Abstract:
Optical Network Terminals (ONTS) receive and transmit fiber optic data signals to a premises, such as a home or office, and generate heat, which must be dissipated. An outdoor installation may introduce additional heat loads over an indoor installation. An ONT designed for outdoor use may be overbuilt for indoor use and an ONT designed for indoor use may overheat in an outdoor location. Making separate ONTs for indoor and outdoor use is expensive. A heat sink according to an embodiment of the present invention is attachable to an exterior portion of an ONT and provides extra heat dissipation capability in hotter environments. Other embodiments place the heat sink in a fiber optic cable slack storage region. Other embodiments include interchangeable, different-capacity, heat sinks, and the ONT determines the capacity of the heat sink and operates at a power level appropriate for the heat sink capacity, i.e., thermal dissipation capability.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Optical Network Terminals (ONTS) are typically used to connect fiber optic cable from a telecommunications service provider to data lines, such as ethernet, telephone, and cable television, to a premises, such as an office or a home. The ONTs may be placed in many different locations at the premises, including an indoor placement and an outdoor placement. 
         [0002]    Electrical components in the ONTs generate heat, which must be dissipated. An ONT may include on-board provisions for heat dissipation, such as vents in an exterior housing of the ONT. However, these on-board heat dissipation provisions may not be adequate for all environments. For example, the on-board heat dissipation provisions may be adequate for an ONT installed inside an air-conditioned premises, but may not be adequate for an outdoor installation in a region where temperatures regularly exceed 100° F. Designing an ONT with on-board heat dissipation provisions capable of handling the worst possible thermal conditions may be over-built and, as a result, overly expensive for easier thermal conditions. Likewise, designing and manufacturing different ONTs uniquely suited to different environments may be overly expensive by reducing economies of scale. 
       SUMMARY OF THE INVENTION 
       [0003]    An example embodiment of the present invention includes an optionally installed heat sink, external from an Optical Network Terminal (ONT), configured to transfer heat away from the ONT electronics. The heat sink may be installed on the ONT when the ONT is used in hotter environments. In some embodiments, the heat sink may be used to arrange stored slack fiber optic cable. 
         [0004]    In some embodiments, the heat sink is one of several different capacities of heat sinks. The ONT may automatically detect the capacities of the heat sink and automatically operate at a power level that generates heat at a rate that the heat sink is capable of dissipating. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The foregoing will be apparent from the following more particular description of example embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments of the present invention. 
           [0006]      FIG. 1  is a network diagram showing typical configurations for an Optical Network Terminal (ONT) with an external heat sink according to an example embodiment of the present invention at a premises and connected to an external data network; 
           [0007]      FIG. 2  is a close-up diagram showing the parts of an ONT; 
           [0008]      FIG. 3  is a bottom-view diagram of an ONT base with an external heat sink installed according to an example embodiment of the present invention; 
           [0009]      FIG. 4  is a side-view diagram of an ONT on a base with an external heat sink installed according to an example embodiment of the present invention; 
           [0010]      FIGS. 5A and 5B  are example flow diagrams of procedures performed by an ONT to identify whether an external heat sink or type of heat sink is connected to the ONT; 
           [0011]      FIG. 6A  is a side-view schematic diagram of a base with a door blocking airflow from a vent according to an example embodiment of the present invention; 
           [0012]      FIG. 6B  is a side-view schematic diagram of the base of  FIG. 6A  with the door opened by a heat sink according to an example embodiment of the present invention; 
           [0013]      FIG. 7  is a schematic diagram of a series of ONTs with external heat sinks connected via a heat transfer conduit according to an example embodiment of the present invention; 
           [0014]      FIG. 8  is a schematic diagram of a series of ONTs with external heat sinks connected via heat transfer conduits to an active cooling device according to an example embodiment of the present invention; and 
           [0015]      FIG. 9  is a schematic diagram of an ONT mounted to an outdoor surface of a wall and connected to a heat sink mounted to an interior surface of the wall according to an example embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    A description of example embodiments of the invention follows. 
         [0017]      FIG. 1  shows a typical configuration  100  of a network to a premises  102 .  FIG. 1  shows premises  102  as a house. It should be understood that the premises  102  may be any type of structure, such as an office building or a factory, for example. In this configuration, an Optical Network Terminal (ONT)  105   a ,  105   b  is attached to the side of the premises  102 . The ONT  104   a  is in communication with an external data network  108  by a fiber optic cable  106 . An alternative placement for the ONT  104   b  is shown inside the house  102 . The alternatively-placed ONT  104   b  is still connected to a fiber optic cable (not shown). The ONT  104   a  or  104   b  communicates with the external network  108 , carrying data to various devices within the premises  102 , such as a computer  114  or a television  112 , for example. The ONTs  104   a ,  104   b  each include a respective, externally mounted, heat sink  105   a ,  105   b  according to an embodiment of the present invention. 
         [0018]      FIG. 2  shows an ONT for use within a premises. The ONT  204  has various connector ports for power  206 , for the fiber optic cable  208 , and for various connections such as ethernet  210   a , telephone connections  210   b ,  210   c , and coaxial cable  210   d . The ONT  204  is supported by a base  202 . The ONT  204  also has vents  212  on its side configured to release heat generated by normal operations of the electrical components within the ONT  204 . The ONT  204  includes electronics (not shown), and an external heat sink  205 , according to an embodiment of the present invention, is connected to the electronics in a manner providing thermal communication through an enclosure  203  of the ONT  204  to enable the external heat sink  205  to provide cooling for the electronics. It should be understood that the electronics are an example of possible heat sources that may be within the enclosure  203  that are in thermal communication with the external heat sink  205 . 
         [0019]    The ONT may be capable of dissipating a certain amount of heat via internal cooling structures, such as heat sinks or exchangers, cooling fins, etc. (not shown), and releasing the heat through vents  212 . The vents  212  may or may not be sized for all possible placements of the ONT  204 . For example, if the ONT is placed inside of a house where the climate is controlled, then a minimal amount of cooling may be necessary. Alternatively, if the ONT is placed in a hot outdoor environment, then a significantly higher amount of cooling is necessary. ONTs are either specifically designed for a specific application, e.g., indoor vs. outdoor vs. extremely hot outdoor location, or are overbuilt to handle the worst possible environments, which substantially increases the cost of the ONTs. 
         [0020]    In some embodiments, the ONT  204  enclosure  203  is made of a plastic material or other material that is a poor thermal conductor. Therefore, the enclosure  203  may have ports, holes, or other structural features that enable the external heat sink to connect thermally to the heat source within the enclosure  203 . 
         [0021]      FIG. 3  shows an embodiment of the present invention with a base  300  having walls  312  defining a cavity  314 . In the center of the cavity  314  resides a heat sink  305 . The heat sink  305  has cooling fins  306 . A fiber optic cable  302  enters through hole  310  and wall  312  and wraps around the heat sink  305 , once as shown or multiple times, before exiting through hole  308  in the top of the base  300 . The heat sink  305  is in thermal contact or thermal communication with the electrical components (not shown) in the ONT mounted on top of the base  300 . The heat sink removes additional heat from those electrical components, thereby allowing the electrical components to be operated at a higher power level than they would in the absence of the heat sink  305 . 
         [0022]    It should be understood that the heat sink  305 , optionally a heat exchanger, can be coupled to the electrical components, i.e., heat source, through the enclosure (not shown) of the ONT enclosing the electrical components at locations other than from within the cavity  314  of the base  300 , such as on a rear side of the enclosure. Because the heat sink  305  may be thermally hot, a guard (not shown) may be employed to protect users. 
         [0023]      FIG. 4  is a side view of an embodiment of the present invention showing an ONT  402  mounted on top of a base  404 . The base has a cavity  412  that is partially filled by a heat sink  405 . The heat sink  405  is in contact with the electrical components  408  inside the ONT  402 . The example heat sink  405  interfaces with the electrical components  408  at two contact points  410 . Typically, the interface between the heat sink  405  and the electrical components or heat source  408  is conductive contact. In other words, portions of the electrical components  408  which are generating heat are in direct physical contact with a portion of the heat sink  405  such that heat is transferred through conductance from the heat source  408  to the heat sink  405 . The heat sink  405  draws heat energy away from the electrical components  408  and dissipates that heat from the surrounding air. 
         [0024]    The heat sink  405  may include a groove  414  around its perimeter to arrange stored slack cable, e.g., a fiber optic cable (not shown), that enters through hole  416  in the side of the base  404  and exits through a hole  418  in the top of the base  404 . By arranging stored slack cable, such as the fiber optic cable  302  of  FIG. 3 , the heat sink  405  functions in a way it is not normally used in addition to functioning as a heat sink. Moreover, the heat sink  405  may be configured to provide the arranging as a function of a minimum bend radius parameter of the stored slack cable. Other forms of arranging include holding the cable within a compartment (not shown) of the heat sink  405 , providing a spool (not shown) about which the cable is wound, and so forth. 
         [0025]    The heat sink  405  may be one of several capacities of heat sinks. The term “capacity” as it relates to heat sinks is intended to mean the heat dissipation capability of the heat sink. Heat dissipation capability is only partly related to the physical size, i.e., mass, of the heat sink. In transient heat transfer circumstances, such as when both a heat source and a heat sink are starting from a cold/ambient temperature and the heat source is warming towards its operating temperature, a physically larger heat sink may be able to absorb more heat from the warming heat source. In steady state heat transfer circumstances, when both the heat source and heat sink have reached stable operating temperatures, the heat dissipation capability is dependent on heat transfer to a surrounding medium, which is typically air. Heat transfer to a surrounding medium, such as air, may be enhanced by adding, for example, “fins” of material, i.e., cooling fins, that increase the surface area of the heat sink in contact with the surrounding medium. These fins do not substantially increase the physical size, i.e., mass, of the heat sink. Hence, the term “capacity” as it relates to heat sinks means the capability of a heat sink to remove and dissipate heat from a heat source. Thus, a heat sink with more heat dissipation capability has more capacity than a heat sink with less heat dissipation capability. Embodiments of ONTs according to the present invention may be configured to be attached to various external heat sinks of different capacities. 
         [0026]      FIG. 4  is an example of the present invention that shows an ONT  402  and base  404 ; electronics  408  in the ONT  402  and heat sink  406  in the base  404  are connected via contact points  410 . The contact points&#39;  410  configuration, e.g., size and placement, may be common to all ONTs and heat sink sizes such that different sized heat sinks may be interchangeably connected to the ONTs. 
         [0027]    Embodiments of the ONTs, such as the ONT shown in  FIG. 4 , include structure and logic (not shown), such as software, to determine automatically the capacity of the heat sink attached to contact points  410  and, in turn, provide information or control used in the ONT&#39;s operating the electronics  408 , accordingly. The interface used to determine the capacity of the heat sink may be mechanical, electrical, or a combination thereof, for example. For example, each different capacity heat sink may include a uniquely shaped or sized pin (not shown) configured to fit into a receptacle (not shown) at a contact point  410  of the ONT  402 . The example receptacle is enabled to determine the shape or size of the pin to determine the capacity of the heat sink. The determined capacity information may then be provided to the electronics  408  to determine an operating power level at which the electronics may be operated In alternative embodiments, the interface used to determine the capacity of the heat sink may be electrical. For example, the means may include electrical contacts (not shown) on the electronics  408  and the heat sink  405  such that when the heat sink  405  is connected to the electronics  408 , an electrical circuit is closed. A resistor or capacitor or other electrical component may be associated with the electrical contacts (not shown) on the heat sink. The resistor, capacitor, or other electrical component may have different properties for each size of heat sink such that the ONT electronics  408  can read identify the capacity of the heat sink  406  by detecting the electrical properties of the closed circuit. 
         [0028]    The electronics  408  may also employ an environment sensing thermocouple  422  to supplement its knowledge of the capacity of the heat sink  406 . For example, if the electronics  408  via the environment sensing thermocouple  422  detects a temperature (e.g., cold) suitable to operate itself at a power level beyond the capacity of the heat sink  406 , the electronics  408  can do so. It should be understood that the thermocouple  422  is an example of an environment sensor and that other sensors, such as a sensor for determining airflow across the heat sink  406 , may also or alternatively be employed. It should also be understood that traditional or custom measurements and calculations to determine effective capacity of the heat sink  406  may be employed by the electronics  408 . 
         [0029]      FIG. 5A  is an example flow diagram  500   a  describing how an ONT according to an embodiment of the present invention may operate. Following startup  502 , the ONT establishes operation at a minimum operating power level  504 . At the minimum operating power level  504 , the ONT electronics generate a minimum amount of heat that the ONT is capable of dissipating without any external heat sink. After establishing minimum operating power  504 , the ONT determines whether an external heat sink is attached  506 . The ONT continues operating at minimum power levels  504  if no external heat sink is detected  508 . If the ONT detects an external heat sink, then the ONT operates at a higher power level  510 , i.e., offer more or enhanced data services, thereby generating additional heat that the external heat sink is capable of dissipating. After establishing the higher operating level, the ONT continuously or periodically returns to detect the external heat sink  506 . If the heat sink is removed, accidentally or on purpose, then the ONT reverts to the minimum operating power level  504 . 
         [0030]      FIG. 5B  is an example flow diagram  506  describing how an ONT according to an embodiment of the present invention may operate in the presence of a heat sink of a certain capacity out of many different heat sink capacities. Following startup  502 , the heat sink establishes operation at a minimum operating power level  504 . At the minimum operating power level  504 , the ONT electronics generate a minimum amount of heat that the ONT is capable of dissipating without any external heat sink. After establishing minimum operating power at  504 , the ONT determines whether an external heat sink is attached  506 . The ONT continues operating at minimum power levels  504  if no external heat sink is detected  508 . If the ONT detects an external heat sink, then the ONT determines the capacity of the heat sink  509 . The ONT operates at a higher power level  511 , i.e., offer more or enhanced data services, thereby generating additional heat, matching the capacity of the external heat sink. After establishing the higher operating level, the ONT continuously or periodically returns to detect the external heat sink  506 . If the heat sink is removed, accidentally or on purpose, then the ONT reverts to the minimum operating power level  504 . Likewise, if the heat sink is swapped for a different heat sink with a different capacity, the ONT changes operating power level to match the capacity of the different heat sink  509 ,  511 . 
         [0031]      FIGS. 6A and 6B  show an embodiment of a base with at least one vent  618 , which, in some embodiments, may only open in the presence of a heat sink  614 . As discussed earlier, a heat sink&#39;s capability to dissipate heat is dependent on its ability to move heat to a surrounding medium, such as air. Air circulation further improves heat transfer from a heat sink to air. Thus, vents on a base for an ONT improve heat dissipation capability of a heat sink installed in the base as described above. However, vents may not always be employed as they may introduce dust and moisture. The partially-depicted base shown in  FIGS. 6A and 6B , defined by top  602 , bottom  606 , and wall  604 , has a door  608  mounted by a hinge  610  to the bottom  606 . The hinge  610  may include a spring  612  that maintains the door  608  in a closed position, blocking air that enters through vent  618  from passing into an interior portion  620  of the base. When a heat sink  614  is installed in the base, as shown in  FIG. 6B , the door  608  is pushed down, creating a path for hot air  616  to escape through the vent  618  and for cool air (not shown) to enter through the vent  618 . 
         [0032]      FIG. 7  shows an embodiment in which two or more ONTs  702 ,  704  and their respective bases  706 ,  708  are linked together. Each base  706 ,  708  includes a heat sink  710 ,  712 . The heat sinks  710 ,  712  may be connected by a heat transfer conduit  714 , typically a channel of heat-conducting metal, such that a hotter heat sink may send some heat to a cooler heat sink. Such a configuration may be advantageous where a single premises uses multiple ONTs. At any given time, one particular ONT, ONT  702  for example, may experience higher usage than the remaining ONTs (ONT  704 , for example). In such a case, a first ONT  702  generates more heat than a second ONT  704 , and a first heat sink  710  corresponding to the first ONT  702  has to dissipate more heat than a second heat sink  712  corresponding to the second ONT  704 . In this case, as the first heat sink  710  becomes hotter than the second heat sink  712 , some heat energy flows via the conduit  714  from the first heat sink  710  to the second heat sink  712 . By any of the mechanisms described above, the ONT(s) may detect the presence of additional heat sinks and adjust behavior accordingly, e.g., operate at a higher or lower power level, enable or disable video services, and so forth. 
         [0033]      FIG. 8  shows an embodiment in which one or more ONTs  802 ,  804  and their respective bases  806 ,  808  are linked to an active cooling device  816 , such as a fan. As in  FIG. 7 , heat sinks  810 ,  812  in bases  806 ,  806 , respectively, are connected to a heat transfer conduit  814 . The heat transfer conduit  814  is also connected to an active cooling device, such as the fan  816 . In the case of an active cooling mechanism, the heat transfer conduit may be an air plenum through which air is blown to interact with the heat sinks  810 ,  812 . The fan  816  or other cooling device, such as a forced air heat exchanger, is capable of dissipating more heat than the heat sinks  810 ,  812 . The fan  816  may be active at all times or may be activated only when ONTs  802 ,  804  are operating above a threshold power level. A person having ordinary skill in the art understands that the active cooling device may be attached to a single ONT. By any of the mechanisms described above, the ONT may detect the presence of an active cooling device and adjust its behavior accordingly, i.e., operate at a higher power level. 
         [0034]      FIG. 9  shows an embodiment  900  in which a heat sink  910  is connected to an ONT  902  via a heat transfer conduit  916  such that the heat sink  910  is located in a different environment from the ONT  902 . In  FIG. 9 , the ONT  902  and base  904  are mounted to a wall  908  outdoors. The base  904  optionally may carry a heat sink  906 . The base  904  also carries a portion of heat transfer conduit  916 , which passes through a hole  914  in the wall  908  to a second heat sink  910  located on an indoors side of the wall  908 . As shown in  FIG. 9 , the heat transfer conduit  916  is partially covered by a secondary cover  918 . Also, indoors, the heat sink  910  may optionally be covered by a cover  912 . By moving the heat sink  910  to an indoor surface of the wall  908 , the heat sink  910  may be exposed to cooler air temperatures than the heat sink  906  on the exterior surface of the wall  908 . The lower air temperatures enable greater heat dissipation. By any of the mechanisms described above, the ONT  902  may detect the presence of the heat sink in the indoors environment and adjust its behavior accordingly, e.g., operate at a higher power level. 
         [0035]    It should be understood that the ONT  902  includes logic, such as logic implementing the example procedures of  FIGS. 5A and 5B , in the form of mechanical, electrical, firmware, or software to adjust behavior of the ONT  902  in the presence of various types or capacities of heat sinks. In the case of software, it should be understood that the processor may be any language suitable to adjust behavior of the ONT and optionally independent of or integrated into a general purpose or application-specific electronics within the ONT  902  used to support traffic operations. The software may be stored on any form of processor readable media and loaded and executed by a processor as understood in the art. The software may self-recognize presence or capacity of a heat sink attached to the ONT or by triggered by some event, such as closure or opening of a mechanical switch caused by attachment or detachment of a heat sink or provisioning by a management node elsewhere in a network to which the ONT  902  is in communication. 
         [0036]    While this invention has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.