They are commonly used for tight coating of fibers to produce tight buffered optical fiber cables which are mainly used for indoor riser and plenum applications. Standard sheath colours are: Black, orange, red, green, blue and aqua. At the same time, it must have. In reality, cable sheath selection has a direct impact on fire safety, outdoor durability, installation flexibility, and long-term maintenance cost. Choosing the wrong sheath material may not cause immediate failure, but it often leads to accelerated aging, regulatory issues, or repeated field. Sheathing has three core values for use in fiber optic design: Protect the fiber. Glass fiber and plastic fiber is fragile. GL FIBER here's a guide to help you choose the right outer sheath material: 1.