Current-sensitive fiber bragg grating device with double-helix structure

Abstract

The utility model belongs to the technical field of fiber bragg grating sensing, and particularly relates to a current sensitive fiber bragg grating device with a double-helix structure, which structurally comprises a broadband light source, an optical fiber sensor and a spectrograph. The device is based on an optical fiber sensing principle, a femtosecond laser is used for processing a spiral microgroove in a single-mode optical fiber cladding, a nano-copper material is filled, when current passes through the nano-copper in the spiral microgroove, a Joule heating effect is generated, the refractive index of the single-mode optical fiber cladding is periodically modulated according to the influence of the structure and the temperature of the spiral microgroove, and the refractive index of the single-mode optical fiber cladding is adjusted. When only the spiral microgroove 1 or the spiral microgroove 2 is powered on, the optical fiber is modulated into an LPFG structure with the period of 120 microns, and when the spiral microgroove 1 and the spiral microgroove 2 are powered on at the same time, the optical fiber is modulated into an LPFG structure with the period of 60 microns. By monitoring the change of the transmission spectral line of the LPFG, the accurate measurement of the current can be realized.

Description

Technical Field

[0001] The utility model relates to the technical field of optical fiber grating sensing, in particular to a current-sensitive optical fiber grating device with a double helix structure. Background Art

[0002] Generally speaking, any periodic refractive index modulation in an optical waveguide can be called a "grating". Fiber Bragg Grating refers specifically to a type of optical passive device with periodic refractive index modulation formed in an optical fiber. According to the period of the refractive index modulation, a grating with a period of several hundred nanometers is called a Bragg fiber grating (FBG), and a grating with a period of hundreds of microns is called a long-period fiber grating (LPFG). In terms of being used as a sensor, the grating period of a long-period fiber grating is longer than that of a Bragg fiber grating. The core mode and cladding mode of the optical fiber transmitting in the same direction need to achieve phase matching conditions, which makes the attenuation peak-to-peak value of the long-period fiber grating more sensitive to changes in the external environment. Therefore, the long-period fiber grating has better performance in terms of temperature, strain, and bending sensitivity. As a new type of fiber grating, the long-period fiber grating has the advantages of low insertion loss, wide bandwidth, low back reflection, high sensitivity to changes in the external environment, simple production, and low cost. Therefore, long-period fiber grating has a very broad development prospect in the fields of communication and sensing.

[0003] The utility model proposes a design scheme for a double-helix structure current-sensitive fiber Bragg grating device. Two spiral microgrooves with the same period are processed in the cladding of a single-mode optical fiber using a femtosecond laser, and then nano-copper material is filled in the spiral microgrooves. By injecting current into the nano-copper in the spiral microgrooves, a Joule heating effect is generated, which will cause the temperature of the spiral microgrooves to rise, thereby changing the refractive index of the single-mode optical fiber cladding and forming a periodic temperature distribution. According to the structure of the spiral microgrooves and the influence of temperature, the refractive index of the single-mode optical fiber cladding is periodically modulated to form an LPFG structure. By monitoring the changes in the LPFG transmission spectrum, accurate measurement of the current can be achieved. Utility Model Content

[0004] In view of the above-mentioned problems, the utility model proposes a double-helix structure current-sensitive fiber Bragg grating device, which can realize the measurement of current.

[0005] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0006] like Figure 1 , Figure 2 and Figure 3As shown, the double helix structure current sensitive fiber Bragg grating device comprises a broadband light source (1), an optical fiber sensor (2) and a spectrometer (3), characterized in that: the optical fiber sensor (2) comprises a spiral microgroove 1 (2-1), a spiral microgroove 2 (2-2) and a nano copper material (2-3), wherein two spiral microgrooves with the same period are processed in the cladding of a single-mode optical fiber with a core diameter of 9 μm and a cladding diameter of 125 μm using a femtosecond laser system, and the nano copper material (2-3) is filled in the spiral microgroove 1 (2-1) and the spiral microgroove 2 (2-2) of the optical fiber sensor (2); when only the spiral microgroove 1 (2-1) or the spiral microgroove 2 (2-2) is energized, the optical fiber is modulated into a LPFG structure with a period of 120 μm; when the spiral microgroove 1 (2-1) and the spiral microgroove 2 (2-2) are energized at the same time, the optical fiber is modulated into a LPFG structure with a period of 60 μm. The femtosecond laser processing system comprises a three-dimensional workbench (4), a femtosecond laser (5), a CCD (6) and an objective lens (7). The single-mode optical fiber is fixed on the three-dimensional workbench (4) with a positioning accuracy of X 1 μm×Y 1 μm×Z 0.5 μm. The laser beam is focused on the surface of the optical fiber through the objective lens (7). The processing process of the femtosecond laser is observed in real time through the CCD (6) image. The three-dimensional workbench (4) causes the single-mode optical fiber to generate a rotational motion with a rotation speed of ω and a reciprocating motion with an axial speed of v. At this time, the pitch of the spiral microgroove is When a femtosecond laser processing system is used to process a spiral microgroove, the three-dimensional workbench (4) controls the rotation speed of the single-mode optical fiber to be 12r / min and the feed speed to be 1.44mm / min, and finally a microstructure with a groove width of 5-10μm, a groove depth of 1-5μm, and a pitch of 120μm can be prepared. The optical fiber sensor (2) uses a cadmium selenide optical fiber with a high thermo-optical coefficient. By injecting current into the nano-copper in the spiral microgroove, a Joule heating effect is generated, which will cause the temperature of the spiral microgroove to rise, thereby changing the refractive index of the single-mode optical fiber cladding, forming a periodic temperature distribution. According to the structure of the spiral microgroove and the influence of temperature, the refractive index of the single-mode optical fiber cladding is periodically modulated. When only the spiral microgroove 1 (2-1) or the spiral microgroove 2 (2-2) is energized, the optical fiber is modulated into a LPFG structure with a period of 120μm. When the spiral microgroove 1 (2-1) and the spiral microgroove 2 (2-2) are energized at the same time, the optical fiber is modulated into a LPFG structure with a period of 60μm. By monitoring the changes in the LPFG transmission line, accurate measurement of the current can be achieved.

[0007] The utility model discloses a double helix structure current sensitive fiber Bragg grating device. According to the structure of the spiral microgroove and the influence of temperature, the refractive index of the cladding of the single-mode optical fiber is periodically modulated. When only the spiral microgroove 1 (2-1) or the spiral microgroove 2 (2-2) is energized, the optical fiber is modulated into an LPFG structure with a period of 120 μm. When the spiral microgroove 1 (2-1) and the spiral microgroove 2 (2-2) are energized at the same time, the optical fiber is modulated into an LPFG structure with a period of 60 μm. By monitoring the changes in the LPFG transmission spectrum, accurate measurement of the current can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 Schematic diagram of the workflow of the utility model

[0009] Figure 2 Schematic diagram of the specific structure of the utility model

[0010] Figure 3 Schematic diagram of the processing system of the utility model DETAILED DESCRIPTION

[0011] The utility model will be described in further detail below in conjunction with the accompanying drawings.

[0012] As shown in the figure, a double helix structure current sensitive fiber Bragg grating device includes a broadband light source (1), an optical fiber sensor (2), a spectrometer (3), a spiral microgroove 1 (2-1), a spiral microgroove 2 (2-2), and a nano copper material (2-3). The specific implementation steps are as follows:

[0013] Step 1: Processing spiral micro grooves

[0014] 1) Fixing the single-mode optical fiber on a three-dimensional workbench (4) with a positioning accuracy of X 1 μm × Y 1 μm × Z 0.5 μm;

[0015] 2) The light beam is focused on the surface of the optical fiber through the objective lens (7), and the processing process of the femtosecond laser is observed in real time through the CCD (6) image. The three-dimensional workbench (4) causes the single-mode optical fiber to generate a rotational motion with a rotation speed of ω and a reciprocating motion with an axial speed of v. At this time, the pitch of the spiral microgroove is

[0016] 3) The three-dimensional workbench (4) controls the rotation speed of the single-mode optical fiber to be 12 r / min and the feed speed to be 1.44 mm / min;

[0017] 4) Make Figure 2 The two periodic spiral microgroove structures shown: the groove width is 5-10μm, the groove depth is 1-5μm, and the pitch is 120μm spiral microgroove.

[0018] Step 2: Filling with nano copper material

[0019] 1) dispersing the nano copper particles in an isopropanol solvent and suspending them uniformly in the solvent;

[0020] 2) filling the prepared solution into the optical fiber microgrooves by centrifugation and making the nano-copper particles evenly distributed in the microgrooves;

[0021] 3) Drying the optical fiber and solidifying the nano copper particles to form a conductive layer;

[0022] 4) Using physical vapor deposition (PVD), additional copper film is deposited into the micro-grooves and the film is adjusted to a suitable thickness.

[0023] The specific experimental process is as follows:

[0024] Two spiral microgrooves with the same period are processed in the cladding of a single-mode optical fiber using a femtosecond laser, and then nano-copper materials are filled in these two spiral microgrooves. By injecting current into the nano-copper in the spiral microgrooves, the Joule heating effect is generated, which will cause the temperature of the spiral microgrooves to rise, thereby changing the refractive index of the single-mode optical fiber cladding and forming a periodic temperature distribution. According to the structure of the spiral microgrooves and the influence of temperature, the refractive index of the single-mode optical fiber cladding is periodically modulated. When only spiral microgrooves 1 (2-1) or spiral microgrooves 2 (2-2) are energized, the optical fiber is modulated into an LPFG structure with a period of 120μm. When spiral microgrooves 1 (2-1) and spiral microgrooves 2 (2-2) are energized at the same time, the optical fiber is modulated into an LPFG structure with a period of 60μm. By monitoring the changes in the LPFG transmission spectrum, accurate measurement of the current can be achieved.

Claims

1. A double helix structure current sensitive fiber Bragg grating device, comprising a broadband light source (1), a fiber sensor (2) and a spectrometer (3), characterized in that: The optical fiber sensor (2) comprises a spiral microgroove 1 (2-1), a spiral microgroove 2 (2-2) and a nano copper material (2-3). Two spiral microgrooves with the same period are processed in the cladding of a single-mode optical fiber with a core diameter of 9 μm and a cladding diameter of 125 μm using a femtosecond laser processing system, and the nano copper material (2-3) is filled in the spiral microgroove 1 (2-1) and the spiral microgroove 2 (2-2) of the optical fiber sensor (2). When only the spiral microgroove 1 (2-1) or the spiral microgroove 2 (2-2) is energized, the optical fiber is modulated into an LPFG structure with a period of 120 μm. When the spiral microgroove 1 (2-1) and the spiral microgroove 2 (2-2) are energized at the same time, the optical fiber is modulated into an LPFG structure with a period of 60 μm.

2. A double helix structure current sensitive fiber Bragg grating device according to claim 1, characterized in that: The femtosecond laser processing system comprises a three-dimensional workbench (4), a femtosecond laser (5), a CCD (6) and an objective lens (7). The femtosecond laser processing system prepares spiral microgrooves with a groove width of 5-10 μm, a groove depth of 1-5 μm and a pitch of 120 μm on the surface of a single-mode optical fiber.

3. The double helix structure current sensitive fiber Bragg grating device according to claim 1, characterized in that: The optical fiber sensor (2) adopts cadmium selenide optical fiber with a high thermo-optical coefficient.

4. The double helix structure current sensitive fiber Bragg grating device according to claim 1, characterized in that: The nano copper material (2-3) is uniformly filled in the optical fiber microgrooves to form a stable conductive layer.

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