KI 7340/7740 UM-12
25
RETURN LOSS METER MANUAL OPERATION
KI7340C Series instruments measure Optical Return Loss (ORL)
using the Optical Continuous Wave Reflectometer (OCWR) method,
the meter detects the accumulated reverse power at the point of
measurement.
This method is accurate and suitable for acceptance testing. However,
it cannot locate a reflection source, and has limited optical range.
ORL meter calibrated wavelengths correspond to light source
operational wavelengths.
Operation
Note: no warm up needed. Ensure all connectors are clean.
Connect DUT to the left port of instrument, select [Return Loss] to
display ORL measurement, and [-/+] to change the wavelengths as
required. ORL will now be displayed in dB RL. To improve accuracy,
the following offsets may be used:
•
ORL Zero Function
•
User Calibration Mode (UCAL)
These offsets can be also set in Autotest mode.
To re-set to factory defaults, select [Return Loss], [
], [Default] then
[ Set ] to store.
ORL Zero Function
This compensates for stray (residual) reflections prior to making a low
level measurement. Using this feature, the instrument can read
accurately up to 10 dB below the stray reflection level, however at the
expense of increased noise when making low level measurements.
To set up the stray optical condition and to block all light, use a small
diameter mandrel wrap.
On the hidden keypad, select [Return Loss], [RL - NF].
To display the stored value, select [
] and then [Max/Min]. To adjust
the stored value, press [-/+], and then [Set] to store.
Perform the zero function whenever the stray ORL condition may have
changed.
Note the following limitations:
If the zeroed value is x dB, then
•
from x to (x+10) dB, resolution is limited to 0.1 dB.
•
from x to (x-10) dB, resolution is limited to 1 dB, which is
also the display range limit.
User Calibration Mode (UCAL)
Return loss is affected by twice the forward loss. To compensate for
this in a test jig, set up the reference optical condition:
•
on the hidden keypad, select [Return Loss] and [RL- Adj].
The offset value will be shown on the left of the display.
•
select [RL- Adj] again to show reference only, then press [-
/+] to adjust the display to the required value and [Set] to
store. A non-zero value is always displayed on left of display.
•
The usual ORL value for an unmated PC polish connector is
-14.26 dB.
