Fiber textbook DTS Flashcards
what is a phonon
what is SOP
OTDRs use the fraction of the scattered light that falls within the acceptance solid angle of the fibre in the return direction. The fraction of the scattered light that is captured depends on the characteristics of the fibre but is typically between ____% and ___%.
Molecular vibrations occur at very high frequency (~10 THz),
and they cause ____scattering; in contrast, lower-frequency vibrations in the hypersonic range (10–
30 GHz in this case) give rise to ____scattering.
The anti-Stokes process is dependent on the population density of the _____that are used in the process. In Raman scattering, the energy of the phonon is of similar order to the unit thermal energy kBT (where kB is Boltzmann’s constant [~1.38 × 10−23 J/K] and T is the temperature) and so the population density is strongly temperature dependent. The intensity of the anti-Stokes Raman band is therefore temperature sensitive.
A typical optical fibre sensor system (Figure 1.2) consists of the sensor itself that is _____ by the input light which it
modulates in accordance with the value of the measurand.
A typical optical fibre sensor system (Figure 1.2) consists of the sensor itself that is probed by the input light which it
modulates in accordance with the value of the measurand.
The technological ancestry of DOFSs is to be found in the development of
In general, multiplexed sensor systems are ___complex and often perform _____ than single-point sensors
the local variations of the refractive index that are involved in inelastic scattering are caused by thermally driven vibrations carried by phonons. The heat in the material is held in the form of
____ vibrations (stretching, bending or rotation of inter-atomic bonds) or _____ vibrations (longerscale
periodic movement of the material).
what is a patch panel
Scattering occurs when the medium through which the incident wave travels is not perfectly homogeneous;
i.e. its _________ varies locally
what is attenuation
the local variations of the refractive index that are involved in \_\_\_\_\_scattering are caused by thermally driven vibrations carried by phonons. The heat in the material is held in the form of molecular vibrations (stretching, bending or rotation of inter-atomic bonds) or lattice vibrations (longerscale periodic movement of the material).
what is the difference between INTRINSIC VS. EXTRINSIC OPTICAL FIBRE SENSORS
When the scattered light emerges at a lower frequency than the incident light, the scattered photon has given up energy, in the form of an additional phonon, to the medium in the interaction; the resulting new spectral features are known as ____lines or bands. In the opposite case, where the scattering has increased the frequency, energy has been transferred from the medium to the light. This is known as ____ scattering, a process in which a phonon is removed and its energy is incorporated in the scattered photon.
a pulse is attenated (loss of flux intensity) by what 3 reasons
