Patent Publication Number: US-2017353006-A1

Title: Multifunctional circuit for monitoring fiber cable health

Description:
TECHNICAL FIELD 
     The technology disclosed herein relates to high-power fiber and fiber-coupled lasers. More particularly, the disclosed technology relates to managing excess heat in an optical fiber connector. 
     BACKGROUND 
     The use of high-power fiber-delivered lasers is increasing in popularity for a variety of applications such as materials processing, cutting, welding, and/or additive manufacturing. Fiber-coupled lasers include fiber-delivered lasers, disk lasers, diode lasers, direct diode lasers, diode-pumped solid state lasers, and lamp-pumped solid state lasers; fiber-delivered lasers are the most prevalent fiber-coupled laser source. In these systems, optical power is delivered from the laser to a work piece via an optical fiber, which typically includes a connector at the end. Intermediate fibers between the fiber-coupled laser and the work piece may also be employed, and these intermediate fibers also typically include connectors at both ends. These connectors are typically designed to precisely align the beam emerging from the fiber to maintain pointing of the output beam through the downstream optics and to facilitate multiple connection/disconnection cycles. Some problems that may arise in the fiber connectors can result in mechanical breakage of the fiber and/or destruction of the fiber as a result of excess heat which can cause damage to the internal environment in the fiber connector. 
     Some conventional industrial fiber-delivered lasers systems include simple two-wire circuits (sometimes referred to as “interlock circuits”) to monitor and indicate the presence of hazardous conditions in the fiber connector and/or the fiber cable. These simple circuits open when a hazard is recognized and shut the laser off. This interlock circuit is available if the cable is plugged into an appropriate receptacle. When the cable is properly mated to the receptacle, the two wires of the circuit are connected to one another and complete an interlock circuit. These same two wires run the length of the fiber cable and provide additional functionality by opening the circuit when subject to significant mechanical or thermal stress. Such stress may be due to a variety of fiber optic faults that cause burning, or by mechanical means such as being pinched by machinery. In these cases, the fragility of the wires allows them to sever which opens the circuit and safely shuts off the laser system. This system is fairly rigid, is only effective in the event of a catastrophic fault and does not enable resetting the laser system to a functional state. 
     Other conventional industrial fiber-delivered laser systems offer similar functionality and compatibility, but with the addition of a thermostatic switch located in series with the receptacle contacts. The thermostatic switch is located in the distal (output) head of the fiber cable and will open if the assembly reaches or exceeds some critical temperature that may damage the hardware. Once cooled, the thermostatic switch resets to allow operation of the laser to resume. However, such a system provides no information on the conditions inside the connector prior to a critical event causing shut-down and it does not allow users to manually set temperature thresholds. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, are incorporated in and constitute a part of this specification and, together with the description, explain the advantages and principles of the presently disclosed technology. 
         FIG. 1  illustrates an example fiber delivered laser system including a multifunctional two-wire circuit for monitoring fiber cable health comprising a thermistor (or equivalent resistive circuit that varies resistance with temperature); 
         FIG. 2  illustrates an example of a circuit for enabling monitoring health of a fiber delivered laser; 
         FIG. 3  is a schematic illustrating an example connector including a backward compatible circuit for detecting temperature in a fiber delivered laser system; and 
         FIG. 4  illustrates an example of a circuit for enabling an example multifunctional circuit for monitoring fiber delivered laser fiber cable health. 
     
    
    
     DETAILED DESCRIPTION 
     As used in this application and in the claims, the singular forms “a,” “an,” and “the” include the plural forms unless the context clearly dictates otherwise. Additionally, the term “includes” means “comprises.” Further, the term “coupled” does not exclude the presence of intermediate elements between the coupled items. 
     The systems, apparatus, and methods described herein should not be construed as limiting in any way. Instead, the present disclosure is directed toward all novel and non-obvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with one another. The disclosed systems, methods, and apparatus are not limited to any specific aspect or feature or combinations thereof, nor do the disclosed systems, methods, and apparatus require that any one or more specific advantages be present or problems be solved. Any theories of operation are to facilitate explanation, but the disclosed systems, methods, and apparatus are not limited to such theories of operation. 
     Although the operations of some of the disclosed methods are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language set forth below. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed systems, methods, and apparatus can be used in conjunction with other systems, methods, and apparatus. Additionally, the description sometimes uses terms like “produce” and “provide” to describe the disclosed methods. These terms are high-level abstractions of the actual operations that are performed. The actual operations that correspond to these terms will vary depending on the particular implementation and are readily discernible by one of ordinary skill in the art. 
     In some examples, values, procedures, or apparatus&#39; are referred to as “lowest”, “best”, “minimum,” or the like. It will be appreciated that such descriptions are intended to indicate that a selection among many used functional alternatives can be made, and such selections need not be better, smaller, or otherwise preferable to other selections. Examples are described with reference to directions indicated as “above,” “below,” “upper,” “lower,” and the like. These terms are used for convenient description, but do not imply any particular spatial orientation. 
     Conventional interlock circuits in fiber delivered laser systems include a resistor and are configured to detect resistance in order to monitor whether the circuit is within a predetermined range of a threshold resistance level. This conventional method of monitoring the circuit enables detection of catastrophic events such as mechanical and/or thermal destruction of the fiber. However, merely measuring for a threshold resistance as in the conventional interlock circuit does not provide the benefits that monitoring of the fiber environments at select locations and/or identify conditions that precede a fiber failure would. Conditions that precede a fiber failure may be quickly rising temperatures, erratic temperatures or sustained slightly higher than normal temperatures. Thus, the conventional method is limited to discovering failure conditions after the damage to the fiber has already occurred and does not help to prevent future fiber failures. What is needed is a simple method of detecting conditions in the environment around a fiber in a fiber delivered laser system prior to a catastrophic failure that is compatible with existing hardware and circuitry so that impending catastrophic failures can be detected and avoided in existing systems without expensive upgrades. 
     Temperature Sensitive Circuit 
       FIG. 1  illustrates an example fiber delivered laser system  100  including a circuit  102  for monitoring temperature. Laser system  100  includes a laser module  106  for generating a laser beam to be transmitted via fiber  124  to fiber coupler  128 . Fiber coupler  128  is configured to couple fiber  124  to any of many different types of lasing devices such as a fiber-to-fiber coupler  114 , a process head  112 , fiber-to-fiber switch  116 , test station  118  or the like, or any combination thereof. In an example, fiber coupler  128  includes a chamber  126  and housing  130  encasing at least a portion of circuit  102  and fiber  124 . Circuit  102  is enclosed in fiber conduit  104  that runs through chamber  126  of fiber coupler  128 . Fiber conduit  104  may also enclose fiber  124 . 
     In an example, circuit  102  may be coupled to processor  120 . Processor  120  may be disposed in laser module  106  which may include one or more laser diodes  134  coupled to fiber  124  configured to pump an optical beam along fiber  124 . Processor  120  may be coupled to laser diode controller  136  configured to control the one or more laser diodes  134 . Circuit  102  may extend from processor  120  to connector  108 . Connector  108  may be configured to mate with a receptacle  110  which is configured to close circuit  102 . Receptacle  110  may be disposed in any of a variety of devices compatible with fiber coupler  128 , such as, for example, fiber-to-fiber coupler  114 , process head  112 , fiber-to-fiber switch  116 , test station  118  or the like, or any combination thereof. Alternatively, circuit  102  may be closed without having to couple fiber coupler  128  to receptacle  110 . For example, circuit  102  may be closed within connector  108 . 
     A multitude of conditions may arise within fiber delivered laser coupler  128  that may result in mechanical or thermal damage to fiber coupler  128  and/or optical fiber  124 . Such conditions include: backscattered light reflecting from a workpiece back into the fiber housing  130  and/or optical fiber  124 , contamination within the fiber housing  130  or on the optical fiber  124 , irregularities in the optical fiber  124 , problems removing waste heat, mechanical stress on coupler  128  and/or fiber  124 , photo-darkening of the optical fiber  124  and/or a variety of other fiber or mechanical failures. 
     In an example, multifunctional circuit  102  is configured to be temperature sensitive to enable temperature monitoring within fiber housing  130  of fiber coupler  128  in order to detect and prevent damage to fiber  124 . Circuit  102  includes a temperature sensitive variable resistance element (TSVRE)  138 . TSVRE  138  is a device configured to respond to temperature changes by varying resistance. In an example, the TSVRE may be a NTC (negative temperature coefficient) thermistor or a PTC (positive temperature coefficient) thermistor. Accordingly, processor  120  is configured to calculate temperatures based on resistance detected in circuit  102 . Processor  120  may calculate temperatures according to a variety of methods for example based on an algorithm with the processor and/or by reference to a table mapping various resistance values to temperatures. Thus, a variety of temperature related conditions indicating that a failure is imminent in fiber-delivered laser system  100  (e.g., a fast temperature rise or a temperature outside of a predetermined range) can be detected by processor  120 . Such conditions may be detected wherever TSVRE  138  is disposed and/or coupled. TSVRE  138  may be disposed in a variety of locations within chamber  126  in fiber coupler  128 . Such locations may be selected based on susceptibility to temperature fluctuations and/or vulnerability to damage due to temperature fluctuations. In another example, TSVRE  138  may be disposed and/or coupled to a section of fiber-to-fiber coupler  114 , process head  112 , fiber-to-fiber switch  116 , test station  118  or the like, or any combination thereof. Temperatures may be detected by circuit  102  in a section of fiber-to-fiber coupler  114 , process head  112 , fiber-to-fiber switch  116 , test station  118  or the like, or any combination thereof where TSVRE  138  is located. Processor  102  may also be able to detect catastrophic failures based on resistance values measured in circuit  102  where, for example, circuit  102  is open due to a catastrophic thermal or mechanical event. 
     In an example, processor  120  may be programmed to initiate or trigger various actions based on detection in circuit  102  of a temperature outside of a pre-determined temperature, within a range of temperatures and/or upon detection of other temperature related fault indicators in laser system  100 . Such actions may include disrupting, disabling and/or throttling one or more laser diodes  134  and/or initiating other evasive action to prevent or mitigate damage to any portion of laser system  100  by sending commands to laser diode controller  136  based on temperature data derived from readings of the temperature sensitive circuit  102 . Furthermore, because circuit  102  can detect temperature via processor  120 , temperature information can be stored in memory  132  and/or provided to a user via graphical user interface (GUI)  122 . Such stored temperature data may be used to identify temperature behavior or patterns associated with laser damaging fault conditions which may be used to predict and respond to future fault conditions. For example, processor  120  may identify a pattern of temperature fluctuation associated with an identifiable fault condition (the fault condition may be automatically recognized by the processor  120  or user and associated with the pattern by the processor or manually associated by the user). Subsequently, during operation of the fiber-delivered laser system  100  processor  120  may detect the identified pattern to predict the fault condition. In an example, processor  120  is configured to identify a pattern of temperature fluctuation that precedes an identifiable fault condition and to associate the fault condition with the pattern where identifying the fault condition triggers the association. Again, identifying the fault condition may be automated or done manually by a user. Processor  120  may be further configured to trigger a laser diode  134  shutdown based on detecting the identified pattern to prevent the fault condition from causing a failure in the fiber-delivered laser system  100 . 
     Likewise, stored data may be viewed by a user on GUI  122  and used to make administrative decisions such setting different temperature thresholds or manual over-ride conditions, for example. 
       FIG. 2  illustrates an example circuit  102  for monitoring temperature in a fiber-delivered laser system  100 . In an example, circuit  102  includes a first wire  202  and a second wire  204 . Second wire  204  includes a temperature sensitive variable resistance element such as a thermistor  206 . In an example, thermistor  206  is in thermal contact with one or more locations of an inner chamber  126  of fiber coupler  128  (see  FIG. 1 ). Thermistor  206  responds to temperature change at the one or more locations of inner chamber  126  by changing resistance. 
     In an example, connector  108  houses contacts  208  and  210 . When fiber coupler  128  is mated to a device having a receptacle  110 , contacts  208  and  210  couple to respective ones of contacts  212  and  214  to close circuit  102 . Similarly, contact  216  of wire  202  and contact  218  of wire  204  are coupled to processor  120  closing circuit  102  on the processor  120  side. When circuit  102  is closed, processor  120  is configured to calculate temperature based on resistance in circuit  102 . Processor  120  may comprise a mapping ability or other algorithm to determine temperature based on resistance values measured in circuit  102 . 
     In an example, processor  120  may be programmed to trigger shutdown of laser system  100  in the event that a temperature outside of a threshold temperature is detected in circuit  102 . Circuit  102  allows the temperature of the fiber to be monitored prior to shut-down. This visibility allows users to better avoid system shutdown due to fiber cable faults. 
     Backward Compatibility 
     In an example, circuit  102  may be backward compatible with conventional fiber-delivered laser systems programmed to read resistance in a multi-wire circuit. As discussed above, many conventional fiber-delivered laser systems have a two-wire detector system often referred to as an “interlock system.” The conventional interlock system is connected to a processor that is configured to detect a range of resistance levels in the two-wire circuit to identify and shut down a laser system in the event of catastrophic failure. These conventional systems are agnostic to what is driving the resistance. In an example, circuit  102  is configured to integrate with or replace a conventional interlock circuit. In conventional laser systems catastrophic failures are indicated when the interlock circuit is open. Furthermore, conventional interlock circuits are considered ‘closed’ within a range of resistance values. Thus, circuit  102  can be configured to provide a resistance within the range expected by a pre-existing conventional processing algorithm in a conventional processor (rather than processor  120 ) by, for example, combining thermistor  206  with a resistor to keep the resistance in circuit  102  within an expected range for the conventional system. Therefore, in the event that circuit  102  is connected to a conventional system that is not programmed to determine temperatures based on resistance values, the conventional processor can still read resistance values from circuit  102  to identify catastrophic events as it is programmed to do. This enables users to use a connector  108  including circuit  102  on a legacy or conventional fiber-delivered lasers system to operate in the conventional way without having to upgrade the conventional system. Alternatively, a conventional laser system can easily be upgraded to utilize circuit  102  by adding a simple processor  120  configured to not only detect that a circuit is providing resistance within a predetermined range of resistance values to identify the presence of a failure but to also determine temperature based on the particular resistance values read. 
       FIG. 3  is a schematic illustrating an example connector  300  including a backward compatible circuit  302  for detecting temperature configured to integrate with or replace an interlock circuit for a conventional laser system. Circuit  302  is configured to detect temperatures in connector  300  and to be backward compatible with conventional laser systems configured to read resistance values in an interlock circuit within a particular range to identify catastrophic failure modes. 
     In an example, circuit  302  is disposed within chamber  304 . Circuit  302  comprises first wire  306 , second wire  308  and thermistor  310 . First wire  306  and second wire  308  are coupled to respective contacts  314  and  316  to engage receptacle  110  (see  FIG. 1 ) and close circuit  102 . Resistor  312  is connected to circuit  102  in series with thermistor  310 . However, there may be a plurality of resistors  312  that may be connected in parallel and in series with thermistor  310 . Resistor  312  may enable backward compatibility by adding resistance to circuit  302  to bring the resistance of circuit  302  to within a predetermined range expected by a legacy laser system (under normal operating conditions). The resistance range may be selected based on the particular laser application. In an example, the range may be between about 1.0 kΩ and 60.0 kΩ. In a laser system comprising a conventional interlock circuit, circuit  302  can be integrated without requiring an upgrade to the system and will still provide resistance values useful for the conventional processor to identify failure events. Such failure events may identified by detection of a resistance value outside of the expected range. 
     In an example, circuit  302  can also be used to detect temperature in an upgraded laser system. Detection of temperature within connector  300  is useful for a variety of reasons. For example, detecting temperature makes it possible to introduce user settable temperature limits and/or alerts as well as data logging of excessively hot or cold temperatures that may be useful to inform warranty decisions. Accordingly, processor  120  may create an event log identifying relevant temperature events. Such events may be communicated to an interested party (e.g., a manufacturer) via any of a variety of wireless or wireline communication systems. Detecting abnormal temperatures may also warn of an impending failure or other anomalies in the connector  300  or elsewhere in the laser system  100 . 
     In an example, connector  300  is configured to dissipate unwanted light in several locations such as first light diffusing structure  318  and/or second light diffusing structure  320 . Light dissipation can generate significant heat. Thermistor  310  may be attached to printed circuit board (PCB)  320  and potted in or near a first light diffusing structure  318  and/or a second light diffusing structure  320 . Because thermistor  310  will change resistance based on the temperature of its environment, processor  120  may be configured to read the variable resistance and correlate the resistance to a particular temperature. This information may be stored in memory in a variety of data structures and claimed subject matter is not limited in this regard. Processor  120  may further store temperature data in memory  132  to be accessed by a user. Processor  120  may be programmed to respond to detection of a particular temperature, temperatures within a particular range and/or fluctuation of temperatures by sending commands to controller  136  to respond to the detected temperature readings. Responses may vary, for example, commands may be sent to one or more laser diodes  134  to shut down upon detection of temperatures outside of a predetermined threshold range or where wide fluctuations in temperatures are detected. These types of temperature readings may indicate impending failure of the laser modules and/or non-linearities in the fiber  124  causing hot spots. 
       FIG. 4  is a schematic of an example circuit  400  for detecting temperature in a fiber-delivered laser coupler. Circuit  400  runs from a fiber connector to a laser module that houses a processor  402 . On a connector side  404  of circuit  400  a thermistor  406  is connected with a resistor  410  to create a voltage divider. Voltage at node  420  is read by the processor  402 . In an example, processor  402  identifies the temperature of an environment within which thermistor  406  is located based on the voltage determined at node  420 . Thermistor  406  may be located in a variety of areas within the fiber connector to identify areas of out-of-threshold temperatures. Optionally, thermistor  406  may be disposed on a PCB  414  coupled as a network of one or more resistors  412  where some resistors may be connected in parallel and/or in series. Optional resistor  412  is configured to provide a resistance in circuit  400  in a range expected by a legacy laser module as discussed above in order to maintain backward compatibility of circuit  400 . 
     In view of the many possible embodiments to which the principles of the disclosed technology may be applied, it should be recognized that the illustrated embodiments are only preferred examples and should not be taken as limiting the scope of the disclosure. Alternatives specifically addressed in these sections are merely exemplary and do not constitute all possible alternatives to the embodiments described herein. For instance, various components of apparatuses described herein may be combined in function and use. We therefore claim all that comes within the scope and spirit of the appended claims.