YOKOGAWA DTSXL, User Manual, Page: 263 / 289

< PART – C Operation and Maintenance >
C-10
IM 39J06B40-01EN 14th Edition: May 30, 2022
C2.2. Temperature Calibration
The DTSX3000 uses intensity data of the Raman backscatter in its temperature
calculation. As the Raman scatter intensity varies with the sensor optical fiber used,
splice loss and other factors, these configuration conditions need to be used to calibrate
the DTSX3000. This section describes the procedure and precautions for temperature
calibration.
The DTSX3000 introduces a temperature calibration approach, which uses a new
temperature compensation formula based on the Raman scatter principle. Compared to
the general correction approach using linear correction coefficients, this temperature
calibration approach reduces temperature correction errors even at temperatures
faraway from the temperature that was used for calibration. It not only simplifies the
temperature calibration workflow tremendously but also greatly reduces errors due to
temperature correction calculations. For compatibility reasons, temperature correction
using linear correction coefficients is also provided as an option, but we recommend
selecting temperature calibration using the new compensation formula for the
DTSX3000.
SEE ALSO
For details on parameters related to temperature calibration, see Section B7.3.3, “Calibration.”
C2.2.1. Temperature Calibration Procedure
To perform temperature calibration, follow the steps described below.
1. Determine sensor optical fiber sections
Temperature calibration is required for each spliced section of the sensor optical
fiber so the first step is to split the sensor optical fiber into sections at sensor optical
fiber connection points.
2. Determine differential loss values
Differential loss configuration is required for single-ended measurement but not for
double-ended measurement. A differential loss value must be specified for each
sensor optical fiber section. This value is obtained by first ensuring that the
temperature distribution over a section is uniform, and then adjusting the loss value
so that the measured temperature is constant over the section. In applications
where it is difficult o achieve a uniform temperature distribution over a section
and/or the temperature difference within a section is relatively small, the loss value
can also be obtained by measuring the temperatures at two or more positions
within the section, and then adjusting the loss value so that the temperature
difference measured by the DTSX3000 is the same as the actual temperature
difference.
In general, this differential loss value varies with the optical fiber manufacturer and
the optical fiber lot. For sensor optical fibers from the same lot from the same
manufacturer, the same value measured for any one section can be used for other
sections.