Abstract:
An optoelectronic module for converting and coupling an information-containing electrical signal with an optical fiber including a housing having an electrical input for coupling with an external electrical cable or information system device and for transmitting and receiving information-containing electrical signals over such input, and a fiber optic connector adapted for coupling with an external optical fiber for transmitting and receiving an optical signal; an electro-optical subassembly coupled to the information containing electrical signal and converting it to and/or from a modulated optical signal corresponding to the electrical signal; and an electromagnetic shield including (i) a latchable top cover; (ii) an O-ring metallic seal surrounding the optical ports; and (iii) a spring-clip finger shaped sleeve circumferentially surrounding the optical ports.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is related to U.S. Pat. No. 7,534,054. 
         [0002]    This application is related to U.S. patent application Ser. No. 11/499,120. 
         [0003]    This application is related to U.S. patent application Ser. No. 12/437,815. 
         [0004]    This application is related to U.S. patent application Ser. No. 11/712,725. 
     
    
     BACKGROUND 
       [0005]    1. Field of the Invention 
         [0006]    The invention relates to optical communications devices, such as transmitters, receivers, and transceivers used in high throughput fiber optic communications links in local and wide area networks and storage networks, and in particular to electromagnetic shielding of such devices. 
         [0007]    2. Description of the Related Art 
         [0008]    Communications networks have experienced dramatic growth in data transmission traffic in recent years due to worldwide Internet access, e-mail, and e-commerce. As Internet usage grows to include transmission of larger data files, including content such as full motion video on-demand (including HDTV), multi-channel high quality audio, online video conferencing, image transfer, and other broadband applications, the delivery of such data will place a greater demand on available bandwidth. The bulk of this traffic is already routed through the optical networking infrastructure used by local and long distance carriers, as well as Internet service providers. Since optical fiber offers substantially greater bandwidth capacity, is less error prone, and is easier to administer than conventional copper wire technologies, it is not surprising to see increased deployment of optical fiber in data centers, storage area networks, and enterprise computer networks for short range network unit to network unit interconnection. 
         [0009]    Such increased deployment has created a demand for electrical and optical transceiver modules that enable data system units such as computers, storage units, routers, and similar devices to be optionally coupled by either ran electrical cable or an optical fiber to provide a high speed, short reach (less than 50 meters) data link within the data center. 
         [0010]    A variety of optical transceiver modules are known in the art to provide such interconnection that include an optical transmit portion that converts an electrical signal into a modulated light beam that is coupled to a first optical fiber, and a receive portion that receives a second optical signal from a second optical fiber and converts it into an electrical signal. The electrical signals are transferred in both directions over electrical connectors that interface with the network unit using a standard electrical data link protocol. 
         [0011]    The optical transmitter section includes one or more semiconductor lasers and an optical assembly to focus or direct the light from the lasers into an optical fiber, which in turn, is connected to a receptacle or connector on the transceiver to allow an external optical fiber to be connected thereto using a standard SC, FC or LC connector. The semiconductor lasers are typically packaged in a hermetically sealed can or similar housing in order to protect the laser from humidity or other harsh environmental conditions. The semiconductor laser chip is typically a distributed feedback (DFB) laser with dimensions a few hundred microns to a couple of millimeters wide and 100-500 microns thick. The package in which they are mounted typically includes a heat sink or spreader, and has several electrical leads coming out of the package to provide power and signal inputs to the laser chips. The electrical leads are then soldered to the circuit board in the optical transceiver. The optical receive section includes an optical assembly to focus or direct the light from the optical fiber onto a photodetector, which in turn, is connected to a transimpedance amplifier/limiter circuit on a circuit board. The photodetector or photodiode is typically packaged in a hermetically sealed package in order to protect it from harsh environmental conditions. The photodiodes are semiconductor chips that are typically a few hundred microns to a couple of millimeters wide and 100-500 microns thick. The package in which they are mounted is typically from three to six millimeters in diameter, and two to five millimeters tall and has several electrical leads coming out of the package. These electrical leads are then soldered to the circuit board containing the amplifier/limiter and other circuits for processing the electrical signal. 
         [0012]    Optical transceiver modules are therefore packaged in a number of standard form factors which are “hot pluggable” into a rack mounted line card network unit or the chassis of the data system unit. Standard form factors set forth in Multiple Source Agreements provide standardized dimensions and input/output interfaces that allow devices from different manufacturers to be used interchangeably. Some of the most popular MSAs include XENPAK (see www.xenpak.org), X2 (see www.X2 msa.org), SFF (“small form factor”), SFP (“small form factor pluggable”), XFP (“10 Gigabit Small Form Factor Pluggable”, see www.XFPMSA.org), and the 300-pin module (see www.300pinmsa.org). 
         [0013]    Customers and users of modules are interested in such miniaturized transceivers in order to increase the number of interconnections or port density associated with the network unit, such as, for example in rack mounted line cards, switch boxes, cabling patch panels, wiring closets, and computer I/O interfaces. 
       SUMMARY 
     1. Objects of the Invention 
       [0014]    It is an object of the present invention to provide an optoelectronic module in a small pluggable standardized form factor with an electromagnetic interference (EMI) shield that forms the top cover of the module. 
         [0015]    It is also another object of the present invention to provide a module for use in an optical fiber transmission system with an O-ring electromagnetic shield surrounding the optical ports. 
         [0016]    It is still another object of the present invention to provide an optical transceiver with a spring-clip finger shaped electromagnetic shield adjacent to the optical ports. 
         [0017]    Some implementations may achieve fewer than all of the foregoing objects. 
       2. Features of the Invention 
       [0018]    Briefly, and in general terms, the present invention provides an optical transceiver for converting and coupling an information-containing electrical signal with an optical fiber comprising a housing including an electrical connector with a plurality of electrical conductors for coupling with an external electrical cable or information system device and for transmitting and/or receiving an information-containing electrical signal having a data rate at least 5 Gigabits per second on each interface, and a fiber optic connector adapted for coupling with an external optical fiber for transmitting and/or receiving an optical communications signal having a data rate at least 5 Gigabits per second; at least one electro-optical subassembly in the housing for converting between an information-containing electrical signal and a modulated optical signal corresponding to the electrical signals; and an O-ring shaped deformable electromagnetic shield mounted adjacent to and surrounding the optical beam port of said electro-optical subassembly. 
         [0019]    Additional objects, advantages, and novel features of the present invention will become apparent to those skilled in the art from this disclosure, including the following detailed description as well as by practice of the invention. While the invention is described below with reference to preferred embodiments, it should be understood that the invention is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional applications, modifications and embodiments in other fields, which are within the scope of the invention as disclosed and claimed herein and with respect to which the invention could be of utility. 
         [0020]    Some implementations or embodiments may incorporate or implement fewer of the aspects or features noted in the foregoing summaries. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    These and other features and advantages of this invention will be better understood and more fully appreciated by reference to the following detailed description when considered in conjunction with the accompanying drawings, wherein: 
           [0022]      FIG. 1A  is a perspective view of a transceiver module in accordance with one embodiment. 
           [0023]      FIG. 1B  is an enlarged view of a portion of  FIG. 1A  illustrating the latching portion of the cover. 
           [0024]      FIG. 1C  is an enlarged view of a portion of  FIG. 1A  illustrating the pivoting portion of the cover. 
           [0025]      FIG. 2A  is a schematic sectional view of a cover in a first position relative to a base according to one embodiment. 
           [0026]      FIG. 2B  is a schematic sectional view of the cover in a subsequent second position relative to the base according to one embodiment. 
           [0027]      FIG. 2C  is a schematic sectional view of the cover in a subsequent third position relative to the base according to one embodiment. 
           [0028]      FIG. 3  is a perspective view of a transceiver module in accordance with one embodiment. 
           [0029]      FIG. 4A  is an enlarged front perspective view of an EMI shield according to one embodiment. 
           [0030]      FIG. 4B  is an enlarged rear perspective view of the EMI shield of  FIG. 4A . 
           [0031]      FIG. 5A  is an enlarged view of the EMI shield from a different perspective depicting the fingers making contact with the gasket around the periphery of the optical ports. 
           [0032]      FIG. 5B  is a sectional view of the EMI shield depicted in  FIG. 5A  through the  5 B- 5 B plane in that Figure. 
           [0033]      FIG. 6A  is a top perspective view of an optical transceiver with a cut-away view through the housing of the transceiver into the interior of the housing illustrating the transmitter and receiver assemblies according to one embodiment. 
           [0034]      FIG. 6B  is an enlarged view of a portion of  FIG. 6A  illustrating the EMI shield. 
           [0035]      FIG. 7A  is a sectional view of  FIG. 3  cut along line  7 A- 7 A illustrating the housing and the shield. 
           [0036]      FIG. 7B  is an enlarged view of a portion of  FIG. 7A  illustrating the positioning of the shield relative to the housing. 
           [0037]      FIG. 8  is a sectional view of  FIG. 3  cut along line  8 - 8 . 
           [0038]      FIG. 9  is a sectional view of  FIG. 3  cut along line  9 - 9 . 
       
    
    
       [0039]    Additional objects, advantages, and novel features of the present invention will become apparent to those skilled in the art from this disclosure, including the following detailed description as well as by practice of the invention. While the invention is described below with reference to preferred embodiments, it should be understood that the invention is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional applications, modifications and embodiments in other fields, which are within the scope of the invention as disclosed and claimed herein and with respect to which the invention could be of utility. 
       DETAILED DESCRIPTION 
       [0040]    Details of the present invention will now be described including exemplary aspects and embodiments thereof. Referring to the drawings and the following description, like reference numbers are used to identify like or functionally similar elements, and are intended to illustrate major features of exemplary embodiments in a highly simplified diagrammatic manner. Moreover, the drawings are not intended to depict every feature of the actual embodiment nor the relative dimensions of the depicted elements, and are not drawn to scale. 
         [0041]    The present invention relates generally to electromagnetic shielding components for optical communications modules such as transmitters, receivers, and transceivers used in high speed fiber optic communications systems. 
         [0042]    Referring now to  FIG. 1 , there is shown an exemplary pluggable optical transceiver module  10  according to a preferred embodiment of the present invention. The transceiver module  10  houses an electro-optical assembly  200 , an electrical connector  205 , and a fiber optic connector  206 . In this particular embodiment, the module  10  is compliant with the IEEE 802.3ae 10GBASE-LR Physical Media Dependent sub-layer (PMD) and is implemented in the SFP+ form factor having a length of 56.5 mm, a width of 14 mm, and a height of 12 mm. It is to be noted, however, that in other embodiments the transceiver module  10  may be configured to operate under various other standard protocols (such as Fibre Channel or SONET) and be manufactured in various alternate form factors such as XENPAK, X2, etc. The module  10  is preferably a 10 Gigabit transceiver having a single 10 Gbps distributed feedback laser that enables three hundred meter transmission of an optical signal at least three hundred meters over a single legacy installed multimode fiber or a distance from 10 to 40 km over a single standard single mode fiber. 
         [0043]    The transceiver module  10  includes a two-piece housing  100  including a base  101  and a cover  102 . The base  101  includes side walls  103  and an intermediate wall  113 . The base  101  has a rectangular cross-sectional shape with the two side walls  103  being relatively short, and a longer intermediate wall  113 . The base  101  further includes a gap  104  opposite from the intermediate wall  103  that leads into an interior  105 . The gap  104  may be positioned at the top or bottom of the housing  100 . The base  101  further includes open opposing ends  106 ,  107  for the fiber optic connector  206  and the electrical connector  205  respectively. 
         [0044]    The base  101  also includes a first cavity  108  towards the end  107  and a second cavity  109  towards the end  106  for receiving the cover  102 . The first cavity  108  includes a rounded shape and extends into each of the side walls  103  at an angle away from the end  106  and the top edge of the side walls  103 . The second cavity  109  includes a narrow neck and a wider bottom section, with the bottom section extending under a protrusion  110  in the side wall  103 . In one embodiment, the second cavity  109  extends across the width of the base  101 . 
         [0045]    The cover  102  is removably connected to the base  101  and can pivot between open and closed orientations. The cover  102  includes an elongated shape sized to extend across the gap  104  and enclose the interior space  105 . A first end of the cover  102  includes an enlarged connector  111  shaped to fit within the first cavity  108 . The connector  111  may include two separate members positioned on the lateral edges of the cover  102  that fit into cavities  108  formed in each of the side walls  103 . The sectional shape of the connector  111  may correspond to the first cavity  108 , such as each having a circular shape as illustrated in the Figures. The corresponding circular shapes provide for pivoting the cover  102  between the open and closed orientations. A second end of the cover  102  includes a latch  112  that engages with the second cavity  109 . The latch  112  includes a substantially L-shape with a narrow neck and an enlarged foot. This shape corresponds to the shape of the second cavity  109 . The latch  112  may extend across the width of the cover  102 . 
         [0046]      FIGS. 2A-2C  illustrate the steps of connecting the cover  102  to the base  101 . As illustrated in  FIG. 2A , the cover  102  is initially inserted into the base  101  with the connector  111  on the first end of the cover  102  being partially inserted into the first cavity  108  and the latch  112  on the second end of the cover  102  being partially inserted into the second cavity  109 . The latch  112  is inserted into the second cavity  109  an amount for the enlarged foot section to be positioned below the protrusion  110 . As illustrated in  FIG. 2B , the cover  102  is fully inserted into the base  101  and then slid in the direction indicated by the arrow. This sliding movement seats the connector  111  into the first cavity  108  and the latch  112  into the second cavity  109 . As illustrated in  FIG. 2C , an extension  128  is also positioned in the second cavity  109  to maintain the cover  102  attached to the base  101 . 
         [0047]    The cover  102  may also include a step  117  at the second end as illustrated in  FIGS. 7A and 7B . The step  117  forms an abutment surface and a shelf  116  for a shield  120  as will be explained in detail below. 
         [0048]    The housing  100 , including the base  101  and the cover  102 , may be constructed of die-case or milled metal, preferably die-cast zinc, although other materials also may be used, such as specialty plastics and the like. Preferably, the particular material used in the housing construction assists in reducing electromagnetic interference (EMI). The base  101  and cover  102  may be constructed from the same or different materials. The housing  100  may also include contact strips (not shown) to ground the module  10  to an external chassis ground as well. 
         [0049]    The fiber optic connector  206  is positioned at the end  106  of the housing  100 . The end  106  of the base  101  has a front  160 . The front  160  includes a pair of receptacles  161 ,  162  separated by an intermediate wall  165  and configured to receive fiber optic connectors (not shown) which mate with ports  203 ,  204 . In one embodiment, the connector receptacles  161 ,  162  are configured to receive industry standard LC duplex connectors. As such, keying channels are provided to ensure that the LC connectors are inserted into the receptacles  161 ,  162  in their correct orientation. Further, as shown in the exemplary embodiment, the connector receptacle  161  is intended for an LC receiver connector, and the connector receptacle  162  receives an LC transmitter connector. 
         [0050]    The base  101  also includes a notch  114  in proximity to the end  106  as illustrated in  FIG. 1A . The notch  114  may extend completely around the periphery of the base  101 , or around a limited portion of the periphery. A gasket  140  is positioned within the notch  114  and provides an electromagnetic shield. The gasket  140  may include an annular shape and extend around the periphery of the base  101 . The gasket  140  may extend completely around the periphery of the base  101 , or a portion of the periphery and include spaced-apart ends  141 ,  142  that are separated by a gap. In one embodiment as illustrated in  FIG. 1A , the gasket  140  extends around a portion of the periphery with the ends  141 ,  142  positioned on opposing sides of a clip  163 . The gasket  140  may be constructed from a variety of materials, including but not limited to engineering plastics, fabric, metal, and wire mesh. In one embodiment, the gasket  140  is constructed from a deformable material and includes a metalized outer surface. The gasket  140  may be constructed from one or more materials, or may include different inner and outer materials. In one embodiment, gasket  140  includes a metalized outer surface that extends over a different interior material. The gasket  140  may include a variety of sectional shapes, including circular, oval, and polygonal. 
         [0051]    An electromagnetic shield  120  may extend over the gasket  140  and the base  101  at a point towards the end  106  as illustrated in  FIG. 3 . The shield  120  is illustrated in  FIGS. 4A and 4B  and includes an annular shape with a first end  122  formed by a sleeve  121  and a second end  123  with fingers  126  positioned around a portion of the periphery. The sleeve  121  includes a generally rectangular shape with a central opening that corresponds to the housing  100 . A slot  124  extends through the sleeve  121  and between the fingers  126  to adjust a size of the shield  120 . The sleeve  121  includes one or more extensions  125  that extend radially inward into the central opening. Another extension  128  extends radially inward into the central opening from an opposing side of the sleeve  121  from the extensions  125 . The extension  128  fit within the second cavity  109  to maintain the cover  102  in the closed orientation as illustrated in  FIG. 2C . 
         [0052]    The fingers  126  are spaced around a majority of the periphery of the shield  120 . The fingers  126  do not extend around the shield  120  adjacent to the extension  128 . The fingers  126  include a curved shape with a concave portion that faces inward towards the central opening and towards the housing  100  when the shield  120  is connected to the housing  100 . The concave portion is sized to receive the gasket  140  and contact against the outer surface of the gasket  140 . 
         [0053]    The shield  120  is constructed of a relatively thin material. The fingers  126  each include a relatively narrow width that allows for radial flexing. The shield  120  may be constructed from a variety of materials, including but not limited to stainless steel, phosphor bronze, and beryllium copper. 
         [0054]      FIGS. 5A and 5B  illustrate the shield  120  and gasket  140  positioned around ports  203 ,  204  of a transmitter assembly  201  and receiver assembly  202  respectively. The ports  203 ,  204  are aligned with the receptacles  161 ,  162  respectively (see  FIG. 1A ). For purposes of clarity, the housing  100  is not illustrated in  FIG. 5A  or  5 B. 
         [0055]      FIGS. 6A and 6B  illustrate the shield  120  positioned on the housing  100 . The shield  120  provides an electromagnetic shield for the components of the transceiver module  10 . The fingers  126  extend over the base  101  and the gasket  140 . The relatively sizing between these elements may cause the fingers  126  to be biased radially outward such that they apply a compressive force against the housing  101  and gasket  140  to maintain an effective attachment. The base  101  may further include a clip  163  that fits within the cutout  127  in the shield  120 . 
         [0056]    The housing  100  may also include features to accommodate the shield  120 . As illustrated in  FIGS. 7A and 7B , the intermediate wall  113  of the housing may include a notch  115  that receives the extensions  125  that extend outward from the sleeve  121  of the shield  120 . The cover  102  may also include the step  117  that forms the shelf  116  that receives the sleeve  121  of the shield  120 . The step  117  also forms an abutment surface that contacts against the end  122  of the shield  102 . 
         [0057]    O-rings  170  may be positioned on the electro-optical assembly  200  to provide a further EMI shield. The O-rings  170  include an annular shape with an enclosed central region that extends around one of the ports  203 ,  204  as illustrated in  FIGS. 5A ,  5 B,  8 , and  9 . The O-rings  170  may be constructed of an elastic material and have various shapes. Further, the O-rings  170  may include various sectional shapes. In one embodiment, the O-rings  170  include circular shapes and sectional shapes. The O-rings  170  may be constructed from the same materials as the gasket  140  described above. 
         [0058]    The O-rings  170  are positioned along the ports  203 ,  204  of the transmitter and receiver assemblies  201 ,  202 . The O-rings  170  are positioned with an inner side contacting against one of the ports  203 ,  204 , and the outer side contacting against the housing  100 . The ports  203 ,  204  may include flanges  207  that form corners that are contacted by the O-rings  170 . Embodiments may include a single O-ring  170  positioned along the ports  203 ,  204 , with other embodiments featuring multiple O-rings  170  positioned along one or both ports  203 ,  204 . 
         [0059]    In one embodiment, the electro-optical assembly  200  holds three subassemblies or circuit boards, including a transmit board, a receive board, and a physical coding sublayer/physical medium attachment board, which is used to provide an electrical interface to external computer or communications units (not shown). Aspects of the electro-optical assembly  200  are disclosed in U.S. Pat. No. 7,534,054, and U.S. patent application Ser. Nos. 11/499,120, 12/437,815, and 11/712,725 each of which is incorporated herein in their entireties. 
         [0060]    One embodiment is the use of the housing  100  and shielding aspects in a pluggable 10 Gigabit transceiver. The same principles are applicable in other types of optical transceivers suitable for operating over both multimode (MM) and single mode (SM) fiber using single or multiple laser light sources, single or multiple photodetectors, and an appropriate optical multiplexing and demultiplexing system. The designs are also applicable to a single transmitter or receiver module, or a module as either a transmitter, receiver, or transceiver to communicate over different optical networks using multiple protocols and satisfying a variety of different range and distance goals. 
         [0061]    While the invention has been illustrated and described as embodied in a transceiver for an optical communications network, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
         [0062]    While particular embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from this invention and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the scope of this invention. Furthermore, it is to be understood that the invention is solely defined by the appended claims. 
         [0063]    It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is as “including, but not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations).