Abstract:
The present invention relates to systems, apparatuses, and methods for the automated manufacture of optical fiber devices including a fiber magazine and a plurality of fiber cassettes within the magazine. The cassettes include alignment members and optical fiber in which the devices are to be formed. A plurality of work stations include assemblies for processing the fiber in the cassettes and reciprocal alignment structures corresponding to the alignment members of the cassettes.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    Not Applicable  
         STATEMENT REGARDING FEDERA118Y SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    Not Applicable  
         BACKGROUND OF THE INVENTION  
         [0003]    The present invention is directed generally to the manufacture of optical fiber components. More particularly, the invention relates to systems, apparatuses, and methods for the automated manufacture of optical fiber components.  
           [0004]    The development of digital technology provided the ability to store and process vast amounts of information. While this development greatly increased information processing capabilities, it was soon recognized that in order to make effective use of information resources it was necessary to interconnect and allow communication between information resources. Efficient access to information resources requires the continued development of information transmission systems to facilitate the sharing of information between resources. One effort to achieve higher transmission capacities has focused on the development of optical transmission systems. Optical transmission systems can provide high capacity, low cost, low error rate transmission of information over long distances.  
           [0005]    Optical communication systems transmit optical signals over optical fiber. As the demand for transmission capacity increases more information must be transmitted over optical fibers. This demand has lead to the development of wavelength division multiplexed (WDM) systems where multiple information carrying optical wavelengths are multiplexed together on a single optical fiber. The WDM signals are demultiplexed, switched, and otherwise processed and manipulated to transmit large amounts of data. Various devices have been developed to process and manipulate WDM signals. Optical fiber devices are an important type of optical device that are based upon optical fiber. Optical fiber devices are easily integrated into optical fiber communication systems. Examples of optical fiber devices are fiber Bragg gratings (FBGs), DFB fiber lasers, couplers, modulators, and Mach-Zehnder interferometers. A FBG can be used to filter WDM signals, which is a very import function in WDM systems. The manufacturing process for FBGs provide an example of the manufacturing process for optical fiber devices. Therefore, the manufacturing process for a FBG is discussed to illustrate the present invention. The present invention can be used to manufacture other types of optical fiber devices as well.  
           [0006]    Holograpically induced gratings have become well known in the art. Holographically induced devices are generally produced by exposing an optical fiber to an interference pattern produced by intersecting radiation beams, typically in the ultraviolet frequency range. The intersecting beams can be produced interferometrically using one or more radiation sources or using a phase mask.  
           [0007]    The manufacture of devices may include the following steps: hydrogenation, stripping, writing, annealing, recoating, packaging, measuring, and baking. Each step is briefly discussed below.  
           [0008]    Hydrogenation involves diffusing hydrogen or deuterium into optical fiber that increases the sensitivity of the fiber to the ultraviolet light used to write the grating. The increased sensitivity results in better reflection and bandwidth performance for the resulting device. Hydrogenation typically occurs in a chamber that controls the temperature, concentration, and pressure of the hydrogen. Usually, a large amount of fiber, either cut to lengths or still on a spool, is hydrogenated all at once. While hydrogenation improves the performance of devices, hydrogenation is not required; therefore this step is optional.  
           [0009]    Optical fibers have a core with an outer cladding and jacket. In order to irradiate the fiber core and write the grating, this jacket must be removed or stripped. A stripping tool strips the coating off of the fiber. The stripping tool is used by holding the fiber at one end and running the stripping tool over the section to be stripped. After the fiber is stripped it is cleaned. These operations are often performed manually.  
           [0010]    Once the fiber is stripped it is ready to be written. The fiber must be precisely mounted in the writing machine. Both the position and tension of the fiber must be set and controlled. The writing machine radiates the fiber with ultraviolet light to write the grating. The loading and mounting of the fiber presents a great challenge as the fiber is manually loaded into the machine. Variations in the loading will affect the final yield and performance of the devices because the writing process is sensitive to mechanical stability and variation in the location of the fiber.  
           [0011]    After the device is written, the reflection characteristics of the device may be measured. Next, the device may be annealed. Annealing involves a controlled heating of the device and is also known as accelerated aging. Annealing helps to set the characteristics of the device. The temperature and time of the annealing depends on the fiber type, device type and specification, and measured device parameters, if available. The device can be heated in a variety of ways including, for example, a heat gun, hot gas or liquid, heater block, or heated metal plate. After annealing, the device is measured, and if the device is outside the device specification, the device is again heated, because heating a device can shift the reflection wavelength downward. This is called trimming. Trimming parameters depend upon the device, fiber type, and the amount of wavelength shift required. Trimming can be repeated for a set number of cycles or until the device is within specification.  
           [0012]    Next, the annealed device may be recoated. The device is placed in a mold and coating material is injected into the mold. A curing lamp cures the coating material, and then the molds are opened and disengaged. The recoated device can be measured again to ensure that the device still is within specification. The molds used are typically made of two pieces. Mating and alignment of the molds is difficult resulting in failed devices. Curing is often done manually and adds variability to the resulting devices due to shrinkage of the coating material.  
           [0013]    The recoated device next may be packaged. A typical package is a long slender quartz package with a slot. The operator positions the device within the slot, typically using a microscope because the fiber is very small. The operator places a tension on the device. This tension is typically zero, but other values of tension may be applied to shift the reflection wavelength into specification. Next, adhesive is applied at either end of the package over the fiber to securely fasten the device to the package. The operator cures the adhesive using a heat gun. Many of these steps are performed manually, which results in increased device variability and decreased device performance.  
           [0014]    Finally, the device may undergo baking and final measurement. The device is baked at a low temperature to further set the device. This baking is typically in the range of 4-24 hours. A final measurement determines that the finished device meets the required specification.  
           [0015]    Currently typical device manufacturing processes move the device from step to step using a tray or as a bare fiber. At each step of the process, the operator manually places the device in any required fixtures for the processing step. The tension of the fiber must also be set for various processing steps, and often this is done using a manual adjustment. During the various processing steps, a fiber breakage test can be done by placing a large tension of the fiber to determine if the fiber has been damaged during processing. The fiber is then removed from the processing fixture and returned to the tray. Also, some of the process steps may use multiple fixtures to complete the process step. This involves further manual handling of the fiber.  
           [0016]    The device is measured at various points throughout the manufacturing process. This ensures that the device is within specification prior to performing the next processing step. Measuring the device involves the splicing of the device to the measurement system. The splicing operation involves manual handling of the fiber. Then the device must be cut from the measurement system. Alternatively, a measurement port may be attached to the ends of each fiber. The measurement ports are then plugged into a measuring device. This approach still requires significant fiber handling to perform measurements.  
           [0017]    Currently the manufacture of optical fiber devices as described above involves significant manual labor and handling of the fiber. Repeated handling of the fiber causes the fiber to degrade and even to fail resulting in lower device yields and degraded performance. These problems are increased when a portion of the fiber is stripped as required for the manufacture of devices. In addition, many of the manufacturing steps involve manual operations by an operator. For example, devices are extremely sensitive to heat and tension, so if these parameters are not carefully controlled, performance and yield of the devices are reduced. Therefore, manual operations affecting these parameters introduce greater variability into the resulting devices. Again this results in lower device yields and degraded performance. The use of manual labor in the manufacture of devices also greatly increases the final cost of devices.  
           [0018]    The manufacturing steps described above for processing FBGs may also be used in manufacturing other optical fiber devices. The steps may be identical or similar, but they also have the same problems as described with the manufacture of FBGs.  
           [0019]    Therefore there remains a need to improve the manufacture of optical fiber devices. The present invention introduces automation into the optical fiber device manufacturing process to overcome the problems with present method of manufacture. The present invention reduces the variability of optical fiber device characteristics and cost while increasing yield and performance. These advantages and others will become apparent from the following detailed description.  
         BRIEF SUMMARY OF THE INVENTION  
         [0020]    The present invention is directed to methods, systems, and apparatuses for the automated manufacture of optical fiber devices. Work stations perform various steps in the manufacture of optical fiber devices. Fiber cassettes hold the optical fiber device and provide the vehicle for transporting the optical fiber devices from one work station to another. The fiber cassettes may also provide measurement ports to allow for measurement of the optical fiber device during processing. To provide for greater manufacturing efficiencies, the fiber cassettes can be ganged together in a magazine. The magazine allows for concurrent processing of the optical fiber devices contained in the magazine resulting in improved manufacturing throughput. In addition, each work station can be connected to a manufacturing control system. The manufacturing control system is a system that tracks each optical fiber device throughout the manufacturing process and that controls the manufacturing process. Fiber cassettes and magazines reduce touch times resulting in lower cost and improved yields and performance.  
           [0021]    An embodiment of the present invention for the manufacture of optical fiber devices is described herein. Examples of work stations that strip and write a grating into a fiber and that anneal, recoat, package, and measure an optical fiber device are disclosed. These work stations may share a common design and may share various assemblies used to process the optical fiber device. The present invention may also be used to manufacture athermally packaged optical devices.  
           [0022]    Another embodiment of the system for manufacturing optical fiber devices of the present invention includes a fiber magazine, a plurality of fiber cassettes within the magazine, the cassettes including alignment members and optical fiber in which the devices are to be formed, and a plurality of work stations including assemblies for processing the fiber in the cassettes, and including reciprocal alignment structures corresponding to the alignment members of the cassettes. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]    Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings for the purpose of illustrating embodiments only and not for purposes of limiting the same, wherein:  
         [0024]    [0024]FIG. 1 shows an embodiment of a work station according to the present invention;  
         [0025]    [0025]FIGS. 2 and 3 show an embodiment of a fiber cassette according the present invention;  
         [0026]    [0026]FIG. 4 shows a more detailed view one embodiment of the fiber stabilizer according to the present invention;  
         [0027]    [0027]FIG. 5 shows an exploded view of one embodiment of the cassette;  
         [0028]    [0028]FIG. 6 shows a cross-sectional view of one embodiment of the fiber reel;  
         [0029]    [0029]FIG. 7 shows a cross-sectional view of one embodiment of the fiber cage;  
         [0030]    [0030]FIG. 8 shows a magazine for holding cassettes;  
         [0031]    [0031]FIGS. 9 and 10 show one embodiment of a work station according to the present invention;  
         [0032]    [0032]FIG. 11 shows one embodiment of a tension assembly which may be used in a work station;  
         [0033]    [0033]FIG. 12 is a block diagram of one embodiment of a gripper assembly;  
         [0034]    [0034]FIG. 13 is a block diagram of one embodiment of a system for manufacturing a device;  
         [0035]    [0035]FIG. 14 shows one embodiment of a stripping assembly used by the stripping work station to strip the fiber;  
         [0036]    [0036]FIG. 15 shows the three step process that the stripping assembly uses to strip the fiber;  
         [0037]    [0037]FIG. 16 illustrates an annealing assembly found in an annealing work station;  
         [0038]    [0038]FIG. 17 shows a cross-sectional view of one embodiment of a heater;  
         [0039]    [0039]FIG. 18 shows an annealing block according to the present invention;  
         [0040]    [0040]FIG. 19 shows the temperature regions in the annealing block around the FBG and adjacent optical fiber;  
         [0041]    [0041]FIGS. 20 and 21 show a recoating assembly that may be used with the recoating work station to recoat fiber;  
         [0042]    [0042]FIG. 22 shows a cross-sectional view of the recoating assembly illustrating a resin injector;  
         [0043]    [0043]FIGS. 23 and 24 show cross-sectional views of one embodiment of the recoating assembly, with the upper molds, lower mold, and resin injector in the open and closed positions, respectively;  
         [0044]    [0044]FIGS. 25 and 26 show a cross-section view of the open and closed molds through the continuity channels;  
         [0045]    [0045]FIGS. 27 and 28 show the packaging fixture for use in a packaging work station for packaging devices;  
         [0046]    [0046]FIG. 29 shows another view of the packaging fixture; and  
         [0047]    [0047]FIG. 30 shows an adhesive assembly that may be used in a packaging work station. 
     
    
     DESCRIPTION OF THE INVENTION  
       [0048]    [0048]FIG. 1 shows an embodiment of a work station  10  according to the present invention. The work station processes optical fiber into optical fiber devices. The work station receives a magazine  12  that contains fiber cassettes  14 . The cassettes  14  hold optical fiber  18  (see FIGS. 2 and 3) that is processed by the work station  10 . The work station  10  has one or more assemblies  16  that engage and process the fiber  18 . If the work station  10  has multiple assemblies  16 , then multiple fibers  18  may be processed concurrently. Different work stations  10  employing different assemblies  16  may perform a variety of processing tasks. One or more work stations  10  may be used to manufacture an optical fiber device in the optical fiber  18 . The work stations  10  may be built upon a common design, and many of the manufacturing steps performed at one work station  10  may be common to other work stations  10 .  
         [0049]    [0049]FIGS. 2 and 3 show an embodiment of a fiber cassette  14  according to the present invention. The cassette  14  can hold optical fiber  18 , which may include or be processed to form an optical fiber device  20 . The cassette  14  may include a connecting member  22 , receptacles  24 , fiber stabilizers  26 , alignment members  28 , measurement ports  30 , and covers  32 . The fiber cassette  14  holds the fiber  18  and provides the vehicle for processing the fiber and for transporting the fiber  18  to one or more work stations  10 . After the fiber  18  is loaded into the cassette  14 , the fiber may be processed without an operator handling the fiber  18 , which reduces fiber weakening, fiber breakage, and device yield loss. The cassette  14  enables the fiber  18  to be consistently presented to work stations  10  for processing, which ensures the reliability of processing and measurements by reducing the variability in fiber location. Fiber cassettes  14  also reduce operator touch times, resulting in reduced device cost.  
         [0050]    The receptacles  24  provide storage for excess fiber. For example, the length of fiber used to manufacture the device  20  is typically much longer than the device  20  itself, and the receptacles  24  provide storage for that excess fiber. The receptacles  24  shown are round, but other shapes may be used as well. Additionally, the receptacles  24  should be sized to account for the minimum bending radius of the fiber  18  in order to reduce stress placed on the fiber  18 . Alternatively, one or no receptacles  24  may be utilized, such as in a cassette  14  in which excess fiber  18  requiring storage is present at only one side, or at neither side, of the device  20 . For example, the receptacles  24  may be eliminated and the fiber  18  attached to the cassette  14  near the ends of the fiber  18 .  
         [0051]    The connecting member  22  connects the two receptacles  24 . The length and location of the connecting member  22  affects the amount of fiber  18  exposed and the amount of space that the various work stations  10  have to process the device  20 .  
         [0052]    Stabilizers  26  hold the fiber  18  in place, thus preventing the movement of the device  20 . The stabilizers  26  ensure that, as the cassette  14  moves from one work station  10  to another, the device  20  is located in the same position relative to the fiber cassette  19 . Therefore, the work stations  10  do not need to have the capability to locate the device  20 , thereby resulting in reduced cost and complexity of the work stations  10 . Alternatively, the stabilizers  26  may be omitted if, for example, the receptacles  24  or other parts of the cassette  14  are capable of maintaining the location of the device  20  in the cassette  14 , or if the work stations  10  are able to locate the device  20 .  
         [0053]    Alignment members  28  allow the cassette  14  to be properly aligned in a work station  10 . The alignment member  28  may include an opening that is engaged by the work station  10  to align the cassette  14  within the work station  10 . The alignment members  28  may be attached, for example, to the connector member  28  or the receptacle  24 .  
         [0054]    Measurement ports  30  facilitate the measurement of the characteristics of the fiber  18  and/or device  20 . The measurement port  30  may be directly or indirectly attached to the fiber  18 . When the cassette  14  is in a work station  10 , the measurement port  30  can be engaged and used to measure the fiber  18  and/or device  20 . In one embodiment, the measurement port  30  includes a fiber tail that connects to the fiber  18 . After the measurement port is used, the fiber tail may be cut from the fiber  18 , and the fiber tail then attaches to the next fiber  18  inserted into the cassette  14 , without having to replace the measurement port  30  or reconnect the fiber  18  to the measurement port  30 . An alternative to splicing the fiber  18  to the measurement port is to use a ferrule or other connector technique on the fiber  18  and the measurement port  30 . The measurement ports  30  provide an advantage over prior art manufacturing processes where the fiber  18  had to be spliced each time it was measured. The measurement ports  30  allow the work station  10  to measure the device  20  as often as needed and in real time while the device  20  is being processed without requiring additional handling and splicing of the fiber  18 .  
         [0055]    The stabilizer  26 , connecting member  22 , and receptacle  24  may be arranged so that there is a gap  34  (FIGS. 2 and 3) between the fiber  18  and the cassette  14 . This gap  34  allows the work station  10  to engage the fiber  18 , such as to retension of the fiber  18 .  
         [0056]    [0056]FIG. 4 shows a more detailed view of one embodiment of the stabilizer  26 . The stabilizer  26  includes lower and upper grippers  36 ,  38  that grip the fiber  18 . The upper gripper  34  connects to a slide  40  that moves up and down on rods  42  passing through openings  44  in the frame  46 , to disengage and engage, the fiber  18 . A spring may be used to bias the upper gripper  34  in a desired position, such as to bias the upper and lower grippers  36 ,  38  into engagement, unless a sufficient counterforce is applied. The upper gripper  34  may be arranged so that it may be pushed away from the lower gripper  36  by the work station  10 , such as to allow the work station  10  to adjust tension on the fiber  18 . In one embodiment, the grippers  36 ,  38  are made of a compressible material such as rubber that will grip the fiber  18  and hold it in place without damaging it. Other suitable materials may be used as well.  
         [0057]    The stabilizers  26  may take other forms as well. For example, the stabilizer  26  may clamp the grippers  36 ,  38  together using a locking mechanism. The stabilizer  26  may also have a quick release mechanism to allow for easy release of the fiber  18 . Also, the stabilizers  26  may be releasable by the work stations  10 .  
         [0058]    [0058]FIG. 5 shows an exploded view of one embodiment of the cassette  14 . A fiber reel  48  within the receptacle  24  may hold the fiber tail from the measurement port  30 . A fiber cage  50  may hold the excess fiber  18  in which the device  20  is formed. A cover  32  retains the fiber reel  48  and fiber cage  50  within the receptacle  24 . It is also possible to place the fiber  18  within the receptacle  24  without a fiber reel  48  or fiber cage  50 . The tendency of the fiber  18  to uncoil within the receptacle  24  will often allow the fiber  18  to remain securely within the receptacle  24 . FIG. 5 also shows how the receptacles  24  attach to the connecting member  22 . It is not necessary for the connecting member  22  to extend completely behind the receptacles  24 , but the connecting member  22  may attach only to one edge of each receptacle  24 .  
         [0059]    [0059]FIG. 6 shows a cross-sectional view of one embodiment of the fiber reel  48 . The fiber reel  48  includes an opening  52  in which fiber is contained. The opening  52  may be located so as to maintain the minimum bend radius for the fiber. The fiber reel  48  provides storage of fiber, reduces tangling of the fiber, and allows fiber to be removed from the reel as needed. For example, the fiber tail from the measurement port  30  may be stored by winding it onto the fiber reel  48 . Typically, as the size of the reel opening  52  in the fiber reel  48  is reduced, the likelihood that the fiber will tangle is reduced.  
         [0060]    [0060]FIG. 7 shows a cross-sectional view of one embodiment of the fiber cage  50 . The fiber  18  is wound into the cage through the cage opening  54 . The tendency of the fiber  18  to uncoil will allow the fiber  18  to remain securely within the fiber cage  50 . The fiber cage  50  allows for a portion of fiber  18  to be withdrawn from the fiber cage  50  by gripping the fiber  18  and pulling it out. This may be desirable for work stations  10  having space limitations that prevent the processing of the device  20  within the cassette  14 . Upon completion, the work station  10  can feed fiber  18  back into the fiber cage  50 . In addition, the fiber cage allows for easy loading and unloading of fiber  18 , which may be useful during the processing of the fiber  18 . The fiber cage  42  may be used, for example, to store excess fiber  18  that is being processed. The fiber  18  may be wound into the fiber cage  50  prior to processing and then easily removed from the fiber cage  50  after the processing is completed.  
         [0061]    The present invention provides for many variations in fiber storage. For example, a cassette  14  may use neither a fiber reel  48  nor a fiber cage  50 , a cassette  14  may use only a fiber reel  48 , a cassette  14  may use only a fiber cage  50 , or a cassette  14  may use both a fiber reel  48  and fiber cage  50 .  
         [0062]    [0062]FIG. 8 shows a magazine  12  for holding cassettes  14 . The magazine  12  may hold several cassettes  14  to provide for greater manufacturing efficiencies. The magazine  12  provides an efficient vehicle for transporting and processing cassettes  14 . A magazine  12  holding several cassettes  14  maybe inserted into a work station  10 , or into several work stations  10  in succession, thereby making several cassettes available to a work station  10  without the need for human or other intervention to insert or remove additional cassettes. The magazine  12  allows for sequential or concurrent processing of the devices  20  contained in the cassettes  14 , resulting in improved manufacturing throughput. The magazine  12  enables the cassettes  14  to be consistently presented to work stations  10  for processing, which ensures the reliability of processing and measurements by reducing the variability in fiber location. The magazine  12  includes slots  56  into which cassettes  14  are received and supports  58  on which the cassettes  14  rest. The supports  58  may slide up and down within the magazine  12  and may be biased, such as with a spring  60 , to keep the support  58  in a desired position.  
         [0063]    In one embodiment, the supports  58  are biased in a raised position to provide appropriate clearance between the cassette  14  and assemblies  16  in the work station  10 . The cassettes  14  are subsequently lowered by the work station  10  for processing. When a work station  10  receives a magazine  12 , the work station  10  engages the alignment members  28  and pushes the cassette  14  towards the magazine  12  until the cassette  14  comes into contact with the base  62  or something else that limits the motion in the magazine  12 . In another embodiment, the support  58  can have a stop that limits the movement of the cassette  14  in the magazine  12 . When the supports  58  are in their highest position, the device  20  is recessed from the bottom of the magazine  12 , where it is less likely to be damaged. In another embodiment of the magazine  12 , the supports  58  are not present, and the cassettes  14  rest on a ledge  64  or some other support.  
         [0064]    [0064]FIGS. 9 and 10 show one embodiment of a work station  10  according to the present invention. The work station  10  is shown with a magazine  12  loaded with several cassettes  14 . The work station  10  may have a alignment member  66  that engages the alignment member  28  to align the cassette  14 . For example, the work station  10  may have an alignment member  66  that includes pins for use with alignment members  28  in the cassettes  14  that have corresponding openings. The work station  10  may also have an alignment member  66  that is a slot that receives a corresponding alignment member  28  and aligns the cassette  14 .  
         [0065]    The pins and slots in the alignment members  66  can be tapered to facilitate engagement with corresponding openings in alignment member  28  and to allow for variations in the position of the cassette  14  relative to the work station  10 . The pins may be lowered or raised to engage the opening and to align the cassette  14  into a known position. In one embodiment, when the reciprocal alignment members  66  of the work station  10  engage the cassette  14 , the work station  10  pushes the cassette  14  down, and compresses the supports  58 , thereby bringing the devices  20  closer to the assemblies  16  where it may be more convenient to operate on the device  20 .  
         [0066]    The work station  10  may have measurement ports  68  that connect with the measurement ports  30  on the cassette  14  to measure characteristics of the fiber  18  or device before, during, or after processing. For example, the work station  10  may measure the reflection and/or transmission wavelengths during the manufacture of devices  20 , such as FBGs. In that example, the work station  10  may include a heater or other temperature controller to set the device  20  temperature to a known value for the measurement.  
         [0067]    The work station  16  may include one or more assemblies  16  for processing the fiber  18 . The assemblies  16  may all be of the same or different types. The assemblies  16  may move to engage the fibers  18 , or the fibers may be moved so that the assemblies  16  may engage the fibers  18 . If the number of assemblies  16  is less than the total number of cassettes  14  in the magazine  12 , then the assemblies process a first group of fibers  18 , and then the next group, until all of the fibers  18  have been processed. The assemblies may be arranged to process fibers  18  in adjacent cassettes  14  or fibers  18  in nonadjacent cassettes  14 . Also, the work station  16  may move assemblies  16  or the magazine  12  to allow the assemblies  16  to process different groups of fibers  18 .  
         [0068]    Some work stations  10  may control the tension on the fiber  18 . For example, some work stations  10  may perform fiber pull tests to detect cracks or other flaws in the fiber  18 . A fiber pull test places the fiber  18  under a tension, which may be, for example, based upon the maximum tension expected during handling, installation, and operation of the device  20 . If the pull test breaks the fiber  18 , the fiber  18  is discarded; otherwise, the fiber  18  continues to be processed. Tension may also be controlled to set the fiber tension for measurement, packaging, or other processing steps.  
         [0069]    [0069]FIG. 11 shows one embodiment of a tension assembly  70  which may be used in a work station  10  for placing tension on the fiber  18 . The tension assembly  70  has a gripper assembly  72  with grippers  74  that close to grip the fiber  18  (not shown). The tension assembly  70  may raise a release rod  76  to lift and release the upper gripper  34  in the cassette  14 . Next, the tension assembly  70  places tension on the fiber  18  using gripper assembly  72 . The gripper assembly  72  may be attached to a motor that moves the gripper assembly  72  to adjust the tension on the fiber  18 . Various types of motors may be used depending upon how fine the tension control must be. The fiber  18  is anchored to provide resistance to the pulling of the gripper assembly  72 . Anchors may include a stabilizer  26  or another gripper assembly  72 . Once the work station  10  completes processing the fiber  18 , the tension assembly  70  has retensioners  78  that grip the fiber  18 . The grippers  74  release the fiber  18 , and the retensioners  78  place appropriate tension on the fiber  18 . The tension assembly  70  lowers the release rod  76  allowing the upper gripper  34  in the cassette  14  to hold the fiber  18  in place under the tension provided by the retensioners  78 . The retensioners  78  then release the fiber  18 . It is also possible for the retensioners  78  to grip and tension the fiber  18  prior to the grippers  74  releasing the fiber  18 .  
         [0070]    The tension assembly  70  keeps the device  20  in the same location during and after the work station  10  processing. The tension assembly  70  may lower the gripper assembly  72  after gripping the fiber  18  to provide space for other assemblies in the work station  10  to process the fiber  18 . In this case, the tension assembly  70  may include a second gripper assembly  72 , so that the fiber  18  may be gripped in two locations and lowered.  
         [0071]    [0071]FIG. 12 is a block diagram of one embodiment of a gripper assembly  72  that may be used to set the tension on the fiber  18  to zero. Grippers  74  are mounted on a slide  80  that may, for example, ride on a friction free air bearing  82  or other type of bearing. A base  84  connects to the slide  80  via a spring  86  and dash pot  88  that control the motion of the slide  80 . The spring  86  compresses and exerts a force on the slide when it moves towards the spring  86 . The dash pot  88  dampens sudden motions of the slide to smooth out quick movements of the base  84 . The gripper assembly  72  has a strain gauge  90  connected between the base  84  and slide  80  to measure strain, which is indicative of strain in the fiber  18 . The gripper assembly  72  has stops  92  to limit the strain range of the system. A motor  94  or other suitable device drives the base  84 . The gripper assembly  72  controls the motor  94  driving the base  84  via feedback control. The strain gauge  90  produces a signal indicating the strain on the fiber  18  that is then compared to a desired strain setting resulting in an error signal. The error signal drives the motor  94  to compensate for the error.  
         [0072]    The work stations  10  may also be designed to allow for automatic loading and unloading of the magazine  12  from the work station  10 . The magazine  12  may then be conveyed automatically from one work station  10  to another using a conveyer system and then loaded and unloaded into the work stations  10 . This allows for a completely automatic manufacturing process.  
         [0073]    [0073]FIG. 13 is a block diagram of one embodiment of a system for manufacturing a device  20 , such as a FBG. The system includes several work stations  10  to process optical fiber  18 . The system may include more or less work stations  10  than those illustrated, and the work stations  10  may perform the same or different functions. The number, type, and arrangement of work stations  10  will vary depending on the type of device  20  being produced. In the illustrated embodiment, the system includes a hydrogenation work station  96 , a fiber cassette loading work station  98 , a magazine loading work station  100 , a stripping work station  102 , a grating write work station  104 , an annealing work station  106 , a recoating work station  108 , a packaging work station  110 , a measurement work station  112 , a baking work station  114 , a magazine unloading work station  116 , and a cassette unloading work station  118 . The system in the illustrated embodiment also includes a manufacturing control system  120  connected to the work stations via a network  122  to monitor and control the work stations. Each work station includes processing assemblies which perform the particular processing steps of the work stations. The structure and operation of the work station  10  are described below.  
         [0074]    A stripping work station  102  strips the coating from the fiber  18  as required to manufacture certain types of devices  20 , such as FBGs. The stripping work station  102  strips each of the fibers  18  in the magazine  12 . The stripping work station  102  has stripping assemblies  124  (see FIG. 14) to strip the fibers  18 . Also, the stripping work station  102  may employ a tension assembly  70  to place tension on the fiber  18  to facilitate stripping. Alternatively, the stabilizers  26  may be used to maintain sufficient tension on the fiber  18  during stripping. The stripping work station  102  may have only one stripping assembly  124  for processing one cassette  14  in the magazine  12  at a time. The stripping work station  102  may also have multiple stripping assemblies  124 , and if the number of stripping assemblies  124  is the same as the number of cassettes  14  in the magazine  12 , the fibers  18  can all be stripped at the same time. Otherwise, the stripping work station  102  may use multiple stripping assemblies  124  to strip multiple fibers  18  and then continues to the remaining fibers  18  until all the fibers  18  have been stripped. The stripping work station  102  may identically control the multiple stripping assemblies  124 , that is, each stripping assembly  124  strips the same length and location of fiber  18  in each cassette  14 . Alternatively, the stripping work station  102  may control each stripping assembly  124  independently to allow each assembly to strip each fiber  18  differently.  
         [0075]    [0075]FIG. 14 shows one embodiment of the stripping assembly  124  used by the stripping work station  102  to strip the fiber  18 . The stripping assembly  124  uses two blades  126  to strip the fiber  18 . The stripping assembly  124  may use plastic blades because they decrease the potential damage to the fiber  18  during stripping, or blades made of other materials my be used as well.  
         [0076]    [0076]FIG. 15 shows a three step process that the stripping assembly  124  may use to strip the fiber  18 . First, the stripping assembly  124  closes the blades  126  on the fiber  18  and moves the blades  126  along the path  128 . In the first step  128 , the stripping assembly  124  starts the blades  126  near the first edge  130 . During the first stripping step  128  the stripping assembly only traverses part of the length of fiber  18  to be stripped. The stripping assembly  124  then releases the blades  126  and rotates them  1800 .  
         [0077]    In the second step  132 , the stripping assembly  124  moves the stripping assembly  124  to position the blades  126  near the second edge  134 . The stripping assembly  124  closes the blades  126  to engage the fiber  18  and moves toward the first edge  130  along the fiber  18 . Again, the blades  126  do not begin stripping at the second edge  134 . The stripping assembly  124  continues the second step  132  until the blades  126  reach the desired location of the first edge  130 . The second step  132  leaves the fiber  18  cleanly stripped to the first edge  130 .  
         [0078]    In the third step  136 , the stripping assembly  124  rotates the blades  126  180° and strips the fiber  18  back towards the second edge  134  leaving the fiber  18  cleanly stripped to the second edge  134 . Alternatively, the stripping assembly  124  may strip the fiber  18  using only one or two stripping steps resulting in a first edge  130  and a second edge  134  that are not as clean as in the three step process.  
         [0079]    Returning to FIG. 13, the writing work station  104  writes the device  20  by using the interference pattern from two different ultraviolet light sources to change the structure of the fiber  18 . The writing work station  104  may have a gripper assembly  72  to set the tension of the fiber  18  because the tension on the fiber  18  during writing affects the characteristics of the resulting device  20 .  
         [0080]    The annealing work station  106  anneals the device  20 . Annealing involves heating the device  20  to high temperature, such as to stabilize the device  20 . Annealing is also known as accelerated aging. After a device  20  is annealed it may be measured, and if the device  20  is not within specification it can be further heated to bring the device  20  performance back into specification. This additional heating is known as trimming. The annealing work station  106  includes an annealing assembly  138  (see FIG. 16) to anneal the device  20 . The annealing work station may also include a tension assembly  70 . To measure the device  20 , the annealing work station  106  may have a heater and measurement ports  68 . The annealing work station  106  may have one or multiple annealing assemblies  138  for annealing devices  20 . If the annealing work station  106  has multiple annealing assemblies  138 , the annealing work station  106  operates the annealing assemblies  138  concurrently in order to increase the throughput of the annealing work station  106 . Each annealing assembly  138  may be independently controlled because each device  20  may have different annealing and trimming requirements.  
         [0081]    [0081]FIG. 16 illustrates an annealing assembly  138  found in an annealing work station  106 . The annealing assembly  138  includes an annealing block  140  that anneals the device  20 . The annealing assembly  138  may also include a heater to heat the device  20  during measurement.  
         [0082]    [0082]FIG. 17 shows a cross-sectional view of one embodiment of a heater  142 . The heater  142  may heat the device  20  directly or indirectly. For example, the heater  142  may heat a gas and then use the heated gas to heat the device  20 . That approach is advantageous because it allows more control over contaminants and impurities to which the device  20  is exposed. Nitrogen gas is particularly suitable because of its stability and low cost. In one embodiment, nitrogen gas enters the heater  142  at an inlet  144  near the bottom of the heater  142 . The nitrogen diffuses through a lower porous ceramic block  146  into a cavity  148  with a heater element  150 . The nitrogen flows through the cavity  148  and passes around the heater element  150 . The heater element  150  heats the nitrogen. The heated nitrogen then passes from the cavity  148  through an upper porous ceramic block  152  that reduces temperature gradients in the heated nitrogen. As the heated nitrogen diffuses out of the upper porous ceramic block  152 , it surrounds and heats the fiber  18  (not shown) situated between the heater heads  154 . The heater  142  may have thermo-couplers  156  that provide feedback to control the heater element  150 . Gases other than nitrogen may also be used with the heater  142 . Also, the ceramic blocks  146 ,  152  may be made of other materials that are porous and capable of withstanding the temperatures pr  
         [0083]    [0083]FIG. 18 shows an annealing block  140  according to the present invention. The annealing block  140  is similar to the heater  142 . However, the annealing block  140  may use a different heater element  150  to produce higher temperatures than required by the heater  90 . The annealing block  140  may also use different annealing heads  158 . The annealing heads  158  may vary in length or otherwise because it is sometimes desirable for the annealing heads  158  to be approximately the same length as the device  20  being annealed.  
         [0084]    The annealing block  140  may also include jets  160  to cool portions of the fiber  18  that are not to be annealed. Cooling of the fiber  18  can be important because the annealing process often exceeds 150° C. and can degrade the coating of the fiber  18  and cause other damage to fiber  18 . In the illustrated embodiment, jets  160  on each side of the annealing heads  158  blow a curtain of air  164  on and/or under the fiber  18  adjacent to the device  20  to protect the adjacent fiber  18  from the heat of annealing. It has been found that an effective way to cool the fiber  18  is to direct air under the fiber  18  in order to keep the hot air rising from the annealing block  140  away from the fiber  18 . The jets  160  may also cool the fiber  18  by directing air at the fiber  18  itself. The jets  160  may utilize nitrogen or other gases for cooling. Nitrogen is advantageous because of its stability and low cost, although other gases may also be used. The annealing block  140  may include interchangeable parts, such as the annealing heads  158  and jets  160 , which may be frequently changed to accommodate different devices  20 .  
         [0085]    [0085]FIG. 19 shows the temperature regions in the annealing block  140  around the device  20  and adjacent optical fiber  18 . A high temperature region  162  results from the flow of heated nitrogen and envelops the device  20 . The curtain of air  164  prevents the heated air from enveloping the coated portions of the optical fiber  18 , and thus limits the extent of the high temperature region  162 .  
         [0086]    The annealing work station  106  may use the following steps to anneal the device  20 . The annealing work station  106  accepts a magazine  12  containing cassettes  14 . The annealing work station  106  may first measure the device  20  prior to annealing, such as with a measurement heater  142 , gripping assembly  68 , and measurement ports  68  as previously described. If annealing work station  106  determines that the device  20  fails to meet the specification, the device  20  is failed and no further processing is done. If the device  20  meets the specification, the annealing work station  106  anneals the device  20  using an annealing block  140 . The annealing block  140  heats the device  20  to a specified temperature for a specific time. Typical annealing temperatures may be 250-400° C., and typical annealing times may be 5-15 minutes. The annealing work station  106  selects the time and temperature parameters based upon the type of fiber  18  used to manufacture the device  20  and the characteristics of the device  20  itself. Also, the annealing work station  106  may use a varying heat profile during annealing. For example, the annealing work station  106  may anneal the device  20  for 5 minutes at 300° C., then 5 minutes at 350° C., and finally 5 minutes at 400° C. If the annealing work station  106  measures the device  20  prior to annealing, the annealing work station  106  may adjust the annealing parameters based upon the measured characteristics of the device  20 .  
         [0087]    After the annealing, the annealing work station  106  may measure the device  20  characteristics, and if the device  20  is within specification, then the processing is complete, otherwise the device  20  may be trimmed. Trimming or heating and then cooling the device  20  can cause the reflection wavelength of a FBG or other devices  20  to shift downward. Therefore, if the measured wavelength is greater than the specified wavelength, the annealing work station  106  can tune the device  20  by trimming the device  20 . If the measured wavelength is less than the specified wavelength, then the device  20  is rejected, or the annealing work station  106  may further trim the device  20 , resulting in a device  20  meeting the specifications for a device  20  with a different reflection wavelength. After trimming, the annealing work station may measure the device  20  again. If the device  20  is within specification, the processing is complete; otherwise, the annealing work station  106  may perform additional trimming iterations until either the device  20  meets specification or until the annealing work station  106  completes a certain number of iterations.  
         [0088]    The recoating work station  108  recoats the device  20  after the annealing work station  106  anneals the device  20 . The recoating work station  108  places the device  20  in a mold and injects resin into the mold. The recoating work station  108  cures the resin. The recoating work station uses a recoating assembly  196  (see FIGS. 20 and 21) to recoat the device  20 . Also, the recoating work station  108  may have one or multiple recoating assemblies  166 . Multiple assemblies will allow for increased throughput by taking advantage of multiple cassettes  14  grouped in the magazine  12 . In addition, the recoating work station  108  may include a tension assembly  70  and may measure the device  20 .  
         [0089]    [0089]FIGS. 20 and 21 show a recoating assembly  196  that may be used with the recoating work station  108  to recoat fiber  18 . FIG. 20 shows the recoating assembly  196  in the “closed” position, as it would be when recoating fiber  18 . FIG. 21 shows the recoating assembly in the “open” position, as it would be when fiber was to be added or removed from the assembly. The recoating assembly  196  has upper molds  168  and a lower mold  170  which come together to form a mold cavity  172  (shown in FIG. 24) in which the recoating of fiber  18  occurs. The molds  168 ,  170  may be made of quartz, which is readily available, inexpensive, and easily machined. Other materials may be used as well, as long as they allow curing energy to reach the mold cavity  172  (see FIG. 24). Also, the recoating assembly  196  may have a fiber guide  174  to guide the fiber  18  (not shown) into the mold cavity for recoating. The recoating assembly  196  may also have energy sources  176  that produce energy that is coupled into the mold cavity to cure the recoating resin. The energy sources may be, for example, optical, RF, or thermal sources. The molds  168 ,  170  may include continuity channels  178  for checking that the mold cavity  172  has been properly formed.  
         [0090]    [0090]FIG. 22 shows a cross-sectional view of the recoating assembly  196  illustrating a resin injector  180  that opens into the mold cavity  172  and provides a coating resin that is used to recoat the fiber  18 . The resin injector  180  is shown as being integral with the lower mold  170 , although it may also be integrated into other molds or it may be oriented between molds  168 ,  170 .  
         [0091]    [0091]FIGS. 23 and 24 show cross-sectional views of one embodiment of the recoating assembly  196 , with the upper molds  168  and lower mold  170  in the open and closed positions, respectively. The recoating assembly  196  closes the upper molds  168  upon the lower mold  170  to form the mold cavity  172  (FIG. 24). Some or all of the molds  168 ,  170  may have freedom of movement beyond that which is required to close the molds  168 ,  170 . The additional freedom of movement allows the molds  168 ,  170  to self align themselves and better form the mold cavity  172 . Alternatively, the molds  168 ,  170  may not have this additional freedom of movement if the assembly  196  offers sufficient precision to properly form the mold cavity  172 . The resin injector  180  has an injector port  182  into the mold cavity  172  for injecting resin around the fiber  18  (not shown). The resin injector has a needle valve  184  to control the flow of resin into the mold cavity  172 . The needle valve  184  may only open when resin is injected into the mold cavity  172 . When the resin is cured, the needle valve  184  is closed, ensuring that the resin in the resin injector  180  and injector port  182  is not cured. The recoating assembly  196  has energy couplers  186  that couple energy from a energy sources  176  (shown in FIGS. 20 and 21) and direct it onto lower mirrors  188 . The lower mirrors  188  reflect the energy to upper mirrors  190  that reflect the energy towards the mold cavity  172 , where the energy cures the resin surrounding the device  20 . Also, energy may be delivered via alternate pathways, for example, direct lamps or fiber guides.  
         [0092]    [0092]FIGS. 25 and 26 show a cross-section view of the open and closed molds  168 ,  170 . The each of the molds has a continuity channel  178 . When the molds  168 ,  170  close properly, they align and seal the continuity channel  178 . Also, the molds  168 ,  170  may have additional continuity channels  178  to ensure proper alignment.  
         [0093]    In one embodiment, the recoating assembly  196  may operate as follows. A tension assembly  70  places the fiber  18  under tension. The recoating assembly  196  uses the fiber guides  174  to guide and align the fiber  18  into the lower mold  170 . The upper molds  168  close, forming the mold cavity  172  around the fiber  18 . The recoating work station  108  places the continuity channel  178  under pressure. If the pressure holds, the mold is properly sealed and recoating may begin. Otherwise, the mold may be opened and closed again or checked prior to recoating to ensure proper alignment. The self aligning features of the molds and the alignment check results in improved recoating of the device  20 . The resin injector  180  injects resin into the mold cavity  172 . The needle valve  184  closes the injector port  182  to prevent the curing of resin in the injector port  182 . The energy source  176  emits energy that is coupled and reflected to the resin filled mold cavity  172 . The energy cures the resin. Finally, the recoating assembly  196  opens the upper molds, releasing the recoated device  20 . Also, the intensity of the energy used to cure the resin may be varied during the curing process to decrease the shrinkage of the resin. For example, the intensity of the energy source  176  may be increased during the curing process.  
         [0094]    A packaging work station  110  packages the device  20  by attaching the fiber  18  to a package  194  (see FIGS. 27 and 28) with adhesive. A packaging fixture  192  (see FIGS. 27 and 28) hold packages  194  for processing by the packaging work station  110 . A device  20  may be packaged so that there is a predetermined tension on the device  20  because tension on a device  20  affects the device characteristics, such as shifts in the reflection wavelength of a FBG. Therefore, the packaging work station  110  may have to control the tension of the fiber  18 . The packaging work station  110  can use a tension assembly  70  as previously described. The packaging work station  110  may mount the gripper assembly  72  on a friction free air bearing  164  and may use servo control to set the tension to the desired value. The packaging work station  110  may also include an adhesive assembly  196  (see FIG. 30) that may apply and cure adhesive. The packaging work station  110  may have multiple tension assemblies  70  and adhesive assemblies  166  so that multiple devices  20  may be packaged concurrently.  
         [0095]    [0095]FIGS. 27 and 28 show the packaging fixture  192  for use in a packaging work station  110  for packaging devices  20 . The packaging fixture  192  provides a fixed alignment and location between a package  194  and the fiber  18 . The packaging fixture  192  has spring loaded retainers  198  that hold the package  194  in place against alignment wall  200 . Also, the packaging fixture  192  has alignment grooves  202  that guide the fiber  18  into a fixed location. The relative location of the alignment walls  200  and alignment groves  150  determine how accurately the fiber  18  is placed and aligned in the package  194 .  
         [0096]    [0096]FIG. 29 shows another view of the packaging fixture  192 . This view illustrates the alignment between the alignment groove  202  and the package  194  as it is held in place against the alignment walls  200  by the retainers  198 .  
         [0097]    [0097]FIG. 30 shows an adhesive assembly  196  that maybe used in a packaging work station  110 . The adhesive assembly  196  has an adhesive dispenser  204  that dispenses adhesive. Also, the adhesive assembly  196  has energy sources  206  that deliver energy to cure the adhesive. The energy sources  206  may use, for example, light energy, RF energy, or thermal energy to cure the adhesive depending on the type of adhesive used.  
         [0098]    The packaging workstation  110  may package a device  20  according to the following steps. First, an operator loads packages  194  into the packaging fixture  192 . The operator then places the loaded packaging fixture  192  and a magazine  12  containing cassettes  14  in the packaging work station  110 . The packaging work station  110  then places the fibers  18  in the fiber guides  150 . The fiber guides  150  align the fiber  18  within the package  194 . Often the device  20  is packaged so that the device  20  has a predetermined tension, because tension on the fiber  18  may affect device characteristics, such as, the shift of the reflection and/or transmission wavelengths in FBGs. The packaging work station  110  has the gripper assembly  72  grip the fiber  18  and adjust the tension to the predetermined value. In the case of adjusting the tension to zero, the tension can be set to within the control resolution of the packaging work station  110 , and to decrease the tension even closer to zero, the grippers  74  slightly release to relieve any residual tension in the fiber  18 , but the grippers  74  do not completely let go of the fiber  18 . Now, the device  20  may be attached to the package  194 .  
         [0099]    The packaging work station  110  moves the adhesive assembly  196  to the first attachment point, and the adhesive dispenser  204  places adhesive over the fiber  18 . The packaging work station  110  moves the adhesive assembly  196  a fixed distance from the adhesive and turns on the energy source  206  to cure the adhesive. Adhesive shrinkage typically increases the stress on the fiber  18 , and hence the tension on the device  20 . The packaging work station  110  may reduce adhesive shrinkage by varying the distance between the energy source  206  and the adhesive as a function of time. For example, the energy source  206  may first cure the adhesive for a fixed interval of time at a first distance. Then the packaging work station  110  moves the energy source  206  closer and cures for another interval of time. This can then be repeated for a number of steps. This curing process results in increasing energy intensity as the adhesive cures, which may reduce the shrinkage of the adhesive during curing. Next, the packaging work station  110  moves the adhesive assembly  196  to the other end of the package  194 , and the dispenser assembly again dispenses and cures adhesive. Alternatively, the adhesive assembly can also dispense adhesive at both ends of the package  194  and then use both energy sources  206  to cure both adhesives at once.  
         [0100]    If the packaging work station  110  has a measurement capability, then additional adjustment of the device  20  characteristics can be accomplished during packaging, because tension on the fiber  18  may affect the device  20  characteristics. For example, tension shifts the reflection and transmission wavelengths of a FBG. While the packaging work station  110  sets the tension of the fiber  18 , the packaging work station  110  may measure the device  20  characteristics. If the characteristics of the device  20  need to be adjusted, the packaging work station  110  determines an additional error signal that is used to adjust the tension of the device  20 , resulting in the desired characteristics.  
         [0101]    A measurement work station  112  provides the ability to measure the characteristics of the devices  20  at any point of the manufacturing process. Some work stations may have to measure the device  20  during processing, so those work stations should have a measurement capability. On the other hand, other work stations my not have to measure the device  20  during processing, so those work stations may not have a measurement capability. The measurement work station  112  may heat the device  20  to a known temperature and then measure the device  20  via the measurement ports  30  in the cassette  14 . Also, the measurement work station  112  may use a tension assembly  70  to place a known tension on the fiber  18  during the measurement.  
         [0102]    A baking oven  114  bakes the devices  20  after they are packaged. It is desirable to have the devices  20  baked in the cassettes  14  in order to minimize the handling of the fiber  18 . Typical baking temperatures are 70°-110° C., so the cassettes  14  should be made from materials that can withstand those temperatures if baking is required. After the fibers  18  are baked, the measurement work station  112  may measure the devices  20  to determine if the devices  20  are still with in specification.  
         [0103]    A manufacturing control system  120  (see FIG. 13) controls the overall manufacturing of the devices  20 . The manufacturing control  120  system may be implemented as software running on a computer system. The manufacturing control system  120  may also have a network  122  connecting the computer system to work stations to be controlled. The computer system may be a stand alone computer, or it may be distributed across computers found in each work station.  
         [0104]    A machine readable identifier may be affixed to each cassette  14  and magazine  12  that facilitates the control of the manufacturing process. The machine readable identifier could be, for example, a bar code, data matrix, or alphanumeric. The identifier allows for each device  20  to be tracked throughout the manufacturing process and for the collection and storage of information relating to the device  20 . The machine readable identifier also allows the manufacturing control system  120  to automatically convey the magazines  12  and cassettes  14  from work station to work station when the manufacturing process employs a conveyor system. The manufacturing control system  120  may use the conveyor system to control what work stations operate on a specific magazine  12  and cassette  14 .  
         [0105]    Each device  20  may be assigned a unique ID number. Further identifying information may include, for example, fiber type, fiber lot, device type, reflection wavelength, reflection bandwidth, pass band ripple, pass band roll off, and sidelobe level. This information may be captured in a device database. Each work station may determine the process parameters for each device based upon identifying information for the device  20 . These process parameters are included in a database as part of the manufacturing control process. Specifications for devices to be manufactured can be input into the database and used to derive the process parameters to manufacture the device.  
         [0106]    The work stations measure the devices  20  throughout the manufacturing process, and the manufacturing control system  120  captures that data in the device database. Also, the manufacturing control system  120  can analyze the measured data and modify existing process parameters. For example, different lots of the same fiber type may have a varying reflection wavelength versus temperature characteristic. Therefore, during annealing, the annealing work station  106  may compensate for these variations resulting in better reflection wavelength characteristics. In addition, the manufacturing control system  120  may contain process parameters that depend upon the specific work stations. For example, if there are multiple packaging work stations, each may use different parameters for adhesive curing based upon variations in the results obtained by the different work stations. The work station specific parameters may be stored in the manufacturing control system  120  or locally on the work station.  
         [0107]    During the manufacturing process, if a device  20  fails a test, the manufacturing control system  120  records information related to the failure. These failures can later be analyzed to identify problems in the manufacturing process. Also, the manufacturing control system  120  identifies the operator during the various manufacturing steps, so operator problems can be identified and corrected. During annealing if, for example, a FBG produces with a reflection wavelength that is outside of the specified value, the manufacturing control system can determine if the FBG now fits or can be made to fit the specification for another FBG type. This results in greater yields.  
         [0108]    The manufacturing control system  120  also allows the data collected to be viewed and analyzed in many different ways. For example, the manufacturing control system  120  may generate daily yields or device yields, daily throughput, or failure types. The manufacturing control system  120  may also perform statistical analysis of various device performance characteristics, for example, bandwidth, reflection wavelength, sidelobe levels, and pass band ripple. In addition, the manufacturing control system  120  allows an operator to determine where any given device  20  is in the manufacturing process.  
         [0109]    Many variations and modifications can be made to the present invention without departing from its scope. For example, all the work stations may operate on single cassettes  14  instead of a magazine  12 . It is also possible for some work stations to operate only on single cassettes  14 , while other work stations work on cassettes  14  loaded into magazines  12 . Also, portions of the manufacturing process may be partially automated by using a mechanical assist to carry out manual operations. Many other variations, modifications, and combinations are taught and suggested by the present invention, and it is intended that the foregoing specification and the following claims cover such variations, modifications, and combinations.