12 - Submarine fiber

Abstract

This chapter outlines the basic principles of fiber design and manufacture and provides a detailed analysis of the optical properties. The manufacture of optical fibers for high-performance applications requires precise control of the refractive index and diameter variations to minimize fluctuations of optical properties in the fiber. In the fiber manufacturing process, controlled variations in the refractive index profile of the fiber's core are achieved by introducing dopants, such as germania and fluorine into the silica host medium. This is generally accomplished using techniques, such as outside vapor deposition (OVD), modified chemical vapor deposition (MCVD), plasma-activated chemical vapor deposition (PCVD), and vapor axial deposition (VAD). All of these deposition methods involve the oxidation of precursor gas mixtures to form glass layers that define the fiber structure. The key fiber attribute in many wavelength-division multiplexing transmission systems is the attenuation of the optical fiber, which determines the amplifier or repeater spacing and is a key consideration in system design and cost. While low-baseline attenuation is desirable, it is also important that the value remain stable during the cabling process and lifetime of the system. An additional requirement is that the attenuation should be uniform across the transmission window.