Optical Fiber Cable for Use in Pit and Harsh Environments

Abstract

The optical fiber cable includes a braided core (1) having a plurality of helical grooves and one or more optical fibers (4a - 4c) arranged along one or more of the helical grooves (3a - 3c) of the braided core (1). The elongated structure braided to form the braided core (1) is composed of, for example, braided ropes (2a - 2c) or monolithic wires (2d - 2f). The outer layer disposed on the outer surface of the braided core (1) is composed of a metal layer (5) or a flexible plastic layer (6).

Description

Technical Field

[0001] <Cross - Reference to Related Applications> This disclosure claims priority to and is filed with reference to U.S. Provisional Patent Application No. 63 / 348,235, filed on June 2, 2022, and U.S. Provisional Patent Application No. 63 / 368,702, filed on July 18, 2022. The entire contents of each of these applications are incorporated herein by reference for all purposes.

[0002] This disclosure relates to fiber optic cables for use in mines and harsh environments.

Background Art

[0003] Distributed fiber optic sensing (DFOS) technology has been developed for a variety of applications including sensing of strain, temperature, pressure, and sound, and for a variety of environments including harsh environments such as the oil and gas industry, the civil engineering field, and military applications. The fiber optic cables used in such systems can include multiple optical fibers and can utilize, for example, a combination of Rayleigh scattering and Brillouin scattering analysis to determine various parameters.

[0004] At reasonable costs, the reliability and adaptability of these technologies continue to be emphasized. For example, fiber optic cables with outer jackets can provide inaccurate strain results if the outer jacket becomes loose. Additionally, fiber optic cables need to withstand high lateral pressure. Finally, there has been a challenge in ensuring the ability to reliably make various connections to fiber optic cables in a quick and cost - effective manner.

Summary of the Invention

[0005] The optical fiber cable is provided with a braided core having a plurality of spiral grooves and one or more optical fibers arranged along one or more spiral grooves of the braided core. Here, the elongated structure braided to form the braided core is composed of, for example, a braided rope or a monolithic wire, and the outer layer arranged on the outer surface of the braided core is composed of a metal layer or a flexible plastic layer.

Brief Description of Drawings

[0006] Regarding other features and advantages according to the present disclosure, it is considered to be clarified from the following detailed description shown as exemplary embodiments together with the attached drawings.

[0007]

Figure 1

[0008]

Figure 2

[0009]

Figure 3A

[0010]

Figure 3B

[0011] <Detailed Description> The following is a detailed description regarding embodiments of an optical fiber cable, particularly an in-pit and harsh environment optical fiber cable.

[0012] The optical fiber cable according to an embodiment of the present disclosure includes a braided core. An exemplary braided core 1 for an optical fiber cable is shown in FIG. 1. The braided core 1 in the present embodiment is composed of three braided ropes 2a, 2b, and 2c, and these braided ropes themselves are braided together to define three helical grooves 3a, 3b, and 3c. The material of the strands constituting the braided ropes 2a, 2b, and 2c is, for example, a steel wire or a polymer wire. As an example of the polymer wire, K-FRP, which means a Kevlar fiber-reinforced plastic wire (Kevlar is a registered trademark), can be mentioned. As will be described later, in the optical fiber cable using the braided core 1, one or more optical fibers are arranged in one or more of the helical grooves 3a, 3b, and 3c, and a metal layer is provided outside the braided core 1 and the optical fiber.

[0013] FIG. 2 is a schematic cross-sectional view of an optical fiber cable using a braided core 1a similar to the braided core 1 in FIG. 1. However, in this braided core, instead of the braided ropes 2a, 2b, and 2c, elongated structures 2d, 2e, and 2f, which are monolithic wires made of steel or polymer, that is, piano wires, are used as the strands of the braided core 1a. Due to the braided structure of the braided core 1a, helical grooves 3d, 3e, and 3f are formed again. As shown in FIG. 2, the optical fibers 4a, 4b, and 4c are respectively arranged in the grooves 3d, 3e, and 3f.

[0014] In Embodiment 1 according to FIGS. 1 and 2, the diameters of the braided ropes 2a, 2b, 2c, or the monolithic wires 2d, 2e, 2f can be 3.37 mm, and the diameter of the optical fiber can be, for example, 1.2 mm. The optical fiber of the present Embodiment 1 can also be a multi-core fiber module in order to increase redundancy and increase the options for optical fiber connection. Alternatively, a single-core optical fiber of a smaller size can be used, and in this case, the miniaturization of the braided core is also possible. Furthermore, an outer layer (such as a metal layer 5 made of steel or the like) is disposed on the outer surfaces of the braided core 1a and the optical fibers 4a, 4b, 4c, and as a result, the optical fiber cable is armored. Although three optical fibers 4a, 4b, 4c are depicted in FIG. 2, the number of optical fibers can be one or two, leaving the other grooves empty. This also applies to Embodiment 2 related to FIGS. 3A and 3B described later.

[0015] FIGS. 3A and 3B are schematic cross-sectional views of an optical fiber cable in which a flexible plastic sheath 6 is provided on the outer surfaces of the braided core and the optical fibers instead of the outer surface being armored. In Embodiment 2 related to these FIGS. 3A and 3B, since a relatively soft sheath is used instead of the relatively hard armor coating as in Embodiment 1 related to FIG. 2, the optical fibers 4d, 4e, 4f each have a highly durable overcoat 7a, 7b, 7c such as thermoplastic elastomers (TPE).

[0016] The optical fiber cables shown in FIGS. 3A and 3B are different from each other in that the optical fiber cable in FIG. 3A uses three braided ropes 8a, 8b, 8c to form three elongated elements of the braided core, while the optical fiber cable in FIG. 3B uses three monolithic wires 9a, 9b, 9c as the three elongated elements of the braided core. It should be noted that in Embodiment 2 related to FIG. 3A, each braided rope 8a, 8b, 8c has a structure in which a central strand and six strands having substantially the same diameter around it are spirally wound.

[0017] In Embodiment 2 according to FIGS. 3A and 3B, the diameters of the braided ropes 8a, 8b, 8c, or the monolithic wires 9a, 9b, 9c are 1.6 mm, and the diameters of the optical fibers 4d, 4e, 4f (including their overcoats 7a, 7b, 7c) are, for example, 0.5 mm for single-core optical fibers. However, these optical fibers 4d, 4e, 4f can also be multi-core fiber modules of larger sizes, and braided cores of larger sizes can be used. And as described above, by using multi-core fiber modules, redundancy can be increased and options for optical fiber connections can be expanded. It should be noted that in all embodiments, each diameter is selected to be within the circle defined by the maximum diameter of the braided core and spaced inward therefrom (for example, in Embodiment 1 according to FIG. 2, it is within the inner circumference of the metal layer 5 and is spaced therefrom. Also, in Embodiment 2 according to FIGS. 3A and 3B, it is within the inner circumference of the sheath 6 and is spaced from the inner circumference of the sheath 6).

[0018] The optical fiber cable according to the present disclosure is designed to prevent the optical fiber from slipping due to the loosening of the outer tube, so that the strain can be accurately measured. Further, such an optical fiber cable has high strength in the lateral direction and, unlike other designs, is not covered by other wires, so the connection to the optical fiber is relatively easy.

[0019] Those skilled in the art will understand that the present disclosure can be implemented in other specific forms without departing from its spirit or essential features. Therefore, the presently disclosed embodiments are considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is indicated by the appended claims rather than the foregoing description, and all changes within the meaning and scope and the scope of equivalents thereof are intended to be included therein.

Claims

1. An armored core having a plurality of spiral grooves, and One or more optical fibers arranged along one or more spiral grooves of the armored core, an optical fiber cable for underground and harsh environments.

2. The armored core is formed by braiding a plurality of wires, and the optical fiber cable for underground and harsh environments according to claim 1, characterized in that.

3. The wire is a steel wire, and the optical fiber cable for underground and harsh environments according to claim 2, characterized in that.

4. The wire is a polymer wire, and the optical fiber cable for underground and harsh environments according to claim 2, characterized in that.

5. The armored core is formed by braiding a plurality of braided ropes, and the optical fiber cable for underground and harsh environments according to claim 1, characterized in that.

6. The armored core is formed by braiding three elongated structures, and the optical fiber cable for underground and harsh environments according to claim 1, characterized in that.

7. The optical fiber cable for underground and harsh environments according to claim 1, further comprising an outer layer disposed on the outer surfaces of the armored core and one or more of the optical fibers.

8. The outer layer includes a flexible plastic layer, and the optical fiber cable for underground and harsh environments according to claim 7, characterized in that.

9. The outer layer includes a metal layer, and the optical fiber cable for underground and harsh environments according to claim 7, characterized in that.

10. At least one of the one or more optical fibers is provided with a fiber module having two or more cores, and the optical fiber cable for underground and harsh environments according to claim 1, characterized in that.

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