JP3112572B2 - Optical fiber tip processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber to be coupled to an optical semiconductor device, and more particularly, to a technique of a method for processing a spherical end of an optical fiber.

[0002]

2. Description of the Related Art In the light propagation in the coupling between an optical fiber and an optical circuit or an optical module, the light propagation in the optical fiber depends on the refractive index at the interface between the core and the clad in accordance with the incident angle of the light. The refractive index of the portion is higher than the refractive index of the cladding portion). For this purpose, a microlens system is used at the tip of the fiber. However, since it is difficult to manufacture and mount a microlens system for an optical fiber, conventionally, a spherical fiber that is more compact and more economical than an optical fiber using a lens system is used. This spherical fiber has a simplified optical system by processing the tip of the optical fiber into a spherical surface, thereby reducing the size and cost of the fiber itself.
As a conventional method of processing a spherical fiber, J. App1.
Phys. , Vol. 44, no. 6, pp2756 ~
2758 (1973). This technique will be described with reference to FIG. 3. The glass fiber 10 includes a core portion 10 a made of silica and a clad portion 1.
0b, the tip 10c of the glass fiber 10 is melted by the flame 11 from the burner 12, and the tip 10c is made spherical by the surface tension of the molten glass. Further, as a method for melting the tip portion 10c of the glass fiber 10, electric discharge machining using a carbon dioxide gas laser or the like is known.

[0003]

As described above, the conventional method of processing a front-end fiber is a method of simply melting the front end portion of the fiber and forming the front end portion by the surface tension. By controlling the size of the flame and the amount of heat, it melted, and the fiber tip had to be spherically machined. As described above, since the accuracy of the spherical tip of the fiber itself is determined only by controlling the flame, the radius of curvature of the spherical part is likely to vary, and the precision of the spherical part is reduced. It was bad. Furthermore, even in the case of mass-producing the spherical fiber, there is a disadvantage that the radius of curvature of each of the spherical fibers is not constant, and the productivity is extremely low.

Accordingly, an object of the present invention is to provide a method of processing a spherical surface of an optical fiber tip which can improve the accuracy of the spherical processing of the distal end of the optical fiber and improve the productivity accompanying the processing accuracy. is there.

[0005]

According to the first aspect of the present invention, as a method for processing a spherical surface of an optical fiber tip, a groove having a predetermined depth from the surface of the optical fiber is provided at a predetermined position from the end face of the optical fiber tip. The optical fiber tip is locally heated and melted, and the optical fiber tip is subjected to spherical processing.
According to the second aspect of the present invention, as the spherical surface processing method of the optical fiber tip portion according to the first aspect, the entirety of the optical fiber tip portion is removed to a predetermined depth, and the optical fiber tip portion is locally heated and melted, Apply spherical processing to the tip of the optical fiber. Claim 3
According to the invention described above, as a method for processing the spherical surface of the optical fiber tip portion according to the first aspect, a relative position between the exposure mask and the optical fiber is passed through an exposure mask using a photolithography technique at a predetermined position from the end surface of the optical fiber tip portion. A mask for etching is formed while rotating the optical fiber while keeping the position constant, a groove is formed at a predetermined position from the tip of the optical fiber by etching, and the tip of the optical fiber is locally heated and melted to form a light. Apply spherical processing to the fiber tip.

[0006]

According to the method of the present invention, a groove having a predetermined depth from the surface of an optical fiber is formed at a predetermined position from an end surface of the distal end of the optical fiber. Heat and melt.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for processing a spherical surface of an optical fiber tip according to the present invention will be described in detail with reference to FIGS. FIG. 1 conceptually shows an optical fiber tip portion by a spherical surface processing method of the optical fiber tip portion of the present invention.
In FIG. 1, an optical fiber 1 is formed of a fiber such as a quartz-based or multi-component glass-based fiber. This optical fiber 1
Is composed of a core 1a made of silica or the like whose main material has the lowest loss in the near-infrared wavelength region and a clad 1b, and the refractive index of the core 1a is higher than that of the clad 1b. Is totally reflected at the boundary surface between the core 1a and the cladding 1b.

Next, a method for processing the spherical surface of the distal end portion 1c of the optical fiber 1 will be described. First, the tip 1 of the optical fiber 1
A groove 1d having a predetermined depth is formed at a predetermined position from the end face c from the outer peripheral surface of the optical fiber 1. The groove 1d is formed in a substantially U-shaped cross section by a precision processing device or the like at a depth up to about the middle of the thickness of the clad 1b. The distal end portion 1c of the optical fiber 1 having the groove 1d formed in this way is melted from the front thereof by the discharge of an electric discharge machine such as a carbon dioxide laser machine. Due to this melting, the tip portion 1c is smoothly and accurately spherically processed.

As described above, by forming the groove 1d at a predetermined position from the end face of the distal end portion 1c of the optical fiber 1,
The volume of the tip 1c can be adjusted in advance. Then, the diffusion of heat during spherical processing can be suppressed, and the distal end 1c of the optical fiber 1 can be melted and spherically processed while efficiently confining the heat to the distal end 1c for performing spherical processing. Therefore, the radius of curvature of the spherical surface 1e having been subjected to spherical processing can be adjusted to be constant, and the production capacity associated with excellent processing accuracy can be increased, so that overall improvement in productivity and cost reduction can be achieved. it can.

FIG. 2 shows each step in another embodiment in which the spherical end of the optical fiber tip is processed by photolithography. In step a, the tip 1 of the optical fiber 1
A photoresist 3 is applied to the surface of the tip portion 1c to a predetermined (constant) thickness so as to cover the entirety of the tip c. This photoresist 3 is disposed below the exposure mask 4 on which the optically transparent fine pattern 4a is formed. Then, ultraviolet rays 5a are radiated from the ultraviolet light source (black light) 5 disposed above the exposure mask 4 to the photoresist 3 covering the tip 1c of the optical fiber 1 through the pattern 4a. At this time, the optical fiber 1 is rotated in the direction of the arrow while supporting the optical fiber 1 while keeping the relative position of the optical fiber 1 and the exposure mask 3 constant. As a result, an opening 3a for etching is formed at a predetermined position from the end face of the tip 1c of the optical fiber 1 by exposure.

After the development, in step b, the tip 1c of the optical fiber 1 including the opening 3a is immersed in a container 7 filled with an etching solution 6 such as buffered hydrofluoric acid. As a result, the optical fiber 1 in the opening 3a formed by the exposure is removed by etching to form a groove 1d. After the step b, as a step b ', the photoresist formed in the step a may be peeled off, and a certain amount of the tip 1c may be removed with the etching solution 6 in the container 7. This makes it possible to miniaturize the spherical processing, and it is possible to stably perform the fine spherical processing.

Next, in step c, the tip 1c of the optical fiber 1 having the groove 1d etched is disposed between the electrodes 8, 8 of an electric discharge machine or the like. Then, the discharge of the electrodes 8,8, melting the tip 1c. In step d, the melted tip portion 1c is spherically machined by its surface tension, and the radius of curvature of the spherical surface 1e is determined by the volume of the melted portion.

As described above, by forming the groove 1d at a predetermined position from the end surface of the tip 1c of the optical fiber 1,
The groove 1d adjusts the volume of the distal end portion 1c in advance, suppresses the diffusion of heat during spherical processing, and can efficiently perform spherical processing while confining heat to the distal end portion 1c. Therefore, the tip portion 1c of the optical fiber 1 can be smoothly and accurately spherically processed, and the radius of curvature of the spherically processed spherical surface 1e can be made constant, thereby improving productivity due to excellent processing accuracy. And cost reduction.

The method for processing the spherical surface of the distal end portion 1c of the optical fiber 1 according to the present invention is not limited to the above embodiment, but can be variously modified. For example, a flame or a laser beam can be used for the melting method of the distal end portion 1c of the optical fiber 1 in addition to the electric discharge machining in the above embodiment. Further, the groove 1d formed in the tip 1c may be a part of the outer periphery instead of the whole. Then, as a method of removing the optical fiber in the groove 1d portion, machining using a cutter or the like may be used instead of precision machining equipment.

[0015]

According to the above-described method for processing a spherical surface of an optical fiber tip, a groove having a predetermined depth from the surface of the optical fiber is formed at a predetermined position from the end face of the optical fiber tip. Since the portion is locally heated and melted, it is possible to improve the accuracy of the spherical processing of the distal end portion of the optical fiber and to improve the productivity accompanying the processing accuracy.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an optical fiber tip according to an embodiment of a method for processing a spherical surface of an optical fiber tip according to the present invention.

FIG. 2 is a process chart according to one embodiment of a method for processing a spherical surface of an optical fiber tip portion according to the present invention.

FIG. 3 is a conventional diagram of a conventional method for processing a spherical surface of an optical fiber tip.

[Explanation of symbols]

 Reference Signs List 1 optical fiber 1a core 1b clad 1c tip 1d groove 1e spherical surface 2 light emitting element 3 photoresist 4 exposure mask 5 ultraviolet light source 6 etching solution

Claims (3)

(57) [Claims] A groove having a predetermined depth from the surface of the optical fiber is formed at a predetermined position from the end surface of the front end of the optical fiber, and the front end of the optical fiber is locally heated and melted to form a spherical surface on the front end of the optical fiber. A spherical surface processing method for an optical fiber tip portion, wherein the spherical surface is processed. 2. The optical fiber according to claim 1, wherein the optical fiber tip is entirely removed to a predetermined depth, the optical fiber tip is locally heated and melted, and the optical fiber tip is subjected to spherical processing. Method of spherical surface processing of optical fiber tip part. 3. An etching method for rotating an optical fiber while maintaining a relative position between the exposure mask and the optical fiber at a predetermined position from an end surface of an optical fiber tip portion by using a photolithography technique while maintaining a relative position between the exposure mask and the optical fiber. A mask is formed, a groove is formed at a predetermined position from the tip of the optical fiber by etching, and the tip of the optical fiber is locally heated and melted to perform spherical processing on the tip of the optical fiber. 2. The method for processing a spherical surface of an optical fiber tip according to claim 1.