Speckle wavelength measuring device with miniaturization and strong anti-interference

Abstract

The invention is suitable for the technical field of wavelength measurement, and provides a speckle wavelength measurement device with miniaturization and strong anti-interference, which comprises a single-mode fiber, a dislocation welding multimode fiber, a CCD (Charge Coupled Device) camera and a computer which are sequentially arranged along a light path, the single-mode optical fiber is connected with the dislocation welding multimode optical fiber; the dislocation welding multimode optical fiber is formed by a first short multimode optical fiber and a second short multimode optical fiber through axial dislocation welding. The CCD camera is connected with the dislocation welding multimode optical fiber; and the computer is connected with the CCD camera and is used for processing the speckle pattern acquired by the CCD camera. The device is small in size, and the stability, the anti-interference performance and the resolution ratio of a measurement system can be effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of wavelength measurement technology, and in particular relates to a speckle wavelength measurement device that combines miniaturization and strong anti-interference capabilities. Background Technology

[0002] Laser wavelength, as a reference parameter in optical measurement, plays a central role in fields such as precision metrology, fiber optic communication, spectral analysis, and environmental sensing.

[0003] Traditional wavelength measurement techniques primarily rely on the principle of interferometry, resulting in large, complex optical structures for interferometric wavelength meters. Mainstream interferometers (such as Fizeau and Mach-Zehnder interferometers) require precision optical components (such as wedge-shaped window mirrors, beam splitters, and reference cavity mirrors) and long optical paths. To achieve high accuracy, multiple interferometers are often cascaded, further increasing packaging complexity.

[0004] The rise of speckle wavelength meters in recent years has provided a new path for miniaturization and low cost. Speckle wavelength meters encode wavelengths into speckle patterns through the intermodal dispersion effect of multimode fiber, offering significant advantages such as simple structure and low cost. However, their core problem lies in poor environmental interference resistance. The refractive index and length of multimode fiber are affected by temperature, leading to changes in the speckle pattern. Mechanical vibration alters the phase of fiber modes, causing random shifts in the speckle energy center and reducing measurement repeatability. Summary of the Invention

[0005] The purpose of this invention is to provide a speckle wavelength measurement device that combines miniaturization and strong anti-interference capabilities, thereby addressing the problems mentioned in the background art.

[0006] The present invention is implemented as follows: a speckle wavelength measurement device that combines miniaturization and strong anti-interference includes a single-mode fiber, a staggered fusion spliced ​​multimode fiber, a CCD camera and a computer arranged sequentially along the optical path. The single-mode fiber is connected to the misaligned fusion spliced ​​multimode fiber to receive the incident laser generated by the laser and to transmit the incident laser to the misaligned fusion spliced ​​multimode fiber. The misaligned fusion spliced ​​multimode fiber is formed by axially misaligned fusion splicing of a first short multimode fiber and a second short multimode fiber. It is used to receive incident laser light transmitted through a single-mode fiber and to cause the incident laser light to be scattered at the end face, forming randomly distributed bright and dark spots. The CCD camera is connected to the misaligned fusion spliced ​​multimode fiber and is used to record the speckle pattern formed by incident light passing through the misaligned fusion spliced ​​multimode fiber. The computer is connected to a CCD camera and is used to process the speckle patterns acquired by the CCD camera.

[0007] A further technical solution is that the misaligned welding process is achieved through the following steps: Firstly, a first short multimode fiber and a second short multimode fiber are provided; Then, the coating layers at the ends of the first and second short multimode fibers are stripped using fiber processing tools to obtain a bare fiber area of ​​a predetermined length. Then, a high-purity solvent is used to clean the bare fiber area, and a fiber optic cleaver is used to cut the cleaned fiber end face to form a flat end face that meets the requirements of fusion splicing. Finally, the fusion splicer is operated to create a preset axial offset between the core of the first short multimode fiber and the core of the second short multimode fiber, and then fusion splices them to form a permanent splice with a fixed axial misalignment.

[0008] A further technical solution involves applying a protective coating to the weld joint after the misaligned welding is completed. The coating material is acrylate.

[0009] In a further technical solution, the misaligned fusion spliced ​​multimode optical fiber is encapsulated in a butterfly-shaped encapsulation shell and fixed to the upper surface of the thermally conductive medium by a fixing material; the thermally conductive medium is disposed above the thermoelectric cooler and is in close thermal contact with the thermoelectric cooler.

[0010] In a further technical solution, the total length of the misaligned fusion spliced ​​multimode optical fiber is 0.2m-1m.

[0011] In a further technical solution, the axial offset ranges from 10% to 40% of the core diameter of the first and second short multimode fibers.

[0012] In a further technical solution, the numerical aperture of the first short multimode fiber and the second short multimode fiber is 0.18-0.22.

[0013] This invention provides a speckle wavelength measurement device that combines miniaturization and strong anti-interference capabilities. In use, the incident laser light is provided by the laser source and enters the misaligned fusion spliced ​​multimode fiber 3 via a single-mode fiber 6. As the incident light propagates within the misaligned fusion spliced ​​multimode fiber 3, different modes of light waves are scattered at the end faces. These scattered light waves interfere with each other in space, forming randomly distributed bright and dark spots. The speckle pattern formed by the incident light passing through the misaligned fusion spliced ​​multimode fiber 3 is recorded by a CCD camera 4. The CCD camera 4 transmits the acquired speckle pattern to a computer 5, where the speckle pattern is processed. This device is small in size and can effectively improve the stability, anti-interference capabilities, and resolution of the measurement system. Attached Figure Description

[0014] Figure 1 A schematic diagram of a speckle wavelength measurement device that combines miniaturization and strong anti-interference capabilities, provided in an embodiment of the present invention; Figure 2A schematic diagram of the structure of a misaligned fusion spliced ​​multimode fiber in a speckle wavelength measurement device that combines miniaturization and strong anti-interference capabilities, provided in an embodiment of the present invention; Figure 3 A top view schematic diagram of the package of a speckle wavelength measurement device that combines miniaturization and strong anti-interference capability, provided for an embodiment of the present invention; Figure 4 A side cross-sectional view of the package of a speckle wavelength measurement device that combines miniaturization and strong anti-interference capability, provided in an embodiment of the present invention; Figure 5 The temperature control effect of a speckle wavelength measurement device that combines miniaturization and strong anti-interference capability provided by an embodiment of the present invention; Figure 6 The wavelength measurement results of a speckle wavelength measurement device that combines miniaturization and strong anti-interference capability provided in an embodiment of the present invention; Figure 7 This is a speckle pattern measured by a standard multimode fiber and this device.

[0015] In the attached diagram: 1. First short multimode fiber; 2. Second short multimode fiber; 3. Misaligned fusion spliced ​​multimode fiber; 4. CCD camera; 5. Computer; 6. Single-mode fiber; 7. Butterfly-shaped encapsulation shell; 8. Thermal conductive medium; 9. Fixing material; 10. Thermoelectric cooler. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0017] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0018] like Figure 1 As shown, a speckle wavelength measurement device with miniaturization and strong anti-interference capability is provided in one embodiment of the present invention, including a single-mode fiber 6, a staggered fusion spliced ​​multimode fiber 3, a CCD camera 4 and a computer 5 arranged sequentially along the optical path; The single-mode fiber 6 is connected to the misaligned fusion spliced ​​multimode fiber 3 to receive the incident laser generated by the laser and to transmit the incident laser to the misaligned fusion spliced ​​multimode fiber 3. The misaligned fusion spliced ​​multimode fiber 3 is formed by axially misaligned fusion splicing of the first short multimode fiber 1 and the second short multimode fiber 2. It is used to receive the incident laser transmitted through the single-mode fiber 6 and to cause the incident laser to be scattered at the end face, forming randomly distributed bright and dark spots (i.e. speckle pattern). The CCD camera 4 is connected to the misaligned fusion spliced ​​multimode fiber 3 and is used to record the speckle pattern formed by the incident light passing through the misaligned fusion spliced ​​multimode fiber 3. The computer 5 is connected to the CCD camera 4 and is used to process the speckle pattern acquired by the CCD camera 4.

[0019] In this embodiment of the invention, staggered fusion splicing is used to excite more higher-order modes in the first short multimode fiber 1 and the second short multimode fiber 2, significantly increasing the number of modes transmitted in the output fiber. The more modes there are, the more complex the interference between modes, and the better the randomness of the speckle pattern. The speckle pattern formed on the output end face or in the far field has higher contrast and stronger randomness. The short multimode fiber enhances the anti-interference capability of the system. In use, the incident laser is provided by the laser and enters the staggered fusion spliced ​​multimode fiber 3 through the single-mode fiber 6. When the incident light is transmitted in the staggered fusion spliced ​​multimode fiber 3, the light waves of different modes are scattered at the end face. These scattered light waves interfere with each other in space, forming randomly distributed bright and dark spots. The speckle pattern formed by the incident light passing through the staggered fusion spliced ​​multimode fiber 3 is recorded by the CCD camera 4. The CCD camera 4 transmits the acquired speckle pattern to the computer 5, where the speckle pattern is processed.

[0020] In practice, data is first acquired using a standard laser at a standard temperature. After acquisition, the laser under test is used; the laser light passes through this device and forms a speckle pattern on the CCD camera 4. Due to the phase difference... ,in, This is the wavelength value. The optical path difference; the position, size and shape of each bright and dark spot in the speckle pattern strongly depend on the wavelength value. Therefore, each speckle pattern corresponds to a specific wavelength value. Thus, computer 5 uses an algorithm to analyze and process the speckle pattern to obtain the final wavelength value.

[0021] like Figure 2 As shown, in a preferred embodiment of the present invention, the misaligned welding process is implemented through the following steps: First, a first short multimode fiber 1 and a second short multimode fiber 2 are provided; Then, the coating layers at the ends of the first short multimode fiber 1 and the second short multimode fiber 2 are stripped using fiber processing tools to obtain a bare fiber area of ​​a predetermined length. Then, a high-purity solvent is used to clean the bare fiber area, and a fiber optic cleaver is used to cut the cleaned fiber end face to form a flat end face that meets the requirements of fusion splicing. Finally, the fusion splicer is operated to create a preset axial offset between the core of the first short multimode fiber 1 and the core of the second short multimode fiber 2, and then fusion splices them to form a permanent splice with a fixed axial misalignment.

[0022] In this embodiment of the invention, the alignment reference between the core of the first short multimode fiber 1 and the second short multimode fiber 2 is the core, not the cladding.

[0023] In a preferred embodiment of the present invention, after the misaligned welding is completed, a coating protection operation is performed on the welding point to provide mechanical strength and environmental protection for the welding point.

[0024] In this embodiment of the invention, the coating material may be acrylate, and the refractive index of the coating material should be higher than that of the optical fiber cladding.

[0025] like Figure 3 and Figure 4 As shown, in a preferred embodiment of the present invention, the misaligned fusion spliced ​​multimode optical fiber 3 is encapsulated in a butterfly-shaped encapsulation shell 7 and fixed to the upper surface of the thermally conductive medium 8 by a fixing material 9; the thermally conductive medium 8 is disposed above the thermoelectric cooler 10 and maintains good thermal contact with the thermoelectric cooler 10 to provide effective temperature conduction and control.

[0026] In this embodiment of the invention, a thermistor for temperature monitoring is also provided at the heat-conducting medium 8. The thermistor leads and the leads of the thermoelectric cooler 10 are connected to the pins outside the butterfly-shaped package shell 7 through gold wires, thereby making an electrical connection with the external temperature control circuit. The external temperature control circuit drives the thermoelectric cooler 10 according to the thermistor feedback signal to maintain the temperature stability of the environment where the misaligned fused multimode optical fiber 3 is located.

[0027] In a preferred embodiment of the present invention, the total length of the misaligned fusion spliced ​​multimode optical fiber 3 is 0.2m-1m.

[0028] In a preferred embodiment of the present invention, the axial offset ranges from 10% to 40% of the core diameter of the first short multimode fiber 1 and the second short multimode fiber 2. For example, if the core diameter is 50 μm, the axial offset can be from 5 μm to 20 μm.

[0029] In a preferred embodiment of the present invention, the numerical aperture of the first short multimode fiber 1 and the second short multimode fiber 2 is 0.18-0.22.

[0030] In a preferred embodiment of the present invention, the heat-conducting medium 8 may be ceramic or metal.

[0031] In a preferred embodiment of the present invention, the fixing material 9 may be a UV adhesive.

[0032] The following is a specific embodiment used to verify the effectiveness of this device.

[0033] Two multimode optical fibers with a length of 0.5m (i.e., the first short multimode fiber 1 and the second short multimode fiber 2) were selected, with a core diameter of 105μm and a numerical aperture of 0.22.

[0034] Using a high-precision fiber optic fusion splicer, the end faces of the two multimode fibers are cleaned, and then the two multimode fibers are axially offset and fused together with an offset of 15μm. After splicing, an acrylic coating is applied to protect the splice joint to ensure its mechanical strength and long-term reliability.

[0035] The misaligned fusion spliced ​​multimode optical fiber 3 is fixed on the ceramic thermally conductive medium 8 and installed inside the butterfly-shaped encapsulation shell 7. An integrated thermoelectric cooler 10 and a thermistor, through an external temperature control circuit, stabilize the internal temperature at 25°C ± 0.02°C, achieving a temperature control effect as described above. Figure 5 As shown.

[0036] A tunable laser (tuning range 1350nm-1400nm) was used as the reference light source, and 101 calibration wavelengths were output in 0.5nm steps.

[0037] For each wavelength, a corresponding reference speckle pattern is acquired using CCD camera 4 and stored in the calibration database.

[0038] Connect the laser to be tested to the device and collect its speckle pattern.

[0039] A convolutional neural network (CNN) model (existing technology is used here and will not be elaborated further) is used to calculate the similarity between the speckle pattern to be tested and each reference speckle pattern in the calibration database. , The higher the value, the closer the wavelength to be measured is to the reference wavelength. The closer.

[0040] The wavelength to be measured is calculated using an interpolation algorithm, as shown in the formula: ; in, For similarity, For reference wavelength, The wavelength to be measured, This represents the number of reference wavelength points.

[0041] The results are as follows Figure 6 As shown, when measuring a laser with a known wavelength of 1388.4 nm, the standard deviation of the system output result is 0.00043 nm. This result fully demonstrates that the device provided in this embodiment has high-precision and high-stability wavelength measurement capabilities.

[0042] The test results using ordinary multimode fiber and the test results of this device are processed to calculate the structural similarity index of the acquired speckle patterns. The formula is: ; in, and These represent the reference image and the image to be compared, respectively. yes The average value, yes The average value, yes variance yes variance yes and covariance, and It is a constant used to maintain stability.

[0043] like Figure 7 As shown, from A multi-dimensional quantitative comparison shows that misaligned fusion splicing of multimode optical fibers... Both peak and average values ​​are higher than those of ordinary multimode fiber, combined with The positive correlation between structural fidelity and resolution leads to the conclusion that misaligned fusion spliced ​​multimode fiber outperforms ordinary multimode fiber in terms of resolution; The larger fluctuation range also indicates high sensitivity to detailed structures, further supporting the judgment of superior resolution. The speckle pattern resolution is significantly improved by using staggered fusion spliced ​​multimode fiber.

[0044] Therefore, this device is smaller in size, improves the fiber's resistance to changes in the external environment, and also improves the resolution of speckle.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A speckle wavelength measurement device that combines miniaturization and strong anti-interference capabilities, characterized in that, It includes a single-mode fiber, a staggered fusion spliced ​​multimode fiber, a CCD camera, and a computer arranged sequentially along the optical path; The single-mode fiber is connected to the misaligned fusion spliced ​​multimode fiber to receive the incident laser generated by the laser and to transmit the incident laser to the misaligned fusion spliced ​​multimode fiber. The misaligned fusion spliced ​​multimode fiber is formed by axially misaligned fusion splicing of a first short multimode fiber and a second short multimode fiber. It is used to receive incident laser light transmitted through a single-mode fiber and to cause the incident laser light to be scattered at the end face, forming randomly distributed bright and dark spots. The CCD camera is connected to the misaligned fusion spliced ​​multimode fiber and is used to record the speckle pattern formed by incident light passing through the misaligned fusion spliced ​​multimode fiber. The computer is connected to a CCD camera and is used to process the speckle patterns acquired by the CCD camera.

2. The speckle wavelength measurement device with miniaturization and strong anti-interference capability according to claim 1, characterized in that, The misaligned welding process is achieved through the following steps: Firstly, a first short multimode fiber and a second short multimode fiber are provided; Then, the coating layers at the ends of the first and second short multimode fibers are stripped using fiber processing tools to obtain a bare fiber area of ​​a predetermined length. Then, a high-purity solvent is used to clean the bare fiber area, and a fiber optic cleaver is used to cut the cleaned fiber end face to form a flat end face that meets the requirements of fusion splicing. Finally, the fusion splicer is operated to create a preset axial offset between the core of the first short multimode fiber and the core of the second short multimode fiber, and then fusion splices them to form a permanent splice with a fixed axial misalignment.

3. The speckle wavelength measurement device with miniaturization and strong anti-interference capability according to claim 2, characterized in that, After the misaligned welding is completed, a protective coating is applied to the weld joint. The coating material is acrylate.

4. The speckle wavelength measurement device with miniaturization and strong anti-interference capability according to claim 1, characterized in that, The misaligned fusion spliced ​​multimode optical fiber is encapsulated in a butterfly-shaped encapsulation shell and fixed to the upper surface of the thermally conductive medium by a fixing material; the thermally conductive medium is placed above the thermoelectric cooler and is in close thermal contact with the thermoelectric cooler.

5. The speckle wavelength measurement device with miniaturization and strong anti-interference capability according to claim 1, characterized in that, The total length of the misaligned fusion spliced ​​multimode fiber is 0.2m-1m.

6. The speckle wavelength measurement device with miniaturization and strong anti-interference capability according to claim 2, characterized in that, The axial offset ranges from 10% to 40% of the core diameter of the first and second short multimode fibers.

7. The speckle wavelength measurement device with miniaturization and strong anti-interference capability according to claim 1, characterized in that, The numerical aperture of the first and second short multimode fibers is 0.18-0.22.

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