Image transmitting optical fiber with shape sensing function and preparation method thereof

Abstract

The invention relates to an image-transmitting optical fiber with a shape sensing function and a preparation method thereof, the optical fiber comprises an outer cladding and an image-transmitting surface layer, the outer cladding wraps the periphery of the image-transmitting surface layer, the image-transmitting surface layer comprises a common cladding and image-transmitting fiber cores tightly arranged in the common cladding at intervals, and the image-transmitting fiber cores are arranged in the common cladding at intervals. And a sensing fiber core with three or more cores is arranged in the image transmitting surface layer and close to the inner circumferential surface of the outer cladding. The sensing optical fiber and the image transmitting optical fiber are integrated, the diameter is small, the optical fiber can enter a small channel conveniently, and a small-size endoscope with a shape sensing function can be manufactured; the integrated image transmission sensing optical fiber can realize synchronous operation of the shape sensing module and the image transmission module, is excellent in bending performance and high in spatial resolution, can realize real-time image transmission and synchronous shape reconstruction, and has a three-dimensional shape sensing function and an image transmission function.

Description

Technical Field

[0001] The invention relates to an image transmission optical fiber with shape sensing function and a preparation method thereof, belonging to the technical field of image transmission and sensing optical fibers. Technical Background

[0002] Image transmission fiber is the core functional component of medical endoscopes. It is used to enter the human body through the natural channels of the human body or through a small incision made during surgery to directly observe the changes in relevant parts during diagnosis and treatment. At present, there are two inconveniences in the work and diagnosis of endoscopes in the body: First, due to the small working space of the endoscope and the complex environment, the error caused by the passive deformation during the insertion of the endoscope has an unignorable impact on the control accuracy of the endoscope. For example, the terminal bifurcation of the bronchus of the lung is complex. When using an ultra-fine endoscope for bronchial examination, medical staff are prone to deviations when operating according to the endoscopic image, resulting in the wrong bronchial bifurcation. At this time, if the endoscope has a three-dimensional shape sensing function and restores the shape of the path along the way in real time, it can be discovered and avoided first; second, the endoscope can usually only perform two-dimensional imaging. When the lesion is found, it cannot provide the doctor with three-dimensional information of the lesion tissue, which is not conducive to the doctor's timely judgment of the condition. At this time, if the endoscope has a three-dimensional shape sensing function, it can provide three-dimensional information of the lesion tissue in real time, which is very beneficial for the doctor to diagnose the condition in a timely and accurate manner.

[0003] In order to realize the three-dimensional shape sensing function of the endoscope, it is currently achieved by adding an additional shape sensing component inside the endoscope probe. The diameter of the sensor described in Chinese patent CN113587842A is as high as 1.2mm, which needs to be inserted into the endoscope insertion tube for use. Usually, the diameter of the Wanxin image transmission fiber optic endoscope probe is only about 1mm. Although this method can increase the sensing function of the endoscope, it greatly increases the size of the endoscope, making the modified endoscope unusable in small channel organs such as pulmonary bronchial branches and pancreas. The shape sensing module and the image transmission module of the endoscope of this type of structure are independent in physical scale, which not only increases the volume of the endoscope probe, increases the bending radius of the endoscope, sacrifices flexibility, and reduces the accuracy of shape sensing, but also in actual application, when the endoscope is bent multiple times, there is inevitably mutual misalignment between the shape sensing module and the image transmission module, resulting in the degradation of the synchronization of sensing and image transmission, which is not conducive to accurate diagnosis. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an image-transmitting optical fiber with shape sensing function and a preparation method thereof in view of the deficiencies in the above-mentioned prior art. The image-transmitting optical fiber can integrate the sensing optical fiber with the image-transmitting optical fiber. It not only has a thin diameter, which is convenient for entering small channels, but also can realize the synchronous operation of the shape sensing module and the image-transmitting module, thereby enhancing the performance of the endoscope.

[0005] The image transmission optical fiber technology solution adopted by the present invention to solve the above-mentioned problems is:

[0006] It includes an outer cladding and an image transmission surface layer, wherein the outer cladding is coated on the outer periphery of the image transmission surface layer, and the image transmission surface layer includes a common cladding and image transmission fiber cores closely spaced in the common cladding, and three or more sensing fiber cores are arranged in the image transmission surface layer adjacent to the inner periphery of the outer cladding.

[0007] According to the above solution, the sensing fiber core is adjacent to the inner peripheral surface of the outer cladding or is connected to the inner peripheral surface of the outer cladding.

[0008] According to the above scheme, the sensing fiber core is a single-core sensing fiber core, and the number of the single-core sensing fiber cores is 3 to 10. The single-core sensing fiber cores are distributed in the image transmission surface layer at intervals along the circumferential direction.

[0009] According to the above scheme, the sensing fiber core is a multi-core sensing fiber core, the number of cores of the multi-core sensing fiber core is 2 to 10, and the number of the multi-core sensing fiber core is 1 or more.

[0010] According to the above scheme, the sensing fiber core includes a single-core sensing fiber core and a multi-core sensing fiber core.

[0011] According to the above scheme, the outer cladding diameter is 100-1000μm, the image transmission surface layer diameter is 80-900μm, the image transmission fiber core diameter is 1.0-3.0μm, preferably 1.5-2.5μm, the core spacing is 2-5μm, preferably 2.5-4μm, the number of image transmission fiber cores is more than 3000, the NA (numerical aperture) is 0.3-0.4, preferably 0.33-0.38, the transmittance of 4-meter optical fiber in the 480-650nm band is >85%, and the resolution is ≥143lp / mm.

[0012] According to the above scheme, the core diameter of the sensing fiber core is 7-9 μm, preferably 7.5-8.5 μm, and the NA is 0.1-0.2.

[0013] According to the above scheme, the sensing fiber core is used for shape sensing, with a spatial resolution of ≤1.5 cm, a shape reconstruction time of <1.5 seconds, and a shape reconstruction error of <2%.

[0014] According to the above scheme, the sensing fiber core is a single-core sensing fiber core, there are three single-core sensing optical fibers, and the single-core sensing fiber cores are evenly spaced along the circumferential direction in the image transmission surface layer adjacent to the inner circumference of the outer cladding or connected to the inner circumference of the outer cladding.

[0015] According to the above scheme, the sensing fiber core is a multi-core sensing fiber core, the number of cores of the multi-core sensing fiber core is 3, and the multi-core sensing fiber core is 1, which is arranged in the image transmission surface layer adjacent to the inner circumference of the outer cladding or connected to the inner circumference of the outer cladding.

[0016] The technical solution of the above-mentioned method for preparing the image transmission optical fiber of the present invention is:

[0017] First, prepare a quartz glass sleeve, prepare a sensing multi-core monofilament or / and a sensing single-core monofilament, prepare an image-transmitting high-NA monofilament,

[0018] The image transmission high NA single wire is piled up and filled into the quartz glass sleeve until the inner hole of the quartz glass sleeve is filled. At the same time, the sensing multi-core single wire or / and the sensing single-core single wire are placed in the quartz glass sleeve close to the tube wall to make an image transmission optical fiber combination preform rod.

[0019] Finally, the combined preform rod is placed on a drawing tower for drawing to obtain an image-transmitting optical fiber, wherein the image-transmitting high-NA monofilament is drawn to become an image-transmitting fiber core, and the sensing single-core monofilament or / and sensing multi-core monofilament is drawn to become a sensing fiber core.

[0020] According to the above scheme, before drawing, the composite preform rod filled with multi-core glass fibers is heated to melt and shrink it into a solid preform rod.

[0021] According to the above scheme, the grating is etched on the sensing fiber core adjacent to the inner surface of the outer cladding by mask method or femtosecond direct writing method. The etching requirements are: uniformly spaced etching with a spacing between 0.2 and 2 cm. The reflectivity after etching is 10 to 40%, the 3dB bandwidth is 0.2 to 0.3nm, and the side mode suppression ratio is 10 to 15dB, forming a sensing fiber core engraved with a grating.

[0022] According to the above scheme, the wire drawing temperature is 1700-2000°C, preferably 1800-1980°C, and the wire drawing speed is 20-200 m / min, preferably 25-50 m / min.

[0023] The method of using the image transmission optical fiber of the present invention in image transmission and shape transmission is as follows:

[0024] For the image-transmitting optical fiber with a sensing core engraved with a grating, the wavelength change is demodulated into stress change by a demodulator. The grating demodulator with multi-channel simultaneous demodulation function is connected to the sensing core through an optical fiber fan-in and fan-out module. The data output by the demodulator is then processed in real time by the data processing module, the received central wavelength drift is converted into strain, and the strain detected by the shape sensing module is restored to a three-dimensional shape.

[0025] For the imaging optical fiber with a sensing core without grating, an optical frequency domain reflectometer (OFDR) device is connected to the sensing core through an optical fiber fan-in and fan-out module. The OFDR system is used to test the time domain curve of the optical fiber before and after deformation. A fixed comparison window length is selected, and the reference distance signal and the measurement signal are intercepted by the comparison window. The comparison windows are intercepted in sequence, and each comparison window is a sensing unit. The sensing segment is divided into several small sensing units, and each sensing unit is continuously distributed. The time domain curve in a sensing unit is inverse Fourier transformed, and the time domain signal in the comparison window is converted into a frequency domain signal to obtain the frequency domain information of the reference signal and the measurement signal. The reference signal and the measured frequency domain signal of a sensing unit are demodulated by a cross-correlation algorithm to obtain the central wavelength frequency shift information before and after loading. All sensing units are cross-correlated and calculated in sequence to obtain the central wavelength frequency shift information of each sensing core. Then, the strain detected by the shape core is restored to a three-dimensional shape through a data processing module.

[0026] The beneficial effects of the present invention are as follows: 1. The sensing optical fiber and the image transmission optical fiber are integrated into one, and the diameter is thin, which is convenient for entering small channels, and can be made into a small-sized endoscope with shape sensing function; 2. The integrated image transmission sensing optical fiber can realize the synchronous operation of the shape sensing module and the image transmission module, has excellent bending performance, high spatial resolution, can achieve real-time image transmission and synchronous shape reconstruction, and has three-dimensional shape sensing function and image transmission function. It can be used to prepare an endoscope with shape sensing function, which enhances the detection accuracy and use performance of the endoscope, and is conducive to optimizing the diagnostic function of the endoscope. 3. The preparation method of the present invention is simple and effective. The arrangement of the sensing fiber core in the inner peripheral surface of the adjacent outer cladding can facilitate the etching of the grating. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the optical fiber end face structure of Example 1 of the present invention.

[0028] Figure 2 This is a schematic diagram of the optical fiber end face structure of Example 7 of the present invention.

[0029] Figure 3 This is the resolution picture of Example 1 of the present invention.

[0030] Figure 4 This is a transmittance picture of Example 1 of the present invention at 480-650nm.

[0031] Figure 5 The shape reconstruction effect (right) of the image transmission optical fiber (left) of Example 1 of the present invention. DETAILED DESCRIPTION

[0032] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with embodiments.

[0033] The optical fiber of the present invention includes an outer cladding 1 and an image transmission surface layer 2, wherein the outer cladding is coated on the outer periphery of the image transmission surface layer, and the image transmission surface layer includes a common cladding and image transmission fiber cores closely spaced in the common cladding, and three or more sensing fiber cores are arranged in the image transmission surface layer adjacent to the inner periphery of the outer cladding.

[0034] The sensing fiber core is a single-core sensing fiber core 3, and there are three single-core sensing optical fibers. The single-core sensing fiber cores are circumferentially spaced and distributed in the image transmission surface layer adjacent to the inner circumference of the outer cladding or connected to the inner circumference of the outer cladding. The sensing fiber core can also be a multi-core sensing fiber core 4, and the number of cores of the multi-core sensing fiber core is 3. There is one multi-core sensing fiber core, which is arranged in the image transmission surface layer adjacent to the inner circumference of the outer cladding or connected to the inner circumference of the outer cladding.

[0035] Embodiment 1:

[0036] Preparation of core rods and preform rods: PCVD deposition process was used to deposit two core rods of different specifications using pure silicon liner tubes. The two core rods were extended and stretched into two different types of monofilaments, one was image transmission monofilaments, the number of which was 5000, and the other was sensor monofilaments, the number of which was 3. The main parameters of the two monofilaments are shown in Table 1. Then the monofilaments were assembled with an outer diameter of 46 mm and an inner diameter of 43 mm outer sleeve into a preform rod, in which the three sensor monofilaments were evenly arranged along the inner wall of the sleeve at an interval of 29 mm. The main parameters of the two monofilaments are shown in Table 1.

[0037]

[0038] Table 1

[0039] Drawing: The above-mentioned preform rods are placed on a drawing tower and drawn at a speed of 30m / min at 1960°C to obtain optical fibers with a glass portion of about 250μm and a coating portion of about 350μm. The image-transmitting single filament becomes an image-transmitting fiber core after drawing, and the sensing single filament becomes a sensing fiber core after drawing. The main parameters of the optical fiber are shown in Table 2.

[0040]

[0041] Table 2

[0042] Application performance test: Take 4 meters of the above-mentioned optical fiber, and use the mask method to etch gratings on the three sensing fiber cores on the periphery of the optical fiber. The etching parameters are: grating spacing is 1mm / piece, reflectivity after etching is 25%, 3dB bandwidth is 0.23nm, and side mode suppression ratio is 12dB. The grating demodulator with three-way simultaneous demodulation function is connected to the above-mentioned three sensing fiber cores through the optical fiber fan-in and fan-out module, and then the data output by the demodulator is processed in real time through the data processing module, the received central wavelength drift is converted into strain, and the strain detected by the shape sensing module is restored to a three-dimensional shape. The remaining cores of the optical fiber are used for image transmission. The main parameters obtained from the test are shown in Table 3.

[0043]

[0044] Table 3

[0045] It can be seen from the above embodiments that the optical fiber designed in the present invention has good image transmission performance without increasing the size of the optical fiber, and at the same time has a three-dimensional shape sensing function, and the demodulation speed, accuracy and error all meet the use requirements.

[0046] Embodiment 2-6:

[0047] Preparation of core rods and preform rods: PCVD deposition process was used to deposit two core rods of different specifications using pure silicon liner. The two core rods were extended and stretched into two different types of monofilaments, one for image transmission and the other for sensing. The monofilaments were then assembled with outer sleeves into preform rods, in which the sensing monofilaments were evenly arranged along the inner wall of the sleeve. The parameters, quantity and sleeve parameters of the two monofilaments are shown in Table 4.

[0048]

[0049] Table 4

[0050] Drawing: The preform rods of the above-mentioned Examples 2 to 6 are placed on a drawing tower and drawn at a speed of 30 m / min at 1970°C to obtain optical fibers of different geometric sizes, wherein the image transmission single filament becomes the image transmission fiber core (2) after drawing, and the sensing single filament becomes the sensing fiber core (3) after drawing. The main parameters of the optical fibers are shown in Table 5.

[0051]

[0052] Table 5

[0053] Application performance test: Take 4 meters of the above optical fiber, use the mask method to etch gratings on the three sensing fiber cores on the periphery of the optical fiber. The etching parameters are shown in Table 6. Connect the grating demodulator with three-way simultaneous demodulation function to the three sensing fiber cores through the optical fiber fan-in and fan-out module. Then, process the data output by the demodulator in real time through the data processing module, convert the received central wavelength drift into strain, and restore the strain detected by the shape sensing module to a three-dimensional shape. The remaining cores of the optical fiber are used for image transmission. The main parameters obtained from the test are shown in Table 6.

[0054]

[0055] Table 6

[0056] It can be seen from Examples 2-6 that the optical fiber designed in the present invention has a sensing core etched into a grating, which has good image transmission performance without increasing the size of the optical fiber, and also has a three-dimensional shape sensing function, and the demodulation speed, accuracy and error all meet the use requirements.

[0057] Embodiment 7-11:

[0058] Preparation of core rod and preform rod: PCVD deposition process is used to prepare core rod by deposition with pure silicon sleeve. The core rod is stretched and then used as image transmission monofilament. Then the monofilament and a multi-core monofilament are assembled with outer sleeve into preform rod. The multi-core monofilament is placed against the inner wall of the sleeve. The parameters, quantity and sleeve parameters of the above two monofilaments are shown in Table 7.

[0059]

[0060] Table 7

[0061] Drawing: The preform rods of Examples 7 to 11 are mounted on a drawing tower and drawn at a speed of 35 m / min at 1950°C to obtain optical fibers of different geometric sizes, wherein the image transmission single filament becomes the image transmission fiber core (2) after drawing, and the sensing single filament becomes the sensing fiber core (4) after drawing. The main parameters of the optical fibers are shown in Table 8.

[0062]

[0063]

[0064] Table 8

[0065] Application performance test: Take 4 meters of the above optical fiber, connect the optical frequency domain reflectometer (OFDR) equipment to the sensing core through the optical fiber fan-in and fan-out module, use the OFDR system to test the time domain curve before and after the optical fiber is deformed, select a fixed comparison window length, and perform comparison window interception on the reference distance signal and the measurement signal. The comparison window is intercepted in sequence. Each comparison window is a sensing unit. The sensing segment is divided into several small sensing units, and each sensing unit is continuously distributed. The time domain curve in a sensing unit is inverse Fourier transformed, and the time domain signal in the comparison window is converted into a frequency domain signal to obtain the frequency domain information of the reference signal and the measurement signal. The reference signal and the measured frequency domain signal of a sensing unit are demodulated by the cross-correlation algorithm to obtain the central wavelength frequency shift information before and after loading. All sensing units are cross-correlated and calculated in sequence to obtain the central wavelength frequency shift information of each sensing core, and then the strain detected by the shape core is restored to a three-dimensional shape through the data processing module. The remaining cores of the optical fiber are used for image transmission. The main parameters obtained by the test are shown in Table 9.

[0066]

[0067] Table 9

[0068] It can be seen from Examples 7-11 that the optical fiber designed in the present invention has a sensing core that matches OFDR through fan-in and fan-out, and has good image transmission performance without increasing the size of the optical fiber, while also having a three-dimensional shape sensing function, and the demodulation speed, accuracy and error all meet the use requirements.

Claims

1. An image-transmitting optical fiber with shape sensing function, comprising an outer cladding and an image-transmitting surface layer, wherein the outer cladding is coated on the outer periphery of the image-transmitting surface layer, and the image-transmitting surface layer comprises a common cladding and an image-transmitting fiber core closely spaced in the common cladding, characterized in that Three or more sensing fiber cores are arranged in the image transmission surface layer adjacent to the inner peripheral surface of the outer cladding layer.

2. The image-transmitting optical fiber with shape sensing function according to claim 1, characterized in that The sensing fiber core is adjacent to the inner peripheral surface of the outer cladding or is connected to the inner peripheral surface of the outer cladding.

3. The image-transmitting optical fiber with shape sensing function according to claim 1 or 2, characterized in that The sensing fiber core is a single-core sensing fiber core, and the number of the single-core sensing fiber cores is 3 to 10. The single-core sensing fiber cores are distributed in the image transmission surface layer at intervals along the circumferential direction.

4. The image-transmitting optical fiber with shape sensing function according to claim 1 or 2, characterized in that The sensing fiber core is a multi-core sensing fiber core, the number of cores of the multi-core sensing fiber core is 2 to 10, and the number of the multi-core sensing fiber core is 1 or more.

5. The image-transmitting optical fiber with shape sensing function according to claim 1 or 2, characterized in that The sensing fiber core includes a single-core sensing fiber core and a multi-core sensing fiber core.

6. The image-transmitting optical fiber with shape sensing function according to claim 1 or 2, characterized in that The outer cladding diameter is 100-1000μm, the image transmission surface layer diameter is 80-900μm, the image transmission fiber core diameter is 1.0-3.0μm, the core spacing is 2-5μm, the number of image transmission fiber cores is more than 3000, the NA is 0.3-0.4, the transmittance of 4-meter optical fiber in the 480-650nm band is >85%, and the resolution is ≥143lp / mm.

7. The image-transmitting optical fiber with shape sensing function according to claim 6, characterized in that The core diameter of the sensing fiber core is 7-9 μm, and the NA is 0.1-0.

2.

8. The image-transmitting optical fiber with shape sensing function according to claim 6, characterized in that The sensing fiber core is used for shape sensing, with a spatial resolution of ≤1.5 cm, a shape reconstruction time of <1.5 seconds, and a shape reconstruction error of <2%.

9. The image-transmitting optical fiber with shape sensing function according to claim 1 or 2, characterized in that The sensing fiber core is a single-core sensing fiber core, there are three single-core sensing optical fibers, and the single-core sensing fiber cores are distributed at intervals along the circumferential direction in an image transmission surface layer adjacent to the inner circumference of the outer cladding or connected to the inner circumference of the outer cladding.

10. The image-transmitting optical fiber with shape sensing function according to claim 1 or 2, characterized in that The sensing fiber core is a multi-core sensing fiber core, the number of cores of the multi-core sensing fiber core is 3, and the multi-core sensing fiber core is 1, which is arranged in the image transmission surface layer adjacent to the inner peripheral surface of the outer cladding or connected to the inner peripheral surface of the outer cladding.

11. A method for preparing an image-transmitting optical fiber with shape sensing function according to any one of claims 1 to 10, characterized in that First, prepare a quartz glass sleeve, prepare a sensing multi-core monofilament or / and a sensing single-core monofilament, prepare an image-transmitting high-NA monofilament, The image transmission high NA single wire is piled up and filled into the quartz glass sleeve until the inner hole of the quartz glass sleeve is filled. At the same time, the sensing multi-core single wire or / and the sensing single-core single wire are placed in the quartz glass sleeve close to the tube wall to make an image transmission optical fiber combination preform rod. Finally, the combined preform rod is placed on a drawing tower for drawing to obtain an image-transmitting optical fiber, wherein the image-transmitting high-NA monofilament is drawn to become an image-transmitting fiber core, and the sensing single-core monofilament or / and sensing multi-core monofilament is drawn to become a sensing fiber core.

12. The method for preparing an image-transmitting optical fiber with shape sensing function according to claim 11, characterized in that Before drawing, the composite preform filled with multi-core glass fibers is heated to melt and shrink it into a solid preform.

13. The method for preparing an image-transmitting optical fiber with shape sensing function according to claim 11, characterized in that The wire drawing temperature is 1700-2000°C, and the wire drawing speed is 20-200m / min.

14. The method for preparing an image-transmitting optical fiber with shape sensing function according to claim 11, characterized in that For the sensing fiber core adjacent to the inner peripheral surface of the outer cladding, a grating is etched by a mask method or a femtosecond direct writing method. The etching requirements are: uniformly spaced etching with a spacing between 0.2 and 2 cm, a reflectivity of 10 to 40% after etching, a 3dB bandwidth of 0.2 to 0.3 nm, and a side mode suppression ratio of 10 to 15 dB, forming a sensing fiber core engraved with a grating.

15. A method for using the image transmission optical fiber with shape sensing function according to any one of claims 1 to 10 in image transmission and shape transmission, characterized in that For the image-transmitting optical fiber with a sensing core engraved with a grating, the wavelength change is demodulated into stress change by a demodulator. The grating demodulator with multi-channel simultaneous demodulation function is connected to the sensing core through an optical fiber fan-in and fan-out module. The data output by the demodulator is then processed in real time by the data processing module, the received central wavelength drift is converted into strain, and the strain detected by the shape sensing module is restored to a three-dimensional shape.

16. A method for using the image transmission optical fiber with shape sensing function according to any one of claims 1 to 10 in image transmission and shape transmission, characterized in that For the imaging optical fiber with a sensing core without grating, an optical frequency domain reflectometer (OFDR) device is connected to the sensing core through an optical fiber fan-in and fan-out module. The OFDR system is used to test the time domain curve of the optical fiber before and after deformation. A fixed comparison window length is selected, and the reference distance signal and the measurement signal are intercepted by the comparison window. The comparison windows are intercepted in sequence, and each comparison window is a sensing unit. The sensing segment is divided into several small sensing units, and each sensing unit is continuously distributed. The time domain curve in a sensing unit is inverse Fourier transformed, and the time domain signal in the comparison window is converted into a frequency domain signal to obtain the frequency domain information of the reference signal and the measurement signal. The reference signal and the measured frequency domain signal of a sensing unit are demodulated by a cross-correlation algorithm to obtain the central wavelength frequency shift information before and after loading. All sensing units are cross-correlated and calculated in sequence to obtain the central wavelength frequency shift information of each sensing core. Then, the strain detected by the shape core is restored to a three-dimensional shape through a data processing module.

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