CN100374888C - Optical fiber - Google Patents
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- CN100374888C CN100374888C CNB2004800089414A CN200480008941A CN100374888C CN 100374888 C CN100374888 C CN 100374888C CN B2004800089414 A CNB2004800089414 A CN B2004800089414A CN 200480008941 A CN200480008941 A CN 200480008941A CN 100374888 C CN100374888 C CN 100374888C
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Abstract
An optical fiber includes: a core at a center; a first cladding layer; a second cladding layer; and a third cladding layer. A maximum refractive index of the core is greater than any of maximum refractive indices of the first cladding layer, the second cladding layer, and the third cladding layer, and the maximum refractive index of the second cladding layer is smaller than any of the maximum refractive indices of the first and the third cladding layer. Additionally, a ratio of a<SUB>2</SUB>/a<SUB>1 </SUB>is not less than about 2.5 and not more than about 4.5, where a 1 represents the radius of the core, and a 2 represents the radius of an outer periphery of the first cladding layer, and a relative refractive index difference of the core with respect to a maximum refractive index of the third cladding layer is not less than 0.20% and not more than 0.70%.
Description
Technical Field
The present invention relates to an optical fiber having excellent bending characteristics.
Priority is claimed in this application for Japanese patent application No. 2003-107760 applied on 11/4/2003, japanese patent application No. 2003-199270 applied on 18/7/2003, and Japanese patent application No. 2004-18514 applied on 27/1/2004, the contents of which are incorporated herein by reference.
Background
Japanese patent publication No. 2618400 discloses a method in which a cladding layer is provided on the circumference of a central core portion and the cladding layer is formed on the circumference of the central core portionAn optical fiber is provided with a refractive index groove having a low refractive index. In the optical fiber having the above-described configuration, effects such as reduction in dispersion slope and reduction in bending loss can be expected, but in order to produce such effects, the core radius is assumed to be a 1 Let the radius of the inner edge of the refractive index groove be a 2 When it is necessary to make a 2 /a 1 The value of (B) is in the range of 1.5 to 3.5.
For a long time, in order to expand the transmission capacity of a trunk line and a long-distance system, the development of a transmission system and an optical fiber using WDM (Wave Length Division Multiplexing) has been in the spotlight. An optical fiber for WDM transmission is required to have characteristics of suppressing nonlinear effects and dispersion control. In recent years, optical fibers with a reduced dispersion slope and optical fibers with little OH-based loss increase have been proposed for systems spanning distances of several hundred kilometers, such as subways.
However, in The case where introduction of an optical Fiber (FTTH) into offices and homes is considered, it is required To have characteristics different from those of optical fibers for transmission. That is, when an optical fiber is laid in a building or a house, it may be necessary to perform an extremely small bend having a bend diameter of 30mm Φ or 20mm Φ. It is also important that when the excess length is gathered, even if it is wound with a small bending radius, no loss increase occurs. I.e. capable of withstanding small diameter bends, is a very important property of the fiber facing FTTH. In addition, it is also important to have good connectivity to optical fibers (most commonly single mode fibers for 1.3 μm range) laid between base stations and buildings and houses. Furthermore, low cost is required for such applications.
Conventionally, a single mode optical fiber and a multimode optical fiber for a 1.3 μm range have been generally used as optical fibers for wiring in offices and homes.
However, the lower limit of the bending diameter of these optical fibers is generally allowed to be about 60mm Φ, and during the laying, it is necessary to pay attention to the fact that the bending diameter does not exceed the allowable range.
Recently, an optical fiber has been developed which can reduce MFD (mode field diameter) within a range conforming to g.652 of the International standard ITU-T (International telecommunications Union-telecommunications Standardization) for single-mode optical fibers (hereinafter abbreviated as SMF) in the 1.3 μm range, thereby reducing the allowable bend diameter to 30mm Φ.
However, a smaller bending diameter is desired for optical fibers for wiring in buildings and homes. Although it is said that a small-bend-diameter optical fiber is produced, there are problems that a loss of connection with a conventional optical fiber is excessively large and a manufacturing cost is high.
In the research report OFT2002-81 of the institute of electrical and information communication technology, a proposal of using photonic crystal fibers for wiring in homes and buildings has been studied. A photonic crystal fiber is an optical fiber having a void structure in the vicinity of the center of the optical fiber, and although properties that an optical fiber having a conventional structure does not have can be expected, the present situation is inferior to the conventional optical fiber in terms of manufacturability.
It is also desirable for conventional optical fibers for cables to have high bending resistance. For example, if an optical fiber that can be bent less is used for laying in a package for connecting cables, the efficiency of the connecting and drawing operation can be improved, and the volume of the package can be reduced. In addition, in the wiring work, work may be performed in a state where communication is performed in a portion other than the working optical fiber. In this case as well, if an optical fiber having a small bending loss is used, the line (live line) in communication can be prevented from being affected by accidental contact or the like during operation.
Disclosure of Invention
In view of the above circumstances, an object of the present invention is to provide an optical fiber which has a small bending loss, has good connectivity with a general transmission optical fiber, and can be manufactured at low cost.
To solve the above problems, the present invention provides an optical fiber comprising: a core portion disposed at the center; a first coating layer disposed on a circumference of the core; fitting for mixingA second coating layer disposed on the circumference of the first coating layer; a third coating layer disposed on the circumference of the second coating layer, wherein the core isIs larger than any of the maximum refractive indices of the first to third clad layers, and the maximum refractive index of the second clad layer is smaller than any of the maximum refractive indices of the first and third clad layers, and the radius of the core is defined as a 1 The outer edge radius of the first cladding layer is defined as a 2 When a is 2 /a 1 Is 2.5 to 4.5, the specific refractive index difference of the core is 0.20% to 0.70% when the maximum refractive index of the third clad layer is taken as a reference, and the specific refractive index difference of the first clad layer is preferably-0.10% to 0.00% when the maximum refractive index of the third clad layer is taken as a reference.
The cut-off wavelength of the optical fiber of the present invention is preferably 1260nm or less.
The refractive index volume V of the second clad layer expressed by the following formula (1) is preferably 25%. Mu.m 2 And the above.
The refractive index volume V of the second cladding layer is preferably 50%. Mu.m 2 And the above.
In the above-mentioned formula (1),
r: the radius of the beam is the radius of the beam,
Δ n (r): the specific refractive index difference having a radius r, based on the maximum refractive index of the third clad layer,
a 2 : the outer edge radius of the first cladding layer,
a 3 : the outer radius of the second cladding.
According to the present invention, the following optical fiber can be obtained: when the increase in bending loss at a wavelength of 1550nm, which is generated when a unimodal optical fiber having a unimodal refractive index distribution without a second cladding and having the same cutoff wavelength is wound ten times around a mandrel having a diameter of 20mm, is set to 1, the bending loss ratio expressed by the ratio of the increase in bending loss measured in the same manner is 0.4 or less.
According to the present invention, the following optical fiber can be realized: when the increase in bending loss at a wavelength of 1550nm, which is generated when a unimodal optical fiber having the same cutoff wavelength and a unimodal refractive index distribution without the second cladding layer is wound ten times around a mandrel having a diameter of 15mm, is set to 1, the bending loss ratio expressed by the ratio of the increase in bending loss measured in the same manner is 0.55 or less.
According to the present invention, the following optical fiber can be realized: when the film is wound with a bending diameter of 20mm, the bending loss at a wavelength of 1550nm is 0.05dB per turn or less.
According to the present invention, the following optical fiber can be realized: when wound at a bending diameter of 20mm, the bending loss value at a wavelength of 1650nm is 0.05dB per turn or less.
Furthermore, an optical fiber having a mode field diameter of 8.3 μm or more at a wavelength of 1550nm can be obtained.
According to the present invention, the following optical fiber can be realized: when wound with a bending diameter of 15mm, the bending loss value at a wavelength of 1550nm is 0.05dB per turn or less.
According to the present invention, the following optical fiber can be realized: when wound at a bending diameter of 15mm, the bending loss value at a wavelength of 1650nm is 0.05dB per turn or less.
Furthermore, an optical fiber having a mode field diameter of 7.8 μm or more at a wavelength of 1550nm can be obtained.
According to the present invention, the following optical fiber can be realized: when the Mode Field Diameter (MFD) value at 1550nm of a monomodal optical fiber having a monomodal refractive index distribution without a second clad layer and the same cutoff wavelength is set to 1, the ratio of the MFD values measured in the same manner is 0.98 or more.
According to the present invention, an optical fiber having a mode field diameter of 7.3 μm or more at a wavelength of 1310nm can be realized.
According to the present invention, an optical fiber having a mode field diameter of 6.8 μm or more at a wavelength of 1310nm can be realized.
Further, an optical fiber having a bending loss value at a wavelength of 1550nm of 0.05dB per turn and below when wound at a bending diameter of 10mm can be obtained.
According to the present invention, the following optical fiber can be realized: when wound at a bending diameter of 10mm, the bending loss value at a wavelength of 1650nm is 0.05dB per turn or less.
According to the present invention, an optical fiber having a mode field diameter of 7.3 μm or more at a wavelength of 1550nm can be realized.
Furthermore, an optical fiber having a mode field diameter of 6.3 μm or more at a wavelength of 1310nm can be obtained.
According to the present invention, the following optical fiber can be realized: the mode field diameter at a wavelength of 1310nm is 7.9 μm or more, and the bending loss value at a wavelength of 1550nm is 1dB or less per turn when the film is wound with a bending diameter of 20 mm.
According to the present invention, the following optical fiber can be realized: when wound with a bending diameter of 20mm, the bending loss value at a wavelength of 1550nm is 0.5dB per turn or less.
According to the present invention, an optical fiber having a mode field diameter of 7.3 μm or more at a wavelength of 1550nm can be realized.
Furthermore, an optical fiber having a mode field diameter of 6.3 μm or more at a wavelength of 1310nm can be obtained.
According to the present invention, the following optical fiber can be realized: the mode field diameter at a wavelength of 1310nm is 7.9 μm or more, and the bending loss value at a wavelength of 1550nm is 1dB or less per turn when the film is wound with a bending diameter of 20 mm.
According to the present invention, the following optical fiber can be realized: when wound at a bending diameter of 20mm, the bending loss value at a wavelength of 1550nm is 0.5dB per turn or less.
Furthermore, an optical fiber having a zero dispersion wavelength of 1300nm to 1324nm can be obtained.
According to the present invention, an optical fiber having less bending loss and excellent connectivity to a general transmission optical fiber can be obtained at low cost.
Drawings
FIG. 1 is a graph showing a refractive index profile in one embodiment of an optical fiber of the present invention.
FIG. 2 is a graph showing the relationship between the position of the second coating layer and MFD in test example 1.
Fig. 3 is a graph showing the relationship between the position of the second clad layer and the bending loss in test example 1.
Fig. 4 is a graph showing a refractive index distribution in an example according to the present invention.
Fig. 5 is a graph showing a refractive index distribution in an example according to the present invention.
Fig. 6 is a graph showing a refractive index distribution in an example according to the present invention.
Fig. 7 is a graph showing a refractive index distribution in an example according to the present invention.
Detailed Description
Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments, and for example, components of the embodiments may be appropriately combined with each other.
The present invention will be described in detail below. FIG. 1 is a graph showing a refractive index profile in one embodiment of an optical fiber of the present invention.
The optical fiber of the present embodiment has a radius a at the center thereof 1 Maximum refractive index of n 1 The core 1 of (1). On the circumference of the core 1, an outer edge radius a is provided 2 Maximum refractive index of n 2 On the circumference of the first cladding layer 2, an outer edge radius a is provided 3 Maximum refractive index of n 3 The second clad layer 3. The second cladding 3 is provided with an outermost layer of optical fiber having an outer edge radius of a 4 Maximum refractive index of n 4 And a third clad layer 4.
In the present specification, the maximum refractive index means a value where the radius of the outer edge of a certain layer is defined as "a n The outer edge radius of one inner layer of the layer is set as a n-1 When a is n-1 And a n The maximum refractive index in between. Wherein n is an integer of 1 or more, and a 0 =0 (μm). In the step-like refractive index profile shown in FIG. 1, at a n-1 To a n In between, the refractive index remains stable, and this refractive index becomes the maximum refractive index. However, as shown in fig. 4 to 7 described later, when the refractive index distribution in each layer is sought, the maximum refractive index defined in the above-described manner is used.
In the optical fiber of the present invention, the maximum refractive index n of the core 1 1 Is larger than the maximum refractive index n of each of the first to third clad layers 2, 3, 4 2 、n 3 、n 4 Of the second clad layer 3, the maximum refractive index n of the foregoing second clad layer 3 3 Smaller than the respective maximum refractive indices n of the first and third cladding layers 2, 4 2 、n 4 Any one of the above.
The refractive index profile of the optical fiber is formed by adding a dopant such as germanium or fluorine. In VAD (Vapor-phase Axial Deposition) and CVD (Chemical Vapor Deposition) processes used in optical fiber production, a blurred refractive index distribution also appears at the interface of each layer due to diffusion of a dopant.
In the optical fiber shown in fig. 1, the refractive index of the first cladding 2 is almost stable in the radial direction, and the refractive index profile is almost completely stepped. The refractive index distribution of the optical fiber of the present invention does not necessarily have to be completely stepped, and when the refractive index is not stepped, the effect of the present invention can be obtained as in the case of the step by using the value of each layer diameter defined by the following formula. First, the radius a of the core 1 is set 1 Is defined as: from the reduction of the specific refractive index difference to the maximum of the specific refractive index difference in the core 1Large value of delta 1 1/10 of the distance from the center. Further, the outer radii a of the first cladding layer 2 and the second cladding layer 3 are set to be equal to each other 2 、 a 3 Is defined as: a distance from a position where a differential value d Δ (r)/dr (r represents a radius) of a radial distribution Δ (r) of the specific refractive index difference reaches an extremum to the center.
By using the radius defined in this way, a step-like refractive index distribution having equivalent characteristics (hereinafter, also referred to as step conversion) can be calculated. In the present invention, even if the actual refractive index distribution does not have a step shape, if the refractive index distribution calculated by such step conversion satisfies the predetermined refractive index relationship according to the present invention, the desired effect of the present invention can be obtained. In the embodiments of the present specification, the specific refractive index difference of the equivalent stepped profile subjected to the step conversion in the aforementioned sequence is comprehensively expressed.
In this specification, the specific refractive index difference Δ of each layer i (unit:%), in order to obtain the maximum refractive index n of the third clad layer 4 4 For reference, the following formula (2) is used.
(wherein i is an integer of 1 to 3, and n is i Is the maximum refractive index of the aforementioned layers. )
In the case where the core is composed of one layer, as shown in FIG. 1, if the specific refractive index difference Δ of the core 1 is increased 1 The bending loss can be further reduced but the MFD will tend to decrease. Further, Δ 1 After reduction, a larger MFD can be obtained, but the bending loss will be deteriorated. The present invention is characterized in that an optical fiber having excellent bending characteristics can be obtained even for MFD of the same degree as that of the unimodal type by providing the second clad layer 3. In the present invention, though Δ 1 The value of (A) is not particularly limited, but if Δ is defined as 1 When the content is set to the range of 0.20 to 0.70%, preferably 0.25 to 0.65%, an optical fiber having excellent connection characteristics with a general SMF and excellent bending characteristics can be obtained.
The specific refractive index difference Δ of the first cladding layer 2 2 The content of the compound is 0.05% or less, preferably 0.00% or less. And preferably-0.10% or more.
Δ 2 After the increase, the cut-off wavelength increases, and it is impossible to realize the cut-off wavelength of 1260nm or less. Whereas if the specific refractive index difference Δ of the first cladding layer 2 is 2 Too small, the mode field closure effect based on the first cladding layer 2 will be enhanced, which is advantageous for reducing bending loss, but disadvantageous for expanding MFD and thus improving connectivity. Therefore, it is preferable to set Δ within a range in which a desired cutoff wavelength, a good bending loss, and a desired MFD can be simultaneously achieved 2 . Generally, let Δ 2 When the content is not less than-0.10%, the desired effect can be obtained.
Specific refractive index difference Δ of the second clad layer 3 3 As will be described later, the design range is defined by the refractive index volume V.
Outer peripheral diameter (a) of third coating layer 4 4 2 times) the outer diameter of the optical fiber, typically 125 μm. In recent years, products for small optical devices having an outer diameter of about 80 μm have been commercialized. Although the present invention is applicable to the same range of outer diameters as those of the conventional optical fiber, the present invention is not limited to the above range.
Although it may be defined by the radius a of the core 1 1 The cutoff wavelength is controlled, but then, when the cutoff wavelength is further shortened, the bending loss tends to increase. Therefore, the specific refractive index difference Δ of the bonding core 1 1 And the radius a of the core 1 is appropriately selected in accordance with the required MFD, cutoff wavelength, and bending loss 1 。
Ratio of outer edge radius of first clad layer 2 to radius of core 1 (a) 2 /a 1 ) And indicates the position of the second cladding layer 3. In the present invention, the value is 2.5 or more, preferably 3.0 or more. By making use of a 2 /a 1 The second clad layer 3 is provided at a position within the above range, and as shown in FIGS. 2 to 3 described in detail later, the mode field diameter (Modefield) can be adjustedDiameter, also referred to as MFD in this specification) is suppressed to be low, and bending loss characteristics can be improved.
Even if a 2 /a 1 If too large, an effect of reducing bending loss can be expected. However, a 2 /a 1 After increase, due to Δ 2 The change in optical characteristics, particularly the change in cutoff wavelength, caused by the change in (2) is significant, and the manufacturability is deteriorated. In addition, a 2 /a 1 If the size is increased, the effect of providing the second cladding layer 3 is reduced, and it is difficult to perform single-mode transmission. Thus, a 2 /a 1 Is 4.5 or less.
Outer edge radius a of the second cladding layer 3 3 The refractive index volume V is defined by the refractive index volume V described later, as well as the specific refractive index difference Δ.
The optical fiber can be used for communication over a wide range of wavelength bands ranging from 1300nm to 1600 nm. In the ITU-T standard, an optical fiber for the 1300nm range is specified as G.652. The lower limit wavelength of the 1300nm range is generally considered to be 1260nm, and the cutoff wavelength of 1260nm or less is also specified in the section of G.652 standard. For single mode transmission in a wide range from 1300nm to 1600nm, it is also desirable for the optical fiber of the present invention to have a cut-off wavelength of 1260nm or less. The cutoff wavelength has a trade-off relationship with the optical characteristics of MFD and bending loss, and the refractive index distribution is set according to the desired characteristics.
It was found that the bending loss ratio was a 2 /a 1 The value of (C) and the value of V have a correlation. Specifically, the bending loss ratio tends to decrease as V increases, and the relationship between V and bending loss is represented by a 2 /a 1 The value of (d), i.e., the position of the low-curvature layer. In the present invention, to achieve better bending lossThe refractive index volume (V) of the second clad layer represented by the above formula (1) is preferably 25%. Mu.m 2 And above, e.g. 50%. Mu.m 2 And the above are more preferable. When 1260nm or more of single-mode transmission is considered, the value of V is preferably 110%. Mu.m 2 And the sameThe following steps.
According to the present invention, by providing the second clad layer, the loss due to bending can be effectively reduced.
For example, as shown in tables 1 to 4 described later in detail, when a unimodal optical fiber configured to obtain the same cutoff wavelength with a unimodal refractive index distribution without the second clad layer 3 and the above-described bend loss increase value are set to 1, the bend loss increase ratio of the optical fiber according to the present invention (referred to as the bend loss ratio in the present specification) at the wavelength of 1550nm can be reduced to 0.4 or less, preferably to 0.15 or less, with respect to the bend loss increase value (measured wavelength 1550nm, the same applies hereinafter) generated when the optical fiber is wound on a mandrel having a diameter of 20mm (20 mm Φ, hereinafter also referred to simply as 20 Φ) for ten turns.
According to the present invention, an optical fiber with less loss due to bending can be obtained. Specifically, the bending loss ratio at a wavelength of 1550nm, which is generated when a mandrel having a diameter of 15mm (15 mm. Phi., hereinafter also referred to simply as 15. Phi.) is wound ten times, can be reduced to 0.55 or less, preferably 0.25 or less.
The optical fiber according to the present invention, when wound with a bending diameter of 20mm, can reduce the bending loss value at a wavelength of 1550nm to 0.05dB per turn or less. Here, the bending loss value per turn can be calculated by dividing the bending loss value generated when, for example, ten turns are wound on a mandrel of a prescribed diameter by 10.
When the steel sheet is wound with a bending diameter of 20mm, the bending loss at a wavelength of 1650nm may be reduced to 0.05dB per turn or less.
According to the present invention, an optical fiber having a large mode field diameter, in which the bend-based loss can be suppressed to be low, can be realized. Specifically, an optical fiber having a mode field diameter of 8.3 μm or more at a wavelength of 1550nm can be obtained.
According to the optical fiber of the present invention, the bending loss value at a wavelength of 1550nm can be reduced to 0.05dB per turn or less when the optical fiber is wound with a bending diameter of 15 mm.
When the steel sheet is wound with a bending diameter of 15mm, the bending loss at a wavelength of 1650nm may be reduced to 0.05dB per turn or less.
According to the present invention, an optical fiber having a large mode field diameter, in which a bend-based loss can be suppressed to be low, can be realized. Specifically, an optical fiber having a mode field diameter of 7.8 μm or more at a wavelength of 1550nm can be obtained.
According to the present invention, an optical fiber having a large mode field diameter, in which bending-based loss can be suppressed to be low, can be realized. Specifically, an optical fiber having a mode field diameter of 7.3 μm or more at a wavelength of 1310nm can be obtained.
Specifically, an optical fiber having a mode field diameter of 6.8 μm or more at a wavelength of 1310nm can be obtained.
The bending loss at a wavelength of 1550nm can be reduced to 0.05dB per turn or less when the film is wound with a bending diameter of 10 mm.
According to the optical fiber of the present invention, the bending loss value at a wavelength of 1650nm can be reduced to 0.05dB per turn or less when the optical fiber is wound with a bending diameter of 10 mm.
According to the present invention, an optical fiber having a large mode field diameter, in which the bend-based loss can be suppressed to be low, can be realized. Specifically, an optical fiber having a mode field diameter of 7.3 μm or more at a wavelength of 1550nm can be obtained.
Specifically, an optical fiber having a mode field diameter of 6.3 μm or more at a wavelength of 1310nm can be obtained.
According to the present invention, the mode field diameter at a wavelength of 1310nm is 7.9 μm or more, and the bending loss value at a wavelength of 1550nm can be reduced to 1dB or less per turn when the film is wound with a bending diameter of 20 mm.
According to the present invention, an optical fiber having a zero dispersion wavelength of 1300nm to 1324nm can be obtained.
Here, the wavelength 1550nm range is a wavelength range widely used for communication together with the wavelength 1310nm range, and in these wavelength ranges, it is important that the transmission loss and the bending loss thereof are small. In particular, in the use of wiring in houses, etc., there is a possibility that a slight bending such as bending with a small diameter or winding may be performed in the bending of the wall corner and the drawing of the optical fiber in the connection box up to the wall corner. Therefore, the bending characteristics at a small bending diameter such as 20mm and 15mm are important. Furthermore, for line monitoring, a wavelength range of 1650nm and below is envisaged, and thus a small bending loss even at 1650nm becomes an important characteristic.
The optical fiber of the present invention provided with the second clad layer 3 has a feature that the reduction of MFD can be suppressed and the bending loss can be greatly reduced as compared with the unimodal type. Specifically, when the MFD of the optical fiber of the present invention at a wavelength of 1550nm is defined as M1, and the MFD of a single-mode optical fiber at 1550nm, which is configured to have the same cutoff wavelength with a single-mode refractive index distribution without the second clad layer 3, is defined as M2, the value of M1/M2 can be 0.98 or more.
Further, the optical fiber of the present invention achieves the aforementioned various features by providing the second clad 3. For example, a Non-Zero-Dispersion-Shifted Fiber (NZ-DSF) developed for WDM communication requires a complicated core refractive index profile, and the optical Fiber of the present invention has an advantage that it can be manufactured at a low cost since the characteristics can be improved without changing the core refractive index profile.
(examples)
The effects of the present invention will be described below with reference to specific examples.
The "cut-off wavelength" values in the test examples and examples below were determined using a method based on ITU-T G.650.Definitions and test methods for linear, deterministic characteristics of single-mode fibers and cable. In the following experimental examples and examples, the cutoff wavelength means a 2m fiber cutoff unless otherwise specified.
(test example 1)
Specific refractive index difference Δ of core 1 1 ：0.52％，
The specific refractive index difference Δ of the first cladding layer 2 2 ：0％，
Specific refractive index difference Δ of the second clad layer 3 3 ：-0.20％，
Ratio of thickness of second clad layer 3 to core radius (a) 3 -a 2 )/a 1 ＝3.0
Outer diameter of optical fiber: 125 μm
Cutoff wavelength: the design was 1250nm, and thus an optical fiber was produced.
Seek out a 2 /a 1 Change in MFD and change in bending loss when the value of (d) is changed. The MFD and the bending loss were measured at 1550nm.
The bending loss was measured by increasing the loss when a predetermined length of the optical fiber was wound on a 20mm diameter mandrel for ten turns. That is, if the power of light emitted from the optical fiber before winding on the mandrel is P1 (unit: dBm) and the power of emitted light during winding is P2 (unit: dBm), P1-P2 (dB) is taken as the bending loss. The results are shown in fig. 2 and 3.
The dashed lines in the figure represent the MFD and the bending loss value of a monomodal optical fiber configured to obtain the same cutoff wavelength with a monomodal refractive index distribution without the second clad layer 3.
As can be seen from the results of fig. 3, by providing the second clad 3, the bending characteristics can be greatly improved as compared with the unimodal optical fiber. It can also be seen that with a 2 /a 1 With increasing values, the bending loss tends to increase gradually.
As can be seen from the results of FIG. 2, at a 2 /a 1 In the region where the value of (d) is less than 3.0, the MFD is drastically reduced compared with the unimodal type. In order to keep the connection loss with an optical fiber having a large MFD, such as ITU-T652 standard, small, it is necessary to suppressThe reduction in MFD. Such as making a 2 /a 1 When the MFD is 2.5 or more, the MFD can be ensured to be 98% or more for the unimodal type, and the problematic connection characteristics can be maintained.
As can be seen from the foregoing results, by making a 2 /a 1 The value is 2.5 times or more, preferably 3.0 times or more, and a large MFD and a small bending loss can be realized.
(test example 2)
Optical fibers were produced by setting the parameters as shown in the following table 1, and the cutoff wavelength and the effective core cross-sectional area (a) were measured by a known method eff ) MFD, wavelength dispersion, dispersion slope, and zero dispersion wavelength.
The cut-off wavelength was measured using a Transmitted Power Technique as described in ITU-T G.650.1 Definitions and test methods for line, defined statistical attributes of single-mode fibers and cable, 5.3.1. In general, a method (bending method) of measuring a cutoff wavelength from a Power loss when an optical fiber is bent with a small diameter is also widely used in Transmitted Power technology. However, the optical fiber manufactured in this trial has a large bending loss in the higher-order mode, and it is difficult to perform accurate cutoff measurement by the bending method. Therefore, the measurement was performed by a method (multimode reference method) in which evaluation was performed based on the power when passing through the multimode optical fiber.
The bending loss characteristics were measured by the same method as in test example 1. The measurement wavelengths were 1550nm and 1650nm. The diameters of the mandrels are 20mm, 15mm and 10 mm. When the measured bending loss is small, the number of bending times (number of curls) is increased as appropriate, and after the bending loss that can ensure the measurement accuracy is obtained, the bending loss is converted into the bending loss per ten windings. In addition, the table also shows the loss increase (bend loss increase in dB/m) per unit length. When Px represents a bending loss (P1-P2 (dB)) when the core is wound around a 20mm Φ core ten times, the loss increase Py per unit length is expressed by the following equation.
Px (unit: dB/m) = Py/(π × 0.02 × 10)
The refractive index volume (V) is calculated from the above formula (1).
Sample nos. 1, 5, 9, 12, 21, 28, 35, 38 are unimodal fibers without the second cladding 3.
The bending loss ratios of samples No.2 to 4 are ratios of bending loss values when samples No.2 to 4 were wound ten times, assuming that the bending loss when sample No.1 was wound ten times was 1. Similarly, the bending loss ratios of samples No.6 to No. 8 are based on sample No.5, the bending loss ratios of samples No.10 and No. 11 are based on sample No.9, the bending loss ratios of samples No.13 to No. 20 are based on sample No.12, the bending loss ratios of samples No.22 to No. 27 are based on sample No.21, the bending loss ratios of samples No.29 to No. 34 are based on sample No.28, the bending loss ratios of samples No.36 and No. 37 are based on sample No.35, and the bending loss ratios of samples No.39 and No. 40 are based on sample No. 38.
Further, the samples Nos. 16, 18, 24 to 27, and 32 have a large V value, and the cutoff wavelength cannot be reduced to the same extent as the reference sample. Therefore, these samples may not be described in terms of the bending loss ratio. Further, under the partial measurement conditions of the samples No.35, 38, the bending loss could not be evaluated excessively. Therefore, in some of samples No.36, 37, 39, and 40, the bending loss ratio may not be described. Tables 2 to 4 show the measurement results.
TABLE 1
| Test specimen No. | Δ 1 [％] | Δ 2 [％] | Δ 3 [％] | a 1 [μm] | a 2 [μm] | a 3 [μm] | a 2 /a 1 | a 3 /a 1 | V [％μm 2 ] | 2a 2 /MFD at1550nm |
| 1 | 0.65 | 0.00 | - | 3.04 | 9.12 | - | 3.0 | - | - | - |
| 2 | 0.65 | 0.00 | -0.30 | 3.01 | 7.83 | 12.05 | 2.6 | 4.0 | 25 | 2.1 |
| 3 | 0.65 | 0.00 | -0.30 | 2.99 | 8.97 | 13.46 | 3.0 | 4.5 | 30 | 2.4 |
| 4 | 0.65 | 0.00 | -0.40 | 2.99 | 8.98 | 13.48 | 3.0 | 4.5 | 40 | 2.4 |
| 5 | 0.60 | 0.00 | - | 3.18 | 9.53 | - | 3.0 | - | - | - |
| 6 | 0.60 | 0.00 | -0.30 | 3.13 | 8.14 | 13.16 | 2.6 | 4.2 | 32 | 2.1 |
| 7 | 0.60 | 0.00 | -0.30 | 3.12 | 9.35 | 14.03 | 3.0 | 4.5 | 33 | 2.4 |
| 8 | 0.60 | 0.00 | -0.40 | 3.12 | 9.35 | 14.03 | 3.0 | 4.5 | 44 | 2.4 |
| 9 | 0.58 | 0.00 | - | 4.85 | 14.55 | - | 3.0 | - | - | - |
| 10 | 0.58 | -0.05 | -0.30 | 3.32 | 9.97 | 14.95 | 3.0 | 4.5 | 37 | 2.6 |
| 11 | 0.58 | -0.10 | -0.30 | 3.44 | 10.31 | 15.47 | 3.0 | 4.5 | 40 | 2.7 |
| 12 | 0.52 | 0.00 | - | 3.43 | 10.30 | - | 3.0 | - | - | - |
| 13 | 0.52 | 0.00 | -0.20 | 3.35 | 10.04 | 15.40 | 3.0 | 4.6 | 27 | 2.4 |
| 14 | 0.52 | 0.00 | -0.20 | 3.31 | 13.23 | 18.53 | 4.0 | 5.6 | 34 | 3.2 |
| 15 | 0.52 | 0.00 | -0.40 | 3.36 | 10.08 | 15.45 | 3.0 | 4.6 | 55 | 2.4 |
| 16 | 0.52 | 0.00 | -0.40 | 3.35 | 10.06 | 20.13 | 3.0 | 6.0 | 122 | 2.4 |
| 17 | 0.52 | 0.00 | -0.40 | 3.31 | 13.25 | 18.55 | 4.0 | 5.6 | 67 | 3.2 |
| 18 | 0.52 | 0.00 | -0.40 | 3.31 | 13.26 | 23.20 | 4.0 | 7.0 | 145 | 3.2 |
| 19 | 0.52 | 0.00 | -0.60 | 3.36 | 10.08 | 13.78 | 3.0 | 4.1 | 53 | 2.4 |
| 20 | 0.52 | 0.00 | -0.60 | 3.32 | 13.27 | 16.93 | 4.0 | 5.1 | 66 | 3.2 |
| 21 | 0.45 | 0.00 | - | 3.72 | 11.15 | - | 3.0 | - | - | - |
| 22 | 0.45 | 0.00 | -0.25 | 3.61 | 10.82 | 16.23 | 3.0 | 4.5 | 37 | 2.4 |
| 23 | 0.45 | 0.00 | -0.35 | 3.61 | 10.83 | 16.25 | 3.0 | 4.5 | 51 | 2.4 |
| 24 | 0.45 | 0.00 | -0.40 | 3.61 | 10.84 | 21.68 | 3.0 | 6.0 | 141 | 2.4 |
| 25 | 0.45 | 0.00 | -0.40 | 3.57 | 14.27 | 24.98 | 4.0 | 7.0 | 168 | 3.2 |
| 26 | 0.45 | 0.00 | -0.60 | 3.62 | 10.85 | 19.90 | 3.0 | 5.5 | 167 | 2.4 |
| 27 | 0.45 | 0.00 | -0.60 | 3.57 | 14.28 | 23.20 | 4.0 | 6.5 | 201 | 3.2 |
| 28 | 0.35 | 0.00 | - | 4.28 | 12.84 | - | 3.0 | - | - | - |
| 29 | 0.35 | 0.00 | -0.40 | 4.10 | 12.31 | 16.42 | 3.0 | 4.0 | 47 | 2.4 |
| 30 | 0.35 | 0.00 | -0.40 | 4.15 | 10.79 | 14.94 | 2.6 | 3.6 | 64 | 2.2 |
| 31 | 0.35 | 0.00 | -0.20 | 4.05 | 16.19 | 28.33 | 4.0 | 7.0 | 108 | 3.2 |
| 32 | 0.35 | 0.00 | -0.40 | 4.10 | 12.31 | 24.63 | 3.0 | 6.0 | 182 | 2.4 |
| 33 | 0.35 | 0.00 | -0.25 | 4.14 | 10.35 | 14.49 | 2.50 | 3.50 | 25.71 | 2.06 |
| 34 | 0.35 | 0.00 | -0.25 | 4.10 | 12.29 | 16.38 | 3.00 | 4.00 | 29.35 | 2.44 |
| 35 | 0.32 | 0.00 | - | 4.51 | 13.54 | - | 3.00 | - | - | - |
| 36 | 0.32 | 0.00 | -0.25 | 4.29 | 12.86 | 17.15 | 3.00 | 4.00 | 32.17 | 2.44 |
| 37 | 0.32 | 0.00 | -0.25 | 4.29 | 12.86 | 19.30 | 3.00 | 4.50 | 51.71 | 2.44 |
| 38 | 0.25 | 0.00 | - | 5.21 | 15.63 | - | 3.00 | - | - | - |
| 39 | 0.25 | 0.00 | -0.25 | 4.86 | 14.57 | 19.43 | 3.00 | 4.00 | 41.27 | 2.44 |
| 40 | 0.25 | 0.00 | -0.25 | 4.92 | 12.29 | 17.21 | 2.50 | 3.50 | 36.27 | 2.07 |
TABLE 2
| Test specimen No. | Cut-off Wavelength of light [μm] | A eff at1310nm [μm 2 ] | MFD at1310nm [μm] | A eff at1550nm [μm 2 ] | MFD at1550nm [μm] | Zero dispersion Wavelength of light [nm] | At 1550nm Wavelength of (2) Dispersion (dispers) ps/nm/km] | At 1550nm Dispersion of (2) Slope of [ps/nm 2 /km] |
| 1 | 1.25 | 34.2 | 6.58 | 42.4 | 7.44 | 1359.4 | 11.9 | 0.054 |
| 2 | 1.25 | 33.8 | 6.55 | 41.6 | 7.37 | 1353.7 | 13.2 | 0.059 |
| 3 | 1.25 | 33.7 | 6.54 | 41.8 | 7.39 | 1361.3 | 12.3 | 0.058 |
| 4 | 1.25 | 33.7 | 6.54 | 41.8 | 7.39 | 1360.0 | 12.5 | 0.059 |
| 5 | 1.25 | 37.2 | 6.86 | 46.1 | 7.75 | 1350.6 | 12.8 | 0.055 |
| 6 | 1.25 | 36.7 | 6.82 | 45.2 | 7.68 | 1348.3 | 13.7 | 0.060 |
| 7 | 1.25 | 36.6 | 6.81 | 45.4 | 7.70 | 1353.0 | 13.1 | 0.059 |
| 8 | 1.25 | 36.6 | 6.81 | 45.3 | 7.69 | 1352.2 | 13.2 | 0.059 |
| 9 | 1.25 | 38.5 | 6.98 | 47.7 | 7.89 | 1347.2 | 13.1 | 0.055 |
| 10 | 1.25 | 37.8 | 6.87 | 45.7 | 7.67 | 1332.0 | 14.5 | 0.057 |
| 11 | 1.25 | 32.8 | 6.82 | 44.8 | 7.55 | 1318.6 | 15.6 | 0.056 |
| 12 | 1.25 | 43.2 | 7.39 | 53.4 | 8.34 | 1337.5 | 14.1 | 0.056 |
| 13 | 1.25 | 42.3 | 7.32 | 52.4 | 8.28 | 1341.5 | 14.1 | 0.059 |
| 14 | 1.25 | 41.9 | 7.30 | 52.4 | 8.29 | 1347.0 | 13.3 | 0.057 |
| 15 | 1.25 | 42.4 | 7.33 | 52.4 | 8.27 | 1339.4 | 14.5 | 0.060 |
| 16 | 1.45 | 42.3 | 7.33 | 52.3 | 8.27 | 1339.7 | 14.4 | 0.060 |
| 17 | 1.25 | 41.9 | 7.30 | 52.4 | 8.29 | 1346.6 | 13.4 | 0.057 |
| 18 | 1.55 | 41.9 | 7.31 | 52.5 | 8.29 | 1346.5 | 13.4 | 0.057 |
| 19 | 1.25 | 42.4 | 7.33 | 52.3 | 8.26 | 1338.5 | 14.7 | 0.061 |
| 20 | 1.25 | 42.0 | 7.31 | 52.5 | 8.29 | 1345.9 | 13.5 | 0.058 |
| 21 | 1.25 | 50.3 | 7.97 | 62.0 | 8.98 | 1326.5 | 15.2 | 0.058 |
| 22 | 1.25 | 48.9 | 7.88 | 60.6 | 8.90 | 1330.8 | 15.3 | 0.060 |
| 23 | 1.25 | 49.0 | 7.88 | 60.5 | 8.89 | 1329.9 | 15.4 | 0.061 |
| 24 | 1.51 | 49.0 | 7.88 | 60.6 | 8.89 | 1329.5 | 15.5 | 0.061 |
| 25 | 1.60 | 48.6 | 7.86 | 60.7 | 8.92 | 1335.2 | 14.5 | 0.058 |
| 26 | 1.58 | 49.1 | 7.88 | 60.5 | 8.88 | 1328.6 | 15.7 | 0.062 |
| 27 | 1.62 | 48.6 | 7.86 | 60.7 | 8.92 | 1335.1 | 14.6 | 0.059 |
| 28 | 1.25 | 65.7 | 9.09 | 80.5 | 10.22 | 1311.9 | 16.9 | 0.059 |
| 29 | 1.25 | 63.2 | 8.95 | 78.0 | 10.08 | 1316.1 | 16.9 | 0.062 |
| 30 | 1.26 | 63.5 | 8.95 | 77.2 | 10.00 | 1310.2 | 17.9 | 0.064 |
| 31 | 1.25 | 62.5 | 8.92 | 78.2 | 10.12 | 1320.7 | 16.1 | 0.060 |
| 32 | 1.46 | 63.2 | 8.95 | 78.0 | 10.08 | 1316.0 | 16.9 | 0.063 |
| 33 | 1.25 | 63.43 | 8.95 | 77.43 | 10.03 | 1311.7 | 17.5 | 0.063 |
| 34 | 1.25 | 63.07 | 8.94 | 78.04 | 10.09 | 1317.0 | 16.7 | 0.061 |
| 35 | 1.25 | 72.39 | 9.53 | 88.50 | 10.71 | 1307.6 | 17.4 | 0.060 |
| 36 | 1.25 | 69.07 | 9.36 | 85.41 | 10.56 | 1312.9 | 17.2 | 0.062 |
| 37 | 1.25 | 69.09 | 9.36 | 85.41 | 10.56 | 1312.8 | 17.2 | 0.062 |
| 38 | 1.25 | 94.52 | 10.87 | 114.82 | 12.18 | 1298.4 | 18.5 | 0.061 |
| 39 | 1.25 | 88.57 | 10.60 | 109.38 | 11.94 | 1303.9 | 18.2 | 0.063 |
| 40 | 1.25 | 89.07 | 10.60 | 108.38 | 11.85 | 1300.0 | 18.9 | 0.063 |
TABLE 3
| Test specimen No. | Bending loss at 1550nm | ||||||||
| 20φ | 15φ | 10φ | |||||||
| [dB/m] | ×10t [dB] | Bending of Loss ratio | [dB/m] | ×10t [dB] | Bending of Loss ratio | [dB/m] | ×10t [dB] | Bending of Loss ratio | |
| 1 | 0.002 | 0.001 | - | 0.015 | 0.007 | - | 1.063 | 0.334 | - |
| 2 | 0.000 | ＜0.001 | - | 0.003 | 0.002 | 0.00 | 0.142 | 0.045 | 0.13 |
| 3 | 0.001 | ＜0.001 | - | 0.003 | 0.002 | 0.00 | 0.136 | 0.043 | 0.13 |
| 4 | 0.000 | ＜0.001 | - | 0.002 | 0.001 | 0.00 | 0.067 | 0.021 | 0.06 |
| 5 | 0.009 | 0.006 | - | 0.067 | 0.042 | - | 3.517 | 2.210 | - |
| 6 | 0.002 | 0.001 | 0.00 | 0.011 | 0.005 | 0.12 | 0.302 | 0.142 | 0.06 |
| 7 | 0.002 | 0.002 | 0.00 | 0.012 | 0.006 | 0.14 | 0.349 | 0.164 | 0.07 |
| 8 | 0.001 | ＜0.001 | 0.00 | 0.007 | 0.003 | 0.08 | 0.167 | 0.079 | 0.04 |
| 9 | 0.017 | 0.011 | - | 0.115 | 0.054 | 1.30 | 5.257 | 2.477 | 1.12 |
| 10 | 0.002 | 0.001 | 0.00 | 0.007 | 0.003 | 0.08 | 0.172 | 0.081 | 0.04 |
| 11 | 0.001 | ＜0.001 | 0.00 | 0.004 | 0.002 | 0.04 | 0.083 | 0.039 | 0.02 |
| 12 | 0.133 | 0.084 | - | 0.731 | 0.344 | - | 25.75 | 8.090 | - |
| 13 | 0.043 | 0.027 | 0.32 | 0.159 | 0.075 | 0.22 | 3.020 | 0.949 | 0.12 |
| 14 | 0.051 | 0.032 | 0.39 | 0.179 | 0.084 | 0.24 | 3.111 | 0.977 | 0.12 |
| 15 | 0.012 | 0.007 | 0.09 | 0.035 | 0.016 | 0.05 | 0.485 | 0.152 | 0.02 |
| 16 | 0.001 | ＜0.001 | - | 0.002 | 0.001 | - | 0.013 | 0.004 | - |
| 17 | 0.014 | 0.009 | 0.11 | 0.040 | 0.019 | 0.06 | 0.504 | 0.158 | 0.02 |
| 18 | 0.001 | ＜0.001 | - | 0.002 | 0.001 | - | 0.016 | 0.005 | - |
| 19 | 0.012 | 0.008 | 0.09 | 0.037 | 0.017 | 0.05 | 0.522 | 0.164 | 0.02 |
| 20 | 0.015 | 0.009 | 0.11 | 0.043 | 0.020 | 0.06 | 0.556 | 0.175 | 0.02 |
| 21 | 0.845 | 0.531 | - | 3.280 | 1.546 | - | 71.12 | 22.34 | - |
| 22 | 0.214 | 0.134 | 0.25 | 0.553 | 0.260 | 0.17 | 6.454 | 2.028 | 0.25 |
| 23 | 0.109 | 0.068 | 0.13 | 0.253 | 0.119 | 0.08 | 2.493 | 0.783 | 0.10 |
| 24 | 0.004 | 0.003 | 0.00 | 0.006 | 0.003 | 0.00 | 0.023 | 0.007 | - |
| 25 | 0.005 | 0.003 | 0.01 | 0.006 | 0.003 | 0.00 | 0.023 | 0.007 | - |
| 26 | 0.002 | 0.001 | 0.00 | 0.002 | 0.001 | 0.00 | 0.007 | 0.002 | - |
| 27 | 0.002 | 0.001 | 0.00 | 0.002 | 0.001 | 0.00 | 0.007 | 0.002 | - |
| 28 | 14.00 | 8.796 | - | 37.98 | 17.90 | - | 516 | 162 | - |
| 29 | 1.854 | 1.165 | 0.13 | 3.036 | 1.431 | 0.08 | 19.12 | 6.007 | 0.04 |
| 30 | 0.637 | 0.400 | 0.05 | 0.911 | 0.429 | 0.02 | 4.592 | 1.443 | 0.01 |
| 31 | 0.367 | 0.231 | 0.03 | 0.426 | 0.201 | 0.01 | 1.546 | 0.486 | 0.06 |
| 32 | 0.015 | 0.010 | 0.00 | 0.011 | 0.005 | 0.01 | 0.019 | 0.006 | - |
| 33 | 4.150 | 2.608 | 0.30 | 8.028 | 3.783 | 0.21 | 66.11 | 20.77 | 0.13 |
| 34 | 4.180 | 2.626 | 0.30 | 7.764 | 3.659 | 0.20 | 59.93 | 18.83 | 0.12 |
| 35 | 30.20 | 18.98 | - | 76.23 | 35.92 | - | Can not measure | Can not measure | - |
| 36 | 7.290 | 4.580 | 0.24 | 11.84 | 5.579 | 0.16 | 75.97 | 23.87 | - |
| 37 | 3.220 | 2.023 | 0.11 | 4.548 | 2.143 | 0.06 | 23.33 | 7.330 | - |
| 38 | 160.0 | 100.5 | - | 321.3 | 151.4 | - | Can not measure | Can not measure | - |
| 39 | 22.50 | 14.14 | 0.14 | 26.81 | 12.63 | 0.08 | 111.9 | 35.16 | - |
| 40 | 21.60 | 13.57 | 0.14 | 26.37 | 12.43 | 0.08 | 114.0 | 35.80 | - |
TABLE 4
| Test specimen No. | Bending loss at 1650nm | ||||||||
| 20φ | 15φ | 10φ | |||||||
| [dB/m] | ×10t [dB] | Bending of Loss ratio | [dB/m] | ×10t [dB] | Bending of Loss ratio | [dB/m] | ×10t [dB] | Bending of Loss ratio | |
| 1 | 0.024 | 0.015 | - | 0.152 | 0.071 | - | 6.327 | 1.988 | - |
| 2 | 0.008 | 0.005 | 0.00 | 0.035 | 0.017 | 0.23 | 0.892 | 0.280 | 0.14 |
| 3 | 0.008 | 0.005 | 0.33 | 0.035 | 0.017 | 0.23 | 0.829 | 0.260 | 0.13 |
| 4 | 0.005 | 0.003 | 0.00 | 0.020 | 0.009 | 0.13 | 0.421 | 0.132 | 0.07 |
| 5 | 0.095 | 0.060 | - | 0.502 | 0.316 | - | 16.60 | 5.215 | - |
| 6 | 0.023 | 0.011 | 0.18 | 0.084 | 0.040 | 0.13 | 1.522 | 0.478 | 0.09 |
| 7 | 0.027 | 0.013 | 0.21 | 0.095 | 0.045 | 0.14 | 1.709 | 0.537 | 0.10 |
| 8 | 0.016 | 0.008 | 0.13 | 0.054 | 0.025 | 0.08 | 0.839 | 0.264 | 0.05 |
| 9 | 0.159 | 0.075 | 1.26 | 0.772 | 0.364 | 1.15 | 22.47 | 7.059 | 1.35 |
| 10 | 0.018 | 0.008 | 0.14 | 0.057 | 0.027 | 0.09 | 0.871 | 0.274 | 0.05 |
| 11 | 0.010 | 0.005 | 0.08 | 0.031 | 0.015 | 0.05 | 0.450 | 0.141 | 0.03 |
| 12 | 0.863 | 0.542 | - | 3.522 | 1.660 | - | 83.83 | 26.34 | - |
| 13 | 0.281 | 0.176 | 0.33 | 0.781 | 0.368 | 0.22 | 10.23 | 3.214 | 0.12 |
| 14 | 0.325 | 0.204 | 0.38 | 0.854 | 0.403 | 0.24 | 10.31 | 3.238 | 0.12 |
| 15 | 0.080 | 0.050 | 0.09 | 0.183 | 0.086 | 0.05 | 1.762 | 0.553 | 0.02 |
| 16 | 0.007 | 0.004 | - | 0.011 | 0.005 | - | 0.052 | 0.016 | - |
| 17 | 0.094 | 0.059 | 0.11 | 0.203 | 0.096 | 0.06 | 1.781 | 0.560 | 0.02 |
| 18 | 0.009 | 0.006 | - | 0.013 | 0.006 | - | 0.063 | 0.020 | - |
| 19 | 0.083 | 0.052 | 0.10 | 0.194 | 0.091 | 0.06 | 1.915 | 0.602 | 0.02 |
| 20 | 0.098 | 0.061 | 0.11 | 0.216 | 0.102 | 0.06 | 1.972 | 0.619 | 0.02 |
| 21 | 3.724 | 2.340 | - | 11.26 | 5.305 | - | 176 | 55.16 | - |
| 22 | 0.958 | 0.602 | 0.26 | 1.956 | 0.922 | 0.17 | 16.78 | 5.272 | 0.10 |
| 23 | 0.500 | 0.314 | 0.13 | 0.923 | 0.435 | 0.08 | 6.726 | 2.113 | 0.04 |
| 24 | 0.022 | 0.014 | - | 0.024 | 0.011 | - | 0.073 | 0.023 | - |
| 25 | 0.024 | 0.015 | - | 0.025 | 0.012 | - | 0.073 | 0.023 | - |
| 26 | 0.010 | 0.006 | - | 0.009 | 0.004 | - | 0.024 | 0.007 | - |
| 27 | 0.011 | 0.007 | - | 0.010 | 0.005 | - | 0.024 | 0.008 | - |
| 28 | 36.35 | 22.84 | - | 81.39 | 38.36 | - | 860 | 270 | - |
| 29 | 5.060 | 3.179 | 0.14 | 7.001 | 3.299 | 0.09 | 35.28 | 11.08 | 0.04 |
| 30 | 1.873 | 1.777 | 0.05 | 2.269 | 1.069 | 0.03 | 9.220 | 2.897 | 0.01 |
| 31 | 1.026 | 0.645 | 0.03 | 1.019 | 0.480 | 0.01 | 3.016 | 0.948 | 0.00 |
| 32 | 0.050 | 0.031 | - | 0.032 | 0.015 | - | 0.046 | 0.014 | - |
| 33 | 11.20 | 7.037 | 0.31 | 18.19 | 8.571 | 0.22 | 118.4 | 37.21 | 0.14 |
| 34 | 11.05 | 6.943 | 0.30 | 17.29 | 8.146 | 0.21 | 106.2 | 33.35 | 0.12 |
| 35 | 68.87 | 43.27 | - | 146.9 | 69.20 | - | Can not measure | Can not measure | - |
| 36 | 16.82 | 10.57 | 0.24 | 23.44 | 11.04 | 0.16 | 122.5 | 38.48 | - |
| 37 | 7.585 | 4.766 | 0.11 | 9.229 | 4.349 | 0.06 | 38.767 | 12.18 | - |
| 38 | 265.4 | 166.8 | - | 466.4 | 219.8 | - | Can not measure | Can not measure | - |
| 39 | 38.48 | 24.18 | 0.14 | 40.92 | 19.28 | 0.09 | 146.3 | 45.95 | - |
| 40 | 37.85 | 23.78 | 0.14 | 41.10 | 19.37 | 0.09 | 151.9 | 47.71 | - |
As can be seen from the results in tables 1 to 4, the bending loss can be reduced in the case where the low refractive index layer is provided. By comparing the bending loss ratio parameters of the bending loss according to the presence or absence of the low refractive index layer, the effect of reducing the bending loss can be easily seen. For example, in the case of bending loss of 1550nm and 20mm Φ, the bending loss per ten windings of sample Nos. 21, 28, 35 and 38 without the low refractive index layer exceeded 0.5dB. In particular, in the case of sample Nos. 35 and 38, a bending loss exceeding 10dB occurred. However, the bending loss ratios of samples Nos. 22, 23, 29 to 34, 36, 37, 39 and 40 are all 0.4 or less. For sample nos. 22, 23, 30, 31, the bending loss per ten windings was less than 0.5dB. As shown in samples Nos. 1, 5, 9 and 12, even in the structure in which the low refractive index layer is not provided, the design can be made such that 20 mm. Phi. And ten windings are 0.5db or less. However, in the structure not provided with these low refractive index layers, the MFD would be lower than 7.5 μm at 1310nm, and the connection loss with SMF tends to deteriorate compared with the design using the low refractive index layer of the present invention, and thus is not good in this point. In addition, although the bending loss of nos. 29, 33, 34, 36, 37 under 20mm Φ and ten-winding conditions exceeded 1dB, the loss reduction of 5dB or more was achieved for nos. 28, 35, which served as the reference, and only bending loss of several dB occurred. These samples have the MFD, cutoff wavelength, and zero dispersion wavelength of a single-mode optical fiber defined by ITU-T g.652 standard, and also have the effect of greatly suppressing the increase in loss due to bending, and also have the effect of suppressing the increase in loss due to bending generated during cable laying for ordinary lines.
On the other hand, although the refractive index volume V is 110%. Mu.m 2 The samples Nos. 16, 18, 24 to 27, and 32 above have extremely small bending loss, but have a long cutoff wavelength, and thus cannot realize 1260nm or less of single-mode transmission, which is the object of the present invention.
For an optical fiber to which such a low refractive index layer is added, a design capable of maintaining MFD with almost no incremental loss can be made even for a smaller diameter of 15mm Φ. For example, in samples Nos. 13 to 15, 17, 19 and 20, the bending loss at 1550nm, 15 mm. Phi. And ten windings was 0.1dB or less, and the MFD at 1310nm was also about 7.3. Mu.m. Even in the unimodal type in which no low refractive index layer is provided, the bending loss under the condition of 15mm Φ and ten windings can be made 0.1dB or less at 1550nm by adopting the structures of nos. 1, 5 and 9. However, the MFD at 1310nm will be less than 6.9 μm, deteriorating the connection characteristics with SMF compared to an optical fiber of the present invention structure having equivalent bending characteristics.
Similarly, in samples Nos. 1, 5 and 9 having an extremely small bending loss at 15 mm. Phi., the bending loss occurs at 10 mm. Phi. (also referred to simply as 10. Phi.). Even 10mm phiA very small bending diameter also reduces the bending loss by using a structure with an additional low refractive index layer. For example, samples Nos. 2 to 4 and 6 to 8 have almost the same MFD as samples Nos. 1 and 5, respectively, and the bending loss of 0.13 or less was obtained under the conditions of 1550mm and 10 mm. Phi. Samples Nos. 10 and 11 have smaller bending loss than samples Nos. 6 to 8 having the same MFD at 1310 nm. The reason for this is to adjust a number of 2 Is set to be negativeThe effect after the value.
(example 1)
Fig. 4 shows the refractive index profile of the optical fiber in this example.
The region shown in fig. (a) was generated by VAD for the optical fiber of this example. Then, the core material obtained by VAD was extended and then externally attached to form the region (b). Then, the base material is elongated and then attached again to form a region (c). When forming the region (b), siF is introduced during vitrification 4 Gas, and F is added, thereby obtaining a refractive index lower than that of silicon. FIG. 4 shows the result of measuring the refractive index distribution of the mother material obtained by the above-mentioned steps with a pre-analyzer (trade name: MODEL2600, manufactured by Photon Kinetics/York technology Co.). As can be seen from this figure, the refractive index profile of the optical fiber of the present example is not completely stepped, but the effects of the present invention can be obtained.
The parameters of the optical fiber of the present embodiment are as follows.
Radius a of core 1 1 ：3.09μm
Radius a of the first cladding layer 2 2 ：11.83μm
Radius a of the second cladding layer 3 3 ：16.95μm
Ratio a of the radius of the first cladding layer 2 to the radius of the core 1 2 /a 1 ：3.83
Outer diameter of optical fiber: 125 μm
Refractive index volume (V) of second clad layer 3: 36.8%. Mu.m 2
Further, the core diameter a is used 1 Specific refractive index difference Δ to core 1 1 After conversion in steps, a 0.50% specific refractive index difference Delta of the first clad layer was obtained 2 Is-0.03%, and the specific refractive index difference Delta of the second clad layer 3 Is-0.25%.
For the optical fiber of this example, the transmission loss, cut-off wavelength, MFD, chromatic dispersion, dispersion slope, zero dispersion wavelength, and bending loss were measured at a wavelength of 1550nm. The results are shown in Table 5. The measured connection loss with a single mode optical fiber for soldering in the ordinary 1.3 μm range specified in the ITU-T standard g.652 entry is 0.18dB at 1550nm, which is not a problem.
The cut-off wavelength of a 2m optical fiber was measured by a measurement method based on ITU-T standard G.650.1 Definitions and test methods for linear, and defined statistical attributes of single-mode fibers and cable.
Comparative example 1
In example 1, an optical fiber in which the refractive index profile of the optical fiber was changed to a monomodal type without the second clad 3 was produced.
That is, the core base material up to the region (a) used in example 1 was subjected to the region (c) only without being subjected to the region (b) to be attached, and thus an optical fiber base material was produced. In this case, the thickness of the region (c) was adjusted so that the cutoff wavelength was about the same as that of example 1.
The optical fiber obtained was measured for each optical property in the same manner as in example 1. The results are also shown in Table 5.
TABLE 5
| Item | Unit of | Measuring wavelength | Example 1 | Comparative example 1 | |
| Transmission loss | [dB/km] | 1550nm | 0.208 | 0.205 | |
| Cut-off wavelength | [μm] | - | 1.20 | 1.20 | |
| MFD | [μm] | 1310nm | 7.37 | 7.35 | |
| 1550nm | 8.54 | 8.51 | |||
| Wavelength dispersion | [ps/nm/km] | 1550nm | 11.43 | 14.50 | |
| Slope of dispersion | [ps/nm 2 /km] | 1550nm | 0.060 | 0.060 | |
| Zero dispersion wavelength | [nm] | - | 1381 | 1342 | |
| Loss of bending | 20φ×10t | [dB] | 1550nm | 0.08 | 0.15 |
| 1650nm | 0.38 | 2.33 | |||
| 15φ×10t | [dB] | 1550nm | 0.34 | 0.64 | |
| 1650nm | 1.11 | 6.22 | |||
| 10φ×10t | [dB] | 1550nm | 1.40 | 10.2 | |
| 1650nm | 3.90 | 62.0 | |||
(example 2)
Fig. 5 shows the refractive index profile of the optical fiber in this example. The optical fiber of this example was manufactured by the same process as in example 1. Fig. 5 shows the result of measuring the refractive index distribution of the base material by a pre-analyzer. As can be seen from this figure, the refractive index profile of the optical fiber of this example is not completely stepped, but the effect of the present invention can be obtained.
The parameters of the optical fiber of this embodiment are as follows.
Radius a of core 1 1 ：3.40μm
Radius a of the first cladding layer 2 2 ：11.48μm
Radius a of the second cladding layer 3 3 ：16.45μm
Ratio a of the radius of the first cladding layer 2 to the radius of the core 1 2 /a 1 ：3.37
Outer diameter of optical fiber: 125 μm
Refractive index volume (V) of second clad layer 3: 55.8%. Mu.m 2
Further, the core diameter a is used 1 Specific refractive index difference Δ to core 1 1 After conversion in steps, a 0.40% specific refractive index difference Delta of the first cladding layer was obtained 2 Is-0.02%, and the specific refractive index difference Delta of the second cladding layer 3 Is-0.4%.
The optical fiber of this example was measured for transmission loss, cut-off wavelength, MFD, chromatic dispersion, dispersion slope, zero dispersion wavelength, and bend loss at a wavelength of 1550nm, similarly to example 1. The results are shown in Table 6. As in example 1, the measured connection loss was 0.05dB at 1550nm, and this value was not problematic.
Comparative example 2
In example 2, an optical fiber in which the refractive index profile of the optical fiber was changed to a monomodal type without the second clad 3 was produced.
That is, the core base material up to the region (a) used in example 1 was subjected to the region (c) only without the region (b) being attached, and thus an optical fiber base material was produced. In this case, the thickness of the region (c) was adjusted so that the cutoff wavelength was about the same as in example 2.
The optical fiber obtained was measured for each optical property in the same manner as in example 2. The results are also shown in Table 6.
TABLE 6
| Item | Unit | Measuring wavelength | Example 2 | Comparative example 2 | |
| Transmission loss | [dB/km] | 1550nm | 0.215 | 0.212 | |
| Cut-off wavelength | [μm] | - | 1.22 | 1.22 | |
| MFD | [μm] | 1310nm | 8.27 | 8.42 | |
| 1550nm | 9.49 | 9.50 | |||
| Wavelength dispersion | [ps/nm/km] | 1550nm | 14.03 | 15.92 | |
| Slope of dispersion | [ps/nm 2 /km] | 1550nm | 0.064 | 0.060 | |
| Zero dispersion wavelength | [nm] | - | 1351 | 1326 | |
| Loss of bending | 20φ×10t | [dB] | 1550nm | 0.69 | 2.09 |
| 1650nm | 1.67 | 17.29 | |||
| 15φ×10t | [dB] | 1550nm | 1.02 | 5.43 | |
| 1650nm | 3.21 | 31.19 | |||
| 10φ×10t | [dB] | 1550nm | 2.20 | 41.8 | |
| 1650nm | 4.80 | 122 | |||
(example 3)
Fig. 6 shows the refractive index profile of the optical fiber in this example.
For the optical fiber of this example, the region shown in (a) in the figure was generated by MCVD. In the figure, (b) shows a starting quartz tube in the CVD method. The core material obtained by the MCVD method is externally attached to form a region (c). Fig. 6 shows the result of measuring the refractive index distribution of the base material by a pre-analyzer. As can be seen from this figure, although the refractive index profile of the optical fiber of this embodiment is not completely step-shaped, the effects of the present invention can be obtained.
The parameters of the optical fiber of this embodiment are as follows.
Radius a of core 1 1 ：3.12μm
Radius a of the first cladding layer 2 2 ：10.30μm
Radius a of the second cladding layer 3 3 ：16.62μm
Ratio a of the radius of the first cladding layer 2 to the radius of the core 1 2 /a 1 ＝3.30
Outer diameter of optical fiber: 125 μm
Refractive index volume (V) of second clad layer 3: 42.0%. Mu.m 2
Further, the core diameter a is used 1 Specific refractive index difference Δ to core 1 1 After conversion in steps, a difference Δ of 0.52% in the specific refractive index of the first clad layer was obtained 2 Is-0.07%, and the specific refractive index difference Delta of the second clad layer 3 Is-0.25%.
The optical fiber of this example was measured for transmission loss, cut-off wavelength, MFD, chromatic dispersion, dispersion slope, zero dispersion wavelength, and bend loss at a wavelength of 1550nm, similarly to example 1. The results are shown in Table 7 below.
The measured connection loss was 0.29dB at 1550nm as in example 1.
Comparative example 3
In example 3, an optical fiber in which the refractive index profile of the optical fiber was changed to a monomodal type without the second clad 3 was produced.
That is, in example 3, in the MCVD process of the synthesis region (a), a fluorine-based gas was used to synthesize a low refractive index layer corresponding to the second clad layer, but in this comparative example, a core base material was prepared by synthesizing a refractive index layer substantially equal to that of silicon without using the fluorine-based gas. Then, the core base material is attached to the outside of the region (c) to produce an optical fiber base material. At this time, the thickness of the region (c) was adjusted so that the cutoff wavelength was about the same as that of example 3.
The optical fiber obtained was measured for each optical property in the same manner as in example 3. The results are also shown in Table 7.
TABLE 7
| Item | Unit of | Measuring wavelength | Example 3 | Comparative example 3 | |
| Transmission loss | [dB/km] | 1550nm | 0.216 | 0.215 | |
| Cut-off wavelength | [μm] | - | 1.23 | 1.23 | |
| MFD | [μm] | 1310nm | 7.12 | 7.20 | |
| 1550nm | 8.03 | 8.05 | |||
| Wavelength dispersion | [ps/nm/km] | 1550nm | 13.03 | 15.35 | |
| Slope of dispersion | [ps/nm 2 /km] | 1550nm | 0.057 | 0.057 | |
| Zero dispersion wavelength | [nm] | - | 1352 | 1325 | |
| Bending loss | 20φ×10t | [dB] | 1550nm | 0.02 | 0.05 |
| 1650nm | 0.15 | 0.33 | |||
| 15φ×10t | [dB] | 1550nm | 0.08 | 0.66 | |
| 1650nm | 0.34 | 2.79 | |||
| 10φ×10t | [dB] | 1550nm | 0.30 | 8.80 | |
| 1650nm | 0.96 | 21.5 | |||
(example 4)
Fig. 7 shows the refractive index profile of the optical fiber in this example.
The region shown in fig. (a) is generated by the VAD method for the optical fiber of this example. Then, the core material obtained by VAD was extended and then externally attached to form the region (b). Then, the base material is elongated and then attached again to form a region (c). When the region (a) is formed, CF is introduced into the burner for synthesizing the inner coating 4 Gas, thereby obtaining a refractive index lower than that of quartz. When forming the region (b), siF is introduced during vitrification 4 Gas, and F is added, thereby obtaining a refractive index lower than that of silicon. Fig. 7 shows the result of measuring the refractive index distribution of the base material by a pre-analyzer. As can be seen from this figure, in the present embodiment as well, the effect of the present invention can be obtained although the distribution of the optical fibers is not completely stepped.
The parameters of the optical fiber of this embodiment are as follows.
Radius a of core 1 1 ：3.15μm
Radius a of the first cladding layer 2 2 ：10.37μm
Radius a of the second cladding layer 3 3 ：16.62μm
Ratio a of the radius of the first cladding layer 2 to the radius of the core 1 2 /a 1 ：3.30
Outer diameter of optical fiber: 80 μm
Refractive index volume (V) of second clad layer 3: 42.2%. Mu.m 2
Further, the core diameter a is used 1 Specific refractive index difference Δ to core 1 1 After fractional conversion, a difference Δ in the specific refractive index of the first cladding layer of 0.56% is obtained 2 Is-0.09%, and the specific refractive index difference Delta of the second cladding layer 3 Is-0.25%.
The optical fiber of this example was measured for cutoff wavelength, transmission loss, MFD, wavelength dispersion, dispersion slope, zero dispersion wavelength, and bending loss in the same manner as in example 1. The results are shown in Table 8. The measurement wavelengths of the respective properties are shown in the table.
In this example, the 2m fiber cut-off wavelength is 1.30 μm, slightly longer than 1.26 μm. A cable cut-off wavelength evaluation was carried out using a 22m optical fiber based on ITU-T standard G.650.1 Definitions and test methods for linear, scientific attributes of single-mode fiber and cable, and 5.3.4alternative test method for the cut-off wavelength (lcc) of the cable fiber, and as a result, the optical fiber of this example was 1.23 μm, and no use problem was confirmed.
As in example 1, the measured connection loss was 0.4dB at 1550nm.
Comparative example 4
In example 4, an optical fiber having a structure in which the refractive index profile of the optical fiber was changed to that in which the second clad 3 was not provided was manufactured.
That is, the core base material up to the region (a) used in example 4 was subjected to the region (c) only without the region (b) being attached, and thus an optical fiber base material was produced. I.e. the first cladding layer remains below the value of silicon. At this time, the thickness of the region (c) was adjusted so that the cutoff wavelength was about the same as in example 4.
The optical properties of the obtained optical fiber were measured in the same manner as in example 4. The results are also shown in Table 8.
TABLE 8
| Item | |||||
| Transmission loss | [dB/km] | 1550nm | 0.205 | 0.204 | |
| Cut-off wavelength | [μm] | - | 1.30 | 1.30 | |
| Cut-off wavelength of cable | 1.23 | 1.24 | |||
| MFD | [μm] | 1310nm | 6.90 | 7.02 | |
| 1550nm | 7.77 | 7.82 | |||
| Wavelength dispersion | [ps/nm/km] | 1550nm | 13.07 | 15.27 | |
| Slope of dispersion | [ps/nm 2 /km] | 1550nm | 0.057 | 0.058 | |
| Zero dispersion wavelength | [nm] | - | 1353 | 1.327 | |
| Loss of bending | 20φ×10t | [dB] | 1550nm | ＜0.01 | ＜0.01 |
| 1650nm | ＜0.01 | 0.05 | |||
| 15φ×10t | [dB] | 1550nm | 0.06 | 0.07 | |
| 1650nm | 0.16 | 0.51 | |||
| 10φ×10t | [dB] | 1550nm | 0.10 | 1.30 | |
| 1650nm | 0.74 | 5.9 | |||
Industrial applicability
The present invention relates to an optical fiber having excellent bending characteristics. According to the present invention, an optical fiber having a small loss due to bending and having good connectivity to a normal transmission optical fiber can be obtained at low cost.
Claims (21)
1. An optical fiber having:
a core portion disposed at the center;
a first coating layer disposed on a circumference of the core;
a second coating layer disposed on a circumference of the first coating layer;
a third coating layer disposed on the circumference of the second coating layer,
the optical fiber is characterized in that it is,
the maximum refractive index of the core is higher than any one of the maximum refractive indices of the first cladding layer, the second cladding layer and the third cladding layer, and the maximum refractive index of the second cladding layer is lower than any one of the maximum refractive indices of the first cladding layer and the third cladding layer, and
when the radius of the core is set as a 1 The outer edge radius of the first cladding layer is defined as a 2 When a is 2 /a 1 Has a value of between 2.5 and 4.5,
when the maximum refractive index of the third cladding layer is used as a reference, the specific refractive index difference of the core is 0.20% to 0.70%,
the specific refractive index difference of the first cladding layer is-0.10% to 0.00% with reference to the maximum refractive index of the third cladding layer.
2. The optical fiber of claim 1, wherein: the cut-off wavelength is 1260nm or less.
3. The optical fiber of claim 1, wherein: the volume V of the refractive index of the second clad layer is 50%. Mu.m 2 And the above.
4. The optical fiber of claim 1, wherein: when the increase in bending loss at a wavelength of 1550nm, which is generated when a unimodal optical fiber having a unimodal refractive index distribution without a second cladding and having the same cutoff wavelength is wound ten times around a mandrel having a diameter of 20mm, is set to 1, the bending loss ratio expressed as the ratio of the similarly measured increase in bending loss values is 0.4 or less.
5. The optical fiber of claim 1, wherein: when the increase in bending loss at a wavelength of 1550nm, which is generated when a unimodal optical fiber having a unimodal refractive index distribution without a second cladding and having the same cutoff wavelength is wound ten times around a mandrel having a diameter of 15mm, is set to 1, the bending loss ratio expressed by the ratio of the similarly measured increase in bending loss values is 0.55 or less.
6. The optical fiber of claim 1, wherein: when the film is wound with a bending diameter of 20mm, the bending loss at a wavelength of 1550nm is 0.05dB per turn or less.
7. The optical fiber of claim 6, wherein: when the steel sheet is wound with a bending diameter of 20mm, the bending loss at a wavelength of 1650nm is 0.05dB per turn or less.
8. The optical fiber of claim 6, wherein: the mode field diameter at a wavelength of 1550nm is 8.3 μm or more.
9. The optical fiber of claim 6, wherein: when the film is wound with a bending diameter of 15mm, the bending loss at a wavelength of 1550nm is 0.05dB per turn or less.
10. The optical fiber of claim 9, wherein: when the film is wound with a bending diameter of 15mm, the bending loss at a wavelength of 1650nm is 0.05dB per turn or less.
11. The optical fiber of claim 9, wherein: the mode field diameter at a wavelength of 1550nm is 7.8 μm or more.
12. The optical fiber of claim 1, wherein: when a mode field diameter value at 1550nm of a monomodal optical fiber having a monomodal refractive index distribution without a second clad layer and having the same cutoff wavelength was set to 1, the ratio of the mode field diameter values measured in the same manner was 0.98 or more.
13. The optical fiber of claim 6, wherein: the mode field diameter at a wavelength of 1310nm is 7.3 μm or more.
14. The optical fiber of claim 9, wherein: the mode field diameter at a wavelength of 1310nm is 6.8 μm or more.
15. The optical fiber of claim 9, wherein: when the film is wound with a bending diameter of 10mm, the bending loss at a wavelength of 1550nm is 0.05dB per turn or less.
16. The optical fiber of claim 14, wherein: when the film is wound with a bending diameter of 10mm, the bending loss at a wavelength of 1650nm is 0.05dB per turn or less.
17. The optical fiber of claim 14, wherein: the mode field diameter at a wavelength of 1550nm is 7.3 μm or more.
18. The optical fiber of claim 6, wherein: the mode field diameter at a wavelength of 1310nm is 6.3 μm or more.
19. The optical fiber of claim 1, wherein: the mode field diameter at a wavelength of 1310nm is 7.9 μm or more, and the bending loss value at a wavelength of 1550nm when the film is wound with a bending diameter of 20mm is 1dB or less per turn.
20. The optical fiber of claim 1, wherein: when the film is wound with a bending diameter of 20mm, the bending loss at a wavelength of 1550nm is 0.5dB per turn or less.
21. The optical fiber of claim 19, wherein: the zero dispersion wavelength is 1300nm to 1324 nm.
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| CN104932052A (en) * | 2014-03-20 | 2015-09-23 | 株式会社藤仓 | Polarization-maintaining optical fiber |
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| CN101861537A (en) | 2007-11-19 | 2010-10-13 | 三菱电线工业株式会社 | Optical fiber and method for producing the same |
| US8081855B2 (en) * | 2008-02-22 | 2011-12-20 | Sumitomo Electric Industries, Ltd. | Optical fiber and optical cable |
| JP2010064915A (en) * | 2008-09-09 | 2010-03-25 | Shin-Etsu Chemical Co Ltd | Method for producing optical fiber preform |
| KR20100091710A (en) * | 2009-02-11 | 2010-08-19 | 엘에스전선 주식회사 | Method for manufacturing optical fiber improvement of bending loss and optical fiber manufactured using the same |
| JP5478116B2 (en) * | 2009-05-20 | 2014-04-23 | 信越化学工業株式会社 | Optical fiber |
| EP2352046B1 (en) * | 2010-02-01 | 2018-08-08 | Draka Comteq B.V. | Non-zero dispersion shifted optical fiber having a short cutoff wavelength |
| US9279935B2 (en) | 2010-12-23 | 2016-03-08 | Prysmian S.P.A. | Low macrobending loss single-mode optical fibre |
| CN105158843B (en) * | 2015-08-31 | 2018-10-12 | 中天科技光纤有限公司 | A kind of thin footpath bend insensitive fiber and preparation method thereof |
| US9989699B2 (en) * | 2016-10-27 | 2018-06-05 | Corning Incorporated | Low bend loss single mode optical fiber |
| CN108983351A (en) * | 2018-07-19 | 2018-12-11 | 江苏南方光纤科技有限公司 | A kind of counter-bending single mode optical fiber and preparation method thereof |
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| CN1400481A (en) * | 2001-07-31 | 2003-03-05 | 古河电气工业株式会社 | Fiber, fiber element and light transmission method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104932052A (en) * | 2014-03-20 | 2015-09-23 | 株式会社藤仓 | Polarization-maintaining optical fiber |
| CN104932052B (en) * | 2014-03-20 | 2018-01-30 | 株式会社藤仓 | Polarization maintaining optical fibre |
Also Published As
| Publication number | Publication date |
|---|---|
| CN100549740C (en) | 2009-10-14 |
| CN1768282A (en) | 2006-05-03 |
| CN101055330A (en) | 2007-10-17 |
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