Detection unit with increased detection length and distributed physical quantity measuring device

Abstract

The present invention discloses a detection unit with increased detection length, which is used to extend the detection range of a distributed physical quantity measurement device, and is characterized in that it includes: a fiber optic coupler, wherein the fiber optic coupler includes a main body, which is used to couple the distributed physical quantity remote detection device to introduce detection light into at least a first port of the main body; a second port including a reflective structure to provide reference light to the main body; and a third port for coupling with a sensing fiber to introduce measurement light including information about the measured physical quantity into the main body. The present invention applies a distributed physical quantity detection unit with increased detection length to a distributed physical quantity measurement device based on optical frequency domain reflection technology. The system measurement length is no longer occupied between the measuring host and the measured structure, and the sensing fiber can be arranged far away from the host, which is suitable for measurement occasions where the measuring host and the measured structure are far apart. The present invention also discloses a corresponding distributed measurement device.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber sensing and relates to a device for detecting physical quantities. Background Art

[0002] Distributed physical quantity measurement based on the principle of optical frequency domain reflection technology is a technical means to achieve distributed measurement of physical quantities. Related earlier literature includes: [1] Distributed measurement of static strain in an optical fiber with multiple Bragg gratings at nominally equal wavelengths [J]. Applied Optics, 1998, 37(10): 1741-1746; [2] High-spatial-resolution distributed strain measurement in optical fiber with Rayleigh scatter [J]. Applied Optics, 1998, 37(10): 1735-1740. According to prior art reports, the sensing or measurement length of distributed physical quantity measurement devices based on the principle of optical frequency-domain reflectometry is limited. This is partly due to the nonlinear correction method. For example, when an auxiliary interferometer is used as an external clock to sample the measurement interference optical path, the maximum measurement length is one-quarter of the auxiliary interferometer's optical path difference (Song, J., et al., Long-Range High Spatial Resolution Distributed Temperature and Strain Sensing Based on Optical Frequency-Domain Reflectometry. IEEE Photonics Journal, 2014. 6(3): p. 1-8.). In addition, the maximum measurement distance is also related to the phase noise of the light source and the system noise level. In actual engineering and system design, the maximum measurement length is often not just the above two factors, but a comprehensive consideration of factors such as the demodulation speed of distributed physical quantities, data volume, and accuracy. However, it is certain that although the longer the measurement length, the better in pursuit of instrument performance, this length is limited in actual systems or products. Generally, in distributed physical quantity measurement devices based on the principle of optical frequency-domain reflectometry for sensing or measurement, the measurement length is generally only a dozen meters. This length limits the device's applicability in certain situations, particularly when the measurement host and the structure under test are far apart. The fiber optic cable between the measurement host and the structure under test is very long, and this portion of the fiber optic cable consumes a portion of the system's measurement length, significantly reducing the length of the sensing fiber that can actually be used on the structure under test.To address this issue, the present invention introduces a remote probe into a distributed physical quantity measurement device. This allows the optical fiber between the measurement host and the structure being measured to consume no measurement length. This invention is highly valuable in practical engineering applications. It alleviates the system's pressure on measurement length, allowing the entire measurement length to be used for the structure being measured. Summary of the Invention

[0003] Some embodiments of the present application provide a detection unit for increasing the detection length, which is used to extend the detection range of a distributed physical quantity measurement device, comprising: a fiber optic coupler, the fiber optic coupler comprising a main body, used to couple the distributed physical quantity remote detection device to introduce detection light into at least a first port of the main body; a second port comprising a reflective structure to provide reference light to the main body; and a third port for coupling with a sensing optical fiber to introduce measurement light including information of a measured physical quantity into the main body; wherein the main body is configured to be able to transmit the detection light introduced from the first port to the second port and the third port, and to cause the reference light from the second port and the measurement light from the third port to interfere and be transmitted to the first port.

[0004] Other embodiments of the present application provide a distributed physical quantity detection device with increased detection length, which has an extended detection range, and includes a fiber optic coupler, the fiber optic coupler including a main body for coupling the distributed physical quantity measurement device to introduce detection light into at least a first port of the main body; a second port including a reflective structure to provide reference light to the main body; and a third port for coupling with a sensing optical fiber to introduce measurement light including information of the measured physical quantity into the main body; wherein the main body is configured to be able to transmit the detection light introduced from the first port to the second port and the third port, and to transmit the reference light from the second port and the measurement light from the third port to the first port; a measurement host of the distributed physical quantity measurement device includes a laser light source that provides continuously tuned detection laser, a fiber optic circulator, and a single-ended photodetector, the fiber optic circulator being used to export the detection laser to the fiber optic path and export the measurement light including information of the measured physical quantity returned by the fiber optic path to the single-ended photodetector; and a buffered optical cable including at least one fiber optic path, wherein one end of the fiber optic path is coupled to the fiber optic circulator and the other end is coupled to the first port of the fiber optic coupler.

[0005] Other embodiments of the present application provide a detection unit that increases the detection length, which is used to extend the detection range of a distributed physical quantity measurement device, comprising: a fiber optic coupler, the fiber optic coupler comprising a main body, used to couple the distributed physical quantity measurement device to introduce detection light into at least a first port of the main body; a second port comprising a reflective structure to provide reference light to the main body; a third port for coupling with a sensing optical fiber to introduce measurement light including information of a measured physical quantity into the main body, and a fourth port for outwardly exporting the measurement light; wherein the main body is configured to be able to transmit the detection light introduced from the first port to the second port and the third port, and to interfere with the reference light from the second port and the measurement light from the third port and transmit them to the first port and the fourth port.

[0006] Some other embodiments of the present application provide a distributed physical quantity detection device with increased detection length, which has an extended detection range and includes: a measurement host including a laser light source providing a continuously tuned detection laser, an optical fiber circulator, and a differential photodetector, wherein the optical fiber circulator is used to guide the detection laser and guide the returned interference light including the measured physical quantity information to the differential photodetector; a fiber optic coupler, wherein the fiber optic coupler includes a body for coupling the measurement host to introduce the detection light into at least a first port of the body; a second port including a reflective structure to provide a reference light to the body; and a second port for coupling with a sensing fiber to guide the measurement light including the measured physical quantity information. A third port is introduced into the body, and a fourth port is used to output the measurement light outward; wherein, the body is configured to be able to transmit the detection light introduced from the first port to the second port and the third port, and to interfere the reference light from the second port and the measurement light from the third port and transmit them to the first port and the fourth port; a buffered optical cable includes at least a first optical fiber path and a second optical fiber path, wherein one end of the first optical fiber path is coupled to the optical fiber circulator and the other end is coupled to the first port of the optical fiber coupler, and one end of the second optical fiber path is coupled to the fourth port and the other end is coupled to the differential photodetector.

[0007] The beneficial effects of the present invention are as follows: the present invention integrates a distributed physical quantity detection unit with increased detection length into a distributed physical quantity measurement device based on optical frequency domain reflection technology, so that the system measurement length is no longer occupied between the measuring host and the structure to be measured, and the sensing optical fiber can be arranged far away from the host, which is suitable for measurement occasions where the measuring host and the structure to be measured are far apart. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 Schematic diagram of a distributed physical quantity detection device with increased detection length according to an embodiment of the present application; Figure 1In the figure, 1 is the measurement host, 2 is the remote detection box, 3 is the buffer cable, 4 is the sensing fiber, and 5 is the structure to be measured. DETAILED DESCRIPTION

[0009] like Figure 1 As shown, the distributed physical quantity detection device for increasing detection distance described in the present invention comprises three components: a measurement host 1, a remote detection box 2, a relay device between the host and the sensing fiber, and a buffered optical cable 3, which connects the measurement host and the remote detection box and contains an internal fiber path. A sensing fiber 4 can be connected to the remote detection box 2 and attached to the surface of a structure 5 to be measured.

[0010] The sensing principle for remote detection of distributed physical quantities is the optical frequency domain reflection principle. Its sensing principle and basic structure can be found in references [1-2] described in the background technology. By injecting a continuous probe light with a linearly varying wavelength into the coherent optical structure, the scattered or reflected signals at different locations in the sensing fiber are detected. Because the scattered or reflected light at different locations in the sensing fiber space has different time delays with the local oscillator light, the different time delays are converted into carrier waves of different frequencies through coherent interference. By performing time-frequency analysis on the detected interference signal, the Rayleigh scattering spectrum of the sensing fiber under test can be obtained, and then the measured value can be obtained by detecting the spectral frequency shift. The measurement device generally includes a tunable laser as the system light source, a main interferometer as a module for detecting scattering or reflection in the sensing fiber, and an auxiliary fiber interferometer for correcting the nonlinearity of the light source tuning.

[0011] In the prior art, all measurement modules, except for the sensing fiber, are typically stored within the measurement host. In this setup, if the measurement host is far from the structure being measured, the fiber between the host and the structure being measured is very long, and this fiber occupies a portion of the system's measurement length, significantly reducing the length of the sensing fiber actually available for use on the structure being measured. To address this issue, the present invention introduces a distributed physical quantity detection device that increases the detection length within the distributed physical quantity measurement apparatus. This ensures that the fiber between the measurement host and the structure being measured does not occupy the measurement length. The present invention will be described below in conjunction with the device.

[0012] In the first embodiment, a tunable laser 1 outputs a continuously tunable wavelength laser beam, which serves as the device's light source. This beam is split into two beams by a first fiber coupler in the measurement host. One beam serves as reference light and is injected into the auxiliary interferometer module for monitoring or correcting laser tuning nonlinearity. The other beam, serving as probe light, is connected to port a of a fiber circulator (the fiber circulator in the device has the following characteristics: a in, c out, c in, b out). Port b of the fiber circulator is connected to port a of a differential photodetector, port c of the fiber circulator is connected to the first interface of the measurement host, and port b of the differential photodetector is connected to the second interface of the measurement host. The measurement host 1 also includes an acquisition module, a computer, and a display. The acquisition module is used to collect the photoelectric signals output by the differential photodetector and the auxiliary photodetector within the auxiliary interferometer module. The auxiliary interferometer module consists of a typical Michelson fiber interferometer, including a second fiber coupler in the measurement host, a delay fiber, a first Faraday rotator mirror, a second Faraday rotator mirror, and an auxiliary photodetector.

[0013] The buffered optical cable 3 connects the measurement host 1 and the remote detection box 2. It contains two optical fiber pathways: a first optical fiber pathway and a second optical fiber pathway. The buffered optical cable 3 is a bundle of multiple optical fibers. Specifically, it can be a bundled bundle with an outer armored structure or other protective sheathing structure and inner fiber optics. Alternatively, it can be a bundled bundle with no outer sheath and simply multiple discrete optical fiber pathways. The former is generally used for simplicity and to minimize external interference.

[0014] Remote detection box 2, a transfer device between the host and the sensing fiber, includes a 2×2-port remote detection box first coupler. Ports a and d of the remote detection box first coupler connect to the first and second optical fiber pathways of the two optical fibers in the buffered optical cable. Port b of the remote detection box first coupler is connected or configured to have a function or structure that can achieve light reflection. The other port is connected to the remote detection box second port, which in turn connects to the sensing fiber 4. Here, the term "remote" refers to the measurement host at the proximal end.

[0015] Functionally, the remote detection box's first coupler, remote detection box circulator, remote detection box Faraday reflector, and its attached optical fiber together constitute the main interferometer. This structure is a Michelson-type fiber interferometer. Signal light enters port a of the remote detection box's first coupler, is split by the remote detection box's first coupler, and one path passes through port b and is reflected by the remote detection box's Faraday reflector, serving as the interferometer's reference arm. The other path enters the remote detection box's second interface and enters sensing fiber 4. Rayleigh scattered or reflected return light from sensing fiber 4, i.e., measurement light, is transmitted to port c of the remote detection box's first coupler. This signal light, i.e., measurement light, interferes with the return light from the reference arm. After interference, the signal returns from ports a and d of the remote detection box's first coupler via buffered optical cable 3 to the measurement host 1.

[0016] The second embodiment differs from the first embodiment in that a single-ended detection structure and a single-ended photoelectric detector are used in the measuring host 1. In this case, port a of the second coupler of the remote detection box is connected to the first interface of the remote detection box, and the buffered optical cable includes a first optical fiber path.

[0017] The structural differences between the two embodiments primarily lie in their differential and single-ended detection designs. Differential detection eliminates common-mode noise in the signal, further improving the system's signal-to-noise ratio. For the basic principles of differential detection, refer to page 31 of "Optical Simulation and Research in FMCW LiDAR" (published by Harbin Institute of Technology, 2013).

[0018] The function of the Faraday reflector in the remote detection box is to reflect light. Its structure can also be coated with a reflection-enhancing film or the tail of the optical fiber can be polished into a flat connector.

[0019] In both embodiments, the main interferometer structure is located in the remote detection box 2, rather than in the measurement host 1 as in the prior art. This separated design means that the starting position of the optical fiber sensing is not located at the interface position of the measurement host 1, but is located at a position after the remote detection box circulator and at the same optical path as the main interferometer reference arm. By adjusting the length of the corresponding optical fiber, this position can be located at the fourth interface of the remote detection box. The buffer cable 3 between the measurement host 1 and the remote detection box 2 does not occupy the measurement length, so the remote detection box and the sensing fiber connected thereto can be placed far away from the host. For example, if the system is designed to measure a length of 10 meters, the length of the buffer cable can far exceed this distance, such as 50 meters.

[0020] Since the wavelength tuning of the laser is nonlinear, that is, the output optical frequency does not increase linearly with time, if a fixed sampling rate is used to sample each output signal, the sampling points are not equally spaced at optical frequencies. This effect worsens the spatial resolution of the sensing or measurement system. The above-mentioned method of using the auxiliary interferometer output signal to perform nonlinear correction on the measurement state main interferometer output signal and the measurement state wavelength monitoring output signal has several different implementation methods: the auxiliary interferometer signal can be synchronized with other signals and collected at a fixed sampling rate using an acquisition device, and then the main interferometer output signal or the wavelength monitoring output signal can be subjected to nonlinear correction in the data processing module. The method is to perform Hilbert expansion on the auxiliary interferometer output signal, perform phase unwrapping, and then divide the phase into equal parts, such as according to The radian is divided equally to obtain corresponding sampling points, and then these sampling points are used to resample the main interferometer output signal and the wavelength monitoring output signal. The resampled main interferometer output signal and the wavelength monitoring output signal are signals that have corrected nonlinearity. In addition, there are also implementation forms of correcting nonlinearity using post-processing software methods such as non-uniform Fourier transform, de-skewing filter, and PNC phase compensation. In addition, the sinusoidal signal output by the auxiliary interferometer can be used as the clock of the acquisition device, and this clock can be used as the acquisition clock for the main interferometer output signal and the wavelength monitoring output signal to acquire these two signals. Considering the existing prior art, this part will not be elaborated on.

[0021] The sensing optical fiber 4 can be a common single-mode optical fiber, such as Coning SMF-28, or a sensing optical fiber inscribed with a weak reflection fiber grating array with equal central wavelength, or a sensing optical fiber with enhanced Rayleigh scattering.

[0022] The above description is only the preferred specific embodiments of the present invention. These specific embodiments are all different implementation methods based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

[0023] The present invention can also be implemented through the following examples:

[0024] 1. A detection unit for increasing detection length, used to extend the detection range of a distributed physical quantity measurement device, characterized by comprising:

[0025] An optical fiber coupler comprising a body for coupling the distributed physical quantity remote detection device to introduce detection light into at least a first port of the body; a second port comprising a reflective structure to provide reference light to the body; and a third port for coupling with a sensing optical fiber to introduce measurement light including information about the physical quantity to be measured into the body;

[0026] The body is configured to transmit the detection light introduced from the first port to the second port and the third port, and to cause the reference light from the second port and the measurement light from the third port to interfere and transmit to the first port.

[0027] 2. The detection unit for increasing the detection length according to Example 1 is characterized in that it further comprises a buffered optical cable having one end coupled to the first port, and the other end of the buffered optical cable can be connected to the distributed physical quantity measurement device.

[0028] 3. The detection unit for increasing the detection length according to Example 1, characterized in that the second port is made into an optical fiber end structure capable of reflecting light or is connected to a light reflecting unit.

[0029] 4. The detection unit with increased detection length according to Example 3 is characterized in that the reflection unit is a Faraday reflector or a reflective enhancement film.

[0030] 5. The detection unit for increasing the detection length according to Example 1, further comprising a housing covering the optical fiber coupler.

[0031] 6. The detection unit with increased detection length according to Example 5 is characterized in that: the housing has an interface for connecting the first, second and third ports to an external structure.

[0032] 7. A distributed physical quantity detection device with increased detection length, having an extended detection range, characterized in that the device comprises:

[0033] A fiber coupler comprising a body for coupling a distributed physical quantity measurement device to introduce probe light into at least a first port of the body; a second port comprising a reflective structure for providing reference light to the body; and a third port for coupling with a sensing fiber to introduce measurement light including information about a measured physical quantity into the body; wherein the body is configured to transmit the probe light introduced from the first port to the second and third ports, and to transmit the reference light from the second port and the measurement light from the third port to the first port.

[0034] The measuring host of the distributed physical quantity measuring device includes a laser light source for providing continuously tuned detection laser light, an optical fiber circulator, and a single-ended photodetector, wherein the optical fiber circulator is used to guide the detection laser light to the optical fiber path and guide the measurement light including the measured physical quantity information returned by the optical fiber path to the single-ended photodetector; and

[0035] The buffered optical cable comprises at least one optical fiber channel, wherein one end of the optical fiber channel is coupled to the optical fiber circulator, and the other end of the optical fiber channel is coupled to the first port of the optical fiber coupler.

[0036] 8. The distributed physical quantity detection device with increased detection length according to Example 7 is characterized in that the laser light source is a tunable laser.

[0037] 9. The distributed physical quantity detection device with increased detection length according to Example 7 is characterized in that the optical fiber coupler is a 1×2-port optical fiber coupler.

[0038] 10. The distributed physical quantity detection device with increased detection length according to Example 7, wherein the laser light source is configured to output wavelength continuously tuned laser light.

[0039] 11. The distributed physical quantity detection device with increased detection length according to Example 7 is characterized in that: the measurement host also includes an auxiliary interferometer module for monitoring or correcting laser tuning nonlinearity, the measurement host includes a first fiber optic coupler of the measurement host, and the first fiber optic coupler of the measurement host is configured to split the laser emitted by the laser light source to the auxiliary interferometer module.

[0040] 12. The distributed physical quantity detection device with increased detection length according to Example 11 is characterized in that: the auxiliary interferometer module is based on a typical Michelson fiber interferometer, which includes a second fiber coupler of the measurement host, a delay fiber, a first Faraday rotator mirror, a second Faraday rotator mirror, and an auxiliary path photodetector.

[0041] 13. The distributed physical quantity detection device for increasing the detection length according to Example 7 is characterized in that: the optical fiber circulator includes port a, port b and port c, wherein light enters from port a and exits from port c, and light enters from port c and exits from port b; the laser light source coupled to the port a is used to receive detection light, the port b is connected to the input end of the single-ended photodetector, and the port c is coupled to the buffered optical cable through the first interface of the measurement host for transmitting detection light and receiving measurement light.

[0042] 14. The distributed physical quantity detection device with increased detection length according to Example 11 is characterized in that: the measurement host also includes an acquisition module for acquiring the photoelectric signal output by the single-ended photodetector, or the single-ended photodetector and the auxiliary circuit photodetector inside the auxiliary interferometer module.

[0043] 15. The distributed physical quantity detection device with increased detection length according to Example 14, wherein the measurement host further comprises a processor coupled to the acquisition module for on-site data processing.

[0044] 16. The distributed physical quantity detection device with increased detection length according to Example 15, wherein the measurement host further comprises a display coupled to the processor for providing on-site display.

[0045] 17. The distributed physical quantity detection device with increased detection length according to Example 11 is characterized in that it also includes a sensing fiber coupled to the third port of the fiber coupler, wherein the sensing fiber is an ordinary communication fiber, a sensing fiber with a weak reflection fiber grating array with equal central wavelengths that is continuously inscribed with fixed length intervals or without intervals, or a sensing fiber with enhanced Rayleigh scattering.

[0046] 18. The distributed physical quantity detection device with increased detection length according to Example 11, characterized in that: the buffer optical cable does not occupy the sensing length of the device.

[0047] 19. A detection unit for increasing detection length, used to extend the detection range of a distributed physical quantity measurement device, characterized by comprising:

[0048] A fiber optic coupler comprising a body for coupling the distributed physical quantity measurement device to introduce detection light into at least a first port of the body; a second port comprising a reflective structure to provide reference light to the body; a third port for coupling with a sensing optical fiber to introduce measurement light including information about the measured physical quantity into the body; and a fourth port for outwardly conducting the measurement light.

[0049] The body is configured to transmit the detection light introduced from the first port to the second port and the third port, and to interfere with the reference light from the second port and the measurement light from the third port and transmit them to the first port and the fourth port.

[0050] 20. The detection unit for increasing detection length according to Example 19, further comprising a buffered optical cable having one end coupled to the first port and the fourth port, and the other end of the buffered optical cable coupled to the distributed physical quantity measurement device.

[0051] 21. The detection unit for increasing the detection length according to Example 19, wherein the second port is made into an optical fiber end structure capable of reflecting light or is connected to a light reflecting unit.

[0052] 22. The detection unit for increasing the detection length according to Example 21, wherein the reflection unit is a Faraday reflector or a reflection-enhancing film.

[0053] 23. The detection unit for increasing the detection length according to Example 19, further comprising a housing covering the optical fiber coupler.

[0054] 24. The detection unit for increasing the detection length according to Example 23, wherein the housing has an interface for connecting the first, second, third and fourth ports to an external structure.

[0055] 25. A distributed physical quantity detection device with increased detection length, having an extended detection range, characterized in that the device comprises:

[0056] A measurement host, comprising a laser light source for providing continuously tuned detection laser light, a fiber optic circulator, and a differential photodetector, wherein the fiber optic circulator is used to guide the detection laser light and guide the returned interference light including information of the measured physical quantity to the differential photodetector;

[0057] A fiber optic coupler comprising a body for coupling to the measurement host to introduce probe light into at least a first port of the body; a second port comprising a reflective structure for providing reference light to the body; a third port for coupling to a sensing fiber to introduce measurement light including information about a measured physical quantity into the body; and a fourth port for externally conducting the measurement light; wherein the body is configured to transmit the probe light introduced from the first port to the second and third ports, and to cause interference between the reference light from the second port and the measurement light from the third port and transmit the interference to the first and fourth ports;

[0058] The buffered optical cable comprises at least a first optical fiber channel and a second optical fiber channel, wherein one end of the first optical fiber channel is coupled to the optical fiber circulator and the other end is coupled to the first port of the optical fiber coupler, and one end of the second optical fiber channel is coupled to the fourth port and the other end is coupled to the differential photodetector.

[0059] 26. The distributed physical quantity detection device with increased detection length according to Example 25 is characterized in that the laser light source is a tunable laser.

[0060] 27. The distributed physical quantity detection device with increased detection length according to Example 25, wherein the optical fiber coupler is a 2×2 port optical fiber coupler.

[0061] 28. The distributed physical quantity detection device with increased detection length according to Example 25 is characterized in that the laser light source is configured to output wavelength continuously tuned laser.

[0062] 29. The distributed physical quantity detection device with increased detection length according to Example 25 is characterized in that: the measurement host also includes an auxiliary interferometer module for monitoring or correcting laser tuning nonlinearity, the measurement host includes a first fiber optic coupler of the measurement host, and the first fiber optic coupler of the measurement host is configured to split the laser emitted by the laser light source to the auxiliary interferometer module.

[0063] 30. The distributed physical quantity detection device with increased detection length according to Example 29 is characterized in that: the auxiliary interferometer module is based on a typical Michelson fiber interferometer, which includes a second fiber coupler of the measurement host, a delay fiber, a first Faraday rotation mirror, a second Faraday rotation mirror, and an auxiliary path photodetector.

[0064] 31. The distributed physical quantity detection device for increasing the detection length according to Example 25 is characterized in that: the optical fiber circulator includes port a, port b and port c, wherein light enters from port a and exits from port c, and light enters from port c and exits from port b; the laser light source coupled to port a is used to receive detection light, the port b is connected to the first input end of the differential photodetector, and the port c is coupled to the buffered optical cable through the first interface of the measurement host for transmitting detection light and receiving measurement light.

[0065] 32. The distributed physical quantity detection device with increased detection length according to Example 29 is characterized in that: the measurement host also includes an acquisition module for acquiring the photoelectric signal output by the photoelectric detector, or the photoelectric detector and the auxiliary circuit photoelectric detector inside the auxiliary interferometer module.

[0066] 33. The distributed physical quantity detection device with increased detection length according to Example 32 is characterized in that the measurement host further includes a processor coupled to the acquisition module for on-site data processing.

[0067] 34. The distributed physical quantity detection device with increased detection length according to Example 33, wherein the measurement host further comprises a display coupled to the processor for providing on-site display.

[0068] 35. The distributed physical quantity detection device with increased detection length according to Example 25 is characterized in that it also includes a sensing optical fiber coupled to the third port of the optical fiber coupler, wherein the sensing optical fiber is an ordinary communication optical fiber, a sensing optical fiber with a weak reflection optical fiber grating array with equal central wavelengths that is continuously written with fixed length intervals or without intervals, or a sensing optical fiber with enhanced Rayleigh scattering.

[0069] 36. The distributed physical quantity detection device with increased detection length according to Example 25 is characterized in that: the buffered optical cable does not occupy the sensing length of the device.

[0070] 37. A distributed physical quantity detection device with increased detection length, characterized in that the device includes: a measurement host, including a tunable laser, which outputs a continuously tuned wavelength laser as the device light source, and also includes a circulator, a differential photodetector, a fiber coupler, an acquisition module, and a processor; a remote detection box, used as a transfer device between the measurement host and the sensing optical fiber, including a 2×2-port fiber coupler, the two ports on one side of the coupler are connected to two optical fibers in a buffered optical cable, and one of the two ports on the other side is connected or configured to have a function or structure that can achieve light reflection, and the other is connected to the sensing optical fiber; and a buffered optical cable, used to connect the measurement host and the remote detection box, including two optical fiber paths.

[0071] 38. A distributed physical quantity detection device with increased detection length, characterized in that the device includes: a measurement host, including a tunable laser that outputs continuously tuned wavelength laser light as the device's light source, and also includes a circulator, a photodetector, an acquisition module, and a processor; a remote detection box, used as a transfer device between the measurement host and the sensing optical fiber, including a 1×2-port fiber coupler, the port on one side of the coupler is connected to a buffered optical cable, one of the two ports on the other side is connected or configured to have a function or structure that can achieve light reflection, and the other is connected to the sensing optical fiber; and a buffered optical cable, used to connect the measurement host and the remote detection box, including an optical fiber path.

[0072] 39. In the distributed physical quantity detection device with increased detection length described in Example 38, the sensing optical fiber is an ordinary single-mode optical fiber, or an optical fiber engraved with a weakly reflective fiber grating array with equal central wavelengths, or an optical fiber with enhanced Rayleigh scattering.

[0073] 40. The distributed physical quantity detection device with increased detection length according to Example 38 or 39 is characterized in that the function or structure capable of realizing light reflection is a Faraday reflector or a reflection-enhancing film or the tail of the optical fiber is ground into a flat connector.

[0074] 41. The distributed physical quantity detection device with increased detection length according to Example 38 or 39 is characterized in that the buffer optical cable does not occupy the measurement length of the device.

Claims

1. A detection unit with increased detection length, used to extend the detection range of a distributed physical quantity measurement device, characterized in that: include: An optical fiber coupler comprising a body, configured to couple the distributed physical quantity remote detection device to introduce detection light into at least a first port of the body; a second port including a reflective structure for providing reference light to the body; and a third port for coupling with a sensing optical fiber to introduce measurement light including information of a measured physical quantity into the body; The body is configured to transmit the detection light introduced from the first port to the second port and the third port, and to cause the reference light from the second port and the measurement light from the third port to interfere and transmit to the first port.

2. The detection unit for increasing the detection length according to claim 1, characterized in that: The device further includes a buffered optical cable having one end coupled to the first port, and the other end of the buffered optical cable can be connected to the distributed physical quantity measurement device.

3. The detection unit for increasing the detection length according to claim 1, characterized in that: The second port is made into an optical fiber end structure capable of reflecting light or is connected to a light reflecting unit.

4. The detection unit for increasing the detection length according to claim 3, characterized in that: The reflection unit is a Faraday reflector or a reflective enhancement film.

5. The detection unit for increasing the detection length according to claim 1, characterized in that: Also included is a housing covering the optical fiber coupler.

6. The detection unit for increasing the detection length according to claim 5, characterized in that: The housing has an interface for connecting the first, second and third ports to an external structure.

7. A distributed physical quantity detection device with increased detection length, having an extended detection range, characterized in that: The device includes: A fiber coupler comprising a body for coupling a distributed physical quantity measurement device to introduce probe light into at least a first port of the body; a second port comprising a reflective structure for providing reference light to the body; and a third port for coupling with a sensing fiber to introduce measurement light including information about a measured physical quantity into the body; wherein the body is configured to transmit the probe light introduced from the first port to the second and third ports, and to transmit the reference light from the second port and the measurement light from the third port to the first port. The measuring host of the distributed physical quantity measuring device includes a laser light source for providing continuously tuned detection laser light, an optical fiber circulator, and a single-ended photodetector, wherein the optical fiber circulator is used to guide the detection laser light to the optical fiber path and guide the measurement light including the measured physical quantity information returned by the optical fiber path to the single-ended photodetector; and The buffered optical cable comprises at least one optical fiber channel, wherein one end of the optical fiber channel is coupled to the optical fiber circulator, and the other end of the optical fiber channel is coupled to the first port of the optical fiber coupler.

8. The distributed physical quantity detection device with increased detection length according to claim 7, characterized in that: The laser light source is a tunable laser.

9. The distributed physical quantity detection device with increased detection length according to claim 7, characterized in that: The optical fiber coupler is a 1×2-port optical fiber coupler.

10. The distributed physical quantity detection device with increased detection length according to claim 7, characterized in that: The laser light source is configured to output wavelength continuously tunable laser light.

11. The distributed physical quantity detection device with increased detection length according to claim 7, characterized in that: The measurement host also includes an auxiliary interferometer module for monitoring or correcting laser tuning nonlinearity. The measurement host includes a first fiber coupler of the measurement host, and the first fiber coupler of the measurement host is configured to split the laser light emitted by the laser light source to the auxiliary interferometer module.

12. The distributed physical quantity detection device with increased detection length according to claim 11, characterized in that: The auxiliary interferometer module is based on a typical Michelson fiber interferometer, which includes a measurement host, a second fiber coupler, a delay fiber, a first Faraday rotator mirror, a second Faraday rotator mirror, and an auxiliary photodetector.

13. The distributed physical quantity detection device with increased detection length according to claim 7, characterized in that: The optical fiber circulator includes port a, port b and port c, wherein light enters from port a and exits from port c, and light enters from port c and exits from port b; The laser light source coupled to the a port is used to receive detection light, the b port is connected to the input end of the single-ended photodetector, and the c port is coupled to the buffered optical cable through the first interface of the measurement host for transmitting detection light and receiving measurement light.

14. The distributed physical quantity detection device with increased detection length according to claim 7, characterized in that: The measurement host further includes an acquisition module for acquiring photoelectric signals output by the single-ended photoelectric detector, or the single-ended photoelectric detector and the auxiliary circuit photoelectric detector inside the auxiliary interferometer module.

15. The distributed physical quantity detection device with increased detection length according to claim 14, characterized in that: The measurement host further includes a processor coupled to the acquisition module for on-site data processing.

16. The distributed physical quantity detection device with increased detection length according to claim 15, characterized in that: The measurement host further includes a display coupled to the processor for providing on-site display.

17. The distributed physical quantity detection device with increased detection length according to claim 11, characterized in that: It also includes a sensing optical fiber coupled to the third port of the optical fiber coupler, wherein the sensing optical fiber is an ordinary communication optical fiber, a sensing optical fiber with a weak reflection fiber grating array with equal central wavelengths that is continuously written with fixed length intervals or without intervals, or a sensing optical fiber with enhanced Rayleigh scattering.

18. The distributed physical quantity detection device with increased detection length according to claim 11, characterized in that: The buffered optical cable does not occupy the sensing length of the device.

19. A detection unit with increased detection length, used to extend the detection range of a distributed physical quantity measurement device, characterized in that: include: an optical fiber coupler comprising a body, configured to couple the distributed physical quantity measurement device to introduce the probe light into at least a first port of the body; A second port including a reflective structure for providing reference light to the body; a third port for coupling with a sensing optical fiber to introduce measurement light including information of a measured physical quantity into the body; and a fourth port for guiding the measurement light outward; The body is configured to transmit the detection light introduced from the first port to the second port and the third port, and to interfere with the reference light from the second port and the measurement light from the third port and transmit them to the first port and the fourth port.

20. The detection unit for increasing the detection length according to claim 19, characterized in that: The device further includes a buffered optical cable having one end coupled to the first port and the fourth port, and the other end of the buffered optical cable coupled to the distributed physical quantity measurement device.

21. The detection unit for increasing the detection length according to claim 19, characterized in that: The second port is made into an optical fiber end structure capable of reflecting light or is connected to a light reflecting unit.

22. The detection unit for increasing the detection length according to claim 21, characterized in that: The reflection unit is a Faraday reflector or a reflective enhancement film.

23. The detection unit for increasing the detection length according to claim 19, characterized in that: Also included is a housing covering the optical fiber coupler.

24. The detection unit for increasing the detection length according to claim 23, characterized in that: The housing has an interface for connecting the first, second, third and fourth ports to an external structure.

25. A distributed physical quantity detection device with increased detection length, having an extended detection range, characterized in that The device includes: A measurement host, comprising a laser light source for providing continuously tuned detection laser light, a fiber optic circulator, and a differential photodetector, wherein the fiber optic circulator is used to guide the detection laser light and guide the returned interference light including information of the measured physical quantity to the differential photodetector; A fiber optic coupler comprising a body for coupling to the measurement host to introduce probe light into at least a first port of the body; a second port comprising a reflective structure for providing reference light to the body; a third port for coupling to a sensing fiber to introduce measurement light including information about a measured physical quantity into the body; and a fourth port for externally conducting the measurement light; wherein the body is configured to transmit the probe light introduced from the first port to the second and third ports, and to cause interference between the reference light from the second port and the measurement light from the third port and transmit the interference to the first and fourth ports; The buffered optical cable comprises at least a first optical fiber channel and a second optical fiber channel, wherein one end of the first optical fiber channel is coupled to the optical fiber circulator and the other end is coupled to the first port of the optical fiber coupler, and one end of the second optical fiber channel is coupled to the fourth port and the other end is coupled to the differential photodetector.

26. The distributed physical quantity detection device with increased detection length according to claim 25, characterized in that: The laser light source is a tunable laser.

27. The distributed physical quantity detection device with increased detection length according to claim 25, characterized in that: The optical fiber coupler is a 2×2 port optical fiber coupler.

28. The distributed physical quantity detection device with increased detection length according to claim 25, characterized in that: The laser light source is configured to output wavelength continuously tunable laser light.

29. The distributed physical quantity detection device with increased detection length according to claim 25, characterized in that: The measurement host also includes an auxiliary interferometer module for monitoring or correcting laser tuning nonlinearity. The measurement host includes a first fiber coupler of the measurement host, and the first fiber coupler of the measurement host is configured to split the laser light emitted by the laser light source to the auxiliary interferometer module.

30. The distributed physical quantity detection device with increased detection length according to claim 29, characterized in that: The auxiliary interferometer module is based on a typical Michelson fiber interferometer, which includes a measurement host, a second fiber coupler, a delay fiber, a first Faraday rotator mirror, a second Faraday rotator mirror, and an auxiliary photodetector.

31. The distributed physical quantity detection device with increased detection length according to claim 25, characterized in that: The fiber circulator includes port a, port b and port c, wherein light enters from port a and exits from port c, and light enters from port c and exits from port b; the laser light source coupled to port a is used to receive detection light, the port b is connected to the first input end of the differential photodetector, and the port c is coupled to the buffered optical cable through the first interface of the measurement host for transmitting detection light and receiving measurement light.

32. The distributed physical quantity detection device with increased detection length according to claim 25, characterized in that: The measurement host further includes an acquisition module for acquiring photoelectric signals output by the photoelectric detector, or the photoelectric detector and the auxiliary circuit photoelectric detector inside the auxiliary interferometer module.

33. The distributed physical quantity detection device with increased detection length according to claim 32, characterized in that: The measurement host further includes a processor coupled to the acquisition module for on-site data processing.

34. The distributed physical quantity detection device with increased detection length according to claim 33, characterized in that: The measurement host further includes a display coupled to the processor for providing on-site display.

35. The distributed physical quantity detection device with increased detection length according to claim 25, characterized in that: It also includes a sensing optical fiber coupled to the third port of the optical fiber coupler, wherein the sensing optical fiber is an ordinary communication optical fiber, a sensing optical fiber with a weak reflection fiber grating array with equal central wavelengths written continuously with fixed length intervals or without intervals, or a sensing optical fiber with enhanced Rayleigh scattering.

36. The distributed physical quantity detection device with increased detection length according to claim 25, characterized in that: The buffered optical cable does not occupy the sensing length of the device.

37. A distributed physical quantity detection device with increased detection length, characterized in that: The device includes: a measurement host, including a tunable laser that outputs continuously tuned wavelength laser light as the device's light source, and also includes a circulator, a photodetector, an acquisition module, and a processor; a remote detection box, used as a transfer device between the measurement host and the sensing optical fiber, including a 1×2-port optical fiber coupler, the port on one side of the coupler is connected to a buffered optical cable, one of the two ports on the other side is connected or configured to have a function or structure that can achieve light reflection, and the other is connected to the sensing optical fiber; and a buffered optical cable, used to connect the measurement host and the remote detection box, including an optical fiber path; the sensing optical fiber is an ordinary single-mode optical fiber, or an optical fiber with a weakly reflective fiber grating array with equal central wavelength, or an optical fiber with enhanced Rayleigh scattering.

38. The distributed physical quantity detection device with increased detection length according to claim 37, characterized in that: The function or structure capable of realizing light reflection is a Faraday reflector or a reflection-enhancing film or the tail of the optical fiber is ground into a planar connector.

39. The distributed physical quantity detection device with increased detection length according to claim 37, characterized in that: The buffered optical cable does not take up any measuring length of the device.

Images