JP2019028348A - Optical fiber lateral input/output device - Google Patents

Abstract

To provide an optical fiber lateral input/output device capable of attaining compatibility between a reduction in bending loss and an improvement in input/output efficiency of light when, after a bending is formed in a tubed optical fiber, the light is input/output to/from the bent part using a probe.SOLUTION: An optical fiber lateral input/output device according to the present invention forms a bending in a coated optical fiber by pressing thereagainst at only one point. Accordingly, there is no need to squeeze a protection tube over a whole recessed curve surface, and a side pressure is exerted on the coated optical fiber at only one place, thus causing small bending loss and having a small influence on active communication. Further, an input/output efficiency can be increased by limiting an amount by which the protection tube is squeezed, to an amount by which a gap between the protection tube and the coated optical fiber is eliminated.SELECTED DRAWING: Figure 4

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 that bends an optical fiber with respect to an optical fiber (optical fiber with a tube) covered with a protective tube and inputs / outputs light using a probe from the bent portion has been proposed (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 protective tube 32 covers the core 31 made of a core, a clad, and a coating, and a gap exists between the core 31 and the protective tube 32.

  When such an optical fiber with a tube is bent, the protective tube and the optical fiber core are different in rigidity, so that they are not bent uniformly as shown in FIG. 2, and the gap is generated between the optical fiber core and the tube. Due to the presence 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 remarkably reduced. To do.

  Therefore, Patent Document 1 proposes a side input / output device having a mechanism for crushing the protective tube so that there is no gap when the optical fiber with the tube is bent. FIG. 3 is a diagram illustrating an optical fiber side input / output device disclosed in Patent Document 1. In FIG. In the lateral input / output device of Patent Document 1, an optical fiber with a tube is sandwiched between a jig having a convex curved surface and a jig having a concave curved surface, and the optical fiber with a tube is pressed by the convex curved surface to form a guide groove dug into the concave curved surface. It is the structure which pushes in and crushes a protection tube over the whole concave curved surface.

JP2015-121460A

T.A. 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 it crushes the protective tube over the entire concave curved surface.
(1) Since the protective tube is crushed over the entire bent portion and the straight portion, a side pressure is applied not only to the bent portion but also to the optical fiber core wire at the straight portion, resulting in an increase in bending loss and a great influence on the current communication.
(2) The input / output efficiency increases as the bending increases to increase the amount of leaked light that can be collected by the probe, but only the vicinity of the apex of the bent portion contributes to the input / output efficiency. In the conventional method of crushing the protective tube over the entire bending portion and the straight portion, bending loss other than the bending loss of the bending portion is generated. That is, in the method of Patent Document 1, the bending loss and the input / output efficiency are in a trade-off relationship. If the bending of the optical fiber is reduced, the bending loss of the straight portion is reduced, but the amount corresponding to the reduced bending loss is reduced. I / O efficiency of the system is reduced

  In order to solve the above-described problems, the present invention reduces bending loss and improves light input / output efficiency when bending light is input to and 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 presses only the apex of bending the optical fiber with a tube and limits the amount of crushing the protective tube near the apex. .

Specifically, the optical fiber side input / output device according to the present invention is:
A concave portion that is curved in the longitudinal direction with respect to the optical fiber with the tube having a structure in which the protective tube covers the core wire across the gap, and light is input to and output from the core wire of the optical fiber with the tube that is bent. A first jig having a holding portion for holding the probe optical fiber;
A second jig having a convex portion that comes into contact with only a 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 approaches the convex portion of the second jig so that the closest distance S between the concave portion of the first jig and the convex portion of the second jig satisfies S> 0. A pressing portion that applies a pressing force to the optical fiber with a tube to form the bend,
Is provided.

  The optical fiber side input / output device forms a bend in the optical fiber core wire by pressing only one point. For this reason, it is not necessary to crush the protective tube over the entire concave curved surface, the side pressure to the optical fiber core wire is only one place, the bending loss is small, and the influence on the current communication is small. Furthermore, by limiting the amount of crushing the protective tube to an amount that eliminates the gap between the protective tube and the optical fiber core wire, the input / output efficiency can be increased.

  Therefore, the present invention provides an optical fiber side that can achieve both a reduction in bending loss and an improvement in light input / output efficiency when bending is performed on an optical fiber with a tube and light is input / output from the bent portion using a probe. One-way input / output device can be provided.

In the second jig of the optical fiber side input / output device according to the present invention, the tip shape of the convex portion is a part of a side surface of a cylinder, and the bus line of the cylinder and the direction in which the pressing force is applied Perpendicular to the longitudinal direction of the optical fiber with 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 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 side input / output device according to the present invention, the closest distance S is such that when the bending portion is formed on the optical fiber with a tube by the pressing portion, the bending loss of the optical fiber with the tube is allowed. And a value designed so that the light input efficiency from the probe optical fiber to the optical fiber with the tube and the light output efficiency from the optical fiber with the tube to the probe optical fiber are not less than a specified value. It is characterized by being.

For example, when side 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 In order to satisfy the requirement of −30 dB or more, the closest distance S is set to 0.755 mm or more and 0.84 mm or less.
When side 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 In order to satisfy the requirement of −30 dB or more, the closest distance S is set to 0.63 mm or more and 0.69 mm or less.

  The optical fiber side input / output device according to the present invention further includes an adjustment unit that varies 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 tube and the central axes of all the probe optical fibers are on the same plane. It is characterized by that. If the tube thickness of the optical fiber with tube is different, the central axis of the leaked light or incident light is different. For this reason, with a single probe optical fiber, the input / output efficiency may decrease depending on the thickness of the tube of the optical fiber with tube. In this optical fiber side input / output device, a plurality of probe optical fibers are arranged in advance, and input / output is performed using any one of the probe optical fibers to prevent a decrease in input / output efficiency.

  The present invention provides an optical fiber side entrance that can reduce bending loss and improve light input / output efficiency when a tube is bent and light is input / output from the 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 apparatus which concerns on this invention. It is a figure explaining the 2nd jig | tool 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 apparatus 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 figure explaining the relationship of the input-output efficiency with a probe optical fiber with respect to the amount of crushing. 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 figure explaining the relationship of the input-output efficiency with a probe optical fiber with respect to the amount of crushing. It is a figure explaining the optical fiber side input / output apparatus 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 the present specification and drawings, the same reference numerals denote the same components.

(Embodiment 1)
FIG. 4 is a diagram for explaining the outline of the optical fiber side input / output device 301 of the present embodiment. The optical fiber side input / output device 301 is:
Light is applied to the concave portion 21 that is bent in the longitudinal direction with respect to the optical fiber 101 with the tube having a structure in which the protective tube 32 covers the core wire 31 with the gap interposed therebetween, and to the core wire 31 of the optical fiber with tube 101 that is bent. A first jig 11 having a holding part 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 with only a portion that becomes the apex of the bending 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 so 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. A pressing portion (not shown) that applies a pressing force in a direction in which the optical fiber 101 with a tube approaches the optical fiber 101 with a tube,
Is provided.

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 direction in which the pressing force is applied to the generatrix of the cylinder (Z direction) and the longitudinal direction of the optical fiber with a tube ( It is perpendicular to the (X direction) (Y direction).
Here, the radius r of the cylindrical side surface of the convex portion 22 satisfies r ≦ Rd−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 the first jig 11 and the second jig 12 form a bend in the optical fiber 101 with a tube, 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 the appearance of the optical fiber 101 with a tube near the apex of the bending to be formed. 6A shows a state before the protective tube 32 is crushed, and FIG. 6B shows a state after the second jig 12 is pushed in the direction of the first jig 11 by the pressing force and the protective tube 32 is crushed. Explains.

  In FIG. 6B, “X” is the crushing amount (pushing amount of the second jig 12), and “S” is the first jig 11 and the second jig 12 when the second jig 12 is pushed. 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 to eliminate the gap between the protective tubes 32). Details of the closest distance S and the push amount X will be described later.

  As shown in FIG. 6B, the optical fiber side input / output device 301 reduces the light intensity of the leaked light due to the air gap by eliminating the air gap between the core wire 31 and the protective tube 32 near the apex of the bend. Can be prevented. Further, in the optical fiber side input / output device 301, since the side pressure applied to the core wire 31 due to the pressing force is only near the apex of bending, the loss due to the side pressure can be reduced and the influence on the working communication can be reduced.

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

  That is, the closest distance S is the bending loss of the optical fiber 101 with the tube being less than an allowable value when the bending portion is formed on the optical fiber 101 with the tube by the pressing portion, and the light with the tube from the probe optical fiber 50. This is a value designed so that the light input efficiency to the fiber 101 and the light output efficiency from the tube-equipped optical fiber 101 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: 0.275mm
-Diameter d of optical fiber core wire: 0.25 mm
-Concave curved surface radius of curvature R: 2.125 mm
-Curvature radius of curvature r: 1.0 mm

  FIG. 7A is a diagram for explaining the relationship of the bending loss of the optical fiber with tube 101 to the crushing amount X. FIG. Here, the crushing 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 = D−S. In this embodiment, the crushing amount X = 0.9-S. As shown in FIG. 7A, since the bending loss increases as the crushing amount X increases, the bending loss increases when the crushing amount X is increased too much, and the influence on the working communication becomes large. 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 for explaining 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 having a GRIN lens connected to the tip as described in Non-Patent Document 1. Each time the crushing amount X is changed, the probe optical fiber 50 is aligned so that the input / output efficiency is maximized. In the mark of FIG. 7B, the square point is the output efficiency, and the white square point is the input efficiency. 7B is a normalized leakage light amount P calculated by substituting the bending loss L of FIG. 7A into the following equation, and is leaked from the bent optical fiber. It shows the amount of light.

  From the square points and white square points in FIG. 7B, it can be seen that increasing the crushing amount X improves the input / output efficiency. It can also be seen that when the crushing amount X is 0.1 mm or more, the difference between the input / output efficiency and P decreases. This means that when the crushing amount X is 0.1 mm or more, there is no gap in the optical fiber 101 with a tube. The tube-equipped optical fiber 101 used in this specific example has a gap width of D−2t−d = 0.1 mm, which is consistent with the experimental results.

  From the above, in order to obtain high input / output efficiency while suppressing bending loss, which is the object of the present invention, it is desirable that the tube crushing amount X 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 gap of the optical fiber 101 with a tube, for example, when the output efficiency is required to be −30 dB or more, the crushing amount X is set to 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 using a protective tube having a dimension different from that of Example 1 and a tube thickness t as follows. 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 wire: 0.25 mm
-Concave curved surface radius of curvature R: 2.125 mm
-Curvature radius of curvature r: 1.0 mm

  FIG. 8A is a diagram for explaining the relationship of the bending loss of the optical fiber with tube 101 to the crushing amount X. FIG. FIG. 8B is a diagram for explaining the relationship of input / output efficiency with the probe optical fiber 50 with respect to the crushing amount X. 8A and 8B, it can be seen that as the crushing amount X is increased except for the crushing amount X and the crushing amount X is increased, the bending loss is increased and the input / output efficiency is also improved.

  For example, in order to make the bending loss 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 gap is D-2t-d = 0.25 mm, the gap 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 specific example as well as in specific example 1, in order to obtain high input / output efficiency while suppressing bending loss, it is desirable to set the tube crushing amount X to 0.25 mm or more and 0.27 mm or less. For example, when the output efficiency is required to be −30 dB or more, the crushing amount X may be set to 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 is summarized for each specific example below. 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, the bending loss and input / output efficiency measured around 0.1 mm are as shown in FIGS.
[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 = D−X and D = 0.9 mm, S may be set to 0.755 to 0.84 mm.
(Specific example 2)
[Step 3] Since D-2t-d = 0.2 mm, the bending loss and input / output efficiency measured around 0.2 mm are as shown in FIGS.
[Step 4] In order to satisfy all of A, B and C, it can be seen from FIGS. 4A and 4B that the crushing amount X should be 0.21 to 0.27 mm.
[Step 5] Since S = D−X and D = 0.9 mm, S may be 0.63 to 0.69 mm.

(Embodiment 3)
The optical fiber side input / output device of the present embodiment further includes an adjustment unit (not shown) that varies the closest distance S to the optical fiber side input / output device 301 of the first embodiment. To do. In order to deal with tube-equipped optical fibers having different dimensions as in the specific example of the second embodiment, it is desirable to include an adjustment unit that adjusts the crushing amount X according to the dimensions of the tube-equipped optical fibers.

  For example, in the case of the optical fiber with a tube according to the first specific example of the second embodiment, the adjustment unit is S in the case of the optical fiber with a tube according to the second specific example so that S is 0.755 to 0.84 mm. Is adjusted to 0.63 to 0.69 mm.

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

  In this way, by providing the adjustment unit in the optical fiber side input / output device, it is possible to adapt to the optical fiber cores with tubes having different dimensions. A side input / output device having various characteristics can be realized.

(Embodiment 4)
FIG. 9 is a diagram illustrating the optical fiber side input / output device 302 of the present embodiment. The optical fiber side input / output device 302 has a structure in which the probe optical fiber 50 has a plurality of optical fibers 55 arranged in parallel to the optical fiber side input / output device 301 of the first embodiment. The axis and the central axis of all optical fibers 55 are on the same plane.

  When the dimensions of the optical fiber with tube 101 are different, the optimum alignment position of the probe optical fiber 50 is different in the direction α in the figure. This is because the leak position varies depending on the tube thickness. Therefore, the optical fiber side input / output device 302 uses a 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, light can be input / output through any one of the optical fibers 55 even if the tube thickness of the optical fiber with tube 101 is different. Therefore, the optical fiber side input / output device 302 can input / output light from the side of the bent portion without reducing the input / output efficiency even when the dimensions of the optical fiber with tube 101 are different. In particular, 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 inputs / outputs light using a probe optical fiber from the bent part, reducing the bending loss and reducing the influence on the current communication, and high input / output efficiency Can be obtained.

11: 1st jig | tool 12: 2nd jig | tool 21: Concave part 22: Convex part 31: Core wire 32: Protection tube 50: Probe optical fiber 51: Holding part 55: Optical fiber 101: Optical fiber 301 with a tube 301, 302: Optical fiber side input / output device

Claims (7)

A concave portion that is curved in the longitudinal direction with respect to the optical fiber with the tube having a structure in which the protective tube covers the core wire across the gap, and light is input to and output from the core wire of the optical fiber with the tube that is bent. A first jig having a holding portion for holding the probe optical fiber;
A second jig having a convex portion that comes into contact with only a 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 approaches the convex portion of the second jig so that the closest distance S between the concave portion of the first jig and the convex portion of the second jig satisfies S> 0. A pressing portion that applies a pressing force to the optical fiber with a tube to form the bend,
Optical fiber side input / output device. In the second jig, the tip shape of the convex part is a part of a side surface of the cylinder, and the generating line of the cylinder is perpendicular to the direction in which the pressing force is applied and the longitudinal direction of the optical fiber with tube. ,
The radius r of the side surface of the cylinder is 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 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 the bending loss of the optical fiber with the tube being less than an allowable value when the bending portion is formed on the optical fiber with the tube by the pressing portion with the pressing force, and the light with the tube from the probe optical fiber. The light input efficiency to the fiber and the light output efficiency from the optical fiber with a tube to the probe optical fiber are values designed so as to be a specified value or more. Optical fiber side input / output device.   The optical fiber side input / output device according to any one of claims 1 to 3, wherein the closest distance S is not less than 0.755 mm and not more than 0.84 mm.   The optical fiber side input / output device according to any one of claims 1 to 3, 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 any one of claims 1 to 5, further comprising an adjustment unit that varies the closest distance S. The probe optical fiber has 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.

Images