Optical fibers Rayleigh scattering

Nonconventional fluorimeters and sensors that incorporate optical waveguide coupling possess less optical attenuation in the near-IR as compared with the UV/vis-ible because of the reduction in Rayleigh scattering. The temporal dispersion is also reduced in the near-IR for the same reason, e.g., 80 psec/nm/km at 900 nm as compared with 1 nsec/nm/km at 400 nm for a single-mode fiber. 

The preparation of transparent (inorganic or organic) glasses is the main problem for optical fibers. Since the Rayleigh scattering is proportional to the fourth power of the... 

The connection balance of the optical line the overall loss is the sum of several losses, viz, those due to the fiber-source coupling, to Rayleigh scattering and the absorption in the fibers, the optical losses due to the optode geometry, to the connectors, the multiplexing, and the Hber-detector coupling. In process control, all losses must remain constant to avoid disturbing the measurement. 

RGURE 18-11 Fiber-optic Raman spectrometer with spectrograph and CCD detector The bandpass filter (BP) is used to isolate a single laser line. The band-rejection filter (BR) minimizes the Rayleigh-scattered radiation. 

For Raman spectra, on the other hand, an experimental advantage is that samples can be thicker compared to those needed for infrared. Also, fiber optics techniques may be employed for measurements in local regions using Raman spectra. A disadvantage is that Raman measurements give problems in samples that are turbid as a consequence of Rayleigh scattering by inclusions. 

Rayleigh scattered radiation. Two lenses were nsed collimate the light from the telescope output, which was directed into the fiber optic from which the focusing objective had been removed. The output of the fiber was directly coupled to the entrance sht of the Andor spectrograph. 

Philipp, L., Mario, W., Sascha, L. Katerina, K. [2010]. Distributed humidity sensing based on rayleigh scattering in polymer optical fibers. Proceedings of SPIE in Fourth European Workshop on Optical Fibre Sensors, Vol. 7653, SPIE, Porto, Portugal, p>p. 1—4. 

Pahnieri, L., Schenato, L., 2013. Distributed optical fiber sensing based on rayleigh scattering. Open Opt. J. 7 (Suppl.l, M7), 104-127. 

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