Patent Application
20060245712
1. The Field of the Invention
Embodiments of the present invention relate to the field of testing devices and, more specifically, to testing devices for use with various types of optoelectronic modules.
2. The Relevant Technology
Optoelectronic modules are commonly employed in fiber optic data transmission networks in the transmission and receipt of binary data signals. One such optoelectronic module is an optoelectronic transceiver module that can include, among other things, an optical transmitter, such as a laser, that receives electrical data signals, translates the electrical data signals to optical data signals, and then transmits the optical data signals. Further, the optoelectronic transceiver can also include an optical receiver, such as a photodiode, which receives optical data signals, translates the optical data signals to electrical data signals, and then transmits the electrical data signals. Optoelectronic transceivers can also include a printed circuit board (PCB) containing various control circuitry for the optical transmitter and/or optical receiver.
In the manufacture of optoelectronic transceiver modules, each transceiver is tested to ensure that it functions properly. Since optoelectronic transceivers operate in environments characterized by any number of varying conditions, such as temperature and supply voltage for example, the transceivers are typically tested under conditions similar to those likely to be experienced in the intended operating environment.
However, for a number of reasons, testing optoelectronic transceiver modules has proven to be a costly activity. One of the aspects of the optoelectronic module that can be tested is the ability of the module to function over a wide temperature range. Typically, this has been accomplished by attaching the module to a testing board and placing the entire test board and transceiver module combination into an oven for testing over a range of temperatures. This approach to testing has proven problematic because the printed circuit boards used as the testing boards can be very expensive and/or not reliable when operating in the same temperature range as the optoelectronic modules. Therefore, when these boards are heated, they can fail, resulting in increased time and expense to conduct the tests on the modules, as well as time and expense to repair any damage to the test boards. Also, due to the presence of air currents within the oven, precise control of the module temperature is difficult to achieve. Additionally, according to the various different standards used for manufacturing and testing optoelectronic modules, the module temperature must be checked at one or more specific locations on the module's casing. Attaching temperature sensors at the appropriate location by hand can sometimes be very time consuming.
Another problem encountered in module construction and testing is the possibility of an unintentional electrical short between the active electronic components in the module, and the external case. To test for these types of shorts, a known voltage potential can be applied to and measured on the case.
One approach to such problems has been to test the optoelectronic module components individually, and then assemble the module. While such an approach may help to eliminate the problem of determining which particular component is malfunctioning when the module is tested as a whole, such an approach may not provide useful information concerning the performance of the assembled module. The module still must be tested after final assembly to ensure that all connections are working properly. Thus, typical testing evolutions have involved a time consuming, and expensive, two step testing process where the module was tested firstly in the oven at one temperature and then secondly in the oven at a second temperature.
Embodiments of the present invention provide a test apparatus comprising a fixed first portion and a second portion connectable to the first portion. In some embodiments, the second portion can be pivotally attached to the first portion. Mounted to the second portion can be at least one testing device that can be used to test an optoelectronic module. Examples of such a testing device can include, but are not limited to, a temperature sensor, a ground test spring, and a thermoelectric cooler. Examples of optoelectronic modules that can be tested with the apparatus can include, but are not limited to, a SFF module, a SFP module, a XFP module, and a GBIC module.
In one embodiment according to the present invention, the testing device can include a printed circuit board (PCB) and a first portion attached to the PCB. A second portion can be attached to the first portion. The second portion can include at least one testing device that can be used to test an optoelectronic module disposed between the first portion and the second portion. The optoelectronic module can be electrically and mechanically connected to at least one of the PCB and the first portion. Additionally, in some embodiments, the at least one testing device can be electrically connected to an electrical circuit or host device that is external to the apparatus. In other embodiments, an electrical probe can be connected to the host device to facilitate additional testing of the optoelectronic module. The testing device can include, by way of example and not limitation, a temperature sensor, a thermal electric cooler (TEC) and a spring test contact.
These and other objects and 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 which 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:
Embodiments of the present invention provide a test apparatus comprising a fixed first portion and a second portion connectable to the first portion. In some embodiments, the second portion can be pivotally attached to the first portion. Mounted to the second portion can be at least one testing device that can be used to test an optoelectronic module. Examples of such a testing device can include, but are not limited to, a temperature sensor, a spring test contact, and a thermoelectric cooler. Examples of optoelectronic modules that can be tested with the apparatus can include, but are not limited to, a SFF module, a SFP module, a XFP module, and a GBIC module.
One embodiment of a test apparatus is shown in
In some embodiments, base 102 can be attached to a stabilizing platform 108. Platform 108 can be a printed circuit board (PCB) that contains electrical circuitry to connect a device under test (DUT) 110 (illustrated in phantom in
In the embodiment illustrated in
Base 102 can also include one or more elevated portions 124. In the embodiment illustrated in
The top portion 104 can include left and right side rails 130, 132 respectively, connected by one or more cross braces. In the embodiment shown in
Also connected to top portion 104 is PCB 150. In this embodiment, PCB 150 is removably attached to front cross brace 134, using, by way of example and not limitation, one or more mechanical fasteners 151, or any other type of fastener that allows PCB 150 to be easily attached and removed from top portion 104. Specific details concerning board 150 will be discussed below.
In this embodiment, platform 108 can be any rigid structure that provides sufficient support for apparatus 100. Examples of such materials include, but are not limited to, plastics of various types, glass, ceramics, composites, or any other material that provides sufficient structural support. In some embodiments, platform 108 can be a printed circuit board that includes electrical components, traces, and connections that can be used in the testing process.
Base 102 and top 104 can comprise metal, plastic, composites, or any other materials that provide sufficient structural rigidity to hold DUT 110 in a fixed position while testing is performed. Specific details concerning the materials and structure of base 102 and top 104 are provided for the purposes of illustration only. Other structures and materials are also possible, and fall within the scope of the embodiments of the invention.
In the embodiment illustrated in
In this embodiment, guide member 114 is designed to facilitate the positioning of a GBIC module as DUT 110. The guide member 114 allows a GBIC module to slide into apparatus 100 such that the electrical connectors on a rear of the GBIC electrically and mechanically connect to interface 112. In some embodiments, an industry standard GBIC guide member 114 can be used. However, other modules, electronic, or optoelectronic devices can also be tested using specific embodiments of the invention. Such modules can include, by way of example and not limitation, SFF, SFP, and XFP modules. In some embodiments, an industry standard SFP and XFP guide member can be used. Alternately, a specific design for these guide members, and/or the SFF guide member, can be adopted notwithstanding any industry standard. Any structure designed to guide movement of a DUT within apparatus 100 is contemplated to fall within the scope of the embodiments. Alternately, other similar guide structures can be included with or integrated into top 104 or base 102.
While, in this embodiment, guide member 114 is a cage-like structure designed to position DUT 110 within apparatus 100, other structures, including, but not limited to, guide rails, guide slots, lateral and/or rear pins, lateral and/or rear posts, and lateral and/or rear stops, can also be used. The guide member 114 can be sized and configured to guide a specific type of module. Likewise, in this embodiment, guide member 114 comprises plastic. However, other materials including, but not limited to, metals, ceramics, composites, etc., can also be used.
With continued reference to
The PCB 150 can be designed to test specific types of modules. In one embodiment, PCB 150 can include one or more testing devices such as but not limited to, (i) one or more short circuit testing devices 152 to ensure that the case is electrically isolated from the internal module components, (ii) one or more temperature sensors 154 that measure a temperature of DUT 110 at a specific point, and (iii) additional testing circuitry 156. The additional testing circuitry 156 can include one or more electrical pads 158 that provide an electrical connection between PCB 150 and pins 128 in pogos 126. In addition to the testing circuitry on PCB 150, other testing circuitry can include one or more electrical probes 159 mounted on PCB 150. Probe(s) 159 can be used, by way of example and not limitation, if DUT 110 does not have a top cover. Probe(s) 159 can be used, again by way of example and not limitation, to test the electrical properties of one or more subassemblies in DUT 110, for choosing proper values for the DC/AC bias resistors, for programming microcontrollers, and for performing other electrical testing and/or pre-shipment setup of DUT 100.
Additionally, one or more thermal electric coolers (TEC, not shown) can be used to cool, heat, and test DUT 110 at different temperatures without subjecting the entire testing apparatus to the temperature extremes experienced when putting the entire apparatus in an oven for temperature testing. The TEC can be part of PCB 150, or a separate component that is attached to arm 134. The use of a TEC as the testing device allows for testing to be done at multiple temperatures over various temperature ranges. This testing can be accomplished quickly and easily, since the TEC efficiently raises or lowers the module temperature to a desired level much quicker that ambient air circulating in an oven.
In one embodiment, PCB 150 uses a pair of short circuit testing devices 152 to electrically test the casing of DUT 110. In this embodiment, short circuit testing devices 152 take the form of a pair of metallic springs, although other similar structures can be used. For example, one spring can be connected to a positive terminal of a power supply through a first adjustable resistor, while the other spring can be connected to a negative terminal of the power supply through a second adjustable resistor. When short circuit testing devices 152 contact the case of DUT 110 (made of a conductive material), the expected divider output voltage can be measured to verify that no foreign voltage exists on the case.
One problem with making this measurement is that it must be done over a range from 0 volts to a maximum DUT power supply voltage. This is because, under certain circumstances, it is possible for a short to exist that is not “caught” when using fixed resistors. For example, if a test voltage of about 1.5 volts is used, and the DUT 110 has a short circuit to a component that carries about 1.5 volts, this short circuit would not be noticed. The test would measure the expected value of 1.5 volts even though a short was present.
One way to overcome this problem is to use a variable resistor and test over a range of voltages. For example, in one embodiment, the tester can sweep the divider output voltage by changing the adjustable resistor values and measuring the expected voltages across the casing. This method can bring the probability of foreign voltage escapes to zero.
In another embodiment, PCB 150 can include temperature sensor 154. The temperature sensor 154 can be located on PCB 150 such that, when top 104 is lowered to engage DUT 110, sensor 154 contacts a point on the casing of DUT 110 that corresponds with a desired temperature testing point. Various standards setting organizations provide specific areas on the external casing where temperature testing is required to be done. These external points may, although they need not, correspond to the point on the casing above the laser transmitter in the DUT 110. This point is often the hottest part of the casing. This temperature measurement is used to determine if the DUT 110 is operating within acceptable operational parameters. For example, there is a Multisource Agreement (MSA) standard for SFF, SFP, XFP, GBIC, etc., modules that determines the specific testing point and the temperature range for normal operation of the module. Therefore, the specific location of temperature sensor 154 on PCB 150 and also the location of PCB 150 on top 104 can vary depending on the specific type of module to be tested. For example, in the embodiment illustrated in
The board 150 can be electrically connected to additional testing circuitry or an external host device, shown generally as reference numeral 170 in
In operation, catch 122 can mate with hook 138 on the ends of corresponding left and right rails 130, 132, respectively. In the embodiment shown in
Apparatus 100 allows for the testing of many different types of modules by using a specific PCB 150 and platform 108, having various components, such as temperature sensor 154, located at different positions for each DUT 110 to be tested. The PCBs 150 can have different thicknesses and/or be biased in a downward direction to facilitate adequate contact between, for example, temperature sensor 154 and the casing of DUT 110. This biasing can be accomplished, by way of example and not limitation, by placing one or more springs or other biasing mechanism (not shown) between a back side of PCB 150 and arm 134. This biasing mechanism, in conjunction with mechanical fasteners 151 can be designed and positioned to allow PCB 150 to adjust to the position of DUT 110 when top portion 104 is lowered. These springs can then press PCB 150 relatively flush onto DUT 110 when top portion 104 is lowered.
An alternate embodiment of the apparatus of the present invention is illustrated in
As previously discussed, apparatus 200 can include different versions of platform 208 and a PCB 250 attached to top 204 that are specifically tailored to provide testing for various types of optoelectronic modules. In this embodiment, platform 208 can include a left and right guide member 210a and 210b, respectively, and a rear guide member 210c, that facilitate the alignment of an SFF module 110 (shown in phantom in
The PCB 250 can include a temperature sensor 252 and additional testing circuitry 259. In this embodiment, temperature sensor 252 is specifically positioned such that it can contact a top portion of the case of the SFF module at an appropriate temperature measuring point. The additional testing circuitry 259 can include one or more electrical pads 258 which are positioned such that pins 228 in base 202 can form an electrical connection with PCB 250 when top 204 is lowered onto an SFF module to be tested.
Embodiments of the present invention provide several advantages over testing mechanisms in the prior art. While the basic design remains the same, various embodiments of the invention can be used to test many different kinds of modules. The design facilitates the easy interchange of one module with another, thus making the testing process for many modules much more efficient. The use of a TEC and temperature sensors allows for the rapid testing of the module over a range of temperatures. This temperature cycle testing is much more efficient that using, for example, the prior art oven. The modules can be rapidly heated or cooled to any desired temperature for testing purposes.
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 and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.
