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1783 results about "Line width" patented technology

The linewidth (or line width) of a laser, e.g. a single-frequency laser, is the width (typically the full width at half-maximum, FWHM) of its optical spectrum . More precisely, it is the width of the power spectral density of the emitted electric field in terms of frequency, wavenumber or wavelength. Similarly,...

COTDR (coherent detection based optical time-domain reflectometry) fused long-distance coherent detection brilouin optical time-domain analyzer

The invention discloses a COTDR (coherent detection based optical time-domain reflectometry) fused long-distance coherent detection brilouin optical time-domain analyzer which comprises a narrow-linewidth laser, two couplings, a microwave signal source, an electro-optic modulator, an isolator, a long-distance sensing optical fiber, an optical circulator, a 3 db coupling, a pulse modulator, an Er-doped fiber amplifier, a scrambler, a pulse signal generator, a balancing photoelectric detector, an electrical frequency spectrum analyzer, a data processing module and an acousto-optic modulator. According to the invention, the signal-to-noise ratio of BOTDA (brilouin optical time domain analysis) is improved by using a coherent detection method, a non-local effect of a BOTDA system is reduced in a double-sideband detection mode, and the sensing distance is more than 70 km under the condition of no light amplification such as raman; and according to the invention, the COTDR is fused to a coherent detection based BOTDA system, and the system can run in a breakpoint testing mode, so that the defect that the traditional BOTDA can not run when a sensing fiber has breakpoints and can not carry out positioning on breakpoints is effectively overcome, thereby enhancing the adaptability and practicability of the sensing system.
Owner:NANJING UNIV

Terahertz plane adsorbing material

The invention provides a terahertz plane adsorbing material, belonging to the technical field of electromagnetic function materials and relating to an electromagnetic-wave absorbing material. The terahertz plane adsorbing material comprises a substrate, a metal reflecting layer, a dielectric layer and an artificial electromagnetic medium layer; wherein, the metal reflecting layer is a continuous metal film and is arranged on the surface of the substrate; the dielectric layer is arranged between the metal reflecting layer and the artificial electromagnetic medium layer; the artificial electromagnetic medium layer is composed of artificial electromagnetic medium units which are arrayed periodically, each unit is a centro-symmetric figure formed by metal film lines with line width which is t and comprises two sing-opening metal rings which are connected backwards with long edges at two sides of an electric snap ring resonator. The terahertz plane adsorbing material provided by the invention has two strong-absorption frequency ranges, so as to provide selective adsorption and detection at different frequency ranges, and the terahertz radiation with wider spectral range can be adsorbed, so as to improve the performance and efficiency of the terahertz plane adsorbing material.
Owner:UNIV OF ELECTRONIC SCI & TECH OF CHINA

Self-correlation optical fiber communication system based on mode division multiplexing

The invention discloses a self-correlation optical fiber communication system based on mode division multiplexing. The self-correlation optical fiber communication system based on mode division multiplexing comprises an optical carrier input unit, optical signal modulation units, a wavelength division multiplexing unit, a mode division multiplexing and demultiplexing unit, a wavelength division multiplexing unit and coherent reception units. The mode division multiplexing and reconciliation multiplexing unit comprises a mode multiplexer and mode demultiplexer, and the mode multiplexer and the mode demultiplexer are connected through few-mode optical fibers. The optical carrier input unit is connected with each optical signal modulation unit, the wavelength division multiplexing unit and the mode multiplexer through single-mode optical fibers. The mode multiplexer is connected with the mode demultiplexer through few-mode optical fibers. The mode demultiplexer is connected with the wavelength division multiplexing unit and each coherent reception unit through single-mode optical fibers. The optical carrier input unit is further connected with the wavelength division multiplexing unit. The self-correlation optical fiber communication system based on mode division multiplexing eliminates an expensive narrow line width adjustable local oscillator light source which is arranged at a reception end, enables a laser to be conveniently managed and maintained, is free from using frequency offset estimation in a digital signal processor (DSP) and phase retrieval algorithm, reduces complexity of the DSP and has the advantages of being high in spectrum effectiveness and big in nonlinearity tolerance.
Owner:HUAZHONG UNIV OF SCI & TECH
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