CN107764434B - FBG temperature sensor response measuring method based on FP etalon - Google Patents
FBG temperature sensor response measuring method based on FP etalon Download PDFInfo
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Abstract
The invention discloses a FBG temperature sensor response time measuring system and method based on FP etalon, wherein the FBG temperature sensor response time measuring system comprises the following steps: broadband light emitted by the ASE light source (1) firstly enters one port of the optical circulator (3) through the optical isolator (2), and then light beams are emitted from two ports of the optical circulator (3) and enter the FBG temperature sensor (4); the reflected light of the FBG temperature sensor (4) enters the two ports of the optical circulator (3) again, the reflected light is emitted from the three ports of the optical circulator (3) and enters the FP etalon (5) to be interfered, the photoelectric detector (6) detects the interference light intensity in real time, and the light intensity signal is acquired by the data acquisition system (7) in real time; converting the wavelength change of the FBG sensor into light intensity change through the FP etalon, detecting the light intensity change through the photoelectric detector, and simultaneously acquiring a light intensity signal in real time by the data acquisition system; and then calculating the wavelength change condition of the FBG temperature sensor according to an interference intensity formula of the FP etalon to finally obtain the response time of the FBG temperature sensor. The FBG temperature sensor has the advantages of simple structure, simplicity and convenience in operation, high response time measurement accuracy and capability of being applied to engineering practice.
Description
Technical Field
The invention belongs to the field of optical fiber sensors, and particularly relates to a method for measuring response time of an FBG temperature sensor.
Background
In 1978, k.o.hill et al discovered the photosensitivity of germanium-doped fibers and demonstrated the feasibility of forming gratings on the fiber core. This results in a new type of fiber passive device FBG, i.e. fiber bragg grating (fiber bragg grating). With the continuous improvement of the FBG writing technology and the increasing abundance of application results, FBG is one of the most promising and representative optical fiber passive devices. The application research of the sensor in a plurality of sensing fields such as temperature, strain, pressure and the like also enters a brand new development stage.
When the ambient temperature of the FBG temperature sensor changes, the heat transfer speed is related to the heat transfer mode, the temperature difference and the packaging mode of the sensor. In the case of the first two determinations, the manner of packaging becomes a major factor. The FBG temperature sensor temperature transmission speed is typically characterized by a response time. When the FBG sensor with different packaging modes is used for temperature measurement, the response time of the sensor needs to be known. The temperature field distribution in most cases can be regarded as static or quasi-static, the temperature changes relatively slowly, and most FBG temperature sensors can meet the temperature measurement requirement. However, in some special situations, such as the requirement of fast speed for ocean temperature measurement, severe temperature change in the aerospace field, etc., the fiber grating temperature sensor is required to have a fast enough response time to meet the requirement of fast temperature measurement. If a sensor with a long response time is used for rapid temperature detection, an error between the measured temperature value and the actual temperature value may be caused.
The response time of the fiber grating temperature sensor brings uncertainty to the measurement result to a certain extent, so that the response time and the test method of the fiber grating sensor are deeply discussed, and the method has important significance for reasonably selecting the packaging form of the sensor in practical application. Accordingly, a FBG temperature sensor response time system and measurement method based on FP etalon is presented herein.
Disclosure of Invention
Based on the prior art, the invention provides an FBG temperature sensor response measuring device and method based on an FP etalon, which are used for realizing the response time of the FBG temperature sensor to the temperature change when the measurement environment temperature changes.
The invention provides a FBG temperature sensor response time measuring method based on an FP etalon, which is based on a measuring system comprising an ASE light source 1, an optical isolator 2, an optical circulator 3, an FBG temperature sensor 4, an FP etalon 5, a photoelectric detector 6 and a data acquisition system 7; the ASE light source is connected with the input end of the optical isolator, the output end of the optical isolator 2 is connected with one port of the optical circulator 3, two ports of the optical circulator 3 are connected with the FBG temperature sensor 4, three ports of the optical circulator 3 are connected with the input port of the FP etalon 5, and the output port of the FP etalon 5 is connected with the photoelectric detector 6; the photoelectric detector 6 is connected with a data acquisition system 7; wherein: broadband light emitted by the ASE light source 1 firstly enters the optical circulator 1 through the optical isolator 2, and then light beams are emitted from two ports of the optical circulator 3 and enter the FBG temperature sensor 4; the reflected light of the FBG temperature sensor 4 enters the two ports of the optical circulator 3 again, the reflected light is emitted from the three ports of the optical circulator 3 and enters the FP etalon 5 to interfere, the photoelectric detector 6 detects the interference light intensity in real time, and the light intensity signal is acquired by the data acquisition system 7 in real time; the method comprises the following steps:
connecting the ASE light source, the photoelectric detector and a power supply of the signal acquisition system; placing the FBG temperature sensor into a constant-temperature water bath at 70 ℃ from a room temperature environment, and collecting a light intensity signal received by a photoelectric detector when the FBG temperature sensor changes due to the external environment temperature and the wavelength changes suddenly;
calculating the change condition of the wavelength lambda of the FBG temperature sensor in the period from the room temperature environment to the 70 ℃ water bath environment according to the FP etalon interference intensity formula (1):
wherein α represents the absorption ratio of FP etalon metal coating, ρ represents the interface reflectance, IiRepresenting the intensity of incident light, F the etalon finesse coefficient, delta the phase difference, h the etalon cavity length, theta the interference tilt angle,
representing phase changes introduced by the etalon metal coating;
obtaining the response time T of the FBG temperature sensor according to the formulas (2) and (3)r：
Tr＝Ts-To(3)
In the formula, TλDenotes the time corresponding to the wavelength λ of the FBG temperature sensor, and f (λ) denotes the time index corresponding to the wavelength λ of the sensor, and has a value equal to the light intensity I of the interference light of the FP etalontCorresponding time index f (I)t) F represents the sampling frequency of the data acquisition system;
Tsrepresents the time, T, corresponding to the FBG temperature sensor wavelength being 90% of the steady stateoRepresenting the time corresponding to the wavelength of the FBG temperature sensor being 10% of the steady state, the two parameter values are given according to the equations (2-1) (2-2):
wherein f(s) is a time index corresponding to the wavelength of the FBG temperature sensor being 90% of a steady state, and f (o) is a time index corresponding to the wavelength of the FBG temperature sensor being 10% of the steady state.
Compared with the prior art, the FBG temperature sensor response measurement system and the FBG temperature sensor response measurement method based on the FP etalon have the advantages of simple structure, simplicity and convenience in operation, high response time measurement precision of the FBG temperature sensor and capability of being applied to engineering practice.
Drawings
FIG. 1 is a schematic structural diagram of an FBG temperature sensor response measuring device based on an FP etalon according to the invention;
FIG. 2 is a diagram showing the variation of light intensity collected by the data collection system when the FBG temperature sensor response time is actually measured by using the FBG temperature sensor response measurement method based on the FP etalon provided by the invention;
reference numerals: 1. an ASE light source; 2. an optical isolator; 3. an optical circulator; 4. an FBG temperature sensor; 5. an FP etalon; 6. a photodetector; 7. a data acquisition system.
Detailed Description
The technical scheme of the invention is further explained by the specific embodiment in combination with the attached drawings.
Fig. 1 is a schematic structural diagram of a FBG temperature sensor response time measuring system based on an FP etalon. The system comprises an ASE light source 1, an optical isolator 2, an optical circulator 3, an FBG temperature sensor 4, an FP etalon 5, a photoelectric detector 6 and a data acquisition system 7; the ASE light source 1 is connected with the input end of an optical isolator 2, the output end of the optical isolator 2 is connected with one port of an optical circulator 3, two ports of the optical circulator 3 are connected with an FBG temperature sensor 4, three ports of the optical circulator 3 are connected with an input port of an FP etalon 5, and an output port of the FP etalon 5 is connected with a photoelectric detector 6; signals of the photoelectric detector 6 are collected by the data collecting system 7 in real time;
broadband light emitted by the ASE light source 1 firstly enters one port of an optical circulator 3 through an optical isolator 2, and then light beams are emitted from two ports of the optical circulator 3 to enter an FBG temperature sensor 4; the reflected light of the FBG temperature sensor 4 enters the two ports of the optical circulator 3 again, the reflected light is emitted from the three ports of the optical circulator 3 and enters the FP etalon 5 to interfere, the photoelectric detector 6 detects the interference light intensity in real time, and the light intensity signal is acquired by the data acquisition system 7 in real time;
the FBG temperature sensor response time measuring method based on the FP etalon converts the wavelength change of the FBG sensor into the light intensity change through the FP etalon, detects the light intensity change through the photoelectric detector, and simultaneously, a data acquisition system acquires a light intensity signal in real time; and then calculate the wavelength change situation of FBG temperature sensor according to the interference intensity formula of FP etalon, finally obtain FBG temperature sensor's response time, include the following steps specifically:
connecting the ASE light source, the photoelectric detector and a power supply of the signal acquisition system; placing the FBG temperature sensor in a constant-temperature water bath at 70 ℃ from a room temperature environment (24 ℃), and collecting a light intensity signal received by a photoelectric detector when the FBG temperature sensor changes due to the external environment temperature and the wavelength changes suddenly;
calculating the change condition of the wavelength lambda of the FBG temperature sensor in the period of time according to the FP etalon interference intensity formula (1)
Wherein α is the absorption ratio of FP etalon metal coating, ρ is the interface reflectance, IiIs the incident light intensity, F is the etalon fineness coefficient, delta is the phase difference, h is the etalon cavity length, theta is the interference tilt angle,
these parametric value device manufacturers provide for the phase change introduced by the etalon metal coating. For a defined etalon, the intensity of the interference light ItOnly with respect to the FBG temperature sensor reflection wavelength lambda. After the correlation calculation is carried out by the formula (1), the change condition of the wavelength lambda of the FBG temperature sensor in the time from the room temperature environment to the water bath (70 ℃) environment can be known.
The time constant is an index of the response time of the FBG temperature sensor, and the time constant is defined as the time required for the sensor to change from the initial temperature to the steady-state temperature of 63.2% when the measured ambient temperature suddenly changes. In practice, the time taken for the temperature of the sensor itself to change from 10% to 90% of the steady state value is also used. Since the wavelength variation and the temperature variation are linearly related, the response time T of the FBG temperature sensor can be obtained according to the formulas (2) and (3)rThe response time of the FBG temperature sensor is obtained according to the equations (2) and (3):
Tr＝Ts-To(3)
in the formula, TλF (λ) is the time index corresponding to the wavelength λ of the FBG temperature sensor, and has a value equal to the optical intensity I of the interference light of the FP etalontCorresponding time index f (I)t) The index can be obtained by processing signals acquired by a signal acquisition system, and f is the sampling frequency of the data acquisition system;
Tsthe time T corresponding to the FBG temperature sensor wavelength being 90% of the steady stateoFor the time corresponding to the wavelength of the FBG temperature sensor being 10% of the steady state, these two parameter values are obtained according to the equations (2-1) (2-2):
wherein f(s) is a time index corresponding to the wavelength of the FBG temperature sensor being 90% of a steady state, and f (o) is a time index corresponding to the wavelength of the FBG temperature sensor being 10% of the steady state.
Claims (1)
1. A FBG temperature sensor response time measuring method based on FP etalon is based on a measuring system comprising an ASE light source (1), an optical isolator (2), an optical circulator (3), an FBG temperature sensor (4), the FP etalon (5), a photoelectric detector (6) and a data acquisition system (7); the ASE light source (1) is connected with the input end of the optical isolator (2), the output end of the optical isolator (2) is connected with one port of the optical circulator (3), two ports of the optical circulator (3) are connected with the FBG temperature sensor (4), three ports of the optical circulator (3) are connected with the input port of the FP etalon (5), and the output port of the FP etalon (5) is connected with the photoelectric detector (6); the photoelectric detector (6) is connected with a data acquisition system (7); broadband light emitted by the ASE light source (1) firstly enters one port of the optical circulator (3) through the optical isolator (2), and then light beams are emitted from two ports of the optical circulator (3) to enter the FBG temperature sensor (4); the reflected light of the FBG temperature sensor (4) enters the two ports of the optical circulator (3) again, the reflected light is emitted from the three ports of the optical circulator (3) and enters the FP etalon (5) to be interfered, the photoelectric detector (6) detects the interference light intensity in real time, and the light intensity signal is acquired by the data acquisition system (7) in real time; the method is characterized by comprising the following steps:
connecting the ASE light source, the photoelectric detector and a power supply of the signal acquisition system; placing the FBG temperature sensor into a constant-temperature water bath at 70 ℃ from a room temperature environment, and collecting a light intensity signal received by a photoelectric detector when the FBG temperature sensor changes due to the external environment temperature and the wavelength changes suddenly;
calculating the change condition of the wavelength lambda of the FBG temperature sensor in the period from the room temperature environment to the 70 ℃ water bath environment according to the FP etalon interference intensity formula (1):
wherein α represents the absorption ratio of FP etalon metal coating, ρ represents the interface reflectance, IiRepresenting the intensity of incident light, F the etalon finesse coefficient, delta the phase difference, h the etalon cavity length, theta the interference tilt angle,
representing phase changes introduced by the etalon metal coating;
obtaining the response time T of the FBG temperature sensor according to the formulas (2) and (3)r：
Tr＝Ts-To(3)
In the formula, TλDenotes the time corresponding to the wavelength λ of the FBG temperature sensor, and f (λ) denotes the time index corresponding to the wavelength λ of the sensor, and has a value equal to the light intensity I of the interference light of the FP etalontCorresponding time index f (I)t) F represents the sampling frequency of the data acquisition system;
Tsrepresents the time, T, corresponding to the FBG temperature sensor wavelength being 90% of the steady stateoRepresenting the time corresponding to the wavelength of the FBG temperature sensor being 10% of the steady state, the two parameter values are given according to the equations (2-1) (2-2):
wherein f(s) is a time index corresponding to the wavelength of the FBG temperature sensor being 90% of a steady state, and f (o) is a time index corresponding to the wavelength of the FBG temperature sensor being 10% of the steady state.
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