CN104764474B - Fibre optical sensor based on light beam orbit angular momentum - Google Patents

Abstract

In the optical fiber sensor disclosed in the present invention, the laser is used to output the fundamental mode Gaussian beam. The optical fiber sensing unit divides the fundamental mode Gaussian beam into a first beam and a second beam, modulates the first beam into an orbital angular momentum beam, and uses the second beam and the orbital angular momentum beam to form an interference beam and outputs the interference beam to the beam expander . A beam expander expands the interfering beam. The measurement unit divides the interference beam passing through the beam expander into a first sub-interference beam and a second sub-interference beam, measures the first optical power corresponding to the first sub-interference beam and the second optical power corresponding to the second sub-interference beam, and obtains the second Variation values of the first optical power and the second optical power. In the above optical fiber sensor, the optical fiber sensing unit divides the fundamental mode Gaussian beam into two beams and then outputs an interference beam, and the measurement unit measures the optical power change value of the two interference beams. In the subsequent processing process, the optical power change value can be used It is used to calculate the change amount of the optical path difference, and then realize the function of the sensor.

Description

Optical Fiber Sensor Based on Beam Orbital Angular Momentum

technical field

The invention relates to the field of sensors, and more specifically relates to a Mach-Zehnder interferometer optical fiber sensor based on the coherent detection of beam orbital angular momentum.

Background technique

The orbital angular momentum mode of light is a propagation mode with a spiral phase plane. The order of the orbital angular momentum can be any integer, and the beams of different order orbital angular momentum are orthogonal to each other. This unique phase characteristic and The topological structure makes it attract much attention in fields such as basic research and applied research.

Although the orbital angular momentum mode of light has been extensively studied, there is still no relevant literature on its application in the field of sensing, and there is a technical gap. In the field of communication, the orbital angular momentum mode of light is used to improve communication capacity, and a new type of optical fiber capable of simultaneously transmitting multiple orbital angular momentum modes has become a research hotspot in recent years as a carrier for long-distance and large-capacity information transmission. The development of this new type of optical fiber makes it possible to use optical fiber sensors based on the orbital angular momentum of light beams.

Contents of the invention

The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the present invention needs to provide an optical fiber sensor based on the orbital angular momentum of light beams.

A fiber optic sensor based on beam orbital angular momentum, including a laser, an optical fiber sensing unit, a beam expander, and a measuring unit, where the optical fiber sensing unit, the beam expander, and the measuring unit are sequentially placed along the optical path of the light output by the laser .

The laser is used to output a fundamental mode Gaussian beam. The optical fiber sensing unit is used to divide the fundamental mode Gaussian beam into a first beam and a second beam, modulate the first beam into an orbital angular momentum beam, and use the second beam and the orbital angular momentum beam to form an interference beam and Outputting the interference beam to the beam expander. The beam expander is used to expand the interference beam. The measuring unit is used to divide the interference beam passing through the beam expander into a first sub-interference beam and a second sub-interference beam, and measure the first optical power corresponding to the first sub-interference beam and the power corresponding to the second sub-interference beam. the second optical power and obtain the change value of the first optical power and the second optical power.

In the above optical fiber sensor, the optical fiber sensing unit divides the fundamental mode Gaussian beam into two beams and then outputs an interference beam, and the measurement unit measures the optical power change value of the two interference beams. In the subsequent processing process, the optical power change value can be used It is used to calculate the change amount of the optical path difference, and then realize the function of the sensor.

In some embodiments, the optical fiber sensing unit includes an optical fiber beam splitter, a sensing optical fiber, a liquid crystal spatial light modulator, a first optical fiber collimator, a second optical fiber collimator, a polarizer, and a first beam splitting prism. The fiber beam splitter is used to split the fundamental mode Gaussian beam into the first beam and the second beam, and the first beam enters the liquid crystal space through the first fiber collimator, the polarizer and the first beam splitter in sequence A light modulator, the liquid crystal spatial light modulator is used to modulate the first beam into the orbital angular momentum beam and transmit it to the first dichroic prism. The sensing fiber is connected to the fiber beam splitter and the second fiber collimator, and is used to transmit the second light beam to the second fiber collimator, and the second fiber collimator is used to transmit the second light beam to the first dichroic prism. The first dichroic prism is used for forming the interference beam from the orbital angular momentum beam and the second beam and outputting the interference beam to the beam expander.

In some embodiments, the optical fiber sensing unit includes an optical fiber beam splitter, a sensing optical fiber, a liquid crystal spatial light modulator, a first optical fiber collimator, a second optical fiber collimator, a polarizer, and a first beam splitting prism.

The optical fiber beam splitter is used to split the fundamental mode Gaussian beam into the first beam and the second beam, and the first beam enters the liquid crystal spatial light modulator through the first fiber collimator and the polarizer in turn, and the liquid crystal The spatial light modulator is used to modulate the first beam into the orbital angular momentum beam and transmit it to the first beam splitting prism. The sensing fiber is connected to the fiber beam splitter and the second fiber collimator, and is used to transmit the second light beam to the second fiber collimator, and the second fiber collimator is used to transmit the second light beam to the first dichroic prism. The first dichroic prism is used for forming the interference beam from the orbital angular momentum beam and the second beam and outputting the interference beam to the beam expander.

In some embodiments, the optical fiber sensing unit includes a fiber beam splitter, a sensing fiber, a liquid crystal spatial light modulator, a first fiber collimator, a second fiber collimator, a third fiber collimator, a fourth Fiber collimator, polarizer and first beam splitting prism. The fiber beam splitter is used to split the fundamental mode Gaussian beam into the first beam and the second beam, and the first beam enters the liquid crystal spatial light modulator through the first fiber collimator and the polarizer in sequence.

The liquid crystal spatial light modulator is used for modulating the first beam into the orbital angular momentum beam and transmitting the orbital angular momentum beam to the third fiber collimator. The third fiber collimator is connected to the sensing fiber and used for coupling the orbital angular momentum beam to the sensing fiber. The sensing fiber is connected to the third fiber collimator and the fourth fiber collimator, and is used to transmit the orbital angular momentum beam to the fourth fiber collimator, and the fourth fiber collimator is used to track the The angular momentum beam is transmitted to the first dichroic prism. The second optical fiber collimator is connected with the optical fiber beam splitter and used to transmit the second light beam to the first beam splitting prism. The first dichroic prism is used for forming the interference beam from the orbital angular momentum beam and the second beam and outputting the interference beam to the beam expander.

In some embodiments, the liquid crystal spatial light modulator is a reflective liquid crystal spatial light modulator.

In some embodiments, the liquid crystal spatial light modulator is a transmissive liquid crystal spatial light modulator.

In some embodiments, the measurement unit includes a second dichroic prism, a third dichroic prism, a fifth fiber collimator, a sixth fiber collimator, an imaging device, and an optical power meter. The second dichroic prism is used to reflect the correction light to the camera device, and transmit the interference beam passing through the beam expander to the third dichroic prism. The imaging device is used for imaging with the correction light for correcting the positions of the fifth fiber collimator and the sixth fiber collimator. The third dichroic prism is used to divide the interference beam passing through the beam expander into the first sub-interference beam and the second sub-interference beam, and transmit the first sub-interference beam to the fifth fiber collimator, and reflecting the second sub-interference beam to the sixth fiber collimator. The fifth fiber collimator is used to transmit the first sub-interference beam to the optical power meter. The sixth fiber collimator is used to transmit the second sub-interference beam to the optical power meter. The optical power meter is used to measure the first optical power corresponding to the first sub-interference beam and the second optical power corresponding to the second sub-interference beam, and obtain the change value of the first optical power and the second optical power.

In some embodiments, the sensing fiber is an orbital angular momentum fiber, and the orbital angular momentum fiber includes: a core layer from the inside to the outside, and the material of the core layer is pure silica, air or silica doped with a co-dopant, The co-dopant includes one of fluorine and phosphorus compounds; an annular region disposed around the core layer and doped with a co-dopant, the co-dopant comprising germanium; and a cladding disposed around the annular region .

In some embodiments, the diameter of the core layer is 500nm-6000nm, and the thickness of the annular region is 500nm-6000nm.

In some embodiments, the positions of the fifth fiber collimator and the sixth fiber collimator are on the same circumference relative to the interference beam passing through the beam expander, and the fifth fiber collimator and the sixth fiber collimator The angle between the fiber collimator and the center of the circle satisfies Where n is a positive integer, L is the order of the orbital angular momentum beam and is an integer.

In some embodiments, the sensing fiber is a standard single mode fiber or multimode fiber.

Additional aspects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and comprehensible from the description of the embodiments in conjunction with the following drawings, wherein:

Fig. 1 is the structural representation of the optical fiber sensor of preferred embodiment of the present invention;

Fig. 2 is the interference image schematic diagram of the optical fiber sensor of preferred embodiment of the present invention;

3 is a schematic diagram of the relationship between the optical power of the optical fiber sensor and the optical path difference variation in a preferred embodiment of the present invention;

Fig. 4 is another structural representation of the optical fiber sensor of preferred embodiment of the present invention;

5 is a schematic diagram of another interference image of an optical fiber sensor in a preferred embodiment of the present invention;

6 is another schematic diagram of the relationship between the optical power of the optical fiber sensor and the optical path difference variation in a preferred embodiment of the present invention;

Fig. 7 is another schematic structural view of the optical fiber sensor of the preferred embodiment of the present invention;

Figure 8 is a schematic cross-sectional view of the sensing fiber used in the fiber optic sensor of the preferred embodiment of the present invention; and

Fig. 9 is another structural schematic diagram of the optical fiber sensor according to the preferred embodiment of the present invention.

detailed description

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

In the description of the present invention, it should be understood that the terms "first" and "second" are used for description purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly indicating the quantity of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of said features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

In the description of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connected, or integrally connected; may be mechanically connected, may be electrically connected or may communicate with each other; may be directly connected, or indirectly connected through an intermediary, may be internal communication between two components or interaction between two components relation. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, components and configurations of specific examples are described below. Of course, they are only examples and are not intended to limit the invention. Furthermore, the present disclosure may repeat reference numerals and/or reference letters in different instances, such repetition is for the purpose of simplicity and clarity and does not in itself indicate a relationship between the various embodiments and/or arrangements discussed. In addition, various specific process and material examples are provided herein, but one of ordinary skill in the art may recognize the use of other processes and/or the use of other materials.

Referring to Fig. 1, the optical fiber sensor 100 based on the optical beam orbital angular momentum of the first preferred embodiment of the present invention comprises a laser 102, an optical fiber sensing unit 104, a beam expander 106 and a measuring unit 108, the optical fiber sensing unit 104, the The beam expander 106 and the measurement unit 108 are sequentially placed along the optical path of the light output by the laser 102 .

The laser 102 is used to output a fundamental mode Gaussian beam. For example, the fundamental mode Gaussian beam has a wavelength of 1550 nm.

The optical fiber sensing unit 104 is used to split the fundamental mode Gaussian beam into a first beam and a second beam, modulate the first beam into an orbital angular momentum beam, and use the second beam and the orbital angular momentum beam to form an interference beam And output the interference beam to the beam expander 106 .

Specifically, the fiber sensing unit 104 includes a fiber beam splitter 110, a sensing fiber 112, a liquid crystal spatial light modulator 114, a first fiber collimator 116, a second fiber collimator 118, a polarizer 120 and a first beam splitter Prism 122.

The fiber beam splitter 110 is used for splitting the fundamental mode Gaussian beam into two beams, the first beam and the second beam. The first light beam enters the liquid crystal spatial light modulator 114 through the first fiber collimator 116 , the polarizer 120 and the first dichroic prism 122 in sequence. In this embodiment, the first dichroic prism 122 is a non-polarizing dichroic prism.

The first light beam becomes parallel light after passing through the first fiber collimator 116 . Afterwards, the first light beam passes through the polarizer 120 and is reflected by the first dichroic prism 122 to the liquid crystal spatial light modulator 114 .

The liquid crystal spatial light modulator 114 is used for modulating the first beam into the orbital angular momentum beam and transmitting it to the first dichroic prism 122 . For example, the liquid crystal spatial light modulator 114 modulates the first beam into an L-order orbital angular momentum beam. In this embodiment, the liquid crystal spatial light modulator 114 is a reflective liquid crystal spatial light modulator. The liquid crystal spatial light modulator 114 reflects the orbital angular momentum beam to the first dichroic prism 122 .

The sensing fiber 112 is connected to the fiber splitter 110 and the second fiber collimator 118 , and is used to transmit the second light beam to the second fiber collimator 118 . In this embodiment, the sensing optical fiber 112 is a G.652 standard single-mode optical fiber. It can be understood that, in other embodiments, the sensing fiber 112 can be other standard single-mode fiber or multi-mode fiber.

The second fiber collimator 118 is used to transmit the second light beam to the first dichroic prism 122 . After the second light beam passes through the second fiber collimator 118 , it becomes a parallel light beam and enters the first dichroic prism 122 .

The first dichroic prism 122 is used for forming the interference beam from the orbital angular momentum beam and the second beam and outputting the interference beam to the beam expander 106 . The orbital angular momentum beams respectively reaching the first beam splitting prism 122 interfere with the second beam in the first beam splitting prism 122 to form interference beams and transmit to the beam expander 106 .

The beam expander 106 is used to expand the interference beam to form expanded beam.

The measurement unit 108 is used to divide the interference beam passing through the beam expander 106 into a first sub-interference beam and a second sub-interference beam, and measure the first optical power corresponding to the first sub-interference beam and the second sub-interference beam corresponding to the second optical power and obtain the change value of the first optical power and the second optical power.

Specifically, the measurement unit 108 includes a second dichroic prism 124 , a third dichroic prism 126 , a fifth fiber collimator 128 , a sixth fiber collimator 130 , an imaging device 132 and an optical power meter 134 .

The second dichroic prism 124 is used to reflect the correction light to the camera device 132 , and transmit the interference beam passing through the beam expander 106 to the third dichroic prism 126 . The calibration light can be used to calibrate the positions of the fifth fiber collimator 128 and the sixth fiber collimator 130 before the fiber sensor 100 takes measurements.

The camera device 132 is used for imaging with the corrected light for correcting the positions of the fifth fiber collimator 128 and the sixth fiber collimator 130 . The camera device 132 can be an infrared camera. For example, before the measurement by the fiber sensor 100 , a calibration light source (not shown), such as an infrared light source, may be placed at the light incident end of the second fiber collimator 118 . The calibration light emitted by the calibration light source enters the first dichroic prism 122 through the second fiber collimator 118 . The light beam emitted by the laser 102 enters the first beam splitting prism 122 through the fiber beam splitter 110 , the first fiber collimator 116 , the polarizer 120 , the first beam splitting prism 122 and the liquid crystal spatial light modulator 114 . The first light beam and the correction light interfere in the first dichroic prism 122 to generate correction interference light. The interfering light for correction passes through the beam expander 106 and reaches the second dichroic prism 124 . Part of the interfering light for correction enters the imaging device 132 through the second dichroic prism 124 . The fifth fiber collimator 128 and the sixth fiber collimator 130 can be placed according to the interference light image observed on the imaging device 132, so that the positions of the fifth fiber collimator 128 and the sixth fiber collimator 130 are relative to The expanded beams passing through the beam expander 106 are on the same circumference.

The third dichroic prism 126 is used to divide the interference beam into the first sub-interference beam and the second sub-interference beam, and transmit the first sub-interference beam to the fifth fiber collimator 128, and the second The sub-interference beams are reflected to the sixth fiber collimator 130 . In this embodiment, both the second beam splitting prism 124 and the third beam splitting prism 126 are non-polarizing beam splitting prisms.

The fifth fiber collimator 128 is used to transmit the first sub-interference beam to the optical power meter 134 . The sixth fiber collimator 130 is used to transmit the second sub-interference beam to the optical power meter 134 .

The optical power meter 134 is used to measure the first optical power corresponding to the first sub-interference beam and the second optical power corresponding to the second sub-interference beam and obtain the change value of the first optical power and the second optical power.

Before the optical fiber sensor 100 is tested, the fifth optical fiber collimator 128 and the sixth optical fiber collimator 130 can be placed according to the interference image formed by the interference light according to the sample observed on the infrared camera 132, so that the fifth optical fiber collimator The positions of the collimator 128 and the sixth fiber collimator 130 are on the same circle relative to the beam expander light passing through the beam expander 106, and the fifth fiber collimator 128 and the sixth fiber collimator 130 are relative to The angle α between the center of the circle satisfies Wherein n is a positive integer, for example, n can interfere with the period of the beam, and L is the order of the orbital angular momentum beam, which is an integer. The sensing fiber 112 is the sensing part of the fiber optic sensor 100 . Changes in external factors cause changes in the length and shape of the sensing fiber 112, thereby introducing changes in the optical path difference, changing the interference beam, and then making the first sub-interference beam received by the fifth fiber collimator 128 and the sixth fiber collimator 130 The received optical power of the second interference sub-beam changes. The optical power change value can be measured by the optical power meter 134 . According to the change value of the optical power measured by the optical power meter 134 , the change amount of the optical path difference can be calculated to realize the function of the sensor.

For example, when the fifth fiber collimator 128 and the sixth fiber collimator 130 are calibrated by infrared rays, the interference light intensity distribution diagram observed by the imaging device 132 is shown in FIG. 2 . The placement of the fifth fiber collimator 128 and the sixth fiber collimator 130 and its position relative to the expanded beam light are shown in Figure 2, wherein the fifth fiber collimator 128 and the sixth fiber collimator 130 are relative to Angle α=45° at the center of the circle.

During the experiment, the liquid crystal spatial light modulator 114 modulates the first beam into an L=-1 order orbital angular momentum beam. Adjust the position of the second fiber collimator 118 so that when the optical path difference increases by 1 wavelength, the interference fringe rotates 360° counterclockwise, and the optical power of the first sub-interference beam sum and the second sub-interference beam are measured in the optical power meter 134 The optical power of the light beam is shown by the dots and hollow boxes in Fig. 3 respectively, and the solid curve and dotted curve in Fig. 3 are the fitting curves of the power measurement values respectively.

According to the optical power curve of the first sub-interference beam received by the fifth fiber collimator 128 is about a quarter ahead of the optical power curve of the second sub-interference beam received by the sixth fiber collimator 130 , it can be judged that the optical path difference is increasing, and the specific value of the optical path difference change can be obtained according to the change of the optical power value, thus realizing the function of the sensor.

To sum up, in the above-mentioned optical fiber sensor 100, the optical fiber sensing unit 104 divides the fundamental mode Gaussian beam into two beams and outputs an interference beam, and the measurement unit 108 measures the optical power change value of the two interference beams. In the subsequent processing process, The change value of the optical power can be used to calculate the change amount of the optical path difference, and then realize the function of the sensor.

Further, the optical fiber sensor 100 based on the optical beam orbital angular momentum in the present invention is the first time that the orbital angular momentum mode is used in the sensing field. The optical fiber sensor 100 is a new type of Mach-Zehnder interferometer-type optical fiber sensor, which uses the coherent detection of the orbital angular momentum of the beam, and its measurement accuracy can reach the sub-wavelength level, and can complete the measurement of variables such as temperature, pressure, and bending deformation. . By using the optical power meter 134 to measure the change of the optical power received by the two fiber collimators 128 and 130, the magnitude and direction of the change of the optical path difference can be measured. As the absolute value |L| of the order of the orbital angular momentum mode used increases, its measurement accuracy gradually decreases, so that the measurement accuracy can be changed by changing the value of |L|, so as to select the appropriate measurement in different application scenarios Accuracy, improve measurement efficiency.

Referring to FIG. 4 , the second preferred embodiment of the present invention provides a fiber optic sensor 200 . The optical fiber sensor 200 in this embodiment is basically the same as the optical fiber sensor 100 in the first preferred embodiment, except that the optical fiber sensing unit 202 in this embodiment is different.

The optical fiber sensing unit 202 of this embodiment includes a fiber beam splitter 204, a sensing fiber 206, a liquid crystal spatial light modulator 208, a first fiber collimator 210, a second fiber collimator 212, a polarizer 214 and a first Dichroic prism 216.

The fiber beam splitter 204 is used to split the fundamental mode Gaussian beam (for example, the wavelength is 1550nm) output by the laser 218 into a first beam and a second beam, and the first beam passes through the first fiber collimator 210 and the polarizer in sequence 214 into the liquid crystal spatial light modulator 208. The first light beam becomes parallel light after passing through the first fiber collimator 210 . Afterwards, the first light beam enters the liquid crystal spatial light modulator 208 through the polarizer 214 .

The liquid crystal spatial light modulator 208 is used for modulating the first beam into an orbital angular momentum beam and transmitting it to the first dichroic prism 216 . For example, the liquid crystal spatial light modulator 208 modulates the first beam into an L-order orbital angular momentum beam. In this embodiment, the liquid crystal spatial light modulator 208 is a transmissive liquid crystal spatial light modulator. The liquid crystal spatial light modulator 208 transmits the orbital angular momentum beam to the first dichroic prism 216 .

The sensing fiber 206 connects the fiber beam splitter 204 and the second fiber collimator 212, and is used to deliver the second light beam to the second fiber collimator 212, and the second fiber collimator 212 is used for The second light beam is transmitted to the first dichroic prism 216 . In this embodiment, the sensing optical fiber 206 is a G.652 standard single-mode optical fiber. It can be understood that, in other embodiments, the sensing fiber 206 can be other standard single-mode fiber or multi-mode fiber.

The first dichroic prism 216 is used for forming the interference beam from the orbital angular momentum beam and the second beam and outputting the interference beam to the beam expander 220 .

During the experiment, the interference light intensity distribution diagram observed by the imaging device 222 is shown in FIG. 5 . The angle α=5° between the fifth fiber collimator 224 and the sixth fiber collimator 226 relative to the circle center.

The liquid crystal spatial light modulator 208 modulates the first beam into an L=+10 order orbital angular momentum beam. The position of the second fiber collimator 212 is adjusted so that when the optical path difference increases by 10 wavelengths, the interference fringes rotate 360° counterclockwise. The optical power of the first sub-interference beam and the optical power of the second sub-interference beam measured by the optical power meter 228 are respectively shown as dashed curves and solid curves in FIG. 6 .

According to the optical power curve of the first sub-interference beam received by the fifth fiber collimator 224 is about a quarter ahead of the optical power curve of the second sub-interference beam received by the sixth fiber collimator 226 , it can be judged that the optical path difference is increasing, and the specific value of the optical path difference can be obtained according to the change of the optical power value. Since L=10, the interference fringe rotates by 36° when the optical path difference changes by 1 wavelength. Therefore, the measurement accuracy of the optical fiber sensor 200 in this embodiment is lower than that of the optical fiber sensor 100 in the first preferred embodiment, and the function of measurement accuracy conversion is realized.

Referring to FIG. 7 , a third preferred embodiment of the present invention provides a fiber optic sensor 300 . The optical fiber sensor 300 in this embodiment is basically the same as the optical fiber sensor 100 in the first preferred embodiment, except that the optical fiber sensing unit 302 in this embodiment is different.

The optical fiber sensing unit 302 of this embodiment includes an optical fiber beam splitter 304, a sensing optical fiber 306, a liquid crystal spatial light modulator 308, a first optical fiber collimator 310, a second optical fiber collimator 312, and a third optical fiber collimator 314 , a fourth fiber collimator 316 , a polarizing plate 318 and a first dichroic prism 320 .

The fiber beam splitter 304 is used to split the fundamental mode Gaussian beam (for example, the wavelength is 1550nm) output by the laser 322 into a first beam and a second beam, and the first beam passes through the first fiber collimator 310 and the polarizer in sequence 318 into the liquid crystal spatial light modulator 308 . The first light beam becomes parallel light after passing through the first fiber collimator 310 . Afterwards, the first light beam enters the liquid crystal spatial light modulator 308 through the polarizer 318 .

The liquid crystal spatial light modulator 308 is used for modulating the first beam into an orbital angular momentum beam and transmitting the orbital angular momentum beam to the third fiber collimator 314 . For example, the liquid crystal spatial light modulator 308 modulates the first beam into an L-order orbital angular momentum beam. In this embodiment, the liquid crystal spatial light modulator 308 is a reflective liquid crystal spatial light modulator. The liquid crystal spatial light modulator reflects 308 the OAM beam to a third fiber collimator 314 .

The third fiber collimator 314 is connected to the sensing fiber 306 and used for coupling the OAM beam to the sensing fiber 306 .

The sensing fiber 306 is connected to the third fiber collimator 314 and the fourth fiber collimator 316, and is used to transmit the orbital angular momentum beam from the third fiber collimator 314 to the fourth fiber collimator 316. In this embodiment, the sensing optical fiber 306 is an orbital angular momentum optical fiber, and the orbital angular momentum optical fiber 306 sequentially includes: a core layer, an annular region arranged around the core layer and doped with a co-dopant, and an annular region arranged on the cladding around the annular region.

As a further preference, the material of the core layer is pure quartz, air or quartz doped with co-dopants. The co-dopants include one of fluorine and phosphorus compounds.

As a further preference, the co-dopant includes germanium.

As a further preference, the diameter of the core layer is 500nm-6000nm.

As a further preference, the thickness of the annular region doped with the co-dopant is 500nm˜6000nm.

The fourth fiber collimator 316 is used to transmit the OAM beam to the first dichroic prism 320 .

The second optical fiber collimator is connected with the optical fiber beam splitter and used to transmit the second light beam to the first beam splitting prism. In this embodiment, the second fiber collimator 312 is connected to the fiber splitter 304 through a transmission fiber 324, and the transmission fiber 324 can be a standard single-mode fiber or a multi-mode fiber, such as a G.652 standard single-mode fiber.

The first dichroic prism 320 is used for forming the interference beam from the orbital angular momentum beam and the second beam and outputting the interference beam to the beam expander 326 .

During the experiment, the liquid crystal spatial light modulator 308 modulates the first light beam into an L=1-order orbital angular momentum beam, and is coupled to the sensing fiber 306 for transmission through the third fiber collimator 314, and then passed through the fourth fiber collimator 316 emerge and transmit through the first dichroic prism 320 . The second light beam interferes with the parallel orbital angular momentum beam in the first dichroic prism 320, and the interfering beam becomes beam expander light through the beam expander 326. The sub-interference beam and the second sub-interference beam are respectively received by the fifth fiber collimator 330 and the sixth fiber collimator 332 , and the received optical power is measured by the optical power meter 334 . In this experiment, the transmission fiber 324 is a G.652 standard single-mode fiber, the core layer of the sensing fiber 306 is pure silica, the diameter of the core layer is 1500nm, the annular region is doped with germanium, and the thickness of the annular region is 2000nm. FIG. 8 is a cross-sectional view of the orbital angular momentum fiber 306 observed by an optical microscope. For other experimental processes of the optical fiber sensor 300 in this embodiment, reference may be made to the specific experimental process of the optical fiber sensor in the above embodiment, which will not be described in detail here.

To sum up, in the above-mentioned optical fiber sensor 300, the optical fiber sensing unit 302 divides the fundamental mode Gaussian beam into two beams and outputs an interference beam, and the measurement unit measures the optical power change value of the two interference beams. In the subsequent processing process, the The change value of the optical power can be used to calculate the change amount of the optical path difference, and then realize the function of the sensor.

Referring to FIG. 9 , a fourth preferred embodiment of the present invention provides a fiber optic sensor 400 . The optical fiber sensor 400 in this embodiment is basically the same as the optical fiber sensor 100 in the first preferred embodiment, except that the optical fiber sensing unit 402 in this embodiment is different.

The optical fiber sensing unit 402 of this embodiment includes an optical fiber beam splitter 404, a sensing optical fiber 406, a liquid crystal spatial light modulator 408, a first optical fiber collimator 410, a second optical fiber collimator 412, and a third optical fiber collimator 414 , a fourth fiber collimator 416 , a polarizing plate 418 and a first dichroic prism 420 .

The fiber beam splitter 404 is used to split the fundamental mode Gaussian beam (for example, the wavelength is 1550nm) output by the laser 422 into a first beam and a second beam, and the first beam passes through the first fiber collimator 410 and the polarizer in sequence 418 into the liquid crystal spatial light modulator 408 . The first light beam becomes parallel light after passing through the first fiber collimator 410 . Afterwards, the first light beam enters the liquid crystal spatial light modulator 408 through the polarizer 418 .

The liquid crystal spatial light modulator 408 is used for modulating the first beam into an orbital angular momentum beam and transmitting the orbital angular momentum beam to the third fiber collimator 414 . For example, the liquid crystal spatial light modulator 408 modulates the first beam into an L-order orbital angular momentum beam. In this embodiment, the liquid crystal spatial light modulator 408 is a transmissive liquid crystal spatial light modulator. The liquid crystal spatial light modulator 408 transmits the OAM beam to the third fiber collimator 414 .

The third fiber collimator 414 is connected to the sensing fiber 406 and used for coupling the OAM beam to the sensing fiber 406 .

The sensing fiber 406 is connected to the third fiber collimator 414 and the fourth fiber collimator 416, and is used to transmit the orbital angular momentum beam from the third fiber collimator 414 to the fourth fiber collimator 416. In this embodiment, the sensing optical fiber 406 is an orbital angular momentum optical fiber, and the orbital angular momentum optical fiber 406 sequentially includes: a core layer, an annular region arranged around the core layer and doped with a co-dopant, and an annular region arranged on the cladding around the annular region.

As a further preference, the material of the core layer is pure quartz, air or quartz doped with co-dopants. The co-dopants include one of fluorine and phosphorus compounds.

As a further preference, the co-dopant includes germanium.

As a further preference, the diameter of the core layer is 500nm-6000nm.

As a further preference, the thickness of the annular region doped with the co-dopant is 500nm˜6000nm.

The fourth fiber collimator 416 is used to transmit the OAM beam to the first dichroic prism 420 .

The second fiber collimator 412 is connected to the fiber beam splitter 404 and is used to transmit the second light beam to the first beam splitting prism 420 . In this embodiment, the second fiber collimator 412 is connected to the fiber splitter 404 through a transmission fiber 424, and the transmission fiber 424 can be a standard single-mode fiber or a multi-mode fiber, such as a G.652 standard single-mode fiber.

The first dichroic prism 420 is used for forming an interference beam from the OAM beam and the second beam and outputting the interference beam to the beam expander 426 .

The specific experimental process of the optical fiber sensor 400 in this embodiment can refer to the experimental process of the optical fiber sensor in the above embodiment, and will not be elaborated here.

To sum up, in the above-mentioned optical fiber sensor 400, the optical fiber sensing unit 402 divides the fundamental mode Gaussian beam into two beams and outputs an interference beam, and the measurement unit measures the optical power change value of the two interference beams. In the subsequent processing process, the The change value of the optical power can be used to calculate the change amount of the optical path difference, and then realize the function of the sensor.

In the description of this specification, reference to the terms "one embodiment", "some embodiments", "exemplary embodiments", "example", "specific examples", or "some examples" etc. A specific feature, structure, material, or characteristic described in an embodiment or an example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the described specific features, structures, materials or characteristics may be combined in any suitable manner in any one or more embodiments or examples.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the invention is defined by the claims and their equivalents.

Claims (9)

1. A kind of 1. fibre optical sensor based on light beam orbit angular momentum, it is characterised in that including laser, Fibre Optical Sensor unit, Beam expander and measuring unit, the light path for the light that the Fibre Optical Sensor unit, the beam expander and the measuring unit export along the laser It is sequentially placed；

   The laser is used to export fundamental-mode gaussian beam；

   The Fibre Optical Sensor unit is used to the fundamental-mode gaussian beam being divided into the first light beam and the second light beam, by first beam modulation Into orbital angular momentum light beam, and form interfering beam using second light beam and the orbital angular momentum light beam and export the interference light Beam is to the beam expander；

   The beam expander is used to be enlarged the interfering beam；

   The measuring unit is used to that the first sub- interfering beam and the second sub- interference light will to be divided into by the interfering beam of the beam expander Beam, measure the second luminous power corresponding to the first luminous power corresponding to the first sub- interfering beam and the second sub- interfering beam and obtain Obtain first luminous power and the changing value of second luminous power；

   The Fibre Optical Sensor unit includes fiber optic splitter, sensor fibre, LCD space light modulator, the first optical fiber collimator, the Two optical fiber collimators, polarizer and the first Amici prism；

   The fiber optic splitter is used to the fundamental-mode gaussian beam being divided into first light beam and second light beam, and first light beam is successively Enter the LCD space light modulator by first optical fiber collimator, the polarizer and first Amici prism, the liquid crystal is empty Between optical modulator be used to first beam modulation into the orbital angular momentum light beam and being sent to first Amici prism；

   The sensor fibre connects the fiber optic splitter and second optical fiber collimator, and for by second light beam be sent to this Two optical fiber collimators, second optical fiber collimator are used to second light beam being sent to first Amici prism；

   First Amici prism is used to forming the interfering beam and exporting this orbital angular momentum light beam and second light beam to do Light beam is related to the beam expander；

   The measuring unit includes the second Amici prism, the 3rd Amici prism, the 5th optical fiber collimator, six fiberses collimater, taken the photograph As device and light power meter；

   Second Amici prism is used for reflection correction light to the camera device, and is transmitted through the interfering beam of the beam expander extremely 3rd Amici prism；

   The camera device is used to be imaged using the correction light for correcting the 5th optical fiber collimator and the six fiberses The position of collimater；

   3rd Amici prism be used for by by the beam expander the interfering beam be divided into the first sub- interfering beam and this second Sub- interfering beam, and the first sub- interfering beam is transmitted through the 5th optical fiber collimator, and the second sub- interfering beam is anti- It is incident upon the six fiberses collimater；

   5th optical fiber collimator is used to the first sub- interfering beam being sent to the light power meter；

   The six fiberses collimater is used to the second sub- interfering beam being sent to the light power meter；

   The light power meter is used to measure the first luminous power corresponding to the first sub- interfering beam and the second sub- interfering beam is corresponding The second luminous power and obtain first luminous power and the changing value of second luminous power；

   The fibre optical sensor includes correction light source, and the correction is arranged on the light inputting end of second optical fiber collimator with light source, should Correction light source is used to launch the correction light to second Amici prism.
2. A kind of 2. fibre optical sensor based on light beam orbit angular momentum, it is characterised in that including laser, Fibre Optical Sensor unit, Beam expander and measuring unit, the light path for the light that the Fibre Optical Sensor unit, the beam expander and the measuring unit export along the laser It is sequentially placed；

   The laser is used to export fundamental-mode gaussian beam；

   The Fibre Optical Sensor unit is used to the fundamental-mode gaussian beam being divided into the first light beam and the second light beam, by first beam modulation Into orbital angular momentum light beam, and form interfering beam using second light beam and the orbital angular momentum light beam and export the interference light Beam is to the beam expander；

   The beam expander is used to be enlarged the interfering beam；

   The measuring unit is used to that the first sub- interfering beam and the second sub- interference light will to be divided into by the interfering beam of the beam expander Beam, measure the second luminous power corresponding to the first luminous power corresponding to the first sub- interfering beam and the second sub- interfering beam and obtain Obtain first luminous power and the changing value of second luminous power；

   The Fibre Optical Sensor unit includes fiber optic splitter, sensor fibre, LCD space light modulator, the first optical fiber collimator, the Two optical fiber collimators, polarizer and the first Amici prism；

   The fiber optic splitter is used to the fundamental-mode gaussian beam being divided into first light beam and second light beam, and first light beam is successively Enter the LCD space light modulator by first optical fiber collimator and the polarizer, the LCD space light modulator is used for will First beam modulation is into the orbital angular momentum light beam and is sent to first Amici prism；

   The sensor fibre connects the fiber optic splitter and second optical fiber collimator, and for by second light beam be sent to this Two optical fiber collimators, second optical fiber collimator are used to second light beam being sent to first Amici prism；

   First Amici prism is used to forming the interfering beam and exporting this orbital angular momentum light beam and second light beam to do Light beam is related to the beam expander；

   The measuring unit includes the second Amici prism, the 3rd Amici prism, the 5th optical fiber collimator, six fiberses collimater, taken the photograph As device and light power meter；

   Second Amici prism is used for reflection correction light to the camera device, and is transmitted through the interfering beam of the beam expander extremely 3rd Amici prism；

   The camera device is used to be imaged using the correction light for correcting the 5th optical fiber collimator and the six fiberses The position of collimater；

   3rd Amici prism be used for by by the beam expander the interfering beam be divided into the first sub- interfering beam and this second Sub- interfering beam, and the first sub- interfering beam is transmitted through the 5th optical fiber collimator, and the second sub- interfering beam is anti- It is incident upon the six fiberses collimater；

   5th optical fiber collimator is used to the first sub- interfering beam being sent to the light power meter；

   The six fiberses collimater is used to the second sub- interfering beam being sent to the light power meter；

   The light power meter is used to measure the first luminous power corresponding to the first sub- interfering beam and the second sub- interfering beam is corresponding The second luminous power and obtain first luminous power and the changing value of second luminous power；

   The fibre optical sensor includes correction light source, and the correction is arranged on the light inputting end of second optical fiber collimator with light source, should Correction light source is used to launch the correction light to second Amici prism.
3. A kind of 3. fibre optical sensor based on light beam orbit angular momentum, it is characterised in that including laser, Fibre Optical Sensor unit, Beam expander and measuring unit, the light path for the light that the Fibre Optical Sensor unit, the beam expander and the measuring unit export along the laser It is sequentially placed；

   The laser is used to export fundamental-mode gaussian beam；

   The Fibre Optical Sensor unit is used to the fundamental-mode gaussian beam being divided into the first light beam and the second light beam, by first beam modulation Into orbital angular momentum light beam, and form interfering beam using second light beam and the orbital angular momentum light beam and export the interference light Beam is to the beam expander；

   The beam expander is used to be enlarged the interfering beam；

   The measuring unit is used to that the first sub- interfering beam and the second sub- interference light will to be divided into by the interfering beam of the beam expander Beam, measure the second luminous power corresponding to the first luminous power corresponding to the first sub- interfering beam and the second sub- interfering beam and obtain Obtain first luminous power and the changing value of second luminous power；

   The Fibre Optical Sensor unit includes fiber optic splitter, sensor fibre, LCD space light modulator, the first optical fiber collimator, the Two optical fiber collimators, the 3rd optical fiber collimator, the 4th optical fiber collimator, polarizer and the first Amici prism；

   The fiber optic splitter is used to the fundamental-mode gaussian beam being divided into first light beam and second light beam, and first light beam is successively Enter the LCD space light modulator by first optical fiber collimator and the polarizer；

   The LCD space light modulator is used for first beam modulation into the orbital angular momentum light beam and by the orbital angular momentum Light beam is sent to the 3rd optical fiber collimator；

   3rd optical fiber collimator connects the sensor fibre, and is used for the orbital angular momentum light beam coupling to the sensor fibre；

   The sensor fibre connects the 3rd optical fiber collimator and the 4th optical fiber collimator, and is used for the orbital angular momentum light beam The 4th optical fiber collimator is sent to, the 4th optical fiber collimator is used to the orbital angular momentum light beam being sent to first light splitting Prism；

   Second optical fiber collimator is connected with the fiber optic splitter and is used to second light beam being sent to first Amici prism；

   First Amici prism is used to forming the interfering beam and exporting this orbital angular momentum light beam and second light beam to do Light beam is related to the beam expander；

   The measuring unit includes the second Amici prism, the 3rd Amici prism, the 5th optical fiber collimator, six fiberses collimater, taken the photograph As device and light power meter；

   Second Amici prism is used for reflection correction light to the camera device, and is transmitted through the interfering beam of the beam expander extremely 3rd Amici prism；

   The camera device is used to be imaged using the correction light for correcting the 5th optical fiber collimator and the six fiberses The position of collimater；

   3rd Amici prism be used for by by the beam expander the interfering beam be divided into the first sub- interfering beam and this second Sub- interfering beam, and the first sub- interfering beam is transmitted through the 5th optical fiber collimator, and the second sub- interfering beam is anti- It is incident upon the six fiberses collimater；

   5th optical fiber collimator is used to the first sub- interfering beam being sent to the light power meter；

   The six fiberses collimater is used to the second sub- interfering beam being sent to the light power meter；

   The light power meter is used to measure the first luminous power corresponding to the first sub- interfering beam and the second sub- interfering beam is corresponding The second luminous power and obtain first luminous power and the changing value of second luminous power；

   The fibre optical sensor includes correction light source, and the correction is arranged on the light inputting end of second optical fiber collimator with light source, should Correction light source is used to launch the correction light to second Amici prism.
4. 4. the fibre optical sensor as described in claim 1 or 3, it is characterised in that the LCD space light modulator is reflection type liquid Brilliant spatial light modulator.
5. 5. fibre optical sensor as claimed in claim 2 or claim 3, it is characterised in that the LCD space light modulator is transmission-type liquid Brilliant spatial light modulator.
6. 6. fibre optical sensor as claimed in claim 3, it is characterised in that the sensor fibre is orbital angular momentum optical fiber, the rail Road angular momentum optical fiber includes successively from inside to outside：

   Sandwich layer, the material of the sandwich layer is pure quartz, air or the quartz mixed with codopant, and the codopant includes fluorine, phosphatization One kind in compound；

   It is arranged on the core layer and includes germanium mixed with the annular region of co-dopant, the co-dopant；And

   It is arranged on the covering of the annular region circumference.
7. 7. fibre optical sensor as claimed in claim 6, it is characterised in that a diameter of 500nm~6000nm of the sandwich layer, the ring The thickness in shape region is 500nm~6000nm.
8. 8. the fibre optical sensor as described in claim any one of 1-3, it is characterised in that the 5th optical fiber collimator and the 6th The position of optical fiber collimator relative to the interfering beam by the beam expander on same circumference, and the 5th optical fiber collimator Meet with six fiberses collimater relative to the angle in the circumference center of circleWherein n is positive integer, L It is the exponent number of the orbital angular momentum light beam and is integer.
9. 9. fibre optical sensor as claimed in claim 1 or 2, it is characterised in that the sensor fibre is standard single-mode fiber or more Mode fiber.