Special optical fiber

Abstract

This application relates to a special optical fiber, comprising a core layer and an outer cladding layer arranged sequentially from the inside to the outside along the radial direction of the special optical fiber, wherein the core layer includes a silicon nitride layer. The special optical fiber provided by this application incorporates a silicon nitride layer, disposed within the outer cladding layer. Silicon nitride has excellent thermal conductivity, enabling rapid dissipation of heat accumulated within the core / cladding layer, preventing localized hotspots that could degrade fiber quality and increasing the damage threshold. Silicon nitride remains stable at temperatures above 1200°C in an inert atmosphere and is unlikely to react with other substances, completely solving the problem of polymer carbonization. In terms of mechanical and chemical protection, silicon nitride acts as a chemical barrier. The dense, non-porous structure of the silicon nitride film gives this special optical fiber resistance to salt spray and hydrogen sulfide corrosion. Silicon nitride is a more effective Compton scatterer than silicon dioxide, reducing gamma photons incident deep within the optical fiber and improving its irradiation performance.

Description

Technical Field

[0001] This application relates to the field of optical fiber and cable, and in particular to a special type of optical fiber. Background Technology

[0002] Specialty optical fibers are generally used in extreme environments. For ordinary optical fibers, extreme environments will damage the transmission performance of the optical fiber and make it impossible to transmit signals.

[0003] In high-temperature environments such as oil wells, ordinary optical fibers have poor thermal conductivity and thermal stability. This is because polymers (such as acrylates) have extremely low thermal conductivity (≈0.2 W / m·K). Heat accumulates in the fiber core / inner cladding and cannot be quickly dissipated, leading to localized high temperatures in the optical fiber and a decrease in fiber quality. In addition, polymers will carbonize at high temperatures. If there is no barrier layer to prevent this, it will contaminate the surface of the optical fiber and cause damage. Therefore, ordinary optical fibers are difficult to meet the requirements of high-temperature environments such as oil wells. Summary of the Invention

[0004] This application provides a special optical fiber with excellent thermal conductivity, good thermal stability, and radiation resistance.

[0005] This application provides a special optical fiber, which includes a core layer and an outer cladding layer arranged sequentially from the inside to the outside along the radial direction of the special optical fiber, wherein the core layer includes a silicon nitride layer.

[0006] In some embodiments, the core layer further includes a refractive index transition layer located between the silicon nitride layer and the outer cladding layer.

[0007] In some embodiments, the refractive index transition layer is made of germanium-doped silicon dioxide; And / or, the outer cladding layer is made of silicon dioxide.

[0008] In some embodiments, the special optical fiber is a single-mode optical fiber, the diameter of the silicon nitride layer is 9um ± 1um, the diameter of the refractive index transition layer is 1 ± 0.5um, and the diameter of the cladding layer is 125um ± 1um.

[0009] In some embodiments, the special optical fiber is a multimode optical fiber, the diameter of the silicon nitride layer is 50um ± 2.5um, the diameter of the refractive index transition layer is 5 ± 2.5um, and the diameter of the cladding layer is 125um ± 1um.

[0010] In some embodiments, the core layer further includes an inner core layer, the silicon nitride layer is located outside the inner core layer, and an inner cladding layer is disposed between the silicon nitride layer and the inner core layer, the refractive index of the inner cladding layer being less than the refractive index of the inner core layer.

[0011] In some embodiments, the special optical fiber is a single-mode optical fiber, the inner core has a diameter of 9 μm ± 1 μm, the inner cladding has a diameter of 35 ± 5 μm, the silicon nitride layer has a diameter of 40 μm ± 5 μm, and the outer cladding has a diameter of 125 μm ± 1 μm.

[0012] In some embodiments, the special optical fiber is a multimode optical fiber, the inner core has a diameter of 50 μm ± 2.5 μm, the inner cladding has a diameter of 70 ± 5 μm, the silicon nitride layer has a diameter of 80 μm ± 5 μm, and the outer cladding has a diameter of 125 μm ± 1 μm.

[0013] In some embodiments, the inner core layer is made of germanium-doped silicon dioxide; And / or, the inner cladding is made of silicon dioxide; And / or, the outer cladding layer is made of silicon dioxide.

[0014] In some embodiments, a coating is provided on the outside of the outer cladding layer.

[0015] The beneficial effects of the technical solution provided in this application include: The special optical fiber provided in this application incorporates a silicon nitride layer within the outer cladding. Silicon nitride possesses excellent thermal conductivity, ranging from 30 to 35 W / m·K, enabling rapid dissipation of heat accumulated in the core / cladding. This prevents localized hotspots that could degrade fiber quality and improve the damage threshold. Furthermore, silicon nitride remains stable in an inert atmosphere at temperatures above 1200℃ (air temperatures above 800℃), making it difficult to react with other substances and completely resolving the polymer carbonization problem.

[0016] In terms of mechanical and chemical protection, silicon nitride acts as a chemical barrier. Silicon nitride films have a dense, non-porous structure with a gas permeability of <10. -10 cm 2 Silicon nitride is chemically inert. On the one hand, it is resistant to salt spray, with an annual corrosion rate of <0.1 nm in 5% NaCl solution. On the other hand, it is resistant to hydrogen sulfide (H2S) and does not react with sulfides.

[0017] Under irradiation, radiation causes electrons to detach from atoms, creating free electrons / holes. These electrons or holes are captured by defects, forming absorption centers, which reduces fiber attenuation. In resisting gamma rays, silicon nitride is a more effective Compton scatterer than silicon dioxide, reducing gamma photons incident deep within the fiber and improving its irradiation performance. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of the structure of a special optical fiber provided in an embodiment of this application; Figure 2 This is a schematic diagram of another structure of the special optical fiber provided in the embodiments of this application.

[0020] In the figure: 1. Core layer; 10. Silicon nitride layer; 11. Refractive index transition layer; 12. Inner core layer; 13. Inner cladding layer; 2. Outer cladding layer; 3. Coating layer. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] See Figure 1 and Figure 2 As shown in the figure, this application provides a special optical fiber, which includes a core layer 1 and an outer cladding layer 2 arranged sequentially from the inside to the outside along the radial direction of the special optical fiber, wherein the core layer 1 includes a silicon nitride layer 10.

[0023] The special optical fiber provided in this application incorporates a silicon nitride layer 10, which is disposed within the outer cladding layer 2. Silicon nitride (Si3N4) exhibits excellent thermal conductivity, with a thermal conductivity coefficient of 30–35 W / m·K, enabling rapid dissipation of heat accumulated in the fiber core / cladding. This prevents localized hotspots from forming in the optical fiber, thus avoiding fiber quality degradation and increasing the damage threshold. Furthermore, silicon nitride remains stable in an inert atmosphere at temperatures above 1200℃ (air temperatures above 800℃), making it difficult to react with other substances and completely resolving the polymer carbonization problem.

[0024] In terms of mechanical and chemical protection, silicon nitride acts as a chemical barrier. Silicon nitride films have a dense, non-porous structure with a gas permeability of <10. -10 cm 2Silicon nitride is chemically inert. On the one hand, it is resistant to salt spray, with an annual corrosion rate of <0.1 nm in 5% NaCl solution. On the other hand, it is resistant to hydrogen sulfide (H2S) and does not react with sulfides.

[0025] Under irradiation, radiation causes electrons to detach from atoms, thereby generating free electrons / holes. These electrons or holes are captured by defects, forming absorption centers, which reduces fiber attenuation.

[0026] It is understandable that the average atomic number ≈ the total number of protons / the total number of atoms. Both silicon dioxide and silicon nitride have an average atomic number of 10. Compton scattering is the interaction between photons and "free" electrons, and its probability is proportional to the number of electrons per unit volume of the material, i.e., the electron density. The electron density of silicon nitride is approximately 3.2 g / cm³. 3 The electron density of silicon dioxide is approximately 2.2 g / cm³. 3 Silicon nitride contains more atoms and electrons within the same volume. Therefore, its electron density is much higher than that of silicon dioxide. In resisting gamma rays, silicon nitride is a more efficient Compton scatterer than silicon dioxide, reducing gamma photons incident deep within optical fibers and thus improving the irradiation performance of the fiber.

[0027] The optical fiber provided in this application embodiment can be used in extreme environments (high radiation environment, high temperature oil well environment, high corrosion environment, etc.), and can ensure normal signal and is difficult to fail.

[0028] In one example, see Figure 1 As shown, the core layer 1 further includes a refractive index transition layer 11, which is located between the silicon nitride layer 10 and the outer cladding layer 2.

[0029] Because silicon nitride has a higher refractive index and silicon dioxide has a lower refractive index, a direct drop from a higher refractive index to a lower refractive index along the radial direction of the optical fiber can lead to excessive interfacial stress and fiber loss. To overcome this problem, a refractive index transition layer is added, with its refractive index gradually changing radially to fall between the two. This allows for a smooth transition from a high refractive index to a low refractive index, resulting in a more stable change in interfacial stress.

[0030] The refractive index transition layer 11 is made of germanium-doped silicon dioxide. Germanium (Ge) has good lattice matching with quartz glass, resulting in extremely low introduced losses. It is easily controlled precisely using vapor deposition processes (such as MCVD and VAD). It exhibits very high transparency in the communication bands (1310 nm, 1550 nm). Alternatively, the refractive index transition layer 11 can also be made of silicon dioxide doped with aluminum, phosphorus, titanium, erbium, or ytterbium.

[0031] In the above example, the special optical fiber includes a silicon nitride layer 10, a refractive index transition layer 11, and an outer cladding layer 2 arranged sequentially.

[0032] The refractive index of silicon nitride layer 10 is 2.0 to 2.1.

[0033] The outer cladding layer 2 is made of silicon dioxide. The refractive index of the outer cladding layer 2 is 1.4 to 1.5.

[0034] The refractive index transition layer 11 has a gradually decreasing refractive index, which gradually decreases radially from 2.0 to 2.1 to 1.4 to 1.5.

[0035] If the above-described special optical fiber is a single-mode optical fiber, the diameter of its silicon nitride core layer 10 is 9 μm ± 1 μm. The diameter of its refractive index transition layer 11 is 1 ± 0.5 μm. The diameter of its outer cladding layer 2 is 125 μm ± 1 μm.

[0036] If the above-described special optical fiber is a multimode optical fiber, the diameter of its silicon nitride core layer 10 is 50 μm ± 2.5 μm. The diameter of its refractive index transition layer 11 is 5 ± 2.5 μm. The diameter of its outer cladding layer 2 is 125 μm ± 1 μm.

[0037] See another example. Figure 2 As shown, the core layer 1 further includes an inner core layer 12, the silicon nitride layer 10 is located outside the inner core layer 12, and an inner cladding layer 13 is disposed between the silicon nitride layer 10 and the inner core layer 12. The refractive index of the inner cladding layer 13 is less than that of the inner core layer 12.

[0038] In the above example, the special optical fiber includes an inner core layer 12, an inner cladding layer 13, a silicon nitride layer 10, and an outer cladding layer 2 arranged sequentially.

[0039] The inner core layer 12 is made of germanium-doped silicon dioxide. The refractive index of the inner core layer 12 is 1.45 to 1.55.

[0040] The inner cladding 13 is made of silicon dioxide. The refractive index of the inner cladding 13 is 1.4 to 1.5.

[0041] The refractive index of silicon nitride layer 10 is 2.0 to 2.1.

[0042] The outer cladding layer 2 is made of silicon dioxide. The refractive index of the outer cladding layer 2 is 1.4 to 1.5.

[0043] If the above-mentioned special optical fiber is a single-mode optical fiber, the diameter of its inner core 12 is 9um±1um, the diameter of its inner cladding 13 is 35±5um, the diameter of its silicon nitride layer 10 is 40um±5um, and the diameter of its outer cladding 2 is 125um±1um.

[0044] If the above-mentioned special optical fiber is a multimode optical fiber, the diameter of its inner core 12 is 50um±2.5um, the diameter of its inner cladding 13 is 70±5um, the diameter of its silicon nitride layer 10 is 80um±5um, and the diameter of its outer cladding 2 is 125um±1um.

[0045] Further, see Figure 1 and Figure 2 As shown, a coating 3 is provided on the outside of the outer layer 2. The diameter of the coating is 245um ± 10um.

[0046] Example 1: See Figure 1 As shown, a special optical fiber includes a core layer 1, an outer cladding layer 2, and a coating layer 3 arranged sequentially from the inside to the outside along the radial direction of the special optical fiber. The core layer 1 includes a silicon nitride layer 10 and a refractive index transition layer 11 along the radial direction of the special optical fiber.

[0047] This single-mode fiber has a maximum NA of 1.07, and its long-wavelength attenuation can be reduced to 0.25 dB / km. Its MFD is 9 μm. It can operate for extended periods in oil well and irradiated environments, withstand temperatures from 150°C to -60°C, and can tolerate a maximum radiation dose of 1 mgy.

[0048] Example 2: See Figure 2 As shown, a special optical fiber includes a core layer 1, an outer cladding layer 2, and a coating layer 3 arranged sequentially from the inside to the outside along the radial direction of the special optical fiber. The core layer 1 includes an inner core layer 12, an inner cladding layer 13, and a silicon nitride layer 10 along the radial direction of the special optical fiber.

[0049] The transmission performance of optical fiber is not much different from that of ordinary single-mode / multimode optical fiber.

[0050] When this special optical fiber is a single-mode fiber, the MFD is 9µm and the attenuation is 0.20dB / km.

[0051] When this special optical fiber is multimode, it can reach OM3 level, with an 850nm bandwidth ≥2200MHz·km and an 850nm attenuation ≤3dB / km. The 1300nm attenuation ≤1dB / km.

[0052] It can work for a long time in oil wells and irradiated environments, and can withstand high temperatures of 150℃ and low temperatures of -60℃. The maximum radiation dose it can withstand is 1MGy.

[0053] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship 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, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0054] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0055] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this 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 this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A special optical fiber, characterized in that, It includes a core layer (1) and an outer cladding layer (2) arranged sequentially from the inside to the outside along the radial direction of the special optical fiber, wherein the core layer (1) includes a silicon nitride layer (10). The core layer (1) further includes a refractive index transition layer (11) located between the silicon nitride layer (10) and the outer cladding layer (2); or, the core layer (1) further includes an inner core layer (12), the silicon nitride layer (10) located outside the inner core layer (12), and an inner cladding layer (13) disposed between the silicon nitride layer (10) and the inner core layer (12), wherein the refractive index of the inner cladding layer (13) is less than the refractive index of the inner core layer (12).

2. The special optical fiber as described in claim 1, characterized in that: The refractive index transition layer (11) is made of germanium-doped silicon dioxide; And / or, the outer cladding layer (2) is made of silicon dioxide.

3. The special optical fiber as described in claim 1, characterized in that: The special optical fiber is a single-mode optical fiber, the diameter of the silicon nitride layer (10) is 9um±1um, the diameter of the refractive index transition layer (11) is 1±0.5um, and the diameter of the outer cladding layer (2) is 125um±1um.

4. The special optical fiber as described in claim 1, characterized in that: The special optical fiber is a multimode optical fiber, the diameter of the silicon nitride layer (10) is 50um±2.5um, the diameter of the refractive index transition layer (11) is 5±2.5um, and the diameter of the outer cladding layer (2) is 125um±1um.

5. The special optical fiber as described in claim 1, characterized in that: The special optical fiber is a single-mode optical fiber. The diameter of the inner core layer (12) is 9um ± 1um, the diameter of the inner cladding layer (13) is 35 ± 5um, the diameter of the silicon nitride layer (10) is 40um ± 5um, and the diameter of the outer cladding layer (2) is 125um ± 1um.

6. The special optical fiber as described in claim 1, characterized in that: The special optical fiber is a multimode optical fiber. The diameter of the inner core layer (12) is 50um ± 2.5um, the diameter of the inner cladding layer (13) is 70 ± 5um, the diameter of the silicon nitride layer (10) is 80um ± 5um, and the diameter of the outer cladding layer (2) is 125um ± 1um.

7. The special optical fiber as described in claim 1, characterized in that: The inner core layer (12) is made of germanium-doped silicon dioxide; And / or, the inner cladding (13) is made of silicon dioxide.

8. The special optical fiber as described in claim 1, characterized in that: The outer layer (2) is provided with a coating (3).

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