JPS63287807A - Photodetector made of two-input optical fiber - Google Patents

Abstract

PURPOSE:To improve the accuracy of mounting a photodetecting element and to provide a stable high-reliability device by receiving the two input signals from two optical fibers in the same element and sloping the end faces of the optical fibers relative to optical fiber axes with a photodetecting device made of two-input optical fibers. CONSTITUTION:The optical fibers 1, 2 are fixed at the end parts to a ferrule 12 by bringing the respective optical fiber axes 3, 4 into parallel tight contact with each other. The end face 10 thereof is so worked integrally as to be perpendicular to the plane constituted of two pieces of the optical fiber axes 3, 4 and to be flush diagonally at phi angle with the optical fiber axes 3, 4. Central axes 5, 6 of the exit beam light refracted by the end face 10 of the optical fibers 1, 2 are refracted at the theta angle with the optical fiber axes 3, 4 and the spacing thereof is made smaller than the spacing between the optical fiber axes 3 and 4. Such beam light is condensed to a small photodetecting area of the photodetecting element 9 and is superposedly received therein. The position of a holder B22 inserted into a metallic fitting 23 is adjusted while the amt. of tolerance is adjusted; thereafter, the outside circumferential part of the holder B22 is welded and fixed to the fitting 23 at the time of assembly. The amt. of tolerance is thereby increased and the safe photodetecting device having the high reliability is obtd.

Description

[Detailed Description of the Invention] [Summary] The present invention is a two-input optical fiber light receiving device that receives two-power signals from two optical fibers using the same element, converts them into electrical signals, and outputs them. The end face is sloped with respect to the optical fiber axis, and the emitted beam light is refracted at the end face.
The effect of reducing the distance between the optical fiber axes is obtained, which has a good effect on the subsequent condensing light receiving system, and particularly contributes to improving the mounting accuracy of the light receiving element, resulting in a stable and highly reliable light receiving device.
Furthermore, the speed of the device can be increased.

[Industrial application field]

The present invention relates to a light receiving device that receives human input signals from two optical fibers with the same element, converts them into electrical signals, and outputs them, and relates to a two-input optical fiber light receiving device that receives light stably and with high reliability.

With the commercialization of optical fiber cables, optical communication systems using them have been developed and put into practical use at a rapid pace, achieving higher speeds, larger capacities, and longer distances, and reaching a stage where they surpass the conventional coaxial cable system. It is.

This optical communication system receives optical signals from optical fibers,
A light receiving device that converts into an electrical signal is a key device of an optical receiving section, and is required to have high reliability.

[Conventional technology]

Figure 3 shows a diagram of the optical system configuration of a conventional two-person light receiving device.
Figure 4 (al is an enlarged view of the beam light on the light receiving surface at the A position, the same figure (bl is the same diagram at the B position, Figure 5 (al is the tolerance characteristic at the A position, the same figure (b) is an enlarged view of the beam light on the light receiving surface at the B position) Shows the same characteristics.

A common method for receiving optical signals from multiple optical fibers in a superimposed manner is to connect a light receiving device to each optical fiber and superimpose the output electrical signals. Therefore, it is necessary to have the same characteristics, which is not desirable from an economical and reliability standpoint.If there are fewer than four optical fibers, there is a light receiving device that condenses the output light of multiple optical fibers and receives the light in a superimposed manner on the same light receiving element. , - As an example, an input light receiving device with two optical fibers is shown in FIG.

In two independent single-core optical fiber cables, the optical fibers 1.2 are made up of a core and a cladding layer from which the outer protective coating has been removed, and the optical fiber axes 3.4 are parallel to each other, and the ends are fixed in close contact with each other. The end face 11 is integrally processed into the same plane perpendicular to the optical fiber axes 3 and 4.

Furthermore, on the extension of the center line 71 between the optical fiber shafts 3 and 4, a condenser lens 8 and a light receiving element 9 are arranged with the two axes aligned at a predetermined interval.

The light beams emitted from the end faces 11 of the optical fibers 1 and 2 form a beam whose optical axes coincide with the respective optical fiber axes 3 and 4, and whose spread extends to the aperture angle of the optical fibers 1.2. , this is condensed by a condensing lens 8, and further 2
The distance between the light beams emitted by the book is also refracted.

The light is reduced and focused on a small light-receiving area of the light-receiving element 9,
Superimposed light reception is performed.

Since the magnitude 9 interval of the input beam light changes depending on the position on the center line 71 of the light receiving surface, the distance deviation on the center line 71 of the light receiving element 9 can be finely adjusted.

At this time, the beam light on the circular light receiving surface becomes as shown in the enlarged view of Figure 4, and the X connecting the centers of the two beam lights 53 and 63
When the center of the circular light-receiving surface 91 moves on the axis, the relationship between the distance X and the light-receiving current I is as shown in the tolerance characteristic in FIG.
64 are each 1 (section 5 (7) where 10% received light amount overlaps
The axial distance is used as the tolerance amount.

This tolerance defines the lower limit of the assembly accuracy of the optical system, and is determined to ensure stable and highly reliable light reception by taking into account deviations in the optical system caused by temperature fluctuations during use and aging. be.

[Problem that the invention seeks to solve]

However, beam light 53.63 on the light receiving surface at positions A and B on the center line 71 in FIG.
) As shown in the enlarged view of (b), the diameter of the beam light becomes small at the A position, and the diameter becomes large at the B position, and the interval is slightly reduced.

On the other hand, as shown in FIG. 5, the tolerance S is larger at the A position than at the B position.

However, the dimensions and characteristics of the optical fiber 1.2, the condenser lens 8
The maximum tolerance amount is uniquely determined by the characteristics of and the light-receiving area of the light-receiving element 9.

In addition, the actual tolerance amount is further reduced due to processing dimensional accuracy and assembly accuracy.

Therefore, when greater tolerance is required,
There is no choice but to improve the performance and precision of component parts.

However, it is not possible to reduce the diameter of the optical fiber 1.2 for this purpose, and all other fibers have been made with the highest performance, and it has been difficult to make the diameter larger than that.

In addition, as speeds increase, the light-receiving surface of light-receiving elements tends to become smaller, and there is also a desire to maintain the same amount of tolerance as conventional devices even when using such elements, which limits the ability to achieve higher speeds. was giving.

In view of this problem, the present invention provides a new two-person optical fiber light receiving device that further improves the tolerance without changing the component parts.

[Means for solving problems]

As shown in the principle diagram of the present invention in FIG. 1, the above problems are as follows:
In a two-input optical fiber light receiving device in which optical signals from two independent optical fibers 1.2 are simultaneously received by the same light receiving element, the ends of the two optical fibers 1.2 are connected to the optical fiber shafts 3 and 4. are brought into close contact with each other in parallel, and their end faces 10 are integrally processed so that they are in the same plane perpendicular to the plane formed by the two optical fiber axes 3 and 4 and oblique to the optical fiber axis 3.4, This problem is solved by the two-input optical fiber light receiving device of the present invention, in which the condenser lens 8 and the light receiving element 9 are arranged on the center line 7 of the center axis 5.6 of the two beams of light emitted from the end face 10. .

[For production]

That is, the emitted beam light is refracted at the oblique end face of the optical fiber, and the distance between the beam optical axes is narrower than the distance between the optical fiber axes.
Even if the optical system is the same thereafter, the amount of tolerance will be large and the objective will be achieved.

Since the end surfaces 10 of the optical fibers 1 and 2 are sloped at an angle of φ with respect to the optical fiber axes 3 and 4, the central axes 5 and 6 of each of the output beams are θ with respect to the optical fiber axes 3 and 4. Since the optical fiber axes 3.4 are parallel, the refracted central axes 5.6 are also parallel, and the distance between them is determined by the following equation with respect to the distance between the optical fiber axes 3 and 4. Reduced.

cos (gf-φ+θ) / cos (9f-φ)
Here, φ>θ, and there is a certain relationship between φ and θ according to the law of refraction, and the slope angle φ of the end face 10 becomes smaller from 90° without causing total reflection at the end face 10. , the refraction angle θ becomes large, and the interval between the central axes 5.6 of the light beams becomes narrower.

In this way, the distance between the central axes 5 and 6 of the emitted beam light is shortened, and the light is then focused by the condenser lens 8 and received in a superimposed manner on the light receiving surface of the light receiving element 9, but this optical system is different from the conventional example described above. Even if it is the same product and configured with the same accuracy, the tolerance can be easily increased.

As described above, as the amount of tolerance increases, a stable and highly reliable light receiving device can be obtained, and it is also possible to increase the speed of the device.

Explain.

The same reference numerals indicate the same objects throughout the figures.

FIG. 2 shows a configuration diagram of an embodiment of the present invention.

In two independent single-core single-mode optical fiber cables, two optical fibers 1.2 each consisting of a core whose outer protective coating is removed and a cladding layer are connected to each other's optical fiber shafts 3.
．． 4 are parallel and in close contact with each other and their ends are fixed to the ferrule 12, and the end surface 10 is perpendicular to the plane formed by the two optical fiber axes 3 and 4, and at an angle of φ degrees with respect to the optical fiber axes 3 and 4. They are machined as one piece so that they are on the same diagonal plane.

The central axis 5.6 of the output beam refracted at the end face 10 of the optical fiber 1.2 is refracted at θ degrees with respect to the optical fiber axis 3.4, and the spread to the opening angle of the optical fiber 1.2 is slightly expanded. The center line 7 of this central axis 5.6
A spherical condenser lens 8 and a light receiving element 9 of an APD (apalanche photodiode) are arranged on the top with their axes aligned at predetermined intervals.

Since the optical fiber axes 3.4 are parallel, the refracted central axis 5.
6 are also parallel, and the distance between them is the same as the optical fiber axes 3 and 4.
The distance is reduced from 0, and the light is focused on a small light-receiving area of the light-receiving element 9, and the light is received in a superimposed manner.

In this configuration, first, the ferrule 12 is fastened to the center of the flange (=J fitting 13) with a ring nut 15 via a coil spring 14.
The protrusion on the outer periphery of 2 is fitted into the inner recess of the flanged metal fitting 13 to prevent rotation.

The condensing lens 8 is fixed using a cylindrical lens holder 16 with a stepped inner hole and a threaded outer periphery, a ring nut 17 that is screwed into the inner hole, and an end surface that is inclined to the refraction angle of the output beam light. The lens fitting 18 has a threaded inner hole, and the inclined end surface of the lens fitting 18 is connected to the flanged fitting 13
The lens holder 16 is screwed into the inner hole of the lens fitting 18, the end surface is butted against the tip of the ferrule 12, and the condenser lens 8 is housed in the inner hole step. Then, the ring nut 17 is screwed in and fastened to assemble the end face 10 of the optical fibers 1, 2 and the condensing lens 8 with an accurate inclination and distance.

Finally, the light-receiving element 9 is fixed by using a holder A21, which has a cylindrical shape with an L-shaped cross section and a threaded outer periphery, which encloses the light-receiving element 9 and fixes it by soldering. an elongated cylindrical holder B22 configured to protrude;
It is comprised of a metal fitting 23 into which the holder B22 is inserted, the end surface of which is brought into contact with the end surface of the lens metal fitting 18, and the optical axes of the condenser lens 8 and the light receiving element 9 are aligned and screwed together.

During assembly, the position of the holder B22 inserted into the metal fitting 23 is adjusted while measuring the amount of tolerance, and the outer peripheral part of the holder B22 is welded and fixed to the end of the metal fitting 23 at the best point.

In this example, when φ-55° and θ=21°, the distance between the center axes 5 and 6 of the beam light is 0.678 compared to the conventional example, which is 1 ( By using an APD with a light-receiving surface having a diameter of 10 μm, the amount of tolerance could be increased by 1.5 times compared to the conventional example.

The above embodiment is an example, and the type of optical fiber, condenser lens, light receiving element, mounting, and assembly structure are not limited to those described above.

[Effects of the Invention] As described above, the amount of tolerance can be increased without changing the component parts or increasing the dimensional accuracy, and a stable and highly reliable light receiving device can be obtained. It is also possible to achieve higher speeds.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the principle of the present invention, Fig. 2 is a block diagram of an embodiment of the present invention, Fig. 3 is a block diagram of the optical system of a conventional example of a two-person light receiving device, and Fig. 4 is a diagram of the structure of the optical system on the light receiving surface. An enlarged view of the beam light, Figure 5, shows the tolerance characteristics. In the figure, 1.2 is the optical fiber, 3.4 is the optical fiber axis, and 5.6
is the center axis, 7 and 71 are the center lines, 8 is the condenser lens,
9 is the light receiving element, = Mi\ -r Mi button! Addition: ;=+, -7Σ 16 is a lens holder, 18 is a lens fitting, 21 is a holder A1, 22 is a holder B, 23 is a metal fitting, 5
3.63 is the beam light, 54.64 is the light receiving characteristic, and 91 is the light receiving surface. −−7−i7 ・−−”：Demani [5 ji

Claims (1)

[Claims] A two-input optical fiber light receiving device that simultaneously receives optical signals from two independent optical fibers (1) and (2) using the same light receiving element, converts them into electrical signals, and outputs them. The ends of the optical fibers (1) and (2) are connected to the optical fiber shafts (3) and (4).
) are brought into close contact with each other in parallel, and their end surfaces (10) are connected to the two optical fiber shafts (3) (4).
) is perpendicular to the plane formed by the optical fiber axes (3) (4
), and the central axis (
5) A two-input optical fiber light-receiving device characterized in that a condenser lens (8) and a light-receiving element (9) are arranged on the center line (7) between (6) and (6).