JDS Uniphase RM3 Series, User Manual

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6. Terminate the measurement jumper just before the output connector, and hold the
termination point steady (figure 5a for single-mode (except 980nm), and figure 5b for single-
mode (980nm) and multimode).
NOTE: The termination technique is different depending on the type of the Backreflection Meter
used: single-mode (except 980 nm), single-mode (980nm) or multimode. Please refer to the
Termination Techniques section above.
7. Press the Store BR
0
key. The key lamp lights to indicate that the background backreflection
has been stored. The BR
0
value is used in the calculation of the DUT backreflection at the
selected wavelength.
8. Remove the termination.
Measuring Backreflection
To measure backreflection and power from a unit after setting up the meter (see the Setting Up
the Meter for Backreflection Measurements section):
1. Clean the output connector of the measurement jumper and the input connector of the DUT,
and mate the two.
2. Press the
λ
key to select the wavelength at which the measurement is to be made.
3. Terminate the measurement jumper immediately after the DUT, and hold the termination
point steady. The meter displays the backreflection between the two termination points that
is caused by the fiber, all connections, and the DUT. This area is shown within the dashed
line in Figure 6a for single-mode (except 980nm), and in Figure 6b for single-mode (980nm)
and multimode.
4. If necessary, terminate the fiber for BR
0
again just before the DUT to eliminate the
backreflection caused by the fiber and all connections before the DUT.
5. Press the Store BR
0
key. The key lamp lights to indicate that the function is on.
6. If the backreflection setup has been done previously (BR
0
light is on), press the BR
0
button
to delete the currently stored BR
0
value. The BR
0
light turns off.
7. Press
λ
and repeat step 6 to delete the stored BR
0
value for another wavelength.
8. Release the termination. The meter now displays the backreflection of the DUT only.
9. If a measurement is to be made at a second wavelength, repeat steps 1 through 8.
The small amount of reflections that BR
0
represents can be polarization sensitive, and multiple
reflections can cause interference effects that can make the reflections very sensitive to
temperature. To ensure accurate backreflection measurements below -65 dB (-25 dB for
multimode):
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