Fiber Optic Tutorials

This is a continuation from the previous tutorial - the Rabi frequency.   1. Introduction Forward error correction (FEC) in optical communications has been first demonstrated in 1988. Since then, coding technology has evolved significantly. This pertains not only to the codes but also to encoder and decoder architectures. Modern high-speed optical communication systems require high-performance FEC engines that support throughputs of 100 Gbit/s or multiples thereof, that have low power consumption, that realize net coding gains (NCGs) close to the theoretical limits at a target bit error rate (BER) of less than \(10^{-15}\), and that are preferably adapted to...

This is a continuation from the previous tutorial - rare earth-doped fibers.   Both the linear susceptibility approach and the rate equation analysis we have developed in the past several tutorials are approximations—though usually very good approximations—to the exact dynamics of an atomic system with an external signal applied. If a very strong (or very fast) signal is applied to an atomic transition, however, the exact nonlinear behavior of the atomic response becomes more complicated, and the rate-equation approximation is no longer adequate to describe the atomic response. In this tutorial, therefore, we explore the conditions under which the rate-equation approximation...

This is a continuation from the previous tutorial - retardation plates.   1. Introduction Rare earth (RE) doping of optical fibers dates back to the 1960s and was one of the forces driving development of guided wave optical fibers. The goal was to exploit the long path length provided by wave-guiding media to improve operation of Nd, Er, and Er/Yb fiber lasers. Then, as now, the fiber consisted of regions with raised refractive index to guide light and some distribution of RE ions that interacted with this light. Very simply, the goal remains to exploit the optical activity of the...

This is a continuation from the previous tutorial - non-normal-incidence reflection and transmission polarizers.   1. Introduction The theory of retardation plates and especially quarter-wave retarders is given in later tutorial series. The basic relation for retardation plates is \[\tag{9}N\lambda=d(n_e-n_o)\] where \(n_o\) is the refractive index of the ordinary ray, \(n_e\) is the refractive index of the extraordinary ray, \(d\) is the physical thickness of the plate, and \(\lambda\) is the wavelength. Retardation plates are generally made of mica, stretched polyvinyl alcohol, and quartz, although other stretched plastics such as cellophane, Mylar, cellulose acetate, cellulose nitrate, sapphire, magnesium fluoride, and...

This is a continuation from the previous tutorial - dichroic and diffraction-type polarizers.   By far the largest class of polarizers used in the infrared and ultraviolet spectral regions (where dichroic sheet polarizers and calcite polarizing prisms cannot be used) is the so-called pile-of-plates polarizers from which light is reflected (or transmitted) at non-normal incidence. Since most of these polarizers operate at angles near the Brewster or polarizing angle, they are frequently called Brewster angle polarizers. The plane-parallel plates which are used for Brewster angle transmission polarizers are generally thick enough to ensure that although multiple reflections occur within each...