JP2009105282A - Optical data link - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical data link which reduces the degradation of its high-frequency characteristic by using a flexible printed circuit board (FPC), and prevents its positional discrepancy generated by such an elastic repulsion that its OSA suffers from a heat transferring sheet, and further, can prevent the generation of the crosstalk between its elements. <P>SOLUTION: The optical data link is so constituted as to connect an optical module which has a package mounting optical elements and a sleeve having the inserted ferrule of an optical connector, with a circuit board via an FPC 17, and as to store and support the resultant device in its housing. The FPC 17 has a signal-line layer and a solid electrode layer, and has a signal-line circuit portion which connects its connecting portion with the electrode portion of the optical module and its connecting portion 17b with the circuit board, by a signal line 17g, and further, has an extended portion 17c formed integrally on the lateral side of the connecting portion with the electrode portion of the optical module. The extended portion 17c of the FPC 17 is so supported by a supporting portion provided in the side wall of the housing as to hold the electrode-portion side of the optical module. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical data link using a flexible printed circuit board.

An optical data link such as an optical transceiver that transmits and receives an optical signal includes an optical module on which a photoelectric conversion element (optical element) is mounted, and a circuit board on which an electronic circuit that exchanges electrical signals with the optical module is mounted. Electrode portions such as lead pins for electrical connection are led out from the optical module.
For example, in the optical transceiver disclosed in Patent Document 1, the optical module and the circuit board are electrically connected by directly bonding the electrical pads and lead pins on the circuit board with solder or the like. Further, in this optical transceiver, the periphery of the lead pin is covered with a bracket connected to the ground potential, thereby suppressing the occurrence of crosstalk between the light emitting element and the light receiving element.

Further, in an optical transceiver for high-speed optical communication, a flexible printed circuit (FPC) is used as a connection means between the lead pins of the optical module and the circuit board (see, for example, Patent Documents 2 and 3). Thereby, the deterioration of the high frequency characteristics due to the inductance component of the lead pin is reduced.
JP 2003-107297 A US Pat. No. 5,632,630 JP 2007-67380 A

  Among optical modules, those of a CAN type package in which a lens-equipped shell is attached to a stem on which a photoelectric conversion element is mounted are optical subassemblies in which a sleeve into which an optical connector ferrule is inserted is attached to the lens-equipped shell ( As OSA (Optical Sub-Assembly), it is held and mounted on the optical data link. Since the OSA, that is, the photoelectric conversion element mounted on the optical module generates heat, for example, a silicon thermal conductive sheet may be sandwiched between the stem and the optical data link housing in order to dissipate heat to the outside of the optical data link. . In this case, a compression repulsive force of the heat conductive sheet acts on the stem, and if this repulsive force is too large, the OSA sleeve tilts in the optical receptacle, or the stem causes an axial displacement with respect to the sleeve.

When the circuit board and the OSA are connected by the lead pin, the rigidity of the lead pin has an effect of supporting the repulsive force. However, as in the optical data link disclosed in Patent Documents 2 and 3, the circuit board and the OSA lead pin are effective. It is not possible to prevent the OSA sleeve from tilting in the optical receptacle against the repulsive force only by connecting the electrode part such as the FPC with FPC.
Also, in the optical data link disclosed in Patent Documents 2 and 3, unlike the one disclosed in Patent Document 1, a bracket for preventing the occurrence of crosstalk between the light emitting element and the light receiving element is provided so as to cover the lead pin. As a result, there is room for improvement in noise countermeasures.

  The present invention has been made in view of the above circumstances, and is intended to reduce the deterioration of high frequency characteristics using FPC, and prevents the OSA from being displaced due to the elastic repulsive force received from the heat conductive sheet. Another object of the present invention is to provide an optical data link that can prevent the occurrence of crosstalk between elements.

  In order to solve the above problems, an optical data link of the present invention connects an optical module having a package in which an optical element is mounted and a sleeve into which a ferrule of an optical connector is inserted, to a circuit board through a flexible printed circuit board, A flexible printed circuit board, which is housed and held in a housing, has a wiring layer and a solid layer, and is a signal in which a connection part between an electrode part of an optical module and a connection part between a circuit board are connected by a signal line. A line circuit part and an extension part formed integrally on the side of the connection part with the electrode part, and holding the optical module by supporting the extension part by a support part provided on the side wall of the housing Features.

  Moreover, this invention is used suitably when the heat conductive sheet is arrange | positioned between the optical module and the housing | casing. In addition, the solid electrode part in the bending part of the extension part of a flexible substrate may be formed in mesh shape.

  According to the present invention, an FPC having an extension formed with a solid layer connected to the ground potential is used for electrical connection between the circuit board and the optical module, so that the extension can be supported by the housing. The position of the module can be maintained, and the shielding property can be enhanced by covering the lead pin of the optical module with the extension portion.

  FIG. 1 is an external view of an optical data link according to the present invention, and FIG. 2 is an enlarged view of a main part of the optical data link according to the present invention. FIG. 3 is a perspective view of a transmitting OSA (TOSA: Transmitting Optical Sub-Assembly), and FIG. 4 is a diagram showing the relationship between the TOSA and the circuit board in the optical data link. FIG. 5 is a perspective view of a flexible printed circuit board (FPC) used for electrical connection between the TOSA and the circuit board, and FIG. 6 is an enlarged view of main parts of the TOSA, the lower housing, and the FPC.

  The optical data link 1 is, for example, an optical transceiver that is used by being detachably attached to a host device body, and as shown in FIG. 1, an opening 2 into which an optical connector (not shown) is inserted at one end thereof. Is formed. The optical data link 1 is inserted into the host device from the end opposite to the opening 2. The opening 2 is provided in a lower casing 15 that constitutes the casing of the optical data link 1, and configures an optical receptacle described later. By inserting an optical connector into the opening 2 and optically coupling the optical fiber in the optical connector and the photoelectric conversion element of the optical module in the optical data link 1, the optical data link 1 can perform both optical transmission and optical reception. Demonstrate the function. The optical data link 1 can ground the casing by bringing the fingers 3 provided around the casing into contact with the host device.

  As shown in FIG. 2, the optical data link 1 includes a TOSA 11 that converts an electrical signal into an optical signal, a receiving OSA (ROSA: Receiving Optical Sub-Assembly) (not shown) that converts an optical signal into an electrical signal, The circuit board 13 (refer FIG. 4) which mounts the electronic circuit which transmits / receives an electrical signal with TOSA11 / ROSA is provided. The optical data link 1 further includes an upper housing (not shown) and a lower housing 15 that sandwich the TOSA 11 / ROSA and the circuit board 13 from above and below. The housing of the optical data link 1 that accommodates and holds the TOSA 11 / ROSA and the like is formed by an upper housing and a lower housing 15 and a cover that covers them.

  The lower housing 15 is mounted with a transmission optical module mounting portion 15a on which a portion of a TOSA 11 optical module 11a (see FIG. 3) to which an FPC according to the present invention to be described later is attached and a ROSA optical module portion are mounted. The receiving optical module mounting portion 15b and the circuit board holding portion 15c for holding the circuit board 13 are provided. An optical receptacle 15d for receiving the optical connector is provided at the end of the lower housing 15 opposite to the circuit board holding portion 15c.

  The transmitting optical module mounting portion 15a and the receiving optical module mounting portion 15b are separated by a partition wall 15e. The lower housing 15 is provided with a wall 15f between the optical receptacle 15d that opens to the outside and the transmission and reception optical module mounting portions 15a and 15b.

  The wall 15f has an insertion hole 15g through which the OSA sleeve is inserted. Although not visible in FIG. 1, a similar insertion hole is formed not only on the wall 15f on the receiving optical module mounting portion 15b side but also on the transmitting optical module mounting portion 15a side. The insertion hole 15g allows the sleeve 11b (see FIG. 3) of the TOSA 11 to be positioned in the optical receptacle 15d of the lower housing 15 when the assembly of the optical data link 1 is completed. The ferrule of the optical connector inserted into the can be received. The insertion hole 15g can also function as a support portion for the OSA sleeve.

  Further, the lower housing 15 has FPC support portions 15h that support the FPC in the partition wall 15e and the side wall 15i. The FPC support unit 17 includes a surface parallel to the optical axis direction of the optical data link 1 and parallel to the bottom surface of the housing (upper housing). In the example shown in the figure, the FPC support portion is formed as a step portion. However, the FPC support portion only needs to be able to support an extension portion of an FPC described later. For example, the partition 15e is formed in a table shape without a step, and this stand The part may function as an FPC support part.

  The optical data link 1 also includes a heat conductive sheet (not shown) for radiating heat generated from the TOSA 11 and an FPC 17 that electrically connects the TOSA 11 and the circuit board 13. Although not shown, the optical data link 1 includes an FPC similar to the FPC 17 in order to electrically connect the ROSA and the circuit board 13. When the optical data link 1 is completely assembled, at least a heat conductive sheet is sandwiched between the TOSA 11 and the upper housing. Thereby, in the optical data link 1, the heat generated inside the TOSA 11 can be radiated to the outside through the heat conductive sheet and the upper casing.

  For example, as shown in FIG. 3, the TOSA 11 is an optical module with a sleeve in which a sleeve 11b is attached to an optical module 11a, and has an outer shape in which cylindrical members are connected coaxially. The optical module 11a bears a photoelectric conversion function, and its package is a CAN type package in which a lens-equipped shell 11d is attached to a stem 11c on which a semiconductor laser (LD: Laser Diode) is mounted. In the optical module 11a, a plurality of electrode portions (lead pins) 11e are led out from the stem 11c.

The LD on the stem 11c is electrically connected to some lead pins 11e by wire bonding or the like, and the lead pins 11e are electrically connected to the circuit board 13 via the FPC 17 (see FIG. 4). ). Thus, the LD can receive an electrical signal from the circuit board 13 via the lead pin 11e, convert the received electrical signal into an optical signal, and send the optical signal to the sleeve 11b. The lead pin 11e is attached to the stem by, for example, glass sealing.
The sleeve 11b is attached to the side opposite to the lead pin 11e side of the optical module 11a. This sleeve 11b guides the ferrule of the optical connector inserted into the optical receptacle of the lower housing 15, and achieves optical coupling between the optical fiber in the ferrule and the LD of the optical module 11a.

  Since ROSA is substantially the same as TOSA 11, detailed description and illustration thereof are omitted, but instead of LD, a semiconductor light receiving element (PD: Photo Diode) that converts an optical signal into an electric signal is provided.

  As shown in FIG. 4, the FPC, which is one of the features of the present optical data link, is for electrically connecting the circuit board 13 and the TOSA 11, and is bent so as to cover the lead pins 11e of the TOSA 11. Used. The FPC 17 includes an FPC main body portion 17a, a circuit board connection portion 17b, an extension portion 17c, and a bent portion 17d.

  As shown in FIG. 5, one end portion of the FPC 17, that is, the end portion of the FPC main body portion 17 a functions as a module electrode connecting portion that is electrically connected to the lead pin 11 e of the TOSA 11. Is formed. A pad may be used instead of the through hole. In addition, a circuit board connecting portion 17b for connection to the circuit board 13 is provided at the other end of the FPC 17, and the circuit board connecting portion 17b is connected to the wiring (electrode pad) 13a of the circuit board 13. A terminal (electrode pad) 17f to be connected is formed.

  Further, the optical module electrode connecting portion and the circuit board connecting portion 17b at the end of the FPC main body portion 17a (that is, the through hole 17e and the electrode pad 17f) are connected to the FPC main body portion 17a by a wiring (signal line) 17g. A connected signal line circuit portion is formed. The connection between the lead pin 11e of the TOSA 11 and the through hole 17e of the FPC 17 is mainly performed by soldering, but may be performed by a general electric connection means such as a conductive adhesive or pressure bonding.

  The extension portion 17c has a portion having a predetermined width and extending in the optical axis direction of the optical data link 1 (extending direction of the housing) and a bent portion 17d. The extended portion includes the bent portion 17d. Through the FPC main body 17a. The extension portion 17c is integrally formed on the side of the optical module electrode connection portion. The end portion of the extension portion 17c opposite to the heat conductive sheet side is supported on a plane parallel to the optical axis of the FPC support portion 15h of the lower housing 15 to be attached to the FPC main body portion 17a. The stem 11c (that is, the electrode part side of the optical module) of the TOSA 11 is held. In other words, the extension portion 17c constitutes a support portion that supports the TOSA 11 by contacting the FPC support portion of the lower housing 15 (the support portion is parallel to the bottom surface of the housing). The extension portion 17c covers the periphery of the lead pin 11e of the TOSA 11 together with the FPC main body portion 17a. In particular, the extension 17c blocks between the lead pin 11e of the TOSA 11 and the lead pin of the adjacent OSA.

  The FPC 17 preferably includes at least two conductor layers. For example, the FPC 17 includes a wiring layer including the signal line 17g as the first conductor layer, and a solid layer (surface) as the second conductor layer. Of the outermost layer). The solid layer is provided so as not to be electrically connected to the through hole 17e and the electrode pad 17f electrically connected to the through hole 17e. Further, the solid layer potential is connected to a predetermined potential together with the stem 11c of the TOSA 11 in order to prevent crosstalk. This has the following effects.

  When an OSA having a CAN type module is mounted on an optical transceiver, a high frequency signal passes through a lead pin protruding from the stem, and an electric field is generated around the lead pin. This electric field jumps into the lead pin of the adjacent OSA and the line connected to that pin, for example, the TOSA signal affects the ROSA signal (crosstalk occurs between the TOSA and the ROSA). In other words, the reception sensitivity may deteriorate. However, in the present optical data link 1, since the solid layer connected to a predetermined potential (for example, ground potential) is provided in the extended portion of the FPC that serves to support the TOSA 11 and covers the lead pins, a shield structure is formed. Therefore, the above problem (crosstalk between adjacent OSAs, etc.) does not occur.

  Further, in the present optical data link 1, the FPC signal line connecting the lead pin and the terminal pad of the circuit board is covered with the solid layer, so that the reception sensitivity is not lowered.

  The FPC 17 is bent and used as described above, but is formed in a flat plate shape when the production is completed. In a state where the FPC 17 is formed in a flat plate shape, a direction perpendicular to the direction connecting the portion and the electrode pad 17f from the portion where the through hole 17e is formed (optical module connection portion) (in this example, the signal line and The extension portion 17c is provided in the right-angled direction, and the extension portion 17c is bent 90 degrees at the bending portion 17d during use. An FPC support portion 15h (see FIG. 1) on which the bent extension portion 17c is placed may be provided in the optical data link 1 casing.

In the above description, the solid layer is formed only on one side (one side) of the FPC 17. Thereby, rather than forming a solid layer on both sides (both sides) of the FPC 17, it is possible to maintain the flexibility that is the original characteristic of the FPC.
The bent portion 17d may be preformed with a jig or the like. Further, the solid layer of the bent portion 17d (portion surrounded by a dotted line in FIG. 5) is preferably made into a mesh and has low rigidity.

As described above, the FPC 17 has the extension portion 17c extending in the optical axis direction of the optical data link 1 when mounted, and heat conduction between the upper housing and the optical module 11a of the TOSA 11 when assembly is completed. The optical module 11a is pushed in the direction perpendicular to the optical axis by the stress from the sheet. At this time, as shown in FIG. 6, the lower housing 15 is provided with the FPC support portion 15h provided on the partition wall 15e and the outer wall 15i. Can support.
As a result, even if the force applied to the optical module 11a of the TOSA 11 is large due to the stress described above, the optical module 11a causes an axial shift with respect to the sleeve 11b supported by the insertion hole 15g (see FIG. 2) of the lower housing 15. It is possible to prevent the sleeve 11b from being inclined in the optical receptacle 15d.

  Thus, in the present invention, paying attention to the fact that the FPC is flexible in the direction perpendicular to the surface but has high rigidity in the direction along the surface, the OSA supports the OSA stem by the FPC, and the OSA is heated. A structure that resists the elastic repulsion force received from the conductive sheet is incorporated in the optical data link. Thereby, the position shift of OSA can be suppressed. Further, since the OSC signal pin is surrounded and shielded by the solid layer of the FPC having the extension, the shielding property can be improved and the crosstalk between the adjacent OSAs can be suppressed. Moreover, EMI radiation noise can be reduced. The above effects can be realized by a low-cost FPC.

  In addition, suppression of crosstalk between OSAs is performed by preparing a metal bracket connected to the ground potential and covering the periphery of the lead pin between the OSA and the circuit board as disclosed in Patent Document 1. Can do. However, in this method, the number of parts increases because the bracket is lowered, and solder connection between the bracket and the ground or between the bracket and the OSA is necessary. On the other hand, the optical data link of the present invention is connected to the ground potential and the part covering the periphery of the lead pin is formed integrally with the FPC, so there is no need to increase the number of parts and no new solder connection or the like is required. Therefore, it can be manufactured at low cost.

  In the above description, the TOSA has been mainly described. However, when the other OSA is ROSA, the ROSA is also electrically connected to the circuit board by the same FPC board as in FIG. 5, and the extension part of the FPC is supported by the FPC support part of the lower casing. The lead pin may be covered with an extension portion of the FPC connected to a predetermined potential.

1 is an external view of an optical data link according to the present invention. It is a principal part enlarged view of the optical data link which concerns on this invention. It is a perspective view of TOSA of this optical data link. It is a figure which shows the relationship between TOSA and a circuit board in this optical data link. It is a perspective view of FPC of this optical data link. It is a principal part enlarged view of TOSA, a lower housing | casing, and FPC.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical data link, 11 ... TOSA, 11a ... Optical module, 11b ... Sleeve, 11c ... Stem, 11d ... Shell, 11e ... Lead pin, 13 ... Circuit board, 13a ... Wiring, 15 ... Lower housing, 15a ... For transmission Optical module mounting portion, 15b... Receiving optical module mounting portion, 15c. ... FPC, 17a ... FPC main body part, 17b ... circuit board connecting part, 17c ... extension part, 17d ... bending part, 17e ... through hole, 17f ... electrode pad, 17g ... signal line.

Claims (3)

An optical data link formed by connecting an optical module having a package in which an optical element is mounted and a sleeve into which a ferrule of an optical connector is inserted, to a circuit board through a flexible printed circuit board, and holding and holding the optical module in a housing,
The flexible printed circuit board includes a wiring layer and a solid layer, a signal line circuit unit in which a connection part between the electrode part of the optical module and a connection part between the circuit board are connected by a signal line, and the electrode part. An optical data link comprising: an extension portion integrally formed on a side of the connection portion; and holding the optical module by supporting the extension portion with a support portion provided on a side wall of the housing. .   The optical data link according to claim 1, wherein a heat conductive sheet is disposed between the optical module and the housing.   The optical data link according to claim 1, wherein the solid electrode portion in the bent portion of the extension portion of the flexible substrate is formed in a mesh shape.

Images