Quasi-single-mode optical fiber with large mode field effective area

Abstract

The utility model discloses a quasi single mode fiber with a large mode field effective area, which comprises a fiber core, an inner cladding, a ring core layer and an outer cladding, the fiber core is wrapped by the inner cladding, the inner cladding is wrapped by the ring core layer, the ring core layer is wrapped by the outer cladding, and the refractive index of the fiber core is larger than that of the inner cladding, the ring core layer and the outer cladding. The refractive index of the ring core layer is larger than that of the inner cladding and that of the outer cladding, and the refractive index of the inner cladding is equal to that of the outer cladding. According to the embodiment of the utility model, while the effective area of the optical fiber fundamental mode is increased, the coupling crosstalk between the fundamental mode and the high-order mode can be effectively suppressed, the communication power threshold of the optical fiber fundamental mode can be further increased on the premise of not adopting complex mode selective excitation, and the optical fiber can be widely applied to the technical field of optical communication.

Description

TECHNICAL FIELD

[0001] The utility model relates to optical communication technical field especially relates to a quasi single mode optical fiber of large mode field effective area. BACKGROUND

[0002] With the development and maturity of information industry, the demand of large data center and user's network application for communication capacity is more and more urgent. At present, as the backbone of communication network, optical fiber communication link mainly bases on single mode optical fiber, and is facing the communication capacity bottleneck caused by optical fiber nonlinear effect. There are two means to break through the optical fiber communication capacity bottleneck, one is to improve the threshold of optical fiber communication power, and the other is to develop more space channels by using mode division multiplexing optical fiber technology. The latter needs complex mode multiplexing system, and the implementation difficulty and cost in actual optical fiber link are higher. The former has certain potential in improving the threshold of optical fiber communication power with the maturity of optical fiber preparation technology.

[0003] At present, improving the mode field effective area is the main method to improve the optical fiber power threshold. Generally, communication optical fiber is divided into single mode optical fiber and few mode (multi-mode) optical fiber. The mode field effective area of single mode optical fiber is close to the upper limit under the condition of ensuring low loss and single mode. While the few mode (multi-mode) optical fiber can improve the mode field area by introducing high order mode, but in actual application, it will face the problems of mode selective excitation and mode channel crosstalk. SUMMARY

[0004] Therefore, the purpose of the utility model embodiment is to provide a quasi single mode optical fiber of large mode field effective area, which can effectively suppress the coupling crosstalk between the fundamental mode and high order mode while increasing the effective area of the fundamental mode of the optical fiber, and further increase the communication power threshold of the fundamental mode of the optical fiber without using complex mode selective excitation.

[0005] The utility model embodiment provides a quasi single mode optical fiber of large mode field effective area, which comprises a fiber core, an inner cladding, a ring core layer and an outer cladding, the inner cladding wraps the fiber core, the ring core layer wraps the inner cladding, the outer cladding wraps the ring core layer, the refractive index of the fiber core is greater than the refractive index of the inner cladding, the ring core layer and the outer cladding, the refractive index of the ring core layer is greater than the refractive index of the inner cladding and the outer cladding, and the refractive index of the inner cladding is equal to the refractive index of the outer cladding.

[0006] Optionally, the relative refractive index difference between the fiber core and the inner cladding satisfies the following relationship:

[0007]

[0008] Wherein, Δn1 represents the relative refractive index difference between the core and the inner cladding, n1 represents the refractive index of the core, and n3 represents the refractive index of the inner cladding.

[0009] Optionally, the relative refractive index difference between the core and the inner cladding ranges from 0.2% to 0.3%.

[0010] Optionally, the outer radius of the core ranges from 9 to 10 μm.

[0011] Optionally, the relative refractive index difference between the ring core layer and the inner cladding satisfies the following relationship:

[0012]

[0013] Wherein, Δn2 represents the relative refractive index difference between the ring core layer and the inner cladding, n2 represents the refractive index of the ring core layer, and n3 represents the refractive index of the inner cladding.

[0014] Optionally, the inner diameter of the ring core layer ranges from 12 to 18 μm.

[0015] Optionally, the thickness of the ring core layer ranges from 3.5 to 4.5 μm.

[0016] Optionally, the material of the quasi-single-mode optical fiber comprises a quartz material and / or a quartz doped material.

[0017] Optionally, the quasi-single-mode optical fiber supports a group angular order of a guided mode of the core being less than or equal to 1.

[0018] The embodiment of the present application has the following beneficial effects: the quasi-single-mode optical fiber with a large-mode-area effective area increases the mode field area of a fiber fundamental mode by increasing the radius of the intermediate core, and modulates the fiber fundamental mode and high-order modes by reasonably setting the refractive indexes of the inner cladding and the ring core layer; compared with a general single-mode optical fiber, the quasi-single-mode optical fiber with a large-mode-area effective area increases the mode field area by increasing the fiber normalized parameter; in addition, the ring core layer makes the mode field of the high-order mode deviate outward, and the effective refractive index thereof is closer to the cladding, so that the transmission loss of the high-order mode is larger, the crosstalk between the high-order mode and the fundamental mode is reduced, the influence of intermodal dispersion on communication is reduced, the fundamental mode channel can be improved in communication power threshold without using complex mode selective excitation, and the deterioration caused by obvious intermodal crosstalk does not occur. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Fig. (a) is a sectional view of a quasi-single-mode optical fiber with a large-mode-area effective area provided by the embodiment of the present application;

[0020] Figure 1The middle (b) is a refractive index distribution diagram on a section diameter line of the large-mode-area quasi-single-mode optical fiber provided by the embodiment of the utility model;

[0021] Figure 2 The middle (b) is a refractive index distribution diagram on a section diameter line of the large-mode-area quasi-single-mode optical fiber provided by the embodiment of the utility model; DETAILED DESCRIPTION

[0022] The utility model will be further explained in detail in combination with the drawings and specific embodiments.

[0023] Referring to Figure 1 The embodiment of the utility model provides a kind of large-mode-area quasi-single-mode optical fiber, including core (1), inner cladding (2), ring core layer (3) and outer cladding (4), inner cladding (2) is wrapped core (1), ring core layer (3) is wrapped inner cladding (2), outer cladding (4) is wrapped ring core layer (3), the refractive index of core (1) is greater than the refractive index of inner cladding (2), ring core layer (3) and outer cladding (4), the refractive index of ring core layer (3) is greater than the refractive index of inner cladding (2) and outer cladding (4), the refractive index of inner cladding (2) is equal to the refractive index of outer cladding (4).

[0024] Wherein, Figure 1 In the middle (a), auxiliary line 1 identifies the outer interface of intermediate core, auxiliary line 2 identifies the outer interface of inner cladding, auxiliary line 3 identifies the outer interface of ring core layer, and auxiliary line 4 identifies the outer interface of outer cladding. Figure 1 The transverse refractive index distribution of the optical fiber shown in the middle (b) is step type.

[0025] It should be noted that the structure design and refractive index setting of the large-mode-area quasi-single-mode optical fiber in the embodiment of the utility model make the mode group supported by the core of the quasi-single-mode optical fiber include the fundamental mode and not more than one high-order mode group.The principle of the ring core layer is to modulate the mode field and effective refractive index of the high-order mode group respectively.Due to the larger mode field diameter of the high-order mode, the energy is more distributed in the ring core layer and close to the outer cladding, that is, the effective refractive index of the high-order mode can be changed by changing the refractive index of the ring core layer without basically affecting the effective refractive index of the fundamental mode, so that the effective refractive index of the high-order mode is reduced and closer to the cladding refractive index, the high-order mode loss is increased and the crosstalk between the high-order mode and the fundamental mode is reduced.

[0026] Wherein, the design of the large-mode-area quasi-single-mode optical fiber can be applied to optical fiber communication C band (1530nm-1565nm).

[0027] Optionally, the relative refractive index difference of the core and the inner cladding satisfies the following relationship:

[0028]

[0029] wherein Δn1 represents a relative refractive index difference between the core and the inner cladding, n1 represents a refractive index of the core, and n3 represents a refractive index of the inner cladding.

[0030] Optionally, the relative refractive index difference between the core and the inner cladding ranges from 0.2% to 0.3%.

[0031] It should be noted that the relative refractive index difference between the core and the inner cladding, the refractive index of the core, and the refractive index of the core are determined according to actual applications, and the embodiments are not specifically limited.

[0032] Optionally, the outer radius of the core ranges from 9 to 10 μm.

[0033] It should be noted that the outer radius of the core is determined according to actual applications, and the embodiments are not specifically limited.

[0034] In a specific embodiment, as shown in FIG. 1, the relative refractive index difference Δn1 between the intermediate core and the inner cladding is 0.2% to 0.3%, and the outer radius r1 of the intermediate core is 9 to 10 μm. Figure 2 Optionally, the relative refractive index difference between the annular core layer and the inner cladding satisfies the following relationship:

[0035]

[0036]

[0037] wherein Δn2 represents a relative refractive index difference between the annular core layer and the inner cladding, n2 represents a refractive index of the annular core layer, and n3 represents a refractive index of the inner cladding.

[0038] It should be noted that the relative refractive index difference between the annular core layer and the inner cladding, the refractive index of the annular core layer, and the refractive index of the inner cladding are determined according to actual applications, and the embodiments are not specifically limited.

[0039] Optionally, the inner diameter of the annular core layer ranges from 12 to 18 μm.

[0040] Optionally, the thickness of the annular core layer ranges from 3.5 to 4.5 μm.

[0041] It should be noted that the inner diameter and the thickness of the annular core layer are determined according to actual applications, and the embodiments are not specifically limited.

[0042] In a specific embodiment, as shown in FIG. 1, the refractive index of the inner cladding is consistent with the refractive index of the outer cladding, the relative refractive index difference Δn2 between the annular core layer and the outer cladding is less than or equal to Δn1, that is, the refractive index of the annular core layer does not exceed the refractive index of the intermediate core. The interface radius r2 of the inner cladding is 12 to 18 μm, and the thickness t of the annular core layer is 4±0.5 μm. Figure 2

[0043] ​​Optionally, the quasi-single-mode fiber may be made of quartz and / or quartz-doped materials.

[0044] Among them, the intermediate core, ring core layer and cladding of quasi-single-mode optical fiber can be made of pure quartz material and / or quartz material doped with elements such as Ge and P.

[0045] Optionally, the quasi-single-mode fiber supports a core with a core angular order of less than or equal to 1.

[0046] In one specific embodiment, the quasi-single-mode fiber supports a transmission mode group with an angular order l≤1 at 1550nm, and the fiber core supports no more than one higher-order mode group in addition to the fundamental mode.

[0047] In this embodiment, by controlling the intermediate fiber core parameters Δn1 and r1, the number of mode groups supported by the fiber core is kept to no more than 2, thus avoiding the impact of too many high-order modes on the communication of the fundamental mode.

[0048] The implementation of this utility model embodiment has the following beneficial effects: Quasi-single-mode fiber with a large effective mode area increases the mode field area of ​​the fiber's fundamental mode by increasing the radius of the intermediate core. The fundamental mode and higher-order modes are modulated separately by rationally setting the refractive indices of the inner cladding and the ring core. Compared to ordinary single-mode fiber, quasi-single-mode fiber with a large effective mode area increases the mode field area by increasing the fiber normalization parameter. Furthermore, the ring core shifts the mode field of higher-order modes outwards, making its effective refractive index closer to the cladding, thereby increasing the transmission loss of higher-order modes, reducing crosstalk between higher-order modes and the fundamental mode, and minimizing the impact of intermodal dispersion on communication. Without employing complex mode-selective excitation, the fundamental mode channel can achieve increased communication power threshold without significant degradation caused by intermodal crosstalk.

[0049] The above is a detailed description of the preferred embodiments of the present utility model. However, the present utility model is not limited to the described embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present utility model. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A large-mode-field effective-area quasi-single-mode optical fiber, characterized in that, The fiber includes a core, an inner cladding, a ring core layer, and an outer cladding, the inner cladding wraps the core, the ring core layer wraps the inner cladding, the outer cladding wraps the ring core layer, the core has a refractive index greater than the refractive indexes of the inner cladding, the ring core layer, and the outer cladding, the ring core layer has a refractive index greater than the refractive indexes of the inner cladding and the outer cladding, and the refractive index of the inner cladding is equal to the refractive index of the outer cladding.

2. The quasi-single mode optical fiber according to claim 1, characterized in that, The relative refractive index difference between the core and the inner cladding satisfies the following relationship: where Δn1 represents the relative refractive index difference between the core and the inner cladding, n1 represents the refractive index of the core, and n3 represents the refractive index of the inner cladding.

3. The quasi-single mode optical fiber according to claim 1, characterized in that, The relative refractive index difference between the core and the inner cladding ranges from 0.2% to 0.3%.

4. The quasi-single mode optical fiber according to claim 1, characterized in that, The outer radius of the core ranges from 9 to 10 μm.

5. The quasi-single mode optical fiber according to claim 1, characterized in that, The relative refractive index difference between the ring core layer and the inner cladding satisfies the following relationship: where Δn2 represents the relative refractive index difference between the ring core layer and the inner cladding, n2 represents the refractive index of the ring core layer, and n3 represents the refractive index of the inner cladding.

6. The quasi-single mode optical fiber according to claim 1, characterized in that, The inner diameter of the ring core layer ranges from 12 to 18 μm.

7. The quasi-single mode optical fiber according to claim 1, characterized in that, The thickness of the ring core layer ranges from 3.5 to 4.5 μm.

8. The quasi-single mode optical fiber according to claim 1, characterized in that, The material of the quasi-single-mode optical fiber includes a quartz material and / or a quartz doped material.

9. The quasi-single mode optical fiber according to claim 1, characterized in that, The core of the quasi-single-mode optical fiber supports a group of conducting modes with an angular order less than or equal to 1.

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