WO2021228273A1 - 一种应用于小尺寸火源监测的光纤光栅传感方法 - Google Patents

一种应用于小尺寸火源监测的光纤光栅传感方法 Download PDF

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WO2021228273A1
WO2021228273A1 PCT/CN2021/099390 CN2021099390W WO2021228273A1 WO 2021228273 A1 WO2021228273 A1 WO 2021228273A1 CN 2021099390 W CN2021099390 W CN 2021099390W WO 2021228273 A1 WO2021228273 A1 WO 2021228273A1
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spectrum
area
fbgs
overall
temperature
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PCT/CN2021/099390
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English (en)
French (fr)
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李政颖
王立新
王洪海
郭会勇
姜德生
王加琪
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武汉理工大学
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Priority to US17/387,995 priority Critical patent/US11313737B2/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
    • G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
    • G01K11/3206—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres at discrete locations in the fibre, e.g. using Bragg scattering
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K1/00—Details of thermometers not specially adapted for particular types of thermometer
    • G01K1/02—Means for indicating or recording specially adapted for thermometers
    • G01K1/026—Means for indicating or recording specially adapted for thermometers arrangements for monitoring a plurality of temperatures, e.g. by multiplexing
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/06—Electric actuation of the alarm, e.g. using a thermally-operated switch
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K3/00—Thermometers giving results other than momentary value of temperature
    • G01K3/08—Thermometers giving results other than momentary value of temperature giving differences of values; giving differentiated values
    • G01K3/14—Thermometers giving results other than momentary value of temperature giving differences of values; giving differentiated values in respect of space
    • G01K2003/145—Hotspot localization
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
    • G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/02—Monitoring continuously signalling or alarm systems
    • G08B29/04—Monitoring of the detection circuits
    • G08B29/043—Monitoring of the detection circuits of fire detection circuits
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/18—Prevention or correction of operating errors
    • G08B29/185—Signal analysis techniques for reducing or preventing false alarms or for enhancing the reliability of the system

Definitions

  • the present invention relates to the technical field of small-size fire source monitoring, in particular to a fiber grating sensing method applied to small-size fire source monitoring.
  • Optical fiber sensor temperature measurement technology has the advantages of anti-electromagnetic interference, anti-corrosion, long detection distance and large reuse capacity. It has replaced traditional electrical fire detection technology in many fields such as petroleum and petrochemical, electric power, tunnel transportation, and has become the mainstream Fire detection technology.
  • Fire detection technology not only needs to be able to achieve long-distance and large-scale monitoring, but also needs to monitor the temperature rise along the fire detection line intensively. Therefore, early warning is given when the fire source is small, and the fire is extinguished in the budding state.
  • FBG fiber Bragg grating
  • the technology based on fiber Bragg grating (FBG) temperature sensing is a mature technology in the fire detector market. It uses the temperature sensitivity of the center wavelength of the FBG to measure the temperature of the environment where the FBG is located, and has a signal-to-noise ratio. High, fast response speed and other advantages.
  • FBG can only sense its own temperature changes, and the optical fiber between FBG and FBG does not have the ability to sense. Therefore, this technology is a quasi-distributed sensing technology.
  • the detection ability of small-sized fire sources mainly depends on adjacent The spacing between FBGs.
  • Traditional FBG temperature sensing systems mainly have two networking methods: one is based on wavelength division multiplexing (WDM) technology, where multiple FBGs with different wavelengths and strong reflectivity are welded in series to form a sensor.
  • WDM wavelength division multiplexing
  • the interval between the network and FBG can be set arbitrarily according to needs, so it can realize the perception of small-scale fire sources.
  • the number of multiplexing of the system is only a few dozen at most, which is difficult to achieve large-scale long-distance detection; the other is the networking method based on time division multiplexing (TDM) technology.
  • TDM time division multiplexing
  • the multiplexing capacity of the system can reach hundreds.
  • the interval between FBGs (usually on the meter level) is limited by the pulse width of the pulsed light source and the bandwidth of the hardware circuit, and it is difficult for the system to detect small-sized fire sources.
  • the FBG sensor network adopts industrial fiber drawing tower preparation technology, and continuously writes the sensor grating at multiple points during the fiber drawing process, avoiding welding loss and increasing the sensor network
  • the mechanical strength can realize the writing of tens of thousands of gratings on an optical fiber, and it has the characteristics of high spatial resolution, large system capacity, long detection distance, and high flexibility.
  • the preparation of the sensor network has made a qualitative leap, in the sensor network using the TDM technology networking mode, the demodulation system is always limited by the pulse width of the pulsed optical signal, and it is impossible to shorten the distance between adjacent FBGs in a true sense. It is impossible to realize long-distance, large-capacity and high-density small-scale fire source monitoring.
  • the present invention provides a fiber grating sensing method applied to small-scale fire source monitoring.
  • the densely distributed FBG sensor network is divided into several larger areas, and pulses with a wider pulse width are used.
  • the light obtains the overall spectral information of different areas, which not only guarantees the spatial resolution of the system but also realizes the monitoring of small-scale fire sources.
  • the present invention proposes a fiber grating sensing method for small-scale fire source monitoring.
  • the densely distributed FBG sensing network is divided into several larger areas, and pulsed light with a wider pulse width is used to obtain The overall spectral information of different regions not only ensures the spatial resolution of the system but also realizes the monitoring of small-scale fire sources.
  • the technical scheme of the present invention is realized as follows:
  • the present invention provides a fiber grating sensing method applied to small-scale fire source monitoring, including the following steps:
  • the pulse width of a single pulsed optical signal covers all FBGs in an area.
  • the pulse width of the pulsed optical signal is recorded as t, and the period is recorded as T;
  • t 2n eff D/c, T>2n eff L fiber /c, where n eff is the refractive index of the fiber core, and c is the propagation speed of light in vacuum;
  • S5. Summarize and classify the characteristics of the overall regional spectrum, establish different data processing mechanisms according to the characteristics of the overall regional spectrum, and obtain detailed temperature information, thereby realizing the monitoring of small-scale fire sources.
  • the value range of ⁇ L in S1 is: 8-20 cm.
  • the characteristics of the overall area spectrum in S5 include four characteristics, which are respectively denoted as Feature 1, Feature 2, Feature 3, and Feature 4;
  • Feature 1 When all FBGs in the area are under the same conditions, that is, the center wavelengths of all FBGs in the area change together with temperature, and the spectrum of all FBGs is superimposed into an overall area spectrum, and the overall area spectrum shape is similar to that of a single FBG. However, the peak intensity is m times the peak intensity of a single FBG, and the spectrum of the whole area shows the characteristics of overall movement;
  • Feature 2 When the environment of only a single FBG in the area changes, mark the single FBG as FBG#n, and the spectrum of FBG#n gradually separates from the overall area spectrum and moves toward the long wavelength direction, while the overall area spectrum The main peak intensity of is reduced to (m-1)/m of the spectral peak intensity of the whole area under feature 1;
  • Feature 3 is: when multiple FBGs in the area are affected by the same temperature and change, the overall area spectrum shows that the main peak intensity drops to (mx)/m of the overall area spectral intensity under Feature 1, where x is the number of affected FBGs. The peak intensity increases to x/m and moves left and right with temperature;
  • Feature 4 is: when multiple FBGs in the area change under the influence of different temperatures, the overall area spectrum shows that the main peak intensity drops to (mx)/m of the overall area spectral intensity under Feature 1, where x is the number of affected FBGs, and side peaks The shape of is changed with the temperature of each FBG.
  • the width of the spectrum of the entire region represents the temperature gradient of the FBG in the region, and the intensity distribution of the side peaks is related to the number of FBGs on different temperature gradients.
  • the data processing mechanism in S5 includes the following steps:
  • the side lobe intensity is denoted as S Right , and the wavelength value ⁇ Left_i corresponding to the intensity of the leftmost sg times S Left of the overall area spectrum and the wavelength value ⁇ Right_i corresponding to the intensity of the rightmost sg times S Right of the overall area spectrum are recorded as The calibration value of the system, where the value of sg is selected according to the power fluctuation of the system;
  • the overall regional spectrum of region i belongs to feature 2.
  • the highest temperature value of region i: T i C+k*( ⁇ Right - ⁇ Right_i ), ⁇ Right is the rightmost sg of the overall regional spectrum The wavelength value at times the intensity of S Right;
  • region i C+k*( ⁇ Right - ⁇ Right_i ), and the temperature of other FBGs is C +k*( ⁇ - ⁇ i );
  • the overall area spectrum of area i belongs to feature 3.
  • the FBGs in area i are divided into two groups.
  • the FBGs in each group are affected by the same temperature and the number of FBGs in each group is m*MAX L /(MAX L +MAX R ) and m*MAX R /(MAX L +MAX R ) to obtain the wavelength values ⁇ L and ⁇ R corresponding to the peak points MAX L and MAX R.
  • the overall area spectrum of area i belongs to feature 4.
  • the highest temperature of area i is C+k*( ⁇ Right - ⁇ Right_i ), the lowest temperature is C+k*( ⁇ Left - ⁇ Left_i ), ⁇ Left It is the wavelength value at sg times the intensity of S Right at the leftmost side of the spectrum of the whole area.
  • the optical fiber grating sensing method applied to small-scale fire source monitoring of the present invention has the following beneficial effects:
  • the identical UWFBG sensor network of the present invention also has a small-scale fire source perception. It also has long-distance fire detection capabilities;
  • the spatial resolution of the identical UWFBG sensor network is D, and the spatial resolution D is constant.
  • the pulse width of a single pulsed optical signal covers an area All FBGs use pulsed light with a wider pulse width to obtain the overall spectral information of different areas.
  • the pulse width of the optical signal can improve the system's perception resolution without increasing the requirements for the hardware circuit, truly shorten the interval between adjacent FBGs, improve the system's perception resolution, and realize the detection of small-scale fire sources;
  • the present invention can provide detailed and accurate temperature information based on reference values and calibration values, or simply provide simple abnormal temperature (high temperature) data based on calibration values to increase response speed. So as to realize the rapid warning of small-sized fire sources.
  • FIG. 1 is a schematic diagram of a large-capacity identical UWFBG sensing network structure in a fiber grating sensing method for small-size fire source monitoring according to the present invention
  • FIG. 2 is a schematic diagram of the characteristic changes of the regional spectrum in different situations in a fiber grating sensing method applied to small-scale fire source monitoring according to the present invention
  • Fig. 3 is a schematic flow diagram of a fiber grating sensing method applied to small-scale fire source monitoring according to the present invention
  • Fig. 4 is a block diagram of a demodulation system according to the third embodiment of the present invention.
  • Traditional FBG temperature sensing systems mainly have two networking methods: one is based on wavelength division multiplexing (WDM) technology, where multiple FBGs with different wavelengths and strong reflectivity are welded in series to form a sensor.
  • WDM wavelength division multiplexing
  • the interval between the network and FBG can be set arbitrarily according to needs, so it can realize the perception of small-scale fire sources.
  • the number of multiplexing of the system is only a few dozen at most, which makes it difficult to achieve large-scale long-distance detection;
  • the other is a networking method based on time division multiplexing (TDM) technology, where multiple FBGs with the same wavelength and weak reflectivity are welded in series to form a sensor network. Since it is no longer limited by the bandwidth of the light source, the system is multiplexed The capacity can reach hundreds. However, the interval between FBGs (usually on the meter level) is limited by the pulse width of the pulsed light source and the bandwidth of the hardware circuit, and it is difficult for the system to detect small-sized fire sources. At the same time, due to the weak reflectivity of FBG (in order to avoid the crosstalk problem between FBGs), the welding loss introduced by too many welding points causes the signal-to-noise ratio of the FBG sensor at the end of the sensor network to be poor.
  • TDM time division multiplexing
  • each FBG corresponds to a different extension.
  • the serial network is changed to a parallel network. This method can undoubtedly realize the detection of small-scale fire sources, because the arrangement of multiple sensing fibers breaks through the limitation of space factors. However, this method does not improve the demodulation system.
  • the length of the delay fiber corresponding to each FBG is also limited by the pulse width of the pulse light source and the bandwidth of the hardware circuit. At the same time, the loss introduced by the splitter and other devices is also limited. The reuse capacity of the system.
  • the preparation of FBG sensor network no longer requires multiple FBGs for welding.
  • the industrial fiber drawing tower preparation technology is adopted to write sensor gratings continuously at multiple points during the fiber drawing process. Welding loss also increases the mechanical strength of the sensor network. It can write tens of thousands of gratings on an optical fiber. It has the characteristics of high spatial resolution, large system capacity, long detection distance, and high flexibility.
  • the preparation of the sensor network has made a qualitative leap, in the sensor network using the TDM technology networking mode, the demodulation system is always limited by the pulse width of the pulsed optical signal, and it is impossible to shorten the distance between adjacent FBGs in a true sense.
  • the interval that is, the spatial resolution (perceived resolution) of the system is determined by the pulse width of the pulsed light signal.
  • the shorter the pulse width the higher the spatial resolution (perceptual resolution) of the system, but the higher the bandwidth requirements of the hardware circuits in the system.
  • the spatial resolution is the minimum distance between two adjacent fire sources that can be identified by the distributed grating sensor along the fiber length distribution, and is determined by the pulse width of the pulsed light signal;
  • the perception resolution is the characterization of the distributed grating
  • the researchers In the demodulation system based on FBG sensing, the researchers always default the system's perception resolution to the system's spatial resolution. Therefore, the system has always been limited by the pulse width of the pulsed optical signal, and cannot achieve long-distance, large-capacity, and high-density Small size fire source monitoring.
  • the networking method based on wavelength division multiplexing (WDM) technology has only a few dozen multiplexes at most, making it difficult to achieve large-scale long-distance detection; in the networking method based on time division multiplexing (TDM) technology, There are two problems: (1) The interval between FBGs (usually on the meter level) is limited by the pulse width of the pulsed light source and the bandwidth of the hardware circuit, making it difficult for the system to detect small-scale fire sources; (2) the system’s perception The resolution defaults to the spatial resolution of the system. Therefore, the system has always been limited by the pulse width of the pulsed light signal, and cannot achieve long-distance, large-capacity, high-density, and small-scale fire source monitoring.
  • WDM wavelength division multiplexing
  • TDM time division multiplexing
  • This embodiment is a networking mode based on time division multiplexing (TDM) technology.
  • TDM time division multiplexing
  • this embodiment uses ultra-large capacity FBG online writing technology to produce
  • UWFBG ultra-weak fiber grating
  • the interval ⁇ L is equivalent to the size of the fire source. Further preferably, the value range of ⁇ L is: 8-20 cm.
  • the beneficial effect of this step is that the use of FBG with ultra-low reflectivity in the identical UWFBG sensor network can greatly increase the multiplexing capacity of the identical UWFBG sensor network. Therefore, the identical UWFBG sensor network also has a small size. Along with source sensing capability, it also has long-distance fire detection capability.
  • the 2N areas are respectively denoted as area #1, area #2, area #3...area #2N. Since temperature changes in different regions will not affect adjacent regions, the spatial resolution of the identical UWFBG sensor network is D, and the spatial resolution D has been determined when the length of the region is set. Therefore, the spatial resolution of this embodiment The rate D will not change.
  • optical fiber is divided into several sensing areas of equal length, and the number and parameters of FBG in each area are the same, which avoids complicated networking modes and reduces the difficulty of demodulation.
  • the pulse width of a single pulsed optical signal covers all FBGs in an area.
  • the pulse width of the pulsed optical signal is recorded as t, and the period is recorded as T;
  • t 2n eff D/c, T>2n eff L fiber /c, where n eff is the refractive index of the fiber core, and c is the propagation speed of light in vacuum;
  • the pulse width of a single pulsed optical signal covers all FBGs in an area, that is, the pulse width of a single pulsed optical signal covers m FBGs.
  • the sensing resolution of the identical UWFBG sensor network is determined by the number of FBGs covered by a single pulsed optical signal. The more FBGs covered by a single pulsed optical signal, the higher the sensing resolution of the identical UWFBG sensor network.
  • the shorter the pulse width of the pulse signal the higher the spatial resolution of the system, but the higher the bandwidth requirement of the hardware circuit in the system.
  • the existing hardware circuit cannot meet the requirements and cannot be truly meaningful. Shorten the interval between adjacent FBGs, thereby improving the spatial resolution of the system, and realizing the purpose of small-scale fire source monitoring.
  • this step under the premise of ensuring the spatial resolution of the traditional FBG sensing system, only the number of FBGs covered by a single pulsed light signal can be increased to improve the sensing resolution of the system, and pulsed light with a wider pulse width can be used to obtain different areas.
  • the overall spectrum information can realize the detection of small-scale fire sources, reduce the requirements for hardware circuits, and truly shorten the interval between adjacent FBGs.
  • the requirement of the pulse width t of the pulsed light signal is: t ⁇ 2n eff D/c, as long as the pulse width t satisfies t ⁇ 2n eff D/c, the front and back two FBGs can be distinguished.
  • the beneficial effect of this step is that the two concepts of spatial resolution and perceptual resolution have been distinguished in this embodiment so far, and the two concepts of spatial resolution and perceptual resolution have been distinguished, which guarantees the spatial resolution of the traditional FBG sensing system.
  • the two concepts of spatial resolution and perceptual resolution have been distinguished, which guarantees the spatial resolution of the traditional FBG sensing system.
  • only increasing the number of FBGs covered by a single pulsed optical signal improves the system’s perception resolution, reduces the requirements for hardware circuits, truly shortens the interval between adjacent FBGs, and improves the system’s perception resolution. Detection of small-scale fire sources.
  • the beneficial effect of this step is: because the identical UWFBG in each region has the same optical parameters, the superimposed regional spectrum is still affected by the external temperature. Compared with the traditional FBG sensing technology, the information contained in the regional spectrum is More abundant (wavelength-intensity-shape information), which is more conducive to the temperature detection of small-sized fire sources.
  • S5. Summarize and classify the characteristics of the overall regional spectrum, establish different data processing mechanisms according to the characteristics of the overall regional spectrum, and obtain detailed temperature information, thereby realizing the monitoring of small-scale fire sources.
  • the beneficial effects of this step are: the use of simple feature extraction algorithms to obtain fire temperature information in different areas not only ensures the spatial resolution of the system but also realizes the monitoring of small-scale fire sources. At the same time, due to the simple demodulation algorithm, the temperature of the system The detection speed is fast.
  • this embodiment uses a large-capacity identical and ultra-weak reflectivity FBG sensor network to replace single-mode optical fiber, which is used in the sensor network.
  • the manufacturing process does not introduce too many complicated processing techniques, and the detection of small-sized fire sources is realized by reducing the distance between the gratings.
  • the temperature detection process under the premise of ensuring the same spatial resolution, since the sensing information contained in the wavelength-intensity-shape of the spectral domain is more abundant than the information contained in the Raman scattering signal, it can further improve the small size of the fire.
  • Source detection capability since the sensing information contained in the wavelength-intensity-shape of the spectral domain is more abundant than the information contained in the Raman scattering signal, it can further improve the small size of the fire.
  • this embodiment only adopts a simple TDM networking method to reduce the spatial resolution of the FBG demodulation system based on the OTDR technology. Distinguish from the two concepts of perceptual resolution, pulse light with a wider pulse width is used to obtain the overall spectral information of different areas, and the fire temperature information of different areas is obtained by using a simple feature extraction algorithm, which not only ensures the spatial resolution of the system but also It realizes the monitoring of small-sized fire sources, reduces the complexity and construction difficulty of the system, and improves the robustness and reliability of the system.
  • this embodiment establishes different data processing mechanisms according to the characteristics of the overall regional spectrum.
  • the characteristics of the overall regional spectrum include four characteristics, which are marked as Feature 1, Feature 2, Feature 3, and Feature 4, respectively.
  • Feature 1 to Feature 4 The specific description of Feature 1 to Feature 4 will be described in detail below.
  • Feature 1 When all FBGs in the area are under the same conditions, that is, the center wavelengths of all FBGs in the area change with temperature. As shown in Figure 2(a), the spectrum of all FBGs is superimposed into an overall area spectrum. All FBGs in the whole area are identical gratings, so the spectral shape of the whole area is similar to that of a single FBG but the peak intensity is m times the peak intensity of a single FBG, and the whole area spectrum shows the characteristics of overall movement;
  • Feature 2 When the environment of only a single FBG in the area changes, mark the single FBG as FBG#n, and the shape of the regional spectrum of FBG#n will change, as shown in Figure 2(b), FBG #n's spectrum gradually separates from the overall regional spectrum and moves toward the long wavelength direction, and at the same time, the main peak intensity of the overall regional spectrum drops to (m-1)/m of the overall regional spectral peak intensity under feature 1.
  • Feature 3 is: when multiple FBGs in the area are affected by the same temperature and change, that is, as the fire becomes larger, the number of affected FBGs gradually increases.
  • the overall area spectrum will be based on Feature 2, and the main peak intensity continues Decrease, while the side peak intensity further increases, as shown in Figure 2(c).
  • the overall area spectrum shows that the main peak intensity drops to (m-x)/m of the overall area spectrum intensity under Feature 1, where x is the number of affected FBGs, and the side peak intensity increases to x/m, and moves left and right with temperature;
  • Feature 4 is: when multiple FBGs in the area are affected by different temperatures and change, that is, the size of the fire source is small, and the temperature gradient in the space affects multiple FBGs around the fire source, as shown in Figure 2(d) below, the removed spectrum It is located at different center wavelengths, but the center wavelength of the grating closest to the fire source deviates the farthest.
  • the overall area spectrum shows that the main peak intensity is reduced to (mx)/m of the overall area spectrum intensity under Feature 1, where x is the number of affected FBGs, and the shape of the side peaks changes with the temperature of each FBG.
  • the width of the spectrum represents the size of the temperature gradient of the FBG in the region, and the intensity distribution of the side peaks is related to the number of FBGs on different temperature gradients.
  • the data processing mechanism of this embodiment includes the following steps:
  • the side lobe intensity is denoted as S Right , and the wavelength value ⁇ Left_i corresponding to the intensity of the leftmost sg times S Left of the overall area spectrum and the wavelength value ⁇ Right_i corresponding to the intensity of the rightmost sg times S Right of the overall area spectrum are recorded as The calibration value of the system, where the value of sg is selected according to the power fluctuation of the system to avoid the sidelobe intensity from affecting the acquisition of the wavelength values on both sides of the overall area spectrum;
  • the overall regional spectrum of region i belongs to feature 2.
  • the highest temperature value of region i: T i C+k*( ⁇ Right - ⁇ Right_i ), ⁇ Right is the rightmost sg of the overall regional spectrum The wavelength value at times the intensity of S Right;
  • region i C+k*( ⁇ Right - ⁇ Right_i ), and the temperature of other FBGs is C +k*( ⁇ - ⁇ i );
  • the overall area spectrum of area i belongs to feature 3.
  • the FBGs in area i are divided into two groups.
  • the FBGs in each group are affected by the same temperature and the number of FBGs in each group is m*MAX L /(MAX L +MAX R ) and m*MAX R /(MAX L +MAX R ) to obtain the wavelength values ⁇ L and ⁇ R corresponding to the peak points MAX L and MAX R.
  • the overall area spectrum of area i belongs to feature 4.
  • the highest temperature of area i is C+k*( ⁇ Right - ⁇ Right_i ), the lowest temperature is C+k*( ⁇ Left - ⁇ Left_i ), ⁇ Left It is the wavelength value at sg times the intensity of S Right at the leftmost side of the spectrum of the whole area.
  • this embodiment provides a simple feature extraction algorithm to obtain fire temperature information in different areas, which not only ensures the spatial resolution of the system but also realizes the monitoring of small-scale fire sources. At the same time, due to the simple demodulation algorithm, The temperature detection speed of the system is fast;
  • this embodiment can provide detailed temperature information, or only provide simple abnormal temperature (high temperature) data to increase the response speed, thereby realizing rapid warning of small-sized fire sources.
  • any sensitive part of the detector with a length of 100mm can quickly detect high temperature changes. It can be seen that how to improve the ability of optical fiber fire detection technology to monitor small-scale (100mm) fire sources is very important in fire prevention work.
  • this embodiment combines a practical case to further explain the fiber grating sensing method applied to small-scale fire source monitoring of the present application. details as follows:
  • Step 1 Continuously write 10,000 FBGs with a reflectivity of -47dB and a center wavelength of 1550nm on a single optical fiber.
  • the interval between FBGs is 10cm. Since each grating is sensitive to the external environment, the sensor network can perceive a fire source with a minimum size of 10 cm.
  • Step 2 In order to ensure the spatial resolution of the fire detection technology, the location of the fire source is usually accurate to within 1m to be enough for firefighters to diagnose the heat source, so the spatial resolution is set to 1m. That is, every 1m long area of the FBG sensor network is regarded as a sensing area, which is divided into 1000 areas, namely area #1, area #2, area #3...area #1000, and each area contains 10 FBGs;
  • the spectrum range of the pulsed light signal is 1548 ⁇ 1552nm broadband light.
  • the reflection spectrum signals of all FBGs in each area will overlap to form a whole new "area spectrum" signal.
  • the signal arrives at the spectral restoration unit at different times, so different regions can be divided in time. Then the restored regional spectrum signal is sent to the data processing unit for final demodulation of sensor information.
  • Step 5 The regional spectrum contains information such as the wavelength, intensity and the cumulative shape of multiple gratings in the region.
  • the fire scenarios that may occur in the actual project and the characteristics of the regional spectrum under the corresponding scenarios are summarized and classified as follows:
  • Typical scenario 1 When there is no external temperature disturbance, the center wavelength of the 10 FBGs in a single area remains the same, and the spectral intensity also remains the same. When the pulsed light is input into the area, the reflection spectrum signals of all gratings are superimposed. At 1550 nm, a regional spectral signal with an intensity 10 times that of a single grating is formed, as shown in regional spectrum 1 in Figure 2(a), which is similar to the shape of a single grating spectrum.
  • the regional spectrum will also change accordingly, as shown in the regional spectrum 2, regional spectrum 3 and regional spectrum 4 in Figure 2(a), as the FBG center in the region As the wavelength shifts to the right, the regional spectrum also shifts to the right;
  • Typical scenario 2 When the environment where only a single FBG is located in the area changes, as shown in Figure 2(b), the center wavelength of a single grating increases from 1550nm to 1550.2nm, 1550.3nm and 1550.5nm after being heated. The other 9 FBGs in the area are unaffected, so their reflection spectra remain basically unchanged. As the center wavelength of a single grating changes, the center wavelength of the fiber grating gradually separates from the regional spectrum. The source temperature increases and shifts to the long wavelength direction. Since a single grating moves out of the regional spectrum, the main peak intensity of the regional spectrum will gradually change from 1 to 0.9 with the removal of one of the grating spectra. The center wavelength is always 1550nm, while the separated spectrum (side peak) changes from 0.1 The intensity gradually moves to the long wavelength direction;
  • Typical scenario 3 When multiple fiber gratings in the area are affected by the same temperature and change, that is, as the influence range of the fire source increases, multiple fiber gratings are affected, as shown in Figure 2(c), as the heat The number of fiber gratings increased from 0, 3, 6 to 9, and the intensity of the original regional spectrum was gradually reduced from 1, to 0.7, 0.4 and then 0.1; and the intensity of the removed spectrum gradually increased from 0 to 0.3, 0.6 To 0.9;
  • Typical scenario 4 When multiple FBGs in the area are affected by different temperatures and change, that is, the size of the fire source is small, and the temperature gradient of the space affects multiple FBGs around the fire source, the degree of wavelength shift of each FBG is different, and they are at different levels. At the position of the center wavelength, the regional spectrum shows different intensity-wavelength graphs.
  • the main peak intensity of the regional spectrum will decrease from 1 to 0.5, as shown in Figure 2( d)
  • the shifted spectrum is at a different center wavelength, so the width of the side peak will be very wide, which means that the range of the temperature gradient affects from 1550nm to 1550.75nm, and the highest temperature is The wavelength of the FBG at the location (at the small-scale fire source) is most affected, drifting to 1550.75nm; if half (5) of the FBGs are affected by different temperatures and drift to 1550.15nm, 1550.30nm, 1550.45nm, 1550.75, respectively nm, 1550.75nm, the main peak intensity of the regional spectrum will decrease from 1 to 0.5, as shown in regional spectrum 3 in Figure 2(d), the
  • Area spectrum 4 represents the FBG wavelength at the location of the highest temperature (at the small-scale fire source) that has the greatest impact, drifting to 1550.75nm, and two FBGs are affected by the same temperature and drifting to 1550.3nm.
  • the system obtains the regional spectrum signal of each area in real time and performs temperature detection. Take the regional spectrum 2 and the regional spectrum 4 in Figure 2(a) as examples.
  • the coordinates of the maximum value of the two spectra are (1550.15nm, 1 ) And (1550.45nm, 1), compared with regional spectrum 1, have the same maximum value. Therefore, it is judged that these two spectra are typical scenario 1.
  • the temperature value of regional spectrum 2 and regional spectrum 4 is 35°C And 65°C, the temperature coefficient is 1°C/10pm.
  • take the rightmost wavelength values of 1550.33nm and 1550.63nm at 0.9/10 intensity in regional spectrum 2 and regional spectrum 4, and the temperature values calculated using this reference value are also 35°C and 65°C.
  • the center wavelength of a single grating increases from 1550nm to 1550.2nm and 1550.5nm after heating.
  • the maximum values of the two regional spectra are (1550.00 nm, 0.901) and (1550.00nm, 0.9), relative to the reference value of the system, the intensity has dropped by less than 1/10, so it is judged that the spectra of these two regions are both typical scenario 2.
  • the temperature values calculated from the two regional spectra are 37°C and 66°C respectively, and The temperature value calculated according to the actual wavelength change should be 40°C and 70°C, with errors of 3°C and 4°C respectively.
  • the temperature value obtained by the present invention has an error with the true value, but compared with the optical fiber distributed Raman temperature measurement system, the present invention has a great improvement in performance.
  • the measurement value of the Raman temperature measurement system is the average temperature value within 1m.
  • the temperature values obtained are 22°C and 25°C, and the errors are 18°C and 45°C, respectively. This will cause the system to fail to respond to the fire source. Although the results obtained by the present invention have errors, the error is only less than 5°C, and can respond normally. Small size fire source.
  • the spectral data of the area that does not meet the above conditions is judged as typical scenario 4, that is, multiple FBGs are affected by different temperatures, as shown in Figure 2(d).
  • 0.511 is not equal to the reference value 1 reserved by the system and is less than 0.9, so it can It is determined that there are multiple FBGs in the spectrum of this region that are affected by temperature, and because the spectrum of this region has only one peak point, the spectrum of this region will be judged as typical scenario 4.
  • the FBG with the lowest temperature in this region is 21°C, with an error of 1°C; when the system obtains the region spectrum 3, find the The peak can get 2 peaks (1550.0nm, 0.511) and (1550.75nm, 0.201). Since 0.511 ⁇ 0.9 and 0.511+0.201 ⁇ 1, the spectrum of this region is judged as typical scenario 4.
  • the reference value we can know the There are 5 FBGs in the area at a temperature of 20°C, and 2 FBGs at a temperature of 95°C. According to the calibration value, the maximum value in this area is 93°C and the error is 2°C.
  • this embodiment can provide detailed and accurate temperature information based on the reference value and the calibration value, or simply provide a simple abnormal temperature (high temperature) based on the calibration value. Data, increase the response speed, so as to realize the rapid warning of small-sized fire sources. Although there is an error in the method of using the calibration value, it is far closer to the true value than the result obtained by the distributed optical fiber Raman temperature measurement system.

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Abstract

一种应用于小尺寸火源监测的光纤光栅传感方法，将空间分辨率和感知分辨率两个概念区分开，在保证传统FBG传感系统的空间分辨率的前提下，仅增加单个脉冲光信号覆盖下的FBG的数量而不改变脉冲光信号的脉宽，从而提高系统的感知分辨率而不增加对硬件电路的要求，真正缩短相邻FBG之间的间隔，提高系统的感知分辨率，既保证了系统的空间分辨率又实现了小尺寸火源的监测；通过采用简单的特征提取算法获取不同区域的火灾温度信息，系统的温度探测速度快。

Description

一种应用于小尺寸火源监测的光纤光栅传感方法 技术领域
本发明涉及小尺寸火源监测技术领域，尤其涉及一种应用于小尺寸火源监测的光纤光栅传感方法。
背景技术
光纤传感测温技术因具有抗电磁干扰、抗腐蚀、探测距离长和复用容量大等优点，已在石油石化、电力、隧道交通等众多领域取代传统的电类火灾探测技术，成为主流的火灾探测技术。然而随着科技的发展，人们对火灾的起始和发展过程有了清晰的认识，火灾探测技术不仅需要能够实现长距离、大范围的监测，还需要在火灾探测沿线密集的监测温升情况，从而在火源较小的情况下进行预警，将火灾扑灭在萌芽状态。
基于光纤布拉格光栅(FBG)温度传感的技术，是火灾探测器市场上一种成熟的技术，利用FBG的中心波长对温度敏感这一特性对FBG所处环境的温度进行测量，具有信噪比高、响应速度快等优势。但是FBG只能感知其自身的温度变化，FBG与FBG之间的光纤并不具备感知能力，因此该技术是一种准分布式传感技术，对小尺寸火源的探测能力主要取决于相邻FBG之间的间距。
传统的FBG温度传感系统主要有两种组网方式：一种是基于波分复用(WDM)技术的组网方式，将多个不同波长的强反射率的FBG串联焊接在一起构成传感网络，FBG之间的间隔可以根据需要任意设置，因此能够实现小尺寸火源的感知。但是由于受到光源带宽和焊接损耗的影响，系统的复用数量最多只有几十个，难以实现大规模长距离的探测；另一种是基于时分复用(TDM)技术的组网方式，将多个相同波长的弱反射率的FBG串联焊接在一起构成传感网络，由于不再受到光源带宽的限制，系统的复用容量可以达到数百个。但是FBG之间的间隔(通常为米级)受脉冲光源的脉宽及硬件电路的带宽的限制，系统难以实现小尺寸火源的探测。
随着在线光纤光栅刻写技术的出现，FBG传感网络采用工业光纤拉丝塔制备技术，在光纤拉制过程中连续多点写入传感光栅，避免了焊接损耗，同时也增加了传感网络的机械强度，可以实现在一根光纤上刻写上万个光栅，具备空间分辨率高、系统容量大、探测距离长、灵活性高等特点。虽然传感网络的制备得到了质的飞跃，但在利用TDM技术组网方式的传感网络中，解调系统始终受到脉冲光信号的脉宽限制，无法实现真正意义上缩短相邻FBG之间的间隔，无法实现长距离大容量高密度的小尺寸火源监测。
因此，为解决上述问题，本发明提供一种应用于小尺寸火源监测的光纤光栅传感方法，将密集分布的FBG传感网络分为若干个较大的区域，使用脉宽较宽的脉冲光获取不同区域的整体光谱信息，既保证了系统的空间分辨率又实现了小尺寸火源的监测。
发明内容
有鉴于此，本发明提出了一种应用于小尺寸火源监测的光纤光栅传感方法，将密集分布的FBG传感网络分为若干个较大的区域，使用脉宽较宽的脉冲光获取不同区域的整体光谱信息，既保证了系统的空间分辨率又实现了小尺寸火源的监测。
本发明的技术方案是这样实现的：本发明提供了一种应用于小尺寸火源监测的光纤光栅传感方法，包括以下步骤：
S1、在单根光纤上连续地刻写了n个等间距的FBG构成大容量全同UWFBG传感网络，相邻FBG之间的间隔为ΔL，将全同UWFBG传感网络的有效探测长度记为L fiber，则L fiber＝n*ΔL；
S2、将全同UWFBG传感网络分为2N个等长的区域，每个区域内分布着m个FBG，每个区域的长度记为D，则D＝m*ΔL＝L fiber/2N，全同UWFBG传感网络的空间分辨率为D，并且空间分辨率D恒定不变；
S3、将脉冲光信号输入至全同UWFBG传感网络中，单个脉冲光信号的脉宽覆盖一个区域内所有FBG，将脉冲光信号的脉宽记为t，周期记为T；t＝2n effD/c，T>2n effL fiber/c，其中n eff为光纤纤芯的折射率，c为真空中光的传播速度；
S4、当脉冲光信号输入至全同UWFBG传感网络中后，每个区域内的m个FBG的反射谱信号叠加形成一个整体区域光谱信号；
S5、对该整体区域光谱的特征进行归纳并分类，根据该整体区域光谱的特征建立不同的数据处理机制，获取详细的温度信息，从而实现小尺寸火源的监测。
在以上技术方案的基础上，优选的，S1中ΔL的取值范围为：8-20cm。
在以上技术方案的基础上，优选的，S5中整体区域光谱的特征包括四个特征，分别记为特征1、特征2、特征3和特征4；
特征1为：区域内所有的FBG处于同一条件下时，即区域内所有FBG的中心波长一起随温度变化，所有FBG的光谱叠加为一个整体区域光谱，该整体区域光谱形状与单个FBG的光谱相似但峰值强度为单个FBG峰值强度的m倍，同时该整体区域光谱呈现整体移动的特征；
特征2为：区域内仅单个FBG所处的环境发生变化时，将该单个FBG记为FBG#n，FBG#n的光谱逐渐从整体区域光谱中分离出来向长波长方向移动，同时整体区域光谱的主峰强度降为特征1下整体区域光谱峰值强度的(m-1)/m；
特征3为：区域内多个FBG受到相同的温度影响发生变化时，整体区域光谱呈现出主峰强度降为特征1下整体区域光谱强度的(m-x)/m，x为受影响FBG的数量，旁峰强度增加至x/m，且随温度左右移动；
特征4为：区域内多个FBG受到不同温度影响发生变化时，整体区域光谱呈现出主峰强度降为特征1下整体区域光谱强度的(m-x)/m，x为受影响FBG的数量，旁峰的形状则随着各个FBG所受温度的变化而变化，整个区域光谱的宽度代表了区域内FBG的温度梯度大小，旁峰的强度分布则与不同温度梯度上的FBG的数量相关。
进一步优选的，S5中数据处理机制包括以下步骤：
S101、系统初始化：保持全同UWFBG传感网络中所有的FBG处于同一参考温度C下，获取此时各个区域的整体区域光谱的最大值以及相对应的波长值作为系统的参考值，将整体区域光谱的最大值记为M i，其相对应的波长值记为 λ i，i表示第i个区域，获取区域光谱两侧的旁瓣强度，将左侧旁瓣强度记为S Left，将右侧旁瓣强度记为S Right，记录整体区域光谱最左侧sg倍S Left的强度所对应的波长值λ Left_i和整体区域光谱最右侧sg倍S Right的强度所对应的波长值λ Right_i作为系统的标定值，其中sg的取值根据系统的功率波动取值；
S102、系统实时运行时，获取区域i的整体区域光谱的最大值MAX以及MAX所对应的波长值λ，将MAX与M i相比较；
若相等，则区域i的整体区域光谱属于特征1，区域i的最高温度值记为T i，T i＝C+k*(λ-λ i)，k为FBG的温度/波长系数；
若不等，则进行S103；
S103、判断区域i的整体区域光谱的最大值MAX是否满足MAX≥(m-1)/m*M i；
若满足，则执行S104；若不满足，则遍历整体区域光谱数据，寻找两个峰值点MAX L和MAX R，并执行S105；
S104、将MAX所对应的波长值λ并与λ i相比较；
若λ与λ i相等，则区域i的整体区域光谱属于特征2，区域i的最高温度值：T i＝C+k*(λ Right-λ Right_i)，λ Right为整体区域光谱最右侧sg倍S Right强度处的波长值；
若λ与λ i不相等，则区域i的整体区域区域光谱属于特征4，区域i内的最高温度为T i＝C+k*(λ Right-λ Right_i)，其它FBG所处温度值为C+k*(λ-λ i)；
S105、判断峰值点MAX L和MAX R的强度之和是否等于M i；
若等于，则区域i的整体区域光谱属于特征3，区域i内FBG被分为两组，每组内FBG受同一温度影响且每组内FBG数量分别为m*MAX L/(MAX L+MAX R)和m*MAX R/(MAX L+MAX R)，获取峰值点MAX L和MAX R对应的波长值λ L和λ R，区域i内两组FBG的温度信息分别为：T L＝C+k*(λ L-λ i)，T R＝C+k*(λ R-λ i)；
若不等于，则区域i的整体区域光谱属于特征4，区域i的最高温度为C+k*(λ Right-λ Right_i)，最低温度为C+k*(λ Left-λ Left_i)，λ Left为整体区域光谱最左侧sg倍S Right强度处的波长值。
本发明的一种应用于小尺寸火源监测的光纤光栅传感方法相对于现有技术具有以下有益效果：
(1)在全同UWFBG传感网络中采用反射率超弱的FBG可以大大提高全同UWFBG传感网络的复用容量，因此本发明的全同UWFBG传感网络也在具有小尺寸火源感知能力的同时也具有长距离的火灾探测能力；
(2)将光纤分成若干个等长的传感区域，每个区域的FBG数量和参数相同，避免了复杂的组网方式，降低了解调难度；
(3)将空间分辨率和感知分辨率两个概念区分开，全同UWFBG传感网络的空间分辨率为D，并且空间分辨率D恒定不变，单个脉冲光信号的脉宽覆盖一个区域内所有FBG，使用脉宽较宽的脉冲光获取不同区域的整体光谱信息，在保证传统FBG传感系统的空间分辨率的前提下，仅增加单个脉冲光信号覆盖下的FBG的数量而不改变脉冲光信号的脉宽，从而提高系统的感知分辨率而不增加对硬件电路的要求，真正缩短相邻FBG之间的间隔，提高系统的感知分辨率，从而实现小尺寸火源的探测；
(4)由于各个区域内的全同UWFBG具有相同的光学参数，因此叠加后的区域光谱仍受外界温度的影响，与传统FBG传感技术相比，该区域光谱所包含的信息更加丰富(波长-强度-形状信息)，更加有利于小尺寸火源的温度检测；
(5)通过采用简单的特征提取算法获取不同区域的火灾温度信息，系统的温度探测速度快；
(6)对于不同的小尺寸火源监测场景，本发明可以根据参考值和标定值提供详细且准确的温度信息，也可以只根据标定值提供简单的异常温度(高温)数据，增加响应速度，从而实现小尺寸火源的快速预警。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付 出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为本发明一种应用于小尺寸火源监测的光纤光栅传感方法中大容量全同UWFBG传感网络结构示意图；
图2为本发明一种应用于小尺寸火源监测的光纤光栅传感方法中不同情境下区域光谱的特征变化示意图；
图3为本发明一种应用于小尺寸火源监测的光纤光栅传感方法的流程示意图；
图4为实施例3适用于本发明的解调系统框图。
具体实施方式
下面将结合本发明实施方式，对本发明实施方式中的技术方案进行清楚、完整地描述，显然，所描述的实施方式仅仅是本发明一部分实施方式，而不是全部的实施方式。基于本发明中的实施方式，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施方式，都属于本发明保护的范围。
实施例1
传统的FBG温度传感系统主要有两种组网方式：一种是基于波分复用(WDM)技术的组网方式，将多个不同波长的强反射率的FBG串联焊接在一起构成传感网络，FBG之间的间隔可以根据需要任意设置，因此能够实现小尺寸火源的感知。但是由于受到光源带宽和焊接损耗的影响，系统的复用数量最多只有几十个，难以实现大规模长距离的探测；
另一种是基于时分复用(TDM)技术的组网方式，将多个相同波长的弱反射率的FBG串联焊接在一起构成传感网络，由于不再受到光源带宽的限制，系统的复用容量可以达到数百个。但是FBG之间的间隔(通常为米级)受脉冲光源的脉宽及硬件电路的带宽的限制，系统难以实现小尺寸火源的探测。同时由于FBG的反射率较弱(为了避免FBG之间的串扰问题)，过多的焊接点引入的焊接损耗造成传感网络尾端FBG传感器的信号信噪比较差。
为了克服TDM技术中FBG的反射率太弱造成的信噪比差的问题，将多个 相同波长的强反射率的FBG并联焊接在分路器上构成传感网络，每个FBG对应不同的延时光纤，即为了提高FBG的反射率而又不引入串扰等问题，将串联网络改为并联网络。这种方法无疑可以实现小尺寸火源的感知，因为多根传感光纤的布设突破了空间因素的限制。但这种方法并未对解调系统进行改进，每个FBG对应的延时光纤的长度同样受到脉冲光源的脉宽及硬件电路带宽的限制，同时由分路器等器件引入的损耗也限制了系统的复用容量。
随着在线光纤光栅刻写技术的出现，FBG传感网络的制备不再需要多个FBG进行焊接，采用工业光纤拉丝塔制备技术，在光纤拉制过程中连续多点写入传感光栅，避免了焊接损耗，同时也增加了传感网络的机械强度，可以实现在一根光纤上刻写上万个光栅，具备空间分辨率高、系统容量大、探测距离长、灵活性高等特点。虽然传感网络的制备得到了质的飞跃，但在利用TDM技术组网方式的传感网络中，解调系统始终受到脉冲光信号的脉宽限制，无法实现真正意义上缩短相邻FBG之间的间隔，即系统的空间分辨率(感知分辨率)由脉冲光信号的脉宽决定。脉宽越短，系统的空间分辨率(感知分辨率)越高，但对系统中硬件电路的带宽要求也越高。值得一提的是，空间分辨率是表征分布式光栅传感器沿光纤长度分布上能够识别的两个相邻火源的最小距离，由脉冲光信号的脉宽决定；感知分辨率是表征分布式光栅传感器沿光纤长度分布上能够识别的火源的最小尺寸。可见，空间分辨率和感知分辨率是两个概念。在基于FBG传感的解调系统中，研究人员始终将系统的感知分辨率默认为系统的空间分辨率，因此系统一直受到脉冲光信号的脉宽的限制，无法实现长距离大容量高密度的小尺寸火源监测。
综上，基于波分复用(WDM)技术的组网方式，其复用数量最多只有几十个，难以实现大规模长距离的探测；基于时分复用(TDM)技术的组网方式中，存在两个问题：(1)FBG之间的间隔(通常为米级)受脉冲光源的脉宽及硬件电路的带宽的限制，系统难以实现小尺寸火源的探测；(2)将系统的感知分辨率默认为系统的空间分辨率，因此系统一直受到脉冲光信号的脉宽的限制，无法实现长距离大容量高密度的小尺寸火源监测。
本实施例是基于时分复用(TDM)技术的组网方式，为了解决时分复用 (TDM)技术的组网方式中遇到的两个问题，本实施例利用超大容量FBG在线刻写技术制作的长距离、高密度、大容量的全同超弱光纤光栅(UWFBG)传感阵列作为传感网络，提供了一种应用于小尺寸火源监测的光纤光栅传感方法，具体包括以下步骤：
S1、在单根光纤上连续地刻写了n个等间距的FBG构成大容量全同UWFBG传感网络，相邻FBG之间的间隔为ΔL，将全同UWFBG传感网络的有效探测长度记为L fiber，则L fiber＝n*ΔL；
本实施例中，间隔ΔL与火源尺寸相当。进一步优选的，ΔL的取值范围为：8-20cm。
本步骤的有益效果为：在全同UWFBG传感网络中采用反射率超弱的FBG可以大大提高全同UWFBG传感网络的复用容量，因此该全同UWFBG传感网络也在具有小尺寸火源感知能力的同时也具有长距离的火灾探测能力。
S2、将全同UWFBG传感网络分为2N个等长的区域，每个区域内分布着m个FBG，每个区域的长度记为D，则D＝m*ΔL＝L fiber/2N，全同UWFBG传感网络的空间分辨率为D，并且空间分辨率D恒定不变；
如图1所示，将2N个区域分别记为区域#1、区域#2、区域#3…区域#2N。由于不同区域内的温度变化不会影响相邻区域，因此全同UWFBG传感网络的空间分辨率为D，并且空间分辨率D在设置区域长度时就已经确定，因此，本实施例的空间分辨率D不会改变。
本步骤的有益效果为：将光纤分成若干个等长的传感区域，每个区域的FBG数量和参数相同，避免了复杂的组网方式，降低了解调难度。
S3、将脉冲光信号输入至全同UWFBG传感网络中，单个脉冲光信号的脉宽覆盖一个区域内所有FBG，将脉冲光信号的脉宽记为t，周期记为T；t＝2n effD/c，T>2n effL fiber/c，其中n eff为光纤纤芯的折射率，c为真空中光的传播速度；
本实施例中，单个脉冲光信号的脉宽覆盖一个区域内所有FBG，即单个脉冲光信号的脉宽覆盖m个FBG。全同UWFBG传感网络的感知分辨率由单个脉冲光信号覆盖下的FBG数量决定，单个脉冲光信号覆盖下的FBG数量越多，全 同UWFBG传感网络的感知分辨率越高。
传统传感技术中，脉冲信号的脉宽越短，系统的空间分辨率越高，但对系统中硬件电路的带宽要求也越高，而现有的硬件电路达不到要求，无法真正意义上缩短相邻FBG之间的间隔，进而提高系统的空间分辨率，实现小尺寸火源监测的目的。本步骤中，可以在保证传统FBG传感系统的空间分辨率的前提下，仅增加单个脉冲光信号覆盖下的FBG的数量提高系统的感知分辨率，使用脉宽较宽的脉冲光获取不同区域的整体光谱信息，从而实现小尺寸火源的探测，降低对硬件电路的要求，真正实现缩短相邻FBG之间的间隔。
传统的FBG传感系统中，脉冲光信号的脉宽t的要求是：t＜2n effD/c，只要脉宽t满足t＜2n effD/c，就可以区分开前后两个FBG。本实施例中，因为要顾及脉冲光信号脉宽需要覆盖每个区域内所有的光栅，若脉宽t小于2n effD/c，则无法覆盖区域内所有的光栅；若脉宽t大于2n effD/c，则无法区分前后两个分区，所以，本实施例中，t＝2n effD/c。
本步骤的有益效果为：本实施例至此已经将空间分辨率和感知分辨率两个概念区分开，将空间分辨率和感知分辨率两个概念区分开，在保证传统FBG传感系统的空间分辨率的前提下，仅增加单个脉冲光信号覆盖下的FBG的数量提高系统的感知分辨率，降低对硬件电路的要求，真正缩短相邻FBG之间的间隔，提高系统的感知分辨率，从而实现小尺寸火源的探测。
S4、当脉冲光信号输入至全同UWFBG传感网络中后，每个区域内的m个FBG的反射谱信号叠加形成一个整体区域光谱信号；
本步骤的有益效果为：由于各个区域内的全同UWFBG具有相同的光学参数，因此叠加后的区域光谱仍受外界温度的影响，与传统FBG传感技术相比，该区域光谱所包含的信息更加丰富(波长-强度-形状信息)，更加有利于小尺寸火源的温度检测。
S5、对该整体区域光谱的特征进行归纳并分类，根据该整体区域光谱的特征建立不同的数据处理机制，获取详细的温度信息，从而实现小尺寸火源的监测。
本步骤的有益效果为：通过采用简单的特征提取算法获取不同区域的火灾温度信息，既保证了系统的空间分辨率又实现了小尺寸火源的监测，同时由于解调算法简单，系统的温度探测速度快。
本实施例的有益效果为：相比于基于拉曼散射技术的分布式光纤测温系统，本实施例利用大容量全同超弱反射率FBG传感网络取代单模光纤，在传感网络的制作工艺中并不会引入太多复杂的加工工艺，通过降低光栅之间的间距实现小尺寸火源的探测。同时在温度检测过程中，在保证相同空间分辨率的前提下，由于光谱域波长-强度-形状所包含的传感信息比拉曼散射信号所包含的信息更加丰富，因此可以进一步提高小尺寸火源的探测能力；
与传统的基于TDM+WDM+SDM复合组网方式实现的FBG火灾探测技术相比，本实施例仅采用一种简单的TDM组网方式，将基于OTDR技术的FBG解调系统中的空间分辨率和感知分辨率两个概念区分开，使用脉宽较宽的脉冲光获取不同区域的整体光谱信息，通过采用简单的特征提取算法获取不同区域的火灾温度信息，既保证了系统的空间分辨率又实现了小尺寸火源的监测，又降低了系统的复杂度和施工难度，提高了系统的鲁棒性、可靠性。
实施例2
在实施例1的基础上，本实施例根据整体区域光谱的特征建立不同的数据处理机制，在介绍数据处理机制的具体过程之前，先介绍整体区域光谱的特征。本实施例中，整体区域光谱的特征包括四个特征，分别记为特征1、特征2、特征3和特征4。以下详细介绍特征1～特征4的具体描述。
特征1为：区域内所有的FBG处于同一条件下时，即区域内所有FBG的中心波长一起随温度变化，如图2(a)所示，所有FBG的光谱叠加为一个整体区域光谱，由于区域内所有FBG均为全同光栅，因此该整体区域光谱形状与单个FBG的光谱相似但峰值强度为单个FBG峰值强度的m倍，同时该整体区域光谱呈现整体移动的特征；
特征2为：区域内仅单个FBG所处的环境发生变化时，将该单个FBG记为 FBG#n，FBG#n的区域光谱的形状则会发生改变，如图2(b)所示，FBG#n的光谱逐渐从整体区域光谱中分离出来向长波长方向移动，同时整体区域光谱的主峰强度降为特征1下整体区域光谱峰值强度的(m-1)/m；
特征3为：区域内多个FBG受到相同的温度影响发生变化时，即随着火势的变大，受影响FBG的数量逐渐增加，此时整体区域光谱会在特征2的基础上，主峰强度继续下降，而旁峰强度进一步增加，如图2(c)所示。整体区域光谱呈现出主峰强度降为特征1下整体区域光谱强度的(m-x)/m，x为受影响FBG的数量，旁峰强度增加至x/m，且随温度左右移动；
特征4为：区域内多个FBG受到不同温度影响发生变化时，即火源尺寸很小，空间的温度梯度影响了火源周围多个FBG时，如下图2(d)所示，移出的光谱处于不同的中心波长的位置，但距离火源最近的光栅的中心波长偏离的最远。整体区域光谱呈现出主峰强度降为特征1下整体区域光谱强度的(m-x)/m，x为受影响FBG的数量，旁峰的形状则随着各个FBG所受温度的变化而变化，整个区域光谱的宽度代表了区域内FBG的温度梯度大小，旁峰的强度分布则与不同温度梯度上的FBG的数量相关。
基于上述四个特征，如图3所示，本实施例的数据处理机制包括以下步骤：
S101、系统初始化：保持全同UWFBG传感网络中所有的FBG处于同一参考温度C下，获取此时各个区域的整体区域光谱的最大值以及相对应的波长值作为系统的参考值，将整体区域光谱的最大值记为M i，其相对应的波长值记为λ i，i表示第i个区域，获取区域光谱两侧的旁瓣强度，将左侧旁瓣强度记为S Left，将右侧旁瓣强度记为S Right，记录整体区域光谱最左侧sg倍S Left的强度所对应的波长值λ Left_i和整体区域光谱最右侧sg倍S Right的强度所对应的波长值λ Right_i作为系统的标定值，其中sg的取值根据系统的功率波动取值，避免旁瓣强度影响整体区域光谱两侧波长值的获取；
S102、系统实时运行时，获取区域i的整体区域光谱的最大值MAX以及MAX所对应的波长值λ，将MAX与M i相比较；
若相等，则区域i的整体区域光谱属于特征1，区域i的最高温度值记为T i， T i＝C+k*(λ-λ i)，k为FBG的温度/波长系数；本实施例中，区域i的最高温度值记为T i也可以表示为T i＝C+k*(λ Right-λ Right_i)，λ Right为光谱最右侧sg倍S Right强度处的波长值。
若不等，则进行S103；
S103、判断区域i的整体区域光谱的最大值MAX是否满足MAX≥(m-1)/m*M i；
若满足，则执行S104；若不满足，则遍历整体区域光谱数据，寻找两个峰值点MAX L和MAX R，并执行S105；
S104、将MAX所对应的波长值λ并与λ i相比较；
若λ与λ i相等，则区域i的整体区域光谱属于特征2，区域i的最高温度值：T i＝C+k*(λ Right-λ Right_i)，λ Right为整体区域光谱最右侧sg倍S Right强度处的波长值；
若λ与λ i不相等，则区域i的整体区域区域光谱属于特征4，区域i内的最高温度为T i＝C+k*(λ Right-λ Right_i)，其它FBG所处温度值为C+k*(λ-λ i)；
S105、判断峰值点MAX L和MAX R的强度之和是否等于M i；
若等于，则区域i的整体区域光谱属于特征3，区域i内FBG被分为两组，每组内FBG受同一温度影响且每组内FBG数量分别为m*MAX L/(MAX L+MAX R)和m*MAX R/(MAX L+MAX R)，获取峰值点MAX L和MAX R对应的波长值λ L和λ R，区域i内两组FBG的温度信息分别为：T L＝C+k*(λ L-λ i)，T R＝C+k*(λ R-λ i)；
若不等于，则区域i的整体区域光谱属于特征4，区域i的最高温度为C+k*(λ Right-λ Right_i)，最低温度为C+k*(λ Left-λ Left_i)，λ Left为整体区域光谱最左侧sg倍S Right强度处的波长值。
本实施例的有益效果为：本实施例提供简单的特征提取算法获取不同区域的火灾温度信息，既保证了系统的空间分辨率又实现了小尺寸火源的监测，同时由于解调算法简单，系统的温度探测速度快；
对于不同的小尺寸火源监测场景，本实施例可以提供详细的温度信息，也可以只提供简单的异常温度(高温)数据，增加响应速度，从而实现小尺寸火 源的快速预警。
实施例3
根据国家标准GB16280-2014《线型感温火灾探测器》所述，探测器任一段长度为100mm的敏感部件能够迅速检测高温变化。可见，如何提高光纤类火灾探测技术对小尺寸(100mm)火源的监测能力在火灾预防工作中至关重要。在实施例2的基础上，本实施例结合一个实际案例对本申请的应用于小尺寸火源监测的光纤光栅传感方法进一步解释。具体如下：
步骤1：在单根光纤上连续刻写10000个反射率为-47dB，中心波长为1550nm的FBG，如图1所示，FBG之间间隔为10cm。由于每个光栅都对外界环境敏感，因此该传感网络可以感知到最小10cm尺寸的火源。同时，该传感阵列的有效探测长度为L fiber＝n*ΔL＝1km；
步骤2：为保证火灾探测技术的空间分辨率，通常情况下对于火源的定位精确到1m的范围内足够消防人员进行热源的诊断，因此空间分辨率设置为1m。即将FBG传感网络每1m长的区域作为一个传感区域，共分为1000个区域，即区域#1、区域#2、区域#3…区域#1000，每个区域内包含10个FBG；
步骤3：为了将各个区域的信号在传感网络中区分开，根据OTDR原理，输入至传感网络的脉冲光信号的脉宽t＝10ns，周期T与光纤光栅阵列总长度有关，T>10us。在实际系统中通常取20us避免光纤光栅阵列中多重反射的影响；
步骤4：如图4所示，系统控制单元通过驱动模块控制产生脉宽t＝10ns，周期T＝20us的脉冲光信号，脉冲光信号的频谱范围为1548～1552nm的宽带光，当脉冲光输入至光纤光栅阵列中后，每个区域内所有FBG的反射谱信号会发生重叠形成一个整体的新的“区域光谱”信号。该信号在不同的时间到达光谱还原单元，因此可以在时间上将不同的区域划分开。接着还原后的区域光谱信号被送入数据处理单元进行最终的传感信息解调。
步骤5：区域光谱包含区域内的波长、强度以及多个光栅累加后的形状等信息，此处对实际工程中可能发生的火灾情景及相应情景下区域光谱的特征进 行归纳并分类如下：
典型情景1：在没有外界温度扰动的时候，单个区域内10个FBG的中心波长保持一致不变，光谱强度也保持一致，当脉冲光输入到该区域时，所有光栅反射谱信号叠加，在波长1550nm处形成一个强度为单个光栅10倍的区域光谱信号，如图2(a)中区域光谱1所示，该光谱与单个光栅光谱的形状相似。若存在一火源使所有FBG的中心波长同时改变，则区域光谱也会随之改变，如图2(a)中区域光谱2、区域光谱3和区域光谱4所示，随着区域内FBG中心波长的右移，区域光谱也随之右移；
典型情景2：当区域内仅单个FBG所处的环境发生变化时，如图2(b)中所示，单个光栅受热后中心波长从1550nm增加至1550.2nm、1550.3nm及1550.5nm，由于该光栅所处的区域内其它9个FBG未受影响，因此它们的反射光谱基本不变，而随着单个光栅中心波长的变化，该光纤光栅的中心波长逐渐从区域光谱中分离出来，且随着火源温度的增加而向长波长方向移动。由于单个光栅移出区域光谱，此时区域光谱的主峰强度随着其中一个光栅光谱的移出，强度从1逐渐变为0.9，中心波长一直为1550nm，而分离出的光谱(旁峰)则从0.1的强度处逐渐向长波长方向移动；
典型情景3：当区域内多个光纤光栅受到相同的温度影响发生变化时，即随着火源影响范围的增大，多个光纤光栅受影响，如图2(c)所示，随着受热光纤光栅数量从0个，3个，6个增加到9个，原有区域光谱的强度从1，逐渐较小至0.7，0.4再到0.1；而移出的光谱强度逐渐从0增加至0.3，0.6再到0.9；
典型情景4：当区域内多个FBG受到不同温度影响发生变化时，即火源尺寸很小，空间的温度梯度影响了火源周围多个FBG时，各个FBG波长移动的程度不同，分别处于不同的中心波长的位置，区域光谱呈现出不同的强度-波长曲线图。若有一半(5个)的FBG受到不同温度的影响后分别漂移至1550.15nm，1550.30nm，1550.45nm，1550.60nm，1550.75nm，则区域光谱的主峰强度会从1降至0.5，如图2(d)中区域光谱2所示，移出的光谱处于不同的中心波长的位置，因此产生的旁峰的宽度将会很宽，代表着温度梯度影响的范围从1550nm波及到1550.75nm，而最高温所在位置处(小尺寸火源处)的FBG波长受影响 最大，飘移到了1550.75nm处；若有一半(5个)的FBG受到不同温度的影响后分别漂移至1550.15nm，1550.30nm，1550.45nm，1550.75nm，1550.75nm，则区域光谱的主峰强度会从1降至0.5，如图2(d)中区域光谱3所示，移出的光谱处于不同的中心波长的位置，因此产生的旁峰的宽度将会很宽，代表着温度梯度影响的范围从1550nm波及到1550.75nm，同时1550.75nm处的强度为0.2，说明在火源处有2个FBG同时受到影响且中心波长都飘移到了1550.75nm；同理，区域光谱4代表最高温所在位置处(小尺寸火源处)的FBG波长受影响最大，飘移到了1550.75nm处，有两个FBG受到同一温度的影响飘移至1550.3nm处。
根据不同情景下区域光谱的特征建立不同的数据处理机制，获取详细的温度信息，从而实现小尺寸火源的监测。具体的数据处理机制如下：
系统初始化：保持传感网络中所有的FBG处于同一温度20℃下，如图2(a)中区域光谱1所示，此处强度值采用相对强度来表示，由于单个区域内光栅数量为10，因此单个FBG在1/10强度以下逐渐飘移出光谱。取区域光谱1的最大值坐标为(1550.0nm，1)，即波长值为1550.0nm时光谱的强度最大为1，作为系统的参考值。获取光谱两侧旁瓣强度S Left＝0.012和S Right＝0.011，sg取1.1，同时记录光谱最左侧0.0132强度处的波长值1549.82nm与最右侧0.0121强度处的波长值1550.18nm作为标定值。
系统实时运行：系统实时获取各个区域的区域光谱信号并进行温度检测，以图2(a)中区域光谱2和区域光谱4为例，两个光谱中最大值的坐标分别为(1550.15nm，1)和(1550.45nm，1)，与区域光谱1相比，具有相同的最大值，因此判断这两个光谱为典型情景1，进一步地，区域光谱2和区域光谱4的温度值即为35℃和65℃，温度系数取1℃/10pm。同时取区域光谱2和区域光谱4中0.9/10强度处的最右侧波长值1550.33nm和1550.63nm，利用此参考值计算的温度值同样为35℃和65℃。
当区域内单个FBG受热温度低和受热温度高时，如图2(b)中单个光栅受热后中心波长从1550nm增加至1550.2nm和1550.5nm，首先获取两个区域光谱的最大值分别为(1550.00nm，0.901)和(1550.00nm，0.9),与系统的参考值相对，强 度下降了1/10以内，因此判断这两个区域光谱均为典型情景2。取这两个光谱中最右侧0.0121强度处的波长值分别为1550.35nm和1550.64nm，根据初始化记录的标定值1550.18nm，两个区域光谱计算得到的温度值分别为37℃和66℃，而根据实际波长变化量计算得到的温度值应为40℃和70℃，误差分别为3℃和4℃。虽然在只有单个FBG受热的情境下，本发明得到的温度值与真实值存在误差，但相比于光纤分布式拉曼测温系统，本发明在性能上有很大的改进。对于拉曼测温系统而言，如果在1m空间范围内分别存在一个40℃和70℃的10cm尺寸的小火源，由于拉曼测温系统的测量值为1m范围内的平均温度值，因此得到的温度值分别为22℃和25℃，误差分别为18℃和45℃，这将导致系统无法响应火源，而本发明得到的结果虽然存在误差，但误差仅小于5℃，可以正常响应小尺寸火源。
当区域内多个光纤光栅受到相同的温度影响发生变化时，如图2(c)中3个FBG同时受热。通过数据遍历可以得到该区域光谱均有两个峰值，分别为(1550.0nm，0.7)和(1550.5nm，0.3)同时满足0.7+0.3＝1的关系，因此可以判断该区域光谱属于典型情景3。根据系统的参考值(1550.0nm，1)可以得出该区域内有10*0.7/(0.7+0.3)＝7个FBG受热20℃+1℃/10pm*(1550nm-1550nm)＝20℃，10*0.3/(0.7+0.3)＝3个FBG受热20℃+1℃/10pm*(1550.5nm-1550nm)＝70℃。取该区域光谱中最右侧0.0121强度处的波长值1550.66nm，根据初始化记录的标定值1550.18nm计算得到的温度值为68℃，误差为2℃。同理，当有9个FBG受热时，根据参考值可以得出该区域有1个FBG受热20℃，9个FBG受热70℃，根据标定值计算得到的温度值为70℃，误差为0。
不满足以上条件的区域光谱数据则被判断为典型情景4，即多个FBG受到不同温度的影响，如图2(d)中所示。以区域光谱2和区域光谱3为例，当系统得到区域光谱2后，通过寻找峰仅得到一个峰值(1550.0nm，0.511)，0.511与系统保留的参考值1不相等，且小于0.9，因此可以判断出该区域光谱内有多个FBG受到温度的影响，又因为该区域光谱仅有1个峰值点，因此该区域光谱会被判断为典型情景4。通过峰值点可以得出系统中有5个FBG处于20℃温度下，其它FBG受不同温度的影响，且通过该区域光谱中最右侧0.0121强度处的波长值 1550.89nm与标定值1550.18nm可以得出该区域内温度最高的FBG为91℃，误差为4℃。通过该区域光谱中最左侧0.0132强度处的波长值1549.83nm与标定值1549.82nm可以得出该区域内温度最低的FBG为21℃，误差为1℃；当系统得到区域光谱3后，通过寻峰可以得到2个峰值(1550.0nm，0.511)和(1550.75nm，0.201)，由于0.511＜0.9且0.511+0.201＜1，因此该区域光谱被判断为典型情景4，同理，根据参考值可知该区域有5个FBG处在20℃温度下，2个FBG处在95℃温度下，根据标定值可知该区域最大值为93℃，误差为2℃。
本实施例的有益效果为：对于不同的小尺寸火源监测场景，本实施例可以根据参考值和标定值提供详细且准确的温度信息，也可以只根据标定值提供简单的异常温度(高温)数据，增加响应速度，从而实现小尺寸火源的快速预警。虽然采用标定值的方法存在误差，但远比基于分布式光纤拉曼测温系统得到的结果更接近于真实值。
以上所述仅为本发明的较佳实施方式而已，并不用以限制本发明，凡在本发明的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

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  1. 一种应用于小尺寸火源监测的光纤光栅传感方法，其特征在于：包括以下步骤：
    S1、在单根光纤上连续地刻写了n个等间距的FBG构成大容量全同UWFBG传感网络，相邻FBG之间的间隔为ΔL，将全同UWFBG传感网络的有效探测长度记为L fiber，则L fiber＝n*ΔL；
    S2、将全同UWFBG传感网络分为2N个等长的区域，每个区域内分布着m个FBG，每个区域的长度记为D，则D＝m*ΔL＝L fiber/2N，全同UWFBG传感网络的空间分辨率为D，并且空间分辨率D恒定不变；
    S3、将脉冲光信号输入至全同UWFBG传感网络中，单个脉冲光信号的脉宽覆盖一个区域内所有FBG，将脉冲光信号的脉宽记为t，周期记为T；t＝2n effD/c，T>2n effL fiber/c，其中n eff为光纤纤芯的折射率，c为真空中光的传播速度；
    S4、当脉冲光信号输入至全同UWFBG传感网络中后，每个区域内的m个FBG的反射谱信号叠加形成一个整体区域光谱信号；
    S5、对该整体区域光谱的特征进行归纳并分类，根据该整体区域光谱的特征建立不同的数据处理机制，获取详细的温度信息，从而实现小尺寸火源的监测；
    所述S5中整体区域光谱的特征包括四个特征，分别记为特征1、特征2、特征3和特征4；
    所述特征1为：区域内所有的FBG处于同一条件下时，区域内所有FBG的中心波长一起随温度变化，所有FBG的光谱叠加为一个整体区域光谱，该整体区域光谱形状与单个FBG的光谱相似但峰值强度为单个FBG峰值强度的m倍，同时该整体区域光谱呈现整体移动的特征；
    所述特征2为：区域内仅单个FBG所处的环境发生变化时，将该单个FBG记为FBG#n，FBG#n的光谱逐渐从整体区域光谱中分离出来向长波长方向移动，同时整体区域光谱的主峰强度降为特征1下整体区域光谱峰值强度的(m-1)/m；
    所述特征3为：区域内多个FBG受到相同的温度影响发生变化时，整体区 域光谱呈现出主峰强度降为特征1下整体区域光谱强度的(m-x)/m，x为受影响FBG的数量，旁峰强度增加至x/m，且随温度左右移动；
    所述特征4为：区域内多个FBG受到不同温度影响发生变化时，整体区域光谱呈现出主峰强度降为特征1下整体区域光谱强度的(m-x)/m，x为受影响FBG的数量，旁峰的形状则随着各个FBG所受温度的变化而变化，整个区域光谱的宽度代表了区域内FBG的温度梯度大小，旁峰的强度分布则与不同温度梯度上的FBG的数量相关；
    所述S5中数据处理机制包括以下步骤：
    S101、系统初始化：保持全同UWFBG传感网络中所有的FBG处于同一参考温度C下，获取此时各个区域的整体区域光谱的最大值以及相对应的波长值作为系统的参考值，将整体区域光谱的最大值记为M i，其相对应的波长值记为λ i，i表示第i个区域，获取区域光谱两侧的旁瓣强度，将左侧旁瓣强度记为S Left，将右侧旁瓣强度记为S Right，记录整体区域光谱最左侧sg倍S Left的强度所对应的波长值λ Left_i和整体区域光谱最右侧sg倍S Right的强度所对应的波长值λ Right_i作为系统的标定值，其中sg的取值根据系统的功率波动取值；
    S102、系统实时运行时，获取区域i的整体区域光谱的最大值MAX以及MAX所对应的波长值λ，将MAX与M i相比较；
    若相等，则区域i的整体区域光谱属于特征1，区域i的最高温度值记为T i，T i＝C+k*(λ-λ i)，k为FBG的温度/波长系数；
    若不等，则进行S103；
    S103、判断区域i的整体区域光谱的最大值MAX是否满足MAX≥(m-1)/m*M i；
    若满足，则执行S104；若不满足，则遍历整体区域光谱数据，寻找两个峰值点MAX L和MAX R，并执行S105；
    S104、将MAX所对应的波长值λ并与λ i相比较；
    若λ与λ i相等，则区域i的整体区域光谱属于特征2，区域i的最高温度值： T i＝C+k*(λ Right-λ Right_i)，λ Right为整体区域光谱最右侧sg倍S Right强度处的波长值；
    若λ与λ i不相等，则区域i的整体区域区域光谱属于特征4，区域i内的最高温度为T i＝C+k*(λ Right-λ Right_i)，其它FBG所处温度值为C+k*(λ-λ i)；
    S105、判断峰值点MAX L和MAX R的强度之和是否等于M i；
    若等于，则区域i的整体区域光谱属于特征3，区域i内FBG被分为两组，每组内FBG受同一温度影响且每组内FBG数量分别为m*MAX L/(MAX L+MAX R)和m*MAX R/(MAX L+MAX R)，获取峰值点MAX L和MAX R对应的波长值λ L和λ R，区域i内两组FBG的温度信息分别为：T L＝C+k*(λ L-λ i)，T R＝C+k*(λ R-λ i)；
    若不等于，则区域i的整体区域光谱属于特征4，区域i的最高温度为C+k*(λ Right-λ Right_i)，最低温度为C+k*(λ Left-λ Left_i)，λ Left为整体区域光谱最左侧sg倍S Right强度处的波长值。
  2. 如权利要求1所述的一种应用于小尺寸火源监测的光纤光栅传感方法，其特征在于：所述S1中ΔL的取值范围为：8-20cm。
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