MBR5 User Manual
MBR5 Rev 007
5
When making power measurements, the MBR5 meter will automatically correct
for dark current if the value has been stored. The power displayed (P) in dBm is
calculated from the total current measured when the light source to be
measured is illuminating the detector (Itot) and the value of the leakage or dark
current (Id) measured, using the following equation:
(
)
CAL
I
I
P
d
tot
+
−
•
=
log
10
Where “CAL” is the factory calibration value and is dependent on the
wavelength.
Output Port
The output ports of the MBR5 meter are equipped with an ultra-‐low
backreflection APC connector. To prevent damage to the output port
connectors, a measurement jumper (also called “launch cable”) must be used
for all measurements, even for measuring a component with an APC connector.
Hybrid Jumpers
The MBR5 meter is supplied with a hybrid measurement jumper and a hybrid
calibrated jumper. The measurement jumper has an APC connector at the input
end. The other end on the standard measurement jumper is UPC but, by
changing measurement jumpers, this end is user-‐selected to be compatible with
the input connector of the DUT; for example SC/UPC or APC or LC/APC or UPC.
The calibrated jumper has an APC connector at the input end and a UPC
connector at the output end.
Remember to use the measurement jumper for measurement purposes only
and to use the calibrated jumper for calibration verification purposes only. The
calibrated jumper has a label attached to it identifying it as such.
Coherence Length
Reflected light from multiple reflections can change the backreflection
measured by the MBR5 meter. This variation typically shows up as noise or drift
in the signal. The internal light source is designed to have low coherence length
(typically less than 10 cm). Thus, interference effects are typically seen only
between very closely spaced components such as non-‐contacting connectors.
Extreme care must be taken to avoid damaging the connector when
plugging and unplugging the launch cable. Connection must be kept
clean and should be inspected before every mating (this means both
connectors, the FC/APC on the launch cable and the FC/APC
connector on the MBR5 meter). Please refer to the Cleaning
Connectors section on page 36 for more information.