MBR5 User Manual
MBR5 Rev 007
38
6.
Connect the FC/UPC end to the detector adapter
7.
Select Absolute mode
8.
Make sure that output power is above -‐10 dBm for all laser sources
9.
Take an IL reference for each wavelength. Select Relative mode by
pressing and holding the Power button until zero.
10.
Select BR mode
11.
Terminate the calibrated jumper by applying a mandrel wrap in the
middle
12.
Verify BR readings to be below -‐65 dB for all wavelengths
13.
Relase the mandrel wrap and verify that BR value is within the
following ranges: 14.7 dB ± 0.4 dB for 1310 nm and 14.8 dB ±0.4 dB
for 1490, 1550 and 1625 nm for single-‐mode fiber and 14.4dB +/-‐
0.4dB at 850nm 14.5dB +/-‐ 0.4dB at 1310nm for multimode fiber.
Loss and Reflection issues
Backreflection measurement accuracy is greatly impacted by losses before the
DUT and by reflections before and after the DUT.
Losses before the DUT
When a DUT is connected to the MBR5 meter, insertion loss of the connectors
before the DUT affects the backreflection reading. As light travels from the
MBR5 meter and returns, it goes through the connectors twice, so the effect of
the losses is doubled. If the insertion loss is close to 0.15 dB, its effect is
compensated automatically by the meter. If the insertion loss differs
substantially from 0.15 dB, follow the measurement procedures described at
the end of the LOSS AND POWER MEASUREMENTS” section on page 21.
Reflections before the DUT
When a device is connected to the BR5 meter, the reflections from the
connectors affect the backreflection reading. The front panel FC/APC
connections must have backreflection levels below -‐65 dB for single-‐mode (-‐45
dB for multimode). To ensure that the MBR5 meter automatically compensates
for backreflections, follow the set-‐up procedure described in the
“BACKREFLECTION MEASUREMENTS” section on page 15, and ensure that the
backreflection does not change from the time of the setup.
Reflections after the DUT
When making a backreflection measurement, the fiber after the DUT must be
terminated to eliminate the reflections from the end of the fiber (see the
“TERMINATION TECHNIQUES” section on page 25). For the greatest accuracy
when making very low backreflection measurements, terminate the fiber near
the DUT to eliminate reflections from the fiber itself.
