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Fiber Coatings, Buffering and Cabling Materials

What is an Optical Fiber Coating/Buffer?

Optical fiber coatings/buffers play an important role in protecting the fiber from its intended environment. The coating protects the glass fiber from mechanical and environmental stresses in application. The primary coating may be applied in a single or dual layer. Coatings are applied during the fiber draw process and before touching any external surface. For additional protection, a layer of buffer material may be added. The buffer material provides additional mechanical protection for the fiber and helps preserve the waveguide.

What is a Fiber Optic Cable Jacket?

An optical cable structure protects optical fibers from environmental damage. Cable structure includes buffers, strength members, and jackets. Many factors influence the design of fiber-optic cables. The cable design relates to the intended application of the cable.

Fiber Optic Coatings

Acrylate Fiber Coating: Photocurable liquid coating compositions adapted to provide primary coatings for optical glass fibers. Standard telecoms optical fibers use a dual coating of acrylate (a softer inner coating and a harder outer layer). Specialty fibers typically use one coat.
High-Temperature Acrylate: High-temperature acrylate is used because of its resistance to steam and cable gels or when the fiber will be used in a harsh environment requiring extra protection. Typically used in industrial sensing and military/aerospace applications.
Fluoroacrylate: Non-toxic and rugged, this coating is ideal for medical applications. It adheres to the class surface of the silica “healing” micro-defects thereby improving the tensile strength of the fiber and retarding static fatigue. Used in industrial applications where the hard polymer enables a connector to be crimped directly onto the fiber and the fiber cleaved mechanically. More information on Lightera HCS Crimp & Cleave technology can be found on this website. This fluoroacrylate may be used as a cladding or a coating material for optical fiber.
Silicone Coating: Resistant to water vapor and a range of chemicals, silicone is soft, and requires buffering for protection, usually with thermoplastics like ETFE, PFA or PEEK. Silicone dampens attenuation inducing compression and is easily strippable.
Acrylate Coating: Typically used to coat optical fibers designed for distributed temperature sensing applications. Depending on the grade of Acrylate, mid-temperature range up to 135 ºC for up to 20 years and higher temperatures up to 200 ºC, can be supported. Optical fibers using this coating combination are protected against moisture across the temperature range. They are resistant to water and chemicals and are cushioned for deployment and service in harsh environments.
Polyimide: Polyimide coatings from Lightera are designed for optical fiber in harsh temperature sensing and communications environments. A thin, hard polymer coating provides mechanically strong fiber with excellent chemical resistance, small cross-section, and long-term high-temperature exposure. Lightera polyimide provides excellent thermal stability and some of the highest operating temperatures: continuous lifetime temperatures of 275 °C for up to 80 years, 300 °C for up to 13 years, 325 °C for up to 2.2 years, as well as short-term (24 hours) excursions as high as 450 °C.
Carbon: This coating, applied a few angstroms thick, extends fiber lifetime significantly and can be used with other coating materials. Used in applications where the optical fiber will be exposed to high stress, and/or installed in a tight coil, and/or there will be exposure to high humidity. Often the coating of choice when long lifetime of the optical fiber is a requirement.
Polyetheretherketone PEEK: Frequently used as a tertiary layer where other coatings like carbon and silicone may comprise other layers. PEEK provides a high Young’s modulus outer layer with excellent chemical and abrasion resistance, low thermal expansion, and is a zero-halogen material providing low smoke and toxicity.
Polybutylene terephthalate PBT: Polybutylene Terephthalate (PBT) delivers excellent short-term mechanical properties, such as high strength, toughness and stiffness as well as good practical impact. PBT’s high heat-deflection temperatures and high temperature index ratings help components withstand both short term thermal excursions and long-term heat exposure. It has robust chemical resistance to a wide range of chemicals. Optical fibers and fiber optic cables jacketed with PBT would be used in aerospace, utilities and industrial applications.
Polypropylene PP: Polypropylene may be used as an alternative to polyvinyl chloride (PVC) as a buffer for optical fiber in LSZH cable. It emits less smoke and no toxic halogens, which may lead to production of acid in high-temperature conditions.
Polyethylene PE: PE has excellent properties of moisture and weather resistance and has good electrical properties over a wide temperature range. It’s also abrasion resistant. Typically used as a jacket material for Outside Plant fiber optic cables.
LSZH (Low-Smoke, Zero Halogen) PE-PP: LSZH jacket is free of halogenated materials which can be transformed into toxic and corrosive matter during combustion. LSZH is a good cable jacket choice for enclosed installations.
Polyvinylchloride PVC: PVC is usually low-cost, flexible, fairly rugged. It can be formulated to function in a variety of environments and applications. It is used as a cable jacket material for both indoor and outdoor cables.
Polyvinylidene Fluoride PVDF: A PVDF coating does not react with most solvents and chemicals. It offers excellent resistance to abrasions and wear, high dielectric strength, is resistant to weathering, and can extinguish itself in the case of a fire. They also do not produce much smoke if there is a fire. This coating is a good choice for indoor plenum cables.
Polyurethane TPU: Properties of TPU include: high abrasion resistance, low-temperature performance, high shear strength, high elasticity, transparency and oil and grease resistance. Used in industrial grade cables.
Halogen Free Flame Retardant Polyurethane HFFR: Halogen-free, flame retardant (HFFR) thermoplastic polyurethane (TPU) compositions are replacing halogen-containing, flame retardant TPU compositions in a number of applications including, but not limited to, the insulation and protective jackets for the wire and cable associated with personal electronic devices and cables deployed in enclosed spaces. These HFFR TPU compositions can provide excellent flame-retardant performance and mechanical properties including excellent flexibility.
Hytrel® TPE: Thermoplastic polyester elastomers (TPE) provide the flexibility of rubbers and the strength of plastics. The material offers excellent flex fatigue and broad use temperature. It resists tearing, flex-cut growth, creep and abrasion, showing outstanding toughness while resisting hydrocarbons and many other fluids. It is used in several of the Lightera cables designed for reliable use in aircraft applications.
Ethylene Tetrafluoroethylene ETFE: ETFE [poly(ethene-co-tetrafluoroethene) has excellent resistance to extremes of temperature, excellent chemical resistance, good mechanical strength with excellent tensile strength and elongation. It has superior physical properties compared to most fluoropolymers. It also exhibits outstanding resistance to weather and aging. ETFE is typically used as a buffer for the Lightera HCS® fibers used in industrial datacom applications.
Perfluoroalkoxy Teflon™ PFA: Optical fiber cables buffered with Teflon™ fluoropolymers gain exceptional resistance to high temperatures, chemical reaction, corrosion, and stress cracking. The material is well suited for cables deployed in harsh applications.

We are here to help.

The team at Lightera has years of experience developing fiber optic coating solutions. Serving a range of industries, we work closely with all our clients to ensure coatings meet their specific needs, no matter how unusual or complex. To learn more about our optical fibers, reach out to our team of experts today to discuss your optic fiber and fiber optic cable specifications and needs.