Abstract:
An electro-optic package comprising an optoelectric module with a receptacle assembly, an optoelectric assembly fixedly attached to the receptacle assembly, the optoelectric assembly being in communication with the optoelectric module, wherein the optoelectric assembly includes optoelectronic circuitry and the optoelectronic circuitry includes at least one electrical connection for communication with external electronic circuitry, and wherein the electro-optic package forms a discrete package.

Description:
CROSS-REFERENCED TO RELATED APPLICATION 
   This application claims the benefit of U.S. Provisional Application No. 60/357,514, filed 15 Feb. 2002. 

   FIELD OF THE INVENTION 
   This invention relates to optical-to-electrical and electrical-to-optical packages and, more particularly, to discrete optical-to-electrical or electrical-to-optical packages. 
   BACKGROUND OF THE INVENTION 
   Most optical-to-electrical and electrical-to-optical modules used in the various communications fields, are incorporated into packages containing one or more pairs of optical-to-electrical and electrical-to-optical modules. The modules are generally used in pairs for two-way communication and multiple pairs may be incorporated in a single package to provide multiple communication channels. Generally, one of the major problems in this industry is the transmission of light from the optical fiber to a light receiving device or the transmission of light from a light generating device to the optical fiber without being affected by assembly tolerances, temperature changes, component changes, and the like. It should be understood by those skilled in the art that the term “light” is a generic term that includes any electromagnetic radiation that can be modulated and transmitted by optical fibers or other optical transmission lines. 
   Here it will be understood that the optoelectric modules are used to communicate between an optical fiber and an optoelectric device, such as a light source (e.g. a laser, light emitting diode, etc.) generally referred to as a transmission module, or between an optical fiber and a light receiving device (e.g. a photodiode, PIN diode, PN diode, etc.) generally referred to as a receiving module. In this disclosure both transmission and receiving modules or packages are referred to generically as optoelectric modules or packages and the term “optoelectric” is intended to encompass both optical-to-electrical and electrical-to-optical. 
   Generally, one of the problems with optoelectric packages is the amount of time and effort required in the fabrication and assembly. Another problem that arises is that much of the time and effort in assembly and mounting is applied in alignment of the various components so that light generated by, for example a laser, reaches the core of an optical fiber and light emanating from an optical fiber must be directed onto a photodiode or the like. To overcome many of these problems, the industry has generally provided multiple communication channels in a single package. However, there are many applications in which discrete components or packages are useful and/or desirable. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring to the drawings: 
       FIG. 1  is an end view of an embodiment of an optoelectric module; 
       FIG. 2  is a sectional view as seen from the line  2 — 2  of  FIG. 1 ; 
       FIGS. 3 ,  4 ,  5 ,  6 ,  7 ,  8  and  9  illustrate various views of components in another embodiment of an optoelectric module or package in accordance with the present invention; 
       FIGS. 10 ,  11  and  12  illustrate various views in another embodiment of an optoelectric module or package; 
       FIGS. 13 ,  14 ,  15 ,  16  and  17  illustrate various views in an embodiment of a clam-shell type of optoelectric package in accordance with the present invention; 
       FIGS. 18 ,  19  and  20  illustrate various views of a housing for mounting an optoelectric module; 
       FIGS. 21 ,  22  and  23  illustrate an optoelectric module for use with the housing of  FIG. 18 ; 
       FIGS. 24 ,  25 ,  26  and  27  illustrate an optoelectric package including the housing of  FIG. 18  and the optoelectric module of  FIG. 21 ; 
       FIGS. 28 and 29  are two isometric views of the optoelectric package of  FIG. 24  pigtailed with an optical fiber; and 
       FIGS. 30 and 31  are isometric and partial side sectional views, respectively, of detachable optical fiber apparatus. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIGS. 1 and 2 , an end view and a sectional view are illustrated of one embodiment of an optoelectric module  10  for use in accordance with the present invention. It will be understood by those skilled in the art that modules of the type discussed herein generally include a pair of channels, one of which receives electrical signals, converts the electrical signals to optical (light) beams by way of a laser or the like and introduces them into one end of an optical fiber, which then transmits the modulated optical beams to external apparatus. The second channel of the module receives modulated optical beams from an optical fiber connected to the external apparatus, conveys the modulated optical beams to a photodiode or the like, which converts them to electrical signals. In the following description, the apparatus and methods can generally be used in either of the channels but, since the optical portions of the two channels are substantially similar and since a major purpose of this invention is to provide discrete packages, only one channel will be discussed with the understanding that the description applies equally to both channels. 
   Module  10  of  FIG. 1  includes a receptacle assembly  11  and an optoelectric assembly  12  aligned and affixed together, as will be disclosed in more detail below. Receptacle assembly  11  is designed to receive an optical fiber  14  in communication therewith, in a manner that will become clear presently. Optical fiber  14  includes a glass core  15 , a cladding layer  16 , and a ceramic ferrule  17 . Receptacle assembly  11  includes an elongated cylindrical receptacle  20  defining a fiber receiving opening  21  at one end and a mounting flange  22  at the opposite end. 
   Receptacle  20  has a radially outward directed step  24  formed in the outer periphery to operate as a stop in the mounting process. Progressing from the end defining opening  21  toward the end defining flange  22 , receptacle  20  has two radially outwardly directed steps  32  and  33 . Step  32  provides a surface or stop for the mounting of an optical spacer  35  and step  33  provides a surface or a stop for the positioning of an optical lens assembly  36 . In some embodiments desiring a high degree of moisture integrity, spacer  35  may be formed of glass and sealed tightly against step  32  by some convenient means, such as epoxy or the like. In this embodiment, lens assembly  36  is formed of plastic and may be, for example, molded to simplify manufacturing of module  10 . It should be understood that the term “plastic” is used herein as a generic term to describe any non-glass optical material that operates to transmit optical beams of interest therethrough and which can be conveniently formed into lenses and the like. For example, in most optical modules used at the present time the optical beams are generated by a laser that operates in the infrared band and any materials that transmit this light, including some oxides and nitrides, come within this definition. 
   Lens assembly  36  defines a central opening for the transmission of light therethrough from an end  37  to an opposite end  38 . A lens  39  is integrally formed in the central opening a fixed distance from end  37 . Lens assembly  36  is formed with radially outwardly projecting ribs or protrusions in the outer periphery so that it can be press-fit into receptacle  20  tightly against spacer  35 . Thus, lens assembly  36  is frictionally held in place within receptacle  20  and, in this embodiment, holds spacer  35  fixedly in place. Also, lens  39  is spaced a known distance from spacer  35 . In this preferred embodiment, optical fiber  14  is inserted into receptacle  20  so that glass core  15  buts against spacer  35 , which substantially reduces or suppresses return reflections. Further, by forming spacer  35  of glass material with an index of refraction similar to the index of refraction of glass core  15 , spreading of the light beam is substantially reduced and lower optical power is required to collimate the beam. 
   Optoelectric assembly  12 , in this preferred embodiment, utilizes a custom multilayer ceramic package including High Temperature Co-fired Ceramic (HTCC) or Low Temperature Co-fired Ceramic (LTCC) technology to provide mounting surfaces and electrical interconnects. For purposes of explanation only, assembly  12  is illustrated with a base ceramic layer  40  and a ceramic layer  42  positioned thereon. One or more spacer rings  43  may be positioned on ceramic layer  42  to provide sufficient distance for components mounted thereon, if required. In this example a laser  45  is mounted on the upper surface of ceramic layer  42  and positioned to transmit light generated therein to a lens block  46 . Alternatively, laser  45  could be a photodiode or the like. In this example, lens block  46  is mounted on ceramic layer  42  by some convenient attachment method, such as using extending ears (not shown). A Kovar ring  47  is attached on spacer rings  43 , preferably by brazing, and a flat or stepped lid  48  is affixed to Kovar ring  47  by some convenient means, such as welding. A primary purpose of these procedures is to enclose laser  45  (or the photodiode) in a hermetically sealed chamber. However, a hermetic seal is not necessary in many embodiments in which the laser or photodiode used is either separately sealed or is not sensitive to atmospheric conditions. Connections to the electrical components can be, for example, by coupling through base ceramic layer  40 . 
   A window  50  is sealed in lid  48  so as to be aligned with lens block  46 . Lens block  46  redirects light from laser  45  at a ninety degree angle out through window  50  and may include one or more lenses or optical surfaces (not illustrated). Further, as illustrated in  FIG. 2 , window  50  is affixed to the underside of lid  48  by some convenient means, such as solder glass, solder, epoxy or some appropriate adhesive, so as to hermetically seal the light transmitting opening through lid  48 . If a hermetic seal is not required, window  50  and any lenses incorporated therein can be formed (e.g. molded) from plastic. Lens block  46  may be molded from plastic for convenience in manufacturing. 
   Optoelectric package  12  is affixed to receptacle assembly  11  with flange  22  of receptacle  20  butting against the upper surface of lid  48 . Further, optoelectric package  12  is optically aligned with receptacle assembly  11  so that light from laser  45  is directed into core  15  of optical fiber  14  or light from core  15  of optical fiber  14  is directed onto an active surface of a photodiode. When alignment has been achieved, receptacle assembly  11  is fixed to optoelectric package  12  by some convenient means, such as welding or adhesive. A module similar to the one described above is illustrated in  FIGS. 21 ,  22 , and  23 . 
   Turning now to  FIG. 3 , module  10 , generally as described above, is illustrated as an optoelectric package by fixedly attaching an electrical board  52  including some electrical devices such as amplifiers, drivers, and the like, and/or electrical connections for external circuitry. Board  52  can be a printed circuit board, a ceramic board, a laminated ceramic board, etc. Referring additionally to  FIG. 4 , a connection board  53  is illustrated that can be used in conjunction with or instead of electrical board  52 . Connection board  53  is preferably constructed of some rigid material, such as a hard plastic or ceramic, and provides external electrical connection terminals either on the back side of the upright portion or on the lower side of the horizontal portion (or both). 
   Referring additionally to  FIG. 5 , a connection board  54 , similar to that illustrated in  FIG. 4 , is shown, with leads  55  extending outwardly from the horizontal portion (or alternately from the upright portion), rather than the terminals of board  53  in  FIG. 4 . A bottom view of connection board  54  is illustrated in  FIG. 6 . It will be understood that either board  53  or board  54  can be constructed in the L-shape illustrated or in a single surface, depending upon the specific application. In the case of the L-shaped board, a piece of flex lead may be used to connect terminals and or components on the two orthogonal surfaces. 
   Turning now to  FIGS. 7 ,  8 , and  9 , a package  60  is illustrated showing another embodiment. In this embodiment, an optical assembly  61  is affixed to the end of a ferrule  62  and includes a prism  63  for redirecting light at a ninety degree angle. Generally optics (e.g. similar to that described in conjunction with module  10 ) are included in optical assembly  61  so that collimated light is sent to or received from an optoelectric assembly  64 . Optoelectric assembly  64  includes any optoelectric devices (e.g. photodiodes, lasers, etc.), drivers, modulators, amplifiers, etc. as well as leads or terminals for connecting package  60  to an external component. Thus, in this embodiment, the module is optically coupled to an optoelectric assembly, rather than being electrically coupled. 
   As illustrated best in  FIGS. 8 and 9 , an outer surface of optoelectric assembly  64  can include terminals or leads  65 , as illustrated in  FIG. 11  or  12 , for electrically attaching package  60  to an external component or board  66  (see  FIG. 7 ). In a slightly different embodiment, illustrated in  FIG. 10 , ferrule  62  supplies light directly to optoelectric assembly  64 , without changing direction. In each of these embodiments, the ferrule and various boards can be encapsulated, or otherwise sealed together, to form a discrete package which generally may be mounted by soldering the leads or terminals to external equipment. 
   Turning now to  FIG. 13 , a clam shell type of housing  70  for enclosing and mounting a discrete optoelectric module is illustrated in an exploded perspective view. Housing  70  includes a lower portion  71  and a mating upper portion  72  constructed to encircle an optoelectric module, such as module  10 , described above. In this embodiment, module  10  has a connection board  54 , with leads  55  (or a connection board  64  with leads  65 ) extending therefrom, attached to the end as can be best seen in  FIG. 15 . It will be understood that leads  55  may extend downwardly through lower portion  71  of housing  70  (see leads  55   a  in  FIGS. 13 and 14 ) for electrical connection to external equipment and/or they may extend rearwardly (see leads  55   b  in  FIGS. 13 and 14 ), depending upon the external equipment and the specific application. 
   Upper portion  72  is matingly engaged over module  10  and lower portion  71  and the two portions are sealed together by any convenient means, such as adhesive, soldering, etc. to provide the complete package illustrated in  FIG. 16 . In one embodiment, the inner surfaces of portions  71  and  72  of clam shell housing  70  include a metal (or conductive) lining to provide electromagnetic interference (hereinafter referred to as “EMI”) protection for the finished package. The package can be surface mounted using, for example, leads  55   a  for electrical and physical connection. In a different embodiment, illustrated schematically in  FIG. 17 , the module can include two separate components  75  and  76  that communicate optically, rather than electrically. Components  75  and  76  can then be placed in clam shell housing  70 , which may be constructed to align components  75  and  76  optically. 
   Turning now to  FIGS. 18 ,  19 , and  20 , another housing  80  is illustrated for enclosing and mounting a discrete optoelectric module. Housing  80  has a substantially rectangular cross-section with a small opening  81  at one end and a larger opening or substantially hollow interior  82  accessible at the other end. A pair of mounting pins  84  extend from the lower surface for surface mounting the complete package. It will of course be understood that other shapes, both interior and exterior, may be devised for specific applications, and other or additional mounting pins or other mounting devices may be devised for specific mounting situations. 
   Turning to  FIGS. 21 ,  22 , and  23 , an optoelectric module  10 , with a multilayer hermetic ceramic package including a connection board (e.g., connection board  64 ) having outwardly extending leads  65  attached thereto, is provided. Module  10  may be, for example, similar to the optoelectric module described and illustrated in  FIGS. 1 and 2 . Optical fiber receiving opening  21  in receptacle  20  can best be seen in  FIG. 23 . 
   Referring additionally to  FIGS. 24 ,  25 ,  26 , and  27 , module  10  of  FIG. 21  is placed in housing  80  of  FIG. 20  so that the end of receptacle  20  extends slightly through opening  81 . Also, as can best be seen in  FIG. 24  or  26 , connection board  64  is positioned to seal opening  82  in housing  80 . Alternatively, connection board  64  is sealed in opening  82  by some convenient means, such as epoxy or the like. In a preferred embodiment, module  10  is press fitted directly into housing  80 . In some embodiments housing  80  may be lined with metal or completely formed of metal to provide EMI shielding. 
   Referring additionally to  FIGS. 28 and 29 , the optoelectric package, including optoelectric module  10  enclosed in housing  80 , is illustrated in a discrete pigtail arrangement. In this arrangement one end of an optical fiber  14  is engaged in opening  21  in receptacle  20 . This may be a fixed connection or a plug-in type of connection with an outer element (ferrule  17  illustrated in  FIG. 2 ) that is frictionally engaged in the end of receptacle  20 . The opposite end of optical fiber  14  has a connection  87  which is designed to mate with external equipment or another length of optical fiber. Generally connection  87  is a standard off-the-shelf connection which will mate with any standard external equipment. 
   Turning to  FIGS. 30 and 31 , one embodiment of detachable optical fiber apparatus, generally designated  100 , is illustrated. Apparatus  100  includes a collar  102  fixedly attached to the front surface of, for example, housing  80 . Collar  102  is further constructed with a central opening to allow the end of receptacle  20  (see  FIG. 2 ) to protrude therethrough. An opposed pair of flexible fingers  104  are mounted to, or formed as an integral part of, collar  102  so as to extend forwardly on each side of receptacle  20 . Each flexible finger  104  has an inwardly projecting catch  106 . Each catch  106  is formed with a forward cam surface and a rearward perpendicular catch surface. 
   A mating optical fiber  114 , is provided with a plastic housing  120  defining outwardly projecting shoulders  122 . A spring ferrule  124  is affixed to housing  120  so as to initially engage receptacle  20  for guidance and to recede into housing  120  as housing  120  is moved into engagement with fingers  104 . As housing  120  is moved into engagement with fingers  104 , shoulders  122  initially engage the cam surfaces of catches  106  and force fingers  104  apart. Upon further movement, the fingers  104  close behind shoulders  122  with the catch surfaces of catches  106  fixedly engaged behind shoulders  122 , in this position ferrule  124  and optical fiber  114  are optically connected to receptacle  20 . 
   Housing  120  can be quickly and easily disengaged from fingers  104  and housing  80  by using a hand tool, such as tool  125 , illustrated in  FIG. 31 . Tool  125  includes a pair of spaced apart stiff fingers  126  designed to be positioned on opposite sides of housing  120 . The protruding ends of fingers  126  are slanted outwardly and rearwardly so as to engage the cam surfaces of catches  106  of fingers  104  and spread fingers  104  outwardly to release shoulders  122  from the catch surfaces. Housing  120  can then be easily pulled away from engagement with fingers  104  and housing  80 . 
   Various changes and modifications to the embodiments herein chosen for purposes of illustration will readily occur to those skilled in the art. To the extent that such modifications and variations do not depart from the spirit of the invention, they are intended to be included within the scope thereof which is assessed only by a fair interpretation of the following claims.