JPS62150307A - Light receiving element with optical fiber - Google Patents

Abstract

PURPOSE:To obtain an optical receiver having an excellent performance by fixing an optical fiber by a supporting body which has been brought to bending to a prescribed shape, in a light receiving element. CONSTITUTION:In a supporting body 8 which has been brought to bending to a prescribed shape, an optical fiber 5 is inserted and fixed, and it is fixed to a photodetector in a connecting part 4. The optical fiber 5 is inserted into the supporting body 8 consisting of a copper pipe, and thereafter, the supporting body is brought to bending, and it is aligned and fixed by using a usual fine motion base so that the light receiving sensitivity becomes maximum, to a light receiving part of an InGaAs PIN photodiode. In this state, the sensitivity being equal to the sensitivity when a conventional light receiving element with an optical fiber has been used linearly is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Purpose of the invention (a) Industrial application field The present invention relates to a light receiving element that converts light into an electrical signal, which is essential in communication systems using optical fibers and in the field of optical measurement. It is something.

(b) Conventional technology The photodetector includes a single photodetector (Figure 2) and one integrated with an optical fiber (commonly known as pinogtail quib).
・Figure 3). In the single photodetector shown in FIG. 2, a photodiode (such as a Si or Ge PIN photodiode) that converts light to electricity is housed in a package 2 having a light transmission window 1. Light is incident from above. The electric signal is electric II 3, 3'
taken out from

For example, as shown in FIG. 3, the light-receiving element with an optical fiber includes a photodetector and an optical fiber 5 at a junction 1. It is fixed and integrated. By integrating with the optical fiber in this way, it becomes possible to take in light from the direction of pressure by utilizing the flexibility of the optical fiber. Easy to handle.

1. Small optical receiver); As shown in FIG. 4, the light receiving element with optical fiber is housed and mounted in the outer box 6 together with the electronic circuit components.Usually, the optical fiber is wound once or several times into a loop. The end of the optical fiber is connected to the optical connector 7 or taken out to the outside of the outer box 6 without being connected to the optical connector (not shown in the figure).

Optical fiber like this? The reason for winding it in a loop is that it is easier to make the optical fiber with a certain length for mounting purposes, it is easier to repair the optical fiber in case it breaks, and it is also convenient when using an optical receiver. This includes allowances for expansion and contraction of various parts due to fluctuations in ambient temperature. The external dimensions of a compact optical receiver generally range from several tens of mm to about 100 to 200 mm.

When a light-receiving element with an optical fiber is incorporated into an optical receiver having such external dimensions, the bending radius of the above-mentioned optical fiber loop is approximately 10 mm to 100 mm.

(C) Problems to be Solved by the Invention Conventionally, when assembling this type of light receiving element with an optical fiber, the optical fiber was aligned with the light receiving part of the photodetector in a state where the optical fiber was almost straight, linearly or gently bent. This is done by fixing it at the position where it is maximum. When an optical fiber aligned and fixed in such a state is actually used, it will be bent with a small radius of curvature of about 10 mm to 100 to 200 mm, as described above.

By the way, in the conventional optical fiber-equipped light receiving element shown in FIG. 3, the connecting portion 4. Measurements have revealed that when an optical fiber is bent in the vicinity of , the sensitivity of the light-receiving element changes as the radius of curvature R increases. Based on the sensitivity when the optical fiber is straight, the decrease in sensitivity when bent with the radius of curvature R is the excess loss (dB), then the curvature/radius R
The relationship between the reciprocal of and the excess loss is shown in Figure 5. That is, when the radius of curvature is 30 mm, it is 0.5 dB and 20 m
An excess loss of 1 dB occurs at m. This value is a non-negligible value compared to the loss occurring in connections between optical fibers and optical connectors, and poses a problem in terms of the performance of the optical receiver and the design of the optical transmission system using it.

(d) Means for Solving the Problems The present invention was made based on the following considerations regarding the cause of the occurrence of the above-mentioned excessive loss.

In other words, by bending an optical fiber, the pattern of light radiation from the end face of the optical fiber deviates from the pattern of radiation from the end face when the optical fiber is straight. In this case, the amount of light incident on the photodetector is smaller than when the optical fiber is straight. The optical fiber has a small radius of curvature.
As the radius of curvature of the optical fiber decreases, the deviation of the radiation pattern becomes larger. Therefore, the smaller the radius of curvature of the optical fiber, the more apparently the sensitivity of the light-receiving element decreases, that is, the excess loss increases.

The present invention eliminates such problems and eliminates excessive loss when the optical fiber is bent and mounted.
The purpose of the present invention is to provide a light-receiving element with an optical fiber and a method for manufacturing the same, which allows the maximum sensitivity of the light-receiving element to be obtained.
It has the following characteristics.

(e) Function The optical fiber-equipped light-receiving element of the present invention is formed by connecting and fixing an optical fiber fixed to a support body bent into a predetermined shape with respect to a photodetector that converts light into an electrical signal. It is characterized by this. Further, the manufacturing method is characterized in that an optical fiber fixed to a support body previously shaped into a predetermined shape is aligned and fixed to a light receiving part of a photodetector.8(f) Embodiment FIG. 1 is an outline diagram showing one embodiment of a light receiving element with an optical fiber according to the present invention.

In FIG. 1, a support 8 is bent into a predetermined shape.
An optical fiber 5 is inserted into and fixed to the photodetector at the connecting portion 1.

The support 8 was used as a copper pipe having an inner diameter of 1 mm, an outer diameter of 2 mm%, and a length of 80 mm, and the optical fiber 5 was a graded index type optical fiber having a core diameter of 50 μm, a cladding diameter of 125 μm, and an NA of 0.2.

After inserting the optical fiber 5 into the support 8 made of a copper pipe, it was bent with a radius of curvature of 20 mm, and then
The light receiving portion of an InGaAs PIN photodiode having a light receiving diameter of μm was aligned and fixed using a normal fine movement table so that the light receiving sensitivity was maximized. In this state, a sensitivity equivalent to that obtained when using a conventional light receiving element with an optical fiber in a straight line was obtained.

Copper pipes were used as supports because they have a moderate amount of flexibility and are easy to bend, and because they slide easily between the pipes and the optical fibers during bending, undue force is applied to the optical fibers. The reason is that there is little risk.

In addition, the radius of curvature of the bending process is 20 m according to the dimensions of the case of the optical receiver in which this light receiving element with optical fiber is used.
It was set as m. This radius of curvature can be made even smaller, but if it is bent with a small radius of curvature of 20 mm or less, there is a risk that the optical fiber's characteristics will deteriorate or break during long-term use due to the bending stress applied to the optical fiber itself. becomes higher. Therefore, it is appropriate that the radius of curvature is 20 mm or more.

Needless to say, it is possible to have a one-way radius of 200M or more, but when the radius of curvature is large, there is almost no decrease in sensitivity even with a conventional linear optical fiber-equipped light receiving element that is aligned and fixed. Also, it is not a subject of the present invention because it has few advantages in terms of implementation.

In the examples, a copper pipe was used as the support, but the material is not limited to copper, and any material such as stainless steel, aluminum, ceramic, plastic, etc. can be used.

Further, its shape is not limited to a pipe, but may be a flat plate, a template with a concave cross section, a polygonal rod, or any other shape as long as it can support and fix the local fiber.

(g) Effects of the Invention As stated above, the optical fiber-equipped photodetector of the present invention uses a pre-bent optical fiber that is aligned and fixed with respect to the photodetector, so that the end surface caused by the bending of one optical fiber The photodetector will be aligned in accordance with the deformation of the pattern of radiation from the photodetector. Therefore, the maximum sensitivity can be obtained when the optical fiber is in a sharp bend when mounted in a small optical receiver, etc., so the optical reception performance is superior to that when using a conventional optical fiber-attached photodetector. can be configured.

In addition, as a side effect of the optical fiber being protected by the support, mechanically weak connections 4
Another advantage is that it does not apply excessive force to the vicinity, and it is possible to prevent unexpected accidents such as damage to the optical fiber. As described above, the optical fiber-attached light receiving element of the present invention is particularly useful as a light receiving element used in small optical receivers and the like.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of the optical fiber-equipped light receiving element of the present invention, Fig. 2
The figure is an external view of the light director, Figure 3 is the 11 factors of the optical fiber-equipped light-receiving element, Figure 4 is a diagram showing an example of the arrangement of the light-receiving element in the optical receiver, and Figure 5 is the bending radius of the optical fiber. FIG. 3 is a diagram showing the relationship between losses. l...Light entrance window 2...Package 3.3'...Electrode 4...Joint part 5...Optical fiber 6... ... Optical receiver 7 ... Optical connector 8 ... Hollow pipe

Claims (4)

[Claims] (1) A light receiving element consisting of a photodetector that converts light into an electrical signal and an optical fiber that guides the light to the photodetector, in which the optical fiber is fixed with a support that is bent into a predetermined shape. A light-receiving element with an optical fiber characterized by: (2) The optical fiber according to claim 1, characterized in that the optical fiber is fixed to a support body that has been shaped in advance into a predetermined shape and is aligned and fixed to the light receiving part of a photodetector. Additional light receiving element. (3) The radius of curvature of the optical fiber fixed on the support is 20
The optical fiber-attached light receiving element according to claims 1 and 2, characterized in that the length is from mm to 70 mm. (4) The light-receiving element with an optical fiber according to claim 3, wherein the support body is made of a copper pipe, and an optical fiber is inserted and fixed into the copper pipe.