TWI691745B - Method of splicing optical fibers and structure of spliced optical fiber - Google Patents

Abstract

The present invention therefore provides a method of splicing optical fibers. First, a first optical fiber and a second optical fiber are provided, wherein a core diameter of the first optical fiber is smaller than a core diameter of the second optical fiber. After performing a hydrogen loading treatment for the first optical fiber; a thermal expansion core (TEC) treatment is performed for the first optical fiber and the second optical fiber to match the mode-field (MF) of the first optical fiber and the second optical fiber at the fused section between the first optical fiber and the second optical fiber. The present invention further provides a spliced optical fiber, including a first optical fiber part, a second optical fiber part, and a fused section.

Description

Optical fiber fusion splicing method and fusion fiber

The present invention relates to an optical fiber fusion splicing method, in particular, an optical fiber fusion splicing method including a hydrogen-carrying treatment step. The invention also relates to a fusion spliced optical fiber structure.

The monolithic system with fusion-spliced optical fiber elements does not require troublesome alignment and regular maintenance. Because there is no air gap inside, the cavity between the internal fusion elements exhibits Fresnel reflection. It has the advantage of low consumption. Due to the maturity of the arc splice technology, it is now possible to easily form multiple monolithic fiber systems from multiple fiber component assemblies. However, for some large field-mode area (LMA) fibers, such as high power fiber lasers and passive Q-switched fiber lasers, it is necessary Sophisticated optical fiber splicing techniques such as fiber tapering or thermally diffused expanded core (TEC) are used for mode field (MF) adaptation at the end. The thermal expansion fiber core method has been extensively studied and applied to various devices, such as MF adaptor, pump combiner, fiber couplers for laser diodes And mode coupling in twin-core fiber. Different from the optical fiber thermal fusion drawing method, the optical fiber thermal fusion drawing method gives a physical change to the cladding layer (cladding layer), but the thermal expansion fiber core method is to heat the optical fiber of the small fiber core with oxyhydrogen flame to force the The dopant diffusion in the core part. After the core is expanded to the required mode field area, the heated part of the fiber is cut and spliced to another large mode field area fiber. For quartz optical fibers, the core area is determined by the dopant. When germanium (Ge) is used, its diffusion coefficient is about 1×10 ^-15 m ² /s at 1400°C. At this temperature, the heating time that can extend the effective core diameter from 4 micrometers (μm) to 10 μm will exceed one hour. When heating for such a long time and the heating temperature exceeds the melting point of the glass, the optical fiber is easily deformed by its own gravity, making the heating zone too fragile and difficult to withstand the subsequent mode field adaptation process.

In contrast, arc-induced TEC has received little attention. Since the core expansion area formed by the arc is only a few hundred microns, in order to achieve adiabatic (lossless) mode field conversion in such a short core expansion area, the mode field ratio between the two mismatched optical fibers is strictly limited. In addition, the too small core expansion area is difficult to implement in the post-cutting process, so the mode field adaptation can only be completed by applying an arc at the arc intersection of two unmatched fibers, so that the two fibers at the intersection The cores are processed simultaneously and thermally expanded with the same arc power. Despite some shortcomings, the mode adaptation process using the arc method can be completed in tens of seconds, and it is still considered to be one of the fast and effective methods.

The invention then provides a method involving the mode field adaptation process, which can reduce the loss between the two optical fibers after fusion.

The invention thus provides a method for fusion splicing of optical fibers. A first optical fiber and a second optical fiber are provided, the core diameter of the first optical fiber is smaller than the core diameter of the second optical fiber, and then a hydrogen-carrying treatment is performed on the first optical fiber. Subsequently, a thermal expansion core (TEC) treatment is performed on the first optical fiber and the second optical fiber to match the mode field of the first optical fiber on the splice plane to the mode field of the second optical fiber.

The invention further provides a fusion spliced optical fiber, which includes: a first optical fiber part, with There is a first core layer; a second fiber part has a second core layer, the diameter of the first core layer is smaller than the diameter of the second core layer, the first fiber part contains hydrogen, the second fiber part is substantially The upper side does not contain hydrogen; a fusion cut surface is provided at the junction of the first optical fiber portion and the second optical fiber portion, and the mode field of the first optical fiber portion of the fusion cut surface matches the mode field of the second optical fiber portion.

300: the first optical fiber

400: second fiber

302,402: cladding

306: first vertebral body

406: second vertebral body

304,404: core layer

500: Hydrogen loading treatment

600: Thermal diffusion core treatment

700: fusion cut

Figures 1 to 3 show schematic diagrams of a method for splicing optical fibers of the present invention.

Fig. 4 is a schematic diagram of a spliced optical fiber that has not been overloaded with hydrogen.

FIG. 5 shows a schematic diagram of the measuring system designed in the experiment of the present invention, for measuring the instantaneous fusion loss of the arc thermal expansion fiber core method.

Fig. 6 shows two typical transmission curves for measuring any situation where the optical fiber Hi980 and the hydrogen-loaded optical fiber Hi980 are spliced with the optical fiber BP10/125-08.

Figure 7 (a) ~ (c) show the photos of the spliced untreated optical fiber Hi980 (left) and hydrogen-loaded optical fiber Hi980 (right) during the arc thermal diffusion core process at 1.5 seconds, 3 seconds, and 6 seconds. , (D)~(f) show the line graph corresponding to the change of core diameter with time.

Figure 8 shows the transmission loss curves for the three fiber types (hydrogen-treated optical fiber Hi980, untreated optical fiber Hi980 and optical fiber P10/125-08).

In order to enable those with ordinary knowledge in the technical field to which the present invention belongs to understand the present invention further, in the following description, preferred embodiments of the present invention will be listed, and in conjunction with the drawings, the composition of the present invention and the desired implementation will be described in detail Of effect.

The invention relates to a method of optical fiber fusion splicing. Please refer to FIG. 1 to FIG. 3, which are schematic diagrams showing steps of splicing an optical fiber according to the present invention. The method includes the following steps: As shown in FIG. 1, first a first optical fiber 300 and a second optical fiber 400 are provided. The first optical fiber 300 and the second optical fiber 400 are, for example, single mode optical fibers and are composed of silicon dioxide (SiO ₂ ). The first optical fiber 300 has a cladding layer 302 and a core layer 304, and the second optical fiber 400 has a cladding layer 402 and a core layer 404, the core layer 304 and the core layer 404 has a semiconductor dopant, such as germanium. It can be understood that the range of the core layer 304 in the first optical fiber 300 is defined by the semiconductor dopant therein, and the second optical fiber 400 is also the same. Since the present invention is applied to the fusion of optical fibers, the core diameters of the two optical fibers will be different. As shown in FIG. 1, the core diameter d _{1 of the} core layer 304 in the first optical fiber 300 is smaller than the second The core diameter d _{2 of the} core layer 404 in the optical fiber 400. In one embodiment, the outer diameter D _{1 of the} first optical fiber 300 is equal to the outer diameter D _{2 of the} second optical fiber 400, and in another embodiment, the outer diameter D ₁ may also be different from the outer diameter D ₂ . In an embodiment, the ratio of the mode field area of the first optical fiber 300 and the second optical fiber 400 is 1.3-16.

As shown in FIG. 2, the first optical fiber 300 is subjected to a hydrogen-carrying treatment 500. Hydrogen-loading treatment 500 refers to any technology that can inject hydrogen atoms into an optical fiber and generate germanium-oxygen deficiency centers (GODC) effects with the dopants in the fiber core. In one embodiment, the hydrogen-carrying process is to place the first optical fiber 300 in a high-pressure hydrogen environment to allow hydrogen atoms to penetrate into the first optical fiber 300. The high-pressure hydrogen environment is, for example, 1200 pounds per square inch (pound per square inch or pound-force per square inch, psi) to 2000 psi, and the time is about 4 to 14 days.

As shown in FIG. 3, a thermal expansion core (TEC) process is performed on the first optical fiber 300 and the second optical fiber 400. In one embodiment, the thermal diffusion core treatment may use an electric arc, an oxyhydrogen flame, an excimer laser, or a carbon dioxide laser. In the preferred embodiment of the present invention, the thermal diffusion core treatment is performed by an arc. The temperature can reach 1800 degrees to 2000 degrees Celsius and the duration is 2 to 20 seconds. The two optical fibers 400 are adapted by the arc area (usually about 0.4 mm) between the two electrodes. It is worth noting that, unlike the conventional thermal fiber-fiber tapering method, if arc heating is used, there is no need to apply additional tension to the fiber. As shown in FIG. 3, after the thermal fiber core treatment of the first optical fiber 300 and the second optical fiber 400, the dopants in the core layer 304 and the core layer 404 will diffuse and join each other at the arc discharge. Since the first optical fiber 300 is subjected to hydrogen-carrying treatment, its dopant diffusion rate increases due to the germanium-oxygen deficiency centers (GODC) effect, so although the core diameter d1 of the first optical fiber 300 is smaller than the first In the case where the core diameter d2 of the second optical fiber 400 is larger than the doped diffusion speed in the first optical fiber 300 than in the second optical fiber 400, the core diameter of the first optical fiber 300 in the fusion cut surface will eventually approach The core diameter of the second optical fiber 400 enables the two optical fibers to have matching mode field diameters, thereby achieving an ideal fit. In an embodiment, the mode field diffusion rate of the first optical fiber 300 is 4×10 ⁻⁸ to 2×10 ⁻⁷ cm ² /s. It is worth noting that the match of the Mode field diameters guided in the two fiber cores is related to both the core diameter and the numerical aperture, and the numerical aperture is caused by the difference in refractive index between the core and the core Decided. For example, two cores with the same diameter but different doping concentrations of germanium will have a higher numerical aperture (NA value) and a smaller modal diameter than a core with higher germanium doping. In the preferred embodiment of the present invention, since a single-mode fiber is preferably used, the modal field diameter will be slightly larger but very close to the core diameter, so the modal field matching referred to in the present invention may also be referred to as core matching. On the other hand, modal field matching can be defined by measuring the transmission rate between the first optical fiber and the second optical fiber (relevant measurement methods are described below). In an embodiment, the ratio of the mode field area of the first optical fiber 300 and the second optical fiber 400 is 0.9 to 1.1, and the transmission rate between the first optical fiber 300 and the second optical fiber 400 is 0.9 to 1.

Through the above method, a fusion spliced optical fiber structure can be formed. As shown in FIG. 3, the spliced optical fiber includes a first optical fiber portion (that is, the original first optical fiber 300), and has a first core layer 304. A second fiber portion (ie, the original second optical fiber 400) has a second core layer 404, and the diameter of the first core layer 304 is smaller than the diameter of the second core layer 404. The fusion cut 700 is located where the first optical fiber portion 300 and the second optical fiber portion 400 meet. As described above, after the thermal fiber core diffusion process, the mode field of the first optical fiber portion located at the fusion cut 700 is matched with the mode field of the second optical fiber portion 400. Since the range of the mode field in the optical fiber is positively related to the core layer, those with ordinary knowledge in the art can also understand that the first core layer 304 of the first optical fiber portion (fusion joint 700) here also corresponds to the first The second core layer 404 of the two optical fiber parts makes the area and position of the fusion cut plane 700 substantially the same. In addition, the first core layer 304 presents a first vertebral body 306 near the fusion cutting plane 700, the first vertebral body 306 has a first height H ₁ , and the first vertebral body 306 and the fusion cutting plane 700 have an angle α; the second The core layer 404 presents a second vertebral body 406 near the fusion cutting plane 700, and the second vertebral body 406 has a second height H ₂ . Since the first optical fiber 300 is treated with hydrogen, the diffusion critical temperature also decreases, so there is still significant diffusion away from the arc center, so the first height H _{1 of the} first cone 306 is greater than the second height of the second cone 406 H ₂ . In addition, the first core layer 302 after hydrogen treatment also has a structural difference due to the difference in diffusion speed of the dopant. Please refer to Figure 3 and Figure 4, where Figure 4 is a schematic diagram of a spliced optical fiber that has not been overloaded with hydrogen. From the comparison of these two figures, we can see that due to the faster diffusion rate of the hydrogen-carrying dopant, the angle α in Figure 3 (after hydrogen-carrying treatment) is greater than the angle α _{0 in} Figure 4 (without overload hydrogen treatment), making the first The taper slope of a vertebral body 306 becomes smaller. In the preferred embodiment, the angle α approaches 90 degrees, for example, 87.5-89.9 degrees. Since the first cone 306 has a smaller taper slope, it can facilitate the modal field transition, reduce the loss and increase the transmission rate of the optical fiber, so as to obtain better quality fusion spliced optical fiber.

Because the hydrogen-carrying process can be applied to fiber splicing, the splicing time of the two fibers is shortened, and low-loss high-quality fiber components can be formed. It is suitable for various optical components that require fiber splicing, such as resonant cavity and Bragg grating (fiber) Bragg grating (FBG) composed of Q-switched pulsed laser light emitters, or other high-power lasers, but not limited to this. In order to prove that the above method can indeed reduce the penetration loss of optical fiber splicing, the experimental content will be described below to verify.

In order to monitor the transmission loss of instantaneous fusion by the arc thermal expansion fiber core method, and to eliminate inaccuracies caused by power fluctuations and wavelength sensitivity, a measurement system is designed in this embodiment, please refer to FIG. 5. In Figure 5, the power splitter is connected to a self-made 1030nm continuous ytterbium-doped fiber laser (1030nm CW Yb-doped fiber laser), which is used as a light source. The laser power is set to 3 milliwatts (mW). One port of the power splitter 300 is connected to a fiber sample (fiber A. The power ratio R _ref =P ₁ /P ₀ between the two ports of the power splitter 300 is first determined to be 1.53, and the standard deviation is 0.2%. During the core processing, the transmission rate T _m =R _m /R _ref between the optical fibers A and B is obtained by measuring the power ratio R _m =P ₂ /P ₀ between the two output ports.

In this embodiment, the optical fiber B is a large-core single-mode and single-clad fiber model P10/125-08 manufactured by Liekki, and the optical fiber A is a small single-mode optical fiber manufactured by Corning with a line number of Hi980 State fiber (single mode fiber, SMF). At the same time, the original Hi980 and the hydrogen-treated Hi980 were compared and tested. The optical fiber B (P10/125-08) has a core diameter of 10 μm and a numerical aperture (NA) of 0.08; the small core optical fiber Hi980 has a core diameter of 3.5 μm and a numerical aperture of 0.21. According to Marcuse's equation, the mode field area at 1030 nm is calculated as 9.3×10 ^-7 cm ² (A _ob for fiber B) and 1.28×10 ^-7 cm ² (A _oa for fiber A ), the mode field area ratio between the two is 7.25. The hydrogen-carrying process is to load optical fiber A (Hi980) into a pure hydrogen gas bottle with a high pressure of 1700 psi for 2 weeks, and then test it about 30 hours after removal from the gas bottle. The subsequent fiber splicer (fiber splicer) is S178 LDF manufactured by Fitel. Fiber A and fiber B are spliced using standard single-mode-single-mode (SMF-SMF) arc procedures, and then the arc is gradually added manually on the same splice joint without displacement and stretching. In S178 LDF, the arc power range is from 0 to 200, and the preset value is 100 (the actual power value is not shown in the machine specifications). However, even in different splicer manufacturers, the arc power required for standard single-mode-single-mode splicing should be the same, so it can be used as a reference for standardized power. In this experiment, the power of each arc step is set to 100, and then the parameter most relevant to the output performance is the total accumulated arc duration. Record the transmission rate (transmission) after each arc is applied, and finally draw the curve as shown in Figure 6. Fig. 6 shows three typical transmission curves for measuring any case where the optical fiber Hi980 and the hydrogen-loaded optical fiber Hi980 are spliced with the optical fiber BP10/125-08. The duration of each arc is preset to 750 milliseconds. However, due to the slower diffusion rate of the original fiber Hi980, the duration of each additional arc is set to 2 seconds. The transmission loss value (unit: decibel dB) represented by the Y axis is compared with the cumulative arc duration (unit: second) represented by the x axis. In the case of optical fiber P10/125-08 splicing unprocessed optical fiber Hi980, the maximum transmission rate of arc thermal diffusion core processing is about 81.5% (ie -0.89dB), and the required cumulative arc duration is about 27±2 second. If optical fiber P10/125-08 is spliced with hydrogen-loaded optical fiber Hi980, the optimal transmission rate is increased to 94.6% (ie -0.24dB), and the average cumulative arc duration is shortened to 9.8 seconds.

其中R_A是兩個拼接光纖的模場面積比。因此若根據方程式(I)，若光纖P10/125-08與未處理之光纖Hi980光纖拼接而沒有纖核擴散時(即R_Ao=7.25)，理論傳輸損耗為-3.71dB。 On the other hand, if splicing and thermal diffusion core processing is performed in one long arc step instead of applying multiple-step short arcs, then -0.24dB transmission can be achieved, even the arc Duration reduced to 8 seconds. However, it should be noted that there is also a pre-melting duration in each arc step, which means the time to heat the fiber from room temperature to the melting point, that is, the period during which the dopant does not diffuse. In this embodiment, the pre-melting preset is set to 160 milliseconds (ms). Therefore, it can be understood that the above-mentioned thermal diffusion core processing performed in a long arc step can obtain better results (-0.24dB transmission loss within 8 seconds), which can be attributed to less premelting time. In addition, due to the mismatch of the mode fields of the two fibers, the fusion loss between the two fibers caused by the radial offset and angular misalignment can be calculated by the overlapping integral of the mode field amplitude in the spliced fiber. Assuming ideal alignment, the transmission loss T _MFA caused only by the mismatch of the mode field regions can be expressed by the following equation (I):

Where R _A is the ratio of the mode field area of the two spliced fibers. Therefore, according to equation (I), if the optical fiber P10/125-08 is spliced with the untreated optical fiber Hi980 without core diffusion (that is, R _Ao =7.25), the theoretical transmission loss is -3.71dB.

It can be seen from Figure 6 that the optical fiber can enhance the germanium diffusion rate after being treated with hydrogen. Its quantification and analysis are as follows, and please refer to Table 1 together. First, compare the two cases with a transmission loss of -1.5dB, where the loss caused by the slope of the thermal diffusion core transition zone is negligible (for related discussions, please refer to Figure 8 and the discussion below). Equation (I) can be used to deduce the mode field area ratio R _A,tec of thermal diffusion core processing is 3.35 based on the loss of -1.5dB. For the case of hydrogen-loaded optical fiber Hi980 and original Hi980, if you want to achieve a transmission loss of -1.5dB, the cumulative arc duration is 2.25 seconds and 10.75 seconds, respectively. The cumulative arc duration minus the pre-fusion duration (ie: 2.25-0.16×3 and 10.75-0.16×6), the effective diffusion duration of the two groups of optical fibers are 1.77 seconds and 9.79 seconds respectively (marked in Table 1 as τ _d,h and τ _d,o ).

Since the optical fiber P10/125-08 and the untreated optical fiber Hi980 have the same germanium diffusion constant (cm ² /s), and the mode field area difference (△A _o ) of the two increases with the diffusion, so through the following equation (II), the mode field area ratio after arc treatment is set to 3.35 (derived from equation (II)), and the difference in the area of the thermal conductivity diffusion mode field should be 2.13×10 ^-7 cm ² .

In the case of the optical fiber Hi980 spliced optical fiber P10/125-08 after hydrogen treatment, due to the short diffusion duration, the increased area △A _s in the optical fiber P10/125-08 is 3.85×10 ^-8 cm ² (by △ A _o ×(τ _d,h )/τ _d,o comes). In order to achieve the same mode field reference ratio 3.35, according to the following equation (III), the heat diffusion LMA fiber Hi980 hydrogen difference in △ A _HL should be 1.61 × 10 ^-7 cm ^2.

Therefore, it is estimated that the mode expansion rate of the optical fiber Hi980 after hydrogen treatment is about 4.2 times that of the original untreated optical fiber Hi980.

The main advantage of using hydrogen-carrying optical fibers is that in addition to the increase in the area of the thermal diffusion core area after the arc, the difference in the doping diffusion rate between the splicing intersections can also reduce the transmission loss and shrink Shorter processing time. To prove these advantages, we captured images near the fusion zone of the spliced fiber arc to determine the expansion of the core. As shown in Figure 7, the untreated optical fiber Hi980 and the hydrogen-loaded optical fiber Hi980 are spliced together to compare the different cumulative arc duration of the arc thermal diffusion core treatment of 1.5 seconds, 3 seconds and 6 seconds. The photos taken by the splicer are shown in Figure 7 (a) ~ (c). The core contour is defined by the darkest point closest to the bright center of the core in the figure, and the core diameter and change are calculated accordingly, as shown in Figure 7 (d) ~ (f).

As shown in FIG. 7, the core diameter of the hydrogen-loaded optical fiber Hi980 expands to 10 μm within 6 seconds, and has a relatively large transition area. Compared with the untreated optical fiber Hi980, the diffusion rate of germanium after hydrogen treatment is greatly increased. In this embodiment. Since the optical fiber is placed between the two electrode rods (please refer to the description in Figure 3 and the relevant paragraphs again), and the tip of the electric shock rod is used to discharge, the arc area is not large, about 0.4 mm and the temperature at the center of the arc area The highest (about 2000 degrees Celsius), as soon as it leaves the center point, the heating temperature will drop rapidly. The actual situation can be seen in Figure 7, there is still a significant diffusion of the core of the hydrogen-carrying fiber away from the center of the arc (the arc temperature is lower). It can be seen that the optical fiber can reduce the critical diffusion temperature of Ge after carrying hydrogen. However, it should be noted that the above method of defining the critical dimension (CD) by outline, when the critical dimension is smaller, the judgment result will be limited by the resolution of the image. For example, the measurement size of the original optical fiber Hi980 officially announced should be 5 μm instead of 3.5 μm measured by this method. Therefore, the thermal diffusion core area of the untreated optical fiber Hi980 should be larger than that shown in Figure 7 (d) to (f). However, even with the above-mentioned resolution limitations, this does not affect the judgment of the diffusion rate and diffusion trend of germanium.

In order to further understand the cause of loss and the limitation of the mode field adaptation caused by the arc, we changed the optical fibers A and B to the same type of optical fiber, and spliced the two to continue processing with the arc until large-scale transmission loss occurred. In this experiment, three types of optical fibers (hydrogen-treated optical fiber Hi980, untreated optical fiber Hi980 and optical fiber P10/125-08) were tested, and the transmission degrading curve was recorded as shown in Figure 8. Since the losses of mode field mismatch and other misalignment factors are negligible, the subsequent losses should be directly equivalent to the increasing transition slope of the thermal diffusion core region (as represented by L _slp ). In the case of Figure 8, compared to the case where the optical fiber Hi980 is spliced with the optical fiber P10/125-08 as shown in Figure 5, the loss part L _{slp in} Figure 8 should be the optical fiber P10/125-08 and the optical fiber Hi980 The average of the two curves. For example, at an optimal arc duration of 27 seconds (see Figure 6), the loss L _slp is expected to be about -0.23dB (that is, the average of the curves in Figure 8 is 0.13 and 0.33). On the other hand, for the case where the hydrogen-loaded optical fiber Hi980 is spliced with the optical fiber P10/125-08, the loss L _slp is only -0.03dB when the optimal arc duration is 9.8 seconds (see Figure 6), and from There is almost no loss at the P10/125-08 end of the fiber. It is worth noting that in this loss part L _slp is -0.03dB, which is better than the experimental data of -0.24dB in Figure 6, showing that there are other loss mechanisms besides the mismatch between Lslp and mode field size. Why there is a loss gap of 0.21dB is not clear. The inference here may be the asymmetric core expansion caused by the one-dimensional arc discharge, because the ideal mode field adaptation not only needs to match in the area size, but also involves two Does not match the shape of the fiber connection. That is, if a more symmetrical heating source (such as a three-electrode arc splicer) is used to thermally diffuse the core of the fiber, the transmission rate should be further improved.

In summary, the present invention shows that the mode field adaptation by the arc thermal diffusion fiber core method can achieve better results by loading the small fiber core fiber with hydrogen gas treatment. In the mode field adaptation, when the mode field area ratio of the two mismatched fibers is 7.25, the transmission loss decreases from the theoretical value of -3.71dB to -0.24dB during the cumulative arc duration of 9.8 seconds. The diffusion rate of doped germanium in hydrogen-loaded silicon dioxide fiber is estimated to be 4.2 times that of untreated germanium. Since the hydrogen-carrying treatment can enhance the diffusion rate of germanium, the mode field adaptation between two fibers with different core diameters can be effectively achieved in a very short arc time, in which the fiber shape can be kept unchanged. The physical reason for the increased diffusion rate of germanium is the germanium-oxygen vacancy caused by hydrogen molecules near the germanium location and high arc temperature. It is expected that the use of various heat sources, such as CO ₂ lasers and O ₂ -H ₂ flames, can also achieve enhanced mode field adaptation.

300: the first optical fiber

304,404: core layer

400: second fiber

600: Thermal diffusion core treatment

302,402: cladding

700: fusion cut

306: first vertebral body

406: second vertebral body

Claims (16)

An optical fiber fusion method includes: providing a first optical fiber and a second optical fiber, the core diameter of the first optical fiber is smaller than the core diameter of the second optical fiber; performing a hydrogen-carrying treatment on the first optical fiber; and The first optical fiber and the second optical fiber are subjected to a thermal expansion core (TEC) treatment, so that the first optical fiber and the second optical fiber are located at a fusion cut between the first optical fiber and the second optical fiber The mode fields of the second optical fiber match each other. The optical fiber fusion splicing method as described in item 1 of the patent application scope, wherein the hydrogen-carrying treatment includes placing the first optical fiber in a high-pressure hydrogen environment, and the pressure of the high-pressure hydrogen environment is 1200 psi to 2000 psi. The optical fiber fusion splicing method as described in item 1 of the patent application scope, wherein the second optical fiber is not subjected to hydrogen carrying treatment. The method for splicing optical fibers as described in item 1 of the patent application scope, wherein the first optical fiber and the second optical fiber have a dopant therein, and the distribution of the dopant respectively corresponds to the cores of the first optical fiber and the second optical fiber In the diameter, when the thermal diffusion core treatment is performed, the diffusion rate of the dopant in the first optical fiber is greater than the diffusion rate of the dopant in the second optical fiber. The method for splicing optical fiber as described in item 1 of the patent application scope, where the Thermal diffusion core processing includes the use of electric arcs, oxyhydrogen flames, excimer lasers, or carbon dioxide lasers. An optical fiber fusion splicing method as described in item 1 of the patent application scope, wherein the method is a passive Q-switch mechanism for forming pulsed laser light. The optical fiber fusion splicing method as described in item 1 of the patent application scope, wherein the ratio of the mode field area of the first optical fiber to the second optical fiber is 1.3 to 16 before the thermal diffusion core treatment. The method for fusion splicing an optical fiber as described in item 1 of the patent application scope, wherein the ratio of the mode field area of the first optical fiber to the second optical fiber is 0.9 to 1.1 after the thermal diffusion core treatment. The optical fiber fusion splicing method as described in item 1 of the patent application scope, wherein after the thermal diffusion core treatment is performed, the transmission rate between the first optical fiber and the second optical fiber is 0.9 to 1. The optical fiber fusion splicing method as described in item 1 of the patent application scope, wherein the cumulative arc duration of the thermal diffusion core treatment is 2 to 20 seconds. The optical fiber fusion splicing method as described in item 1 of the patent application scope, in which the mode field diffusion rate of the first optical fiber is 4×10 ^-8 ~2×10 ^-7 cm ² / s. A fusion spliced optical fiber, comprising: a first optical fiber part having a first core layer; a second optical fiber part having a second core layer, the diameter of the first core layer is smaller than that of the second core layer Diameter, the first optical fiber portion contains hydrogen, and the second optical fiber portion does not substantially contain hydrogen; and a fusion cut surface is provided where the first optical fiber portion and the second optical fiber portion meet, the fusion cut surface of the The mode field of the first optical fiber part matches the mode field of the second optical fiber part. The fusion spliced optical fiber as described in item 12 of the patent application scope, wherein the ratio of the mode field area of the first optical fiber part to the second optical fiber part is 0.9 to 1.1. The fusion spliced optical fiber as described in item 12 of the patent application scope, wherein the transmission rate between the first optical fiber part and the second optical fiber part is 0.9 to 1. The fusion splicing fiber as described in item 12 of the patent application range, wherein: the first core layer presents a first vertebral body near the fusion cut plane, the first vertebral body has a first height; and the second core layer A second vertebral body is presented near the fusion cut surface, the second vertebral body has a second height, and the first height is greater than the second height. The fusion splicing optical fiber as described in item 15 of the patent application scope, wherein the first vertebral body and the fusion cut plane have an angle, and the angle is 87.5-89.9 degrees.

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