YOKOGAWA DTSXL, User Manual, Page: 259 / 289

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C-6
IM 39J06B40-01EN 14th Edition: May 30, 2022
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Double-ended measurement
Double-ended measurement can be used in distributed temperature measurement
applications where an optical switch is available and the sensor optical fiber can be
looped back.
Double-ended measurement is somewhat more complex than single-ended
measurement but does not require correction for the differential sensor optical fiber loss
between the Stokes light and anti-Stokes light of the Raman scatter because the
measurement results in the forward direction and reverse direction from the switch exit
position to the sensor optical fiber end are combined. However, a value for the total
differential loss between the Stokes light and anti-Stokes light over the full sensor optical
fiber length is still required to correct for absolute-temperature error in double-ended
measurement. Two options are provided for calculating this differential loss value. The
first option is a straight-forward calculation of a fixed default differential loss value from a
user-defined per kilometer differential loss value. The second option is automatic
calculation by the DTSX3000 using the measurement data for two sensor optical fiber
sections (one each on the far end and near end) subjected to the same temperature. In
the second option, the DTSX3000 performs sensor optical fiber loss calibration at each
measurement so the impact on temperature measurement of any sensor optical fiber
darkening or any change in sensor optical fiber loss during temperature measurement is
minimized.
SEE ALSO
For details on temperature correction configuration, see Section B7.3.2, “Double-ended Measurement
Settings.”