JP2012242694A - Optical fiber socket - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber socket capable of simplifying alignment of optical axes of an optical fiber and a photoelectric conversion element and dealing with increases in sensitivity and speed of signal transmission.SOLUTION: A circuit block 2 of a socket 1 includes: a circuit board 21; a molding member 22 that has two fitting holes 22a and having the circuit board 21 inserted thereinto; a photoelectric conversion element 23 for light-receiving; and an output circuit element 24. A sleep block 3 is integrated into the circuit block 2 by fitting fitting projections 3b into the fitting holes 22a. The output circuit element 24 includes a transimpedance amplifier with a limiting amplifier that is provided for each concentric light-receiving element PD of the photoelectric conversion element 23 and an OR circuit element that receives outputs of all the amplifiers and that outputs a signal when any of the outputs has exceeded a specified value. Since a signal is output when any output of the light-receiving element PD has exceeded a specified value, higher sensitivity is achieved for light-receiving.

Description

  The present invention relates to an optical fiber socket into which a ferrule fitted to the tip of an optical fiber is inserted.

  2. Description of the Related Art Conventionally, a light having a substrate on which a photoelectric conversion element is mounted and a sleeve that is fitted and positioned on the substrate, and in which a ferrule is inserted into the sleeve and optical fiber and the photoelectric conversion element are optically coupled in use. A fiber socket is known (for example, see Patent Document 1). In this socket, two fitting holes are formed in the board, two fitting protrusions are provided on the surface of the sleeve facing the board, and the two fitting protrusions are fitted into the two fitting holes, respectively. Thus, the fitting positioning of the substrate and the sleeve is performed. According to this socket, the optical axis alignment of the sleeve and the photoelectric conversion element, and thus the optical fiber and the photoelectric conversion element, can be performed only by fitting the fitting protrusion to the fitting hole and fitting the sleeve to the substrate. The work of aligning the optical axis is said to be easy.

  By the way, when the photoelectric conversion element is a light receiving element, the optical axis alignment for optical coupling is to improve the light receiving sensitivity by reducing the optical coupling loss between the optical fiber and the photoelectric conversion element. Other methods for improving the light receiving sensitivity include the following. That is, it has a plurality of light receiving elements with a small area, a photocurrent detecting means for converting and buffering the photocurrent for each light receiving element, and an adding means for adding the current detected by the photocurrent detecting means. There has been known a light receiving device that achieves high speed and high response (for example, see Patent Document 2).

  In addition, the light-receiving surface is divided into four areas consisting of two point-symmetrical pairs, signals detected by each pair are input to the operational amplifier, and noise cancellation is performed by taking the difference signal, thereby achieving high reliability and high assembly accuracy. There is known a light receiving device that eliminates the need for the above (for example, see Patent Document 3).

JP-A-8-5872 JP 2003-179442 A JP 2007-174328 A

However, the light receiving device as shown in Patent Document 2 described above uses signals added after amplification, and amplifies all signals including low level signals, so that the reliability of the signals is impaired. There is a risk that. In addition, a light receiving device as disclosed in Patent Document 3 can cancel noise, but cannot cope with improvement in sensitivity and speed. In general, in an optical link capable of high-speed signal transmission of Gbps or higher, it is necessary to reduce the light receiving area of the light receiving element (photodiode) to about 0.03 mm ² or less. The higher the speed, the more the light receiving surface of the light receiving element. It is necessary to reduce the area. Therefore, in order to reduce the optical coupling loss between the optical fiber and the light receiving element having a small light receiving surface, it is necessary to increase the alignment accuracy between the optical fiber and the light receiving element. Conventionally, in order to realize this high-precision alignment, a lens is disposed between the optical fiber and the light receiving element, and the alignment between the lens and the light receiving element is performed by active alignment with optical axis adjustment. For this reason, there exists a problem that the optical link system using an optical fiber socket becomes expensive.

  The present invention solves the above-mentioned problem, and can simplify the optical axis alignment of an optical fiber and a photoelectric conversion element, and can be used for an optical fiber that can cope with high sensitivity and high speed signal transmission. The purpose is to provide a socket.

  In order to achieve the above object, an optical fiber socket according to the present invention is a molded member integrally formed by inserting a circuit board in an optical fiber socket into which a ferrule with an optical fiber is inserted, and a circuit. A circuit block having a photoelectric conversion element mounted on a substrate, and a sleeve block having an insertion slot into which a ferrule is inserted, and the circuit block and the sleeve block are an optical axis of the photoelectric conversion element and an axis of the insertion slot The photoelectric conversion elements are formed by arranging a plurality of light receiving elements symmetrically with respect to the optical axis, and the output of any one of the light receiving elements exceeds a predetermined value. The circuit board is provided with an output circuit element that sometimes outputs a signal.

  In this optical fiber socket, each light receiving element may be formed concentrically around the optical axis.

  In this optical fiber socket, each light receiving element may be formed in a grid shape around the optical axis.

  In this optical fiber socket, each light receiving element may be formed in a shape obtained by dividing a circle centered on the optical axis.

  An optical fiber socket for light transmission, including a molded member integrally formed by inserting a circuit board, a circuit block having a photoelectric conversion element mounted on the circuit board, and an insertion opening into which a ferrule is inserted. The circuit block and the sleeve block are positioned so that the optical axis of the photoelectric conversion element coincides with the axis of the insertion slot, and the photoelectric conversion element is a light emitting element. It is used in combination with any one of the above-described optical fiber sockets having a light receiving element.

  According to the optical fiber socket for light reception of the present invention, since a signal is output when the output of any of the plurality of light receiving elements exceeds a predetermined value, high sensitivity to light reception is achieved, and the plurality of light receiving elements Since any one of these may be optically coupled, the optical axis alignment can be simplified. In addition, since one signal of a plurality of light receiving elements arranged symmetrically with respect to the optical axis of the photoelectric conversion element is used, the junction capacitance of the light receiving element can be suppressed to only a small junction capacitance of one light receiving element, and the response speed The light receiving sensitivity can be improved without lowering the signal, and the signal transmission speed can be increased.

(A) is a perspective view of the socket for optical fibers which concerns on one Embodiment of this invention, (b) is an exploded perspective view of the socket, (c) is a top view of the light receiving element with which the socket was equipped. (A) is sectional drawing of the socket, (c) is an exploded sectional view of the socket. The circuit diagram of the signal processing circuit in the socket. The top view which shows the other example of the light receiving element in the socket. The top view which shows the further another example of the light receiving element in the socket. The circuit diagram which shows the other example of the signal processing circuit in the socket. The top view which shows the further another example of the light receiving element in the socket. The top view which shows the further another example of the light receiving element in the socket. The top view which shows the further another example of the light receiving element in the socket.

  Hereinafter, an optical fiber socket for light reception according to an embodiment of the present invention will be described with reference to the drawings. 1 to 3 show an optical fiber socket (hereinafter also simply referred to as a socket) according to this embodiment. The socket 1 is formed by combining a circuit block 2 and a sleeve block 3 as shown in FIGS. 1 (a), (b), (c) and FIGS. 2 (a), (b). The circuit block 2 includes a mounting electrode (not shown), a circuit board 21, a molding member 22 in which the circuit board 21 is inserted and insert-molded, a light receiving photoelectric conversion element 23 mounted on the circuit board 21, and an output circuit. And an element 24. The sleeve block 3 has a shape in which two coaxial cylinders are stacked, and a circular insertion slot for inserting a ferrule 8a fitted to the tip of the optical fiber 8 on the axis L of the cylinder. 3a, a light transmission part 3c, and a recess 3d, and two fitting protrusions 3b on the lower surface.

  The circuit board 21 includes a wiring pattern on a convex substrate in plan view, and the wiring pattern includes a signal line, a power supply line, and a ground line to the photoelectric conversion element 23 and the output circuit element 24. The photoelectric conversion element 23 and the output circuit element 24 are mounted on the convex portion of the circuit board 21. The molding member 22 is a receiving member that receives the sleeve block 3, and is resin-molded with the circuit board 21 inserted. As the resin for the molded member 22, a thermoplastic resin or a thermosetting resin can be used, and glass fibers may be included in these resins. The upper surface of the circuit board 21 and the upper surface of the molding member 22 constitute the same plane. The molding member 22 has a concave shape corresponding to the convex portion of the circuit board 21, and forms a square circuit block 2 in plan view together with the circuit board 21. Two fitting holes 22a are provided in the concave protruding portion of the molding member 22 so as to sandwich the photoelectric conversion element 23 from the left and right. The fitting hole 22a is a circular through hole. In addition, the fitting hole 22a does not need to be a through hole, and may not be circular.

  The photoelectric conversion element 23 includes a plurality of (two in the example of FIG. 1C) light receiving elements PD (photodiodes) on the upper surface thereof. As shown in FIG.1 (c), the light-receiving part of each light receiving element PD consists of a circular area | region and a donut-shaped area | region concentric with this, The anode electrode 23a is provided in these area | regions, respectively. The cathode electrode is provided in common on the back surface of the photoelectric conversion element 23. In the photoelectric conversion element 23, the optical axis of the light receiving element PD, that is, the center position of both light receiving elements PD is arranged at the midpoint position of the line segment connecting the centers of the circles of the two circular fitting holes 22a. Connections are made and implemented.

  The fitting projection 3 b in the sleeve block 3 is a projection that fits into the fitting hole 22 a and is provided symmetrically with respect to the axis L of the sleeve block 3. The light transmission part 3c can be formed into a lens shape in addition to a parallel plate shape, and is made of an optical material that transmits at least a specific wavelength according to the characteristics of the photoelectric conversion element 23, for example, 850 nm. The light transmitting portion 3c is integrally formed when the sleeve block 3 is formed, and the entire sleeve block 3 has light transmittance. Note that the sleeve block 3 may be formed by insert molding in which the light transmitting portion 3c is separately formed of, for example, glass and inserted. In this case, the sleeve block 3 other than the light transmitting portion 3c can be formed of a light non-transmissive resin that is inexpensive and has excellent dimensional accuracy. The recess 3d forms a space for housing (hollow sealing) the photoelectric conversion element 23 and the output circuit element 24. When the photoelectric conversion element 23 and the output circuit element 24 are resin-sealed rather than hollow-sealed, the light transmitting portion 3c may not be provided.

  The assembly process of the socket 1 will be described. After the molding member 22 formed integrally with the circuit board 21 is formed, the photoelectric conversion element 23 and the output circuit element 24 are mounted on the circuit board 21. When mounting the photoelectric conversion element 23, the respective center positions of the two fitting holes 22a are acquired using, for example, an imaging device and an image processing device of a chip mounter. As a method for detecting the circle and its center position by the image processing apparatus, for example, Hough transformation can be used. Here, the dimension of each part is illustrated. The photoelectric conversion element 23 is, for example, a bare chip, and the interval between the two fitting holes 22a is about 4 mm. Therefore, a small area including the two fitting holes 22a can be imaged at a high magnification without increasing the processing load, and the measurement accuracy of the circle shape and the center position can be increased. For example, measurement accuracy and positioning accuracy can be increased to an accuracy of about 10 μm. With reference to the center positions of the two fitting holes 22a, the photoelectric conversion element 23 is positioned at the midpoint position between the two center positions, that is, the optical axis position of the photoelectric conversion element 23 is positioned. Thereby, the photoelectric conversion element 23 is mounted on the circuit board 21 with high positional accuracy, and further, the output circuit element 24 is mounted (may be mounted before the photoelectric conversion element 23), whereby the circuit block 2 Is completed. The sleeve block 3 is completed by resin molding including the light transmitting portion 3c or insert molding in which a separately formed light transmitting portion 3c is inserted.

  The socket 1 is completed by fitting the sleeve block 3 to the circuit block 2. The fitting is completed by fitting the fitting protrusion 3b into the fitting hole 22a and bringing the bottom surface of the sleeve block 3 into contact with the top surface of the circuit block 2. Thereby, the optical axis L of the photoelectric conversion element 23 and the axis L of the sleeve block 3 coincide with each other, and the photoelectric conversion element 23 is hollowly sealed by the sleeve block 3. If necessary, the sealing or adhesive fixing resin may or may not be filled in the gaps between the fitting portions and the contact surfaces of the blocks 2 and 3.

  The dimensional accuracy of each component of the socket 1 is such that the assembled socket 1 can ensure a predetermined assembly accuracy only by positioning accuracy by fitting. That is, each fitting hole 22a and each fitting protrusion 3b are formed with dimensional accuracy that can achieve hollow sealing and optical axis adjustment with respect to the photoelectric conversion element 23 when fitting each other. The dimensional accuracy of the insertion slot 3a and the positional accuracy of the axis L are set to the required assembly accuracy with respect to the optical axis position of the photoelectric conversion element 23. Therefore, the optical axis alignment and optical coupling between the optical fiber 8 and the photoelectric conversion element 23 can be performed by so-called passive alignment only by inserting the ferrule 8a into the sleeve block 3, and the level of the optical signal is monitored by the measuring device. However, active alignment to be performed becomes unnecessary.

  Each dimensional accuracy of the socket 1 is based on the dimensional accuracy of each fitting member by resin molding and the mounting position accuracy of the photoelectric conversion element 23 by image processing. The fitting hole 22a of the molding member 22 can be formed when the molding member 22 is molded, and the maximum molding accuracy that can be realized by the molding technique is 1 μm or less. And position accuracy can be achieved. The resin molding dimensional accuracy of the fitting insertion port 3a and the fitting projection 3b of the sleeve block 3 is the same as described above.

  Next, the photoelectric conversion element 23 and the output circuit element 24 will be described. As shown in FIG. 3, the output circuit element 24 receives the amplifier 24a provided for each light receiving element PD of the photoelectric conversion element 23 and the outputs of all the amplifiers 24a, and any output exceeds a predetermined value. OR circuit element 24b (OR circuit element) that outputs a signal at the same time. The amplifier 24a is, for example, a transimpedance amplifier (TIA) with a limiting amplifier. In the example of FIG. 1C, there are two light receiving elements PD and two amplifiers 24a. The anode electrode 23a of each light receiving element PD is connected to each amplifier 24a, and the cathode electrode is shared and connected to the power supply circuit via the power supply noise filter 24c. Similarly, each amplifier 24a is connected to a power supply circuit via a power supply noise filter 24c.

  The output circuit element 24 amplifies the output currents of the two light receiving elements PD shown in FIG. 1C, and outputs the result to the OR circuit element 24b. The OR circuit element 24b has, for example, a high / low (H / L) signal among the high / low (H / L) signals when the signal from one of the light receiving elements PD has an input optical power larger than a predetermined sensitivity level. (H) A level signal is output. That is, if one of the two light receiving elements PD shown in FIG. 1C and the optical fiber can be optically coupled, the optical coupling between the photoelectric conversion element 23 and the optical fiber is realized. The accuracy of optical axis alignment between the optical fiber and the optical fiber is relaxed. Here, the outputs of all the amplifiers 24a need to be synchronized with each other, and the difference between the maximum value and the minimum value of the time delay amount from the optical input to each light receiving element PD to the signal output of the amplifier 24a. , And set so as to fall within a predetermined tolerance. The predetermined allowable range is, for example, a range in which the determination of the high level and low level of the signal bit is not affected by the variation in the amount of time delay. The variation in the amount of time delay can be suppressed within a predetermined allowable range by optimizing the wiring pattern, wiring wire length, and the like from each light receiving element PD to each amplifier 24a on the output circuit element 24. For example, the above-described wiring patterns and wiring wires (lengths) for each light receiving element PD are arranged symmetrically and optimized by matching the line lengths with each other. Further, the output circuit element 24 may be provided with a synchronization circuit for synchronizing the output of each amplifier 24a.

  According to the socket 1 of the present embodiment, since a signal is output when the output of any of the plurality of light receiving elements PD exceeds a predetermined value, it is possible to increase the sensitivity to light reception. In addition, since any one of the plurality of light receiving elements PD only needs to be reliably optically coupled to the optical fiber, the accuracy of the optical axis alignment between the optical fiber and the photoelectric conversion element 23 can be relaxed, and the optical axis alignment can be performed. It can be simplified. Further, since individual signals of a plurality of light receiving elements arranged symmetrically with respect to the optical axis of the photoelectric conversion element 23 are individually used, the junction capacitance of the light receiving photoelectric conversion element 23 is not the entire junction capacitance but one light reception. Only a small junction capacitance of the element PD can be suppressed. Therefore, the light receiving sensitivity can be improved without lowering the response speed, and it is possible to cope with the increase in signal transmission speed. Further, by forming the light receiving surface of the light receiving element PD in a circular shape and a donut shape, the number of light receiving elements PD can be reduced, and the number of amplifiers 24a can be reduced. Since the number of the amplifiers 24a can be reduced, the size of the output circuit element 24, that is, in the case of an integrated circuit, the chip size can be reduced and the cost can be reduced, and the socket 1 can be reduced in size.

  Moreover, according to the socket 1 of this embodiment, since the precision of optical axis alignment with an optical fiber and the photoelectric conversion element 23 (light receiving element PD) can be eased, it is between an optical fiber and the photoelectric conversion element 23. It is not necessary to provide a lens for facilitating optical axis alignment. Therefore, the light transmission part 3c itself can be omitted without using the light transmission part 3c as a lens. When the light transmission part 3c is omitted, the photoelectric conversion element 23 may be resin-sealed instead of hollow sealing. Conventionally, a transparent resin molded product is generally used as the lens disposed between the optical fiber and the light receiving element PD, and this transparent resin is generally a resin having no heat resistance against the reflow temperature. There is a problem that the reflow mounting cannot be performed on the socket that has it. On the other hand, the socket 1 of the present embodiment can be configured without a lens, and can be realized at low cost as the socket 1 having heat resistance against the reflow temperature.

  4 and 5 show other examples of the photoelectric conversion element 23 for light reception. The photoelectric conversion element 23 shown in FIG. 4 has three light receiving elements PD concentric with each other around the optical axis of the photoelectric conversion element 23. In this case, the output circuit element 24 includes three amplifiers 24a and one OR circuit element 24b. A photoelectric conversion element 23 shown in FIG. 5 includes a common cathode electrode 23b of two light receiving elements PD on the light receiving surface side of the photoelectric conversion element 23 in the photoelectric conversion element 23 shown in FIG. . Since both the anode electrode 23a and the cathode electrode 23b are on the same upper surface, the inter-terminal capacitance can be further reduced and the speed can be increased compared to the case where the electrodes are vertically divided as shown in FIG. It can correspond to the signal transmission.

  FIG. 6 shows another configuration of the output circuit element 24. This configuration is a configuration in which the cathode electrode of each light receiving element PD is independently connected to the power supply circuit via a power supply noise filter 24c (not shown) in the circuit configuration of FIG. In this configuration, each light receiving element PD has a cathode electrode and an anode electrode which are independent from each other, and are individually connected to the output circuit element 24 and the power supply circuit. Such a configuration is applied, for example, when the light receiving element PD is not formed in one photoelectric conversion element 23 but is configured by a set of individual chips. For example, a light receiving element PD of an individual chip can be realized by dicing an existing photodiode array for multi-channel optical communication.

  7, FIG. 8, and FIG. 9 show still another example of the photoelectric conversion element 23 for light reception. The photoelectric conversion element 23 shown in FIG. 7 is configured by arranging four light receiving elements PD on a single chip around the optical axis of the photoelectric conversion element 23. Each light receiving element PD is a photoelectric conversion element. They are arranged symmetrically with respect to the 23 optical axes. Further, the photoelectric conversion element 23 shown in FIG. 8 is modified so that the common cathode electrode 23b of the four light receiving elements PD in the photoelectric conversion element 23 shown in FIG. 7 is provided on the light receiving surface side of the photoelectric conversion element 23. It is an example. Further, the photoelectric conversion element 23 shown in FIG. 9 has a shape obtained by dividing a circle centered on the optical axis of the photoelectric conversion element 23, and is configured by arranging four light receiving elements PD on one chip. Each light receiving element PD has a fan shape, for example, a quarter of a circle. In the photoelectric conversion element 23 having such a configuration, the light receiving surfaces of the plurality of light receiving elements PD can have the same shape, so that the difference in characteristics between the light receiving elements PD can be reduced.

  As described above, according to the socket 1, the effective junction capacitance of the light receiving element PD can be suppressed to prevent the response speed from decreasing, and the light receiving area can be substantially increased to increase the sensitivity. it can. In addition, when using an optical fiber with a large diameter core, a sufficiently large light receiving area can be realized with respect to a light spot formed on the light receiving surface by light spread from the optical fiber of the large diameter core according to its numerical aperture. . Therefore, it is possible to receive light with high sensitivity by reducing the optical coupling loss by the plurality of light receiving elements PD with respect to the optical fiber having the large diameter core. This means that by using an optical fiber with a large core, the optical coupling loss between the light emitting element of the corresponding transmitter, for example, a semiconductor laser such as a VCSEL, and the optical fiber can be reduced.

  Therefore, the optical fiber socket for light transmission includes a circuit block and a sleeve block having the same configuration as the light receiving socket 1, and the photoelectric conversion element is a light emitting element. The socket used in combination with the optical fiber socket is constructed. The light-transmitting socket 1 can use an optical fiber having a large-diameter core because of a large allowable amount based on an increase in sensitivity of the socket 1 on the light-receiving side. In addition, these light receiving and light transmitting sockets are formed on the basis of the mounting position accuracy of the photoelectric conversion element 23, the dimensional accuracy based on the resin molding accuracy, and the increase in sensitivity of the light receiving side socket 1. A lens for optical coupling with the fiber can be eliminated. That is, depending on the required level of the optical loss budget required between the transmitter and the receiver in the optical link, it is possible to eliminate the need for the light receiving lens. Further, the optical link using these light receiving and light transmitting sockets can maintain a high response speed of the light receiving element PD even though the effective light receiving area of the light receiving element PD is large. Therefore, high-speed optical signal transmission (Gbps or higher) is possible. Moreover, since the fitting accuracy between the ferrule (optical plug) and the socket (optical receptacle) can be relaxed, a high-precision alignment component can be eliminated. Furthermore, by not providing the light transmission part 3c as a lens, the socket can be formed of a heat-resistant material that is light non-transmissive and inexpensive and has excellent molding dimensional accuracy, and a socket that can be reflow mounted can be realized. . Such a socket can provide an inexpensive optical link capable of high-speed optical signal transmission.

  The present invention is not limited to the above-described configuration, and various modifications can be made. For example, the configurations of the above-described embodiments can be combined with each other.

DESCRIPTION OF SYMBOLS 1 Optical fiber socket 2 Circuit block 21 Circuit board 22 Molding member 22a Fitting hole 23 Photoelectric conversion element 24 Output circuit element 24a Limiting amplifier 24b OR element 3 Sleeve block 3a Insertion opening 3b Fitting protrusion 3c Light transmission part 3d Recessed part 8 Optical fiber 8a Ferrule PD Light receiving element L Optical axis

Claims (5)

In the optical fiber socket into which the ferrule fitted in the optical fiber is inserted,
A molded member integrally formed by inserting a circuit board, and a circuit block having a photoelectric conversion element mounted on the circuit board;
A sleeve block having an insertion slot into which the ferrule is inserted, and
The circuit block and the sleeve block are positioned so that the optical axis of the photoelectric conversion element coincides with the axis of the insertion slot, and are integrated with each other,
The photoelectric conversion element is formed by arranging a plurality of light receiving elements symmetrically with respect to the optical axis,
An optical fiber socket comprising an output circuit element that outputs a signal when an output of any one of the light receiving elements exceeds a predetermined value.   2. The optical fiber socket according to claim 1, wherein each of the light receiving elements is formed concentrically around the optical axis.   2. The optical fiber socket according to claim 1, wherein each of the light receiving elements is formed in a grid shape around the optical axis.   2. The optical fiber socket according to claim 1, wherein each of the light receiving elements is formed in a shape obtained by dividing a circle centered on the optical axis. A molded member integrally formed by inserting a circuit board, and a circuit block having a photoelectric conversion element mounted on the circuit board;
A sleeve block having an insertion slot into which the ferrule is inserted, and
The circuit block and the sleeve block are positioned so that the optical axis of the photoelectric conversion element coincides with the axis of the insertion slot, and are integrated with each other,
The photoelectric conversion element is a light emitting element;
An optical fiber socket, which is used in combination with the light receiving optical fiber socket according to any one of claims 1 to 4.

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