Fiber Optic Tutorials

This is a continuation from the previous tutorial - working definitions of cutoff wavelength.   Our objective in this tutorial is to give a very brief introduction to the concepts of atomic energy levels and of spontaneous emission between those levels. We attempt to demonstrate heuristically that atoms (or ions, or molecules) have quantum-mechanical energy levels; that atoms can be pumped or excited up into higher energy levels by various methods; and that these atoms then make spontaneous downward transitions to lower levels, emitting radiation at characteristictransition frequencies in the process.   The Helium Spectrum Figure 1.5 illustrates a simple...

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)....