CN111273394B - Multi-core multimode optical fiber - Google Patents
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- CN111273394B CN111273394B CN202010230186.5A CN202010230186A CN111273394B CN 111273394 B CN111273394 B CN 111273394B CN 202010230186 A CN202010230186 A CN 202010230186A CN 111273394 B CN111273394 B CN 111273394B
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Abstract
The invention relates to a multi-core multimode fiber, which comprises a plurality of core layers and a common outer cladding layer, and is characterized in that the number of the core layers is 2, 4 or 8, each core layer is uniformly distributed along the circumferential direction at equal intervals, the interval between 2 core layers of each adjacent core layer is 38-60 mu m, 4 or 8 core layers is 38-48 mu m, each core layer is coated with an inner cladding layer and a sunken cladding layer from inside to outside in sequence to form the multi-core homogeneous multimode fiber, the section of the refractive index of the core layer is parabolic, alpha is 1.9-2.1, the R1 of the core layer is 12-20 mu m, the Delta 1max of the core layer is 0.7-1.7%, the single-side width of the inner cladding layer is 0.5-2.5 mu m, Delta 2 is-0.4-0.0%, the single-side width of the cladding layer is 3-7 mu m, Delta 3 is-0.7% -0.9%, and the common outer cladding layer is a pure silicon dioxide layer. The invention not only can simultaneously support multimode transmission in the wavelength range of 850 nm-950 nm and single mode transmission in O wave band/C wave band, but also can optimize the optical fiber structure and viscosity matching to reduce attenuation, so that the comprehensive performances of crosstalk of the optical fiber, macrobend loss and microbend loss of each channel and the like are in good level.
Description
Technical Field
The invention relates to a space division multiplexing optical fiber for an optical fiber communication system, in particular to a multi-core multimode optical fiber.
Background
In recent years, with the rise of cloud computing, big data and mobile internet, a data center with efficient collaboration among servers and data processing capability becomes an obvious hotspot for increasing the total information amount and information density, so that an urgent requirement is put on the improvement of the interconnection communication rate of the data center. Because the data center interconnection communication has the characteristics of numerous equipment, complex wiring, high interface density and the like, the cost, the power consumption, the complexity and the like of system operation or maintenance are increased by only increasing the modulation bandwidth of a device and increasing the number of optical fiber links or light sources with different stable wavelengths, and therefore, the transmission rate of a single optical fiber/wavelength under the condition of limited bandwidth is increased by adopting a new modulation/multiplexing mode, and the method is regarded as an effective solution for improving the interconnection rate of the data center. On the basis of not increasing the number of optical fiber links, the multi-core optical fiber adopting Space Division Multiplexing (SDM) of multiple spatial channels can realize higher transmission capacity theoretically in unit power consumption, is more suitable for data center interconnection communication with higher requirements on power consumption, and further promotes the application potential of the multi-core optical fiber.
Two major factors currently limiting the application of multi-core optical fibers are bending loss and cross-talk between cores. Because the multi-core optical fiber comprises a plurality of fiber cores, the thickness from the fiber cores to the outer cladding is small, the bending loss is large at the moment, and the transmission performance of the multi-core optical fiber is influenced. On the other hand, energy coupling exists between fiber cores of the multi-core optical fiber, so that inter-core crosstalk is generated, and the transmission error rate is increased.
The existing research and invention patents of the multi-core optical fiber are concentrated on the multi-core single-mode optical fiber or the multi-core few-mode optical fiber, and the research on the multi-core multi-mode optical fiber is less. In a use scene of the data center, most transmission distances are short, and the transmission distance of the multimode optical fiber meets requirements; also, the problem of cross talk between cores in short spaces is not as severe as compared to long distance connections. Therefore, it is possible to prepare a multi-core multimode optical fiber supporting short-distance multimode transmission. The advantage of low cost and low power consumption of the VCSEL laser is benefited, and the short-distance transmission cost can be greatly reduced by combining the multi-core multimode fiber and the VCSEL laser. Furthermore, a multi-core fiber system can be directly connected with silicon photonic and InP chips to achieve high integration and high density interconnection.
On the basis of the multimode transmission multi-core optical fiber, the multimode optical fiber is matched with the single-mode optical fiber by optimizing the fundamental mode field diameter of the multimode optical fiber in combination with the principle of quasi-fundamental mode transmission. When a single-mode laser is adopted, the mode field matching center injection enables most energy to be injected into a fundamental mode, and therefore long-distance quasi-fundamental mode transmission is achieved. Multimode and single-mode transmission systems have various advantages and disadvantages, and in the current situation, it is reasonable to use multimode fibers and cheap VCSEL light sources to carry out short-distance networking construction; and the transmission of the quasi-fundamental mode is carried out in a long distance, and the complexity and the management cost can be reduced by adopting the same optical fiber. When the bandwidth is further upgraded, the single-mode transmission system can be directly transformed without the need of re-laying the optical cable. In addition, when the multimode fiber quasi-fundamental mode is transmitted, the mode field diameter is close to that of the single mode fiber, the actual distance between the optical fields of all fiber cores of the multi-core fiber is larger than the core distance, the crosstalk between the cores is small, and the space division multiplexing is facilitated.
Disclosure of Invention
For convenience in describing the summary of the invention, the following terms are defined:
core rod: a preform comprising a core layer and a partial cladding layer.
Radius: the distance between the outer boundary of the layer and the center point.
Refractive index profile: the relationship between the refractive index of the glass of an optical fiber or an optical fiber preform (including a core rod) and the radius thereof.
The relative refractive index difference, i.e., Δ i, is the relative refractive index difference between the layers of the fiber (excluding the outer cladding) and pure silica:
wherein ni is the refractive index at a position i away from the center of the fiber core; n0 is the refractive index of the pure silica material, and is also typically the refractive index of the outer cladding of the fiber.
The transmission distance that can be supported by multimode optical fibers is greatly limited by the intermodal dispersion that exists in multimode optical fibers, and in order to reduce the intermodal dispersion of the optical fibers, the refractive index profile of the core layer of the multimode optical fiber needs to be designed to have a refractive index profile that decreases continuously and gradually from the center to the edge, which is generally called an "alpha profile". I.e. a refractive index profile satisfying the following power exponential function:
wherein n1 is the refractive index of the optical fiber axis; r is the distance from the axis of the fiber; a is the optical fiber core radius; alpha is a distribution index; Δ 0 is the index of refraction of the core center relative to the cladding.
The relative refractive index difference contribution Δ Ge of the Ge doping of the core layer of the optical fiber is defined by the following equation:
wherein n isGeGe dopant for the core, in pure silica doped without other dopants, causes a change in the refractive index of the silica glass, where ncIs the refractive index of the outer cladding, i.e. the refractive index of pure silica.
The relative refractive index difference contribution Δ F of the optical fiber core layer F doping is defined by the following equation:
wherein n isFF dopant as core, in pure silica doped without other dopants, causes a change in the refractive index of the silica glass, where ncIs the refractive index of the outer cladding, i.e. the refractive index of pure silica.
Effective area of each mode of the fiber:
where E is the electric field associated with propagation and r is the distance from the axis to the point of electric field distribution.
In general, we test the mode field diameter MFD of an optical fiber by a far-field variable aperture method, and determine an equivalent formula of the mode field diameter as follows:
wherein λ is the test wavelength, D is the distance from the plane of the aperture stop to the end face of the optical fiber, x is the radius of the aperture stop, and a (x) is the complementary aperture power transfer function.
The technical problem to be solved by the invention is to provide a multi-core multi-ground optical fiber aiming at the defects in the prior art, which not only can simultaneously support multimode transmission in the wavelength range of 850nm to 950nm and single-mode transmission in an O wave band/C wave band, but also can optimize the optical fiber structure and viscosity matching to reduce attenuation, so that the comprehensive performances of crosstalk of the optical fiber, macrobend loss and microbending loss of each channel and the like are in good level.
The technical scheme adopted by the invention for solving the problems is as follows: the multi-core homogeneous multimode fiber comprises a plurality of core layers and a common outer cladding layer, and is characterized in that the number of the core layers is 2, 4 or 8, each core layer is uniformly distributed at equal intervals along the circumferential direction, the interval between 2 core layers of each adjacent core layer is 38-60 mu m, 4 or 8 core layers is 38-48 mu m, the inner cladding layer and a sunken cladding layer are sequentially coated outside each core layer from inside to outside to form the multi-core homogeneous multimode fiber, the section of the refractive index of the core layer is parabolic, the distribution index alpha is 1.9-2.1, the radius R1 of the core layer is 12-20 mu m, the maximum relative refractive index difference delta 1max of the center of the core layer is 0.7% -1.7%, the single-side width (R2-R1) of the inner cladding layer is 0.5-2.5 mu m, the relative refractive index difference delta 2 is-0.4% -0.0%, the single-side width (R3-R2) of the sunken cladding layer is 3-7 mu m, and the relative refractive index difference delta 3-0.7% -0.9%, the common outer cladding layer is a pure silicon dioxide layer.
According to the scheme, the plurality of core layers are uniformly distributed on the circumference at equal intervals, namely, the center of each core layer is equal to the center of the common outer cladding layer at equal intervals, the diameter of the common outer cladding layer of 2 or 4 core layers is 125 +/-1 mu m, and the diameter of the common outer cladding layer of 8 core layers is 180 +/-1.5 mu m.
According to the scheme, the relative refractive index difference delta 3 of the depressed cladding is-0.8% -0.9%.
According to the scheme, the core layer, the inner cladding layer and the depressed cladding layer of each core of the optical fiber are germanium-fluorine co-doped silica glass layers or fluorine-doped silica glass layers, wherein the fluorine-doped relative refractive index difference contribution amount is-0.02% -0.9%.
According to the scheme, the core layer is gradually changed in fluorine doping contribution amount, the absolute value of the fluorine doping contribution amount is increased from the center position of the core layer to the edge position of the core layer, the fluorine doping contribution amount delta F0 at the center of the core layer is-0.10% -0%, and the fluorine doping contribution amount delta F1 at the edge of the core layer is-0.45% -0.10%; the ratio of germanium and fluorine contributions of the inner cladding is 0.1< | delta Ge/delta F | <0.9, and the ratio of germanium and fluorine contributions of the depressed cladding is | delta Ge/delta F | < 0.1.
According to the scheme, the optical fiber has a bandwidth of 3500MHz-km or more than 3500MHz-km at a wavelength of 850nm, a bandwidth of 2000MHz-km or more than 2000MHz-km at a wavelength of 950nm, and a bandwidth of 500MHz-km or more than 500MHz-km at a wavelength of 1300 nm.
According to the scheme, the diameter of a fundamental mode field of each core of the optical fiber at the wavelength of 1310nm or 1550nm is 8-12 microns.
According to the scheme, at the wavelengths of 850nm and 1310nm, the inter-core crosstalk between any two adjacent cores (side cores) in the optical fiber is < -35dB/km, and the inter-core crosstalk between cores except the adjacent cores is < -55 dB/km; preferably, the intercore crosstalk between any two cores is < -40dB/km, and the intercore crosstalk between cores other than the adjacent cores is < -60dB/1 km.
According to the scheme, the attenuation of each channel of the optical fiber at the wavelength of 850nm is less than or equal to 3dB/km, and the attenuation of each channel at the wavelength of 1310nm is less than or equal to 1.2 dB/km. Preferably, the attenuation of each channel of the optical fiber at the wavelength of 850nm is less than or equal to 2.4dB/km, and the attenuation of each channel at the wavelength of 1310nm is less than or equal to 0.6 dB/km.
According to the scheme, the bending additional loss caused by winding the optical fiber for 2 circles at the wavelength of 850nm by the bending radius of 7.5 mm is less than 0.2 dB; bending additional losses of less than 0.5dB at 1300nm wavelength, caused by 2 turns with a 7.5 mm bending radius.
According to the scheme, the thickness of a single side of a coating layer of the optical fiber is more than or equal to 50 microns; the drawing tension of the optical fiber is 80-200 g.
The invention has the beneficial effects that: 1. in the 2-core or 4-core design, the standard 125-micron optical fiber diameter is adopted, the compatibility with the current device is kept, the occupied space of the standard 125-micron optical fiber diameter is the same as that of the common single-core optical fiber, and the 8-core design ensures the characteristics of high density, low crosstalk and low loss. 2. The reasonable core cladding proportion and the core cladding structure design enable the optical fiber to simultaneously support multimode transmission in a wavelength range of 850nm to 950nm and single-mode transmission in an O and/or C waveband. 3. The germanium-fluorine co-doped functional gradient material is adopted to design and a reasonable fiber core and cladding proportion structure, the germanium-fluorine proportion is strictly controlled, the viscosity matching in the optical fiber is reasonably designed, the defects and section distortion in the optical fiber preparation process are reduced, and the attenuation coefficient of the optical fiber is reduced. 4. The optical fiber sinking structure doped with fluorine deeply is designed, and the cross talk and macrobend loss between cores of the optical fiber are lower through the reasonable design of each layer section of the optical fiber, and the additional attenuation generated when the core layer is closer to the edge of the cladding layer is greatly reduced. 5. The optical fiber has good comprehensive performance parameters such as macrobend loss, microbend loss and the like of each channel in an application waveband. The short-distance signal transmission of a plurality of channels can be carried out by using the space division multiplexing technology, each mode has a low attenuation coefficient, and the space division multiplexing transmission of dense data center wiring can be supported. 6. The optical fiber is prepared by depositing a core rod by adopting a PCVD (plasma chemical vapor deposition) technology and then drawing wires by sleeving the outer sleeve, so that the optical fiber structure with a complex section can be prepared, various structural parameters of the optical fiber can be strictly controlled, and the optical fiber is suitable for large-scale production.
Drawings
Fig. 1 is a commercial VCSEL laser spot size distribution.
FIG. 2 is a schematic representation of a refractive index profile of a core in one embodiment of the invention.
FIG. 3 is a graph of core pitch versus cross-talk between cores, in accordance with one embodiment of the present invention.
Fig. 4 is a schematic cross-sectional structure of an embodiment of the present invention.
Fig. 5 is a schematic cross-sectional structure of a second embodiment of the present invention.
Fig. 6 is a schematic cross-sectional structure of a third embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
With further increase of transmission rate, the spot size of VCSEL lasers matched with multimode fibers tends to decrease. The spot sizes of the emitted light of different types of commercial multimode transceivers of different manufacturers, such as 10G-100G, 850 nm-950 nm, NRZ and PAM4, which are mainstream in the market, are tested, as shown in FIG. 1. The size of a light spot of light emitted by the VCSEL laser is 24-44 mu m after the light passes through the light path. The core diameter of the multimode fiber must be matched to the spot size, taking into account the fact that the fiber needs to be coupled to a transceiver during actual use. With the further increase of the transceiver speed, the light spot is likely to be further reduced, so that the radius range of the core layer is limited to 12-20 μm, and further limited to 13-17 μm.
On the basis, in order to ensure that the MFD can still be matched with that of the standard single-mode optical fiber in a larger core diameter range, the refractive index of the core layer needs to be increased. However, for multimode fibers, the larger the relative refractive index difference of the core layer, the more the intermodal dispersion is severe, and the smaller the transmission bandwidth is. In order to balance high bandwidth and coupling loss with multimode fiber/VCSEL laser, the invention ensures that the relative refractive index difference of the core layer is low, and simultaneously adjusts the relative refractive indexes of the core layer and the inner cladding layer to ensure the controllability of the mode field diameter. In addition, when the core cladding refractive index difference is large, the NA is also large, and the coupling efficiency with the optical module and the multimode optical fiber can be further ensured.
In the fiber profile design, the influence of the geometric parameters and relative refractive index in the profile design on the fundamental mode field diameter is calculated to influence the fiber fundamental mode LP01The mode field diameter of (a) includes the core diameter, the relative refractive index difference and a, the inner cladding thickness and the relative refractive index difference, the thickness and depth of the depressed cladding layer, and the like. Wherein LP is influenced01The mode field diameter of the mode is mainly due to the difference between the core diameter and the core cladding refractive index, the mode field diameter is proportional to the core diameter and inversely proportional to the difference between the relative refractive indexes of the core layer and the cladding layer, and the estimation formula is as follows:
the MFD of the fundamental mode of the actually prepared optical fiber is generally slightly smaller than that calculated by an empirical formula under the influence of factors such as a depressed cladding and deviation in the preparation process. Based on the formula, after the core diameter is determined according to the required matched laser or optical fiber, the range of delta 1 max-delta 2 of the required optical fiber can be calculated according to the required matched working waveband and mode field diameter. And then determining the appropriate core relative refractive index delta 1max and cladding relative refractive index difference delta 2 according to the matching (the coupling loss is too large when the difference is too large) with the refractive index of the optical fiber core to be matched and the high bandwidth condition. According to the doping condition, viscosity matching and bending resistance, the relative sizes of R2 and R3 are determined, and the required compatible laser or optical fiber can be prepared and simultaneously upgraded into a single-mode transmission compatible graded-index optical fiber in the future.
In order to make the multi-core fiber become a solution for data center reception, the number of cores of the multi-core fiber is preferably even, and is preferably 2, 4 or 8, and the multi-core distribution with central symmetry distribution is convenient for spin welding. The 2-core can support the bidirectional transmission of a single optical fiber, and the connection scheme of the 2-core is mature and low in cost. The 4 cores can realize 100Gb/s transmission of a single optical fiber and a single wavelength of 4 multiplied by 25Gb/s, and the 8 cores can realize 400Gb/s transmission of a single optical fiber and a single wavelength of 8 multiplied by 50G (PAM4) without using parallel transmission technologies such as SR4 or PSM4, thereby greatly reducing the density of optical fibers of the data center.
In order to reduce the crosstalk and attenuation among cores of the multi-core optical fiber, a fiber subsidence structure doped with fluorine deeply is designed outside the fiber core, and the additional attenuation generated when the core layer is close to the edge of the cladding layer is greatly reduced through the reasonable design of each layer section of the optical fiber. The depressed cladding had a width of 4 μm and a depth of-0.8% for one embodiment, and the relationship between the adjacent core pitch (pitch) and the nearest neighbor core crosstalk (XT) was theoretically calculated, as shown in FIG. 4. The intercore crosstalk decreases with increasing core pitch, with the intercore crosstalk (XT @850) for the higher order modes at 850nm being much greater than the intercore crosstalk (XT @1310) for the fundamental mode at 1310 nm. In the calculation process, under the condition of 850nm multimode transmission, the crosstalk between cores of a high-order mode is selected to be the maximum value. Assuming that the energy of each mode in the optical fiber is evenly distributed, the crosstalk of the lower order mode is very small, such as XT @850< XT @1310 of the fundamental mode, which is much smaller than-110 dB, so the crosstalk between cores of the actually prepared multi-core optical fiber is much smaller than the calculated value of XT @850, and sometimes even can be ignored. When designing a multi-core profile, the inter-core crosstalk in the quasi-fundamental mode transmission state is very low, and the main limiting factor is the inter-core crosstalk in the high-order mode in the multi-mode transmission state.
In addition, if the transmission distance of the data center is 98% within 150m, the crosstalk between cores of XT @850/150m will be reduced by about 8dB relative to XT @850/1km, and the crosstalk between cores of XT @850/300m will be reduced by about 5dB considering the use case of the very large data center by extending the transmission distance to 300 m. The crosstalk between cores during transmission needs to be less than-30 dB, more preferably less than-40 dB, and under the conditions, the core spacing is more than 38 micrometers.
The thickness of the core to the edge of the outer cladding of the multicore fiber needs to be large enough to ensure that the attenuation of the multicore fiber is small enough to reduce the bending loss and the additional loss, and at least needs to be larger than 10 μm, preferably larger than 15 μm, and more preferably larger than 20 μm. And the sinking cladding which is deeply doped with fluorine (-0.7% -0.9%) is combined, so that the attenuation, the bending loss and the crosstalk among cores of the multi-core optical fiber can be ensured to be low.
The core density of multicore optic fibre is high, and the thickness of its core and cladding is littleer than conventional optic fibre, and the wall thickness of prefabricated stick is on the thin side for a plurality of holes of annular distribution, consequently the wire drawing in-process, in order to ensure that multicore optic fibre's geometry can not take place too big skew, need guarantee that the material viscosity in the wire drawing process is higher, and wire drawing tension is 80 ~ 200g this moment.
The coating material of the optical fiber comprises but is not limited to epoxy acrylate or polyacrylate, and special coatings such as low-refractive-index coatings or high-temperature-resistant coatings can be used in some use scenes. In order to ensure the attenuation and mechanical properties, the unilateral thickness of the coating layer needs to be more than or equal to 50 μm.
A plurality of fiber cores of the multi-core optical fiber are uniformly distributed at equal intervals along the circumferential direction and are arranged in a ring shape, as shown in the attached drawing. The fiber core is a homogeneous multimode fiber, an inner cladding and a sunken cladding are sequentially coated outside each core layer from inside to outside, the radius of the core layer is R1, the relative refractive index difference of the core layer is delta 1, the radius of the inner cladding is R2, the relative refractive index difference of the inner cladding is delta 2, the radius of the sunken cladding is R3, and the relative refractive index difference of the sunken cladding is delta 3.
The structural configuration and the main performance parameters of the 5 embodiments of the optical fiber of the present invention are shown in table 1, wherein the performance parameters of the fiber cores are the average values of the plurality of fiber cores.
TABLE 1 structural arrangement and Main Performance parameters of the optical fibers of the examples
Claims (9)
1. A multi-core multimode fiber comprises a plurality of core layers and a common outer cladding layer, and is characterized in that the number of the core layers is 2, 4 or 8, each core layer is uniformly distributed along the circumferential direction at equal intervals, the interval between 2 core layers of each adjacent core layer is 38-60 mu m, 4 or 8 core layers is 38-48 mu m, the outer cladding layer and a sunken cladding layer are sequentially coated outside each core layer from inside to outside to form the multi-core homogeneous multimode fiber, the section of the refractive index of the core layer is parabolic, the distribution index alpha is 1.9-2.1, the radius R1 of the core layer is 12-20 mu m, the maximum relative refractive index difference delta 1max of the center of the core layer is 0.7% -1.7%, the single-side width (R2-R1) of the inner cladding layer is 0.5-2.5 mu m, the relative refractive index difference delta 2 is-0.4% -0.08%, the sunken single-side width (R3-R2) is 3-7 mu m, and the relative refractive index difference delta 3-0.9% -0.705, the common outer cladding layer is a pure silicon dioxide layer; the fundamental mode field diameter of each core of the optical fiber at the wavelength of 1310nm or 1550nm is 8-12 μm, the fundamental mode field diameter is in direct proportion to the core diameter and in inverse proportion to the relative refractive index difference between the core layer and the cladding, and the estimation formula is as follows:
2. the multi-core multimode fiber according to claim 1, wherein said plurality of core layers are equally spaced around a circumference, i.e. each core layer is equally spaced from the center of the common outer cladding, the diameter of the common outer cladding of said 2 or 4 core layers is 125 ± 1 μm, and the diameter of the common outer cladding of 8 core layers is 180 ± 1.5 μm.
3. The multimode optical fiber as claimed in claim 1 or 2, wherein said depressed cladding has a relative refractive index difference Δ 3 of-0.8% to-0.9%.
4. A multimode optical fiber as claimed in claim 1 or 2, characterized in that the core, the inner cladding and the depressed cladding of each core of said fiber are germanium-fluorine co-doped silica glass layers or fluorine-doped silica glass layers, wherein the fluorine-doped relative refractive index difference contribution is between-0.02% and-0.9%.
5. The multimode optical fiber as in claim 4, wherein said core layer is a graded fluorine doping contribution, the absolute value of the fluorine doping contribution increases from the center of the core layer to the edge of the core layer, the fluorine doping contribution Δ F0 at the center of the core layer is-0.10% to 0%, and the fluorine doping contribution Δ F1 at the edge of the core layer is-0.45% to-0.10%; the ratio of germanium and fluorine contributions of the inner cladding is 0.1< | delta Ge/delta F | <0.9, and the ratio of germanium and fluorine contributions of the depressed cladding is | delta Ge/delta F | < 0.1.
6. The multi-core multimode optical fiber according to claim 1 or 2, characterized in that said fiber has a bandwidth of 3500MHz-km or more at a wavelength of 850nm, a bandwidth of 2000MHz-km or more at a wavelength of 950nm, and a bandwidth of 500MHz-km or more at a wavelength of 1300 nm.
7. The multi-core multimode fiber according to claim 1 or 2, characterized in that at wavelengths of 850nm and 1310nm, the intercore crosstalk between any two adjacent cores in said fiber is < -35dB/km, and the intercore crosstalk between cores other than the adjacent cores is < -55 dB/km.
8. The multi-core multimode optical fiber according to claim 1 or 2, characterized in that said fiber has an attenuation of 3dB/km or less for each channel at a wavelength of 850nm and an attenuation of 1.2dB/km or less for each channel at a wavelength of 1310 nm.
9. The multi-core multimode fiber according to claim 1 or 2, characterized in that said fiber has a bend add loss of less than 0.2dB at a wavelength of 850nm resulting from 2 turns with a 7.5 mm bend radius; a bend additional loss of less than 0.5dB at a wavelength of 1300nm caused by 2 turns at a 7.5 mm bend radius; the drawing tension of the optical fiber is 80-200 g.
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| CN111273394A (en) | 2020-06-12 |
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