Optical Fiber Acrylate Coating?
Acrylate is one of the fiber category. Acrylate has an operating temperature of -40°C to 85°C (-40°F to 185°F). It is suitable for room temperature environments without extreme temperature, vacuum, or pressure requirements. Acrylate coating has Class VI biocompatibility rating.
Because Acrylate coating strips easily and cleanly, the coating is selected most often to manufacture single fiber assemblies. Acrylate coated fibers are usually selected to manufacture single fiber assemblies, but if the Acrylate coating is thin, it can also be used for making bundle assemblies. Acrylate is most commonly used on fibers between 50 and 1,000 microns in diameters and is applied in one layer between 10 and 100 microns in thickness.
Optical fibers with specialty acrylate coatings (single and dual coat designs) were tested at temperatures up to 200°C in normal atmosphere to define fiber properties stability and maximum operating temperatures.
What is Coating in Optical Fiber?
Optical fiber coatings, such as polymeric, metallic and inorganic are routinely applied on fibers. Polymeric coatings, particularly ultraviolet (UV)-cured acrylate are extensively used in the telecommunication industries. Metallic coatings, such as tin coated fibers showed strength values near to the theoretical value of pure silica. Inorganic coatings, such as amorphous carbon coated fibers showed comparable strength and high fatigue resistance for using these fibers as a potential long term reliable fibers. A review of different optical coatings, current status and future direction is presented.
For a standard-size fiber with a 125-µm cladding diameter and a 250-µm coating diameter, 75% of the fiber’s three-dimensional volume is the polymer coating. The core and cladding glass account for the remaining 25% of the coated fiber’s total volume. Coatings play a key role in helping the fiber meet environmental and mechanical specifications as well as some optical performance requirements.
Optic Fiber Coating Function
For standard-sized fibers with a cladding diameter of 125 µm and a cladding diameter of 250 µm, the polymer cladding accounts for 75% of the three-dimensional fiber volume. The core and cladding glass account for the remaining 25% of the total volume of the coated optical fiber. Coatings play a key role in helping optical fibers meet environmental and mechanical specifications, as well as some optical performance requirements.
The function of the coating is to protect the glass surface and protect the glass surface from damage by external factors, such as handling and abrasion. If the fiber is stretched without being coated, the outer surface of the glass cladding will be exposed to air, moisture, other chemical contaminants, nicks, collisions, abrasion, small bends, and other hazards. These phenomena can cause defects on the glass surface. Initially, these defects may be small or even microscopic, but over time, the applied stress, and exposure to water, they will become larger cracks and eventually lead to failure. Therefore, all fibers have a protective coating when stretched.
Key Performance of Optical Fiber Coatings
Important parameters of coatings include the following:
Stripability：
Strip-ability is essentially the opposite of delamination resistance-you don’t want the coating to fall off when using fibers, but you do want to be able to remove short-length coatings during processes such as splicing, installing connectors, and making fusion splices. In this case, the technician will use a special tool to control the length.Refractive Index: Index of refraction is the speed at which light passes through the material, expressed as a ratio to the speed of light in a vacuum. The refractive index of widely used telecom-fiber coatings from major suppliers such as DSM ranges from 1.47 to 1.55. DSM and other companies also offer lower index coatings, which are often used with specialty fibers. Refractive index can vary with temperature and wavelength, so coating indexes typically are reported at a specific temperature, such as 23°C.
Temperature Range:
Temperature range typically extends from -20°C to + 130°C for many of the widely used UV-cured acrylates used with telecom fibers. Higher ranges are available for harsh environments. Ranges extending above +200°C are available with other coating materials, such as polyimide or metal.
Modulus is also called “Young’s Modulus,” or “modulus of elasticity,” or sometimes just “E.” This is a measure of hardness, typically reported in MPa. For primary coatings, the modulus can be in single digits. For secondary coatings, it can be greater than 700 MPa.
Abrasion Resistance：
For some special optical fiber applications, wear resistance is critical, and most communication optical fibers get extra protection from buffer tubes and other cable components. The technical article describes different perforation and abrasion resistance tests. For applications where this is Adhesion and
Resistance to Delamination：
Adhesion and resistance to delamination are important characteristics to assure that the primary coating does not separate from the glass cladding and that the secondary coating does not separate from the primary coating. A standardized test procedure, TIA FOTP-178 “Coating Strip Force Measurement” is used to measure the resistance to delamination.
a critical parameter, the fiber or coating manufacturers can provide details on test methods.
Viscosity and Curing Speed：
Viscosity and curing speed are related to the characteristics of the coating film. These properties are also related to temperature. The control of coating parameters is an important job for drawing engineers, including the control of coating temperature.
Microbending Performance：
Microbending performance is a situation where the coating is critical in helping the glass fiber maintain its optical properties, specifically its attenuation and polarization performance. Microbends differ from macrobends, which are visible with the naked eye and have bend radii measured in millimeters. Microbends have bend radii on the order of hundreds of micrometers or less. These bends can occur during manufacturing operations, such as cabling, or when the fiber contacts a surface with microscopic irregularities. To minimize microbending problems, coating manufacturers have developed systems incorporating a low-modulus primary coating and a high-modulus secondary coating. There also are standardized tests for microbending, such as TIA FOTP-68 “Optical Fiber Microbend Test Procedure.”
Conclusion
The idea of a single “perfect” coating for any specific type of fiber is unlikely, if not impossible. In practice, the coating compositions represent compromises between various parameters, including index of refraction, modulus, temperature performance, and draw-tower requirements. To address the mix of requirements, coating manufacturers have ongoing R&D programs to improve the performance of their resins and achieve a better balance of multiple parameters.
