CN111998968B - Wide temperature range demodulation device and method based on low-frequency agility and sliding window - Google Patents
Wide temperature range demodulation device and method based on low-frequency agility and sliding window Download PDFInfo
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Abstract
The invention provides a demodulation device and a demodulation method for a wide temperature range based on low-frequency agility and a sliding window. Laser emitted by the laser is divided into two beams of laser with the same power through the optical fiber coupler; a beam of first electro-optical modulator driven by an electric pulse signal output by the frequency agility module is modulated into pump light, and the pump light is amplified by the erbium-doped fiber amplifier and enters the single mode fiber to be detected; the other beam of the laser light is modulated into probe light by a second electro-optical modulator driven by a microwave signal output by the up-conversion module, and enters the single-mode optical fiber to be tested from the other end after being subjected to polarization disturbance by the orthogonal polarization scrambler; the pump light and the detection light interact in the single-mode fiber to be detected to generate a backward stimulated Brillouin scattering signal, the lower sideband light beam filtered by the fiber grating filter is received by the photoelectric detector, and the generated electric signal is collected by the collection card. The invention uses the low-frequency agility technology to realize the rapid demodulation of the temperature, the response frequency exceeds 1Hz, and simultaneously, the equipment cost can be reduced and the reliability can be ensured.
Description
Technical Field
The invention relates to the technical field of optical fibers, in particular to a wide temperature range demodulation device and method based on low-frequency agility and a sliding window.
Background
The distributed optical fiber sensor senses the outside temperature by using the optical fiber, has the characteristics of electromagnetic interference resistance, high temperature resistance, corrosion resistance and the like, and can be suitable for various severe environments. Brillouin optical time-domain analysis (BOTDA for short) can measure temperature and strain at the same time, and has been widely applied in the fields of power cables, oil and gas pipelines, fire monitoring and the like.
The Brillouin optical time domain analysis technology realizes distributed sensing of the optical fiber temperature by utilizing the principle that the stimulated Brillouin scattering frequency and the optical fiber temperature change form a linear relation. The pump light and the detection light incident from the two ends of the optical fiber generate Stimulated Brillouin Scattering (SBS) in the optical fiber, when the frequency difference between the pump light and the detection light approaches to the optical fiber Brillouin frequency shift (the single-mode optical fiber Brillouin frequency shift is about 10.8 GHz), the pump light energy is transferred to the detection light, and the Brillouin gain spectrum can be constructed through the intensity of the detection light under different frequencies. By utilizing the principle that the center frequency of the Brillouin gain spectrum and the temperature change are in a linear relation, the temperature information of each point along the optical fiber can be obtained, and therefore the distributed measurement of the temperature of the whole optical fiber is realized.
The traditional BOTDA constructs a Brillouin gain spectrum in a frequency sweeping mode, so that the measurement speed is low, static temperature measurement can be realized only, and the temperature cannot be rapidly demodulated. The dynamic BOTDA system based on the single slope method is simple in structure, dynamic temperature measurement can be achieved without changing traditional BOTDA hardware, but the single mode fiber Brillouin gain spectrum is narrow, and the temperature measurement range achieved by the single slope method is only about 30 ℃. Even if a multi-slope method is used, the maximum temperature measurement range generally does not exceed 300 ℃, and the structure is complicated.
Disclosure of Invention
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. It should be understood that this summary is not an exhaustive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.
The invention discloses a BOTDA principle based on a frequency agile technology, which is the same as the traditional BOTDA principle, namely a Brillouin gain spectrum is constructed, and the distributed temperature sensing is realized by utilizing the principle that the center frequency of the Brillouin gain spectrum is in a linear relation with the temperature. The BOTDA based on the frequency agility technology injects the detection light of all frequencies into the optical fiber at one time, and when in demodulation, the signals of different frequencies are segmented and a Brillouin gain spectrum is constructed, so that the time for scanning the frequency is saved, and the demodulation speed is improved. Because the single-mode fiber Brillouin frequency shift is about 10.8GHz, the frequency of a microwave signal generated by frequency agility is required to be greater than 10GHz, which has high requirements on the bandwidth of a frequency agility module, and causes high hardware cost, complex system and even incapability of realizing the frequency agility module.
The invention provides a demodulation device and a demodulation method for a wide temperature range based on low-frequency agility and a sliding window, which at least solve the problems of high cost and complex system when the existing frequency agility technology is adopted to carry out fast demodulation for the wide temperature range.
According to a first aspect of the present invention, a wide temperature range fast demodulation device based on low frequency agility and sliding window is provided, the wide temperature range fast demodulation device comprises a laser, a fiber coupler, a first electro-optic modulator, a second electro-optic modulator, an erbium-doped fiber amplifier, a quadrature polarization scrambler, an optical isolator, a frequency agility module, an up-conversion module, a first circulator, a second circulator, a fiber grating filter, a photodetector and an acquisition card; the laser emitted by the laser enters the input end of the optical fiber coupler and is divided into two beams of laser with the same power after passing through the optical fiber coupler; one of the two laser beams is modulated into pump light by the first electro-optical modulator driven by an electric pulse signal output by the frequency agility module, amplified by the erbium-doped fiber amplifier, and enters the single mode fiber to be tested from one end of the single mode fiber to be tested after passing through the first circulator; the other laser of the two laser beams is modulated into probe light by the second electro-optical modulator driven by the microwave signal output by the up-conversion module, and then enters the single-mode fiber to be tested from the other end of the single-mode fiber to be tested after being disturbed by the orthogonal deflector and passing through the optical isolator; the pump light and the detection light interact in the single mode fiber to be detected to generate a backward stimulated Brillouin scattering signal, the backward stimulated Brillouin scattering signal passes through the first circulator and enters the fiber grating filter after passing through the second circulator, the filtered lower sideband light beam is received by the photoelectric detector, and the electric signal generated by the photoelectric detector is collected by the collection card.
Furthermore, data acquired by the acquisition card at a single time are equally divided into N sections according to the frequency, a Brillouin gain spectrum is constructed according to the frequency, Brillouin frequency shift is obtained by performing data fitting on the Brillouin gain spectrum, so that temperature values of each point on the single-mode fiber to be detected are calculated, and distributed sensing of the fiber temperature is realized; wherein N is an integer greater than 1.
Further, the fiber coupler is 50: 50.
Furthermore, the frequency agility module has four paths of output; a first output of the four outputs is an electric pulse signal for driving the first electro-optical modulator; the second output of the four outputs is a sine wave signal with continuously changing frequency, the sine wave signal is subjected to frequency boosting by the up-conversion module and then outputs a microwave signal with the frequency bandwidth of 400MHz, and the frequency of the microwave signal is between 10.1 and 12.5 GHz; the third output of the four outputs is a trigger signal for triggering the acquisition card to acquire data; and the fourth output of the four paths of outputs is an orthogonal polarization scrambling signal used for driving the orthogonal polarization scrambler.
Further, the electrical pulse signal, the sine wave signal, the trigger signal and the quadrature offset signal output by the four paths are time-synchronized.
Further, each period comprises N sine wave signals with different frequencies, corresponding to the output N same electric pulse signals; each period corresponds to a trigger signal, and the rising edge of the trigger signal is aligned with the starting end of the period; each of the sine wave signals corresponds to one of the electrical pulse signals.
Furthermore, the optical polarization is detected, and each half cycle corresponds to one trigger signal, so that the polarization states of two adjacent groups of signals acquired by the acquisition card are orthogonal.
Furthermore, the up-conversion module dynamically adjusts the temperature range by using a sliding window mode; when the wide temperature range measurement is carried out, the output frequency of the up-conversion module is changed according to the average temperature of the optical fiber measured last time, so that the frequency of the detection light covers the current temperature range.
Further, the up-conversion module is configured to automatically adjust its output frequency in the following manner: the output frequency of the up-conversion module is increased by 1MHz every time the temperature is increased by 1 ℃.
Further, the up-conversion module is configured to automatically adjust an output frequency of the up-conversion module such that: and setting the average temperature of the optical fiber measured at the previous time as the middle value of the temperature range measured at the current time.
According to the second aspect of the invention, a wide temperature range fast demodulation method based on low-frequency agility and a sliding window is also provided, and the wide temperature range fast demodulation method is realized based on a wide temperature range fast demodulation device; the device for the wide temperature range fast demodulation method comprises a laser, an optical fiber coupler, a first electro-optic modulator, a second electro-optic modulator, an erbium-doped optical fiber amplifier, an orthogonal polarization scrambler, an optical isolator, a frequency agile module, an up-conversion module, a first circulator, a second circulator, an optical fiber grating filter, a photoelectric detector and an acquisition card; the wide temperature range fast demodulation method comprises the following steps: enabling laser emitted by the laser to enter an input end of the optical fiber coupler and be divided into two beams of laser with the same power after passing through the optical fiber coupler; one of the two beams of laser is modulated into pump light by the first electro-optical modulator driven by an electric pulse signal output by the frequency agility module, amplified by the erbium-doped fiber amplifier, and enters the single mode fiber to be tested from one end of the single mode fiber to be tested after passing through the first circulator; the other laser in the two laser beams is modulated into probe light by the second electro-optical modulator driven by the microwave signal output by the up-conversion module, and then enters the single-mode fiber to be tested from the other end of the single-mode fiber to be tested after being disturbed by the orthogonal deflector and passing through the optical isolator; the pump light and the detection light interact in the single mode fiber (15) that awaits measuring, produce the stimulated brillouin scattering signal in the dorsad, the stimulated brillouin scattering signal in the dorsad passes through first circulator get into behind the second circulator the fiber grating filter, the lower sideband light beam of filtering out passes through photoelectric detector receives, the signal of telecommunication that photoelectric detector produced by the acquisition card is gathered.
Furthermore, the signal frequency of the data acquired by the acquisition card at a single time is gradually increased according to the frequency agile output frequency, the data is equally divided into N sections according to the frequency, a Brillouin gain spectrum is constructed according to the frequency, Brillouin frequency shift is obtained by performing data fitting on the Brillouin gain spectrum, so that the temperature value of each point on the single mode fiber to be detected is calculated, and the distributed sensing of the fiber temperature is realized; wherein N is an integer greater than 1.
Further, the fiber coupler is 50: 50.
Furthermore, the frequency agility module has four paths of output; a first output of the four outputs is an electric pulse signal for driving the first electro-optical modulator; the second output of the four outputs is a sine wave signal with continuously changing frequency, the sine wave signal is subjected to frequency boosting by the up-conversion module and then outputs a microwave signal with the frequency bandwidth of 400MHz, and the frequency of the microwave signal is between 10.1 and 12.5 GHz; the third output of the four outputs is a trigger signal for triggering the acquisition card to acquire data; and the fourth output of the four paths of outputs is an orthogonal polarization scrambling signal used for driving the orthogonal polarization scrambler.
Further, the electrical pulse signal, the sine wave signal, the trigger signal and the quadrature offset signal output by the four paths are time-synchronized.
Further, each period comprises N sine wave signals with different frequencies, corresponding to the N same electric pulse signals which are output; each period corresponds to a trigger signal, and the rising edge of the trigger signal is aligned with the starting end of the period; each of the sine wave signals corresponds to one of the electrical pulse signals.
Furthermore, the orthogonal polarization disturbing signal is a pulse signal with a duty ratio of 0.5, and is used for driving the photoelectric detector to disturb polarization of the detected light, and each half cycle corresponds to one trigger signal, so that two adjacent groups of signal polarization states acquired by the acquisition card are orthogonal.
Further, the temperature range is dynamically adjusted by utilizing a sliding window mode; when the wide temperature range measurement is carried out, the output frequency of the up-conversion module is changed according to the average temperature of the optical fiber measured at the previous time, so that the frequency of the detection light covers the current temperature range.
Further, the output frequency is automatically adjusted in the following way: the output frequency of the up-conversion module is increased by 1MHz every time the temperature is increased by 1 ℃.
Further, its output frequency is automatically adjusted such that: and setting the average temperature of the optical fiber measured at the previous time as the middle value of the temperature range measured at the current time.
The demodulation device and the demodulation method based on the low-frequency agility and the sliding window in the wide temperature range realize the rapid demodulation of the temperature by using the low-frequency agility technology, the response frequency exceeds 1Hz, and meanwhile, the equipment cost is reduced and the reliability is ensured. The invention dynamically adjusts the temperature range based on the sliding window mode, realizes the measurement of a wide temperature range, and realizes the rapid demodulation of the wide temperature range, wherein the maximum temperature measurement range exceeds 800 ℃.
These and other advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings.
Drawings
The invention may be better understood by referring to the following description in conjunction with the accompanying drawings, in which like reference numerals are used throughout the figures to indicate like or similar parts. The accompanying drawings, which are incorporated in and form a part of this specification, illustrate preferred embodiments of the present invention and, together with the detailed description, serve to further illustrate the principles and advantages of the invention. Wherein:
fig. 1 is a schematic diagram showing the structure of a low frequency agility and sliding window based wide temperature range demodulation apparatus of the present invention;
FIG. 2 is a schematic diagram showing a frequency agile signal;
fig. 3 is a flow chart illustrating an exemplary process of a low frequency agility and sliding window based wide temperature range demodulation method of the present invention.
Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
Detailed Description
Exemplary embodiments of the present invention will be described hereinafter with reference to the accompanying drawings. In the interest of clarity and conciseness, not all features of an actual implementation are described in the specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the device structures and/or processing steps closely related to the solution according to the present invention are shown in the drawings, and other details not so relevant to the present invention are omitted.
Exemplary device 1
The invention provides a wide temperature range fast demodulation device based on low-frequency agility and a sliding window, which comprises a laser, an optical fiber coupler, a first electro-optic modulator, a second electro-optic modulator, an erbium-doped optical fiber amplifier, an orthogonal polarization scrambler, an optical isolator, a frequency agility module, an up-conversion module, a first circulator, a second circulator, an optical fiber grating filter, a photoelectric detector and an acquisition card; laser emitted by the laser enters the input end of the optical fiber coupler and is divided into two beams of laser with the same power after passing through the optical fiber coupler; one of the two beams of laser is modulated into pump light by the first electro-optical modulator driven by an electric pulse signal output by the frequency agility module, amplified by the erbium-doped fiber amplifier, and enters the single mode fiber to be tested from one end of the single mode fiber to be tested after passing through the first circulator; the other laser in the two laser beams is modulated into probe light by the second electro-optical modulator driven by the microwave signal output by the up-conversion module, is subjected to polarization disturbance by the orthogonal polarization scrambler, passes through the optical isolator and enters the single mode fiber to be tested from the other end of the single mode fiber to be tested; the pump light and the detection light interact in the single mode fiber to be detected to generate a backward stimulated Brillouin scattering signal, the backward stimulated Brillouin scattering signal passes through the first circulator and enters the fiber grating filter after passing through the second circulator, the filtered lower sideband light beam is received by the photoelectric detector, and the electric signal generated by the photoelectric detector is collected by the collection card.
The above-mentioned fast demodulation apparatus based on low frequency agility and sliding window for wide temperature range is described with reference to fig. 1.
As shown in fig. 1, the demodulation apparatus based on the low-frequency agility and wide temperature range of the sliding window comprises a laser 1, a fiber coupler 2, a first electro-optical modulator 3 (IM 1 in the figure), a second electro-optical modulator 4 (IM 2 in the figure), an erbium-doped fiber amplifier 5 (EDFA in the figure), a quadrature polarization scrambler 6 (PS in the figure), an optical isolator 7, a frequency agility module 8, an up-conversion module 9, a first circulator 10 (R1 in the figure), a second circulator 11 (R2 in the figure), a fiber grating filter 12, a photodetector 13 (PD in the figure) and an acquisition card 14.
The laser emitted by the laser 1 enters the input end of the optical fiber coupler 2, and is divided into two beams of laser with the same power after passing through the optical fiber coupler 2, and the two beams of laser are used for modulating the pump light and the probe light respectively. The fibre coupler 2 is for example 50: 50.
One of the two laser beams is modulated into pump light by a first electro-optical modulator 3 driven by an electric pulse signal output by a frequency agility module 8, amplified by an erbium-doped fiber amplifier 5, and enters a single mode fiber 15 to be measured from one end of the single mode fiber 15 to be measured after passing through a first circulator 10.
As shown in fig. 1, the light amplified by the erbium-doped fiber amplifier 5 enters a first port (a port 10-1 in the first circulator 10) of the first circulator 10, and is output from a second port (a port 10-2 of the first circulator 10) of the first circulator 10 and then enters the single-mode fiber 15 to be tested (as shown, for example, enters from the left side of the single-mode fiber 15 to be tested).
The other laser beam of the two laser beams (the two laser beams with the same power output by the optical fiber coupler 2) is modulated into probe light by a second electro-optical modulator 4 driven by a microwave signal output by an up-conversion module 9, and then enters the single mode fiber 15 to be tested from the other end of the single mode fiber 15 to be tested after being subjected to polarization disturbance by an orthogonal polarization disturbance device 6 and an optical isolator 7.
The pump light and the probe light interact in the single-mode fiber 15 to be measured to generate a backward stimulated Brillouin scattering signal. The microwave modulated optical pulses contain upper and lower sidebands, and the lower sideband signal can be used for temperature sensing. The backward stimulated Brillouin scattering signal passes through the first circulator 10 and the second circulator 11 and then enters the fiber grating filter 12, the filtered lower sideband light beam is received by the photoelectric detector 13, and the electric signal generated by the photoelectric detector 13 is collected by the acquisition card 14.
As shown in fig. 1, the backward stimulated brillouin scattering signal enters from the second port 10-2 of the first circulator 10, is output from the third port 10-3 of the first circulator 10, enters the first port 11-1 of the second circulator 11, is output from the second port 11-2 of the second circulator 11 to the fiber grating filter 12, and the lower sideband beam filtered by the fiber grating filter 12 returns to the second port 11-2 of the second circulator 11, enters the second circulator 11, and is output from the third port 11-3 of the second circulator 11 to the photodetector 13.
The data acquired by the acquisition card 14 each time contains all frequency components, and the signal frequency is gradually increased according to the frequency agility output frequency, so that the data can be segmented, and a brillouin gain spectrum can be constructed according to the frequency.
As an example, the data acquired by the acquisition card 14 at a single time may be equally divided into N segments according to the frequency (N frequencies are output by frequency agility), a brillouin gain spectrum is constructed according to the frequency, and brillouin frequency shift is obtained by performing data fitting on the brillouin gain spectrum; the Brillouin frequency shift and the temperature are in a linear relation, and the temperature value of each point on the single-mode optical fiber to be detected can be calculated according to the Brillouin frequency shift, so that the distributed sensing of the optical fiber temperature is realized; wherein N is an integer greater than 1.
As an example, the frequency agility module 8 has four outputs, as shown in fig. 1 and 2.
The first of the four outputs (CH1) is an electrical pulse signal (the 1 st waveform from top to bottom in fig. 2) for driving the first electro-optical modulator 3.
The second of the four outputs (CH2) outputs a sine wave signal (the 2 nd waveform from top to bottom in fig. 2) with continuously varying frequency, and the sine wave signal is up-converted by the up-conversion module 9 (i.e., the sine wave signal is superimposed with the fundamental frequency signal of the up-conversion module 9, wherein the fundamental frequency signal of the up-conversion module 9 is a single-frequency signal with adjustable frequency, the frequency of the single-frequency signal is within the range of 10.0 to 12.0 GHz), and the frequency of the microwave signal is within the range of 10.1 to 12.5GHz, and the frequency of the microwave signal is 400 MHz.
In other words, the maximum frequency that the sine wave signal can be output after being up-converted by the up-conversion module 9 is 12.5GHz, the minimum frequency that can be output is 10.1GHz, but the signal frequency range of single output is 400 MHz. For example, the frequency of the single signal output may be 10.1 to 10.5GHz, or 10.3 to 10.7GHz, or 12.1 to 12.5GHz, or the like.
The third (CH3) of the four outputs is a trigger signal (the 3 rd waveform from top to bottom in fig. 2) for triggering the acquisition card 14 to acquire data.
The fourth (CH4) of the four outputs is a quadrature scrambler signal (the 4 th waveform from top to bottom in fig. 2) that drives the quadrature scrambler 6.
The four paths of output electric pulse signals, sine wave signals, trigger signals and orthogonal offset signals are time-synchronous.
As an example, each period includes, for example, N sine wave signals of different frequencies, corresponding to the N identical electrical pulse signals that are output; each period corresponds to a trigger signal, and the rising edge of the trigger signal is aligned with the starting end of the period; each sine wave signal corresponds to an electrical pulse signal.
As an example, the orthogonal polarization disturbing signal is, for example, a pulse signal with a duty ratio of 0.5, and is used to drive the photodetector 13 to disturb polarization of the detection light, and each half cycle corresponds to one trigger signal, so that polarization states of two adjacent groups of signals acquired by the acquisition card 14 are orthogonal.
Therefore, the four paths of signals are strictly time-synchronized, each sine wave frequency signal corresponds to one pulse signal, the two signals are modulated into optical signals and then interact in the optical fiber to generate stimulated Brillouin scattering signals with corresponding frequencies, one period comprises N sine waves with different frequencies, and N identical electric pulse signals are correspondingly output. N sine waves with different frequencies are used as a signal period, the waveform of each period is repeatedly generated, the rising edge of a trigger signal is aligned with the starting end of the signal period, and each period corresponds to a trigger pulse for triggering an acquisition card to acquire data so as to realize accumulation average.
Because the system measures the single-mode fiber, the polarization fading phenomenon exists, and the signal-to-noise ratio of the whole signal is influenced, so that the embodiment adopts the polarization of the optical signal, and the whole fiber signal is ensured to have higher signal-to-noise ratio. The orthogonal polarization disturbing signal is a pulse signal with 0.5 duty ratio and is used for driving the PS to disturb polarization of the detected light, each half cycle corresponds to an acquisition card trigger signal, polarization states of two adjacent groups of signals acquired by the acquisition cards are orthogonal, and the waveform of the acquisition cards is stable after averaging, so that the polarization fading influence can be eliminated, and the signal-to-noise ratio is improved.
The temperature can be rapidly measured in a distributed mode by using the frequency agile technology, the requirement for the bandwidth of the frequency agile module is lowered through the low-frequency agile technology, the hardware cost is lowered, and the reliability of the system is improved.
As an example, the up-conversion module 9 may dynamically adjust the temperature range, for example, in a sliding window manner; when the wide temperature range measurement is performed, the output frequency of the up-conversion module 9 is changed according to the average temperature of the optical fiber measured last time, so that the frequency of the probe light covers the current temperature range.
Thus, with this example, when a wide temperature range measurement is performed, the temperature range can be dynamically adjusted using a sliding window approach based on the previously measured average temperature of the optical fiber.
Due to the bandwidth limitation of the frequency agile module, the maximum frequency of the output sine wave signal is 500MHz, so that the temperature range of one-time measurement is less than 500 ℃, and the wide temperature range rapid measurement cannot be carried out.
According to the embodiment of the present invention, when the temperature range of the object to be measured is wide for a long time but narrow for a short time, the temperature range can be dynamically adjusted by using, for example, a sliding window method.
For example, if the center frequency is 10.7GHz and the frequency of the sine wave signal is 100-500 MHz, the temperature of 0-400 ℃ can be measured by the signal of 10.8-11.2 GHz. When the central frequency is increased to 11.1GHz, the temperature of 400-800 ℃ can be measured through signals of 11.2-11.6 GHz.
Because the temperature response frequency of the system is 1Hz, the temperature difference is not large before and after 1 second, when the wide temperature range measurement is carried out, the output frequency of the up-conversion module can be changed according to the average temperature of the optical fiber measured at the previous time, the current temperature range can be covered by using the detection light frequency, and the purpose of dynamically adjusting the temperature range is achieved.
For example, the output frequency of the up-conversion module may be automatically adjusted as follows: the output frequency of the up-conversion module is increased by 1MHz every time the temperature is increased by 1 ℃.
The average temperature of the optical fiber measured at the previous time (i.e., the last time) may be set to the middle of the temperature range measured at the current time.
Assuming that the temperature range corresponding to the k-2 (k is a natural number greater than 2) measurement (i.e., the temperature range that can be measured by the microwave signal output after the sine wave signal is up-converted by the up-conversion module) is, for example, T1-T1 +400 ℃, the average temperature of the optical fiber measured at the k-2 is assumed to be Tk-2(Tk-2In the range of T1 to T1+400 ℃); the k-1 measurement can be based on the k-2 measured average temperature T of the optical fiberk-2To adjust the frequency range of the microwave signal so that the frequency range of the adjusted output microwave signal can measure Tk-2The temperature range of +/-200 ℃ is assumed that the average temperature of the optical fiber measured at the k-1 st time is Tk-1(Tk-1At Tk-2In the range of ± 200 ℃); similarly, the k-th measurement can be based on the measured average temperature T of the fiber at the k-1 th measurementk-1To adjust the frequency range of the microwave signal so that the frequency range of the adjusted output microwave signal can measure Tk-1The temperature range of 200 ℃ is assumed that the mean temperature of the fiber measured at the kth time is TkThen T iskAt Tk-1In the temperature range of +/-200 ℃; and so on, and will not be described in detail. For example, the average temperature of the optical fiber measured at the previous time is 210 ℃, and the temperature range corresponding to the previous time is 0-400 ℃, the temperature range corresponding to the current time can be adjusted to 10-410 ℃ (i.e. 210 ± 200 ℃); and so on.
In this way, the use of the sliding window approach can enable wide temperature range measurements by dynamically adjusting the temperature range with limited hardware bandwidth.
Exemplary method 1
Embodiments of the present invention also provide a wide temperature range demodulation method based on low frequency agility and sliding window, which is implemented based on the wide temperature range demodulation apparatus as described above in connection with fig. 1.
As shown in fig. 3, in step S310, the laser emitted from the laser 1 enters the input end of the fiber coupler 2, and is divided into two laser beams with the same power after passing through the fiber coupler 2, and the two laser beams are used for modulating the pump light and the probe light, respectively.
In step S320, one of the two laser beams is modulated into pump light by the first electro-optical modulator 3 driven by the electrical pulse signal output by the frequency agility module 8, amplified by the erbium-doped fiber amplifier 5, and enters the single mode fiber 15 to be measured from one end of the single mode fiber 15 to be measured after passing through the first circulator 10.
In step S330, the other laser beam of the two laser beams is modulated into probe light by the second electro-optical modulator 4 driven by the microwave signal output by the up-conversion module 9, and then the probe light is deflected by the orthogonal deflector 6, passes through the optical isolator 7, and enters the single-mode fiber 15 to be tested from the other end of the single-mode fiber 15 to be tested.
In step S340, the pump light and the probe light interact with each other in the single-mode fiber 15 to be measured to generate a backward stimulated brillouin scattering signal, the backward stimulated brillouin scattering signal passes through the first circulator 10 and the second circulator 11 and then enters the fiber grating filter 12, the filtered lower sideband light beam is received by the photodetector 13, and the electrical signal generated by the photodetector 13 is collected by the collection card 14.
As an example, the signal frequency of the data acquired by the acquisition card 14 at a single time may be gradually increased according to the frequency agile output frequency, the data is equally divided into N segments according to the frequency, a brillouin gain spectrum is constructed according to the frequency, and brillouin frequency shift is obtained by performing data fitting on the brillouin gain spectrum to calculate the temperature value of each point on the single-mode fiber to be measured, so as to realize distributed sensing of the fiber temperature; wherein N is an integer greater than 1.
As an example, the frequency agility module 8 has four outputs, for example.
The first of the four outputs is an electrical pulse signal for driving the first electro-optical modulator 3.
The second output of the four outputs is a sine wave signal with continuously changing frequency, the sine wave signal is subjected to frequency rising by the up-conversion module 9 and then outputs a microwave signal with the frequency bandwidth of 400MHz, and the frequency of the microwave signal is between 10.1 and 12.5 GHz.
The third of the four outputs is a trigger signal that triggers the acquisition card 14 to acquire data.
The fourth output of the four outputs is a quadrature polarization scrambler signal used to drive the quadrature polarization scrambler 6.
The four paths of output electric pulse signals, sine wave signals, trigger signals and orthogonal offset signals are time-synchronous.
As an example, each cycle comprises N sine wave signals of different frequencies, corresponding to the N identical electrical pulse signals output; each period corresponds to a trigger signal, and the rising edge of the trigger signal is aligned with the starting end of the period; each sine wave signal corresponds to an electrical pulse signal.
As an example, the orthogonal polarization disturbing signal is, for example, a pulse signal with a duty ratio of 0.5, and is used for driving the photodetector 13 to disturb polarization of the detection light, where each half cycle corresponds to one trigger signal, so that polarization states of two adjacent groups of signals acquired by the acquisition card 14 are orthogonal.
As an example, the temperature range may be dynamically adjusted using a sliding window approach; when the wide temperature range measurement is performed, the output frequency of the up-conversion module 9 is changed according to the average temperature of the optical fiber measured in the previous time, so that the frequency of the probe light covers the current temperature range.
As an example, its output frequency may be automatically adjusted in the following way: the output frequency of the up-conversion module is increased by 1MHz every time the temperature is increased by 1 ℃.
As an example, the output frequency of the up-conversion module may be automatically adjusted such that: the average temperature of the optical fiber measured at the previous time is set to be the middle value of the temperature range measured at the current time.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this description, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter. Accordingly, many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the appended claims. The present invention has been disclosed with respect to the scope of the invention, which is to be considered as illustrative and not restrictive, and the scope of the invention is defined by the appended claims.
The invention records the following scheme:
the demodulation device is characterized by comprising a laser (1), an optical fiber coupler (2), a first electro-optical modulator (3), a second electro-optical modulator (4), an erbium-doped optical fiber amplifier (5), an orthogonal polarization scrambler (6), an optical isolator (7), a frequency agile module (8), an up-conversion module (9), a first circulator (10), a second circulator (11), an optical fiber grating filter (12), a photoelectric detector (13) and an acquisition card (14);
the laser emitted by the laser (1) enters the input end of the optical fiber coupler (2) and is divided into two beams of laser with the same power after passing through the optical fiber coupler (2);
one of the two laser beams is modulated into pump light by the first electro-optical modulator (3) driven by an electric pulse signal output by the frequency agility module (8), amplified by the erbium-doped fiber amplifier (5), and enters the single mode fiber (15) to be tested from one end of the single mode fiber (15) to be tested after passing through the first circulator (10);
the other laser of the two lasers is modulated into probe light by the second electro-optical modulator (4) driven by the microwave signal output by the up-conversion module (9), and then enters the single-mode fiber (15) to be tested from the other end of the single-mode fiber (15) to be tested after being disturbed by the orthogonal deflector (6) and the optical isolator (7);
the pump light with the probe light is in interact in the single mode fiber (15) that awaits measuring produces the stimulated brillouin scattering signal in the dorsad, the stimulated brillouin scattering signal in the dorsad passes through first circulator (10) get into behind second circulator (11) fiber grating filter (12), and the lower sideband light beam that filters out passes through photoelectric detector (13) are received, the signal of telecommunication that photoelectric detector (13) produced by acquisition card (14) are gathered.
The wide temperature range demodulation device is characterized in that data acquired by the acquisition card (14) at a time are equally divided into N sections according to the frequency, a Brillouin gain spectrum is constructed according to the frequency, Brillouin frequency shift is obtained by performing data fitting on the Brillouin gain spectrum, so that temperature values of each point on a single-mode fiber to be detected are calculated, and distributed sensing of the temperature of the fiber is realized; wherein N is an integer greater than 1.
Scheme 3. the wide temperature range demodulation arrangement according to scheme 1 or 2, characterized in that the fiber coupler (2) is 50: 50.
the first output of the four outputs is an electric pulse signal for driving the first electro-optical modulator (3);
the second output of the four outputs is a sine wave signal with continuously changing frequency, the sine wave signal is subjected to frequency boosting by the up-conversion module (9) and then outputs a microwave signal with the frequency bandwidth of 400MHz, and the frequency of the microwave signal is between 10.1 and 12.5 GHz;
the third output of the four outputs is a trigger signal for triggering the acquisition card (14) to acquire data;
and the fourth output of the four paths of outputs is an orthogonal polarization scrambling signal for driving the orthogonal polarization scrambler (6).
The wide temperature range demodulation device according to claim 5, wherein the electric pulse signal, the sine wave signal, the trigger signal, and the quadrature offset signal outputted from the four outputs are time-synchronized.
The wide temperature range demodulating apparatus according to claim 5, according to claim 6, wherein:
each period comprises N sine wave signals with different frequencies, corresponding to N identical electric pulse signals which are output; each period corresponds to a trigger signal, and the rising edge of the trigger signal is aligned with the starting end of the period; each of the sine wave signals corresponds to one of the electrical pulse signals.
Scheme 7. the wide temperature range demodulation apparatus according to scheme 5 or 6, wherein the orthogonal polarization disturbing signal is a pulse signal with a duty ratio of 0.5, and is used to drive the photodetector (13) to disturb polarization of detection light, and each half cycle corresponds to one trigger signal, so that polarization states of two adjacent groups of signals acquired by the acquisition card (14) are orthogonal.
Scheme 9. the wide temperature range demodulation apparatus according to scheme 8, wherein the up-conversion module (9) is configured to automatically adjust its output frequency in the following manner: the output frequency of the up-conversion module is increased by 1MHz every time the temperature is increased by 1 ℃.
Scheme 11. a wide temperature range demodulation method based on low frequency agility and sliding window, characterized in that the wide temperature range demodulation method is implemented based on a wide temperature range demodulation device;
the demodulation method device with the wide temperature range comprises a laser (1), an optical fiber coupler (2), a first electro-optic modulator (3), a second electro-optic modulator (4), an erbium-doped optical fiber amplifier (5), an orthogonal polarization scrambler (6), an optical isolator (7), a frequency agile module (8), an up-conversion module (9), a first circulator (10), a second circulator (11), an optical fiber grating filter (12), a photoelectric detector (13) and an acquisition card (14);
the wide temperature range demodulation method comprises the following steps:
enabling laser emitted by the laser (1) to enter an input end of the optical fiber coupler (2), and dividing the laser into two beams of laser with the same power after passing through the optical fiber coupler (2);
one of the two laser beams is modulated into pump light by the first electro-optical modulator (3) driven by an electric pulse signal output by the frequency agility module (8), amplified by the erbium-doped fiber amplifier (5), and enters the single mode fiber (15) to be tested from one end of the single mode fiber (15) to be tested after passing through the first circulator (10);
the other laser of the two lasers is modulated into probe light through the second electro-optical modulator (4) driven by the microwave signal output by the up-conversion module (9), and then after being subjected to polarization disturbance by the orthogonal polarization scrambler (6), the probe light enters the single mode fiber (15) to be tested from the other end of the single mode fiber (15) to be tested after passing through the optical isolator (7);
the pump light and the detection light interact in the single-mode optical fiber (15) to be detected to generate a backward stimulated Brillouin scattering signal, the backward stimulated Brillouin scattering signal enters the fiber grating filter (12) after passing through the first circulator (10) and the second circulator (11), the filtered lower sideband light beam is received by the photoelectric detector (13), and the electric signal generated by the photoelectric detector (13) is collected by the collection card (14).
The wide temperature range demodulation method according to the scheme 11 is characterized in that the signal frequency of data acquired by the acquisition card (14) at a single time is gradually increased according to the frequency agile output frequency, the data is equally divided into N sections according to the frequency, a Brillouin gain spectrum is constructed according to the frequency, and Brillouin frequency shift is obtained by performing data fitting on the Brillouin gain spectrum so as to calculate the temperature value of each point on the single mode fiber to be measured, thereby realizing distributed sensing on the temperature of the fiber; wherein N is an integer greater than 1.
the first output of the four outputs is an electric pulse signal for driving the first electro-optical modulator (3);
the second output of the four outputs is a sine wave signal with continuously changing frequency, the sine wave signal is subjected to frequency increase by the up-conversion module (9) and then outputs a microwave signal with the frequency bandwidth of 400MHz, and the frequency of the microwave signal is between 10.1 and 12.5 GHz;
the third output of the four outputs is a trigger signal for triggering the acquisition card (14) to acquire data;
and the fourth output of the four paths of outputs is an orthogonal polarization scrambling signal for driving the orthogonal polarization scrambler (6).
The wide temperature range demodulation method according to claim 15, wherein the electrical pulse signal, the sine wave signal, the trigger signal, and the quadrature offset signal outputted from the four outputs are time-synchronized.
The wide temperature range demodulation method according to claim 15, characterized in that:
each period comprises N sine wave signals with different frequencies, corresponding to N identical electric pulse signals which are output; each period corresponds to a trigger signal, and the rising edge of the trigger signal is aligned with the starting end of the period; each of the sine wave signals corresponds to one of the electrical pulse signals.
Scheme 17. the wide temperature range demodulation method according to scheme 15 or 16, wherein the orthogonal polarization-disturbing signal is a pulse signal with a duty ratio of 0.5, and is used for driving the photodetector (13) to disturb the detection light, and each half cycle corresponds to one trigger signal, so that the polarization states of two adjacent groups of signals acquired by the acquisition card (14) are orthogonal.
Scheme 18. the wide temperature range demodulation method according to any of the schemes 11-17, wherein the temperature range is dynamically adjusted using a sliding window approach; when the wide temperature range measurement is carried out, the output frequency of the up-conversion module (9) is changed according to the average temperature of the optical fiber measured last time, so that the frequency of the detection light covers the current temperature range.
Scheme 19. the wide temperature range demodulation method according to scheme 8, characterized in that its output frequency is automatically adjusted as follows: the output frequency of the up-conversion module is increased by 1MHz every time the temperature is increased by 1 ℃.
Scheme 20. the wide temperature range demodulation method according to scheme 8 or 9, characterized in that the output frequency of the up-conversion module is automatically adjusted such that: and setting the average temperature of the optical fiber measured at the previous time as the middle value of the temperature range measured at the current time.
Claims (8)
1. The wide temperature range demodulating device based on the low-frequency agility and the sliding window is characterized by comprising a laser (1), an optical fiber coupler (2), a first electro-optic modulator (3), a second electro-optic modulator (4), an erbium-doped optical fiber amplifier (5), an orthogonal polarization scrambler (6), an optical isolator (7), a frequency agility module (8), an up-conversion module (9), a first circulator (10), a second circulator (11), an optical fiber grating filter (12), a photoelectric detector (13) and an acquisition card (14);
the frequency agility module (8) has four paths of output;
the first output of the four outputs is an electric pulse signal for driving the first electro-optical modulator (3);
the second output of the four outputs is a sine wave signal with continuously changing frequency, the sine wave signal is subjected to frequency increase by the up-conversion module (9) and then outputs a microwave signal with the frequency bandwidth of 400MHz, and the frequency of the microwave signal is between 10.1 and 12.5 GHz;
the third output of the four outputs is a trigger signal for triggering the acquisition card (14) to acquire data;
the fourth output of the four outputs is an orthogonal polarization scrambling signal for driving the orthogonal polarization scrambler (6);
the up-conversion module (9) dynamically adjusts the temperature range in a sliding window mode; when the wide temperature range measurement is carried out, the output frequency of the up-conversion module (9) is changed according to the average temperature of the optical fiber measured at the previous time, so that the frequency of the detection light covers the current temperature range;
the laser emitted by the laser (1) enters the input end of the optical fiber coupler (2) and is divided into two beams of laser with the same power after passing through the optical fiber coupler (2);
one of the two laser beams is modulated into pump light by the first electro-optical modulator (3) driven by an electric pulse signal output by the frequency agility module (8), amplified by the erbium-doped fiber amplifier (5), and enters the single mode fiber (15) to be tested from one end of the single mode fiber (15) to be tested after passing through the first circulator (10);
the other laser of the two lasers is modulated into probe light by the second electro-optical modulator (4) driven by the microwave signal output by the up-conversion module (9), and then enters the single-mode fiber (15) to be tested from the other end of the single-mode fiber (15) to be tested after being disturbed by the orthogonal deflector (6) and the optical isolator (7);
the pump light with the probe light is in interact in the single mode fiber (15) that awaits measuring produces the stimulated brillouin scattering signal in the dorsad, the stimulated brillouin scattering signal in the dorsad passes through first circulator (10) get into behind second circulator (11) fiber grating filter (12), and the lower sideband light beam that filters out passes through photoelectric detector (13) are received, the signal of telecommunication that photoelectric detector (13) produced by acquisition card (14) are gathered.
2. The wide temperature range demodulation device according to claim 1, wherein the data acquired by the acquisition card (14) at a single time is used for being equally divided into N sections according to the frequency, a Brillouin gain spectrum is constructed according to the frequency, Brillouin frequency shift is obtained by performing data fitting on the Brillouin gain spectrum, so as to calculate the temperature value of each point on the single mode fiber to be detected, and realize distributed sensing on the fiber temperature; wherein N is an integer greater than 1.
3. The wide temperature range demodulation apparatus of claim 2 wherein the electrical pulse signal, the sine wave signal, the trigger signal, and the quadrature perturbation bias signal of the four outputs are time synchronized.
4. The wide temperature range demodulating apparatus according to claim 3, wherein:
each period comprises N sine wave signals with different frequencies, corresponding to N same electric pulse signals which are output; each period corresponds to a trigger signal, and the rising edge of the trigger signal is aligned with the starting end of the period; each of the sine wave signals corresponds to one of the electrical pulse signals.
5. The demodulation device in wide temperature range according to claim 4, wherein the orthogonal polarization disturbing signal is a pulse signal with 0.5 duty cycle, and is used for driving the photodetector (13) to disturb the detection light polarization, and each half cycle corresponds to a trigger signal, so that the polarization states of two adjacent groups of signals collected by the collection card (14) are orthogonal.
6. The wide temperature range demodulation arrangement according to claim 5, wherein the up-conversion module (9) is configured to automatically adjust its output frequency in the following way: the output frequency of the up-conversion module is increased by 1MHz every time the temperature is increased by 1 ℃.
7. The wide temperature range demodulation arrangement according to claim 6, wherein the up-conversion module (9) is configured to automatically adjust its output frequency such that: and setting the average temperature of the optical fiber measured at the previous time as the middle value of the temperature range measured at the current time.
8. The demodulation method of the wide temperature range based on the low-frequency agility and the sliding window is characterized in that the demodulation method of the wide temperature range is realized based on a demodulation device of the wide temperature range;
the wide temperature range demodulation method device comprises a laser (1), an optical fiber coupler (2), a first electro-optic modulator (3), a second electro-optic modulator (4), an erbium-doped optical fiber amplifier (5), an orthogonal polarization scrambler (6), an optical isolator (7), a frequency agile module (8), an up-conversion module (9), a first circulator (10), a second circulator (11), an optical fiber grating filter (12), a photoelectric detector (13) and an acquisition card (14);
the wide temperature range demodulation method comprises the following steps:
enabling the laser emitted by the laser (1) to enter the input end of the optical fiber coupler (2), and dividing the laser into two beams of laser with the same power after passing through the optical fiber coupler (2);
one of the two laser beams is modulated into pump light by the first electro-optical modulator (3) driven by an electric pulse signal output by the frequency agility module (8), amplified by the erbium-doped fiber amplifier (5), and enters the single mode fiber (15) to be detected from one end of the single mode fiber (15) to be detected after passing through the first circulator (10);
the other laser of the two lasers is modulated into probe light by the second electro-optical modulator (4) driven by the microwave signal output by the up-conversion module (9), and then the probe light is subjected to polarization disturbance by the orthogonal polarization disturbance device (6), passes through the optical isolator (7) and then enters the single mode fiber (15) to be tested from the other end of the single mode fiber (15) to be tested;
enabling the pumping light and the detection light to interact in the single-mode optical fiber (15) to be detected to generate a backward stimulated Brillouin scattering signal, enabling the backward stimulated Brillouin scattering signal to enter the fiber grating filter (12) after passing through the first circulator (10) and the second circulator (11), receiving the filtered lower sideband light beam by the photoelectric detector (13), and collecting an electric signal generated by the photoelectric detector (13) by the collection card (14);
when the wide temperature range measurement is carried out, the output frequency of the up-conversion module (9) is changed according to the average temperature of the optical fiber measured in the previous time, so that the frequency of the detection light covers the current temperature range.
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