Fiber Optic Tutorials

This is a continuation from the previous tutorial - performance of representative lenses.   Singlet Figure 39 is a nomogram that allows quick estimation of the performance of a single refracting lens, with the stop at the lens, as a function of refractive index \(N\), dispersion \(V\), F-number, and field of view \(\theta\).   Figure 39  Estimation of single lens spot size as a function of refractive index, dispersion, F-number, and field of view.   Chart A estimates the angular blur diameter \(\beta\) resulting from a singlet with bending for minimum spherical aberration. The angular chromatic blur diameter is given by Chart...

This is a continuation from the previous tutorial - laser oscillation and laser cavity modes.   Figures 27 – 38 present the performance of lenses representing a variety of lens types. The measures of performance provided in each figure have been selected for utilization purposes. Diffraction effects have not been included. Each figure is divided into four sections \(a-d\). Section \(a\) is a drawing of the lens showing the aperture stop. Section \(b\) contains two set of plots. The solid line is for the distortion versus field of view (\(\theta\)) in degrees while the dashed lines show the transmission of...

This is a continuation from the previous tutorial - laser pumping and population inversion.   Adding laser mirrors and hence signal feedback, as we will do in this section, is then the final step necessary to produce coherent laser oscillation and thus to obtain a working laser oscillator.   Condition for Build-Up of Laser Oscillation Suppose in fact that we have a laser rod or a laser tube containing atoms that are properly pumped so as to produce population inversion and amplification on a certain laser transition. To make a coherent oscillator using this medium, we must then add partially...

This is a continuation from the previous tutorial - microbending loss.   Let us now examine in elementary terms the kind of pumping process that can produce the population inversion needed for laser amplification.   Four-Level Pumping Model As a simplified but still quite realistic model of many real laser systems, we can consider the four-level atomic energy system shown in Figure 1.29.   Figure 1.29  A four-level laser pumping system.   We assume here that there is a lowest or ground energy level \(E_0\) and two higher energy levels \(E_1\) and \(E_2\), between which laser action is intended to take...

This is a continuation from the previous tutorial - polarization mode dispersion.   Fibers often exhibit excess loss when they are spooled or cabled as the result of small deflections of the fiber axis that are of random amplitude and are randomly distributed along the fiber. The loss induced in optical fiber by these small random bends and stress in the fiber axis is called microbending loss. Figure 2.16 cartoons the impact of a single microbend, at which, analogous to a splice, power can be coupled from the fundamental mode into higher order leaky modes. Because external forces are transmitted...