CN211826597U

CN211826597U - Weak coupling twenty-mode few-mode optical fiber

Info

Publication number: CN211826597U
Application number: CN202020610410.9U
Authority: CN
Inventors: 杜江兵; 何祖源; 陈心怡; 何枝琴; 沈微宏
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2020-04-22
Filing date: 2020-04-22
Publication date: 2020-10-30
Anticipated expiration: 2030-04-22

Abstract

A weakly-coupled twenty-mode few-mode optical fiber, comprising: the refractive index difference of the middle core, the first ring core and the second ring core relative to the cladding is increased in sequence, the refractive index difference of the third ring core to the fifth ring core relative to the cladding is reduced in sequence, and the middle core and the front two layers of ring cores are covered by the third ring core to the fifth ring core. The utility model discloses a design the structural parameter of each layer of many annular fibre cores for effective refractive index difference between each mode is great, and the intermode is crosstalked and is reduced, realizes the weak coupling characteristic. The few-mode optical fiber can independently transmit signals among all channels under the condition of weak coupling. The preparation is carried out by doping germanium and controlling the number of fiber core layers, and the process is simple. The method can be widely applied to short-distance ultra-large capacity optical transmission systems, and has very wide application prospect.

Description

Weak coupling twenty-mode few-mode optical fiber

Technical Field

The utility model relates to a technique in photoelectric communication field specifically is a few mode optic fibre of twenty modes of weak coupling.

Background

In recent years, various large-scale data centers and cloud computing services have appeared, higher requirements are put on the bandwidth and capacity of an optical network, and the capacity requirement is difficult to meet by using a common single-mode optical fiber. In the prior art, mode division multiplexing is taken as an important means for further improving the optical communication capacity and the spectral efficiency. Due to the complexity and high cost of strongly coupled mode division multiplexing systems, they are only suitable for long distance communication. Different from the strong coupling mode division multiplexing system, the weak coupling mode division multiplexing system adopts the mode multiplexing demultiplexer with the mode selection characteristic and the mode weak coupling transmission optical fiber between the modes, and the receiving end does not need a complex MIMO algorithm, so that the mode can be used as the routing exchange dimension to realize the flexible allocation of the network capacity. Aiming at the design and preparation of novel few-mode optical fibers and optical fiber devices for a weakly coupled mode division multiplexing system, the complexity of the design of MIMO equipment is relieved by adopting the low-DMD gradient index few-mode optical fibers in the prior art, but the design of the section of the refractive index of the low-DMD gradient index few-mode optical fibers needs to be very accurate, the manufacturing process is complex, and the production difficulty is high.

SUMMERY OF THE UTILITY MODEL

The utility model discloses it is not enough to the above-mentioned that prior art exists, provides a few mode fiber of twenty modes of weak coupling, through the structural parameter of sandwich layer and ring core layer in the design, reduces intermode and crosstalks, realizes the weak coupling characteristic, but wide application in short distance large capacity optical transmission system.

The utility model discloses a realize through following technical scheme:

the utility model relates to a few mode fiber of twenty modes of weak coupling, include: the well core sets up five layers ring core and claddings outside it in proper order, wherein: the refractive index difference of the middle core, the first ring core and the second ring core relative to the cladding is increased in sequence, the refractive index difference of the third ring core to the fifth ring core relative to the cladding is reduced in sequence, the middle core and the front two layers of ring cores are covered by the third ring core to the fifth ring core, the whole body supports twenty transmission modes at 1550nm, and the effective refractive index difference between every two adjacent modes is larger than 0.1%.

The outer diameter of the cladding is 62.5-75 μm, and the refractive index of the cladding is 1.445.

The outer diameter of the core is 1.5-2.1 μm, and the refractive index difference between the core and the cladding is 0.02995-0.03355.

The first ring core has an outer diameter of 2.2 to 2.8 μm and a refractive index difference with the cladding of 0.03545 to 0.03725.

The outer diameter of the second ring core is 6.2-6.8 μm, and the refractive index difference between the second ring core and the cladding is 0.03615-0.03795.

The outer diameter of the third ring core is 8.35-8.95 μm, and the refractive index difference between the third ring core and the cladding is 0.03145-0.03405.

The outer diameter of the fourth ring core is 8.958-9.558 μm, and the refractive index difference between the fourth ring core and the cladding is 0.03-0.0318.

The outer diameter of the fifth ring core is 10.68-11.68 mu m, and the refractive index difference between the fifth ring core and the cladding is 0.02175-0.02385.

The twenty transmission modes are specifically as follows: LP01, LP11, LP21, LP02, LP31, LP12, LP41, LP22, LP03, LP51, LP32, LP13, LP61, LP42, LP71, LP04, LP23, LP81, LP33, and LP 14.

The weak coupling twenty-mode few-mode optical fiber determines the initial ranges of the core and each ring core in the optical fiber through the distribution of normalized frequency and effective refractive index difference, so that the optical fiber can generate more than 20 LP modes in the ranges; and then, through neural network reverse design, obtaining a plurality of 20-mode optical fiber examples with effective refractive index difference between all modes larger than 0.1%.

Technical effects

The utility model discloses wholly solve the refracting index and the radius that the prediction function that provides through neural network set up well core and each ring core for the effective refractive index difference of all modes all is greater than 0.1% technical problem in the embodiment optic fibre.

Compared with the prior art, the utility model discloses add five high refractive index rings between well core and cladding, through a plurality of embodiments of neural network reverse prediction, weak point consuming time to make the effective refractive index difference between each mode bigger, thereby cross talk between the mode reduces, realizes the weak coupling characteristic. The few-mode optical fiber does not need to adopt a complex MIMO algorithm to realize multiplexing-demultiplexing of signals under the condition of weak coupling, and signals can be independently transmitted among all channels. The preparation is carried out by doping germanium and controlling the number of fiber core layers, and the process is simple. The method can be widely applied to short-distance ultra-large capacity optical transmission systems, and has very wide application prospect.

Drawings

Fig. 1 is a schematic cross-sectional view of the present invention;

FIG. 2 is a cross-sectional view of the refractive index profile of the present invention;

in the figure: the core comprises a central core 1, a first annular core 2, a second annular core 3, a third annular core 4, a fourth annular core 5, a fifth annular core 6 and a cladding 7.

Detailed Description

As shown in fig. 1 and 2, the present embodiment includes: well core 1 and five layers of ring cores 2 ~ 6 and claddings 7 that set gradually outside it, wherein: the refractive index difference of the middle core 1, the first annular core 2 and the second annular core 3 relative to the cladding 7 is increased in sequence, the refractive index difference of the third annular core 4 to the fifth annular core 6 relative to the cladding 7 is reduced in sequence, the third annular core 4 to the fifth annular core 6 cover the middle core 1 and the first two layers of

annular cores

2 and 3, the whole body supports twenty transmission modes at 1550nm, and the effective refractive index difference between all the modes is larger than 0.1%.

In the characteristic parameters of this embodiment: r is₁～r₆Respectively sequentially comprises the outer diameters r of the central core 1 to the fifth ring core 6₀The outer diameter of the cladding 7; the outer diameter is the distance between the outer edge diameter and the central point of the layer; n is₁～n₆Refractive indices of the central core 1 to the fifth ring core 6, n₀Is the refractive index of the cladding 7.

In this embodiment, the core rod is manufactured according to the design requirements of the optical fiber by a core rod manufacturing process such as a PVCD process, an MVCD process, an OVD process, or a VAD process.

TABLE 1 structural parameters of the present example

In the table: the calculation formula of the refractive index difference is: Δ n_i＝n_i-n₀。

Table 2 performance parameters for this example:

in the table: n is_effIs the effective refractive index; Δ n_effFor the difference between the effective refractive indexes of two adjacent LP modes, the calculation formula is as follows: Δ n_eff＝n_eff,i-n_eff,i-1(ii) a Dispersion is Dispersion; β is the propagation constant.

Obtaining the fiber normalized frequency according to this example

Preferably, V has a value of 11.799 to ensure twenty transmission modes in the fiber.

The utility model discloses a six ring structures, well core and fourth ring core, fifth ring core refracting index are lower, and middle first ring core, second ring core, third ring core refracting index are higher, and the relative refractive index difference of well core and five ring cores and cladding is all within 2.6%, and the relative refractive index difference of well core, first ring core, third ring core, fourth ring core, fifth ring core and second ring core is all in 1%.

The foregoing embodiments may be modified in various ways by those skilled in the art without departing from the spirit and scope of the present invention, which is not limited by the above embodiments but is to be accorded the full scope defined by the appended claims, and all such modifications and variations are within the scope of the invention.

Claims

1. A weakly coupled twenty-mode few-mode optical fiber, comprising: the well core sets up five layers ring core and claddings outside it in proper order, wherein: the refractive index difference of the middle core, the first annular core and the second annular core relative to the cladding is increased in sequence, the refractive index difference of the third annular core, the fourth annular core and the fifth annular core relative to the cladding is decreased in sequence, and the third annular core, the fourth annular core and the fifth annular core cover the middle core and the front two layers of annular cores.

2. The weakly-coupled twenty-mode few-mode optical fiber according to claim 1, wherein the optical fiber supports twenty transmission modes at 1550nm and the effective refractive index difference between each adjacent mode is greater than 0.1%.

3. The weakly coupled twenty-mode few-mode optical fiber as claimed in claim 1, wherein the outer diameter of the cladding is 62.5 to 75 μm, and the refractive index thereof is 1.445.

4. The weakly-coupled twenty-mode few-mode optical fiber according to claim 3, wherein the outer diameter of the core is 1.5 to 2.1 μm, and the difference in refractive index from the cladding is 0.02995 to 0.03355.

5. The weakly-coupled twenty-mode few-mode optical fiber according to claim 3, wherein the first annular core has an outer diameter of 2.2 to 2.8 μm and a refractive index difference with the cladding of 0.03615 to 0.03795.

6. The weakly-coupled twenty-mode few-mode optical fiber according to claim 3, wherein the second annular core has an outer diameter of 6.2 to 6.8 μm and a refractive index difference with the cladding of 0.03615 to 0.03795.

7. The weakly-coupled twenty-mode few-mode optical fiber according to claim 3, wherein the third annular core has an outer diameter of 8.35 to 8.95 μm and a refractive index difference with the cladding of 0.03141 to 0.03305.

8. The weakly-coupled twenty-mode few-mode optical fiber according to claim 3, wherein the fourth ring core has an outer diameter of 8.958 to 9.558 μm, and the difference in refractive index from the cladding is 0.03 to 0.0318.

9. The weakly-coupled twenty-mode few-mode optical fiber according to claim 3, wherein the fifth ring core has an outer diameter of 10.68 to 11.68 μm and a refractive index difference from the cladding of 0.03 to 0.0318.

10. The weakly-coupled twenty-mode few-mode optical fiber as claimed in claim 2, wherein the twenty transmission modes are specifically: LP01, LP11, LP21, LP02, LP31, LP12, LP41, LP22, LP03, LP51, LP32, LP13, LP61, LP42, LP71, LP04, LP23, LP81, LP33, and LP 14.