Principle of Optical Fiber

This chapter briefly describes the fundamentals of optical fibers and provides an introductory review of the development of POFs. 

Silica MMF Silica SMF Proportional to real size core 50/125 9/125 diameter/cladding 

---

Section 9.1 covers basic principles of optical fiber operation, fiber manufacturing, and optical fiber design for the major different types of telecommunications-grade optical fibers currently used. Section 9.2 includes information on fiber optic cable designs and applications, basic optical connectivity products, and relevant industry standards and guidelines for fiber optic cable. 

Marcuse, D. (1981) Principles of Optical Fiber Measurements, Academic Press, New York, pp. 226-232. 

Marcuse D., In Principles of optical fiber measurements. Academic Press, NY, 1981, pp. 141 - 156. 

This chapter provides an overview of the basic principles and designs of such sensors. A chemical sensor to detect trace explosives and a broadband fiber optic electric-field sensor are presented as practical examples. The polymers used for the trace explosive sensor are unpoled and have chromophores randomly orientated in the polymer hosts. The electric field sensor uses a poled polymer with chromophores preferentially aligned through electrical poling, and the microring resonator is directly coupled to the core of optical fiber. 

A.1 Fundamentals of Vapor Phase Synthesis. In this section we will concentrate on the vapor phase synthesis of some structural ceramics, such as carbides and nitrides. The principles described here apply equally well to the production of oxide ceramics, but we reserve some of this description for later sections, particularly with respect to the formation of optical fibers. 

T.2.4.3 Modified CVD Processes for Opticai Fiber Production. The principles of chemical vapor deposition can also be applied to the production of optical fibers. The fundamentals of fiber optics were described in Section 6.3.2.7. We concentrate here on the application of CVD to their production. 

Walt (1998) described the principle of optical sensing using fibers. An optical fiber consists of two concentrically arranged optically transparent media an inner ring, called the core, carries the optical signal, and a thin outer ring, called the clad (made of a lower refractive index material). The refractive index mismatch at the interface of the two media acts as a mirror to help the transmission of light from one end of the fiber to the other end. The phenomena in play here is that of total internal reflection (Walt 1998). 

Based on the basic performance of optic fiber sensors, Krohn (1986) divided optic fiber sensors into two basic classes. In the first class, the transmission of the fiber is directly affected by the physical phenomena being sensed and is referred to as an intrinsic optic fiber sensor. The second class is for optic fiber position sensors which detect position changes and are sensitive to changes in physical property. There are usually five types of sensors according to their different working principles intensity modulated, transmitting, reflective, micro bending... 

The principle of the fiber-optic pH sensor led Vurek et al. [133] to devise a CO2 sensor. Instead of coupling the pH indicator dye to an insoluble polymer, a simple isotonic solution of salt, hydrogencarbonate, and dye was used, which was covered with a C02-permeable silicone-rubber membrane. The sensor s performance was demonstrated in vivo. Similarly, a fluorescein-based C02-sensitive system was reported by Hirschfeld et al. [134]. 

Instrumentation Optical fibers General Principles of Optical... 

FIGURE 6.9 Basic principle of a fiber optic antigen-antibody sensor. (Taken from Anderson G.P., Golden J.P., and Ligler F.S. 1993. IEEE Trans. Biomed. Eng. 41 578.)... 

The principle of the Fiber optic cable is based on the total reflection of a beam at the boundary of a phase with a high refractive index and a phase with a low refractive index (Fig. 4-55). If the cable is bent, the beam nevertheless remains in the inner portion of the fiber (Fig. 4-56). 

FIGURE 16 Schematic principles of bioaffinity fiber-optic biosensors. (a) Detection of intrinsically fluorescent molecule using immobilized antibody, (b) Competition assay using a fluorescent-labeled antigen, (c) Sandwich immunoassay using an immobilized antibody and a fluorescent-labeled antibody. 

FIGURE 17 Principle of DNA fiber-optic biosensors, (a) Single-strand DNA probe molecules, with a sequence complementary to one strand of the target DNA sequence, are immobilized onto the fiber, (b) The fluorescent-labeled sample DNA molecules are first dehybridized and the fiber is dipped into the sample solution, (c) After hybridization, the complementary strands of the target DNA are attached to the probe DNA on the fiber and a fluorescence signal is obtained. 

In the following sections, a brief summary of the fundamentals of optical fibers and waveguides will be given. The basic principles involved in the various components that make up the optical communications system will be discussed. In addition to optical communications, optical fibers and waveguides have unique characteristics that make them... 

Optical property refers to a material s response to exposure to electromagnetic radiation and, in particular, to visible light. This chapter first discusses some of the basic principles and concepts relating to the nature of electromagnetic radiation and its possible interactions with solid materials. Then it explores the optical behaviors of metallic and nonmetal-lic materials in terms of their absorption, reflection, and transmission characteristics. The final sections outline luminescence, photoconductivity, and light amplification by stimulated emission of radiation (laser), the practical use of these phenomena, and the use of optical fibers in communications. 

While the first theoretical investigation of optical fibers dates back to Hondros and Debye in 1910 [9], there was little subsequent interest until highly transparent materials became available in the late sixties and early seventies. The fabrication of optical fibers capable of transmitting light over distances of several kilometres stimulated rapid development of the theoretical analysis of their propagation properties. Whilst, in principle. Maxwell s equations de-... 

More recently, the method of scanning near-field optical microscopy (SNOM) has been applied to LB films of phospholipids and has revealed submicron-domain structures [55-59]. The method involves scanning a fiber-optic tip over a surface in much the same way an AFM tip is scanned over a surface. In principle, other optical experiments could be combined with the SNOM, snch as resonance energy transfer, time-resolved flnorescence, and surface plasmon resonance. It is likely that spectroscopic investigation of snbmicron domains in LB films nsing these principles will be pnrsned extensively. 

Processes such as film extrusion, fiber spinning, injection molding, and drawing tend to impart orientation to products made from semicrystalline polymers. Mechanical, dielectric, and optical properties, to mention only three, are often strongly influenced by orientation. X-ray diffraction offers a direct approach to studying crystallite orientation because the Intensity that is diffracted into a detector placed at an appropriate position is directly proportional to the number of crystal lattice planes that are in the correct orientation for diffraction. The principles of such measurements are well described in textbooks 0,2). 

---