A double-clad square-shaped chalcogenide optical fiber and a method for fabricating an optical fiber grating based thereon

Abstract

This invention discloses a double-clad square chalcogenide optical fiber and a method for fabricating fiber gratings based thereon, belonging to the field of mid-infrared fiber optic device technology. The double-clad square chalcogenide optical fiber disclosed in this invention, by sequentially cladding an inner cladding and an outer cladding around the core layer, and designing the overall cross-sectional shape as square with each side being planar, allows for precise control of the laser focus within the fiber core, improving the efficiency and quality of fiber grating writing. Simultaneously, utilizing the planar structure on the other side of the fiber, the writing process can be monitored in real-time online, ensuring the consistency and performance stability of the grating. This invention has significant application value in the fields of mid-infrared fiber optic sensing, nonlinear optics, and laser technology.

Description

Technical Field

[0001] This invention belongs to the field of mid-infrared fiber optic device technology, specifically relating to a double-clad square chalcogenide optical fiber and a method for fabricating fiber gratings based thereon. Background Technology

[0002] With the rapid development of mid-infrared technology, chalcogenide optical fibers have attracted widespread attention in fiber optic sensing, nonlinear optics, and laser applications due to their high nonlinear coefficient, wide transmission window, and excellent infrared transmission characteristics. Fiber Bragg gratings (FBGs), as a key component, possess extremely high measurement accuracy, enabling precise detection of minute changes and making them suitable for high-precision measurement and monitoring. Furthermore, FBGs are unaffected by electromagnetic fields, making them suitable for measurement and sensing applications in strong electromagnetic environments. In addition, FBGs exhibit long-term stability and reliability, maintaining stable performance even in harsh environments, making them suitable for long-term monitoring and measurement tasks. Due to their excellent characteristics, FBGs are widely used in structural health monitoring, temperature measurement, pressure sensing, vibration monitoring, and other fields, and can replace traditional sensors, improving system performance and reliability.

[0003] However, writing fiber gratings on existing highly nonlinear chalcogenide fibers faces the following technical bottlenecks: 1) Self-focusing effect: Highly nonlinear chalcogenide fibers are prone to self-focusing under the action of high peak power femtosecond lasers, which makes it impossible for the laser to be effectively focused on the core region of the highly nonlinear chalcogenide fiber, greatly limiting the efficiency and accuracy of fiber grating writing; 2) Structural limitations: The circular cross-section of traditional highly nonlinear chalcogenide fibers has a curved surface, which will cause the laser focus to shift during fiber grating writing; in addition, the curved surface structure makes it difficult to observe the core and makes it impossible to perform online writing monitoring. Summary of the Invention

[0004] The purpose of this invention is to provide a double-clad square chalcogenide optical fiber and a fiber grating based thereon, as well as a method for its fabrication and monitoring, in order to solve the technical problem that the fiber curvature effect of existing chalcogenide optical fibers interferes with laser focusing, resulting in poor efficiency and accuracy of femtosecond laser writing gratings.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention discloses a double-clad square chalcogenide optical fiber, which includes a core layer, an inner cladding layer, and an outer cladding layer; the inner cladding layer and the outer cladding layer sequentially cover the outside of the core layer; the core layer and the inner cladding layer have circular cross-sections; and the outer cladding layer has a square cross-section.

[0007] The core layer, inner cladding layer, and outer cladding layer are made from chalcogenide glass raw materials.

[0008] This invention also discloses a method for preparing the above-mentioned double-clad square chalcogenide optical fiber, comprising the following steps:

[0009] The raw materials for chalcogenide glass were pretreated, and then the core material, inner cladding material and outer cladding material were prepared by vacuum high-temperature melting method.

[0010] The core material, inner cladding material and outer cladding material are machined and then sequentially placed into an extrusion die to prepare a double-clad preform by extrusion.

[0011] The double-clad preform is drawn to obtain the core, inner cladding, and outer cladding materials, ultimately resulting in a double-clad square chalcogenide optical fiber.

[0012] Furthermore, the chalcogenide glass raw material includes As. 40 S 60 As 38 S 62 And As 36 S 64 ;

[0013] The chalcogenide glass raw material of the core layer material is As. 40 S 60； The chalcogenide glass raw material for the inner cladding is As. 38 S 62 The chalcogenide glass raw material for the outer cladding layer is As. 36 S 64 .

[0014] Furthermore, the pretreatment of the chalcogenide glass raw material includes polishing and cleaning processes performed sequentially;

[0015] The process parameters for the extrusion method are: extrusion temperature of 280~330℃, protective gas of helium or argon, and extrusion speed of 0.1~0.4mm / min.

[0016] Furthermore, the process parameters for the drawing process are: drawing temperature of 330~380℃, bar feeding speed of 0.2~0.6mm / min, drawing speed of 2-10m / min, and protective gas of helium or argon.

[0017] This invention also discloses a method for fabricating fiber gratings based on the above-mentioned double-clad square chalcogenide optical fiber, comprising the following steps:

[0018] The aforementioned double-clad square chalcogenide fiber was installed in a femtosecond laser direct writing device, and the plane of the double-clad square chalcogenide fiber was adjusted to be perpendicular to the laser incident direction.

[0019] The focus of the femtosecond laser is adjusted to be positioned in the core region of the double-clad square chalcogenide fiber;

[0020] Fiber Bragg gratings are obtained by writing grating structures point by point using femtosecond lasers.

[0021] Furthermore, the femtosecond laser has a center wavelength of 800 nm, a pulse width of 91 fs, and a repetition rate of 0.5~1 kHz.

[0022] Furthermore, the grating period when using a femtosecond laser to write the grating structure point by point is 1292~2200nm.

[0023] Furthermore, the monitoring method during the fabrication of the fiber Bragg grating includes the following steps:

[0024] On the side of the double-clad square chalcogenide fiber perpendicular to the laser incident direction, the relative position of the femtosecond laser focal point and the core of the double-clad square chalcogenide fiber is observed in real time through a microscopic optical system to ensure the writing quality and consistency.

[0025] Furthermore, the microscopic optical system includes a magnifying glass and a CCD imaging system; the magnifying glass and the CCD imaging system are electrically connected.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention discloses a double-clad square chalcogenide optical fiber. By sequentially cladding an inner cladding and an outer cladding around the core layer and designing the overall cross-sectional shape as square, and with each side of the square fiber being a plane, this planar surface design eliminates the focusing effect of the chalcogenide glass lens, thereby reducing the power density of the femtosecond laser used for writing. This eliminates the interference of the traditional fiber curvature effect on laser focusing, further effectively suppressing the self-focusing effect and improving the efficiency and accuracy of the femtosecond laser writing grating.

[0028] This invention also discloses a method for fabricating fiber gratings based on the above-mentioned double-clad square chalcogenide fiber. The method uses femtosecond laser direct writing technology to write the grating in the fiber core. Due to the planar design of the double-clad square chalcogenide fiber, the interference of nonlinear effects on laser focusing is reduced, and the laser focus can be precisely controlled in the fiber core, thereby improving the efficiency and quality of fiber grating writing.

[0029] This invention also discloses a monitoring method for the fabrication of fiber gratings. Utilizing the planar structure on the other side of the optical fiber, the etching process can be monitored in real time, ensuring the consistency and performance stability of the grating. This solves the problem that the curved surface of the circular cross-section of traditional optical fibers causes laser focus shift during grating etching. Furthermore, the curved surface structure makes it difficult to observe the fiber core, hindering online etching monitoring. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the double-clad square chalcogenide optical fiber of the present invention;

[0031] Wherein: 1-core layer; 2-inner cladding layer; 3-outer cladding layer; a-integral structure; b-section;

[0032] Figure 2 This is a schematic diagram illustrating the process of fabricating the fiber Bragg grating of the present invention;

[0033] Figure 3 The image shows the morphology test results of the fiber grating obtained by the present invention.

[0034] Where: a-Main view; b-Side view;

[0035] Figure 4 This is a transmission / reflection spectrum test image of the fiber grating prepared in this invention. Detailed Implementation

[0036] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0037] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0038] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0039] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0040] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0041] like Figure 1 As shown, the first aspect of the present invention provides a double-clad square chalcogenide optical fiber, which optimizes the circular cross-section design of traditional optical fiber into a square structure, wherein the four side surfaces are planar, thereby eliminating the focusing problem caused by the curvature effect in traditional optical fiber and effectively suppressing the self-focusing effect of the femtosecond laser writing process in highly nonlinear optical fiber. The double-clad square chalcogenide optical fiber includes a core layer 1, an inner cladding layer 2 and an outer cladding layer 3.

[0042] The second aspect of the present invention discloses a method for preparing the above-mentioned double-clad square chalcogenide optical fiber, which uses high-purity chalcogenide glass as the base material and prepares high-performance outer cladding 3, inner cladding 2 and core layer 1 by vacuum high-temperature melting method.

[0043] The third aspect of this invention discloses a method for fabricating fiber gratings based on the aforementioned double-clad square chalcogenide optical fiber, such as... Figure 2 As shown, it includes the following steps:

[0044] Step 1: Equipment Debugging

[0045] The double-clad square chalcogenide fiber is installed in the fixture of the femtosecond laser direct writing device, and the plane of the double-clad square chalcogenide fiber is adjusted to be perpendicular to the laser incident direction. A short fiber of the same size as the fiber is placed on the slide to support the cover glass and keep it in a horizontal position. The slide and cover glass are filled with a matching liquid with a refractive index of 1.8 to eliminate aberrations caused by large refractive index differences as much as possible to avoid affecting the writing.

[0046] Step 2: Focus Positioning

[0047] The laser beam shape is determined by adjusting the size of the aperture in the femtosecond laser optical path to ensure that it meets the requirements of circularity and collimation, thus ensuring that the focal position is the same as the reference point on the imaging system. The laser focus is adjusted by the optical system to precisely focus on the core region of the double-clad square chalcogenide fiber. During the writing process, the laser focus is observed relative to the core by exposing the fiber in the fiber core and rotating the fiber using a fiber rotator. This ensures that the insertion position of the grating region is distributed as far as possible in the middle of the core to guarantee sufficient refractive index modulation depth.

[0048] Step 3: Engraving Process

[0049] A fiber grating was obtained by writing the grating structure point by point using a femtosecond laser. The focusing objective used for writing was an Olympus PLN40x objective. The center wavelength of the femtosecond laser was ~800nm, the pulse width was ~91fs, the repetition rate was 1kHz, and the writing power was about 80μW. Based on the laser repetition rate of 1kHz and the pulse energy of 80nJ, the grating period was set to 1292nm (center wavelength ~1550nm, m=4).

[0050] The fourth aspect of the present invention discloses a monitoring method for the fabrication of a fiber Bragg grating, which utilizes the planar structure on the other side of the optical fiber to observe the writing quality in real time through an online monitoring device.

[0051] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0052] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0053] Example 1

[0054] A method for fabricating a double-clad square chalcogenide optical fiber includes the following steps:

[0055] 1) The raw materials for chalcogenide glass are pretreated, and then the core material (As) is prepared by vacuum high-temperature melting. 40 S 60 ), inner cladding material (As 38 S 62 ) and outer cladding material (As 36 S 64 );

[0056] 2) The core material, inner cladding material and outer cladding material are mechanically polished and then sequentially placed into an extrusion die to prepare a double-clad preform by extrusion. The process parameters of the extrusion method are: extrusion temperature of 280℃, protective gas of helium, and extrusion speed of 0.1mm / min.

[0057] 3) The double-clad preform is placed in the fiber drawing tower for drawing to obtain a double-clad square chalcogenide fiber with an outer diameter of 125μm. The process parameters for drawing are: drawing temperature of 330℃, rod feeding speed of 0.2mm / min, drawing speed of 2m / min, and helium as the protective gas.

[0058] Example 2

[0059] A method for fabricating a double-clad square chalcogenide optical fiber includes the following steps:

[0060] 1) The raw materials for chalcogenide glass are pretreated, and then the core material (As) is prepared by vacuum high-temperature melting. 40 S 60 ), inner cladding material (As 38 S 62 ) and outer cladding material (As 36 S 64 );

[0061] 2) The core material, inner cladding material and outer cladding material are mechanically polished and then sequentially placed into an extrusion die to prepare a double-clad preform by extrusion. The process parameters of the extrusion method are: extrusion temperature of 305℃, protective gas of argon, and extrusion speed of 0.25mm / min.

[0062] 3) The double-clad preform is placed in the fiber drawing tower for drawing to obtain a double-clad square chalcogenide fiber with an outer diameter of 125μm. The process parameters for drawing are: drawing temperature of 350℃, rod feeding speed of 0.4mm / min, drawing speed of 6m / min, and protective gas of helium.

[0063] Example 3

[0064] A method for fabricating a double-clad square chalcogenide optical fiber includes the following steps:

[0065] 1) The raw materials for chalcogenide glass are pretreated, and then the core material (As) is prepared by vacuum high-temperature melting. 40 S 60 ), inner cladding material (As 38 S 62 ) and outer cladding material (As 36 S 64 );

[0066] 2) The core material, inner cladding material and outer cladding material are mechanically polished and then sequentially placed into an extrusion die to prepare a double-clad preform by extrusion. The process parameters of the extrusion method are: extrusion temperature of 330℃, protective gas of helium, and extrusion speed of 0.4mm / min.

[0067] 3) The double-clad preform is placed in the fiber drawing tower for drawing to obtain a double-clad square chalcogenide fiber with an outer diameter of 125μm. The process parameters for drawing are: drawing temperature of 380℃, rod feeding speed of 0.6mm / min, drawing speed of 10m / min, and helium as the protective gas.

[0068] Example 4

[0069] A method for fabricating a fiber Bragg grating includes the following steps:

[0070] 1) The raw materials for chalcogenide glass are pretreated, and then the core material (As) is prepared by vacuum high-temperature melting. 40 S 60 ), inner cladding material (As 38 S 62 ) and outer cladding material (As 36 S 64 );

[0071] 2) The core material, inner cladding material and outer cladding material are mechanically polished and then placed into an extrusion die in sequence to prepare a double-clad preform by extrusion. The process parameters of the extrusion method are: extrusion temperature of 330℃, protective gas of argon, and extrusion speed of 0.4mm / min.

[0072] 3) The double-clad preform is placed in the fiber drawing tower for drawing to obtain a double-clad square chalcogenide fiber with an outer diameter of 125μm. The process parameters for drawing are: drawing temperature of 380℃, rod feeding speed of 0.6mm / min, drawing speed of 10m / min, and protective gas of argon.

[0073] Example 5

[0074] A method for fabricating a fiber Bragg grating includes the following steps:

[0075] 1) Equipment debugging

[0076] The double-clad square chalcogenide fiber prepared in Example 1 was installed in the fixture of the femtosecond laser direct writing device. The plane of the double-clad square chalcogenide fiber was adjusted to be perpendicular to the laser incident direction. A short fiber of the same size as the fiber was placed on the slide to support the cover glass and keep it in a horizontal position. A matching liquid with a refractive index of 1.8 was filled in the slide and the cover glass to eliminate the aberrations caused by the large refractive index difference as much as possible so as to avoid affecting the writing.

[0077] 2) Focus Positioning

[0078] The laser beam shape is determined by adjusting the size of the aperture in the femtosecond laser optical path to ensure that it meets the requirements of circularity and collimation, thus ensuring that the focal position is the same as the reference point on the imaging system. The laser focus is adjusted by the optical system to precisely focus on the core region of the double-clad square chalcogenide fiber. During the writing process, the laser focus is observed relative to the core by exposing the fiber in the fiber core and rotating the fiber using a fiber rotator. This ensures that the insertion position of the grating region is distributed as far as possible in the middle of the core to guarantee sufficient refractive index modulation depth.

[0079] 3) Engraving process

[0080] A fiber grating was obtained by writing the grating structure point by point using a femtosecond laser. The focusing objective used for writing was an Olympus PLN40x objective. The center wavelength of the femtosecond laser was 800nm, the pulse width was 91fs, the repetition rate was 1kHz, the writing power was about 80μW, and the grating period was set to 1292nm (center wavelength ~1550nm, m=4).

[0081] Example 6

[0082] A method for fabricating a fiber Bragg grating includes the following steps:

[0083] 1) Equipment debugging

[0084] The double-clad square chalcogenide fiber prepared in Example 2 was installed in the fixture of the femtosecond laser direct writing device. The plane of the double-clad square chalcogenide fiber was adjusted to be perpendicular to the laser incident direction. A short fiber of the same size as the fiber was placed on the slide to support the cover glass and keep it in a horizontal position. A matching liquid with a refractive index of 1.8 was filled in the slide and the cover glass to eliminate the aberrations caused by the large refractive index difference as much as possible so as to avoid affecting the writing.

[0085] 2) Focus Positioning

[0086] The laser beam shape is determined by adjusting the size of the aperture in the femtosecond laser optical path to ensure that it meets the requirements of circularity and collimation, thus ensuring that the focal position is the same as the reference point on the imaging system. The laser focus is adjusted by the optical system to precisely focus on the core region of the double-clad square chalcogenide fiber. During the writing process, the laser focus is observed relative to the core by exposing the fiber in the fiber core and rotating the fiber using a fiber rotator. This ensures that the insertion position of the grating region is distributed as far as possible in the middle of the core to guarantee sufficient refractive index modulation depth.

[0087] 3) Engraving process

[0088] Fiber Bragg gratings were obtained by writing grating structures point by point using a femtosecond laser. The focusing objective used for writing was an Olympus PLN40x objective, with a femtosecond laser center wavelength of 800nm, a pulse width of 91fs, a repetition rate of 0.5KHz, a writing power of about 80μW, and a grating period setting of 2200nm.

[0089] Example 7

[0090] A method for fabricating a fiber Bragg grating includes the following steps:

[0091] 1) Equipment debugging

[0092] The double-clad square chalcogenide fiber prepared in Example 3 was installed in the fixture of the femtosecond laser direct writing device. The plane of the double-clad square chalcogenide fiber was adjusted to be perpendicular to the laser incident direction. A short fiber of the same size as the fiber was placed on the slide to support the cover glass and keep it in a horizontal position. A matching liquid with a refractive index of 1.8 was filled in the slide and the cover glass to eliminate the aberrations caused by the large refractive index difference as much as possible so as to avoid affecting the writing.

[0093] 2) Focus Positioning

[0094] The laser beam shape is determined by adjusting the size of the aperture in the femtosecond laser optical path to ensure that it meets the requirements of circularity and collimation, thus ensuring that the focal position is the same as the reference point on the imaging system. The laser focus is adjusted by the optical system to precisely focus on the core region of the double-clad square chalcogenide fiber. During the writing process, the laser focus is observed relative to the core by exposing the fiber in the fiber core and rotating the fiber using a fiber rotator. This ensures that the insertion position of the grating region is distributed as far as possible in the middle of the core to guarantee sufficient refractive index modulation depth.

[0095] 3) Engraving process

[0096] A fiber grating was obtained by writing the grating structure point by point using a femtosecond laser. The focusing objective used for writing was an Olympus PLN40x objective, the center wavelength of the femtosecond laser was 800nm, the pulse width was 91fs, the repetition rate was 0.75KHz, the writing power was about 80μW, and the grating period was set to 1600nm.

[0097] Figure 3 The image shows the morphology test results of the fiber grating obtained by the present invention. As can be seen from the image, the grating is uniformly written into the core of the double-clad square chalcogenide fiber.

[0098] The prepared fiber Bragg grating was subjected to performance testing. The reflectivity, center wavelength, and bandwidth of the fiber Bragg grating were characterized to verify that it met the design requirements. The light source used for the test was a Leukos ElECTRO MIR 4.8 mid-infrared supercontinuum light source (800nm-4800nm), and the spectrometer was a Yokogawa AQ6377 (1900nm-5500nm) with a maximum resolution of 0.2nm. Two magnifying glasses placed in two dimensions were used in conjunction with the CCD image output to the display screen. The docking effect between the output pigtail of the light source and the FBG fiber was observed by direct docking. The test optical path was that the light source was docked to the FBG fiber, and the tail end of the FBG fiber was connected to the spectrometer for measurement through a bare fiber adapter. Figure 4 The image shows the transmission / reflection spectrum of the fiber optic grating prepared by this invention. The center wavelength of the grating is 1535.4 nm, and the reflectivity of the grating is greater than 95%, thus achieving successful writing of a high-reflectivity grating.

[0099] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for fabricating a fiber Bragg grating, characterized in that, Includes the following steps: The double-clad square chalcogenide fiber was installed in the femtosecond laser direct writing device, and the plane of the double-clad square chalcogenide fiber was adjusted to be perpendicular to the laser incident direction. The focus of the femtosecond laser is adjusted to be positioned in the core region of the double-clad square chalcogenide fiber; Fiber Bragg gratings are obtained by writing grating structures point by point using femtosecond lasers. On the side of the double-clad square chalcogenide fiber perpendicular to the laser incident direction, the relative position of the femtosecond laser focal point and the core of the double-clad square chalcogenide fiber is observed in real time through a microscopic optical system to ensure the writing quality and consistency. The femtosecond laser has a center wavelength of 800 nm, a pulse width of 91 fs, and a repetition rate of 0.5~1 kHz. The double-clad square chalcogenide optical fiber includes a core layer (1), an inner cladding layer (2), and an outer cladding layer (3); the inner cladding layer (2) and the outer cladding layer (3) are sequentially clad around the core layer (1); the core layer (1) and the inner cladding layer (2) have circular cross-sections; the outer cladding layer (3) has a square cross-section and its sides are planar. The core layer (1), inner cladding layer (2) and outer cladding layer (3) are made of chalcogenide glass raw materials.

2. The method for fabricating a fiber Bragg grating according to claim 1, characterized in that, The grating period when using femtosecond lasers to write the grating structure point by point is 1292~2200nm.

3. The method for fabricating a fiber Bragg grating according to claim 1, characterized in that, The microscopic optical system includes a magnifying glass and a CCD imaging system; the magnifying glass and the CCD imaging system are electrically connected.

4. A method for fabricating a double-clad square chalcogenide optical fiber, characterized in that, Includes the following steps: The raw materials for chalcogenide glass were pretreated, and then the core material, inner cladding material and outer cladding material were prepared by vacuum high-temperature melting method. The core material, inner cladding material and outer cladding material are machined and then sequentially placed into an extrusion die to prepare a double-clad preform by extrusion. The double-clad preform is drawn to obtain the core (1), inner cladding (2) and outer cladding (3) by drawing the core material, inner cladding material and outer cladding material, and finally obtains the double-clad square chalcogenide optical fiber as described in claim 1.

5. The method for fabricating a double-clad square chalcogenide optical fiber according to claim 4, characterized in that, The raw materials for the chalcogenide glass include As. 40 S 60 As 38 S 62 And As 36 S 64 ; The chalcogenide glass raw material of the core layer material is As. 40 S 60； The chalcogenide glass raw material for the inner cladding is As. 38 S 62 The chalcogenide glass raw material for the outer cladding layer is As. 36 S 64 .

6. The method for fabricating a double-clad square chalcogenide optical fiber according to claim 4, characterized in that, The pretreatment of the chalcogenide glass raw materials includes polishing and cleaning processes performed sequentially. The process parameters for the extrusion method are: extrusion temperature of 280~330℃, protective gas of helium or argon, and extrusion speed of 0.1~0.4mm / min.

7. The method for fabricating a double-clad square chalcogenide optical fiber according to claim 4, characterized in that, The process parameters for the drawing process are: drawing temperature of 330~380℃, bar feeding speed of 0.2~0.6mm / min, drawing speed of 2-10m / min, and protective gas of helium or argon.

Images