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In physics, backscatter (or backscattering) is the reflection of waves, particles, or signals back to the direction from which they came. It is usually a diffuse reflection due to scattering , as opposed to specular reflection as from a mirror , although specular backscattering can occur at normal incidence with a surface.
An OTDR injects a series of optical pulses into the fiber under test and extracts, from the same end of the fiber, light that is scattered (Rayleigh backscatter) or reflected back from points along the fiber. The scattered or reflected light that is gathered back is used to characterize the optical fiber.
Diffuse reflectance spectroscopy, or diffuse reflection spectroscopy, is a subset of absorption spectroscopy. It is sometimes called remission spectroscopy . Remission is the reflection or back-scattering of light by a material, while transmission is the passage of light through a material.
Diffuse reflection is the reflection of light or other waves or particles from a surface such that a ray incident on the surface is scattered at many angles rather than at just one angle as in the case of specular reflection.
In telecommunications, signal reflection occurs when a signal is transmitted along a transmission medium, such as a copper cable or an optical fiber. Some of the signal power may be reflected back to its origin rather than being carried all the way along the cable to the far end.
Example compounds Allowed reflections Forbidden reflections Simple cubic Po Any h, k, ℓ: None Body-centered cubic Fe, W, Ta, Cr h + k + ℓ = even h + k + ℓ = odd Face-centered cubic (FCC) Cu, Al, Ni, NaCl, LiH, PbS h, k, ℓ all odd or all even h, k, ℓ mixed odd and even Diamond FCC Si, Ge All odd, or all even with h + k + ℓ = 4n
Optical fiber is the most common type of channel for optical communications. The transmitters in optical fiber links are generally light-emitting diodes (LEDs) or laser diodes. Infrared light is used more commonly than visible light, because optical fibers transmit infrared wavelengths with less attenuation and dispersion.
by measuring the scattered reflection off the ground (when the lidar is airborne) or other hard surface. Backscatter from the atmosphere directly gives a measure of clouds and aerosols. Other derived measurements from backscatter such as winds or cirrus ice crystals require careful selecting of the wavelength and/or polarization detected.