KR101738382B1 - Polarization maintaining fiber - Google Patents

Abstract

The present invention relates to a polarization maintaining optical fiber for polarizing wave-guided light by a stress applying unit, and to a method for producing the same. The polarization maintaining optical fiber of the present invention comprises: a core unit (110); a cladding unit (120) formed to wrap the surroundings of the core unit (110); and a pair of stress applying units (130) disposed on the clapping unit to be laterally symmetrical on the basis of the core unit (110). The stress applying units (130) comprise two or more stress applying members (131, 132, 133) disposed to have circular cross-sections of different radiuses (r1, r2, r3) on a single identical axis (C1) on the basis of the core unit (110).

Description

[0001] POLARIZATION MAINTAINING FIBER [0002]

The present invention relates to a polarization maintaining optical fiber in which light to be guided is polarized by a stress applying unit and a method of manufacturing the same.

The polarization maintaining optical fiber is an optical fiber having birefringence different in effective refractive index according to the polarization component of light traveling through the core of the optical fiber. Due to such birefringence, the incident light has different propagation characteristics depending on the polarization components, and energy exchange between the two polarized lights is suppressed. Therefore, even if the incident light travels through the optical fiber, the initial polarization state is maintained.

Birefringence is stress-induced birefringence due to geometrical birefringence due to the geometric deformation of the optical fiber core and asymmetric stress applied to the core. Compared with geometrical birefringence, It is more suitable as a polarization maintaining optical fiber. 1, polarization maintaining optical fibers for optical communication due to asymmetric stress are classified into PANDA (a), elliptical stress (b), Bow-tie (Bow) -Tie) (c) polarization-maintaining optical fiber.

2, the pendant-type polarization maintaining optical fiber includes a core unit 10, a cladding unit 20 formed so as to surround the core unit 10, And a pair of stress applying units (30) arranged in the unit (20).

The stress imparting unit 30 is formed so as to stress the core unit 10 on both sides with the core unit 10 as a center, and a birefringence phenomenon is generated by this stress, so that two principal transmission axes Quot; fast axis "(x axis) and a" slow axis "(y axis).

On the other hand, one of the main parameters in the polarization maintaining optical fiber is a polarization extinction ratio (PER), for example, when the polarized incident light (Linc) aligned with the slow axis is offset from the slow axis It is important to align the polarization axis as well as the fiber core in order to obtain acceptable characteristics.

3 (a) and 3 (b) are a sectional view of the panda polarization maintaining optical fiber, a birefringence according to the optical fiber size (core unit, cladding unit and stress applying unit) The effective stress acting per unit area by the stress applying unit is influenced by the projection angle [theta], so that the stress applying unit .

Japanese Patent Application Laid-Open No. 10-2004-0003845 (published on Jan. 13, 2004)

Published Patent Publication No. 10-2010-0120513 (Published Date: November 16, 2010)

SUMMARY OF THE INVENTION The present invention seeks to improve such a conventional polarization maintaining optical fiber and to provide a polarization maintaining optical fiber which is easy to manufacture and has excellent reproducibility and a manufacturing method thereof.

According to an aspect of the present invention, there is provided a polarization maintaining optical fiber comprising: a core unit; A cladding unit configured to surround the core unit; And a pair of stress imparting units arranged in the cladding unit symmetrically with respect to the core unit as a center, wherein the stress imparting unit comprises a plurality of stress applying units each having a circular shape with different radii And two or more stress imparting members arranged with a cross section.

Preferably, the stress imparting members are characterized in that the stress imparting members disposed inwardly of the stress imparting members disposed on the outer side are smaller in size.

Preferably, the stress applying unit is characterized in that the two imaginary lines connecting in a circumscribed manner with the stress applying members are triangular.

More preferably, the stress imparting member disposed closest to the core unit among the stress imparting members is at least equal to or smaller than the core unit.

Next, a method of manufacturing a polarization maintaining optical fiber according to the present invention comprises the steps of: fabricating an optical fiber preform having a core unit and a cladding unit surrounding the core unit; Forming insertion holes in the optical fiber preform at positions corresponding to the plurality of stress applying members, respectively; Inserting a stress imparting rod into each of the insertion holes; And drawing out the optical fiber preform in which the stress imparting rod is inserted in each insertion hole in a molten state.

The polarization maintaining optical fiber according to the present invention is a pair of stress applying units arranged in a cladding unit so as to be symmetrically symmetrical with respect to a core unit so that the stress imparting units are arranged on two or more coaxial axes It has an excellent PER characteristic and an excellent reproducibility.

Particularly, the bow-tie polarization maintaining optical fiber of the prior art has a problem that the stress applied to the core is a surface angle, and the reproducibility is low because the core is formed in a deposition form during the base material process. Also, Difficulty may arise in terms of reproducibility in each product at the time of splicing, but the present invention is advantageous in high reproducibility since it is understood in machining after optical fiber preform processing.

Next, the manufacturing method of the polarization maintaining optical fiber of the present invention is simple in the manufacturing process and has an excellent effect in mass production.

1 (a), 1 (b) and 1 (c) are sectional structural diagrams of general polarization maintaining optical fibers,
2 is a cross-sectional view of a general PANDA polarization maintaining optical fiber,
3 (a) and 3 (b) are a graph showing the relationship between the cross-sectional view of the panda polarization maintaining optical fiber and the birefringence and the projection angle? According to the optical fiber size (core unit, crating unit and stress applying unit)
4 is a sectional structural view of a polarization maintaining optical fiber according to the present invention.
5 (a), 5 (b), 5 (c) and 5 (d) are cross-sectional structural views of a polarization maintaining optical fiber according to a comparative example and a polarization maintaining optical fiber according to the present invention,
6 (a), 6 (b), 6 (c) and 6 (d) are graphs showing results of stress analysis of the comparative example and the polarization maintaining optical fiber according to the present invention,
7 (a), 7 (b), 7 (c) and 7 (d) schematically illustrate a process of manufacturing a polarization maintaining optical fiber according to the present invention.

The specific structure or functional description presented in the embodiment of the present invention is merely illustrative for the purpose of illustrating an embodiment according to the concept of the present invention, and embodiments according to the concept of the present invention can be implemented in various forms. And should not be construed as limited to the embodiments described herein, but should be understood to include all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Meanwhile, in the present invention, the terms first and / or second etc. may be used to describe various components, but the components are not limited to the terms. The terms may be referred to as a second element only for the purpose of distinguishing one element from another, for example, to the extent that it does not depart from the scope of the invention in accordance with the concept of the present invention, Similarly, the second component may also be referred to as the first component.

Whenever an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but it should be understood that other elements may be present in between something to do. On the other hand, when it is mentioned that an element is "directly connected" or "directly contacted" to another element, it should be understood that there are no other elements in between. Other expressions for describing the relationship between components, such as "between" and "between" or "adjacent to" and "directly adjacent to" should also be interpreted.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. It will be further understood that the terms " comprises ", or "having ", and the like in the specification are intended to specify the presence of stated features, integers, But do not preclude the presence or addition of steps, operations, elements, parts, or combinations thereof.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings, and reference numerals are denoted for only one configuration for the same configuration that is symmetrical.

As illustrated in Fig. 4, the polarization maintaining optical fiber of the present invention includes a core unit 110; A cladding unit 120 configured to surround the core unit 110; The stress applying unit 130 includes a pair of stress applying units 130 arranged symmetrically with respect to the core unit 110 in the cladding unit 120. The stress applying unit 130 includes And two or more stress imparting members 131, 132, and 133 arranged on the axis C1 with circular cross sections having different radii r1, r2, and r3.

The stress imparting unit 130 in this embodiment shows that the first stress imparting member 131, the second stress imparting member 132 and the third stress applying member 133 are disposed in order adjacent to the core unit 110 And the stress applying member may be increased or decreased within a range of at least two or more.

Preferably, the stress imparting members 131, 132, and 133 are gradually increased in size (r1 <r2 <r3) around the core unit 110, and are partially overlapped, circumscribed, .

Further, the two imaginary lines L1 and L2 circumscribing and connecting the respective stress applying members 131, 132 and 133 have a triangular shape.

Preferably, the first stress applying member 131 disposed nearest to the core unit 110 is the same or smaller.

5 (a), 5 (b), 5 (c), and 5 (d) are cross-sectional views of a polarization maintaining optical fiber according to a comparative example and a polarization maintaining optical fiber according to the present invention, The core radius Rc is 3.5 占 퐉, the trench radius Rt is 6 占 퐉, the radius Rs of the stress applying unit is 15 占 퐉 and the distance d of the stress applying unit from the center is 24 占 퐉. On the other hand, the first, second and third embodiments of the present invention are the same size as the comparative example 1, the second stress imparting member 232 is the same size as the stress imparting unit of the comparative example, and the first stress imparting member 231 Respectively. 6 (a), 6 (b), and 6 (b), the stresses of the comparative example and each example were analyzed under the same conditions as those of the first, second, and third embodiments, c) (d) show the stress analysis results of the comparative example and the polarization maintaining optical fiber according to the first, second, and third embodiments of the present invention.

Next, the birefringence and beat length for the comparative example and the first, second, and third embodiments were calculated using the stress analysis results, and the results are shown in Table 1 below.

[Table 1]

As shown in Table 1, in comparison with the comparative example, it can be seen that the embodiments of the present invention have a large birefringence and the bit length is shortened. It can also be seen from the embodiments of the present invention that as the first stress applying member 231 becomes larger, the birefringence increases and the bit length becomes shorter.

7 (a), 7 (b), 7 (c) and 7 (d) are schematic views showing a process of manufacturing a polarization maintaining optical fiber according to the present invention.

7, a method of manufacturing a polarization maintaining optical fiber according to the present invention includes the steps of: (a) fabricating an optical fiber preform comprising a core unit 310 and a cladding unit 320 surrounding the core unit 310; (B) forming insertion holes (331a) and (332a) in the optical fiber preform at positions corresponding to the plurality of stress applying members, respectively; (C) of inserting the stress imparting rods 331 and 332 into the insertion holes 331a and 332a, respectively; (D) of drawing out the optical fiber preform in which the stress imparting rods 331 and 332 are inserted in the respective insertion holes 331a and 332a in a molten state.

(a) is a process of fabricating an optical fiber preform using Modified Chemical Vapor (MCVD) or Vapor-Phase Axial Deposition (VAD). For example, the optical fiber using VAD The base material is manufactured by depositing a soot core deposition burner installed in the reaction chamber and the glass microparticles generated in the clad deposition application burner at the tip of a starting member mounted on a shaft rising while rotating the soot core, And then the porous base material is subjected to dewatering treatment and transparent vitrification treatment to obtain an optical fiber preform comprising the core unit 310 and the cladding unit 320.

(b) is a process of forming insertion holes 331a and 332a at positions corresponding to a plurality of stress applying members on the optical fiber preform, and a known perforation drill can be used for such insertion hole processing, And the plurality of insertion holes 331a and 332a can be formed precisely by processing using ultrasonic waves.

Each of the insertion holes 331a and 332a is subjected to lapping and polishing so that the insertion holes 331a and 332a and the stress imparting rods 331a and 332b are formed at the time of melt drawing of the optical fiber preform through the polishing process. ) 332 in the case where the air bubbles are generated.

(c) is a process of inserting the stress applying rods 331 and 332 into the insertion holes 331a and 332a and assembling them.

the step (d) causes the optical fiber preform in which the stress imparting rods 331 and 332 are inserted in the respective insertion holes to be drawn out from the molten state. At this time, the insertion holes 331a and 332a and the stress imparting rods 331 and 332, The drawing of the optical fiber preform can be performed while adjusting the degree of vacuum (0 to 300 Pa).

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. It will be apparent to those of ordinary skill in the art.

110: core unit 120: cladding unit
130: Stress imparting unit
131, 132, 133: stress applying member

Claims (5)

A core unit;
A cladding unit configured to surround the core unit;
And a pair of stress applying units arranged in the cladding unit symmetrically about the core unit,
Wherein the stress applying unit is constituted by two or more stress applying members arranged on the same axis (C1) with a circular cross section having different radii around the core unit,
Wherein the stress imparting unit has a triangular shape in which two imaginary lines connecting in a circumscribed manner with the stress applying members are triangular. The polarization maintaining optical fiber according to claim 1, wherein the stress imparting members are smaller in size than the stress imparting members disposed on the outer side. delete The polarization maintaining optical fiber according to claim 1 or 2, wherein the stress imparting member disposed closest to the core unit among the stress applying members is at least equal to or smaller than the core unit. delete

Images