JPH03263006A - Light receiving device - Google Patents

Abstract

PURPOSE:To improve the optical coupling efficiency between an optical fiber and a light receiving element by incorporating the optical fiber and a semispherical lens in a ferrule and converging the light from the semispherical lens on the light receiving face of the light receiving element. CONSTITUTION:This device is provided with an axial center hole 11, a lens storage chamber 12 provided on the extension to the axial center hole 11 and a ferrule 10 provided with an outgoing hole 13 opened in a prescribed position of the side wall of the lens storage chamber 12. The optical signal propagated in an optical fiber 1 is conically emitted from the plane end face of the optical fiber 1 and is made incident on a semispherical lens 15 and is turned at 90 deg. by the cut face of the semispherical lens 15 and is reflected toward an exit hole 13 and is converted to a condensed beam by the lens action of the lower spherical face and passes through the exit hole 13 and is converged on a light reception face 6a of a light receiving element 6. The spherical lens is produced and a part or a half of the sphere is removed by polishing to provided the cut face, thereby obtaining the semispherical lens 15. That is, the semispherical lens not only is easy to produce to have a high yield but also has the spherical face of fixed curvature. Thus, the optical coupling efficiency between the fiber 1 and the element 6 is improved.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a light receiving device that optically couples an optical fiber and a light receiving element, and aims to provide a light receiving device that has high optical coupling efficiency and is low cost. In a device including a fiber and a light receiving element mounted with a light receiving surface facing upward on a circuit board parallel to the optical fiber, an axial hole and a lens housing chamber provided on an extension line of the axial hole; , a ferrule having an output hole bored at a predetermined position in a side wall of the lens housing chamber, the end portion of the optical fiber being inserted into the axial hole of the ferrule, and the end portion of the optical fiber being inserted into the axial hole of the ferrule, A hemispherical lens is held such that the spherical surface is in contact with the end surface of the optical fiber and the cut surface is inclined at 45 degrees to the axis of the optical fiber, and the output hole is close to the light receiving surface of the light receiving element. The ferrule is attached to a housing housing the light-receiving element in a facing state.

[Industrial Application Field] The present invention relates to a light receiving device that optically couples an optical fiber and a light receiving element.

In recent years, light receiving devices have been provided in which an electric circuit such as a receiving circuit and a light receiving element are provided on the same circuit board.

At this time, if the optical signal transmission path and the electrical signal line are perpendicular to each other, there is a risk that the entire device will become larger.

Therefore, so-called flat-mounted light-receiving devices are becoming popular, in which a circuit board provided with an electrical signal path and an optical transmission path are installed in parallel.

On the other hand, in order to improve frequency characteristics, the capacitance of the light receiving element is made as small as possible. As a result, the light-receiving surface of the light-receiving element becomes smaller, and the degree of optical coupling decreases.

Therefore, there is a need for a light-receiving device that allows optical signals to efficiently enter a light-receiving element.

[Prior Art] FIG. 2 is a cross-sectional view of a conventional example in which an optical fiber and a light receiving element are combined in a plane mounting type.

In FIG. 2, reference numeral 5 denotes a circuit board made of ceramics or the like, on which a desired electric circuit and a light-receiving element 6 such as a photodiode are mounted, and is housed in a housing 7.

The light-receiving element 6 is a chip-type element having a light-receiving surface 6a on the upper surface, and has an electrode provided on the entire back surface, and the electrode is closely connected to a pattern formed on the circuit board 5, and the light-receiving surface 6a Another ring-shaped electrode is provided around the periphery of the ring-shaped electrode, and this ring-shaped electrode is connected to a pattern that is another electrical signal path.

That is, the light receiving element 6 is mounted on the circuit board 5 with the light receiving surface 6a facing upward and parallel to the upper surface of the circuit board 5.

Reference numeral 20 denotes a so-called spherical tip optical fiber whose output end surface is made spherical after peeling off the outer sheath 2OA at the tip.

The tip sphere of the optical fiber 20 has a tip sphere of 45 mm with respect to the axis.
The hemispherical part 2 is obtained by cutting and polishing on the inclined surface.

For example, a V-shaped groove is provided in the side wall of the housing 7, and with the cut surface facing upward and the hemispherical surface facing the light receiving element 6, the tip optical fiber 20 is inserted horizontally into this groove and supported. Then, the outer circumferential surface of the tip optical fiber 20 and the inner wall of the groove are bonded and fixed using an adhesive side or the like.

Therefore, the optical signal propagating through the optical fiber 20 is almost completely reflected at the cut surface of the hemispherical portion 2 in the downward direction perpendicular to the axis, that is, in the direction of the light receiving element 6, and is reflected downward. Projected onto a spherical surface. Then, the light is emitted from the hemispherical portion 2 so as to be focused by the action of a hemispherical lens, and is focused on the light receiving surface 6a of the light receiving element 6.

The tip of the optical fiber is made from an ordinary optical fiber with a flat end.While rotating the optical fiber, the flat end is heated and melted using an oxyhydrogen burner, and the surface tension of the molten material is used to shape the end into the desired shape. It is manufactured by making it a spherical surface of curvature.

As described above, the light receiving device is mounted in parallel with the axis of the optical fiber close to the top surface of the circuit board. Therefore, the light receiving device becomes smaller than when the optical fiber is mounted perpendicularly to the surface of the circuit board.

[Problem to be solved by the invention]

By the way, in the conventional light-receiving device described above, in which the tip sphere of the optical fiber is cut and polished with a plane inclined at 45 degrees with respect to the axis of the optical fiber, the curvature of the spherical surface of the tip sphere varies, and the optical fiber It is difficult to form a hemispherical portion with a cutting surface at exactly 45 degrees with respect to the axis.

Due to the above, not only the yield of the tip bulb is poor and the cost is high, but also the light convergence characteristics are poor due to the dispersion in the curvature of the tip bulb, and the light receiving There was a problem that the optical coupling efficiency with the device was low.

The present invention was created in view of the above points, and an object of the present invention is to provide a light-receiving device with high optical coupling efficiency and low cost.

[Means to solve the problem]

In order to achieve the above object, the present invention, as illustrated in FIG. A device equipped with a light-receiving element 6 to be mounted, which includes an axial hole 11, a lens accommodating chamber 12 provided on an extension of the axial hole 11, and a side wall of the lens accommodating chamber 12, which is bored at a predetermined position. A ferrule IO having a radiation exit hole 13 is provided.

Then, the end portion of the optical fiber 1 is inserted into the axial hole 11. On the other hand, the hemispherical lens 15 is held in the lens storage chamber 12 so that the spherical surface contacts the end surface of the optical fiber 1 and the cut surface is inclined at 45 degrees to the axis of the optical fiber 1.

The ferrule 10 with the optical fiber l and the hemispherical lens 15 mounted in this way is mounted on the housing 7 housing the light receiving element 6, with the emission hole 13 being close to and facing the light receiving surface 6a of the light receiving element 6. do.

[Function] φ According to the present invention, the optical signal propagated through the optical fiber 1 is emitted from the flat end surface of the optical fiber 1 in a conical shape and is incident on the hemispherical lens 15, and the cut surface of the hemispherical lens 15 forms an angle of 90 degrees. It is reflected in the direction of the exit hole 13 whose direction has been changed. Then, it becomes a condensed beam due to the lens action of the lower spherical surface, and the output hole 13
and converges on the light receiving surface 6a of the light receiving element 6.

On the other hand, the hemispherical lens 15 is obtained by manufacturing a spherical lens, and polishing and removing a part of the sphere or a half of the sphere to provide a cut surface. That is, it is not only easy to manufacture and has a high yield, but also has a constant curvature of the spherical surface.

Therefore, since the convergence of the hemispherical lens 15 is extremely high, the optical coupling efficiency between the optical fiber l and the light receiving element 6 is improved.

〔Example〕

The present invention will be specifically described below with reference to the drawings. Note that the same reference numerals indicate the same objects throughout the figures.

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

In FIG. 1, an electric circuit such as a receiving circuit and a light receiving element 6 such as a photodiode are mounted on the surface of a circuit board 5 made of ceramics or the like.

The light-receiving element 6 that receives the optical signal has a small electric capacity and is a chip type having a narrow light-receiving surface 6a on the front side, and is connected to an electrode (not shown) provided on the entire back surface in close contact with the pattern. The ring-shaped electrodes on the front surface are connected to terminals of other patterns provided on the surface of the circuit board 5 by wire bonding.

That is, the light receiving element 6 is mounted on the circuit board 5 so that the light receiving surface 6a faces upward.

Note that this circuit board 5 is housed in a box-shaped casing 7 having a removable lid on the top surface.

The material of the housing 7 is a material whose thermal expansion coefficient is approximately equal to that of glass, such as a Ni-Co-Fe alloy.

Reference numeral 1 denotes an optical fiber whose outer peripheral surface for transmitting optical signals is protected by a jacket LA (outer diameter approximately 0.9 mm), and the outer diameter of the cladding portion is 125 μm. Then, the outer sheath IA of the terminal portion of the optical fiber I is peeled off to expose the crown, which is then inserted into the ferrule.

15 has a diameter of approximately 2 with the total reflection film 16 formed on the cut surface.
It is a 1w1 hemispherical lens.

This hemispherical lens 15 is made by providing a base having a hemispherical recess, inserting the spherical lens into the recess, polishing and removing a part of the sphere or a half of the sphere, and finishing the cut surface by lapping. It has a smooth surface.

10 is a cylindrical ferrule made of stainless steel, ceramics, or the like.

The ferrule IO is provided with an axial hole 11 having an inner diameter approximately equal to the outer diameter CI25μll1) of the optical fiber 1 in the center thereof, and an outer sheath IA of the optical fiber 1 on one extension line.
By providing a hole with an inner diameter larger than the outer diameter of
The optical fiber 1 is inserted into the optical fiber 1, and the outer cover 18 is fixed using an adhesive.

Also, on the other extension of the axial hole ll, a hemispherical lens 15 is provided.
Round hole-shaped lens housing chamber 1 with an inner diameter slightly larger than the diameter of
2 is provided.

The diameter of the hemispherical lens 15 is larger than the diameter of the hemispherical lens 15 on the side wall of the lens housing chamber 12, which is away from the bottom surface of the lens housing chamber 12 (the interface between the axial hole 11 and the lens housing chamber 12) by a length equal to the radius of the hemispherical lens 15. A small emission hole 13 is also provided.

Furthermore, the ferrule IO has emission holes 13 to 18.
A key 18 is fixed to the inner wall portion of the lens housing chamber 12 at a distance of 0 degrees.

17 is a cylindrical fixed body made of, for example, stainless steel. The outer diameter of the fixed body 17 is slightly smaller than the inner diameter of the lens housing chamber 12, and one end surface is cut with a surface inclined at 45 degrees to the axis.

A key groove into which the key 18 is inserted and slides is provided in the circumferential surface portion diagonally above the cut surface.

The optical fiber 1 is fixed to the ferrule 10 by inserting the end portion of the optical fiber 1 into the axial hole 11 of the ferrule 10 and bonding the outer peripheral surface of the jacket IA to the ferrule 10 using adhesive. are doing.

On the other hand, a hemispherical lens 15 is housed and held in the lens storage chamber 12 with its spherical surface abutting the end surface of the optical fiber 1 and its cut surface inclined at 45 degrees to the axis of the optical fiber 1.

To explain in detail the holding structure of the hemispherical lens 15, first,
So that the cut surface is on the front side and on the opposite side from the emission hole 13,
A hemispherical lens 15 is inserted into the lens housing chamber 12, and its spherical surface is brought into contact with the end surface of the optical fiber 1.

Next, the key groove is aligned with the key 18 and the fixed body 17 is pushed into the lens housing chamber 12.

Then, with the cut surface of the fixed body 17 in close contact with the total reflection film 16 of the hemispherical lens 15, the end face of the fixed body 17 and the end face of the ferrule 10 are fixed using an adhesive.

Or fix it by laser welding or the like.

As described above, the cut surface of the fixed body 17 is in close contact with the cut surface of the hemispherical lens 15, and the key 1 is located on the opposite side from the exit hole 13.
8 is fitted with a keyway, so that the cut surface of the hemispherical lens 15 is inclined at exactly 45 degrees to the axis of the optical fiber l.
In addition, the spherical surface is held in contact with the end surface of the optical fiber 1.

Such a ferrule 10 is inserted into a hole in the side wall of the housing 7 so as to be parallel to the circuit board 5, and with the output hole 13 close to and facing the light-receiving surface 6a of the light-receiving element 6, the outer periphery of the ferrule 10 and the housing It is fixed to the housing 7 by, for example, laser welding or bonding with an adhesive.

Since the ferrule 10 is attached to the housing 7 as described above, the optical signal propagating through the optical fiber 1 exits from the flat end surface of the optical fiber 1 in a conical shape and enters the hemispherical lens 15. Cutting surface of hemispherical lens 15.

That is, the light is reflected by the surface of the total reflection film 16, changes direction by 90 degrees, and travels in the direction of the emission hole 13.

The light is then projected onto the lower spherical surface of the hemispherical lens 15, becomes a condensed beam by the lens action, passes through the exit hole 13, and is converged on the light-receiving surface 6a of the light-receiving element 6.

In this example, a single optical fiber is inserted into a cylindrical ferrule, but by making the outer shape of the ferrule plate-like and providing multiple axial holes in parallel, the optical fiber array and light receiving This can be applied to a light receiving device that is optically coupled to an element array.

〔Effect of the invention〕

As explained above, the present invention incorporates an optical fiber and a hemispherical lens into a ferrule, and is configured to converge the light emitted from the hemispherical lens on the light receiving surface of the light receiving element, thereby achieving the following practical advantages. It has a great effect.

Since the optical fiber has a flat output surface, no special processing is required. On the other hand, since a hemispherical lens is obtained by polishing and removing a portion of a spherical lens to provide a cut surface, it is easy to manufacture and has a high yield. Further, the work of combining the optical fiber and the hemispherical lens is easy. Therefore, the light receiving device of the present invention is low cost.

Since a hemispherical lens is a spherical lens with a cut surface, there is no variation in the curvature of the spherical surface.

Therefore, the convergence of the hemispherical lens 15 is extremely high, and the optical coupling efficiency between the optical fiber and the light receiving element is high.

Furthermore, since the ferrule is fixed to the housing or the like so that it can be easily handled, it is easy to adjust the focal position of the hemispherical lens to match the light-receiving surface.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional example. In the figure, 1 is an optical fiber, 2 is a hemisphere, 5 is a circuit board, 6 is a light receiving element, 6a is a light receiving surface,
7 is a housing, 10 is a ferrule, 11 is an axial hole, 12 is a lens housing chamber, 13 is an exit hole, 15 is a hemispherical lens, 16 is a total reflection film, 17 is a fixed body, and 20 is a tip optical fiber. . Fig. 1 is a side view of grilling example 1 of the present invention; Fig. 2 is a sectional view of the conventional example;

Claims (1)

[Claims] An optical fiber (1) that transmits an optical signal, and an optical fiber (1) that transmits an optical signal.
In a device including a light-receiving element (6) mounted with the light-receiving surface facing upward on a circuit board (5) parallel to 1), an axial hole (11) and an extension of the axial hole (11). A ferrule (10) having a lens accommodating chamber (12) provided on a line and an exit hole (13) bored at a predetermined position in a side wall of the lens accommodating chamber (12), the ferrule (10) The end portion of the optical fiber (1) is inserted into the axial hole (11), and the lens housing chamber (1) is inserted into the optical fiber (1).
2), the spherical surface is in contact with the end surface of the optical fiber (1), and the cut surface is inclined at 45 degrees to the axis of the optical fiber (1);
A hemispherical lens (15) is held, and the exit hole (13)
) is close to and facing the light-receiving surface of the light-receiving element (6), and the ferrule (10) is attached to a housing (7) housing the light-receiving element (6).