KR20170067166A - Current sensor using optical fiber incorporated with quantum dots - Google Patents

Abstract

A polarizer for polarizing a light source input to the optical fiber current sensor; An optical fiber comprising a core and a cladding layer wound on a current-carrying electric wire and having a polarized polarized signal incident on 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 dots, a magneto-optical glass, and a magneto-optical single crystal. The present invention also provides an optical fiber current sensor.

Description

TECHNICAL FIELD [0001] The present invention relates to a current sensor using an optical fiber containing a quantum dot,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber current sensor, and more particularly, to an optical fiber current sensor with improved magneto-optical effect.

Fiber-optic current sensors are lightweight, cost-effective, and are being exploited because they are used to develop almost all fiber optic devices (eg, switch modulators, circulators, isolators, etc.).

Fiber-optic current sensors are certainly more advantageous than glass bulk current sensors because they do not require bulk optics such as polarizers, birefringent plates, and special launching lenses, even though they have low sensitivity

Conventional fiber current sensors include: (a) fiber optic arrays based on fiber Bragg gratings (FBGs) that have disadvantages such as high temperature sensitivity, difficulty handling and high cost of infrared pumping compositions; (b) eumyeonseodo small, lightweight, good property, the existing optical fiber in FIG compatible (a, but the lower the sensitivity of the fiber optic current sensor of a magnetic field the main interest) single-mode optical fiber current sensor, and (c) showing the increased Faraday rotation Eu ^{2 +} anionic A special fiber current sensor, such as a CdSe quantum dot doped fiber with better current sensitivity than doped fiber and single mode fiber current sensors.

However, all such fiber current sensors require large windings of at least 7.5 cm radius in size due to the radiation loss of light due to excessive bending of the optical fiber.

On the other hand, in order to create a portable and small-sized current sensor, the optical fiber used here must be wound as small as possible in a loop size (for example, a radius of 10 mm).

Therefore, existing silica glass optical fibers reported for current sensing are not clearly suitable for making small-sized current sensors.

In this respect, Flint glass fibers having a smaller light-elastic modulus than silica glass fibers are less susceptible to bending and have a current sensitivity that is almost twice as high as that of silica glass fibers, It looked.

However, this flint glass fiber has a disadvantage that it is incompatible with existing optical fiber and network composed of silica glass fiber.

Therefore, the best option to use a visible-light wavelength source at a low cost while making a small, portable current sensor is to use a current-sensitive fiber with a structure of distortion-loss-insensitive fiber (BIF) .

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

It is an object of the present invention to provide a polarimeter for polarizing a light source input to an optical fiber current sensor. An optical fiber comprising a core and a cladding layer wound on a current-carrying electric wire and having a polarized polarized signal incident on 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 a magneto-optical single crystal.

Here, it is preferable that Cd _{0 . 5} Mn _{0 . 5} Te quantum dots, a magneto-optical glass, and a 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 dots, a magneto-optical glass, and a magneto-optical single crystal.

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 glasses, (Terbium Gallium Garnet) or YIG (Yttrium Iron Garnet).

The present invention increases the sensitivity of a current sensor by including a quantum dot in an optical fiber used in a fiber current sensor and thereby enhances the magnetooptical effect. By applying an optical fiber structure with a low optical loss due to optical fiber banding, Can be produced.

1 is a schematic diagram of a typical optical fiber current sensor.
Fig. 2 is a graph showing the Cd _{0 . 5} Mn _{0 . 5} Te, CdSe, Co, and Mn is measured at 660 nm in the Faraday rotation angle of the optical fiber.

All terms including technical terms 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 an optical fiber current sensor that is sensitive to light currents due to insufficient optical loss due to banding of the optical fiber and is sensitive to small currents, and can be manufactured compactly.

FIG. 1 shows a schematic view of a conventional optical fiber current sensor for measuring current flowing in a wire. The light source 11 is polarized by the polarizer 12 and the polarized polarized signal is passed through the optical fiber 13 wound on the electric wire so that the light and the magnetic field propagating inside the optical fiber 13 The polarized signal polarized by the Faraday effect rotates. As the magnitude of the magnetic field induced around the electric wire 14 increases according to the magnitude of the electric current flowing through the electric wire 14 and the magnitude of the magnetic field increases, the Faraday effect increases, so that the larger the electric current flowing through the electric wire 14, The polarimeter 15 measures the degree of rotation of the polarized signal and measures the current flowing through the wire 14. [

In the present invention, in order to fabricate a small current sensor applicable to a small-sized device, the cladding layer described in the prior patent publication " Patent Publication No. 2011-0134869, entitled " Layer, a trench layer and an outer cladding layer, and a core layer and / or an inner cladding layer of the optical fiber contains a Cd _0.5 Mn _0.5 Te quantum dot, a magneto-optical glass, and a magneto-optical single crystal.

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

Here, the magneto-optical glass means a glass whose optical characteristics are changed by a change in applied magnetic field produced by adding a rare earth element such as Tb, Y, Eu to the borosilicate glass composition.

Preferably, the magneto-optic single crystal may be added to the core and / or cladding layer or the inner cladding layer of the optical fiber in a state of quantum dots or very fine powder by pulverization. These magneto-optic single crystals are commonly referred to as chemical components, and TGG (Terbium Gallium Garnet) crystals and YIG (Yttrium Iron Garnet) crystals are the most representative.

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

The present inventors have been able to induce a high Faraday effect by containing 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, and will be described in detail in the following embodiments with reference to the accompanying drawings do. Embodiments of the present invention will be described in order to facilitate those skilled in the art to which the present invention belongs. As will be readily understood by one of ordinary skill in the art, the following embodiments may be modified in various ways within the scope and spirit of the present invention. Wherever possible, the same or similar parts are denoted using the same reference numerals in the drawings.

[ Example ] CD _{0 . 5} Mn _{0 . 5} Te The quantum dot  Magneto-optical properties of optical fibers

Cd _{0 . 5} Mn _{0 . 5} Te quantum dots were fabricated by modified chemical vapor deposition (MCVD). A porous core layer was formed at 1650 ° C using SiCl ₄ and GeCl ₄ in a silica glass tube. After partial sintering, 0.475 g (0.1 M) of nitric acid was added to 5 ml of nitric acid (Junsei Chem., 70% Cd _{0 . 5} Mn _{0 . 5} Te powder (International Crystal Lab.) Was poured into the porous core layer to form Cd _{0 . 5} Mn _{0 . 5} Te quantum dots were fabricated, and the fabricated optical fiber preform was drawn to the optical fiber at below 2000 ° C. After passing the optical fiber through the center of the solenoid (Walker LDJ, 3.0-28-1500DC), the magneto-optical characteristics of the magnetic field were measured using a laser diode (LD) light source with a wavelength of 660 nm and a polarimeter (THORLABs, PA-510) Respectively.

In order to confirm the influence of Mn ions confirmed to exist together in the optical fiber core, Mn ion doped optical fibers were prepared and compared. And Cd _{0 . 5} Mn _{0 . For the} evaluation of the Faraday rotation characteristics of the ₅ Te nanocrystal optical fiber, we compared the cobalt (Co) ion doped fiber with the CdSe quantum doped optical fiber and the common single mode fiber fabricated in this laboratory. As a result of measuring the magnetooptical 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, the Faraday rotation angle was linearly increased as the magnetic field of all the optical fibers was increased as shown in FIG. Cd _{0 . 5} Mn _{0 . 5} Te quantum dots showed a Faraday rotation angle of about 1.5 times and 6 times higher than the optical fiber containing Co and Mn ions under the same magnetic field and about 1.5 times more than the CdSe containing optical fiber and about It was found that the rotation angle increased about twice. In the case of the Mn-doped optical fiber, the Cd _0.5 Mn _0.5 Te quantum dots were more affected than the Mn ions in the increase of Faraday rotation of the optical fiber containing the Cd _0.5 Mn _0.5 Te quantum dots. This is because Cd _{0 . 5} Mn _{0 . 5} Te quantum dot (Zeeman effect). Cd ₀ obtained by using the measured Faraday rotation angle _{. 5} Mn _{0 .} The Verde constants of the ₅ Te quantum dots, Co ion or Mn ion containing optical fibers and SMF were 5.12, 3.54, -1.04 and 2.77 radT ^-1 m ^{- 1} at 660 nm, respectively.

Table 1 below shows Cd _{0 . 5} Mn _{0 . 5} Te quantum dots, Co ions, or Mn ions.

Effective length (m)

Magnetic field (T)
The rotation angle?
Verde constant (rad ^-1 m ^-1 ) Cd _0.5 Mn _0.5 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: Fiber optic 14: Wires
15: Polarimeter

Claims (4)

A polarizer for polarizing a light source input to the optical fiber current sensor;
An optical fiber comprising a core and a cladding layer wound on a current-carrying electric wire and having a polarized polarized signal incident on the polarizer; And
In the core layer and Cd _0, it includes a polarimeter for measuring a change in the polarization signal that has passed through the optical fiber wound on the _{wire. 5} Mn _{0 . 5} Te quantum dots. The optical information recording medium according to claim 1, wherein Cd _{0 . 5} Mn _{0 . 5} Te quantum dots, a magneto-optical glass, and a magneto-optical single crystal. The method of claim 1, wherein 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 dots, a magneto-optical glass, and a magneto-optical single crystal. The photomagnetic glass according to any one of claims 1 to 3, wherein the magneto-optical glass is a quantum dot of FR-5, FR-7, MOS-4, MOS-10, Tb-10, Tb-12 or Tb- Wherein the magneto-optical single crystal is a quantum dot or a fine powder of TGG (Terbium Gallium Garnet) or YIG (Yttrium Iron Garnet).

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