Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Korean Patent Application No. 10-2010-0092542 filed on Sep. 20, 2010, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an optical transmission apparatus and, more particularly, to an optical transmission apparatus including a cooler for controlling the temperature of the optical transmission apparatus. 
     2. Description of the Related Art 
     A WDM-PON (Wavelength Division Multiplexing Passive Optical Network) technique using WDM is a communication technique capable of grouping optical signals of different wavelengths by using a single optical fiber and transmitting the same. 
     The WDM-PON technique has advantages in that it does not cause interference with an optical signal of a different wavelength, guarantees a broadband bi-directional symmetrical service by assigning a unique wavelength to each subscriber, and has excellent security because only a particular subscriber is allowed to receive an optical signal of a particular wavelength. The WDM technique has been commonly used in the existing backbone network and, recently, there is a move to extend the use of the SDM technique even to a subscriber network. 
     In case of optical communication using WDM, because it uses the method of dividing wavelength, compared with existing time division multiplexing and frequency division multiplexing, it requires a thermo-electric cooler for controlling an operational temperature of a light source to have a certain degree in order to ensure temperature stability of an optical module, namely, in order to prevent malfunctions caused by a wavelength transition according to temperature. 
     However, the installation of the cooler in an optical transmission apparatus increases the size of an optical transmission module, which may in turn trigger secondary problems. 
     For example, when a package, a cooler, a substrate, various elements (e.g., a light source, a monitoring element, a reflector, a thermister, and the like), are sequentially stacked, the distance between the package and the elements is increased due to the presence of the cooler. Then, a lead pin of the package for supplying the power of the elements, a bonding wire for connecting the package lead pin and the elements would be lengthened and the signal transmission characteristics of the optical transmission apparatus would deteriorate proportionally. In addition, a cooling load of the cooler increased according to the size of the optical transmission module. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides an optical transmission apparatus having a temperature control function capable of offsetting the height of a cooler by proposing a package with a cavity, to thus reduce the size of the apparatus in spite of the presence of the cooler. 
     Another aspect of the present invention provides an optical transmission apparatus having a temperature control function capable of having a simpler structure by eliminating a support for mounting a monitoring element thereon or a reflector for reflecting light from a light source to the outside. 
     According to an aspect of the present invention, there is provided an optical transmission apparatus including: a package having a cavity; a cooler mounted in the cavity and controlling temperature; and a substrate mounted on the cooler and including a light source mounted thereon to generate light. 
     The package may include: a base having the cavity formed therein; and lead pins penetrating the base. 
     The package may further include an insulator formed to cover the lead pins. 
     The optical transmission apparatus may further include: a reflector mounted on the cooler and totally reflecting light from the light source to the outside. 
     The reflector may include: a bar mirror having a sloped face formed on an area to which light is made incident; and a total reflection coated film formed on the sloped face. 
     The optical transmission apparatus may further include: a support mounted on the cooler; and a monitoring light reception element mounted on the support and receiving light to perform a monitoring operation. 
     The optical transmission apparatus may further include: a reflector mounted on the cooler such that it is positioned in front of the light source, and reflecting a majority of light from the light source to the outside and allowing the remaining portion to be transmitted therethrough. 
     The reflector may include: a bar mirror having a sloped face formed on an area to which light is made incident; a beam splitter coated film formed on the sloped face; and a non-reflection coated film formed on an area from which light is output. 
     The optical transmission apparatus may further include: a monitoring light reception element mounted on the cooler such that it is positioned in front of the light source and the reflector, and performing a monitoring operation upon receiving light made incident through the reflector. 
     The reflector may include: a bar mirror having a sloped face formed on an area to which light is made incident; a beam splitter coated film formed on the sloped face; a total reflection coated film formed on an area from which light is output; and a non-reflection coated film formed on an area that light, which has been reflected by the total reflection coated film, reaches. 
     The optical transmission apparatus may further include: a monitoring light reception element mounted on the non-reflection coated film of the reflector and performing a monitoring operation upon receiving light made incident through the reflector. 
     The optical transmission apparatus may further include: a support mounted on the cooler such that it is positioned in front of the light source, and having a sloped face; and a monitoring light reception element mounted on the sloped face of the support, and reflecting a majority of light from the light source to the outside and receiving the remaining portion of the light to perform a monitoring operation. 
     The monitoring light reception element may include a beam splitter coated film formed on an area to which light is made incident. 
     The light source may include a total reflection coated film to allow light from the light source to be entirely output toward the reflector. 
     The optical transmission apparatus may further include: a thermister mounted on the cooler or the substrate to measure the temperature of the optical transmission apparatus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a view illustrating a light transmission apparatus according to a first exemplary embodiment of the present invention; 
         FIG. 2  is a view illustrating a package according to the first exemplary embodiment of the present invention; 
         FIG. 3A  is a view illustrating a reflector according to the first exemplary embodiment of the present invention; 
         FIG. 3B  is forming method of the reflector according to the first exemplary embodiment of the present invention; 
         FIG. 4A  is a view illustrating a light transmission apparatus according to a second exemplary embodiment of the present invention; 
         FIG. 4B  is a view illustrating the reflector according to a second exemplary embodiment of the present invention; 
         FIG. 5A  is a view illustrating a light transmission apparatus according to a third exemplary embodiment of the present invention; 
         FIG. 5B  is a view illustrating the reflector according to a third exemplary embodiment of the present invention; 
         FIG. 6  is a view illustrating a light transmission apparatus according to a fourth exemplary embodiment of the present invention; and 
         FIG. 7  is a view illustrating a monitoring element of the light emission apparatus according to the fourth exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention may be modified variably and may have various embodiments, particular examples of which will be illustrated in drawings and described in detail. 
     However, it should be understood that the following exemplifying description of the invention is not intended to restrict the invention to specific forms of the present invention but rather the present invention is meant to cover all modifications, similarities and alternatives which are included in the spirit and scope of the present invention. 
     While terms such as “first” and “second,” etc., may be used to describe various components, such components must not be understood as being limited to the above terms. The above terms are used only to distinguish one component from another. For example, a first component may be referred to as a second component without departing from the scope of rights of the present invention, and likewise a second component may be referred to as a first component. The term “and/or” encompasses both combinations of the plurality of related items disclosed and any item from among the plurality of related items disclosed. 
     When a component is mentioned as being “connected” to or “accessing” another component, this may mean that it is directly connected to or accessing the other component, but it is to be understood that another component may exist therebetween. On the other hand, when a component is mentioned as being “directly connected” to or “directly accessing” another component, it is to be understood that there are no other components in-between. 
     The terms used in the present application are merely used to describe particular embodiments, and are not intended to limit the present invention. An expression used in the singular encompasses the expression of the plural, unless it has a clearly different meaning in the context in which it is used. In the present application, it is to be understood that the terms such as “including” or “having,” etc., are intended to indicate the existence of the features, numbers, operations, actions, components, parts, or combinations thereof disclosed in the specification, and are not intended to preclude the possibility that one or more other features, numbers, operations, actions, components, parts, or combinations thereof may exist or may be added. 
     Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meanings as those generally understood by those with ordinary knowledge in the field of art to which the present invention belongs. Such terms as those defined in a generally used dictionary are to be interpreted as having meanings equal to the contextual meanings in the relevant field of art, and are not to be interpreted as having ideal or excessively formal meanings unless clearly defined as having such in the present application. 
     Embodiments of the present invention will be described below in detail with reference to the accompanying drawings, where those components are rendered using the same reference number that are the same or are in correspondence, regardless of the figure number, and redundant explanations are omitted. 
       FIG. 1  is a view illustrating a light transmission apparatus according to a first exemplary embodiment of the present invention. 
     As shown in  FIG. 1 , a light emission apparatus  100  includes a package  10 , a cooler  20  mounted in a cavity  11  to uniformly maintain the temperature of the optical transmission apparatus  100 , a substrate  30  mounted on the cooler  20  and including a light source  41  for generating light, a reflector  42  mounted on the cooler  20  such that it is positioned in front of the light source  41  and reflecting light from the light source  41  to the outside (e.g., an optical fiber), a thermister  43  mounted on the cooler  20  and measuring an internal temperature of the light transmission apparatus  100 , a support  50  mounted on the cooler  20  such that it is positioned behind the light source  41 , and a monitoring element  44  mounted on the support  50  and receiving light from the light source  41  to monitor an operational state of the light source  41 . 
       FIG. 2  is a view illustrating the package according to the first exemplary embodiment of the present invention. 
     With reference to  FIG. 2 , the package  10  includes a base  12  having a cavity  11  formed at a central portion thereof, lead pins  13  penetrating an outer area of the base  12  and transmitting and receiving a signal to and from the internal elements  41  to  44  of the optical transmission apparatus  100 , and insulators  14  formed to cover the respective lead pins  13  to insulate the base  12  and the lead pins  13  and performing impedance matching. 
     The cavity  11  can be generally fabricated through a processing method such as a milling operation, pressing, MIM (Metal Injection Molding), and the like, using a shelf, and the insulators  14  may be implemented through glass soldering, or the like. 
     If the cavity  11  is not formed in the base  12 , the cooler  20 , the substrate  30 , and the internal elements  41  to  44  would be sequentially stacked on an upper surface of the base  12 , increasing the distance between the base  12  and the internal elements  41  to  44  by the height of the cooler  20 . 
     When the distance between the base  12  and the internal elements  41  to  44  increases, the length of the lead pin  13  for connecting the power of the internal elements  41  to  44  would increase. The increase in the length of the lead pins  13  would lead to an increase in noise, loss, crosstalk characteristics of a signal delivered through the lead pins  13  to degrade the overall signal characteristics of the optical transmission apparatus  100 . 
     Thus, in an exemplary embodiment of the present invention, the cavity  11  is formed in the base  11  to offset the height of the cooler  20  to thus shorten the distance between the base  12  and the internal elements  41  to  44 . Accordingly, the length of the lead pins can be shortened and the signal characteristics of the optical transmission apparatus  100  can be improved in proportion to the reduced length of the lead pins  13 . 
     In the present exemplary embodiment, the base  12  and the insulators  14  have a coaxial structure, minimizing exposed portions of the impedance-matched lead pins  13 , thus maintaining the impedance characteristics, and the overall length of signal lines  60  continued from the wire bonding to the lead pins  113  can be reduced to lower an inductance value. 
     Also, in the present exemplary embodiment, the outer area of the base  12  (namely, the peripheral area of the cavity  11 ) is increased to reduce heat resistance through heat sinking, thus increasing a heat release effect of the cooler  20 . 
       FIG. 3A  and  FIG. 3B  are views illustrating a reflector according to the first exemplary embodiment of the present invention. 
     As shown in  FIG. 3A , the reflector  42  includes a bar-like mirror  42   a  having a sloped face formed in an area (namely, an upper corner portion of the side face to which light is made incident) to which light is made incident from the light source  41 , and a total-reflection coated film  42   b  formed on the sloped face to total-reflect light made incident to the reflector  42 , thus reflecting the entirety of the light made incident thereto. The bar mirror  42   a  may be made of a light-transmissive material, such as glass, allowing light transmission therethrough. 
     The reflector  42  may be formed through a process of polishing or cutting a corner of the bar mirror  42   a  in a quadrangular shape as shown in  FIG. 3B , in consideration of a fabrication cost. 
     The structure of the optical transmission apparatus can be simplified by eliminating a support of the monitoring element according to second and third exemplary embodiments of the present invention. 
       FIG. 4A  and  FIG. 4B  are views illustrating a light transmission apparatus according to a second exemplary embodiment of the present invention. 
     With reference to  FIG. 4A , in the light transmission apparatus  100 , the monitoring element  44  is mounted on the surface of the cooler  20  such that it is positioned in front of the light source  41  and the reflector  42 , while the support  50  of the monitoring element  44  in the first exemplary embodiment of the present invention is eliminated. 
     To this end, as shown in  FIG. 4B , the reflector  42  includes a bar-like mirror  42   a  having a sloped face formed in an area (namely, an upper corner portion of the side face to which light is made incident) to which light is made incident from the light source  41 , a beam splitter coated film  42   c  formed on the sloped face to reflect a majority of light made incident thereto and allow the remaining portion of the light to be transmitted therethrough, and a non-reflection coated film  42   d  formed in an area from which light is output (namely, a lower corner of the side from which light is output) to allow light, which is made incident thereto, to be entirely transmitted therethrough. In this case, the sloped face of the bar mirror  42   a  may have a slope angle ranging from 45 degrees or 41 degrees to 49 degrees. 
     Also, in order to increase a monitoring efficiency of the monitoring element  44 , a total-reflection coated film  41   a  may be additionally formed on a rear surface of the light source  41  to allow light, from the light source  41 , to be entirely output to the front side of the light source  41  (namely, toward the reflector  42  and the monitoring element  44 ). 
     Accordingly, when the light source  41  generates light, a majority of the light from the light source  41  is externally reflected by the beam splitter coated film  42   c  and the remaining portion of the light is made incident to the monitoring element  44  through the bar mirror  42   a  and the non-reflection coated film  42   b . The monitoring element  44  receives the portion of light to monitor a current state of the light source  41 . 
     Accordingly, the light transmission apparatus  100  according to the second exemplary embodiment of the present invention is able to monitor the quantity of light of the light source  41  even without the support  50 . 
       FIG. 5A  and  FIG. 5B  are views illustrating a light transmission apparatus according to a third exemplary embodiment of the present invention. 
     With reference to  FIG. 5A , in the light transmission apparatus  100 , the monitoring element  44  is mounted on an upper surface of the reflector  42  and the support  50  of the monitoring element  44  is eliminated. 
     To this end, as shown in  FIG. 5B  the reflector  42  includes a bar-like mirror  42   a  having a sloped face formed in an area (namely, an upper corner portion of the side face to which light is made incident) to which light is made incident from the light source  41 , a beam splitter coated film  42   c  formed on the sloped face to reflect a majority of light made incident thereto and allow the remaining portion of the light to be transmitted therethrough, a total-reflection coated film  42   e  formed in an area from which light is output (namely, a lower corner of the side from which light is output) to allow light, which is made incident thereto, to be totally reflected, and a non-reflection coated film  42   f  formed in an area that reflected by the total-reflection coated film  42   e  reaches (namely, an upper portion of the bar mirror  42   a ) to allow light, which is made incident thereto, to be entirely transmitted therethrough. 
     Also, the total-reflection coated film  41   a  may be additionally formed on a rear surface of the light source  41  to allow light, from the light source  41 , to be entirely output to the front side of the light source  41  (namely, toward the reflector  42  and the monitoring element  44 ). 
     Accordingly, when the light source  41  generates light, a portion of the light from the light source  41  reaches the total-reflection coated film  42   e  through the beam splitter coated film  42   c , the bar mirror  42   a , the total reflection coated film  42   e , and the non-reflection coated film  42   f , and is then totally reflected again by the total reflection coated film  42   e  so as to be transmitted to the upper surface of the bar mirror  42   a . The monitoring element  44  receives light made incident thereto to monitor a current state of the light source  41 . 
     Accordingly, the light transmission apparatus  100  according to the second exemplary embodiment of the present invention is able to monitor the quantity of light of the light source  41  even without the support  50 . 
     In addition, the structure of the light transmission apparatus can be simplified by eliminating the reflector according to a fourth exemplary embodiment of the present invention. 
       FIG. 6  is a view illustrating a light transmission apparatus according to a fourth exemplary embodiment of the present invention. 
     As shown in  FIG. 6 , in the light transmission apparatus, a support  50  having a sloped face is provided and mounted on the cooler  20  such that it is positioned in front of the light source  41 . As shown in  FIG. 7 , the monitoring element  44 , having a beam splitter coated film  44  formed in an area to which light from the light source  41  is made incident, is positioned on the sloped face of the support  50 . 
     Also, the total-reflection coated film  41   a  may be additionally formed on a rear surface of the light source  41  to allow light, from the light source  41 , to be entirely output to the front side of the light source  41  (namely, toward the reflector  42  and the monitoring element  44 ). 
     Then, light from the light source  41  is entirely made incident to the monitoring element  44 . The monitoring element  44  reflects a majority of light made incident through the beam splitter coated film  44   a  and receives the remaining portion of the light to perform a monitoring operation. 
     Namely, the monitoring element  44  according to the fourth exemplary embodiment of the present invention serves as a reflector as well as the monitoring element, whereby the light transmission apparatus does not need to have an additional reflector. 
     As set forth above, according to exemplary embodiments of the invention, the light transmission apparatus having a temperature control function includes a package having a cavity and offsets the height of the cooler through the cavity, whereby the length of signal lines connecting the lead pins of the package or connecting from the wire bonding to the lead pins can be reduced to improve the signal transmission characteristics of the light transmission apparatus. Also, because the cooler is mounted on the surface of the package, the heat releasing characteristics of the cooler can be improved, and because light from the light source can be discharged by using the reflector mounted on the cooler, the light source can be mounted on the surface and accordingly, the temperature control characteristics can be improved. 
     In addition, the fabrication process of the light transmission apparatus can be simplified by eliminating the support for mounting the monitoring element thereon or the reflector for reflecting light from the light source to thus lower a fabrication cost, and a cooling load of the cooler can be reduced by the reduced number of elements and, accordingly, power consumption can be also reduced. 
     Moreover, because the monitoring element is positioned in front of the light source to monitor the state of the light source, a light output resistance, noise generation, and the like, caused by an external reflection can be reduced. 
     While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.

Technology Category: 5