TB 9-6625-2309-35
data points.
This is a close approximation of constant
horizontal scale error due to TS-4320 OFTS timing circuitry
not in sync with out going optical pulse as it passes through
OFTS fiber connector. Absolute value of location offset should
be less than or equal to 1.00 meter to be in tolerance. Scale
deviation is slope of least squares line fitted to data points.
This is a close approximation of relative error due to the OFTS
too high while a negative value indicates it is too low. If slope
of least squares line is extreme; i.e., the far end of least squares
line is beyond dashed boundry lines, this condition is usually
an indication of incorrect oscillator frequency on DAS 1A2A4
circuit card. If least squares line is beyond boundry lines but
this is not due to extreme slope (above or below), this is an
indication of ZERO-KM SETTING requiring adjustment.
Location readout error is worst-case summation of both the
OFTS data point sampling error and the calibrator cursor
placement error on leading edge of FOCUS generated pulse.
This is shown by spread of two data points in second cluster.
This amount of random error is to be expected in normal
operation at maximum range. (TD-260C will have a normal
spread of 2 meters, TD-261C - 4 meters and TD-285C - 8
meters).
(20) If OFTS calibration software indicates out-of-tolerance condition for TI, perform
b below.
b. Adjustments.
Perform adjustments in
Section IV and
repeat paragraph 8.
9. Attenuation
Scale Non-linearity
a. Performance Check
(1) Connect equipment as shown in figure 3, CONNECTION A. Connect ST END of
OPTICAL FIBER JUMPER CABLE to LIGHTWAVE MULTIMETER OPTICAL INPUT
and connect FC END to FOCUS-SWCM OPTICAL IO (fig. 3).
(2) Adjust FOCUS-SWCM controls as indicated in (a) through (c) below:
(a) Set LD BIAS CURRENT switch to LD PULSED.
(b) Set SWITCHED ATTN switch to OUT.
(c) Adjust VAR ATTN 1 control for approximately -27 dBm optical power
amplitude indication at 850 nm on lightwave multimeter and record indication.