JP2002040271A - Terminal structure for optical fiber and method for treating terminal of optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple, lightweight and inexpensive terminal structure for an optical fiber. SOLUTION: In the terminal structure for the optical fiber, an optical filler 15 is provided in the end surface of the optical fiber 1, and the optical fiber is optically connected to the optical filler 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber terminal structure and a terminal processing method for guiding a laser beam to a required position.

[0002]

2. Description of the Related Art When a laser beam is used in a medical device, a processing machine, a measuring machine, or the like and is separated from a laser light source to a laser beam emitting position, the laser beam is guided by an optical fiber from the laser light source to the emitting position. ing.

For example, in the medical field, a laser device has recently been used for treatment. The treatment site is a limited narrow space, and therefore, the shape of the terminal of the treatment machine for performing a treatment is small and sharp. or,
A laser light source that generates a laser beam includes a power supply, a control circuit,
Since it is composed of an optical system and the like, a certain size is required. Therefore, the laser light source cannot be placed at the terminal of the treatment machine, and when it is provided at the terminal, it becomes difficult to freely operate the terminal.

An optical fiber guides a laser beam from a laser light source to a terminal portion, makes the terminal portion small, and enables free operation of the terminal portion. In addition, since medical instruments or processing machines substantially emphasize output power,
A multi-mode optical fiber is used as an optical fiber for guiding a laser beam.

In a surveying instrument, a laser beam is used for measuring a distance or forming a reference line or a reference plane.

In a laser beam used in a surveying instrument, the characteristics and quality of the laser beam, such as maintaining the polarization of the laser beam, stabilizing the wavelength, and maintaining the mode, are emphasized, not the output power.

[0007] The characteristics of the laser light source are easily affected by the environmental temperature. In order to maintain a stable transverse mode, the measuring unit and the laser light source, which is a heat source, are separated, the measuring unit and the laser light source are connected by an optical fiber, and the laser beam is transmitted by the optical fiber. The measurement unit and the heat source are separated from each other so that they can be routed. In the case of a visible laser beam mainly used for measurement and the like, the transverse mode is preferably a zero-order Gaussian beam, and a single-mode optical fiber that maintains polarization is mainly used.

As shown in FIG. 7, the above-mentioned optical fiber usually comprises a core portion 1a for transmitting a laser beam, a clad portion 1b surrounding the core, and a coating portion 2. The coating portion 2 further comprises the cladding portion. It comprises a buffer 2a surrounding 1b and an outer skin 2b. Hereinafter, the core 1a and the clad 1b are referred to as an optical fiber 1 for convenience. The terminal of the optical fiber 1 has the core part 1a, the clad part 1b surrounding the core part 1a, a ferrule (protective tube) 3 fitted to the terminal, and a pipe 4 fitted to the ferrule. 4 is connected to a laser light source or an optical system of the apparatus.

The tip of the optical fiber 1 is polished to a mirror surface so as not to be scattered or polarized when emitting a laser beam. The diameter of the optical fiber 1 is 0.125 mm or less at the cladding 1b. The ferrule 3 is fitted to the terminal because it is very thin and fragile, and the optical fiber 1 is polished integrally with the ferrule 3 while being protected by the ferrule 3.

The pipe 4 further protrudes from the end face of the optical fiber 1 in order to protect the end face of the optical fiber 1 and to enlarge the emission diameter of the laser beam to a required value as described later. A collimator lens 5 for converging a laser beam is fixed to the tip of the pipe 4. still,
The collimator lens 5 may simply be a protective glass. Since the end face of the optical fiber 1 and the space formed between the end face and the collimator lens 5 transmit a laser beam of high density energy, it must be kept highly clean.

Referring to FIG. 8, an example of use of the optical fiber 1 will be described.

The optical fiber 1 connects a laser emitting section 6 and a laser projecting optical system 7 via an incident end 8 and an emitting end 9. The laser emitting unit 6 includes a laser light source 11, a condenser lens 12, and the like. The laser projection optical system 7 includes a lens such as a collimator lens 13, and changes a beam diameter of a laser beam to be projected. To a desired state.

A laser beam 14 emitted from the laser light source 11 with a spread is condensed on the incident end face of the optical fiber 1 by the condensing lens 12,
Incident on. The incident laser beam 14 is guided by the optical fiber 1 and is emitted from one emission end face.

The collimator lens 13 converts the laser beam 14 emitted from the exit end face of the optical fiber 1 into parallel light. The laser projection optical system 7 has a required configuration according to the characteristics of the device, and the collimator lens 13 may be omitted.

The laser beam 14 emitted from the laser projection optical system 7 is used for predetermined treatment, processing, and measurement.

The power density when the laser beam 14 enters and exits the end face of the optical fiber is several tens of kW / cm ² .

For example, in the case of a single mode fiber used for a measuring instrument, the core diameter of the optical fiber is about 4 μm. Even if the required output is 10 mW, the power density at the end face of the optical fiber is as high as 80 kW / cm ² . With such a power density, dirt on the end face and attached dust are burned and the end face itself is destroyed, resulting in fatal deterioration of beam characteristics. Although depending on the laser power, the emission diameter of the laser beam to the outside is desirably about 10 times or more the fiber diameter. As shown in FIG. 9, the emission angle θ of the laser beam emitted from the optical fiber depends on the wavelength, the core diameter, etc., but is about 10 ° for a single mode fiber and about 20 ° for a multimode fiber. For this purpose, the end face of the optical fiber 1 and the collimator lens 5 shown in FIG. The exit diameter is enlarged to prevent end face damage.

[0018]

However, such a structure is
This is a complicated structure that keeps the output end face polished cleanly and holds the collimator lens 5. For this reason, there is a problem that the terminal of the optical fiber 1 becomes large and heavy, and the small size and flexibility of the optical fiber 1 are impaired.

In the field of optical communication, a method is known in which the core diameter of an optical fiber near the end face is widened by a thermal diffusion method or the like to relax the tolerance of the axial deviation. However, this method only increases the beam diameter by at most about two times, and also requires a heat treatment and maintenance, increases the number of manufacturing steps, and is expensive.

[0020]

The present invention relates to a terminal structure of an optical fiber in which an optical filler is provided on an end face of an optical fiber, and the optical fiber and the optical filler are optically continuous.
In addition, the present invention relates to a terminal structure of an optical fiber in which a pipe is disposed at an end of an optical fiber and an optical filler is filled in a hollow portion of the pipe, and an optical fiber having the same refractive index as that of the optical fiber. The present invention relates to the terminal structure of an optical fiber in which the optical filler is an ultraviolet curable resin, and the optical filler relates to the terminal structure of an optical fiber formed by a sol-gel method. Is related to the terminal structure of the optical fiber formed by melting the powdered glass, the cross-sectional area is such that the optical filler does not give a diffraction effect to the laser beam, and the laser is so large that it does not damage the end face of the optical filler. The present invention relates to the terminal structure of an optical fiber having a length in which a light beam spreads, and also relates to the terminal structure of an optical fiber having an end face of an optical filler having a curvature and a lens effect. , Polarization separation, Long plate in which according to the terminal structure of an optical fiber having a length having a function such as an optical effect.

Also, the present invention relates to a method for terminating an optical fiber in which an end of an optical fiber is filled with an optical filler and an abutment plate is brought into contact with an end face of the optical filler and cured. The present invention relates to a terminal processing method for an optical fiber having a concave portion on a contact surface, and also relates to a terminal processing method for an optical fiber having a convex portion on a contact surface of a backing plate. The present invention relates to a terminal processing method for an optical fiber having a concave surface portion, and further relates to a terminal processing method for an optical fiber in which a contact surface of a backing plate is a type of a diffractive optical element.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, the same components as those in FIG. 7 are denoted by the same reference numerals.

The optical fiber 1 has a core 1a and a clad 1
b, the terminal protruding from the covering portion 2 is fitted with a ferrule 3 for protecting the terminal.
, A pipe 4 is fitted, the pipe 4 has an inner diameter of φ,
It covers the end of the optical fiber 1 and protrudes by L from the end of the optical fiber 1 (see FIG. 9).

The hollow portion of the pipe 4 is connected to the optical fiber 1
Filled with an optical filler (optical member) 15 having the same refractive index as described above and cured. The optical filler 15 and the end face of the optical fiber 1 are in close contact with each other, and the optical filler 15 is
At the boundary with the above, there is an optically continuous state without light refraction, reflection and the like.

The end face of the optical filler 15 after filling is made a mirror surface so as not to scatter light.

In order to realize a mirror surface, it is conceivable to grind the optical filler 15 together with the pipe 4, or to press a mirror plate against the optical filler 15 and harden it, as will be described later.

The laser beam 14 emitted from the optical fiber 1 at an angle of θ expands while passing through the optical filler 15. The amount of protrusion L of the pipe 4 is determined by the laser beam 14 at the time of emission from the end face of the optical filler 15.
Is set to be about 10 times larger than the diameter of the end face of the optical fiber 1.

By directly contacting the optical filler 1 with the end face of the optical fiber 1, the end face of the optical fiber 1 is completely prevented from being contaminated with dust and the like, and the end face of the optical fiber 1 is prevented from being contaminated. It does not matter if it is not a mirror surface or flat.

The size of the optical filler 15 may have an optical length and diameter such that the expanded beam diameter is not affected by the diffraction effect due to the boundary. For example, in the case of an optical filler having a thickness of 0.3 mm with respect to an optical fiber having a core diameter of 4 μm, the beam diameter increases about 10 times. In order not to receive the diffraction effect, it is sufficient that the optical filler is filled in a region two to three times the beam diameter, and a multimode fiber having a core diameter of 80 to 120 μm is sufficient. Of course, if the optical length becomes longer, the necessary cross-sectional area becomes larger so as not to receive the diffraction effect.

The ferrule 3 is originally an optical fiber 1
The ferrule 3 can be omitted if the optical fiber 1 is held at the center of the pipe 4 and the optical filler 15 is filled.

Although the optical filler 15 is made of an ultraviolet curable resin, the optical filler 15 may be formed by melting powdered glass, or may be a crystal or a sol-gel material.

Referring to FIG. 2, the terminal processing of the optical fiber 1 will be described.

In the example shown in FIG. 2, instead of the ferrule 3, or as a means for holding the optical fiber 1 at the center of the pipe 4, the tip of the optical fiber 1 is coated with resin.

Hereinafter, description will be made in order.

The coating material is removed, the optical fiber 1 is protruded by a required length, and the optical fiber 1 is cut using a cutting jig (FIG. 2.1).

In order to improve the positional accuracy of the optical fiber 1, the optical fiber 1 is bonded and fixed to a glass capillary 16 or a ferrule (coating resin). It is preferable to use an ultraviolet-curable adhesive for the adhesion because distortion is small and deterioration of beam quality is suppressed. Further, a thermosetting adhesive may be used. At this time, care should be taken to prevent contamination by contact with the end surface of the coating resin 16 (FIG. 2.2).

The pipe 4 is fitted to the coating resin 16 so as to protrude by a required length (FIG. 2.3), and the optical filler 15 having the same refractive index as that of the core portion 1a is cured by ultraviolet rays. 4 and the mirror 4 is pressed against the tip of the pipe 4. At this time, the corresponding plate 17 transmits ultraviolet light, and when the pressing plate 17 is pressed against the tip of the pipe 4, the optical filler 15 and the pressing plate 1 are pressed.
7 so that there is no gap between them (Fig. 2.4). The optical filler 15 is irradiated with ultraviolet rays through the backing plate 17 to cure the optical filler 15. Since the backing plate 17 is a mirror surface, the end surface of the hardened optical filler 15 is also a mirror surface and need not be polished (FIG. 2.4).

The end face of the optical filler 15 is immersed in a surface coating solution 18 (for example, a fluorine-based solvent).

By pulling up the optical fiber 1 and drying the end face of the optical filler 15, the end face of the optical filler 15, ie, the end face of the laser beam, is subjected to reflection coating (FIG. 2.5).

As described above, the shape of the end face of the optical filler 15 is determined by the backing plate 17. Therefore, by using the plate 17 having the concave portion 19 shown in FIG. 4 as the corresponding plate 17, the end face of the optical filler 15 can be formed into a convex shape as shown in FIG.

When the end face of the optical filler 15 is convex, a lens effect is produced, and a lens portion 21 is formed on the end face.
The laser beam emitted by the lens unit 21 can be a parallel beam. Thus, the collimator lens can be omitted, and the terminal structure of the optical fiber 1 can be simplified.
It can be lightweight.

The end face of the optical filler 15 can be arbitrarily processed by appropriately selecting the surface shape and properties of the backing plate 17. For example, a convex portion may be formed on the backing plate 17 to diffuse an emitted laser beam, or a convex portion and a concave portion may be formed on the plate 17 so that the emitted laser beam is partially condensed. It is possible to obtain a luminous flux state according to the application such as diffused light. Further, in addition to the above-described lens effect, the surface may be formed as a type of a diffractive optical element to have a diffractive effect. Further, the optical filler 15 is provided with optical anisotropy, and has a polarization separation effect using its polarization characteristics, and is adjusted to a specific length.
It is also possible to function as a wave plate.

In the present invention, as shown in FIG.
It goes without saying that the present invention can be carried out at the input end of the optical fiber 1 on which the laser beam from 1 is incident.

FIG. 6 shows still another embodiment. In the other embodiment, the optical filler 15 is made of a solid material such as glass, and the optical filler 15 and the optical fiber 1 are combined with each other. The optical fiber 1 and the optical filler 15 are bonded between the end faces with a filler or an adhesive 22 having the same refractive index as that of the optical filler 15, thereby realizing a state without optical gap.

[0046]

As described above, according to the present invention, the optical fiber terminal does not need to have a closed structure, and the collimator lens and the like can be omitted. It can handle high output without being damaged by the power laser beam, and the continuity of light is secured by the terminal structure, so it is not reflected or diffracted on the end face of the optical fiber, the surface of the optical member, etc., and interference noise is reduced. A laser beam of high quality can be obtained with a small amount, and the end face of the optical filler is formed with a backing plate. It is effective.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a process for processing a terminal structure of an optical fiber according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing another embodiment of the present invention.

FIG. 4 is a cross-sectional view of a backing plate used in the other embodiment.

FIG. 5 is an explanatory diagram showing an embodiment when the present invention is applied to an input end of an optical fiber.

FIG. 6 is a sectional view showing still another embodiment of the present invention.

FIG. 7 is a sectional view showing a conventional example.

FIG. 8 is an explanatory view showing a state in which an optical fiber is used.

FIG. 9 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical fiber 1a Core part 1b Cladding part 2 Coating part 2a Buffer 2b Outer skin 3 Ferrule 4 Pipe 6 Laser light emitting part 7 Laser light projection optical system 11 Laser light source 14 Laser beam 15 Optical filler 16 Glass capillary or ferrule 17 Backing plate 18 Surface Coating solution 19 Concave surface 21 Lens

Claims (14)

[Claims] 1. An optical filler is provided on an end face of an optical fiber,
A terminal structure of an optical fiber, wherein the optical fiber and the optical filler are optically continuous. 2. The optical fiber terminal structure according to claim 1, wherein a pipe is provided at an end of the optical fiber, and a hollow portion of the pipe is filled with an optical filler. 3. The optical fiber terminal structure according to claim 1, wherein the optical fiber and the optical filler have the same refractive index. 4. The terminal structure of an optical fiber according to claim 1, wherein the optical filler is a UV-curable resin. 5. The optical fiber terminal structure according to claim 1, wherein the optical filler is formed by a sol-gel method. 6. The optical fiber terminal structure according to claim 1, wherein the optical filler is formed by melting glass powder. 7. The laser beam according to claim 1, wherein the optical filler has a cross-sectional area that does not give a diffraction effect to the laser beam, and a length that the laser beam spreads so as not to damage the end face of the optical filler. 6. The terminal structure of one of the optical fibers in any one of 6. 8. The terminal structure of an optical fiber according to claim 1, wherein an end face of the optical filler has a curvature and has a lens effect. 9. The terminal structure of an optical fiber according to claim 1, wherein the optical filler has a polarization property, and has a length having an optical action such as polarization separation and a wavelength plate action. 10. An end processing method for an optical fiber in which an end of an optical fiber is filled with an optical filler and an abutment plate is brought into contact with an end surface of the optical filler and cured. 11. The method for terminating an optical fiber according to claim 10, wherein a concave portion is formed on the contact surface of the backing plate. 12. The optical fiber terminal processing method according to claim 10, wherein a convex portion is formed on the contact surface of the backing plate. 13. The optical fiber terminal treatment method according to claim 10, wherein a convex portion and a concave portion are formed on the contact surface of the backing plate. 14. The method according to claim 10, wherein the contact surface of the backing plate is a diffractive optical element type.