Fiber Optic Tutorials

This is a continuation from the previous tutorial - introduction to lenses for image formation and manipulation.   1. Introduction The cutoff wavelength of a single-mode optical fiber is the wavelength above which only a single bound mode, the fundamental LP01 mode, propagates. For numerous reasons concerning transmission performance (bandwidth, multipath interference, modal noise, etc.), it is desirable to operate fibers in the regime where only the fundamental mode propagates. (This discussion does not address the intentional use of multimoded fibers for short-reach applications, where as many as 10- to 18-mode groups may be allowed to propagate at the operating...

This is a continuation from the previous tutorial - what is a laser?   Basics This tutorial provides a basic understanding of using lenses for image formation and manipulation. The principles of image formation are reviewed first. The effects of lens shape, index of refraction, magnification, and F-number on the image quality of a singlet lens are discussed in some detail. Achromatic doublets and more complex lens systems are covered next. A representative variety of lenses is analyzed and discussed. Performance that may be expected of each class of lens is presented. The tutorial concludes with several techniques for rapid...

This is a continuation from the previous tutorial - linear lightwave propagation in an optical fiber.   Lasers are devices that generate or amplify coherent radiation at frequencies in the infrared, visible, or ultraviolet regions of the electromagnetic spectrum. Lasers operate by using a general principle that was originally invented at microwave frequencies, where it was called microwave amplification by stimulated emission of radiation, or maser action. When extended to optical frequencies this naturally becomes light amplification by stimulated emission of radiation, or laser action. This basic laser or maser principle is now used in an enormous variety of devices...

This is a continuation from the previous tutorial - Fourier transform for periodic signals.     1. Physical Structure of a Telecommunication Optical Fiber Optical fibers are fabricated by first depositing high-purity silica soot, doped with germania (GeO2) to raise the index of refraction or fluorine (F) to lower the index of refraction, to form a core rod of 1 cm or more in diameter and 1 m or more in length. Fabrication methods  include processes known in the industry as ‘‘modified chemical vapor deposition’’ (MCVD), outside vapor deposition (OVD), vapor axial deposition (VAD), and plasma chemical vapor deposition (PCVD)....

This is a continuation from the previous tutorial - representation of aperiodic signals with continuous-time Fourier transform.   In the previous tutorial, we introduced the Fourier transform representation and gave several examples. While our attention in that tutorial was focused on aperiodic signals, we can also develop Fourier transform representations for periodic signals, thus allowing us to consider both periodic and aperiodic signals within a unified context. In fact, as we will see, we can construct the Fourier transform of a periodic signal directly from its Fourier series representation. The resulting transform consists of a train of impulses in the frequency domain, with...