Fiber, multimode

Figure 7.9 Refractive index profiles of three common types of optical glass fiber multimode step index, multimode graded index, and single mode.

Criterion for slow variation Local modes of bent fibers Multimode fibers and rays References... 

Fig. 3. Types of optical fiber (a) multimode stepped index, (b) multimode graded index, and (c) single-mode stepped index.

Step-Index Multimode. The step-index multimode fiber has a sharp difference between the index of refraction of the core and that of the cladding (Fig. 16.8a). Light propagation in such a fiber is... 

Single Mode. The single-mode fiber has a step-index profile (Fig. 16.6c) and a small core diameter (typically 10 im) such that only one mode can travel through it. This is now the preferred system, particularly for long-distance transmission. The normal light source for multimode fibers is the light-emitting diode (LED). But... 

The direct melt process economically produces thick optical fibers (250-400 pm in diam.), which is advantageous, but their relatively high attenuation (3-20 dB/km) due to impurities is not. As a result, they are limited to short distance multimode applications. 

CVD yields fibers with low loss (< 0.5 dB/km) which are suitable for both mono- and multimode long-distance applications. It has emerged as the strongest technology for high-volume, low- cost production. ]... 

The 6 Nd YAG lasers pump the DM0, preamplifier and power amplifier (Fig. 19, Friedman et al., 1998). The YAG lasers are built from commercially available flashlamp/laser rod assemblies, acousto-optic Q-switches and frequency doubling crystals (LBO and KTP). Most of the mirror mounts and crystal holders are commercial. Nd YAGs are frequency doubled to 532 nm using a nonlinear crystal. The Nd YAG rod and nonlinear crystal are both in the pump laser cavity to provide efficient frequency conversion. The 532 nm light is coupled out through a dichroic and fed to multimode fibers which transport the light to the DM0 and amplifier dye cells. 

Newby K., Reichert W.M., Andrade J.D., Benner R.E., Remote spectroscopic sensing of chemical adsorption using a single multimode optical fiber, Appl. Optics 1984 23 1812. 

The pH measurement can by realized using sol-gel films and evanescent-wave sensors method74. To incorporate a near-infrared pH sensitive fluorescent dye, a thin-film coating on the core of a multimode fiber was used. By evanescent wave excitation an absorption or fluorescent based sensor can be realized for use in high pH regions. 

Fig. 2.7 Temperature profiles for a 30mL sample of 1-methyl-2-pyrrolidone heated under open-vessel microwave irradiation conditions [19]. Multimode microwave heating at different maximum power levels for 6 min with temperature control using the feedback from a fiber-...

Chiba, A. Fujiwara, H. Hotta, J. Takeuchi, S. Sasaki, K., Fano resonance in a multimode tapered fiber coupled with a microspherical cavity, Appl. Phys. Lett. 2005, 86, 261106... 

Ruddy, V. MacCraith, B. D. Murphy, J. A., Evanescent wave absorption spectroscopy using multimode fibers, J. Appl. Phys. 1990, 67, 6070 6074... 

The levitated laser dye droplet was optically pumped by a pulsed (pulse length 5 ns, repetition rate 10 Hz), frequency-doubled Nd YAG laser (2 = 532 nm) in free-space optical setup. Droplet light emission was collected by a multimode optical fiber placed at an angle of approximately 50° relative to pump laser beam. Collected light was analyzed in a fixed-grating spectrometer with a resolution of FWHM 0.15 nm. 

Multimode optical fibers, 11 131, 132 intermodal dispersion in, 11 134 Multimode stepped index optical fiber, 11 131, 132... 

Multilayer Langmuir-Blodgett films doped with a cyanine dye have been deposited on the surface of a quartz multimode optical fiber and the fluorescence properties investigated. 49 The fluorescence intensity of the films was found to be a periodic function of the number of layers due to the waveguide properties of the films. 

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