Fiber Optic Tutorials

This is a continuation from the previous tutorial - introduction to integrated optics.   1. Introduction Photosensitivity is another amazing feature of most specialty optical fibers (SOFs). The photosensitivity phenomenon is different from photo-darkening and radiation-darkening, which induces excess losses. There is then no added background losses due to the fiber Bragg gratings (FBGs) inscribed in the fiber’s core besides filtered wavelengths. Photosensitivity of a medium is defined as its capacity to have its refractive index permanently changed by a modification of its physical or chemical properties through light exposition. Photosensitivity is a complex phenomenon because of the diversity of...

This is a continuation from the previous tutorial - dispersive prisms and gratings.   1. Introduction The field of integrated optics is concerned with the theory, fabrication, and applications of guided wave optical devices. In these structures, light is guided along the surface region of a wafer by being confined in dielectric waveguides at or near the wafer surface; the light is confined to a cross-sectional region having a typical dimension of several wavelengths. Guided wave devices that perform passive operations analogous to classical optics (e. g., beam splitting) can be formed using microelectronic-based fabrication techniques. By fabricating devices in...

This is a continuation from the previous tutorial - LDPC-coded differential modulation decoding algorithms.   Introduction Spectroradiometers (Fig. 1) are radiometers designed specifically to allow determination of the wavelength distribution of radiation. This category of measurement systems usually consists of those in which separation of the radiation into its spectral components, or dispersion, is accomplished by the use of an optical element possessing a known functional dependence on wavelength—specifically, prisms and diffraction gratings.   Figure 1. Basic spectroradiometer. Glossary \(A_p\) prism angle \(B\) prism base \(D_p\) angle of minimum derivation \(d\) grating constant \(E\) irradiance \(N\) number of slits \(n\)...

This is a continuation from the previous tutorial - laser pumping and population inversion.   The decoders we consider (which can include simplified versions such as binary message passing decoders) rely on the knowledge of the channel. The communication channel, or an equivalent communication channel comprising the physical channel as well as various inner receiver and signal processing stages, can be characterized by its conditional probability \(P(z|y)\), that is, the probability of observing \(z\) at the receiver assuming a transmitted modulation symbol \(y\in\boldsymbol{\mathcal{M}}\). Note that we restrict ourselves to memoryless channels, which can be achieved in practice by sufficiently long...

This is a continuation from the previous tutorial - polarization maintaining fibers.   The atomic rate equations introduced in the two previous tutorials are of great value in analyzing laser pumping, population inversion, and gain saturation in laser systems. The primary objective of this tutorial is to illustrate this point by solving the atomic rate equations and examining these solutions for some simple but important atomic systems.   1. Steady-State Laser Pumping and Population Inversion One of the most common applications for rate equations is in analyzing laser pumping. In this section, therefore, we will develop and solve the rate equations to...