Abstract:
An optical sub-assembly module comprises a receptacle combined with a light emitting device. The receptacle has an optical axis and a one-piece condensing device with a dual lens structure and aligning with the optical axis. The light emitting device is either a traditional LED, a laser diode, a light emitting component with a TO-CAN structure, or a photo detector (PD). The light may radiate through an opening in the pervious direction of the outer seal of each light emitting device. The pervious side of the light emitting chip in each light emitting device may be designed without micro lenses. The optical sub-assembly module is capable of improving the light coupling effect with the one-piece dual lens structure in the receptacle. The combination process of the receptacle and the light emitting device is compatible with the existing process. Each light emitting device has an opening at its outer seal end and a light emitting chip without micro lens structure to lower production costs. The opening structure brings the lens of the receptacle closer to the light emitting chip to improve the light condensing effect.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an optical subassembly, and more particularly to a combination of a semiconductor light emitting device and a plastic receptacle. The optical subassembly is used in the field of fiber optic communication, and the receptacle is combined with a fiber ferrule.  
         [0003]     2. Description of the Prior Arts  
         [0004]     Fiber optic communication is to transform the electrical signals emitted from the emitting end into optical signals, and then the optical signals are guided into an optical fiber and transmitted to the receiving end, after that the optical signals are transformed into electrical signals again. The emission and reception of the optical signals should be achieved by optical subassembly. For communication products, the quality requirement of the components is pretty high. The components need to be sealed with the method of hermetic sealing method, so as to prevent their operation from being damaged by outer atmospheric surrounding.  
         [0005]     A conventional optical subassembly contains at least a diode on a header, a lens or a system of lenses, and a precise mechanical port for docking a fiber/ferrule assembly. It generally includes a receptacle and a light emitting/receiving optoelectronic device, wherein the receptacle is defined with a passage for insertion of a fiber ferrule. The light emitting/receiving device is employed to generate/receive optical signals. Namely, the optical subassembly in the system is also called the coupling unit. It can be concluded that an optical subassembly plays an important role in the optical communication. The optical power and light coupling efficiency provided by the optical subassembly decide the quality of signal transmission through a fiber. To improve the optical power and light coupling efficiency, the optical subassembly should be equipped with or formed with an optical beam transformation system, e.g., lenses, or it should be equipped with the light emitting device that can provide high output power.  
         [0006]     Referring to  FIG. 1 , wherein an optical subassembly  10  includes a light emitting device  11  (ball-lens To-can) and a receptacle  12 . The light emitting device  11  refers to laser diode or light emitting diode, and the receptacle  12  is made by plastic injection molding, along the axis of which is defined with a through passage  17  and an optical axis  18 . The light emitting device  11  is combined with the receptacle  12  and an end of an optical fiber  13  is inserted in the passage  17  of the receptacle  12  and located opposite to the light emitting device  11 . By such arrangements, after optical signals are emitted from the light emitting device  11 , the optical signals can enter in the optical fiber  13 . However, due to the divergence angle of the light emitted from the light emitting device  11 , the light is unable to directly and totally enter in the optical fiber  13 . In this case, a lens  14  can be disposed between the receptacle  12  and the light emitting device  11  in order to gather the light emitted by the light emitting device and guide it into the optical fiber  13 . The lens  14  can be a spherical lens and disposed in alignment with the light emitting chip  16  on the top cap  15  of the light emitting device  11 .  
         [0007]     Since the spherical lens  14  is disposed on the top cap  15 , there is assembly tolerance between the lens  14  and the light emitting chip  16 , and it also has assembly tolerance when the light emitting device is assembled to the receptacle  12 , thereby it is susceptible to the deviation of the lens  14  from the optical axis  18  of the receptacle  12 , and some optical signals cannot be conducted to the optical fiber  13  by the lens  14 . Moreover, the light coupling efficiency of the spherical lens  14  is low, thereby the operation of the optical subassembly  10  doesn&#39;t reach the optimum level. As concerns the light emitting device  11 , the top cap  15  of which should be defined with a spherical lens  14 , thus the cost is increased.  
         [0008]     Referring to  FIG. 2A , wherein a commonly-used conventional optical subassembly  20  includes a receptacle  22  and a light emitting device  21  (it is called flat-window TO-can). The receptacle  22  is defined with a passage  27  that has a close end. The close end of the passage  27  is defined with a lens  23 , and an optical axis  28  is defined in the axial direction of the passage  27 . The light emitting device  21  includes a metal cap  24  interiorly provided with a light emitting chip  25 , the metal cap  24  is defined with a glass plate  26  on the top surface thereof. By such arrangements, the light emitted from the light emitting chip  25  can penetrate the glass plate  26  and then be gathered by the lens  23 .  
         [0009]     Since the glass plate  26  on the cap  24  has no light-gathering power, it doesn&#39;t matter whether the light emitting chip  25  is aligned to the cap  24  or not, the light emitting chip  25  can be aligned to the optical axis  28  by taking advantage of light coupling when assembling the light emitting device  21  to the receptacle  22 , and the lens  23  is formed by plastic injection molding, such that the light coupling efficiency of the aspherical lens is effectively improved. However, since the light emitting chip  21  should be equipped with the glass plate  26 , the component cost of the optical subassembly  20  is increased.  
         [0010]     On the other hand, when the lens  23  is located close to the light emitting chip  25 , the light with a large divergence angle emitted by the light emitting chip  25  still can be projected in the scope of the lens  23 . However, since the glass plate  26  is disposed on the cap  24  of the light emitting device  21 , it limits the approaching distance between the lens  23  and the light emitting chip  25 . Although the distance between the lens  23  and the light emitting chip  25  can be shortened by reducing the height of the cap  24 , the light emitting device  21  has a certain regular specification as usual. If the height of the metal cap  24  is attributably changed and the quantity of the changed metal cap  24  is not large enough, the component cost of the optical subassembly  20  will also be increased. Vice versa, the light emitting chip  25  can be moved to be close to the lens  24  by increasing the height of the light emitting chip  25 , but the production cost will be increased again.  
         [0011]     The U.S. Pat. No. 5,973,862 discloses an optical subassembly, wherein the receptacle is provided with plural grip fingers for holding the spherical lens, however, it is unable to reduce the cost since the light emitting device is still provided with glass. On the other hand, the light coupling efficiency of the spherical lens is low, and the distance between the spherical lens and the light emitting chip in the light emitting device can not be shortened any more.  
         [0012]     The U.S. Pat. No. 6,547,455 also discloses an optical subassembly, which uses a dual-lens device to increase the light coupling. However, since the light emitting device is provided with glass, the cost is relatively high, and the lens is unable to move closer to the light emitting chip in the light emitting device. Furthermore, installing the dual glass lens in the receptacle brings the possible shifting of the optical axial position, so that it may cause the misalignment with the light emitting device or the fiber. As a result, the structure with the dual lens in the receptacle is adverse to the light coupling effect.  
         [0013]     The operation speed of the conventional optical subassembly of a LED module can reach 155 Mb/s at least, which can satisfy the requirement for the general users in local area network. The LED optical subassembly has the advantage of low cost in case of a large quantity of user terminals. However, the divergence angle of the LED device is rather large, only a lens is not enough to focus the light. In this case, the LED optical subassembly should be additionally equipped with a lens or lenses structure so as to improve the coupling effect. With reference to  FIG. 2B , wherein the LED chip  110  includes an epitaxial portion  112  that is made of plural layers of semiconductor materials, including an active layer  114  that can generate light output by current injection. The epitaxial portion  112  is grown on a substrate  116 , and the substrate  116  is provided with a monolithically integral micro lens  118 . Since the substrate is almost transparent, the light emitted from the active region  114  will pass through the substrate and then to be focused by the micro lens  118 , and thus the light coupling efficiency is accordingly improved.  
         [0014]     However, to etch a micro lens  118  on the substrate  116 , it should precisely control the etching uniformity on the whole wafer. In fact, the process is not easy to be controlled in production. As a result, the production cost is relatively increased. Furthermore, if the substrate  116  is thick, it will affect the light-gathered efficiency due to the light divergence. The substrate  116  has to be lapped to a desired thickness in order to improve the light-gathered efficiency. The thin substrate  116  is thus susceptible to be broken into pieces, leading to a reduced process yield.  
         [0015]     On the other hand, since the light is emitted via the substrate  116 , that is to say that the light is emitted from the backside of the chip, the on-wafer auto testing for the chips is difficult. The latter process is not easy to be controlled. Moreover, when passing through the chip  110 , the light is initially focused by the micro lens  118  and then refocused by the lens of the receptacle. If the misalignment of the optical axis happens during the chip process, for example, if an error is appeared when making and aligning the micro lens on the substrate, the light coupling efficiency is drastically decreased. The transmitter optical subassembly comprised of the LED and the receptacle thus fails to meet the requirement of the specification and cannot be qualified for applications. The assembly of the monolithic integral lens of the LED and the single lens of package element can be provided enough output power in the conventional LED optical subassembly. But there are still some problems needed to be solved, such as manufacture inconvenience, high production cost, and power degradation by misalignment, and incompatibility with on-wafer testing, as mentioned above.  
         [0016]     The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional optical subassembly.  
       SUMMARY OF THE INVENTION  
       [0017]     To overcome the disadvantages of the above-mentioned optical subassemblies, there is provided an improved optical subassembly in accordance with the present invention.  
         [0018]     The objective of the present invention is to provide an optical subassembly module comprising a light emitting device and a receptacle. The receptacle has a dual-lens structure that forms a single unit together with the receptacle to collect the light emitted from the light emitting device more effectively and ensure a better light coupling efficiency with the light emitting device.  
         [0019]     The secondary object of the present invention is to provide an optical subassembly, which includes a receptacle and a light emitting device, wherein the light emitting device provided with a light emitting chip in an outer seal. An end of the outer seal is open structured and located opposite to the light emitting chip. Such arrangements can substantially reduce the production cost of the light emitting device.  
         [0020]     The other object of the present invention is to provide an optical subassembly that includes a receptacle and a light emitting device, wherein the receptacle is provided with a lens, and an outer seal of the light emitting device is interiorly provided with a light emitting chip. The lens can enter the outer seal so as to be located close to the light emitting chip, such that more optical signals emitted from the light emitting device can be focused by the lens.  
         [0021]     Another advantage of the present invention is that the optical subassembly is not provided with glass plate piece, which has no problem of light reflection, thereby, the light coupling efficiency is increased.  
         [0022]     The above-mentioned light emitting device refers to the light emitting device with metal seal, such as TO-CAN or LED sealed with epoxy resin. The components of the optical subassembly is fully compatible with conventional manufacturing infrastructure. The advantages lead to good performance, easy fabrication, high yield, and low cost simultaneously all together for mass production, that is beneficial for wide applications.  
         [0023]     The present invention will become more obvious from the following description when taken in connection with the accompanying drawings, which shows, for purpose of illustrations only, the preferred embodiments in accordance with the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]      FIG. 1  is a cross sectional view of a conventional optical subassembly;  
         [0025]      FIG. 2A  is a cross sectional view of another conventional optical subassembly;  
         [0026]      FIG. 2B  is a partial structural view of a conventional light-emitting chip;  
         [0027]      FIG. 3A  is a schematic view of an optical sub-assembly module comprising a traditional light emitting device and a receptacle with a dual-lens structure;  
         [0028]      FIG. 3B  is a cross sectional view of an optical subassembly in accordance with the present invention;  
         [0029]      FIG. 4  is another cross sectional view of an optical subassembly in accordance with the present invention, wherein the lens is defined close to the light emitting chip, and the chamber is hermetically sealed;  
         [0030]      FIG. 5  is another cross sectional view of an optical subassembly in accordance with the present invention for showing the lens defined close to the light emitting chip;  
         [0031]      FIG. 6  is another cross sectional view of an optical subassembly in accordance with the present invention, wherein the light emitting device is a surface emitting diode;  
         [0032]      FIG. 7  is a cross sectional view of an optical subassembly in accordance with the present invention;  
         [0033]      FIG. 8  is a cross sectional view of a light-emitting chip in accordance with the present invention;  
         [0034]      FIG. 9  is another cross sectional view of a light-emitting chip in accordance with the present invention;  
         [0035]      FIG. 10  is a cross sectional view of another optical subassembly in accordance with the present invention;  
         [0036]      FIG. 11  is a cross sectional view of an optical subassembly for showing a receptacle having a single lens and a light/receiving device having hermetic sealing;  
         [0037]      FIG. 12  is a cross sectional view of an optical subassembly for showing a receptacle having a single lens and a light/receiving device having non-hermetic sealing;  
         [0038]      FIG. 13  is a cross sectional view of an optical subassembly for showing a light/receiving device having non-hermetic sealing and a chip having a hermetic sealing package.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0039]     Referring to  FIG. 3A , the optical subassembly module  30  comprises a light emitting/receiving device  50 . The light emitting/receiving device  50  is either a traditional LED, a laser diode, a light emitting component with a TO-CAN structure of metal shell or glass, or a photo detector.  
         [0040]     Referring to  FIG. 3B , wherein an optical subassembly  30  in accordance with the present invention is shown and generally comprises: a plastic receptacle  32  and a light emitting device  52 , and the plastic receptacle  32  is assembled with the light emitting device  52 .  
         [0041]     The receptacle  32  can be in form of the SC, ST, LC and the likes, taking ST receptacle as an example, wherein the receptacle  32  is defined with a passage  34  which has an open end  36  and a close end  38 . The close end  38  as least is provided with a lens, both opposite surfaces of the close end  38  are defined with lenses  42  and  44  respectively. An optical axis  46  in alignment with the lenses  42 ,  44  defined in the passage  34  along the axial direction thereof. It is easy to form the opposite lenses  42 ,  44  in alignment with the optical axis  46  on the receptacle  32  due to the technology of plastic injection molding is highly developed. Furthermore, at the end of the receptacle  32  opposite the passage  34  is provided with a chamber  48 , and the lens  44  corresponds to the chamber  48 . The lens  44  with a larger diameter is more efficient in light gathering.  
         [0042]     The lens  42 ,  44  is formed directly inside the receptacle  32 , so no shifting occurs to the relative position between the lens structure and the receptacle  32 . As a result, correct light coupling is assured by the combination of the receptacle  32  and the light emitting device  52 .  
         [0043]     Furthermore, the light emitting device  52  includes an outer seal  54  and a light emitting chip  56 . The outer seal  54  can be made of metal, an end  58  of which is defined with a through aperture  62 . The light emitting chip  56  is received in the outer seal  54  and disposed in alignment with the aperture  62 . It is worthy to note that the aperture  62  in the outer seal  54  is open structured without being covered by any object.  
         [0044]     During the sealing process, the light emitting device  52  is disposed in the chamber  48  of the receptacle  32 , and then via the aperture  62  the light emitting chip  56  is aligned o the optical axis  46  and the focal point thereof using optical coupling techniques, the light emitting device  52  and the receptacle  32  are temporally fixed with adhesive  72  (UV glue), and then permanently fixed with adhesive  74 , thus the chamber  48  of the receptacle  32  is closed and the emitting chip  56  is enclosed in the receptacle.  
         [0045]     Referring to  FIG. 4 , after the temporary fix by the adhesive  72 , the adhesive  76  is used to fill up the air gap between the outer seal  54  and the inner wall of he chamber  48  so as to make the light emitting device  52  adhere with the receptacle  32 . Due to the low viscosity of the adhesive  76  and the effect of its surface tension, the adhesive  76  will flow beneath the adhesive  72 , stay on the periphery of the outer seal  54 , and result in a isolated space in the chamber  48 . The space condition depends on the gluing process environment at that time, e.g., vacuum or nitrogen ambience. The lens  44  and the light emitting chip  56  will not be contaminated by the adhesive  76  and the light coupling efficiency will not be affected. Finally, they are permanently fixed with the adhesive  74 .  
         [0046]     Furthermore, according to the above-mentioned structures, the chamber  48  further can be vacuumed or filled with inactive gases, such as nitrogen, so as to keep the light emitting chip  56  from oxidation. In addition, our experimental results showed that the elements could be sealed 100% by this sealing method. However, the conventional sealing method can&#39;t meet the requirement if the light emitting device  52  is non-hermetic sealing.  
         [0047]     Furthermore, if the sealant of the adhesive  76  is soft, e.g., silicone, the adhesive  74  must be adopted to increase the bonding strength. And, if the bonding strength of the sealant of the adhesive  76  is strong enough, the adhesive  74  and  76  can be the same and even a single glue, for example, UV glue or AB epoxy, can be used to replace the two adhesives  74  and  76 .  
         [0048]     The specification of the light emitting device  52  in the above-mentioned embodiments is the same as that of the conventional light emitting device. The distinction of the present invention is that the top surface of the light emitting device  52  in the above-mentioned embodiments is not equipped with glass plate or any cover. The present invention rules out the high cost component of the light emitting device  52 , thereby, the material cost is substantially reduced.  
         [0049]     In addition, the sealing process of the light emitting device  52  and the receptacle  32  is compatible with the conventional methods, thus the process cost will not be increased despite the structure of the light emitting device  52  is changed.  
         [0050]     Referring to  FIG. 5 , since the top surface of the light emitting device  52  has no cover structure, the lens  44  can be made closer to the light emitting chip  56 . The lens  44  can be extended even into the outer seal  54 , such that the lens  44  and the light emitting chip  56  can be located more closely. In this case, most of the light emitted by the light emitting chip  56  can be projected over the lens  44 , especially for a large divergence angle. The light gathered power can thus be substantially improved.  
         [0051]     Referring to  FIG. 6 , an optical subassembly in accordance with another embodiment of the present invention includes a receptacle  32  and a light emitting device  80 . The structure of the receptacle  32  is the same as that of the above-mentioned embodiment, and the assembly method for the light emitting device  80  and the receptacle  32  is also identical with the above-mentioned embodiment. The outer seal  82  of the light emitting device  80  is a layer of epoxy resin, and a light emitting chip  84  is disposed in the outer seal  82 . This is a cost-effective packaging method widely used in the conventional LEDs. It is to be noted that the top surface of the outer seal  82  is defined with an open aperture  86  that is not covered/sealed by any objected.  
         [0052]     Taking the light emitting device  80  as an example, although the beam divergence angle of the light emitting device  80  is relatively large, since the top surface of the outer seal  82  of the light emitting diode  80  is open, the lens  44  of the receptacle  32  can be made close to the light emitting chip  84 , such that most of the beams can be projected over the lens  44  and the light-gathered power is accordingly improved.  
         [0053]     In addition, since the receptacle  32  in accordance with the embodiments of the present invention are provided with two opposite lenses  42 ,  44 . The light emitted by the light emitting devices  80  after two light-gathered processes can be focused into a smaller beam spot so as to be aligned well to an optical fiber, which makes the production easier.  
         [0054]     In the above-mentioned embodiments, the light emitting device and receptacle can be in a hermetic seal condition. However, a non-hermetic seal condition may be also used if there is no reliability issue on the light emitting device. If special passivation is applied for the semiconductor device, normal operation can be sustained without any damage in the atmospheric environment.  
         [0055]     Referring to  FIG. 7 , an optical subassembly includes a receptacle  32  and a LED  90 . The receptacle  32  is formed with a passage  34 , and an optical axis  46  is defined in the passage  34 . The passage  34  has an open end  36  and a close end  38 . Two opposite lenses  42 ,  44  are formed on the either side of the close end  38 . The two lenses  42 ,  44  can be along to the optical axis  46 . Furthermore, at an end of the receptacle  32  is formed a chamber  48  and the lens  44  is disposed in the chamber  48 .  
         [0056]     The LED  90  is disposed in the chamber  48  and aligned to the optical axis  46  and its focus. And the LED  90  includes an outer seal  92  interiorly provided with a light-emitting chip  94 , wherein the outer seal  92  is made of epoxy resin for hermetically sealing the light-emitting chip  94 , such that the LED is a conventional type LED.  
         [0057]     Referring to  FIG. 8 , the light-emitting chip  94  includes an epitaxial portion  95  and a substrate  96 , wherein the substrate  96  is disposed at a side of the epitaxial portion  95 , and another side of the epitaxial portion  95  is combined with a layer  97  of P-type material. When using a relative thick P-type material layer  97  and adhering it with silver glue or AuSn solder, the short circuit of the light-emitting chip  94  can be prevented during package process, wherein the P-type material layer  97  can be an electroplated metal layer or a wafer-bonded conductive substrate. Furthermore, the epitaxial portion  95  comprises plural epitaxial layers, including a layer of active region  98  that can provide light source.  
         [0058]     The surface of the substrate  96  is not specially provided with a micro lens, but formed with a transparent surface  99 , such that the light emitted from the active region  98  can pass through the transparent surface  99 . The LED that allows the light to pass through the substrate  96  is called Back-side Bottom-emitting Flat LED.  
         [0059]     Referring to  FIG. 9 , wherein a light-emitting chip  94  in accordance with another embodiment of the present invention is shown and includes a flat transparent surface  100  formed at a side of the epitaxial layer  95 , and the flat transparent surface  100  is located away from the substrate  96 . In this case, the light emitted from the active region  98  will pass through the transparent surface  100  at a side of the epitaxial portion  95 , but not pass through the substrate  96 . The LED that allows the light to pass through the side of the epitaxial portion  95  is called Front-side Top-Emitting Flat LED. Particularly, the light-emitting chip  94  has no micro lens in the direction that the light passes through.  
         [0060]     The surface of the neither Front-side Top-emitting Flat LED nor Back-side Bottom-emitting Flat LED is provided with a micro lens, so the production of the light-emitting chip  94  is easy and the cost is low.  
         [0061]     Referring to  FIG. 7 , when the LED  90  is assembled to the receptacle  32 , and the light emitted from the LED  90  will be focused twice by the lenses  44  and  42 , so as to reduce the coupling loss of the emitting light. By this way, it ensures that enough light will be coupled into a fiber despite the beam divergence angle of a LED is large.  
         [0062]     In addition, since light-emitting chip  94  has no micro lens, the light passing through the transparent surface are focused by the lenses  42  and  44 , thereby, the possible optical misalignment can be avoided in the fabrication process of the flat LED as well as the ball-lens TO-can package. In other words, the combination of the LED  90  and the receptacle  32  in accordance with the present invention can make alignment easier. On the other hand, the package type of the LED  90  is the same as that of the conventional LED. In addition, the combination of the LED  90  and the receptacle  32  is compatible with the conventional package process. Therefore, the manufacturing processes are pretty easy, mature, cost-effective, and suitable for mass production. Since light-emitting chip  94  has no micro lens, the light-emitting chip  94  has different choices for light emitting directions. As a result, the on-wafer LED testing before package can be carried out on a whole wafer, e.g., Front-side Top-emitting Flat LED.  
         [0063]     With reference to  FIG. 10 , the outer seal  92  is provided at a top surface thereof with an opening  101 , and the length of the lens  44  is increased, so as to shorten the distance between the light-emitting chip  94  and the lens  44 , and even the lens  44  can enter the opening  101 , thus the distance between the light-emitting chip  94  and the lens  44  is further decreased. By such arrangements, most of the light can be projected into the lens  44  despite the beam divergence angle of the LED  90  is large, so as to achieve a good coupling effect.  
         [0064]     Referring to  FIG. 11 , an optical subassembly includes a receptacle  122  and a device  124 . A chamber  126  and a coupling structure  127  are formed in the receptacle  122 . The coupling structure  127  has a single lens and be located in the chamber  126 .  
         [0065]     The device  124  is a light emitting element or a light receiving element which is assembled in the receptacle  122  and disposed in alignment with the optical axis. The device  124  includes an outer sealing  128  and a chip  132  which is assembled in the outer sealing  128 . If the top surface  129  of the device  124  is a sealing surface then the chip  132  is positioned in a hermetic space. The top surface  129  has a transparent portion which may be transparent glass or resin for light passing through.  
         [0066]     As show in  FIG. 11 , the coupling structure  127  is able to close to the device  124  by a large diameter or an extension portion. Therefore more light emitted from the device  124  can be focused by the coupling structure  127  so that the optical subassembly has a good efficiency for light output.  
         [0067]     As show in  FIG. 12 , the coupling structure  127  has a single lens and close to a light emitting/receiving device  140 . The light emitting/receiving device  140  includes an outer sealing  142  and a chip  144  which is assembled in the outer sealing  142 , and the top surface  143  of the outer sealing  142  has an opening  146 .  
         [0068]     Considering the requirement of the reliability of the chip  144 , the chip  144  must be positioned in a hermetic space. However, the outer sealing  142  is non-hermetic sealing so a space between the chamber  126  and the device  140  has to be a hermetic sealing by an adhesive  148 . But if the reliability of the chip is not a concern, the space between the chamber  126  and the device  140  can be a non-hermetic space.  
         [0069]     As show in  FIG. 13 , a resin  152  is used to preventing the chip  144  from being contacted with air. In this case, even though the outer sealing  142  having an opening, and the space between the chamber  126  and the device  140  is a non-hermetic space, the reliability of the chip  144  meet the requirement.  
         [0070]     Based on the above-mentioned embodiments, the structural features and functions of the present invention are concluded as follows: 
        1) the outer seal of any light emitting devices in accordance with the present invention is defined with an open aperture at an end thereof, and the aperture is aligned with the light emitting chip in the outer seal, such that a lens in the receptacle can be located closely to the light emitting chip, thus the output power is improved.        
 
         [0072]     2) Any light emitting devices in accordance with the present invention are conventional, and the difference is that the outer seal in accordance with the present invention is not equipped with a hermetic sealing cover structure, and thus the cost of the light emitting device can be reduced.  
         [0073]     3) The specification of the optical subassembly in accordance with the present invention is identical to that of a conventional optical subassembly. The production processes and equipments used for the receptacle and light emitting device will not be changed. In other words, the structure of the optical subassembly in accordance with the present invention is compatible with the conventional manufacturing infrastructure.  
         [0074]     4) The receptacle in accordance with the present invention can be provided with two opposite lenses. In this case, light signals can be guided into an optical fiber more efficiently, allowing a larger error occurred in light coupling. Thereby, the production can be easier.  
         [0075]     5) The LED in accordance with the present invention is not provided with a micro lens, and the receptacle assembled with the LED is provided with two opposite lenses. In this case, despite the light emitted from the LED has a large divergence angle, the present invention can achieve a desired coupling effect.  
         [0076]     6) The LED in accordance with the present invention is not provided with a micro lens, thereby the LED structure is simple and low cost.  
         [0077]     7) The package type of the LED is the same as that of the conventional LED, so the sealing of the LED is pretty easy and the package process of the combination of the LED and the receptacle is compatible with the conventional package process; 
        8) The LED in accordance with the present invention is not provided with a micro lens, the LED allows different light-emitting choices, such that the on-wafer testing of the light-emitting chip can be performed on a whole wafer;        
 
         [0079]     While we have shown and described various embodiments in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.