber 11 with a tube. The axis and the central axes of all the optical fibers 55 are on the same plane.

When the dimensions of the optical fiber with tube 101 are different, the optimum centering position of the probe optical fiber 50 is different in the direction α in the figure. This is because the leak position differs depending on the tube thickness. Therefore, the optical fiber side input/output device 302 uses the probe optical fiber 50 in which a large number of optical fibers 55 are arranged in the direction α (see FIG. 9B). With this configuration, it is possible to input and output light using any one of the optical fibers 55 even if the tube optical fibers 101 have different tube thicknesses. Therefore, the optical fiber side input/output device 302 can input/output light from the side of the bent portion without lowering the input/output efficiency even when the dimensions of the optical fiber with tube 101 are different. Particularly, the probe optical fiber 50 in which the optical fibers 55 are arranged in contact with each other as shown in FIG. 9B is desirable.

(Effect of the present invention)
The optical fiber side input/output device according to the present invention can obtain the following effects.
In an optical fiber side input/output device that bends an optical fiber with a tube and uses a probe optical fiber to input and output light from the bent part, reducing the bending loss reduces the influence on the current communication and also has a high input/output efficiency. Can be obtained.

11: 1st jig|tool 12: 2nd jig|tool 21: recessed part 22: convex part 31: core wire 32: protective tube 50: probe optical fiber 51: holding|maintenance part 55: optical fiber 101: optical fiber 301 with a tube, 302: Optical fiber side input/output device

Claims (7)

A concave portion curved in the longitudinal direction with respect to the optical fiber with a tube having a structure in which a protective tube covers the optical fiber with a gap interposed therebetween, and light is input to and output from the optical fiber with the optical fiber with a tube provided with a bend. A first jig having a holding portion for holding the probe optical fiber;
A second jig having a convex portion that comes into contact only with the portion that becomes the apex of the bending formed in the optical fiber with a tube;
A direction in which the concave portion of the first jig and the convex portion of the second jig approach so that the closest distance S between the concave portion of the first jig and the convex portion of the second jig is S>0. A pressing portion for applying a pressing force to pressing the convex portion only with the convex portion to form the bend in the optical fiber with a tube,
Equipped with
In the second jig, the tip shape of the convex portion is a part of the side surface of the cylinder, and the generatrix of the cylinder is perpendicular to the direction in which the pressing force is applied and the longitudinal direction of the optical fiber with a tube. , The radius of the side surface of the cylinder is smaller than the radius of curvature of the concave portion of the first jig, and the convex portion is not deformed when pressing the optical fiber with tube. Output device. The radius r of the side surfaces of the pre-Symbol cylinder r ≦ R-d-2t
The optical fiber side input/output device according to claim 1, wherein
Here, d is the diameter of the core wire of the optical fiber with a tube, t is the thickness of the tube, and R is the radius of curvature of the recess of the first jig. The closest distance S is such that when the pressing portion forms a bend in the optical fiber with a tube by a pressing force, the bending loss of the optical fiber with a tube is equal to or less than an allowable value, and the optical fiber with a tube from the probe optical fiber. The optical input efficiency to the fiber and the optical output efficiency from the optical fiber with a tube to the probe optical fiber are values designed so as to be equal to or more than specified values. Optical fiber side input/output device. 4. The optical fiber lateral input/output device according to claim 1, wherein the closest distance S is 0.755 mm or more and 0.84 mm or less. 4. The optical fiber side input/output device according to claim 1, wherein the closest distance S is 0.63 mm or more and 0.69 mm or less. The optical fiber side input/output device according to claim 1, further comprising an adjusting unit that varies the closest distance S. The probe optical fiber is a structure in which a plurality of optical fibers are arranged in parallel,
7. The optical fiber side input/output device according to claim 1, wherein a central axis of the optical fiber with a tube and a central axis of all the probe optical fibers are on the same plane.

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