Small-diameter multimode optical fiber

Abstract

The present application relates to a small-diameter multimode optical fiber, comprising a core layer, an inner cladding layer, a first depressed cladding layer, a second depressed cladding layer, and an outer cladding layer which are sequentially arranged from inside to outside in the radial direction of the small-diameter multimode optical fiber. The refractive index difference of the first depressed cladding layer relative to pure quartz glass is smaller than that of the second depressed cladding layer relative to the pure quartz glass; and the refractive index difference of the inner cladding layer relative to the pure quartz glass is gradually reduced from inside to outside in the radial direction of the small-diameter multimode optical fiber. According to the present application, the optical fiber has good bending resistance and long-term use stability, meeting the requirements for in-vehicle optical fiber applications.

Description

A thin-diameter multimode optical fiber Technical Field

[0001] The present invention relates to the technical field of optical fibers, and in particular to a thin-diameter multimode optical fiber. Background Art

[0002] With the promotion and popularization of smart cars, cars are becoming more intelligent and automated, which puts higher requirements on the information transmission of cars. The traditional car information signal transmission system has been unable to meet the needs of large amounts of information transmission in modern cars. Therefore, it has become an inevitable trend to use optical cable transmission to replace traditional metal signal lines.

[0003] Due to the special environment of automotive cable installation, limited space, and the presence of numerous bends, higher requirements are placed on the miniaturization, high bend resistance, and stability of optical fibers. In this case, fine-diameter optical fibers require better bending characteristics without compromising signal strength and transmission quality.

[0004] It is difficult for existing ordinary optical fibers to meet the above requirements.

[0005] Summary of the Invention

[0006] The present application provides a thin-diameter multimode optical fiber with good bending resistance and long-term stability, which meets the requirements for vehicle-mounted optical fiber applications.

[0007] The embodiment of the present application provides a thin-diameter multimode optical fiber, which includes a core layer, an inner cladding layer, a first depressed cladding layer, a second depressed cladding layer, and an outer cladding layer arranged in sequence from the inside to the outside along the radial direction of the thin-diameter multimode optical fiber;

[0008] wherein the refractive index difference between the first depressed cladding and pure quartz glass is smaller than the refractive index difference between the second depressed cladding and pure quartz glass;

[0009] The refractive index difference of the inner cladding relative to the pure quartz glass gradually decreases from the inside to the outside along the radial direction of the thin-diameter multimode optical fiber.

[0010] In one embodiment, the refractive index difference of the inner cladding relative to pure silica glass decreases linearly.

[0011] In one embodiment, the refractive index difference between the outer boundary of the inner cladding and pure quartz glass ranges from -0.2% to -0.18%.

[0012] In one embodiment, the width of the inner cladding is 0.5 to 2 μm.

[0013] In one embodiment, the width of the first depressed cladding is 5-9 μm, and the refractive index difference of the first depressed cladding relative to pure quartz glass ranges from -1.1% to -0.7%.

[0014] In one embodiment, the width of the second depressed cladding is 5-9 μm, and the refractive index difference of the second depressed cladding relative to pure quartz glass ranges from -0.7% to -0.4%.

[0015] In one embodiment, the absolute refractive index of the core layer is distributed in an α-power exponential function as the radius of the narrow-diameter multimode optical fiber increases, and the refractive index difference of the center of the core layer relative to pure quartz glass is the largest;

[0016] n (r) 2 =n 芯层中心 2 [1-2Δ1×(r / R1) α ]

[0017] Among them, n (r) is the absolute refractive index of the core layer at a distance r from the center of the core layer, n 芯层中心 is the absolute refractive index at the center of the core layer, Δ1 is the refractive index difference of the center of the core layer relative to pure quartz glass, and R1 is the radius of the core layer.

[0018] In one embodiment, the value of α ranges from 1.90 to 2.13.

[0019] In one embodiment, the radius of the core layer is 23-27 μm, and the refractive index difference of the center of the core layer relative to pure quartz glass is 0.90% to 1.10%.

[0020] In one embodiment, the outer cladding is pure quartz glass with a radius of 35 to 50 μm.

[0021] The beneficial effects of the technical solutions provided in the embodiments of the present application include:

[0022] This application designs a double depressed cladding, namely a first depressed cladding and a second depressed cladding, and increases the depression depth of the first depressed cladding to achieve an optimal stress difference between the core layer, inner cladding, and depressed cladding. This reduces the sensitivity of the optical fiber bandwidth to wavelength, resulting in both good bending resistance and high bandwidth performance. The second depressed cladding can reduce the interface stress between the outer cladding and the depressed cladding, thereby improving the long-term stability of the optical fiber.

[0023] By designing an inner cladding with a gradually decreasing refractive index, a smooth transition of refractive index is achieved between the core layer and the depressed cladding, reducing stress between the core and the cladding, and reducing microcracks caused by stress inside the optical fiber, thereby improving the long-term reliability of the optical fiber.

[0024] Therefore, the thin-diameter multimode optical fiber provided in this application has good bending resistance and long-term stability, meeting the requirements for vehicle-mounted optical fiber applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0026] FIG1 is a schematic diagram of a thin-diameter multimode optical fiber provided in an embodiment of the present application;

[0027] FIG2 is a schematic cross-sectional view of a thin-diameter multimode optical fiber waveguide structure provided in an embodiment of the present application.

[0028] In the figure: 1, core layer; 2, inner cladding; 3, first depressed cladding; 4, second depressed cladding; 5, outer cladding. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0030] 1 and 2 , an embodiment of the present application provides a thin-diameter multimode optical fiber, comprising a core layer 1, an inner cladding 2, a first depressed cladding 3, a second depressed cladding 4, and an outer cladding 5, which are sequentially arranged from the inside to the outside along the radial direction of the thin-diameter multimode optical fiber; wherein the refractive index difference of the first depressed cladding 3 relative to pure silica glass is less than the refractive index difference of the second depressed cladding 4 relative to pure silica glass; and the refractive index difference of the inner cladding 2 relative to pure silica glass gradually decreases from the inside to the outside along the radial direction of the thin-diameter multimode optical fiber.

[0031] This application utilizes a dual depressed cladding design—a first depressed cladding 3 and a second depressed cladding 4—and increases the depression depth of the first depressed cladding 3 to achieve an optimal stress differential between the core layer 1, inner cladding 2, and the depressed cladding. This reduces the sensitivity of the optical fiber's bandwidth to wavelength, resulting in both excellent bending resistance and high bandwidth performance. The second depressed cladding 4 reduces the interfacial stress between the outer cladding 5 and the depressed cladding, thereby improving the optical fiber's long-term stability.

[0032] By designing an inner cladding 2 with a gradually decreasing refractive index, a smooth transition of refractive index is achieved between the core layer 1 and the depressed cladding, reducing stress between the core and cladding, and reducing microcracks caused by stress inside the optical fiber, thereby improving the long-term reliability of the optical fiber.

[0033] The present application can use silicone rubber as a coating on the outer cladding 5 of the optical fiber, so that the optical fiber can withstand a high temperature of 170° C., thereby expanding its application possibilities in special vehicles.

[0034] 2 , R1 represents the radius of the core layer 1 , R2 represents the radius of the inner cladding 2 , R3 represents the radius of the first depressed cladding 3 , R4 represents the radius of the second depressed cladding 4 , and R5 represents the radius of the outer cladding 5 .

[0035] The core layer 1 has a radius R1 of 23-27 μm. The inner cladding 2 has a width R2-R1 in the range of 0.5-2 μm. The first depressed cladding 3 has a width R3-R2 in the range of 5-9 μm. The second depressed cladding 4 has a width R4-R3 in the range of 5-9 μm. The outer cladding 5 is made of pure quartz glass and has a radius of 35-50 μm.

[0036] This application reduces the radial width R4-R2 of the sunken cladding on one side, thereby reducing the diameter of the optical fiber outer cladding while keeping the core diameter unchanged. This saves space while keeping the performance unchanged, and better meets the needs of automotive use.

[0037] In order to make the expression clearer and avoid unclear issues, the refractive index is explained as follows:

[0038] In this application, the refractive index difference of a layer relative to pure quartz glass refers to the relative refractive index difference, and the relative refractive index difference Δi is calculated using the following formula:

[0039] Δi=(n i -n0) / n i *100%

[0040] Where n0 is the absolute refractive index of pure quartz glass. For this application, when calculating the refractive index difference Δ1 of the center of the core layer 1 relative to the pure quartz glass, n0 in the formula is i is the absolute refractive index of the center of the core layer 1; when calculating the refractive index difference Δ2 of the outer boundary of the inner cladding 2 relative to the pure quartz glass, n in the formula i is the absolute refractive index of the outer boundary of the inner cladding 2; when calculating the refractive index difference Δ3 of the first depressed cladding 3 relative to pure quartz glass, n in the formula i is the absolute refractive index of the first depressed cladding 3; when calculating the refractive index difference Δ4 of the second depressed cladding 4 relative to pure quartz glass, n in the formula i is the absolute refractive index of the second depressed cladding 4.

[0041] In this application, the refractive index difference of the inner cladding 2 relative to pure silica glass gradually decreases from the inside to the outside of the narrow-diameter multimode fiber along the radial direction. In other words, the refractive index difference of the inner cladding 2 relative to pure silica glass is negatively correlated with the radius of the narrow-diameter multimode fiber, thereby alleviating the sudden change in refractive index between the core layer 1 and the depressed cladding.

[0042] For example, the refractive index difference of the inner cladding 2 relative to pure quartz glass decreases linearly.

[0043] For another example, the refractive index difference of the inner cladding 2 relative to pure quartz glass gradually decreases in a curve.

[0044] In this way, by adjusting the functional distribution of the refractive index difference between the inner cladding 2 and pure quartz glass, the refractive index between the core layer 1 and the depressed cladding can be optimized to make the transition smoother, reduce the stress between the core and the cladding, and reduce the microcracks caused by stress inside the optical fiber, thereby improving the long-term reliability of the optical fiber.

[0045] The refractive index difference between the outer boundary of the inner cladding 2 and pure quartz glass ranges from -0.2% to -0.18%.

[0046] As shown in FIG2 , the refractive index difference of the first depressed cladding 3 relative to pure quartz glass is negative and does not change with radius. Preferably, the refractive index difference of the first depressed cladding 3 relative to pure quartz glass ranges from -1.1% to -0.7%.

[0047] 2 , the refractive index difference of the second depressed cladding 4 relative to pure quartz glass is negative and does not vary with radius. Preferably, the refractive index difference of the second depressed cladding 4 relative to pure quartz glass ranges from -0.7% to -0.4%.

[0048] The absolute refractive index of the core layer 1 is graded. Specifically, the absolute refractive index of the core layer 1 is distributed in an α-power exponential function as the radius of the thin-diameter multimode optical fiber increases, and the refractive index difference of the center of the core layer 1 relative to pure quartz glass is the largest.

[0049] n (r) 2 =n 芯层中心 2 [1-2Δ1×(r / R1) α ]

[0050] n (r) is the absolute refractive index of the core layer 1 at a distance r from the center of the core layer 1, n 芯层中心 is the absolute refractive index at the center of the core layer 1 , Δ1 is the refractive index difference of the center of the core layer 1 relative to pure quartz glass, and R1 is the radius of the core layer 1 .

[0051] The value range of α is 1.90~2.13.

[0052] The refractive index difference between the center of the core layer 1 and pure quartz glass is 0.90% to 1.10%.

[0053] Below in conjunction with embodiment and comparative example, further set forth the application.Should be understood that these embodiments are only used to illustrate the application and are not used to limit the scope of the application.In addition, should be understood that after reading the content taught by the application, those skilled in the art can make various changes or modifications to the application, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0054] Example 1

[0055] A thin-diameter multimode optical fiber comprises a core layer 1, an inner cladding 2, a first depressed cladding 3, a second depressed cladding 4 and an outer cladding 5 which are sequentially arranged from inside to outside along the radial direction of the thin-diameter multimode optical fiber.

[0056] The refractive index difference between the first depressed cladding 3 and pure quartz glass is smaller than the refractive index difference between the second depressed cladding 4 and pure quartz glass; the refractive index difference between the inner cladding 2 and pure quartz glass gradually decreases from the inside to the outside along the radial direction of the thin-diameter multimode optical fiber.

[0057] The radius of the core layer 1 is 24.9 μm, the width of the inner cladding 2 is 1.2 μm, the width of the first depressed cladding 3 is 6.5 μm, the width of the second depressed cladding 4 is 6.8 μm, and the outer cladding 5 is pure quartz glass with a radius of 48 μm.

[0058] The refractive index difference between the center of the core layer 1 and pure quartz glass is 0.9987%, the refractive index difference between the outer boundary of the inner cladding 2 and pure quartz glass is -0.1903%, the refractive index difference between the first depressed cladding 3 and pure quartz glass is -0.9858%, and the refractive index difference between the second depressed cladding 4 and pure quartz glass is -0.5489%.

[0059] The attenuation at 850nm is 2.21dB / km, the attenuation at 1300nm is 0.44dB / km, the macrobending loss at 850nm is 0.0286dB, and the macrobending loss at 1300nm is 0.0762dB (bending diameter 30μm, 2 turns), and the effective bandwidth is 6328MHz*km.

[0060] Example 2

[0061] A thin-diameter multimode optical fiber comprises a core layer 1, an inner cladding 2, a first depressed cladding 3, a second depressed cladding 4 and an outer cladding 5 which are sequentially arranged from inside to outside along the radial direction of the thin-diameter multimode optical fiber.

[0062] The refractive index difference between the first depressed cladding 3 and pure quartz glass is smaller than the refractive index difference between the second depressed cladding 4 and pure quartz glass; the refractive index difference between the inner cladding 2 and pure quartz glass gradually decreases from the inside to the outside along the radial direction of the thin-diameter multimode optical fiber.

[0063] The radius of the core layer 1 is 25.2 μm, the width of the inner cladding 2 is 1.1 μm, the width of the first depressed cladding 3 is 6.7 μm, the width of the second depressed cladding 4 is 7.0 μm, and the outer cladding 5 is pure quartz glass with a radius of 49 μm.

[0064] The refractive index difference of the center of the core layer 1 relative to pure quartz glass is 1.0132%, the refractive index difference of the outer boundary of the inner cladding 2 relative to pure quartz glass is -0.1975%, the refractive index difference of the first depressed cladding 3 relative to pure quartz glass is -1.0003%, and the refractive index difference of the second depressed cladding 4 relative to pure quartz glass is -0.5654%.

[0065] The attenuation at 850nm is 2.28dB / km, the attenuation at 1300nm is 0.47dB / km, the macrobending loss at 850nm is 0.0431dB, and the macrobending loss at 1300nm is 0.1083dB (bending diameter 30μm, 2 turns), and the effective bandwidth is 6122MHz*km.

[0066] Example 3

[0067] A thin-diameter multimode optical fiber comprises a core layer 1, an inner cladding 2, a first depressed cladding 3, a second depressed cladding 4 and an outer cladding 5 which are sequentially arranged from inside to outside along the radial direction of the thin-diameter multimode optical fiber.

[0068] The refractive index difference between the first depressed cladding 3 and pure quartz glass is smaller than the refractive index difference between the second depressed cladding 4 and pure quartz glass; the refractive index difference between the inner cladding 2 and pure quartz glass gradually decreases from the inside to the outside along the radial direction of the thin-diameter multimode optical fiber.

[0069] The radius of the core layer 1 is 25.8 μm, the width of the inner cladding 2 is 1 μm, the width of the first depressed cladding 3 is 6.2 μm, the width of the second depressed cladding 4 is 7.2 μm, and the outer cladding 5 is pure quartz glass with a radius of 47.9 μm.

[0070] The refractive index difference between the center of the core layer 1 and pure quartz glass is 0.9875%, the refractive index difference between the outer boundary of the inner cladding 2 and pure quartz glass is -0.1889%, the refractive index difference between the first depressed cladding 3 and pure quartz glass is -0.9702%, and the refractive index difference between the second depressed cladding 4 and pure quartz glass is -0.6020%.

[0071] The attenuation at 850nm is 2.31dB / km, the attenuation at 1300nm is 0.52dB / km, the macrobending loss at 850nm is 0.0325dB, and at 1300nm is 0.0882dB (bending diameter 30μm, 2 turns), and the effective bandwidth is 6232MHz*km.

[0072] Example 4

[0073] A thin-diameter multimode optical fiber comprises a core layer 1, an inner cladding 2, a first depressed cladding 3, a second depressed cladding 4 and an outer cladding 5 which are sequentially arranged from inside to outside along the radial direction of the thin-diameter multimode optical fiber.

[0074] The refractive index difference between the first depressed cladding 3 and pure quartz glass is smaller than the refractive index difference between the second depressed cladding 4 and pure quartz glass; the refractive index difference between the inner cladding 2 and pure quartz glass gradually decreases from the inside to the outside along the radial direction of the thin-diameter multimode optical fiber.

[0075] The radius of the core layer 1 is 24.5 μm, the width of the inner cladding 2 is 1.5 μm, the width of the first depressed cladding 3 is 7.0 μm, the width of the second depressed cladding 4 is 7.2 μm, and the outer cladding 5 is pure quartz glass with a radius of 48.3 μm.

[0076] The refractive index difference between the center of the core layer 1 and pure quartz glass is 0.9885%, the refractive index difference between the outer boundary of the inner cladding 2 and pure quartz glass is -0.1918%, the refractive index difference between the first depressed cladding 3 and pure quartz glass is -0.9905%, and the refractive index difference between the second depressed cladding 4 and pure quartz glass is -0.5879%.

[0077] The attenuation at 850nm is 2.29dB / km, the attenuation at 1300nm is 0.48dB / km, the macrobending loss at 850nm is 0.0531dB, and at 1300nm is 0.0867dB (bending diameter 30μm, 2 turns), and the effective bandwidth is 6005MHz*km.

[0078] Example 5

[0079] A thin-diameter multimode optical fiber comprises a core layer 1, an inner cladding 2, a first depressed cladding 3, a second depressed cladding 4 and an outer cladding 5 which are sequentially arranged from inside to outside along the radial direction of the thin-diameter multimode optical fiber.

[0080] The refractive index difference between the first depressed cladding 3 and pure quartz glass is smaller than the refractive index difference between the second depressed cladding 4 and pure quartz glass; the refractive index difference between the inner cladding 2 and pure quartz glass gradually decreases from the inside to the outside along the radial direction of the thin-diameter multimode optical fiber.

[0081] The radius of the core layer 1 is 25.5 μm, the width of the inner cladding 2 is 1.3 μm, the width of the first depressed cladding 3 is 6.9 μm, the width of the second depressed cladding 4 is 7.3 μm, and the outer cladding 5 is pure quartz glass with a radius of 48.4 μm.

[0082] The refractive index difference between the center of the core layer 1 and pure quartz glass is 0.9785%, the refractive index difference between the outer boundary of the inner cladding 2 and pure quartz glass is -0.1935%, the refractive index difference between the first depressed cladding 3 and pure quartz glass is -0.9967%, and the refractive index difference between the second depressed cladding 4 and pure quartz glass is -0.6675%.

[0083] The attenuation at 850nm is 2.26dB / km, the attenuation at 1300nm is 0.43dB / km, the macrobending loss at 850nm is 0.0488dB, and the macrobending loss at 1300nm is 0.1185dB (bending diameter 30μm, 2 turns), and the effective bandwidth is 6478MHz*km.

[0084] In the description of this application, it should be noted that the terms "upper" and "lower" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0085] It should be noted that, in this application, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element.

[0086] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A small-diameter multimode optical fiber, characterized in that, It includes a core layer (1), an inner cladding layer (2), a first depressed cladding layer (3), a second depressed cladding layer (4) and an outer cladding layer (5) which are sequentially arranged from inside to outside along the radius of the thin-diameter multimode optical fiber; Wherein, the refractive index difference of the first depressed cladding layer (3) relative to pure silica glass is less than the refractive index difference of the second depressed cladding layer (4) relative to pure silica glass; The refractive index difference of the inner cladding layer (2) relative to pure silica glass gradually decreases from inside to outside along the radius of the thin-diameter multimode optical fiber.

2. The thin-diameter multimode optical fiber according to claim 1, characterized in that: The refractive index difference of the inner cladding layer (2) relative to pure silica glass gradually decreases linearly.

3. The thin-diameter multimode optical fiber according to claim 1, characterized in that: The value range of the refractive index difference of the outer boundary of the inner cladding layer (2) relative to pure silica glass is -0.2% to -0.18%.

4. The thin-diameter multimode optical fiber according to claim 1, characterized in that: The width of the inner cladding layer (2) is 0.5 to 2 μm.

5. The thin-diameter multimode optical fiber according to claim 1, characterized in that: The width of the first depressed cladding layer (3) is 5 - 9 μm, and the value range of the refractive index difference of the first depressed cladding layer (3) relative to pure silica glass is -1.1% to -0.7%.

6. The thin-diameter multimode optical fiber according to claim 1, characterized in that: The width of the second depressed cladding layer (4) is 5 - 9 μm, and the value range of the refractive index difference of the second depressed cladding layer (4) relative to pure silica glass is -0.7% to -0.4%.

7. The thin-diameter multimode optical fiber according to claim 1, characterized in that: The absolute refractive index of the core layer (1) is distributed in an α power exponential function along with the increase of the radius of the thin-diameter multimode optical fiber, and the refractive index difference of the center of the core layer (1) relative to pure silica glass is the largest; n (r) 2 = n 芯层中心 2 [1 - 2Δ1×(r / R1) α ​ where n (r) is the absolute refractive index at a distance r from the center of the core layer (1) in the core layer (1), and n 芯层中心 is the absolute refractive index at the center of the core layer (1), and Δ1 is the relative pure Refractive index difference of silica glass, R1 is the radius of the core layer (1).

8. The thin-diameter multimode optical fiber according to claim 7, characterized in that: The value range of α is 1.90 to 2.

13.

9. The thin-diameter multimode optical fiber according to claim 1, characterized in that: The radius of the core layer (1) is 23 - 27 μm, and the refractive index difference of the center of the core layer (1) relative to pure silica glass is 0.90% to 1.10%.

10. The thin-diameter multimode optical fiber according to claim 1, characterized in that: The outer cladding layer (5) is pure silica glass with a radius of 35 - 50 μm.

Images