JPS628110A - Slab type converging optical transmission body - Google Patents

Abstract

PURPOSE:To obtain a multi-terminal LD module with high efficiency by easy assembly and to use light emitted by an ID light source effectively by connecting the LD light source and a fiber array to both ends of a slab lens and making the end surface facing an LD light emission surface wide. CONSTITUTION:The slab lens body 2 decrease in refractive index gradually toward the periphery in the direction (y) perpendicular to a (z)-axis plane containing the optical axis or (x-z) plane (optical axis surface) and is uniform in refractive index in the direction (x) and the direction (z) parallel to the optical axis surface. Then, the length in the optical axis direction [direction (x)] is about n/2 (n: integer >=1) times pitch length determined by the refractive index distribution and both flanks 8 and 8 crossing the optical axis surface at right angles slant at an angle theta to the optical axis. Further, the (z)-directional length of one end surface of this lens 1 is size ZA larger than the (z)-axial width of luminous flux emitted by the protection glass of the LD light source 1 and matched with the width ZB of the fiber array on a fiber side end surface 7, and the flank 8 decreases in width gradually from an end surface 6 to the end surface 7 in the (x) direction.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is a multi-purpose optical fiber that has the function of branching the light output from a 1WA laser diode (hereinafter abbreviated as LD) to a plurality of optical fibers equally and with low loss. The present invention relates to a slab-like convergent optical transmission body suitable for a terminal LD module.

[Prior Art] In an optical fiber communication system, an optical coupling circuit that introduces light output from a light source such as an LD into an optical fiber is an important circuit. Among these, a circuit that evenly branches light from one LD light source to a plurality of optical fibers is useful.

The present inventors previously disclosed in Japanese Patent Application No. 60-97959 a multi-terminal LD module that integrates an LD light source and one fiber terminal, which can be easily assembled. As shown in FIG. 6, the configuration of this multi-terminal LD module is as shown in FIG. Multiple optical fibers are attached to the end face of the slab lens 1G.
The lenses are arranged in a line on the optical axis plane with approximately the same width as the slab lens.

As shown in FIGS. 78 to 7C, this slab lens 10 has a refractive index that changes according to formula 1 from the center to the periphery in the y-axis direction, and in the X direction or two directions perpendicular to the y-axis direction. On the other hand, it is a lens having a uniform refractive index, and the pitch length p is approximately given by Equation 2.

n(y)2=n2(11o2y2)' +11
p=2π/Q.

Here, n is the refractive index of the center, n (y) is the refractive index of the point at the distance my from the center, and qo is a constant.

Furthermore, if we follow the method of diffusing and importing ions giving a high refractive index from the glass surface, which was previously disclosed in Japanese Patent Application No. 59-1469), the numerical aperture in the y-axis direction (N,
A, ) is 0.7, and the maximum divergence angle from the LD light source is 5
Even light that diverges at 0.00 can be sufficiently taken into the lens.

[Problems to be Solved by the Invention] However, in the LD light source 1 currently on the market, the light emitting element 4 is installed approximately one length behind the protective glass 5, as shown in FIG. The laser beam emitted from 5 has a maximum size of about 2- if the divergence angle is large. For this reason, the laser beam becomes larger than the dimensions of the slab lens in seven directions, which are usually matched to the width of the optical fiber array.
When using a conventional slab lens with a rectangular parallelepiped shape,
Depending on the type of LD, part of the light emitted from the LD light source may be vignetted, making it impossible to use the light effectively.

The present invention was made in view of these conventional problems, and provides a slab-like convergent optical transmission body that enables assembly of a highly efficient multi-terminal LD module even when using an LD light source with a large divergence angle. The purpose is to provide.

[Means for Solving the Problems] To achieve the above object, the present invention is directed to a plane in the X and Z directions or an X-Z plane (
Both sides perpendicular to the optical axis (optical axis plane) are tilted with respect to the optical axis, and the length of the end face in the direction perpendicular to both the optical axis and the direction in which the refractive index changes is such that one end face is equal to or greater than the width of the emitted light beam of the laser diode. The other end face has a width equal to the width of a plurality of optical fiber rows arranged in opposition on the optical axis plane.

As described above, in the present invention, since the end surface in contact with the LD light emitting surface is made wide, the light emitted from the LD light source can be used effectively.

[Example] Hereinafter, the present invention will be explained based on the drawings.

As shown in Figure 1, the refractive index of the slab lens 2 gradually decreases toward the periphery in two planes including the optical axis or in the X direction perpendicular to the X-Z plane (optical axis plane). It has a uniform refractive index in the X and Z directions parallel to the surface, and the length in the optical axis direction (X direction) is approximately n/2 (n: 1 or more) of the pitch length determined by the refractive index distribution. is an integer) times
Both side surfaces 8.8 perpendicular to the optical axis plane are inclined at an angle θ with respect to the optical axis. Also, one end surface of this lens 2 is 2
Regarding the length in the direction, the dimension zA is greater than the width in seven directions of the luminous flux emitted from the protective glass of the LD light source 1, and the fiber side end face 7 is matched with the width Z8 of the fiber array 3, and the side surface 8 is along the direction, from end face 6 to end face 7
It has a shape in which the width gradually decreases toward .

In such a shape, the laser beam in the X direction emitted from the LD light source 1 is refracted within the slab lens and focused on the optical axis plane at the output end, as shown in FIG. As shown in Figure 3, the laser beam can go straight through the lens, or
The light is mixed in the lens through repeated total reflections at the lens periphery.1. The light is evenly distributed to the fiber arrays 3 facing each other on the optical axis plane of the output end. It is preferable that the inclination θ between the side surface 8 of the lens and the optical axis satisfies the condition that the laser beam undergoes total reflection on the side surface of the lens.

FIG. 4 shows a case where a reflective film 9 is formed on the oblique side surface 8 of the slab-like lens body 2. As shown in FIG. In this way, the light incident on the side surface 8 from within the slab-shaped lens body is totally reflected, so that loss of optical energy can be prevented.

In addition to high reflection efficiency, this film 9 is required to have strong functional strength and excellent chemical and thermal durability.

Although the purpose of the present invention can be sufficiently achieved with a metal vapor-deposited film such as A42, if a total reflection film obtained by vapor-depositing a transparent material with a low refractive index such as MQF2 is used, it is possible to form a reflective film on the incident end face or the outgoing end face. This is convenient because there is no interference and the incident light and the emitted light are not damaged.

FIG. 5 shows a predetermined length X near both end surfaces following the length in the optical axis direction x 2 having the oblique side surface 8 of the slab-like lens body 2.
Another example is shown in which side surfaces 8a and 8b are formed parallel to the direction (y direction) in which the refractive index decreases over + and X3. In this case, a reflective film 9 may be formed on the side surfaces 8a and 8b as well as the side surface 8.

Next, the manufacturing method and effects of the product of the present invention will be explained.

Optical glass TiF6 (P2O54 in composition weight %)
7.9%, N820 19.8%, K207.
7%.

Al1zo33°7%, T i 02 15.4%
, other 1.6%) 20x 20x 5
am sheet glass weight%r40% AQN03 60
% KNO317) The mixed salt was immersed in molten salt heated to 320°C and treated for 96 hours. The surface was then polished so that it sank against the surface. Immediately, after cutting the glass into two equal parts, the two glass bodies are joined so that the polished surfaces are in contact with each other, and the value of Q is 0.432 mm- when expressed according to equation 1 above. A slab lens raw material having a value of 1 was obtained.

From this raw material, the dimensions shown in Figure 5 are X+-011X2-
13.8011, X3 = O1l, Z＾ −
2.5-1, Process Z8-0.9mm slab lens,
When an LD light source with a maximum divergence angle of 40° (maximum diameter of the luminous flux output from the protective glass surface 1,8+n) was connected to a fiber array consisting of 10 8l-80 fibers (core diameter 80 μm, cladding diameter 90 μm) arranged in a row, the insertion occurred. Loss 1.4d
A highly efficient 10-terminal LD module with B output variation of 0.2 dB was obtained.

Table 1 also shows the performance of a 10-terminal LD module manufactured using a slab lens processed into the shape shown in the table below from the same slab lens raw material as above.

In Examples 6 and 7, a HQF2 film and an Al1 film each having a thickness of 0.5 .mu.I were attached to the side surface of the slab lens by vapor deposition, but the insertion loss was smaller than in Examples 1 to 5, and the effect was recognized.

[Effects of the Invention] According to the present invention, a high-efficiency multi-terminal LD module can be obtained through simple assembly by simply connecting a commercially available LD light source and a fiber array to both ends of a slab lens. Furthermore, since the end face in contact with the light emitting surface 10 is made wide, the light emitted from the LD light source can be used effectively.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing the shape of a slab lens according to the present invention, Fig. 2 is a side view illustrating the state of light rays within the slab lens, and Fig. 3 is a plan view illustrating the state of light rays within the slab lens. , FIG. 4 is a plan view illustrating a reflective film attached to the side surface of a slab lens, FIG. 5 is a plan view showing the shape of a slab lens of another embodiment, and FIG. 6 is a perspective view of a conventional multi-terminal LD module. 7A to 7C are refractive index distribution diagrams of the slab lens used in FIG. 6, and FIG. 8 is a perspective view of a commercially available LD light source. DESCRIPTION OF SYMBOLS 1... Laser diode, 2... Slab-shaped focusing optical transmission body (slab lens), 3... Optical fiber array, 4... LD light emitting element, 5...-LD protective glass,
6... LD side end surface of slab-like focusing optical transmission body, 7...
・Optical fiber side end surface 8 of slab-like focusing optical transmission body...
Side surface, 9...reflective film. Applicant Hoya Co., Ltd. Agent Masayuki Asakura Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. The refractive index gradually decreases in one direction (y direction) perpendicular to the optical axis plane from the optical axis plane toward the periphery, and in directions parallel to the optical axis plane (x and z directions). has a uniform refractive index for There is a slab-like lens body for a terminal laser diode module; both side surfaces (8) (8) perpendicular to the optical axis plane are inclined with respect to the optical axis, and the direction in which the optical axis and refractive index at the end face changes ( The length of the end face in the direction (z direction) perpendicular to both the x and y directions is longer than the width of the emitted light beam of the laser diode at one end face (6), and on the optical axis plane at the other end face (7). A slab-like convergent optical transmission body characterized by having a width equal to the width of a plurality of optical fiber rows arranged in opposition to each other. 2 The inclination of both side surfaces (8) (8) with respect to the optical axis is an angle that satisfies the condition that the light incident on this surface from the slab-like converging light transmission body is totally reflected by the light transmission body. The slab-like focusing optical transmission body according to item 1. 3. Both side surfaces (8) (8) are provided with reflective films (9) that have a function of causing total reflection of light incident on these surfaces from within the slab-like lens body (2). The slab-like focusing optical transmission body described in 2. 4 The slab-like lens body (2) has side surfaces (8a) (8b) parallel to the direction (y direction) in which the refractive index decreases without tilting over a predetermined length (X_1) (X_3) near both end surfaces.
) The slab-like convergent optical transmission body according to claim 1, wherein the slab-like convergent optical transmission body is formed with: