阅读说明：本技术 一种弯曲不敏感单模光纤 (Bending insensitive single mode fiber ) 是由 肖敏 杨思美 柳涛 蔡钊 姜金辰 于 2020-05-24 设计创作，主要内容包括：本发明公开了一种弯曲不敏感单模光纤,包括由内至外依次排列的芯层、内包层、以及外包层,所述内包层具有压应力,其压应力的绝对值大于芯层压应力,且其芯层压应力的绝对值介于10MPa～40MPa之间,其内包层压应力的绝对值介于20MPa～50MPa之间。本发明在光纤芯层周围引入具有压应力分布的内包层结构,能够调节芯层光波电磁场的功率分布与限制能力,LP01模式以外的高阶模能够通过内包层结构迅速泄露,而内包层保持适度的压应力分布能够阻隔和缓冲外界温度和作用力对芯层的影响,从而大幅降低光纤在弯曲状态下的附加损耗,光纤对极端温度的适应性能较强,即光纤在极高温和极低温条件下保持弯曲不敏感性能,从而能够扩展光纤的应用温度条件。(The invention discloses a bending insensitive single-mode optical fiber, which comprises a core layer, an inner cladding layer and an outer cladding layer which are sequentially arranged from inside to outside, wherein the inner cladding layer has compressive stress, the absolute value of the compressive stress is greater than that of the core layer, the absolute value of the compressive stress of the core layer is between 10MPa and 40MPa, and the absolute value of the compressive stress of the inner cladding layer is between 20MPa and 50 MPa.)

1. The bending insensitive single-mode optical fiber is characterized by comprising a core layer, an inner cladding layer and an outer cladding layer which are sequentially arranged from inside to outside, wherein the inner cladding layer has compressive stress, and the absolute value of the compressive stress is larger than that of the core layer.

2. The bend insensitive single mode optical fiber according to claim 1, wherein the fiber has a core layer having a compressive stress at room temperature and an absolute value of the core compressive stress between 10MPa and 40MPa, preferably between 15MPa and 35 MPa.

3. The bend insensitive single mode optical fiber according to claim 1, wherein the fiber has an inner cladding with a compressive stress at room temperature and an absolute value of the compressive stress of the inner cladding between 20MPa and 50MPa, preferably between 25MPa and 45 MPa.

4. The bending insensitive single-mode optical fiber is characterized by comprising a core layer, an inner cladding layer and an outer cladding layer which are sequentially arranged from inside to outside, wherein the inner cladding layer has compressive stress, the absolute value of the compressive stress is greater than that of the core layer, and the radius of the core layer is R₁The radius of the inner cladding is R₂When the distance from any point on the cross section of the optical fiber to the center of the optical fiber is x and the absolute value of the compressive stress at any point in the diameter direction is F, the integral value of the compressive stress of the inner cladding expressed by the following formula in the diameter direction is 0.7 MPa.mu.m²Above and 25 MPa.mu.m²The following;

the preferred F value is 1.1 MPa. mu.m²Above and 12 MPa.mu.m²The following;

more preferably, the F value is 2.1 MPa-. mu.m²Above and 5.1 MPa.mu.m²The following.

5. The bend insensitive single mode optical fiber according to any of claims 1 to 4, wherein the core layer is silica glass containing germanium, and the percentage of germanium in the core layer is 2 to 15 mol%, preferably 3 to 7 mol%.

6. The bend insensitive single mode optical fiber according to any of claims 1 to 4, wherein the inner cladding is at least fluorine doped silica glass, wherein the percentage of fluorine is 0 to 6 mol%, preferably 0.3 to 3 mol%.

7. The bend insensitive single mode optical fiber of any of claims 1 to 4, wherein the radius R of the core layer₁3.5-4.5 μm, the radius R of the inner cladding₂Is 13 to 40 μm, preferably 15 to 25 μm.

8. The bend insensitive single mode optical fiber of any of claims 1 to 4, wherein the optical fiber has a wavelength of 1625nm,

an additional loss less than or equal to 0.1dB for a 10 turn bend around a 15 millimeter bend radius;

an additional loss less than or equal to 0.2dB for a bend of 1 turn around a 10 millimeter bend radius;

an additional loss less than or equal to 1.0dB for a bend of 1 turn around a 7.5 millimeter bend radius;

at a wavelength of 1550nm, the wavelength of the light,

an additional loss less than or equal to 0.03dB for a bend of 10 turns around a bend radius of 15 millimeters;

an additional loss less than or equal to 0.1dB for a bend of 1 turn around a 10 millimeter bend radius;

the additional loss is less than or equal to 0.5dB for a bend around 1 turn at a bend radius of 7.5 millimeters.

9. The bend insensitive single mode optical fiber of any of claims 1 to 4, wherein the optical fiber has a cable cut-off wavelength of less than or equal to 1260 nm.

10. The bend insensitive single mode optical fiber of any of claims 1 to 4, wherein the fiber has a temperature added attenuation of less than 0.02dB/km over the wavelength range of 1310nm to 1625nm at-65 ℃ to 85 ℃.

Technical Field

The invention belongs to the field of optical fiber communication transmission, and particularly relates to a bending insensitive single-mode optical fiber suitable for an access network under an extreme temperature condition.

Background

With The continuous development of Optical Fiber transmission technology, FTTx technology is mainly used for access Network Fiber, and has become an important development direction for The construction of communication access Network networks, ranging from local end equipment of regional telecommunication rooms To user Terminal equipment, The local end equipment is Optical line Terminal (Optical L ine Terminal; O L T), The user inner end equipment is Optical Network Unit (ONU) or Optical Network Terminal (Optical Network Terminal; ONT), The FTTB can be classified according To The distance from Optical Fiber To user, and can be divided into 4 service forms such as Fiber To The Cabinet (FTTCab), Fiber To The Curb (Fiber To The Curb; FTTC), Fiber To The Building (Fiber To The Building; FTTB) and Fiber To The user (Fiber To The Home; FTTH) according To The distance from Optical Fiber To user, Verizon has been applied To FTTB and FTTH technology in The field of Optical Fiber To The Premise (Fiber To The Network), and FTTP is used as a hot point medium for The research of The Optical Fiber To The international bend 657, and FTTP is applied To The hot point Network (FTTB) which is not applied To The international Optical Fiber-10-7-FTTB, and The FTTB is applied To The hot point of FTTB-7. FTTB application, which is not applied To The hot point of FTTB-7. FTTB, and The FTTB is applied To The hot point of The international Optical Fiber transmission medium, which is applied To The FTTB-7. FTTB application, which is applied To The hot point of FTTB, The FTTB 2. FTTB, The FTTB is applied To The FTTB, The FTTB is not applied To The FTTB, The FTTB is applied To The FTTB, The.

Considering that the FTTx project has complex application environment, large temperature difference and can reach minus 40 ℃ or even lower under the extreme temperature condition. In order to ensure that the attenuation of an optical fiber link is normal, and an optical communication network can work normally, the development of a bending insensitive single-mode optical fiber which can ensure that various optical fiber parameters are relatively stable under a low-temperature condition is urgently needed.

Disclosure of Invention

Aiming at the defects or improvement requirements of the prior art, the invention provides a bending insensitive single-mode optical fiber suitable for an access network under an extreme temperature condition, and aims to improve the micro-bending resistance of the optical fiber and reduce the additional attenuation caused by temperature change by optimizing the stress structure of the optical fiber, thereby improving the attenuation performance and stability of the optical fiber under the extreme temperature condition, and solving the technical problems that the existing bending insensitive optical fiber is influenced by the temperature change, and has overlarge attenuation and poor performance under the extreme temperature condition.

To achieve the above object, according to one aspect of the present invention, there is provided a bend insensitive single mode optical fiber comprising a core layer, an inner cladding layer, and an outer cladding layer arranged in this order from inside to outside, the inner cladding layer having a compressive stress whose absolute value is greater than that of the core layer.

Preferably, the bending insensitive single mode optical fiber has a core layer with compressive stress at room temperature, and the absolute value of the core layer compressive stress is between 10MPa and 40MPa, preferably between 15MPa and 35 MPa.

Preferably, the bend insensitive single mode optical fiber has an inner cladding with compressive stress at room temperature, and the absolute value of the compressive stress of the inner cladding is between 20MPa and 50MPa, preferably between 25MPa and 45 MPa.

Preferably, the bend-insensitive single-mode optical fiber has a radius of the core layer of R₁The radius of the inner cladding is R₂When the distance from any point on the cross section of the optical fiber to the center of the optical fiber is x and the absolute value of the compressive stress at any point in the diameter direction is F, the integral value of the compressive stress of the inner cladding expressed by the following formula in the diameter direction is 0.7 MPa.mu.m²Above and 25 MPa.mu.m²The following;

the preferred F value is 1.1 MPa. mu.m²Above and 12 MPa.mu.m²The following;

more preferably, the F value is 2.1 MPa-. mu.m²Above and 5.1 MPa.mu.m²The following.

Preferably, the core layer of the bending-insensitive single-mode optical fiber is quartz glass containing germanium, and the molar content percentage of germanium in the core layer is 2-15 mol%, preferably 3-7 mol%.

Preferably, said bend insensitive single mode optical fiber, wherein said inner cladding is at least fluorine doped silica glass, wherein the fluorine content percentage is 0 to 6 mol%, preferably 0.3 to 3 mol%.

Preferably, the bend insensitive single mode optical fiber has a radius R of the core layer₁3.5-4.5 μm, the radius R of the inner cladding₂Is 13 to 40 μm, preferably 15 to 25 μm.

Preferably, said bend insensitive single mode optical fiber, said fiber having an additional loss of less than or equal to 0.1dB for a 10 turn bend around a 15 millimeter bend radius at a wavelength of 1625 nm;

an additional loss less than or equal to 0.2dB for a bend of 1 turn around a 10 millimeter bend radius;

an additional loss less than or equal to 1.0dB for a bend of 1 turn around a 7.5 millimeter bend radius;

at a wavelength of 1550nm, the wavelength of the light,

an additional loss less than or equal to 0.03dB for a bend of 10 turns around a bend radius of 15 millimeters;

an additional loss less than or equal to 0.1dB for a bend of 1 turn around a 10 millimeter bend radius;

the additional loss is less than or equal to 0.5dB for a bend around 1 turn at a bend radius of 7.5 millimeters.

Preferably, said bend insensitive single mode optical fiber has a cable cut-off wavelength less than or equal to 1260 nm.

Preferably, the bend-insensitive single-mode optical fiber has an additional attenuation of less than 0.02dB/km at-65 ℃ to 85 ℃ in the wavelength range of 1310nm to 1625 nm. Generally, compared with the prior art, the above technical solution conceived by the present invention can achieve the following beneficial effects:

according to the invention, the inner cladding structure with compressive stress distribution is introduced around the optical fiber core layer, the power distribution and limiting capability of the core layer light wave electromagnetic field can be adjusted, high-order modes except L P01 mode can be rapidly leaked through the inner cladding structure, the inner cladding can keep proper compressive stress distribution and can obstruct and buffer the influence of external temperature and acting force on the core layer, so that the additional loss of the optical fiber in a bending state is greatly reduced, the adaptability of the optical fiber to extreme temperature is stronger, namely the optical fiber keeps bending insensitivity under extremely high temperature and extremely low temperature conditions, and the application temperature condition of the optical fiber can be expanded.

Drawings

FIG. 1 is a schematic cross-sectional view of a bend insensitive single mode optical fiber of the present invention;

FIG. 2 is a stress structure diagram of a bend insensitive single mode optical fiber according to the present invention;

FIG. 3 is a schematic view showing the cross-sectional structure of the refractive index of examples 11 and 12 of the present invention;

FIG. 4 is a schematic view showing the cross-sectional structure of the refractive index of examples 21, 22 and 23 of the present invention;

FIG. 5 is a schematic view showing the cross-sectional structure of the refractive index of examples 24 and 25 of the present invention;

FIG. 6 is a schematic view showing the cross-sectional structure of the refractive index of examples 13 and 14 of the present invention;

FIG. 7 is a schematic view of the refractive index profile structure of example 15 of the present invention.

The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein: 1-core layer, 2-inner cladding layer and 3-outer cladding layer.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The invention provides a bending insensitive single mode optical fiber, which comprises a core layer, an inner cladding layer and an outer cladding layer which are sequentially arranged from inside to outside; the core layer, the inner cladding layer and the outer cladding layer are all made of quartz substrates, and the inner cladding layer and the core layer of the optical fiber have compressive stress at normal temperature; and the absolute value of the internal package lamination stress is larger than the absolute value of the core layer lamination stress.

The radius of the core layer is R₁The radius of the inner cladding is R₂The distance from any point on the cross section of the optical fiber to the center of the optical fiber is x, the absolute value of the compressive stress of any point in the diameter direction is f, and the parameters of the stress of the inner cladding comprise the numerical value, the direction and the position of the stress. The integral value of the lamination stress of the inner pack expressed by the following formula in the diameter direction is F of 0.7 MPa. mu.m²Above and 25 MPa.mu.m²The following;

among them, the preferable F value is 1.1 MPa. mu.m²Above and 12 MPa.mu.m²The following; more preferably, the F value is 2.1 MPa-. mu.m²Above and 5.1 MPa.mu.m²The following.

The absolute value of the compressive stress of the core layer is between 10MPa and 40MPa, and preferably between 15MPa and 35 MPa; preferably quartz glass doped with germanium and/or fluorine and chlorine; the molar content percentage of germanium in the core layer is 0 to 15 mol%, preferably 2 mol% to 15 mol%, more preferably 3 mol% to 7 mol%; radius R of the core layer₁3.5-4.5 μm;

the absolute value of the compressive stress of the inner cladding is between 20MPa and 50MPa, preferably between 25MPa and 45 MPa; the inner cladding is quartz glass at least doped with fluorine, wherein the mol content percentage of the fluorine is 0 to 6 mol%, preferably 0.3 to 3 mol%, and the inner cladding is a homogeneous material, or comprises a plurality of layered structures distributed in a step shape, or is a material with a gradually-changed composition structure; the gradual change composition comprises various forms such as linear change of the content of doped elements, exponential form change and the like; radius R thereof₂Is 13 to 40 μm, preferably 15 to 25 μm.

The outer cladding layer has a radius R₃Is 62.5 +/-0.5 mu m

The relative refractive index difference delta between the core layer and the inner cladding layer₁₃The maximum value of (A) is in the range of 0.3% -1.4%, and delta is preferably selected₁₃Is between 0.4% and 0.96%, wherein,

the bending insensitive optical fiber provided by the invention has the additional loss of less than or equal to 0.1dB at the wavelength of 1625nm when the bending insensitive optical fiber is bent for 10 circles around the bending radius of 15 mm; an additional loss less than or equal to 0.2dB for a bend of 1 turn around a 10 millimeter bend radius; an additional loss less than or equal to 1.0dB for a bend of 1 turn around a 7.5 millimeter bend radius; an additional loss of less than or equal to 0.03dB for a 10 turn bend around a 15 millimeter bend radius at a wavelength of 1550 nm; an additional loss less than or equal to 0.1dB for a bend of 1 turn around a 10 millimeter bend radius; an additional loss of less than or equal to 0.5dB for a bend of 1 turn around a 7.5 millimeter bend radius; the optical fiber has a cable cut-off wavelength less than or equal to 1260 nm.

Under extreme temperature testing: the additional attenuation of the bending insensitive optical fiber at the temperature of-65 ℃ to 85 ℃ and in the wavelength range of 1310nm to 1625nm is less than 0.02 dB/km.

The invention introduces an inner cladding structure with compressive stress distribution around the core layer of the optical fiber, can adjust the power distribution and the limiting capability of a core layer light wave electromagnetic field, high-order modes except an L P01 mode can be leaked quickly through the inner cladding structure, and the inner cladding layer keeps moderate compressive stress distribution and can obstruct and buffer the influence of external temperature and acting force on the core layer, thereby greatly reducing the additional loss of the optical fiber in a bending state, and the optical fiber has stronger adaptability to extreme temperature, namely the optical fiber keeps bending insensitivity under extremely high temperature and extremely low temperature conditions, thereby expanding the application temperature condition of the optical fiber.

The fiber core of the bending insensitive single-mode optical fiber provided by the invention is formed by quartz glass doped with germanium and/or fluorine and chlorine, and compared with the outer cladding of pure quartz glass, the core layer has low viscosity and large expansion coefficient in a molten state. During the drawing, cooling and forming process, the optical fiber layers are transformed from a molten state to a viscoelastic state and finally cooled to a solid state. The cladding in the viscoelastic state has relatively highest viscosity, the shrinkage of the outer cladding continuously extrudes the inner cladding and the core layer inwards in the rapid cooling process of the optical fiber, the effect is that the inner cladding and the core layer of the optical fiber show stable compressive stress after the optical fiber is cooled to normal temperature, the stress is quantitatively detected by an FSA-100 type stress analyzer, and in a detection map, the compressive stress is a negative value, and the tensile stress is a positive value. The stress distribution of the inner cladding is the main factor influencing the core layer, and the inner cladding plays the effect of separation and buffering to external temperature change, external force effect, provides the protection to the core layer, restricts the leakage of luminous power. The ideal inner cladding stress structure can optimize the temperature-added attenuation of the fiber core to the maximum extent.

The manufacturing process of the bend insensitive single mode fiber comprises the following steps: heating the optical fiber preform with the quartz glass substrate to a viscoelastic state or even a molten state, and drawing and cooling to obtain an optical fiber; the drawing speed is more than 300 m/min, preferably more than 500 m/min; the optical fiber is forced cooled from the drawing furnace to the take-up device at a cooling rate of 1050 to 8500 ℃/s, preferably 4450 to 8000 ℃/s.

The optical fiber is subjected to a tension in the direction of motion of the optical fiber in the viscoelastic state during drawing of the fiber of from 10MPa to 77MPa, preferably from 15MPa to 45MPa, more preferably from 20MPa to 35 MPa.

In the drawing and cooling process, each layer of the optical fiber is converted from a viscoelastic state to a solid state, and the residual stress of the outer cladding and the inner cladding caused by the drawing tension is more than 3 MPa. This residual stress can be removed by heat treatment of the fiber, but the portion of the residual stress that remains during drawing is advantageous for adjusting the stress profile in the inner cladding of the fiber.

These residual stresses may buffer or cancel out the stress effects on the core region of the fiber caused by a portion of the ambient temperature change. The method for testing the residual stress comprises the steps of sampling the optical fibers of the same batch for heat treatment, wherein one heat treatment procedure comprises the steps of slowly heating the optical fibers from normal temperature to 1100 ℃ at a heating rate of less than 10 ℃ per minute, keeping the temperature for 30 minutes, and then slowly cooling the optical fibers to the normal temperature at a cooling rate of less than 10 ℃ per minute, preferably less than 10 ℃ per minute. The difference in residual stress can be determined by measuring and comparing the stress of the heat-treated and non-heat-treated fibers using an FSA-100 thermal stress analyzer.

The following are examples: