TB 9-6625-2309-24
NOTE
Time insertion delay (TID) is given in nanoseconds with each
FOCUS unit on FOCUS Time Insertion Delay Measurement
Worksheet. Time insertion delay may be different for each
wavelength and FOCUS control module. Be sure to use correct
insertion delay for control module and wavelength being used.
(18) Verify entered data is correct then quit data edit page.
(19) Select Generate Report and then Graphic Report screen to view resultant
plot (fig. 7).
NOTE
Two dashed lines on graphical report represent boundaries of
normally acceptable uncertainty for TI.
Beyond 65 km,
boundaries are increased to allow for additional tolerance at
long range. If least squares line fitted to data points is outside
these boundaries, TI is considered out of tolerance (data points
outside of boundaries are acceptable). In this case, verify data
entries and constants on data entry page. Repeat calibration
before TI is adjusted or repaired. Select Graphic Report
(Printer) to print a hard copy if needed. Also, tabular report
can be viewed or printed.
NOTE
Data for each TS-4320 OFTS optical module is divided into two
sets or clusters first cluster near origin and second near end
of optical module horizontal scale rated dynamic range. TI
measurement data is taken for each cluster until a shift is
produced in pulse position. The last data point in cluster will
be lowest actual error for that cluster. The data point
immediately prior to the last data point is the highest error.
Technique is same for second cluster. These four data points
are used to plot a least squares line and calculate location
offset, scale deviation, and maximum location readout error.
Location offset is Y axis intercept of least squares line fitted to
data points.
This is a close approximation of constant
horizontal scale error due to TS-4320 OFTS timing circuitry
not in sync without 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
timing circuitry (oscillator) either running too fast or too slow.
A positive scale deviation value means oscillator frequency is
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
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