Modal power distribution

Keywords Fiber optic sensors Chemical sensors Biosensors Evanescent field sensor Intrinsic fiber optic sensors Multimode fibers Modal power analysis Modal power distribution Spatial intensity modulation Optical far-held pattern... 

The measurements of the distribution and the subsequent redistribution of the modal power can be accomplished by scanning the far-held pattern at the hber end using a CCD camera or by using one or more photodetectors positioned at a specihc location in the far-held zone, as shown in Fig. 29. The modal launcher is a single or array of LEDs, used to excite a limited group of modes within the MM optical hber, and the modal analyzer is the detection system of the modal power positioned at the output end of the optical hber, in the far-held zone. 

The modal power flow along the fiber per unit cross-sectional area, or intensity, is given by the time-averaged Poynting vector S in Table 14-3, where a is the modal amplitude. To describe the change in this distribution with changes in V, we keep the total modal power P fixed, and define a normalized intensity S = S/P = S/ a N. Hence... 

Consider a fiber with small nonuniformities distributed at random throughout the fiber with number density M per unit volume. The total power radiated from length dz of fiber is just the sum of the power radiated by each nonuniformity. If P(z) is the modal power at position z along the fiber, and M is sufficiently large, it follows that... 

It is now well documented that large numbers of particles are emitted from coal-fired power plants in distinct distributions with modal diameters less than 1 pm (1-5). 

Fig. 14-3 Fundamental mode quantities for the step-profile fiber, showing (a) the modal parameter U, the fraction of power in the core fj, and the depth of penetration r, (b) the normalized polarization correction SU/AU, (c) the normalized intensity distribution and (d) the normalized variation in group velocity relative to the left ordinate, and the distortion parameter D relative to the right ordinate. Numerical values are given in Table 14-4.

An exception is the infinite parabolic profile of Section 14-4. The fundamental-mode fields of Table 14-2, page 307, have the simple Gaussian dependence exp( — F ) and other modal properties have very elementary forms, from which their physical behavior is immediately apparent. To these facts we add the observation that the fundamental-mode intensity pattern - and hence the field distribution - for step and clad power-law profiles... 

We define S to be the intensity distribution when there is unit power in the fundamental mode, i.e. a iV = 1, where a is the modal amplitude and N the normalization. If we normalize S with the cross-sectional area within radius p, then Table 15-2 gives... 

It seems then two options are available to reach high-power density electrode on negative side for Li4Ti50i2 nanowires or bi-modal distribution of nano- and micro-sized compounds. 

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