 courtesy of Academic Press. (6.1.22) Case 1.4. Angular misalignment O: Case 1.2. Transverse offset A: (6.1.25) (6.1.23) If a lens is used in between the emitter and fiber, some Case 1.3. Longitudinal offset AZ: modifications to the previous formulas have to be done. What the lens can do for us is to match the output angle of the emitter to the acceptance angle of the (6.1.24) receiving fiber. If properly done, the power coupled into the fiber is multiplied with the lens magnification factor where Z is the Rayleigh range. M: M = drec/dem, (see Fig. 6.1-10). All the preceding formulas need to be corrected for reflection losses. If the refractive index of the medium between the source and the fiber is denoted no, the coupled power into the fiber is optical fiber cores reduced with a factor R, R = (m-mo) (6.1.26) 6.1.2 Optical fiber characterization 6.1.2.1 Optical fiber materials The material is primarily chosen to provide the minimum attenuation. Table 6.1-3 shows order of magnitude Table 6.1-3 Scattering loss for several representative glass materials dB/km Material 633 nm 800 nm 1060 nm Fused silica Soda lime Borosilicate crown Lead silicate Fig. 6.1-9 Different coupling cases. Reprinted from Ref. [1], p. 18, Reprinted from Ref. [1], p. 21, courtesy of Academic Press. courtesy of Academic Press. Optical fiber, cable and connectors CHAPTER 6.1 attenuation at three different wavelengths for four Table 6.1-4 Factors affecting attenuation common glass types. For tele- and data communication fibers, fused silica Intrinsic loss mechanisms glass is the preferred material. To provide guiding of the Tail of infrared absorption by Si-0 coupling light, the core of the fiber is doped with a few molar Tail of ultraviolet absorption due to electron transitions in defects Rayleigh scattering due to spatial fluctuations of the refractive index percentage of a substance that increases the refractive index. It is also possible to dope the cladding such that its Absorption by impurities refractive index becomes lower than the pure