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RM3 SERIES BACKREFLECTION METER
USER’S MANUAL
10112341 Rev 002 Page 23 of 39
Rear Panel
The back of the meter (Figure 4) can vary with the model.
-
25 VA max
Fuse 1A/250V
Figure 4: Back of the Meter
The components on the rear panel are described in Table 6.
Table 6: Rear Panel Components
Component Function
CAL Access to the User CAL value, for calibration purposes.
LOG Foot pedal jack for data logging.
RS232C RS232 serial interface port.
Termination Techniques
Termination is a technique used to block all backreflections beyond a certain point in a network
of components. In all measurement testing, two terminations must be made: the first (for
measuring BR
0
) is made before the DUT, for example, on the RM meter side; the second (for
measuring BR
tot
) is made after the DUT. Both termination points need to be made as close as
possible to the DUT to minimize the errors associated with Rayleigh backscattering in the fiber.
The backreflection of all components and connections between these two points is included in
the equation for calculating the backreflection value (BR) of the DUTs.
Termination Techniques for Single-mode Fiber (except 980 nm)
Termination for single-mode (except 980nm) is performed by mandrel wrapping.
High-attenuation bends in the fiber (bends with a relatively small radius) remove all
backreflection and can be made anywhere along the length of the cable. When measuring
backreflection levels below -60 dB, low-attenuation bends (bends with a relatively large radius)