Abstract:
A method is disclosed for applying glue to a fiber optic coupler composed of a plurality of contiguously extending optical fibers, the fibers extending though the bore of a tube and through a longitudinally adjacent coupling region where the tube is collapsed around the fibers, the fibers being fused together in the coupling region, the diameters of the fibers in the coupling region being smaller than the diameters thereof in the bore. The method comprises: holding the coupler, and simultaneously injecting glue into both ends of the tube bore; wherein the coupler is oriented vertically, the glue being injected into the bore ends by positioning a hollow needle at each of the bore ends, the glue flowing through the needle in the bore at the top end of the tube at a rate greater than it flows through the needle in the bore at the bottom end of the tube.

Description:
This is a division of application Ser. No. 09/043,758, filed Mar. 25, 1998, now U.S. Pat. No. 6,092,394, which was the National Stage of Application No. PCT/US96/15254, filed Sep. 16, 1996 and claims the benefit of U.S. Provisional Application No. 60/004,647, filed Sep. 29, 1995. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to the automated manufacturing of fiber optic couplers. 
     Overclad fiber optic couplers are a type of fused fiber coupler wherein the coupling region is enclosed within a layer of matrix glass which strengthens and encloses the coupling region. To form an overclad fiber optic coupler, the stripped portions of a plurality.of fibers are inserted into the bore of a glass capillary tube to form a coupler preform. The tube bore has enlarged funnel-shaped end portions that facilitate the insertion of optical fibers. The midregion of the coupler preform is heated to collapse the tube onto the fibers; the coupler preform is then stretched until the desired coupling characteristics are obtained. Various types of overclad fiber optic couplers and methods of making such couplers are disclosed in U.S. Pat. No. Re 35,138, U.S. Pat. Nos. 4,902,324, 4,979,972, 5,011,251, 5,251,276 and 5,268,014. The methods disclosed in these patents include many manual operations. 
     In accordance with conventional practice, the manually operated fiber draw apparatus has been oriented such that the tube is vertically positioned. The fibers have been inserted into the tube either on-line or off-line. The off-line fiber insertion process (U.S. Pat. No. 4,902,324) requires that the fibers be tacked to the tube to prevent the fibers from moving with respect to the tube during the step of transferring the coupler preform to the coupler draw apparatus. The tacking glue can cause problems in the resultant coupler. Moreover, the off-line method requires additional steps to transfer the tube to the draw apparatus. The previously employed methods of inserting fibers into the tube either on-line or off-line have been tedious, time consuming processes that are sensitive to the manipulations of each operator. This can affect process reproducibility and thus the optical characteristics of the couplers. 
     Optical fibers must be prepared prior to inserting them into the tube. The protective coating is removed from the portion of the fiber that is to be positioned within the tube during the coupler drawing operation. If the bare portion of the optical fiber is at the end of the fiber, it is preferred that it be provided with a low reflectance termination. An off-line process for forming such a termination is disclosed in U.S. Pat. Nos. 4,979,972 and 5,011,251. Also, the bare fiber portions must be free from contamination. Manual performance of these fiber preparation steps is time consuming and is subject to the particular manipulations of the operator. 
     During the stripping of coating from the fibers, the termination of fibers, and the insertion of the stripped portions of fibers in the overclad tube, the fibers must be precisely positioned. 
     In the manual technique for making overclad fiber optic couplers, the fibers were threaded through the glass tube, the tube was clamped into the draw apparatus. Thereafter, the fiber pigtails extending from the glass tube were inserted through vacuum attachments which were then affixed to the ends of the tubes. Such vacuum attachments are unsuitable for an automated apparatus for manufacturing fiber optic couplers. A preferred heat source for forming overclad fiber optic couplers has been a ring burner that directs flames inwardly toward the glass tube. Heretofore, the glass tube has been manually inserted through the ring burner, and its ends were then clamped. Such a burner is not suitable for use in a fully automated apparatus. 
     In an automated fiber optic coupler manufacturing process, couplers can be made at a greater rate than they could be made by the aforementioned manual process. The heat source must be activated during the stretching of each coupler. This tends to cause the temperature of certain parts of the apparatus near the heat source to become hotter than they did in the manual process. Some of those apparatus parts and the coupler epoxy can be damaged by the higher temperature or can be dimensionally altered whereby process reproducibility is affected. Precautions must be taken to avoid such heat induced damage. 
     After the coupler has been formed by stretching the overclad tube and fibers, a glue such as an ultraviolet (UV) curable epoxy is inserted into the uncollapsed ends of the tube bore to provide the fibers with pull strength. Conventional off-line epoxy applying and curing techniques are not suitable for use in a fully automated coupler making process since they do not result in the application of a sufficient amount of epoxy into both ends of the bore, and since they are time consuming processes. 
     SUMMARY OF THE INVENTION 
     In view of the above mentioned disadvantages of conventional methods of manufacturing fiber optic couplers, it is an object of the present invention to provide an apparatus and method of precisely and automatically manufacturing a fiber optic coupler having predetermined coupling characteristics. Another object is to provide a coupler manufacturing apparatus and method in which opportunities for operator caused process inconsistencies are minimized or eliminated. 
     The present invention-relates to various apparatus components and method steps for making fiber optic couplers. Utilization of the invention in its entirety results in the completely automated production of a fiber optic coupler. However, portions of the inventive method and apparatus can be used to improve conventional methods of the type described above. Whereas the present invention is described in conjunction with the manufacture of overclad fiber optic couplers, certain of the apparatus components can be employed in the manufacture of fused biconic tapered couplers of the type wherein two or more fibers are fused together and elongated, without the use of an outer protective glass tube. 
     The present invention relates to an apparatus for the automated manufacture of fiber optic couplers. Fiber insertion means including adjacently disposed fiber guide tubes insert optical fibers into a glass tube. The fiber guide tubes have fiber input and fiber output ends, the output ends being movable longitudinally with respect to the bore of the glass tube. Means is provided for delivering the optical fibers to the input ends of the fiber guide tubes, with the first ends of the fibers passing through the fiber guide tubes and being deliverable from and retractable into the second ends of the guide tubes. Means is provided for sequentially tensioning each of the optical fibers and for stripping protective coating from the tensioned length of each of the fibers. The apparatus includes coupler draw means that is provided with upper and lower chucks for securing the glass tube at its end regions. The chucks are movable in opposite directions. First and second vacuum seal means evacuate the bore and maintain closed the ends of the glass tube after the stripped regions of the fibers have been inserted into the bore. Heating means heats the glass tube. Programmable control means control the operation of the apparatus. 
     The coupler draw means can include an upper clamping bar that engages an upper V-groove provided in the upper chuck and a lower clamping bar that engages a lower V-groove provided in the lower chuck; the clamping bars apply a repeatable level of force to the glass tube to secure it in the v-grooves. 
     The apparatus can include transfer means for transfering a glass tube from a storage magazine to the chucks. This apparatus can include a holding member provided with a groove, delivery means for delivering a tube from the magazine to the groove, and clamping means for gripping a tube. Means can be included for accurately locating the glass tube in the groove. When it is in a first position, the clamping means engages the glass tube held in the groove. The clamping means then moves to a second position and places the glass tube in the chucks of the coupler draw means. 
     The means for delivering the optical fibers to the fiber insertion means can include at least two optical fiber supplies, and a fiber feed mechanism for paying out a predetermined length of each of the optical fibers from the sources to the fiber insertion means. The programmable control means controls the fiber delivering means, whereby it measures the optical fibers to the predetermined lengths. That is, precise amounts of fiber are advanced from or retracted into the fiber delivering means. 
     The fiber feed mechanism can include input guide tubes for receiving the optical fibers from the reels, and output guide tubes that are connected to the fiber guide tubes of the fiber insertion means. A fiber extending between the input and output guide tubes is disposed between an idler roller and a motor driven roller. When the idler roller engages the motor driven roller, the fiber is delivered to or retracted from the output guide tube. Fittings are connected to the output guide tubes for introducing a gas therein for reducing friction between the fiber guide tubes and the optical fibers. 
     A lubricant dispensing tube can be disposed adjacent the fiber feed tubes and extend a distance beyond the ends of the feed tubes to lubricate the bore of the glass tube as the optical fibers are inserted therethrough. 
     The means for sequentially tensioning each of the optical fibers can include an upper and a lower stripping clamp between which a length of each of the optical fibers is sequentially clamped and tensioned, and the means for stripping the protective coating from the optical fibers can include a stripping nozzle movable transversely and rotatably with respect to the length of optical fiber that is tensioned between the stripping clamps. The stripping nozzle emits a jet of hot inert gas to strip the protective coating away from the length of fiber as the nozzle moves along the coated fiber. 
     The apparatus can include means for providing a low reflectance termination on an optical fiber. A ball termination torch is vertically and horizontally movable with respect to the optical fibers tensioned between the stripping clamps. After the torch severs the fiber, the strippingclamps retracting in opposite directions. 
     Bottom clamp means can be provided for clamping one or more of the optical fibers that extend from that end of the glass tube remote from the fiber insertion means. 
     The heating means is preferably located away from the chucks. After the stripped portions of the fibers are positioned in the tube bore, the heating means moves to a position adjacent the chucks. The heating means can be formed of two sections that close and surround the glass tube. 
     The upper and lower chucks partially shield the glass tube from the heating means, and in addition, the chucks are maintained at a controlled temperature by water-cooling to enhance process reproducibility. 
     After the midregion of the glass tube has been heated, the chucks are moved in opposite directions to stretch the tube. The means for delivering fibers and the upper chucks are preferably mounted on a first movable stage, and the lower chucks and the bottom clamp are preferably mounted on a second movable stage, whereby the means for delivering fibers and the bottom clamp move in opposite directions as the tube is stretched. 
     The apparatus can include dispensing means for dispensing glue into the bore of the glass tube, after a coupler has been formed and means for curing the glue after the glue has been dispensed into the bore. The means for curing the glue can comprise a UV light source sequentially positioned at each of the ends of the glass tube. 
     A further embodiment includes first and second fiber insertion means, each capable of inserting at least two optical fibers into a glass tube. The first and second fiber insertion means are each-provided with at least two adjacent fiber guide tubes that are movable longitudinally with respect to the tube bore. Means are provided for moving the first and second fiber insertion means laterally with respect to the bore. This apparatus is especially useful when used in conjunction with first and second means for forming stripped regions in each of the optical fibers. The first fiber insertion means can be disposed adjacent the glass tube when the second fiber insertion means is disposed adjacent the second means for forming stripped regions. 
     Yet another embodiment pertains to an apparatus for modifying an optical fiber. It includes means for delivering an optical fiber to a fiber guide tube such that the fiber can move out of and into the fiber guide tube. Means is provided for moving the fiber guide tube from one to another of a plurality of work stations. This apparatus can include means for moving the fiber guide tube toward and away from the first work station. 
     The invention also pertains to a method of automatically manufacturing a fiber optic coupler. A glass tube is placed into a coupler draw means where its end regions are gripped by upper and lower chucks. At least two optical fibers are delivered to a fiber insertion means. While a length of each of the optical fibers is tensioned between upper and lower stripping clamps, protective coating is stripped from each of the optical fibers, and the fibers are then inserted through the glass tube such that the stripped regions extend within the bore. The ends of the glass tube are evacuated, and the tube is heated. The end regions of the glass tube are drawn in opposite directions to form a tapered coupling region. The steps of the method are controlled by programmable control means. 
     The glass tube can be gripped in the coupler draw means by securing one of the tube end regions between an upper chuck V-groove and upper clamping bar, and securing the other end region between a lower chuck V-groove and a lower clamping bar, the upper and lower clamping bars applying a force to the glass tube to secure the glass tube in the upper and lower V-grooves. The upper and lower chucks can be maintained at a controlled temperature to improve process reproducibility. 
     The glass tube can be placed into the coupler draw means by automatically transferring the glass tube from a glass tube storage magazine to the draw means. 
     The optical fibers can be delivered to the fiber insertion means by paying out each of the optical fibers from fiber sources to fiber guide tubes of the fiber insertion means. The fiber guide tubes can move longitudinally with respect to the bore of the glass tube. A gas can be introduced into the fiber guide tubes to reduce friction between the fibers and the tubes and to remove debris from the fibers entering the guide tubes. 
     A stripped region can be formed on a fiber by positioning the fiber guide tubes above a lower stripping clamp, and delivering a length of an optical fiber is delivered through one of the fiber guide tubes to the lower stripping clamp which grips the fiber at a first location. The guide tubes are moved upwardly so that the upper stripping clamp can grip the fiber at a second location. The fiber is then tensioned between the first and second locations. A jet of hot inert gas is directed onto a predetermined region of the tensioned fiber to heat it and strip coating therefrom. 
     A low reflectance termination can be provided on an optical fiber prior to inserting it through the glass tube. The fiber is tensioned between two spaced points. A ball termination torch is moved from a given location in a given direction with respect to the optical fiber such that a portion of the flame severs the fiber into two pieces each having a tapered end. At least one of the tapered ends is retracted away from the other of the tapered ends. The torch continues to move such that the flame heats the retracted tapered end to cause it to become shortened-and rounded. 
     A lubricant is preferably dispensed into the glass tube when the optical fibers are inserted therethrough. This can be done by disposing a dispensing tube adjacent the fiber guide tubes, and dispensing the lubricant therefrom. 
     The method can further include dispensing glue into the uncollapsed ends of the bore of the glass tube after the tapered coupling region has been formed. The glue can initially be cured by directing UV light beams at each of the end regions of the glass tube while the glue is being applied to the ends of the bore, the flow of the glue stopping when it contacts the light beams. The glue can be further cured by sequentially positioning a UV light source at each of the end regions of the glass tube after the glue has been dispensed into the bore. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIGS. 1 and 2 schematically illustrate an automated fiber optic coupler manufacturing apparatus. 
     FIG. 3 illustrates the spacial relationship between FIGS. 4 through 7. 
     FIGS. 4 and 5 are front views of the top and bottom portion of the automated fiber optic coupler manufacturing apparatus. 
     FIGS. 6 and 7 are enlarged views of the upper right portion and the central portion of the automated fiber optic coupler manufacturing apparatus. 
     FIG. 8 illustrates a capillary tube transfer aparatus. 
     FIG. 9 is a cross-sectional view of the capillary tube magazine. 
     FIG. 10 schematically illustrates the tube positioning apparatus. 
     FIGS. 11 a  and  11   b  are side and top views, respectively, of the capillary tube retaining chucks. 
     FIG. 12 is a schematic oblique view of the capillary tube retaining chucks and the vacuum seals. 
     FIG. 13 is an end view of the retaining tube. 
     FIG. 14 is a cross-sectional view taken along lines  14 — 14  of FIG.  13 . 
     FIG. 15 a  is an end view in partial cross-sectional view of a fiber feed apparatus. 
     FIG. 15 b  is a cross-sectional view taken along lines  15   b — 15   b  of FIG. 15 a.    
     FIG. 16 is a cross-sectional view of an idler roller used in FIGS. 15 a  and  15   b.    
     FIG. 17 is a side view of a pair of fiber tensioning clamps used in the fiber stripping, severing and end terminating operations. 
     FIGS. 18 a  and  18   b  are top views of the fiber tensioning clamps. 
     FIG. 19 illustrates the stripping nozzle positioning apparatus. 
     FIG. 20 schematically illustrates the operation of the coating stripping nozzle. 
     FIG. 21 is an oblique view of the apparatus that positions the fiber end termination torch. 
     FIGS. 22,  23 ,  24  and  25  schematically illustrate the operation of the fiber end termination torch. 
     FIG. 26 is a front view of the vacuum seals. 
     FIG. 27 is a top view of the vacuum seals. 
     FIG. 28 is a cross-sectional view taken along lines  28 — 28  of FIG. 26 showing the left upper vacuum seal. 
     FIG. 29 is a side view showing the relationship between the tube retaining chuck and the upper right vacuum seal. 
     FIGS. 30 and 31 show side and top views, respectively, of the coupler draw apparatus burner. 
     FIG. 32 shows a view taken along lines  32 — 32  of FIG.  31 . 
     FIGS. 33 and 34 are.side and front views, respectively, of the epoxy application apparatus. 
     FIG. 35 is an oblique view showing the UV light source positioning apparatus. 
     FIG. 36 is a cross-sectional view of tube  12 ′ as it appears in the coupler draw apparatus. 
     FIG. 37 is a partial cross-sectional view of a coupler during application of epoxy to its ends. 
     FIGS. 38 and 39 illustrate guide tube arrangements for supplying six-around-one and eight-around-one fiber configurations. 
     FIG. 40 schematically shows a coupler manufacturing apparatus employing two stripping and terminating stations. 
     FIG. 41 schematically shows an apparatus for positioning an optical fiber at a plurality of work stations. 
    
    
     DETAILED DESCRIPTION 
     Overview of Invention 
     A brief overview of the method and apparatus of the invention will be given by referring to FIGS. 1 and 2 which schematically illustrate an automated fiber optic coupler manufacturing apparatus  10 . In connection with this description, as well as the following more detailed description, steps are described for making a 1×2 overclad fiber optic coupler. All references to x, y and z directions refer to the axes that are illustrated in various figures including FIG.  2 . 
     (1) Tube transfer apparatus  11  including a tube gripper  14  delivers a glass capillary tube  12  from a storage magazine  13  to coupler draw apparatus  63  where its end regions are secured by upper and lower chucks  64  and  65 , respectively. The chucked tube is designated  12 ′. 
     (2) Fibers  16  and  17  are delivered from reels  18  and  19 , respectively, by fiber feed apparatus  23  to fiber insertion fixture  50 . 
     (3) The fibers are sequentially fed from the fiber insertion fixture to a strip/terminate apparatus  56  where the fibers are sequentially secured within clamps  57  and  58  so that a section of coated fiber is tensioned between the two clamps. 
     (4) Stripping nozzle  59  emits a jet of hot inert gas that traverses a region of coated fiber to strip coating therefrom. 
     (5) When appropriate, end termination torch  60  severs the bare fiber that extends between clamps  57  and  58  and forms a low reflectance termination on one or both of the bare severed fiber ends. 
     (6) The fibers are inserted into the tube  12 ′ so that the bare portions of the fibers extend within the bore of the tube. Valve  43  is actuated to dispense drops of alcohol from source  42  through dispensing tube  44  to the upper end of tube  12 ′ to lubricate the bore as the fibers pass therethrough. Bottom clamps  69  are employed to pull and hold taut one or more of the fibers extending from the bottom end of tube  12 ′ while they are being fed to the upper end thereof. 
     (7) The end of one or more fibers that extend through tube  12 ′ are affixed to one or more optical fibers  47  which are connected to one or more light sources in measurement system  46 . 
     (8) Bottom vacuum seals  67  are closed onto the bottom end of tube  12 ′ to withdraw alcohol from the bore. 
     (9) Top vacuum seals  66  are closed on the top end of tube  12 ′ and the bore of tube  12 ′ is evacuated. 
     (10) Split burner  68  is ignited and closes around tube  12 ′ to heat its mid-region. 
     (11) Top and bottom chucks  64  and  65 , respectively, are traversed in opposite directions to stretch tube  12 ′ and form a tapered coupling region. 
     (12) Vacuum seals  66  and  67  are opened. 
     (13) Light beams from upper and lower epoxy locating UV light sources (FIGS. 12 and 37) are directed toward the upper and lower ends of stretched tube  12 ′. 
     (14) Epoxy dispensing apparatus  72  moves to draw apparatus  63 , and epoxy dispensers  73  and  74  are positioned at the top and bottom funnels of tube  12 ′. Epoxy is dispensed through needles into the funnels. As epoxy flows into the uncollapsed ends of the tube bore, the epoxy locating UV beams cure and prevent penetration of epoxy into the bore beyond a predetermined depth. 
     (15) The epoxy dispensing apparatus is withdrawn, and UV light apparatus  70  is sequentially positioned adjacent the top and bottom ends of the newly formed coupler to cure the epoxy. The epoxy locating Uw beams remain energized. 
     (16) The coupler body is released from the draw chucks. The fiber pigtails at the top of the coupler are metered to the desired length and are severed, whereby the coupler can be removed from the automated manufacturing apparatus. 
     Various components of apparatus  10  such as the motors, gas operated cylinders, clamping devices and mass flow controllers for methane and oxygen are controlled by programmable controller  79 . 
     Description of Components 
     All of the components of manufacturing apparatus  10  are secured either directly or by way of supports, brackets and the like to backplate  200 . Not all supports are shown. The orientation of elements with respect to backplate  200  is sometimes given relative to an x-axis, a y-axis or a z-axis. Backplate  200  lies in the x-y plane. Movement of an element in the +z direction means movement away from backplate  200  (out of the sheet of FIGS.  4  and  5 ). 
     FIGS. 8-10 show the tube transfer apparatus  11  in greater detail. A slotted cylinder  84  is rotated  180 E and then back again by a double piston rotary cylinder (not shown). This type of cylinder consists of two pistons that provide linear motion that is converted to rotary motion through a rack and pinion gear device. Capillary tubes  12  are stored in a magazine  13  and are gravity fed to a transfer position (the bottom of the stack of stored tubes) where they fall into slot  83 . Magazine  13  sits in dispensing mechanism  82  which houses cylinder  84 . When cylinder  84  rotates, a single tube is transferred to pick-up position  85  in spaced V-groove members  86 . A cylinder  87  is actuated to cause piston  88  to position one end of tube  12  against stop  89  to precisely locate the tube. The location of stop  89  can be adjusted to accomodate different tube lengths. 
     Mechanism  82  is mounted on stage  101  that can be vertically reciprocated on slide  102  by actuating cylinder  103 . Clamping device  93  is mounted on a stage  94  that can be reciprocated back and forth on slide  95  by actuating cylinder  96 . Clamps  92  are biased open by a spring and are closed by actuating a double piston (pancake) cylinder located within mechanism  93 . 
     Cylinder  96  is actuated to position clamps  92  around the tube that is located in the pickup position in groove members  86 . Mechanism  93  is actuated to cause clamps  92  to engage tube  12 , and cylinder  103  is then actuated to cause the Vgroove member  86  to be translated downwardly. Cylinder  96  is then actuated to retract the clamps away from the magazine. 
     Clamp slide  95  is mounted on an arm  107  that is rotatably connected to support bracket  108  by double piston rotary cylinder mechanism  106 . When mechanism  106  is actuated, arm  107  rotates about  90   E  and positions clamp mechanism  93  in alignment with the coupler draw apparatus  63  where the tube in clamps  92  is directly in front of the V-grooves of chucks  64  and  65 . 
     Various modifications could be made to the disclosed dispensing mechanism. The tubes would not need to be gravity fed if means such as a spring were employed to supply them to cylinder  84 . Moreover, cylinder  84  could be replaced by a wheel having a plurality of slots. A glass tube from the supply-of tubes would enter a slot of the slotted wheel and be rotated until it reached an orientation at which the tube would fall from the slot into grooves  86 . Cylinder  84  could also be replaced by a pair of sequentially operated gates that are capable of preventing movent of the first two tubes in the linear supply of tubes. A first gate holding the last tube would retract so that the last tube could roll to grooved member, while the next to last tube is held by a second gate to prevent the remaining tubes from also rolling to the grooved member. The first gate then moves into position while the second gate retracts to permit the supply of tubes to roll to the first gate. 
     Chucks  64  and  65  are shown in FIGS. 11 a,    11   b,    12  and  29 . None of the support members are shown in the schematic view of FIG.  12 . The chucks include a mounting plate  110  and a V-groove plate  111 . Through a series of support members (also see FIGS. 27 and 28) the mounting plates  110  of upper and lower draw chucks  64  and  65 , respectively, are affixed to vertically movable upper and lower draw stages  299  and  300 , respectively (see FIGS.  4  and  5 ). All of the elements within the upper brackets of FIG. 12 are connected to upper movable stage  299  by support member  283 , and all of the elements within the lower brackets are connected to lower movable stage  300  by support member  284 . Tube clamping bar  113  is pivotally mounted in a recessed region adjacent plate  111  by a bolt  114  that threads into bore  112 . Rod  116  of cylinder  117  is pivotally attached to bar  113 . 
     After cylinder  96  (FIG. 8) has been actuated to position the tube (now designated  12 ′) in the Vgrooves of the chucks  64  and  65 , cylinders  117  are actuated to cause bars  113  secure the tube in the grooves. 
     Since the tube had been-precisely positioned in groove member  86  of the tube transfer apparatus, the ends of the tube are vertically positioned to within about 0.1 mm of the desired location in the coupler draw apparatus so that operations such as epoxy application can be properly performed. Properly positioning the tube also ensures that the coating edge of the stripped fiber will be positioned the proper depth in the tube funnel so that epoxy can be properly introduced into the funnel and bore of the tube. 
     The chucks are designed to achieve the automated loading of the capillary tube while also enabling a repeatable load level to be applied by bar  113  to the tube since bar  113  is actuated by air cylinder  117 . The force applied by bar  113  to the tube can be controlled by regulating the air pressure applied to that cylinder. 
     The chucks partially shield the vacuum seals from the high temperature flame. When the vacuum seals are closed, the elastomeric seals  288  are shielded from the flame by the chucks. The water cooling of the chucks allows the coupler draw process to have a relatively short cycle time since the chucks would otherwise become so hot after a few couplers had been made that process consistency could not be maintained. The coolant water, which is pumped from a temperature controlled reservoir, maintains correct temperature regardless of timing differences between runs. Deviation of chuck temperature from a given temperature range affects the optical properties of the resultant coupler. 
     Apparatus for delivering fibers is shown in FIGS. 1,  2 ,  15   a,    15   b  and  16 . Fiber reels  18  and  19  are non-rotatably mounted and are so positioned with respect to feed apparatus  23  that fibers  16  and  17 , respectively, that are coiled thereon, pay out to the fiber feed apparatus. The ends of fibers  16  and  17  opposite those ends that are delivered to fiber insertion fixture  50  constitute measurement pigtails  20  and  21 , respectively, which are connected to detectors in measurement system  46 . This arrangement is made possible since the reels are restrained from rotating. Management of the fibers extending between reels  18  and  19  can be facilitated by positioning guide funnels  15  between the reels and the fiber feed apparatus. The large ends of the funnels are positioned adjacent the spools. Optionally located in the small ends of the funnels are sponges  22  that are slitted or folded over to encompass the fiber that passes therethrough. The sponges, which are wetted with alcohol, wipe dust and debris from the fibers. Neither the funnels nor the sponges are needed for proper operation of the apparatus. A commercially available air deionizer  33  removes static electricity from the fibers. Such air deionizers can be positioned at various locations on the apparatus to blow deionized air onto the fibers. 
     If rotatable fiber reels were employed, measurement pigtails  20  and  21  could be connected to measurement system  46  by rotatable connectors. Moreover, the fibers need not be stored on reels. Rather, they could be merely coiled or be stored in boxes. 
     The cross-hatched portions of FIGS. 15 a,    15   b  (except for the roller assemblies) are aluminum plates that are fixedly located in the apparatus. Roller  24  is rotated by reversible stepping motor  25 . Located adjacent roller  24  are idler rollers  26 ,  27  and  122  which are actuated by gas operated cyclinders  28 ,  29  and  121 . Roller  24  is provided with a rubber sleeve  119 , and the idler rollers are provided with rubber sleeves  120 . Cylinders  28 ,  29  and  121  normally receive a compressed gas input that biases rollers  26 ,  27  and  122  such that they are spaced from roller  24 . Means such as a spring could also be employed to perform this biasing function. Whereas only the two idler rollers  26  and  27  shown in FIG. 2 are needed to form a 1×2 coupler, the device of FIG. 15 b  also includes two additional idler rollers  122  and their actuating cylinders  121 . To supply more than four optical fibers, apparatus  23  could be provided with additional idler rollers. Alternatively, in addition to apparatus  23 , another fiber feed apparatus similar to apparatus  23  could be employed in manufacturing apparatus  10 . To feed ten fibers, for example, apparatus  10  could employ two fiber feed apparatuses, each feeding five fibers. 
     Cylinders  28 ,  29  and  121  are affixed to roller mounting plates  123  that are attached to movable stages  125  of ball slides. The fixed stages  124  of those ball slides are attached to aluminum plates within the housing. The piston rods are threaded in nuts that are located within fixed yokes. Cylinder  31  is a pancake cylinder from which extend two posts  127  that thread into the metallic block of the clamp  30  which is provided with a synthetic rubber layer  128 . Bar  32  is also provided with a synthetic rubber layer  129 . 
     The ball slides described herein, which were made by Daedal, Inc., Harrison City, Pa., include a stage having a U-shape cross-section and a ball slide positioned within the stage. Ball bearings, which are situtated in spaced openings in (racks) that separate the stage and slide, traverse along (tracks) in both the stage and the ball slide. 
     To feed optical fiber into fiber feed apparatus  23 , the idler rollers and clamps  30  are retracted. The fiber is fed through an input guide tube  132 , over the respective idler roller and into output guide tube  133  which is connected to T-fitting  39 . Output guide tubes  133  are supported by brackets  131  that are positioned by spacers  130 . A sufficient length of fiber is fed into the guide tubes to enable it to extend from the ends of the guide tubes at insertion apparatus  50 . Clamps  30  are then closed. The protruding fibers can be cut by a mechanism (not shown) in apparatus  10 , or they can be manually severed by bending them sharply at the point where they extend from their respective guide tube. The ends of the guide tubes are sufficiently sharp that the fibers become severed at the ends of those tubes. This is the starting position for the coupler making process. 
     T-fittings  38  and  39 , located near the input ends  40  and  41  of the guide tubes, introduce a gas such as nitrogen, air or the like into those tubes. Gas flowing from the input ends  40  and  41  blows dust and debris from the fibers before they enter the tubes. Gas flowing through the guide tubes to the ends thereof at fiber insertion fixture  50  lowers the friction between the guide tubes and the fibers. 
     Motor  25  could be a d.c. servo motor or any other motor that can accurately rotate roller  24  and thus accurately position the fibers. Moreover, clamps  30  could be eliminated if a separate motor were employed for each set of rollers. 
     Fiber insertion apparatus  50  (FIGS. 2 and 4) is affixed to one end of a support arm  55 , the other end of which is connected to a stage  52  which is vertically movable along track  54  as indicated by the arrow. Apparatus  50  includes a retaining tube  51  in which are disposed fiber guide tubes  35  and  36  and alcohol dispensing tube  44 . Tubes  35 ,  36  and  44  are secured to the end of tube  51  by epoxy  45  (FIG.  13 ). Tube  51  was formed of 0.343 cm inside diameter, 0.419 cm outside diameter, 8 gauge 304 stainless steel tubing. For delivering optical fibers having 250 μm outside diameter coating, tubes  35  and  36  were formed of 0.043 cm inside diameter, 0.064 cm outside diameter, 23 gauge 304 stainless steel tubing. 
     Retaining tube  51  and fitting  49  are employed so that tubes  35 ,  36  and  44  can easily be positioned relative to one another. However, retaining tube  51  and fitting  49  can be eliminated by merely gluing tubes  35 ,  36  and  44  together into a triangular array as shown in FIG.  13 . The assembly of tubes can in turn be affixed to support arm  55 . 
     As shown in FIGS. 13 and 14, the end of retaining tube  51  fits over the smaller diameter portion of a brass fitting  49  and butts against the shoulder of the larger diameter end portion. Fitting  49  has a precision bore the diameter of which is just large enough to receive tubes  35 ,  36  and  44 . Guide tubes  35  and  36  protrude a short distance from fitting  49 . A drop  140  of alcohol is shown extending from dispensing tube 44 which protrudes farther than guide tubes  35  and  36  to prevent dispensed alcohol from flowing into the guide tubes. 
     Strip/terminate apparatus  56  is shown in greater detail in FIGS. 17,  18   a  and  18   b.  The apparatus includes two air operated cam-action grippers  151  and  152  which consisted of Sommer ultramatic cam-action grippers Model No. GP-19. Each gripper consists of an actuator mechanism  153  that causes appropriate movement of laterally movable members  154  along cylinders  155 . Affixed to members  154  are L-shaped members  156  to which a fiber gripping elastomeric layer  157  has been applied. 
     Base plate  160  is mounted on stage  161  which is movable along slide  162  which is secured to vertical support plate  163 . Gas operated cylinder  181  is mounted on stage  161 . Piston  182  of cylinder  181  is threaded into plate  163 . 
     Mounted on base plate  160  are linear slides  165  and  166  on which mounting brackets  167  and  168  are movably mounted. The extent of movement of the mounting brackets  167  and  168  is restricted by adjustable screw stops  169 . Four Clippard gas operated pistons (model No. SM-3)  171 - 174  are mounted to brackets on base plate  160 . Pistons  175  and  176  are adapted to engage tab  179  protruding from stage  167 , and pistons  177  and  178  engage tab  180  protruding from stage  168 . 
     Stage  161  is normally retracted against support plate  163 . cylinder  181  is actuated to move stage  161  away from plate  163  to a position along the z-axis where fiber  17  (extending from guide tube  36 ) extends between clamps  156  (clamps  57  and  58  of FIG.  2 ). Mechanisms  154  are actuated to cause clamps  57  and  58  to close on the fiber. Gas operated pistons  172  and  173  are actuated whereby pistons  176  and  177  engage tabs  179  and  180 , respectively. This applies forces to the tabs that tend to move stages  167  and  168  in opposite directions, whereby coated fiber  17  is tensioned between clamps  57  and  58 . 
     The apparatus for positioning stripping nozzle  59  is shown in FIG.  19 . Stripping nozzle  59  is rotatably connected to support bracket  190  by double piston rotary cylinder mechanism  191 . Support member  190  is affixed to the rotatable stage  193  of rotating mechanism  194  that is controlled by motor  195 . Mechanism  194  is supported by an arm  196  that is affixed to stage  197  that is movable vertically along track  198  when motor  199  is energized. 
     When mechanism  191  is actuated by pistons  192 , stripping nozzle  59  rotates to the horizontal position. Actuation of rotary mechanism  194  and motor  199  lowers stripping nozzle  59  and rotates it to a position directly in front of coated fiber  17 . 
     FIG. 20 illustrates the operation of stripping nozzle  59 . The coated optical fiber  210  that was employed in the coupler manufacturing process was a conventional silica-based single-mode optical fiber having-an outside diameter of 125 μm. The optical fiber was provided with a urethane acyrilate coating  212  having an outside diameter of 250 μm. A source  216  of inert gas such as nitrogen was supplied through filter  217  and flowmeter  218  to the inlet pipe  223 . A Convectronics Model 001-10002 tube heater was employed. The diameter of the outlet end of the nozzle was 1.76 mm. Nitrogen continually flowed at a rate of 20.9 standard liters per minute (slpm) into inlet pipe  223 . Hot gas was discharged into vent  234  (FIG. 4) when the stripping nozzle was not in use. The voltage supplied to heater tube  220  was sufficient to provide a gas temperature that is adequate for melting the coating material. A temperature of about 820 E C. is suitable for stripping a urethane acyrilate coating. Stripping nozzle  59  was mounted on a support apparatus  191  that provided it with the various degrees of motion described in connection with FIG.  19 . To simplify this description of FIG. 20, apparatus  191  is described as being capable of rotating about axis  222  as indicated by arrows  226  and  227  and being capable of moving along axis  222  as indicated by arrows  228  and  229 . 
     Coating material  212  was to be removed from coated fiber  210  between points a and b along a section thereof that was held between clamps  57  and  58 . Stripping nozzle  59  was rotated from its resting position to a horizontal orientation. It then traversed downwardly and rotated toward the coated fiber. Referring to FIG. 20, stripping nozzle  59  was rotated about axis  222  in the direction of arrow  226  until the jet of hot gas emanating from the tube heater nozzle  225  was directed a few millimeters to the side of coated fiber  210 . After a short pause, it rotated to position the jet at point a of the coated fiber and immediately began to traverse along axis  222  in the direction of arrow  229 . The distance between the end of nozzle  225  and the coated fiber during the fiber stripping operation was about 2.86 mm. As the hot nitrogen jet emanating from nozzle  225  moved along the coated fiber, coating material was softened and blown from the fiber. The removed coating material was discharged into vent  235  (FIG.  4 ). After coating material had been removed between points a and b along coated fiber  210 , stripping nozzle  59  rotated about axis  222  in the direction of arrow  227  so that hot gas was no longer directed at the fiber. The exposed optical fiber  211  was sufficiently clean that it could be used in the coupler manufacturing processes without further treatment. 
     The low reflectance end termination apparatus of FIG. 21 forms on the ends of optical fibers the low back reflection termination that is required for high performance optical components. Torch  60  is connected to a vertical stage  241  by a support  240 . Stage  241  is vertically moveable along track  242  as motor  243  turns threaded shaft  244 . Vertical track  242  is affixed to stage  245  that is horizontally moveable along track  246  when motor  247  rotates threaded shaft  248 . Track  246  is affixed to the vertical back plate  200  by bracket  249 . In its inactive state, end termination torch  60  is positioned as shown in FIG.  4 . 
     The operation of the fiber severing and end termination torch  60  is illustrated in FIGS. 22-25. Torch  60  had a size 2 tip (0.17 mm nozzle opening). A methane flow rate of 19 standard cubic centimeters per minute (sccm) and an oxygen flow rate of 25.5 sccm to the torch produced an adequate flame. The port velocity of the torch cannot be too high, or the tapered portion of the severed fiber will form a hook. Coated fiber  210  that had been.stripped as described in conjunction with FIG. 20 is tensioned between clamps  57  and  58 . As previously described in conjunction with FIG. 17, cylinders  172  and  173  had been actuated (while cylinders  171  and  174  remain non-activated), whereby pistons  176  and  177  bear against tabs  179  and  180 , respectively, tending to cause clamps  57  and  58  to move in opposite directions and thereby tension the fiber. After stage  241  had lowered torch  60  to the correct vertical position, stage  245  moved at a rate of 38.1 cm/minute to cause flame  260  to pass over fiber  211  at a rate sufficiently fast that the flame had essentially no effect on the fiber. The −z movement of the torch was stopped when the visible, peripheral portion of flame  260  was about 0.25 cm behind the fiber as shown in FIG.  23 . Motor  247  was reversed, and stage  245  moved in the +z direction at a rate of 3.81 cm/minute. As the torch moved forward in the direction of arrow  263 , the outer portion of the flame moved to a position shown in FIG. 24, thereby severing and forming tapered end regions  265  and  266 . When the fiber became severed, clamps  57  and  58  moved in the direction of arrows  271  and  272  until the clamping mechanisms were stopped by set screws  169 . When flame  260  reached the position illustrated in FIG. 25, tapered regions  265  and  266  had been heated to an extent sufficient to cause rounded end terminations  267  and  268  to form under the influence of surface tension. The resultant low reflectance termination had a typical back reflection less than about −55 dB. 
     If clamps  57  and  58  move the same distance (about 1-2 mm has been found to be suitable), a low reflectance ball termination will form on both of the tapered regions. If only top tapered region  265 , for esample, is to be provided with a ball termination, clamp  58  can be moved a greater distance (perhaps a few centimeters) while clamp  57  moves about 1-2 mm, whereby only tapered region  265  is provided with a low reflectance termination, and tapered region  266  is moved out of the influence of the flame. 
     FIGS. 26-29 as well as FIG. 12 illustrate the operation of the apparatus which closes vacuum seals  66  and  67 . Only the upper vacuum seals are illustrated in FIGS. 26-29. FIG. 12 is a schematic diagram that does not include any mounting brackets; it merely illustrates the relative positions of the chucks, vacuum seals and an initially operating pair of uv light sources. Elements included within the top bracket (see left side of drawing) are affixed to the top draw stage  299 . Elements included within the bottom bracket are affixed to the bottom draw stage  300 . Seal  66  is mounted by a bracket  286  to a stage  280  that is capable of horizontal movement along slide  285 . Slide  285  cannot be seen in FIGS. 26 and 27 since it is located within stage  280  when the apparatus is in the neutral position that is illustrated. Ball slides  285  are affixed to support plate  283  by way of seal movement mounting plate  282 . Support plate  283  is affixed to upper stage  299  of the coupler draw apparatus. To facilitate the precise positioning of the upper and lower draw stages  299  and  300  with respect to eachother, they can be affixed to a mounting plate (not shown) which is, in turn, mounted to backplate  200 . 
     The upper left vacuum seal  66  is shown in FIGS. 26 and 28. An elastomeric seal  288  extends around the periphery of a face of metal backplate  289 . Elastomeric seal  288  forms, along with the face of back plate  289 , a cavity  296 . A bore  290  in backplate  289 , which communicates with cavity  296 , is connected to blead valve  76  (FIG.  2 ). Blead valves  76  and  77  allow a controlled flow of air to enter upper left vacuum seal  66  and lower left vacuum seal  67 , respectively. Elastomeric seal  288  is formed of Dow 591LSR, a flame resistant liquid silicone rubber. Seal  288  is glued the surface of backplate  289  with the same liquid silicone rubber from which the seal is made. The seal has four holes into which four locating pins  292  project in order to correctly position the seal on the face of backplate  289 . A cylindrical. depression  287  at the bottom of the elastomeric seal receives the top of the capillary tube  12 ′. 
     The upper right vacuum seal  66  (FIG. 29) is identical to the left upper vacuum seal except that bore  291  in backplate  289  is connected to a vacuum source. FIG. 29 also shows the relationship between the vacuum seal and the draw chuck  64 . Chuck mounting plate  110  is affixed to support plate  283 . 
     Associated with each vacuum seal is an air cylinder  293 , the piston rod  294  of which is affixed to a bracket  295  extending from bracket  286 . Cylinders  293  can be actuated to open or close the vacuum seals. 
     FIG. 12 shows two UV light sources  297  that are traversed to the position shown after the coupler has been drawn and the chucks have been opened. Sources  297  are turned on before epoxy is inserted into the ends of the tube bore, and they are turned off, along with sources  370  and  371 , after the epoxy has been cured. The upper and lower UV sources  297  are attached to upper and lower stages  299  and  300 , respectively, by four-bar links, whereby those UV sources both retract in the direction of arrows  297   a  and move away from eachother after the epoxy has been cured. The function of sources  297  is further described in U.S. Pat. No. 5,268,014, which is incorporated herein by reference. 
     Burner  68  is shown in FIGS. 30-32. The burner comprises two sections  310  and  311  which are affixed to the laterally moving members  312  and  313  of PHD cam action gripper mechanism  315 . The burner, shown in its open position, can be closed by actuating burner close mechanism  314 . Sections  310  and  311  include annular regions  316  and  317 , respectively, each having a plurality of flame ports  319 . The distribution channels within the burner halves were symmetrical, whereby the flames emanating from each of the ports were substantially identical. Gas and oxygen are supplied to each burner section through lines  320 . 
     Burner close mechanism  314  is affixed to a bracket  321  which is affixed to stage  322 . Stage  322  moves in the direction of the double headed arrow along slide  323  which is affixed to support  324 . Support  324  includes a rib  325  having an opening in which cylinder  327  is fixedly mounted. The end of cylinder rod  328  is connected to a yoke at the end of bracket  321 . Support  324  is secured to back plate  200 . 
     It is convenient to ignite the flame when the burner is in its retracted position shown in FIG.  30 . During ignition (and during movement of the burner to tube  12 ′) methane flows at the level that would be required to heat tube  12 ′, but oxygen flows at a reduced level to reduce the amount of heat produced. When the gas and oxygen are turned on, these gases flow up the lower portion of flame shield  330  to silicon carbide resistance ignitor  329 . When the gases ignite, the flame propagates in the +z direction through the channel formed by the flame shield to protect those components located above the burner. After the burner halves close around tube  12 ′, the oxygen flow is increased to provide a sufficiently hot flame to soften the tube so that it can collapse and be stretched. 
     Epoxy application apparatus  72  is shown in FIGS. 33 and 34. Epoxy application devices  340  and  341  are TS 5000 rotary microvalves, which are electrically motorized auger feed mechanisms. Epoxy is delivered to mechanisms  340  and  341  from sources  360  and  361 , respectively, which are pressurized by air supplied by valves  362  and  363 , respectively. Epoxy from mechanisms  340  and  341  deliver the epoxy to the ends of the coupler through hypodermic needles  338  and  339 , respectively (not shown in FIG.  34 ). Devices  340  and  341  are mounted by angular and horizontal adjustment devices to stages  345  and  346  which move vertically along tracks (not shown) when motors  347  and  348 , respectively, are energized. The angular orientation of devices  340  and  341  can be adjusted by loosening a thumbscrew and pivoting mounting plates  334  and  335 , respectively. Plates  334  and  335  are mounted on manual positioning stages  343  and  344  that provide horizontal adjustment in the plane of FIG. 33 when handles  336  and  337  are rotated. When the apparatus is in the dispensing position adjacent tube  12 ′, the dispensing location of the needle tips can be adjusted by the aforementioned angular and horizontal adjustment devices. 
     Stages  345  and  346  are mounted on a support member  350  which is mounted on a rotary stage  352  which rotates with respect to base  353  when motor  354  is energized. Base  353  is affixed to stage  355  which is translatable along track  356  in the x-direction when motor  357  is energized. Track  356  is mounted to back plate  200  by mounting bracket  359 . 
     Apparatus for positioning the UV light source is shown in FIG.  35 . Light is supplied to UV light sources  370  and  371  by light guide cables  372  and  373 , respectively. Sources  370  and  371  are affixed to a post  374  that is connected to the top end of L-shaped support arm  377 . The opposite end of arm  377  is affixed to rotary stage  379  which rotates upon base  380  when motor  378  is activated. Rotary stage base  380  is mounted to a linear stage  381  which moves vertically along track  382  when motor  383  is activated. The resting position of arm  377  is shown in FIG.  35 . 
     The operation of bottom clamps  69  can be understood by referring to FIG.  5 . Clamps  69 , which are Sommer ultramatic cam-action grippers Model No. GP-19, are operated by a mechanism  390  which is mounted on an L-shaped. support arm  391 . The support arm is affixed-to a linear stage  392  which moves vertically along track  393  when motor  394  is energized. Track  393  is mounted on bottom draw stage  300 . 
     Making a Coupler 
     Various 1×2 couplers including the 3 dB achromatic coupler disclosed in U.S. Pat. No. 5,011,251 (which is incorporated herein by reference) were made by the process that is generally described below. The flame temperature, length of pull, and characteristics of the capillary tube and optical fibers depend on the specific type of coupler being made. To make the coupler disclosed in U.S. Pat. No. 5,011,251 the two optical fibers had different chlorine concentrations in their claddings. The outside diameters of the optical fiber and the protective coating were 125 μm and 250 μm, respectively. Doped silica capillary tubes having a length of 34 mm, an inside diameter of 270 μm and an outside diameter of 2.8 mm were utilized. Funnels at the ends of the tubes communicated with the bore. 
     Referring to FIGS. 8,  9  and  10 , a glass capillary tube  12  was transferred from magazine  13  to V-groove members  86  where it was located against stop  89  by piston  88 . Transfer clamps  92  were traversed in the −z direction until they surrounded tube  12 . The clamps were actuated to engage tube  12 , and stage  101  moved downwardly, whereby grooves  86  withdrew from tube  12 . Clamps  92  were then traversed in the +z direction. Arm  107  rotated to position clamps  92  at coupler draw apparatus  63  where the tube was situated in front of draw chucks  64  and  65 . Transfer clamps  92  were traversed in the −z direction, and the end regions of the tube (now designated  12 ′) were placed in the V-grooves of upper and lower chucks  64  and  65 , respectively. The tube was secured by clamping bars  113  (FIGS. 11 b  and  12 ). The transfer clamps were then retracted in the +z direction, and arm  107  was rotated to a vertical position adjacent dispensing mechanism  82 . 
     To deliver fiber  17  to guide tube  36 , cyclinder  29  was actuated, thereby engaging roller  27  onto roller  24 . Motor  25  turned roller  24  in the clockwise direction of arrow  24   a  (FIG.  2 ). When a sufficient amount of fiber had been delivered, idler roller  27  retracted from main roller  24 , and cyclinder  31  was actuated to lower clamp  30  against bar  32  to prevent further movement of the fiber. During the time that fiber  17  was being delivered, a position holding clamp (not shown) clamped fiber  16  against bar  32  to prevent it&#39;s movement. During the delivery of fiber  17  to guide tube  36 , cylinder  31  was actuated to retract clamp  30  from bar  32 . 
     Motor  53  (FIG. 2) was energized to vertically position retaining tube  51  such that guide tubes  35  and  36  and dispensing tube  44  were located just above strip clamp  58 . Motor  25  was rotated clockwise (arrow  24   a ) and cylinders  29  and  31  were appropriately actuated to cause feed apparatus  23  to deliver about 2-3 cm of coated fiber  17  from the end of guide tube  36 . Strip clamp  58  closed on the fiber. Motor  53  was energized to move the guide tube upwardly to a position above strip clamp  57 . The fiber was pulled through guide tube  36  as the retaining tube  51  (and thus guide tube  36 ) moved upwardly. Strip clamp  57  closed on coated fiber  17 . Cylinders  172  and  173  (FIG. 17) were actuated to tension the fiber between the strip clamps  57  and  58  for the coating strip operation. 
     Stripping nozzle  59  was rotated to a horizontal position and was lowered to a y position at which stripping was to start to occur. It was then rotated about rotary mechanism  194  to position the end of nozzle  225  (FIG. 20) adjacent the lower end of the region of coated fiber that was to be stripped. The hot inert gas jet impinged on the coated fiber and then moved upwardly and caused coating to be stripped from a predetermined region of the fiber (about 30 mm long) between the strip clamps. Stripping nozzle  59  rotated in the x-z plane to direct the hot jet-away from the coated fiber and then returned to its resting position. 
     Ball termination torch  60  was lowered from its resting position position to that level at which fiber  17  was to be severed; it then moved in the −z direction at 38.1 cm/minute. After it moved past the fiber, torch  60  reversed direction and traversed the fiber at 3.81 cm/minute, whereby the fiber became severed. Top clamp  57  moved upwardly about 1-2 mm, and bottom clamp  58  moved downwardly a few centimeters so that tapered end  266  was out of the influence of the flame. As torch  60  continued to move in the. +z direction, a rounded, low reflectance termination was formed on tapered region  211 a as described in conjunction with FIGS. 22-25. Strip clamps  57  and  58  were opened, and the small residual piece of fiber was removed from clamp  58 . After the end of fiber  17  had been stripped and terminated, fiber  17  was retracted into guide tube  36 . 
     Sometimes optical fiber has a characteristic referred to as “fiber curl” caused by unequal stresses on different sides of the fiber. This could cause the end of fiber  17  which extends from clamp  57  to bend so that it is out of the influence of flame  260  after the fiber has been severed. This can be prevented by keeping the length of fiber extending downwardly from clamp  57  relatively short. To accomplish this, the distance between clamps  57  and  58  should be relatively short, about 4 cm or less being suitable. 
     Retaining tube  51  was moved to a position such that guide tubes  35  and  36  and dispensing tube  44  were located just above upper strip clamp  57 . Stripping nozzle  59  was rotated to horizontal position, lowered and rotated to a position where the hot jet was directed below dispensing tube  44 . While the stripping nozzle remained stationary, fiber  16  was fed from the guide tube  35  through the heated gas stream. After coating material was stripped from about 2.5-7.6 cm of the fiber, stripping nozzle  59  rotated away from the fiber, and all but about 1.3 cm of fiber  16  was retracted into guide tube  35 . Retaining tube  51  moved downwardly until the end of fiber  16  enterd the capillary tube bore. Fiber  16  was fed through tube  12 ′ until a length appropriate for forming a connection pigtail (about 2 meters, for example) extended from the bottom of the tube. Drops of ethyl alcohol were delivered from dispensing tube  44  while fiber was being fed through tube  12 ′. The end of fiber  16  that had been end stripped was cleaved, and the cleaved end was put into a cam operated fiber splice assembly tool to temporarily connect it to light source fiber  47  of measurement system  46 . 
     Retaining tube  51  was retracted from tube  12 ′, and fiber  16  was delivered at the same speed so there was no relative movement between fiber and tube. When guide tube  35  was above strip clamp  57 , strip clamp  58  closed; strip clamp  57  then closed. The air cylinders  172  and  173  were actuated to tension the fiber between the strip clamp  57  and  58  for the coating strip operation. 
     A section of coating was stripped from fiber  16  in the same manner as previously discussed in connection with fiber  17 . The resultant bare region was slightly shorter than the length of tube  12 ′ (about 30 mm). Strip clamps  57  and  58  then released the fiber. 
     Through fiber  16  was retracted until the stripped region remained about 0.6 cm from the end of the guide tube  35 . The retaining tube and guide tubes were not moving downward toward tube  12 ′ at this time. 
     Bottom clamp  69  closed on that portion of fiber  16  extending from the bottom of tube  12 ′. Motors  53  and  394  were energized, and retaining tube  51  and bottom clamp  69  moved downwardly at the same rate. Drops of alcohol were fed from dispensing tube  44  as the stripped regions of fibers  15  and  16  were simultaneously lowered toward tube  12 ′. As retaining tube  51  was moved toward tube  12 ′, the stripped end of fiber  17  was fed from guide tube  36  until the end of fiber  17  was positioned at about the center of the stripped region of fiber  16 . At this time fiber  17  was no longer fed from guide tube  36 , and both fibers were advanced downwardly by movement of retaining tube  51  and lower clamp  69  until the stripped midregion of fiber  16  was centered in the bore of tube  12 ′. At this time the tip of fiber  17  was located at about the longitudinal center of tube  12 ′. Fiber  17  was then fed from guide tube  36  until the bare region thereof extended adjacent the stripped midregion of fiber  16  through tube midregion  399  as shown in FIG.  36 . 
     If the bare region of fiber  17  were positioned adjacent the bare region of fiber  16  above tube  12 ′, and both fibers advanced together into the bore of tube  12 ′, the surface tension of the alcohol could cause the bare region of fiber  17  to twist about the bare region of fiber  16 . This could affect process reproducibility. The solution to the problem is to deliver the fibers as described above such that the bare region of fiber  16  is positioned in the tube bore first, the tip of fiber  17  being midway down the tube bore and thereafter advancing the bare portion of fiber  17  the remainder of the distance into the bore until both fibers are positioned as shown in FIG.  36 . 
     Bottom vacuum seal  67  was closed, and alcohol was evacuated from the bore of tube  12 ′. During this step, which lasted about 20-60 seconds (20 seconds being typical), air was pulled through the bore of tube  12 ′. Air was also bled into left vacuum seal  67  through valve  77 . 
     During the vacuum purge of alcohol from the tube bore, a reference measurement was made by system  46 . 
     Retaining tube  51  was raised and fibers  16  and  17  were fed through tubes  35  and  36  at the same rate until the bottoms of tubes  35 ,  36  and  44  cleared the top vacuum seals  66 . 
     The top vacuum seals closed, and the bore of tube  12 ′ was evacuated. Air was bled through valve  76  and into one side of the vacuum seal  66  while the other side of vacuum seal  66  was evacauated. This generated a fast moving air stream that removed any alcohol that had accumulated on the top of tube  12 ′. 
     The aspirator function, i.e. the bleading of air through valves  76  and  77 , occurs at any time that vacuum seals are closed. The aspirator function occurs not only during alcohol removal but also during the evacuation of the tube bore during the later described steps of collapsing the tube onto the fibers and stretching the tube to form a coupler. This is not detrimental to the tube collapse step since only a low level of vacuum is required during that step. 
     With methane flowing at a rate of 0.5 slpm (full operating level) and oxygen flowing at a rate of 0.1 slpm (a level below operating level), burner sections  310  and  311  were ignited. Cylinder  327  was actuated to move split burner  68  in the −x direction, whereby burner sections  310  and  311  were positioned such that tube  12 ′ was centered within annular regions  316  and  317  (FIGS.  30 - 32 ). Burner close mechanism  314  was then actuated to cause sections  310  and  311  to close around tube  12 ′. At that time the flow of oxygen was increased to full operating level (1 slpm), and the midregion  399  (FIG. 36) of tube  12 ′ was heated to a sufficiently high temperature to cause it to collapse onto the fibers. The vacuum at this time was 27.9 cm of mercury. About 15-30 seconds after the application of the full intensity flame to, tube  12 ′ (typically 22 seconds for the first pull), stage  299  moved upwardly and stage  300  moved downwardly, whereby the top and bottom chucks  64  and  65  were traversed in opposite directions a total of 13 mm. As soon as the stages started to pull the coupler, the programmable controller reduced the flow of oxygen to the burner to zero in 1 second. Since retaining tube  51  and bottom clamps  69  are mounted on upper and lower draw stages  299  and  300 , respectively, they also move the same distance as chucks  65  and  66 , respectively. 
     Burner  68  opened and retracted in the +x direction away from tube  12 ′. 
     The first pull was intentionally performed such that less than the desired coupling was obtained. An optical measurement was made to determine the amount of coupling that resulted from the first pull. This information was input to the programmable controller, and a second pull was performed. 
     The burner flame was ignited as described above, and the burner again moved in the −x direction and closed about the tube. About 2-10 seconds after the application of the full intensity flame to the tube (typically about 8 seconds), the top and bottom chucks  64  and  65  were again traversed in opposite directions a total of 2.6 mm. As soon as the stages started to pull the coupler, the programmable controller reduced the flow of oxygen to the burner to zero in 0.75 second. The burner opened and retracted in the +x direction. The burner was shut off. 
     The combination of the-tube collapse and stretch steps resulted in the formation of a coupler  400  (FIG. 37) having a tapered coupling region  401 . The length of the coupler was 49.6 mm. 
     The vacuum seals were opened. 
     The epoxy was stored in reservoirs  360  and  361  which were attached to support member  350 . Pressure controllers  362  and  363  pressurized reservoirs  360  and  361  at 24 psi and 33 psi, respectively. The epoxy was a mixture of the following components: (a) 33.11 weight percent ELC 2500, an epoxy resin/photoinitiater blend made by Electrolite Corp., Danbury, Conn., (b) 0.34 weight percent additional photoinitiator, (c) 58.23 weight percent magnesium pyrophosphate filler (screened to 35 μm), and (d) 8.32 weight percent 1.5 μm silica microspheres made by Geltech Corp., Alachus, Fla. The viscosity of the epoxy at 25 E C, 58 E C and 82 E C is approximately 80 poise, 10-15 poise and 4 poise, respectively. 
     Rotary stage  352  rotated 90 E  (in the counter-clockwise direction when observed from the top or +y direction) to position devices  340  and  341  farther away from apparatus backplate  200  so that the epoxy application apparatus would clear other equipment as it traverses toward the draw apparatus  63 . Stage  355  then moved in the −x-direction, and rotary stage  352  rotated further in the above-described direction. This positioned epoxy application devices adjacent coupler  400  (FIG. 37) with the dispensing needles  338  and  339  vertically removed from the ends of the coupler. Motors  347  and  348  were energized to position the needles adjacent the funnels as illustrated in FIG.  37 . The needles can be positioned at (immediately above or into) the funnel during epoxy dispensing. 
     The angular orientation of top needle  338  did not seem to be critical. The size of needle  338  was 22 gauge. With the end of the needle positioned immediately above the top funnel, actuator  340  was energized 1.75 seconds to deliver a drop of epoxy which, assisted by gravity and capillary action, flowed into the top funnel and into the top bore. 
     When a needle  339  of similar size was employed to apply epoxy to the bottom funnel, an insufficient amount of epoxy traveled into the bore. Reasons for this are as follows. The ends of the tube reach a maximum temperature of about 95 E C during the last stretch step. At the time that the epoxy is applied, the temperature of the top and bottom of the tube has decreased to about 82 E C and 58 E C, respectively. Moreover, the temperature continues to decrease as the epoxy is being applied. This causes the viscosity of the epoxy in the bottom funnel to be higher than that in the top funnel as mentioned above. Also, the epoxy in the bottom funnel must flow upwardly. The following steps were taken to ensure the proper application of epoxy to the bottom funnel and bore. The epoxy applied to the bottom funnel was supplied at a higher pressure, and bottom needle  339  was smaller than needle  338 , needle  339  being a size  18  gauge. Needle  339  was oriented at an angle of about 30 E  from vertical. In general, needle  339  should be oriented less than 45 E  from vertical. This enables the tip of needle  339  to be positioned deep in the funnel as shown in FIG.  37 . In addition, the tip of needle  339  is beveled such that its opening is oriented horizontally or nearly horizontally. This causes the epoxy to be directed up the funnel toward the bore. Since the epoxy is applied to the bottom funnel at higher pressure through a smaller needle, it squirts up into the funnel and reaches the bore where it flows upwardly under the influence of capillary action as well as the force caused by a pressure reduction in the bore due to the cooling of the coupler. The same amount of epoxy is applied to the top and bottom funnels. Because of the small needle size, the flow rate into the bottom funnel was lower; therefore, the actuator  341  was energized 4.2 seconds to deliver a similar drop of epoxy to the bottom funnel. 
     After a drop of epoxy was injected into each funnel, the needles were retracted vertically from the funnels and were moved away from the longitudinal axis of tube  12 ′. This caused the epoxy drops to release from the needles. The first application of epoxy was insufficient to completely fill the funnels. If the funnels had been completely filled, an air bubble could have formed and prevented the epoxy from advancing a sufficient distance into the bores. UV light from sources  297  caused the epoxy to cure and cease flowing after it had flowed a predetermined distance into the bores. 
     After about 3-10 seconds (5 seconds is typical) had elapsed to permit the epoxy to traverse through the funnels and into the tube bores by capillary action, needles  338  and  339  were again positioned at the funnels. A second drop of epoxy was dispensed into each funnel; this drop was sufficient to fill each funnel. The epoxy application apparatus then moved to resting position. The epoxy filled the funnels, which were about 2.5 mm deep and extended into the bores a distance of about 3.5 mm. 
     In the resting position of arm  377  (FIG. 35) UV light sources  370 ,  371  are at the same vertical level as upper chuck  64 . Motor  378  is activated to rotate arm  377  in the direction of arrow  385 . When in its fully rotated position, sources  370  and  371  are located immediately above and below upper clamping bar  113 . After the temperature of the coupler is below 40 E C, UV light sources  370 , 371  are energized to cure the epoxy in the upper end of tube  12 ′. The upper clamping bar  113  is optionally open during the time that sources  370 ,  371  are positioned at the upper end of tube  12 ′. The period between the time that the coupler has been heated for stretching purposes and the time that the temperature of the coupler has dropped below 40 E C can be determined empirically. Arm  377  is rotated to retract light sources  370  and  371  a sufficient distance to clear the equipment. Motor  383  is energized to lower the light sources to a level such that when arm  377  is again rotated in the direction of arrow  385  those sources will be immediately above and below lower clamping bar  113  to cure the epoxy in the lower end of coupler  400 . More UV light will reach the epoxy if the lower clamping bar  113  is open at this time. 
     When the coupler is sufficiently cool (30-45 sec) an optical measurement is made. 
     The coupler body is released from the draw chucks. 
     The fiber pigtails at the top of the coupler are metered out by the fiber feed apparatus until about 2 m of fiber extends from the top end of the coupler. The output pigtails are then severed by a cutting tool or by bending fibers  16  and  17  to a tight radius at the ends of guide tubes  35  and  36 . Coupler  400  is removed from the draw. 
     The specific example concerns the formation of 1×2 couplers. The above-described manufacturing apparatus could also be employed to make 1×N couplers of different configurations such as the 1×6 and 1×8, for example. To make a 1×6, guide tubes  410  could be arranged in a six-around-one configuration within a retaining tube  411  (FIG.  38 ). More than one alcohol dispensing tube could be employed. Also, since it may be desirable to maintain the guide tubes in the illustrated close packed array, the alcohol dispensing tubes can be situated outside the retaining tube. Three dispensing tubes  412  are shown as being equally spaced around the retaining tube. 
     To make a 1×8, guide tubes  420  could be arranged in an eight-around-one configuration within a retaining tube  421 , a spacer tube surrounding the central guide tube (FIG.  39 ). Three dispensing tubes  422  are equally spaced around retaining tube  421 . 
     A semi-automatic coupler manufacturing apparatus could employ some of the components shown in FIGS. 4 and 5. The most important components are the fiber feed and insertion devices. When the disclosed fiber feed device is employed, the disclosed vacuum chucks are extremely useful, since the fibers extending from tube  12 ′ are connected to the measuring system and are extending through the feed tubes. However, the tube  12 ′ could be manually inserted into the chucks. If this were done, the chucks could be of different design. Further, a ring burner could be employed if manual tube insertion were employed. A tube would be inserted through the ring burner and then chucked at its ends. After the coupler is formed, it could be released from the chucks, and the epoxy could be applied and cured off-line. 
     The duplication of certain functions would decrease the time required to make a coupler. FIG. 40 shows how apparatus  10  could be modified by employing two stripping and terminating stations  430  and  431 . Each of the stations  430  and  431  is provided with a stripping nozzle, a ball termination torch and a pair of clamps similar to clamps  57  and  58 . Tracks  54  and  54   a  are affixed to a stage  432  that moves horizontally along track  433 . In the situation represented by FIG. 40 fiber insertion apparatus  50  had previously been located adjacent stripping and termination station station  430  so that the fibers within the fiber guide tubes of apparatus  50  have been prepared for insertion into tube  12 ′. Stage  432  has therefore moved to the position shown so that the fibers can be inserted into the tube. Thus, fiber insertion apparatus  50   a  is located adjacent stripping and termination station station  431  so that the fibers within the fiber guide tubes of apparatus  50   a  can be prepared for insertion into tube  12 ′. After the coupler is formed by employing fibers from apparatus  50 , stage  432  moves to the left, another tube  12 ′ is inserted into chucks  64 , and the fibers from apparatus  50   a  are inserted into the tube. 
     The fiber feed apparatus and fiber insertion apparatus shown in FIGS. 2,  15   a,    15   b  and  16  allows one or more fibers to be manipulated remotely while at the same time controlling their absolute position and orientation with respect to a given location and eachother. Such an apparatus could also be employed to position an optical fiber at more than one work station, each of which performs one or more procedures on the fiber. FIG. 41 shows a guide tube  440  in which coated optical fiber  441  is situated. The guide tube can be part of the apparatus shown in FIG. 40 whereby it can be moved vertically or horizontally as indicated by arrows  444  and  443 , respectively. In addition, fiber  441  can traverse through tube  440  in either direction as indicated by arrow  442 . 
     The first work station  445  could be one containing a. stripping nozzle for stripping coating material from the end of fiber  441 . The fiber could be retracted into tube  440 , and that tube could be moved to second work station  446  where the stripped end could be inserted into a grinding machine that forms a lens on the end of the fiber. The lensed fiber could be retracted into tube  440  and moved to third work station  447  where a layer of gold could be deposited thereon by sputtering or the like. The resultant fiber would be suitable for use as a laser diode pigtail. The gold layer enables the fiber to be soldered to a fixture with the lensed end in light receiving relationship with the laser diode.