WO2004053547A1

WO2004053547A1 - Optical fiber terminal, manufacturing method thereof, optical coupler, and optical part

Info

Publication number: WO2004053547A1
Application number: PCT/JP2003/015938
Authority: WO
Inventors: Kiyoshi Morita; Tetsuo Takano; Yoshiatsu Yokoo
Original assignee: Hoya Corp; Kiyoshi Morita; Tetsuo Takano; Yoshiatsu Yokoo
Priority date: 2002-12-12
Filing date: 2003-12-12
Publication date: 2004-06-24
Also published as: JPWO2004053547A1; JP3949137B2; AU2003289054A1

Abstract

There is provided a practical optical fiber terminal capable of sufficiently satisfying the specifications of reflection loss and coupling efficiency normally required in optical parts. The optical fiber terminal has an optical fiber (101) having a core (101a) at the center and a clad (101b) around its external circumference. The optical fiber has an end surface attached to one end surface of a coreless fiber (102, 103) made from a material having a refraction factor substantially identical to the core and uniform. When the light propagating in the core of the optical fiber spreads in the coreless fiber and goes outside from the other end surface of the coreless fiber, the beam diameter is adjusted to be within the coreless fiber external diameter by setting the coreless fiber optical path length to be below 1 mm and the other end surface of the coreless fiber (102, 103) vertical to optical axis of the optical fiber (101).

Description

Description Optical fiber terminal, method for manufacturing the same, optical coupler, and optical component

Technical field

The present invention relates to an optical fiber terminal used for optical communication and the like, a method of manufacturing the same, and an optical coupler and an optical component using the optical fiber terminal.

Background art

With the development of optical communication, miniaturization of optical devices and optical components to be used is desired. Among the methods of performing optical coupling between optical fibers, a lens is installed near the light-emitting end of the optical fiber as an optical coupling method that has a small loss and allows various optical elements to be installed therebetween. In general, a method is generally used in which a light beam emitted from an optical fiber is converted into a parallel light beam, and a similar optical system is assembled on the light receiving side to couple the light to a regenerated optical fiber. An element having a function of converting a light beam emitted from an optical fiber into a parallel light beam is generally called a fiber collimator, and the combination of the optical fiber and the lens is one type of a fiber collimator.

Optical coupling loss and reflection loss are generally used as indices indicating the performance of this type of fiber collimator. The optical coupling loss reflects the luminous flux quality of the parallel luminous flux, and affects the numerical aperture (hereinafter abbreviated as NA) of the optical fiber used, the exit end face shape, aberration at the exit end face, lens performance, and the like. Is done.

On the other hand, the reflected light represented by the reflection loss as an index causes a loss of output energy at the output end of the optical fiber or an effect of impairing the stable operation of the light source. Among the effects of these reflected lights, especially for the stable operation of the light source The effect is one of the major problems in the optical communication field. In recent years, in the field of optical communication, a distributed feedback laser has been generally used as a light source. This type of laser light source is characterized in that laser oscillation tends to be unstable due to so-called return light that travels backward in the optical fiber and reaches the light source, and as a result, output power fluctuates easily. In other words, an increase in the reflected light, in other words, a small return loss means that the return light is large, and increases the fluctuation of the output power.

—Generally, in a fiber collimator, in order to suppress the output fluctuation of the laser light source to a negligible level, the end face reflection loss shown in the following equation (1) is 50 dB The above is required.

End face reflection loss = -1 0 X 1 og (IR / I0) (1) where IR is the amount of reflected light, and 10 is the amount of incident light.

At present, as a method for obtaining the reflection loss, a method is used in which the end face of the optical fiber is inclined with respect to the optical axis. An optical fiber end of this type is obtained by inserting an optical fiber into a glass capillary and polishing the end face of the glass with an angle of about 4 ° to 8 °. As a result, the reflected light at the end face is attenuated in a clad mode, so that a large reflection loss can be obtained. Further, a reflection loss of 60 dB or more can be obtained by combining with the AR coating on the surface. Can be. This method has been the mainstream method because it is an extremely simple method.

By the way, when a collimator using an optical fiber terminal having such a beveled end face is used in an optical component, special attention must be paid. This point will be described with reference to FIG.

In a refractive index distribution lens (GRIN Lens), which is often used as a collimator lens of a fiber collimator, since the imaging state depends on the lens length (Pitch), in the case of 0.25 Pitch, (a ) (GRIN) Lens) When a light source is placed on the end face of 1101, collimated light is emitted from the other end face. Actually, as shown in (b), the refractive index distribution lens (GRIN Lens) 1102 has a lens length of about 0.23 Pitch, and it has an arrangement that allows flexibility in adjusting the position of the light source. I have.

The optical path when the collimated light with this configuration is combined is shown in (c). The light emitted from the optical fiber terminal 1103 is inclined by about 3.8 ° and enters the gradient index lens 1104 due to the influence of the beveled end surface described above. Offset by δ1 from axis. Also, since the end face of the GRIN lens 110 4 is inclined similarly to the end face of the optical fiber terminal 110 3, the angle with respect to the GRIN lens 110 4 Therefore, the outgoing beam has a certain angle (0) with respect to the optical axis of the outgoing light from the optical fiber end 1103. Therefore, in this collimator combination, optical coupling cannot be performed unless the original optical axis is shifted by δ2 in order to match the optical axes. It is for this reason that position adjustment is difficult when performing optical coupling with a conventional collimator.

In order to eliminate the optical path shift as described above, all the optical fiber ends and the lens end faces should be perpendicular to the optical axis. However, in this case, all end face reflections will be reflected as return light. The reflection loss caused by the refractive index difference between the glass end surface and air is 14.7 dB, and even if good AR coating (R 0.2%: 27 dB) is applied to this. However, the reflection loss at the end face is about 42 dB, and the above-mentioned required specification of 50 dB or more cannot be achieved.

As a means for solving such a problem, there has been known a structure in which a coreless fiber is fused to an end face of an optical fiber and a required return loss is obtained by diffusing a light beam in the coreless fiber ( See Patent Document 1). This structure increases the diameter of the emitted light beam so that the reflected light and It uses the principle of increasing the return loss by reducing the overlap integral with a single defield diameter (about 10 μm). According to this structure, when the end face of the optical fiber is set to 0 ° to 6 ° and the length of the coreless fiber is set to 1 to 4 mm, a reflection loss of 60 dB or more is obtained in combination with the AR coat. It is said that you can do it.

In addition, a structure using a graded index (GI) fiber has been proposed as a configuration of a collimator having an optical fiber end face perpendicular to the optical axis (see Patent Document 2). Figures 17 (a) and 17 (b) show an example of the structure of this collimator and the state in which light is transmitted. First, in Fig. 17 (a) and (b), reference numeral 1201 denotes an optical fiber (SMF), reference numeral 122 denotes a coreless fiber, reference numeral 124 denotes a graded index (GI) fiber, and reference numeral 120 denotes a fiber. 4C indicates an emission end, 1207 indicates a beamwest diameter, 1208 indicates reflected light from an end face, and 1211 indicates a beamwest distance. As shown in Fig. 17 (a), this structure is an optical fiber end structure having a light condensing function, and the beam West distance of light from the outgoing end 1204C is 1 2 1 1 It is described that the optical fiber end structure is capable of variably setting a desired value and a beamwest diameter of 127, respectively, that is, independently and variably setting them.

Patent Document 1: Japanese Patent Application Laid-Open No. 7-281054

Patent Document 2: Japanese Patent Application Laid-Open No. 2003-43073

Disclosure of the invention

However, the present inventors fabricated and evaluated an optical fiber terminal with a coreless fiber using a standard fiber having an outer diameter of 125 μπι, and as a result, showed that the reflection loss was 60 dB or more. As a result of investigating the coupling efficiency of a pair of collimators by placing a lens in front of the fiber, the coupling efficiency greatly depends on the coreless fiber length.When the coreless fiber length is 1 mm or more, the coupling efficiency dramatically increases. I found it to get worse.

It was also found that it is extremely difficult to accurately control the length of the coreless fiber when fabricating an optical fiber terminal connected to a coreless fiber having a desired length of less than 1 mm.

Further, in the collimator having a configuration including the optical fiber (SMF) 1201, the coreless fiber 122, and the GI fiber 122 described with reference to FIG. 7 As shown in FIG. 7 (b), the end face reflected light 128 at the emission end 124C is focused back to the same position as the light emission position. Here, in order to reduce the end face reflected light 128, it is conceivable to apply AR coating to the emitting end 1204C. However, with the current capability of the AR coating film, even if the AR coating is applied as described above, the end face reflected light 128 of about 42 dB returns, and the reflection of 50 dB or more, which is generally required, is required. Loss cannot be realized.

The present invention has been made in view of the above circumstances, and has a practical optical fiber terminal capable of sufficiently satisfying the specifications of the reflection loss and the coupling efficiency required for ordinary optical components, and an optical terminal using the same. It is an object of the present invention to provide a component and an optical coupler, and to provide a manufacturing method capable of easily manufacturing the optical fiber terminal.

The optical fiber terminal according to the first aspect of the present invention includes a core made of a material having substantially the same uniform refractive index as the core, on an end face of an optical fiber having a core at the center and a cladding at the outer periphery thereof. In an optical fiber terminal in which one end surface of a fiberless fiber is joined, the beam diameter when the light transmitted through the core of the optical fiber spreads inside the coreless fiber and exits from the other end surface of the coreless fiber is the coreless fiber. The feature is that the optical path length of the coreless fiber is set to be within the outer diameter of the coreless fiber. By setting the output beam diameter within the outer diameter of the coreless fiber, the It is possible to perform optical coupling exactly the same as the optical coupling. As a result, the straightness of the emitted beam is excellent, and the levels of reflection loss and coupling efficiency required for practical use can be obtained.

The optical fiber terminal according to the second aspect of the present invention is the optical fiber terminal according to the first aspect, wherein an optical path length of the coreless fiber is less than 1 mm. Even if the length of the coreless fiber is limited within this range, a return loss of 50 dB or more can be easily ensured after the AR coating. Therefore, there is no problem in practical use. In addition, features such as no misalignment and easy assembly adjustment are not affected at all by limiting the length of the coreless fiber to less than 1 mm.

An optical fiber terminal according to the third aspect of the invention is characterized in that, in the first or second aspect, the outer diameter of the optical fiber is different from the outer diameter of the coreless fiber. As long as the fusion does not hinder, even if the diameter of the coreless fiber is different from the diameter of the optical fiber, the same performance as the inventions of claims 1 and 2 can be obtained. In addition, in this optical fiber terminal, since there is a diameter difference between the optical fiber and the coreless fiber, the position of the fusion point can be easily recognized, and there is an advantage that the length of the coreless fiber can be easily adjusted.

The optical fiber terminal according to claim 4 is the optical fiber terminal according to claim 1 or 2.

The optical fiber and the coreless fiber have substantially the same outer diameter, and the central axis of the optical fiber and the central axis of the coreless fiber are shifted from each other and joined. I do. As long as the fusion does not hinder, even if the center axis of the optical fiber and the center axis of the coreless fiber are different, the same performance as the inventions of claims 1 and 2 can be obtained. In this optical fiber terminal, the fusion point between the optical fiber and the coreless fiber is Due to the step, the position of the fusion point can be easily recognized, and the length of the coreless fiber can be easily adjusted.

The optical fiber terminal of the invention according to claim 5 is the optical fiber terminal according to any one of claims 1 to 4, wherein the other end surface of the coreless fiber is perpendicular to an optical axis of the optical fiber. It is characterized by being formed in That is, the angle of the incident and outgoing end of the light is 0 ° within the processing tolerance range with respect to the plane perpendicular to the axis of the light emitted from the fiber. Therefore, the light emitted from the optical fiber always coincides with the optical axis, which enables optical coupling on a straight groove, which has been impossible by the displacement of the light beam due to the oblique end surface. The invention set forth in claim 6 is characterized in that, in any one of claims 1 to 5, an antireflection film is provided on the other end surface of the coreless fiber. By applying an anti-reflection film (AR coating) 'according to the intended wavelength on the other end surface of the coreless fiber (the end surface opposite to the joint side with the optical fiber), reduction of direct return light and other light Optical interference with the element, ghost, and the like are prevented, and good optical coupling characteristics can be obtained.

An invention according to claim 7 is an optical coupler including the optical fiber terminal according to any one of claims 1 to 6,

At least one or more selected from an aspherical lens, a spherical lens, a spherical lens, or a drum lens is arranged on the other end side of the coreless fiber on the optical axis of the optical fiber. It is a coupler. The drum lens is, for example, a spherical lens having a cylindrical shape by centering the periphery of a spherical lens by grinding or polishing.

For example, the combination of the optical fiber terminal and the collimator lens enables optical coupling using collimated light. Also, a combination of an optical fiber terminal and a finite system lens is possible. Like this Combining a fiber end with a lens makes it possible to achieve optical coupling with a low or lower coupling loss than a collimator fabricated using a normal optical fiber end.

Further, due to the combination of the optical fiber end and the collimator lens, as shown in FIG. 17, all the end face reflections from the lens become diffused light, and the light does not return to the light emitting position. Therefore, there is an advantage that the arrangement of the lens does not reduce the reflection loss of the entire system. Also, the beam diameter can be expanded within the range of glass cavities in mm or the outer diameter of the lens, so that the propagation distance can be increased.

An optical component according to claim 8 is a combination of the optical fiber terminal according to any one of claims 1 to 6 and an optical element having an optical multiplexing / demultiplexing function. Features. For example, optical coupling using collimated light is realized by using the above-mentioned optical fiber terminal, and a dielectric multilayer filter having a characteristic of reflecting only a specific wavelength and transmitting other wavelengths is inserted in the meantime. A function of multiplexing / demultiplexing light can be provided. In this case, the use of the above-mentioned optical fiber terminal enables optical coupling between a pair of collimators on a common V-groove formed on the substrate, thereby reducing the number of components and greatly simplifying the process. Is possible.

The invention according to claim 9 is the method for manufacturing an optical fiber terminal according to any one of claims 1 to 6, wherein a first step of coupling the optical fiber and the coreless fiber is provided. And a second step of polishing the other end face of the coreless fiber to adjust the length of the coreless fiber to a desired value. In the second step, the reflection loss of the bonded body of the optical fiber and the coreless fiber is provided. The feature is to adjust the length of the coreless fiber to a desired value while measuring the amount. That is, in the present invention, in the second step of defining the length of the coreless fiber to be bonded to the optical fiber, the coreless fiber is ground and polished while monitoring the reflection loss of the fused optical fiber terminal. Accordingly, the core fiber can be adjusted to a desired length without directly observing the optical fiber and the coreless fiber. In this case, since there is a one-to-one relationship between the coreless fiber length and the return loss, by measuring the return loss on the finish polished surface of the optical fiber end with the core fiber being manufactured. It is possible to define the coreless fiber length with an accuracy of 1 jm. As a result, even when it is difficult to observe the fusion point between the optical fiber and the coreless fiber with an optical microscope, the fusion point can be reliably detected, and accurate adjustment of the length of the coreless fiber is expected. it can.

The invention according to claim 10 is the method for producing an optical fiber terminal according to claim 3, wherein a first step of joining the optical fiber and the coreless fiber having different diameters, A second step of detecting a joining point between the optical fiber and the coreless fiber, and a third step of cutting the coreless fiber at a designated position set with reference to the joining point, wherein the second step The step is characterized in that the joining point is detected using an optical microscope and a defocused microscope image.

The invention according to claim 11 is the method for manufacturing an optical fiber terminal according to claim 4, wherein the optical fibers having substantially the same diameter and the respective central axes of the coreless fibers are mutually aligned. A first step of shifting and joining, a second step of detecting a joining point between the optical fiber and the coreless fiber, and cutting the core fiber at a designated position set with reference to the joining point A third step, wherein in the second step, an optical microscope is used, and the junction is detected by a defocused microscope image. The length of the coreless fiber in the optical fiber terminal according to the present invention must be accurately formed. Therefore, in the invention of claim 10, the diameter of the optical fiber to be joined and the coreless fiber are made different from each other, and in the invention of claim 11, the optical fiber to be joined and the coreless fiber are By displacing the center axes of the fibers with each other, it is possible to detect the joint point between the optical fiber and the coreless fiber, and cut the coreless fiber at a specified position set based on this joint point.

In this case, the detection of the connection point is performed by observing the connection point in a state of a deformed force using a general microscope. By observing the junction with a microscope in a defocused state, it is possible to determine the junction even if the outer diameter of the optical fiber and the coreless fiber is as small as several μm. This is because it has been found for the first time by the present inventor. In other words, according to the research of the present inventors, when the joint point between the optical fiber and the coreless fiber is determined by observing (in a focused state) with a microscope, the difference in outer diameter is large in the method according to the conventional technology. In this case, it can be discriminated, but as the outer diameter difference becomes smaller, it becomes gradually more difficult. When the outer diameter difference becomes about several μm, it is found that it is impossible to determine at all.

However, in the course of this research, the inventor accidentally observed a joint having an outer diameter difference of several μm in a defocused state, and found that this joint could be distinguished. Thus, by using the defocused microscope image, the fusion point after fusion can be identified very easily. This makes it possible to easily produce an optical fiber terminal having an outer diameter almost equal to the outer diameter of the optical fiber and having a desired coreless fiber length. Furthermore, by using this method, the fusion point can be accurately recognized. You can determine the cut portion of the bar, by cutting at that point, it is possible to adjust the length of the coreless fiber with a precision of 1 0 _beta m. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic sectional view of an optical fiber terminal according to an embodiment of the present invention, in which (a) is a configuration diagram of the optical fiber terminal according to the first embodiment, and (b) is an optical fiber terminal according to the second embodiment. FIG. 3C is a configuration diagram illustrating a state in the middle of manufacturing, and FIG. 4C is a configuration diagram of the optical fiber terminal of the first embodiment of the second embodiment.

FIG. 2 is a characteristic diagram showing a relationship between a coreless fiber length and an output beam diameter.

FIG. 3 is a characteristic diagram showing a relationship between a coreless fiber length and a reflection loss. FIG. 4 is a process chart showing a procedure for manufacturing an optical fiber terminal.

Fig. 5 shows the observation image when the fusion point of the optical fiber and the coreless fiber was observed with an optical microscope. (A) is an observation image in focus, and (b) is a deliberate out-of-focus image. It is a figure which shows the observation image in the state (defocused state) which carried out, respectively.

FIG. 6 is an explanatory diagram of a method for manufacturing an optical fiber terminal according to the present invention.

FIG. 7 is an explanatory diagram in the case of measuring the reflection loss of the optical fiber terminal of the present invention.

FIG. 8 is an explanatory diagram in the case of measuring the coupling loss of the optical fiber terminal of the present invention.

FIG. 9 is a configuration diagram of an optical multiplexer / demultiplexer to which the optical fiber terminal according to the present invention is applied, (a) is a plan view, and (b) is a side view.

FIG. 10 is an explanatory diagram of a problem in an optical fiber terminal in which a coreless fiber is joined to an end face of the optical fiber.

FIG. 11 is an explanatory diagram of a problem in the conventional optical coupling. FIG. 12 is a characteristic diagram showing the relationship between the coreless fiber length and the return loss.

FIG. 13 is a characteristic diagram showing the relationship between the coreless fiber length and the coupling loss.

FIG. 14 is a schematic sectional view of an optical fiber terminal according to a different embodiment of the present invention.

FIG. 15 is an explanatory diagram of a method of manufacturing the optical fiber terminal shown in FIG.

FIG. 16 is an explanatory diagram of a configuration of a collimator including an optical terminal and a collimating lens according to the present invention.

FIG. 17 is an explanatory diagram of a configuration of a collimator using a GI fiber according to a conventional technique.

1 0 1 Optical fiber

1 0 1a core

1 0 1 b Cloud

1 0 2 Core ResPhino

1 0 2 a One end face

1 0 2 b Other end

1 0 3 Core ResFin

1 0 3 a One end face

1 0 3 b Other end

4 0 1 Fiber coating

4 0 2 Optical fiber

4 0 3

4 0 4 Objective lens

4 0 5 Fiber cutter blade 4 0 6 Glass drill

4 0 7 Optical fiber terminal

5 0 2 Distorted point

5 0 4 Fiber cutter blade

6 0 1 Optical fiber terminal

6 0 2 Fiber chuck

6 0 3 Objective lens

6 0 4 Huai Park Lever Blade

6 0 5 V-groove for fixing the fiber

6 0 6 Microphone

7 0 1 Return loss measuring instrument

7 0 2 Patch cord

7 0 3 Optical fiber terminal

7 0 4 Connector

8 0 1 LD light source

8 0 2 Patch code

8 0 3 Optical fiber terminal

8 0 4 Optical stage

8 0 5 Collimate lens

8 0 6 Detector

8 0 7 Connector

9 0 1 Glass substrate

9 0 2 collimator

9 0 3 V groove

9 0 4 Wavelength selection filter

9 0 5 Glass substrate for collection 9 0 6 Reflecting mirror

1001 Optical fiber (SMF)

1 0 0 1a core

1 0 0 2 Coreless Phino

1 0 0 3 Beam

1 1 0 1 GRIN lens

1 1 0 2 GRIN lens

1 1 0 3 Optical fiber terminal

1 1 0 4 GRIN lens

1 2 0 0 Optical fiber terminal

1 2 0 1 Optical fiber (SMF)

1 2 0 1a core

1 2 0 1 b Cloud

1 2 0 2 Coreless fiber

1 2 0 3 Optical fiber terminal

1 2 4 4 GI fiber

1 2 0 4 C Injection end

1 2 0 5 Collimate lens

1 2 0 6 Key Villa

1 2 0 7 Beam West Diameter

1 2 0 8 Edge reflected light

1 2 0 9 Edge reflected light

1 2 1 0 Collimated light

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 (a) is a configuration diagram of an optical fiber terminal according to the first embodiment, (b) is a configuration diagram showing a state in the process of manufacturing the optical fiber terminal of the second embodiment, and (c) is a second embodiment. 1 is a configuration diagram of an optical fiber terminal.

The optical fiber terminal shown in Fig. 1 (a) is a single-ended cylindrical fiber with a standard outer diameter of 125 μm having a core 101a at the center and a cladding 101b at the outer periphery. On one end face of the mode optical fiber (SMF) 101, one end face 102a of a coreless fiber (CLF) 102 made of a material having substantially the same uniform refractive index as the core 101a is attached. After welding and setting the length of the coreless fin 102 to less than l mm, the other end face 102b of the coreless fin 102 is illuminated with the light of the optical fin 101. It is polished at 0 ° to the plane perpendicular to the axis.

Here, setting the length of the coreless fin 102 to less than 1 mm is an indispensable condition for an optical fiber terminal for performing optical coupling. By defining the length of the coreless fiber 102 in this manner, the light transmitted through the core 101a of the optical fiber 101 spreads within the coreless fiber 102 and the coreless fiber 102 The beam diameter when emitted from the other end face 102 b to the outside is within the outer diameter of the coreless fiber 102.

In this optical fiber terminal, the light emitted from the core 101a propagates while diffusing through the coreless fiber 102, so that the diameter of the beam emitted from the other end face 102b of the coreless fiber 102 increases. . Since the reflection loss can be increased according to the length of the coreless fiber 102, there is no need to make the exit surface oblique, and as a result, the exit beam goes straight. By setting the length L of the coreless fiber 102 to an appropriate value as described above, the output beam diameter is within the outer diameter of the coreless fiber 102, so it is completely equivalent to a normal optical fiber Optical coupling can be performed. Therefore, the straightness of the output beam is superior to that of the conventional optical fiber terminal having a beveled end face. In addition, it is possible to obtain the reflection loss and the coupling loss of the practically required levels. Also, by using this optical fiber terminal, the optical coupling between the collimators can be performed in a straight line, so that the position adjustment becomes easy.

In order to obtain an optical fiber terminal having such a structure, first, an optical fiber 101 and a coreless fiber 102 are prepared, and the coatings of both are removed to a length that allows sufficient fusion. Subsequently, the coreless fiber 102 is cut at a position of 2 mm from the coating removal position of the coreless fiber 102 using a fiber cleaver to form a fused end face. The fusion end face is similarly made on the optical fiber 101 side. Then, both are installed in a standard single-core fiber splicer, and fusion is performed under appropriate conditions. Normally, the end faces of the fusion-spliced parts are integrated, so that the fusion point cannot be recognized from the appearance or observation with a microscope.

For example, if the fiber core can be viewed directly, as in the case of the Direct Core Monitoring method (DCM method), the fusion point can be accurately determined. However, if it is sufficient to determine the length of the coreless fiber on the order of millimeters, the coreless fiber 102 should be determined using the coreless fiber coating removal position as a guide. ,.

Next, the significance of reducing the length of the coreless fin 102 to less than l mm will be described. Here, for comparison, by cutting the coreless fiber 102 at positions 19 mm, 18 mm, 17 mm, and 16 mm from the coating removal position of the coreless fiber 102, respectively, Samples of coreless fiber-coupled optical fiber terminals with core lengths of 102 mm, 2 mm, 3 mm, and 4 mm were prepared. The end face angle is almost 0 ° for all samples. When the optical characteristics of these four samples were evaluated, the following results were obtained.

First, as for the reflection loss, as shown in Fig. 12, AR coating It was confirmed that the reflection loss in the case of no more than 37 dB. However, the return loss value for the length O mm (without coreless fiber) is set to 14.7 dB. Therefore, it can be seen that when the AR coating is applied, all the samples have a reflection loss of 50 dB or more.

Next, as shown in FIG. 8, the amount of coupling loss of a pair of optical fibers with a coreless fiber was measured using a collimating lens. In FIG. 8, reference numeral 800 denotes an LD light source, reference numeral 800 denotes a patch cord, reference numeral 803 denotes an optical fiber terminal, reference numeral 804 denotes an optical stage, reference numeral 805 denotes a collimating lens, and reference numeral 806 denotes a collimating lens. The detector and 807 are connectors. Light emitted from the LD light source 801 enters the other optical fiber terminal 803 from one optical fiber terminal 803 via the collimating lenses 805, 805, and is detected by the detector 800. Received at 6.

As a result of measuring the amount of coupling loss in such a configuration, as shown in FIG. 13, the coupling loss value was 1 dB or more in all samples. Considering that the AR coating is not applied to the end face of the optical fiber, this coupling loss is a very large value for an optical fiber terminal part, and the collimator currently required cannot be manufactured as it is. I found out.

The cause was considered as follows. That is, as shown in FIG. 10, when light is emitted from the core 1001a of the optical fin 1001, the beam 1003 is spread by diffraction, so that the beam depends on the propagation distance. The diameter r expands. In an optical fiber terminal with a coreless fiber, the beam diameter r at the emission end face depends on the length of the coreless fiber. Therefore, if the length of the coreless fiber 100 exceeds a certain length, the beam diameter r exceeds the optical fiber diameter R. It was thought that diffraction and the like would occur, and that the uniformity of the emitted light would be lost and the coupling loss would increase.

Therefore, the relationship between the coreless fiber length and the output beam diameter was examined. The result Figure 2 shows. From the relationship shown in Fig. 2, when the length of the coreless fiber is determined, the maximum outer diameter of the optical fiber that ideally enables lossless optical coupling is also determined. Now, the beam diameter is defined as the length at which the light intensity is 1 / e ² with respect to the distribution center (hereinafter, the beam diameter is assumed to be based on this definition). At this time, the output beam diameter has already exceeded the standard fiber outer diameter of 125 μιη. This is considered to be the cause of the large coupling loss in the optical fiber terminal with coreless fiber fabricated as described above.

Therefore, under the assumption that the outer diameter of the optical fiber is fixed to a certain value in the optical fiber terminal having the structure of Fig. You need to limit the From the above, in order to fabricate an optical fiber terminal having the structure shown in Fig. 1 (a) and having both the reflection loss and the coupling loss, the standard outer diameter (125 μπι ), We have found that the length of the coreless fiber 102 must be less than 1 mm.

However, it has been found that when actually manufacturing this optical fiber terminal, it is necessary to make a structure to which such a short coreless fiber 102 is added, so that the manufacturing operation becomes considerably difficult.

The inventors of the present invention have conducted intensive studies and, as a result, have come to find a solution to all the problems that have arisen in producing the above-described optical fiber terminal. The details will be described below.

Fig. 4 shows the flow of a typical optical fiber terminal fabrication method. The left diagram (A) is a flowchart, and the right diagram (B) is a diagram schematically showing the contents of each step (a) to (d) in the flowchart. In this flow, first, (a) an optical fiber (SMF) 402 and a coreless fiber (CLF) 402 Perform the fusion splicing process with 3. Splicing of optical fibers is not necessarily limited to fusion, but fusion is easily performed with a commercially available fusion device and is the most excellent means of connection performance and reliability. Connection is used. When connecting, in order to simplify the measurement work to be performed later, prepare a standard optical fiber 402 with an outer diameter of 125 μππι with a connector at one end and an arbitrary length. The film is removed to the extent that the end can be fused (fiber coating 401), and cut using a fiber cleaver to produce a connection end surface. Next, a coreless fiber 403 having an outer diameter of 122 μπι is prepared by an arbitrary length, and the film is removed and the end face is similarly removed.

As a method for reducing the outer diameter of the coreless fiber 400 from the standard diameter, chemical etching can be used. Alternatively, when the coreless fiber 403 is manufactured, the outer diameter may be manufactured. The optical fiber 402 and the coreless fiber 403 are installed in a standard single-core optical fiber fusion splicer, and the outer diameter standard alignment is used to determine the outer diameter standard between ordinary quartz glass single mode fibers. The fusing operation is performed under the fusing conditions.

Fig. 1 (b) shows a state in which the two (optical fiber and coreless fiber) are connected. In the figure, the difference between the outer diameters is exaggerated, but it is difficult to see the difference with an outer diameter difference of about 3 μm. The joints maintain the same strength as normal fusion of same diameter fibres.

After such fusion, a step of cutting the coreless fiber 403 at a predetermined position is performed. This step is divided into (a) a step of accurately determining a fusion point, and (b) a step of cutting the coreless fiber 403 at a position of an accurate length from the fusion point. When materials having substantially the same refractive index are fused and connected, it is very difficult to optically recognize the fusion point because the two cannot be distinguished. If cutting at an approximate length is permitted, it is possible to measure the length based on the film removal point etc. as described in the previous example This method is inadequate when an accurate length measurement of about 10 μm is required for a short length of force less than 1 mm.

If a fiber core can be directly observed by using a DCM optical system, it is possible in principle to determine the fusion point based on the presence or absence of a core. However, this method requires a high-precision stage, a CCD camera and a laser light source, and is a very expensive system. In addition, it is difficult to combine such an optical system with a fiber cutter.Furthermore, if the magnification is large, there is a possibility that the cutting point may be out of the field of view when the coreless fiber length is long. is there.

In order to avoid these problems, it is useful to provide the outer diameter difference between the optical fiber and the coreless fiber as described above. In other words, the provision of the diameter difference makes it easy to determine the fusion point according to the method described below, and determines the coreless fiber length with an accuracy of 10 μm at any length. It is possible to cut it. The details are described below.

The step of judging the fusion point and the step of cutting at the designated length are performed as follows. As shown in Fig. 6, a commercially available ultrasonic fiber cleaver having a fiber cleaver blade 604, a uniaxial stage with a micrometer capable of chucking an SMF (optical fiber terminal) 601 with a coreless fiber Prepare 606, and set the fiber cleaver under the objective lens 603 of the stereomicroscope to observe the cutting point. An observation magnification of about 10 to 20 is sufficient.

Fix the optical fiber end (SMF with coreless fiber) 601 fused with the above-mentioned optical fiber and coreless fiber so that the fusion point comes near the fiber cleaner blade 604. The fiber end 601 is semi-fixed on the V groove 605, and one end of the optical fiber end 601 is chucked to the uniaxial stage 606 with a micrometer using the fiber chuck 602. With micrometer When the stage 606 is sent, the optical fiber terminal 601 being chucked moves by the amount indicated by the scale on the fiber fixing V-groove 605 of the fiber cleaver. .

By the way, as described above, the optical fin (SMF) and the coreless fiber have a very small difference in diameter, but with the difference in diameter used in the present embodiment, the image focus is normally adjusted. Even if the magnified image is observed, the fusion point (arrow position) cannot be recognized, as shown in Fig. 5 (a). In the figure, the left side is the optical fiber (SMF) 402, and the right side is the coreless fin (CLF) 403, and the joining point cannot be confirmed. However, when the image is in focus and slightly defocused, as shown in Fig. 5 (b), a distorted portion 502 appears in the defocused microscope image. Is done. The strained portion 502 coincides with the fusion point between the coreless fins 403 and the optical fiber (SMF) 402. This distortion was not observed when the diameters of the two coincided with each other, and shifted slightly from the image focal position only when a diameter difference of about 2 m (about 1.6% of the diameter) was given. It was confirmed that it was clearly observed at the image position. The direction of shifting may be either the near side or the far side. In addition, 504 in FIG. 5 shows a cutter cutting blade for reference.

Return to FIG. The fusion point found by this method is moved to the uniaxial stage with a micrometer 606, and is placed at the tip of the cutting blade 604 of the fiber cleaver. With this as the origin, the uniaxial stage with a micrometer 606 is sent again by the required length of the coreless fiber, and the coreless fiber is cut at the point where the feed has been completed and cut. In this way, an optical fiber terminal 601 in which a coreless fiber of a desired length is fused to the tip of the optical fiber (SMF) is completed. According to this method, the length of the coreless fiber portion can be controlled with an accuracy of 10 / zm. In this example, since the tip is ground and Z-polished in the subsequent steps, an optical fiber terminal having a coreless fiber length of 100 μm was manufactured in consideration of the grinding amount in advance.

Next, returning to FIG. 4, the step of bonding the glass cavities in (d) will be described. The function as an optical fiber is sufficient at the end of the above work.However, when performing an optical evaluation or mounting on an optical component, the optical fiber terminal is often fixed to a glass gallery 406 and used. Done.

In this example, this optical fiber terminal (SMF with coreless fiber) 40

7 into an outer diameter φ 1.8 mmZ inner diameter 1 2 6 μππΖ 6 mm long glass capillary 40 6, apply a UV adhesive at the time of insertion, cure it, and 7 and glass cavities 406 were fixed. At the time of fixing, it is desirable to fix the cable 406 so that both end faces of the optical fiber terminal 407 coincide with each other. Since the diameter of the coreless fin 400 is 122 μιη, there is a difference of 4 μπι in the inner diameter from the capillary 406, but with such a diameter difference, the optical fiber terminal 407 and the capillary Since the eccentricity between 6 and the increase in the adhesive layer are almost negligible, there is no practical problem. As the adhesive, a thermosetting adhesive may be used.

Next, the optical polishing step (e) of the end face of the optical fiber is performed as follows. Optical polishing is performed to obtain good and stable optical performance. Optical polishing can be easily performed by using a commercially available optical fiber end-face polishing machine. For polishing, fix the glass / scraper 406 to a polishing jig, and rough / primary / secondary polishing

_ Finish polishing in order.

Naturally, the end face is ground by this polishing, and the length of the coreless fiber at the tip of the glass cavities 406, that is, the ends of the optical fiber terminals 407 is shortened. Even if the polishing time is fixed, the actual amount of grinding is often not constant due to the difference in the load pressure applied to the polishing surface or the difference in the condition of the polishing sheet. It is difficult to specify the amount of grinding only by the above.

Also, if the adhesive adheres to the periphery of the fiber, fine distortion cannot be recognized even in the above-described observation using a defocus microscope image, and the fusion point may not be accurately recognized.

Therefore, the following method is adopted in such a case. In this method, as shown in Fig. 3, the relationship between the length of the coreless fiber and the return loss is experimentally obtained. The length of the coreless fiber and the return loss correspond one-to-one. Therefore, at the stage where the final polishing in the polishing process is completed, as shown in Fig. 7, the connector 704 is connected to the patch code 702 of the reflection loss measuring device 701, and the measurement sample (here, optical fiber) By monitoring the reflection loss of the emitting end face of the terminal 703), the length of the coreless fiber can be accurately known.

Therefore, without directly observing the length of the coreless fiber, the length can be easily known accurately by monitoring the return loss. Since the amount of grinding can be finely adjusted by using the monitored values as a guide, an optical fiber terminal with a coreless fiber whose length is controlled with high accuracy of Ιμπι can be manufactured. In the present embodiment, data that grinding was performed about 600 m by one polishing operation was separately obtained, so that an optical fiber terminal having a core fiber length of 100 m was used. By the above-mentioned tip polishing operation, an optical fiber terminal having a coreless fiber length of about 400 μm can be obtained. As described above, the tip of the cavity is polished while measuring the return loss, and the polishing is terminated when the measured return loss reaches the target value [(f) of the flow in FIG. 4].

Finally, by forming an anti-reflection film on the end face of the coreless fiber of the optical fiber terminal manufactured in the above process, the end face reflection, interference, or ghost is suppressed. [4th (G) of the flow of the figure].

Through the above operations, the fabrication of an optical fiber terminal that achieves both high reflection loss and low coupling loss, does not cause optical axis misalignment, and can be mounted on optical components is completed.

Needless to say, the above manufacturing method is an example, and the procedure and method are not limited to this.

Three optical fiber end samples as shown in the table below are manufactured by the above manufacturing method, and the sample names are SampleA to C, respectively. The core fiber length shown in this table is the length determined from the return loss before AR coating. Return loss is the measured value obtained by measuring with a return loss measuring device after AR coating. For comparison, a commercially available SMF (single mode optical fiber) with a 0 ° end face and an AR coating was prepared and used as Sample D.

【table 1 】

Sample A is the output fiber, the other samples are the receiving fibers, and an aspherical collimating lens (F = 3, NA = 0.22) is placed between them as shown in Fig. 8. The coupling loss was measured. As the light source, an LD light source with ぇ = 1.55 / m and sufficient sensitivity in the same wavelength range Using a photodetector, the distance between the collimating lenses was set to 100 mm, and the optical coupling loss was measured. The results are shown in Table 2.

[Table 2]

As shown in the table above, it was demonstrated that a combination of optical fiber terminals with coreless fibers can achieve a coupling loss of about 0.2 dB. This performance is similar to or better than that of a normal optical fiber terminal (Saraple D).

As described above, it has been proved that the above-mentioned manufacturing method can easily manufacture an optical fiber terminal satisfying the target specification and of a practical level. The collimated beam's linearity was also demonstrated because the optical coupling can be performed without changing the optical stage even when the samples are exchanged during coupling loss measurement.

The length of the coreless fiber may be appropriately adjusted in accordance with the required specification of the return loss within a range that satisfies the conditions described in claim 1. Ideally, the end face angle of the coreless fiber is 0 ° in order to provide linearity of the light beam.However, a slight angle within the tolerance range of the polishing process poses a serious problem in practice. Absent.

The preferred calculation range for the length of the coreless fiber is approximately 900 μπι for the longer one. This is because when the beam diameter intensity of light is defined as the length of the l Z e ² in pairs to the distribution center, the beam at the output end The length is approximately i 20 m, which is almost equal to the outer diameter of the standard fiber. However, the longer the coreless fiber is, the larger the loss may be when passing through the glass medium, and if the end face of the optical fiber is chipped, it becomes a factor of beam scattering, so the longer fiber is preferable. The range is determined to be 900 / im or less, more preferably 50 5μπι or less. On the other hand, the shorter usable limit length is 300 μm. This is because in order to achieve a return loss of 50 dB with the optical fiber terminal alone after AR coating, the return loss obtained at the end face without AR coating should be 23 dB or more. It is the required length. However, AR coating does not always provide an ideal return loss of 27 dB. Experimentally, if it is 25 dB or more without AR coating, it is almost certain that 50 dB or more can be obtained. Therefore, the shorter range is preferably 300 μπι or more. From the above, the most preferable length of the coreless fiber for use is 3Ομππι or more and less than 50Ομππι.

The preferred range when the outer diameter of the coreless fiber is different from that of the optical fiber is as follows. When changing the outer diameter, there are two ways: making the fiber thicker and smaller than the standard fiber. In general, an optical fiber terminal is generally inserted into a commercially available glass cabinet, fixed, and used. Therefore, when used within the range of commercial standard products, it is advantageous to make the coreless fiber to be connected thin. The main purpose of changing the diameter is to easily observe the fusion point after fusion, and to make it easier to observe the distortion at the fusion point described above, reduce the diameter by at least 2 m or more. There is a need. The strain point becomes clearer as the diameter difference is larger, but if the diameter difference is too large, eccentricity is likely to occur with respect to the inner diameter of the capillary when fixing to the capillary, and the adhesive used for fixing to the capillary The weather resistance may be degraded due to the inevitable increase in the amount of carbon. Therefore, the coreless A preferable range for the diameter difference of the eyepiece is appropriately smaller than the optical fiber (SMF) by about 2 to 10 μm.

The optical fiber terminals of the first and second embodiments according to the present invention have been described above. In the first and second embodiments, the diameter of the coreless fiber and the diameter of the optical fiber (SMF) are determined in order to easily and accurately grasp the fusion point between the coreless fiber and the optical fiber. He gave a different example. In addition, according to the present invention, in order to easily and accurately grasp the fusion point between the coreless fiber and the optical fiber, the center axes of the optical fiber (SMF) and the coreless fiber are shifted instead of using different diameters. May be joined together. In this way, the same effect as changing the diameter of the two can be obtained by intentionally generating the step, so that the defocused microscopic image can be obtained by using an optical microscope. Thus, the fusion point can be determined very easily. Therefore, an optical fiber terminal according to a third embodiment of the present invention, which has a configuration in which the optical fiber (SMF) and the coreless fiber are bonded with the central axes shifted, will be described with reference to the drawings. In this case, the axis deviation is Ιμπ! About 5 μΐη is preferable. If the deviation is 1 μm or more, it is easy to determine the junction point.If the deviation is 5 μm or less, the relative displacement of the beam emission position does not increase, so the attenuation is out of expectation. And the possibility of affecting the strength of the joint is eliminated.

FIG. 14 shows an optical fiber terminal according to a third embodiment of the present invention, and FIG. 15 shows an outline of the manufacturing process.

First, as shown in FIG. 14, an optical fiber terminal 1200 of the third embodiment has an optical fiber having a central core 120 la and an outer peripheral cladding 120 b. The end face of the fiber (SMF) 1201 is made of a material having substantially the same uniform refractive index as the core 1 201a and having an outer diameter of Coreless fin (CLF) 122, which is almost the same as optical fin (SMF), is arranged and fused. What is important here is that the relative center positions of the optical fiber (SMF) 1201 and the coreless fiber 122 are shifted.

Next, an example of a method for manufacturing the optical fiber terminal shown in FIG. 14 will be described with reference to FIG. The fiber diameter of the optical fiber used is not particularly limited, but here, as a specific example, the optical fiber (SMF) 122 (1 210 1 a, 120) 1b) and the coreless fiber 1 202 will each have a standard outer diameter of 125 m. '

When manufacturing the optical fiber terminal 1200, first, an optical fiber (SMF) 1201 having a standard outer diameter of 125 μπι is prepared. Here, an optical fiber (SMF) 1201 having a connector at one end is prepared for an arbitrary length in order to easily perform a measurement operation to be performed later. The other end of the optical fiber (SMF) 121 is stripped of the coating to the extent that it can be fused, and cut using a fiber talper to make a connection end face. Next, a coreless fiber 122 of the same diameter and having a diameter of 125 / z m is prepared for an arbitrary length, and the coating is removed and the end face is cut in the same manner.

Next, as shown in Fig. 15 (a), the end face of the optical fiber (SMF) 1201 and the end face of the coreless fiber 122 are opposed to each other, and the standard single-core optical fiber fusion is performed. Once installed, perform the outer diameter center alignment once. When the outer diameter reference alignment is completed, as shown in Fig. 15 (b), shift the center position of the 1.5 µπ coreless fiber optic aperturer. Then, as shown in Fig. 15 (c), the outer diameter reference fusion conditions of ordinary quartz glass single mode fibers (by setting the optical fiber fusion splicer TYPE-85SE manufactured by Sumitomo Electric Industries, Ltd. Fiber type: SM FIBER STD, alignment method: Outer diameter Outer diameter: Same conditions) Perform the fusion work and join. By this fusion work, optical fiber

(SMF) The coreless fiber and the coreless fiber are integrated, and the joint strength is adjusted by adjusting the center of the optical fiber by aligning the outer diameter of the same diameter fiber or by aligning the core. It is equivalent to the fusion performed.

The small step caused by this relative deviation produces the same effect as the step generated at the fusion point between the optical fibers with different diameters as described above. Can be applied. Therefore, the step of determining the fusion point and the step of cutting the coreless fiber at the specified length can be performed in exactly the same manner as the fusion of optical fibers having different diameters described above. Optical fiber terminations with similar effects, performance and features can be made.

An embodiment of an optical component using the optical fiber terminal will be described below. Here, an optical multiplexer / demultiplexer having four input / output ports was manufactured using one wavelength selection filter as shown in FIG.

Fig. 9 (a) is a schematic diagram of the optical multiplexing / demultiplexing module viewed from above. The optical paths in the module are shown by thin lines in the figure. In this module, a wavelength selection filter 904, a correction glass substrate 905, and a reflection mirror 906 are arranged on a glass substrate 901 and a V-groove 903 provided in the glass substrate 901 The collimator 902 is located at the bottom.

The wavelength-division multiplexed light input from “In” is split into transmitted light and reflected light by the wavelength selection filter 904, and output to “Drop Port” and “0 ut Port”, respectively. You. Further, the externally inserted light is incident from “Add Port J”, passes through the wavelength selection filter 904, and is multiplexed into “Out Port J.” The collimator 90 used here No. 2 is manufactured by bonding the above-mentioned optical fiber end and the aspherical lens in the same glass tube. The function is the same as that of a normal ADM, but each collimator 902 is fixed on a V-groove 903 on a glass substrate 901, especially the “In” The meter 902 and the “Drop Port” collimator 902 are on a straight V-groove 903. In the conventional collimator, the optical axis shift occurs, and it is impossible to use the V-groove 903 as a guide groove for the optical axis. The axis of the collimator 902 used does not occur at all, so if there is no optical element such as a wavelength selection filter 904 between the collimators 902, there is almost no positional adjustment and light Coupling becomes possible.

If the glass substrate (wavelength selection filter 904) enters obliquely between the collimator lights, the light will be displaced parallel to the original optical axis depending on the thickness of the glass substrate. As shown in the figure, this deviation does not pose a major problem because the original optical axis is maintained by using a similar glass substrate (a glass substrate for correction 905) to maintain the original optical axis. Therefore, in this configuration, all optical paths can be adjusted only by adjusting the angles of the reflection mirrors 906 on both sides of the wavelength selection filter 904. As described above, by using the optical fiber terminal of the present invention, the V-groove 903 serves as a guide groove for the collimator light. Integration is technically possible. Furthermore, assembling can be simplified and adjustment time can be reduced.

Similar results were obtained by using a spherical lens, a spherical lens, and a drum lens instead of the aspheric lens used for the collimator 902.

The embodiments of the optical fiber terminal according to the present invention and the optical component using the optical fiber terminal have been described above. Further, the combination of the optical fiber terminal and the collimator lens according to the present invention enables optical coupling using collimated light. Further, the optical fiber terminal according to the present invention and a finite system Optical coupling is also possible by combination with a lens. Thus, by combining the optical fiber terminal according to the present invention and the lens, it is possible to achieve optical coupling having a low coupling loss equal to or less than that of a collimator manufactured using a normal optical fiber terminal. Become. Therefore, the configuration will be described below with reference to the drawings for a fourth embodiment.

FIG. 16 is an explanatory diagram of a configuration of a collimator including an optical terminal and a collimating lens according to the present invention. In FIG. 16, reference numeral 1201 denotes an optical fiber (SMF), reference numeral 122 denotes a coreless fiber, and reference numeral 123 denotes an optical fiber (SMF) and a coreless fiber. 2 shows an optical fiber terminal having the following. Reference numeral 125 denotes a collimating lens, and reference numeral 125 denotes a cavity such as glass. Further, reference numeral 1209 denotes end face reflected light, and reference numeral 1 210 denotes collimated light.

The light emitted from the optical fiber terminal 123 having the optical fiber (SMF) 1201 and the coreless fin 122 according to the present invention has a collimating lens 12 2 After passing through 05, the collimated light becomes 1 210. At this time, the end face reflected light from the collimating lens lens 125 becomes all scattered light, and the light does not return to the light emitting position of the optical fiber terminal 123. As a result, there is an advantage that the arrangement of the collimating lens 125 does not reduce the reflection loss of the entire system. In addition, the beam diameter of the collimated light 1210 can be widened within the range of a mm or a lens outer diameter, so that the propagation distance can be increased.

It is a preferable configuration to apply the combination of the optical fiber terminal and the collimator lens according to the fourth embodiment to the above-described optical component.

Further, as the variations of the optical component that can be manufactured using the optical fiber terminal according to the present invention, other examples include a collimator array, 2 r> ortmod u 1 e (eg, gain equalizer), isolators, optical switches, optical rangefinders, wavelength meters, interferometers, etc.

Industrial applicability

As described above, according to the present invention, by setting the outgoing beam diameter within the outer diameter of the coreless fiber, it is possible to perform the same optical coupling as a normal optical fiber. As a result, it is possible to provide a practical optical fiber terminal having excellent straightness of the output beam and having a level of reflection loss and coupling loss required by ordinary optical components. Components and optical couplers can be provided.

Claims

The scope of the claims

1. An optical fiber terminal formed by joining one end face of a coreless fiber made of a material having substantially the same uniform refractive index as the core to the end face of an optical fiber having a core at the center and a cladding at the outer periphery thereof. At

The beam diameter force when the light transmitted through the core of the optical fiber spreads inside the coreless fiber and exits from the other end face of the coreless fiber is set to be within the outer diameter of the coreless fiber. An optical fiber terminal characterized in that:

2. The optical fiber terminal according to claim 1, wherein an optical path length of the coreless fiber is less than 1 mm.

3. The optical fiber terminal according to claim 1, wherein an outer diameter of the optical fiber is different from an outer diameter of the coreless fiber.

4. The optical fiber terminal according to claim 1 or 2, wherein the optical fiber and the coreless fiber have substantially the same outer diameter, a central axis of the optical fiber, and the coreless fiber. An optical fiber terminal characterized in that the center axis of the optical fiber is shifted from the center axis.

5. The optical fiber terminal according to any one of claims 1 to 4, wherein the other end surface of the coreless fiber is formed on a surface perpendicular to an optical axis of the optical fiber. .

6. The optical fiber terminal according to any one of claims 1 to 5, wherein an antireflection film is provided on the other end surface of the coreless fiber.

7. An optical coupler including the optical fiber terminal according to any one of claims 1 to 6,

On the other end side of the coreless fiber on the optical axis of the optical fiber, a non-spherical lens, a spherical lens, a spherical lens, or a drum lens is selected. An optical coupler comprising at least one or more optical couplers.

8. An optical component, comprising a combination of the optical fiber terminal according to any one of claims 1 to 6 and an optical element having a light multiplexing / demultiplexing function.

9. The method for manufacturing an optical fiber terminal according to any one of claims 1 to 6, wherein: a first step of coupling the optical fiber and the coreless fiber;

A second step of polishing the other end face of the coreless fiber to adjust the length of the coreless fiber to a desired value,

In the second step, a method of manufacturing an optical fiber terminal, comprising adjusting a length of a coreless fiber to a desired value while measuring a reflection loss amount of a joined body of an optical fiber and a coreless fiber.

10. The method for producing an optical fiber terminal according to claim 3, wherein a first step of joining the optical fiber and the coreless fiber having different diameters,

A second step of detecting a joint point between the optical fiber and the coreless fiber, and a third step of cutting the coreless fiber at a designated position set based on the joint point,

In the second step, a method of manufacturing an optical fiber terminal is characterized in that the junction is detected by using an optical microscope and a defocused microscope image.

11. The method for manufacturing an optical fiber terminal according to claim 4, wherein a first step of joining the central axes of the optical fiber and the coreless fiber having substantially the same diameter so as to be shifted from each other. ,

A second step of detecting a junction between the optical fiber and the coreless fiber; O 2004/053547 and a third step of cutting the coreless fiber at a designated position set based on the junction point,

In the second step, a method for manufacturing an optical fiber terminal, wherein an optical microscope is used and the junction is detected by a defocused microscope image.