A multi-core optical fiber suitable for integrated sensing

Abstract

This invention belongs to the field of optical fiber communication technology and discloses a multi-core optical fiber suitable for integrated communication and sensing. It includes a common cladding and a fiber core. The common cladding surrounds the outer periphery of the fiber core. The fiber core includes a transmission core located at the center of the multi-core optical fiber and multiple sensing cores surrounding the transmission core. From the inside out, the transmission core includes a first core layer, a first inner cladding, and a first recessed layer. From the inside out, the sensing cores include a second core layer, a second inner cladding, and a second recessed layer. This invention enables simultaneous communication transmission and sensing functions, ensuring high-capacity transmission while also enabling the monitoring of sensing parameters.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber communication technology, and more specifically, relates to a multi-core optical fiber suitable for integrated communication and sensing. Background Technology

[0002] Digital oilfields are a concrete manifestation of the digital earth concept in the petroleum industry and a branch of the practical application of digital earth theory. Smart oilfields evolve from digital oilfields, and digital oilfields are the foundation of smart oilfields. To integrate data from oilfield monitoring, facilitate information exchange between the oilfield location and the control center, and enable temporary communication in the special environment of the oilfield, a multi-core optical fiber integrating communication and transmission needs to be developed.

[0003] Existing related research, such as the invention patent "Dual-Signal Transmission Optical Fiber and Transmission Device and Method Using the Optical Fiber," achieves simultaneous transmission of sensing and communication signals in a single-core optical fiber through wavelength division multiplexing (WDM). However, the communication capacity and the parameters that the sensing can detect are limited by the above scheme. Another example is the invention patent "A Multi-Core Few-Mode Sensor-Communication Fusion Access and Transmission System," which utilizes multi-core few-mode optical fiber combined with optical fiber spatial division multiplexing technology. By designing and allocating fiber cores and modes, it achieves the fusion of optical fiber sensing and communication, and applies this technology to the monitoring and transmission of environmental information. This enables real-time sensing of complex environmental parameters (temperature, bending, and strain, etc.), helping to understand the impact of external factors on communication and providing assistance for stable signal transmission. However, the aforementioned patents do not restrict the optical fiber cross-section. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-core optical fiber suitable for integrated communication and sensing, enabling simultaneous transmission of communication and sensing functions.

[0005] The present invention provides a multi-core optical fiber suitable for integrated sensing and communication, comprising: a common cladding and a fiber core, wherein the common cladding surrounds the outer peripheral surface of the fiber core, and the fiber core includes a transmission core located at the center of the multi-core optical fiber and a plurality of sensing cores surrounding the transmission core;

[0006] The transmission core comprises, from the inside out, a first core layer, a first inner cladding layer, and a first recessed layer. The refractive index profile of the first core layer is parabolic, with a distribution index α of 1.8–2.5. The radius R11 of the first core layer is 9–10 μm, and the maximum relative refractive index difference Δ11max at the center of the first core layer is 0.9%–1.3%. The radius R12 of the first inner cladding layer is 14–18 μm, and the relative refractive index difference Δ12 is 0.3%–0.6%. The radius R13 of the first recessed layer is 20–24 μm, and the relative refractive index difference Δ13 is -1.3%–-0.5%.

[0007] The sensing core comprises, from the inside out, a second core layer, a second inner cladding layer, and a second recessed layer; the radius R21 of the second core layer is 3–6 μm, and the relative refractive index difference Δ21 is 0.6%–1.0%; the radius R22 of the second inner cladding layer is 8–12 μm, and the relative refractive index difference Δ22 is 0.1%–0.3%; the radius R23 of the second recessed layer is 13–20 μm, and the relative refractive index difference Δ23 is -1.3%–-0.5%.

[0008] Preferably, the plurality of the sensing cores are distributed at equal intervals along the circumferential direction around the transmission core.

[0009] Preferably, the number of the sensing cores is three, and the three sensing cores are arranged in an equilateral triangle.

[0010] Preferably, the core structure of the sensing core is step-type.

[0011] Preferably, the core spacing P between the transmission core and the sensing core is 50–70 μm.

[0012] Preferably, the common outer layer is a pure silicon dioxide layer.

[0013] Preferably, the diameter of the common outer cladding layer is 200–300 μm.

[0014] Preferably, the attenuation of both the transmission core and the sensing core at a wavelength of 1550nm is less than 0.24dB / km.

[0015] Preferably, the macrobending loss of both the transmission core and the sensing core at a wavelength of 1550nm, with a bending radius of R30mm for 100 turns, is less than or equal to 0.1dB.

[0016] Preferably, at a wavelength of 1550nm, the inter-core crosstalk between the transmission core and the sensing core is less than -30dB.

[0017] One or more technical solutions provided in this invention have at least the following technical effects or advantages:

[0018] The multi-core optical fiber provided by this invention comprises two types of cores, each capable of performing a specific target function. Through rational design, communication transmission and sensing functions can be simultaneously achieved, ensuring high-capacity transmission while also enabling the monitoring of sensing parameters (such as oil well temperature and vibration). Furthermore, the multi-core optical fiber provided by this invention exhibits excellent performance, including low inter-core crosstalk, low transmission attenuation, and excellent macro-bending performance. This multi-core optical fiber can be applied to oilfield transmission systems for information exchange, as well as to other communication networks requiring both communication transmission and sensing capabilities. Attached Figure Description

[0019] Figure 1 A schematic diagram of an end face structure for a multi-core optical fiber suitable for integrated sensing and communication, provided as an embodiment of the present invention;

[0020] Figure 2 A schematic diagram of the refractive index profile of the transmission core in a multi-core optical fiber suitable for integrated sensing and communication, provided as an embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of the refractive index profile of a sensing core in a multi-core optical fiber suitable for integrated sensing and communication, provided as an embodiment of the present invention. Detailed Implementation

[0022] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0023] This invention provides a multi-core optical fiber suitable for integrated sensing and communication, see [link / reference]. Figure 1 The multi-core optical fiber includes a common cladding and a core, wherein the common cladding surrounds the outer peripheral surface of the core, and the core includes a transmission core 10 located at the center of the multi-core optical fiber and a plurality of sensing cores 20 surrounding the transmission core 10. That is, the multi-core optical fiber provided by this invention contains two types of cores: the transmission core 10 located in the middle, and the plurality of sensing cores 20 located at the edges.

[0024] Specifically, multiple sensing cores 20 may be distributed at equal intervals along the circumference of the transmission core 10. For example, there may be three sensing cores 20 arranged in an equilateral triangle. The core spacing P between the transmission core 10 and the sensing cores 20 is 50–70 μm.

[0025] See Figure 2 The transmission core comprises, from the inside out, a first core layer, a first inner cladding layer, and a first recessed layer. The refractive index profile of the first core layer is parabolic, with a distribution index α (Alpha) of 1.8 to 2.5, indicating that the first core layer has a gradient structure. The radius R11 of the first core layer is 9 to 10 μm, and the maximum relative refractive index difference Δ11max at the center of the first core layer is 0.9% to 1.3%. The radius R12 of the first inner cladding layer is 14 to 18 μm, and the relative refractive index difference Δ12 is 0.3% to 0.6%. The radius R13 of the first recessed layer is 20 to 24 μm, and the relative refractive index difference Δ13 is -1.3% to -0.5%.

[0026] See Figure 3The sensing core comprises, from the inside out, a second core layer, a second inner cladding layer, and a second recessed layer. The radius R21 of the second core layer is 3–6 μm, and the relative refractive index difference Δ21 is 0.6%–1.0%. The radius R22 of the second inner cladding layer is 8–12 μm, and the relative refractive index difference Δ22 is 0.1%–0.3%. The radius R23 of the second recessed layer is 13–20 μm, and the relative refractive index difference Δ23 is -1.3%–-0.5%. The core structure of the sensing core is step-type.

[0027] The aforementioned relative refractive index difference (Δ) is the relative refractive index difference between each layer of the fiber core and the common outer cladding layer, which is a pure silicon dioxide layer, and the diameter D of the common outer cladding layer is 200-300 μm.

[0028] Based on the above structural and parameter design, taking the structure of the fiber core including a transmission core located at the center of the multi-core optical fiber and three sensing cores (denoted as sensing core 1, sensing core 2 and sensing core 3) surrounding the transmission core as an example, five specific embodiments are given below, and the main structural parameters and main performance parameters of the multi-core optical fiber are provided. See Table 1 and Table 2 for details.

[0029] Table 1 Main structural parameters of multi-core optical fiber

[0030]

[0031]

[0032] Table 2 Main performance parameters of multi-core optical fiber

[0033]

[0034] Based on Tables 1 and 2, the attenuation of both the transmission core and the sensing core at a wavelength of 1550 nm is less than 0.24 dB / km. The macro-bending loss of both the transmission core and the sensing core at a wavelength of 1550 nm, with a bending radius of R30 mm for 100 turns, is less than or equal to 0.1 dB. At a wavelength of 1550 nm, the inter-core crosstalk between the transmission core and the sensing core is less than -30 dB. That is, the inter-core crosstalk between adjacent fiber cores is less than 30 dB, allowing multiple fiber cores to be accommodated in the same fiber, thus improving the space utilization of the optical fiber.

[0035] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A multi-core optical fiber suitable for integrated sensing and communication, characterized in that, include: A common cladding and a fiber core, the common cladding surrounding the outer peripheral surface of the fiber core, the fiber core comprising a transmission core located at the center of a multi-core optical fiber and a plurality of sensing cores surrounding the transmission core; The transmission core comprises, from the inside out, a first core layer, a first inner cladding layer, and a first recessed layer. The refractive index profile of the first core layer is parabolic, with a distribution index α of 1.8–2.

5. The radius R11 of the first core layer is 9–10 μm, and the maximum relative refractive index difference Δ11max at the center of the first core layer is 0.9%–1.3%. The radius R12 of the first inner cladding layer is 14–18 μm, and the relative refractive index difference Δ12 is 0.3%–0.6%. The radius R13 of the first recessed layer is 20–24 μm, and the relative refractive index difference Δ13 is -1.3%–-0.5%. The sensing core comprises, from the inside out, a second core layer, a second inner cladding layer, and a second recessed layer; the radius R21 of the second core layer is 3–6 μm, and the relative refractive index difference Δ21 is 0.6%–1.0%; the radius R22 of the second inner cladding layer is 8–12 μm, and the relative refractive index difference Δ22 is 0.1%–0.3%; the radius R23 of the second recessed layer is 13–20 μm, and the relative refractive index difference Δ23 is -1.3%–-0.5%.

2. The multi-core optical fiber suitable for integrated sensing and communication as described in claim 1, characterized in that, Multiple sensing cores are distributed at equal intervals along the circumferential direction around the transmission core.

3. The multi-core optical fiber suitable for integrated sensing and communication as described in claim 1, characterized in that, The number of the sensing cores is three, and the three sensing cores are arranged in an equilateral triangle.

4. The multi-core optical fiber suitable for integrated sensing and communication as described in claim 1, characterized in that, The core structure of the sensing chip is step-type.

5. The multi-core optical fiber suitable for integrated sensing and communication as described in claim 1, characterized in that, The spacing P between the transmission core and the sensing core is 50–70 μm.

6. The multi-core optical fiber suitable for integrated sensing and communication as described in claim 1, characterized in that, The common outer cladding layer is a pure silicon dioxide layer.

7. The multi-core optical fiber suitable for integrated sensing and communication as described in claim 1, characterized in that, The diameter of the common outer cladding is 200–300 μm.

8. The multi-core optical fiber suitable for integrated sensing and communication as described in claim 1, characterized in that, Both the transmission core and the sensing core exhibit attenuation of less than 0.24 dB / km at a wavelength of 1550 nm.

9. The multi-core optical fiber suitable for integrated sensing and communication as described in claim 1, characterized in that, At a wavelength of 1550nm, the macro-bending loss of both the transmission core and the sensing core, when bent 100 times with a bending radius of R30mm, is less than or equal to 0.1dB.

10. The multi-core optical fiber suitable for integrated sensing and communication as described in claim 1, characterized in that, At a wavelength of 1550nm, the inter-core crosstalk between the transmission core and the sensing core is less than -30dB.

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