Fiber Optic Tutorials

This is a continuation from the previous tutorial - landscape lenses and the influence of stop position.   Optical intensity of light decreases during transmission in a straight fiber because of various absorption and scattering mechanisms. This is represented mathematically in Eq. (2.3) when the longitudinal propagation constant, \(\beta\), is a complex number. The imaginary part of \(\beta\) is the longitudinal decay constant. The decrease in optical power during transmission is often referred to as ‘‘attenuation’’ or ‘‘loss.’’ For modern silica-based fibers, the attenuation within the wavelength range from about 1300 to 1600 nm is dominated by Rayleigh scattering, which...

This is a continuation from the previous tutorial - stimulated atomic emissions.   The first lens used for photography was designed in 1812 by the English scientist W. H. Wollaston about a quarter of a century before the invention of photography. He discovered that a meniscus lens with its concave surface towards the object could produce a much flatter image field than the simple biconvex lens commonly used at that time in the camera obscuras. This lens became known as the landscape lens and is illustrated in Fig. 12. Wollaston realized that if the stop was placed an appropriate amount...

This is a continuation from the previous tutorial - impact of profile design on macrobending losses.   Having introduced spontaneous (downward) transitions, we will now look at the stimulated (upward and downward) transitions that are the essential processes in all kinds of laser and maser action.   Atomic Absorption Lines Suppose we now examine more carefully the absorption of radiation by a collection of atoms as a function of the wavelength of the incident radiation. Figure 1.16 shows a very elementary example of a grating spectrometer such as might be used for such measurements. (A tunable laser would be a...

This is a continuation from the previous tutorial - single element lens.   1. The Depressed Cladding Fiber Design Historically both matched and depressed clad single-mode optical fibers have been widely deployed in telecommunications networks. For example, the original AT&T standard single-mode fiber was a depressed clad fiber with \(\text{MFD}=8.8\) μm. A depressed cladding design has an annular ring of \(\Delta\lt0\), often called a trench, between the raised index core and the silica cladding. In this case, the effective \(\Delta\) should be measured between the up-doped core and down-doped trench, so that the depressed clad design has a higher effective \(\Delta\)...

This is a continuation from the previous tutorial - atomic energy levels and spontaneous emission.   It is well known that the spherical aberration of a lens is a function of its shape factor or bending. Although several definitions for the shape factor have been suggested, a useful formulation is \[\tag{23}\mathscr{K}=\frac{c_1}{c_1-c_2}\] where \(c_1\) and \(c_2\) are the curvatures of the lens with the first surface facing the object. By adjusting the lens bending, the spherical aberration can be seen to have a minimum value. The power of a thin lens or the reciprocal of its focal length is given by...