Fiber textbook DAS (Mayte)

Question 1

_____ scattering in glasses is sensitive to strain and temperature in its frequency and intensity,
whereas the _____ strain-dependent frequency shift is only readily detected in crystalline [1] or reasonably
ordered solid materials such as polymer fibres with aligned molecular chains [2]. I

Answer 1

Question 2

In materials that support shear stress, such as glasses, Brillouin scattering exists with both ______ acoustic (pressure waves) and ______ acoustic (shear waves)

Answer 2

Question 3

The frequency ν_B of the Brillouin LA lines is dictated by the condition of the ____and _____wavefronts
matching

Answer 3

Question 4

what is the equation for frequency shift of Brillouin lines

Answer 4

Question 5

how is Brillouin different than Ramen scattering

Answer 5

Question 6

what does BOTDR stand for

Answer 6

Question 7

SpBS is an inelastic process that results from the interaction between an incident wave (the probe wave in our case) and thermally driven _______ fluctuations that travel
at the speed of sound.

Answer 7

Question 8

Secondly, the _____ linewidth of the Brillouin process allows optical amplification and heterodyne
techniques to be employed for enhancing the signal quality; this has enabled Brillouin measurements
to be carried out over extremely long distances.

Answer 8

Question 9

In contrast with Raman scattering, where the interaction is with molecular vibrations, i.e. optical phonons, here the interactions occur with _____phonons, i.e. _____of the lattice.

Answer 9

Question 10

how is strain rate converated to strain

Answer 10

Question 11

The spectral width of the spontaneous Brillouin backscatter is dictated by the ____ of the thermal phonons.

Answer 11

Question 12

The lifetime of the hypersonic phonons is a function of _____ and _____, and it is known that the attenuation of the hypersonic wave (which determines the phonon lifetime) is a function of its frequency.

Answer 12

Question 13

Brillouin scattering is an _____ scattering process that occurs in optical fibres

Answer 13

Question 14

what does SpBS stand for

Answer 14

Question 15

In a radially non-uniform fibre, the Brillouin contribution of each part of the ___ and ____ will generally be at a different shift, and this effect broadens the Brillouin linewidth.

Answer 15

Question 16

Brillouin scattering differs from Raman scattering in that the frequency shift is much ____(~10 GHz vs. ~13 THz for Raman scattering) and its natural linewidth is also
far ____(~30 MHz vs. ~6 THz).

Answer 16

Question 17

what is SBS

Answer 17

Question 18

what is an acousto-optic modulator

Answer 18

Question 19

The frequency shift of Brillouin depends on the _____ composition and ____ of the fiber

Answer 19

Question 20

the Brillouin backscatter is _____ than the Ramen backscatter

Answer 20

Question 21

The spectral width of the spontaneous Brillouin backscatter is dictated by the ____of the thermal phonons

Answer 21

Question 22

In a radially non-uniform fibre, the Brillouin contribution of each part of the core and cladding will
generally be at a different shift, and this effect _____the Brillouin linewidth

Answer 22

Question 23

For the Brillouin spectrum, In essence, as the numerical aperture increases, so does the range of ____that is captured by
the waveguide broadens.

Answer 23

Question 24

Brillouin scattering is the interaction between at least one optical signal (in the case of spontaneous scattering)
and acoustic waves resulting in a third, ____wave

Answer 24

Question 25

The frequency shift and the intensity of the spontaneous Brillouin backscatter are sensitive to temperature
and strain. These relationships can be described with a ______, the elements of which will be
discussed next

Answer 25