A circular polarization optical fiber polarizer and an optical fiber sensing system including the same

Abstract

The present invention provides a circular polarization fiber polarizer and an optical fiber sensing system including the circular polarization fiber polarizer, wherein the circular polarization fiber polarizer includes a packaging shell and a linear polarization fiber collimator, a crystal wave plate and a circular polarization fiber collimator arranged in sequence along the light propagation direction inside the packaging shell; the crystal wave plate is an achromatic crystal wave plate; the slow axis or fast axis of the linear polarization fiber collimator is aligned with the slow axis or fast axis of the crystal wave plate at 45° or ‑45°; the slow axis or fast axis of the circular polarization fiber collimator is aligned with the slow axis or fast axis of the crystal wave plate at 0° or 180°; the linear polarization fiber collimator is connected with a linear polarization-maintaining optical fiber, and the linear polarization-maintaining optical fiber extends to the outside of the packaging shell; the circular polarization fiber collimator is connected with a circular polarization-maintaining optical fiber, and the circular polarization-maintaining optical fiber extends to the outside of the packaging shell. The above scheme of the present application has higher stability and controllability, and the optical fiber sensing system including the circular polarization fiber polarizer has higher precision.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber sensing, and in particular to a circular polarization optical fiber polarizer and an optical fiber sensing system comprising the circular polarization optical fiber polarizer. Background Art

[0002] λ / 4 wave plates are widely used in fiber optic sensing systems such as fiber optic current sensors to achieve conversion between linear polarization modes and circular polarization modes of light waves.

[0003] The λ / 4 wave plate used in the existing optical fiber sensing system is usually a λ / 4 optical fiber wave plate, and its access method is as follows: Figure 1 As shown, the linear polarization maintaining optical fiber 11 and the λ / 4 optical fiber wave plate 12, and the λ / 4 optical fiber wave plate 12 and the circular polarization maintaining optical fiber 13 are connected by fusion, thereby forming a first fusion point 121 and a second fusion point 122, which have the following problems in application:

[0004] First, since the optical fiber itself is a stress-sensitive material and can be used for pressure and temperature sensing, the λ / 4 optical fiber wave plate 12 is also very susceptible to mechanical stress and temperature stress during use; second, the phase delay angle of the λ / 4 optical fiber wave plate 12 is related to the central wavelength. When the central wavelength of the sensing optical path drifts, the phase delay angle of the λ / 4 optical fiber wave plate 12 will also change; third, when the λ / 4 optical fiber wave plate 12 is fused with the linear polarization-maintaining optical fiber 11 and the circular polarization-maintaining optical fiber 13, it is impossible to distinguish between the 45° off-axis angle and the -45° off-axis angle, so that the polarity of the optical fiber sensing detection cannot be controlled. The above three factors will affect the accuracy of the optical fiber sensing system. Summary of the invention

[0005] The technical problem to be solved by the present invention is that the existing optical fiber sensing system uses a λ / 4 optical fiber wave plate, which is subject to external stress (temperature stress and mechanical stress) resulting in unstable accuracy. To this end, the present invention proposes a circularly polarized optical fiber polarizer and an optical fiber sensing system including the same.

[0006] In view of the above technical problems, the present invention provides the following technical solutions:

[0007] In a first aspect, the present application provides a circular polarization optical fiber polarizer, comprising:

[0008] A packaging shell and a linear polarization fiber collimator, a crystal wave plate and a circular polarization fiber collimator which are arranged in sequence along the light propagation direction inside the packaging shell; wherein:

[0009] The crystal wave plate is an achromatic crystal wave plate;

[0010] The slow axis or the fast axis of the linear polarization fiber collimator is aligned with the slow axis or the fast axis of the crystal wave plate at 45° or -45°;

[0011] The slow axis or the fast axis of the circular polarization fiber collimator is aligned with the slow axis or the fast axis of the crystal wave plate at 0° or 180°;

[0012] The linear polarization fiber collimator is connected to a linear polarization maintaining fiber, and the linear polarization maintaining fiber extends to the outside of the packaging shell; the circular polarization fiber collimator is connected to a circular polarization maintaining fiber, and the circular polarization maintaining fiber extends to the outside of the packaging shell.

[0013] In some embodiments of the circularly polarized fiber polarizer, the operating wavelength band of the crystal wave plate covers at least the range of (λ±250nm), wherein λ is the central wavelength of the transmitted optical signal.

[0014] In some embodiments of the circularly polarized fiber polarizer, the birefringence phase delay angle of the crystal wave plate is [90°+e], wherein e takes a value in the range of [0°, 30°].

[0015] The circular polarization fiber polarizer described in some embodiments, when the circular polarization fiber polarizer is used to convert linear polarization light into elliptically polarized light or circularly polarized light, one end of the linear polarization maintaining optical fiber is used as the input end;

[0016] When the circular polarization optical fiber polarizer is used to convert elliptically polarized light or circularly polarized light into linearly polarized light, one end of the circular polarization maintaining optical fiber serves as an input end.

[0017] In some embodiments, the circularly polarized fiber polarizer, the distance between the linearly polarized fiber collimator and the crystal wave plate, and the distance between the crystal wave plate and the circularly polarized fiber collimator are all within a set distance range.

[0018] In the circularly polarized fiber polarizer described in some embodiments, the overall length of the packaging shell is less than a set length threshold.

[0019] In some embodiments, the circular polarization fiber polarizer is composed of a fiber collimator and a circular polarization maintaining fiber.

[0020] In a second aspect, the technical solution of the present application provides a fiber optic sensing system comprising the circularly polarized fiber polarizer as described in any one of the first aspects.

[0021] In some embodiments, the optical fiber sensing system is an optical fiber current sensor, and the circularly polarized optical fiber polarizer is used as a λ / 4 wave plate in the optical fiber sensing ring of the optical fiber current sensor.

[0022] In the fiber optic sensing system described in some embodiments, the circularly polarized fiber of the circularly polarized fiber polarizer is a fiber jumper, and the circularly polarized fiber collimator is connected to the circularly polarized maintaining fiber with a reflector via the fiber jumper.

[0023] In some embodiments, when the optical fiber sensing system is an optical fiber current sensor, the packaging shell of the circularly polarized optical fiber polarizer is made of high magnetic permeability material.

[0024] The technical solution of the present invention has the following technical effects compared with the prior art:

[0025] The invention provides a circular polarization fiber polarizer and an optical fiber sensing system including the same, wherein the circular polarization fiber polarizer comprises a packaging shell and a linear polarization fiber collimator, a crystal wave plate and a circular polarization fiber collimator which are arranged in sequence along the light propagation direction inside the packaging shell; the crystal wave plate is an achromatic crystal wave plate; the slow axis or the fast axis of the linear polarization fiber collimator is aligned with the slow axis or the fast axis of the crystal wave plate at 45° or -45°; the slow axis or the fast axis of the circular polarization fiber collimator is aligned with the slow axis or the fast axis of the crystal wave plate at 0° or 180°; the linear polarization fiber collimator is connected with a linear polarization maintaining optical fiber which extends to the outside of the packaging shell; the circular polarization fiber collimator is connected with a circular polarization maintaining optical fiber which extends to the outside of the packaging shell. The above scheme of the present application uses a crystal wave plate and a linear polarization fiber collimator and a circular polarization fiber collimator to realize the conversion of linear polarization light and elliptically polarized light / circularly polarized light in a spatial optical path. Since there is no optical fiber and optical fiber fusion point, it can overcome the shortcomings of the prior art that the optical fiber is easily affected by stress, the phase delay angle changes, and the off-axis angle is uncontrollable. Therefore, the circular polarization fiber polarizer provided in the present scheme has higher stability and controllability, and the optical fiber sensing system including the circular polarization fiber polarizer has higher accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, which will help to understand the objects and advantages of the present invention, wherein:

[0027] Figure 1 It is a schematic diagram of the structure when the optical fiber wave plate is fused in the optical fiber sensing system in the prior art;

[0028] Figure 2 This is a schematic diagram of the structure of a circularly polarized optical fiber polarizer provided in an embodiment of the present application;

[0029] Figure 3 for Figure 2 Schematic diagram of the axis angles of the linear polarization fiber collimator, crystal wave plate and circular polarization fiber collimator in the circular polarization fiber polarizer shown. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0032] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] The present application embodiment provides a circular polarization optical fiber polarizer, such as Figure 2 As shown, it includes a linear polarization fiber collimator 21, a crystal wave plate 22, a circular polarization fiber collimator 23, and a packaging shell 24, a linear polarization maintaining fiber 25, and a circular polarization maintaining fiber 26. Specifically, the linear polarization fiber collimator 21, the crystal wave plate 22, and the circular polarization fiber collimator 23 are sequentially arranged inside the packaging shell 24 along the light propagation direction; wherein the crystal wave plate 22 is an achromatic crystal wave plate; as shown in FIG. Figure 3 As shown, the slow axis or fast axis of the linear polarization fiber collimator 21 is aligned with the slow axis or fast axis of the crystal wave plate 22 at 45° or -45°; the slow axis or fast axis of the circular polarization fiber collimator 23 is aligned with the slow axis or fast axis of the crystal wave plate 22 at 0° or 180°. The linear polarization-maintaining optical fiber 25 connected to the linear polarization fiber collimator 21 extends to the outside of the packaging shell 24; the circular polarization-maintaining optical fiber 26 connected to the circular polarization fiber collimator 23 extends to the outside of the packaging shell 24.

[0035] The circular polarization fiber polarizer provided in the above embodiment can be applied to fiber optic sensor devices, for example, it can be used in the fiber optic sensing ring of the fiber optic current sensor. At this time, the circular polarization fiber polarizer is suitable for a variety of installation methods, such as a fixed fiber optic sensing ring, a flexible winding packaged fiber optic sensing ring, etc. The fiber optic sensing ring made with the circular polarization fiber polarizer can reduce the sensitivity of the fiber optic sensing ring to mechanical stress and temperature stress, and improve the measurement accuracy of the fiber optic current sensor.

[0036] In the circular polarization fiber polarizer, the subtending angle between the linear polarization fiber collimator 21 and the crystal wave plate 22 is 45° or -45°, and the subtending angle between the circular polarization fiber collimator 23 and the crystal wave plate 22 is 0° or 180°. The processing is simple and batch control is easy to achieve. When used in a fiber current sensor, the polarity of the fiber sensing ring can be guaranteed to be consistent. The packaging shell 24 enables the circular polarization fiber polarizer to achieve an integrated packaging design, which is easier to couple with other devices in the fiber sensing system; moreover, the circular polarization fiber polarizer is insensitive to wavelength changes and external environmental stress.

[0037] Combination Figure 3 As shown in the diagram of the axis, when the linear polarized light in the X direction or Y direction enters Figure 2 The circular polarization fiber polarizer shown corresponds to Figure 3 The linear polarized light is shown as an axis diagram 211. After passing through the linear polarization fiber collimator 21, the linear polarized light enters the crystal wave plate 22 at an angle of 45° or -45° and is decomposed into two orthogonal linear polarized lights, corresponding to Figure 3 The deflection result of the linear polarized light is shown as 221. After the two orthogonal linear polarized lights pass through the crystal wave plate 22, a phase delay of [90°+e] is generated.

[0038] When e≠0, the linear polarized light is converted into elliptically polarized light. After the elliptically polarized light passes through the circularly polarized fiber collimator 23, it corresponds to Figure 3 The circularly polarized light is aligned with the axis as shown in the result 231, enters the circular polarization maintaining optical fiber 26, and is transmitted in an elliptically polarized state mode to other optical devices connected to the circular polarization optical fiber polarizer.

[0039] When e=0, the linear polarized light in the X direction or the Y direction enters the circular polarization fiber polarizer, and after passing through the linear polarization fiber collimator 21, the linear polarized light enters the crystal wave plate 22 at an angle of 45° or -45°, and is decomposed into two beams of orthogonal linear polarized light. After the two beams of orthogonal linear polarized light pass through the crystal wave plate 22, a phase delay of 90° is generated, and the linear polarized light is converted into circular polarized light. After passing through the circular polarization fiber collimator 23, the circular polarized light enters the circular polarization maintaining optical fiber 26, and is transmitted in a circular polarization state mode to other optical devices connected to the circular polarization fiber polarizer.

[0040] Further, preferably, when the circular polarization fiber polarizer is used to convert linear polarized light into elliptically polarized light or circularly polarized light, one end of the linear polarization maintaining optical fiber 25 is used as the input end; when the circular polarization fiber polarizer is used to convert elliptically polarized light or circularly polarized light into linear polarized light, one end of the circular polarization maintaining optical fiber 26 is used as the input end. Specifically:

[0041] When e≠0, when the linear polarized light in the X direction enters the circular polarization fiber polarizer from the port of the linear polarization fiber collimator 21, its output is left-handed (or right-handed) elliptically polarized light. At this time, when the linear polarized light in the Y direction enters the circular polarization fiber polarizer from the port of the linear polarization fiber collimator 21, its output is right-handed (or left-handed) elliptically polarized light. Further, when the elliptically polarized light enters the circular polarization fiber polarizer along the port of the circular polarization fiber collimator 23, if the elliptically polarized light can be decomposed into two beams of orthogonal linear polarized light with a phase difference of [90°+e], then these two beams of orthogonal linear polarized light are phase compensated when transmitted in the crystal wave plate 22, so that the phase difference between the two beams of orthogonal linear polarized light becomes 0°, and after synthesis, they become linear polarized light. Therefore, at this time, the output from the port of the linear polarization fiber collimator 21 is a linear polarized light; if the elliptically polarized light can be decomposed If the two orthogonal linear polarized lights have a phase difference not equal to [90°+e], the two orthogonal linear polarized lights cannot obtain complete phase compensation when transmitting in the crystal wave plate 22. At this time, the polarized light output from the port of the linear polarization fiber collimator 21 can still be regarded as the synthesis of two orthogonal linear polarized lights. If the phase difference of the two orthogonal linear polarized lights is close to 0°, the amplitudes of the two orthogonal linear polarized lights emitted from the port of the linear polarization fiber collimator 21 are also quite different, and the amplitude of one linear polarized light is much larger than that of the other.

[0042] When e=0, when the linear polarized light in the X direction enters the circular polarized fiber polarizer from the port of the linear polarized fiber collimator 21, its output is left-handed (or right-handed) circular polarized light, and at this time, when the linear polarized light in the Y direction enters the circular polarized fiber polarizer from the port of the linear polarized fiber collimator 21, its output is right-handed (or left-handed) circular polarized light. When the circular polarized light enters the circular polarized fiber polarizer from the port of the circular polarized fiber collimator 23 in the reverse direction, since the circular polarized light is the synthesis of two orthogonal linear polarized lights with a phase difference of 90°, the circular polarized light can be decomposed into two orthogonal linear polarized lights with a phase difference of 90°, and the two beams of orthogonal linear polarized light are phase compensated when transmitted in the crystal wave plate 22, so that the phase difference between the two beams of orthogonal linear polarized light becomes 0° or 180°, and becomes linear polarized light after synthesis, so what is emitted from the port of the linear polarized fiber collimator 21 is linear polarized light. Furthermore, when the phase difference between the two orthogonal linearly polarized lights becomes 0° and 180°, the synthesized linearly polarized lights in these two cases are also orthogonal to each other.

[0043] In specific applications, when the left-handed circularly polarized light enters the port of the circularly polarized optical fiber collimator 23 in reverse, if the phase difference of the two orthogonal linear polarized lights after the decomposition of the left-handed circularly polarized light becomes 0° after passing through the crystal wave plate 22, then when the right-handed circularly polarized light enters the port of the circularly polarized optical fiber collimator 23 in reverse, the phase difference of the two orthogonal linear polarized lights after the decomposition thereof will also become 180° after passing through the crystal wave plate 22. Similarly, when the right-handed circularly polarized light enters the port of the circularly polarized optical fiber collimator 23 in reverse, if the phase difference of the two orthogonal linear polarized lights after the decomposition of the right-handed circularly polarized light becomes 0° after passing through the crystal wave plate 22, then when the left-handed circularly polarized light enters the port of the circularly polarized optical fiber collimator 23 in reverse, the phase difference of the two orthogonal linear polarized lights after the decomposition thereof will also become 180° after passing through the crystal wave plate 22. Furthermore, when the left-handed circularly polarized light and the right-handed circularly polarized light simultaneously enter the port of the circularly polarized optical fiber collimator 23 in opposite directions, two beams of orthogonal linearly polarized light are output from the port of the linearly polarized optical fiber collimator 21 .

[0044] Preferably, in the circularly polarized fiber polarizer described in some schemes, the working band of the crystal wave plate 22 covers at least the range of (λ±250nm), wherein λ is the central wavelength of the transmitted optical signal. In this way, it can be ensured that the crystal wave plate 22 is insensitive to wavelength changes. Among them, the crystal wave plate 22 has an achromatic effect. Birefringence is one of the basic optical properties of optical crystals. When a beam of light passes through a birefringent crystal, it will be decomposed into two orthogonal beams of light. By changing the thickness of the crystal, the phase difference between the two beams of light can be adjusted to prepare a λ / 4 wave plate with different polarization modulation characteristics. Therefore, the thickness of the crystal wave plate 22 described in this scheme can be determined according to the function to be achieved, and it can be obtained by processing using an existing achromatic crystal. In specific implementation, the working band of the crystal wave plate 22 covers the range of (λ±250nm), and it has a wider working wavelength range, which minimizes the impact of wavelength changes.

[0045] Furthermore, in the circularly polarized optical fiber polarizer, the birefringence phase delay angle of the crystal wave plate 22 is [90°+e], wherein e is in the range of [0°, 30°]. The crystal wave plate 22 can adjust the phase difference between the two beams of light, and the range of phase delay can be selected between 90°-120°.

[0046] Preferably, the circular polarization maintaining optical fiber 26 connected to the circular polarization optical fiber collimator is an optical fiber jumper, thereby making it easy to connect and disassemble the circular polarization optical fiber polarizer with other components. When the circular polarization optical fiber polarizer fails, only the circular polarization optical fiber polarizer can be replaced without affecting other components connected thereto.

[0047] The embodiment of the present application also provides a fiber optic sensing system including the circular polarization fiber polarizer described in any of the above solutions. The circular polarization fiber polarizer provided in the embodiment of the present application is an optical integrated device, the key parameters of which are controllable and can be prefabricated in batches, which greatly improves the production efficiency of the fiber optic sensing system, reduces the product manufacturing cycle, and improves the product process consistency.

[0048] Further preferably, the optical fiber sensing system is an optical fiber current sensor, and the circular polarization optical fiber polarizer is used as a λ / 4 wave plate in the optical fiber sensing ring of the optical fiber current sensor. The circular polarization optical fiber polarizer can be applied to the optical fiber sensing ring of the optical fiber current sensor, and is suitable for a variety of installation methods, such as a fixed optical fiber sensing ring and a flexible winding packaged optical fiber sensing ring. The optical fiber sensing ring made with the circular polarization optical fiber polarizer can reduce the sensitivity of the optical fiber sensing ring to mechanical stress and temperature stress, and improve the measurement accuracy of the optical fiber current sensor.

[0049] In specific applications, the fiber optic current sensor consists of a collection module and a fiber optic sensing ring; the polarization-maintaining transmission cable of the collection module is fused with the linear polarization fiber collimator 21 of the circular polarization fiber polarizer at 0°, and the two orthogonal linear polarized lights are uniformly injected into the X-axis (fast axis) and Y-axis (slow axis) of the linear polarization maintaining optical fiber 25, and then enter the linear polarization fiber collimator 21. When the two orthogonal linear polarized lights pass through the λ / 4 achromatic crystal wave plate (i.e., the crystal wave plate 22) at an angle of 45°, they are converted into left-handed and right-handed circularly polarized lights respectively. The two circularly polarized lights enter the circular polarization fiber collimator 22 through the coupling at the end face, and the left-handed and right-handed circularly polarized lights are transmitted in the circular polarization maintaining optical fiber 26 of the circular polarization fiber collimator 22, and are transmitted to the reflector end with the circular polarization maintaining optical fiber through the circular polarization maintaining optical fiber.

[0050] The existing optical fiber wave plates are made of polarization-maintaining optical fiber materials, and their birefringence parameters determine the phase delay angle when making the wave plates. The birefringence parameters of polarization-maintaining optical fibers are related to the wavelength, which causes the phase delay angle of the optical fiber wave plates to be extremely sensitive to wavelength changes. In the circularly polarized optical fiber polarizer of the above embodiment of the present application, a crystal wave plate 22 is used as a wave plate element, which can achieve a stable phase delay angle in a larger wavelength range, so it is not sensitive to wavelength changes. In addition, in the circularly polarized optical fiber polarizer of the present application, the λ / 4 crystal wave plate and the linear polarization optical fiber collimator 21 and the circular polarization optical fiber collimator 22 are spatially coupled and have no direct contact. Therefore, when the optical fibers of the linear polarization optical fiber collimator 21 and the circular polarization optical fiber collimator 22 are subjected to mechanical stress (tension, torsion, bending force) and temperature stress, the crystal wave plate 22 will not be affected. Therefore, the ability of the circularly polarized optical fiber polarizer of the present application to resist mechanical stress and temperature stress is higher than the performance of the optical fiber wave plate, which solves this problem from the perspective of light transmission scheme.

[0051] Furthermore, the circular polarization fiber collimator 23 is composed of a fiber collimator and a circular polarization maintaining fiber. In the present application, the circular polarization pigtail of the circular polarization fiber polarizer is made into a fiber jumper. When the circular polarization fiber polarizer is damaged, only the circular polarization fiber polarizer in the fiber sensing ring can be replaced without replacing the circular polarization maintaining fiber with a reflector. If the circular polarization maintaining fiber with a reflector is damaged, the circular polarization fiber polarizer does not need to be replaced, and only the circular polarization maintaining fiber with a reflector is replaced. This solution can achieve rapid replacement without affecting the product measurement accuracy. This application solution can improve the convenience of fiber sensing ring maintenance and reduce the manufacturer's maintenance cost.

[0052] Preferably, if the optical fiber sensing system is an optical fiber current sensor, the encapsulation shell 24 in the circular polarization optical fiber polarizer is made of high magnetic permeability material, and the so-called high magnetic permeability material refers to a ferromagnetic material with a magnetic permeability of about 100 or more. If the optical fiber sensing system is other detection equipment, the encapsulation shell 24 can also be made of other materials, such as non-magnetic materials, etc., and the selection is made according to the actual situation. In the optical fiber current sensor, the optical fiber sensing ring includes a circular polarization optical fiber polarizer, a reflector, and a circular polarization maintaining optical fiber connecting the two. The circular polarization optical fiber polarizer and the reflector are connected to form a closed point. In order to accurately measure the conductor current in the optical fiber sensing ring, it is required that there is no gap at the closed point to avoid magnetic field leakage. Therefore, in this scheme, the encapsulation shell 24 in the circular polarization optical fiber polarizer is made of high magnetic permeability material, and the reflector is also encapsulated in a high magnetic permeability material shell. The two high magnetic permeability shells are sealed and connected to achieve the effect of no gap at the closed point. Obviously, the above embodiment is only an example for clear explanation, and is not a limitation of the implementation method. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. However, the obvious changes or modifications derived from this are still within the protection scope of the present invention.

Claims

1. A circular polarization optical fiber polarizer, characterized in that: include: A packaging shell and a linear polarization fiber collimator, a crystal wave plate and a circular polarization fiber collimator which are arranged in sequence along the light propagation direction inside the packaging shell; wherein: The crystal wave plate is an achromatic crystal wave plate; The slow axis or the fast axis of the linear polarization fiber collimator is aligned with the slow axis or the fast axis of the crystal wave plate at 45° or -45°; The slow axis or the fast axis of the circular polarization fiber collimator is aligned with the slow axis or the fast axis of the crystal wave plate at 0° or 180°; The linear polarization fiber collimator is connected to a linear polarization maintaining fiber, and the linear polarization maintaining fiber extends to the outside of the packaging shell; the circular polarization fiber collimator is connected to a circular polarization maintaining fiber, and the circular polarization maintaining fiber extends to the outside of the packaging shell; The crystal wave plate, the linear polarization fiber collimator, and the circular polarization fiber collimator are spatially coupled to realize the conversion of linear polarization light and elliptically polarized light / circularly polarized light in the form of a spatial optical path; The packaging shell is made of high magnetic permeability material.

2. The circularly polarized optical fiber polarizer according to claim 1, characterized in that: The operating wavelength band of the crystal wave plate at least covers the range of (λ±250nm), wherein λ is the central wavelength of the transmitted optical signal.

3. The circularly polarized optical fiber polarizer according to claim 1, characterized in that: The birefringence phase delay angle of the crystal wave plate is [90°+e], wherein e takes a value in the interval [0°, 30°].

4. The circularly polarized optical fiber polarizer according to any one of claims 1 to 3, characterized in that: When the circular polarization fiber polarizer is used to convert linear polarized light into elliptically polarized light or circularly polarized light, one end of the linear polarization maintaining fiber serves as an input end; When the circular polarization optical fiber polarizer is used to convert elliptically polarized light or circularly polarized light into linearly polarized light, one end of the circular polarization maintaining optical fiber serves as an input end.

5. The circularly polarized optical fiber polarizer according to claim 4, characterized in that: The distance between the linear polarization fiber collimator and the crystal wave plate and the distance between the crystal wave plate and the circular polarization fiber collimator are both within a set distance range.

6. The circularly polarized optical fiber polarizer according to claim 5, characterized in that: The overall length of the packaging shell is less than a set length threshold.

7. The circularly polarized optical fiber collimator according to claim 1, characterized in that: The circular polarization optical fiber collimator consists of an optical fiber collimator and a circular polarization maintaining optical fiber.

8. An optical fiber sensing system comprising the circular polarization optical fiber polarizer according to any one of claims 1 to 7.

9. The optical fiber sensing system according to claim 8, characterized in that: There are optical signals in both linear polarization state and circular polarization state in the optical path of the optical fiber sensing system, and the optical signals need to be converted between the linear polarization state and the circular polarization state; The circular polarization optical fiber polarizer is used as a λ / 4 wave plate in the optical fiber sensing system to realize the function of converting the optical signal between a linear polarization state and a circular polarization state.

10. The optical fiber sensing system according to claim 9, characterized in that: The optical fiber sensing system is an optical fiber current sensor; The optical fiber sensing ring in the optical fiber current sensor includes the circular polarization optical fiber polarizer, the reflector and the circular polarization maintaining optical fiber connecting the two. The circular polarization optical fiber polarizer and the reflector are connected to form a closed point. The reflector is encapsulated in a shell of a high magnetic permeability material and is sealed and connected to the encapsulation shell of the circular polarization optical fiber polarizer.

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