An optical fiber drawing device and drawing control method

Abstract

This invention discloses an optical fiber drawing device and a drawing control method, belonging to the field of optical fiber manufacturing. The optical fiber drawing method with automatic control of the optical fiber cutoff wavelength described in this invention transmits the optical fiber cutoff wavelength measured by an optical fiber testing instrument to the drawing production line controller. Furthermore, by transmitting the preform core rod test data to the drawing production line controller, it adds a step involving the core diameter and the relative refractive index difference of the core and cladding at various axial positions of the core rod in the optical fiber drawing control process. It also incorporates a corresponding automatic control method for the drawing furnace temperature, overcoming the shortcomings of current adjustments based on the experience of production workers. Simultaneously, it reduces the lag in adjusting the optical fiber cutoff wavelength during the drawing process, achieving stable automatic control of the optical fiber cutoff wavelength, and ensuring production efficiency and optical fiber quality.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber manufacturing, and in particular to an optical fiber drawing device and a drawing control method. Background Technology

[0002] Currently, the production process of optical fiber preforms mainly adopts a two-step method: first, the preform core is manufactured, and then the preform cladding is manufactured. There are four main core manufacturing technologies: modified chemical vapor deposition (MCVD), microwave plasma chemical vapor deposition (PCVD), external vapor deposition (OVD), and axial vapor deposition (VAD). Outer cladding manufacturing technologies mainly include external vapor deposition (OVD), the sleeve method, and plasma spraying.

[0003] The manufacturing technology of the core rod often determines the performance of the drawn optical fiber, while the cladding preparation technology determines the cost. During the core rod preparation process, factors such as the flow rate of the deposition raw material gas, the rotation speed of the guide rod, the ventilation pressure, and laser effects can all cause variations in the uniformity of the core rod's axial diameter and refractive index parameters, thus affecting optical parameters such as the cutoff wavelength, mode field diameter, and zero-dispersion wavelength of the optical fiber. In the optical fiber preform drawing process, traditional methods control the cutoff wavelength of the fiber by controlling the furnace temperature. However, with continuous improvements in process technology and equipment manufacturing, the speed of optical fiber drawing is increasing, and the length of the fiber spool is growing. The latest metal spools can wind 1000km of fiber. Adjusting the furnace temperature solely based on the parameters tested from the previous fiber spool will still introduce a certain lag. Especially since the axial parameters of the core rod in the optical fiber preform are not stable, untimely adjustments can easily lead to unqualified fiber parameters and ultimately, fiber failure.

[0004] Patent CN103030272A provides a fiber drawing method for automatic cutoff wavelength control. It feeds back the cutoff wavelength data from fiber testing to the fiber drawing production line controller, and uses fuzzy control theory to automatically control the heating power of the drawing furnace, thus achieving automatic control of the fiber cutoff wavelength. However, controlling the drawing furnace power alone cannot achieve precise control of the furnace temperature. Furthermore, this method still exhibits significant lag in furnace temperature adjustment and does not fully consider the changes in fiber parameters caused by variations in the core rod parameters in the preform, which can easily lead to fiber instability or even failure. Summary of the Invention

[0005] To overcome the above-mentioned technical defects, the present invention provides an optical fiber drawing device and a drawing control method to solve the problems involved in the background art.

[0006] This invention provides an optical fiber drawing device and a drawing control method, comprising:

[0007] Fiber optic drawing equipment;

[0008] A fiber drawing furnace is installed on the upper part of the fiber drawing equipment; an optical fiber preform is installed on the upper part of the fiber drawing furnace, and one end of the optical fiber preform is inserted into the hot zone of the furnace cavity of the fiber drawing furnace;

[0009] Fiber optic testing instruments are suitable for detecting the cutoff wavelength of optical fibers produced by fiber drawing equipment.

[0010] A core rod testing instrument is suitable for detecting the axial data of the core rod in the optical fiber preform; the axial data of the core rod includes the core diameter and the relative refractive index difference of the core and cladding at various axial positions of the optical fiber preform.

[0011] The fiber drawing production line controller is connected to the fiber testing instrument, the core rod testing instrument, and the fiber drawing furnace to acquire the cutoff wavelength and core rod axial data of the produced fiber and adjust the fiber production temperature in the fiber drawing furnace.

[0012] Preferably or optionally, it also includes a temperature testing device;

[0013] The temperature testing device is installed inside the drawing furnace and is connected to the drawing production line controller for signal detection, and is suitable for detecting the temperature of the hot zone of the furnace cavity.

[0014] Preferably or optionally, the wire drawing furnace employs graphite resistance heating or coil induction heating.

[0015] Preferably or optionally, the wire drawing production line controller is a programmable logic controller (PLC).

[0016] The present invention also includes a fiber drawing control method based on the aforementioned fiber drawing device, comprising:

[0017] Step 1: The core rod testing instrument acquires the core diameter and the relative refractive index difference of the core and cladding at various axial positions of the optical fiber preform and transmits them to the fiber drawing production line controller; the initial set value of the core diameter and the relative refractive index difference of the core and cladding are preset in the production line controller.

[0018] Step 2: Install the optical fiber preform on the upper part of the drawing furnace and insert one end of the optical fiber preform into the hot zone of the furnace cavity.

[0019] Step 3: The optical fiber preform is heated in a drawing furnace. After the drawing temperature and drawing speed are increased to a stable level, the optical fiber drawing equipment performs optical fiber drawing.

[0020] Step 4: The optical fiber produced by the optical fiber drawing equipment is measured by an optical fiber testing instrument. The measured cutoff wavelength of the optical fiber is then transmitted to the drawing production line controller.

[0021] Step 5: The fiber drawing production line controller determines whether the cutoff wavelength of the optical fiber produced by the fiber drawing equipment falls within the control range; if yes, proceed to step 6; if no, control the drawing furnace to raise or lower the furnace temperature until the cutoff wavelength of the produced optical fiber falls within the control range, and then proceed to step 6.

[0022] Step 6: Maintain the furnace temperature and drawing speed of the drawing furnace as in Step 5, and determine whether the core diameter at the current position of the optical fiber preform axis is greater than the initial set value of the core diameter; if yes, slowly increase the furnace temperature of the drawing furnace; if no, slowly decrease the furnace temperature of the drawing furnace.

[0023] Step 7: Maintain the furnace temperature and drawing speed of the drawing furnace as in Step 6, and determine whether the relative refractive index difference of the core and cladding at the current position of the optical fiber preform axis is greater than the initial set value of the relative refractive index difference of the core and cladding. If yes, slowly increase the furnace temperature of the drawing furnace; if no, slowly decrease the furnace temperature of the drawing furnace.

[0024] Step 8: Repeat steps 5 to 7 until the fiber preform is drawn.

[0025] Preferably or optionally, in step 1, the fiber drawing production line controller uses the core diameter at the axial starting point of the fiber preform core as the initial setting value for the core diameter; and uses the relative refractive index difference of the core and cladding at the axial starting point of the fiber preform core as the setting value for the relative refractive index difference of the core and cladding.

[0026] Preferably or optionally, in step 5, the method for controlling the temperature of the drawing furnace to rise or fall is as follows:

[0027] If the cutoff wavelength of the optical fiber is lower than the control range, the drawing production line controller controls the drawing furnace to lower the furnace temperature until the cutoff wavelength of the produced optical fiber falls within the control range; if the cutoff wavelength of the optical fiber is higher than the control range, the drawing production line controller controls the drawing furnace to raise the furnace temperature until the cutoff wavelength of the produced optical fiber reaches the control range.

[0028] Preferably or optionally, in step 3, the stable wire drawing temperature is 2100-2300℃, and the stable wire drawing speed is 2700-3000m / min.

[0029] Preferably or optionally, in step 5, the control range is 1260nm-1280nm;

[0030] The heating or cooling rate of the wire drawing furnace is 5-10℃ / s.

[0031] Preferably or optionally, in steps 6 and 7, the heating or cooling rate of the wire drawing furnace is 0.1 to 3°C / s.

[0032] This invention relates to an optical fiber drawing device and a drawing control method. Compared with the prior art, it has the following advantages: The optical fiber automatic cutoff wavelength control drawing method of this invention transmits the optical fiber cutoff wavelength measured by the optical fiber testing instrument to the drawing production line controller. Furthermore, by transmitting the preform core rod test data to the drawing production line controller, it adds a step involving the core layer diameter and the relative refractive index difference of the core and cladding layers at various axial positions of the core rod in the optical fiber drawing control process. It also incorporates a corresponding automatic control method for the drawing furnace temperature, thus overcoming the shortcomings of current adjustments based on the experience of production workers. Simultaneously, it reduces the lag in adjusting the optical fiber cutoff wavelength during the drawing process, achieving stable automatic control of the optical fiber cutoff wavelength and ensuring production efficiency and optical fiber quality. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the optical fiber drawing device in this invention.

[0034] Figure 2 This is a columnar distribution diagram of the cutoff wavelength and quantity of the optical fiber produced in Embodiment 1 of the present invention.

[0035] Figure 3 This is a columnar distribution diagram of the cutoff wavelength and quantity of the optical fiber produced in Embodiment 2 of the present invention.

[0036] Figure 4 This is a columnar distribution diagram of the cutoff wavelength and quantity of the optical fiber produced in Example 3 of this invention.

[0037] Figure 5 This is a columnar distribution diagram of the cutoff wavelength and quantity of the optical fiber produced in Comparative Example 1 of this invention.

[0038] Figure 6 This is a columnar distribution diagram of the cutoff wavelength and quantity of the optical fiber produced in Comparative Example 2 of this invention.

[0039] Figure 7 This is a columnar distribution diagram of the cutoff wavelength and quantity of the optical fiber produced in Comparative Example 3 of this invention.

[0040] The attached diagram is labeled as follows: 1. Optical fiber preform; 2. Drawing furnace; 3. Optical fiber drawing equipment; 4. Temperature testing device; 5. Drawing production line controller; 6. Data transmission network cable; 7. Core rod testing instrument; 8. Data transmission network cable; 9. Optical fiber testing instrument; 10. Control network cable. Detailed Implementation

[0041] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0042] See appendix Figure 1 An optical fiber drawing device includes: an optical fiber preform 1, a drawing furnace 2, a temperature testing device 4, an optical fiber drawing equipment 3, a drawing production line controller 5, a control network cable 10, data transmission network cables 6 and 8, a core rod testing instrument 7, and an optical fiber testing instrument 9.

[0043] The optical fiber preform 1 is prepared using a two-step process. The optical fiber preform 1 is suspended above the drawing furnace 2. During production, the optical fiber preform 1 is inserted into the hot zone of the drawing furnace 2. The drawing furnace 2 uses graphite resistance heating or coil induction heating and is installed above the optical fiber drawing equipment 3. The core rod testing instrument 7 is connected to the drawing production line controller 5 via a data transmission network cable 6 to transmit test data on the axial direction of the core rod in the optical fiber preform 1. The axial data of the core rod includes the core diameter and the relative refractive index difference of the core and cladding at various axial positions of the optical fiber preform 1. The optical fiber testing instrument 9 is also connected to the drawing production line controller 5 via a data transmission network cable 8 to transmit test data from the previous optical fiber tray. The drawing production line controller 5 is connected to the drawing furnace 2 via a control network cable 10 to automatically control the optical fiber production temperature inside the drawing furnace 2.

[0044] In a further embodiment, the wire drawing production line controller 5 is a programmable logic controller (PLC). The core rod testing instrument 7 and the optical fiber testing instrument 9 are both manufactured by PK Corporation, USA; the core rod testing instrument 7 is model PK2600, and the optical fiber testing instrument 9 is model PK2300AG.

[0045] In a further embodiment, the optical fiber drawing device further includes a temperature testing device 4, which is installed inside the drawing furnace 2 to detect the temperature inside the furnace. Since the heating temperature set in the drawing furnace 5 may deviate from the actual temperature inside the furnace 5, and the actual temperature inside the furnace 5 is not equivalent to the optical fiber production temperature, the temperature testing device 4 is installed inside the drawing furnace near the drawing area. The temperature testing device 4 is a thermometer or temperature sensor, ensuring that the temperature detected by the device is as close as possible to the optical fiber production temperature. This achieves precise control of the optical fiber cutoff wavelength, guaranteeing production efficiency and optical fiber quality.

[0046] The theoretical formula for calculating the cutoff wavelength of optical fiber is as follows:

[0047]

[0048]

[0049] Where: a represents the fiber core, n1 represents the core refractive index, n2 represents the cladding refractive index, and Δn represents the relative refractive index difference between the core and cladding. It can be seen that the core diameter and the relative refractive index difference between the core and cladding, which are test parameters along the core rod's axial direction, directly affect the fiber's cutoff wavelength, and the fiber cutoff wavelength is positively correlated with both the core diameter and the relative refractive index difference. Therefore, the applicant has designed a fiber drawing control method for the aforementioned fiber drawing device, including the following steps:

[0050] Step 1: The core rod testing instrument acquires the core diameter and the relative refractive index difference of the core and cladding at various axial positions of the optical fiber preform and transmits them to the fiber drawing production line controller; the initial set value of the core diameter and the relative refractive index difference of the core and cladding are preset in the production line controller.

[0051] Specifically, the fiber drawing production line controller uses the core diameter at the axial starting point of the fiber preform core as the initial setting value for the core diameter; and uses the relative refractive index difference of the core and cladding at the axial starting point of the fiber preform core as the setting value for the relative refractive index difference of the core and cladding.

[0052] Step 2: Install the optical fiber preform on the upper part of the drawing furnace and insert one end of the optical fiber preform into the hot zone of the furnace cavity.

[0053] Step 3: The optical fiber preform is heated in a drawing furnace. After the drawing temperature and speed are increased to a stable level, the optical fiber drawing equipment performs optical fiber drawing. The stable drawing temperature is 2100-2300℃ and the stable drawing speed is 2700-3000m / min.

[0054] Step 4: The optical fiber produced by the optical fiber drawing equipment is measured by an optical fiber testing instrument. The measured cutoff wavelength of the optical fiber is then transmitted to the drawing production line controller.

[0055] Step 5: The fiber drawing production line controller determines whether the cutoff wavelength of the optical fiber produced by the fiber drawing equipment falls within the control range; if yes, proceed to step 6; if no, control the drawing furnace to raise or lower the furnace temperature until the cutoff wavelength of the produced optical fiber falls within the control range, and then proceed to step 6; the control range is 1260nm-1280nm.

[0056] Specifically, the method for controlling the temperature increase or decrease of the drawing furnace is as follows: if the cutoff wavelength of the optical fiber is lower than the control range, the drawing production line controller controls the drawing furnace to decrease the furnace temperature until the cutoff wavelength of the produced optical fiber falls within the control range, and then proceeds to step 6; if the cutoff wavelength of the optical fiber is higher than the control range, the drawing production line controller controls the drawing furnace to increase the furnace temperature. The rate of temperature increase or decrease in the drawing furnace is 5–10℃ / s.

[0057] Step 6: Maintain the furnace temperature and drawing speed of the drawing furnace as in Step 5, and determine whether the core diameter at the current position of the optical fiber preform axis is greater than the initial set value of the core diameter; if yes, slowly increase the furnace temperature; if no, slowly decrease the furnace temperature; the rate of increase or decrease of the furnace temperature is 0.1 to 3°C.

[0058] Step 7: Maintain the furnace temperature and drawing speed of the drawing furnace as in Step 6, and determine whether the relative refractive index difference of the core and cladding at the current position of the optical fiber preform axis is greater than the initial set value of the relative refractive index difference of the core and cladding. If yes, slowly increase the furnace temperature; if no, slowly decrease the furnace temperature. The rate of increase or decrease of the furnace temperature is 0.1 to 3°C.

[0059] Step 8: Repeat steps 5 to 7 until the fiber preform is drawn.

[0060] The present invention will be further described below with reference to the embodiments. The examples described are intended to explain the present invention and should not be construed as limiting the present invention.

[0061] Example 1

[0062] The fiber drawing device and drawing control method in this embodiment are the same as those described above. Here, only some of the different parameters are explained and introduced.

[0063] In this embodiment, the optical fiber preform is prepared using a two-step VAD+OVD process, with an average diameter of 150 mm. The fiber drawing furnace maintains a temperature of 2100℃ and a drawing speed of 2800 m / min during the stabilization phase. In step S5, the fiber testing instrument measures the fiber cutoff wavelength to be 1266 nm, which meets the cutoff wavelength control range. The furnace temperature remains at 2100℃. In step S6, the furnace temperature is automatically controlled based on the core rod's test data, with a heating or cooling rate of 1℃ / s to achieve automatic control of the fiber cutoff wavelength.

[0064] The axial test data of the fiber preform core in this embodiment are shown in Table 1, and the cutoff wavelength data of the produced fiber are shown in Appendix 1. Figure 2 As shown.

[0065] Table 1. Axial data of the optical fiber preform core in Example 1

[0066]

[0067] Example 2

[0068] The fiber drawing device and drawing control method in this embodiment are the same as those described above. Here, only some of the different parameters are explained and introduced.

[0069] In this embodiment, the optical fiber preform is prepared using the VAD+sleeve method, and the average diameter of the sleeve preform is 200mm. After the optical fiber preform reaches a stable temperature at 2300℃, the drawing speed is 2900m / min. In step 5, the optical fiber testing instrument measures the cutoff wavelength of the optical fiber to be 1220nm. If the cutoff wavelength in step 5 does not meet the control range, the furnace temperature of the drawing furnace is reduced to 2180℃ at a cooling rate of 5℃ / s. The cutoff wavelength is then measured again to be 1270nm, which meets the cutoff wavelength control range. In step 7, the furnace temperature of the drawing furnace is automatically controlled based on the test data of the core rod, with a heating or cooling rate of 0.5℃ / s, thus achieving automatic control of the optical fiber cutoff wavelength.

[0070] The axial test data of the fiber preform core in this embodiment are shown in Table 2, and the cutoff wavelength data of the produced fiber are shown in the appendix. Figure 3 As shown.

[0071] Table 2. Core axial data of optical fiber preforms in Example 2

[0072]

[0073] Example 3

[0074] The fiber drawing device and drawing control method in this embodiment are the same as those described above. Here, only some of the different parameters are explained and introduced.

[0075] In this embodiment, the optical fiber preform is prepared using the VAD+sleeve method, and the average diameter of the sleeve preform is 150 mm. After the optical fiber preform reaches a stable temperature at 2100℃, the drawing speed is 2700 m / min. In step 5, the optical fiber testing instrument measures the cutoff wavelength of the optical fiber to be 1320 nm. Since the cutoff wavelength in step 5 does not meet the control range, the furnace temperature of the drawing furnace is increased to 2200℃ at a heating rate of 7℃ / s, and the cutoff wavelength is measured again to be 1275 nm, which meets the cutoff wavelength control range. In step 6, since the cutoff wavelength does not meet the control range, the furnace temperature of the drawing furnace is further increased to 2250℃ at a heating rate of 0.5℃ / s, and the cutoff wavelength is measured again to be 1270 nm, which meets the cutoff wavelength control range. In step 7, the furnace temperature of the drawing furnace is automatically controlled based on the test data of the core rod, with a heating or cooling rate of 0.5℃ / s, thus achieving automatic control of the optical fiber cutoff wavelength.

[0076] The axial test data of the fiber preform core in this embodiment are shown in Table 3, and the cutoff wavelength data of the produced fiber are shown in the appendix. Figure 4 As shown.

[0077] Table 3. Axial data of the optical fiber preform core in Example 3

[0078]

[0079]

[0080] Comparative Example 1

[0081] The fiber drawing device in this embodiment is the same as in Embodiment 1, and the drawing control method only includes steps 1 to 5. Steps 6 to 8 are not involved; only some of the different parameters are explained and introduced here.

[0082] In this embodiment, changes in the axial parameters of the optical fiber preform are not considered; the furnace temperature of the drawing furnace is controlled solely based on the cutoff wavelength test data from the lower plate of the optical fiber preform drawing process. The optical fiber preform is fabricated using a two-step VAD+OVD process, with an average diameter of 150 mm. The axial parameters of the optical fiber preform are essentially the same as those in Example 1. The furnace temperature during the stable phase of the optical fiber drawing furnace is 2100℃, and the drawing speed is 2800 m / min. In step 5, the optical fiber testing instrument measures the cutoff wavelength of the optical fiber to be 1266 nm, which meets the cutoff wavelength control range. The furnace temperature remains at 2100℃ to continue drawing the optical fiber.

[0083] The cutoff wavelength data for the manufactured optical fibers are attached. Figure 5 As shown.

[0084] Comparative Example 2

[0085] The fiber drawing device in this embodiment is the same as in embodiment 2. The drawing control method only includes steps 1 to 5, and does not involve steps 6 to 8. Here, only some of the different parameters are explained and introduced.

[0086] In this embodiment, the axial parameter variation of the optical fiber preform is not considered; the furnace temperature of the drawing furnace is controlled solely based on the cutoff wavelength test data of the optical fiber preform drawing tray. The optical fiber preform is prepared using the VAD+sleeve method, with an average diameter of 200 mm. The axial parameters of the optical fiber preform are basically the same as those in Example 2. After the optical fiber preform reaches a stable temperature of 2300℃, the drawing speed is 2900 m / min. In step 5, the optical fiber testing instrument measures the cutoff wavelength to be 1220 nm. If the cutoff wavelength in step 5 does not meet the control range, the furnace temperature of the drawing furnace is reduced to 2180℃ at a cooling rate of 5℃ / s. The cutoff wavelength is then measured again to be 1270 nm, which meets the cutoff wavelength control range. The furnace temperature remains at 2180℃ to continue drawing the optical fiber.

[0087] The cutoff wavelength data for the manufactured optical fibers are attached. Figure 6 As shown.

[0088] Comparative Example 3

[0089] The fiber drawing device in this embodiment is the same as in embodiment 1. The drawing control method only includes steps 1 to 5, and does not involve steps 6 to 8. Here, only some of the different parameters are explained and introduced.

[0090] In this embodiment, the axial parameter variation of the optical fiber preform is not considered; the furnace temperature of the drawing furnace is controlled solely based on the cutoff wavelength test data of the optical fiber preform drawing tray. The optical fiber preform is prepared using the VAD+sleeve method, with an average diameter of 150 mm. The axial parameters of the optical fiber preform are basically the same as those in Example 2. After the optical fiber preform reaches a stable temperature of 2100℃, the drawing speed is 2700 m / min. In step 5, the optical fiber testing instrument measures the cutoff wavelength to be 1320 nm. Since the cutoff wavelength in step 5 does not meet the control range, the furnace temperature of the drawing furnace is increased to 2200℃ at a heating rate of 7℃ / s. The cutoff wavelength is then measured again to be 1275 nm, which meets the cutoff wavelength control range. The furnace temperature is maintained at 2180℃ to continue drawing the optical fiber.

[0091] The cutoff wavelength data for the manufactured optical fibers are attached. Figure 7 As shown.

[0092] in conclusion

[0093] In Examples 1 to 3, by transmitting the preform core test data to the fiber drawing production line controller, a step was added to control the fiber drawing process by incorporating the core diameter and the relative refractive index difference of the core cladding at various axial positions of the core rod. In Comparative Examples 1 to 3, the furnace temperature of the fiber drawing furnace was controlled solely based on the cutoff wavelength test data from the fiber preform drawing tray. (Comparative Appendix) Figure 2 and attached Figure 5 It can be seen that the cutoff wavelength of the optical fiber produced in Example 1 is concentrated in the range of 1260–1282 nm, while the cutoff wavelength of the optical fiber produced in Comparative Example 1 is concentrated in the range of 1180–1320 nm; (Comparison Appendix) Figure 3 and attached Figure 6 The cutoff wavelength of the optical fiber produced in Example 2 is concentrated in the range of 1220–1290 nm, while the cutoff wavelength of the optical fiber produced in Comparative Example 2 is concentrated in the range of 1220–1330 nm; (Comparative Appendix) Figure 4 and attached Figure 7 The cutoff wavelength of the optical fiber produced in Example 2 is concentrated in the range of 1260-1340 nm, while the cutoff wavelength of the optical fiber produced in Comparative Example 2 is concentrated in the range of 1220-1340 nm. Compared with Examples 1 to 3, the optical fiber obtained has a higher concentration of cutoff wavelength, higher stability, and better optical fiber quality.

[0094] Furthermore, in Examples 1 to 3, by transmitting the preform core rod test data to the fiber drawing production line controller, a step is added to control the fiber drawing process by incorporating the core diameter and the relative refractive index difference of the core cladding at various axial positions of the core rod. A corresponding automatic temperature control system for the drawing furnace is also included. This overcomes the shortcomings of current adjustments based on the experience of production workers, reduces the phenomenon of adjusting the fiber cutoff wavelength during the drawing process, achieves stable automatic control of the fiber cutoff wavelength, and ensures production efficiency.

[0095] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. A method for controlling optical fiber drawing, characterized in that, This control method is based on an optical fiber drawing device, which includes: Fiber optic drawing equipment; A fiber drawing furnace is installed on the upper part of the fiber drawing equipment; an optical fiber preform is installed on the upper part of the fiber drawing furnace, and one end of the optical fiber preform is inserted into the hot zone of the furnace cavity of the fiber drawing furnace; Fiber optic testing instruments are suitable for detecting the cutoff wavelength of optical fibers produced by fiber drawing equipment; core rod testing instruments are suitable for detecting the axial data of the core rod in the optical fiber preform. The core rod axial data includes the core diameter and the relative refractive index difference of the core and cladding at various axial positions of the optical fiber preform. The fiber drawing production line controller is connected to the fiber testing instrument, the core rod testing instrument, and the fiber drawing furnace to acquire the cutoff wavelength and core rod axial data of the produced fiber and adjust the fiber production temperature in the fiber drawing furnace. The control method includes: Step 1: The core rod testing instrument acquires the core diameter and the relative refractive index difference of the core and cladding at various axial positions of the optical fiber preform and transmits them to the fiber drawing production line controller; the initial setting values ​​of the core diameter and the relative refractive index difference of the core and cladding are preset in the production line controller. Step 2: Install the optical fiber preform on the upper part of the drawing furnace and insert one end of the optical fiber preform into the hot zone of the furnace cavity. Step 3: The optical fiber preform is heated in a drawing furnace. After the speed is increased to reach a stable drawing temperature and a stable drawing speed, the optical fiber drawing equipment performs optical fiber drawing. The stable drawing temperature is 2100-2300℃, and the stable drawing speed is 2700~3000m / min. Step 4: The optical fiber produced by the optical fiber drawing equipment is measured by an optical fiber testing instrument. The measured cutoff wavelength of the optical fiber is then transmitted to the drawing production line controller. Step 5: The fiber drawing production line controller determines whether the cutoff wavelength of the optical fiber produced by the fiber drawing equipment falls within the control range; if yes, proceed to step 6; if no, control the drawing furnace to raise or lower the furnace temperature until the cutoff wavelength of the produced optical fiber falls within the control range, and then proceed to step 6; the control range is 1260nm-1280nm; the rate at which the drawing furnace temperature is raised or lowered is 5-10℃ / s. Step 6: Maintain the furnace temperature and drawing speed of the drawing furnace as in Step 5, and determine whether the core diameter at the current position of the optical fiber preform axis is greater than the initial set value of the core diameter; if yes, slowly increase the furnace temperature; if no, slowly decrease the furnace temperature; the rate at which the furnace temperature is increased or decreased is 0.1 to 3℃ / s. Step 7: Maintain the furnace temperature and drawing speed of the drawing furnace as in Step 6, and determine whether the relative refractive index difference of the core and cladding at the current position of the optical fiber preform axis is greater than the initial set value of the relative refractive index difference of the core and cladding. If yes, slowly increase the furnace temperature of the drawing furnace; if no, slowly decrease the furnace temperature of the drawing furnace. The rate of increase or decrease of the furnace temperature is 0.1 to 3℃ / s. Step 8: Repeat steps 5 to 7 until the fiber preform is drawn.

2. The optical fiber drawing control method according to claim 1, characterized in that, The fiber drawing device also includes a temperature testing device; The temperature testing device is installed inside the drawing furnace and connected to the drawing production line controller signal, and is suitable for detecting the temperature of the hot zone of the furnace cavity of the drawing furnace.

3. The optical fiber drawing control method according to claim 1, characterized in that, The wire drawing furnace uses graphite resistance heating or coil induction heating.

4. The optical fiber drawing control method according to claim 1, characterized in that, The wire drawing production line controller uses a programmable logic controller (PLC).

5. The optical fiber drawing control method according to claim 1, characterized in that, In step 1, the fiber drawing production line controller uses the core diameter at the axial starting point of the fiber preform core as the initial setting value for the core diameter; and uses the relative refractive index difference of the core and cladding at the axial starting point of the fiber preform core as the initial setting value for the relative refractive index difference of the core and cladding.

6. The optical fiber drawing control method according to claim 1, characterized in that, In step 5, the method for controlling the temperature of the drawing furnace to rise or fall is as follows: If the cutoff wavelength of the optical fiber is lower than the control range, the drawing production line controller controls the drawing furnace to lower the furnace temperature until the cutoff wavelength of the produced optical fiber falls within the control range; if the cutoff wavelength of the optical fiber is higher than the control range, the drawing production line controller controls the drawing furnace to raise the furnace temperature until the cutoff wavelength of the produced optical fiber falls within the control range.

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