MBR5 User Manual
MBR5 Rev 007
26
When measuring backreflection levels below -‐60 dB, low-‐attenuation bends
(bends with a relatively large radius) need to be made just before the high-‐
attenuation bends in order to offset the small amount of reflection caused by
the high-‐attenuation bends.
1.
Use the supplied rod and use the appropriate section depending on
the fiber type as described above. The required number of turns
will vary with BR0 value of the MBR5 meter. Wind the
Measurement jumper around the rod until Br0 is at MAX and no
longer decreases. For example, wind until BR0 remains at -‐68dB
MAX regardless of number of turns. Unwind until BR0 goes below -‐
68dB again and then add 1 turn. Count number of turns and use the
same numbr of turn after your DUT for best BR accuracy.
2.
To minimize any memory of the bends in the jumper jacket, do not
pull on the jumper while winding, and occasionally wind it in the
opposite direction.
Figure 13: Mandrel Wrap Termination Technique (Single-‐Mode)
Remember also that index-‐matching technique described below can also be use
on single-‐mode fiber with UPC connectors when expected BR is greater
than -‐65dB.
Index-‐Matching Technique (for Multimode Fiber)
Termination for multimode fiber is performed by using index-‐matching
gel/block.
1.
Insert ferrule into an index matching gel/block to terminate all
reflections. When using an index matching block, apply light
pressure and move the angle of the ferrule slightly until the lowest
BR value is achieved. See Figure 14.
Mandrel Wrap
Measurement
Jumper
FC/APC
850
1310
1550
DETECTOR
CHANNEL
1
MENU
LOCAL
BR
BR
O
POWER
REF DARK
MBR5 Backreflection Meter
-65.0dB 1310
1
BACKREFLECTION
I
O
