WO2011152555A1

WO2011152555A1 - Optical transceiver with block to dissipate heat from tosa to cover

Info

Publication number: WO2011152555A1
Application number: PCT/JP2011/062878
Authority: WO
Inventors: Kuniyuki Ishii; Hiromi Kurashima
Original assignee: Sumitomo Electric Industries, Ltd.
Priority date: 2010-06-01
Filing date: 2011-05-31
Publication date: 2011-12-08
Also published as: JP2012015488A

Abstract

An optical transceiver that installs a TOSA with a bottom plate providing a path to dissipate heat externally is disclosed. The bottom plate thermally couples with the cover of the transceiver through a block with good thermal conductivity by a belt that elastically binds the block with the TOSA. The path to dissipate heat is bent in substantially right angle by the block. Because the belt elastically binds the block, but thermally comes in contact to the TOSA, no stress causes the coupling status of the TOSA.

Description

DESCRIPTION

Title of Invention

OPTICAL TRANSCEIVER WITH BLOCK TO DISSIPATE HEAT FROM TOSA TO COVER

Technical Field

[0001] The present invention relates to an optical transceiver, in particular, the invention relates to an optical transceiver that installs a TOSA thermally coupled with a cover through a block.

Background Art

[0002] An optical transceiver generally includes a transmitter optical subassembly (hereafter denoted as TOSA), a receiver optical subassembly (hereafter denoted as ROSA), and a circuit board that mounts circuits communicating with the TOSA, the ROSA, and the host system with which the optical transceiver is mounted. The TOSA, and the ROSA, installs a semiconductor optical device, such as a laser diode

(hereafter denoted as LD) for the TOSA and a photodiode for the ROSA. When the TOSA or the ROSA generates large heat, it is inevitable to dissipate heat generated therein to the outside of the transceiver. The United State Patent published as US20040105633 A has disclosed such an optical transceiver with a path to dissipate heat from the optical subassemblies (hereafter denoted as OSA) to the housing. Another prior art of a Japanese Patent Application published as JP-2007-227707A has disclosed an optical transceiver with a function to secure a path to dissipate heat from the OSA to the metal cover.

[0003] Fig. 11 shows an example of a conventional arrangement of the path to dissipate heat from the OSA 101 to the housing, 102 and 103. The OSA 101 includes a package 101a that installs, in a case of a TOSA, an LD that generates heat, electrodes 101b, and a sleeve 101c. To the electrodes 101b, a flexible printed circuit (hereafter denoted as FPC) 104 that is extended to the circuit board is attached. The heat generated within the package 101a is dissipated to the housing, 102 and

103, through thermal sheets, 106a and 106b, put between the package 101a and respective inner surfaces, 102a and 103a, of the housing. The thermal sheet has a good thermal conductivity. As shown in Fig. 11, the conventional arrangement of the TOSA 11, the top and bottom surfaces of the package 101a may provide the path to dissipate heat.

[0004] While, when the OSA has another type of a package, what is called as, a package comprised of a multi-layered ceramics, only the bottom plate to which the FPC 104 is attached may provide a surface to dissipate heat therefrom. That is, a thermal sheet is hard to be put between the package 101a and the cover, 102 and 103; an additional component is necessary to bend the path to dissipate heat from the package to the cover.

Summary of Invention

[0005] An aspect of the present invention relates to an optical transceiver that includes a TOSA, a metal cover, and a block. The

TOSA has a package with a bottom plate to dissipate heat to an outside of the TOSA. The bottom plate extends in a direction. The metal cover installs the TOSA therein and includes an inner surface extending in substantially perpendicular to the direction. The block is attached to the bottom plate and the inner surface of the cover. A feature of the present invention is that the block secures a path to dissipate heat from the package to the cover as bending the path substantially in right angle.

[0006] The block may thermally couple with the inner surface of the cover through a thermal sheet or thermal gel put therebetween; while the block may be directly attached to the bottom plate without any substantial member. Moreover, one of embodiments of the present invention has a feature that the block is movable along the direction above to absorb stress to be introduced in said package. The block may have a surface attached to the bottom plate whose area is wider than an area of said bottom plate to secure the effective area to heat transfer from the bottom plate to the block. The optical transceiver may further include a metal belt to fasten the block to the package.

Brief Description of Drawings

[0007] The foregoing and other purposes, aspects and advantages will be better understood from the following detailed description of a preferred embodiment of the invention with reference to the drawings, in which:

[0008] ig. 1 shows an outer appearance of an optical transceiver implemented with an optical subassembly according to an embodiment of the present invention;

[0009] Fig. 2 shows an inside of the optical transceiver shown in Fig. 1,

[0010] Fig. 5 is a cross section of a portion of the optical transceiver according to an embodiment of the present invention;

[0011] Fig. 4 is a cross section of a portion of the optical transceiver according to another embodiment of the present invention;

[0012] Fig. 5 is a perspective view, part of which is broken to show an inside thereof, of the optical subassembly shown in Figs. 3 and 4;

[0013] Fig. 6 is an outer appearance of the optical subassembly shown in Fig. 5;

[0014] Figs. 7 A and 7B show a ROSA and a TOSA, respectively, each installed within the optical transceiver shown in Figs. 1 and 2, where each OSA provides a FPC board attached thereto;

[0015] Figs. 8A and 8B each shows a status where the TOSA illustrated in Fig. 7B is assembled within the housing of the optical transceiver;

[0016] Figs. 9 A and 9B are perspective views of the block attached to the TOSA;

[0017] Figs. 10A and 10B show a band to fasten the block with the TOSA; and

[0018] Fig. 11 is a cross section of an optical transceiver that installs a conventional TOSA.

Description of Embodiments

[0019] Details of the present invention will be described as referring to accompanying drawings. The optical transceiver 10 whose outer appearance is illustrated in Fig. 1 may install an OSA according to one embodiment of the present invention. Specifically, the optical transceiver 10 installs a TOSA, a ROSA, and a circuit board that mounts electronic components communicating with the TOSA, ROSA and the host system thereon within a housing including an upper cover 11 and a lower cover 12.

[0020] The covers, 11 and 12, may be made of metal to show functions to shield the electronic components and to dissipate heat generated by the electronic components and the OSAs. In particular, a plurality of fins 11a formed in the upper cover 11 enhances the heat dissipation. The front side of the housing, 11 and 12, includes a flange 13 and an optical receptacle 14. The flange covers a port provided in the host system onto which the transceiver 10 is to be mounted; while, the optical receptacle receives an external optical connector. A portion of the circuit board 15a extrudes from the rear end of the transceiver 10, which provides a function of an electrical plug to be plugged into an electrical connector in the host system to establish the communication between the transceiver 10 and the host system. The description assumes that the front of the transceiver 10 corresponds to a side where the optical receptacle 14 is formed, while, the rear side thereof corresponds to a side where the electrical plug 15a is formed.

[0021] Fig. 2 shows an inside of the transceiver 10 by removing the upper cover 11. The lower cover 12 mounts the circuit board 15 on which some ICs 19 and passive components are mounted. The front of the lower housing 12 mounts the TOSA 21 and the ROSA 31, where the OSAs communicate with the circuit on the circuit board 15 through respective FPCs, 27 and 34.

[0022] A light-emitting device, typically a laser diode (hereafter denoted as LD), mounted in the TOSA 21 and the IC 19 mounted on the circuit board 15 are the primary device to generate heat among the components installed within the optical transceiver 10. The embodiment according to the present invention provides a mechanism to dissipate heat efficiently from the TOSA 21. Specifically, a block 16 is attached to the ceramic package 22 of the TOSA 21 by a band 17 such that the block 16 may thermally couple with the ceramic package. This block 16 thermally couples with the upper cover 11 by interposing a thermal gel or a thermal sheet therebetween. The arrangement above may dissipate heat generated by the LD in the TOSA 21 to the upper cover 11 through the ceramic package of the TOSA 21 and the block 16.

[0023] Figs. 3 and 4 are the cross section of the TOSA 21, the block 16 and the upper cover 11 constituting the heat dissipating mechanism described above. The TOSA 21, where details thereof will be described later by referring to Figs. 5 to 7, includes the ceramic package 22, a sleeve 24 and a joint sleeve 23 coupling the sleeve 24 with the package 22. The TOSA 21 of one embodiment of the present invention may dissipate heat generated therein from the rear end, not from sides of the package 22. Accordingly, the rear surface 25a of the package 22 makes a right angle to the inner surface lib of the upper cover 11 to which the heat is to be conducted.

[0024] The belt 17 may fasten the block 16 to the ceramic package 22 such that the block 16 is pushed against the rear surface 25a of the ceramic package 22. Specifically, the block 16 in the front surface thereof is directly abutted against the rear surface 25αοϊ the ceramic package 22 without any interposer therebetween by the belt 17. Because the belt is made of material with an elastic characteristic, where a belt 27 is made of stainless steel in the present embodiment, the block 16 is effectively pushed against the rear surface 25a of the ceramic package 22 so as to show an effective thermal coupling therebetween.

[0025] The block 16 comes in contact with the upper cover 11 through a thermal sheet and the like to secure the heat dissipating path. The block 16 may be made of metal, such as aluminum, copper, zinc, and the like, or ceramics with a good thermal conductivity, typically, aluminum nitride (A1N). The upper cover 11 may be also made of metal such as aluminum, copper, zinc, and the like. Because a microscopically rough surface of the block 16, or that of the inner surface lib of the upper cover 11, degrades the heat transfer, a thermal sheet 18, a thermal gel 18a shown in Fig. 4, and the like may be effective to secure the good thermal transfer between the block 16 to the upper cover 11.

[0026] Fig. 3 is an embodiment where the thermal sheet 18 is put between the block 16 and the upper cover 11. The thermal sheet 18 may be a resin sheet made of elastomer, such as silicone rubber, improving the thermal conductivity by containing thermally conductive powders of metal, ceramics and so on. The thermal sheet 18 may elastically deform between the upper cover 11 and the block 16 so as to compensate the roughness of the surfaces. Thus, the heat conducted to the block 16 from the package 22 may be effectively dissipated to the upper cover 11. Thicker thermal sheet occasionally becomes a barrier for the heat conduction because the thermal conductivity of the resin for the thermal sheet 18 is inherently inferior to that of metal.

[0027] Fig. 4 is another embodiment of the present invention. This embodiment provides a thermal gel 18a put between the block 16 and the upper cover 11. The thermal gel 18a, or the thermal grease, may be expanded thin enough so as to absorb dimensional tolerance of components easily, which prevents the components from receiving stress.

[0028] As illustrated in Figs. 3 and 4, the TOSA 21 is assembled between the upper 11 cover and the lower cover 12 at the sleeve portion 24 thereof such that the position along the optical axis thereof may be aligned. The block 16 is attached to the rear surface 25a of the package 22 by the belt, which automatically determines the position of the block 16 along the axis. While, the block 16 is movable along a direction perpendicular to the axis, which is denoted by an arrow a in Figs. 3 and 4, which may absorb the dimensional tolerance of the block 16 and covers, 11 and 12. Specifically, the total thickness of the block 16 and the thermal sheet 18 for embodiment shown in Fig. 3 is about 10% greater than a space between the covers, 11 and 12; accordingly, assembling the block 16 between the covers, 11 and 12, the block 16 tightly comes in thermally contact with the upper cover 11 by crushing the thermal sheet 18.

[0029] Figs. 5 to 7 show the TOSA 21 to be installed in the optical transceiver 10 of the present invention. The TOSA 21 includes the multi-layered ceramic package 22, the sleeve 24, which optically couples the device in the package 22 with the external optical fiber, and the joint sleeve 23 that assembles the sleeve 24 with the package 22. The ceramic package 22, as shown in ig. 5, includes a side wall 22a by the stack of the ceramics, a portion of which 22a forms an electrode 22b to communicate electrically with an external circuit. The side wall 22a puts the ceiling 22f thereon through the sealing ring 22c. The ceiling 22f has a cylindrical portion 22d to receive a bore of the joint sleeve 23. The bore of the cylindrical portion 22d is covered by the window 22g to seal the inside of the package air-tightly. The bottom of the package

22 is covered by the metal bottom plate 25. [0030] The bottom plate 25 mounts the thermo-electric cooler (hereafter denoted as TEC) 26. The TEC 26 has a top plate and a bottom plate, where the top plate mounts the LD thereon, while, the bottom plate comes in thermally contact with the bottom plate 25. Thus, the LD on the top plate may be effectively cooled/heated so as to keep the temperature thereof in constant. The heat generated by the TEC 2 J as a result of the temperature control of the LD may be effectively dissipated to the bottom plate 25 from the bottom plate of the TEC 26. The package 22 further installs, in addition to the LD and the TEC 26, a photodiode to monitor the light output from the LD, a lens to concentrate the light emitted from the LD on the end of the coupling fiber 24c.

[0031] The joint sleeve 23 may optically align the sleeve 24 with the package 22, exactly the LD in the package 22. Specifically, adjusting the overlap length against the cylindrical portion 22d of the package 22, the optical alignment in the direction Z along the optical axis may be carried out; while, sliding the sleeve 24 on the flange of the joint sleeve 23, the optical alignment in the XY plane perpendicular to the optical axis may be performed.

[0032] The sleeve 24 receives a ferrule attached to a tip of the external fiber, which is not illustrated in Figs. 5 to 7. The sleeve has a bore 24a to receiver the ferrule and a stub 24b with the coupling fiber 24c in a center thereof. The light, which is emitted from the LD in the package 22 and concentrated on the end of the coupling fiber 24, may propagate in the external fiber through the coupling fiber and the interface between the external fiber and the end opposite to the end where the light is concentrated.

[0033] The bottom plate 25 protrudes from the surface of the layered ceramics. A portion of the surface of the layered ceramics not covered by the bottom plate 25 has a plurality of electrodes 22b to which the FPC substrate 27, as shown in Fig. 7B, is connected to secure the electrical path to the circuit board 15. The ROSA 31 shown in Fig. 7 A has a coaxial package 32 and a sleeve 33. Another FPC 34 electrically connects the ROSA 31 also to the circuit board 15.

[0034] Figs. 8 A and 8B show an intermediate assembly of the TOSA 21, the block 16 with the belt 17 and the circuit board 15 viewed from respective directions. As shown in Figs. 8A and 8B, the belt 17 assembles the block 16 with the package 22. Specifically, the block 16 with a block shape comes by one surface of the block in contact with the surface of the bottom plate 25 by the belt 17. The belt 17 has a U-shaped cross section with two arms, 17a and 17b, and sets the block

16 and the package 22 within a gap formed by these two arms, 17a and 17b.

[0035] The belt 17, as described later, is set to the TOSA 21 from the direction b in Fig. 8 A so as to insert the necked portion of the joint sleeve 23 into the U-shaped cut 17d thereof, and to be supported in the package 22 by the top tab 17 f and the side tab 17 e. Then, the belt 17 receives the block 16 between the rear arm 17b and the bottom plate 25 of the package 22 from the direction C shown in Fig. 8B. The top tab 17h in the rear arm 17b and a force abutting the block 16 against the bottom plate 25 of the package 22, which is caused by the elasticity of the belt 17 and the mating of the ribbed portion 17g of the belt 17 with the groove 16c of the block, support the block 16. The legs, 16d and 16e, of the block determine the horizontal level of block 16 by coming in contact with the bottom cover 12. The FPC substrate 27 connected to the TOSA 21 is extended between the legs, 16d and 16e, to be connected to the circuit board 15.

[0036] Figs. 9A and 9B show an example of the block 16 viewed from the top (Fig. 9 A) and from the bottom (Fig. 9B). The block 16, as described, may be made of metal or ceramics with preferable thermal conductivity. The block 16 includes a block portion 16a with a front surface 16b coming in contact with the bottom plate 25 of the package 22, and another surface opposite to the front surface 16b and including a groove 16c to receive the ribbed portion of the belt 17. The bottom of the block portion 16a includes a pair of two legs, 16d and 16e, in respective ends thereof which abut against the bottom cover 12. The top surface 16f of the block portion 16a thermally couples with the inner surface of the upper cover 11. The block 16 of the present embodiment attaches the front surface 16b directly, namely, without putting any materials, to the bottom plate 25 of the package. However, some material, such as thermal sheet, thermal gel and so on, may be put between the front surface 16b and the bottom plate 25 to enhance the heat transfer.

[0037] Figs. 10A and 10B show an example of the belt 17. The belt of the present embodiment may be formed by stamping a metal sheet, for instance, a stainless steel. The belt 17 of the present embodiment includes two arms, 17a and / 7b, and a bridge / 7c, where they form the U-shaped cross section. The front arm 17a has two branches 17k separated by a U-shaped cut 17 d. Each branches 17k includes a side tab 17 e and a top tab 17 f. The U-shaped cut 17 d receives a necked portion of the joint sleeve 23 from the side thereof, while the side tab 17 e and the top tab 17 f support the package 22. Specifically, Inserting the necked portion of the joint sleeve 23 into the U-shaped cut 17 d and pushing the package 22 forward until the front surface of the package 22 abuts against the branches 17k, the package 22 may be supported by the side tab 17e and the top tab 17f.

[0038] Another arm 17b includes a ribbed portion 17g protruding inwardly and another top tab 17h. The belt 17 is arranged so as to set the tab 17h downward. Accordingly, the top tab 17h, cooperating with the top tab 17 f in the front arm 17a may support the block 16 set between the arms, 17a and 17b. The ribbed portion 17g elastically pushes the block 16 frontward by being set within the groove 16c in the rear surface 16a of the block 16.

[0039] The optical transceiver 10 of the present embodiment positions the TOSA 21 between the covers, 11 and 12, so as to align optically with respect to the receptacle 14. The belt 17, as described above, is assembled with the package 22 of the TOSA 21, which forces the belt 17 to be set to the covers, 11 and 12. On the other hand, the block 16 is necessary to be securely attached to the covers, 11 and 12, to ensure the heat conducting path. Therefore, when the block 16 is precisely positioned to the package 22, unintentional stress is sometimes affected to the TOSA 21, which may disrupts the optical alignment between the device in the package 22 and the sleeve 24.

[0040] Accordingly, the block 16 is necessary to be fixed to the bottom plate 25 movably to compensate the dimensional tolerance of the components. Moreover, the front surface 16b is preferable to be wider than the bottom plate 25, which makes the bottom plate 25 securely in contact with the block 16 even when the relative position between the package 22 and the block 16 varies. Also, the width of the groove 16c in the block 16 is preferable to be wider than a width of the ribbed portion 17g such that the groove 16c may show a function of the guide for the belt 17 even when the relative position between the block 16 and the package 22 varies.

[0041] Thus, the optical transceiver 10 according to the present embodiment includes the block put between the TOSA 21 and the upper cover 11. Because the TOSA 21 has the arrangement that only the bottom plate is able to provide the path to dissipate heat to the external of the package, and the bottom plate extends in perpendicular to the primary surface of the cover, an additional component is necessary to secure the path to dissipate heat to the cover. The TOSA 21 of the present embodiment provides the block 16 that comes in physically and thermally contact with not only the bottom plate but the inner surface of the cover. Accordingly, the block 16 of the present invention may provide an effective path to dissipate heat of the TOSA 21 to the cover.

[0042] Moreover, because the TOSA 21 is positioned to the cover so as to align optical with the receptacle; while, the block 16 is positioned so as to be physically and thermally in contact with the cover, a stress brought to the block 16 may cause the misalignment in the TOSA 21 when the block 16 is tightly fixed to the TOSA 21. The block 16 of the present embodiment solves this subject by being loosely fixed to the TOSA 21 within the belt / 7.

[0043] Although the present invention has been fully described in conjunction with the preferred embodiment thereof with reference to the accompanying drawings, it is to be understood that various changes and modifications may be apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims, unless they depart therefrom.

Claims

1. An optical transceiver, comprising:

a TOSA having a package with a bottom plate to dissipate heat to an outside of said TOSA, said bottom plate extending in a direction; a metal cover for installing said TOSA therein, said cover including an inner surface extending in substantially perpendicular to said direction; and

a block attached to said bottom plate of said package and said inner surface of said cover,

wherein said block secures a path to dissipate heat from said package to the cover as bending said path substantially in right angle.

2. The optical transceiver of claim 1,

wherein said block is attached to said inner surface of said cover through a thermal sheet.

3. The optical transceiver of claim 1,

wherein said block is attached to said inner surface of said cover through a thermal gel.

4. The optical transceiver of claim 1,

wherein said block is directly attached to said package.

5. The optical transceiver of claim 1,

wherein said block is movable along said direction.

6. The optical transceiver of claim 5,

wherein said block includes a surface attached to said bottom plate, and

wherein said surface of said block has an area greater than an area of said bottom plate.

7. The optical transceiver of claim 1,

further comprising a belt made of metal to fasten said block to said package.

8. The optical transceiver of claim 7,

wherein said block includes a block portion and a pair of legs, said block portion having a side surface attached to said bottom plate of said package and a top surface making substantially right angle to said side surface, said top surface being thermally in contact with said inner surface of said cover, said legs extending from said block portion and coming in contact to another inner surface of said cover facing said inner surface to which said block is attached.

9. The optical transceiver of claim 7,

wherein said belt has a front arm, a rear arm and a bridge, said block and said package being put between said front arm and said rear arm,

wherein said front arm and said rear arm have a tab to support said block thereon.

10. The optical transceiver of claim 9,

wherein said rear arm of said belt has a ribbed portion, and said block has a groove in a surface opposite to a surface coming in contact to said package, said ribbed portion being set within said groove.

11. The optical transceiver of claim 1,

wherein said bottom plate of said package mounts a thermo-electric cooler thereon, said thermo-electric cooler mounting a semiconductor laser diode thereon,

wherein said thermo-electric cooler generates heat to keep a temperature of said semiconductor laser diode in constant.

12. The optical transceiver of claim 1,

wherein said block is made of ceramics with good thermal conductivity.