Abstract:
According to one embodiment of the invention, a system comprising a housing including an opening to receive an optical connector, and an electromagnetic inductive (EMI) shield independent of the optical connector to cover a portion of the opening to reduce emissions of EMI radiation generated by the optical connector from the transceiver housing. According to another embodiment of the invention, a method comprising connecting an optical connecter to an optical port of a housing in an optical module, the housing comprising an opening to receive to the optical connector; and shielding a portion of an opening in the housing to reduce emissions of EMI radiation generated by the optical connector from the housing.

Description:
FIELD 
   Embodiments of the invention relate to electromagnetic inductive (EMI) shields, and more particularly to a system and method for shielding optical modules from EMI emissions. 
   BACKGROUND 
   Optical communication, such as by fiber-optic cables, is in widespread use today. Optical communication allows for larger volumes of information to transmitted at faster velocities across a network with reduced occurrence of degradation of signal integrity, when compared to electrical communication using metallic conductors such as copper wires. 
   Though an effective form of transfer of information, optical communication is not without shortcomings. One such shortcoming is in the area of signal conversion from an optical signal to an electrical signal. This conversion is often necessary because currently, most of the devices which ultimately use the information carried by the optical signal, such as personal computers, operate by using electrical signals. To this end, optical modules such as transceiver are often used to convert optical signals into electrical signals, and vice versa. 
   Typically, a transceiver includes an optical port for receiving an optical connector of a fiber optics cable, and associated signal processing circuitry for converting optical signals received through fiber optics cable into electrical signals. The use of transceiver s, however, is not without shortcomings. 
   In some transceiver s, an opening in the transceiver housing which allows for an optical connector to be connected to the transceiver housing via an optical port is too large for certain class of optical connectors, resulting in the emission of the optical port&#39;s electromagnetic inductive (EMI) radiation from the opening. This emission or escaping of EMI radiation may cause interferences resulting in reduction or loss of integrity of the transmitted information. In addition, many transceiver housings include several optical ports for receiving multiple optical connectors. This scenario further exacerbates the effects of the EMI radiation as each optical connector can interfere with other optical connectors of the transceiver housing, and vice versa. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention may best be understood by referring to the following description and accompanying drawings that are used to illustrate embodiments of the invention. 
       FIG. 1  is an exploded perspective view of an apparatus in which exemplary embodiments of the invention may be practiced. 
       FIGS. 2-3  are additional perspective views of an apparatus in which exemplary embodiments of the invention may be practiced. 
       FIGS. 4A-D  are additional views of the exemplary embodiments of the invention. 
       FIG. 5  is a flow chart illustrating an exemplary process according to an exemplary embodiment of the invention. 
   

   DETAILED DESCRIPTION 
   Embodiments of the invention generally relate to systems and methods for shielding optical modules from electromagnetic inductive (EMI) emissions. Herein, one embodiment of the invention may be applicable to optical modules for converting optical signals to electrical signals and vice versa, used in a variety of telecommunication devices, which are generally considered stationary or portable electronic devices. Examples of a telecommunication device may include, but are not limited or restricted to a computer, a set-top box, telephone systems, networking equipment, and the like. 
   Reference in the specification to the term “one embodiment of the invention” or “an embodiment of the invention” means that a particular feature, structure, or characteristic described in connection with the embodiment of the invention is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment of the invention” in various places in the specification are not necessarily all referring to the same embodiment of the invention. In the following description, numerous details are set forth. It will be apparent, however, to one skilled in the art, that the embodiments of the invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the embodiments of the invention. 
   Also in the following description are certain terminologies used to describe features of the various embodiments of the invention. For example, the term “optical module” refers to a peripheral that converts optical signals to electrical signals (and vice versa) so as to create a link between systems that operate based on electrical signals, such as telecommunication devices, and optical medium such as fiber optics cables that transfer data at optical speeds, such as 10 giga-hertz (GHz). The term “Faraday cage” refers to an apparatus that substantially encloses a secondary apparatus and blocks outside electric fields and electromagnetic radiation from reaching the seconday apparatus so to protect the secondary apparatus. The cage may be made of an unbroken conducting material, like the metal box surrounding a sensitive radio receiver, or a wire mesh, like that in the door of a microwave oven. 
     FIG. 1  is an exploded perspective view of an exemplary portion of an apparatus  100  in which embodiments of the invention may be practiced. In an exemplary embodiment of the invention, the apparatus  100  is an optical module for converting optical signals into electrical signals and vice versa. As shown in  FIG. 1 , the apparatus  100  includes an enclosure assembly  105  (shown in exploded form) mounted on a printed circuit board assembly (PCBA)  120 . The enclosure assembly  105  includes a clip  140 , a heat sink  130 , and a cage assembly  120  mounted on a connector  150 . The cage assembly  120 , such as a Faraday cage for example, receives a housing  110 , such as a transceiver housing, a transmitter housing, or a receiver housing, via insertion into an opening  121  of the cage assembly  120 , such as in the direction of the arrow  170  as shown in  FIG. 1 . Suitably the housing  110  is a transmitted housing  110  as used throughout the detailed description. The transceiver housing  110  includes at least one opening  111  through which an optical connector  160  is inserted, such as in the direction of the arrow  172 , as described in greater detail in conjunction with  FIGS. 2-4  below. The transceiver housing  110  is generally inserted into the cage assembly  120  up to approximately line  112  shown in  FIG. 1 , leaving the opening  111  exposed. 
     FIG. 2  is a perspective view of the transceiver housing  110  in which embodiments of the invention may be practiced. As shown in  FIG. 2 , the transceiver housing  110  includes a base cover portion  210 , and a top cover portion  200  coupled to the base portion  210  that has a major external surface  112  with a thickness “d 1 ”, and a latch mechanism  240 . In an exemplary embodiment of the invention, a portion of the opening  111 , such as opening portion  230  is located on the external surface  112  on a proximal end portion  110   a  distal from the end portion  110   b  that is inserted first into the cage assembly  120 . The opening portion  230  may include additional opening portions  230   a  and  230   b.    
   The transceiver housing  110  also includes optical connector ports  211   a  and  211   b,  each capable of receiving (through the opening  111  of  FIG. 1 ) optical connectors of different types, such as standard optical connector  160   a,  or a specialized optical connector  160   b.  The optical connectors  160   a  and  160   b  couple one or more optical medium  161 , such as a fiber optics cables for example, to the transceiver housing  110 . In an exemplary embodiment of the invention, standard optical connector  160   a,  such as a Lucent Connector, lacks shielding as part of the connector  160   a,  and thus may cause emissions of EMI radiation from the transceiver housing  110  through the opening portions  230   a  and  230   b  that are located in proximity of the optical connector ports  211   a  and  211   b.    
     FIG. 3  is another perspective view of the transceiver housing  110  of  FIG. 2  showing embodiments of the invention. As shown in  FIG. 3 , an exemplary embodiment of the invention includes an electromagnetic inductive (EMI) shield  330 , such as EMI shields  330   a  and  330   b  for example, to cover portions of the opening  111 , such as opening portions  230   a  and  230   b,  respectively. The EMI shield  330  is configured to reduce emissions of EMI radiation generated by the optical connector  160   a  from the transceiver housing  110 . In an exemplary embodiment of the invention, the EMI shields  330   a  and  330   b  are independent of the optical connector  160   a  and are removable from the transceiver housing  110 . As shown in  FIG. 3 , the EMI shields  330   a  and  330   b  are substantially co-extensive with the opening portions  230   a  and  230   b,  respectively, to substantially cover the opening portions  230   a  and  230   b.  It is contemplated that the EMI shield  300  may include a plurality of interlocking EMI shields, such as EMI shields  330   a  and  330   b  to cover portions of the opening portion  230 , such as opening portions  230   a  and  230   b,  respectively, or a may be a single EMI shield  300  covering opening portion  230 . 
   As shown in  FIG. 3 , each of the EMI shields  330   a  and  330   b  include a bottom portion facing the optical connector  160   a,  such as bottom portions  330   a   2  and  330   b   2 , respectively, and a top portion, such as top portions  330   a   1  and  330   b   1 , respectively, that are substantially coextensive with the bottom portions,  330   a   2  and  330   b   2 , respectively. In an exemplary embodiment of the invention, the EMI shields  330   a  and  330   b  are of a “d 2 ” thickness. 
   In an exemplary embodiment of the invention, one or more of the EMI shields  330   a  and  330   b  are of a metal-based composition, such as metallized plastic, sheet metal and die-cast zinc composition. In another exemplary embodiment of the invention, one or more of the EMI shields  330   a  and  330   b  are of a carbon-based composition, such as carbon-filled plastic and conductive plastic composition. EMI shields  330   a  and  330   b  may also be color-coded to match the optical wavelength of the apparatus  100  for ease of selecting an EMI-shield most effective for use with a particular apparatus  100 . 
     FIGS. 4A-D  are additional illustrations of exemplary embodiments of the EMI shield  300 . For simplicity, a single EMI shield  300  is shown in  FIGS. 4A-D  covering the opening portion  230 , although each EMI shield  300  shown may include a plurality of interlocking EMI shields, such as EMI shields  330   a  and  330   b,  to cover portions of the opening portion  230 , such as opening portions  230   a  and  230   b.    
     FIG. 4A  is a perspective view of an exemplary embodiment of the EMI shield  300 . As shown in  FIG. 4A , the exemplary EMI shield  300  includes a top portion  331  and a bottom portion  332 . The top portion includes a protruding flange portion  331   a  and the bottom portion includes a protruding flange portion  332   a.  As shown in  FIG. 4B  of a cross-sectional view of the major surface  112  taken along the line  350  ( FIG. 3 ), the flange portions  331   a  and  332   a  are used for securing the EMI shield  330  to the major surface  112 . First, a substantially downward vertical force is applied to the EMI shield  330 , such as in the direction shown by arrow  4   a,  which causes the EMI shield  330  to slightly flex to allow passage of the flange portions  332   a  through opening  230 . Following the passage of the flange portion  332   a  through opening  230 , the EMI shield  330  reverts back to its original shape so to “snap” into place. The flange portions  331   a  and  332   a  then restrict the movement of the EMI shield  300  to hold the EMI shield  330  in place as shown in  FIG. 4B . The EMI shield  330  can also be thereafter removed by applying a upward vertical force to the EMI shield  330 , such as in the direction shown by arrow  4   b,  which causes the EMI shield  330  to slightly flex to allow passage of the flange portion  332   a  through opening  230 , so as to “unsnap” the EMI shield  330  out of the opening  230 . Suitably, the EMI shield  330  is of composition sufficiently flexible to allow the EMI shield  330  to slightly flex to allow passage of the flange portions  332   a  through opening  230 . 
     FIG. 4C  is a cross-sectional view (taken along the line  350  in  FIG. 3 ) of another exemplary embodiment of the EMI shield  300  inserted into the opening  230 . As shown in  FIG. 4C , the opening  230  includes an edge portion  112   a  which allows for the bottom portion  332  of the EMI shield  300  to rest on the edge portion  112   a.  The EMI shield  300  is substantially co-extensive with the opening  230  so that friction forces between the boundaries of the EMI shield  300  and the opening  230  can hold the EMI shield  300  in place. Suitably, the EMI shield  300  is of a “d 2 ” thickness that is substantially the same as the thickness “d 1 ” of the major surface  112  so that the top portion  331  the EMI-shield  330  is substantially co-planar (i.e. flush) with the major surface  112 . 
     FIG. 4D  is another cross-sectional view (taken along the line  350  in  FIG. 3 ) of another exemplary embodiment of the EMI shield  300  inserted into the opening  230 . As shown in  FIG. 4D , the exemplary EMI shield  300  includes a top portion  331  which has a flange portion  331   c.  The flange portion  331   c  allows for the EMI shield  300  to rest on the major surface  112  substantially co-extensive with the opening  230 . Suitably, the bottom portion  332  of the EMI shield  300  is substantially co-extensive with the opening  230  so that friction forces between the boundaries of the EMI shield  330  and the opening  230  can hold the EMI shield  300  in place. 
     FIG. 5  is an exemplary flow chart, which in conjunction with  FIGS. 1-4D , illustrates an exemplary process according to an embodiment of the invention. As shown in  FIG. 5 , following start (block  500 ), an optical connecter  160   a,  is connected to the transceiver housing  110  via an optical port  211   b  through an opening  111  (block  510 ). Next, a portion of the opening  111  in the transceiver housing  110 , such as opening portions  230   a  and  230   b  ( FIG. 2 ), are shielded (block  520 ). As shown in  FIG. 3 , removable EMI shields  330   a  and  330   b  are placed in the opening portions  230   a  and  230   b,  respectively, such as in the direction of the arrows  3 , to reduce the escaping of EMI radiation emanating from the optical connector  165   a  from the transceiver housing  110  through the opening portions  230   a  and  230   b.  Suitably, an EMI shield is selected which corresponds to an optical wavelength of the optical module, such as based on a coding of the EMI shield, such as a color-coding. Referring to  FIG. 5 , following the shielding operations, the optical module is ready to operate with reduced EMI radiation emission. The flow then ends (block  530 ). 
   For simplicity, the apparatus  100  in  FIG. 1  is shown supporting a single transceiver housing  110  with a pair of connector ports  211   a  and  211   b  (shown in  FIG. 2 ), although apparatus  100  may support multiple transceiver housings  110 , each having a one or more connector ports. It should be noted that the various features of the foregoing embodiments of the invention were discussed separately for clarity of description only and they can be incorporated in whole or in part into a single embodiment of the invention having all or some of these features.