Chiral coupling core optical fiber and preparation method thereof

Abstract

The invention discloses a chiral coupling core optical fiber and a preparation method thereof. The glass part of the optical fiber comprises a central fiber core forming an optical waveguide structure and a wrapping layer wrapping the central fiber core. One or more satellite cores are arranged in the cladding, and the satellite cores periodically revolve around the central fiber core; the satellite core is provided with at least one adjustable satellite core, and the distance DI between the geometric center of the satellite core on the cross section and the geometric center of the central fiber core changes along with the difference of the axial position L of the cross section. According to the chiral coupling core optical fiber provided by the invention, the number of required satellite fiber cores is reduced, and the design and manufacturing difficulty of the chiral coupling core optical fiber is greatly reduced. According to the preparation method of the chiral coupling core optical fiber, the phase angle of the eccentric core rod is changed through rotation of the eccentric core rod, adjustment of the distance between the core layer of the eccentric core rod and the center of the preform rod is achieved, and flexible change of a satellite core and a center fiber core is achieved in the optical fiber drawing process.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical fibers, and more specifically, relates to a chiral coupled core optical fiber and a preparation method thereof. Background Art

[0002] Chiral coupled core fiber, also known as 3C fiber, consists of satellite core, central core and cladding. The satellite core rotates periodically around the central core. By adjusting the diameter of the satellite core, the size of the refractive index, the distance between the satellite core and the central core and the rotation period of the satellite core, the high-order mode in the central core and the mode in the satellite core are quasi-phase matched, so that the high-order mode in the central core is coupled to the satellite core and lost, thereby achieving large mode field single mode.

[0003] As the laser power increases further, in order to suppress the nonlinear effects in the optical fiber, the required mode field area of ​​the optical fiber becomes larger and larger. In the case of a large mode field, more high-order modes may be transmitted in the optical fiber. In order to achieve a large mode field single mode, more satellite cores are designed in the chiral coupled core diameter optical fiber to improve the beam quality. However, the design of more satellite cores increases the risk of fiber preform explosion and reduces the yield rate. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides a chiral coupled core optical fiber and a preparation method thereof, the purpose of which is to achieve the effect of coupling and attenuation with each high-order mode through a satellite core with an adjustable distance from the central fiber core, thereby reducing the number of satellite cores and thus reducing the design and manufacturing difficulty of the chiral coupled core optical fiber, thereby solving the technical problem that the existing chiral coupled core optical fiber adopts multiple satellite cores to achieve a single-mode large mode field, resulting in high design and manufacturing difficulty.

[0005] To achieve the above object, according to one aspect of the present invention, there is provided a chiral coupled core optical fiber, the glass portion of which includes a central core forming an optical waveguide structure and a cladding covering the central core;

[0006] One or more satellite cores are arranged in the cladding, and the satellite cores periodically revolve around the central fiber core;

[0007] The satellite core has at least one adjustable satellite core, and the distance I between the geometric center of the satellite core and the geometric center of the central fiber core in the cross section changes with the different axial positions L of the cross section.

[0008] Preferably, for the chiral coupled core optical fiber, the distance DI between the geometric center of the adjustable satellite core and the geometric center of the central core on the cross section of the optical fiber segment is within a preset range, and the total axial length thereof is greater than or equal to a preset threshold.

[0009] Preferably, for the chiral coupled-core optical fiber, the distance DI between the geometric center of the adjustable satellite core and the geometric center of the central core in the cross section changes periodically with the axial position L of the cross section.

[0010] Preferably, the chiral coupled core optical fiber, its adjustable satellite core revolves with an orbital radius R and an orbital pitch P, and rotates with a helical radius r and a helical pitch p; the orbital radius R is the distance between the helical center and the geometric center of the central fiber core on the cross section, the orbital pitch P is the optical fiber length corresponding to one circle of the helical center around the geometric center axis of the optical fiber, the helical radius r is the distance between the helical center and the geometric center of the adjustable satellite core on the cross section, and the helical pitch p is the optical fiber length corresponding to one circle of the geometric center of the adjustable satellite core around the geometric center axis of the helical.

[0011] Preferably, the chiral coupled core optical fiber has an orbital radius R of the adjustable satellite core between 10 and 50 μm, a helical radius r of the adjustable satellite core between 0 and 20 μm, an orbital pitch P of the adjustable satellite core less than 1 m, and a helical pitch p of the adjustable satellite core less than 1 m.

[0012] Preferably, the central core diameter d of the chiral coupled core optical fiber is c is 10 to 100 μm, and the satellite core size d c Less than 50μm, the size of the satellite core is smaller than the central core.

[0013] Preferably, the numerical aperture of the central core of the chiral coupled-core optical fiber is between 0.05 and 0.1, and the numerical aperture of the satellite core is between 0.02 and 0.5.

[0014] Preferably, the chiral coupled-core optical fiber has a cladding with a satellite core, and the satellite core is an adjustable satellite core; or

[0015] The cladding is provided with a plurality of satellite cores, wherein at least one satellite core is a regular polygon.

[0016] According to another aspect of the present invention, there is provided a method for preparing the chiral coupled core optical fiber, comprising the following steps:

[0017] (1) preparing a chiral coupled core optical fiber preform assembly, wherein the chiral coupled core optical fiber preform assembly comprises a nested eccentric core rod and an eccentric hole sleeve;

[0018] The eccentric core rod has an outer layer for forming a partial cladding and a core layer for forming an adjustable satellite core, and a radial distance D between the geometric center axis of the core layer and the geometric center axis of the outer contour of the eccentric core rod r It is the product of spiral radius r and stretch ratio, and its outer diameter D vIt is twice the product of the sum of half the adjustable satellite core size and the helical radius r and the stretching ratio;

[0019] The eccentric hole sleeve is a sleeve used to form a central fiber core and possible other satellite cores, and has an eccentric circular hole for inserting an eccentric core rod; the radial distance D between the center axis of the circular hole and the center axis of the outer contour of the eccentric hole sleeve is R is the product of the orbital radius R and the stretching ratio, and the aperture D h Slightly larger than the outer diameter of the eccentric mandrel;

[0020] (2) inserting the eccentric core rod into the eccentric hole sleeve as an optical fiber preform rod for drawing and forming, during which the phase angle of the eccentric core rod is adjusted by rotating the eccentric core rod, and when it is at a preset axial position, the distance di between the core layer geometric center of the eccentric core rod and the outer contour geometric center of the eccentric hole sleeve on the cross section is adjusted to be the product of the preset value of the distance DI between the geometric center of the adjustable satellite core and the geometric center of the central fiber core on the cross section here and the drawing ratio, so that the distance DI between the geometric center of the adjustable satellite core and the geometric center of the central fiber core on the cross section here of the drawn optical fiber is the preset value;

[0021] The phase angle θ of the eccentric core rod refers to the angle between the geometric center axis of the eccentric core rod and the geometric center axis of the outer contours of the core layer and the eccentric hole sleeve on the cross section of the optical fiber preform rod. Its size is determined according to the cosine theorem as follows:

[0022]

[0023] Where θ is the phase angle of the eccentric mandrel, D R D is the radial distance between the center axis of the circular hole and the center axis of the outer contour of the eccentric hole casing. r is the radial distance between the geometric center axis of the core layer of the eccentric core rod and the geometric center axis of the outer contour of the eccentric core rod, di is the distance between the geometric center of the core layer of the eccentric core rod and the geometric center of the outer contour of the eccentric hole sleeve on the cross section, DI is the distance between the geometric center of the adjustable satellite core and the geometric center of the central core on the cross section of the optical fiber, and DR is the stretching ratio.

[0024] Preferably, in the method for preparing the chiral coupled core optical fiber, the adjustable satellite core revolves with an orbital radius R and an orbital pitch P and rotates with a helical radius r and a helical pitch p, and step (2) determines the rotation speed V of the optical fiber preform according to the orbital pitch P and the drawing speed V. R , according to the spiral pitch p of the adjustable satellite core and the drawing speed V, the rotation speed V of the eccentric mandrel is determined r ;Specifically,

[0025] The rotation speed V of the optical fiber preform R The calculation method is as follows:

[0026] V R=V / P

[0027] Where, V is the drawing speed, V R is the rotation speed of the preform, generally in rpm, and P is the revolution pitch;

[0028] Rotation speed V of the eccentric mandrel r The calculation method is as follows:

[0029] V r =V / p

[0030] Where, V is the drawing speed, V r is the rotation speed of the eccentric mandrel, generally expressed in rpm, and P is the orbital pitch.

[0031] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0032] The chiral coupled core optical fiber provided by the present invention adopts a satellite core with an adjustable distance from the middle core to achieve coupling and attenuation of multiple high-order modes, reduce the number of required satellite cores, greatly reduce the design and manufacturing difficulty of the chiral coupled core optical fiber, and achieve large mode field single-mode output.

[0033] The method for preparing a chiral coupled core optical fiber provided by the present invention changes the phase angle of an eccentric core rod by rotating the eccentric core rod, thereby adjusting the distance between the core layer of the eccentric core rod and the center of the preform rod, and realizing flexible changes in the satellite core and the central core during the optical fiber drawing process. Both step adjustment and continuous adjustment are possible to achieve periodic spiral, and there is no need to change the axial structure of the preform rod, thereby greatly reducing the difficulty of preparing the preform rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the assembly of the eccentric core rod and the eccentric hole sleeve of the present invention;

[0035] Figure 2 is a schematic diagram of the fiber core end face design provided in Example 1 of the present invention;

[0036] Figure 3 is a schematic diagram of the fiber core end face design provided by Embodiment 2 of the present invention;

[0037] Figure 4 It is a schematic diagram of the fiber core end face design provided in Example 3 of the present invention.

[0038] In all the drawings, the same figure marks are used to represent the same elements or structures, wherein: 1 is an eccentric core rod, 11 is a core layer of the eccentric core rod, 2 is an eccentric hole sleeve, 21 is an eccentric hole sleeve for forming a high refractive index region of the central core, 01 is the central core, 02 is an adjustable satellite core, 03 is a cladding, and 04 is a square satellite core. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] The optical fiber includes a glass part and an organic coating part. The glass part of the chiral coupled core optical fiber provided by the present invention includes a central core forming an optical waveguide structure and a cladding covering the central core; one or more satellite cores are arranged in the cladding, and the satellite cores periodically revolve around the central core;

[0041] The satellite core has at least one adjustable satellite core, and the distance DI between the geometric center of the satellite core and the geometric center of the central fiber core in the cross section changes with the different axial positions L of the cross section.

[0042] In chiral coupled core optical fiber, satellite cores are distributed around the central core in a spiral shape. This chiral coupling structure allows high-order modes to be coupled into the satellite cores and generate high losses therein, while the fundamental mode is transmitted in the central core with extremely low losses. The design of 3C optical fiber achieves effective coupling and loss of high-order modes by satisfying the quasi-phase matching (QPM) condition. This involves precisely controlling the size of the satellite core, the radial distance from the central core to the satellite core, and the pitch of the satellite core's revolution around the central core, so that the high-order modes propagating in the central core match the satellite core, thereby coupling the high-order modes into the satellite core and losing them. The present invention cleverly utilizes the adjustment of the radial distance from the central core to the satellite core, so that it changes with the change of the axial position, thereby achieving the matching of the same satellite core to multiple different high-order modes. Therefore, the adjustable satellite core can achieve effective coupling and loss for multiple different high-order modes of the central core, simplifying the difficulty of optical fiber design while making the transmission mode in the large mode field central core closer to single mode.

[0043] In a specific chiral coupling structure, when other factors do not change, the radial distance between the central fiber core and the satellite core determines its ability to couple to a specific high-order mode. When matching different high-order modes, the radial distance between the central fiber core and the satellite core is different, that is, the distance DI between the geometric center of the adjustable satellite core and the geometric center of the central fiber core on the cross section changes with the different axial positions L of the cross section. The distance DI between the geometric center of the adjustable satellite core and the geometric center of the central fiber core on the cross section can be within a preset range to match a certain high-order mode. In order to make the adjustable satellite core match different high-order modes, by changing the distance between the satellite core and the central fiber core, different high-order modes can be directionally coupled and consumed. The distance DI between the geometric center of the adjustable satellite core and the geometric center of the central fiber core on the cross section is within a preset range of optical fiber segments, and the sum of their axial lengths is greater than or equal to a preset threshold, which can be expressed as:

[0044]

[0045] In the formula, l DI is the sum of the axial lengths of the fiber section where the distance DI between the geometric center of the adjustable satellite core and the geometric center of the central fiber core on the cross section is within the preset range, l is the axial length of the fiber section where the distance DI between the geometric center of the adjustable satellite core and the geometric center of the central fiber core on the cross section is within the preset range, L Range It is the preset threshold value when the DI of the chiral coupled core fiber is in the Range when applied.

[0046] Different preset ranges can couple to different high-order modes. Different coupling performances are allocated to different high-order modes when designing optical fibers, that is, corresponding preset ratios are set for different preset ranges.

[0047] For example, according to the fiber end face design, when the distance DI between the satellite core geometric center and the central fiber core geometric center is in Range 1, the LP01 mode loss is 1dB / m, the LP11 mode loss is 20dB / m, and the LP21 mode loss is 100dB / m. When the distance DI between the satellite core geometric center and the central fiber core geometric center is in Range 2, the LP01 mode loss is 0.8dB / m, the LP11 mode loss is 60dB / m, and the LP21 mode loss is 15dB / m. When applied, there is no need to design two satellite cores. An adjustable satellite core can be used instead of multiple satellite cores. The single-mode requirement can be met when the cumulative optical fiber length in Range 1 reaches 5m and the cumulative optical fiber length in Range 2 reaches 5m. The optical fiber segments in Range 1 and Range 2 can be continuous or distributed. For example, the distance DI between the geometric center of the 5m adjustable satellite core and the geometric center of the central core of the first optical fiber is in Range 1, and the distance DI between the geometric center of the 5m adjustable satellite core and the geometric center of the central core of the second optical fiber is in Range 2. By changing the position of the satellite cores, each high-order mode can be effectively lost, thereby enabling the optical fiber to achieve single-mode transmission.

[0048] In a preferred embodiment, the distance DI between the geometric center of the adjustable satellite core and the geometric center of the central core in the cross section changes periodically with the cross section axial position L. The adjustable satellite core that changes periodically can repeatedly couple the excited high-order modes and propagate attenuation in the adjustable satellite core.

[0049] In order to conveniently realize the periodic change of the distance DI between the geometric center of the adjustable satellite core and the geometric center of the central fiber core on the cross section with the axial position L of the cross section, the adjustable satellite core revolves with an orbital radius R and an orbital pitch P and rotates with a spiral radius r and a spiral pitch p; the orbital radius R is the distance between the spiral center and the geometric center of the central fiber core on the cross section, the orbital pitch P is the optical fiber length corresponding to one circle of the spiral center around the geometric center axis of the optical fiber, the spiral radius r is the distance between the spiral center and the geometric center of the adjustable satellite core on the cross section, and the spiral pitch p is the optical fiber length corresponding to one circle of the geometric center of the adjustable satellite core around the geometric center axis of the spiral.

[0050] Therefore, the distance DI between the geometric center of the adjustable satellite core and the geometric center of the central fiber core on the cross section varies between [Rr, R+r]; when DI is the minimum value Rr, the adjustable satellite core is at the perigee, and when DI is the maximum value R+r, the adjustable satellite core is at the apogee.

[0051] Preferably, the orbital radius R of the adjustable satellite core is between 10 and 50 μm, the spiral radius r of the adjustable satellite core is between 0 and 20 μm, the orbital pitch P of the adjustable satellite core is less than 1 m, and the spiral pitch p of the adjustable satellite core is less than 10 m. The central core diameter d c is 10 to 100 μm, and the satellite core size d c Less than 50μm, the size of the satellite core is smaller than the central core. The size of the satellite core refers to the diameter of the smallest circle that includes the satellite core cross section.

[0052] Generally speaking, the numerical aperture of the central fiber core is between 0.05 and 0.1, and the numerical aperture of the satellite core is between 0.02 and 0.5.

[0053] The chiral coupled core optical fiber provided by the present invention comprises the following steps:

[0054] (1) preparing a chiral coupled core optical fiber preform assembly, wherein the chiral coupled core optical fiber preform assembly comprises a nested eccentric core rod and an eccentric hole sleeve;

[0055] The eccentric core rod has an outer layer for forming a partial cladding and a core layer for forming an adjustable satellite core, and a radial distance D between the geometric center axis of the core layer and the geometric center axis of the outer contour of the eccentric core rod r It is the product of spiral radius r and stretch ratio, and its outer diameter D v It is twice the product of the sum of half the adjustable satellite core size and the spiral radius r and the stretching ratio; that is:

[0056] D r = r * DR;

[0057]

[0058] Where DR is the stretch ratio, d c is the adjustable satellite core size, D r It is the radial distance between the geometric center axis of the core layer and the geometric center axis of the outer contour of the eccentric core rod, which is generally greater than or equal to 0.5mm; D v It is the outer diameter of the eccentric core rod, generally greater than or equal to 5mm.

[0059] The eccentric core rod is prepared according to the following method: a concentric core rod in which a cladding and a core layer for forming an adjustable satellite core are concentrically nested is made, and the concentric core rod is subjected to eccentric machining to obtain the eccentric core rod.

[0060] The eccentric hole sleeve is a sleeve used to form a central fiber core and possible other satellite cores, and has an eccentric circular hole for inserting an eccentric core rod; the radial distance D between the center axis of the circular hole and the center axis of the outer contour of the eccentric hole sleeve is Ris the product of the orbital radius R and the stretching ratio, and the aperture D h Slightly larger than the outer diameter of the eccentric mandrel, generally slightly larger than the outer diameter of the eccentric mandrel, so that after the eccentric mandrel is inserted into the eccentric circular hole, there is a gap between the outer wall and the inner wall of the eccentric circular hole, so that the eccentric mandrel can rotate relative to the eccentric circular hole; that is:

[0061] D R =R*DR

[0062] D h >D v

[0063] Where D R is the radial distance between the center axis of the circular hole and the center axis of the outer contour of the eccentric hole casing, R is the orbital radius, DR is the stretching ratio, that is, the ratio of the outer diameter of the preform rod to the outer diameter of the stretched optical fiber, D h is the diameter of the circular hole, D v is the outer diameter of the eccentric mandrel.

[0064] The method for preparing the eccentric hole sleeve is as follows: a solid glass rod for forming the optical fiber glass part other than the adjustable satellite core including the central core and the cladding is prepared according to the optical fiber end face design, and a circular hole is punched in the area of ​​the solid glass rod for forming the cladding.

[0065] (2) Inserting the eccentric core rod into the eccentric hole sleeve as an optical fiber preform rod for drawing and forming, during which the phase angle is adjusted by rotating the eccentric core rod, and when it is at a preset axial position, the distance di between the core layer geometric center of the eccentric core rod and the outer contour geometric center of the eccentric hole sleeve on the cross section is adjusted to be the product of a preset value of the distance DI between the geometric center of the adjustable satellite core and the geometric center of the central fiber core on the cross section here and the stretching ratio, so that the distance DI between the geometric center of the adjustable satellite core and the geometric center of the central fiber core on the cross section here of the drawn optical fiber is the preset value; that is, di = DI*DR.

[0066] The phase angle θ of the eccentric core rod refers to the angle between the geometric center axis of the eccentric core rod and the geometric center line of the outer contour of the core layer and the eccentric hole sleeve on the cross section of the optical fiber preform rod, such as Figure 1 As shown, its size is determined according to the cosine theorem as follows:

[0067]

[0068] Where θ is the phase angle of the eccentric mandrel, D R D is the radial distance between the center axis of the circular hole and the center axis of the outer contour of the eccentric hole casing. ris the radial distance between the geometric center axis of the core layer of the eccentric core rod and the geometric center axis of the outer contour of the eccentric core rod, di is the distance between the geometric center of the core layer of the eccentric core rod and the geometric center of the outer contour of the eccentric hole sleeve on the cross section, DI is the distance between the geometric center of the adjustable satellite core and the geometric center of the central core on the cross section of the optical fiber, and DR is the stretching ratio.

[0069] The typical structure of the adjustable satellite core orbits with an orbit radius R and an orbit pitch P and rotates with a spiral radius r and a spiral pitch p. The rotation speed V of the optical fiber preform is determined according to the orbit pitch P and the drawing speed V. R , according to the spiral pitch p of the adjustable satellite core and the drawing speed V, the rotation speed V of the eccentric mandrel is determined r . Specifically,

[0070] The rotation speed V of the optical fiber preform R The calculation method is as follows:

[0071] V R =V / P

[0072] Where, V is the drawing speed, V R is the rotation speed of the preform rod, generally in rpm, and P is the orbital pitch.

[0073] Rotation speed V of the eccentric mandrel r The calculation method is as follows:

[0074] V r =V / p

[0075] Where, V is the drawing speed, V r is the rotation speed of the eccentric mandrel, generally expressed in rpm, and P is the orbital pitch.

[0076] The following are examples:

[0077] Example 1

[0078] The chiral coupled core optical fiber provided in this embodiment has an end face structure as follows: Figure 2 As shown, there is a satellite core, which is an adjustable satellite core;

[0079] The central fiber core has a diameter of 30 μm and a numerical aperture of 0.065;

[0080] The adjustable satellite core is circular, with a diameter of 10 μm and a numerical aperture of 0.1;

[0081] The cladding diameter is 250μm and is pure quartz cladding.

[0082] The adjustable satellite core orbits with an orbit radius R and an orbit pitch P and rotates with a spiral radius r and a spiral pitch p. The orbit radius R is 40 μm, the orbit pitch P is 10 mm, the spiral radius r is 5 μm, and the rotation pitch is 1 m.

[0083] The chiral coupled core optical fiber provided in this embodiment has a draw ratio DR=200, and its preparation method comprises the following steps:

[0084] (1) preparing a chiral coupled core optical fiber preform assembly, wherein the chiral coupled core optical fiber preform assembly comprises a nested eccentric core rod and an eccentric hole sleeve;

[0085] The eccentric mandrel has a core layer diameter of 2 mm, and a radial distance D between the geometric center axis of the core layer and the geometric center axis of the outer contour of the eccentric mandrel. r is 1mm, and its outer diameter D v The diameter of the core layer is 8 mm and is prepared as follows: a concentric core rod is made in which a cladding and a core layer for forming an adjustable satellite core are concentrically nested, and the concentric core rod is subjected to eccentric machining to obtain the eccentric core rod.

[0086] The outer diameter of the eccentric hole sleeve is 50 mm, the diameter of the high refractive index area used to form the central core is 6 mm, and the radial distance D between the center axis of the circular hole and the center axis of the outer contour of the eccentric hole sleeve is R 8mm, aperture D h The preparation method is as follows: a solid glass rod for forming the glass part of the optical fiber other than the adjustable satellite core including the central core and the cladding is prepared according to the optical fiber end face design, and a circular hole is punched in the area of ​​the solid glass rod for forming the cladding.

[0087] (2) Determine the rotation speed V of the optical fiber preform according to the revolution pitch P and the drawing speed V R , according to the spiral pitch p of the adjustable satellite core and the drawing speed V, the rotation speed V of the eccentric mandrel is determined r .

[0088] In this embodiment, the drawing speed V is 3m / min, and the rotation speed V of the preform is R The rotation speed V of the eccentric mandrel is 300 rpm. r is 3rpm.

[0089] The chiral coupled core optical fiber provided in this embodiment can realize single-mode transmission with a length of 10 m, and the mode field diameter is 27.5 μm.

[0090] Example 2

[0091] The chiral coupled core optical fiber provided in this embodiment has an end face structure as follows: Figure 3 As shown, there are two satellite cores, the round one is an adjustable satellite core, and the square one is a non-adjustable satellite core;

[0092] The central fiber core has a diameter of 40 μm and a numerical aperture of 0.06;

[0093] The circular adjustable satellite core is circular, with a diameter of 5 μm and a numerical aperture of 0.09;

[0094] Square non-adjustable satellite core, size 3μm, numerical aperture 0.12;

[0095] The cladding diameter is 400μm and is pure quartz cladding.

[0096] The circular satellite core orbits with an orbit radius R and an orbit pitch P, and rotates with a spiral radius r and a spiral pitch p: the orbit radius R is 50 μm, and the orbit pitch P is 6 mm; the spiral radius r of the circular adjustable satellite core is 4 μm, and the spiral pitch p is 1 m; the orbit radius of the square satellite core is 100 μm;

[0097] The chiral coupled core optical fiber provided in this embodiment has a draw ratio DR=150, and its preparation method comprises the following steps:

[0098] (1) preparing a chiral coupled core optical fiber preform assembly, wherein the chiral coupled core optical fiber preform assembly comprises a nested eccentric core rod and an eccentric hole sleeve;

[0099] The eccentric mandrel is a circular eccentric mandrel with a core layer diameter of 0.75 mm and a radial distance D between the geometric center axis of the core layer and the geometric center axis of the outer contour of the eccentric mandrel. r is 0.6mm, and its outer diameter D v 7mm;

[0100] The preparation method is as follows: a concentric core rod in which a cladding and a core layer for forming an adjustable satellite core are concentrically nested is made, and the concentric core rod is subjected to eccentric machining to obtain the eccentric core rod.

[0101] The outer diameter of the eccentric hole sleeve is 60 mm, and the diameter of the high refractive index area used to form the central core is 6 mm; the size of the high refractive index area used to form the square satellite core is 0.45 mm, and the radial distance D between the axis of the area and the geometric center axis of the outer contour of the eccentric hole sleeve is R 15mm; with an eccentric circular hole, the radial distance D between the center axis of the circular hole and the center axis of the outer contour geometry of the eccentric hole casing R 7.5mm, aperture D h 7mm;

[0102] The preparation method is as follows: according to the optical fiber end face design, a square core area including a central core and a cladding is punched and assembled, and a circular hole is punched in the area of ​​the solid glass rod used to form the cladding.

[0103] (2) Determine the rotation speed V of the optical fiber preform according to the revolution pitch P and the drawing speed V R , according to the spiral pitch p of the adjustable satellite core and the drawing speed V, the rotation speed V of the eccentric mandrel is determined r .

[0104] In this embodiment, the drawing speed V is 6m / min, and the rotation speed v of the preform is R is 1000rpm, the rotation speed v of the first eccentric mandrel r is 6rpm.

[0105] The chiral coupled core optical fiber provided in this embodiment can realize single-mode transmission with a length of 12 m, and the mode field diameter is 36.5 μm.

[0106] Example 3

[0107] The chiral coupled core optical fiber provided in this embodiment has an end face structure as follows: Figure 4 As shown, there is a satellite core, which is an adjustable satellite core;

[0108] The central fiber core has a diameter of 34 μm and a numerical aperture of 0.06;

[0109] The adjustable satellite core is circular, with a diameter of 8 μm and a numerical aperture of 0.1;

[0110] The cladding diameter is 800μm and is pure quartz cladding.

[0111] The adjustable satellite core has a distance DI from the geometric center of the central fiber core that changes in steps between the perigee 40μm and the apogee 45μm. The orbital radius R is 42.5μm, the orbital pitch P is 6mm, the spiral radius r is 2.5μm, and it changes every 7m.

[0112] The chiral coupled core optical fiber provided in this embodiment has a draw ratio DR=125, and its preparation method comprises the following steps:

[0113] (1) preparing a chiral coupled core optical fiber preform assembly, wherein the chiral coupled core optical fiber preform assembly comprises a nested eccentric core rod and an eccentric hole sleeve;

[0114] The eccentric mandrel has a core layer diameter of 1 mm, and a radial distance D between the geometric center axis of the core layer and the geometric center axis of the outer contour of the eccentric mandrel. r is 0.3125mm, and its outer diameter D v The diameter of the core layer is 6 mm and is prepared as follows: a concentric core rod is made in which a cladding and a core layer for forming an adjustable satellite core are concentrically nested, and the concentric core rod is eccentrically machined to obtain the eccentric core rod.

[0115] The outer diameter of the eccentric hole sleeve is 100 mm, the diameter of the high refractive index area used to form the central core is 4.25 mm, and the radial distance D between the center axis of the circular hole and the center axis of the outer contour of the eccentric hole sleeve is R The aperture D is 5.3125 mm. h The preparation method is as follows: a solid glass rod for forming the glass part of the optical fiber other than the adjustable satellite core including the central core and the cladding is prepared according to the optical fiber end face design, and a circular hole is punched in the area of ​​the solid glass rod for forming the cladding.

[0116] (2) Determine the rotation speed V of the optical fiber preform according to the revolution pitch P and the drawing speed V R , according to the spiral pitch p of the adjustable satellite core and the drawing speed V, the rotation speed V of the eccentric mandrel is determined r .

[0117] In this embodiment, the drawing speed V is 3m / min, and the rotation speed V of the preform is R The rotation speed is 300 rpm, and the eccentric mandrel takes 140 seconds to adjust the core layer from the perigee to the apogee or from the apogee to the perigee.

[0118] The chiral coupled core optical fiber provided in this embodiment can realize single-mode transmission with a length of 14 m and a mode field diameter of 30 μm.

[0119] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A chiral coupled core optical fiber, characterized in that: The glass portion thereof includes a central core forming an optical waveguide structure and a cladding covering the central core; One or more satellite cores are arranged in the cladding, and the satellite cores periodically revolve around the central fiber core; The satellite core has at least one adjustable satellite core, and the distance DI between the geometric center of the satellite core and the geometric center of the central fiber core in the cross section changes with the different axial positions L of the cross section.

2. The chiral coupled core optical fiber according to claim 1, characterized in that: The optical fiber section in which the distance DI between the geometric center of the adjustable satellite core and the geometric center of the central core on the cross section is within a preset range has a total axial length greater than or equal to a preset threshold.

3. The chiral coupled core optical fiber according to claim 1, characterized in that: The adjustable satellite core has a distance DI between its geometric center and the geometric center of the central fiber core in the cross section that changes periodically with the axial position L of the cross section.

4. The chiral coupled core optical fiber according to claim 3, characterized in that: The adjustable satellite core revolves with an orbital radius r and an orbital pitch P and rotates with a spiral radius r and a spiral pitch p; the orbital radius R is the distance between the spiral center and the geometric center of the central fiber core on the cross section, the orbital pitch P is the optical fiber length corresponding to one circle of the spiral center around the geometric center axis of the optical fiber, the spiral radius r is the distance between the spiral center and the geometric center of the adjustable satellite core on the cross section, and the spiral pitch p is the optical fiber length corresponding to one circle of the geometric center of the adjustable satellite core around the geometric center axis of the spiral.

5. The chiral coupled core optical fiber according to claim 4, characterized in that: The orbital radius R of the adjustable satellite core is between 10 and 50 μm, the spiral radius r of the adjustable satellite core is between 0 and 20 μm, the orbital pitch P of the adjustable satellite core is less than 1 m, and the spiral pitch p of the adjustable satellite core is less than 1 m.

6. The chiral coupled core optical fiber according to claim 1, characterized in that: The central core diameter d c is 10 to 100 μm, and the satellite core size d c Less than 50μm, the size of the satellite core is smaller than the central core.

7. The chiral coupled core optical fiber according to claim 1, characterized in that: The numerical aperture of the central fiber core is between 0.05 and 0.1, and the numerical aperture of the satellite core is between 0.02 and 0.

5.

8. The chiral coupled core optical fiber according to claim 1, characterized in that: The cladding is provided with a satellite core, and the satellite core is an adjustable satellite core; or The cladding is provided with a plurality of satellite cores, wherein at least one satellite core is a regular polygon.

9. A method for preparing a chiral coupled core optical fiber according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) preparing a chiral coupled core optical fiber preform assembly, wherein the chiral coupled core optical fiber preform assembly comprises a nested eccentric core rod and an eccentric hole sleeve; The eccentric core rod has an outer layer for forming a partial cladding and a core layer for forming an adjustable satellite core, and a radial distance D between the geometric center axis of the core layer and the geometric center axis of the outer contour of the eccentric core rod r It is the product of spiral radius r and stretch ratio, and its outer diameter D v It is twice the product of the sum of half the adjustable satellite core size and the helical radius r and the stretching ratio; The eccentric hole sleeve is a sleeve used to form a central fiber core and possible other satellite cores, and has an eccentric circular hole for inserting an eccentric core rod; the radial distance D between the center axis of the circular hole and the center axis of the outer contour of the eccentric hole sleeve is R is the product of the orbital radius R and the stretching ratio, and the aperture D h Slightly larger than the outer diameter of the eccentric mandrel; (2) inserting the eccentric core rod into the eccentric hole sleeve as an optical fiber preform rod for drawing and forming, during which the phase angle of the eccentric core rod is adjusted by rotating the eccentric core rod, and when it is at a preset axial position, the distance di between the core layer geometric center of the eccentric core rod and the outer contour geometric center of the eccentric hole sleeve on the cross section is adjusted to be the product of the preset value of the distance DI between the geometric center of the adjustable satellite core and the geometric center of the central fiber core on the cross section here and the drawing ratio, so that the distance DI between the geometric center of the adjustable satellite core and the geometric center of the central fiber core on the cross section here of the drawn optical fiber is the preset value; The phase angle θ of the eccentric core rod refers to the angle between the geometric center axis of the eccentric core rod and the geometric center axis of the outer contours of the core layer and the eccentric hole sleeve on the cross section of the optical fiber preform rod. Its size is determined according to the cosine theorem as follows: Where θ is the phase angle of the eccentric mandrel, D R D is the radial distance between the center axis of the circular hole and the center axis of the outer contour of the eccentric hole casing. r is the radial distance between the geometric center axis of the core layer of the eccentric core rod and the geometric center axis of the outer contour of the eccentric core rod, di is the distance between the geometric center of the core layer of the eccentric core rod and the geometric center of the outer contour of the eccentric hole sleeve on the cross section, DI is the distance between the geometric center of the adjustable satellite core and the geometric center of the central core on the cross section of the optical fiber, and DR is the stretching ratio.

10. The method for preparing a chiral coupled core optical fiber according to claim 9, characterized in that: The adjustable satellite core revolves at an orbital radius R and an orbital pitch P and rotates at a spiral radius r and a spiral pitch p. Step (2) determines the rotation speed V of the optical fiber preform according to the orbital pitch P and the drawing speed V. R , according to the spiral pitch p of the adjustable satellite core and the drawing speed V, the rotation speed V of the eccentric mandrel is determined r ;Specifically, The rotation speed V of the optical fiber preform R The calculation method is as follows: V R =V / P Where, V is the drawing speed, V R is the rotation speed of the preform, generally in rpm, and P is the revolution pitch; Rotation speed V of the eccentric mandrel r The calculation method is as follows: V r =V / p Where, V is the drawing speed, V r is the rotation speed of the eccentric mandrel, generally expressed in rpm, and P is the orbital pitch.

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