Fiber Optic Tutorials

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...

This is a continuation from the previous tutorial - multidimensional optimized optical modulation formats.   Some of the most useful polarizers available employ either dichroism or diffraction effects. These polarizers come in sheet form, sometimes in large sizes, are easily rotated, and produce negligible beam deviation. Also, they are thin, lightweight, and rugged, and most can be made in any desired shape. The cost is generally much less than that of a prism-type polarizer. Furthermore, both types are insensitive to the degree of collimation of the beam, so that dichroic or diffraction-type polarizers can be used in strongly convergent or...

This is a continuation from the previous tutorial - atomic rate equations.   1. Introduction The development of advanced digital signal processing (DSP) to enable intradyne coherent optical receivers caused a paradigm shift within optical communications, and there is little doubt that the future of optical transport will be coherent. Coherent receivers ideally map the optical signal to the electrical domain, which enables a lot of novel advanced communication algorithms to be implemented in optical links, for example, digital equalization and advanced modulation. One of the most profound developments was that intradyne receivers enabled all four quadratures of the optical...