JP3821638B2 - Light receiving device for POF communication - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light receiving device with a connection part for optical communication using a plastic optical fiber (POF), and relates to a technique that is excellent in incident efficiency of signal light and reduces connection loss during optical transmission.
[0002]
[Prior art]
An optical communication reception system using POF includes a reception system on one end side of an optical signal transmission path using POF. The receiving system has a light receiving element such as a photodiode (PD), and optically connects signal light from the POF to the light receiving element. Hitachi, Toshiba, Matsushita Electric Industrial, Hamamatsu Photonics, etc. can be cited as the source of the light receiving element or the light receiving semiconductor component.
[0003]
The reception performance in such an optical communication system is greatly influenced by the incident efficiency and transmission efficiency of signal light. The current light-receiving device assumes a very thin quartz fiber (diameter of several μm), and has a structure that makes it difficult for a POF having a diameter of several hundred μm to effectively receive signal light.
[0004]
The current light receiving device has a lens interposed between a quartz fiber and a light receiving element. However, this requires not only precise connection but high cost and poor versatility, but when it is applied to POF, it has a problem of causing large connection loss due to reflection on the lens surface.
[0005]
In addition, there is an active movement to standardize connection parts for POF. Movements to standardize at the level of individual companies, Japan or the world are being carried out (home electronics companies, Japan Electronic Machinery Manufacturers Association, POF consortium).
[0006]
In order to reduce connection loss in an optical communication system, the present inventor has a coupling structure (lensless coupling, Japanese Patent Application Laid-Open No. Hei 10) that interposes a light guide having a light guide path surrounded by a reflective surface between an optical fiber and a light receiving element. 10-221573).
[0007]
The present inventor has eagerly investigated further practical application, and has found a method that enables efficient POF communication by interposing an incident light control type light guide component even when a commercially available connection component is used. is there. A commercially available connection part, an efficient light guide part and a light receiving semiconductor part are integrated and connected to POF to realize lensless joining with little transmission loss of signal light.
[0008]
[Problems to be solved by the invention]
The present invention provides a light receiving device for POF communication that has good incidence of signal light and low connection loss. The current light receiving device and connection device are developed on the premise of industrial use (quartz fiber), and development of a low-cost and simple general-purpose product for consumer use (POF) is desired.
[0009]
[Means for Solving the Problems]
The present invention is a light receiving device for POF communication in which a highly efficient light guide component and a light receiving semiconductor component are integrated with a commercially available connection component. The optical axes of the components are aligned and the end faces of the components are in close contact with each other. Yes. Commercially available connection parts can be obtained from Molex, AMP or the like.
[0010]
[Problems to be solved by the invention]
The present invention is an apparatus for optically coupling a plastic optical fiber (POF) and a light receiving element, and its structure is composed of a POF connection part, a light guide part for guiding signal light, and a light receiving semiconductor part. The optical axis of each component is coincident and the end faces of each component are in close contact, the light guide body component is surrounded by a reflective surface, and has a light guide path that is tapered toward the light receiving element, The circular diameter of the end face of the light guide path is equal to or greater than the POF on the POF side and equal to or less than the light receiving part of the light receiving element on the POF side, and a refractive index of 1.30 to 1.60 inside the light guide path of the light guide component. Hardness JIS (A type) Filled with a flexible light transmitting body which is a transparent resin (silicone resin, epoxy resin, acrylic resin, thermoplastic resin, etc.) having a characteristic of 60 degrees or less, and The number of light receiving semiconductor parts is increased The light receiving element is flip-mounted on the circuit board. The circuit board has a light passage hole for guiding the signal light to the light receiving portion of the light receiving element. It is a light receiving device for POF communication, which is sealed with a certain light transmitting body. Examples of the shape of the light guide include a spheroid, a rotating paraboloid, and a truncated cone.
[0011]
According to a second aspect of the present invention, there is provided a light receiving device for POF communication in which a connection component and a light guide component, or a light guide component and a light receiving semiconductor component are in close contact with each other through the flexible light transmitting body. .
[0014]
When using a commercially available connection component, it is necessary to integrate a highly efficient light guide component and a light receiving semiconductor component, align the optical axes of the components, and bring the end faces into close contact. The signal light is transmitted from the POF and effectively enters the light receiving element through the light guide. Each component may be attached by either the fixing method or the detaching method as long as the optical axis alignment accuracy can be obtained. The light guide body component and the light receiving semiconductor component are preferably bonded and fixed or manufactured in a composite manner. This is because a high-precision joining technique is required for mounting both parts, and transmission loss is caused if the optical axes of both parts are shifted.
[0015]
The structure of the light guide path is a shape that is surrounded by a reflective surface and tapers toward the light receiving element side. The end face (circle) dimension is equal to or greater than POF on the POF side, and the light receiving element side is the light receiving portion of the light receiving element. It is preferable that it is equivalent or less. This is because the signal light from the POF is guided to the light guide and is effectively incident on the light receiving portion of the light receiving element.
[0016]
In general, the core diameter (250 μm to 900 μm) of POF is larger than the light receiving portion (100 μm to 500 μm) of the light receiving element. When POF is classified by composition, it can be classified into two types: polymethyl methacrylate resin (Clave, Mitsubishi Rayon) and fluorine resin (Asahi Glass).
[0017]
It is preferable that the light guide path of the light guide body component is filled with a light transmitting body. The effect of preventing reflection of signal light and improving airtightness can be obtained.
[0018]
In addition, assuming integration of parts with poor accuracy, it is preferable that the interface between the connection part and the light guide part and / or the interface between the light guide part and the light receiving semiconductor part are in close contact with each other through the light transmitting body. It is possible to prevent optical transmission loss due to reflection at the interface gap.
[0019]
The light receiving semiconductor component preferably has a structure in which a light receiving element, an amplifying element, and the like are combined, and at least a signal light passage is preferably sealed with a light transmitting body. In order to realize a general-purpose high-speed transmission type thin, thin and small device required by the consumer market, a composite plastic package is required.
[0020]
The light receiving semiconductor component preferably has a structure in which the light receiving element is flip-mounted on a circuit board in which a light passage hole for guiding signal light to the light receiving element is processed. This is because shortening the total distance of the light guide path from the POF to the light receiving element leads to a reduction in transmission loss. Furthermore, it is preferable that the light-transmitting hole is sealed with a light transmitting body on the airtight surface.
[0021]
The refractive index of the light transmitting body is preferably in the range of 1.30 to 1.60, and the hardness is preferably JIS (A type) 70 degrees or less. It is possible to minimize loss due to reflection and refraction when the refractive index is almost the same as that of an optical fiber. If the hardness is too high, the adhesion is deteriorated and transmission loss due to generation of a gap is caused. Further, it is preferable to select a light transmissive material from a resin having a proven record and a stable quality, a silicone resin, an acrylic resin, an epoxy resin, a thermoplastic resin, and derivatives of these resins.
[0022]
Consumer light-receiving devices are required to be inexpensive and small. That is, resin sealing is preferable to metal sealing. The light transmitting body of the present invention is a transparent sealing material for a light receiving element, and is required to have a function of protecting the light receiving element from a natural environment and a human handling environment. Since the light receiving element is sensitive to environmental fluctuations, the light transmitting body is required to firmly protect the light receiving element. Commercial products can be selected from product catalogs such as Shin-Etsu Chemical, Toshiba Silicone, Toagosei, Nippon Kayaku and Asahi Kasei. It is also possible to purchase intermediate products from these manufacturers to produce the desired light-transmitting body and its derivatives.
[0023]
FIG. 1 shows an example of a light receiving device for POF communication according to the present invention (cross section viewed from the side in the connection direction). (1) shows the state of each part, and (2) shows the state of each part. The connection component 11 is integrated with a highly efficient light guide component 12 and a light receiving semiconductor component 13. The light guide component has a light guide path 15 surrounded by a reflecting surface, and the light receiving semiconductor component is composed of a light transmission hole 17, a light receiving element 18, and a circuit board 19. The light guide body component has an end face larger than POF and an end face equivalent to the light receiving element light receiving portion. Note that the connecting parts are commercially available products (eg, PN type, SMI type, etc.), and 10 is a portion where the POF end face is exposed when POF is connected.
[0024]
FIG. 2 shows another example of the light receiving device for POF communication according to the present invention. Reference numeral 21 denotes a connection part, 22 denotes a light guide part, 23 denotes a light receiving semiconductor part, 25 denotes a light guide path, 27 denotes a light passage hole, 28 denotes a light receiving element, and 29 denotes a circuit board. The structure of the light receiving semiconductor component is different from that of FIG. 1, and the back surface of the light receiving element is gold-bonded and sealed with resin. Further, the connection component and the light guide component are in close contact with each other through the light transmitting body 24. Further, the light guide is filled with the same light transmitting body.
[0025]
FIG. 3 is a view showing still another example of the light receiving device for POF communication according to the present invention. Reference numeral 31 is a connection part, 32 is a light guide part, 33 is a light receiving semiconductor part, 35 is a light guide path, 37 is a light passage hole, and 38 is a light receiving element. The light receiving semiconductor component has a general structure, in which a light receiving element is mounted on a lead frame 39 and sealed with a transparent material (light transmitting body) 40.
[0026]
FIG. 4 exemplifies the structure of a composite light receiving semiconductor component. The component mounting method (electrical connection and sealing method) is different. (A) is a semiconductor element bump-bonded (flip-mounted) to a circuit board. (C) is due to conventional backside mounting and gold wire bonding. (B) shows the electrical connection between the semiconductor element and the circuit board using bumps and gold wires. 40 is a transparent material, 46 is an amplifying element, 47 is a light passage hole, 48 is a light receiving element, and 49 is a circuit board or a lead frame. The light passage hole is filled with a light transmitting body.
[0027]
Embodiment
Embodiments of the present invention will be specifically described with reference to examples and comparative examples. In each example, the same product made by Nihon Molex, PD made by Infineon, and one side circuit board made by Mitsui Mining Co., Ltd. were used.
[0028]
[Example 1]
A light receiving device for POF communication having a structure as shown in FIG. 1 was manufactured. The connection component 11 is a commercially available SMI type connector. The light guide member 12 is a prototype made by injection-molding PPS resin and has a truncated cone-shaped light guide 15 which is plated. The light receiving semiconductor component is a prototype in which an electric circuit and a light transmission hole 17 are first processed on a single-sided circuit board 19, a hollow frame for storing the PD 18 is attached, and a circuit board on which the PD is mounted is finally attached. . The light passage hole was sealed with a light transmitting material (transparent epoxy resin, manufactured by Nippon Kayaku Co., Ltd.). When this light receiving device and POF were connected and the connection loss was measured, it was 0.3 dB.
[0029]
POF is a polymethyl methacrylate optical fiber (manufactured by Mitsubishi Rayon) having a refractive index of 1.50 and a core diameter of 0.9 mm, and the cured epoxy resin has a refractive index of 1.49 and a hardness of 58. .
[0030]
[Example 2]
A commercially available connecting component 21, a highly efficient light guide component 22 and a light receiving semiconductor component 23 were integrated to manufacture a light receiving device as shown in FIG. The light guide member is a molded product similar to that of the first embodiment, but the light guide 25 is filled with a light transmitting member. The PD is flip-mounted on the same one-side circuit board as in the embodiment, and the light receiving part is sealed with a light transmitting body. The back surface of the PD is connected with a gold wire and sealed and protected with a commercially available liquid material for black semiconductor (manufactured by NAMICS). Further, the connection component and the light guide component are in close contact with each other through a thin film of light transmitting material. When this light receiving device and POF were connected in the same manner as in Example 1 and the loss was measured, a numerical value of 0.2 dB was shown.
[0031]
The light transmitting material used in this example is a silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd.) and has a cured product characteristic of a refractive index of 1.50 and a hardness of 41.
[0032]
[Example 3]
In Example 1, a light receiving device as shown in FIG. 3 was assembled and the connection loss was measured in the same manner as in Example 1 except that a commercially available transparent resin-encapsulated part CAI (manufactured by Infineon) was used as the light receiving semiconductor component. The numerical value is 1.2 dB, which is inferior to the other examples, but is superior to the comparative example.
[0033]
[Comparative Example 1]
In Example 1, the connection component and the light receiving semiconductor component were integrated without using the light guide component. The connection loss of this light receiving device was measured and found to be 6.2 dB.
[0034]
[Comparative Example 2]
In Example 3, the connection component and the light receiving semiconductor component were integrated without using the light guide component. The connection loss of this light receiving device showed a value of 3.8 dB.
[0035]
In the comparative example, it is considered that the signal light from the POF is reflected and / or scattered to cause transmission loss.
[0036]
[Reference example]
In Example 1, a component as shown in FIG. 4B in which a light receiving element and an amplifying element are mounted in combination is used as a light receiving semiconductor component. In general, a method of electrically connecting an amplification component to the light receiving semiconductor component of Example 1 is normal. However, it has recently been applied to reduce power consumption and increase the speed of electrical signal transmission, and the effectiveness has been confirmed in this embodiment.
[0037]
【The invention's effect】
The present invention provides to the market a light receiving device for POF communication that has good incidence of signal light and low connection loss. According to the present invention, a general-purpose light receiving device for consumer use can be supplied, and high-speed communication can be performed in a general home.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a light receiving device of the present invention.
FIG. 2 is a diagram showing an example of a light receiving device of the present invention.
FIG. 3 is a diagram showing an example of a light receiving device according to the present invention.
FIG. 4 is a diagram showing a composite example of the light receiving semiconductor component of the present invention.
[Explanation of symbols]
10 POF end face exposed parts 11, 21, 31 Connection parts 12, 22, 32 Light guide parts 13, 23, 33 Light receiving semiconductor parts 15, 25, 35 Light guide paths 17, 27, 47 Light passing holes 18, 28, 38, 48 Light receiving element 19, 29, 39, 49 Circuit board or lead frame 24 Interface 40 between connecting part and light guide part Transparent material 46 Amplifying element

Claims (2)

In an apparatus for optically coupling a plastic optical fiber (POF) and a light receiving element, the structure is composed of a connecting part to POF, a light guide part for guiding signal light, and a light receiving semiconductor part. The optical axes are aligned and the end faces of each component are in close contact, and the light guide component is surrounded by a reflective surface and tapers toward the light receiving element (spheroid, rotating paraboloid, truncated cone, etc. ), The circular diameter of the end face of the light guide path is equal to or greater than the POF on the POF side and equal to or less than the light receiving part of the light receiving element on the POF side, and is refracted inside the light guide path of the light guide component. Flexible light transmission which is a transparent resin (silicone resin, epoxy resin, acrylic resin, thermoplastic resin, etc.) having a ratio of 1.30 to 1.60 and a hardness of JIS (A type) 60 degrees or less That the body is filled and A semiconductor component includes a light receiving element and an amplifying element, and the light receiving element is flip-mounted on the circuit board. The circuit board has a light passage hole for guiding the signal light to the light receiving portion of the light receiving element. A light receiving device for POF communication, wherein a light hole is sealed with the flexible light transmitting body . The light receiving device for POF communication according to claim 1, wherein the connection component and the light guide component or the light guide component and the light receiving semiconductor component are in close contact with each other through the flexible light transmitting body .

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