CN101006371B - Single-mode optical fiber - Google Patents

Abstract

A single-mode optical fiber has a prescribed mode field diam MFD1 (mum) at a first wavelength lambda 1 (mum), in which a bending loss when measured at a second wavelength lambda 2 (mum) and wound with a bending radius r (mm) is Lb (dB) for one bending, a connection loss with an optical fiber that has a prescribed mode field diameter MFD2 (mum) at the first wavelength lambda 1 (mum) is Ls (dB) for one connection point at the second wavelength lambda 2 (mum), and an mode field diameter dependence of a total loss coefficient calculated by a formula (1) has a local minimal value in a range of MFD1+-0.5 mum, with the formula (1) being as follows: L = ws*Ls + wb*Lb...(1) ws + wb = 1...(2), ws > 0 , wb > 0 , wherein ws and wb in the formula (1) represent dimensionless weighting factors and are set within a range that satisfies the range of the formula (2) and the formula (3).

Description

Single-mode fiber

Technical field

The present invention relates to a kind of single-mode fiber (hereinafter referred to as SMF), this single-mode fiber can be suitable for use as purposes, particularly requirements such as optical fiber access and small parts and have the optical fiber than low bend loss, has good flexural property and connection performance.

The application advocates right of priority to 2004-233111 number application of Japan's patented claim that proposed on August 10th, 2004 and the 2005-120996 number application of Japan's patented claim that proposed on April 19th, 2005, and quotes its content at this.

Background technology

At present, (wavelength-division multiplex: transmission system Wavelength Division Multiplexing) and the exploitation of optical fiber become increasingly active to have used WDM for the transmission capacity that enlarges main line, long distance-like.The WDM transmission requires to have characteristics such as the nonlinear effect of inhibition and chromatic dispersion control with optical fiber.In recent years, people have proposed the optical fiber that increases towards the optical fiber system with several hundred kilometers left and right sides span, that reduced chromatic dispersion gradient that is known as Metropolitan Area Network (MAN) and the loss that almost not do not cause because of OH etc.

When considering optical fiber inserted in office and the family (FTTH:Fiber To The Home), require to have and be different from the characteristic of these transmission with optical fiber.When at office building or dwelling house inner ply fiber, might produce the very little like this bending of 30mm, 20mm.And when the unnecessary optical fiber of arrangement, even if it is important to reel with less bending diameter, also can avoid taking place loss increases.That is,, can bear less bending diameter and be its very important characteristic as optical fiber towards FTTH.And, itself and also be aspect very important one in the base station to the connectivity of employed optical fiber between office building or the dwelling house (mostly being the SMF of common wavelength 1.3 μ m).

Patent documentation 1: No. 2004/0213531 instructions of U.S. Patent Application Publication

Patent documentation 2: international No. 01/27667 pamphlet of WO that discloses

Non-patent literature 1:I.Sakabe, et al., " Enhanced Bending Loss InsensitiveFiber and New Cables for CWDM Access Network, " Proceedings of the53rd IWCS, pp.112-118 (2004)

Non-patent literature 2:S.Matsuo et al, " Bend-insensitive and low-splice-lossoptical fiber for indoor wiring in FTTH ", OFC2004, ThI3

Non-patent literature 3: assistant rattan ら, " light ア Network セ ス uses the bent げ of path to ying type light Off ア イ バ ", the ソ サ イ エ テ イ of Electricity feelings Reported Communications Society in 2003 conference, B-10-30

Non-patent literature 4: Ikeda ら, “ Jie Continuous Damage lose the low low Qu げ Damage loss of gloss Off ア イ バ of type that subtracts ", the research Reported of Electricity feelings Reported Communications Society accuses, OCS2003-43

Non-patent literature 5: all ら, " in the brilliant Off ア of the Off オ ト ニ ツ ク Knot イ バ residence, join in the PVC Le self-criticism of Line ヘ Fitness Yong に Seki The Ru ", the research Reported of Electricity feelings Reported Communications Society accuse, OFT2002-81

Non-patent literature 6: Yao ら, " one self-criticism of ホ one リ one Off ア イ バ real usefulnessization に Seki The Ru ", the research Reported of Electricity feelings Reported Communications Society accuse, OFT2002-82

In the past, in office or family, generally using common wavelength was SMF or the multimode optical fiber of 1.3 μ m.Yet these optical fiber in the past generally only allow to reach the bending diameter about 60mm, therefore need take more care when it is laid, so that it does not produce excessive bending.

In addition, recently G.652 being in the scope of benchmark with the ITU-T of the international standard of SMF as wavelength 1.3 μ m, allow that by reducing mode field diameter (hereinafter referred to as MFD) SMF that allows bending diameter to reach 30mm has realized commercialization, but, when being used for the wiring of office building and premises, hope is the SMF of corresponding littler bending diameter.

Yet in general, the MFD of SMF that has strengthened flexural property is less and have a problem that makes the connection performance deterioration.

That is, under the environment of supposition minor diameter bending, the parameter that becomes the index that determines best optical fiber parameter is also not known.

Summary of the invention

The present invention In view of the foregoing makes, its purpose be to provide a kind of in the circuit of supposition minor diameter bending loss characteristic reach best SMF.

In order to reach above-mentioned purpose, the invention provides following a kind of SMF, comprising: have radius r ₁, refractive index n ₁Central core; With surround above-mentioned central core and have constant refractive index n _cCovering; And n ₁＞n _c, in first wavelength X ₁MFD (the MFD that has regulation under (μ m) ₁(μ m)), utilize second wavelength X ₂(μ m) measure, the bending loss when reeling with bending radius r (mm) is at every turn (every circle) L _b(dB), with in first wavelength X ₁The MFD that has regulation under (μ m) ₂The junction loss of the optical fiber of (μ m) is in second wavelength X ₂(μ m) each connecting portion down is L _s(dB), the MFD dependence of the total loss coefficient L that use following formula (1) calculates is at MFD ₁Reach minimal value in the scope of ± 0.5 μ m,

L＝w _s·L _s+w _b·L _b …(1)

w _s+w _b＝1 …(2)

w _s＞0，w _b＞0 …(3)

In the formula (1), w _sAnd w _bBeing nondimensional weight coefficient, is to set in the scope that satisfies following formula (2) and (3).

In addition, the invention provides a kind of SMF, in first wavelength X ₁MFD (the MFD that has regulation under (μ m) ₁(μ m)), utilize second wavelength X ₂(μ m) measure, the bending loss when reeling with bending radius r (mm) is each L _b(dB), and number of bends be t _b, and in first wavelength X ₁MFD (the MFD that has regulation under (μ m) ₂(μ m)) the junction loss of optical fiber, in second wavelength X ₂(μ m) is each connecting portion L down _s(dB) and connecting portion be n _sThe place, the MFD dependence of the total loss coefficient L that use following formula (4) calculates is at MFD ₁Reach minimal value in the scope of ± 0.5 μ m,

L＝n _s·L _s+t _b·L _b …(4)

Wherein, n _s＞0, t _b＞0.

In SMF of the present invention, preferred junction loss L _sBelow 0.5dB.

In SMF of the present invention, preferred MFD ₁The variable quantity of total loss coefficient L when changing ± 0.3 μ m is below 0.4dB.Further the advantageous variant amount is below 0.2dB.

In SMF of the present invention, preferred bending radius r is less than 15mm.

In SMF of the present invention, preferred bending radius r=10mm, second wavelength X ₂During=1550nm, bending loss L _bBelow 0.05dB.

In SMF of the present invention, preferred bending radius r=7.5mm, second wavelength X ₂During=1550nm, bending loss L _bBelow 0.05dB.

Preferably, in SMF of the present invention, comprising: have radius r ₁, refractive index n ₁Central core; With surround this central core and have the refractive index n of constant _cCovering; And n ₁＞n _c

Preferably, in SMF of the present invention, comprising: have radius r ₁, refractive index n ₁Central core; Be arranged at the periphery of this central core and have radius r ₂, refractive index n ₂Inboard covering; Be arranged at the periphery of this inboard covering and have radius r ₃, refractive index n ₃Groove; And be arranged at the periphery of this groove and have radius r _c, refractive index n _cOutside covering; And n ₁＞n _c＞n ₃, n ₁＞n ₂＞n ₃

Preferably, in SMF of the present invention, first wavelength X ₁=1310nm, MFD ₂In the scope that satisfies international standard ITU-T specification G.652.

Preferably, in SMF of the present invention, junction loss is for carrying out the junction loss that mechanical connection is measured to each optical fiber.

Preferably, in SMF of the present invention, junction loss connects the junction loss of measuring for each optical fiber being carried out welding.

Preferably, in SMF of the present invention, junction loss connects the junction loss of measuring for each optical fiber being carried out connector.

Preferably, in SMF of the present invention, the diameter of covering is in 125 μ m ± 1 μ m.

Preferably, in SMF of the present invention, the central value of the diameter of covering is in the scope of 60 μ m～100 μ m.

In addition, the invention provides a kind of SMF, in first wavelength X ₁MFD (the MFD that has regulation under (μ m) ₁(μ m)), utilize second wavelength X ₂(μ m) measure, the bending loss when reeling with bending radius r (mm) is each L _b(dB), with in first wavelength X ₁MFD (the MFD that has regulation under (μ m) _2i(μ m)) the junction loss of optical fiber, in second wavelength X ₂(μ m) is each connecting portion L down _Si(dB), the MFD dependence of the total loss coefficient L that use following formula (A) calculates is at MFD ₁Reach minimal value in the scope of ± 0.5 μ m.

[formula 1]

$L=\underset{i}{\overset{n}{\mathrm{\Σ}}}{w}_{\mathrm{si}}\·L_{\mathrm{si}}+w_b\·L_b$

$\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{w}_{\mathrm{si}}+w_b=1...\left(A\right)$

w _si＞0，w _b＞0

In the formula, n represents the quantity of the optical fiber that is connected with SMF of the present invention, w _SiRepresent nondimensional weight coefficient, L _SiThe junction loss (dB) of representing SMF of the present invention and i optical fiber.

In addition, the invention provides a kind of SMF, in first wavelength X ₁MFD (the MFD that has regulation under (μ m) ₁(μ m)), utilize second wavelength X ₂(μ m) measure, the bending loss when reeling with bending radius r (mm) is each L _b(dB), and number of bends be t _b, with first wavelength X ₁MFD (the MFD that has regulation under (μ m) _2i(μ m)) the junction loss of optical fiber, in second wavelength X ₂(μ m) is each connecting portion L down _Si(dB) and connecting portion be n _SiThe place, the MFD dependence of the total loss coefficient L that use following formula (B) calculates is at MFD ₁Reach minimal value in the scope of ± 0.5 μ m.

[formula 2]

$L=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{n}_{\mathrm{si}}\·L_{\mathrm{si}}+t_b\·L_b...\left(B\right)$

In the formula, n represents the quantity of the optical fiber that is connected with SMF of the present invention, n _SiThe number of times that is connected of representing SMF of the present invention and i optical fiber, L _SiThe junction loss (dB) of representing SMF of the present invention and i optical fiber.

Preferably, in above-mentioned SMF, junction loss L _SiBelow 0.1dB.

Preferably, in above-mentioned SMF, MFD ₁The variable quantity of total loss coefficient L when changing ± 0.3 μ m is below 0.4dB.

Preferably, in above-mentioned SMF, MFD ₁The variable quantity of total loss coefficient L when changing ± 0.3 μ m is below 0.2dB.

Must consider that SMF of the present invention can realize the light transmission less and stable with respect to the loss variable quantity of state variation under the service condition that the crooked loss that causes with being connected with Conventional SMF of minor diameter takes place.

Because SMF of the present invention is in the circuit that is assumed to the minor diameter bending, it is best that its loss characteristic can reach, and can be suitable for use as therefore that optical fiber inserts and purposes such as small parts, particularly require the low SMF of minor diameter bending loss.

Description of drawings

Fig. 1 is the curve map of the single peak type index distribution of expression SMF of the present invention.

Fig. 2 is the result's of expression embodiment 1 MFD dependence (single peak type, curve map r=10mm) of bending loss.

The summary construction diagram of the connection structure of supposition when Fig. 3 A is the wiring of expression premises.

The summary construction diagram of the connection structure of supposition when Fig. 3 B is the wiring of expression premises.

Fig. 4 is the result's of expression embodiment 1 the dependent curve map of MFD of junction loss.

Fig. 5 is the result's of expression embodiment 1 the dependent curve map of MFD of total loss coefficient.

Fig. 6 is the result's of expression embodiment 1 the dependent curve map of MFD of total loss coefficient.

Fig. 7 is the result's of expression embodiment 2 MFD dependence (single peak type, curve map r=7.5mm) of bending loss.

Fig. 8 is the result's of expression embodiment 2 the dependent curve map of MFD of total loss coefficient.

Fig. 9 is the result's of expression embodiment 2 the dependent curve map of MFD of total loss coefficient.

Figure 10 is the curve map of the fluted body index distribution of expression SMF of the present invention.

Figure 11 is the result's of expression embodiment 3 the curve map of MFD dependence (r=10mm) of bending loss.

Figure 12 is the result's of expression embodiment 3 the dependent curve map of MFD of total loss coefficient.

Figure 13 is the result's of expression embodiment 3 the dependent curve map of MFD of total loss coefficient.

Figure 14 is the result's of expression embodiment 4 the curve map of MFD dependence (r=7.5mm) of bending loss.

Figure 15 is the result's of expression embodiment 4 the dependent curve map of MFD of total loss coefficient.

Figure 16 is the result's of expression embodiment 4 the dependent curve map of MFD of total loss coefficient.

Figure 17 A is a curve map of representing other index distribution of SMF of the present invention for example.

Figure 17 B is a curve map of representing other index distribution of SMF of the present invention for example.

Figure 17 C is a curve map of representing other index distribution of SMF of the present invention for example.

Figure 17 D is a curve map of representing other index distribution of SMF of the present invention for example.

Figure 17 E is a curve map of representing other index distribution of SMF of the present invention for example.

Figure 17 F is a curve map of representing other index distribution of SMF of the present invention for example.

Symbol description: 1... fibre core; 2... covering; 3... inboard covering; 4... groove; 5... outside covering; 6... inboard covering; 7,8... outside fibre core; 9... first groove; 10... low index ellipsoid; 11... stringing bar; 12... splice tray; 13... branch line optical cable; 14... leading in cable; 15...ONU; 16... commuting case; 17... inside cable; 18... wall; 19... the cable of Belt connector; 20... the joints of optical fibre; 100,200,300A, 300B, 300C, 300D, 300E, 300F...SMF.

Embodiment

To the embodiment of SMF of the present invention be described below.

First embodiment of SMF of the present invention is characterised in that, in first wavelength X ₁MFD (the MFD that has regulation under (μ m) ₁(μ m)), utilize second wavelength X ₂(μ m) measure, the bending loss when reeling with bending radius r (mm) is every circle L _b(dB), with in first wavelength X ₁The MFD that has regulation under (μ m) ₂The junction loss of the optical fiber of (μ m) is in second wavelength X ₂(μ m) is each connecting portion L down _s(dB), at this moment, the MFD dependence of the total loss coefficient L that use following formula (1) calculates is at MFD ₁Reach minimal value in the scope of ± 0.5 μ m.

L＝w _s·L _s+w _b·L _b...(1)

In following formula (1), w _sAnd w _bBeing nondimensional weight coefficient, is the environment for use according to supposition, sets in the scope that satisfies following formula (2) and (3).

w _s+w _b＝1...(2)

w _s＞0，w _b＞0...(3)

Second embodiment of SMF of the present invention is characterised in that, in first wavelength X ₁MFD (the MFD that has regulation under (μ m) ₁(μ m)), utilize second wavelength X ₂(μ m) measure, the bending loss when reeling with bending radius r (mm) is every circle L _b(dB), the crooked number of turns is t _b, and in first wavelength X ₁MFD (the MFD that has regulation under (μ m) ₂(μ m)) the junction loss of optical fiber, in second wavelength X ₂(μ m) is each connecting portion L down _s(dB) and connecting portion be n _sThe place, at this moment, the MFD dependence of the total loss coefficient L that use following formula (4) calculates is at MFD ₁Reach minimal value in the scope of ± 0.5 μ m.

L＝n _s·L _s+t _b·L _b...(4)

Wherein, n _s＞0, t _b＞0.

Must consider under the service condition that the crooked loss that causes with being connected with Conventional SMF takes place by minor diameter, the SMF of the present invention that uses the parameter of the total loss coefficient L that calculates by above-mentioned formula (1) or formula (4) to design can realize the Optical Fiber Transmission less and stable with respect to the loss variable quantity of state variation.

In first, second embodiment, the MFD of the optical fiber that is connected with SMF of the present invention sometimes ₂Form by a plurality of numerical value.For example, in the common manufacturing process of optical fiber, can be with certain manufacturing center's value (mean value of the MFD of the optical fiber of manufacturing) as MFD ₂(μ) estimate MFD.In addition, connect the optical fiber that adopts manufacturing center's value to be different from the MFD of SMF of the present invention sometimes.For example, in Fig. 3 A, SMF of the present invention is being applied under the occasion of leading in cable 14, can considering following two kinds of situations.First kind of situation is branch line optical cable 13, (optical network unit: optical network unit) 15 all use the situation of the optical fiber of identical MFD, this situation is equivalent to first, second embodiment to ONU.On the other hand, at the connecting portion of ONU, also use sometimes and compare the littler crooked enhanced type SMF of MFD with above-mentioned illustrative Conventional SMF.Manufacturing center's value of the MFD of Conventional SMF is about 9.2 μ m under 1310nm, and manufacturing center's value of the MFD of crooked enhanced type SMF is about 8.6 μ m.Under this kind occasion,, can tackle by formula (1), formula (4) are carried out following variation.

Formula (1) can change as following formula (A).

[formula 3]

$L=\underset{i}{\overset{n}{\mathrm{\Σ}}}{w}_{\mathrm{si}}\·L_{\mathrm{si}}+w_b\·L_b$

$\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{w}_{\mathrm{si}}+w_b=1...\left(A\right)$

w _si＞0，w _b＞0

In the formula, n represents the quantity of the optical fiber that is connected with SMF of the present invention, w _SiRepresent nondimensional weight coefficient, L _SiThe junction loss (dB) of representing SMF of the present invention and i optical fiber.

In addition, formula (4) can change as following formula (B).

[formula 4]

$L=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{n}_{\mathrm{si}}\·L_{\mathrm{si}}+t_b\·L_b...\left(B\right)$

In the formula, n represents the quantity of the optical fiber that is connected with SMF of the present invention, n _SiThe number of times that is connected of representing SMF of the present invention and i optical fiber, L _SiThe junction loss (dB) of representing SMF of the present invention and i optical fiber.

Above-mentioned first wavelength X ₁And second wavelength X ₂Can from the Optical Fiber Transmission wavelength region may of having used SMF, select, for example can in wavelength is the scope of 1260nm～1650nm, select.Wavelength is the transmission wavelength that the scope of 1260nm～1625nm is used as SMF.In addition, the scope of 1625nm～1650nm is used as the wavelength that line supervision is used.

The minor diameter bending radius that above-mentioned bending radius r is supposed in the time of can being set at practical application SMF of the present invention, preferably this bending radius r is less than 15mm.

In SMF of the present invention, use bending radius r=7.5mm or 10mm, utilize second wavelength X as the evaluation wavelength of bending loss ₂The bending loss L of every circle that=1550nm measured _bPreferably below 0.05dB.If this bending loss L _bSurpass 0.05dB, then therefore the loss meeting is not desirable because of crooked the increasing of minor diameter of multi-turn.

Above-mentioned junction loss be to SMF of the present invention carry out mechanical connection with SMF (hereinafter referred to as Conventional SMF) as normal optical transmission road, welding is connected or connector connects and the junction loss of mensuration.In SMF of the present invention, utilize second wavelength X ₂The junction loss L of each connecting portion that (μ m) measures _sPreferably below 0.5dB.If this junction loss L _sSurpass 0.5dB, then the loss meeting increases when having a plurality of connecting portion, is not desirable therefore.In addition, the Conventional SMF that is connected with SMF of the present invention mostly is the wavelength 1.3 μ m SMF G.652 based on international standard ITU-T.

For SMF of the present invention, in order to make the MFD dependence of the total loss coefficient L that calculates by above-mentioned formula (1) or (4), at MFD ₁Reach minimal value in the scope of ± 0.5 μ m, as long as set poor, the various parameters such as index distribution radially of specific refractivity of core diameter, MFD, fibre core-covering, the shape of its material, index distribution etc. can suitably be set.Material as SMF can be identical with Conventional SMF, uses quartz glass etc.In addition, SMF of the present invention can be identical with the manufacture method of Conventional SMF, can utilize known in the past various manufacture method manufacturing.

Fig. 1 is an example as SMF of the present invention, the curve map of the index distribution of expression single peak type (step change type).

SMF100 of the present invention with index distribution of this single peak type comprises: have radius r ₁, refractive index n ₁Central core 1; Surround this central core 1 and have the refractive index n of constant _cCovering 2, and n ₁＞n _cThe diameter of covering 2 is preferably in 125 μ m ± 1 μ m.In addition, the central value of cladding diameter is not limited to 125 μ m.For example, in the optical fiber that needs the so minimum bending radius of r=5mm, in order to reduce fracture probability, effective method is to form cladding diameter thinner.Therefore, the central value of cladding diameter can be set in the scope of 60 μ m～100 μ m according to the service condition of optical fiber in good time.

In addition, Figure 10 is other example as SMF of the present invention, the curve map of the index distribution of expression fluted body.

SMF200 of the present invention with index distribution of this fluted body comprises: have radius r ₁, refractive index n ₁Central core 1; Be arranged at the periphery of this central core 1 and have radius r ₂, refractive index n ₂Inboard covering 3; Be arranged at the periphery of this inboard covering 3 and have radius r ₃, refractive index n ₃Groove 4; And be arranged at the periphery of this groove 4 and have radius r _c, refractive index n _cOutside covering 5; And n ₁＞n _c＞n ₃, n ₁＞n ₂＞n ₃The diameter of outside covering 5 is preferably in 125 μ m ± 1 μ m.In addition, the central value of cladding diameter is not limited to 125 μ m, also can set in the scope of 60 μ m～100 μ m in good time.

And the present invention can be applied to have the various index distribution shown in Figure 17 A～F

SMF300A with the index distribution shown in Figure 17 A comprises: the central core 1 of single peak type and double-deck covering, and the refractive index of inboard covering 6 is higher than outside covering 5.

SMF300B with the index distribution shown in Figure 17 B is provided with outside covering 5 in the outside of the central core 1 with trapezoidal index distribution, and has and central core 1 has at interval, refractive index is high outside fibre core 7.

SMF300C with the index distribution shown in Figure 17 C, in the outside of central core 1, be disposed with the minimum groove 4 of inboard covering 6, the outside fibre core 8 of high index of refraction, the refractive index of low-refraction, the outside covering 5 of low-refraction with triangular refractive index distribution.

SMF300D with the index distribution shown in Figure 17 D in the outside of the central core 1 with reverse U shape shape index distribution, is disposed with groove 4, the outside covering 5 of low-refraction.

SMF300E with the index distribution shown in Figure 17 E, in the outside of central core 1, be disposed with refractive index minimum first groove 9, refractive index higher outside fibre core 8, second groove 4 of low-refraction, outside covering 5 with trapezoidal or triangular refractive index distribution.

SMF300F with the index distribution shown in Figure 17 F, except the central portion that makes central core 1 is a region of low refractive index 10 and its arranged outside high-refractive-index regions forms central core 1, identical with the structure of Figure 17 E, in the outside of central core 1, be disposed with refractive index minimum first groove 9, refractive index higher outside fibre core 8, second groove 4 of low-refraction, outside covering 5.

Embodiment

(embodiment 1)

Present embodiment is the index distribution of utilizing single peak type shown in Figure 1, the example that the optkmal characteristics when supposition has been applied radius and reaches 10mm crooked SMF100 design.

Fig. 2 represents to utilize the index distribution of single peak type, and the MFD of the wavelength 1310nm when making cable cut-off wavelength be 1260nm and is that 1550nm, radius are the relation that applies the bending loss of ten circles when crooked under the situation of 10mm at wavelength.

As shown in Figure 2, along with the increase of MFD, bending loss reduces.From this Fig. 2 as can be known, as employed SMF in requiring crooked strong environment, preferably make the as far as possible little design of MFD.

Yet, in actual environment for use, except bending loss, also must consider junction loss.Fig. 3 A, B are the figure of the connection structure of representing that for example the premises wiring is supposed the time, in 3A, B, symbol 11 expression stringing bars, 12 expression splice trays, 13 expression branch line optical cables, 14 expression leading in cables, 15 expression ONU (Optical Network Unit), 16 expression commuting cases, 17 expression inside cables, 18 expression walls, the cable of 19 expression Belt connectors, the 20 expression joints of optical fibre.

For example, as shown in Figure 3A, the leading in cable 14 that is connected with branch line optical cable 13 in splice tray 12 is directly connected in the mode of ONU15, might introduce in splice tray 12 and being connected of other optical fiber.And, with being connected of ONU15 in, also might introduce and being connected of other optical fiber.In addition, if the wire laying mode shown in supposition Fig. 3 B, then supposition uses two ends to have the cable 19 of the Belt connector of connector 20.In such cases, introduce at two positions at least possibly and being connected of other optical fiber.

Branch line optical cable 13 grades are used the Conventional SMF of ITU-T.G.652 regulation widely, and about connection performance, preferred consideration is connected with this Conventional SMF.

Fig. 4 is the result that the junction loss of the optical fiber 100 of single peak type (Fig. 1) and Conventional SMF (MFD during wavelength 1310nm is 9.2 μ m) is estimated.For optical fiber junction loss each other, as D.Marcuse, " Loss analysis of single-mode fibersplicess ", Bell syst.Tech.J.vol.56, no5, pp703, May, shown in 1977, can utilize following formula (5), estimate by the joint efficiency that the MFD according to two kinds of optical fiber calculates.

T _g＝(2·w ₁·w ₂/(w ₁ ²+w ₂ ²)) ²·exp(-2d ²/(w ₁ ²+w ₂ ²))...(5)

In the formula, T _gThe expression coupling efficiency, 2w ₁, 2w ₂The MFD of expression optical fiber, d represents the axle offset amount.

Junction loss is to produce because of the MFD difference of two kinds of optical fiber that connected or the axle offset of field etc.Thus, along with the increase of the skew of MFD the increase of the skew that departs from 9.2 μ m (among the Fig. 4 along with), junction loss also increases.Hence one can see that, and MFD is lower than the design of 6.5 μ m, though can make bending loss highly stable, from the viewpoint that connects, is very unsettled design.

Fig. 5 represents the MFD dependence based on the total loss coefficient of the method evaluation of the present invention of formula (1).If λ ₁=1310nm, λ ₂=1550nm, r=10mm, MFD ₂=9.2 μ m, w _s=w _b=0.5.As shown in Figure 5, total loss coefficient L is at MFD ₁Reach minimum during=7.0 μ m.

Therefore, in the past with bending loss as the SMF (sample 2) of the designing institute preferred L FD=6.5 μ m of index and the SMF (sample 1) of the preferred L FD=7.0 μ m of the method according to this invention institute, the loss of having estimated under the various situations changes.Evaluation result is as shown in table 1.In addition, in table 1～table 4, appreciation condition is meant the combination of the connecting portion and the crooked number of turns.

[table 1]

Sample 1 is Δ=0.58%, r shown in Figure 1 ₁=3.26 μ m, sample 2 are Δ=0.65%, r ₁=3.07 μ m.Cladding diameter is 125 μ m, and cable cut-off wavelength is 1260nm.

Use the loss maximal value of method manufactured samples 1 of the present invention, be suppressed in according to about 73% of the sample 2 of previous methods.In addition, the loss variable quantity under the service condition of supposition also is suppressed in roughly 83%.

Fig. 6 represents to suppose the MFD dependence of the total losses when 2 connections and r=10mm, ten enclose bending.As seen from the figure, near MFD, can obtain roughly minimum total losses by the determined 7.0 μ m of method of the present invention.

In addition, if use the zone of being determined by method of the present invention, also the variation of the total losses that the fluctuation by MFD can be caused suppresses lessly.For example, near the MFD by the determined MFD=7.0 μ of method of the present invention m, with respect to the variation of the MFD about ± 0.3 μ m, the variable quantity of total losses is about 0.2dB.Yet, in the example of previous methods, the total losses variable quantity is suppressed under the occasion of same degree in desire, allow the fluctuation of MFD hardly.On the contrary, under the occasion that the MFD that allows same degree changes, the total losses variable quantity is about 0.8dB, when being to use method of the present invention about four times.

According to above-mentioned example as can be known, less by the SMF of method design of the present invention by comprehensive loss crooked and that connection causes, and even the inevitable variation that optical fiber MFD takes place in the supposition manufacturing, its composite loss variation is also very little.This means by using this optical fiber, in line design, can need not additional too much allowance, can design efficiently.

(embodiment 2)

Present embodiment is identical with the foregoing description 1, be the index distribution of utilizing so-called single peak type shown in Figure 1, the example that the optkmal characteristics when supposition has been applied radius and reaches 7.5mm crooked SMF100 design.

Fig. 7 represents to utilize the index distribution of single peak type, the MFD of the wavelength 1310nm when making cable cut-off wavelength be 1260nm, be that 1550nm, radius are the relation that applies the bending loss of ten circles when crooked under the situation of 7.5mm at wavelength.Along with the increase of MFD, bending loss reduces.Identical with the occasion of r=10mm, the SMF as using in requiring the strong environment of bending preferably makes the as far as possible little design of MFD.Yet, shown in embodiment 1, in such zone, the problem that the junction loss of existence and Conventional SMF increases.

Fig. 8 represents the MFD dependence based on the total loss coefficient of the method evaluation of the present invention of formula (1).If λ ₁=1310nm, λ ₂=1550nm, bending radius r=7.5mm, MFD ₂=9.2 μ m, w _s=w _b=0.5.As shown in Figure 8, total loss coefficient L is at MFD ₁Reach minimum during=6.8 μ m.

Therefore, to will be in the past with bending loss as the SMF (sample 4) of the designing institute preferred L FD=6.3 μ m of index and the SMF (sample 3) of the preferred L FD=6.8 μ m of the method according to this invention institute, the loss of having estimated under the various situations changes.Evaluation result is as shown in table 2.

[table 2]

Sample 3 is Δ=0.61%, r shown in Figure 1 ₁=3.17 μ m, sample 4 are Δ=0.71%, r ₁=2.92 μ m.Cladding diameter is 125 μ m, and cable cut-off wavelength is 1260nm.

Use the loss maximal value of method manufactured samples 3 of the present invention, be suppressed in according to about 66% of the sample 4 of previous methods.And the loss variable quantity under the service condition of supposition also is suppressed in roughly 80%.

Fig. 9 represents to suppose the MFD dependence of the total losses when 2 connections and bending radius r=7.5mm, ten enclose bending.As seen from the figure, near MFD, can obtain roughly minimum total losses by the determined 6.8 μ m of method of the present invention.

In addition, if use the zone of being determined by method of the present invention, also the variation of the total losses that the fluctuation by MFD can be caused suppresses lessly.For example, near by the determined MFD=6.8 μ of method of the present invention m,, then the variable quantity of total losses can be suppressed at about 0.2dB if MFD is suppressed in the scope of 6.60～6.95 μ m.Yet, in the example of previous methods, the total losses variable quantity is suppressed under the occasion of same degree in desire, allow the fluctuation of MFD hardly.On the contrary, under the occasion that the MFD that allows same degree changes, the total losses variable quantity is about 0.8dB, about the twice when being to use method of the present invention.

According to above-mentioned example as can be known, less by the SMF of method design of the present invention by comprehensive loss crooked and that connection causes, and even supposition manufacturing is gone up the variation of inevitable generation optical fiber MFD, its composite loss changes also very little.This means by using this optical fiber, in line design, can need not additional too much allowance, can design efficiently.

(embodiment 3)

Present embodiment is to utilize index distribution shown in Figure 10, the example that the optkmal characteristics when supposition has been applied radius and reaches 10mm crooked SMF200 design.

Figure 11 represents to utilize Fig. 1, index distribution shown in Figure 10, the MFD of the wavelength 1310nm when making cable cut-off wavelength be 1260nm, be that 1550nm, radius are the relation that applies the bending loss of ten circles when crooked under the situation of 10mm at wavelength.The index distribution of Figure 10 is compared as can be known with the index distribution of Fig. 1, can be reduced the bending loss under same MFD.Yet along with the increase of MFD, the trend that bending loss reduces is constant.According to the method for designing that only is conceived to bending loss in the past, preferred MFD is 7.0 μ m.

Figure 12 represents the MFD dependence based on the total loss coefficient of the method evaluation of the present invention of formula (1).If λ ₁=1310nm, λ ₂=1550nm, bending radius r=10mm, MFD ₂=9.2 μ m, w _s=w _b=0.5.As shown in Figure 12, total loss coefficient L is at MFD ₁Reach minimum during=8.2 μ m.

Therefore, in the past with bending loss as the SMF (sample 6) of the designing institute preferred L FD=7.0 μ m of index and the SMF (sample 5) of the preferred L FD=8.2 μ m of the method according to this invention institute, the loss of having estimated under the various situations changes.The evaluation result of the sample 1,2 under the index distribution of the Fig. 1 shown in evaluation result and the embodiment 1 together is shown in table 3.

[table 3]

Sample 5 is Δs shown in Figure 10 ₁=0.40%, Δ ₂=0.0%, Δ ₃=-0.25%, r ₁=3.56 μ m, r ₂=11.75 μ m, r ₃=17.80 μ m, sample 6 is Δs ₁=0.54%, Δ ₂=0.0%, Δ ₃=-0.25%, r ₁=3.03 μ m, r ₂=10.00 μ m, r ₃=15.15 μ m.Cladding diameter is 125 μ m, and cable cut-off wavelength is 1260nm.

The loss maximal value of sample 5, loss variable quantity present and are lower than the value of unimodal index distribution having been used the embodiment 1 (sample 1) of method of the present invention.This is the result that the total loss coefficient MFD dependence from Figure 12 also can be contemplated to, and is the effect that the improvement of index distribution brings.Yet, the index distribution of fluted body is used method of the present invention and the loss maximal value of the sample 5 produced, be suppressed at according to about about 55% of the sample 6 of previous methods.And under the service condition of supposition, the loss variable quantity has improved more than 10%.Compare with the method for designing in the past (sample 2) of single peak type, improved about 33～65%.

Figure 13 represents to suppose the MFD dependence of the total losses when 2 connections and bending radius r=10mm, ten enclose bending.As seen from the figure, near MFD, can obtain roughly minimum total losses by the determined 8.2 μ m of method of the present invention.

In addition, if also use the zone of being determined by method of the present invention in the present embodiment, then the variation of the total losses that also fluctuation by MFD can be caused suppresses lessly.For example, though supposition have ± MFD about 0.3 μ m changes, the variable quantity of total losses also can be below 0.05dB, and is very little.In the sample 6 of in the past method for designing, under the occasion that the MFD that has supposed same degree changes, the loss that can expect about 0.5dB changes.

According to above-mentioned example as can be known, less by the SMF of method design of the present invention by comprehensive loss crooked and that connection causes, and even supposition manufacturing is gone up the variation of inevitable generation optical fiber MFD, its composite loss changes also very little.This means by being suitable for this optical fiber, in line design, can need not additional too much allowance, can design efficiently.

(embodiment 4)

Present embodiment is to utilize index distribution shown in Figure 10, the optkmal characteristics when supposition has been applied radius and reaches 7.5mm crooked SMF200 and the example that designs.

Figure 14 represents to utilize Fig. 1, index distribution shown in Figure 10, the MFD of the wavelength 1310nm when making cable cut-off wavelength be 1260nm, be that 1550nm, radius are the relation that applies the bending loss of ten circles when crooked under the situation of 7.5mm at wavelength.The index distribution of the index distribution of Figure 10 and Fig. 1 more as can be known, can be reduced the bending loss under same MFD.Yet along with the increase of MFD, the trend that bending loss reduces is constant.According to the method for designing that only is conceived to bending loss in the past, preferred MFD is 6.8 μ m.

Figure 15 represents the MFD dependence based on the total loss coefficient of the method evaluation of the present invention of formula (1).If λ ₁=1310nm, λ ₂=1550nm, bending radius r=7.5mm, MFD ₂=9.2 μ m, w _s=w _b=0.5.As shown in Figure 15, total loss coefficient L is at MFD ₁Reach minimum during=8.2 μ m.

Therefore, in the past with bending loss as the SMF (sample 8) of the designing institute preferred L FD=6.8 μ m of index and the SMF (sample 7) of the preferred L FD=7.2 μ m of the method according to this invention institute, the loss of having estimated under the various situations changes.The evaluation result of the sample 3,4 under the index distribution of the Fig. 1 shown in evaluation result and the embodiment 2 together is shown in table 4.

[table 4]

Sample 7 is Δs shown in Figure 10 ₁=0.52%, Δ ₂=0.0%, Δ ₃=-0.25%, r ₁=3.10 μ m, r ₂=10.23 μ m, r ₃=15.50 μ m, sample 8 is Δs ₁=0.57%, Δ ₂=0.0%, Δ ₃=-0.25%, r ₁=2.94 μ m, r ₂=9.70 μ m, r ₃=14.70 μ m.Cladding diameter is 125 μ m, and cable cut-off wavelength is 1260nm.

The loss maximal value of sample 7, loss variable quantity present and are lower than the value of unimodal index distribution having been used the embodiment 2 (sample 3) of method of the present invention.This is the effect that the improvement of index distribution brings.The index distribution of fluted body shown in Figure 10 is used the sample 7 that method of the present invention is produced, the loss variable quantity under the service condition of being supposed be equal to according to the sample 8 of previous methods, but the loss maximal value is suppressed at roughly about 82%.Compare with the method for designing in the past (sample 4) of the single peak type of Fig. 1, loss maximal value, variable quantity are suppressed at about half.

Figure 16 represents to suppose the MFD dependence of the total losses when 2 connections and bending radius r=7.5mm, ten enclose bending.As seen from the figure, near MFD, can obtain roughly minimum total losses by the determined 7.2 μ m of method of the present invention.

In addition, if also use the zone of being determined by method of the present invention in the present embodiment, then the variation of the total losses that also fluctuation by MFD can be caused suppresses lessly.When the MFD about supposition ± 0.2 μ m changed, the variable quantity of total losses was about 0.13dB.In design section in the past, for the loss that is controlled to be same degree changes, the variation of MFD only allows about ± 0.05 μ m.Supposing ± occasion that the MFD of 0.2 μ m changes under, the loss that can expect about 0.6dB changes.

By above-mentioned example as can be known, less by the SMF of method design of the present invention by comprehensive loss crooked and that connection causes, even and suppose and make the variation of going up inevitable generation optical fiber MFD that its composite loss variation is also very little.This means by being suitable for this optical fiber, in line design, can need not additional too much allowance, can design efficiently.

In addition, in the various embodiments described above, used 1310nm, used 1550nm as the evaluation wavelength of bending loss, but for this wavelength, also be not particularly limited to embodiment as the evaluation wavelength of MFD.In each above-mentioned embodiment, in order to carry out comparison G.652, and used the MFD of wavelength 1310nm with ITU-T.In addition, at the wavelength that now generally is used for optical communication, wavelength 1550nm belongs to long wavelength side.Because the bending loss of optical fiber has more near the long wavelength side tendency of deterioration all the more, therefore the evaluation wavelength as bending loss uses 1550nm.

In addition, in the various embodiments described above,, use the value that calculates by formula (1) as the evaluation of junction loss.By using the measured value of the junction loss that causes by welding connection, mechanical connection, connector connection etc., can further carry out the optimization of SMF accurately.

In addition, in the various embodiments described above, making cladding diameter is 125 μ m, but the present invention is not limited to this.For example, in order to allow the bending below the 5mm, from guaranteeing the viewpoint of reliability, the preferred refinement cladding diameter.As required, preferably select the cladding diameter of 60～100 μ m.

Claims (19)

1. a single-mode fiber is characterized in that, comprising:

Has radius r ₁, refractive index n ₁Central core; With

Surround above-mentioned central core and have constant refractive index n _cCovering;

And n ₁＞n _c,

In first wavelength X ₁The mode field diameter MFD that has regulation down ₁,

Utilize second wavelength X ₂Measure, the bending loss when reeling with bending radius r is each L _b,

With in first wavelength X ₁The mode field diameter MFD that has regulation down ₂The junction loss of optical fiber, in above-mentioned second wavelength X ₂Each connecting portion is L down _s,

The mode field diameter dependence of the total loss coefficient L that use following formula (1) calculates is at MFD ₁Reach minimal value in the scope of ± 0.5 μ m,

L＝w _s·L _s+w _b·L _b …(1)

w _s+w _b＝1 …(2)

w _s＞0，w _b＞0 …(3)

In the formula (1), w _sAnd w _bBeing nondimensional weight coefficient, is to set in the scope that satisfies following formula (2) and (3),

Above-mentioned first wavelength X ₁, mode field diameter MFD ₁And MFD ₂, and second wavelength X ₂Unit be μ m, the unit of bending radius r is mm, bending loss L _b, L _sUnit be dB.

2. single-mode fiber according to claim 1 is characterized in that,

Above-mentioned junction loss Ls is below 0.5dB.

3. single-mode fiber according to claim 1 is characterized in that,

Bending radius r is less than 15mm.

4. single-mode fiber according to claim 3 is characterized in that,

In above-mentioned bending radius r=10mm, above-mentioned second wavelength X ₂During=1550nm, above-mentioned bending loss L _bBelow 0.05dB.

5. single-mode fiber according to claim 3 is characterized in that,

In above-mentioned bending radius r=7.5mm, above-mentioned second wavelength X ₂During=1550nm, above-mentioned bending loss L _bBelow 0.05dB.

6. single-mode fiber according to claim 1 is characterized in that,

Above-mentioned first wavelength X ₁=1310nm, above-mentioned mode field diameter MFD ₂In the scope that satisfies international standard ITU-T specification G.652.

7. single-mode fiber according to claim 1 is characterized in that,

Above-mentioned junction loss is that each optical fiber is carried out mechanical connection and the junction loss measured.

8. single-mode fiber according to claim 1 is characterized in that,

Above-mentioned junction loss is each optical fiber to be carried out welding connect and the junction loss of mensuration.

9. single-mode fiber according to claim 1 is characterized in that,

Above-mentioned junction loss is each optical fiber to be carried out connector connect and the junction loss of mensuration.

10. single-mode fiber according to claim 1 is characterized in that,

The diameter of above-mentioned covering is in 125 μ m ± 1 μ m.

11. single-mode fiber according to claim 1 is characterized in that,

The central value of the diameter of above-mentioned covering is in the scope of 60 μ m～100 μ m.

12. a single-mode fiber is characterized in that, comprising:

Has radius r ₁, refractive index n ₁Central core;

Be arranged at the periphery of above-mentioned central core and have radius r ₂, refractive index n ₂Inboard covering;

Be arranged at the periphery of above-mentioned inboard covering and have radius r ₃, refractive index n ₃Groove; And

Be arranged at the periphery of above-mentioned groove and have radius r _c, refractive index n _cOutside covering;

And n ₁＞n _c＞n ₃, n ₁＞n ₂＞n ₃,

In first wavelength X ₁The mode field diameter MFD that has regulation down ₁,

Utilize second wavelength X ₂Measure, the bending loss when reeling with bending radius r is each L _b,

With in first wavelength X ₁The mode field diameter MFD that has regulation down ₂The junction loss of optical fiber, in above-mentioned second wavelength X ₂Each connecting portion is L down _s,

The mode field diameter dependence of the total loss coefficient L that use following formula (1) calculates is at MFD ₁Reach minimal value in the scope of ± 0.5 μ m,

L＝w _s·L _s+w _b·L _b …(1)

w _s+w _b＝1 …(2)

w _s＞0，w _b＞0 …(3)

In the formula (1), w _sAnd w _bBeing nondimensional weight coefficient, is to set in the scope that satisfies following formula (2) and (3),

Above-mentioned first wavelength X ₁, mode field diameter MFD ₁And MFD ₂, and second wavelength X ₂Unit be μ m, the unit of bending radius r is mm, bending loss L _b, L _sUnit be dB.

13. single-mode fiber according to claim 12 is characterized in that,

The diameter of above-mentioned outside covering is in 125 μ m ± 1 μ m.

14. single-mode fiber according to claim 12 is characterized in that,

The central value of the diameter of above-mentioned outside covering is in the scope of 60 μ m～100 μ m.

15. a single-mode fiber is characterized in that, comprising:

Has radius r ₁, refractive index n ₁Central core; With

Surround above-mentioned central core and have constant refractive index n _cCovering;

And n ₁＞n _c,

In first wavelength X ₁The mode field diameter MFD that has regulation down ₁,

Utilize second wavelength X ₂Measure, the bending loss when reeling with bending radius r is each L _b,

With in first wavelength X ₁The mode field diameter MFD that has regulation down _2iThe junction loss of optical fiber, in above-mentioned second wavelength X ₂Each connecting portion is L down _Si,

The mode field diameter dependence of the total loss coefficient L that use following formula (A) calculates is at MFD ₁Reach minimal value in the scope of ± 0.5 μ m,

[formula 1]

$L=\underset{i}{\overset{n}{\mathrm{\Σ}}}{w}_{\mathrm{si}}\·L_{\mathrm{si}}+w_b\·L_b$

$\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{w}_{\mathrm{si}}+w_b=1...\left(A\right)$

w _si＞0，w _b＞0

In the formula, n represents the quantity of the optical fiber that is connected with above-mentioned single-mode fiber, w _SiRepresent nondimensional weight coefficient, L _SiThe junction loss of representing above-mentioned single-mode fiber and i optical fiber,

Above-mentioned first wavelength X ₁, mode field diameter MFD ₁And MFD _2i, and second wavelength X ₂Unit be μ m, the unit of bending radius r is mm, bending loss L _b, L _SiUnit be dB.

16. single-mode fiber according to claim 15 is characterized in that,

Above-mentioned junction loss L _SiBelow 0.1dB.

17. single-mode fiber according to claim 15 is characterized in that,

Above-mentioned MFD ₁The variable quantity of above-mentioned total loss coefficient L when changing ± 0.3 μ m is below 0.4dB.

18. single-mode fiber according to claim 17 is characterized in that,

MFD ₁The variable quantity of above-mentioned total loss coefficient L when changing ± 0.3 μ m is below 0.2dB.

19. a single-mode fiber is characterized in that, comprising:

Has radius r ₁, refractive index n ₁Central core;

Be arranged at the periphery of above-mentioned central core and have radius r ₂, refractive index n ₂Inboard covering;

Be arranged at the periphery of above-mentioned inboard covering and have radius r ₃, refractive index n ₃Groove; And

Be arranged at the periphery of above-mentioned groove and have radius r _c, refractive index n _cOutside covering;

And n ₁＞n _c＞n ₃, n ₁＞n ₂＞n ₃,

In first wavelength X ₁The mode field diameter MFD that has regulation down ₁,

Utilize second wavelength X ₂Measure, the bending loss when reeling with bending radius r is each L _b,

With in first wavelength X ₁The mode field diameter MFD that has regulation down _2iThe junction loss of optical fiber, in above-mentioned second wavelength X ₂Each connecting portion is L down _Si,

The mode field diameter dependence of the total loss coefficient L that use following formula (A) calculates is at MFD ₁Reach minimal value in the scope of ± 0.5 μ m,

[formula 1]

$L=\underset{i}{\overset{n}{\mathrm{\Σ}}}{w}_{\mathrm{si}}\·L_{\mathrm{si}}+w_b\·L_b$

$\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{w}_{\mathrm{si}}+w_b=1...\left(A\right)$

w _si＞0，w _b＞0

In the formula, n represents the quantity of the optical fiber that is connected with above-mentioned single-mode fiber, w _SiRepresent nondimensional weight coefficient, L _SiThe junction loss of representing above-mentioned single-mode fiber and i optical fiber,

Above-mentioned first wavelength X ₁, mode field diameter MFD ₁And MFD _2i, and second wavelength X ₂Unit be μ m, the unit of bending radius r is mm, bending loss L _b, L _SiUnit be dB.

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