Bruker IFS 125M, User Manual, Page: 122 / 228

122 IFS 125M User Manual Bruker Optik GmbH
Maintenance 6
6.10 Cleaning housing
The outer spectrometer surface can be cleaned only by using a dry or damp cloth. Do
not use detergents with organic solvents, acid or base!
7 It is necessary that the polarization planes of the laser and the fiber match
exactly. Otherwise, the output polarization is unstable and very sensitive to
slight movements or bends of the fiber. Thus, the polarization contrast has to
be measured and optimized.
• Turn the polarizer in the fiber collimator tool until the power reading is at a
minimum
c
.
• Note value P
min
.
• Turn the polarizer by 90 degree.
• Read P
max
and calculate the ratio P
max
/P
min
. If the ratio is insufficient
(<= 100), proceed as follows:
☞
Mark the inner cylindrical part (indicated by yellow circle on the figure
shown in step 1) of the coupling head, so that you can see its rotational
orientation relative to the fixed outer part.
☞
Turn the inner part a few degrees clockwise.
☞
Bring the intensity back to a maximum using the tilting screws (1 in
figure 6.9).
☞
Measure the polarization contrast again. If the ratio increased, turn the
inner cylindrical part further into the same direction. If the ratio
decreased, turn the inner part into the opposite direction (behind the
mark). As soon as the ratio is large enough, repeat step 6 to maximize
the intensity again.
8 • Lock the coupling head by the clamp screw, located between the two bolts
(5 in figure 6.9).
• Observe the output power during fixing. If it drops, compensate with very
fine adjustments of screws (1) or (4).
9 Check whether the power at the fiber output is stable (within 90%) when you
unplug/plug the fiber at the coupler a few times.
a. The Si-diode of the fiber collimator tool gives usually lower power readings than the stand-alone Si-di-
ode. Thus, after maximizing the intensity with the fiber collimator tool, read the power with the power-
meter or stand-alone Si-diode to calculate the ratio P
out
/P
in
.
b. Both ends of the fiber patch cord are polished slightly different. Try to find the end which can be adjusted
to the maximum throughput and mark it accordingly.
c. If no fiber collimator tool is available, you may use the power-meter or stand-alone Si-diode with a po-
larizer in front of either one of them. Make sure that no stray-light enters the device, especially when the
polarizer is at minimum position.
Table 6.31: Readjusting fiber-coupling head