阅读说明：本技术 一种多芯光纤忆阻器件及“擦、写、读”方案 (Multi-core optical fiber memristor and erasing, writing and reading scheme ) 是由 金威 程思莹 李翔 李亚茹 张毅博 张亚勋 张羽 刘志海 杨军 苑立波 于 2021-09-01 设计创作，主要内容包括：本发明提供一种多芯光纤忆阻器件及“擦、写、读”方案。该多芯光纤忆阻器件及“擦、写、读”方案,包括“读、写、擦”激光输出模块、多芯光纤忆阻器、“读”多芯探测模块,其中多芯光纤忆阻器包括多芯光纤、光学相变材料薄膜和防氧化增反膜。在多芯光纤端面后依次镀有光学相变材料薄膜和防氧化增反膜来构造多芯光纤忆阻器；各个纤芯中注入“擦、写”脉冲激光分别对各纤芯端面的光学相变材料的相态进行调控,不同相态下的光学相变材料反射率存在差异,通过“读”连续激光读取每个纤芯的存储状态,从而实现多芯非易失性全光存储。该多芯光纤忆阻器件基于空分复用理念提升单芯光纤非易失性存储的维度,可极大地提高通信、存储容量,突破当前普通单模光纤信息容量极限。(The invention provides a multi-core optical fiber memristor and an erasing, writing and reading scheme. The multi-core optical fiber memristor comprises a read, write and erase laser output module, a multi-core optical fiber memristor and a read multi-core detection module, wherein the multi-core optical fiber memristor comprises a multi-core optical fiber, an optical phase-change material film and an anti-oxidation reflection increasing film. Sequentially plating an optical phase change material film and an anti-oxidation reflection increasing film behind the end face of the multi-core optical fiber to construct a multi-core optical fiber memristor; the phase states of the optical phase change materials on the end faces of the fiber cores are respectively regulated and controlled by injecting erasing and writing pulse laser into the fiber cores, the reflectivity of the optical phase change materials in different phase states is different, and the storage state of each fiber core is read by reading continuous laser, so that multi-core nonvolatile all-optical storage is realized. The multi-core optical fiber memristor improves the dimensionality of single-core optical fiber nonvolatile storage based on the space division multiplexing concept, can greatly improve communication and storage capacity, and breaks through the information capacity limit of the current common single-mode optical fiber.)

1. A multi-core optical fiber memristor device and an erasing, writing and reading scheme comprise a reading, writing and erasing laser output module (1, 2, 3, 4, 5 and 6), a multi-core optical fiber memristor (7) and a reading multi-core detection module (8, 9, 10 and 11);

the reading, writing and erasing laser output module comprises a reading, writing and erasing continuous light laser (1), a light pulse generating module (2), a one-to-N optical fiber coupler (3), a one-to-two optical fiber coupler array (4), an optical fiber circulator array (5) and a multi-core optical fiber fanning-in device (6);

the 'reading, writing and erasing' continuous light laser (1) comprises 'erasing and writing' seed source lasers (101-107) and a 'reading' continuous light laser (108);

the erasing and writing seed source lasers (101-107) respectively output continuous lasers with different wavelengths to the optical pulse generation module (2);

the reading continuous laser (108) outputs detection continuous laser, and the output wavelength is not consistent with the wavelength of the erasing and writing seed source lasers (101-107);

the 'reading, writing and erasing' continuous optical laser (1) and the upper computer (11) interactively regulate and control parameters such as wavelength, intensity and the like of output continuous laser;

the optical pulse generating module (2) comprises a dense wavelength division multiplexer (1), (201), an intensity modulator (202), an erbium-doped pulse fiber amplifier (203), a dense wavelength division multiplexer (2), (204) and an electric pulse generator (205);

the wavelength channels of the dense wavelength division multiplexers 1(201) and 2(204) are matched with the seed source lasers (101-107) for erasing and writing;

the dense wavelength division multiplexers.1 and 201 have the functions of combining continuous lasers with different wavelength channels output by the seed source lasers (101-107) for erasing and writing into a single fiber and inputting the continuous lasers into an intensity modulator (202) for light intensity modulation;

the modulation pulse source of the intensity modulator (202) is provided by an electric pulse generator (205), the function of the modulation pulse source is to perform intensity modulation on an input optical signal, when the intensity modulator (202) is in a proper static working point, the electric pulse generator (205) sends out an electric pulse, and the optical signal passing through the intensity modulator (202) receives the electric pulse modulation, so that the pulse light is generated;

the erbium-doped pulse optical fiber amplifier (203) amplifies the optical pulse signal output by the intensity modulator (202) to realize high-power pulse optical signal output;

the dense wavelength division multiplexer 2(205) receives the optical pulse signals with the wavelengths output by the erbium-doped pulse fiber amplifier 203 and separates the wavelengths into respective wavelength channels;

the erbium-doped pulse fiber amplifier (203), the electric pulse generator (204) and the upper computer (11) are interacted to realize the output of optical pulse signals with target intensity;

the one-to-N optical fiber coupler (3) equally divides the energy of the detection continuous laser emitted by the reading continuous laser (108) and inputs the energy into the one-to-two optical fiber coupler array (4);

the one-to-two optical fiber coupler array (4) comprises a plurality of one-to-two optical fiber couplers (401-407), couples the detection continuous laser equally divided by the one-to-N optical fiber coupler (3) with optical pulse signals incident to respective wavelength channels, and inputs the optical pulse signals into the optical fiber circulator array (5);

the optical fiber circulator array (5) comprises a plurality of optical fiber circulators (501-507), and the optical fiber circulators transmit light energy of respective wavelength channels from a port 1 to a port 2 and transmit light energy reflected by a rear-end device from the port 2 to a port 3;

the multicore optical fiber fanning-in device (6) couples optical signals of respective wavelength channels into corresponding fiber cores of multicore optical fibers;

the multi-core optical fiber memristor (7) comprises a multi-core optical fiber (701), an optical phase change material film (702) and an anti-oxidation reflection increasing film (703);

the multi-core optical fiber (701) at least has two fiber cores, and pulse lasers with different parameters are introduced into each fiber core;

the optical phase change material film (702) is made of a chalcogenide compound, specifically a germanium-antimony-tellurium alloy (Ge)₂Sb₂Te₅) Silver indium antimony tellurium alloy (AgInSbTe), and the like;

the optical phase-change material film (702) has at least two phase states, a crystalline state and an amorphous state, and is in an intermediate state between the crystalline state and the amorphous state, and the reflectivity of different phase states in a communication waveband is different;

the optical phase-change material film (702) is combined with the end face of the multi-core optical fiber (701) in a radio frequency magnetron sputtering mode;

the material of the anti-oxidation reflection-increasing film (703) is Indium Tin Oxide (ITO) or gold film (Au), and the like, so that the optical phase-change material film (702) is prevented from being exposed in the air and being oxidized, and the reflection of a communication waveband is increased;

the anti-oxidation and anti-reflection film (703) is combined with the optical phase-change material film (702) in a radio frequency magnetron sputtering mode;

the multicore optical fiber memristor (7) is welded with a multicore optical fiber pair output by the multicore optical fiber fanning-in device (6), so that optical signals of various wavelength channels can be transmitted to corresponding fiber cores of the multicore optical fiber memristor (7);

the reading multi-core detection module comprises an optical fiber filter array (8), a photoelectric detector array (9), a collection card (10) and an upper computer (11);

the optical fiber filter array (8) comprises a plurality of optical fiber band-pass filters (801-807) and has the function of only allowing the wavelength optical signals for detecting continuous laser to pass through;

the photoelectric detector array (9) comprises a plurality of single PIN photoelectric detectors (901-907), and has the function of monitoring the size of an optical signal reflected by each fiber core of the multi-core optical fiber memristor (7) in real time, namely reading the storage information of each fiber core;

the photoelectric detector array (9) is output to an acquisition card (10) to realize electric signal acquisition;

the acquisition card (10) and the upper computer (11) are interacted to realize information transmission;

the number of channels in the erasing and writing seed source lasers (101-107), the dense wavelength division multiplexer (1) (201), the dense wavelength division multiplexer (2) (204), the one-to-two optical fiber coupler array (4), the optical fiber circulator array (5), the multi-core optical fiber fanning-in device (6), the optical fiber filter array (8) and the photoelectric detector array (9) is matched with the number of fiber cores of the multi-core optical fiber memristor (7);

the multi-core optical fiber memristor device and the erasing, writing and reading scheme are that an optical phase-change material film (702) and an anti-oxidation reflection-increasing film (703) are sequentially plated behind the end face of a multi-core optical fiber (701) to construct a multi-core optical fiber memristor (7); the phase states of the optical phase change materials on the end faces of the fiber cores are respectively regulated and controlled by injecting erasing and writing pulse laser into the fiber cores, the reflectivity of the optical phase change materials in different phase states is different, and the storage state of each fiber core is read by reading continuous laser, so that multi-core nonvolatile all-optical storage is realized.

The technical field is as follows:

the invention belongs to the technical field of optical information, and particularly relates to a multi-core optical fiber memristor and an erasing, writing and reading scheme.

Background art:

in recent years, with the development of space division multiplexing technology and the development of multi-core optical fiber sensing technology, multi-core optical fiber has become an important development direction of current optical fiber technology. The multi-core optical fiber has a plurality of independent fiber cores in a common cladding region, can realize the transmission of space division multiplexing optical signals, greatly improves the communication capacity, and breaks the capacity limit of the current common single-mode optical fiber. Currently, multicore fibers are developed in the fields of communication (Xinzhong, Zhang qi, Yangbang, Tianqinghua, Zhang zong rain, Tianfeng, Wang cham, Yanrajing, Shengxia, Wangxin, Lvkai, Song XiuMin.) and a multicore fiber communication method [ P ]. Beijing City: CN109104244A,2018-12-28.), sensing (Du, Zhang taimen, He Jun, Wang Yi Ping, multicore fiber pressure sensor and multicore fiber pressure sensing system [ P ]. Guangdong province: CN209400111U,2019-09-17.), the multicore fiber technology is urgently waited to break through, and the development of new functions of the multicore fibers is very significant.

The invention provides a multi-core optical fiber memristor device and an erasing, writing and reading scheme, wherein an optical phase-change material film and an anti-oxidation anti-reflection film are sequentially plated behind the end surface of a multi-core optical fiber to construct the multi-core optical fiber memristor; the phase states of the optical phase change materials on the end faces of the fiber cores are respectively regulated and controlled by injecting erasing and writing pulse laser into the fiber cores, the reflectivity of the optical phase change materials in different phase states is different, and the storage state of each fiber core is read by reading continuous laser, so that multi-core nonvolatile all-optical storage is realized.

The invention content is as follows:

the invention aims to provide a multi-core optical fiber memristor and an erasing, writing and reading scheme, and multi-space-dimension nonvolatile storage is realized in a single fiber.

A multi-core optical fiber memristor device and an erasing, writing and reading scheme comprise a reading, writing and erasing laser output module (1, 2, 3, 4, 5 and 6), a multi-core optical fiber memristor (7) and a reading multi-core detection module (8, 9, 10 and 11);

the reading, writing and erasing laser output module comprises a reading, writing and erasing continuous light laser (1), a light pulse generating module (2), a one-to-N optical fiber coupler (3), a one-to-two optical fiber coupler array (4), an optical fiber circulator array (5) and a multi-core optical fiber fanning-in device (6);

the 'reading, writing and erasing' continuous light laser (1) comprises 'erasing and writing' seed source lasers (101-107) and a 'reading' continuous light laser (108);

the erasing and writing seed source lasers (101-107) respectively output continuous lasers with different wavelengths to the optical pulse generation module (2);

the reading continuous laser (108) outputs detection continuous laser, and the output wavelength is not consistent with the wavelength of the erasing and writing seed source lasers (101-107);

the 'reading, writing and erasing' continuous optical laser (1) and the upper computer (11) interactively regulate and control parameters such as wavelength, intensity and the like of output continuous laser;

the optical pulse generating module (2) comprises a dense wavelength division multiplexer (1), (201), an intensity modulator (202), an erbium-doped pulse fiber amplifier (203), a dense wavelength division multiplexer (2), (204) and an electric pulse generator (205);

the wavelength channels of the dense wavelength division multiplexers 1(201) and 2(204) are matched with the seed source lasers (101-107) for erasing and writing;

the dense wavelength division multiplexers.1 and 201 have the functions of combining continuous lasers with different wavelength channels output by the seed source lasers (101-107) for erasing and writing into a single fiber and inputting the continuous lasers into an intensity modulator (202) for light intensity modulation;

the modulation pulse source of the intensity modulator (202) is provided by an electric pulse generator (205), the function of the modulation pulse source is to perform intensity modulation on an input optical signal, when the intensity modulator (202) is in a proper static working point, the electric pulse generator (205) sends out an electric pulse, and the optical signal passing through the intensity modulator (202) receives the electric pulse modulation, so that the pulse light is generated;

the erbium-doped pulse optical fiber amplifier (203) amplifies the optical pulse signal output by the intensity modulator (202) to realize high-power pulse optical signal output;

the dense wavelength division multiplexer 2(205) receives the optical pulse signals with the wavelengths output by the erbium-doped pulse fiber amplifier 203 and separates the wavelengths into respective wavelength channels;

the erbium-doped pulse fiber amplifier (203), the electric pulse generator (204) and the upper computer (11) are interacted to realize the output of optical pulse signals with target intensity;

the one-to-N optical fiber coupler (3) equally divides the energy of the detection continuous laser emitted by the reading continuous laser (108) and inputs the energy into the one-to-two optical fiber coupler array (4);

the one-to-two optical fiber coupler array (4) comprises a plurality of one-to-two optical fiber couplers (401-407), couples the detection continuous laser equally divided by the one-to-N optical fiber coupler (3) with optical pulse signals incident to respective wavelength channels, and inputs the optical pulse signals into the optical fiber circulator array (5);

the optical fiber circulator array (5) comprises a plurality of optical fiber circulators (501-507), and the optical fiber circulators transmit light energy of respective wavelength channels from a port 1 to a port 2 and transmit light energy reflected by a rear-end device from the port 2 to a port 3;

the multicore optical fiber fanning-in device (6) couples optical signals of respective wavelength channels into corresponding fiber cores of multicore optical fibers;

the multi-core optical fiber memristor (7) comprises a multi-core optical fiber (701), an optical phase change material film (702) and an anti-oxidation reflection increasing film (703);

the multi-core optical fiber (701) at least has two fiber cores, and pulse lasers with different parameters are introduced into each fiber core;

the optical phase change material film (702) is made of a chalcogenide compound, specifically a germanium-antimony-tellurium alloy (Ge)₂Sb₂Te₅) Silver indium antimony tellurium alloy (AgInSbTe), and the like;

the optical phase-change material film (702) has at least two phase states, a crystalline state and an amorphous state, and is in an intermediate state between the crystalline state and the amorphous state, and the reflectivity of different phase states in a communication waveband is different;

the optical phase-change material film (702) is combined with the end face of the multi-core optical fiber (701) in a radio frequency magnetron sputtering mode;

the material of the anti-oxidation reflection-increasing film (703) is Indium Tin Oxide (ITO) or gold film (Au), and the like, so that the optical phase-change material film (702) is prevented from being exposed in the air and being oxidized, and the reflection of a communication waveband is increased;

the anti-oxidation and anti-reflection film (703) is combined with the optical phase-change material film (702) in a radio frequency magnetron sputtering mode;

the multicore optical fiber memristor (7) is welded with a multicore optical fiber pair output by the multicore optical fiber fanning-in device (6), so that optical signals of various wavelength channels can be transmitted to corresponding fiber cores of the multicore optical fiber memristor (7);

the reading multi-core detection module comprises an optical fiber filter array (8), a photoelectric detector array (9), a collection card (10) and an upper computer (11);

the optical fiber filter array (8) comprises a plurality of optical fiber band-pass filters (801-807) and has the function of only allowing the wavelength optical signals for detecting continuous laser to pass through;

the photoelectric detector array (9) comprises a plurality of single PIN photoelectric detectors (901-907), and has the function of monitoring the size of an optical signal reflected by each fiber core of the multi-core optical fiber memristor (7) in real time, namely reading the storage information of each fiber core;

the photoelectric detector array (9) is output to an acquisition card (10) to realize electric signal acquisition;

the acquisition card (10) and the upper computer (11) are interacted to realize information transmission;

the number of channels in the erasing and writing seed source lasers (101-107), the dense wavelength division multiplexer (1) (201), the dense wavelength division multiplexer (2) (204), the one-to-two optical fiber coupler array (4), the optical fiber circulator array (5), the multi-core optical fiber fanning-in device (6), the optical fiber filter array (8) and the photoelectric detector array (9) is matched with the number of fiber cores of the multi-core optical fiber memristor (7);

the multi-core optical fiber memristor device and the erasing, writing and reading scheme are that an optical phase-change material film (702) and an anti-oxidation reflection-increasing film (703) are sequentially plated behind the end face of a multi-core optical fiber (701) to construct a multi-core optical fiber memristor (7); the phase states of the optical phase change materials on the end faces of the fiber cores are respectively regulated and controlled by injecting erasing and writing pulse laser into the fiber cores, the reflectivity of the optical phase change materials in different phase states is different, and the storage state of each fiber core is read by reading continuous laser, so that multi-core nonvolatile all-optical storage is realized.

The invention has the beneficial effects that:

the invention endows the multi-core fiber with the capability of nonvolatile storage, inherits the characteristics of the multi-core fiber, improves the dimensionality of the single-core fiber nonvolatile storage based on the space division multiplexing concept, greatly improves the communication and storage capacity, and breaks through the limit of the information capacity of the current common single-mode fiber. The multi-core optical fiber memristor and the erasing, writing and reading scheme provided by the invention are hopeful to be compatible with the current multi-core optical fiber communication and sensing technology so as to promote the development of the current optical fiber technology.

Description of the drawings:

fig. 1 is a schematic diagram of a multi-core fiber memristor device and an erasing, writing and reading scheme provided by the invention.

The specific implementation mode is as follows:

for clearly explaining the multi-core fiber memristor device and the erasing, writing and reading scheme, the invention is further described with reference to the embodiments and the drawings, but the scope of the invention should not be limited thereby.

As shown in fig. 1, a seven-core optical fiber memristor (7) is taken as an example for explanation:

a seven-core optical fiber memristor device and an erasing, writing and reading scheme comprise a reading, writing and erasing laser output module (1, 2, 3, 4, 5 and 6), a seven-core optical fiber memristor (7) and a reading seven-core detection module (8, 9, 10 and 11).

The laser output module for reading, writing and erasing comprises a continuous laser (1) for reading, writing and erasing, an optical pulse generating module (2), a one-to-N optical fiber coupler (3), a one-to-two optical fiber coupler array (4), an optical fiber circulator array (5) and a seven-core optical fiber fanning-in device (6).

The 'reading, writing and erasing' continuous light laser (1) comprises 'erasing and writing' seed source lasers (101-107) and a 'reading' continuous light laser (108); the seed source erasing and writing lasers (101-107) respectively output continuous lasers with different wavelengths to the optical pulse generating module (2); the 'reading' continuous laser (108) outputs detection continuous laser, and the output wavelength is not consistent with the wavelength of the 'erasing and writing' seed source lasers (101-107); the 'reading, writing and erasing' continuous optical laser (1) and the upper computer (11) interactively regulate and control parameters such as wavelength, intensity and the like of output continuous laser.

The optical pulse generating module (2) comprises a dense wavelength division multiplexer (1), (201), an intensity modulator (202), an erbium-doped pulse fiber amplifier (203), a dense wavelength division multiplexer (2), (204) and an electric pulse generator (205); the wavelength channels of the dense wavelength division multiplexers 1 and 201 and the dense wavelength division multiplexers 2 and 204 are matched with the seed source lasers (101-107) for erasing and writing; the dense wavelength division multiplexers.1 and 201 have the functions of combining continuous lasers of different wavelength channels output by the seed source lasers (101-107) for erasing and writing into a single fiber and inputting the single fiber into an intensity modulator (202) for light intensity modulation; the modulation pulse source of the intensity modulator (202) is provided by an electric pulse generator (205), the function of the modulation pulse source is to carry out intensity modulation on an input optical signal, when the intensity modulator (202) is in a proper static working point, the electric pulse generator (205) sends out an electric pulse, and the optical signal passing through the intensity modulator (202) receives the electric pulse modulation, so that the pulse light is generated; the erbium-doped pulse fiber amplifier (203) amplifies the optical pulse signal output by the intensity modulator (202) to realize high-power pulse optical signal output; a dense wavelength division multiplexer 2(205) receives the optical pulse signals of each wavelength output by the erbium-doped pulse optical fiber amplifier 203 and separates the wavelengths into respective wavelength channels; the erbium-doped pulse fiber amplifier (203), the electric pulse generator (204) and the upper computer (11) are interacted to realize the optical pulse signal output of the target intensity.

The one-to-N optical fiber coupler (3) equally divides the energy of the detection continuous laser emitted by the reading continuous laser (108) and inputs the energy into the one-to-two optical fiber coupler array (4); the one-to-two optical fiber coupler array (4) comprises seven one-to-two optical fiber couplers (401-407), couples the detection continuous laser equally divided by the one-to-N optical fiber coupler (3) with optical pulse signals incident to respective wavelength channels, and inputs the optical pulse signals into the optical fiber circulator array (5); the optical fiber circulator array (5) comprises seven optical fiber circulators (501-507), the optical energy of each wavelength channel is transmitted from the port 1 to the port 2, and the optical energy reflected by a rear-end device is transmitted from the port 2 to the port 3; the seven-core optical fiber fanning-in device (6) couples the optical signals of the respective wavelength channels into the corresponding fiber cores of the seven-core optical fibers.

The seven-core optical fiber memristor (7) comprises a seven-core optical fiber (701), an optical phase change material film (702) and an anti-oxidation reflection increasing film (703).

The seven-core optical fiber (701) at least has two fiber cores, and pulse lasers with different parameters are introduced into each fiber core; the optical phase change material film (702) is made of chalcogenide, specifically germanium-antimony-tellurium alloy (Ge)₂Sb₂Te₅) Silver indium antimony tellurium alloy (AgInSbTe), and the like; the optical phase-change material film (702) has at least two phase states, a crystalline state and an amorphous state, and an intermediate state between the crystalline state and the amorphous state, and the reflectivity of different phase states in a communication waveband is different; the optical phase-change material film (702) is combined with the end face of the seven-core optical fiber (701) in a radio frequency magnetron sputtering mode; the material of the anti-oxidation reflection-increasing film (703) is Indium Tin Oxide (ITO) or gold film (Au), and the like, so that the optical phase-change material film (702) is prevented from being exposed to the airThe gas is oxidized, and the reflection of the communication wave band is increased; the anti-oxidation and anti-reflection film (703) is combined with the optical phase-change material film (702) in a radio frequency magnetron sputtering mode.

The seven-core optical fiber memristor (7) is welded with the seven-core optical fiber pair output by the seven-core optical fiber fanning-in device (6), so that optical signals of various wavelength channels can be transmitted to corresponding fiber cores of the seven-core optical fiber memristor (7).

The seven-core reading detection module comprises an optical fiber filter array (8), a photoelectric detector array (9), a collection card (10) and an upper computer (11).

The optical fiber filter array (8) comprises seven optical fiber band-pass filters (801-807) and has the function of only allowing the wavelength optical signals for detecting continuous laser to pass through; the photoelectric detector array (9) comprises seven single PIN photoelectric detectors (901-907), and has the function of monitoring the size of optical signals reflected by each fiber core of the seven-core optical fiber memristor (7) in real time, namely reading the storage information of each fiber core; the photoelectric detector array (9) is output to an acquisition card (10) to realize the acquisition of electric signals; the acquisition card (10) and the upper computer (11) are interacted to realize information transmission;

the number of channels in the erasing and writing seed source lasers (101-107), the dense wavelength division multiplexer (1) (201), the dense wavelength division multiplexer (2) (204), the one-to-two optical fiber coupler array (4), the optical fiber circulator array (5), the seven-core optical fiber fanning-in device (6), the optical fiber filter array (8) and the photoelectric detector array (9) is matched with the number of fiber cores of the seven-core optical fiber memristor (7).

The seven-core optical fiber memristor device and the scheme of erasing, writing and reading comprises the steps that an optical phase-change material film (702) and an anti-oxidation reflection increasing film (703) are sequentially plated behind the end face of a seven-core optical fiber (701) to construct a seven-core optical fiber memristor (7); the phase states of the optical phase change materials on the end faces of the fiber cores are respectively regulated and controlled by injecting erasing and writing pulse laser into the fiber cores, the reflectivity of the optical phase change materials in different phase states is different, and the storage state of each fiber core is read by reading continuous laser, so that seven-core nonvolatile all-optical storage is realized.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.