Method of making a non-zero dispersion-shifted optical fiber preform, preform and optical fiber made thereby

Abstract

The application relates to a non-zero dispersion-shifted fiber preform manufacturing method and a prepared preform and fiber, which comprises the following steps: manufacturing an initial core rod, depositing multiple core layers in a quartz liner tube through a PCVD process, melting and shrinking into the initial core rod in a melting and shrinking device after the deposition, manufacturing an inner cladding sleeve, the inner cladding sleeve is a doped quartz glass tube with a wall thickness of 6-9 mm, a relative refractive index difference in a gradually-distributed manner, high in the inner part and low in the outer part, and a convex shape in the upper part, manufacturing a core rod, inserting the initial core rod into the inner cladding sleeve, and low-pressure melting and shrinking into a core rod with the core layer and the inner cladding integrated in a melting and shrinking device, manufacturing a fiber preform, and depositing a pure silica outer cladding through an OVD process, or sleeving a pure silica outer sleeve on the core rod, and then performing sintering or melting and shrinking treatment, so that a non-zero dispersion-shifted fiber preform is manufactured. The application not only can guarantee deposition processing precision, but also has high efficiency. The manufactured fiber can find a more optimal balance among dispersion, nonlinear effect and bending loss.

Description

TECHNICAL FIELD

[0001] The application relates to a non-zero dispersion-shifted fiber preform manufacturing method, a prepared preform and an optical fiber, and belongs to the technical field of optical communication and transmission. BACKGROUND

[0002] In the field of optical fiber communication, a non-zero dispersion-shifted single-mode optical fiber (NZ-DSF) is a key technology developed to solve the limitations of traditional optical fibers in a wavelength division multiplexing (WDM) system. Traditional single-mode optical fibers (corresponding to ITU-T standard G.652 optical fibers) have zero dispersion at a 1310 nm window, but have high dispersion (about 17 ps / (nm·km)) at a 1550 nm window, which limits the long-distance transmission rate. Although the 1550 nm window has lower loss (about 0.2 dB / km), the dispersion causes signal pulse broadening, and dispersion compensation modules need to be frequently used. A dispersion-shifted DSF optical fiber (corresponding to ITU-T standard G.653 optical fiber) moves the zero dispersion point from 1310 nm to 1550 nm through waveguide design, thereby reducing the dispersion of the 1550 nm window. However, this characteristic causes serious four-wave mixing (FWM) nonlinear effects in the WDM system, leading to inter-channel crosstalk and restricting the application of dense wavelength division multiplexing (DWDM). The non-zero dispersion-shifted optical fiber (G.655) is an optical fiber developed for DWDM transmission technology, which can overcome the problems of large dispersion of G.652 optical fibers (non-dispersion-shifted optical fibers) at a low-loss 1550 nm wavelength and serious four-wave mixing of G.653 optical fibers (dispersion-shifted optical fibers), and has become the preferred fiber type for operator-related optical fiber communication systems.

[0003] A non-zero dispersion-shifted optical fiber preform is composed of a core layer, an inner cladding layer and an outer cladding layer. The core layer includes 2-4 core layer layers with different refractive index distributions, the inner cladding layer also includes 2-4 cladding layers with different refractive index distributions, and the outer cladding layer is a pure silica glass layer. Due to the complex refractive index profile structure of the core layer and the inner cladding layer, especially the small diameter of the core layer, the control range of the diameter and the refractive index is narrow, and the precision requirement is high, so the plasma chemical vapor deposition method is mostly used to deposit the core layer and the inner cladding layer layer by layer to obtain a core rod with an integrated core layer and inner cladding layer, and then the outer cladding glass provided by the OVD outer vapor deposition technology is matched to form a complete optical fiber preform. In the production process of the above-mentioned non-zero dispersion-shifted optical fiber core rod, not only the deposition process of each layer needs to be accurately controlled, but also the deposition efficiency is low, and the problem of low work efficiency will be more prominent especially when processing and depositing the inner cladding layer with a large diameter range. In addition, the inner cladding layer structure of the existing non-zero dispersion-shifted optical fiber also has aspects that can be further improved. SUMMARY

[0004] The technical problem to be solved by the present application aims at the above-mentioned problems of the prior art, and provides a manufacturing method of a non-zero dispersion-shifted optical fiber preform, the prepared preform and optical fiber, which can ensure deposition processing precision and has high work efficiency.

[0005] The manufacturing method technical solution for solving the above-mentioned problems is as follows:

[0006] An initial core rod is first prepared, a quartz liner is used to deposit a plurality of core layers of the non-zero dispersion-shifted optical fiber preform core rod in the liner by a PCVD process, and the initial core rod is fused and shrunk into a final core rod in a fusion and shrinking device after the deposition is completed, the plurality of core layers are three layers, the relative refractive index difference of the plurality of core layers decreases layer by layer, the relative refractive index difference is 0.2-0.7%, and the core diameter ranges from 7 mm to 18 mm,

[0007] An inner cladding sleeve is prepared, the inner cladding sleeve is a doped quartz glass tube, the wall thickness is 6-10 mm, the relative refractive index difference is gradually distributed, is high in the inner cladding and is low in the outer cladding, is convex upward, the relative refractive index difference of the inner surface (inner edge of the inner cladding) of the sleeve is 0.1-0.2%, and the relative refractive index difference of the outer surface (outer edge of the inner cladding) is -0.2-0%,

[0008] A core rod is prepared, the initial core rod is inserted into the inner cladding sleeve, and the core rod is fused and shrunk into a core rod with the core layer and the inner cladding integrated in a low-pressure fusion and shrinking device,

[0009] An optical fiber preform is prepared, the core rod is used to deposit a pure silica outer cladding by an OVD process, or the core rod is sleeved with a pure silica outer sleeve, and is treated by sintering or fusion and shrinking, so that the non-zero dispersion-shifted optical fiber preform is prepared.

[0010] According to the above scheme, the wall thickness of the quartz liner is 2-5 mm, and the relative refractive index difference is -0.1-0%.

[0011] According to the above scheme, the matching relationship between the core diameter of the initial core rod and the wall thickness of the inner cladding sleeve is that the initial core rod with a core diameter of 11-20 mm is matched with the inner cladding sleeve with a wall thickness of 6-8 mm, and the initial core rod with a core diameter of 20-28 mm is matched with the inner cladding sleeve with a wall thickness of 8-10 mm.

[0012] According to the above scheme, the low-pressure fusion and shrinking of the core rod is controlled in the range of 0-50 mbar in terms of absolute pressure and 1600-2200 DEG C in terms of temperature.

[0013] According to the above scheme, the quartz liner is deposited by an OVD process and is treated by sintering.

[0014] According to the above scheme, the inner cladding sleeve is deposited by an OVD process and is treated by sintering.

[0015] According to the scheme, the outer cladding wall thickness of the optical fiber preform is 35-65mm.

[0016] According to the scheme, the core layer of the core rod of the optical fiber preform is 3 layers, the relative refractive index difference of the first core layer is 0.6-0.7%, the diameter is 3-6mm, the relative refractive index difference of the second core layer is 0.4-0.6%, the diameter is 5-12mm, and the relative refractive index difference of the third core layer is 0.3-04%, the diameter is 7-18mm.

[0017] According to the scheme, the inner cladding of the core rod of the optical fiber preform is 2 layers, the first inner cladding is composed of a quartz liner, and the second inner cladding is composed of an inner cladding sleeve.

[0018] The non-zero dispersion-shifted optical fiber preform of the application is made according to the above scheme, that is, the initial core rod, the inner cladding sleeve and the outer cladding or the pure silica outer sleeve are integrated.

[0019] The non-zero dispersion-shifted optical fiber of the application is made by drawing the optical fiber preform made according to the above scheme.

[0020] According to the scheme, the attenuation of the non-zero dispersion-shifted optical fiber at the wavelength of 1383nm is ≤0.5dB / km, the attenuation at the wavelength of 1550nm is ≤0.195dB / km, and the attenuation at the wavelength of 1625nm is ≤0.200dB / km.

[0021] According to the scheme, the dispersion slope of the non-zero dispersion-shifted optical fiber is ≤0.075ps / (nm²·km), the zero dispersion wavelength is ≤1520nm, the dispersion in the range of 1530nm-1565nm is 2-6ps / (nm·km), and the dispersion in the range of 1565nm-1625nm is 4.5-11.2ps / (nm·km).

[0022] According to the scheme, the mode field diameter of the non-zero dispersion-shifted optical fiber at the wavelength of 1550nm is 9.2-10μm, the cabling cutoff wavelength is ≤1450nm, and the fiber bending performance is ≤0.03dB in the test of winding 100 turns at a diameter of 60mm.

[0023] The beneficial effects of the present application are: 1. The present application introduces a bushing and a sleeve to replace the PCVD deposition inner cladding of the core rod, which reduces the PCVD deposition time of a single core rod by about 9 times, breaks the dependence of the single device on the non-zero dispersion shift optical fiber preform, and effectively improves the work efficiency. 2. The core layer and the inner cladding layer of the present application adopt a two-step matching and then shrinking method, which avoids the core rod scrap caused by the mismatch of the core layer and the inner cladding layer in one-time deposition, and has a wider manufacturing tolerance. 3. The sleeve in the present application adopts an upper convex type graded refractive index distribution. Because the inner cladding layer of the non-zero dispersion shift optical fiber plays a regulating role on the dispersion characteristics, the mode field distribution and the bending loss of the optical fiber, the second inner cladding layer Clad2 formed can not only simplify the multi-layer step structure, but also find a better balance between dispersion, non-linear effect and bending loss. 4. The non-zero dispersion shift optical fiber preform prepared has the core layer with the highest refractive index in the innermost layer, which is used for strong beam confinement, and has 2-3 step core layers outside, which are used for fine-tuning the waveguide dispersion and the effective mode field diameter. The bushing is used as the first inner cladding layer Clad1 in the inner cladding layer, and the constant refractive index cooperates with the step core layer to form the main waveguide. The sleeve forms the second inner cladding layer Clad2 in the inner cladding layer, which forms a refractive index lifting area after Clad1, attracts the mode field to gather and increase the effective area. Then gradually decreases to be lower than Clad1, provides a continuous light potential barrier, so that the mode field can be more smoothly transitioned to the outside, which not only ensures the increase of the effective area, but also has a shielding effect on the bending leakage. In addition, the convex gradual distribution makes the change of the refractive index lifting area dn / dr more smooth, and the dependence of the waveguide dispersion on the wavelength is weaker, so as to obtain a lower dispersion slope. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a radial structure schematic diagram of the non-zero dispersion shift optical fiber preform of the present application.

[0025] Figure 2 It is a refractive index profile schematic diagram of the non-zero dispersion shift optical fiber of the present application. DETAILED DESCRIPTION

[0026] The present application will be further described in detail below in combination with the drawings and examples.

[0027] An embodiment of the present application is as follows Figure 1 , 2As shown, the pure silica quartz buffer tube with a relative refractive index difference of 0 and a wall thickness of 4 mm is selected to deposit 3 core layers 1 by PCVD process, the core layer refractive index decreases layer by layer, after deposition, the initial core rod is obtained by collapsing at 2100℃ in a collapsing device, the initial core rod diameter is 20.4 mm, the relative refractive index difference of the 3 core layers is in the range of 0.3~0.7%, then match the inner cladding sleeve with a wall thickness of 8.5 mm, the inner cladding sleeve is a doped quartz glass tube, the relative refractive index difference is gradually distributed, higher inside and lower outside, convex upward, the relative refractive index difference of the inner surface of the sleeve (inner edge of the inner cladding) is 0.2%, the relative refractive index difference of the outer surface (outer edge of the inner cladding) is -0.1%, the inner cladding sleeve is sleeved into the initial core rod, after completion of the sleeve, low pressure collapsing is carried out in the collapsing device, the absolute pressure of the low pressure collapsing is controlled at 15 mbar, the temperature is controlled at 1800℃, after collapsing, the core rod with the core layer and the inner cladding is made, the inner cladding of the optical fiber preform core rod is 2 layers, the first inner cladding 2 is composed of a quartz buffer tube, and the second inner cladding 3 is composed of an inner cladding sleeve. The core rod is deposited with a pure silica outer cladding by OVD process, and a pure silica outer cladding 4 with a wall thickness of 45 mm is formed by sintering, that is, a non-zero dispersion shift optical fiber preform rod is made. Or the core rod is configured with a pure silica outer sleeve tube, and a pure silica outer cladding with a wall thickness of 45 mm is formed by collapsing treatment, and a complete optical fiber preform rod is made.

[0028] The preform manufactured in the embodiment is drawn into fibers by a drawing tower at a drawing speed of 1500 m / min, and the non-zero dispersion shift optical fiber manufactured has the following parameters: the relative refractive index difference Δn1 of the first core layer is 0.7%, the diameter is 4.5 μm, the relative refractive index difference Δn2 of the second core layer is 0.4%, the diameter is 8.2 μm, the relative refractive index difference Δn3 of the third core layer is 0.3%, the diameter is 11.9 μm, the relative refractive index difference Δn4 of the first inner cladding layer is 0, the diameter is 20.4 μm, the inner surface relative refractive index difference Δn5 of the second inner cladding layer is 0.2%, the outer surface relative refractive index difference Δn6 is -0.1%, the diameter is 40.3 μm, the outer cladding layer is a pure silica glass outer cladding layer, the relative refractive index difference Δn7 is 0. The attenuation of the optical fiber at 1383 nm is 0.349 dB / km, the attenuation at 1550 nm is 0.193 dB / km, the attenuation at 1625 nm is 0.199 dB / km, the dispersion slope is 0.0717 ps / (nm2·km), the zero dispersion wavelength is 1484 nm, the dispersion in the range of 1530 nm-1565 nm is 3.23-5.74 ps / (nm·km), the dispersion in the range of 1565 nm-1625 nm is 5.74-10 ps / (nm·km), the mode field diameter at 1550 nm is 9.37 μm, the cabling cutoff wavelength is 1288 nm, and the fiber bending performance has a bending loss of 0.011 dB in the test of winding 100 turns at a diameter of 60 mm.

Claims

1. A method for manufacturing a non-zero dispersion-shifted optical fiber preform, characterized in that... First, an initial core rod is fabricated. Then, a non-zero dispersion-shifted fiber preform core rod is deposited inside a quartz liner using the PCVD process. The multi-layered core is deposited and then shrunk in a shrinking apparatus to form an initial core rod. The multi-layered core consists of three layers, with the relative refractive index difference decreasing layer by layer. The relative refractive index difference is 0.2~0.7%, and the core diameter ranges from 7~18 mm. Specifically, the relative refractive index difference Δn1 of the first core layer is 0.6~0.7% and the diameter is 3~6 mm; the relative refractive index difference Δn2 of the second core layer is 0.4~0.6% and the diameter is 5~12 mm; and the relative refractive index difference Δn3 of the third core layer is 0.3~0.4% and the diameter is 7~18 mm. An inner cladding sleeve is fabricated. The inner cladding sleeve is a doped quartz glass tube with a wall thickness of 6-10 mm. The relative refractive index difference exhibits a gradual distribution, higher on the inside and lower on the outside, and is convex upwards. The relative refractive index difference on the inner surface of the sleeve is 0.1-0.2%, and the relative refractive index difference on the outer surface is -0.2-0%. To fabricate a mandrel, the initial mandrel is inserted into the inner cladding sleeve and then low-pressure shrunk in a shrunking device to form a mandrel containing both the core layer and the inner cladding layer as a single unit. To fabricate an optical fiber preform, a pure silica cladding layer is deposited on the core rod using the OVD process, or a pure silica outer tube is fitted over the core rod. Through sintering or melting and shrinking treatment, a non-zero dispersion shift optical fiber preform is fabricated.

2. The method for manufacturing a non-zero dispersion-shifted optical fiber preform according to claim 1, characterized in that... The quartz liner has a wall thickness of 2-5 mm and a relative refractive index difference of -0.1-0%.

3. The method for manufacturing a non-zero dispersion-shifted optical fiber preform according to claim 1 or 2, characterized in that... The matching relationship between the initial mandrel diameter and the inner cladding sleeve wall thickness is as follows: for an initial mandrel diameter of 11~20mm, an inner cladding sleeve with a wall thickness of 6~8mm is selected; for an initial mandrel diameter of 20~28mm, an inner cladding sleeve with a wall thickness of 8~10mm is selected.

4. The method for manufacturing a non-zero dispersion-shifted optical fiber preform according to claim 1 or 2, characterized in that... The absolute pressure of the low-pressure melting is controlled within the range of 0~50mbar, and the temperature is controlled within the range of 1600℃~2200℃.

5. The method for manufacturing a non-zero dispersion-shifted optical fiber preform according to claim 1 or 2, characterized in that... The quartz liner is formed by external spraying deposition using the OVD process and then sintered.

6. The method for manufacturing a non-zero dispersion-shifted optical fiber preform according to claim 1 or 2, characterized in that... The inner cladding sleeve is formed by external spraying deposition using the OVD process and then sintered.

7. The method for manufacturing a non-zero dispersion-shifted optical fiber preform according to claim 1 or 2, characterized in that... The outer cladding thickness of the optical fiber preform is 35~65mm.

8. The method for manufacturing a non-zero dispersion-shifted optical fiber preform according to claim 1 or 2, characterized in that... The optical fiber preform core has two inner cladding layers: the first inner cladding layer is composed of a quartz liner, and the second inner cladding layer is composed of an inner cladding sleeve.

9. A non-zero dispersion-shifted optical fiber preform, characterized in that... The non-zero dispersion shifted optical fiber preform is manufactured according to any of the manufacturing methods described in claims 1-8, that is, it is formed by integrating an initial core rod, an inner cladding sleeve, and an outer cladding.

10. A non-zero dispersion-shifted optical fiber, characterized in that... The non-zero dispersion shifted optical fiber is drawn into fiber by drawing the optical fiber preform made according to claim 9 through a drawing tower.

11. The non-zero dispersion-shifted optical fiber according to claim 10, characterized in that... The optical fiber has an attenuation of ≤0.5dB / km at the 1383nm band, ≤0.195dB / km at the 1550nm band, and ≤0.200dB / km at the 1625nm band.

12. The non-zero dispersion-shifted optical fiber according to claim 10, characterized in that... The non-zero dispersion-shifted fiber has a dispersion slope ≤ 0.075 ps / Zero dispersion wavelength ≤1520nm, dispersion in the range of 1530nm~1565nm is 2~6ps / The dispersion in the 1565nm~1625nm range is 4.5~11.2ps / .

13. The non-zero dispersion-shifted optical fiber according to claim 10, characterized in that... The non-zero dispersion shifted fiber has a mode field diameter of 9.2μm-10μm at a wavelength of 1550nm, a cabling cutoff wavelength of ≤1450nm, and a bending loss of ≤0.03dB in a test of 100 turns with a diameter of 60mm.

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