Sensing optical signal 90-degree turning and shaping method and sensing optical signal 90-degree turning and shaping device

Abstract

The invention discloses a 90-degree turning and shaping method and device for sensing optical signals, and belongs to the technical field of optical fiber pressure sensing. According to the method, the end face of the transmission optical fiber is subjected to beveling processing and plated with the high-reflection film to form an optical path turning and reflecting face, a traditional discrete prism is replaced, the structure integrates the turning function and the optical function of a lens set through the optical fiber end face, meanwhile, the problems of the size bottleneck of the discrete prism and bending loss of an all-optical-fiber structure are solved, and the optical fiber transmission efficiency is improved. The long-term stability and signal integrity of the optical system are guaranteed, and the pressure of the closed space is reliably measured. The device is mainly composed of a transmission optical fiber, a packaging shell, a shaping lens and a pressure sensitive structure. An inclined plane reflection structure is machined at the end, located in a probe, of the transmission optical fiber. The packaging shell is used for accommodating and fixing the optical assembly; and the shaping lens is fixedly arranged in a light path in the packaging shell. The compactness of the structure of the optical fiber pressure sensor can be remarkably improved.

Description

Technical Field

[0001] This invention relates to a method and apparatus for shaping optical signals by refraction, specifically to a fiber optic pressure sensor structure with 90-degree optical signal refraction, belonging to the field of fiber optic pressure sensing technology. Background Technology

[0002] The fiber optic Fabry-Perot (FP) pressure sensor is a fiber optic sensor that measures pressure using the FP interferometry principle. Its working principle is as follows: the light signal undergoes two reflections within the sensor cavity, creating interference. When external pressure is applied to the sensor, the change in cavity length leads to a change in wavelength, which can then be used to calculate the magnitude of the pressure signal. The technical characteristics of the fiber optic FP pressure sensor include high sensitivity, the ability to detect minute pressure changes, good temperature compensation performance, and superior resistance to electromagnetic interference.

[0003] In current fiber optic FP pressure sensing technology, both diaphragm-based and all-fiber optic systems are significantly limited by their physical dimensions when used in confined spaces. All-fiber structures are constrained by the minimum achievable length of the hollow capillary. When measuring in confined spaces, to meet the sensor size requirements, the fiber is often bent and routed to reduce the sensor size, but this leads to a sharp attenuation of transmitted optical signal energy and a decrease in the system's signal-to-noise ratio. Diaphragm-based structures are limited by their packaging units, and their radial and axial dimensions are difficult to further reduce with current technology. The problems caused by the contradiction between size and performance directly affect the reliability, measurement accuracy, and versatility of the sensing system, becoming a key common bottleneck restricting the large-scale engineering application of fiber optic FP pressure sensors in high-end miniaturized equipment and confined spaces.

[0004] Researchers have already begun miniaturizing fiber optic FP pressure sensors. Wang Ruinan et al. proposed a Fabry-Perot fiber optic pressure sensor based on MEMS micro / nano fabrication technology. This sensor uses a direct bonding method between a sensitive diaphragm and a glass substrate to form a micrometer-scale FP cavity. A through-hole in the glass substrate allows for vertical alignment and insertion of the single-mode fiber. The fiber end face and the inner surface of the diaphragm directly form an interference cavity. However, this structure cannot meet the measurement requirements in confined spaces. Large-angle bending leads to a sharp increase in optical energy loss during fiber transmission, resulting in decreased demodulation accuracy. Application number CN201910880584 proposes a miniature diaphragm-type fiber optic end FP pressure sensor. This sensor fuses an optical fiber and a hollow tubular structure of the same diameter as the fiber together, then fixes a pressure-sensitive diaphragm of the same diameter as the fiber to the other end face of the hollow tube. This sensor has a compact structure, with dimensions similar to the fiber diameter. However, in confined spaces, this also results in an excessively large bending radius of the transmission fiber, exacerbating energy loss and leading to inaccurate demodulation results. Sun Xiaojie et al. proposed a fiber optic path folding sensing probe based on a prism and collimating lens. The transmission fiber is placed close to the collimating lens, and the collimated optical signal is then folded by the prism, achieving optical path folding while avoiding fiber bending. However, the right-angle prism used has a significant volume, and the two optical fibers must maintain sufficient lateral spacing to accommodate the prism structure, directly limiting the compression of the probe's radial dimensions. Furthermore, the complex assembly relationship between the prism and the two collimating lens groups not only increases the structural size but also introduces alignment error risks, hindering deployment and stable application in extremely confined spaces.

[0005] In existing technologies, there are two main approaches to pressure measurement in confined spaces, both of which have inherent bottlenecks: First, the scheme based on discrete prisms to achieve optical path folding is limited by the physical size of the prisms (typically with a side length ≥1mm) and the minimum installation spacing of side-by-side optical fibers. This makes it difficult to compress the radial diameter of the probe to below 3mm, preventing its radial placement into extremely confined spaces with an inner diameter ≤2mm. Second, to circumvent the aforementioned size limitations, an all-fiber structure using capillary tubes fused to transmission fibers is employed. While this allows for probe miniaturization, it requires bending the transmission fiber at the sensor's rear end with a small radius to accommodate the confined space. This introduces significant bending losses, leading to a sharp attenuation of the transmitted optical signal energy and a decrease in the system's signal-to-noise ratio and demodulation accuracy. These problems collectively restrict the reliable application of fiber optic pressure sensors in high-end miniaturized equipment and confined spaces. Summary of the Invention

[0006] To address the problems of excessive energy loss and signal quality degradation caused by fiber optic bending in confined spaces in existing technologies, this invention aims to provide a method and apparatus for 90-degree refraction and shaping of sensing optical signals. By obliquely cutting and depositing a high-reflectivity film on the end face of the transmission fiber, a refraction and reflection surface is formed, replacing the traditional discrete prism. This structure integrates the refraction function with the optical function of the lens group through the fiber end face, overcoming the size limitations of discrete prisms and the bending loss problems of all-fiber structures. While ensuring the long-term stability and signal integrity of the optical system, it enables reliable measurement in confined spaces inaccessible by traditional technologies. This invention significantly improves the compactness of the 90-degree refraction and shaping device for sensing optical signals.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] This invention discloses a method for 90-degree refraction and shaping of sensing optical signals. By obliquely cutting and depositing a high-reflectivity film on the end face of the transmission optical fiber, a refraction and reflection surface is formed, replacing the traditional discrete prism to form a shaping lens group. This optimizes the probe's radial diameter to below 1.5 mm, thus enabling it to adapt to curved channels with an inner diameter ≥ 1.8 mm. The light-emitting optical surface of the shaping lens group and the pressure-sensitive diaphragm directly constitute a Fabry-Perot interferometer cavity, giving the lens group both beam shaping and interference sensing functions, enabling pressure measurement in confined spaces.

[0009] This invention discloses a 90-degree refraction and shaping device for sensing optical signals, used to implement the aforementioned 90-degree refraction and shaping method for sensing optical signals. The device mainly comprises a transmission optical fiber, a housing, a pressure-sensitive structure, a shaping lens, and a pressure-sensitive diaphragm. The transmission optical fiber is located inside the probe, and its end is processed with an oblique reflective structure. The housing is used to accommodate and fix the optical components. The shaping lens is fixedly disposed in the optical path inside the housing. The pressure-sensitive structure includes a pressure-sensitive diaphragm, which is disposed opposite to the optical surface of the shaping lens. The oblique reflective structure refracts the incident light path by 90 degrees and guides it to the shaping lens; the light-emitting surface of the shaping lens and the pressure-sensitive diaphragm form a FP interference cavity.

[0010] Furthermore, the end bevel of the transmission optical fiber is preferably a 45-degree bevel, and its surface is coated with a metal or dielectric high-reflectivity film to achieve efficient optical path deflection.

[0011] Furthermore, the shaping lens group preferably uses an aspherical lens or a cemented doublet lens group composed of positive and negative lenses to effectively correct the aberrations introduced by the folding of the inclined plane and ensure that the output beam has good parallelism and beam uniformity.

[0012] Furthermore, the light-emitting optical surface of the shaping lens group serves as the fixed reflective surface of the FP interferometer cavity. This surface may be coated with a partial reflective film to form an optimized FP interferometer cavity structure with the pressure-sensitive diaphragm.

[0013] Furthermore, the transmission optical fiber, shaping lens group, and pressure-sensitive diaphragm are integrated and fixed by a high-precision packaging shell to ensure the relative position stability between each optical element, thereby improving the reliability and long-term stability of the entire sensor structure.

[0014] Furthermore, the encapsulation housing is provided with a fixing groove structure for precisely positioning the shaping lens.

[0015] Furthermore, the pressure-sensitive structure is sealed to the encapsulation housing using a high-temperature adhesive.

[0016] Furthermore, the transmission optical fiber, shaping lens, and pressure-sensitive structure are arranged sequentially along the optical path within the encapsulation housing to form an integrated sensing probe structure.

[0017] Furthermore, the relative positions of the inclined reflective structure, the shaping lens, and the pressure-sensitive structure allow the light signal to be refracted and shaped before being incident perpendicularly onto the pressure-sensitive diaphragm.

[0018] Beneficial effects:

[0019] 1. The present invention discloses a method and apparatus for 90-degree refraction and shaping of a sensing optical signal. By integrating the optical path refraction function into the end face of the optical fiber, replacing independent reflector or prism elements, an optical path refraction and reflection surface is formed, replacing the traditional discrete prism. This allows the radial diameter of the probe to be optimized to below 1.5mm, thereby enabling it to adapt to curved channels with an inner diameter ≥1.8mm. This significantly simplifies the internal structure of the sensor probe, achieving a smaller size while improving the product's spatial adaptability.

[0020] 2. The present invention discloses a method and apparatus for 90-degree refraction and shaping of a sensing optical signal. The shaping lens used has the dual functions of beam shaping and optical sensing, which can reduce the energy loss introduced by beam divergence and aberration, and is conducive to improving the quality of the optical signal and the reliability of the system in long-term operation.

[0021] 3. The present invention discloses a method and apparatus for 90-degree refraction and shaping of sensing optical signals. Based on the beneficial effects 1 and 2, it can overcome the size bottleneck of discrete prisms and the bending loss problem of all-fiber structures. While ensuring the long-term stability and signal integrity of the optical system, it can also achieve reliable pressure measurement of closed spaces that cannot be reached by traditional technology by beveling and coating the end face of the transmission fiber with a high-reflectivity film, and radially inserting the sensor into the target space in the form of a rigid straight probe. Pressure measurement is performed through the internally integrated 90° optical path refraction. Attached Figure Description

[0022] Figure 1 This is a cross-sectional structural schematic diagram of an embodiment of a 90-degree refraction and shaping device for sensing optical signals according to the present invention;

[0023] Figure 2 This invention uses a double cemented lens group as an alternative embodiment of the shaping lens;

[0024] Among them, 1-transmission optical fiber, 2-encapsulation shell, 3-transmission optical signal, 4-fixing groove, 5-shaping lens, 6-pressure sensitive diaphragm, 7-pressure sensitive structure, 8-shaping beam, and 9-doublet lens. Detailed Implementation

[0025] To better illustrate the purpose and advantages of the present invention, the invention will be further described below in conjunction with the accompanying drawings and examples.

[0026] Example 1:

[0027] like Figure 1 As shown, this embodiment discloses a 90-degree optical signal refraction and shaping device, including a transmission optical fiber 1, an encapsulation housing 2, a shaping lens 5, a fixing groove 4, a pressure-sensitive diaphragm 6, and a pressure-sensitive structure 7. The components are precisely assembled and integrated within a cylindrical metal or ceramic encapsulation housing 2.

[0028] The transmission optical fiber 1 (such as a single-mode optical fiber) is inserted into the encapsulation housing 2. Its end inside the housing is precisely machined into a 45° bevel, and a high-reflectivity film is coated on the bevel to form an optical path deflection and reflection surface. The optical signal 3 enters from the transmission optical fiber 1 and undergoes a 90° optical path deflection after reaching the beveled reflection surface.

[0029] The refracted light signal immediately enters the shaping lens 5. In this embodiment, the shaping lens 5 is an aspherical lens, which is fixedly installed in a preset lens fixing slot inside the encapsulation housing 2. It can correct and collimate the refracted light signal to produce a shaped beam 8 with good parallelism and uniform light intensity distribution.

[0030] The shaped beam 8 is directed perpendicularly towards the pressure-sensitive diaphragm 6 within the pressure-sensitive structure 7. The pressure-sensitive structure 7 is sealed to the encapsulation housing 2 using high-temperature adhesive. The pressure-sensitive diaphragm 6 and the light-emitting surface of the shaping lens 5 are precisely parallel and opposite to each other, together forming an FP interference cavity. This surface of the shaping lens 5 serves as the fixed reflecting surface of the interference cavity and can be coated with a thin film of appropriate reflectivity to optimize the interference effect.

[0031] like Figure 2As shown, as another implementation, the difference between this embodiment and Embodiment 1 is that a cemented doublet lens 9 is used instead of a single aspherical lens 5 as the shaping lens group. This lens group consists of a positive lens and a negative lens, which can more effectively correct aberrations, especially in situations requiring a larger working distance or stricter spot quality requirements. The cemented doublet lens 9 is also fixed in the lens fixing groove of the packaging housing 2, and its light-emitting side surface serves as the fixed reflecting surface of the FP interference cavity, forming an interference cavity with the pressure-sensitive diaphragm 6 in the pressure-sensitive structure 7.

[0032] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for 90-degree refraction and shaping of a sensed optical signal, characterized in that: By beveling and depositing a high-reflectivity film on the end face of the transmission optical fiber, a light path refraction and reflection surface is formed, replacing the traditional discrete prism to form a shaping lens group. This optimizes the radial diameter of the probe to below 1.5mm, thus enabling it to adapt to curved channels with an inner diameter ≥1.8mm. The light-emitting optical surface of the shaping lens group and the pressure-sensitive diaphragm directly form a Fabry-Perot interferometer cavity, giving the lens group both beam shaping and interference sensing functions, enabling pressure measurement in confined spaces.

2. A device for 90-degree refraction and shaping of a sensor optical signal, used to implement the method for 90-degree refraction and shaping of a sensor optical signal as described in claim 1, characterized in that: It is mainly composed of a transmission optical fiber (1), a packaging shell (2), a shaping lens (5), and a pressure-sensitive structure (7); the end of the transmission optical fiber (1) located inside the probe is processed with a beveled reflective structure; the packaging shell (2) is used to accommodate and fix the optical components; the shaping lens (5) is fixedly set in the optical path inside the packaging shell (2); The pressure-sensitive structure (7) includes a pressure-sensitive diaphragm (6) which is disposed opposite to the optical surface of the shaping lens (5); the inclined reflective structure folds the incident light path by 90 degrees and guides it to the shaping lens (5); the light-emitting side surface of the shaping lens (5) and the pressure-sensitive diaphragm (6) form an FP interference cavity.

3. The 90-degree refraction and shaping device for sensing optical signals as described in claim 2, characterized in that: The end bevel of the transmission optical fiber (1) is preferably a 45-degree bevel, and its surface is coated with a metal or dielectric high-reflection film for optical path deflection.

4. The 90-degree refraction and shaping device for sensing optical signals as described in claim 2, characterized in that: The shaping lens (5) group is preferably an aspherical lens or a cemented doublet lens group composed of positive and negative lenses, so as to effectively correct the aberrations introduced by the folding of the inclined plane and ensure that the output beam has good parallelism and spot uniformity.

5. The 90-degree refraction and shaping device for sensing optical signals as described in claim 2, characterized in that: The light-emitting optical surface of the shaping lens (5) group serves as the fixed reflective surface of the FP interference cavity. This surface is coated with a partial reflective film to form an optimized FP interference cavity structure with the pressure-sensitive diaphragm (6).

6. The 90-degree refraction and shaping device for sensing optical signals as described in claim 2, characterized in that: The transmission optical fiber (1), the shaping lens (5) group and the pressure-sensitive diaphragm (6) are integrated and fixed by a high-precision encapsulation housing (2) to ensure the relative position stability between each optical element.

7. The 90-degree refraction and shaping device for sensing optical signals as described in claim 2, characterized in that: The encapsulation housing (2) has a fixing groove structure (4) inside for precisely positioning the shaping lens (5).

8. The 90-degree refraction and shaping device for sensing optical signals as described in claim 2, characterized in that: The pressure-sensitive structure (7) is sealed to the encapsulation housing (2) by a high-temperature adhesive.

9. The 90-degree refraction and shaping device for sensing optical signals as described in claim 2, characterized in that: The transmission optical fiber (1), the shaping lens (5), and the pressure-sensitive structure (7) are arranged sequentially along the optical path within the encapsulation housing (2) to form an integrated sensing probe structure.

10. The 90-degree refraction and shaping device for sensing optical signals as described in claim 2, characterized in that: The relative positions of the inclined reflective structure, the shaping lens (5), and the pressure-sensitive structure (7) allow the light signal to be refracted and shaped before being incident perpendicularly onto the pressure-sensitive diaphragm (6).

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