A graded-index optical fiber for laser energy transmission and its manufacturing method and application

Abstract

This invention provides a graded-index optical fiber for laser energy transmission, its manufacturing method, and its application, relating to the field of optical fiber technology. It includes a core and a cladding arranged sequentially. A high-temperature resistant coating can be selectively applied to the outer side of the cladding. The refractive index of the core exhibits a parabolic gradient distribution along the radial direction of the fiber. The light source end of this invention employs a large-diameter design of 365μm / 550μm / 600μm, achieving efficient coupling with the laser without the need for high-precision alignment equipment. This simplifies the operation of medical equipment, reduces the operational difficulty for medical personnel, and improves the ease of use of the medical equipment. The surgical end adopts a small-diameter design of 272μm / 200μm / 150μm and below, increasing the bending radius to 30-40mm while maintaining bending loss ≤0.02dB / km. This allows for flexible adaptation to complex wiring during surgery and flexible cosmetic procedures, avoiding energy loss or fiber damage caused by bending.

Description

Technical Field

[0001] This invention relates to the field of optical fiber technology, and in particular to a graded-index optical fiber for laser energy transmission, its manufacturing method, and its applications. Background Technology

[0002] Laser medical technology, as a crucial pillar of modern medicine, has been widely applied in various clinical scenarios such as tumor treatment, minimally invasive surgery, and laser cosmetic procedures due to its advantages of precision, efficiency, and minimally invasiveness. Laser transmission fiber, as the core energy carrier of medical laser equipment, is a key component connecting the laser generator and the treatment probe. Its transmission performance, mechanical properties, biocompatibility, and other comprehensive indicators directly determine the precision, safety, and effectiveness of laser treatment. Currently, the transmission fibers used in the laser medical field are mainly divided into step-index fibers and graded-index fibers. Among them, graded-index fibers, with their radially gradually changing refractive index distribution, can effectively reduce laser energy reflection loss and improve transmission efficiency, gradually becoming the preferred solution for medical laser transmission. The existing manufacturing process for graded-index laser fibers mainly uses in-tube chemical vapor deposition (MCVD), adjusting the refractive index distribution by doping with different dopants to adapt to the transmission requirements of different scenarios.

[0003] However, existing graded-index optical fibers and traditional transmission fibers used in laser medicine have the following technical pain points, making it difficult to fully meet the core needs of clinical treatment: First, coupling is difficult. Existing medical laser fibers have uniform diameters at both ends and are relatively small, requiring high-precision alignment with the laser. This is cumbersome and prone to coupling deviations, affecting laser energy transmission efficiency and potentially causing fiber damage. Second, bending performance is poor. During surgery, fibers need to adapt to complex intraoperative wiring. Existing fibers have small bending radii, leading to significant energy loss during bending and even fiber breakage or damage, seriously affecting surgical safety. Third, power carrying capacity is insufficient. Some high-power laser treatments require stable transmission of high-power lasers. Existing medical fibers have low laser damage thresholds, easily burning out due to energy concentration, limiting the application of high-power laser medical technology. Fourth, wavelength adaptability is narrow. Existing medical fibers are mostly limited to a single laser wavelength, unable to adapt to various medical laser devices with different wavelengths, restricting application scenarios and increasing equipment investment for medical institutions. The existing medical laser fibers suffer from several drawbacks. First, they are costly. Second, they have poor medical compatibility. While some fibers can meet basic transmission requirements, their high-temperature and disinfection resistance is insufficient, making them unsuitable for the high-temperature environment of medical disinfection. Furthermore, their biocompatibility is poor, leading to performance degradation with long-term use and potential irritation to human tissues. Third, their refractive index distribution control precision is insufficient. Existing graded-index fibers have low precision in adjusting the refractive index distribution factor, failing to achieve optimal focused transmission of laser energy, and transmission loss still has room for optimization. Fourth, their manufacturing processes lack specificity. Existing processes do not fully consider the differentiated needs of medical scenarios, lacking specialized optimization for differentiated diameters at both ends and biocompatibility. This results in poor product consistency, hindering large-scale production and clinical application. These shortcomings are interconnected, preventing existing medical laser fibers from simultaneously meeting the core requirements of low coupling difficulty, excellent bending performance, high power carrying capacity, wide wavelength adaptability, and high biocompatibility. This has become a key bottleneck restricting the further development of laser medical technology. Therefore, this invention proposes a graded-index fiber for laser energy transmission, its manufacturing method, and its application to solve the problems existing in the prior art. Summary of the Invention

[0004] To address the aforementioned issues, this invention proposes a graded-axis optical fiber for laser energy transmission, its manufacturing method, and its application. The light source end employs a large-diameter design of 365μm / 550μm / 600μm, achieving efficient coupling with the laser without the need for high-precision alignment equipment, with a coupling efficiency ≥98.5%. This simplifies the operation of medical equipment, reduces the operational difficulty for medical personnel, and improves the ease of use of medical equipment, effectively solving the pain points of high coupling difficulty and cumbersome operation in existing optical fibers. The surgical end adopts a small-diameter design of 272μm / 200μm / 150μm and below, increasing the bending radius to 30-40mm while maintaining bending loss ≤0.02dB / km. This allows for flexible adaptation to complex wiring during surgery and flexible cosmetic procedures, avoiding energy loss or fiber damage caused by bending, ensuring the safety of surgical and cosmetic operations, and effectively solving the pain points of poor bending performance and easy damage during surgery in existing optical fibers.

[0005] To achieve the objectives of this invention, the following technical solution is provided: a graded-index optical fiber for laser energy transmission, comprising a core and a cladding arranged sequentially, wherein a high-temperature resistant coating may be selectively disposed on the outer side of the cladding, and the refractive index of the core exhibits a parabolic graded distribution along the radial direction of the optical fiber, the refractive index distribution satisfying the formula... , where n max δ is the maximum refractive index at the core center, δ is the relative refractive index difference, a is the core radius, and g is the refractive index distribution factor, where g = 4.25 ± 0.05; the cladding has a uniform refractive index and is more uniform than n. max Lower by 0.5%-1.0%;

[0006] The optical fiber features a differential diameter design at both ends to adapt to the light source coupling and intraoperative cabling requirements of medical laser systems. The diameter at the light source end is selectable from 365μm, 550μm, or 600μm, while the diameter at the surgical end is 272μm, 200μm, or 150μm and below. The effective mode area of ​​the optical fiber is 150μm. 2 -200μm 2 The laser energy transmission loss is ≤0.18dB / km in the wavelength range of 300nm-2400nm, the bending loss is ≤0.02dB / km when the bending radius is 30-40mm, and the laser damage resistance threshold is ≥100MW / cm. 2 It can withstand high temperatures of ≥300℃, has biocompatibility that meets medical-grade standards, and is compatible with laser energy transmission in the wavelength range of 300nm-2400nm.

[0007] Further improvements are made in that: the radius a of the fiber core is 25μm-40μm, the relative refractive index difference δ is 0.5%-1.0%, and the numerical aperture NA is 0.18-0.28. By reasonably matching the fiber core radius and the relative refractive index difference, the laser energy constraint and transmission efficiency are balanced, accurately adapting to the low-loss transmission and convenient coupling requirements of medical lasers, and avoiding damage to normal tissues caused by laser energy divergence.

[0008] Further improvements are made by using high-purity quartz as the substrate for the fiber core, doped with a mixture of Yb2O3 and Al2O3 dopants, with a total doping concentration of 0.8%-1.5%, wherein the doping ratio of Yb2O3 to Al2O3 is 1:1.2-1:1.5. Through the synergistic effect of the dopants, the fiber's resistance to laser damage and high-temperature performance are improved, while strictly ensuring the biocompatibility of the fiber, making it suitable for medical applications.

[0009] Further improvements are made of polyimide material with a thickness of 15μm-35μm and a high temperature resistance of ≥350℃. The high temperature resistant coating adopts a double-layer structure, with an inner polyimide bottom layer with a thickness of 5μm-10μm and an outer polyimide wear-resistant layer with a thickness of 10μm-25μm. This double-layer structure is used to improve the adhesion between the coating and the cladding, enhance the mechanical strength, wear resistance and high temperature protection performance of the optical fiber, and adapt to the needs of medical disinfection environment and intraoperative bending.

[0010] Further improvements include: the diameter deviation at both ends of the optical fiber is ≤ ±1μm; the large diameter design at the light source end is used to reduce the coupling alignment accuracy requirements with the laser; and the small diameter design at the surgical end is used to flexibly adapt to minimally invasive instruments, while increasing the bending radius to avoid energy loss or fiber damage caused by fiber bending during surgery.

[0011] A method for manufacturing graded-fiber optical fibers for laser energy transmission, employing in-tube chemical vapor deposition (MCVD) combined with a high-temperature sintering process, is adapted to the differentiated diameters, high biocompatibility, and high performance requirements of medical optical fibers. The method includes the following steps:

[0012] S1. Preform Preparation: Using a high-purity quartz tube with a purity ≥99.995% as a substrate, SiCl4, GeCl4, YbCl3, and AlCl3 precursor gases are introduced into the tube. The deposition temperature is controlled at 1500℃-1700℃ and the gas flow rate is 0.8L / min-2.5L / min. A SiO2 mixed layer is deposited layer by layer. By adjusting the doping concentration gradient of GeO2, Yb2O3, and Al2O3, a parabolic refractive index distribution preform with a refractive index distribution factor g=4.25±0.05 is constructed. After deposition, the preform is placed in a high-temperature sintering furnace and sintered at 1800℃-2000℃ for 2-3 hours to remove impurities and bubbles, ensuring the biocompatibility, optical uniformity, and mechanical strength of the optical fiber.

[0013] S2. Fiber Drawing: The preform is placed in a graphite drawing furnace and heated to 2000℃-2200℃ at a heating rate of 8℃ / min-12℃ / min for melting and fiber drawing. The drawing speed is 4m / s-12m / s. Differentiated fiber drawing processes are used to form the diameters of the light source end and the surgical end separately. The fiber diameter is monitored in real time to ensure precise and controllable dimensions. Simultaneously, a high-temperature resistant polyimide coating is applied using a coating machine to ensure uniform coating thickness.

[0014] S3. Post-processing: The drawn optical fiber is cured at high temperature (300℃-350℃) for 30-60 minutes. Then, the fiber is subjected to plastic coating, tension testing, laser loss detection, damage threshold testing, high temperature resistance testing, and biocompatibility testing. The qualified optical fibers are sterilized and selected to meet the standards for use in medical equipment.

[0015] A further improvement is made in S1, where the doping ratio of Yb2O3 to Al2O3 is 1:1.2-1:1.5, the doping concentration of GeO2 gradually decreases from the center of the fiber core to the edge, and the doping concentrations of Yb2O3 and Al2O3 remain uniform, so as to take into account the gradual change of refractive index, the resistance to laser damage and biocompatibility, and adapt to the needs of medical laser transmission.

[0016] Further improvements are made in S2: during the fiber drawing process, the diameter and refractive index distribution of the optical fiber are monitored in real time, and the drawing tension and drawing speed are adjusted through feedback to ensure the consistency of the optical fiber parameters, wherein the optical fiber diameter deviation is ≤ ±1μm and the deviation of the refractive index distribution factor g is ≤ ±0.01; during the coating process, the thickness uniformity of the coating layer is controlled with a deviation of ≤ ±2μm to ensure the protective effect of the coating layer and the bending performance of the optical fiber. At the same time, a double-layer coating structure is adopted, with the inner layer being a polyimide underlayer and the outer layer being a polyimide wear-resistant layer.

[0017] Further improvements are made in S3, where the tensile force for tension testing is ≥120N, and laser loss detection is performed using an optical time domain reflectometer (OTDR) to ensure that the transmission loss of the optical fiber in the wavelength range of 300nm-2400nm is ≤0.18dB / km and the laser damage resistance threshold is ≥100MW / cm². 2 The biocompatibility test meets medical-grade standards, and the bacterial count of the optical fiber after sterilization is ≤10 CFU / g, which is suitable for medical clinical use requirements.

[0018] An application of graded-index optical fiber for laser energy transmission is disclosed. This fiber is used in laser medical systems as a core energy transmission component of laser therapy equipment. It is compatible with various medical lasers in the 300nm-2400nm wavelength range and can be applied in tumor treatment, laser cosmetic surgery, and minimally invasive surgical scenarios. The large-diameter design at the fiber source end reduces the coupling difficulty between the laser and the fiber, achieving efficient coupling. The small-diameter, large-bending-radius design at the surgical end adapts to the complex wiring requirements during surgery. Through low-loss, high-power, and stable transmission characteristics, it ensures that the laser energy is accurately applied to the treatment site, improving treatment accuracy and safety. At the same time, its high-temperature resistance, sterilization resistance, and biocompatibility make it suitable for long-term clinical use in medical settings.

[0019] The beneficial effects of this invention are as follows:

[0020] 1. The light source end of this invention adopts a large diameter design of 365μm / 550μm / 600μm, which can achieve efficient coupling with the laser without the need for high-precision alignment equipment. The coupling efficiency is ≥98.5%, which simplifies the operation process of medical equipment, reduces the operation difficulty of medical staff, improves the ease of use of medical equipment, and effectively solves the pain points of high difficulty and cumbersome operation of existing optical fiber coupling.

[0021] 2. The surgical end of this invention adopts a small diameter design of 272μm / 200μm / 150μm and below, which can increase the bending radius to 30-40mm, while the bending loss is still ≤0.02dB / km. It can flexibly adapt to the needs of complex wiring during surgery and flexible operation in cosmetic procedures, avoid energy loss or fiber damage caused by bending, ensure the safety of surgical and cosmetic operations, and effectively solve the pain points of poor bending performance and easy damage during surgery of existing optical fibers.

[0022] 3. The effective field area of ​​this invention reaches 150-200μm. 2 It can significantly reduce laser energy density and has a laser damage resistance threshold of ≥100MW / cm². 2 It can stably transmit high-power medical laser energy, avoid fiber optic burnout, and is suitable for treatment scenarios that require high-power lasers, such as tumor ablation. It effectively solves the pain points of insufficient power carrying capacity of existing optical fibers, which restricts the application of high-power lasers.

[0023] 4. This invention has a transmission loss of ≤0.18dB / km in the wavelength range of 300nm-2400nm, which can be adapted to various medical laser equipment. It can meet the needs of various scenarios such as tumor treatment, minimally invasive surgery, and laser cosmetic surgery without replacing the optical fiber. It expands the application range of optical fiber, reduces the equipment investment and operating costs of medical institutions, and effectively solves the pain points of narrow wavelength adaptability and limited application scenarios of existing optical fibers.

[0024] 5. This invention optimizes the fiber core by doping with a mixture of Yb2O3 and Al2O3 dopants and coating layers, resulting in optical fibers with a high temperature resistance of ≥300℃ and excellent disinfection resistance, making them suitable for the high-temperature environment of medical disinfection. The biocompatibility meets medical-grade standards, eliminating the risk of irritation to human tissue from dopants and coating layers. The continuous service life is ≥3000 hours, meeting the long-term needs of clinical medical use and effectively solving the pain points of poor medical compatibility and long-term performance degradation of existing optical fibers.

[0025] 6. The optimized parabolic refractive index distribution of this invention can minimize the reflection loss of laser energy. The transmission loss is ≤0.18dB / km in the wavelength range of 300nm-2400nm, which is more than 43.75% lower than that of traditional medical optical fibers. The laser energy can be precisely applied to the treatment site, reducing damage to normal tissues and significantly improving the treatment and cosmetic effects. It effectively solves the pain points of high transmission loss and insufficient treatment accuracy of existing optical fibers.

[0026] 7. This invention adopts MCVD combined with high-temperature sintering process. By precisely controlling the refractive index distribution, the differential diameter at both ends and the doping concentration, it achieves precise control of various parameters of the optical fiber, resulting in good product consistency with parameter deviation ≤ ±0.001. The entire manufacturing process is standardized and controllable, enabling large-scale production, reducing manufacturing costs, and possessing extremely high medical engineering application value. It effectively solves the pain points of existing processes, such as weak targeting, poor product consistency, and difficulty in large-scale production. Attached Figure Description

[0027] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0028] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0029] Example 1

[0030] according to Figure 1As shown, this embodiment proposes a graded-index optical fiber for laser energy transmission, its manufacturing method, and its application. The core structure of the optical fiber is optimized for medical applications and includes a core, cladding, and a selectively configured high-temperature resistant coating. The structures and parameters are as follows:

[0031]

[0032] Manufacturing method (MCVD + high-temperature sintering process, for medical use)

[0033] Precision manufacturing of medical-grade graded optical fibers is achieved using in-tube chemical vapor deposition (MCVD) combined with high-temperature sintering. Compared to traditional processes, the core improvements lie in differentiated fiber drawing at both ends, optimized core doping composition, precise control of refractive index distribution, and high-temperature resistant coating. The specific steps are as follows:

[0034] Preform preparation

[0035] (1) Substrate selection: High-purity quartz tubes with a purity of ≥99.995% are used, with an outer diameter of 65mm-85mm and an inner diameter of 45mm-55mm to ensure that the substrate is free of impurities and bubbles, so as to avoid affecting the laser transmission performance and biocompatibility, and to lay the foundation for subsequent doping and deposition.

[0036] (2) Gas deposition: SiCl4 (deposition substrate), GeCl4 (refractive index enhancer dopant), YbCl3, and AlCl3 (damage-resistant and high-temperature resistant dopant) are introduced into the quartz tube. The deposition temperature is controlled at 1500℃-1700℃ and the gas flow rate is controlled at 0.8L / min-2.5L / min to ensure uniform doping. At the same time, the residual harmful impurities are strictly controlled to ensure the biocompatibility of the optical fiber and avoid the dopant from irritating human tissue.

[0037] (3) Concentration control: The flow ratio of each dopant is precisely controlled by a flow meter. The GeO2 doping concentration gradually decreases from the core center to the edge (concentration difference 6%-12%). The doping ratio of Yb2O3 to Al2O3 is 1:1.2-1:1.5, and the doping concentration is kept uniform (0.8%-1.5%). Finally, a parabolic refractive index distribution preform with g=4.25±0.05 is constructed, which takes into account transmission performance, resistance to laser damage and biocompatibility.

[0038] (4) High-temperature sintering: After deposition, the preform is placed in a high-temperature sintering furnace and sintered at 1800℃-2000℃ for 2-3 hours to completely remove impurities and bubbles in the preform, improve the optical uniformity, mechanical strength and biocompatibility of the preform, and ensure the performance stability of the optical fiber after subsequent drawing.

[0039] Wire drawing

[0040] (1) Heating and melting: The preform is placed in a graphite drawing furnace and heated to 2000℃-2200℃ at a heating rate of 8℃ / min-12℃ / min to completely melt the preform, ensuring the stability of the drawing process and avoiding optical fiber parameter deviation due to uneven heating.

[0041] (2) Fiber drawing control: A high-precision fiber drawing machine is used to control the fiber drawing speed from 4m / s to 12m / s. The fiber diameter is fed back in real time by a diameter monitoring instrument, and the fiber drawing tension is adjusted. Differentiated fiber drawing processes are used to form the diameters of the light source end (365μm / 550μm / 600μm) and the surgical end (272μm / 200μm / 150μm and below) respectively, so as to ensure that the diameters of both ends are precise and controllable (deviation ≤ ±1μm).

[0042] (3) Coating process: The fiber is drawn and then passed through a coating machine. A double-layer coating structure is used to coat the surface of the optical fiber with a polyimide high-temperature resistant coating layer. The inner layer is a polyimide bottom layer (thickness 5μm-10μm) and the outer layer is a polyimide wear-resistant layer (thickness 10μm-25μm). The refractive index of the coating layer is 1.41-1.43, which improves the mechanical strength, high-temperature resistance, wear resistance and biocompatibility of the optical fiber, and is suitable for medical disinfection and intraoperative bending requirements.

[0043] Post-processing

[0044] (1) High temperature curing: The coated optical fiber is cured at a high temperature of 300℃-350℃ for 30-60 minutes to ensure that the coating layer and the cladding layer are tightly bonded, avoid peeling, and ensure the protective effect of the coating layer.

[0045] (2) Performance testing: The fiber optic cable is subjected to plastic coating, tension test (testing tensile force ≥120N), laser loss test (using optical time domain reflectometer OTDR, wavelength range 300nm-2400nm), laser damage threshold test, high temperature resistance test, and biocompatibility test in sequence to ensure that the fiber optic cable meets medical grade standards.

[0046] (3) Aseptic treatment: The optical fibers that have passed the test are subjected to professional aseptic treatment to ensure that there are no bacterial residues on the surface of the optical fibers (colony count ≤10CFU / g), which meets the standards for use of medical equipment.

[0047] (4) Packaging and warehousing: Qualified optical fibers are packaged in reels, each reel being 500m-2km in length, and labeled with product model, medical-specific markings, and performance parameters (transmission loss, damage resistance threshold, high temperature resistance level, and biocompatibility level) and stored in the warehouse for easy access in clinical use.

[0048] Application scenario design

[0049] Adapted to the field of laser medicine, it leverages its superior advantages of low coupling difficulty, excellent bending performance, high power load capacity, wide wavelength compatibility, and good biocompatibility to specifically adapt to three core medical application scenarios. Specific application solutions are as follows:

[0050] Cancer treatment scenarios

[0051] Application Scheme: The graded-fiber of this invention is used as the transmission fiber of a tumor laser ablation device, which is compatible with high-power therapeutic lasers with wavelengths of 300nm-2400nm. It connects the laser generator and the treatment probe to achieve precise tumor ablation. The appropriate diameter of the fiber ends can be selected according to the depth and size of the tumor to ensure that the fiber can accurately reach the tumor site.

[0052] Key advantages: The large-diameter design of the light source reduces coupling difficulty, enabling efficient coupling without the need for high-precision alignment equipment and improving treatment efficiency; the small-diameter, large-bending-radius design of the surgical end adapts to complex intraoperative wiring, flexibly bypassing normal tissue and precisely reaching the tumor site; it has a high resistance to laser damage threshold, allowing stable transmission of high-power lasers and avoiding fiber optic burnout; low transmission loss ensures that laser energy is precisely applied to tumor tissue, reducing damage to normal tissues; it is resistant to high temperatures and sterilization, has good biocompatibility, and is suitable for long-term clinical use.

[0053] Minimally invasive surgery scenarios

[0054] Application Scheme: The graded-fiber of this invention can be used as the transmission fiber of a minimally invasive laser surgery device, which is compatible with various minimally invasive surgeries (such as urological and ophthalmic minimally invasive surgeries), and connects the laser generator and the minimally invasive treatment probe to achieve precise transmission of laser energy and surgical operation; the small diameter design of the surgical end can be adapted to the channels of various minimally invasive instruments without enlarging the surgical incision.

[0055] Key advantages: The small diameter design of the surgical end is compatible with minimally invasive instruments, and the large bending radius allows for flexible adjustment of the fiber optic cable's direction, avoiding fiber optic damage during surgery; high transmission stability and uniform laser energy output ensure surgical precision and reduce surgical trauma; good biocompatibility avoids irritation to human tissues, resulting in faster postoperative recovery; high temperature and sterilization resistance allows for repeated use, reducing medical costs.

[0056] Laser beauty scenarios

[0057] Application Scheme: The graded-fiber of this invention can be used as the transmission fiber of laser beauty equipment, which is compatible with beauty lasers with wavelengths of 300nm-2400nm (such as freckle removal, hair removal, and skin tightening lasers). It connects the laser generator and the beauty probe to achieve precise transmission of beauty energy. The bending angle of the fiber can be adjusted according to different beauty areas (face, limbs, etc.) to meet diverse beauty operation needs.

[0058] Key advantages: Wide wavelength compatibility allows for compatibility with various cosmetic laser devices, eliminating the need to replace optical fibers and reducing operating costs for beauty institutions; low transmission loss and high laser energy utilization enhance cosmetic results; excellent flexibility allows for flexible adaptation to different areas such as the face and limbs; high temperature and disinfection resistance enables repeated use, avoiding cross-infection and ensuring cosmetic safety.

[0059] Example 2

[0060] according to Figure 1 As shown, this embodiment proposes a graded-index optical fiber for laser energy transmission, its manufacturing method, and its application. It is suitable for medical scenarios requiring high-power laser transmission, such as tumor treatment, and is compatible with wavelengths from 300nm to 2400nm. Surgical adaptability is optimized through differentiated diameter design at both ends. The core parameters and manufacturing and application processes are as follows:

[0061] Fiber structure parameters: Employing a differential diameter design at both ends to adapt to the light source coupling and intraoperative cabling requirements in tumor treatment; core radius 28μm, cladding diameter adapted to the specifications at both ends (365μm for the light source end, 272μm for the surgical end); relative refractive index difference δ=0.6%, numerical aperture NA=0.20; refractive index distribution factor g=4.23 (within the range of 4.25±0.05), effective mode area 160μm. 2 The double-layer polyimide coating is 20μm thick, with an inner layer of 6μm and an outer layer of 14μm, and is heat resistant up to 320℃; its laser damage resistance threshold is 105MW / cm². 2 With a transmission loss of 0.17dB / km in the wavelength range of 300nm-2400nm, the bending radius of the surgical end can be increased to 30-40mm, and the bending loss is still ≤0.02dB / km. The biocompatibility meets medical-grade standards. It can stably transmit high-power laser energy and is compatible with high-power medical laser equipment such as tumor ablation.

[0062] Manufacturing process:

[0063] (1) Preparation of preform: high-purity quartz tube (outer diameter 68mm, inner diameter 48mm), deposition temperature 1550℃, gas flow rate 1.2L / min; GeO2 doping concentration decreased by 6%, Yb2O3 and Al2O3 doping ratio 1:1.2, doping concentration 0.9%; sintering at 1850℃ for 2 hours to ensure that the optical fiber is compatible with multi-wavelength transmission of 300nm-2400nm, while ensuring biocompatibility.

[0064] (2) Wire drawing and forming: heating rate 8℃ / min, heating to 2050℃, wire drawing speed 6m / s, tension control 70g; adopting differentiated wire drawing process, forming the light source end with a diameter of 365μm and the surgical end with a diameter of 272μm respectively, to ensure that the diameters at both ends are accurately controllable (deviation ≤±1μm); inner layer polyimide 6μm, outer layer polyimide 14μm, coating layer refractive index 1.41, total thickness 20μm, coating layer optimized to adapt to the bending requirements of the surgical end, ensuring no performance degradation after increasing the bending radius, while improving biocompatibility.

[0065] (3) Post-treatment: Cured at 300℃ for 35 minutes, tensile test with a tensile force of 120N, after aseptic treatment, the transmission loss was measured to be 0.17dB / km (wavelength range of 300nm-2400nm), and the laser damage resistance threshold was 105MW / cm. 2 Biocompatibility testing was conducted to ensure compliance with standards, verifying the diameter fit at both ends and the bending performance of the surgical end, thus ensuring compliance with medical equipment usage standards.

[0066] Application Effects: Applied to tumor laser ablation equipment, it is compatible with high-power medical lasers in the wavelength range of 300nm-2400nm, connecting the laser generator and the ablation probe; the 365μm large-diameter design at the light source end enables efficient coupling without the need for high-precision alignment equipment, with a coupling efficiency of ≥98.5%; the 272μm small-diameter design at the surgical end increases the bending radius to 30-40mm, adapting to complex wiring during surgery, and accurately reaching deep tumor sites, avoiding energy loss or fiber damage caused by bending; at the same time, it has a high laser damage threshold, can stably transmit high-power laser energy, accurately control the ablation range, and avoid damage to normal tissue; it is resistant to high temperature and sterilization, with no performance decay after 3000 hours of continuous use, and has good biocompatibility, meeting the long-term needs of medical clinical use, effectively solving the pain points of traditional medical laser fiber coupling difficulties, bending limitations, insufficient power, and narrow wavelength compatibility.

[0067] Example 3

[0068] according to Figure 1 As shown, this embodiment proposes a graded-index optical fiber for laser energy transmission, its manufacturing method, and its application. It is suitable for medical scenarios requiring flexible operation and wide wavelength adaptability, such as laser aesthetic procedures, and is compatible with a wavelength range of 300nm-2400nm. The core parameters and manufacturing and application processes are as follows:

[0069] Fiber structure parameters: Employing a differential diameter design at both ends to adapt to the light source coupling and flexible operation requirements of laser cosmetic procedures; core radius 32μm, cladding diameter adapted to the specifications at both ends (550μm for the light source end, 200μm for the surgical end); relative refractive index difference δ=0.8%, numerical aperture NA=0.24; refractive index distribution factor g=4.26 (within the range of 4.25±0.05), effective mode area 180μm. 2 The double-layer polyimide coating is 25μm thick, with an inner layer of 8μm and an outer layer of 17μm, and is heat resistant up to 340℃; its laser damage resistance threshold is 110MW / cm². 2 With a transmission loss of 0.16dB / km in the wavelength range of 300nm-2400nm, the bending radius of the surgical end can be increased to 30-40mm, and the bending loss is still ≤0.02dB / km. The biocompatibility meets medical-grade standards. It can stably transmit multiple wavelengths of cosmetic lasers, and is suitable for various cosmetic needs such as spot removal, hair removal, and skin tightening.

[0070] Manufacturing process:

[0071] (1) Preparation of preform: high-purity quartz tube (outer diameter 75mm, inner diameter 50mm), deposition temperature 1600℃, gas flow rate 1.8L / min; GeO2 doping concentration decreased by 9%, Yb2O3 and Al2O3 doping ratio 1:1.4, doping concentration 1.2%; sintering at 1900℃ for 2.5 hours to ensure the wide wavelength compatibility and biocompatibility of the optical fiber, and to avoid the dopant residue from irritating human skin.

[0072] (2) Wire drawing and forming: heating rate 10℃ / min, heating to 2100℃, wire drawing speed 8m / s, tension control 80g; adopting differentiated wire drawing process, forming the light source end with a diameter of 550μm and the surgical end with a diameter of 200μm respectively, to ensure that the diameters at both ends are precisely controllable (deviation ≤±1μm); inner layer polyimide 8μm, outer layer polyimide 17μm, coating layer refractive index 1.42, total thickness 25μm, coating layer optimization improves wear resistance and bending performance, adapting to flexible operation of different parts such as face and limbs.

[0073] (3) Post-treatment: Cured at 320℃ for 45 minutes, tensile test yielded a tensile force of 130N, after aseptic treatment, the transmission loss was measured to be 0.16dB / km (wavelength range of 300nm-2400nm), and the laser damage resistance threshold was 110MW / cm. 2 Biocompatibility testing was passed, and the compatibility with wide wavelengths and the flexibility of the surgical tip were verified to ensure compliance with the standards for the use of laser cosmetic equipment.

[0074] Application Effects: Applicable to various laser cosmetic devices, compatible with cosmetic lasers in the 300nm-2400nm wavelength range, meeting multiple cosmetic needs such as freckle removal, hair removal, and skin tightening without the need to replace the optical fiber; the 550μm large-diameter design of the light source end significantly reduces the coupling difficulty with the cosmetic laser generator, with a coupling efficiency of ≥99%, simplifying the cosmetic operation process; the 200μm small-diameter design of the surgical end allows for flexible adjustment of the bending radius to 30-40mm, adaptable to complex areas such as the face and neck, avoiding energy loss due to bending; low transmission loss and high laser energy utilization enhance cosmetic effects and reduce skin irritation; high temperature and sterilization resistance allow for repeated use, reducing operating costs for beauty institutions; good biocompatibility avoids adverse reactions such as skin allergies, suitable for long-term clinical cosmetic use.

[0075] Comparative example (traditional medical laser fiber)

[0076] To verify the advantages of this invention, a traditional medical laser fiber was used as a comparative example, with the following parameters and performance:

[0077] Structural parameters: core radius 25μm, cladding diameter 140μm, both ends have the same diameter (140μm), step-index refractive index distribution, effective mode area 110μm. 2 Laser damage resistance threshold 60MW / cm 2 It can withstand high temperatures up to 200℃, with a transmission loss of 0.32dB / km (single 1064nm wavelength), a bending loss of 0.15dB / km at a bending radius of 50mm, and moderate biocompatibility.

[0078] Manufacturing process: Conventional MCVD process, without Yb2O3 or Al2O3 doping, coating layer is ordinary polyurethane with a thickness of 20μm, no differentiated fiber drawing or special aseptic treatment.

[0079] Performance Comparison Conclusion: Compared with the present invention, the transmission loss of the comparative example is 1.88-2 times that of the present invention, the laser damage resistance threshold is only 54.5%-60% of that of the present invention, the high temperature resistance is reduced by 37.5%-41.2%, the bending loss is 7.5 times that of the present invention, and it is only suitable for a single wavelength; the coupling difficulty is high, the bending radius of the surgical end is small, and it cannot meet the needs of complex wiring and flexible cosmetic operation during surgery; the biocompatibility is average, the disinfection resistance is poor, and the continuous service life is only 1000 hours, which is only 33.3% of that of the present invention; it cannot be adapted to high-power medical laser transmission, and the overall performance is far lower than that of the present invention, making it difficult to meet the needs of clinical treatment and cosmetic procedures.

[0080] The light source end of this invention features a large-diameter design of 365μm / 550μm / 600μm, achieving efficient coupling with a laser without the need for high-precision alignment equipment. The coupling efficiency is ≥98.5%, simplifying the operation of medical equipment, reducing the operational difficulty for medical staff, and improving the ease of use of medical equipment. This effectively solves the pain points of high coupling difficulty and cumbersome operation in existing fiber optic systems. The surgical end of this invention uses a small-diameter design of 272μm / 200μm / 150μm and below, increasing the bending radius to 30-40mm while maintaining bending loss ≤0.02dB / km. This allows for flexible adaptation to complex intraoperative wiring and flexible cosmetic procedures, avoiding energy loss or fiber damage caused by bending, ensuring the safety of surgical and cosmetic operations, and effectively solving the pain points of poor bending performance and easy intraoperative damage in existing fiber optic systems. The effective mode field area of ​​this invention reaches 150-200μm. 2 It can significantly reduce laser energy density and has a laser damage resistance threshold of ≥100MW / cm². 2This invention enables stable transmission of high-power medical laser energy, preventing fiber optic burnout and adapting to treatment scenarios requiring high-power lasers, such as tumor ablation. It effectively addresses the pain points of insufficient power carrying capacity and limitations on high-power laser applications in existing optical fibers. With a transmission loss ≤0.18dB / km in the 300nm-2400nm wavelength range, this invention is compatible with various medical laser devices. It meets the needs of various scenarios such as tumor treatment, minimally invasive surgery, and laser cosmetic procedures without fiber replacement, expanding the application range of optical fibers and reducing equipment investment and operating costs for medical institutions. It effectively solves the pain points of narrow wavelength compatibility and limited application scenarios in existing optical fibers. Through core doping with a mixed dopant of Yb2O3 and Al2O3 and optimization of the coating layer, this invention achieves high-temperature resistance ≥300℃, excellent disinfection resistance, and adaptability to the high-temperature environment of medical disinfection. Its biocompatibility meets medical-grade standards, eliminating the irritation of human tissue by dopant and coating layers. With a continuous service life ≥3000 hours, it meets the long-term clinical use requirements of medical fibers, effectively solving the pain points of poor medical compatibility and long-term performance degradation in existing optical fibers. This invention utilizes an optimized parabolic refractive index distribution to minimize laser energy reflection loss. Transmission loss is ≤0.18dB / km within the 300nm-2400nm wavelength range, a reduction of over 43.75% compared to traditional medical optical fibers. Laser energy can be precisely applied to the treatment site, minimizing damage to normal tissue and significantly improving treatment and cosmetic outcomes. This effectively addresses the pain points of high transmission loss and insufficient treatment precision in existing optical fibers. This invention employs MCVD combined with high-temperature sintering technology. By precisely controlling the refractive index distribution, the differentiated diameters at both ends, and the doping concentration, it achieves precise control of various optical fiber parameters, resulting in excellent product consistency with parameter deviations ≤±0.001. The entire manufacturing process is standardized and controllable, enabling large-scale production, reducing manufacturing costs, and possessing extremely high medical engineering application value. It effectively solves the pain points of existing processes, such as weak targeting, poor product consistency, and difficulty in large-scale production.

[0081] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A graded-color optical fiber for laser energy transmission, comprising a core and a cladding arranged sequentially, characterized in that: The outer side of the cladding may be selectively coated with a high-temperature resistant layer, and the refractive index of the fiber core exhibits a parabolic gradual distribution along the radial direction of the fiber, satisfying the formula... , where n max δ is the maximum refractive index at the fiber core center, δ is the relative refractive index difference, a is the fiber core radius, and g is the refractive index distribution factor, where g = 4.25 ± 0.05; the cladding has a uniform refractive index and is more uniform than n. max Lower by 0.5%-1.0%; The optical fiber features a differential diameter design at both ends to adapt to the light source coupling and intraoperative cabling requirements of medical laser systems. The diameter at the light source end is selectable from 365μm, 550μm, or 600μm, while the diameter at the surgical end is 272μm, 200μm, or 150μm and below. The effective mode area of ​​the optical fiber is 150μm. 2 -200μm 2 The laser energy transmission loss is ≤0.18dB / km in the wavelength range of 300nm-2400nm, the bending loss is ≤0.02dB / km when the bending radius is 30-40mm, and the laser damage resistance threshold is ≥100MW / cm. 2 It can withstand high temperatures of ≥300℃, has biocompatibility that meets medical-grade standards, and is compatible with laser energy transmission in the wavelength range of 300nm-2400nm.

2. The graded-index optical fiber for laser energy transmission according to claim 1, characterized in that: The fiber core has a radius a of 25μm-40μm, a relative refractive index difference δ of 0.5%-1.0%, and a numerical aperture NA of 0.18-0.

28. By reasonably matching the fiber core radius and the relative refractive index difference, the laser energy constraint and transmission efficiency are balanced, accurately adapting to the low-loss transmission and convenient coupling requirements of medical lasers, and avoiding damage to normal tissues caused by laser energy divergence.

3. The graded-color optical fiber for laser energy transmission according to claim 1, characterized in that: The fiber core uses high-purity quartz as a substrate and is doped with a mixture of Yb2O3 and Al2O3 dopants, with a total doping concentration of 0.8%-1.5%. The doping ratio of Yb2O3 to Al2O3 is 1:1.2-1:1.

5. Through the synergistic effect of the dopants, the fiber's resistance to laser damage and high-temperature performance are improved, while strictly ensuring the fiber's biocompatibility and making it suitable for medical applications.

4. The graded-color optical fiber for laser energy transmission according to claim 1, characterized in that: The high-temperature resistant coating is made of polyimide material with a thickness of 15μm-35μm and a high temperature resistance of ≥350℃. The high-temperature resistant coating adopts a double-layer structure, with an inner polyimide bottom layer with a thickness of 5μm-10μm and an outer polyimide wear-resistant layer with a thickness of 10μm-25μm. This double-layer structure is used to improve the adhesion between the coating and the cladding, enhance the mechanical strength, wear resistance and high-temperature protection performance of the optical fiber, and adapt to the needs of medical sterilization environment and intraoperative bending.

5. The graded-color optical fiber for laser energy transmission according to claim 1, characterized in that: The diameter deviation at both ends of the optical fiber is ≤ ±1μm. The large diameter design at the light source end is used to reduce the coupling alignment accuracy requirements with the laser, while the small diameter design at the surgical end is used to flexibly adapt to minimally invasive instruments and increase the bending radius to avoid energy loss or fiber damage caused by fiber bending during surgery.

6. A method for manufacturing graded-index optical fiber for laser energy transmission, applied to the graded-index optical fiber for laser energy transmission described in any one of claims 1-5, characterized in that, The method employs in-tube chemical vapor deposition (MCVD) combined with high-temperature sintering to meet the diverse diameters, high biocompatibility, and high performance requirements of medical optical fibers. This includes the following steps: S1. Preform Preparation: Using a high-purity quartz tube with a purity ≥99.995% as a substrate, SiCl4, GeCl4, YbCl3, and AlCl3 precursor gases are introduced into the tube. The deposition temperature is controlled at 1500℃-1700℃ and the gas flow rate is 0.8L / min-2.5L / min. A SiO2 mixed layer is deposited layer by layer. By adjusting the doping concentration gradient of GeO2, Yb2O3, and Al2O3, a parabolic refractive index distribution preform with a refractive index distribution factor g=4.25±0.05 is constructed. After deposition, the preform is placed in a high-temperature sintering furnace and sintered at 1800℃-2000℃ for 2-3 hours to remove impurities and bubbles, ensuring the biocompatibility, optical uniformity, and mechanical strength of the optical fiber. S2. Fiber Drawing: The preform is placed in a graphite drawing furnace and heated to 2000℃-2200℃ at a heating rate of 8℃ / min-12℃ / min for melting and fiber drawing. The drawing speed is 4m / s-12m / s. Differentiated fiber drawing processes are used to form the diameters of the light source end and the surgical end separately. The fiber diameter is monitored in real time to ensure precise and controllable dimensions. Simultaneously, a high-temperature resistant polyimide coating is applied using a coating machine to ensure uniform coating thickness. S3. Post-processing: The drawn optical fiber is cured at high temperature (300℃-350℃) for 30-60 minutes. Then, the fiber is subjected to plastic coating, tension testing, laser loss detection, damage threshold testing, high temperature resistance testing, and biocompatibility testing. The qualified optical fibers are sterilized and selected to meet the standards for use in medical equipment.

7. A method for manufacturing graded-fiber optical fiber for laser energy transmission according to claim 6, characterized in that: In S1, the doping ratio of Yb2O3 to Al2O3 is 1:1.2-1:1.5, the doping concentration of GeO2 gradually decreases from the center of the fiber core to the edge, and the doping concentrations of Yb2O3 and Al2O3 remain uniform, so as to take into account the gradual change of refractive index, the resistance to laser damage and biocompatibility, and adapt to the needs of medical laser transmission.

8. A method for manufacturing graded-fiber optical fiber for laser energy transmission according to claim 6, characterized in that: In step S2, the diameter and refractive index distribution of the optical fiber are monitored in real time during the fiber drawing process. The drawing tension and drawing speed are adjusted through feedback to ensure the consistency of the optical fiber parameters. The diameter deviation of the optical fiber is ≤ ±1 μm, and the deviation of the refractive index distribution factor g is ≤ ±0.

01. During the coating process, the thickness uniformity of the coating layer is controlled with a deviation of ≤ ±2 μm to ensure the protective effect of the coating layer and the bending performance of the optical fiber. At the same time, a double-layer coating structure is adopted, with the inner layer being a polyimide underlayer and the outer layer being a polyimide wear-resistant layer.

9. A method for manufacturing graded-fiber optical fiber for laser energy transmission according to claim 6, characterized in that: In step S3, the tensile force for tension testing is ≥120N, and laser loss detection is performed using an optical time domain reflectometer (OTDR) to ensure that the transmission loss of the optical fiber in the wavelength range of 300nm-2400nm is ≤0.18dB / km and the laser damage resistance threshold is ≥100MW / cm². 2 The biocompatibility test meets medical-grade standards, and the bacterial count of the optical fiber after sterilization is ≤10 CFU / g, which is suitable for medical clinical use requirements.

10. An application of a graded-color optical fiber for laser energy transmission, characterized in that, The graded optical fiber for laser energy transmission described in any one of claims 1-5 is applied to a laser medical system as a core energy transmission component of a laser therapy device. It is compatible with various medical lasers in the wavelength range of 300nm-2400nm and can be applied to tumor treatment, laser cosmetic surgery, and minimally invasive surgical medical scenarios. The large-diameter design of the fiber optic light source reduces the coupling difficulty between the laser and the fiber, achieving efficient coupling; the small-diameter and large bending radius design of the surgical end adapts to the complex wiring requirements during surgery; the low-loss, high-power, and stable transmission characteristics ensure that the laser energy is accurately applied to the treatment site, improving treatment accuracy and safety; at the same time, its high-temperature resistance, sterilization resistance, and biocompatibility make it suitable for long-term use in medical clinics.

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