JP2000352629A - Optical fiber with lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical fiber superior in coupling efficiency with a laser beam and capable of coarse alignment with ease while the direction of a lens part is observed for the semiconductor laser, by forming in the core the lens part which is a projected line orthogonally crossing the optical axis of the core and which has a partially circular cross section in the orthogonal plane perpendicular to the longitudinal direction of the projected line. SOLUTION: The optical fiber 1 with a lens is provided with a core 1a and a clad 1b and, in a diametrical direction in the core 1a and the clad 1b parts of the fiber end face 1c, a lens part 1d consisting of a projected line orthogonally crossing the optical axis of the core 1a is formed. The lens part 1d is used for the purpose of circularly converging the elliptically shaped laser beam by sharply refracting in the major axis direction by the far field pattern emitted from a semiconductor laser. Accordingly, the lens part 1d is formed at least in the core 1a. In addition, the lens part 1d is formed so that its cross sectional shape in an orthogonal plane perpendicular to the longitudinal direction of the lens part 1d constitutes essentially a part of a circle including a part of ellipse, hyperbola, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber with a lens provided with a lens portion on an end face and used for optical communication and the like.

[0002]

2. Description of the Related Art A light emitting element module used in an optical communication system includes a semiconductor laser (hereinafter referred to as an "LD") as a light source.
), An optical fiber and a lens. The lens is used for efficiently condensing the laser light emitted from the LD on the core end face of the optical fiber. At this time, in order to obtain high optical coupling efficiency, the light emitting element modules perform optical axis alignment, that is, alignment, between the LD, the optical fiber, and the lens, and are mutually fixed at a position where the optical coupling power is maximized. You.

[0003] As such a light emitting element module, for example, an optical module in which a spherical optical fiber having a spherical projection serving as a lens portion at an end portion is optically coupled to a working surface of a light receiving and emitting element has been proposed (see, for example, Japanese Patent Application Laid-Open No. H11-157556). JP-A-6-324236). In the optical module, an outer peripheral edge protruding from the spherical projection is formed outside the spherical projection (lens), and the outer peripheral edge is brought into contact with the periphery of the emission end face of the LD to thereby provide a spherical projection. And LD achieve a stable coarse alignment in a short time. Then, after the spherical projection and the LD are roughly aligned, the final position in the light transmission direction between the spherical projection and the LD is obtained by precision alignment, and the spherical optical fiber and the LD are fixed to each other at that position. ing. At this time, since the spherical optical fiber has no direction dependency in the circumferential direction of the spherical projection, position adjustment in the circumferential direction is unnecessary.

[0004]

By the way, in the LD, the far field pattern of the emitted laser light is elliptical, whereas in the optical fiber, the cross section of the core on which the laser light enters is circular. . For this reason, in a light emitting device module that optically couples an LD with an optical fiber, in order to couple the laser light emitted from the LD to the core of the optical fiber with low loss and high efficiency, the laser light must be far-field coupled. An aspheric lens that refracts the pattern more strongly in the major axis direction than in the minor axis direction is required. That is, when the elliptical laser light passes through the aspherical lens, the far field pattern is focused from the elliptical shape to a circular shape, and is coupled to the core of the optical fiber with high efficiency.

However, the aspheric lens is not rotationally symmetric with respect to the optical axis. For this reason, in the light emitting element module, it is necessary to rotate the aspherical lens around the optical axis to adjust the laser light emitted from the LD to an optimum position. Therefore, the optical module disclosed in the above publication is not satisfactory in terms of the coupling efficiency between the laser light and the spherical optical fiber.

Moreover, in the above optical module, even if the spherical projection is simply replaced with an aspheric lens, an outer peripheral edge is formed around the periphery. For this reason, in the optical module, when the outer peripheral edge is brought into contact with the LD at the time of manufacturing, the aspherical lens cannot be seen from the outside because it is obstructed by the outer peripheral edge, and the orientation of the aspherical lens with respect to the LD is changed. do not know.

Therefore, in the manufacture of the optical module, it is difficult to coarsely align the position of the aspherical lens around the optical axis with respect to the laser beam, so that a stable coarse alignment cannot be performed. There was a problem of cost. The present invention has been made in view of the above points, and provides an optical fiber with a lens having excellent coupling efficiency with a laser beam and capable of easily performing coarse alignment while observing the direction of a lens unit with respect to an LD. The purpose is to do.

[0008]

According to the present invention, in order to achieve the above object, at least a core portion of an end face of an optical fiber is provided with a ridge orthogonal to an optical axis of the core and a longitudinal direction of the ridge. This is a configuration in which a lens portion having a cross-sectional shape in a plane orthogonal to a part of a substantial circle is formed.

Preferably, around the lens portion, an observation portion for slightly observing the lens portion and observing the lens portion is formed, and a positioning wall having a flat end surface is provided. Here, "a cross-sectional shape is a part of a substantially circular" used in the claims of the present specification means that the cross-sectional shape of a ridge serving as a lens part is a part of a circle, an ellipse, or a hyperbola or non-circular shape. It refers to a part of a spherical surface or the like, and is used in the following meaning in the following description.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical fiber with a lens according to the present invention will be described below in detail with reference to FIGS. As shown in FIG. 1, the optical fiber with a lens 1 has a core 1a and a clad 1b, and a lens formed of a ridge perpendicular to the optical axis of the core 1a on the core 1a and the clad 1b of the fiber end face 1c. The portion 1d is formed in the diameter direction. The lens unit 1d is used to strongly refract laser light having an elliptical far-field pattern emitted from the LD in the major axis direction to converge it into a circular shape. Therefore, as shown in FIG. 2, the lens portion 1d is formed at least in the portion of the core 1a. In order to exert the above function, the lens portion 1d has a substantially rectangular cross section on a surface orthogonal to the longitudinal direction of the lens portion 1d, such as a part of a circle, an ellipse, or a part of a hyperbola or an aspheric surface. Formed to be part of a circle.

At this time, the lens unit 1d is, for example, as shown in FIG.
As shown in FIG. 2A, a hyperbolic projection 2 is formed in the opening 2a.
b is formed using the metal mask 2 on which is formed. That is, the end face of the optical fiber F cut into a mirror surface is shown in FIG.
Is dry-etched on the end face of the optical fiber F while reciprocating the metal mask 2 in the direction of the arrow in the figure so that the apex of the projection 2b passes through the center of the core of the optical fiber F. Formed. The metal mask 2 is made of, for example, nickel or the like, and is the same in other embodiments described below.

As shown in FIG. 3 (b), the lens portion 1d has a quartz glass wire 3 having substantially the same etching rate as the optical fiber F disposed at the center of the core of the optical fiber F end face. Similarly, it can be formed by performing dry etching. At this time, the optical fiber F
By arranging the wire 3 made of quartz glass as shown in (a), the end face was etched as shown by the dotted line in FIG. 4 (b), and the lens portion 1d was formed on the fiber end face 1c shown in FIG. It is processed into an optical fiber 1 with a lens. Here, the same material as the quartz glass wire is used in other embodiments described below.

Here, as a means of dry etching, plasma etching, sputter etching, ion beam etching, neutral beam etching or the like can be used. The optical fiber with lens 1 in which the lens portion 1d is formed on the fiber end face 1c in this manner is the one shown in FIG.
As shown in FIG. 5, the lens unit 1d is disposed so as to face the emission surface 6a of the LD 6 placed on the LD carrier 5, and positions the lens unit 1d so as to be orthogonal to the long diameter of the emitted laser light in the far field pattern. Outgoing surface 6a
And the LD is abutted against the LD in a roughly aligned state.
Therefore, the optical fiber with lens 1 is excellent in the coupling efficiency with the laser light, and the LD 6 while looking at the lens portion 1d.
, Coarse alignment with respect to the LD 6 can be easily performed in a short time.

Here, the optical fiber with a lens has a core 8a and a cladding 8b like the optical fiber with a lens 8 shown in FIG. 6, and the core 8a and the cladding 8b on the fiber end face are provided with the core 8a. A lens portion 8d is formed in the diametric direction, which is formed of a ridge perpendicular to the optical axis, and has a sectional shape that is a part of a substantial circle such as a part of a circle or an ellipse or a part of a hyperbola or aspheric surface. The positioning walls 8e may be formed on both sides of the lens portion 8d.

Each positioning wall 8e is used for easily positioning the optical fiber with lens 8 in the butting direction when the optical fiber with lens 8 is butted with the LD.
A gap-shaped observation portion 8f that projects slightly more than that of the lens portion 8d at both ends to observe the direction of the lens portion 8d is formed, and the end face is formed flat. At this time, the lens portion 8d and the positioning wall 8e are, like the lens portion 1d of the optical fiber with lens 1, for example, as shown in FIG. 7, a metal mask 9 having an opening 9a formed with an elliptical projection 9b. It is formed by using. That is, the metal mask 9 shown in FIG. 7 is disposed on the end surface of the optical fiber F cut into a mirror surface, and the apex of the projection 9b passes through the center of the core of the optical fiber F.
The end face of the optical fiber F is formed by dry etching while the metal mask 9 is reciprocated in the direction of the arrow in the figure.

Accordingly, the optical fiber with lens 8 is positioned in the abutting direction by the respective positioning walls 8e and abuts against the LD, and the lens section 8f is formed by the observation section 8f formed between the lens section 8d and the positioning wall 8e. 8
The coarse alignment is performed on the LD while observing the direction of d. For this reason, the optical fiber with a lens 8 is excellent in coupling efficiency with laser light similarly to the optical fiber with a lens 1 and is positioned with respect to the LD while observing the direction of the lens unit 8d by the observation unit 8f. Therefore, coarse alignment with respect to the LD can be easily performed in a short time.

In the following, a lens part alone or a lens part and a positioning wall formed so that the cross-sectional shape becomes a part of a substantial circle such as a part of a circle or an ellipse or a part of a hyperbola or an aspherical surface. A modification of the optical fiber with a lens, which has the same effect as the optical fiber with a lens 1 and the optical fiber with a lens 8, will be described. First,
As in the optical fiber with lens 10 shown in FIG.
A lens portion 10d having a core 10a and a clad 10b, and having a ridge perpendicular to the optical axis of the core 10a is formed in a groove 10
e and is formed in the diameter direction through
Positioning walls 10f may be formed on both sides of d.
The optical fiber with lens 10 has a gap between the lens portions 10d at both ends of each concave groove 10e and the positioning wall 10f.
This is the observation unit 10g when performing coarse alignment with respect to the LD.

At this time, the lens portion 10d, the concave groove 10e, and the positioning wall 10f have, as shown in FIG. 8B, an elongated opening 11a formed at the center on the end surface of the optical fiber F cut into a mirror surface. A metal mask 11 to which a wire rod 11b made of quartz glass is fixed is disposed at the center of the opening 11a so as to extend in the longitudinal direction, and is formed by dry etching.

Further, like the optical fiber with lens 12 shown in FIG. 9A, it has a core 12a and a clad 12b, and the optical axis of the core 12a is orthogonal to the core 12a and the clad 12b on the fiber end face. A lens portion 12d formed of a projecting ridge is formed in the diameter direction, and the lens portion 12d
A positioning wall 12f may be formed around the periphery of d through a concave groove 12e. Then, in the optical fiber with lens 12, the gap between the lens portion 12 d at the end of each concave groove 12 e and the positioning wall 12 f becomes the observation portion 12 g when the center is roughly aligned with the LD.

In this case, as shown in FIG. 9B, the lens portion 12d, the concave groove 12e, and the positioning wall 12f correspond to the end face of the optical fiber F cut into a mirror surface and the shape of the positioning wall 12f at the center. An elongated opening 13a is formed, and a metal mask 13 to which a quartz glass wire 13b is fixed is disposed at the center of the opening 13a so as to extend in the longitudinal direction,
It is formed by performing dry etching.

Further, like the optical fiber with lens 14 shown in FIG. 10A, the optical fiber has a core 14a and a clad 14b, and the optical axis of the core 14a is orthogonal to the core 14a and the clad 14b on the fiber end face. A lens portion 14d made of a ridge is formed in the diameter direction, and the lens portion 1d is formed.
A horseshoe-shaped positioning wall 14f may be formed around the periphery surrounding 4d via a concave groove 14e. At this time, the optical fiber with lens 14 is connected to the lens portion 1 at the end of each groove 14e.
The gap between the positioning wall 4d and the positioning wall 14f becomes the observation unit 14g when performing coarse alignment with respect to the LD.

The lens portion 14d, the concave groove 14e, and the positioning wall 14f are formed by performing dry etching on the end face of the optical fiber F using a metal mask 15 shown in FIG. In the metal mask 15, a keyhole-shaped opening 15a corresponding to the shape of the positioning wall 14f is formed at the center.
A quartz glass wire 15b is fixed to the center of 5a so as to extend in the longitudinal direction.

On the other hand, the optical fiber with a lens is shown in FIG.
As in the optical fiber 16 with a lens shown in (a), it has a core 16a and a clad 16b, and has a fiber end face 16c.
A configuration in which a lens portion 16d made of a ridge is formed in the portion of the core 16a and the cladding 16b of the above. At this time, the lens portion 16d is orthogonal to the optical axis of the core 16a, the outer peripheral side is wide as shown in FIG. 12A, the core 16a is narrow as shown in FIG. The cross-sectional shape is formed to be a part of a substantial circle such as a part of a circle, an ellipse, a hyperbola, or a part of an aspheric surface.

At this time, the lens section 16d is
As shown in (b), two metal masks 17 and 18 having triangular projecting pieces 17a and 18a are attached to the projecting pieces 17a and 17a.
The end of the optical fiber F is formed by performing dry etching on the end surface of the optical fiber F while reciprocating in the direction of the arrow in FIG.

FIG. 13 shows an optical fiber with a lens.
Like the optical fiber with a lens 20 shown in (a), the optical fiber has a core 20a and a clad 20b, and a lens portion 20d made of a ridge is formed in a diameter direction on the core 20a and the clad 20b on the fiber end face. , Lens unit 20
d at three locations surrounding the positioning wall 20f through the concave groove 20e.
May be formed. At this time, in the optical fiber with lens 20, the gap at the end of each groove 20 e becomes the observation portion 20 g when the center is roughly aligned with the LD.

Here, the lens portion 20d, the concave groove 20e, and the positioning wall 20f are formed by the metal mask 2 shown in FIG.
1, the end face of the optical fiber F is formed by dry etching. In the metal mask 21, a Y-shaped slit 21a corresponding to the shape of the concave groove 20e is formed at the center, and a quartz glass wire 20b is fixed to the center of the slit 20a so as to extend in the longitudinal direction. The metal mask 21
The optical fiber F is etched by disposing the wire 20b on the core.

FIG. 14 shows an optical fiber with a lens.
As in the optical fiber 22 with a lens shown in (a), a core 22a and a clad 22b are provided, and a lens portion 22d made of a ridge is formed in a diameter direction on the core 22a and the clad 22b on the fiber end surface, Concave grooves 22e are provided on both sides of the lens portion 22d, and the positioning walls 2 are provided on both ends of the lens portion 22d.
2f may be formed respectively. At this time, the optical fiber with lens 22 serves as an observation unit when the gap at the end of each concave groove 22e is roughly aligned with the LD.

Here, the lens portion 22d, the concave groove 22e and the positioning wall 22f are formed by the metal mask 2 shown in FIG.
3, the end face of the optical fiber F is formed by dry etching. In the metal mask 23, a rectangular opening 23a corresponding to the shape of the concave groove 22e is formed at the center, and the opening 2a is formed.
A wire 23b made of quartz glass is fixed at the center in the longitudinal direction of 3a so as to straddle the opening 23a. Metal mask 23
Is arranged so that the wire 23b is located on the core, and the optical fiber F is etched.

As described above, in the optical fiber with a lens of the present invention, a lens portion composed of a ridge is formed on the end face of the optical fiber, and a positioning wall is provided around the lens portion as necessary. At this time, in the optical fiber with a lens, the shapes of the lens portion and the positioning wall to be formed are not limited to those described above, and various shapes may be used as long as they can be formed using a metal mask in accordance with the object of the present invention. There is a shape.

For example, as shown in FIG. 15A, an optical fiber 24 with a lens has a core 24a and a clad 24b.
In the part, a lens portion 24d formed of a ridge is formed in the diameter direction, and a concave groove 24e is formed along the lens portion 24d and in a direction perpendicular to the forming direction of the lens portion 24d,
The positioning walls 24 are formed at four locations divided by the concave grooves 24e.
f may be formed respectively. At this time,
The optical fiber with a lens 24 serves as an observation unit when the gap at the end of each concave groove 24e is roughly aligned with the LD.

Also, as shown in the optical fibers 26, 28, and 30 with lenses shown in FIGS.
a, 28a, 30a and claddings 26b, 28b, 30b
And the cores 26a, 28a, 30a of the fiber end faces.
In the clad portions 26b, 28b, 30b, lens portions 26d, 28d, 30d formed of ridges are formed in the diameter direction, and the concave grooves 2 are formed around the lens portions 26d, 28d, 30d.
6e, 28e, 30e, a plurality of positioning walls 26.
f, 28f, and 30f may be formed respectively. At this time, the optical fibers with lenses 26, 28, 3
0 indicates that the gap at the end of each of the grooves 26e, 28e, 30e is L
This is an observation unit when coarse alignment is performed with respect to D.

[0032]

According to the first aspect of the present invention, there is provided an optical fiber with a lens which has excellent coupling efficiency with a laser beam and can easily perform coarse alignment while observing the direction of a lens portion with respect to an LD. can do. According to the second aspect of the invention, when the optical fiber with the lens is abutted against the LD prior to the coarse alignment, the positioning in the abutting direction can be easily performed.

[Brief description of the drawings]

FIG. 1 is a perspective view of an optical fiber with a lens according to the present invention.

FIG. 2 is a front view of the optical fiber with a lens shown in FIG. 1;

3A is a front view of a metal mask used when forming a lens portion on the optical fiber with a lens of FIG. 1; FIG. 3B is a perspective view showing an arrangement of a quartz glass wire and an optical fiber;

FIG. 4 is a side view (a) in which a quartz glass wire is disposed on an optical fiber and a side view (b) showing a state after performing dry etching on the optical fiber.

FIG. 5 is a perspective view illustrating a state in which the optical fiber with a lens of FIG.

FIG. 6 is a perspective view showing another embodiment of the optical fiber with a lens of the present invention.

FIG. 7 is a front view of a metal mask used when forming a lens portion and a positioning wall on the optical fiber with a lens of FIG. 6;

FIG. 8 is a perspective view (a) showing still another embodiment of the optical fiber with a lens of the present invention, and a front view (b) of a metal mask used for forming a lens portion, a concave groove and a positioning wall.

FIG. 9 is a perspective view (a) showing another embodiment of the optical fiber with a lens of the present invention, and a front view (b) of a metal mask used for forming a lens portion, a concave groove and a positioning wall.

FIG. 10 is a perspective view (a) showing still another embodiment of the optical fiber with a lens of the present invention, and a front view (b) of a metal mask used for forming a lens portion, a concave groove and a positioning wall.

FIG. 11 is a perspective view (a) showing another embodiment of the optical fiber with a lens of the present invention, and a front view (b) showing a state where two metal masks used for forming a lens portion are combined.

12A is a cross-sectional view of the lens portion of the optical fiber with a lens of FIG. 11A cut on the outer peripheral side of the optical fiber, and FIG.

FIG. 13 is a perspective view (a) showing still another embodiment of the optical fiber with a lens of the present invention, and a front view (b) of a metal mask used for forming a lens portion and a positioning wall.

FIG. 14 is a perspective view (a) showing another embodiment of the optical fiber with a lens of the present invention, and a front view (b) of a metal mask used for forming a lens portion and a positioning wall.

FIG. 15 is a perspective view showing various other modifications of the lens portion and the positioning wall formed on the optical fiber with a lens according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 optical fiber with lens 1a core 1b clad 1c fiber end face 1d lens part 2 metal mask 3 wire rod (made of quartz glass) 8 optical fiber with lens 8a core 8b clad 8d lens part 8e positioning wall 9 metal mask 10,12 light with lens Fiber 10a, 12a Core 10b, 12b Cladding 10d, 12d Lens 10f, 12f Positioning wall 11, 13 Metal mask 14, 16 Optical fiber with lens 14a, 16a Core 14b, 16b Cladding 14d, 16d Lens 14f Positioning wall 15, 17 , 18 Metal mask 20, 22 Optical fiber with lens 20a, 22a Core 20b, 22b Cladding 20d, 22d Lens part 20f, 22f Positioning wall 21, 23 Metal mask 24, 26 Optical fiber with lens 2 4a, 26a Core 24b, 26b Cladding 24d, 26d Lens part 24f, 26f Positioning wall 28, 30 Optical fiber with lens 28a, 30a Core 28b, 30b Cladding 28d, 30d Lens part 28f, 30f Positioning wall

Continuing on the front page (72) Inventor Takashi Shigematsu 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd. (72) Inventor Kenji Suzuki 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Industrial Co., Ltd. F term (reference) 2H050 AC03 AC87

Claims (2)

[Claims] At least a core portion of an end face of an optical fiber has a ridge perpendicular to an optical axis of the core, and a cross-sectional shape of a surface perpendicular to a longitudinal direction of the ridge is a part of a substantial circle. An optical fiber with a lens, wherein a certain lens portion is formed. 2. A positioning wall, which projects slightly beyond the lens part, forms an observation part for observing the lens part, and has a flat end face around the lens part. The optical fiber with a lens according to claim 1.