CN210072132U

CN210072132U - Single mode optical fiber

Info

Publication number: CN210072132U
Application number: CN201921090928.8U
Authority: CN
Inventors: 张学军
Original assignee: Hangzhou Jinxing Tong Optical Fiber Technology Co Ltd
Current assignee: Hangzhou Jinxing Tong Optical Fiber Technology Co Ltd
Priority date: 2019-07-12
Filing date: 2019-07-12
Publication date: 2020-02-14
Anticipated expiration: 2029-07-12

Abstract

The utility model provides a single mode fiber, including sandwich layer and cladding, the sandwich layer outside be equipped with the cladding, the cladding include first cladding and second cladding, first cladding inboard link to each other with the sandwich layer outside, the inboard of first cladding outside and second cladding link to each other, the sandwich layer be the SiO2 quartz glass who dopes germanium (Ge) element, the diameter 2r1 of sandwich layer be 7.5um to 8.5um, first cladding be the SiO2 quartz glass who dopes fluorine (F) element, first cladding diameter 2r2 be 25um to 40um, the second cladding be the gradient SiO2 quartz glass who dopes fluorine (F) element, second cladding diameter 2r3 be 125 um. The utility model has the advantages that: the design and manufacture of the optical fiber can be adjusted by a plurality of variables, namely the core layer diameter r1, the first cladding diameter r2 and the refractive index difference values delta 1, delta 2, delta 3 and delta 4, so that the internal stress generated in the fiber drawing process can be reduced, the Rayleigh scattering of the optical fiber is reduced, and the loss value of the optical fiber is further reduced integrally.

Description

Single mode optical fiber

Technical Field

The utility model belongs to communication optical fiber makes the field, especially relates to a single mode fiber.

Background

The single-mode optical fiber is designed based on the fact that a certain difference exists between refractive indexes of a core layer and a cladding layer, so that light in a transmission waveband can generate total reflection in the core layer of the optical fiber for transmission. Therefore, in design and manufacture, the core layer or the cladding layer is doped based on pure SiO2 quartz, and the main dopants used are a positive dopant which increases the refractive index of the quartz glass by germanium (Ge), phosphorus (P) and the like, and a negative dopant which decreases the refractive index of the quartz glass by fluorine (F), boron (B) and the like. The density fluctuation and viscosity fluctuation of the quartz glass can be caused by the existence of the dopant, so that the Rayleigh scattering of the optical fiber is increased, and the transmission loss of the optical fiber is increased. Improving the refractive index difference between the core and the cladding is an effective means for improving the bending performance of the optical fiber, but the impurity doping concentration in the core cladding is increased, and the transmission loss of the optical fiber is increased.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a single mode fiber, its diameter that has certain bending property, decay low, control the optical fiber core layer to a certain extent again, density fluctuation and the concentration fluctuation of dopant in the optical fiber of will reducing as far as possible at optic fibre wire drawing in-process again reduce the rayleigh scattering to minimum.

The technical scheme of the utility model is that: a single mode optical fiber comprises a core layer and a cladding layer, wherein the cladding layer is arranged on the outer side of the core layer and comprises a first cladding layer and a second cladding layer, the inner side of the first cladding layer is connected with the outer side of the core layer, the outer side of the first cladding layer is connected with the inner side of the second cladding layer,

the core layer is SiO2 quartz glass doped with germanium (Ge) element, the diameter 2r1 of the core layer is 7.5um to 8.5um, and the refractive index difference delta 1 of the core layer relative to the refractive index of pure SiO2 quartz glass is 0.0025 to 0.0045;

the first cladding is SiO2 quartz glass doped with fluorine (F), the diameter 2r2 of the first cladding is 25um to 40um, and the refractive index difference delta 2 of the refractive index of the first cladding relative to pure SiO2 quartz glass is-0.001 to-0.002;

the second cladding is gradient fluorine (F) element-doped SiO2 silica glass, the diameter of the second cladding 2r3 is 125um, the refractive index difference delta 3 of the outside glass of the second cladding relative to pure SiO2 silica glass ranges from-0.0005 to 0, the refractive index difference delta 4 of the inside glass of the second cladding relative to the refractive index of the first cladding ranges from 0 to 0.0005, and the outside refractive index of the second cladding is greater than the inside refractive index of the second cladding.

Further, the core layer and the cladding layer are obtained by one-time deposition by VAD (axial vapor deposition), but not limited to VAD, and can comprise OVD (outside vapor deposition).

Further, the Mode Field Diameter (MFD) of the single mode fiber at 1310nm is 8.7 um-9.5 um.

Further, the cut-off wavelength (. lamda.c) of the optical fiber is 1250nm to 1330 nm.

Further, the ratio MFD/λ c (MAC value) of the fiber mode field diameter MFD to the cutoff wavelength λ c is less than 7.5.

The utility model has the advantages and positive effects that: due to the adoption of the technical scheme, the design and the manufacture of the optical fiber can be adjusted by a plurality of variables, namely the core diameter r1, the first cladding diameter r2 and the refractive index difference delta 1, delta 2, delta 3 and delta 4;

the attenuation of the optical fiber, especially the attenuation at 1550nm, can be reduced to about 0.17dB/km by reducing the delta 1 and increasing the absolute value of the delta 2;

the absolute value of delta 2 is increased by reducing the r1 value, the bending resistance of the optical fiber is improved, and the bending loss at 1550nm is controlled within 0.75dB (the bending radius is 10mm, 1 turn);

by adjusting the values of delta 3 and delta 4, the viscosity of the core layer and the cladding layer of the optical fiber can be well matched, the internal stress generated in the fiber drawing process can be reduced, the Rayleigh scattering of the optical fiber can be reduced, and the loss value of the optical fiber can be further reduced integrally.

Drawings

Fig. 1 is a schematic structural diagram of the present invention.

In the figure:

1. core layer 2, first cladding layer 3, and second cladding layer

Detailed Description

As shown in FIG. 1, the technical solution of the present invention is a single mode optical fiber, comprising a core layer 1 and a cladding layer, wherein the cladding layer is arranged outside the core layer 1, the cladding layer comprises a first cladding layer 2 and a second cladding layer 3, the inner side of the first cladding layer 2 is connected with the outer side of the core layer 1, the outer side of the first cladding layer 2 is connected with the inner side of the second cladding layer 3,

the core layer 1 is SiO2 quartz glass doped with germanium (Ge) element, the diameter 2r1 of the core layer 1 is 7.5um to 8.5um, and the refractive index difference delta 1 of the core layer 1 relative to the refractive index of pure SiO2 quartz glass is 0.0025 to 0.0045;

the first cladding 2 is SiO2 quartz glass doped with fluorine (F), the diameter 2r2 of the first cladding 2 is 25um to 40um, and the refractive index difference delta 2 of the refractive index of the first cladding 2 relative to the refractive index of pure SiO2 quartz glass is-0.001 to-0.002;

the second cladding 3 is SiO2 silica glass doped with fluorine (F) in a gradient manner, the diameter 2r3 of the second cladding 3 is 125um, the refractive index difference delta 3 between the refractive index of the outer glass of the second cladding 3 and the refractive index of pure SiO2 silica glass ranges from-0.0005 to 0, the refractive index difference delta 4 between the refractive index of the inner glass of the second cladding 3 and the refractive index of the first cladding 2 ranges from 0 to 0.0005, and the outer refractive index of the second cladding 3 is larger than the inner refractive index of the second cladding 3.

In this embodiment, the core layer 1 and the cladding layer are obtained by one deposition using VAD (axial vapor deposition), but not limited to VAD, and may include OVD (outside vapor deposition).

In this embodiment, the Mode Field Diameter (MFD) of the single mode fiber at 1310nm is 8.7 um-9.5 um.

In this embodiment, the cut-off wavelength (. lamda.c) of the optical fiber is 1250nm to 1330 nm.

In this embodiment, the ratio MFD/λ c (MAC value) of the fiber mode field diameter MFD to the cutoff wavelength λ c is less than 7.5.

In the design of the optical fiber section, the core layer is doped with Ge element to improve the refractive index, the refractive index difference of the optical fiber section relative to pure SiO2 quartz glass is delta 1, and the diameter of the core layer is 2r 1. The first cladding layer is uniformly doped with F element for lowering the refractive index, the refractive index difference is Δ 2 with respect to pure SiO2 quartz glass, and the diameter of the second cladding layer is 2r 2. The second cladding is doped with F element in gradient, and is used for matching the viscosity difference of a core cladding of the optical fiber preform in the drawing process and inhibiting the F element in the second cladding from expanding outwards, the refractive index difference of the inner side of the second cladding relative to the second cladding is delta 4, the refractive index difference of the outer side of the second cladding relative to pure SiO2 quartz glass is delta 3, and the diameter of the second cladding is 2r 3. Table 1 designs the cross-sectional structure for 8 different parameters.

TABLE 1 fiber Profile design parameters for embodiments of the invention

The manufacturing method of the single mode fiber comprises the following steps:

the core rod for manufacturing the optical fiber preform by the VAD method comprises a core layer and a first cladding layer, wherein the core layer and the first cladding layer are simultaneously deposited by 1 burner respectively, gases such as SiCl4, GeCl4, H2, O2 and Ar are introduced into the burner for depositing the core layer, and gases such as SiCl4, CF4, H2, O2 and Ar are introduced into the burner for depositing the cladding layer. The ratio of SiCl4 to GeCl4 in the core burner was used to adjust the Δ 1 magnitude and the ratio of SiCl4 to CF4 in the cladding burner was used to adjust the Δ 2 magnitude.

And placing the powder loose body after deposition in a quartz high-temperature furnace for dehydration and sintering, then extending on an extension lathe, placing the manufactured core rod on refractive index detection equipment (PK2600) for testing, and adjusting the VAD deposition process according to the test result until a cross section meeting the design requirements of 8 embodiments is obtained.

And (3) manufacturing a cladding of the optical fiber preform by adopting an OVD (optical fiber deformation device) method, depositing SiO2 powder with rated weight outside the core rod according to the design requirement of 2 x 2r1 to form a cladding loose body product, and in the deposition process, adjusting the flame temperature to ensure that the density of the loose body is continuously reduced along with the increase of deposition time.

And (3) placing the cladding loose body product into a quartz high-temperature furnace, adjusting the furnace temperature to 1200 ℃, introducing He and CF4 gases, wherein the He is 20L/min, the CF4 is 2L/min, adjusting the opening of a furnace opening to enable the pressure in the furnace to be 300Pa, and keeping the pressure for 90min to enable CF4 to fully penetrate into the loose body. And then stopping introducing CF4, reducing the He flow to 10L/min, adjusting the exhaust speed of a furnace opening to ensure that the pressure in the furnace is-100 Pa, keeping the pressure for 30min, recovering the He flow to 20L/min, keeping the pressure in the furnace at 20Pa, introducing Cl2 with the flow of 0.5L/min, raising the temperature to 1500 ℃, and sintering the cladding loose body product to form the transparent preform. And (3) carrying out optical parameter test on the preform to check whether the delta 3 and the delta 4 meet the design requirements, and enabling the delta 3 and the delta 4 to meet the design requirements by adjusting parameters such as the ratio of He to CF4, the pressure value in the furnace, the temperature and the like.

And drawing the optical fiber preform, wherein before drawing the preform, the preform is extended to an optical rod with about 80mm and uniform diameter, and then the optical fiber preform is placed into an optical fiber drawing tower for drawing, wherein in order to obtain better optical fiber attenuation performance, the drawing speed is controlled at 1500m/min, the drawing temperature is controlled at 1950 ℃, and the drawing tension is controlled between 250g and 300 g.

The resulting fiber performance parameters are shown in table 2:

TABLE 2 optical fiber Performance parameters for embodiments of the present invention

According to the performance parameters of the optical fiber of the above embodiment, the optical fiber meets g.652d, and when (Δ 1- Δ 2) is greater than 0.005 and the MFD is less than 9.15, the optical fiber meets the requirement of the g.657a standard, and more preferably, when (Δ 1- Δ 2) is 0.0055, Δ 3 is-0.0005, and Δ 4 is 0, and the core diameter of the optical fiber is controlled to 7.8um, a single-mode optical fiber with lower attenuation and better bending resistance is easily obtained.

The above embodiment describes the relevant contents of the present invention by fabricating the core rod of the optical fiber preform by VAD, but the present invention is not limited to fabricating the core rod by VAD, and is also applicable to fabricating the core rod by OVD.

While one embodiment of the present invention has been described in detail, the description is only a preferred embodiment of the present invention, and should not be considered as limiting the scope of the present invention. All the equivalent changes and improvements made according to the application scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A single mode optical fiber, characterized by: comprises a core layer and a cladding layer, the cladding layer is arranged on the outer side of the core layer, the cladding layer comprises a first cladding layer and a second cladding layer, the inner side of the first cladding layer is connected with the outer side of the core layer, the outer side of the first cladding layer is connected with the inner side of the second cladding layer,

the core layer is SiO2 quartz glass doped with Ge element, the diameter 2r1 of the core layer is 7.5um to 8.5um, and the refractive index difference delta 1 of the core layer relative to pure SiO2 quartz glass is 0.0025 to 0.0045;

the first cladding is SiO2 quartz glass doped with fluorine F element, the diameter 2r2 of the first cladding is 25um to 40um, and the refractive index difference delta 2 of the refractive index of the first cladding relative to pure SiO2 quartz glass is-0.001 to-0.002;

the second cladding is SiO2 silica glass doped with F element in gradient, the diameter of the second cladding 2r3 is 125um, the refractive index difference delta 3 of the outside glass of the second cladding relative to the pure SiO2 silica glass is-0.0005 to 0, the refractive index difference delta 4 of the inside glass of the second cladding relative to the refractive index of the first cladding is 0 to 0.0005, and the outside refractive index of the second cladding is larger than the inside refractive index of the second cladding.

2. A single mode optical fiber as claimed in claim 1, wherein: the core layer and the cladding layer are obtained by one-time deposition by VAD axial vapor deposition, but not limited to VAD, and can comprise OVD external vapor deposition.

3. A single mode optical fiber as claimed in claim 1, wherein: the mode field diameter MFD of the single mode fiber at 1310nm is 8.7 um-9.5 um.

4. A single mode optical fiber as claimed in claim 1, wherein: the cut-off wavelength lambdac of the optical fiber is 1250 nm-1330 nm.

5. A single mode optical fiber as claimed in claim 1, wherein: the ratio MFD/lambda cMAC of the fiber mode field diameter MFD to the cut-off wavelength lambdac is less than 7.5.