US 7559704 B2
A system for retaining an optical subassembly in a shell of a communications module is disclosed. The system reduces stress imposed on a hermetic package of the optical subassembly during lead interconnection procedures while ensuring thermal contact of the package with a thermal pad mounted in the shell. In one embodiment, the system includes a spring clip comprising a head portion that defines a seating surface, as well as first and second arms. The seating surface is shaped to engage an outer surface of a nosepiece of the optical subassembly. The first and second arms extend from the head portion so as to define a “U”-shaped configuration with the head portion. The head portion is shaped so as to provide a resilient force against a flange of the nosepiece when the flange and spring clip are received in a groove defined in the shell during assembly.
1. In a communications module, a system for retaining an optical subassembly in a shell of the communications module, the optical subassembly including a hermetic package coupled to a nosepiece, the nosepiece including a flange, the system comprising:
a groove defined by a portion of the shell, the groove being located proximate the optical subassembly and configured to receive the flange of the nosepiece; and
a spring clip for insertion in the groove so as to engage an outer surface of the nosepiece and secure the flange within the groove, wherein the spring clip is resilient and is at least partially concavely shaped resulting in a spring force urging one side of the spring clip against a surface of the flange and another side of the spring clip against a surface of the groove thereby securing the optical subassembly within the groove by a friction fit.
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10. A method for installing a transmitter subassembly in a shell of an optical transceiver module, the transmitter assembly including a nosepiece attached to an optoelectronic package, the method comprising:
positioning the transmitter assembly in the shell such that a flange of the nosepiece is received in a groove defined by the shell;
placing a spring clip in the groove to secure the flange in a predetermined position such that the optoelectronic package is positioned proximate a printed circuit board of the optical transceiver module, wherein the spring clip is resilient and is concavely shaped resulting in a spring force urging one side of the spring clip against a surface of the flange and another side of the spring clip against a surface of the groove thereby securing the optical subassembly within the groove by a friction fit; and
by a plurality of electrical leads, electrically connecting conductive features of the optoelectronic package with corresponding conductive features of the printed circuit board.
11. The method for installing as defined in
placing the spring clip in the groove to secure the flange in a predetermined position such that the optoelectronic package thermally couples with a thermal pad interposed between the optoelectronic package and the shell.
12. The method for installing as defined in
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14. The method for installing as defined in
placing the spring clip in the groove such that first and second arms of the spring clip engage portions of the groove.
15. The method for installing as defined in
placing the spring clip in the groove such that a head portion of the spring clip resiliently deforms in the groove.
16. The method for installing as defined in
17. A spring clip for use in securing an optical subassembly in a shell of an optical transceiver module, the spring clip comprising:
a head portion defining a seating surface, the seating surface being shaped to engage an outer surface of a nosepiece of the optical subassembly; and
first and second arms extending from the head portion so as to define a “U”-shaped configuration with the head portion, wherein the head portion is shaped so as to provide a resilient force against a flange of the nosepiece when the seating surface engages the nosepiece outer surface, wherein the spring clip is resilient and is concavely shaped resulting in a spring force urging one side of the spring clip against a surface of the flange thereby securing the optical subassembly within a groove by a friction fit.
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This application claims the benefit of the U.S. Provisional Patent Application No. 60/789,325, filed Apr. 5, 2006, and entitled “HORSESHOE SPRING FOR SECURING AN OPTICAL NOSEPIECE DURING OPTICAL ALIGNMENT,” which is incorporated herein by reference in its entirety.
1. Technology Field
The present invention generally relates to optical transceiver modules. In particular, the present invention relates to a system for securing an optical subassembly within an optical transceiver while still allowing for its interconnection with other transceiver components.
2. The Related Technology
Fiber optics technology is increasingly used for transmitting voice and data signals. As a transmission medium, light provides a number of advantages over traditional electrical communication techniques. For example, optical signals allow for extremely high transmission rates and very high bandwidth capabilities. Also, optical signals are resistant to electro-magnetic interferences that would otherwise interfere with electrical signals. Light also provides a more secure signal because it doesn't allow portions of the signal to escape from the fiber optic cable as can occur with electrical signals in wire-based systems. Light also can be conducted over greater distances without the signal loss typically associated with electrical signals on copper wire.
While optical communications provide a number of advantages, the use of light as a transmission medium presents a number of implementation challenges. In particular, the data carried by an optical signal must be converted to an electrical format when received by a device, such as a network switch. Conversely, when data is transmitted to the optical network, it must be converted from an electrical signal to an optical signal. A number of protocols define the conversion of electrical signals to optical signals and transmission of those optical, including the ANSI Fibre Channel (FC) protocol. The FC protocol is typically implemented using a transceiver module at both ends of a fiber optic cable. Each transceiver module typically contains a laser transmitter circuit capable of converting electrical signals to optical signals, and an optical receiver capable of converting received optical signals back into electrical signals.
Typically, a transceiver module is electrically interfaced with a host device—such as a host computer, switching hub, network router, switch box, computer I/O and the like—via a compatible connection port. Moreover, in some applications it is desirable to miniaturize the physical size of the transceiver module to increase the port density, and therefore accommodate a higher number of network connections within a given physical space. In addition, in many applications, it is desirable for the module to be hot-pluggable, which permits the module to be inserted and removed from the host system without removing electrical power. To accomplish many of these objectives, international and industry standards have been adopted that define the physical size and shape of optical transceiver modules to ensure compatibility between different manufacturers. For example, in 2000, a group of optical manufacturers developed a set of standards for optical transceiver modules called the Small Form-factor Pluggable (“SFP”) Transceiver Multi-Source Agreement (“MSA”), incorporated herein by reference. In addition to the details of the electrical interface, this standard defines the physical size and shape for the SFP transceiver modules, and the corresponding host port, so as to insure interoperability between different manufacturers' products. There have been several subsequent standards, and proposals for new standards, including the XFP MSA for 10 Gigabit per second modules using a serial electrical interface, that also define the form factors and connection standards for pluggable optoelectronic modules, such as the published draft version 0.92 (XFP MSA), incorporated herein by reference.
Regardless of the particular form factor employed, it is of common concern in the design of transceiver modules to interconnect components residing within the transceiver module securely and accurately, while at the same time preventing damage to the components during interconnection. By way of example an optical subassembly, such as a transmitter optical subassembly (“TOSA”) that houses a laser for the production of optical data signals, must form a secure electrical attachment to a printed circuit board (“PCB”) when the two components are included within an optical transceiver module (“transceiver”). Most often, this electrical interconnection is achieved via a plurality of electrical leads that extend from the TOSA and are each soldered to contact pads correspondingly positioned on the PCB. Such interconnection enables electrical data signals originating with a host device with which the optical transceiver module is operatively connected to be transferred from the PCB to the TOSA laser, where they are converted to an optical data signal.
Notwithstanding the secure connection that must be achieved between it and the PCB, the TOSA further includes a nosepiece that must be precisely positioned within a port of the transceiver to enable interconnection of the nosepiece with a connectorized optical fiber. Positioning of the TOSA during assembly must be such that the TOSA is properly positioned within the port while also acceptably oriented so as to enable connection of its leads with the PCB. However, know methods for facilitating such positioning and orientation are also apt to produce unreasonable amounts of stress or strain on the TOSA structure or on the TOSA-PCB lead interconnections themselves. If such stress and strain exceeds nominal limits, breakage or misalignment of the TOSA or the lead interconnections may occur, which can result in rejection of the component or entire transceiver if detected, or in sub-optimal subassembly performance if not detected.
In light of this, a need exists for an interconnection scheme between optical subassemblies and other components within a module, such as an optical transceiver module, that solves the above challenges while ensuring optimum performance of the module. In addition, the module should be implemented in a manner that meets existing standard form factors and does not interfere with other module components.
The present invention has been developed in response to the above and other needs in the art. Briefly summarized, embodiments of the present invention are directed to a system for retaining an optical subassembly in a shell of a communications module. The system reduces stress imposed on a hermetic package of the optical subassembly during lead interconnection procedures while ensuring thermal contact of the package with a thermal pad mounted in the shell.
In one embodiment, the system includes a spring clip comprising a head portion that defines a seating surface, as well as first and second arms. The seating surface is shaped to engage an outer surface of a nosepiece of the optical subassembly. The first and second arms extend from the head portion so as to define a “U”-shaped configuration with the head portion. The head portion is shaped so as to provide a resilient force against a flange of the nosepiece when the flange and spring clip are received in a groove defined in the shell during assembly.
These and other features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.
To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
Reference will now be made to figures wherein like structures will be provided with like reference designations. It is understood that the drawings are diagrammatic and schematic representations of exemplary embodiments of the invention, and are not limiting of the present invention nor are they necessarily drawn to scale.
Moreover, embodiments of the present retention system for securing the transmitter optical subassembly within the optical transceiver module are configured such that no undue stress or strain is imposed on the subassembly or its leads, thereby preserving its integrity and preventing damage thereto. Further, embodiments of the retention system are removable to allow for changeout of the transmitter optical subassembly should repair or replacement thereof be needed. In addition, the present retention system can provide enhanced shielding of electromagnetic interference (“EMI”) that may otherwise escape the module, thereby reducing a potential source of EMI in the operating environment.
Note that the embodiments to be described herein focus on implementation of the present invention in an optical transceiver module. However, the invention should not be so limited, but is understood to extend to other optoelectronic and communications devices where improved component retention is desired. The optical transceiver module to be described below includes various components to enable the reception and transmission of optical signals to and from a host system that is operably connected to the transceiver. The host system can be included as a node in an optical communications network, for instance, and can employ the transceiver in communicating via optical signals with other components of the network.
1. Exemplary Operating Environment
Reference is first made to
An edge connector 60 including a plurality of conductive pads 62 is located on an end of the PCB 50 to enable the transceiver 100 to electrically interface with a host (not shown here). As such, the PCB 50 facilitates electrical communication between the TOSA 10/ROSA 20 and the host. In addition, the above-mentioned components of the transceiver 100 are partially housed within a shell 70. The shell 70 cooperates with an enclosure, shown at 300 in
In greater detail, the shell 70 further includes a front end 80 that defines two ports 82. Front nosepiece portions of both the TOSA 10 and the ROSA 20 each reside within corresponding volumes defined by the ports 82. The TOSA and ROSA nosepieces are positioned within the ports 82 in such a way as to facilitate their respective interconnection with corresponding connectorized optical fibers (
The PCB 50 is retained within the cavity defined by the shell 70 by mounting pins 84. Alternatively, the PCB 50 can be secured to the shell 70 in other ways, including screws, adhesive, etc.
While it has been described in some detail here, the optical transceiver 100 is described by way of illustration only, and not by way of restricting the scope of the invention. For example, the optical transceiver 100 can be configured in one embodiment to be suitable for optical signal transmission and reception at one of a variety of per-second data rates, including but not limited to 1 Gbit, 2 Gbit, 4 Gbit, 8 Gbit, 10 Gbit, or higher bandwidth fiber optic links. Furthermore, the principles of the present invention can be implemented in optical transceivers of any form factor such as XFP, SFP and SFF, without restriction. Nevertheless, the transceiver 100 shown in the accompanying figures has an SFP form factor and a data rate of 2.5 Gbit/sec for use in DWDM applications, for example.
Briefly, during operation the optical transceiver 100 receives a data-containing optical signal from a fiber via the ROSA 20. The ROSA 20 acts as an opto-electric transducer by transforming the received optical signal into an electrical signal. The ROSA 20 provides the resulting electrical signal to a post-amplifier (not shown), where the signal is conditioned before being forwarded to the host device. Similarly, a data-containing electrical signal can be sent by the host device to the transceiver 100 for transmission to the communications network. The electrical signal is conditioned by a laser driver before being forwarded to the TOSA 10, where the electrical signal is converted to an optical signal and launched on to an optical fiber operably connected to the TOSA. As such, the TOSA 10 operates as an electro-optic transducer.
2. TOSA Retention System
As generally shown in
As best seen in
Though integrally formed in one embodiment, the nosepiece 212 can be further described as including a base portion 216 that is adjacent the assembly interface 214, a connector portion 218, and a flange 220. The connector portion 218 extends into the volume defined by the port 82 and is shaped and configured to operably mate with a connectorized optical cable received via the front opening of the port 82. Interior portions of the base portion 216 and connector portion 218 cooperate to define an optical path through which optical signals produced by the light source disposed in the hermetic portion 210 can pass for launching into the connectorized optical cable or other suitable waveguide. A suitably sized and positioned optical window (not shown) is provided in the hermetic package 210 at the assembly interface 214 to permit the optical signals to pass from the hermetic package to the optical path.
The flange 220 of the nosepiece 212 is defined between the base portion 216 and the connector portion 218 and extends radially outward a predetermined distance. So configured, the flange 220 acts as a reference point for securing the position of the TOSA 10 within the shell 70. In particular, the flange 220 is configured in the illustrated embodiment to cooperate with the spring clip 200 in securing the TOSA position, as will be described. Note that the particular shape and position of the flange can be modified from what is explicitly shown herein while still residing within the claims of the present invention.
The end of the hermetic package 210 opposite the assembly interface 214 includes portions of the electrical interface 30 for electrically connecting the TOSA 10 to the PCB 50. In detail, a plurality of conductive leads 230 are shown extending between and attached to corresponding conductive contact pads 232 of the hermetic package 210 and contact pads 234 of the PCB, best seen in
It is especially important that the interconnection of the leads 230 between the hermetic package of the TOSA 10 and the PCB 50 be established such that inadvertent disconnection is unlikely and that potential for stress imposition on the leads is reduced or eliminated so as to avoid lead connection failure during transceiver operation. It is further important that the TOSA 10 be maintained in a substantially fixed position during such lead interconnection such that a cohesive bond is formed between the leads 230 and the contact pads 232 and 234. Note here that other electrical lead interconnection structures and schemes can be employed between the TOSA and the PCB. However, regardless of the particular lead interconnection scheme used, the importance of maintaining the TOSA in a relatively fixed position during such lead interconnection remains generally important. Thus the principles of the present invention apply to other lead interconnection schemes not explicitly shown here.
As seen in
As was discussed in connection with the leads 230, it is important to maintain the TOSA hermetic package 210 in a fixed position during assembly such that a secure engagement of the thermal pad 240 with the hermetic package surface is achieved, thereby providing a suitable thermal path from the TOSA to the shell 70, where the heat can then be dissipated. Moreover, it is important to maintain adequate contact of the thermal pad 240 with the hermetic package 210 during the entire operational lifetime of the module 100 so as to preserve an adequate heat path that does not change over time. Movement or vibration of the TOSA 10 within the shell 70 during module operation, however, can jeopardize this continual contact by causing the thermal pad to become detached from the TOSA 10.
In accordance with embodiments of the present invention, the TOSA retention system is configured to meet the TOSA retention requirements as explained above, that is, retention of the TOSA in a substantially fixed position so as to enable proper attachment of the leads 230 between the hermetic package 210 and the PCB 50, as well as to prevent detachment, via vibration or other cause, of the hermetic package 210 from the thermal pad 240 or other suitable heat transfer device. Moreover, the TOSA retention system described in connection with embodiments disclosed herein secures the TOSA without imposing undue stress or strain on TOSA components, portions, or structures, so as to prevent damage thereto during lead or thermal pad interconnection.
As already mentioned, the TOSA retention system according to illustrated embodiments herein includes the spring clip 200. As best shown in
Note that the arm 254A of the spring clip 200 is relatively longer than the arm 254B. This is to accommodate the particular shape of the groove 202 and to ensure proper orientation of the spring clip 200 when it is installed. If the spring clip 200 were to be installed with the arms 254A and 254B reversed, the spring clip 200 would not completely seat in the groove 202 about the connector portion 218, and would also prevent the enclosure from sliding on to the shell 70 in the manner seen in
The spring clip 200 includes a proximal surface 262 shown in
Reference is now made to
When fully seated in the groove 202, the spring clip 200 engages the nosepiece 212 of the TOSA 10 about a portion of the cylindrical connector portion 218, as best shown in
The spring clip 200 can secure the position of the TOSA 10 within the shell 70 once the TOSA position has been established. In one embodiment, the desired TOSA position is determined by first placing the TOSA and thermal pad 240 in the shell 70 in the general orientation shown in
Once the proper x-y position of the TOSA nosepiece connector portion 218 has been set, the spring clip 200 is inserted about the connector portion into the groove 202 until the seating surface 258 seats on the cylindrical surface of the connector portion, while the connector portion is maintained in its set x-y position. The engagement of the spring clip 200 with the outer cylindrical surface of the connector portion 218 is such that a normal, or interference, fit is created therebetween by virtue of the spring force exerted by the spring clip. This, together with the interference fit achieved between the spring clip 200 and the groove 202, enables the spring clip to secure the desired x-y position of the connector portion 218 of the TOSA nosepiece 212 within the port 82, as already described. By virtue of engagement of the spring clip 200, the nosepiece connector portion 218 is also fixed in the light propagating z-direction.
Note that the spring clip seating surface and nosepiece connector portion can define complementary shapes other than cylindrical, such as square for example, while still maintaining the connector portion position, as desired. Note also that the spring clip and related structures can be modified such that engagement of the clip with other portions of the TOSA/nosepiece is possible.
With the TOSA nosepiece 212 secured, the hermetic package 210 is also substantially secured with respect to both the PCB 50 and the interior surface of the shell 70. So secured, the hermetic package 210 of the TOSA 10 is positioned such that interconnection of the leads 232 of the hermetic package with the leads 234 of the PCB 50 via the leads 230, as well as thermal communication of the hermetic package with the shell 70 via the thermal pad 240 (
Also, and as described earlier, retention of the TOSA by the TOSA retention system as described herein assists in ensuring continual contact between the hermetic package 210 and the thermal pad 240 by reducing vibration therebetween, a major source of thermal pad separation. In greater detail, it is noted that the TOSA assembly 10 is configured such that the connector portion 218 of the nosepiece 212 is movable through a relatively small range of movement, i.e., approximately 0.002 inch measured from the tip of the nosepiece, with respect to the inner surfaces of the respective port 82. This movement range provides a limited amount of compliance to the nosepiece, which eases the insertion and removal of fiber optic connectors into and from the port. Note that the tolerance between the fiber optic connector ferrule and the inner diameter of the nosepiece is substantially close, i.e., 3 microns of tolerance gap or less.
As such, it is necessary to provide such limited movement of the TOSA assembly nosepiece 212 while still securing the hermetic package 210 such that it maintains compressive engagement with the compliant thermal pad 240. As such, the spring clip 200 is configured such that it provides sufficient force on the TOSA assembly 10 to maintain the hermetic package 210 in compressive engagement with the thermal pad 240.
In accordance with present embodiments, the spring clip 200 is removable from engagement with the TOSA 10 so as to enable replacement of the spring clip, the TOSA, or both. Thus changeout procedures for the TOSA are substantially simplified.
Embodiments of the present invention further enhance reduction of electromagnetic interference (“EMI”) emission from the transceiver. In particular, the spring clip 200 urges the TOSA nosepiece flange 220 against the groove surfaces 208A, as has been described above. This configuration helps to “seal” the transceiver front end and ensures that no spacing exists between the groove 202 and the flange 220, where EMI could otherwise escape and exit the transceiver via the ports 82 of the shell front end 80, for example. Thus, use of the spring clip 200 and the properly sized groove 202 can assist in reducing the potential for the transceiver front end in emitting potentially harmful EMI.
The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative, not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.