KR20140028214A - Current sensor using optical fiber incorporated with quantum dots - Google Patents

Abstract

Polarizer for polarizing the light source input to the optical fiber current sensor; An optical fiber made up of a core and a cladding layer wound around a wire through which a current flows and to which a polarized polarized signal is incident from the polarizer; And a polarimeter for measuring a change in the polarized signal passing through the optical fiber wound on the wire, wherein at least one selected from the group consisting of Cd _0.5 Mn _0.5 Te quantum dots, magneto-optical glass, and magneto-optical single crystals on the core layer It provides an optical fiber current sensor comprising a.

Description

Current sensor using optical fiber containing quantum dots {CURRENT SENSOR USING OPTICAL FIBER INCORPORATED WITH QUANTUM DOTS}

The present invention relates to an optical fiber current sensor, and more particularly, to an optical fiber current sensor having an improved magneto-optical effect.

Much research has been done because of the advantages that fiber-optic current sensors are lightweight, cost-effective and used in the development of virtually all fiber optic devices (eg switch modulators, circulators and isolators, etc.).

Fiber optic current sensors have certain advantages over glass bulk current sensors, even if their sensitivity is small, because they do not require bulk optics such as polarizers, birefringent plates, and special launching lenses.

Conventional fiber optic current sensors include: (a) fiber arrays based on fiber Bragg gratings (FBG), which have disadvantages such as high temperature sensitivity, handling difficulties and high cost of infrared pumping compositions, and (b) very portable. A single-mode fiber optic current sensor (but low sensitivity of the fiber optic current sensor to magnetic fields is of primary concern), which is light and small, but compatible with existing optical fibers, and (c) doped with Eu2 + anions with increased Faraday rotation. Specialty fiber current sensors such as CdSe quantum dot doped fibers with better current sensitivity than fiber and single mode fiber current sensors.

However, all these optical fiber current sensors require a large winding of at least 7.5 cm radius because the radiation loss of light occurs due to excessive bending of the optical fiber.

On the other hand, in order to make a portable and small current sensor, the optical fiber used here should be wound to as small a loop size as possible (eg a radius of 10 mm).

Therefore, conventional silica glass optical fibers reported for current sensing are clearly not suitable for making small size current sensors.

In this respect, the flint glass fiber having a small photo-elastic coefficient compared to the silica glass fiber is insensitive to bending and increases the current sensitivity by almost twice as much as that of the silica glass fiber. Seemed.

However, this flint glass fiber is incompatible with existing optical fibers and networks composed of silica glass fiber.

Therefore, the best option to use a visible wavelength band source at a low price while creating a small and portable current sensor is to use a high-sensitivity optical fiber while utilizing the structure of a distortion-loss insensitive fiber (BIF). Will be.

In order to solve the above problems of the prior art, it is an object of the present invention to provide an optical fiber current sensor having an improved magneto-optical effect.

An object of the present invention as described above is a polarizer for polarizing the light source input to the optical fiber current sensor; An optical fiber made up of a core and a cladding layer wound around a wire through which a current flows and to which a polarized polarized signal is incident from the polarizer; And a polarimeter for measuring a change in the polarization signal that has passed through the optical fiber wound on the wire, the core layer Cd _{0 .5} Mn _{0 .5} Te quantum dot, a magneto-optical glass and the light from the group consisting of single crystal magnetic Achieved by an optical fiber current sensor containing at least one selected.

In this case, preferably contains additionally at least one selected from the group consisting of the cladding layer with Mn _{0 .5 0 .5} Cd Te quantum dot, a magneto-optical glass, and magneto-optical single crystal.

Preferably, the cladding layer is composed of the inner cladding layer, the trench layer and the outer cladding layer, the inner cladding layer Cd _{0 .5} Mn _{0 .5} Te quantum dot, a magneto-optical and magneto-optical glass selected from the group consisting of single crystals Additionally contains at least one or more.

Preferably, the magneto-optical glass is a quantum dot or fine powder of FR-5, FR-7, MOS-4, MOS-10, Tb-10, Tb-12 or Tb-15 glass, and the magneto-optical single crystal is TGG (Terbium Gallium Garnet) or YIG (Yttrium Iron Garnet) quantum dots or fine powder.

The present invention improves the magneto-optical effect by containing quantum dots in the optical fiber used in the optical fiber current sensor, thereby improving the sensitivity of the current sensor, and applying a small current sensor by applying an optical fiber structure with low optical loss due to the bending of the optical fiber. I can make it.

1 is a schematic diagram of a general optical fiber current sensor.
Figure 2 is a Cd _{0 .5 0 .5} Mn graph the Faraday rotation angle of Te, CdSe, the optical fiber-containing Co, Mn and showing the value measured at 660nm in accordance with the present invention.

All terms including technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Predefined terms are further interpreted as having a meaning consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or very formal meanings unless defined otherwise.

The present invention provides a fiber-optic current sensor that can be made compact by showing a light loss due to the bending of the optical fiber and sensitive response to a small current.

Figure 1 shows a schematic diagram of a typical optical fiber current sensor for measuring the current flowing through the wire. The light source 11 is polarized by the polarizer 12, and the polarized polarized signal passes through the optical fiber 13 wound around the wire and receives light and magnetic field that propagate inside the optical fiber 13 by induction of a magnetic field by electric current. The polarization signal polarized by the Faraday effect rotates because it proceeds in the same direction. As the magnitude of the current flowing in the wire 14 increases, the magnitude of the magnetic field induced around the wire 14 increases and the Faraday effect increases as the magnitude of the magnetic field increases, so that the greater the magnitude of the current flowing through the wire, the more the polarization signal is. Since the rotation is performed, the current flowing through the wire 14 may be measured by measuring the degree of rotation of the polarization signal in the polarizer 15.

In the present invention, in order to manufacture a small current sensor that can be applied to a small device, the inner cladding of the cladding layer, which is described in the present inventors' patent publication No. 2011-0134869, title of the invention: low bending loss optical fiber a layer, the trench layer and the use of the separating structure to the outside cladding layer and the core layer of the optical fiber at the same time and / or the internal cladding layer may contain a Mn _{0 .5 0 .5} Cd Te quantum dot, a magneto-optical glass, and magneto-optical single crystal.

Preferably, the magneto-optical glass is FR-5 and FR-7 of Schott, Germany, MOS-4 and MOS-10 of MolTech GmbH, Germany, and Foxtech Photonics Co., Ltd. Tb-10, Tb-12, and Tb-15 of Foctek Photonics Inc., China, which are pulverized and contained in the core and / or the cladding layer or the inner cladding layer of the optical fiber in the form of quantum dots or very fine powder. .

Here, the magneto-optical glass refers to a glass whose optical properties change with a change in the applied magnetic field produced by adding rare earth elements such as Tb, Y, and Eu to the borosilicate glass composition.

Preferably, the magneto-optical single crystal may be pulverized and added to the core and / or cladding layer or inner cladding layer of the optical fiber in quantum dots or very fine powder state. This magneto-optical single crystal is collectively referred to as a chemical component, and the most common is the TGG (Terbium Gallium Garnet) crystal and YIG (Yttrium Iron Garnet) crystal.

The present invention may be applied to an optical fiber composed of a core layer and a cladding layer, which is a general optical fiber structure, but may preferably be applied only to the core layer and / or the inner cladding layer of the optical fiber structure shown in the prior patent of the present inventors.

The inventors were able to induce a high Faraday effect by including Cd _0.5 Mn _0.5 Te quantum dots in the core layer and / or the cladding layer or the inner cladding layer of the optical fiber, which will be described in detail with reference to the accompanying drawings in the following examples. do. Embodiments of the present invention will be described so that those skilled in the art can easily practice the present invention. As can be easily understood by those skilled in the art, the embodiments described below may be modified in various forms without departing from the concept and scope of the present invention. Where possible, the same or similar parts are represented using the same reference numerals in the drawings.

[ Example ] CD _{0 .5} Mn _{0 .5} Te Quantum dots  Magneto-optical Properties of Fibers Contained

Mn _{0 .5 0 .5} Cd Te of the quantum dot-containing optical fiber preform was produced by a modified chemical vapor layer chakbeop (MCVD). After the partial sintering process, a porous core layer was formed at 1650 ° C using SiCl ₄ and GeCl ₄ inside the silica glass tube, and 0.475 g (0.1 M) was added to 5 ml nitric acid (Junsei Chem., 70%). Mn _{0 .5 0 .5} Cd Te powder (International Crystal Lab.) to infiltrate the mixed solution on a porous core layer Cd _{0 .5 0 .5} Mn were fabricated is a Te-containing quantum dot optical fiber preform, thus making the optical fiber The base material was drawn out to the optical fiber at 2000 ° C or less. After passing the optical fiber through the center of the solenoid (Walker LDJ, 3.0-28-1500DC), the magneto-optical characteristics according to the change of the magnetic field were measured using a 660 nm laser diode (LD) light source and polarizer (THORLABs, PA-510). Measured.

In order to confirm the influence of Mn ions found to exist together in the optical fiber core, Mn ion-added optical fibers were prepared and compared. _{0 .5 0 .5} Mn and Cd were compared to evaluate the Faraday rotation properties of the Te-containing quantum dot optical fiber, with a cobalt (Co) ion-doped optical fiber with the addition of a CdSe quantum dot optical fiber manufactured in the lab and normal single mode fiber. As a result of measuring the magneto-optical characteristics of each optical fiber through a polarimeter by applying a magnetic field parallel to the optical fiber through the increase of the solenoid current value, as shown in FIG. 2, the Faraday rotation angle increased linearly as the magnetic field increased. _{0 .5 0 .5} Cd Mn case of the Te-containing quantum dot optical fiber was under the same magnetic field when the absolute value exhibited about 1.5 times and 6 times higher than the Faraday rotation angle of the optical fiber containing the Co ions and Mn ions, than CdSe-containing fiber The rotation angle was increased about 1.5 times and about 2 times than SMF. Show that the Mn ions is increased in the negative direction for the doped fiber _{0 .5} Cd Mn _{0 .5} the Faraday rotation increase in the Te-containing quantum dot optical fiber Cd than Mn ion Mn _{0 .5 0 .5} Te quantum effect a zoom could see the michyeoteum, which is due to be due to the Cd _{0 .5} Mn _{0 .5} zeeman effect (zeeman effect) of Te quantum dots. Obtained using the Faraday rotation angle measured Mn _{0 .5 0 .5} Cd Te quantum dots, Co ions or Mn ions Verde constant of the optical fiber and the SMF is contained, respectively 5.12, 3.54, -1.04 at 660 nm wavelength of 2.77 radT ^{- 1} m ^{- 1} .

In Table 1 of Cd _{0 .5 0 .5} Mn Te quantum dots, and showed the magnetic and optical properties of Co ions or Mn ions containing optical fibers.

Effective length (m)

Magnetic field (T)
Rotation angle (θ)
Verde constant (rad ^-1 m ^-1 ) Mn _{0 .5 0 .5} Cd Te-doped fiber 0.7 0.142 29.18 5.12 Co doped fiber 0.7 0.142 20.18 3.54 CdSe Doped Fiber 0.7 0.142 20.28 3.56 Mn Doped Fiber 0.7 0.142 -5.93 -1.04 SMF 0.7 0.142 15.82 2.77

While the illustrative embodiments of the present invention have been shown and described, various modifications and alternative embodiments may be made by those skilled in the art. Such variations and other embodiments will be considered and included in the appended claims, all without departing from the true spirit and scope of the invention.

11: light source 12: polarizer
13: optical fiber 14: electric wire
15: polarimeter

Claims (4)

Polarizer for polarizing the light source input to the optical fiber current sensor;
An optical fiber made up of a core and a cladding layer wound around a wire through which a current flows and to which a polarized polarized signal is incident from the polarizer; And
Includes a polarimeter for measuring a change in the polarization signal that has passed through the optical fiber wound on the wire, and the core layer Cd _{0 .5} Mn _{0 .5} Te quantum dot, a magneto-optical and magneto-optical glass selected from the group consisting of single crystals Optical fiber current sensor comprising at least one or more. According to claim 1, Cd Mn _{0 .5 0 .5} Te quantum dot, a magneto-optical glass and fiber optic current sensor in the optical magnetic group consisting of a single crystal characterized in that it additionally contains at least one or more selected in the cladding layer. The method of claim 1, wherein the cladding layer inside the cladding layer, the trench layer and consisting the outer cladding layer, Cd _{0 .5 0 .5} Mn in the inner cladding layer Te quantum dot, a magneto-optical glass and an optical magnetic group consisting of a single crystal Optical fiber current sensor further comprises at least one selected from. The method of claim 1, wherein the magneto-optical glass is a quantum dot of FR-5, FR-7, MOS-4, MOS-10, Tb-10, Tb-12 or Tb-15 glass or The fine powder, and the magneto-optical single crystal is a quantum dot or fine powder of TGG (Terbium Gallium Garnet) or YIG (Yttrium Iron Garnet).

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