111 results about "Single mode fiber transmission" patented technology

A method and apparatus for obtaining three-dimensional surface measurements using phase-sensitive spectrally encoded imaging is described. Both transverse and depth information is transmitted through a single-mode optical fiber, allowing this technique to be incorporated into a miniature probe.

A partially coherent Optical Time Domain Reflectometry (OTDR) apparatus has a light source comprising a directly modulated semiconductor Distributed FeedBack (DFB) laser diode for transmitting partially coherent light pulses along a monomode optical fibre. Light Rayleigh backscattered from the light pulses as they travel along the optical fibre is output from the end of the fibre into which the light pulses are transmitted to a Fibre Bragg Grating (FBG) filter. The FBG filter reduces the supectral width of light received at a photodetector. In one embodiment, the supectral width of the FBG filter is around one fifth of the supectral width of the light pulse after it has travelled around 1 km along the optical fibre. As a consequence of reducing the supectral width of the light received at the photodetector, the FBG filter increases the temporal coherence of the light. So, the FBG filter can ensure that the detected light is sufficiently coherent that a temporal supeckle pattern can be detected at the photodetector. At the same time, the light traveling in the optical fibre can be relatively supectrally broad so that non-linear effects in the optical fibre, such as Brillouin scattering, can be reduced.

The invention discloses a laser gas analyzer for multicomponent multiplexing measurement, comprising a laser driving control circuit, three packaged lasers, an optical fiber beam combiner, a collimating lens, an optical receiving module and a signal processing and display module, wherein the laser driving control circuit modulates and drives the three packaged lasers to emit different laser light rays needing to be modulated in wavelength; the laser light emitted by each packaged laser is transmitted through a single-mode optical fiber; the single-mode optical fibers are combined into an optical fiber beam through the optical fiber beam combiner; the laser light is emitted from the tail part of the optical fiber beam, and enters into the optical receiving module for collection and light-splitting detection after collimation in the collimating lens; and a signal obtained after light-splitting detection is transmitted to the signal processing and display module for processing so that real-time concentrations of a plurality of gases needing to be detected can be obtained. According to the invention, multiplexing detection is carried out on the laser lights with various wavelengths in an optical fiber beam mode; and such a method is capable of effectively avoiding optical noise aroused by the processing of a wavelength division multiplexing device, improving the accuracy of the analyzer measuring concentrations and reducing the cost.

The invention discloses an ultra wide band microwave photon long-distance range radar device based on chaos laser. The ultra wide band microwave photon long-distance range radar device based on chaos laser is characterized in that an ultra wide band chaos signal is used as a radar detection signal; the radar detection signal is transmitted via a long single mode fiber, is converted into a corresponding electric signal at a long-distance antenna terminal and is transmitted via an ultra wide band antenna; a detection signal is received by the ultra wide band antenna of the same model after being reflected when meeting a space target part; the laser is subjected to linear modulation, the signal is converted into a corresponding optical signal and is then transmitted via the single mode fiber to return to a center station; data processing is carried out in the data processing center to obtain and display target distance information; and therefore, the space precise positioning of the long-distance target is realized. The ultra wide band microwave photon long-distance range radar device based on the chaos laser is used for monitoring the military radar, the radar system on the mountain top and the island with severe environment and the industrial areas with severe or dangerous environment in real time.

A clock transfer device is designed to perform long-distance transfer of a reference clock, which is generated based on a high-precision frequency standard, toward a remote place. The clock transfer device includes a first mode-locked laser for generating a first optical pulse train having a first repetition frequency and a first wavelength, and a second mode-locked laser for generating a second optical pulse train having a second repetition frequency and a second wavelength. The first optical pulse train is introduced into a resonator of the second mode-locked laser via a wavelength multiplexing coupler so that the second repetition frequency is passively synchronized with the first repetition frequency; then, the second optical pulse train is transmitted via a single mode fiber.

The invention relates to the technical field of low-concentration gas detection and in particular relates to a trace nitrous oxide gas detection device. The device comprises an infrared laser output module, an N2O absorption gas chamber and a signal processing module, wherein the central wavelength of laser output by the infrared laser output module is matched with the position of an N2O gas absorption peak; the N2O absorption gas chamber comprises a hollow microstructure fiber; micro pores are formed in the peripheral wall of the hollow microstructure fiber along the radial direction; the laser output by the infrared laser output module is transmitted to one end of the hollow microstructure fiber by virtue of a single mode fiber; laser subjected to N2O gas absorption in the hollow microstructure fiber is output to the signal processing module from the other end of the hollow microstructure fiber by virtue of a multimode fiber; and the N2O gas content is calculated by the signal processing module according to the laser loss. The problem that the light path is short is fundamentally solved when the gas concentration is detected by a tunable laser spectral absorption method; and moreover, the transmission loss is avoided, and the accuracy and reliability of the measurement result are improved.

The invention relates to an optical fiber wave-guide optical secondary module that includes illuminator, multimode fiber, light splitter, optical fiber, and light checking device. The invention improves the permissible level of illuminator by multimode fiber that could save the extra contraposition mechanism and decrease cost and increase transmitting efficiency.

It is possible to reduce a drop in output power in a positive-dispersion element used as a pulse compressor, thus improving multiphoton-excitation efficiency. Also, reducing the size of the positive-dispersion element makes it easier to attach it to a microscope main body and to accommodate it therein, thus improving maneuverability. The invention provides a laser microscope including a laser light source for emitting ultrashort-pulsed laser light; a pulse expander for expanding the ultrashort-pulsed laser light emitted from the laser light source; a large-diameter single-mode fiber for transmitting the ultrashort-pulsed laser light expanded by the pulse expander; a pulse compressor for compressing the ultrashort-pulsed laser light transmitted by the single-mode fiber; and a microscope main body for irradiating a specimen with the ultrashort-pulsed laser light compressed by the pulse compressor.

A pressure sensing apparatus has a light source for transmitting pulses of light along a monomode optical fibre. The polarisation of light backscattered from the light pulses in the optical fibre is detected by a polarisation processing unit (PPU) and a photo detector. The optical fibre is adapted to deform asymmetrically under the influence of applied external isotropic pressure, e.g. from a fluid. The deformation causes the birefringence of the optical fibre to change proportionally to the applied pressure. The change in birefringence can be determined from the detected polarisation of the backscattered light, allowing detection of pressure distribution in the fluid. Importantly, the construction of the optical fibre is such that the birefringence beat length of the optical fibre at the wavelength of light propagated by the fibre remains more than twice the spatial length of the light pulses transmitted along the optical fibre. Applications of the invention include detection of fluid flow; location of an interface between two fluids of different density; and tsunami detection.

The invention provides a modular interface temperature sensor of a liquid-core optical fiber, belongs to the field of optics, and aims at solving the problem that the liquid is injected into a hollow optical fiber or photonic crystal fiber to prepare a high-sensitivity temperature sensor in the prior art. The modular interface temperature sensor comprises an ASE broadband light source, a temperature sensitive module and a spectrum analyzer; a beam outputted by the ASE broadband light source is incident into the temperature sensitive module; the beam outputted by the temperature sensitive module is incident into the spectrum analyzer; the temperature sensitive module comprises an incident end single-die optical fiber, the liquid-core optical fiber and an outgoing end single-die optical fiber; the liquid-core optical fiber consists of a liquid fiber core and a quartz cladding layer; the base die light transmitted by the incident end single-die optical fiber is spread to the incident part of the liquid-core optical fiber and divided into two parts, one part is spread through the liquid fiber core of the liquid-core optical fiber to form a fiber core die B1, and while another part is spread along the quartz cladding layer to form a cladding layer die B2; the fiber core die B1 and the cladding layer die B2 are spread to the outgoing end of the liquid-core optical fiber to be combined again and then transmitted into the incident end single-die optical fiber to generate modular interface.

The invention discloses an optical fiber evanescent wave form quartz enhanced photoacoustic spectrum sensor and a gas measurement method. The sensor is composed of a semiconductor laser source, a front single-mode optical fiber, a tapered optical fiber, a quartz tuning fork and a rear single-mode optical fiber, wherein the semiconductor laser source, the front single-mode optical fiber, the tapered optical fiber and the rear single-mode optical fiber are arranged in sequence along a light beam transmission direction; and the tapered optical fiber penetrates through a fork leg of the quartz tuning fork. Semiconductor laser is transmitted to the tapered optical fiber through the front single-mode optical fiber, and an evanescent wave field with strong energy is generated on the tapered optical fiber; gas to be detected absorbs the energy of the evanescent wave field to generate sound waves; and the quartz tuning fork receives a sound wave signal to invert gas concentration. The novel full-optical-fiber evanescent wave form quartz enhanced photoacoustic spectrum sensor is constructed aiming at sensing detection of trace gas; and compared with a traditional lens transmission system, the optical fiber evanescent wave form quartz enhanced photoacoustic spectrum sensor has the extremely low insertion loss, the stability of a sensor system is extremely improved, the structure is simple and the volume is small.

The invention discloses an optical fiber micrometric displacement sensor based on Mach-Zehnder interference and a manufacturing method of the optical micrometric displacement sensor. The optical fiber micrometric displacement sensor is composed of an input single mode optical fiber, a first micrometric bending structure optical fiber, a conductive single mode optical fiber, a second micrometric bending structure optical fiber and an output single mode optical fiber; light is transmitted to the first micrometric bending structure optical fiber through the input single mode optical fiber and is divided into two parts in the first micrometric bending structure optical fiber; one part is transmitted as a fiber core basic mode in the first micrometric bending structure optical fiber; the other part is transmitted as a cladding mode in cladding of the first micrometric bending structure optical fiber; light transmitted as the fiber core basic mode is transmitted to a fiber core of the second micrometric bending structure optical fiber through the conductive single mode optical fiber; light transmitted as the cladding mode is transmitted to cladding in the second micrometric bending structure optical fiber through the conductive single mode optical fiber; part of the light transmitted as the cladding mode is coupled with the fiber core of the second micrometric bending structure optical fiber and interference light is formed by the light coupled with the fiber core and the light transmitted as the fiber core basic mode and the interference light is output through the output single mode optical fiber; the optical fiber micrometric displacement sensor based on Mach-Zehnder interference has the advantages of being high in sensitivity, simple in manufacture and low in cost.

The invention relates to a photoelectric composite cable for radar. The cable is connected between a radar antenna and a radar control center and used for transmitting electric signals and optical signals, and the photoelectric composite cable for the radar comprises a cable core and an outer sheath coated outside the cable core. A shielding layer is arranged between the cable core and the outer sheath, the cable core comprises a power source unit, an optical unit and a data unit, the power source unit comprises three power lines, the optical unit comprises a plurality of single mode optical fibers, a waterproof layer coated outside the single mode optical fibers and an optical unit protection layer coated outside the waterproof layer, the data unit comprises a plurality of data line pairs, and the shielding layer comprises an inner shielding layer coated outside the cable core and an outer shielding layer coated outside the inner shielding layer. Bilayer shielding is arranged, so that shielding effects are good, and interferences of electromagnetic waves can be effectively avoided; and the single mode optical fibers are used for transmitting the optical signals, so that transmission loss is small and transmission distance is long under high frequency, remote control of the radar antenna can be realized, and the photoelectric composite cable for the radar is applicable to different service environments.

The invention relates to a real-time and quantitative method for monitoring the energy-saving and emission-reduction of a production line for cement produced by the dry method, belonging to the field of energy-saving and monitoring methods. The monitoring method is as follows: high-temperature gas analytic devices with the function of mobile phone communication are respectively installed on the outlets of a tail smoke chamber of a rotary kiln and a decomposing furnace, and are used for the continuous on-line measurement and analysis of the component content of high-temperature waste gas; a medium temperature gas analysis meter is installed on the outlet of a preheater, and is used for the measurement and the analysis of the component content of the waste gas of the preheater; a powder measuring apparatus is installed on the outlet of a chimney, and is used for the measurement of the content of powder discharged from the chimney of a production line; and the high-temperature gas analytic devices, the gas analysis meter and the powder measuring meter are respectively in transmission connection with a computer by single mode fibers, and the computer and an intelligent mobile phone form wireless communication by a mobile phone communication module so as to transmit displayed pictures of the computer. The method adopts the computer as a monitoring reservoir, information is transmitted into the mobile phone by wireless telecommunication transmission, and the method has the advantages of easy monitoring and easy execution.

The invention discloses a wideband-simulated photon link dispersion decline compensation scheme based on an intensity modulation diversity transmitter. A wideband-simulated photon link dispersion decline compensation mechanism consisting of a sending end and a receiving end is adopted, wherein the sending end consists of a light source and an intensity modulation diversity transmitter, and the receiving end consists of a single-mode fiber and a photoelectric detector; and mutual compensation is achieved through diversity transmission by utilizing the characteristic that the two paths of intensity signals of the diversity transmitter have different dispersion decline frequency points in the transmission of the single-mode fiber. According to the invention, under the condition that only one light source and one modulator is used, the wideband-simulated photon link dispersion decline compensation scheme which can enable the maximum power fluctuation of a radio-frequency signal to be 4-dB in the 20G Hz bandwidth range is finally obtained by adjusting the analyzing degree of two paths of modulating signals and delay inequality, and the scheme has the advantages of simple structure, low cost, easiness in achievement and large compensation range.

The invention provides a non-contact remote water level detecting method based on chaos laser, which is characterized in that an ultra wide band chaos signal serves as a detection signal and reaches a remote antenna terminal after being transmitted by long single mode optical fiber to be transformed into a corresponding electrical signal to be emitted by an ultra wide band antenna, the detection signal is received by an ultra wide band antenna of the same type after being partially reflected at the water level, after a laser is linearly modulated, the electrical signal is transformed into a corresponding optical signal and then is transmitted by signal mode optical fiber, the optical signal returns to a data processing center to be subjected to data processing, so that water surface elevation information is obtained and is displayed, and finally remote water level real-time monitoring is realized. The method can be used for the remote water level real-time monitoring of dangerous environments, such as flood protection and emergency engineering, coal, flood control stations of alpine and gorge regions, seas and sea island resource development workstations.

The invention provides a multi-beam broadband frequency modulation pulse laser waveform concentrated measuring apparatus. The measured multi-beam frequency modulation pulse light in the apparatus passes optical-electro-optical conversion modules. Channels output narrowband continuous light provided with different wavelengths and including the information of the measured light. The continuous light is transmitted to the corresponding waveband input end of a fiber wavelength division multiplexing switch module via single-mode fibers and narrowband long pulse light is output. The narrowband long pulse light is input into a fiber time division multiplexing module via a single-mode fiber and a single single-mode fiber outputs a series of long pulse optical signals with equal time delay. The long pulse optical signals pass a fiber amplifier and are transmitted to a photoelectric detector via a fiber. The photoelectric detector outputs an electric signal which enters an oscilloscope via a cable. Output data is transmitted to a computer via a network cable to be processed. The multi-beam broadband frequency modulation pulse laser waveform concentrated measuring apparatus is high in reliability, capable of transmitting information for long distance, and especially suitable for large high-power laser device multi-beam broadband frequency modulation pulse time waveform concentrated measurement.

The invention discloses a radio-over-fiber communication method based on hexagonal constellation forming iteration, and the method comprises the following steps: at an input end, converting an original signal into multiple binary data streams through serial-parallel conversion, and identifying and adding labels to the binary data streams; performing constellation compression on the processed signal through a probability matcher, and compressing a 32QAM constellation diagram into a 25QAM constellation diagram; carrying out successive iteration on the signal after constellation compression to obtain an optimal constellation compression ratio, and then carrying out constellation mapping to obtain a 19QAM constellation diagram; modulating the signal subjected to constellation mapping into twopaths of optical signals with different frequency bands through a modulator, enabling the signals to sequentially enter an optical fiber amplifier to adjust the signal power and then transmitting thesignals to an optical attenuator through a single-mode optical fiber to be processed, enabling a photoelectric converter to convert the optical signals into electric signals, enabling an electric power amplifier to adjust the power of the electric signals, and finally performing wireless transmission is conducted; at a receiving end, sequentially carrying out constellation demapping, analog-to-digital conversion and parallel-to-serial conversion on the received signal to obtain original data.

The invention discloses a DFT spread spectrum OOFDM method and system based on LDPC coding probability shaping mapping. The DFT spread spectrum OOFDM method comprises the steps of generating a pseudorandom binary bit stream; Sending the binary bit stream into an LDPC encoder and an interleaver to generate an interleaved binary bit stream; Mapping the bit stream based on a probability codebook to obtain a PS-QAM signal; Performing P-point discrete Fourier transform and subcarrier mapping on the PS-QAM signal to complete spectrum spreading; carrying out Q-point fast Fourier inversion on the spread signal, then adding a cyclic prefix, generating a digital PS-OFDM baseband signal, converting the digital PS-OFDM baseband signal into an analog PS-OFDM baseband signal through digital/analog conversion, and modulating the analog PS-OFDM baseband signal onto an optical carrier through a light intensity modulator to obtain PS-OFDM baseband signal; sending the OOFDM signal to a single-mode optical fiber for transmission, and modulating the signal to obtain an original input signal. The OOFDM signal peak-to-average power ratio can be reduced, and the sensitivity of the optical receiver is improved.