Fibers, numerical aperture

The observed F depends on several variables, particularly the fiber numerical aperture, sample depth, interfiber distances, filter losses, and so fourth Similarly, an SNR figure of merit may be determined empirically, which would Incorporate SNR degradation due to fiber background. Equation (12.7) for is identical to Eq. (4.25), and both are based on experimetnally determined variables ... 

NA fiber numerical aperture S delta function unit vector... 

Fiber Numerical Aperture and acceptance cone. (Courtesy of Corning Cable Systems LLC and Corning ... 

The abihty of a waveguide to collect light is determined by the numerical aperture (NA) which defines the maximum angle at which light entering the fiber can be guided. 

The upgrade of a frequency-domain fluorescence lifetime imaging microscope (FLIM) to a prismless objective-based total internal reflection-FLIM (TIR-FLIM) system is described. By off-axis coupling of the intensity-modulated laser from a fiber and using a high numerical aperture oil objective, TIR-FLIM can be readily achieved. The usefulness of the technique is demonstrated by a fluorescence resonance energy transfer study of Annexin A4 relocation and two-dimensional crystal formation near the plasma membrane of cultured mammalian cells. Possible future applications and comparison to other techniques are discussed. 

Fiber Fiber diameter (pm) Spectral region (nm) Typical bandwidth (nm) Numerical aperture... 

As the analyte or any other species that may be present changes in concentration, the refractive index (RI) of the sample medium also changes. A large change in the RI may interfere with the fluorescent signal because the numerical aperture of the fiber is proportional to the RI as shown in the relation below ... 

Finally, the numerical aperture of the fiber ophc cable can be affected by the refractive index of the cladding medium. A large numerical aperture is desirable as it allows the fiber to support an addihonal number of guided modes. The numerical aperture N.A is defined as... 

Numerical Aperture (NA). Numerical aperture describes an angle just outside the a fiber s end face that determines the largest angle that a light ray can have to the fiber axis and still be captured and propagate within the fiber. The formula from Snell s law governing the numerical aperture number of a fiber is... 

Most optical fibers have numerical apertures between 0.15 and 0.4, and these correspond to light acceptance half-angles of about 8 and 23 degrees. Typically, fibers having high NAs exhibit greater loss and lower bandwidth. 

The N.A. is the numerical aperture of the fiber and defines the cone of acceptance in terms of refractive indices only. The half-angle o of the cone of acceptance is given by (9.28). 

Table 2.1 shows the efficiencies for the generation of FSB (f b) for various optical fibers, together with information about their manufacturer, product number, core, cladding and outer diameters, numerical aperture (NA), and material [28]. Data for some other optical fibers have been added to the table [28]. 

There is no inherent sample size restriction, large or small, but is fixed by the optical components used in the instrument. The diffraction limit of light, roughly a few cubic micrometers depending on the numerical aperture of the optics used and the laser s wavelength, sets the lower bound.7 In a process application, the type of fiber optics used also affects sample volume examined. Macroscopic to microscopic samples can be measured with the appropriate selections of laser wavelength, laser power, and optics. 

The properties of optical fibers are often characterized by the numerical aperture NA = n sin0. It is given by ... 

The range of acceptance angles for an optical fiber is generally stated as the numerical aperture (NA). For the case of the square-cut fiber shown in... 

Figure 12.1. Schematic of light propagation in a typical multimode fiber, y is the acceptance angle and is related to the numerical aperture.

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