Patent Publication Number: US-11657684-B2

Title: Temperature indicator for optical module

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 16/919,832, filed Jul. 2, 2020, the entirety of which are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to optical modules, and more particularly, to identifying a safe touch surface temperature on the optical module. 
     BACKGROUND 
     Over the past several years, there has been a tremendous increase in the need for higher performance communications networks. Increased performance requirements have led to an increase in energy use resulting in greater heat dissipation from components. As power dissipation increases, cooling of components is becoming very difficult. The surface temperature of removable components such as optical modules installed in a network device may reach temperatures that are unsafe for human touch. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG.  1 A  is a perspective of an optical module with a temperature indicator strip inserted into a line card, in accordance with one embodiment. 
         FIG.  1 B  is a front view of the optical module and line card. 
         FIG.  2 A  is a perspective of the optical module of  FIG.  1 A . 
         FIG.  2 B  is a front view of the optical module of  FIG.  2 A . 
         FIG.  3    illustrates changes in temperature of the optical module. 
         FIG.  4 A  is a perspective of an optical module with a temperature indicator handle indicating a safe touch temperature, in accordance with one embodiment. 
         FIG.  4 B  is a perspective of the optical module of  FIG.  4 A  with the temperature indicator handle indicating a temperature exceeding a safe touch temperature limit. 
         FIG.  5 A  is a front view of the optical module of  FIG.  4 A . 
         FIG.  5 B  is a front view of the optical module of  FIG.  4 B . 
         FIG.  6 A  is a front view of a line card with a plurality of optical modules installed with the temperature indicator handles indicating a safe touch temperature. 
         FIG.  6 B  is a front view of the line card and optical modules of  FIG.  6 A  with the temperature indicator handles indicating a temperature exceeding the safe touch temperature limit. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     Overview 
     In one embodiment, an apparatus generally comprises an optical module comprising a first end for insertion into a network device and a second end extending from the network device when the optical module is inserted into the network device and a temperature indicator thermally coupled to the optical module and extending from the second end of the optical module. The temperature indicator provides an indication that a surface temperature of the optical module exceeds a predefined safe touch temperature limit. 
     In another embodiment, an apparatus generally comprises a line card comprising a plurality of optical module ports and a plurality of optical modules inserted into the optical module ports, each of the optical modules comprising a temperature indicator thermally coupled to a housing of the optical module. The temperature indicator provides an indication that a surface temperature of the optical module exceeds a predefined safe touch temperature limit and is viewable with the optical module inserted into the line card. 
     In yet another embodiment, an apparatus comprises an optical module comprising a first end for electrically coupling the optical module to a network device and a second end comprising an optical connector, and a temperature indicator strip thermally coupled to the optical module and extending from the second end of the optical module. The temperature indicator strip is configured to change between a first color indicating that a surface temperature of the optical module is below a predefined safe touch temperature limit and a second color indicating that the surface temperature of the optical module exceeds the predefined safe touch temperature limit. 
     Further understanding of the features and advantages of the embodiments described herein may be realized by reference to the remaining portions of the specification and the attached drawings. 
     Example Embodiments 
     The following description is presented to enable one of ordinary skill in the art to make and use the embodiments. Descriptions of specific embodiments and applications are provided only as examples, and various modifications will be readily apparent to those skilled in the art. The general principles described herein may be applied to other applications without departing from the scope of the embodiments. Thus, the embodiments are not to be limited to those shown, but are to be accorded the widest scope consistent with the principles and features described herein. For purpose of clarity, details relating to technical material that is known in the technical fields related to the embodiments have not been described in detail. 
     As performance requirements increase, optical modules continue to increase in speed and power. As optical power dissipation increases, cooling of optical components is becoming very difficult. For example, pluggable optical modules (transceivers) have limited heat sink surface availability and use of a riding heatsink is not very effective in terms of heat conduction between surfaces. Due to the high power dissipation and limited cooling, optical modules operate at high temperatures, resulting in hot external metal surfaces. The surface temperature of the optical module may reach temperatures that are unsafe for human touch. Heat conduction within a metal shell of the optical module body may result in the optical module reaching high temperatures, including a portion of the module that is outside of the chassis, which may reach temperatures above 55° C. and even up to 75° C. or higher. A safe touch surface temperature to protect maintenance personnel may be limited to 48° C. for example, however, this limit is often exceeded during operation due to cooling limitations. The problem is further compounded by the optical density on line cards, fabric cards, and route processor/controller cards. Since there is little room to work, a technician may hold onto whatever he can reach to remove the module. In addition to a risk of burn injury, there is also a risk of damage or even possibly fire when a hot module is removed and placed on a surface that is not safe for exposure to high temperatures. Therefore, it is important for the technician to be able to easily identify if the optical module is safe to touch to avoid burn injuries or other damage. 
     The embodiments described herein provide a temperature indicator integrated into an optical module to indicate when a surface of the optical module exceeds a safe touch temperature (i.e., too hot to safely touch) and when it is safe to touch and remove the module. The temperature indicator allows maintenance personnel to easily identify when an external surface of the optical module is below a safe touch temperature limit so that the user knows when it is safe to remove the optical module without risk of burn injury. The embodiments described herein may provide compliance with any number of safety standards and prevent burn injury due to accidental touch, thereby providing an improved user experience. 
     It is to be understood that the term “optical module” as used herein refers to any modular optical component (e.g., optical transceiver module) configured for insertion and removal from a modular electronic system (network device), which may include insertion and removal from a line card. The term “line card” as used herein refers to any type of card (e.g., line card, fabric card, service card, route processor card, controller card, or other card) that may be installed in the network device. Also, it is to be understood that the terms front, rear, above, or below as may be used herein are only relative terms and that the network device may have ports for receiving the optical modules located on any face. For example, the term “front face” as used herein refers to an exposed or accessible side of the network device in which ports are located. 
     Referring now to the drawings, and first to  FIGS.  1 A and  1 B , a perspective and front view of an optical module  10  with a temperature indicator (temperature indicator strip, temperature indicator tab)  12  is shown in accordance with one embodiment inserted into an optical module port  11  in line card  14 . In one or more embodiments, an apparatus comprises the optical module  10  comprising a first end for insertion into the network device (e.g., line card  14  of network device) and a second end extending from the network device when the optical module is inserted into the network device, and the temperature indicator  12  thermally coupled to the optical module (e.g., thermally coupled to a housing of the optical module) and extending from the second end of the optical module. As described in detail below, the temperature indicator  12  is configured to sense a surface temperature of the optical module through thermal conduction between an optical module housing and the temperature indicator and provide an indication that the surface temperature of the optical module exceeds a predefined safe touch temperature limit. The temperature limit may be selected based on module type or environment, or may be based on a standard (e.g., NEBS GR63 touch safe temperature limit of 48° C., UL 60950 touch safe temperature limit of 60° C., or any other standard). 
     The optical module  10  may be a pluggable transceiver module in any form factor (e.g., SFP (Small Form-Factor Pluggable), QSFP (Quad Small Form-Factor Pluggable), QSFP-DD, CFP (C Form-Factor Pluggable), CFP2, CXP (100G/Common Transceiver Pluggable), and the like) operable within a network device (e.g., line card  14 ). The optical module  10  may, for example, be plugged into a module based switch, router, or other optical platform port. A cable  16  connected to the optical module  10  at an optical connector  17  ( FIG.  1 B ) may carry, for example, data (e.g., fiber optics, optical array, fabric) or data and power. The optical transceiver module  10  operates as an engine that bidirectionally converts optical signals to electrical signals or in general as an interface to a network element copper wire or optical fiber. A host for the pluggable optical module  10  may include the line card  14  comprising a printed circuit board (PCB)  15  and electronic components and circuits operable to interface telecommunications lines in a telecommunications network. The host may be configured to perform one or more operations and receive any number or type of pluggable transceiver modules  10  configured for transmitting and receiving signals. 
     In the example shown in  FIGS.  1 A and  1 B , the optical module  10  comprises a pull-release handle (pull tab)  19 . While the handle  19  may assist with insertion or removal of the optical module  10 , removal of the optical module typically involves grabbing onto an end of a case (housing)  24  of the optical module extending from the line card ( FIG.  1 A ). In the example shown in  FIGS.  1 A and  1 B , the temperature indicator strip  12  is located generally within (or adjacent to) an opening defined by the handle  19  of the optical module  10  and may extend above the handle for easy viewing of the temperature indicator strip. The temperature indicator strip  12  may be customized for different types of modules without any changes to existing handle designs. The temperature indicator strip  12  may be thermally connected (embedded) within (or on) the optical module surface (external surface of housing  24 ) to provide improved correlation with the optical module surface temperature. The temperature indicator strip  12  extends outward from the second end of the optical module housing  24  so that it is easily visible to indicate if the outer surface of the module is safe to touch or too hot to touch (i.e., exceeds safe human touch operating temperature as suggested by regulatory compliance standards or other specified temperature limit). This helps to prevent burn injury to a technician (operator, maintenance personnel, user) and lets the technician known when it is safe to remove the optical module  10  from the network device during OIR (Online Insertion and Removal). 
     In one or more embodiments, a change in the optical module surface temperature is identified by a change in color of the temperature indicator  12 . For example, as described below, the temperature indicator strip  12  may comprise a thermochromic (also referred to as thermochromatic) pigment (substance, compound) (or other temperature changing material) configured to change from a first color to a second color at the predefined safe touch temperature limit and return to the first color when the surface temperature of the optical module falls below the predefined safe touch temperature limit (reversable color changing properties). 
     It is to be understood that the line card  14  shown in  FIGS.  1 A and  1 B  and the optical module  10  inserted therein is only an example and the line card (e.g., line card, fabric card, route processor card, controller card, and the like) may include any number of ports  11  for receiving any number or type of optical modules in any arrangement. 
       FIG.  2 A  is a perspective and  FIG.  2 B  is a front view of the optical module  10  removed from the line card. The optical module  10  comprises a first end  20  for insertion into a network device (e.g., line card of a modular electronic system) and a second end  22  extending from the network device when the optical module is inserted into the network device (as shown in  FIG.  1 A ). The first end  20  of the optical module  10  defines an electrical interface and the second end defines an optical interface between the optical module and one or more optical fibers. The first end  20  of the optical module  10  comprises an electrical connector (e.g., multiple contact edge type connector) for electrically coupling the optical module  10  to the network device (e.g., through optical module cage interface at the PCB  15 ) and the second end  22  of the optical module comprises one or more of the optical connectors  17  (e.g., MPO (Multi-fibre Push On) connector or LC duplex connector) ( FIGS.  1 A,  2 A, and  2 B ). The optical module housing  24  may conform to industry standards packaging dimensions and may be formed from any suitable material. 
     As previously noted, the optical module  10  may include the pull-release handle (pull tab)  19 , which may assist with insertion or removal of the optical module  10 . As shown in  FIG.  2 A , the handle  19  may be generally U-shaped and extend outward from a front face (second end  22 ) of the optical module housing  24 . The handle  19  may also be used to operate a latch mechanism to release the optical module  10 . As shown in  FIGS.  2 A and  2 B , the temperature indicator strip  12  may be positioned to extend outward from the second end  22  of the optical module  10  and at least partially above the handle  19  so that it is easily viewable from a front end of the optical module ( FIG.  2 B ). The temperature indicator strip  12  is secured (coupled) to the optical module housing (case)  24  and therefore provides a close approximation as to the surface temperature of the optical module housing. 
       FIG.  3    illustrates color changes in the temperature indicator strip  12  as the optical module surface temperature increases (as viewed from left to right in  FIG.  3   ). The temperature indicator strip  12  may comprise, for example, a rubber (or other flexible material) strip with one or more thermochromic pigments. The temperature indicator  12  is configured to change color when a temperature of the thermochromic pigment deviates from a predetermined or calibrated temperature threshold. The thermochromic pigments may be customized for different color schemes and activation temperatures, which are calibrated with the optical module surface temperature. The temperature indicator strip  12  is thermally coupled to the module surface to provide correlation with the optical module surface temperature. 
     In one embodiment, the thermochromic pigment is capable of undergoing a first thermochromic change from a first state (first color) to a second state (second color). For example, the temperature indicator strip  12  may be configured to change between a first color indicating that a surface temperature of the optical module is below a predefined safe touch temperature limit and a second color indicating that the surface temperature of the optical module exceeds the predefined safe touch temperature limit. In the example shown in  FIG.  3   , the temperature indicator  12  comprises more than one thermochromic pigment or compound, each sensitive to a different temperature limit so that the temperature indicator is capable of changing between at least three colors, each of the colors indicating a different temperature range. For example, a yellow color may indicate that the optical module surface temperature is below a first predefined temperature limit and is safe to touch. A pink color may indicate that the optical module surface temperature is above the first predefined limit but below a second predefined limit to indicate that the optical module is cooling but may still be too hot for safe touch. A purple color may indicate that the optical module surface temperature is above the second predefined limit and should not be touched. It is to be understood that any color schemes may be used and the colors and number of color changes used may be different than described herein. 
     It is to be understood that the shape and size of the temperature indicator strip  12  may be different than shown herein without departing from the scope of the embodiments. In one example, the strip  12  may generally correspond in size and shape to an opening defined by the handle  19  and vary according to the size of the optical module and handle. The temperature indicator strip  12  may be designed to correspond to different types of handle (pull tab) designs, without impacting the accessibility of the module front side port or requiring any design change to the handle. 
       FIGS.  4 A and  4 B  are perspectives and  FIGS.  5 A and  5 B  are front views illustrating another example of an optical module  40  with a temperature indicator (temperature indicator handle)  42 , in accordance with one embodiment. As previously described, the handle  42  extends outward from the second end of the optical module and is positioned above cables  46 . In one or more embodiments, a portion of the handle  42  is made with thermochromic pigments impregnated into a base thermoplastic resin material (or other suitable thermally conductive material) forming the handle (or a portion of the handle). In the example shown in  FIGS.  4 A- 5 B , a reference color is added to a first portion  44   a  of the handle  42  for comparison with a second portion  44   b  containing the temperature sensitive thermochromic material. The first portion  44   a  displays a reference color that remains unchanged and the second portion  44   b  displays a color that changes based on the surface temperature of the optical module  40 . In one example, the second portion  44   b  may change from blue (cold) to yellow (hot). In one example, when the color on the two portions  44   a ,  44   b  of the temperature indicator handle  42  are different ( FIGS.  4 A and  5 A ), the optical module has cooled and is safe to remove. When the color on the two portions  44   a ,  44   b  matches ( FIGS.  4 B and  5 B ), the optical module  40  is hot and not safe to remove, thereby indicating that the user should wait until the second portion  44   b  changes to a different color than the first portion  44   a . The change in color is easily viewable from a front end of the optical module extending from the network device as shown in  FIGS.  5 A and  5 B . In one or more embodiments, the optical module  40  may include a tag (sticker, label) on the exposed end with a key identifying cold and hot color patterns of the temperature indicator handle  42 . 
       FIGS.  6 A and  6 B  illustrate an implementations on a line card  60  comprising a plurality of optical module ports  61  for receiving a plurality of optical modules  40  (e.g., CFP2 form factor) and  62  (e.g., QSFP form factor).  FIG.  6 A  is a front view of the line card  60  and optical modules  40 ,  62  that have cooled and are safe to remove (colors on each portion  44   a ,  44   b  of the temperature indicator handle  42  are different).  FIG.  6 B  is a front view of the line card  60  and optical modules  40 ,  62  when the optical modules are hot (exceed safe touch temperature limit) (colors on each portion  44   a ,  44   b  of the temperature indicator handle matches). As shown in  FIGS.  6 A and  6 B  the temperature indicator is always visible, even in high port density systems. 
     It is to be understood that the colors and use of a reference color, or whether the colors match when the optical module surface is hot, as described above is only an example and other colors or configurations may be used without departing from the scope of the embodiments. Also, the optical modules  40 ,  62  may cool at different rates based on a location within the network device, module type, or operating conditions. Thus, one or more of the optical modules  40 ,  62  shown in  FIGS.  6 A and  6 B  may be sufficiently cooled (safe to remove) while one or more of the optical modules are still hot (unsafe to remove). 
     In another example, a liquid crystal layer or label may be placed on the temperature indicator (strip  12 , handle  42 , or exposed metal surface of the optical module housing  24  as shown in  FIG.  1 A ). The liquid crystal changes color in response to heat, thereby creating a visual indication of the temperature of the outer surface of the optical module. A label made of microencapsulated thermochromic liquid crystals (TLC) may be used to display module surface temperature. The crystals are sensitive to temperature and change their position/twist so as to affect the absorbed and reflected light. A backlit hot surface caution label may also be used (e.g., positioned on handle, temperature indicator strip, or exposed portion of housing). The caution symbol may be added on top of encapsulated TLC film to highlight the hot surface symbol only when the temperature exceeds the safe touch temperature limit. In this example, the hot surface symbol is illuminated only after the temperature exceeds a specified threshold value. The label is reversible and becomes dark when the module surface cools down. 
     The embodiments described herein may operate in the context of a data communications network including multiple network devices. The network may include any number of network devices in communication via any number of nodes (e.g., routers, switches, gateways, controllers, edge devices, access devices, aggregation devices, core nodes, intermediate nodes, or other network devices), which facilitate passage of data over one or more networks. One or more of the network devices may comprise one or more optical modules with the temperature indicator described herein. The network device may include one or more processor, memory, and network interfaces, with one or more of these components located on a line card removably inserted into the network device. The network devices may communicate over or be in communication with one or more networks, which may include any number or arrangement of network communications devices (e.g., switches, access points, routers, or other devices) operable to route (switch, forward) data communications. 
     Although the method and apparatus have been described in accordance with the embodiments shown, one of ordinary skill in the art will readily recognize that there could be variations made without departing from the scope of the embodiments. Accordingly, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.