Fiber 1 to Fiber 12: Blue, Orange, Green, Brown, Slate, White, Red, Natural, Yellow, Violet, Rose and Aqua. Fiber 25 to Fiber 36: same base color but with two black ring marks. The cable contains optical fibers for data transmission and telecom purposes and is installed instead of a ground wire. Fiber 37 to. ation on high voltage overhead power lines. Furthermore this specification contains information concerning the quality assurance during manufacturing, the final accepta ce tests. ace unit for optical fibres. The loose tube construction prevents fibre strain at any stage f installation ardless of the cable design. — Bi-directional average for each and every fiber (but.