Small-size radiation-resistant bending-insensitive energy transfer multimode optical fiber and preparation method thereof

Abstract

The invention discloses a small-size radiation-resistant bending insensitive energy transfer multimode optical fiber and a preparation method thereof. The multimode optical fiber comprises a core layer, a platform layer, a first sunken cladding layer, a second cladding layer, a third sunken cladding layer, a fourth cladding layer, a fifth sunken cladding layer and an outer cladding layer which are sequentially arranged from inside to outside. By reducing the diameter of the core layer, the number of available modes and the inter-mode dispersion and group delay between the modes, the optical fiber can be transmitted in ten modes, meanwhile, the optical fiber has good viscosity performance due to reasonable doping, the section of the optical fiber is optimally designed, and the low-group delay performance of the multimode optical fiber is improved; the refractive index of the outer cladding is higher than that of the core layer; by adding the second cladding layer and the fourth cladding layer, the stress and viscosity between the sunken cladding layer and the core layer can form continuity, and the abrupt change area is eliminated, so that the attenuation of the optical fiber and the group delay of the optical fiber are reduced; by adding the first, third and fifth sunken cladding layers, the bending loss resistance of the optical fiber is enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical communication, and particularly relates to a small-size radiation-resistant, bend-insensitive, energy-transfer multi-mode optical fiber and a preparation method thereof. Background Art

[0002] With the rapid development of optical communication technology, optical fibers have been widely used in high-radiation fields such as aerospace, deep-sea exploration, and nuclear reactors. Due to the large amount of radiation in the above-mentioned environments, electrons and holes generated during radiation are extremely easy to combine with defects inside the optical fiber, resulting in the formation of color centers inside the optical fiber. The existence of color centers will cause absorption peaks in the visible and ultraviolet bands of the optical fiber, thereby causing radiation damage to the optical fiber, and ultimately leading to a significant reduction in the signal transmission ability of the optical fiber. Therefore, it is urgent to improve the radiation tolerance of optical fibers.

[0003] Currently, the commonly adopted method in the industry to improve the radiation resistance of optical fibers is: using high-purity silica as the core to avoid the formation of optical absorption color centers in the developed radiation-resistant optical fibers under long-term low-dose-rate and short-term high-dose-rate radiation; using a certain amount of fluorine element doped in silica to make a low-refractive-index cladding to form the light guiding interface of the optical fiber, avoiding the formation of radiation-induced defect color centers while ensuring the transmission performance of the optical fiber. Summary of the Invention

[0004] In order to solve the technical problems existing in the prior art, the purpose of the present invention is to provide a small-size radiation-resistant, bend-insensitive, energy-transfer multi-mode optical fiber and a preparation method thereof.

[0005] In order to achieve the above purpose and reach the above technical effects, the technical solution adopted by the present invention is as follows:

[0006] A small-size radiation-resistant, bend-insensitive, energy-transfer multi-mode optical fiber includes a core layer, a platform layer, a first depressed cladding, a second cladding, a third depressed cladding, a fourth cladding, a fifth depressed cladding, and an outer cladding, which are arranged in sequence from the inside to the outside.

[0007] Further, the refractive index profile of the core layer is parabolic, the distribution index α is 1.9 - 2.2, the radius R1 is 14 μm - 16 μm, and the maximum relative refractive index difference Δ1 at the center of the core layer is -0.45% - -0.35%.

[0008] Further, the radius R2 of the platform layer differs from the radius R1 of the core layer by 1 μm - 2 μm, and the relative refractive index difference Δ2 of the platform layer is -0.45% - -0.35%.

[0009] Further, the relative refractive index difference Δ3 of the first depressed cladding is -0.95% - -0.85%, and the radius R3 of the first depressed cladding differs from the radius R2 of the platform layer by 4 μm - 11 μm.

[0010] Further, the radius R4 of the second cladding differs from the radius R3 of the first depressed cladding by 3 μm to 11 μm, and the relative refractive index difference of the second cladding is -0.02% to 0%.

[0011] Further, the relative refractive index difference Δ4 of the third depressed cladding is -0.45% to -0.35%, and the radius R5 of the third depressed cladding differs from the radius R4 of the second cladding by 3 μm to 5 μm.

[0012] Further, the relative refractive index difference of the fourth cladding is -0.02% to 0%, and the radius R6 of the fourth cladding differs from the radius R5 of the third depressed cladding by 3 μm to 11 μm.

[0013] Further, the relative refractive index difference Δ5 of the fifth depressed cladding is -0.95% to -0.85%, and the radius R7 of the fifth depressed cladding differs from the radius R6 of the fourth cladding by 3 μm to 5 μm.

[0014] Further, the small-sized radiation-resistant and bend-insensitive energy-transfer multimode optical fiber can be transmitted within ten modes, and the ten mode transmission modes are: LP01, LP11a, LP12a, LP11b, LP12b, LP02, LP31a, LP21a, LP31b, and LP21b. The maximum value of its group delay is less than 150 ps / km, and the outer cladding is a pure silica glass layer with an outer cladding radius R8 of 62 μm to 63 μm.

[0015] The present invention also discloses a method for preparing a small-sized radiation-resistant and bend-insensitive energy-transfer multimode optical fiber, comprising the following steps:

[0016] S1, preparing a core layer by using a reduced-pressure plasma chemical vapor deposition method:

[0017] S2, respectively preparing a platform layer, a first depressed cladding, a second cladding, a third depressed cladding, a fourth cladding, and a fifth depressed cladding by using a plasma chemical vapor deposition method;

[0018] S3, preparing an outer cladding by using a conventional liner and sleeve;

[0019] S4, combining the core layer, the platform layer, the first depressed cladding, the second cladding, the third depressed cladding, the fourth cladding, the fifth depressed cladding, and the outer cladding to form an optical fiber preform;

[0020] S5, drawing the optical fiber preform to obtain the required small-sized radiation-resistant and bend-insensitive energy-transfer multimode optical fiber.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] The present invention discloses a small-sized radiation-resistant and bend-insensitive energy-transfer multimode optical fiber and a preparation method thereof. By reducing the core diameter, the number of available modes is reduced, the inter-modal dispersion and group delay between modes are reduced. At the same time, reasonable doping endows the optical fiber with good viscosity performance, and the cross-section of the optical fiber is optimized to improve the low group delay performance of the multimode optical fiber. Emphasis is placed on the design and optimization of fluorine doping in the core layer, platform layer, and depressed cladding. For the platform layer, fluorine or co-doping with other dopants is used, and the fluorine doping ratio is variable and can be adjusted according to the stress and viscosity tests of the optical fiber. By selecting an appropriate variable fluorine doping amount and width, the optimal stress difference between the core layer and the depressed cladding is achieved. For the outer cladding, the second cladding, and the fourth cladding, a pure silica glass layer is used. The refractive index of the outer cladding is higher than that of the core layer to improve the radiation resistance of the optical fiber. At the same time, the second cladding and the fourth cladding transmit laser, enabling the optical fiber to have the function of communication-energy transfer integration. For the number of modes, the core radius is designed to be 14 μm, and the difference between the highest and lowest refractive indices of the core layer is 0.45%, enabling the optical fiber to have ten transmission modes. The transmission wavelength is in the C band of 1535 nm - 1570 nm, and the maximum value of its group delay is less than 150 ps / km. A stress-balanced structure - the platform layer is designed to enable the stress and viscosity between the depressed cladding and the core layer to form continuity, eliminating the abrupt region, thereby reducing the optical fiber attenuation and the group delay of the optical fiber. The first, third, and fifth depressed claddings are added to enhance the anti-bending loss ability of the optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the refractive index profile of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The present invention will be described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making the protection scope of the present invention more clearly defined.

[0025] The following gives a brief overview of one or more aspects to provide a basic understanding of these aspects. This overview is not an exhaustive survey of all contemplated aspects, and is neither intended to identify key or decisive elements of all aspects nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that follows.

[0026] As Figure 1 shown, a small-sized radiation-resistant and bend-insensitive energy-transfer multimode optical fiber includes a core layer, a platform layer, a first depressed cladding, a second cladding, a third depressed cladding, a fourth cladding, a fifth depressed cladding, and an outer cladding, which are arranged in sequence from the inside to the outside.

[0027] In the present invention, the refractive index profile of the core layer is parabolic, the distribution index α is 1.9 to 2.2, the radius R1 of the core layer is 14 μm to 16 μm, and the maximum relative refractive index difference Δ1 at the center of the core layer is -0.45% to -0.35%.

[0028] The radius R2 of the platform layer differs from the radius R1 of the core layer by 1 μm to 2 μm, and the relative refractive index difference Δ2 of the platform layer is -0.45% to -0.35%.

[0029] The relative refractive index difference Δ3 of the first depressed cladding is -0.95% to -0.85%, and the radius R3 of the first depressed cladding differs from the radius R2 of the platform layer by 4 μm to 11 μm.

[0030] The radius R4 of the second cladding differs from the radius R3 of the first depressed cladding by 3 μm to 11 μm, and the relative refractive index difference of the second cladding is -0.02% to 0%.

[0031] The relative refractive index difference Δ4 of the third depressed cladding is -0.45% to -0.35%, and the radius R5 of the third depressed cladding differs from the radius R4 of the second cladding by 3 μm to 5 μm.

[0032] The relative refractive index difference of the fourth cladding is -0.02% to 0%, and the radius R6 of the fourth cladding differs from the radius R5 of the third depressed cladding by 3 μm to 11 μm.

[0033] The relative refractive index difference Δ5 of the fifth depressed cladding is -0.95% to -0.85%, and the radius R7 of the fifth depressed cladding differs from the radius R6 of the fourth cladding by 3 μm to 5 μm.

[0034] The outer cladding is a pure silica glass layer, and the radius R8 of the outer cladding is 62 μm to 63 μm.

[0035] The core layer uses a graded refractive index. The diameter of the core layer is slightly smaller than that of a conventional multimode optical fiber, and the number of available modes is reduced to ten modes. The refractive index of the outer cladding is higher than that of the core layer, which can improve the radiation resistance of the core layer.

[0036] The platform layer is doped with fluorine or co-doped with fluorine and other dopants. The fluorine doping ratio is the same as the fluorine doping ratio at the outermost end of the core layer. The fluorine doping ratio is variable and can be adjusted according to the stress and viscosity tests of the optical fiber. The appropriate variable fluorine doping amount and width are selected to achieve the optimal stress difference between the core layer and the depressed cladding.

[0037] For the first, third, and fifth depressed claddings, fluorine doping or co-doping with fluorine and other dopants is used, and the doping amount (excluding fluorine) is higher than that of the platform layer.

[0038] The dopant is fluorine or a combination of fluorine and chlorine.

[0039] For the second and fourth claddings, pure silica is used, and the refractive index is the same as that of the outer cladding to ensure the stability of energy transmission under irradiation conditions. The second and fourth claddings can transmit laser, and the transmission efficiency is greater than 90%, enabling the optical fiber to have the function of integrating communication and energy transmission.

[0040] Through reasonable design of the waveguide structure and doping system, the present invention ensures that the optical fiber has ten transmission modes, reduces the mode dispersion of the optical fiber, and thus reduces the group delay of the optical fiber. The ten mode transmission modes are: LP01, LP11a, LP12a, LP11b, LP12b, LP02, LP31a, LP21a, LP31b, and LP21b, and the maximum value of the group delay is less than 150 ps / km.

[0041] The optical fiber of the present invention reduces the mode dispersion, optimizes the viscosity of the optical fiber, and improves the radiation resistance of the optical fiber, enabling the optical fiber to have good radiation resistance and bending resistance while having the ability of integrating communication and energy transmission.

[0042] The optical fiber of the present invention can reach a transmission distance of 3000 km at a wavelength of 1550 nm based on MFMP (mirror flip mode arrangement).

[0043] The present invention also discloses a preparation method of a small-size radiation-resistant and bending-insensitive energy-transmitting multimode optical fiber, including the following steps:

[0044] S1, preparing the core layer by using the reduced-pressure plasma chemical vapor deposition method:

[0045] S2, respectively preparing the platform layer, the first depressed cladding, the second cladding, the third depressed cladding, the fourth cladding, and the fifth depressed cladding by using the plasma chemical vapor deposition method;

[0046] S3, preparing the outer cladding by using a conventional liner and sleeve;

[0047] S4, combining the core layer, the platform layer, the first depressed cladding, the second cladding, the third depressed cladding, the fourth cladding, the fifth depressed cladding, and the outer cladding to form an optical fiber preform;

[0048] S5, drawing the optical fiber preform to obtain the required small-size radiation-resistant and bending-insensitive energy-transmitting multimode optical fiber.

[0049] Example 1

[0050] As Figure 1 shown, a small-size radiation-resistant and bending-insensitive energy-transmitting multimode optical fiber includes a core layer, a platform layer, a first depressed cladding, a second cladding, a third depressed cladding, a fourth cladding, a fifth depressed cladding, and an outer cladding which are arranged in sequence from inside to outside.

[0051] Among them, the refractive index profile of the core layer is parabolic, the distribution index α is 2, the radius R1 of the core layer is 14 μm, and the maximum relative refractive index difference Δ1 at the center of the core layer is -0.45%.

[0052] The radius R2 of the platform layer differs from the radius R1 of the core layer by 1.5 μm, that is, R2 - R1 = 1.5 μm, and the relative refractive index difference Δ2 of the platform layer is -0.45%.

[0053] The relative refractive index difference Δ3 of the first depressed cladding is -0.90%, and the radius R3 of the first depressed cladding differs from the radius R2 of the platform layer by 8 μm.

[0054] The relative refractive index difference of the second cladding is 0%, and the radius R4 of the second cladding differs from the radius R3 of the first depressed cladding by 6 μm.

[0055] The relative refractive index difference Δ4 of the third depressed cladding is -0.45%, and the radius R5 of the third depressed cladding differs from the radius R4 of the second cladding by 3 μm.

[0056] The relative refractive index difference of the fourth cladding is 0%, and the radius R6 of the fourth cladding differs from the radius R5 of the third depressed cladding by 6 μm.

[0057] The relative refractive index difference Δ5 of the fifth depressed cladding is -0.90%, and the radius R7 of the fifth depressed cladding differs from the radius R6 of the fourth cladding by 3 μm.

[0058] The outer cladding is a pure silica glass layer, and the radius R8 of the outer cladding is 62 μm.

[0059] A preparation method of a small-size radiation-resistant bend-insensitive energy-transfer multimode optical fiber includes the following steps:

[0060] S1, preparing a core layer doped with two elements of fluorine and chlorine by a reduced-pressure plasma chemical vapor deposition method:

[0061] Specifically, using SiCl4, CF4, and O2 as raw materials, a core rod (i.e., the core layer) with a maximum relative refractive index difference Δ1max of -0.45% and a distribution index α of 2 is prepared through deposition and melt shrinkage;

[0062] S2, preparing the platform layer, the first depressed cladding, the second cladding, the third depressed cladding, the fourth cladding, and the fifth depressed cladding respectively by a plasma chemical vapor deposition method;

[0063] S3, preparing the outer cladding by using a purchased liner tube and a casing tube;

[0064] S4, combining the core layer, the platform layer, the first depressed cladding, the second cladding, the third depressed cladding, the fourth cladding, the fifth depressed cladding, and the outer cladding to make an optical fiber preform;

[0065] S5. Draw the optical fiber preform to obtain the small-size radiation-resistant bend-insensitive energy-transfer multimode optical fiber.

[0066] The optical fiber of this embodiment has ten transmission modes, which reduces the modal dispersion of the optical fiber, thereby reducing the group delay of the optical fiber. The ten mode transmission modes are: LP01, LP11a, LP12a, LP11b, LP12b, LP02, LP31a, LP21a, LP31b, and LP21b. At a wavelength of 1550 nm, the maximum value of the group delay of the optical fiber is less than 150 ps / km. The energy transfer efficiency of the optical fiber is > 90%.

[0067] For parts or structures not specifically described in the present invention, existing technologies or existing products can be used, and no further elaboration will be provided here.

[0068] The above are only embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural or equivalent process transformation made using the content of the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A small-sized radiation-resistant and bending-insensitive energy-transfer multimode optical fiber, characterized in that It includes a core layer, a platform layer, a first depressed cladding layer, a second cladding layer, a third depressed cladding layer, a fourth cladding layer, a fifth depressed cladding layer and an outer cladding layer which are arranged in sequence from the inside to the outside.

2. The small-size radiation-resistant bending-insensitive energy-transfer multimode optical fiber according to claim 1, wherein The refractive index profile of the core layer is parabolic, the distribution index α is 1.9 - 2.2, the radius R1 is 14μm - 16μm, and the maximum relative refractive index difference Δ1 at the center of the core layer is -0.45% - -0.35%.

3. A small-size radiation-resistant bend-insensitive energy-transfer multimode optical fiber according to claim 1, characterized in that, The radius R2 of the platform layer differs from the radius R1 of the core layer by 1μm - 2μm, and the relative refractive index difference Δ2 of the platform layer is -0.45% - -0.35%.

4. A small-size radiation-resistant and bend-insensitive energy-transfer multimode optical fiber according to claim 1, wherein, The relative refractive index difference Δ3 of the first depressed cladding layer is -0.95% - -0.85%, and the radius R3 of the first depressed cladding layer differs from the radius R2 of the platform layer by 4μm - 11μm.

5. A small-sized radiation-resistant bending-insensitive energy-transfer multimode optical fiber according to claim 1, characterized in that The radius R4 of the second cladding layer differs from the radius R3 of the first depressed cladding layer by 3μm - 11μm, and the relative refractive index difference of the second cladding layer is -0.02% - 0%.

6. The multi-mode fiber for energy transfer that is small-sized, radiation-resistant, and insensitive to bending according to claim 1, wherein The relative refractive index difference Δ4 of the third depressed cladding layer is -0.45% - -0.35%, and the radius R5 of the third depressed cladding layer differs from the radius R4 of the second cladding layer by 3μm - 5μm.

7. A small-size radiation-resistant and bending-insensitive energy-transfer multimode optical fiber according to claim 1, characterized in that The relative refractive index difference of the fourth cladding layer is -0.02% - 0%, and the radius R6 of the fourth cladding layer differs from the radius R5 of the third depressed cladding layer by 3μm - 11μm.

8. A small-size radiation-resistant bend-insensitive energy-transfer multimode optical fiber according to claim 1, characterized in that, The relative refractive index difference Δ5 of the fifth depressed cladding layer is -0.95% - -0.85%, and the radius R7 of the fifth depressed cladding layer differs from the radius R6 of the fourth cladding layer by 3μm - 5μm.

9. A small-size radiation-resistant bend-insensitive energy-transfer multimode optical fiber according to claim 1, characterized in that, The small - size radiation - resistant and bend - insensitive energy - transfer multimode optical fiber can transmit within ten modes. The ten mode transmission modes are: LP01, LP11a, LP12a, LP11b, LP12b, LP02, LP31a, LP21a, LP31b and LP21b, and the maximum value of its group delay is less than 150ps / km; the outer cladding is a pure silica glass layer, and the radius R8 of the outer cladding is 62μm - 63μm.

10. A method for preparing a small-sized radiation-resistant and bending-insensitive energy-transfer multimode optical fiber, characterized in that, It includes the following steps: S1, preparing the core layer by using the reduced - pressure plasma chemical vapor deposition method: S2, respectively preparing the platform layer, the first depressed cladding layer, the second cladding layer, the third depressed cladding layer, the fourth cladding layer and the fifth depressed cladding layer by using the plasma chemical vapor deposition method; S3, preparing the outer cladding by using a conventional liner and casing; S4, combining the core layer, the platform layer, the first depressed cladding layer, the second cladding layer, the third depressed cladding layer, the fourth cladding layer, the fifth depressed cladding layer and the outer cladding to make an optical fiber preform; S5, drawing the optical fiber preform to obtain the required small - size radiation - resistant and bend - insensitive energy - transfer multimode optical fiber.

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