Assessment of a Rubidium ESFADOF Edge-Filter as ... - tuprints

136 5 Discussion of the Experimental Results
0.06
0.05
~
T(∆ν)
∆ν S
= -75 MHz
Transmission
0.04
0.03
0.02
0.01
0.00
2×10 -5
1×10 -5
∂ ∆ν
~ T(∆ν)
∂ ∆ν
~ T(-(∆ν-2∆νS ))
MHz -1
-1×10 -5 0
-2×10 -5
1×10 -5
∂ ∆ν
~ T(∆ν) - ∂∆ν
~ T(-(∆ν-2∆νS ))
5×10 -6
MHz -1
-5×10 -6 0
-1×10 -5
-7.875 GHz -6.875 GHz +6.725 GHz +7.725 GHz
-15 -10 -5 0 5 10 15
∆ν / GHz
Fig. 5.23: Evaluating the symmetry according to the discussion of
Sec. 5.2.3: The plot shows the ESFADOF transmission spectrum,
which corresponds to Fig. 5.22, its first derivative, the symmetric
inversion of the first derivative with respect to the symmetry
point ∆ν S (dashed dotted line). The last row shows, similar to
Figs. 5.10 and 5.11 , the difference between the derivative and
its symmetric inversion and quantifies the increase in measurement
accuracy when exploiting the symmetry. The broken lines
indicate the spectral region of interest of the Brillouin-lidar with
respect to the symmetry point. The derivative of the ESFADOF
spectrum and its symmetric inversion exhibit in the region of interest
already a high degree of congruence, though the symmetry
has not been optimized. The periodic structures emerge from a
crosstalk between the different signals on the A/D-card. Again, a
very effective compensation of small frequency fluctuations of the
Brillouin-lidar laser results.