Claims:TECHNICAL FIELD
[0001] The present disclosure relates to an optical fiber manufacturing equipment and more particularly, relates to a high speed optical fiber draw tower and optical fiber drawing method.

BACKGROUND
[0002] During optical fiber manufacturing, a capstan drive controls and maintains a drawing speed at which the optical fiber is drawn. Since this process faces a fluctuation in the drawing speed, thereby causing generation of residual voltage into a capstan drive of draw tower. Hence, there exists a requirement for removal of excess voltage. In the same context, a prior art reference “JPH10287442A” discloses a preform feeding device that measures diameter of optical fiber during drawing of optical fiber from a preform and ensures controlling of drawing speed of optical fiber to ensure uniform outer diameter of optical fiber. Another prior art reference “CN107840568B” relates to an intelligent optical fiber drawing machine to ensure uniform diameter of optical fiber through controlling speed and ensuring that drawing furnace is devoid of air to prevent quality degradation of optical fiber. Another prior art reference “CN203021452U” teaches a drawing controlling system in order to control cut-off wavelength of an optical fiber. Yet another prior art reference “CN106904824A” teaches about a high precision for diameter to be maintained through a wire drawing apparatus.
[0003] As the draw tower runs in a diameter control mode, the capstan drive synchronizes its speed to maintain diameter of the optical fiber to a nominal value. However, at a high-speed rate, a sudden spike in the diameter leads to sudden speed variation in the capstan speed to maintain the diameter to the nominal value, which results in generation of high residual voltage inside the capstan drive with no path to dissipate, leading to tripping of the capstan drive.
[0004] Therefore, there exists a need for an improved technique which solves the aforesaid drawbacks.

OBJECT OF THE DISCLOSURE
[0005] A principal object of the present disclosure is to provide an optical fiber draw tower and optical fiber drawing method.
[0006] Another object of the present disclosure is to remove residual/excess voltage in an optical fiber drawing system by using a shunt module in connection with a capstan drive that prevents tripping of the capstan drive due to fluctuation in optical fiber drawing speed.

SUMMARY
[0007] Accordingly, the present disclosure provides an optical fiber draw tower. The optical fiber draw tower comprises a preform feed system near a top end of the optical fiber draw tower, wherein the preform feed system holds a preform and inserts the preform into the optical fiber draw tower furnace as a lower end of the preform is melted to form an optical fiber. The optical fiber draw tower further comprises a diameter measurement gauge for measuring diameter of the optical fiber and a capstan drive in connection with PLC controller and with the preform feed system works in synchronization to maintain diameter of the optical fiber measured by the diameter measurement gauge. In diameter control mode the capstan speed loop is run period less than 150 milliseconds. The diameter of the optical fiber is maintained is less than 210 microns and variation in the diameter of the optical fiber is +/- 10 microns.
[0008] The optical fiber draw tower further comprises a shunt module electrically coupled with the capstan drive. The shunt module dissipates residual voltage that is resulted due to change in the draw speed. The draw speed is more than 2600m/min and the voltage at capstan drive is maintained at less than 900 volts as the capstan drive will trip above this voltage. The shunt module comprises a resistor, a heat sink , cooling fan and a thermal switch, wherein the heat sink is used to dissipate the heat generated be resistor and cooling fan is used to cooling the resistor coil .
[0009] Accordingly, the present disclosure provides a method of drawing an optical fiber. The method comprises melting a preform into the optical fiber in an optical fiber draw tower, measuring diameter of the optical fiber using a diameter measurement gauge and adjusting preform insertion speed based on the measured diameter of the optical fiber, wherein change in the diameter of fiber changes draw speed of the optical fiber and change in the draw speed results in generation of residual voltage in the capstan drive. The draw speed is adjusted at a time period of 100 milliseconds.
[0010] The method further comprises dissipating the residual voltage into heat, whereby the diameter of the optical fiber is maintained less than 210 microns and the variation in the diameter of the optical fiber is +/- 10 microns. The method further comprises maintaining the capstan drive voltage less than 900 volts. The capstan drive will trip above this voltage.
[0011] These and other aspects herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the invention herein without departing from the spirit thereof.

BRIEF DESCRIPTION OF FIGURES
[0012] The invention is illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the drawings. The invention herein will be better understood from the following description with reference to the drawings, in which:
[0013] FIG. 1 illustrates an optical fiber draw tower.
[0014] FIG. 2 illustrates a process associated with the optical fiber draw tower.
[0015] FIG. 3 illustrates a circuit schematic of a shunt module in conjunction with FIG. 1 and FIG. 2.
[0016] FIG. 4 is a flow chart representing a method of drawing an optical fiber.

DETAILED DESCRIPTION
[0017] In the following detailed description of the invention, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be obvious to a person skilled in the art that the invention may be practiced with or without these specific details. In other instances, well known methods, procedures and components have not been described in detail so as not to unnecessarily obscure aspects of the invention.
[0018] Furthermore, it will be clear that the invention is not limited to these alternatives only. Numerous modifications, changes, variations, substitutions and equivalents will be apparent to those skilled in the art, without parting from the scope of the invention.
[0019] The accompanying drawings are used to help easily understand various technical features and it should be understood that the alternatives presented herein are not limited by the accompanying drawings. As such, the present disclosure should be construed to extend to any alterations, equivalents and substitutes in addition to those which are particularly set out in the accompanying drawings. Although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are generally only used to distinguish one element from another.
[0020] In opening, simultaneous reference is made to FIG. 1 through FIG. 2, in which FIG. 1 illustrates an optical fiber draw tower 100 and FIG. 2 illustrates a process 200 associated with the optical fiber draw tower 100.
[0021] The optical fiber draw tower 100 comprises, but not limited to, a preform feed system 102, a diameter measurement gauge 112, a capstan drive 114 and a shunt module 116. The optical fiber draw tower 100 may also be referred to as a draw tower or a high-speed optical fiber draw tower.
[0022] The preform feed system 102 may also be referred to as a preform holding device or a preform insertion device. The preform feed system 102 is configured to hold and insert a preform 104 inside the optical fiber draw tower 100. The preform feed system 102 is installed near a top end 108 of the optical fiber draw tower 100 that holds and inserts the preform 104, where a lower end 110 of the preform 104 is melted to form an optical fiber 106.
[0023] The preform 104 is a glass preform i.e., silica preform. Further, an optical fiber refers to a medium associated with transmission of information over long distances in the form of light pulses. The optical fiber uses light to transmit voice and data communications over long distances when encapsulated in a jacket/sheath. The optical fiber may be of ITU.T G.657.A2 category. Alternatively, the optical fiber may be of ITU.T G.657.A1 or G.657.B3 or G.652.D or a multi-core or other suitable category. The ITU.T, stands for International Telecommunication Union-Telecommunication Standardization Sector, is one of the three sectors of the ITU. The ITU is the United Nations specialized agency in the field of telecommunications and is responsible for studying technical, operating and tariff questions and issuing recommendations on them with a view to standardizing telecommunications on a worldwide basis. The optical fiber may be a bend insensitive fiber that has less degradation in optical properties or less increment in optical attenuation during multiple winding/unwinding operations of an optical fiber cable.
[0024] The preform feed system 102 may include a motor with screw drive, a chuck to hold the preform 104 and an x-y positioning system to center the preform feed system 102 over the optical fiber draw tower 100. The rate at which the preform 104 is fed downward into the optical fiber draw tower 100 is determined by a draw speed, a preform diameter, and a specified fiber diameter. A handle diameter of the preform feed system 102 is equal to that of the preform diameter.
[0025] In order to measure diameter of the optical fiber 106, the optical fiber draw tower 100 utilizes the diameter measurement gauge 112, where the optical fiber 106 may have a diameter less than 210 microns. Small changes in the optical fiber draw tower 100, for example, but not limited to, change in preform temperature, inert gas flow, or other draw conditions cause fluctuations in fiber diameter, where the fluctuation/variation in the diameter of the optical fiber 106 is less than 210 microns. To monitor such fluctuations, the optical fiber draw tower 100 utilizes the diameter measurement gauge 112 that runs continuously.
[0026] The diameter measurement data is fed into a diameter-control loop that adjusts the draw speed of the optical fiber 106. Further, a preform feed system speed is adjusted based on the measured diameter of the optical fiber 106. In some cases, there may be a secondary control loop to adjust the preform feed (or preform insertion speed). These control loops use the diameter measurement gauge 112 to make rapid adjustments. The diameter measurement gauge 112 measures diameter of the optical fiber 106 in the optical fiber draw tower 100 accurately with the help of at least one camera and at least one laser device, where light (laser beam) from the at least one laser device generates diffraction pattern and the at least one camera measures diameter of the optical fiber 106 accurately. That is, the diameter of the optical fiber 106 is measured through the diffraction pattern. Typically, during diameter measurement, every object placed in the measuring field interrupts the laser beam and casts its shadow into a receiver. By measuring a shadow time, an outside diameter of a part can be exactly computed. In such a case, the receiver is the at least one camera that displays the shadow of the object whose diameter needs to be measured.
[0027] The measured diameter of the optical fiber 106 is fed to a PLC (Programmable Logic Controller) 202 for controlling components of the optical fiber draw tower 100 as per the draw speed of the optical fiber 106. The data from the PLC 202 is fed to the capstan drive 114 that controls the draw speed of the optical fiber 106. The capstan drive 114 is used to control and maintain the draw speed so that the diameter of the optical fiber 106 is maintained. The capstan drive 114 drives the capstan motor 204 and a capstan wheel 206. The capstan drive 114 is integrated through the PLC 202 with the preform feed system 102 and calibrates the draw speed based on the diameter of the optical fiber 106 measured by the diameter measurement gauge 112, wherein change in the preform insertion speed changes the draw speed of the optical fiber 106. The capstan drive 114 calibrates the draw speed at a period less than 150 milliseconds, where the draw speed is more than 2600m/min. However, during this process, a residual voltage is generated. The residual voltage, resulted due to draw speed variation of the optical fiber 106, is dissipated through the shunt module 116 in the form of heat into the surrounding environment, where the shunt module 116 is electrically coupled, through bus or terminal, with the capstan drive 114 and the capstan drive voltage is maintained for less than 900 volts. The capstan drive will trip above this voltage. The purpose of connecting the shunt module 116 with the capstan drive 114 is that since the capstan drive 114 has a PID (Proportional, Integral, Derivative) loop, which fluctuates the draw speed after every period less than 150 milliseconds and as the draw speed fluctuates, the residual voltage is generated which is removed the moment it is generated.
[0028] The shunt module 116, as shown in FIG. 3, comprises a cooling fan 302, a diode 304, a resistor 306, a heat sink 308, a load 310, a shunt resistor 312 and a thermal switch 314.
[0029] The diode 304 allows the flow of current in the shunt module 116 and the resistor 306 regulates excessive bus voltage by passing the current through the resistor 306 that dissipates the current as heat and minimizes drive faults. To increase more power, the external shunt resistor 312 may be connected externally and optionally.
[0030] The resistor 306 is coupled with the heat sink 308. Heating of the resistor 306 due to the residual voltage heats up the heat sink 308 which transfers the heat on a conduction means. In other words, the heat sink 308 is made of Aluminium which gets heated up due to hot resistor, which is getting heated by excess voltage generation and hence excess voltage is getting dissipated in the form of heat. The heat sink 308 redirects the heat flow away, while the cooling fan 302 utilizes convection means. In the shunt module 116, effective heat transfer is done through employing different mode of heat transfer methods.
[0031] Further, the thermal switch 314, which is an electromechanical device, opens and closes contacts to control the flow of electrical current in response to temperature change. The thermal switch 314 cuts off the current to the shunt module 116 when temperature limit is exceeded, thereby preventing potential burn out or failure of the shunt module 116.
[0032] The shunt module 116 may have a drive voltage of 230/460 Volts, a resistance of 28.75 Ohm, a peak power about 5.7/22.5 KW, a peak current about 14/28 Amp, a continuous power of about 200 W, a capacitance of 470 mF, a short circuit current of 200 Amp and a weight about 3.10 Kg. Of course, other ratings (values) are known, foreseeable, and unforeseeable, and each of these is readily apparent to those of skill in the art upon reading the present disclosure.
[0033] Advantageously, the shunt module 116, which is in connection with the capstan drive 114, ensures working simultaneously with the capstan drive 114 and since the shunt module 116 has a resistor coil, the same gets heated in direct proportion with that of fluctuation in the draw speed, hence excess/residual voltage is removed in the form of heat. Further, the shunt module 116 and the capstan drive 114 while working simultaneously ensure removal of the residual voltage from the optical fiber draw tower 100 while controlling and maintaining the draw speed. The residual voltage is checked periodically at a predefined time, for example, less than 150 milliseconds, thus preventing tripping of the optical fiber draw tower 100. Due to aforementioned arrangement, a high draw speed is possible (>2600 m/min) without tripping and draw breaks are also eliminated. Since the components of the optical fiber draw tower 100 are expensive, the aforementioned arrangement keeps them safe.
[0034] FIG. 4 is a flow chart 400 representing a method of drawing the optical fiber 106. It may be noted that in order to explain the flow chart 400, references will be made to the elements explained in FIG. 1 through FIG. 3.
[0035] At step 402, the method includes melting the preform 104 to form the optical fiber 106 in the optical fiber draw tower 100.
[0036] At step 404, the method includes measuring the diameter of the optical fiber 106 using the diameter measurement gauge 112.
[0037] At step 406, the method includes adjusting the preform insertion speed based on the measured diameter of the optical fiber 106, wherein change in the preform insertion speed changes the draw speed and diameter of the optical fiber 106 and diameter in the draw speed results in generation of the excess/residual voltage resulting in change in the residual voltage. The draw speed is adjusted at every period less than 150 milliseconds and the Capstan voltage is maintained for less than 900 volts as the capstan drive will trip above this voltage.
[0038] At step 408, the method includes dissipating the residual voltage into heat, whereby the diameter of the optical fiber 106 is less than 210 microns and variation in the diameter of the optical fiber 106 is +/-10 microns.
[0039] It may be noted that the flow chart 400 is explained to have above stated process steps; however, those skilled in the art would appreciate that the flow chart 400 may have more/less number of process steps which may enable all the above stated implementations of the present disclosure.
[0040] The various actions act, blocks, steps, or the like in the flow chart and sequence diagrams may be performed in the order presented, in a different order or simultaneously. Further, in some implementations, some of the actions, acts, blocks, steps, or the like may be omitted, added, modified, skipped, or the like without departing from the scope of the present disclosure.
[0041] It will be apparent to those skilled in the art that other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention. While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above-described embodiment, method, and examples, but by all embodiments and methods within the scope of the invention. It is intended that the specification and examples be considered as exemplary, with the true scope of the invention being indicated by the claims.
[0042] Conditional language used herein, such as, among others, “can”, “may”, “might”, “may”, “e.g.”, and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain alternatives include, while other alternatives do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more alternatives or that one or more alternatives necessarily include logic for deciding, with or without other input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular alternative. The terms “comprising,” “including,” “having,” and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude additional elements, features, acts, operations, and so forth. Also, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or all of the elements in the list.
[0043] Disjunctive language such as the phrase “at least one of X, Y, Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to present that an item, term, etc., may be either X, Y, or Z, or any combination thereof (e.g., X, Y, and/or Z). Thus, such disjunctive language is not generally intended to, and should not, imply that certain alternatives require at least one of X, at least one of Y, or at least one of Z to each be present.
[0044] While the detailed description has shown, described, and pointed out novel features as applied to various alternatives, it can be understood that various omissions, substitutions, and changes in the form and details of the devices or algorithms illustrated can be made without departing from the scope of the disclosure. As can be recognized, certain alternatives described herein can be embodied within a form that does not provide all of the features and benefits set forth herein, as some features can be used or practiced separately from others.
, Description:CLAIMS
We Claim:

1. An optical fiber draw tower (100), comprising:
a preform feed system (102) near a top end (108) of the optical fiber draw tower (100), wherein the preform feed system (102) holds a preform (104) and inserts the preform (104) into the optical fiber draw tower (100) as a lower end (110) of the preform (104) is melted to form an optical fiber (106);
a diameter measurement gauge (112) for measuring diameter of the optical fiber (106);
a capstan drive (114) coupled with the preform feed system (102), wherein the capstan drive (114) calibrates draw speed based on the diameter of the optical fiber (106) measured by the diameter measurement gauge (112); and
a shunt module (116) electrically coupled with the capstan drive (114), wherein the shunt module (116) dissipates residual voltage, wherein the residual voltage is resulted due to change in the draw speed, whereby the diameter of the optical fiber (106) is less than 210 microns and variation in the diameter of the optical fiber (106) is +/- 10 microns.

2. The optical fiber draw tower (100) as claimed in claim 1, wherein the capstan drive (114) calibrates the draw speed at a period less than 150 milliseconds.

3. The optical fiber draw tower (100) as claimed in claim 1, wherein the shunt module (116) further comprising a resistor (306), a heat sink (308) and a thermal switch (314), wherein the heat sink (308) is heated up due to the residual voltage.

4. The optical fiber draw tower (100) as claimed in claim 1, wherein the draw speed is more than 2600m/min.

5. The optical fiber draw tower (100) as claimed in claim 1, wherein the capstan drive voltage is maintained for less than 900 volts.

6. A method of drawing an optical fiber (106), the method comprising:
melting a preform (104) into the optical fiber (106) in an optical fiber draw tower (100);
measuring diameter of the optical fiber (106) using a diameter measurement gauge (112);
adjusting preform insertion speed based on the measured diameter of the optical fiber (106), wherein change in the preform insertion speed changes draw speed and diameter of the optical fiber (106), wherein change in the draw speed results in generation of residual voltage generated in capstan drive ; and
dissipating the residual voltage into heat, whereby the diameter of the optical fiber (106) is less than 210 microns and variation in the diameter of the optical fiber (106) is +/- 10 microns.

7. The method as claimed in claim 6, wherein the draw speed is adjusted at a time period less than 150 milliseconds.

8. The method as claimed in claim 6 further comprising maintaining the capstan drive voltage for less than 900 volts.