Source: https://patents.google.com/patent/KR101605897B1/en
Timestamp: 2019-11-14 15:31:35
Document Index: 56166447

Matched Legal Cases: ['Application No. 2007', 'Application No. 61', 'Application No. 11', 'Application No. 11', 'Application No. 11', 'Application No. 61', 'Application No. 11', 'Application No. 12']

KR101605897B1 - Bend-insensitive single mode optical fiber - Google Patents
Bend-insensitive single mode optical fiber Download PDF
KR101605897B1
KR101605897B1 KR1020090039426A KR20090039426A KR101605897B1 KR 101605897 B1 KR101605897 B1 KR 101605897B1 KR 1020090039426 A KR1020090039426 A KR 1020090039426A KR 20090039426 A KR20090039426 A KR 20090039426A KR 101605897 B1 KR101605897 B1 KR 101605897B1
KR1020090039426A
KR20090116651A (en
루이-안느 드 몽모리용
씨몽 리샤르
드니 몰랭
마리안느 비고-아스트뤽
삐에르 씨야르
다비드 부아뱅
드라카 콤텍 비.브이.
2008-05-06 Priority to FR08/02503 priority Critical
2008-05-06 Priority to FR0802503A priority patent/FR2930997B1/en
2008-09-30 Priority to US10133708P priority
2008-09-30 Priority to US61/101,337 priority
2008-11-06 Priority to US11200608P priority
2008-11-06 Priority to US61/112,006 priority
2009-05-06 Application filed by 드라카 콤텍 비.브이. filed Critical 드라카 콤텍 비.브이.
2009-11-11 Publication of KR20090116651A publication Critical patent/KR20090116651A/en
2016-03-23 Publication of KR101605897B1 publication Critical patent/KR101605897B1/en
The single mode optical fiber includes a center core, an intermediate cladding, a depression trench, and an external optical cladding, which are directed from the center to the periphery. The central core has a radius (r 1) and the optical cladding and the amount of the refractive index difference (△ n 1); The intermediate cladding has a radius (r 2) and having an optical cladding and the amount of the refractive index difference (△ n 2), △ n 2 is smaller than the refractive index difference (△ n 1) of the core. Depressed trench has a radius (r3) and an optical cladding and a negative refractive index difference (△ n 3). The optical fiber has an MFD (Mode Field Diameter) between 8.6 μm and 9.5 μm at a wavelength of 1310 nm and a bending loss of less than 0.25 × 10 -3 dB / turn for a radius of curvature of 15 mm at a wavelength of 1550 nm. The length of fiber required for attenuation of the LP11 mode reaching 19.3 dB at a wavelength of 1260 nm is less than 90 meters. These fibers can be used in demanding environments such as small optical boxes.
Optical fiber, center core, intermediate cladding, recessed trench, external optical cladding
[0001] BEND-INSENSITIVE SINGLE MODE OPTICAL FIBER [0002]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of optical fiber transmission, and more particularly to a fiber in which bending loss is greatly reduced.
For optical fibers, the refractive index profile is generally defined as the difference between the values of two points on a graph of the function relating the refractive index to the radius of the fiber. Conventionally, the distance r to the center of the fiber appears along the x-axis of the profile. The difference between the refractive index at the distance r and the refractive index of the outer fiber cladding appears along the y-axis (see Figs. 21 to 24). The outer cladding functions as an optical cladding, has a substantially constant refractive index, and such an optical cladding is generally composed of pure silica, but may comprise one or more dopants. The optical fiber refractive index profile is referred to as a " step "profile, a" trapezoidal "profile, or a" triangular "profile for a graph having the form of a corresponding step, trapezoid, or triangle. These curves generally represent the theoretical or reference index profile of the fiber (i.e., the configuration profile). Fiber manufacturing constraints can lead to somewhat different profiles of actual fibers.
The optical fiber conventionally consists of (i) an optical core having a function of transmitting and amplifying optical signals, and (ii) an optical cladding having a function of defining optical signals in the core. For this purpose, the refractive index (n c ) of the core and the refractive index (n g ) of the cladding are n c > n g . As is well known, the propagation of optical signals in a single mode optical fiber is divided into a fundamental mode (known as LP01) guided in the core and a secondary mode guided on a specific radius of the core-cladding assembly.
Conventionally, a stepped index fiber (also referred to as SMF (Single Mode Fiber)) is used as a line fiber for an optical fiber transmission system. These fibers exhibit chromatic dispersion and multi-color diffusion gradients corresponding to certain telecommunications standards.
For the requirements of compatibility between optical systems of different manufacturers, the International Telecommunication Union (ITU) has defined the ITU-T G.652 standard to be compliant with SSMF (Standard Single Mode Fiber).
In this G.652 standard for the transmission fiber, in particular in the range of 8.6 to 9.5 microns for MFD (Mode Field Diameter) at a wavelength of 1310 nm; Up to 1260 nm for cable cut-off wavelength; In the range of 1300 to 1324 nm with respect to the diffusion canceling wavelength (? 0 ); And a maximum polychromatic diffusion gradient of 0.092 ps / (nm 2 · km) (ie, ps / nm 2 / km).
The cable cut-off wavelength is conventionally measured as the wavelength after the optical signal is no longer in the single mode, after propagating the fiber of 22 meters, as defined in subclause 86A of the International Electrotechnical Commission (IEC) 60793-1-44 standard. In most cases, the secondary mode that is most resistant to bending losses is the LP11 mode. Therefore, the cable cut-off wavelength is a wavelength at which the LP11 mode starts to weaken sufficiently after the 22-meter fiber propagation. The proposed method includes the assumption that the optical signal is a single mode when the attenuation of the LP11 mode is 19.3 dB or more.
Also, for a given fiber, the so-called MAC value is defined as the ratio of the MFD of the fiber at 1550 nm to the effective cut-off wavelength (? Ceff ). Conventionally, the cut-off wavelength is measured as the wavelength after which the optical signal is no longer a single mode, after 2 meters of fiber propagation, as defined in the subcircuit 86A of the IEC 60793-1-44 standard. The MAC constitutes a parameter for estimating the performance of the fiber to find a trade-off between the MFD, the effective cut-off wavelength, and the bending loss, in particular.
European Patent Application Nos. 1,845,399 and 1,785,754 show the empirical results of the applicant. These prior applications establish the relationship between the MAC value at a wavelength of 1550 nm and the flexural loss at 1625 nm for a curvature radius of 15 mm in a standard stepped index fiber (SSMF). Each of these European patent applications is incorporated herein by reference in its entirety. In addition, each application establishes that the value of the MAC affects the bending loss of the fiber and reduces this bending loss by lowering the MAC. Reducing the MFD and / or increasing the effective cut-off wavelength reduces the MAC value, but may result in noncompliance with the G.652 standard, so that the fiber is not commercially compatible with some transmission systems.
If the bending loss is reduced while maintaining a specific optical transmission parameter, it is challenging for an application example of a fiber intended for a user optical fiber system called so-called FTTH (Fiber-To-The-Home).
The International Telecommunication Union (ITU) has also defined the ITU-T G.657A and ITU-T G.657B standards, which are met for optical fibers intended for FTTH applications, in particular as a measure against bending loss. . The G.657A standard imposes restrictions on the values of flexural loss, but above all it is intended to maintain compatibility with the G.652 standard in terms of MFD and polychromatic diffusivity. The G.657B standard, on the other hand, has (i) a flexural loss of less than 0.003 dB / turn at a wavelength of 1550 nm for a radius of curvature of 15 mm, (ii) a curvature radius of 0.01 lt; RTI ID = 0.0 &gt; dB / turn. &lt; / RTI &gt;
European Patent Applications Nos. 1,845,399 and 1,785,754 propose a fiber profile with limited bending loss, which in particular corresponds to the standards of the G.657A standard and the G.657B standard. However, the profile described in this European patent application makes it possible to achieve only the flexural loss limit imposed by the G.657B standard.
U.S. Patent No. 7,164,835 and U.S. Patent Application No. 2007/0147756, which are hereby incorporated by reference in their entirety, also describe fiber profiles that exhibit limited bending loss. However, the fibers of these U.S. patents are only applicable to the G.657A and G.657B standards, in particular in terms of MFD and polychromatic diffusivity.
Presently, in certain applications, the reduction in bending loss is fundamental and is fundamental in particular when the fiber is to be stapled or coiled into a miniaturized optical box.
Hole-assisted fiber technology can achieve excellent performance in terms of bending loss, but this technique is complex and costly to implement, so it can be used for fibers intended for FTTH systems, which are low cost systems I can not.
It is therefore necessary to have an optical fiber with resistance to bending losses that is significantly better (e.g., about 10 times better) than the limit imposed by the G675B standard. Fibers that meet these criteria must also be compatible with the G.652 standard in terms of transmission profiles and in particular MFD. (i) the higher order LP11 mode is sufficiently attenuated and (ii) the length of the fiber required for attenuation of the LP11 mode to reach 19.3 dB at a wavelength of 1260 nm is less than 90 meters, Significant improvements in this bending loss can be achieved even if the cut-off wavelength is lost.
For the foregoing, the present invention includes a fiber having a center core, an intermediate cladding, and a recessed trench. The refractive index profile is optimized to improve the flexural loss by a factor of ten compared to the limiting factors imposed by the G.657B standard while maintaining the MFD (mode field diameter) compatible with the G.652 standard and sufficient Ensure attenuation.
In particular, the surface and volume of the depression trench as well as the surface of the core are optimized to significantly improve the bending loss. In the context of the present invention, the surface of the core or the surface of the depression trenches should not extend geometrically, but should correspond to values that take into account two dimensions - the product of the radius and the refractive index. Likewise, the volume of the depression trench corresponds to a value taking into account three dimensions - the product of the square of the radius and the refractive index.
In particular, the present invention proposes a single-mode optical fiber including a center core, an intermediate cladding, a recessed trench, and an external optical cladding from the center to the periphery. The central core has a refractive index difference (△ n 1) of the radius (r 1) and the optical cladding and the positive (+). The intermediate cladding has a refractive index difference (△ n 2) of the radius (r 2) and an optical cladding and the positive (+). The refractive index difference? N 2 is smaller than the refractive index difference? N 1 of the core. Depressed trench has a radius (r 3) and an optical cladding and the negative has a refractive index difference (△ n 3) of the (). The fiber of the present invention has (i) an MFD (Mode Field Diameter) between 8.6 and 9.5 m at a wavelength of 1310 nm, (ii) 0.25 x 10 -3 dB for a wavelength of 1550 nm and a radius of curvature of 15 mm / turn. &lt; / RTI &gt; The length of fiber required for attenuation of LP11 mode reaching 19.3 dB at a wavelength of 1260 nm is less than 90 meters.
According to one embodiment of the fiber according to the invention, the area of the center core (V 01 )
And is between 20.0 x 10 -3 μm and 23.0 x 10 -3 μm.
The area of the depression trench (V 03 )
And is between -55.0 × 10 -3 μm and -30.0 × 10 -3 μm.
The volume integral (V 13 ) of the depression trench
And is between -1200 × 10 -3 μm 2 and -750 × 10 -3 μm 2 .
In a preferred embodiment, the fiber has physical properties and operating parameters with improved resistance to bending loss. For example, the fiber has an effective cut-off wavelength (? Ceff ) in excess of 1350 nm, and the effective cutoff wavelength is measured as the wavelength at which the optical signal becomes single mode after propagating the fiber in excess of 2 meters. The fiber had a flexural loss of less than 7.5 x 10 -3 dB / turn for a radius of curvature of 10 mm at a wavelength of 1550 nm, a flexural loss of less than 0.05 dB / turn at a radius of curvature of 7.5 mm, Has a flexural loss of less than 0.15 dB / turn with respect to the radius.
The fibers disclosed herein also exhibit reduced bending loss at higher wavelengths. For example, at a wavelength of 1625 nm, the fiber has a bending loss of less than 1.5 x 10 -3 dB / turn for a radius of curvature of 15 mm, a bending loss of less than 25 x 10 -3 dB / turn for a radius of curvature of 10 mm Loss, a flexural loss of less than 0.08 dB / turn for a radius of curvature of 7.5 mm, and a flexural loss of less than 0.25 dB / turn for a radius of curvature of 5 mm. At a wavelength of 1550 nm, the fiber has a flexural loss of less than 0.05 dB / turn for a radius of curvature of 7.5 mm. Thus, in a preferred embodiment, the fiber has a cut-off wavelength between 1300 nm and 1400 nm, the cut-off wavelength is greater than 5 meters and the optical signal is measured as a wavelength after the propagation of the fiber is no longer a single mode. The cut-off wavelength is distinguished from the cut-off wavelength which is measured as the wavelength at which the attenuation of the LP11 mode is 19.3 dB or more after the fiber propagation, exceeding 22 m. Such a fiber has a cable cut-off wavelength between 1250 nm and 1300 nm.
The third important measurement in this specification is the theoretical blocking wavelength measured as the wavelength at which the LP11 mode begins to propagate in the leak mode. In one embodiment, the fiber has a theoretical blocking wavelength of 1250 nm or less. The fiber has an attenuation of the LP11 mode exceeding 5 dB after propagating the fiber in excess of 22 meters at a wavelength of 1260 nm.
The above-described operating parameters result from the desired physical properties of the fiber. In one embodiment, the central core of the fiber has a radius between 3.8 and 4.35 micrometers; The intermediate cladding has a radius between 8.5 and 9.7 [mu] m; The recess trenches have a radius of between 13.5 micrometers and 16 micrometers, which can be less than or equal to 15 micrometers, and the center core has a refractive index difference from external light cladding between 5.3 x 10-3 and 5.7 x 10-3 .
As described above, the refractive index profile of the fiber is constructed with respect to the difference between the radius of the fiber and the refractive index value at the points on the external optical cladding. The intermediate cladding has a refractive index difference with the optical cladding between 0.1 x 10-3 and 0.6 x 10-3 . The recess trench has a refractive index difference from the optical cladding between -10.0 x 10 -3 and -0.5 x 10 -3 . The fiber has a zero polychromatic diffusion wavelength between 1300 nm and 1324 nm; The fiber has a multicolor diffusion gradient value at a zero polychromatic diffusion wavelength of less than 0.092 ps / (nm 2. Km).
The invention also relates to an optical box for receiving at least a portion of the fibers disclosed herein. In such a box, the fibers may be arranged with a radius of curvature of less than 15 mm, which may be a dimension of 5 mm. The invention also relates to a subscriber's home (FTTH) optical fiber system comprising at least a part of a fiber according to the invention.
The foregoing and other characteristics of the invention as well as the manner in which it is accomplished are described in more detail in the following detailed description and the accompanying drawings.
The fiber 10 of the present invention includes a center core 11, an intermediate cladding 12, and a recessed cladding 13. Without limiting the scope of the present invention for the purpose of this disclosure, depressed cladding refers to a radial portion of a fiber having a refractive index that is less than the refractive index of the outer optical cladding 14. [ Typically, the center core 11, the intermediate cladding 12, and the recessed cladding 13 are obtained by chemical vapor deposition in a silica tube. The outer optical cladding 14 includes a silica tube and overcladding on the tube. In a preferred embodiment, the overcladding is generally natural silica or doped silica, but may be obtained by any other deposition technique (VAD (Vapor Axial Deposition) or OVD (Outside Vapor Deposition)).
Fig. 2 shows the refractive index profile of the transmission fiber 10 of Fig. The profile of FIG. 2 shows the set profile, i. E., The pre-theoretical profile of the fiber, but the fiber actually obtained after fiber extrusion of the preform may have a slightly different profile.
In the conventionally known method, the optical fiber 10 is obtained by preform drawing. As an example, the parent material may be a very high quality glass tube (pure silica) which eventually forms part of the outer optical cladding 14. The outer optical cladding 14 surrounds the center core 11 and the inner cladding 12, 13 of the fiber 10. This tube is then overcladed and increases its diameter before passing the fiber extrusion operation on the fiber extrusion tower. To make the base material, the tube is generally horizontally mounted and held on both ends of a glass bar on the shelf; The tube is then rotated and locally heated for a deposition process to determine the composition of the base material. These components determine the optical properties of future fibers.
The fiber comprises a central core 11 having a refractive-index difference △ n 1 and the outer cladding 14, which acts as an optical cladding. Fiber 10 also further includes an intermediate cladding (12) and the recessed trench cladding 13 having a refractive-index difference △ n 3 with the outer cladding 14 having a refractive-index difference △ n 2 with the outer optical cladding (14) do. 2, the refractive indices of the center core 11, the intermediate cladding 12, and the recess trenches 13 are substantially constant over the respective widths. Figure 1 shows that the width of the core 11 is defined as its radius r 1 and the width of the cladding is defined by the corresponding outer radius r 2 and r 3 . The outer optical cladding is referred to as r 4 .
To define the set refractive index profile for the optical fiber, the refractive index value of the external optical cladding is generally taken as the reference (n g ). Next, the refractive indexes of the central core 11, the intermediate cladding 12, and the recessed trench cladding 13 are shown in Fig. 2 as the refractive index differences? N 1, 2, 3 . Generally, the outer optical cladding 14 is comprised of silica, but this cladding can be doped to increase or decrease its refractive index-for example, to alter the propagation characteristics of the signal.
Each of the fiber profile portions 21-24 shown in Figure 2 may also be defined based on an integral linking the refractive index variation with the radius of each portion of the fiber 10. [ Thus, for the fiber 10 of the present invention, it is possible to define three areas representing the surface V 01 of the core, the surface V 02 of the intermediate cladding, and the surface V 03 of the depression trench. The expression "surface" does not have to be geometrically understood, but corresponds to a value that takes into account two dimensions. These three areas can be expressed as follows.
Likewise, for the fiber 10 of the present invention, three volume integrals representing the volume V 11 of the core, the volume V 12 of the intermediate cladding, and the volume V 13 of the recess trench can be defined. The expression "volume" does not have to be geometrically understood, but corresponds to a value that considers three dimensions. These three volume integrals can be expressed as follows.
Table I below shows thirty examples of fiber profiles according to a preferred embodiment of the present invention with three SSMF fibers (BIF (Bend Insensitive Fiber)) profiles corresponding to G.657A and G.657B standards and one fiber Profile. Applicants sell BIF with good resistance to bending loss under the trade name BendBrightXS. The values in this table correspond to the configuration profile for each fiber.
The first column of Table I gives the criteria for each example; The next three columns give the values of the radius of core 11, intermediate cladding 12, and recessed trench 13, respectively. The next three columns give corresponding values of the refractive index difference to the external optical cladding 14. [ Refractive index values are measured at a wavelength of 633 nm. Table I also shows the area fraction and volume integral values of the core 11, the intermediate cladding 12, and the recessed trench 13, as described above.
A fiber 10 according to the present invention is a fiber of a stepped index comprising a center core 11, an intermediate cladding 12, and a recessed trench 13. In Table I, the center core 11 has a radius between 3.8 μm and 4.35 μm, preferably between 3.8 μm and 4.05 μm, ie, a radius narrower than the core of the SSMF fiber. The fiber 10 has a refractive index difference Δn 1 (21) with a large external optical cladding 14 between 5.3 × 10 -3 and 5.7 × 10 -3 , that is, a refractive index difference equal to or greater than SSMF . (V 01 ) of the core is between 20.0 × 10 -3 μm and 23.0 × 10 -3 μm, and the volume integral (V 11 ) of the core is between 81 × 10 -3 μm 2 and 91 × 10 -3 μm 2 to be.
Also in Table I, the fiber according to the present invention has a recessed trench 13. The depression trenches 13 have a large volume and can greatly limit the bending loss. Table I shows that the depression trench 13 has a radius r 3 between 13.5 μm and 16 μm and a refractive index difference Δn 3 (23) with the external optical cladding 14 of -10.0 × 10 -3 To -5.0 x 10 &lt; -3 & gt ;.
Further, in Table I is the area of the minute recessed trench as previously described (V 03) yi -55.0 x 10 -3 ㎛ to about -30.0 x 10 -3 and between ㎛, depression volume integral (V 13) of the trench as previously described Is between -1200 × 10 -3 μm 2 and -750 × 10 -3 μm 2 .
According to a preferred embodiment, the radius r 3 of the recessed cladding can be limited to 15 μm to further reduce the manufacturing cost of the fiber (with recessed cladding having a radius greater than 15 μm only in Examples 24 and 30). In fact, the depression trenches 13 can be produced by plasma enhanced chemical vapor deposition (PCVD), so that the silica contains a large amount of fluorine to form deeply embedded cladding. However, the portion of the fiber 10 that corresponds to the tube and PCVD deposition is the most expensive and should be limited as much as possible. It can also be assumed that the recessed trench 13 is created by including microholes or microbubbles instead of fluorine doping. However, fluorine doping is still more controllable in industrial production than the inclusion of microbubbles.
The depression trenches 13, corresponding to the defined plane and volume criteria, provide a good trade-off between bending loss is reduced significantly compared to conventional fibers and a sufficiently constant leakage regime of the LP11 mode at a wavelength of 1260 nm So that it can be accomplished.
As evident from Table IV below, the fibers according to the present invention have a flexural loss 10 times smaller than the limit imposed by the G.657B standard. On the other hand, the fiber according to the present invention does not strictly obey the G.657 standard in terms of cut-off wavelength. As is apparent from Table III below, the other fiber in the present invention has a large effective blocking than 1350 ㎚ wavelength cable block between (λ ceff) and 1250 to 1300 ㎚ ㎚ wavelength (λ cc). Nevertheless, the fibers disclosed herein ensure that the higher order LP11 mode propagates in the 1260 nm leaky mode fashion.
Also in Table I, a preferred embodiment of the fiber has an intermediate cladding 12 between the center core 11 and the recessed trenches 13. This intermediate cladding 12 makes it possible to limit the effect of the depression trench 13 on the propagation of optical signals in the core. Table I shows that with a radius (r 2) and 0.1 x10 -3 to 0.6 x 10 -3 refractive-index difference △ n 2 (22) with the optical cladding between intermediate between the cladding 12 is to 8.5㎛ 9.7㎛ . Table I shows that the area between the middle cladding minutes as previously described (02 V) is 0.5 x 10 -3 ㎛ to 3.0 x10 -3 ㎛. The volume integral (V 12 ) of the intermediate cladding as described above is between 6 × 10 -3 μm 2 and 40 × 10 -3 μm 2 .
The central core 11 of the fiber 10 according to the present invention is capable of combining with the intermediate cladding 12 and in particular the parameters of the optical transmission of the fiber in compliance with the G.652 and G.657A standards in terms of MFD and polychromatic diffusivity . This also helps ensure compatibility with fibers in other optical systems.
Table II (below) shows the optical transmission characteristics of the fiber according to the present invention. The first column repeats the criteria of Table I. The following columns provide MFD values for wavelengths of 1310 nm and 1550 nm, Zero Dispersion Wavelength (ZDW) and Zero Dispersion Slope (ZDS) for each fiber profile.
In Table II, the fiber 10 according to the present invention is compatible with fibers corresponding to the G.652 standard. In particular, in the fiber disclosed herein is 1310 ㎚ 8.6 to zero diffusion wavelength (ZDW) between the mode field diameter (MFD) of the value of the standardized range of 9.5㎛, 1300 to 1324 ㎚, and 0.092 ps / (nm 2 and lt; RTI ID = 0.0 &gt; (km). &lt; / RTI &gt; Each of these values conforms to the G.652 standard.
On the other hand, as shown in Table III (below), the fiber has an effective blocking wavelength? Ceff greater than 1350 nm. As described above, the effective cut-off wavelength is measured as the wavelength at which the optical signal is no longer in the single mode after propagating the fiber in excess of 2 meters as defined in the sub-committee 86A of the IEC 60793-44 standard. This increased effective cut-off wavelength value results in a cable cut-off wavelength value (? Cc ) between 1250 and 1300 nm. The cable cut-off wavelength is measured as the wavelength after the 22-meter fiber propagation as defined in subclause 86A of the IEC 60793-44 standard, where the optical signal is no longer a single mode. When the attenuation of the LP11 mode is 19.3 dB or more, the optical signal is in the single mode. Both the G.652 and G.657 standards give a maximum value of 1260 nm for the cable cut-off wavelength.
It is an object of the improvements disclosed herein to provide a fiber that can be used in all of the transmission bandwidth exhibited by the optical system, that is, the original bandwidth (OB) over 1260 nm to 1360 nm, UL: Ultra-long) bandwidths that can be used as single-mode propagation. The low cut-off wavelength ensures the possibility of using the fiber in all of the available bandwidth.
However, the simulation of Table III (below) shows that the LP11 mode of the higher order is propagated directly from the wavelength of 1260 nm according to the leakage mode. Thus, the fibers disclosed herein can be used in a single mode transmission beyond the original bandwidth (OB: 1260 to 1360 nm).
Table III (below) shows some of the cut-off wavelength values of the fibers according to the present invention. The first column of Table III repeats the criteria of Table I.
The Theoretical Fiber Cutoff column provides the theoretical cutoff wavelength value and corresponds to the transition wavelength between the propagated wave in the LP11 mode and the propagation in the leakage mode in the LP11 mode do. To process wavelengths beyond this effective cut-off wavelength, the LP11 mode is propagated in leaky mode.
The "Standard Fiber Cutoff" column corresponds to the effective cut-off wavelength (λ ceff ) as defined in subclause 86A of the IEC 60793-1-44 standard.
The "5 m Fiber Cutoff" heat corresponds to the cut-off wavelength in which the optical signal is measured as a wavelength that is no longer a single mode after fiber propagation in excess of 5 meters. Therefore, this value corresponds to the effective cut-off wavelength measured after fiber propagation in excess of 5 meters instead of 2 meters of fiber.
The "Standard Cable Cutoff" column corresponds to the cable cut-off wavelength λ cc as defined in subclause 86A of the IEC 60793-1-44 standard. According to the recommendation of the subclause 86A of the IEC 60793-1-44 standard, the cable cut-off wavelength (λ cc ) is obtained by placing the fiber in two 40 mm radial loops and placing the fiber on a mandrel with a radius of 140 mm And the rest (i. E., 21.5 meters of fiber).
The "Straight Cable Cutoff" row refers to a cable cutoff determined by placing the fibers in two loops each having a radius of 40 mm and placing the rest of the fiber (i.e., 21.5 meters of fiber) Wavelength.
The "LP11 LL @ 1260 (LP11 LL @ 1260 after 22m)" row after 22 m represents the leakage loss of the LP11 mode after propagating more than 22 meters of virtually straight fiber.
The "Length - 19.3 dB LP11 LL @ 1260 nm" column shows the length of fiber required to achieve leakage loss of the LP11 mode, which is equal to 19.3 dB, keeping the fiber virtually straight. This represents the distance in which the virtually linearly arranged fibers within the meaning of the G.652 and G.657 standards are in single mode.
In Table III, the standard effective cut-off wavelength (λ ceff ) measured according to the recommendation of subclause 86A of the IEC 60793-1-44 standard is greater than 1350 nm. Similarly, in Table Ⅲ, the standard cable cut-off wavelength (λ cc) measured according to the standard of the lower committee 86A of the IEC 60793-44 standard, imposed by the ㎚ between 1250 to 1300 ㎚, i.e., G.652 and G.657 standards Is often greater than the limit of 1260 nm.
However, in Table III, the LP11 mode nevertheless significantly attenuates from the wavelength of 1260 nm. In fact, the "theoretical" blocking wavelength is less than 1250 nm. Thus, the higher order LP11 mode propagates in the leakage mode regime at the main wavelength, and only the basic mode is kept guided in the inventive fiber from a wavelength of 1260 nm.
Likewise, in Table III, the fiber cutoff wavelength is significantly reduced after propagation within only 5 meter fibers. Thus, the cut-off wavelength at which the optical signal is measured as a wavelength that is no longer a single mode after propagation in excess of 5 meters of fiber is between 1300 nm and 1400 nm for the fiber according to the present invention.
Table III also clearly shows that the LP11 mode has already attenuated after 22 meters of propagation. In particular, the attenuation of the LP11 mode in the fiber 10 according to the present invention is greater than the attenuation of the LP11 mode in the SSMF fiber when the fibers are virtually arranged in a straight line. In fact, for SSMF fibers, it is bend to make the LP11 mode significantly attenuated. Thus, the fiber has an attenuation of the LP11 mode exceeding 5 dB after 22 meters propagation in the straight fiber at a wavelength of 1260 nm.
Table III also shows that attenuation of at least 19.3 dB of the LP11 mode is achieved relatively quickly after propagating below 90 meters instead of 22 meters imposed by the standard.
Thus, strictly obeying the G.652 and G.657 standards in terms of cut-off wavelengths means that the higher-order LP11 mode is sufficiently attenuated from the wavelength of 1260 nm so as not to impair the quality of the propagation of the fundamental mode .
Also, an increase in the effective cut-off wavelength causes the value of the MAC to increase as defined above, resulting in a reduction in the bending loss.
Table IV (below) shows the flexural loss values of the preferred embodiments of the fiber as disclosed herein. The first column of Table IV repeats the criteria of Table I. The next four columns show the flexural loss values (PPC) for each of the curvature radii of 15, 10, 7.5, and 5 mm at a wavelength of 1550 nm. The next four columns show the flexural loss values (PPC) for each of the curvature radii of 15, 10, 7.5, and 5 mm at a wavelength of 1625 nm.
The last column has a Factor of Merit (FOM) indicating the order of magnitude of the increase in flexural loss by the fiber according to the invention, against the limit imposed by the G.657B standard. Thus, the FOM of Table IV is defined as the average of the ratio between the flexural loss of the inventive fiber for each curvature radius measured and the upper limit imposed by the G.657B standard.
Table IV shows the bending loss limits imposed by the G.657B standard at the wavelengths of 1550 nm and 1625 non-meters for each curvature radius in the first line.
In Table IV, the flexural losses of the fiber corresponding to the profile according to the invention are obviously less than the limits imposed by the G.657B standard.
Thus, the fibers described above have a transmittance of less than 0.25 x 10 -3 dB / turn for a radius of curvature of 15 mm compared to the limit of 3 x 10 -3 dB / turn imposed by the G.657B standard at a wavelength of 1550 nm And has a bending loss. The fiber has a flexural loss of less than 7.5 x 10 -3 dB / turn for a radius of curvature of 10 mm, compared to a limit of 0.1 dB / turn imposed by the G.657B standard. The bending loss is less than 0.05 dB / turn for a radius of curvature of 7.5 mm and less than 0.15 dB / turn for a radius of curvature of 5 mm, compared to the limit of 0.5 dB / turn imposed by the G.657B standard.
The bending loss of the 1550 nm wavelength in the fiber according to the invention was imposed by an element larger than 10X compared to the limit of the G.657B standard.
Likewise, the fiber according to the present invention exhibits 1.5 x 10 -3 dB / turn for a radius of curvature of 15 mm, compared to the limit of 10 x 10 -3 dB / turn imposed by the G.657B standard for a wavelength of 1625 nm. Of the bending loss. The bending loss is less than 25 x 10 -3 dB / turn for a radius of curvature of 10 mm, compared to the limit of 0.2 dB / turn imposed by the G.657B standard. The fiber has a flexural loss of less than 0.08 dB / turn for a radius of curvature of 7.5 mm and a flexural loss of less than 0.25 dB / turn for a radius of curvature of 5 mm, compared to a limit of 1 dB / turn imposed by the G.657B standard Loss.
The flexural loss of the 1625 nm wavelength in the fiber according to the present invention was improved by 10 elements compared to the limit of the G.657B standard. Within the framework of the industrial manufacture of optical fiber preforms, a conformity test relative to the standard is performed taking into account only the important features shown in the standard. Therefore, when the G.657B standard imposes a limit of 0.01 dB / turn at a wavelength of 1625 nm for a radius of curvature of 15 mm, the manufacturer shall specify a curvature loss of 0.014 dB / turn at this wavelength for this radius of curvature Allow. Therefore, a curvature loss of less than 1.5 x 10-3 dB / turn for a radius of curvature of 15 mm is at least 10 times better than the limit imposed by the (i.
The column FOM of Table IV clearly improves the bending loss of the fibers of the present invention compared to conventional BIF fibers corresponding to the requirements of the G.657B standard.
The fibers disclosed herein are suitable for use in an optical system mounted in an FTTH type particle home, where the fiber meets large bending stresses due to miniaturization of the optical box or fiber retention instead of staples. The fiber can be placed in a compact optical box in particular. In fact, the optical fibers may be arranged with a radius of curvature of less than 15 mm, e.g., a radius of curvature of about 5 mm. Fiber is compatible with fiber in existing systems, especially in terms of MFD for good fiber-to-fiber bonding. The increase in blocking wavelength is not detrimental due to the large attenuation of the LP11 mode from the wavelength of 1260 nm.
Quot; Microbend Resistant Optical Fiber (Overton) "and co-assigned U.S. Patent Application No. 61 / 041,484 entitled" Microbend Resistant Optical Fiber (Overton) ", each of which is incorporated herein by reference in its entirety, Glass fibers that are not susceptible to bending (e.g., single-mode glass fibers of Draka Comteq available under the trade designation BendBrightXS®) and single-mode glass fibers with very low modulus (For example, DSM Desotech's UV-curable urethane acrylate product available under the trade name DeSolite (R) DP 1011), an exceptionally low loss optical fiber is achieved At least 10 times less microbend sensitivity compared to single mode fiber employing a coating system). Accordingly, it is also within the scope of the present invention to employ the coatings disclosed in U. S. Patent Nos. 60 / 986,737 and 61 / 041,484 with the single mode optical fiber of the present invention.
In this regard, according to IEC's fixed diameter sandpaper drum test (ie, IEC TR6222, Method B, 40-micron grade sandpaper), which provides microbending stress conditions affecting single mode fibers at room temperature, . The IEC TR6222 Microbending Sensitivity Technology report and standard test procedures (e.g., IEC TR6222, Method B (Sandpaper Drum of Fixed Diameter) and Method D (basketweave)) are incorporated herein by reference in their entirety.
This application also includes, by way of reference, the following co-assigned patents, patent applications, and patent application publications, each representing an optical fiber: U.S. Patent No. 4,838,643 entitled " Single Mode Bend Insensitive Fiber for Use in Fiber Optic Guidance Applications " Hodges et al., U.S. Patent Application Publication No. 2007/0127878 A1 and related U.S. Patent Application No. 11 / 556,895 entitled " Single Mode Optical Fiber "(de Montmorillon et al.); U.S. Patent Application Publication No. 2007/0280615 A1 and related U.S. Patent Application No. 11 / 697,994 entitled "Singel Mode Optical Fiber" (de Montmorillon et al.); U.S. Patent No. 7,356,234 and related U.S. Patent Application Publication No. 11 / 743,365 entitled "Chromatic Dispersion Compensating Fiber" (de Montmorillon et al.); U.S. Patent Application Publication No. 2008/0152288 A1 and related U.S. Patent Application No. 11 / 999,333 entitled "Optical Fiber" (Flammer et al.); And U.S. Patent Application No. 61 / 101,337 entitled "Single Mode Optical Fiber" (de Montmorillon et al.).
The optical fiber according to the present invention may further include at least one coating layer (e.g., a primary coating and a secondary coating). At least one of the coating layers (usually a secondary coating) is colorized and / or has other indications to help identify individual fibers. Alternatively, a third ink layer may surround the primary and secondary coatings.
The optical fiber according to the present invention may be developed in various structures such as the structure of an example described below.
For example, one or more inventive fibers may be sealed within the buffer tube. For example, the optical fiber may be deployed in either a single fiber loose buffer tube or a multi-fiber loose buffer tube. In the latter, a plurality of optical fibers may be bundled within a buffer tube or other structure. In this regard, within a multi-fiber loose buffer tube, fiber sub-bundles can be separated into binders (e.g., each fiber sub-bundle is sealed to a binder). In addition, fan-out tubing can be fitted at the end of this loose buffer tube to directly terminate loose buffered optical fibers in field mounted connectors.
As another example, the buffer tube may tightly wrap the outermost optical fiber coating (i.e., the densely buffered fiber), or otherwise encircle the outermost optical fiber coating or ink coating, and may be between about 50 and 100 microns (I. E., Semi-tightly buffered fibers) of the &lt; / RTI &gt;
In an electronically dense buffered fiber, buffering is formed by coating an optical fiber with a curable composition (e.g., an ultraviolet curing material) or a thermoplastic material. The outer diameter of the dense buffer tube is typically less than about 1000 microns (e.g., about 500 microns or about 900 microns) regardless of whether the buffer tube is formed of a hardenable or non-hardenable material.
In the latter semi-tightly buffered fiber, a lubricant may be included between the optical fiber and the buffer tube (e.g., providing a gliding layer).
As is known to those skilled in the art, one example of a buffer-tube sealing optical fiber as disclosed herein is a polyolefin (e.g., polyethylene or polypropylene) including fluorinated polyolefin, a polyester (e.g., polybutylene terephthalate) Amides (e.g., nylon), and other polymeric materials and mixtures thereof. Generally, the buffer tube may be formed of one or more layers. The layers may be homogeneous, or may contain mixtures or compounds of various materials within each layer.
In this regard, the buffer tube may be extruded (e.g., extruded polymeric material) or pultruded (e.g., drawn fiber reinforced plastic). As an example, the buffer tube may comprise a material (e.g., a directional material or a polysulfone material) to provide a high temperature chemical resistance.
The buffer tube typically has a circular cross-section, but the buffer tube may alternatively have an irregular or non-circular shape (e.g., an elliptical or trapezoidal cross-section).
Alternatively, one or more of the optical fibers of the present invention may be encapsulated within an enclosed or shielded metal tube by an outer protective sheath. In either structure, the intermediate buffer tube is not necessarily required.
A plurality of optical fibers as disclosed herein may be sandwiched, encapsulated, and / or bonded to an edge to form an optical fiber ribbon. The optical fiber ribbon can be divided into sub-units (e.g., twelve fiber ribbons that can be split into six fiber sub-units). In addition, a plurality of such optical fiber ribbons may be integrated to form a ribbon stack that may have various sizes and shapes.
For example, a rectangular stack of ribbons or a ribbon stack having a smaller number of optical fibers than the ribbon with the top and bottom optical fiber ribbons facing the center of the stack can be formed. Such an arrangement may be useful to increase the density of the optical element (e.g., optical fiber) in the buffer tube and / or cable.
In general, it is desirable to increase the degree of filling of the transmission elements within a buffer tube or cable that belongs to other limiting elements (e.g., cable or mid-span attenuation). The optical elements themselves can be designed to increase the packing density. For example, the optical fiber may have modified properties such as an improved refractive index profile, core, or cladding dimension, or a primary coating thickness and / or modulus to improve microbending and macrobending characteristics.
As an example, a rectangular ribbon stack with or without a central twist (i.e., "primary twist") may be formed. It will be appreciated by those skilled in the art that the ribbon stack is typically made of a rotating twist so as to bend the tube or cable without applying excessive mechanical stress to the optical fiber during winding, mounting, and use. As a structural modification, a rectangular ribbon stack may be further formed that is twisted (or untwisted) with a coiled configuration (e.g., a helix or wave configuration (e.g., sinusoidal) May have a regular "secondary" deformation.
As will be appreciated by those skilled in the art, such optical fiber ribbons may be located in other peripheral structures, such as cables with or without buffer tubes. In certain limiting factors (e.g., attenuation), it is desirable to increase the density of elements such as optical fibers or optical fiber ribbons in the buffer tube and / or optical fiber cable.
A plurality of buffer tubes (e.g., loose or ribboned fibers), including optical fibers, may be stranded disposed adjacent to and externally around the central strength member. This stranding can be performed in a one-way helical twist, known as "S" or "Z" stranding, or in Reverse Oscillated Lay Stranding, also known as "SZ" stranding. have. Stranding around the central strength member reduces optical fiber deformation when cable strain occurs during mounting and use.
One of ordinary skill in the art will appreciate the advantages of minimizing fiber strain on both the tension cable strain and the longitudinal compression cable strain during mounting or operating conditions.
With respect to the tensile cable deformation that may occur during mounting, the cable may be longer, while the optical fiber may move closer to the neutral axis of the cable, if not removed, to reduce the distortion transferred to the optical fiber. In longitudinal compression deformations that can occur at low operating temperatures due to shrinkage of cable components, the optical fibers move further away from the neutral axis of the cable and, if not removed, reduce the compressive strain that is transferred to the optical fiber.
In one variation, two or more substantially concentric layers of the buffer tube may be disposed about the central strength member. In yet another variation, a plurality of stranding elements (e.g., a plurality of buffer tubes stranded around the strength member) may be stranded together about the periphery of each other or around the primary central strength member.
Alternatively, a plurality of buffer tubes, including optical fibers (e. G., Loose or ribboned fibers), may be positioned exterior to adjacent the central strength member (i. Stranded or disposed intentionally on the central strength member and extending substantially parallel to the central strength member).
Alternatively, the optical fibers of the present invention may be positioned with a central buffer tube (i.e., the central buffer tube cable has a central buffer tube without a central strength member). This central buffer tube cable can position the strength member elsewhere. For example, a metallic or non-metallic strength member (e.g. GRP) may be disposed within the cable sheath itself and / or one or more high strength textile layers (e.g., aramid or non-aramid textile) (E.g., contrhelically) around the central buffer tube (i.e., within the internal space of the cable). Likewise, a strength member may be included in the case of the buffer tube.
In another embodiment, the optical fibers may be located in a slotted core cable. In a slotted core cable, individual optical fibers or optical fibers as fiber ribbons may be positioned in preformed helical grooves (i.e., channels) on the surface of the central strength member to form the slotted core unit. The slotted core unit may be sealed by a buffer tube. One or more of these slotted core units may be located within the slotted core cable. For example, a plurality of slotted core units may be spirally stranded about a central strength member.
Alternatively, the optical fibers may also be stranded in a maxitube cable design that is stranded around each other within a large multi-fiber loose buffer tube, rather than around a central strength member. That is, a large multiple cable loose buffer tube is disposed centrally within the maxi tube cable. For example, these maxi-tube cables can be deployed in optical ground wires (OPGW).
In yet another cabling embodiment, a plurality of buffer tubes may be stranded around each other without a central member. The stranded buffer tubes may be surrounded by a protective tube. The protective tube may function as an outer case of the optical fiber cable or may be further enclosed by an outer covering. The protective tube may be tightly or loosely surrounding the stranded buffer tubes.
As will be appreciated by those skilled in the art, additional elements may be included within the cable core. For example, a copper cable or other active transmission elements may be stranded or otherwise bundled within a cable sheath. Passive elements can also be located in the cable core, such as between the inner wall of the buffer tube and the sealed optical fibers. Alternatively, in one example, the passive elements can be located outside the buffer tube between the corresponding outer walls of the buffer tube and the inner wall of the cable jacket, or within the inner space of the cable without the buffer tube.
For example, to provide moisture shielding and / or to couple optical fibers to the surrounding buffer tubes and / or cable jacketing (e.g., through adhesive, friction, and / or compression) nonwoven, fabrics (e.g., tape), foams, or other materials including hygroscopic materials and / or coated with hygroscopic materials, such as SAP (Super Absorbent Polymer) and SAP powders ) May be employed. One example of a hygroscopic element is disclosed in co-assigned U.S. Patent Application Publication No. 2007/0019915 A1 and related U.S. Patent Application No. 11 / 424,112 entitled "Water Swellable Tape, Adhesive-Backed Coupling When Used Inside a Buffer Tube (Overton et al. "Each of which is incorporated herein by reference in its entirety.
It is also contemplated that one or more passive components (e.g., hygroscopic materials) may be provided with an adhesive (e.g., a hot-melt adhesive or a curable adhesive such as silicone acrylate crosslinked by exposure to actinic radiation) . An adhesive material may be used to couple the hygroscopic element to the optical fibers in the buffer tube. One example configuration of such elements is disclosed in co-assigned U.S. Patent Application Publication No. 2008/0145010 Al "Gel-Free Buffer Tube with Adhesively Coupled Optical Element (Overton et al.)" .
The buffer tubes (or buffer-tubeless cables) may also include thixotropic components between the optical fibers and the inner walls of the buffer tubes. For example, by filling the free space within the buffer tube with a moisture barrier oil-based filler grease, it helps to block moisture intrusion. In addition, the thixotropic filler grease mechanically (i.e., viscously) couples the optical fibers to the surrounding buffer tubes.
These thixotropic filled greases are relatively heavy and dirty, interfering with connection and splicing operation. Thus, the optical fibers of the present invention can be deployed in a dry cable structure (i.e., a grease-free buffer tube).
An example buffer tube structure without thixotropic filling grease is disclosed in co-assigned US patent application Ser. No. 12 / 146,588 entitled " Coupling Composition for Optical Fiber Cables (June 26, 2008, Parris et al. Are incorporated herein by reference. These buffer tubes employ a binding component comprised of a mixture of a polymeric weight elastomeric polymer (e.g., no more than about 35 weight percent) and a low temperature flowing oil (e.g., no less than about 65 weight percent). Unlike thixotropic filled grease, the binding component (e.g. employed as a tacky gel or foam) is usually dry and therefore less messy during splicing.
As will be appreciated by those skilled in the art, a cable-sealing optical fiber as disclosed herein can have a coating formed of various materials of various designs. The cable sheath may be made of, for example, polyethylene, polypropylene, polyvinyl chloride (PVC), polyamide (e.g., nylon), polyester (e.g., PBT), fluoroplastics (e.g., perfluoroethylene propylene, Fluoride, or polyvinylidene difluoride), and ethylene vinyl acetate. The coating and / or buffer tube material may also comprise a nucleating agent, a flame retardant, a smoke-retardant, an antioxidant, a UV absorber, and / or a plasticizer Of other additives.
The cable sheath may be a single jacket formed of a dielectric material (e.g., a non-conductive polymer) with or without supplemental structural components that can be used to improve the strength and protection provided by the cable sheath . For example, one or more metal layers (e.g., steel) tape with one or more dielectric jackets may form a cable sheath. Metallic or fiberglass reinforced rods (e.g., GRP) may also be included in the coating. Also, aramid, fiberglass, or polyester textile fabrics may be employed under various coating materials (e.g., between the cable sheath and the cable cores), for example, a ripcord may be located within the cable sheath.
Like the buffer tube, the optical fiber cable sheath typically has a circular cross-section, but the cable sheath may have a different, irregular or non-circular shape (e.g., oval, trapezoidal, or flat cross-section).
As an example, the optical fiber according to the present invention may be included in a single-fiber drop cable as employed in a multiple dwelling unit (MDU) application. In such a development, the cable jacketing must exhibit crush resistance, puncture resistance, thermal stability, and fire resistance as required by building the cord All. An exemplary material for such a cable jacket is thermally stable flame retardant polyurethane (PUR), which is mechanically flexible enough to protect the optical fiber and facilitate MDU mounting. Alternatively, a flame retardant polyolefin or polyvinyl chloride coating may be used.
Generally, as will be appreciated by those skilled in the art, the strength members are typically formed of rods or wires or fibers that are twisted or spirally wound, and other configurations are known to those skilled in the art.
As disclosed, an optical fiber cable including an optical fiber can be variously deployed including a drop cable, a distribution cable, a feeder cable, a trunk cable, and a stub cable, (E.g., temperature range, resistance to rupture, antimagnetic, and minimum bending radius).
These optical fiber cables can be mounted in ducts, micro ducts, forced air vents, or risers. As an example, an optical fiber cable can be mounted in a conventional duct or micro duct by pulling or blowing (e.g., using compressed air). An example cable attachment method is described in co-assigned U.S. Patent Application Publication No. 2007/0263960 entitled "Coomunication Cable Assembly and Installation Method (Lock et al.)" And U.S. Patent Application No. 12 / 200,095 entitled "Modified Pre- Method (Aug. 28, 2008, Griffioen et al.), Each of which is incorporated herein by reference in its entirety.
As described above, a buffer tube (e.g., loose or ribboned fiber) comprising an optical fiber may be stranded (e.g., around a central strength member). In such an arrangement, the protective outer covering of the optical fiber cable may have a textured outer surface that varies periodically in the longitudinal direction along the cable in a manner that repeats the stranded form of the underlying buffer tube. The woven profile of the protective outer sheath can improve the blowing performance of the optical fiber cable. The woven surface reduces the contact surface between the cable and the duct or micro duct and increases the friction between the blowing medium (e.g., air) and the cable. The protective outer sheath is formed of a material of low coefficient of friction, which can facilitate a blown installation. In addition, the protective outer sheath may be provided with a lubricant to further facilitate blown mounting.
In general, the outer cable diameter of the optical fiber cable is greater than about 70 to 80% of the inner diameter of the duct or micro duct (e.g., about 3,000 to 5,000 feet or more) to satisfactorily achieve long distance blowing performance do.
Compressed air can be used to mount the optical fiber in accordance with the present invention in a fiber system that blows air. In a blown fiber system, a network of unfilled cables or micro ducts is mounted before mounting the optical fiber. The optical fiber can then be blown as needed to the cable that is subsequently mounted to support the changing requirements of the network.
In addition, the optical fiber cable may be embedded directly in the ground or suspended from a pole or pylon as a cable of the air. The cables in the air may be self-supporting, seated, or wired to a support (e.g., a messenger wire or other cable). Examples of the optical fiber cables in air include Overhead Ground Wires (OPGW), All-Dielectric Self-Supporting (ADSS) cables, All-Lash (AD-Lash) cables and Figure- Each is known to the person skilled in the art. The figure-8 cable and its design can be directly embedded or mounted in the duct and optionally can include a toning element, such as a metal wire, so that it can be detected by a metal detector.
In addition, the optical fiber may be further protected by an outer cable sheath, but the optical fiber itself may be further strengthened to include the optical fiber in the breakout cable, allowing for individual routing of the individual optical fibers.
In order to effectively employ the optical fiber of the present invention in a transmission system, a connection is required at various points in the network. Fiber optic connections typically consist of fusion splicing, mechanical splicing, or mechanical connectors.
Attachment ends of the connector may be mounted at the end of the fiber at the factory or in the field (e.g., at a network location) prior to installation into the network. The ends of the connector are in-situ contacted to connect the fibers together or to connect the fibers to passive or active components. For example, a particular fiber optic cable assembly (e.g., a furcation assembly) can separate individual optical fibers from multiple fiber optic cables and transfer them to the connector in a secure manner.
The development of such an optical fiber cable may include supplementary equipment. For example, an amplifier may be included to improve the optical signal. A diffusion compensation module may be mounted to reduce the effects of polychromatic diffusivity and polarization mode diffusivity. A splice box, a pedestal, and a distribution frame may be similarly included. Additional components include, for example, a remote terminal switch, an optical network unit, an optical splitter, and a central office switch.
A cable comprising an optical fiber according to the present invention may be deployed for use in a communication system (e.g., networking or telecommunications). Communication systems include fiber-to-the-node (FTTN), fiber-to-the-telecommuncations (FTTE), fiber-to- curb, fiber-to-the-building (FTTB), and fiber-to-the-home (FTTH)
The optical fiber according to the present invention can also be used in other applications including, but not limited to, an optical fiber sensor or an illumination application (e.g., a lighting device).
In the description and drawings, exemplary embodiments of the invention are disclosed. The present invention is not limited to these exemplary embodiments. Unless otherwise noted, certain terms have been used in a generic and descriptive sense, not for limitation.
1 is a cross-sectional view of a single mode fiber showing a cladding layer at a corresponding radius extending from the center.
FIG. 2 is a view showing a nominal refractive index profile of the single mode fiber of FIG. 1 according to the present invention.
10: Fiber
11: center core
12: Intermediate cladding
13: dimple cladding
14: External optical cladding
1. A single mode optical fiber in which a bending loss is reduced in a refractive index profile measured at a radius extending from a center of an optical fiber toward an external optical cladding,
A center core having a radius r 1 and a refractive index difference DELTA n 1 between the optical cladding and positive (+);
The radius (r 2) and refractive index (△ n 1) than the intermediate cladding having a refractive index difference (△ n 2) of the positive (+) with small optical cladding of the core, wherein the refractive index difference (△ n 2) 0.1 x 10 -3 and 0.6 x 10 -3 ; And
And a depression trench having a radius r 3 and a refractive index difference DELTA n 3 between the optical cladding and the negative,
The area (V 03 ) of the recess trench defined by the following equation is
Between -55.0 × 10 -3 μm and -30.0 × 10 -3 μm,
The volume integral (V 13 ) of the depression trench defined by the following equation is
Between -1200 × 10 -3 μm 2 and -750 × 10 -3 μm 2 ,
The optical fiber has an MFD (Mode Field Diameter) between 8.6 μm and 9.5 μm at a wavelength of 1310 nm and has a bending loss of less than 0.25 × 10 -3 dB / turn for a radius of curvature of 15 mm at a wavelength of 1550 nm And has a flexural loss of less than 0.15 dB / turn for a radius of curvature of 5 mm at a wavelength of 1550 nm,
Mode optical fiber in which the LP11 mode of the optical fiber is attenuated to 19.3 dB at a wavelength of 1260 nm at a length of less than 90 meters.
(V 01 ) of the center core defined by the following expression
A single mode optical fiber having a thickness of 20.0 x 10 -3 m and a thickness of 23.0 x 10 -3 m.
Further comprising an effective blocking wavelength (? Ceff ) greater than 1350 nm,
Wherein the effective cut-off wavelength (? Ceff ) is measured as a wavelength at which the optical signal enters the single mode after propagation of the optical fiber exceeding 2 meters.
A single mode optical fiber further comprising a bending loss of less than 7.5 x 10 -3 dB / turn for a radius of curvature of 10 mm at a wavelength of 1550 nm.
A single mode optical fiber further comprising a bending loss of less than 25 x 10 -3 dB / turn for a radius of curvature of 10 mm at a wavelength of 1625 nm.
Further comprising a cable cut-off wavelength between 1250 nm and 1300 nm, wherein the cable cut-off wavelength is a wavelength at which the attenuation of the LP11 mode is 19.3 dB or more after propagation of the optical fiber exceeding 22 meters.
Further comprising a theoretical cut-off wavelength of 1250 nm or less, wherein the theoretical cut-off wavelength is a wavelength at which the LP11 mode propagates in a leaky mode.
Wherein the center core has a single mode with at least one of a radius r 1 between 3.8 and 4.35 μm and a refractive index difference Δ n 1 between the optical cladding between 5.3 × 10 -3 and 5.7 × 10 -3 Optical fiber.
Wherein the intermediate cladding has a radius r 2 between 8.5 and 9.7 μm.
Wherein the depression trench has a radius (r 3 ) between 13.5 탆 and 16 탆.
Between 1300 ㎚ and 1324 ㎚ zero multicolor diffusion wavelength (ZDW), and 0.092 ps / (nm 2 and km) single mode which is less than the inclusion of at least one of a zero multicolor diffusion slope (ZDS) in multicolor diffusion wavelength more zero Optical fiber.
An optical box for accommodating at least a part of the optical fiber according to claim 1 or 2, wherein the optical fiber has a radius of curvature of less than 15 mm.
An optical fiber system of a subscriber premises (FTTH) comprising at least a part of the optical fiber according to claim 1 or 2.
Mode optical fiber further comprising a bending loss of less than 0.25 dB / turn for a radius of curvature of 5 mm at a wavelength of 1625 nm.
The depressed trench has a radius (r 3), a theoretical cut off of less than 15 ㎛ wavelength, and -10.0 x 10 -3 and -5.0 x 10 -3 at least one of a refractive index difference (△ n 3) with the optical cladding between Mode optical fiber.
An optical box for accommodating at least a part of the optical fiber according to claim 1 or 2, wherein the optical fiber has a radius of curvature of 5 mm.
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