CN101661132A - Bent insensitive single-mode fiber with air cladding layer - Google Patents

Abstract

The invention relates to a bent insensitive single-mode fiber with an air cladding layer, and a waveguiding structure of the bent insensitive single-mode fiber comprises a core layer and a cladding layer which is provided with three subsidiary cladding layers, namely a first cladding layer, a second cladding layer and a third cladding layer, wherein the first cladding layer and the third claddinglayer are pure silicon dioxide glass layers, the second cladding layer is air, and the relative refractive index differences of the core layer and the three cladding layers are relative to the third cladding layer. The parameters of the waveguiding structure are as follows: the relative refractive index difference delta 1 of the core layer is greater than or equal to 0.30% and less than or equal to 0.85%, and the radius r of the core layer is greater than or equal to 3.5 micrometers and less than or equal to 5.0 micrometers; the relative refractive index difference delta 2 of the second cladding layer is greater than or equal to -55.00% and less than or equal to -45.00%, and the radius r2 of the second cladding layer is greater than or equal to 8.0 micrometers and less than or equal to 15.0 micrometers; and the refractive index of each of the first cladding layer and the third cladding layer is a refractive index nc of the pure silicon dioxide glass, the radius r1 of the first claddinglayer is greater than or equal to 6.0 micrometers and less than or equal to 12.5 micrometers, and the radius r3 of the third cladding layer is greater than or equal to 62.0 micrometers and less thanor equal to 63.0 micrometers. The cutoff wavelength of the bent insensitive single-mode fiber is less than or equal to 1310 nm; and under the condition of bending the fiber for one circle with the diameter of 10 mm, the typical bending supplementary loss is less than 0.03 dB.

Description

Bend-insensitive single-mode optical fiber with air cladding layer

Technical field

The present invention relates to a kind of optical fiber, particularly have excellent bending property, be suitable for being collected in the bend-insensitive single-mode optical fiber in terminal box or the closed container with air cladding layer for Access Network, Fiber to the home (FTTH) usefulness.

Background technology

The bending radius of the G.652 standard fiber of present domestic widespread usage is 25mm, the restriction of radius by bending, and optical fiber can not optionally carry out angle and curved and install.

Along with FTTH begins to be deep into residential customer, Optical Access Network construction amount obviously increases, and access network construction requires networking work easier, and the time is shorter.This has under small-bend radius characteristics such as added losses are little, physical strength height with regard to the single-mode fiber that requires to be suitable for Access Network, be convenient to cable wiring manufacture and curl, and can control and lay the connecting loss of optical fiber simultaneously

Below for improving the theoretical foundation of fibre-optical bending performance.

Cutoff wavelength (λ _c) be the key property index of single-mode fiber, as follows with the relation of the structural parameters of optical fiber:

Wherein, ν _cBe normalized cutoff frequency, for step-index single-mode fibers, its value is 2.405; n ₁Be the sandwich layer refractive index, a is the sandwich layer radius, and Δ is a refractive index contrast, and it is defined as:

$\mathrm{\&Delta;}=\frac{{{\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="A2009100353660006H1.png"\; state="\{\{state\}\}">n</figure-callout>}}_1}^2-{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="A2009100353660006H1.png"\; state="\{\{state\}\}">n</figure-callout>}}_2}^2}{2{{\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="A2009100353660006H1.png"\; state="\{\{state\}\}">n</figure-callout>}}_1}^2}---\left(2\right)$

Mode field diameter (2 ω ₀) definition is to think that in the mould field of approximate Gaussian distribution, light intensity drops to 1/e ²Width between 2 also is confirmed to be the spot size of single-mode fiber, and computing formula is:

$\frac{2{\mathrm{\&omega;}}_0}{a}=0.85+0.434{\left(\frac{\mathrm{\&lambda;}}{{\mathrm{\&lambda;}}_c}\right)}^{\frac{3}{2}}+0.0149{\left(\frac{\mathrm{\&lambda;}}{{\mathrm{\&lambda;}}_c}\right)}^6---\left(3\right)$

The characteristic of single-mode fiber bending loss can be used critical bends radius (R _c) characterize, computing formula is:

$R_c\&ap;20\frac{\mathrm{\&lambda;}}{{\mathrm{\&Delta;}}^{3/2}}{(2.748-0.996\frac{\mathrm{\&lambda;}}{{\mathrm{\&lambda;}}_c})}^{-3}---\left(4\right)$

From formula (1)-(4) as seen, for the bonding mode fiber is applicable to 1310nm wavelength and 1550nm wavelength double window mouth light transmission, in the design of preform waveguiding structure, can obtain good fibre-optical bending performance by improving the sandwich layer relative index of refraction and reducing the sandwich layer radius; Simultaneously, in order to control optical fiber and the connecting loss of now having laid optical fiber, the sandwich layer radius value need be set in suitable scope, and the sandwich layer relative index of refraction can not be too high.

In order to realize above-mentioned requirements, existing design philosophy mainly contains: improve the refractive index profile of optical fiber, improve the structure of optical fiber and the paintability of improvement optical fiber etc.

For the refractive index profile that improves optical fiber, the optical fiber of Chinese patent CN101373238A invention has a sandwich layer and two coverings, the sandwich layer refractive index profile is power function and distributes, the refractive index profile of two coverings is ladder pattern distribution, is about to covering near infiltrating certain material (normally fluorine) in the circular annular region of sandwich layer to reduce the refractive index with respect to sandwich layer.The optical fiber of Chinese patent CN1632628A invention has sandwich layer and covering, and wherein covering is divided into five subcontract layers that refractive index is different, and the cladding structure that uses the heterogeneity that centers on the sandwich layer multi-turn is to reduce the refractive index with respect to sandwich layer.But refractive index profile is complicated more, and is just strict more to the requirement of technology, is unsuitable for large-scale production.

Improve the bending resistance of optical fiber for coating, Chinese patent CN1542473A can improve the bending property of optical fiber by improving the bending modulus of coating.But the improvement degree is relatively limited.

In the configuration aspects of improving optical fiber, photonic crystal fiber (PCF) and Holey optical fibres (HAF) have added the airport structure at covering, and the size in hole is approximately several microns.The hole auxiliary type porous optical fiber of Chinese patent CN1981223A invention have refractive index be higher than covering the sandwich layer position, be arranged at the cladding part that contains a plurality of emptying apertures around it, and emptying aperture is provided with identical inside and outside two-layer of dosis refracta.Chinese patent CN1971323A has introduced a kind of optical fiber that equally distributed air aperture is arranged on inner cladding, Chinese patent CN1412584A has also introduced a kind of hollow optic fibre.This type optical fiber has bend-insensitive performance preferably, but since the structure relative complex, the height that manufactures a finished product, and can not carry out compatibility with conventional fiber.

Therefore, from Access Network single-mode fiber characteristic, be necessary in conjunction with the design of optical fiber structure and refractive index profile, crucial what consider is the equilibrium of bending property and sandwich layer relative index of refraction, takes into account dispersion characteristics and aspects such as fibre loss and physical strength.

Optical fiber designs described in the invention has an air cladding layer, by the width of adjusting air cladding layer and the bending property that obtains excellence to the distance of sandwich layer, take into account chromatic dispersion and loss characteristic simultaneously, and its suitable optical parametric and physical dimension make with the connecting loss of optical fiber G.652 very little.

Summary of the invention

Technical matters to be solved by this invention provides a kind of for Access Network, FTTH use, and it is interior and wiring to be convenient to be collected in terminal box or closed container, has the bend-insensitive single-mode optical fiber of air cladding layer.This optical fiber is applicable to 1310nm wavelength and 1550nm wavelength double window mouth, has excellent flexural property, suitable mode field diameter and chromatic dispersion, loss characteristic, be convenient between building and building in cable wiring manufacture and curl.

The present invention provides a kind of bend-insensitive single-mode optical fiber with air cladding layer for the problem that solves above-mentioned proposition, its waveguiding structure comprises sandwich layer and covering, covering is provided with three covering layerings---covering one, covering two, covering three, wherein covering one and covering three all are the pure silicon dioxide glassy layer, covering two is an air, the refractive index contrast of sandwich layer and three covering layerings is all with respect to covering three, and its waveguiding structure parameter is:

The refractive index contrast of sandwich layer: 0.30%≤Δ 1≤0.85%, 3.5 microns≤r of sandwich layer radius≤5.0 microns;

The refractive index contrast of covering two :-55.00%≤Δ 2≤-45.00%, 8.0 microns≤r2 of covering two radiuses≤15.0 microns;

The refractive index of covering one and covering three is pure silicon dioxide glass refraction nc, and 6.0 microns≤r1 of covering one radius≤12.5 microns, covering three radiuses are 62.0 microns≤r3≤63.0 micron.

In fiber core layer,, realize the viscosity coupling between each layer of prefabricated rods simultaneously and reduce stress by mixing monox, germanium oxide and a spot of fluorine or getting suitable refractive index.In prefabricated rod mandrel deposition and burning shrinkage process, feed an amount of helium and reduce the microbubble that forms in the deposition process, improve fiber strength.

By precision control, can obtain designing flexural property, wavelength loss and the dispersion characteristics of the required mode field diameter of optical fiber, excellence to single-mode fiber prefabricated rods waveguiding structure.According to such scheme, fiber cut off wavelength≤1310nm of the present invention, cable cut-off wavelength≤1260nm, in 1310nm long wavelength fiber mode field diameter is the 7.8-10.2 micron, can satisfy the requirement of 1310nm wavelength and 1550nm wavelength double window mouth single-mode optics transmission, optical parametric and physical dimension and optical fiber compatibility G.652, both average connecting losses are less than 0.05dB.Under the situation of the present invention with the crooked circle of 10mm diameter, its typical crooked added losses are less than 0.03dB.The present invention is at 1310nm to 1550nm wavelength coverage CHROMATIC DISPERSION IN FIBER OPTICS absolute value≤17ps/nm*km, and zero-dispersion wavelength is in 1310nm to 1400nm wavelength coverage.

The bend-insensitive single-mode optical fiber prefabricated rods manufacturing with air cladding layer that the present invention relates to adopts VAD technology (VAD) and tiretube process (RIC) to be made.

Description of drawings

Fig. 1 is a bare fibre cross sectional representation of the present invention; Fig. 2 is a bare fibre structural representation of the present invention; Fig. 3 is the directions X refractive index profile synoptic diagram of optical fiber among Fig. 1; Fig. 4 is the Y direction refractive index profile synoptic diagram of optical fiber among Fig. 1.

In Fig. 1, Fig. 2, Fig. 3, Fig. 4,1, sandwich layer, 2, covering one, 3, covering two (being air cladding layer), 4, the double-stranded support stick of tools symmetry in the covering three, 5, covering two.

Embodiment

Adopt VAD technology to make the plug of optical fiber of the present invention, adopt sleeve technology to make final preform, obtain fiber products of the present invention through wire drawing.Its structure of the optical fiber of preparing as shown in Figure 2.The manufacture process of fibre-optical mandrel is as follows: at first set process gas flow and prescription with the VAD method according to the refractive index profile structure of design, deposit sandwich layer 1 and covering 1, form plug, on plug, install support stick then, with tiretube process covering 34 is enclosed within mandrel outer again, covering 23 is arranged between covering 34 and the plug, and connect to have symmetrical double-stranded support stick 5.The preform of this waveguiding structure obtains the bend-insensitive single-mode optical fiber with air cladding layer of the present invention at last through wire drawing, coating, screening, test, packing.

Embodiment:

In Fig. 1, Fig. 2, establish the following waveguiding structure parameter that comprises sandwich layer 1 and three covering layerings and be with respect to covering 34:

The refractive index contrast of sandwich layer 1 is about 0.60%, and the sandwich layer radius is about 4 microns;

The refractive index contrast of covering 23 is about-50.00%, and covering 23 radiuses are about 12 microns;

Covering 1 and covering 34 are the pure silicon dioxide glassy layer, and its refractive index is pure silicon dioxide glass refraction nc.Covering one 2 radiuses are about 10 microns, and covering 34 radiuses are 62.5 microns.

The characteristic of gained optical fiber is as follows:

Fiber cut off wavelength≤1310nm, in 1310nm long wavelength fiber mode field diameter is the 7.8-10.2 micron, under the situation with the crooked circle of 10mm diameter, its typical crooked added losses are less than 0.03dB, chromatic dispersion absolute value≤14ps/nm*km at the 1550nm long wavelength fiber, zero-dispersion wavelength is in 1310nm to 1400nm wavelength coverage, with the average connecting loss of optical fiber G.652 less than 0.05dB.

The optical fiber of gained is excellent in the flexural property performance, as Transmission Fibers, is adapted to Access Network, FTTH use.

Claims (4)

1, a kind of bend-insensitive single-mode optical fiber with air cladding layer, its waveguiding structure comprises sandwich layer and covering, it is characterized in that covering is provided with three covering layerings---covering one, covering two and covering three, wherein covering one and covering three all are the pure silicon dioxide glassy layer, covering two is an air layer, the refractive index contrast of sandwich layer and three covering layerings is all with respect to covering three, and its waveguiding structure parameter is:

The refractive index contrast of sandwich layer: 0.30%≤Δ 1≤0.85%, 3.5 microns≤r of sandwich layer radius≤5.0 microns;

The refractive index contrast of covering two :-55.00%≤Δ 2≤-45.00%, 8.0 microns≤r2 of covering two radiuses≤15.0 microns;

The refractive index of covering one and covering three is pure silicon dioxide glass refraction nc, and 6.0 microns≤r1 of covering one radius≤12.5 microns, covering three radiuses are 62.0 microns≤r3≤63.0 micron.

2,, it is characterized in that its typical crooked added losses are less than 0.03dB with under the situation of described optical fiber with the crooked circle of 10mm diameter by the described bend-insensitive single-mode optical fiber of claim 1 with air cladding layer.

3, by the described bend-insensitive single-mode optical fiber of claim 1 with air cladding layer, cutoff wavelength≤the 1310nm that it is characterized in that described optical fiber, cable cut-off wavelength≤1260nm, in 1310nm long wavelength fiber mode field diameter is the 7.8-10.2 micron, can satisfy the requirement of 1310nm wavelength and 1550nm wavelength double window mouth single-mode optics transmission, with the average connecting loss of optical fiber G.652 less than 0.05dB.

4,, it is characterized in that zero-dispersion wavelength is in 1310nm to 1400nm wavelength coverage at 1310nm to 1550nm wavelength coverage CHROMATIC DISPERSION IN FIBER OPTICS absolute value≤17ps/nm*km by the described bend-insensitive single-mode optical fiber of claim 1 with air cladding layer.

Images