A multi-section tapered structure mid-infrared fiber combiner and a preparation method thereof

Abstract

The application discloses a kind of multi-section conical structure's mid-infrared fiber combiner and preparation method thereof, the mid-infrared fiber combiner includes input optical fiber, glass sleeve and output optical fiber, the numerical aperture of output optical fiber is greater than or equal to input optical fiber, input optical fiber is the conical optical fiber bundle formed by the bundle of multiple conical optical fibers, multiple conical optical fibers are arranged in symmetrical polygon on the cross section of optical fiber bundle, each conical optical fiber is the conical structure of gradually reducing diameter along the direction of light path, glass sleeve is sleeved on the outside of optical fiber bundle, output optical fiber includes front taper area, non-pulling taper area and rear taper area, the input end of front taper area is butt-jointed with the output end of optical fiber bundle, front taper area is the conical structure of gradually increasing diameter along the direction of light path, non-pulling taper area is the cylindrical structure of constant diameter, rear taper area is the conical structure of gradually reducing diameter along the direction of light path.The mid-infrared fiber combiner has high synthesis efficiency, excellent beam quality, strong thermal stability, strong engineering practicability and good popularization prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fiber optics, and particularly relates to a multi-section tapered structure mid-infrared fiber combiner and a preparation method thereof. BACKGROUND

[0002] With the rapid development of mid-infrared laser technology and optical devices, high-power mid-infrared fiber lasers are gradually applied in multiple high-tech fields, such as infrared laser transmission, mid-infrared optical communication, environmental remote sensing, infrared imaging, and medical surgery, etc. Laser in the mid-infrared band (2~5 μm) has extremely important application value in optical detection, gas sensing and infrared transmission, especially in high-sensitivity gas detection and high-power optical transmission. Fiber lasers become an important choice in this field due to their superior thermal management performance and high beam quality. However, with the increasing demand for higher power and higher integration, the existing mid-infrared fiber combiner technology still faces many challenges, especially in terms of mode field matching, power transmission efficiency and device stability, etc.

[0003] At present, most of the traditional mid-infrared fiber combiners rely on single-section tapered fiber combiner structure and use simple spatial coupling method. Although these methods are simple in process, they have significant limitations in high-power applications. First, due to the mode field mismatch between fibers, the coupling efficiency is low, which leads to power loss and system efficiency decline. Second, the mode field mismatch of the fiber will cause the phenomenon of beam quality degradation at the output end of the combiner, which is a key problem in applications requiring high beam quality. In addition, the single-section tapered structure also has some shortcomings in improving the power density and its uniformity, and cannot effectively cope with the problem of heat accumulation in the process of high-power laser transmission.

[0004] With the increasing demand, a new design of mid-infrared fiber combiner is needed to improve the overall performance of the device. In order to overcome the shortcomings of the existing technology, the present application proposes a multi-section tapered structure mid-infrared fiber combiner design. SUMMARY

[0005] In view of the problems of mode field mismatch and uneven power density in the process of high-power transmission of the existing mid-infrared fiber combiner, the present application proposes a multi-section tapered structure mid-infrared fiber combiner and a preparation method thereof. By using a multi-section tapered structure design, the problems of uneven beam, increased transmission loss and heat accumulation caused by the single structure of the traditional fiber combiner are solved, thereby significantly improving the stability and power transmission efficiency of the fiber combiner.

[0006] The technical scheme adopted by the present application to solve the above technical problems is: a multi-section conical structure mid-infrared fiber combiner, comprising an input fiber, a glass sleeve and an output fiber, the numerical aperture (NA) of the output fiber is greater than or equal to the numerical aperture of the input fiber, the input fiber is a conical fiber bundle formed by bundling a plurality of conical fibers, the plurality of conical fibers are arranged in a symmetrical polygon on the cross section of the conical fiber bundle, each of the conical fibers is a conical structure with a diameter gradually decreasing along the optical path direction, the glass sleeve is sleeved outside the conical fiber bundle, and the output fiber is a taper fiber with a three-section structure, the output fiber comprises a front taper zone, an untapered zone and a rear taper zone connected in sequence, the input end of the front taper zone is butted with the output end of the conical fiber bundle, the front taper zone is a conical structure with a diameter gradually increasing along the optical path direction, the untapered zone is a cylindrical structure with a constant diameter, and the rear taper zone is a conical structure with a diameter gradually decreasing along the optical path direction.

[0007] The mid-infrared fiber combiner in the present application solves the problems of uneven light beam, increased transmission loss and heat accumulation of the traditional fiber combiner due to the single structure, thereby significantly improving the stability and power transmission efficiency of the fiber combiner. Specifically, the present application adopts a conical fiber bundle formed by bundling a plurality of conical fibers as the input fiber, and the output fiber adopts a three-section structure with a gradually expanding diameter of the front taper zone, a constant diameter of the untapered zone and a gradually decreasing diameter of the rear taper zone. Among them, the output fiber adopts the conical structure with a gradually expanding diameter of the front taper zone, which can optimize the mode transition of the light beam, reduce the unevenness of the light beam at the butt joint between the front taper zone and the output end of the conical fiber bundle, reduce the divergence angle and improve the light beam coupling efficiency; and the output fiber adopts the conical structure with a gradually decreasing diameter of the rear taper zone, so that the power density of the light beam gradually increases in the rear taper zone, thereby enhancing the focusing property of the light beam and improving the light beam quality. Although the power density of the rear taper zone of the output fiber increases, the overall power density distribution of the fiber combiner is relatively uniform, which can still avoid local heat accumulation and improve the heat management performance of the fiber combiner, thereby further improving the stability and durability of the fiber combiner.

[0008] Preferably, each of the conical fibers is a single-clad soft glass fiber, and the initial fiber of each of the conical fibers before tapering has a core diameter of 28-32 μm and a cladding diameter of 120-130 μm; the output fiber is a single-clad soft glass fiber, the taper zone length of the output fiber is 18-22 mm, and the initial fiber of the output fiber before tapering has a core diameter of 110-120 μm and a cladding diameter of 390-410 μm.

[0009] Preferably, the glass sleeve has an inner diameter of 290-310 μm and an outer diameter of 510-530 μm, and the material composition of the glass sleeve is the same as that of the cladding of each of the conical fibers.

[0010] Preferably, the core diameter of the waist region of the front conical region is 100-110 μm and the cladding diameter is 370-380 μm; the core diameter of the waist region of the rear conical region is 70-80 μm and the cladding diameter is 250-270 μm; and the waist region diameter of the tapered fiber bundle is 320-340 μm.

[0011] A method for fabricating the above-mentioned multi-segment tapered mid-infrared fiber combiner includes the following steps:

[0012] S1. Using multiple soft glass optical fibers as the initial optical fibers of the multiple tapered optical fibers, insert the multiple soft glass optical fibers into a glass sleeve in a symmetrical polygonal arrangement to form an initial optical fiber bundle.

[0013] S2. The initial fiber bundle is fused and tapered to form the tapered fiber bundle;

[0014] S3. Cut and polish the waist end face of the tapered fiber bundle;

[0015] S4. Using a soft glass fiber as the initial fiber of the output fiber, and taking the middle part of the soft glass fiber as the untapered region, the two ends of the untapered region are fused and tapered to form a front taper region and a rear taper region at the two ends of the untapered region, and then the waist end face of the front taper region and the rear taper region are cut and polished to obtain the output fiber.

[0016] S5. Connect the input end of the front cone region of the output optical fiber to the output end of the tapered optical fiber bundle using UV-curable adhesive.

[0017] Preferably, in step S2, the fused tapering of the formed tapered fiber bundle is carried out in a protective gas atmosphere. The fused tapering is heated with a graphite torch, and the tapering power is 20-25 W. The length of the tapered region after fused tapering is 15-25 mm, and the length of the waist region is 10-20 mm.

[0018] Preferably, in step S4, the fused tapering to form the front taper region is performed in a protective gas atmosphere. The fused tapering is heated with a graphite torch and the tapering power is 18-24 W. The parameters of the optical fiber obtained after fused tapering are as follows: the core diameter in the waist region is 100-110 μm, the cladding diameter is 370-380 μm, the taper length is 10-20 mm, and the waist length is 5-10 mm. The fused tapering to form the rear taper region is performed in a protective gas atmosphere. The fused tapering is heated with a graphite torch and the tapering power is 20-28 W. The parameters of the optical fiber obtained after fused tapering are as follows: the core diameter in the waist region is 70-80 μm, the cladding diameter is 250-270 μm, the taper length is 15-30 mm, and the waist length is 5-10 mm.

[0019] Preferably, the protective gas is argon with a purity ≥5N, and the oxygen content in the protective gas is ≤0.5ppm and the water content is ≤1ppm.

[0020] Preferably, in steps S2 and S4, the drawing speed of the molten tapered tube is 0.4-0.8 mm / s, and the flow rate of the protective gas is 400-500 mL / min.

[0021] Preferably, the soft glass optical fibers mentioned in steps S1 and S4 are tellurate glass optical fibers, fluoride glass optical fibers, or chalcogenide glass optical fibers, respectively.

[0022] Compared with existing technologies, this invention has the following advantages: The mid-infrared fiber combiner of this invention, through its multi-segment conical structure design, optimizes the mode transition of the beam, significantly improving the coupling efficiency and beam quality. Furthermore, by reducing higher-order modes generated during high-power laser transmission, it further enhances the focusing and uniformity of the output beam. In addition, the overall power density distribution of the mid-infrared fiber combiner of this invention is relatively uniform, effectively avoiding local heat accumulation, improving the thermal management performance of the fiber combiner, and further enhancing its stability and durability. This, in turn, is beneficial for improving the adaptability and output quality of mid-infrared high-power laser systems. The mid-infrared fiber combiner of this invention achieves efficient laser transmission in the mid-infrared band, featuring high combining efficiency, excellent beam quality, and strong thermal stability. It has strong engineering practicality and good prospects for widespread application, and can meet the needs of mid-infrared laser systems for high-power, highly integrated output devices. Attached Figure Description

[0023] Figure 1 This is a longitudinal sectional view of the overall structure of the multi-segment tapered mid-infrared fiber combiner in Example 1;

[0024] Figure 2 This is a schematic diagram illustrating the effect of inserting three tellurate optical fibers into a glass sleeve in an equilateral triangle arrangement, as shown in Example 1.

[0025] Figure 3 This is a cross-sectional view of a single tellurate optical fiber before tapering in Example 1;

[0026] Figure 4 This is a cross-sectional view of the glass sleeve before tapering in Example 1;

[0027] Figure 5 This is a view of the waist region end face of the tapered fiber bundle prepared in Example 1;

[0028] Figure 6 The simulation diagram shows the optical field distribution of the front cone region cross-section of the output fiber of the multi-segment tapered mid-infrared fiber combiner in Example 1.

[0029] Figure 7 The image shows a simulation of the optical field distribution of the untapered cross-section of the output fiber of the mid-infrared fiber combiner with a multi-segment tapered structure in Example 1.

[0030] Figure 8 The simulation diagram shows the optical field distribution of the rear cone region cross-section of the output fiber of the mid-infrared fiber combiner with a multi-segment tapered structure in Example 1.

[0031] Figure 9 The simulation curves of the relative maximum light intensity density at different end faces of the mid-infrared fiber combiner with a multi-segment tapered structure in Example 1 are shown. Detailed Implementation

[0032] To enable those skilled in the art to more clearly understand the technical solution of the present invention, the mid-infrared fiber combiner and its fabrication method of the present invention will be clearly and completely described below in conjunction with preferred embodiments and accompanying drawings. It should be understood that these embodiments are only used to better illustrate the technical content of the present invention and should not be considered as limiting the scope of protection of the present invention. Any equivalent substitutions, modifications, or improvements made to the present invention without departing from its spirit and substance should fall within the scope of protection of the present invention.

[0033] It should be noted that although tellurate fiber was used in Example 1, the multi-segment tapered structure design and fabrication method of the present invention are also applicable to other types of soft glass optical fibers, such as fluoride fiber and chalcogenide fiber. All devices, components, or structures not specified in this invention employ conventional techniques in the art.

[0034] The protective gas used in Example 1 below is argon with a purity ≥5N, and the oxygen content in the protective gas is ≤0.5 ppm and the water content is ≤1 ppm.

[0035] Example 1: A multi-segment tapered mid-infrared fiber combiner, such as... Figure 1As shown, the mid-infrared fiber combiner includes an input fiber 1, a glass sleeve 2, and an output fiber 3. The numerical aperture of the output fiber 3 is greater than or equal to the numerical aperture of the input fiber 1. The input fiber 1 is a tapered fiber bundle formed by three tapered fibers 11. The three tapered fibers 11 are arranged in an equilateral triangle on the cross-section of the tapered fiber bundle. Each tapered fiber 11 has a tapered structure with a diameter that gradually decreases along the optical path. The glass sleeve 2 is fitted outside the tapered fiber bundle. The output fiber 3 is a tapered fiber with a three-segment structure. The output fiber 3 includes a front tapered region 31, an untapered region 32, and a rear tapered region 33 connected in sequence. The input end of the front tapered region 31 is connected to the output end of the tapered fiber bundle. The front tapered region 31 has a tapered structure with a diameter that gradually increases along the optical path. The untapered region 32 has a cylindrical structure with a constant diameter. The rear tapered region 33 has a tapered structure with a diameter that gradually decreases along the optical path.

[0036] The fabrication method of the multi-segment tapered mid-infrared fiber combiner in Example 1 includes the following steps:

[0037] S1. Using three single-clad tellurate fibers with a core diameter of 30 μm, a cladding diameter of 125 μm, and a length of 30 cm as the initial three tapered fibers, insert these three tellurate fibers into a glass sleeve made of tellurate glass in an equilateral triangular arrangement. Figure 2 As shown, the glass sleeve has an inner diameter of 300 μm and an outer diameter of 520 μm, ensuring the stable alignment of the three tellurate fibers to form an initial fiber bundle with a diameter of 520 μm. All tellurate fibers and the surface of the glass sleeve were wiped with lint-free paper dampened with anhydrous alcohol to ensure the absence of dust or contaminants. The cross-sections of a single tellurate fiber and the glass sleeve before tapering are shown below. Figure 3 and Figure 4 As shown;

[0038] S2. Place two U-shaped fiber clamps with a clamping size of 550 μm into the clamping slots of the displacement platform. Place the initial fiber bundle into the clamps and clamp it. Start the tapering program of the fiber tapering machine - alternating left and right tapering in the same direction. Perform fusion tapering treatment on the initial fiber bundle in a protective gas atmosphere to form a tapered fiber bundle. The fusion tapering uses a graphite burner for heating, the tapering power is 22-25 W, the tapering speed is 0.7 mm / s, and the flow rate of the protective gas is 400-500 mL / min. After fusion tapering, a tapered fiber bundle with a waist diameter of 330 μm, a cone length of 20 mm, and a waist length of 10 mm is obtained. After the fusion tapering is completed, measure the diameter curve of the tapered fiber bundle to ensure that the cone part is linear and the actual diameter of the waist region meets the requirements.

[0039] S3. Cut and polish the waist end face of the tapered fiber bundle, ensuring a smooth fiber end face. The waist end face of the cut tapered fiber bundle should look like this.Figure 5 As shown;

[0040] S4. Place two U-shaped fiber clamps with a clamping size of 500 μm into the clamping slots of the displacement platform. Use a single-clad tellurate fiber with a core diameter of 120 μm and a cladding diameter of 400 μm as the initial fiber for the output fiber. Using the middle section of this soft glass fiber as the untapered region, place and clamp the initial fiber in the clamps. Start the taper program of the fiber tapering machine—alternating left and right single-sided tapering. Melt taper both ends of the untapered region in a protective gas atmosphere, thus forming a front taper region and a rear taper region at both ends of the untapered region, respectively. Improve the beam transmission characteristics through gradual mode field transition and power density optimization. After tapering, cut and polish the waist end faces of the front and rear taper regions to ensure smooth fiber end faces, obtaining the output fiber, wherein:

[0041] The molten taper was heated using a graphite burner. The tapering parameters for the front taper region were: tapering power of 22-23 W, tapering speed of 0.7 mm / s, and protective gas flow rate of 400-500 mL / min. After molten tapering, the resulting front taper region had a core diameter of 110 μm, a cladding diameter of 370 μm, a taper length of 20 mm, and a waist length of 5 mm. After molten tapering, the diameter curve of the front taper region was measured to ensure that the taper region was linear and that the actual waist diameter met the requirements. The tapering parameters for the rear taper region were: tapering power of 22-24 W, tapering speed of 0.7 mm / s, and protective gas flow rate of 400-500 mL / min. After molten tapering, the resulting front taper region had a core diameter of 80 μm, a cladding diameter of 270 μm, a taper length of 20 mm, and a waist length of 5 mm. After the molten tapering process is completed, the diameter curve of the rear tapered region is measured to ensure that the tapered region is linear and the actual diameter of the waist region meets the requirements.

[0042] S5. Place the tapered fiber bundle and the output fiber in the fiber optic clamp on the microscopic platform. Adjust the clamp to precisely align the output end of the tapered fiber bundle with the front tapered section of the output fiber. Cure the connection with UV-curable adhesive to ensure stability and low loss. After alignment, a multi-segment tapered mid-infrared fiber combiner is obtained, its overall structure as shown below. Figure 1 As shown.

[0043] The overall performance of the multi-segment tapered mid-infrared fiber combiner of Example 1 was tested. Test results show that there is no crosstalk between the tapered fibers of the input fiber, and no crosstalk affecting the combining of laser beams in different wavelength bands, achieving an overall transmission efficiency of 85% at a wavelength of 2 μm. Furthermore, a comprehensive simulation test was conducted on the optical field distribution within the operating spectral range (2~5 μm), and the simulation diagram of the optical field distribution of the combiner's output fiber is shown below. Figures 6-8As shown in the simulation curve of relative maximum light intensity density, the following is a diagram. Figure 9 As shown, it is verified that it meets the design requirements.

[0044] like Figures 6-8 In the diagram, the horizontal axis X and the vertical axis Y represent the spatial coordinates on the cross-section of the optical fiber, and the color bars on the right represent the relative intensity distribution of the light field (normalized, the intensity shown is a relative value).

[0045] like Figures 6-8 The simulation diagram of the optical field distribution illustrates that: the fiber bundle taper ratio of the fiber combiner is set to 1.6, the front taper ratio of the output fiber is 1.1, and the rear taper ratio of the output fiber is 1.5. Before tapering, the core diameter and cladding diameter of the three tapered fibers in the input fiber are 30 μm and 125 μm, respectively. After tapering, the core diameter of the resulting three-core fiber is approximately 105 μm. The core diameter of the front taper region of the connected output fiber is approximately 110 μm (slightly larger than the core diameter of the three-core fiber), and the cladding diameter is approximately 363 μm; the core diameter of the rear taper region is approximately 80 μm, and the cladding diameter is approximately 266 μm. Theoretical simulation results show that, under this combiner structure, the beam quality (BPP) of the front taper region of the output fiber is approximately 8.08 mm·mrad, the beam quality (BPP) of the untapered region of the output fiber is approximately 8.15 mm·mrad, and the beam quality (BPP) of the rear taper region of the output fiber is approximately 6.46 mm·mrad, meeting the design requirements.

[0046] Figure 9 The simulation curve of the relative maximum light intensity density is explained as follows: the horizontal axis represents the position Z along the fiber transmission direction, and the vertical axis represents the normalized maximum light intensity density I, where the maximum light intensity density of the input laser is 1; L1 is the maximum light intensity density for different lengths of the input fiber, L2 is the front taper region of the output fiber, L3 is the untapered region of the output fiber, and L4 is the rear taper region of the output fiber. Figure 9 It can be seen that the light intensity density fluctuation in the front taper region of the output fiber is reduced, and the transmission stability is improved; the light intensity density fluctuation in the untapered region of the output fiber is relatively large; the light intensity density in the rear taper region of the output fiber is significantly improved, and the power density is enhanced, which meets the design requirements.

Claims

1. A mid-infrared fiber combiner with a multi-segment conical structure, characterized in that, The system includes an input optical fiber, a glass sleeve, and an output optical fiber. The numerical aperture of the output optical fiber is greater than or equal to that of the input optical fiber. The input optical fiber is a tapered fiber bundle formed by multiple tapered optical fibers arranged in a symmetrical polygonal pattern on the cross-section of the bundle. Each tapered optical fiber is a single-clad soft glass fiber with a tapered structure whose diameter gradually decreases along the optical path. The glass sleeve is fitted over the tapered fiber bundle. The output optical fiber is also a single-clad soft glass fiber and is a tapered fiber with a three-segment structure. The output optical fiber includes a front tapered region, an untapered region, and a rear tapered region connected in sequence. The input end of the front tapered region is connected to the output end of the tapered fiber bundle. The front tapered region is a tapered structure with a gradually increasing diameter along the optical path, the untapered region is a cylindrical structure with a constant diameter, and the rear tapered region is a tapered structure with a gradually decreasing diameter along the optical path.

2. The mid-infrared fiber combiner with a multi-segment conical structure according to claim 1, characterized in that, The initial fiber diameter of each tapered fiber before tapering is 28-32 μm and the cladding diameter is 120-130 μm; the tapered length of the output fiber is 18-22 mm, and the initial fiber diameter of the output fiber before tapering is 110-120 μm and the cladding diameter is 390-410 μm.

3. The mid-infrared fiber combiner with a multi-segment conical structure according to claim 2, characterized in that, The glass sleeve has an inner diameter of 290-310 μm and an outer diameter of 510-530 μm, and the material composition of the glass sleeve is the same as that of the cladding material of each tapered optical fiber.

4. The mid-infrared fiber combiner with a multi-segment conical structure according to claim 2, characterized in that, The core diameter of the waist region of the front conical region is 100-110 μm and the cladding diameter is 370-380 μm; the core diameter of the waist region of the rear conical region is 70-80 μm and the cladding diameter is 250-270 μm; the waist region diameter of the tapered fiber bundle is 320-340 μm.

5. A method for fabricating a mid-infrared fiber combiner with a multi-segment tapered structure as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Using multiple soft glass optical fibers as the initial optical fibers of the multiple tapered optical fibers, insert the multiple soft glass optical fibers into a glass sleeve in a symmetrical polygonal arrangement to form an initial optical fiber bundle. S2. The initial fiber bundle is fused and tapered to form the tapered fiber bundle; S3. Cut and polish the waist end face of the tapered fiber bundle; S4. Using a soft glass fiber as the initial fiber of the output fiber, and taking the middle part of the soft glass fiber as the untapered region, the two ends of the untapered region are fused and tapered to form a front taper region and a rear taper region at the two ends of the untapered region, and then the waist end face of the front taper region and the rear taper region are cut and polished to obtain the output fiber. S5. Connect the input end of the front cone region of the output optical fiber to the output end of the tapered optical fiber bundle using UV-curable adhesive.

6. The method for fabricating the multi-segment tapered mid-infrared fiber combiner according to claim 5, characterized in that, In step S2, the fused tapering of the formed tapered fiber bundle is carried out in a protective gas atmosphere. The fused tapering is heated by a graphite torch with a tapering power of 20-25 W. The length of the tapered region after fused tapering is 15-25 mm and the length of the waist region is 10-20 mm.

7. The method for fabricating the multi-segment tapered mid-infrared fiber combiner according to claim 5, characterized in that, In step S4, the fused tapering to form the front taper region is performed in a protective gas atmosphere. The fused tapering is heated with a graphite torch and the tapering power is 18-24 W. The parameters of the optical fiber obtained after fused tapering are as follows: the core diameter in the waist region is 100-110 μm, the cladding diameter is 370-380 μm, the taper length is 10-20 mm, and the waist length is 5-10 mm. The fused tapering to form the rear taper region is performed in a protective gas atmosphere. The fused tapering is heated with a graphite torch and the tapering power is 20-28 W. The parameters of the optical fiber obtained after fused tapering are as follows: the core diameter in the waist region is 70-80 μm, the cladding diameter is 250-270 μm, the taper length is 15-30 mm, and the waist length is 5-10 mm.

8. The method for fabricating the multi-segment tapered mid-infrared fiber combiner according to claim 6 or 7, characterized in that, The protective gas is argon with a purity ≥5N, and the oxygen content in the protective gas is ≤0.5 ppm and the water content is ≤1 ppm.

9. A method for fabricating a mid-infrared fiber combiner with a multi-segment tapered structure according to claim 6 or 7, characterized in that, In steps S2 and S4, the tapering speed of the molten tapered tube is 0.4-0.8 mm / s, and the flow rate of the protective gas is 400-500 mL / min.

10. The method for fabricating the multi-segment tapered mid-infrared fiber combiner according to claim 5, characterized in that, The soft glass optical fibers mentioned in steps S1 and S4 are tellurate glass optical fibers, fluoride glass optical fibers, or chalcogenide glass optical fibers, respectively.

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