The optical fiber wire does not have sufficient protection. For the core wire, polyamide resin (nylon) is coated over the wire.
The core wire is generally categorized into three types. In addition to 0.25 mm optical fiber core wire (UV core wire), we have 0.9 mm optical fiber core wire and the tape wire; a number of multi-core optical fiber are aligned in parallel by UV cure resin. Figure shows those three types of optical fiber wire core.
Nylon core wire
In nylon core wire, the UV cure resin or the silicon resin is employed for the primary coating, and the polyamide resin, nylon, is used for the secondary coating. For the sake of identification, the secondary coating is colored. The nylon core wire with 0.9 mm outer diameter (the secondary coating diameter) is specially called as 0.9 mm optical fiber core wire. Compared with the optical fiber wire, the nylon core wire is tough, and is superior in usability. The nylon core wire is often used for an optical fiber code and a LAN cable. The secondary coating like nylon is called as buffer. The buffer is categorized into two types, loose buffer and tight buffer. The tight buffer is directly attached on the optical fiber wire. The loose tube buffer utilizes plastic tube with a diameter several times larger than the fiber diameter.
Tape core wire
In tape core wire, a number of 0.25 mm optical fiber wire are aligned in parallel, and are coated in block by the UV cure resin. The tape core wire is used for composing a cable by placing fibers in a groove (tape slot structure). The tape core wires are typically double-core, quadruple-core, and octuple-core types.