Basic Structure of Optical Cable

An optical cable consists of a core, cladding, coating, strengthening fibers, and an outer jacket, each serving to transmit light efficiently and protect the fiber.CoreThe core is the innermost part of the optical fiber and is responsible for carrying light signals. It is typically made of high-purity glass (silicon dioxide) or sometimes plastic, designed to allow light to travel long distances with minimal loss. The core's diameter varies depending on the fiber type: 8–10 µm for single-mode fibers and 50–62.5 µm for multimode fibers. Light travels through the core via total internal reflection, which is enabled by the refractive index difference between the core and cladding .CladdingSurrounding the core is the cladding, which has a slightly lower refractive index than the core. This difference ensures that light remains confined within the core, reducing signal loss and preventing light from escaping. The cladding also provides a protective layer against external contaminants and mechanical damage. Standard cladding diameters are 125 µm or 140 µm, depending on the fiber type .CoatingThe coating is a protective layer applied over the cladding to shield the fiber from physical damage, moisture, and microbending. It does not affect the optical properties but enhances durability during handling, installation, and operation .Strengthening FibersOptical cables often include strengthening fibers or a strength member, such as aramid yarn (Kevlar), fiberglass, or steel wires. These fibers bear mechanical stress, prevent stretching, and protect the delicate core and cladding from tension, crushing, or bending forces, especially in outdoor or long-distance installations .Outer JacketThe outer jacket is the external protective layer that shields the cable from environmental hazards such as moisture, chemicals, abrasion, and UV exposure. Jackets are made from materials like PVC, polyethylene, or LSZH (low-smoke zero-halogen) compounds, depending on the installation environment. Some cables also include ripcords to facilitate easy removal of the jacket for splicing or termination .SummaryIn essence, an optical cable is a carefully engineered assembly where the core transmits light, the cladding confines it, the coating and strengthening fibers protect it, and the outer jacket ensures environmental durability. This layered structure allows optical cables to deliver high-speed, long-distance data transmission reliably in both indoor and outdoor applications .