Gas curing method based on high-brightness broadband light source

Abstract

The invention belongs to the technical field of gas curing, and discloses a gas curing method based on a high-brightness broadband light source, which comprises the steps of carrier gas treatment, solid gas light source construction, solid gas light path construction, solid gas treatment, quality detection and the like. Compared with an existing external irradiation technology, the method adopts a mode that pulses enter a nonlinear optical fiber, a high-brightness broadband light source is generated by utilizing a nonlinear effect, the light source has excellent light beam quality, wide spectrum and high brightness, almost all defects of the optical fiber have corresponding wavelength energy to directly reach a fiber core to improve the performance of the optical fiber, and the optical fiber performance is improved. Gas molecules are more stably left in the material, the carrier gas curing efficiency is improved, defects are reduced, and the service life of the optical fiber is prolonged.

Description

Technical Field

[0001] The present invention relates to the field of gas curing, and in particular to a gas curing method based on a high-brightness wide-band light source. Background Art

[0002] Photodarkening (PD) refers to the phenomenon of light-induced defects that occur when optical fibers operate at high power levels, leading to increased fiber loss. This phenomenon is particularly pronounced in the visible light band. The essence of photodarkening is that electromagnetic waves induce defects in optical fibers. These defects manifest as broadband absorption in the ultraviolet and visible light ranges, causing fiber performance degradation in these bands. The most common defect in quartz optical fibers is the non-bridging oxygen vacancy center (NBOHC) defect, which has a weak absorption band at 630nm. This absorption band significantly increases fiber transmission losses in the visible light band. The photodarkening effect can reduce the service life, reliability, and stability of optical fibers.

[0003] The PD effect causes the output power of fiber lasers to decrease, the laser threshold to increase, and the performance to become unstable during long-term operation, which seriously affects the improvement of the output power of the laser.

[0004] Therefore, studying the mechanism of PD effect and finding ways to reduce or even eliminate it has always been a hot topic of concern for researchers at home and abroad.

[0005] The existing methods to solve the PD effect are mainly the following:

[0006] (1) During the fiber design phase, the fiber structure is designed as a fiber ribbon structure. This method has a suppressive effect on the PD effect, but it is very limited.

[0007] (2) During the fiber preparation phase, co-doping is performed. Cerium ions can be co-doped to effectively suppress the PD effect, but this will increase the numerical aperture of the fiber or introduce other absorption peaks. The preparation process can also be improved at this stage. The sol-gel method can suppress the PD effect better than chemical vapor deposition. However, the suppression of the PD effect is limited.

[0008] (3) After the optical fiber is prepared, the methods at this stage include: loading the optical fiber with hydrogen or deuterium (deuterium is more effective than hydrogen); thermal bleaching or photobleaching; annealing. The problem here is that thermal bleaching will damage the optical fiber coating due to high temperature operation, and photobleaching cannot actually completely bleach the fiber loss, so its effect is limited.

[0009] Introducing carrier gas into optical fibers can alleviate photon darkening. The principle mainly involves the occurrence mechanism of photon darkening and the role of carrier gas.

[0010] The essence of photon darkening is electromagnetic-induced defects in optical fibers. These defects manifest as broadband absorption in the ultraviolet and visible light ranges. These defects capture electrons or holes, forming color centers with specific energies that absorb light. The role of the carrier gas is primarily manifested in two ways: first, gas particles can capture electrons and holes, thereby reducing the concentration of electron-hole pairs and preventing the formation of color centers; second, gas particles can passivate surface defects, reducing the number of surface states and dangling bonds, further improving the performance of the optical fiber.

[0011] However, the problem with loading hydrogen or deuterium into optical fibers is that the gases introduced at high pressure exist primarily in molecular form. When the high pressure is removed, these molecules escape from the fiber, causing the loss reduction effect to diminish over time. Therefore, a method to immobilize the gas particles within the fiber (solidification) is needed.

[0012] There are two main types of solid-gas methods currently proposed. One involves applying an anti-gas coating to lock gas molecules inside the optical fiber. This is costly and expensive. The other involves loading the optical fiber with gas and then irradiating it with strong light.

[0013] The PD effect primarily occurs when defect precursors capture free holes or electrons, forming color centers that block light propagation. The essence of solid-gas irradiation is to direct free gas molecules to defects, causing them to form bonds there. This allows the gas particles to remain stable within the fiber material and fill holes, thereby resolving the PD problem. The formation of color centers during PD darkening is multifaceted, due to the presence of various types of defects within optical fibers. Each defect requires a different solid-gas photon energy (or wavelength).

[0014] Currently, two types of intense light are used for irradiation. One is a broad-spectrum light source, such as a xenon lamp or a halogen lamp. The advantage of this light source is its wide spectrum, extending from ultraviolet to infrared. Because different defects require different photon energies (or wavelengths), broad-spectrum light sources can provide photons of varying energies to target various defects, facilitating solidification. However, due to poor beam quality, these light sources struggle to penetrate the fiber core from the end face, forcing them to irradiate from the outside. This damages the fiber's colloid coating, and due to obstruction by the cladding and the inherently low power density of the light source, the power density of the UV lamp reaching the fiber is very limited, resulting in uneven solidification and poor solidification within the fiber. Another approach to solidification is using a single-wavelength laser, such as a 793nm laser. This high power density and excellent beam quality are well-matched to the low-loss window of quartz fiber, but the single wavelength of the laser is only suitable for specific defect types.

[0015] The present invention aims to provide a new method of solidifying gas, which uses a light source with high beam quality and wide spectrum to solidify gas. The light source enters from the end face of the optical fiber, has high power density, and provides a wide spectrum at the same time, using photons of different wavelengths to promote the combination of gas particles, with high efficiency and significant effect. Summary of the Invention

[0016] In order to overcome the above-mentioned defects, the present invention provides a gas curing method based on a high-brightness wide-band light source to improve the gas curing efficiency.

[0017] To achieve the above object, the present invention provides the following technical solutions:

[0018] A gas curing method based on a high-brightness, wide-band light source comprises the following steps:

[0019] S1 Carrier Gas Treatment: Take a certain length of optical fiber sample and place it in a reactor. Fill the reactor with pre-selected gas and adjust the required environmental parameters to ensure that these parameters remain constant throughout the carrier gas process. At the same time, set the specific carrier gas time;

[0020] S2 solid-gas light source construction: By guiding pulsed light into nonlinear optical fibers, a wide-spectrum light source with high beam quality is generated by leveraging its nonlinear effect;

[0021] S3 solid-gas optical path construction: realize the effective coupling between the optical fiber sample and the output end of the wide-band light source, and can choose direct or indirect coupling. Since the solid-gas light source is a high-beam quality light source output by the optical fiber, it can ensure efficient connection with the optical fiber to be cured;

[0022] S4 solid-gas treatment: Finely adjust the output frequency, pulse width, intensity and irradiation time of the light source to ensure that the light source irradiates the optical fiber sample in a uniform and efficient manner. By optimizing the parameter settings, efficient coupling of the wide-spectrum light source is achieved, which directly acts on the optical fiber core to achieve the desired solid-gas effect;

[0023] S5 quality assessment: Perform quality inspection on various parameters of the optical fiber after solidification.

[0024] Furthermore, the optical fiber samples include finished optical fibers and samples of optical fiber raw materials that have color centers generated during use. If it is a finished optical fiber, the fusion splicing method is more optimal to obtain a smaller loss.

[0025] Furthermore, in the carrier gas treatment step S1, the carrier gas may include but is not limited to hydrogen, deuterium, and mixtures thereof. Different gases used will have different effects on the carrier gas.

[0026] Furthermore, in step S3, the solid-gas optical path is constructed, and the optical fiber sample is connected to the output end of the high-brightness wide-band light source in a spatial coupling or end-to-end manner.

[0027] Further, the step S4 solid gas treatment, high brightness broadband light source wave band range 400-2400nm, frequency 100khz-5Mhz, the use of light source spectrum coverage needs to be as wide as possible, so as to prevent more defects from forming.

[0028] Further, the step S4 solid gas treatment, real-time monitoring of the state of the sample, if the sample is heated, the sample is cooled.

[0029] Further, the step S4 solid gas treatment, maintain the temperature and humidity in the environment at a set value.

[0030] Further, the step S3 solid gas light source design makes use of nonlinear effects.

[0031] In the case of light enough, the refractive index n will change with the light intensity I, this phenomenon is the optical Kerr effect, is directly caused by the refractive index of nonlinear medium change effect, its refractive index n change size and the square of the optical electric field is proportional to.

[0032] In which the refractive index n is composed of linear refractive index n0, and nonlinear refractive index Δn. In the case of large light intensity, the value of nonlinear refractive index is larger, optical Kerr effect will produce greater influence, this is a nonlinear effect. Nonlinear refractive index coefficient n2, is an important parameter to describe the optical Kerr effect, it is proportional to the real part of the third-order susceptibility, and the light intensity is proportional to

[0033] Δn=n2I (1)

[0034] Corresponding to the change of the real part of the third-order refractive index, is the third-order nonlinear optical effect.

[0035] Let the signal light frequency be ω, the pump light frequency ω' self-action and interaction Kerr effect nonlinear polarization intensity is represented as:

[0036] p (3) (ω)=30χ (3) (ω;ω,-ω,ω)|E(ω)| 2 E(ω)

[0037] p (3) (ω)=6ε0χ (3) (ω;ω′,-ω′,ω)|E(ω′)| 2 E(ω) (2)

[0038] During light wave transmission, changes in the refractive index of the medium will cause phase changes in the light, that is, photoinduced refractive index changes modulate the phase: corresponding to the self-acting Kerr effect and the cross-acting Kerr effect, there are self-phase modulation (SPM) and cross-phase modulation (XPM), which are also typical nonlinear effects.

[0039] In addition, the specific spectral broadening process can be characterized by solving the following nonlinear Schrödinger equation:

[0040]

[0041] Among them, ψ=ψ(z,t) represents the complex amplitude of the light wave, z represents the propagation distance, t represents the time, α j The first term on the right side of the equation represents linear transmission, the second term takes into account the effects of higher-order dispersion, and the third term takes into account the nonlinear effects.

[0042] The specific solution of this equation depends on the values ​​of the dispersion coefficient and the nonlinear coefficient. It describes the complex nonlinear effects that occur when a light wave in a nonlinear medium interacts with the nonlinear polarization in the waveguide medium. During this process, the intensity of the light wave changes in the medium, resulting in a change in frequency, thus generating a high-brightness, broadband light source.

[0043] The specific properties of this equation depend on the values ​​of the dispersion coefficient and the nonlinear coefficient. It describes the complex nonlinear spectral broadening effect that occurs when light waves interact with nonlinear polarization in a nonlinear medium. During this process, the intensity of the light waves varies within the medium, resulting in frequency variations and the generation of a broad-spectrum light source. Because this broad-spectrum light is generated in an optical fiber, it exhibits excellent beam quality.

[0044] When selecting nonlinear optical fiber, in order to ensure sufficient width, the zero dispersion wavelength of the nonlinear optical fiber should be close to the wavelength of the pump light source.

[0045] Furthermore, the light source spectrum needs to cover as wide a range as possible to provide energy for gas molecules to bond with different defects, thereby reducing defect formation. The loaded sample can be a finished optical fiber, an optical fiber preform, or other sample that will produce color centers during use. Optical fibers include but are not limited to microstructured optical fibers (photonic crystal fibers, antiresonant fibers, Bragg fibers, etc.), traditional optical fibers with a single structure, etc. The optical fiber material can be pure quartz glass, doped quartz glass, composites, fluorides, silicates, phosphates, germanates, tellurites, sulfides, and other multi-component glass materials or crystals.

[0046] Furthermore, during the curing process, the high-brightness wide-band light source constructed includes but is not limited to a high-brightness wide-band light source generated by a nanosecond laser, a picosecond laser, a femtosecond laser, and the like.

[0047] The laser's gain medium can include, but is not limited to, solids and gases. If a pulsed laser is used, the laser's pulse frequency can be set. Different pulse frequencies result in different curing effects, and the wide-spectrum pump light can be generated regardless of wavelength. The pulse width of the pulsed laser can also be set. Different pulse widths result in different curing effects. The curing time can also be set. Different curing times result in different curing effects.

[0048] Furthermore, the nonlinear optical fiber may be any nonlinear optical fiber such as PCF and doped optical fiber.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The light source utilized in this invention is generated by a single-mode or quasi-single-mode specialty optical fiber, boasting excellent beam quality that matches the numerical aperture and mode of the fiber being cured. Furthermore, the broad spectrum light source generated by the fiber has the advantage, compared to other light sources, of being able to directly penetrate the core of the fiber being cured. This achieves high efficiency without disrupting the fiber's structure or cladding, thus minimizing damage to the fiber.

[0051] When light pulses propagate within a medium, if the optical field intensity is sufficiently high, especially when ultrashort pulses are coupled into an optical fiber, their peak power density is extremely high. This results in a long interaction length within the optical fiber, and a compact waveguide structure is confined, significantly improving nonlinear conversion efficiency. This fiber light source boasts a wide spectral width and high brightness. Regardless of any defects in the fiber, the curing process delivers energy at the corresponding wavelength to improve fiber performance. This can enhance the carrier gas's ability to suppress the photon darkening effect, extending the fiber's lifespan and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other implementation drawings based on the provided drawings without inventive effort.

[0053] The structures, proportions, sizes, etc. illustrated in this specification are intended solely to complement the contents disclosed herein and facilitate understanding and reading by persons skilled in the art. They are not intended to limit the conditions under which the present invention may be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportions, or adjustments in sizes, provided they do not affect the efficacy and objectives of the present invention, shall still fall within the scope of the technical contents disclosed herein.

[0054] Figure 1 The present invention discloses a flow chart of a gas curing method based on a high-brightness wide-band light source.

[0055] Figure 2 This is a laser spectrum diagram used in a gas curing method based on a high-brightness wide-band light source disclosed in the present invention.

[0056] Figure 3 This is a comparison chart showing the time evolution of the normalized intensity of the hydrogen absorption peak at 1240 nm of an optical fiber when it is cured or not using a gas curing method based on a high-brightness wide-band light source disclosed in the present invention.

[0057] Figure 4 This is a schematic diagram of the solid-gas optical path construction steps of a gas solidification method based on a high-brightness wide-band light source disclosed in the present invention, in which the optical fiber sample and the output end of the high-brightness wide-band light source are spatially coupled or end-to-end, a) end-to-end connection, b) spatial coupling. DETAILED DESCRIPTION

[0058] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0059] A gas curing method based on a high-brightness, wide-band light source comprises the following steps:

[0060] S1: Carrier gas treatment

[0061] A 200-meter-long ytterbium-doped active optical fiber was used as the experimental sample; its detailed parameters are shown in Table 1. The optical fiber was placed in a reactor capable of withstanding high temperatures and pressures. The reactor was then filled with a 95% pure nitrogen and hydrogen mixture. Through precise settings in the reactor control system, the experimental conditions were fixed to: a pressure of 8 MPa, a target temperature of 70°C, a temperature ramp time of 10 hours, and a holding time of 100 hours. Temperature stability was ensured throughout the carrier gas treatment process. After the carrier gas treatment was completed, the reactor environment was restored to room temperature and pressure. The optical fiber was then removed and divided into two equal sections, labeled Fiber A and Fiber B.

[0062] Table 1: Various indicators of ytterbium-doped active fiber

[0063] parameter unit index Working wavelength (under normal circumstances) nm 1060 Cladding pump absorption @915nm dB / m 1.60±0.15 Cladding pump absorption near 976nm dB / m 4.8 Fiber core attenuation@1300nm dB / km ≤45.0 Fiber core attenuation@1200nm dB / km ≤30.0 Cladding attenuation@1095nm dB / km ≤15.0 Fiber core diameter um 25.0±1.5 Inner cladding diameter (flat-to-flat) um 255.0±5.0 Coating diameter um 395.0±15.0

[0064] The reactor needs to be capable of high-temperature and high-pressure reactions, and needs to have sufficient safety measures to prevent dangerous situations such as gas leakage and explosion inside the reactor. The reactor needs to be placed in a place with good air circulation to prevent the accumulation of flammable and explosive gases.

[0065] When using carrier gas, you can set the temperature inside the reactor to increase and assist the carrier gas. Different temperatures will produce different carrier gas effects. If you set the temperature to increase, you can set the reactor's heating and holding times. Different times will produce different carrier gas effects. When using carrier gas, you can control the pressure to assist the carrier gas. Different pressures will produce different carrier gas effects.

[0066] S2: Solid-gas light source construction

[0067] A nanosecond pulse fiber laser with a spectral center wavelength of 1064 nanometers, a pulse width of approximately 3 nanoseconds, and a repetition frequency of approximately 700 kHz is selected. The pulsed light is introduced into the nonlinear optical fiber by fusion splicing. By utilizing its nonlinear effect, the high-brightness wide-band light source covering the range of 400-1700nm is realized, which provides the necessary activation energy for the bonding between hydrogen molecules and different defects. The spectral distribution of the wide-spectrum light source is as follows: Figure 3 shown.

[0068] S3: Solid-gas optical path construction

[0069] Fusion coupling technology is used to achieve effective coupling between the optical fiber and the output end of the broadband light source. The fusion splice structure is configured as "broad-spectrum light source pigtail - mode field adapter (i.e., transition fiber) - ytterbium-doped active fiber." The transition fiber used is a quasi-single-mode fiber with a loss controlled between 0.5 and 0.1 dB. This ensures that the light source can illuminate the fiber sample uniformly and efficiently, achieving efficient coupling between the broadband light source and the fiber.

[0070] S4: Solid-gas treatment

[0071] During the solid-gas treatment stage, optical fiber a is placed on a water-cooled plate to maintain its temperature. The laser is then started, and the pulse width of the light source is adjusted to 3 nanoseconds, the repetition frequency is adjusted to 700 kHz, and the solid-gas treatment time is set to 60 hours. The light source acts directly on the optical fiber core, and the light source spectrum covers a wide range, which can prevent more defects from forming.

[0072] S5: Quality Assessment

[0073] The Yb-doped active fiber exhibits a unique hydrogen molecule absorption peak at 1240nm. The absorption peak power of fiber a that has undergone solid-gas treatment and fiber b that has not been treated and only carried out with carrier gas were detected over the next 21 days and their intensity was normalized to obtain Figure 4 The results show that the hydrogen absorption peak at 1240nm of fiber a, after hydrogen fixation, decreases less, indicating less hydrogen loss. Furthermore, after hydrogen fixation using this method, the fiber coating does not experience the yellowing and aging that occurs after xenon lamp pulse irradiation from the side of the fiber.

[0074] This invention utilizes a high-brightness, wide-band light source to address hydrogen fixation. The strong light reaches the fiber core directly, leaving virtually no impact on the coating. This minimizes side effects on the fiber and does not damage the structure of the fiber being fixed with hydrogen, resulting in more efficient hydrogen fixation. This improves the carrier gas's ability to suppress the photon darkening effect, extending the fiber's service life and stability.

[0075] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A gas curing method based on a high-brightness, wide-band light source, characterized in that: Including steps: S1 Carrier Gas Treatment: Take a certain length of optical fiber sample, place it in a reactor, fill the reactor with preselected gas, adjust the reactor environmental parameters and set the carrier gas time; S2 solid-gas light source construction: guides the pump light generated by the laser to the nonlinear optical fiber, and generates a wide spectrum light source with high beam quality based on the nonlinear effect of the optical fiber; S3 solid-gas optical path construction: effectively couple the optical fiber sample processed in step S1 with the output end of the broadband light source generated in step S2; S4 solid-gas treatment: Adjust the output frequency, pulse width, intensity and irradiation time of the wide-spectrum light source generated in step S2 to ensure that the light source irradiates the optical fiber sample in a uniform and efficient manner; at the same time, monitor the temperature of the optical fiber sample to ensure the stable solid-gas process; S5 quality assessment: Perform quality inspection on various parameters of the optical fiber after solidification.

2. The gas curing method based on a high-brightness wide-band light source according to claim 1, characterized in that: The optical fiber sample in step S1 includes optical fiber raw materials including finished optical fibers and optical fiber preforms.

3. The gas curing method based on a high-brightness, wide-band light source according to claim 1, characterized in that: The preselected gas in step S1 includes but is not limited to hydrogen, deuterium and a mixture thereof.

4. The gas curing method based on a high-brightness, wide-band light source according to claim 1, characterized in that: The laser described in step S2 includes but is not limited to a nanosecond laser, a picosecond laser, a femtosecond laser, and the like.

5. The gas curing method based on a high-brightness, wide-band light source according to claim 1, characterized in that: The nonlinear optical fiber described in step S2 is a single-mode or few-mode highly nonlinear optical fiber, the pump light frequency is 100 kHz to 5 MHz, and the generated wide-spectrum light source has a wavelength range of 400 to 2400 nm.

6. The gas curing method based on a high-brightness, wide-band light source according to claim 5, characterized in that: The highly nonlinear optical fiber is a passive photonic crystal fiber (PCF) or a doped optical fiber.

7. The gas curing method based on a high-brightness, wide-band light source according to claim 5, characterized in that: The zero dispersion wavelength of the highly nonlinear optical fiber is located near the wavelength of the pump light.

8. The gas curing method based on a high-brightness, wide-band light source according to claim 1, characterized in that: The effective coupling in step S3 is spatial coupling or end-to-end (butt joint) coupling.

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