649
laser source and an optical switch, and the other power load includes processor, A/D card,
APD detector and LCD display; the two loads are electrically isolated as shown in Figure 1.
The MOPA-structured pulse laser has a large starting current, The instantaneous startup
of pulse laser easily caused the intrinsically safe power supply to shut down. The internal circuit grading start method is used to reduce the impact current, and the parameters of other
circuit board controller capacitors and inductors are determined to meet the requirements of
the intrinsically safe circuit.
3.2 Software design
The embedded Linux system is used to develop the system’s lower computer software, including data acquisition, data processing, temperature demodulation, display, storage, data
transmission, etc. Multi-threaded and multi-tasking processing is adopted, and QT language
is selected for software interface development. A standard modbus communication protocol
data communication is adopted and the upper computer is implemented by WEB software.
When calculating temperature, internal optical fibers can be selected as reference. The concrete formulas are as follows:
1
1
0
T
T 0
C
N
N
N
N
m
T T
hk
C
a
N
s
N
s
N
a
N
=
−
( )
0
T 0 0
T 0
( )
T m
T T
( )
0
T 0 0
T 0
( )
T m
T T
⎡
⎣
⎢
⎡ ⎡
⎣ ⎣
⎤
⎦
⎥
⎤ ⎤
⎦ ⎦
* ln
T 0 is the temperature of the reference region, T m is the temperature of a certain position
of the optical cable, N s
N ( )
T 0
T T is the average value of the Stokes curve intensity in the reference
region, N a
N ( )
T 0
T T is the average value of the anti-Stokes curve in the reference region, N a m
N ( )
T m
T T is
the anti-Stokes intensity at a certain point of the optical cable, N s m
N ( )
T m
T T is the Stokes intensity
at a certain point of the optical cable, and C hk is the constant.
4 TYPICAL DATA ANALYSIS
The following figure is the change curve of monitoring data of spontaneous combustion in
a goaf of a mine. Figure 3, From the curve, the temperature in the 200–450 m area increases
Figure 1. DTS hardware schematic.
Figure 2. Coal mine sel-ignition monitor system.
wind out
laser source and an optical switch, and the other power load includes processor, A/D card,
APD detector and LCD display; the two loads are electrically isolated as shown in Figure 1.
The MOPA-structured pulse laser has a large starting current, The instantaneous startup
of pulse laser easily caused the intrinsically safe power supply to shut down. The internal circuit grading start method is used to reduce the impact current, and the parameters of other
circuit board controller capacitors and inductors are determined to meet the requirements of
the intrinsically safe circuit.
3.2 Software design
The embedded Linux system is used to develop the system’s lower computer software, including data acquisition, data processing, temperature demodulation, display, storage, data
transmission, etc. Multi-threaded and multi-tasking processing is adopted, and QT language
is selected for software interface development. A standard modbus communication protocol
data communication is adopted and the upper computer is implemented by WEB software.
When calculating temperature, internal optical fibers can be selected as reference. The concrete formulas are as follows:
1
1
0
T
T 0
C
N
N
N
N
m
T T
hk
C
a
N
s
N
s
N
a
N
=
−
( )
0
T 0 0
T 0
( )
T m
T T
( )
0
T 0 0
T 0
( )
T m
T T
⎡
⎣
⎢
⎡ ⎡
⎣ ⎣
⎤
⎦
⎥
⎤ ⎤
⎦ ⎦
* ln
T 0 is the temperature of the reference region, T m is the temperature of a certain position
of the optical cable, N s
N ( )
T 0
T T is the average value of the Stokes curve intensity in the reference
region, N a
N ( )
T 0
T T is the average value of the anti-Stokes curve in the reference region, N a m
N ( )
T m
T T is
the anti-Stokes intensity at a certain point of the optical cable, N s m
N ( )
T m
T T is the Stokes intensity
at a certain point of the optical cable, and C hk is the constant.
4 TYPICAL DATA ANALYSIS
The following figure is the change curve of monitoring data of spontaneous combustion in
a goaf of a mine. Figure 3, From the curve, the temperature in the 200–450 m area increases
Figure 1. DTS hardware schematic.
Figure 2. Coal mine sel-ignition monitor system.
wind out