High-bandwidth bend-insensitive multimode optical fiber

Abstract

A high-bandwidth bend-insensitive multimode optical fiber includes a core and a cladding. A refractive index profile of the core has a parabola shape and a distribution index thereof is . The core has a radius of 23-27 m. A maximum relative refractive index difference of a central position of the core is 0.9%-1.2%. The core is a germanium-fluorine co-doped silicon dioxide glass layer. The central position of the core has a minimum amount of fluorine doped, and a mass percentage of fluorine content is C.sub.F,min. A mass percentage of fluorine content of the core changes with the radius according to a function. The cladding successively comprises an inner cladding, a trench cladding, and an outer cladding from inside to outside. The optical fiber reduces bandwidth-wavelength sensitivity while improving bandwidth performance; is compatible with existing OM3/OM4 multimode optical fibers, and support wavelength-division multiplexing technology in a wavelength range of 850-950 nm.

Claims

1. A high-bandwidth bend-insensitive multimode optical fiber, comprising a core and a cladding, wherein: a refractive index profile of the core has a parabola shape and a distribution index thereof is ; the core has a radius R1 of 23 to 27 m, a maximum relative refractive index difference 1.sub.max of a central position of the core is 0.9% to 1.2%, and the core is a germanium-fluorine co-doped silicon dioxide glass layer; the central position of the core has a minimum amount of fluorine doped with a mass percentage of fluorine content being C.sub.F,min, and the mass percentage of the fluorine content of the core changes with a radial position r from the central position of the core according to a following function: $C_F\left(r\right)=C_{F,\min }+C_F^{}\frac{r}{R1}\left(k-\frac{r}{R1}\right),$ wherein k is a constant in a range from 1 to 2.5, C.sub.F is in a range from 310.sup.3 to 1210.sup.3, and the radial position r varies from the central position r=0 to an edge r=R1 of the core, and the mass percentage C.sub.F,min of the fluorine content of the central position of the core is in a range from 0.410.sup.3 to 110.sup.3, and the distribution index of the refractive index profile of the core is in a range from 1.9 to 2.2; and the cladding successively comprises an inner cladding, a trench cladding, and an outer cladding from inside to outside.

2. The high-bandwidth bend-insensitive multimode optical fiber according to claim 1, wherein the inner cladding has a single side width (R2R1) of 3.0 to 6.0 m and a relative refractive index difference 2 of 0.05% to 0.05%; the trench cladding has a single side width (R3R2) of 5.0 to 8.0 m and a relative refractive index difference 3 of 1.0% to 0.4%; and the outer cladding is a pure silicon dioxide glass layer.

3. The high-bandwidth bend-insensitive multimode optical fiber according to claim 1, wherein DMD of the optical fiber at a wavelength of 850 nm meets following standards: DMD Inner Mask (5 to 18 m) and DMD Outer Mask (0 to 23 m) are both smaller than or equal to 0.14 ps/m; and DMD Interval Mask is smaller than or equal to 0.11 ps/m.

4. The high-bandwidth bend-insensitive multimode optical fiber according to claim 1, wherein the optical fiber has a numerical aperture of 0.185 to 0.215.

5. The high-bandwidth bend-insensitive multimode optical fiber according to claim 1, wherein the optical fiber has a bandwidth equal to or larger than 3500 MHz-km at a wavelength of 850 nm, has a bandwidth equal to or larger than 2300 MHz-km at a wavelength of 950 nm, and has a bandwidth equal to or larger than 500 MHz-km at a wavelength of 1300 nm.

6. The high-bandwidth bend-insensitive multimode optical fiber according to claim 1, wherein the optical fiber has an effective-mode bandwidth equal to or larger than 4700 MHz-km at a wavelength of 850 nm, and has an effective-mode bandwidth equal to or larger than 3400 MHz-km at a wavelength of 875 nm.

7. The high-bandwidth bend-insensitive multimode optical fiber according to claim 6, wherein the optical fiber has an effective-mode bandwidth equal to or larger than 2900 MHz-km at a wavelength of 900 nm, has an effective-mode bandwidth equal to or larger than 2800 MHz-km at a wavelength of 925 nm, and has an effective-mode bandwidth equal to or larger than 2500 MHz-km at a wavelength of 950 nm.

8. The high-bandwidth bend-insensitive multimode optical fiber according to claim 1, wherein: when the optical fiber bends 2 circles with a bending radius of 7.5 mm at a wavelength of 850 nm, an additional bending loss caused thereby is smaller than 0.2 dB; and when the optical fiber bends 2 circles with a bending radius of 7.5 mm at a wavelength of 1300 nm, an additional bending loss caused thereby is smaller than 0.5 dB.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically shows a relation between bandwidth of conventional OM3/OM4 multimode optical fibers and wavelength thereof;

(2) FIG. 2 schematically shows a refractive index profile of an optical fiber of the present disclosure;

(3) FIG. 3 schematically shows a refractive index profile of a core of an optical fiber in Embodiment 1 and a doping amount of F in the core, which is a comparative embodiment of the present disclosure;

(4) FIG. 4 schematically shows a relation between bandwidth of the optical fiber in Embodiment 1 and wavelength thereof;

(5) FIG. 5 schematically shows a refractive index profile of a core of an optical fiber in Embodiment 2 and a doping amount of F in the core;

(6) FIG. 6 schematically shows a relation between bandwidth of the optical fiber in Embodiment 2 and wavelength thereof;

(7) FIG. 7 schematically shows a refractive index profile of a core of an optical fiber in Embodiment 3 and a doping amount of F in the core; and

(8) FIG. 8 schematically shows a relation between bandwidth of the optical fiber in Embodiment 3 and wavelength thereof.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(9) The present disclosure will be further explained with reference to the following detailed embodiments.

Embodiment 1

(10) The optical fiber comprises a core and a cladding. A refractive index profile of the core has a parabola shape and a distribution index a thereof is 2.01. The core has a radius R1 of 25.3 m, and a maximum relative refractive index difference 1.sub.max of a central position of the core is 0.98%. The core is GeF co-doped. A mass percentage C.sub.F of F content of the core distributed along the radius is a fixed value 310.sup.3. The cladding successively comprises an inner cladding, a trench cladding, and an outer cladding from inside to outside. The inner cladding has a radius R2 of 29.7 m and a relative refractive index difference 2 of 0.02%. The trench cladding has a radius R3 of 35.9 m and a relative refractive index difference 3 of 0.55%. Measurement results of structure and properties of the obtained optical fiber are shown in Table 1. FIG. 3 schematically shows a refractive index profile of the optical fiber and a doping amount of F in the core. The doping amount of F remains unchanged from the center of the core of the optical fiber to the edge thereof. FIG. 4 schematically shows a relation between bandwidth of the optical fiber and wavelength thereof. The optical fiber can satisfy high bandwidth performance transmission at a conventional window of 850 nm. However, the bandwidth of the optical fiber has a high sensitivity of changing as the wavelength changes, and sharply decreases at a window of 950 nm, which fails to satisfy the requirement for application of the WDM technology in a wavelength range of 850 to 950 nm.

Embodiment 2

(11) A multimode optical fiber manufactured according to the technical solution of the present disclosure.

(12) The optical fiber comprises a core and a cladding. A refractive index profile of the core has a parabola shape and a distribution index a thereof is 2.06. The core has a radius R1 of 24.8 m, and a maximum relative refractive index difference 1.sub.max of a central position of the core is 1.12%. The core is a GeF co-doped silicon dioxide glass layer. A mass percentage of F content of the core distributed along the radius conforms to a following function:

(13) $C_F\left(r\right)=C_{F,\min }+C_F^{}\frac{r}{R1}\left(k-\frac{r}{R1}\right),$
wherein C.sub.F,min is 0, C.sub.F is 510.sup.3, and k is 2.3. The cladding successively comprises an inner cladding, a trench cladding, and an outer cladding from inside to outside. The inner cladding has a radius R2 of 28.8 m and a relative refractive index difference 2 of 0.01%. The trench cladding has a radius R3 of 34.6 m and a relative refractive index difference 3 of 0.42%. The outer cladding is a pure silicon dioxide glass layer and has a radius of 125 m. Measurement results of structure and properties of the obtained optical fiber are shown in Table 1. FIG. 5 schematically shows a refractive index profile of the optical fiber and a doping amount of F in the core. The doping amount of F increases from the center of the core of the optical fiber to the edge thereof. The doping amount of F has a minimum value at the center of the core and a maximum value at the edge of the core. FIG. 6 schematically shows a relation between bandwidth of the optical fiber and wavelength thereof.

Embodiment 3

(14) A multimode optical fiber manufactured according to the technical solution of the present disclosure.

(15) The optical fiber comprises a core and a cladding. A refractive index profile of the core has a parabola shape and a distribution index thereof is 2.09. The core has a radius R1 of 25.5 m, and a maximum relative refractive index difference 1.sub.max of a central position of the core is 1.09%. The core is a GeF co-doped silicon dioxide glass layer. A mass percentage of F content of the core distributed along the radius conforms to a following function:

(16) $C_F\left(r\right)=C_{F,\min }+C_F^{}\frac{r}{R1}\left(k-\frac{r}{R1}\right),$
wherein C.sub.F,min is 0.410.sup.3, C.sub.F is 810.sup.3, and k is 1.8. The cladding successively comprises an inner cladding, a trench cladding, and an outer cladding from inside to outside. The inner cladding has a radius R2 of 30.1 m and a relative refractive index difference 2 of 0.03%. The trench cladding has a radius R3 of 36.2 m and a relative refractive index difference 3 of 0.6%. The outer cladding is a pure silicon dioxide glass layer and has a radius of 125 m. Measurement results of structure and properties of the obtained optical fiber are shown in Table 1. FIG. 7 schematically shows a refractive index profile of the optical fiber and a doping amount of F in the core. The doping amount of F first increases and then decreases from the center of the core of the optical fiber to the edge thereof. The doping amount of F has a minimum value at the center of the core, reaches a maximum value at a certain area inside the core, and then decreases at the edge of the core. FIG. 8 schematically shows a relation between bandwidth of the optical fiber and wavelength thereof.

(17) TABLE-US-00001 TABLE 1 Parameters of Structures and Main Properties of Optical Fibers Embodiment 1 2 3 Parameters of Core 2.01 2.06 2.09 Optical Fiber C.sub.F, min 0 0.4 10.sup.3 Structure C.sub.F 5 10.sup.3 8 10.sup.3 k 2.3 1.8 1.sub.max (%) 0.98 1.12 1.09 2 (%) 0.02 0.01 0.03 3 (%) 0.55 0.42 0.6 R1 (m) 25.3 24.8 25.5 R2 (m) 29.7 28.8 30.1 R3 (m) 35.9 34.6 36.2 Parameters of Numerical Aperture 0.196 0.208 0.203 Optical Fiber DMD Inner Mask @850 nm (ps/m) 0.11 0.05 0.09 Properties DMD Outer Mask @850 nm 0.12 0.07 0.1 (ps/m) DMD Interval Mask @850 nm 0.09 0.04 0.07 (ps/m) OFL Bandwidth @850 nm 4240 9863 6253 (MHz-km) OFL Bandwidth@950 nm 1837 2750 3426 (MHz-km) OFL Bandwidth@1300 nm 546 588 619 (MHz-km) Effective-Mode 4534 11642 7015 Bandwidth@850 nm (MHz-km) Effective-Mode 3490 6741 5029 Bandwidth@875 nm (MHz-km) Effective-Mode 2913 4322 5477 Bandwidth@900 nm (MHz-km) Effective-Mode 2307 3697 6108 Bandwidth@925 nm (MHz-km) Effective-Mode 1959 2975 3960 Bandwidth@950 nm (MHz-km) Macro-Bending Additional Loss 0.08 0.15 0.02 Caused by 2 Circles of Bending With a Bending Radius of 7.5 mm @850 nm (dB) Macro-Bending Additional Loss 0.23 0.36 0.11 Caused by 2 circles of Bending With a Bending Radius of 7.5 mm @1300 nm (dB)

(18) It is shown by the experiments that, regarding multimode optical fibers with an profile, the peak position of a bandwidth-wavelength curve can be changed by changing the value of . However, the peak shape does not change much. In other words, the bandwidth-wavelength sensitivity of the optical fiber will not be obviously changed by adjusting the value of the optical fiber.

(19) However, the shape of the bandwidth-wavelength curve of the optical fiber can be changed by adjusting the F doping amount in a doping system of the core of the optical fiber. For example, the effects of adjusting the bandwidth-wavelength sensitivity of the optical fiber can be realized by changing the doping amount of F in the core or changing the distribution of the doping amount of F in the core along the core radius. By way of broadening peak width of the bandwidth-wavelength curve of the optical fiber, the high bandwidth performance of the optical fiber can be extended to a wider wavelength range, so as to be adapted to the requirement for application of the WDM technology.

(20) In order to manufacture multimode optical fibers with high bandwidth performance, graded-index distribution of the core needs to be precisely controlled. The optical fiber of the present disclosure has special requirements for the doping amount of F in the core. In-tube deposition methods such as plasma chemical vapor deposition (PCVD) and modified chemical vapor deposition (MCVD) can better realize precise control of the refractive index distribution of the core and the doping amount of F in the core. The in-tube deposition method refers to chemical vapor deposition on the inner wall of a liner tube. In this method, reaction gas comes in from one end of the liner tube, and when a heat source moves from the gas inlet end to the other end, a thin glass layer is formed on the inner wall of the liner tube. By reciprocating movements of the heat source along the axial direction of the liner tube, layer-by-layer deposition of thin glass layers is realized. By controlling the reaction gas inflow amount of each layer, precise control of the refractive index profile and the doping amount can be realized. Finally, an optical fiber preform is formed. Then the preform is placed on an optical fiber wire-drawing tower to be wire-drawn as an optical fiber.