CN106116138A - A kind of wire drawing coating processes of minor diameter low-loss bend-insensitive single-mode optical fiber - Google Patents

Abstract

The invention relates to a wire drawing coating process of a small-diameter, low-loss, bend-insensitive single-mode optical fiber. The steps of the wire-drawing coating process of the small-diameter bend-insensitive single-mode optical fiber are as follows: melting wire drawing, annealing, diameter measurement, coating and screening . The advantages of the present invention are: attention should be paid to the tension control of the glass preform during the wire drawing process to improve the bending loss of the optical fiber; PLC control is adopted to measure the outer diameter of the glass optical fiber, and the measurement result is fed back to the PLC control unit. The speed and drawing speed are dynamically controlled to realize the automatic control of the processing process; the improved coating mold is used to coat polyacrylic resin on the optical fiber, which not only reduces the coating thickness of the optical fiber, but also protects the internal optical fiber, and the optical fiber The effect on the performance of the optical fiber is very small; due to the thinning of the coating, the curing power is adjusted in the curing unit to save energy and reduce consumption, obtain the best matching of curing power, and reduce the loss of accessories caused by the fiber curing process.

Description

A drawing coating process for small-diameter low-loss bend-insensitive single-mode optical fiber

technical field

The invention relates to the field of optical fiber manufacturing, in particular to a wire drawing coating process for a small-diameter low-loss bending-insensitive single-mode optical fiber.

Background technique

In China's "Twelfth Five-Year Plan", the new generation of information and communication is included in the seven emerging strategic industries, and it is required to accelerate the construction of ubiquitous and broadband-integrated information network infrastructure, accelerate the integration of three networks, and accelerate the intelligent transformation of important infrastructure. Promote the new generation of mobile communications and next-generation Internet devices, and promote the research and development and demonstration applications of the Internet of Things and cloud computing. The application hotspots of optical fiber and cable are broadband China and smart grid construction.

The communication construction of the metropolitan area network has promoted the large-scale laying of optical cables. For operators, underground pipelines and channel routing resources for laying communication optical cables in cities are gradually scarce. New routes will lead to demolition, capital, time schedule, failure to expand pipeline resources in urban dense areas, and competition with other infrastructure for routing. If we can make full use of scarce routing resources to lay more optical fibers, it will undoubtedly promote urban construction. In this size-constrained environment, the use of smaller-sized single-mode optical fibers can introduce more fiber optic cables in limited space resources to save space and pipe resources. The research on reducing the coating diameter of single-mode optical fiber to a small size is to meet the application mode of this new type of optical fiber cable.

With the continuous development of national technologies such as "Broadband China" and "Internet+", the underground pipelines and channel routing resources for laying communication optical cables in cities are gradually scarce, which puts forward new requirements for current optical fibers and optical cables. The need to reduce the coating diameter of single-mode optical fiber from conventional to small size arises at the historic moment, that is, to reduce the size of the optical cable under the premise of ensuring the current performance. As the core material of the optical fiber cable, the size reduction of the optical fiber, especially the multi-core optical cable, such as 96 cores, 128 cores, 256 cores, etc., can effectively reduce the size of the optical cable; due to the thinning of the coating, it will seriously affect the performance of the optical fiber. Therefore, it is necessary to adjust the refractive index profile structure of the preform, improve the drawing equipment and drawing process conditions, and be able to produce small-sized optical fibers with stable coating diameters.

Contents of the invention

The technical problem to be solved by the present invention is to provide a wire drawing coating process for small-diameter bend-insensitive single-mode optical fibers that significantly reduces the structural size of the optical cable without degrading the performance of the optical cable.

In order to solve the above technical problems, the technical solution of the present invention is: a small-diameter low-loss bend-insensitive single-mode optical fiber drawing coating process, the innovation of which is: the small-diameter low-loss bending-insensitive single-mode optical fiber drawing coating process The covering process steps are as follows:

(1) Fusion drawing: put the preformed rod processed in the previous stage into the heating furnace, the preform is melted, and is thinned into a glass optical fiber at a certain speed under the action of the drawing tension of 100~190g;

(2) Annealing: The fiber drawn into filaments enters the annealing process. The annealing process includes three parts: the annealing high temperature furnace, the heating furnace and the heat preservation tube. After the three-stage annealing process, the optical fiber has been slowly cooled to the assumed surface temperature, effectively The residual internal stress of the optical fiber is eliminated, and the attenuation of the optical fiber is reduced;

(3) Diameter measurement: the outer diameter of the glass optical fiber is measured by a fiber warp measuring instrument, and the measurement result is fed back to the PLC control unit. The PLC control unit adjusts the feeding speed and drawing speed of the preform rod according to the fiber diameter data, which plays a role in fiber drawing. overall control of the process;

(4) Coating: The optical fiber enters the coating process. The coating mold is a hollow columnar structure, and the hollow cavity is filled with acrylic resin coating. During the movement of the optical fiber, the coating in the hollow cavity is evenly adhered to the surface. On the outer surface of the optical fiber, a coating layer with a certain thickness is formed. The coating layer includes a low modulus inner coating and a high modulus outer coating. The size ratio of the inner coating to the outer coating is 0.8~1.2:1;

(5) Curing: The optical fiber enters the irradiation range of the curing lamp. According to the thinning of the coating layer, the curing power of the curing lamp is adjusted to 1800~3000W;

(6) Screening: Due to the reduction in the size of the optical fiber, adjust the speed of the guide wheel of the screening rewinding machine to provide a take-up pulling force of 0.35~0.85g for pulling the optical fiber.

Further, the temperature in the heating furnace in the step (1) is controlled at 1800°C to 2200°C.

Further, the temperature of the heating furnace in the step (2) is between 900°C and 1200°C.

Further, in the step (2), the heating furnace is located 15 cm below the high-temperature annealing furnace, and the insulation pipe is located 20-25 cm below the heating furnace.

Further, in the step (4), the interior of the coating mold includes a conical inner cavity with a large top and a small bottom and a coating hole connected to the lower end of the conical inner cavity. The taper of the conical inner cavity is 3-25° , The coating hole length is 0.8~5mm.

The advantages of the present invention are:

(1) Pay attention to the tension control of the glass preform during the drawing process to improve the bending loss of the optical fiber; use PLC control to measure the outer diameter of the glass optical fiber, and feed back the measurement results to the PLC control unit. By adjusting the feeding speed of the preform and drawing The speed is dynamically controlled to realize the automatic control of the processing process; the improved coating mold is used to coat polyacrylic resin on the optical fiber, and the best coating ratio tested is adopted, which not only reduces the coating thickness of the optical fiber, Moreover, the internal optical fiber is protected and has little impact on the performance of the optical fiber; due to the thinning of the coating, the curing power is adjusted in the curing unit to save energy and reduce consumption, obtain the optimal curing power matching, and reduce the accessory loss caused by the optical fiber curing process.

(2) Adopting an improved coating mold, adjusting the taper and length of the mold, obtaining a pressure gradient range suitable for small-sized optical fibers, and ensuring the coating quality and concentricity requirements.

Description of drawings

Fig. 1 is a cross-sectional view of a small-diameter bend-insensitive single-mode optical fiber in a drawing coating process of a small-diameter low-loss bend-insensitive single-mode optical fiber according to the present invention.

Fig. 2 is a flow chart of a drawing coating process for a small-diameter, low-loss, bend-insensitive single-mode optical fiber of the present invention.

Fig. 3 is a schematic diagram of a coating die for a wire drawing coating process of a small-diameter, low-loss, bend-insensitive single-mode optical fiber according to the present invention.

detailed description

As shown in Figure 1, the nominal diameter of the small-diameter bend-insensitive single-mode optical fiber is 200mm, which includes the core 1, cladding and coating layers from the inside to the outside, and the core 1 layer is a germanium-doped silica glass layer , the cladding includes an inner cladding 2 and an outer cladding 3, the inner cladding 2 is a sunken inner cladding doped with F, the germanium doping amount is reduced in the preform for preparing the optical fiber to reduce the Rayleigh scattering in the core layer, and the cladding adopts a deep Doping with fluorine makes the inner cladding layer 2 of the refractive index section form a depression, and controls the uniform distribution of the radial refractive index and the slope of the refractive index section.

As shown in Figure 2, the drawing coating process steps of the small-diameter bend-insensitive single-mode fiber are as follows:

(1) Fusion drawing: put the preformed rod processed in the previous stage into the heating furnace, the preform is melted, and is thinned into a glass optical fiber at a certain speed under the action of the drawing tension of 100~190g;

(2) Annealing: The fiber drawn into filaments enters the annealing process. The annealing process includes three parts: the annealing high temperature furnace, the heating furnace and the heat preservation tube. After the three-stage annealing process, the optical fiber has been slowly cooled to the assumed surface temperature, effectively The residual internal stress of the optical fiber is eliminated, and the attenuation of the optical fiber is reduced;

(3) Diameter measurement: the outer diameter of the glass optical fiber is measured by a fiber warp measuring instrument, and the measurement result is fed back to the PLC control unit. The PLC control unit adjusts the feeding speed and drawing speed of the preform rod according to the fiber diameter data, which plays a role in fiber drawing. overall control of the process;

(4) Coating: The optical fiber enters the coating process. As shown in Figure 3, the coating mold 6 is a hollow columnar structure. The inside of the coating mold 6 includes a conical inner cavity 7 with a large top and a small bottom and a conical cavity connected to the The coating hole 9 at the lower end of the conical cavity 7, the taper of the conical cavity 7 is 3~25°, the length of the coating hole 9 is 0.8~5mm; the conical cavity 7 is filled with acrylic resin paint, and the optical fiber passes through it in turn Coating the conical inner cavity of the mold 7 and the coating hole 9, during the movement of the optical fiber, the coating in the conical inner cavity 7 is uniformly coated on the outer surface of the optical fiber 8, and passes through the coating hole 9 at the lower end, Form a coating layer with a certain thickness, the coating layer includes a low modulus inner coating and a high modulus outer coating, and the size ratio of the inner coating to the outer coating is 0.8~1.2:1;

(5) Curing: The optical fiber enters the irradiation range of the curing lamp. According to the thinning of the coating layer, the curing power of the curing lamp is adjusted to 1800~3000W;

(6) Screening: Due to the reduction in the size of the optical fiber, adjust the speed of the guide wheel of the screening rewinding machine to provide a take-up pulling force of 0.35~0.85g for pulling the optical fiber.

During the wire drawing process, pay attention to the control of the wire drawing tension. Fiber loss and bending loss are both affected by the drawing tension. Increasing the drawing tension will increase the loss of the fiber, but at the same time it can improve the bending loss. Therefore, in the drawing process, it is necessary to find the appropriate drawing tension to solve the fiber loss and bending loss. The balance control of the product has been verified by experiments. When the tension is in the range of 100~190g, the fiber loss and bending loss of this product can reach the optimal value.

Fiber bending loss can be expressed by a dimensionless parameter:

MAC=MFD/λ

Among them, MFD is the mode field diameter of the fiber, and λ is the cut-off wavelength of the fiber. From the research results, the smaller the MAC, the smaller the bending loss of the fiber. During the drawing process, through the effective control of the MAC value, it is ensured that the macrobending loss of the optical fiber does not decrease significantly with the diameter of the coating.

During the annealing process, the optical fiber is annealed three times. The first time is annealed in the high-temperature annealing furnace of the drawing furnace. The temperature of the optical fiber is slowly lowered in the annealing high-temperature furnace to 1500 degrees. The second annealing is in the heating furnace 15cm below the high-temperature annealing furnace. Middle annealing, to ensure that the temperature of the optical fiber in the heating furnace is 1000~1200 degrees, the third annealing is carried out in the insulation tube 20~50cm below the heating furnace, and the optical fiber is thermally annealed. Through the above three annealing, the temperature of the optical fiber is gradient When the optical fiber is exposed to the cold air environment in the workshop, it is already lower than the assumed temperature of the surface, which has a good annealing effect.

In the coating process, the matching of the thickness of the inner and outer coatings is considered. The high-modulus outer coating bears the radial and lateral pressure of the optical fiber, and the low-modulus inner coating absorbs the external force applied to the optical fiber and acts as a buffer. The properties of the coating resin itself, such as viscosity, modulus, glass transition temperature, etc., affect the bending loss of the optical fiber. Therefore, it is critical to select different performance coating resins and study the thickness of the inner and outer coatings for this 200 μm small-size optical fiber. Combined with theoretical analysis, through the design and analysis of DOE experiment design with three factors of different coatings, inner coating thickness and outer coating thickness, two acrylic resin coatings are selected, and the thickness ratio of the inner and outer coatings is 0.8~1.2:1 The proportional relationship can ensure that the thickness of the inner and outer coatings is sufficient to protect the optical fiber and stabilize the performance of the optical fiber.

During the curing process, due to the thinning of the coating, the curing speed of the coating layer is significantly improved compared with conventional size optical fibers, and the original curing process is no longer applicable. From the perspective of energy saving and consumption reduction, by adjusting the curing power to 1800~3000W, it can meet the requirements of appearance, curing degree and related mechanical properties, obtain the optimal curing power matching, and reduce the additional loss caused by the fiber curing process.

In the screening process, the optical fiber is wound with a certain tension applied by the screening machine. The tension in the process will cause additional loss of the optical fiber, and the optical fiber will break when the tension is high. At the same time, due to the reduction of the size of the optical fiber, the original screening process cannot meet the requirements, so the cable pitch is adjusted to 0.38~0.44mm. Poor cable pitch can easily cause fiber bending loss and poor winding density. Adjust the take-up tension of the screening machine to 0.35~0.85g, control the line speed to keep the tension stable and adjust the line pitch to reduce additional attenuation and bending loss.

Through the production and development of 200μm low-loss bend-insensitive single-mode optical fiber, breakthroughs have been made in key technologies and manufacturing processes such as optical fiber coating mold design, small-size optical fiber curing process, and microbending performance improvement, filling the domestic gap.

The basic principles and main features of the present invention have been shown and described above. Those skilled in the industry should understand that the present invention is not limited by the above-mentioned embodiments. What are described in the above-mentioned embodiments and the description only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have Variations and improvements are possible, which fall within the scope of the claimed invention. The protection scope of the present invention is defined by the appended claims and their equivalents.

Claims (5)

1. A wire drawing coating process for a small-diameter low-loss bend-insensitive single-mode optical fiber. The nominal diameter of the small-diameter bend-insensitive single-mode optical fiber is 200 mm, which includes a core, a cladding, and a coating from the inside to the outside. The cladding layer, the core layer is a germanium-doped silica glass layer, the cladding layer includes an inner cladding layer and an outer cladding layer, and the inner cladding layer is a depressed inner cladding layer doped with fluorine, which is characterized in that: the small-diameter low-loss bending The drawing and coating process steps of insensitive single-mode fiber are as follows: Fusion drawing: Put the preform processed in the early stage into the heating furnace, the preform is melted, and is thinned at a certain speed under the action of the drawing tension of 100~190g to become a glass optical fiber; Annealing: The fiber drawn into filaments enters the annealing process. The annealing process includes three parts: an annealing high temperature furnace, a heating furnace, and a heat preservation tube. Through the three-stage annealing process, the fiber has been slowly cooled to the assumed surface temperature, effectively eliminating the fiber Residual internal stress, and reduce the attenuation of optical fiber; Diameter measurement: The outer diameter of the glass optical fiber is measured by a fiber warp measuring instrument, and the measurement result is fed back to the PLC control unit. The PLC control unit adjusts the feeding speed and drawing speed of the preform according to the fiber diameter data, which plays an integral role in the fiber drawing process. control effect; Coating: The optical fiber enters the coating process. The coating mold is a hollow columnar structure, and the hollow cavity is filled with acrylic resin coating. During the movement of the optical fiber, the coating in the hollow cavity is evenly adhered to the outer surface of the optical fiber. On top, a coating layer with a certain thickness is formed, the coating layer includes a low modulus inner coating and a high modulus outer coating, and the size ratio of the inner coating to the outer coating is 0.8~1.2:1; Curing: The optical fiber enters the irradiation range of the curing lamp. According to the thinning of the coating layer, the curing power of the curing lamp is adjusted to 1800~3000W; Screening: Due to the reduction in the size of the optical fiber, adjust the speed of the guide wheel of the screening and rewinding machine to provide a take-up pulling force of 0.35~0.85g for pulling the optical fiber. 2. The wire drawing coating process for small-diameter, low-loss, bend-insensitive single-mode optical fiber according to claim 1, wherein the temperature in the heating furnace in the step (1) is controlled at 1800°C~2200°C. 3. The wire drawing coating process for small-diameter, low-loss, bend-insensitive single-mode optical fiber according to claim 1, wherein the temperature of the heating furnace in the step (2) is 900°C-1200°C. 4. The drawing coating process of a small-diameter, low-loss, bend-insensitive single-mode optical fiber according to claim 1: characterized in that: in the step (2), the heating furnace is located 15 cm below the annealing high-temperature furnace, and the heat preservation The tube is located 20-25 cm below the furnace. 5. The wire-drawing coating process for small-diameter, low-loss, bend-insensitive single-mode optical fiber according to claim 1, characterized in that: in the step (4), the interior of the coating mold includes upper, lower, and lower The conical inner cavity and the coating hole connected to the lower end of the conical inner cavity, the taper of the conical inner cavity is 3-25°, and the length of the coating hole is 0.8-5mm.