57 results about "Linear dispersion" patented technology

A process for operation of a laser device (1) is described, whereby circulating light pulses each comprising spectral components according to a plurality of longitudinal modes of a resonator configuration (3) are generated in the resonator configuration (3) and subjected to a compensation of group velocity dispersion, and a predetermined linear dispersion is introduced into the light path of the resonator configuration (3), so that at least one mode has a predetermined frequency and/or the mode distance between the modes has a predetermined value. Furthermore, regulations for stabilizing the laser device on the basis of this process and applications of the regulations for the generation for stabilized, ultra-short light pulses, generation of optical frequencies and in the frequency and/or time measuring technique as well as in the spectroscopy are described.

A Fiber-wireless uplink consists of a wireless channel followed by a radio-over-fiber (ROF) link. Typically, nonlinear distortion of the ROF link is the major concern when the radio frequency is only a few GHz. This especially severe in the uplink, because of the multipath fading of the wireless channel. A Hammerstein type decision feedback equalizer is described for the fiber wireless uplink, that compensates for nonlinear distortion of the ROF link as well as linear dispersion of the wireless channel. Since the linear and nonlinear parts of the receiver are separated, tracking the fast changing wireless channel is virtually independent of compensating for the relatively static nonlinearity. Analytical results show that the receiver provides excellent compensation with notably less complexity.

Systems and methods for performing space time coding are provided. Two vector→matrix encoding operations are performed in sequence to produce a three dimensional result containing a respective symbol for each of a plurality of frequencies, for each of a plurality of transmit durations, and for each of a plurality of transmitter outputs. The two vector→matrix encoding operations may be for encoding in a) time-space dimensions and b) time-frequency dimensions sequentially or vice versa.

The present invention relates to a multiple antenna transmitting/receiving apparatus that performs a hybrid automatic repeat request, and a retransmission method thereof. An initial transmission signal is encoded into the form of an initial transmission matrix and transmitted to the receiving apparatus, the initial transmission matrix corresponding to a linear dispersion code, with a result of error checking performed on the initial transmission signal by the receiving apparatus. When an error is detected in the initial transmission signal, a first retransmission signal is generated by encoding the initial transmission signal in the form of a retransmission matrix and transmitted to the receiving apparatus. The retransmission matrix is formed of constituent elements of the initial transmission matrix but different from the initial transmission matrix, and corresponds to a linear dispersion code having the same capacity and diversity gain as those of the initial transmission matrix.

The invention discloses a hyper-spectral compression imaging method and a system thereof. The method comprises the following steps: carrying out first dispersion after imaging and collimation of an object; focusing an optical signal after dispersion and carrying out space intensity modulation; focusing the modulated optical signal again and carrying out second dispersion; focusing the optical signal after second dispersion, carrying out detection by a detector, carrying out acquisition by a computer, carrying out data resolution, and recovering a three-dimensional data cube of a shot object; wherein the first dispersion and the second dispersion are linear dispersion which are realized by employing a Prism-Grating-Prism device, dispersion directions of the first dispersion and the second dispersion are opposite, and the space intensity modulation is realized by employing a spatial light modulator. According to the invention, data amount is reduced, realization of data resolution of high fidelity is facilitated, and miniaturization design and imaging diversification of an imaging system are facilitated.

A spectrometer assembly (10) comprises a light source (11) with a continuous spectrum, a pre-monochromator (2) for generating a spectrum with a relatively small linear dispersion from which a spectral portion is selectable, the spectral bandwidth of such spectral portion being smaller than or equal to the bandwidth of the free spectral range of such order in the echelle spectrum wherein the centre wavelength of the selected spectral interval is measurable with maximum blaze efficiency, an echelle spectrometer (4) with means for wavelength calibration, an entrance slit (21) at the pre-monochromator (2), an intermediate slit assembly (50) with an intermediate slit (3) and a spatially resolving light detector (5) in the exit plane of the spectrometer for the detection of wavelength spectra. The assembly is characterised in that the width of the intermediate slit (3) is larger than the monochromatic image of the entrance slit generated by the pre-monochromator at the location of the intermediate slit, and means for calibrating the pre-monochromator are provided, which are adapted to calibrate the light of the light source with a continuous spectrum on the detector to a reference position.

The invention provides a method for automatically forwardly/reversely tapering a fiber. According to the method, the external envelope of a flame in a fiber heating area in the tapering process is calculated according to the shape of a target fiber, and reciprocating of a flame front is controlled, so that a tapered fiber conforming to a target shape is prepared. Post-treatment of a fiber waveguide is realized by constant-speed reciprocating heating of the dotted flame and simultaneous stretch or compression of two ends of the fiber, and the movement speed of the dotted flame front and the stretch/compression speed of the two ends of the fiber can be optionally adjusted in the forward/reverse tapering process. The linear dispersion characteristic and the nonlinear Kerr characteristic of the tapered fiber can be greatly changed. The tapered fiber can be efficiently and laterally coupled with an external environment. The properties are quite widely applied to fiber optics and a plurality of fields including fiber sensing, optical frequency conversion, super-continuum broadening, quantum optics and the like.

The invention discloses an image compression and reconstruction method based on LCTF (liquid crystal tunable filter) hyperspectral imaging system; the method prevents the precision of a reconstructed image from being affected by nonlinear dispersion of the original CASSI (coded aperture snapshot spectral imaging) system, the problem that coded aperture is unmatched with pixel size of a detector is solved by means of calculating synthetic aperture size, and spatial resolution of the constructed image is improved. The minimum pixel size of the hyperspectral imaging system is the pixel size of the detector; a target spectral image sequence is acquired through the LCTF hyperspectral imaging system; shift is manually added to each single image in the target spectral image sequence, and the shifted image sequences are superposed in order to obtain a mixed image. The use of the method according to the invention is equivalent to linear dispersion, the correspondence between coded aperture pixel and detector pixel can be analyzed, and the precision of a reconstructed mage can be improved.

The invention relates to a filter spectrometer with adjustable linear dispersion rate. Light beams emitted by a light source enter a converging lens. The converging lens converges the light beams to aslit in the focus position of a collimating lens. The light beams going out of the slit are changed into parallel light after passing through the collimating lens, and the parallel light is incidenton the surface of a linear gradient filter. A light-splitting spectrum is detected by a linear array CCD detector according to spectrum information obtained through light splitting by the linear gradient filter, and is transmitted to a computer for processing. The linear array CCD detector is fixed on a rotary adjustable bracket. With the direction in which the resonant cavity layer of the filterchanges thickness fastest as a reference direction, the linear array CCD detector is rotated in such a way that there is an included angle between the length direction of the detector and the reference direction. Then, the transmitted light of the filter is detected, and the dispersion rate can be changed. The linear array CCD detector can move in a two-dimensional direction to measure light within different wavelength ranges. The filter spectrometer has the advantages of simple structure, convenience of use and adjustable linear dispersion rate.

End of line dispersion compensation is applied on a sub-band by sub-band basis. Adequate end-of-line dispersion compensation may be provided for high data rate WDM systems even for optical link lengths of 1000 km or more. Dispersion compensating gratings (DCGs) may be used as the dispersion compensating components. There is a great savings in cost and package volume compared to per-channel compensation schemes.

The invention relates to a method for broadband radio-frequency signal correlation detection based on the time-spectrum convolution principle. The method is used for filtering and matching broadband radio signals and comprises the following steps that step 1, a laser device is used for generating a multi-wavelength laser light source; step 2, the spectrum forming technology is used by generated lasers through an optical filter so that an amplitude-frequency response envelope conjugated with a detected broadband radio-frequency signal time domain waveform can be generated; step 3, the received detected broadband radio-frequency signals are loaded on the lasers after spectrum forming through an electro-optic strength modulator; step 4, the modulated optical signals are introduced to chromatic dispersion delay through a linear chromatic dispersion component; step 5, the optical signals are connected to a photoelectric detector for photovoltaic conversion and an output signal is a detected electric pulse signal after a correlation operation. The method for broadband radio-frequency signal correlation detection based on the time-spectrum convolution principle can effectively avoid offline processing of data and achieve immediate measurement of the broadband radio-frequency signals.

The invention discloses a polarization and hyper-spectral compression imaging method and system. The polarization and hyper-spectral compression imaging system is provided with an objective lens, a polarization modulator, a collimating lens, a first linear dispersion device, a first convex lens, a spatial modulation mask plate, a second convex lens, a second linear dispersion device, a lens and adetector in sequence along the direction of light transmission, wherein the objective lens is used for imaging a target on the polarization modulator. The polarization and hyper-spectral compression imaging method comprises the following steps: imaging the target on the polarization modulator, collimating the emergent light, carrying out first dispersion on the collimated emergent light, carryingout spatial modulation on the dispersed light signal, carrying out second dispersion, projecting the light on the detector, collecting data by using a computer, completing data calculation, and restoring four-dimensional data information of the target. The invention realizes the hyper-spectral instantaneous compression imaging of three-dimensional data cubes in a certain vision field under the control of polarization modulation, greatly reduces the quantity of data received by the detector, improves the signal-to-noise ratio of the system and is especially beneficial to the target imaging of weak light intensity and strong dispersion.

The invention relates to space-time coding for communication systems. There is provided a method of generating a space-time block code (STBC) for encoding a digital data sequence comprising a set of independent symbols to be transmitted through a transmission channel in a communication system, the space-time block code being represented by a set of linear dispersion matrices in a linear dispersionrepresentation, each linear dispersion matrix comprising components having complex values, the method comprising, generating at least some of the linear dispersion matrices depending on component-wise conditions related to a set of selected pairs of the linear dispersion matrices, each pair comprising a first linear dispersion matrix and a second linear dispersion matrix, said component-wise conditions comprising a component-wise condition between the components of the first linear dispersion matrix and the components of the second linear dispersion matrix.

A swept wavelength source for broad bandwidth Raman pump applications includes a source of ultrashort (e.g., picosecond) optical pulses. The pulse train output from the source is then applied as an input to a linear dispersive element (such as a section of negative dispersion-shifting fiber) which functions to “stretch” the ultrashort pulses, causing the pulses to become separated in time, with a continuous shift in the wavelength through the length of the pulse.

The embodiment of the invention provides a large axial chromatic aberration linear dispersion object lens. The object lens comprises a collimating lens group with positive focusing luminosity and a focusing lens group with positive focusing luminosity, the collimating lens group and the focusing lens group are arranged along the optical axis in order between a light source pinhole and measured object, the collimating lens group is close to the light source pinhole, and the focusing lens group is close to the measured object. The object lens system comprehensively considers the balance of the linearity of the dispersion object lens and the system aberration correction, and the collimating lens group and the focusing lens group are both positive lens groups and have the effect of collimation first and then focusing. The collimating lens group includes an aspheric lens to allow the ratio of the axial direction dispersion range of the linear dispersion object lens and the system focal length to be larger than 0.2 so as to entirely reduce the size of the object lens, reduce the processing difficulty and allow the object lens to have excellent linearity; and moreover, an additional arrival aperture diaphragm can limit the incident ray angle, prevent the adjustment process from being difficult because the structure of the dispersion object lens is complicated, and improve the processing precision.

The invention relates to a linear dispersion space-time coding method applicable to any antenna number. The method comprises the following steps of: determining a time length of a coding module and an information symbolic number to be transmitted; randomly generating MT complex vectors u1, u2, ..., uMT, and converting each complex vector into a Hermite matrix; generating an MT-order diagonal matrix D, multiplying D rightwards by the Hermite matrix to acquire a new MT-order square matrix U, randomly selecting L column vectors from the matrix U, and rearranging each column vector from top to bottom and from left to right to form an M*T matrix; and finally calculating L singular values for constructing the matrix respectively, solving sum of square and sum of biquadrate of each group of singular values to acquire two groups of sequences, and finishing coding until the two groups of sequences accord with set conditions. The method is applicable to application occasions of any number of transmitting antennas and receiving antennas and can freely set coding transmission rate.

The invention relates to a method for determining linear dispersion space-time codes when the receiving antenna number is less than the transmitting antenna number. Large limitation exists in the prior art. The method comprises the following steps of: firstly, determining channel using times T (T is not less than M) and constructing layered matrices C1-CN; then constructing N stepped matrices U1-UN in T*T; constructing q=NT encoding matrices Aj, K in M*T, wherein the j is equal to 1 to T, the k is equal to 1 to N, the M is the transmitting antenna number, the N is the receiving antenna number, Aj, k is equal to P.Ck.diag (Uk(:, j)).Q, NT encoding matrices Aj, k are obtained together, and then the linear dispersion space-time codes are determined. The method adopts a trace orthogonal method to achieve approximately optimal channel volume and uses an algebraic method to obtain full set gains. The linear dispersion space-time codes determined in the method of the invention have simple encoding design complexity and simultaneously provide favorable encoding properties.

Methods and apparatus for spatially-shifting and multiplexing optical signals for transmission in a wavelength division multiplexed or dense wavelength division multiplexed optical communication system linearly disperse the optical signals and then spatially, laterally shift the signals. The spatially shifted, dispersed signals are thereafter re-imaged to remove the linear dispersion so that the spatially shifted signals can then be transmitted through the optical communication system. The spatially-shifted, multiplexed signals have a flat passband with sharp transition points so that the transmitted signals are routed through the optical communication system with low loss and high integrity.

Dispersion compensation module is utilized in each chain to carry out distributivity full compensation for dispersion. Position and dispersion quantity of dispersion compensation module in chain are adjusted. With input point of optical signal power as the reference point, accumulated dispersion quantity from any reference point to front of receiver is positive. Total dispersion of system is within dispersion tolerance of receiver. Interaction between effect of self phase modulation (SPM) and dispersion is created to compress expanded pulse. The method is suitable to DWDM system, possible to control the accumulated total residual dispersion. Thus, transmission distance is not limited by linear dispersion. Under current technical condition of dispersion compensation, without need of adding any new part, SPM effect in ultralong distance transmission can be solved in entire C-BAND. The method is reliable through emulation, simulation, experiments and applicable test.

The invention discloses a measuring system of N2 molecule vibration-rotation Raman spectrum. The system comprises an emission unit and an optics reception and signal detection unit. The emission unit irradiates the atmospheric molecules by using the ultraviolet laser with extremely narrow linewidth of 354.8 nm outputted by a seed-injected solid-state laser. The optics reception and signal detection unit collects the signal of the vibration-rotation Raman spectrum produced by the N2 molecule, uses a double grating dispersion system to disperse the light in a range of 384.9-388.6 nm in space with a linear dispersion of 8.3 mm/nm, uses a linear array detector having 32 channels to distinguish and record discrete spectral line signals of O branch (rotation quantum number J=16-2) and S branch (rotation quantum number J=0-14) of N2 molecule vibration-rotation Raman spectrum, and produces inhibition better than 13 order of magnitude for the light near 354.8 nm. The system realizes the distinction and record of N2 molecule Stokes vibration-rotation Raman spectrum, and can obtain temperature information.

The invention discloses an ideal Dirac semimetal Cu2HgSnSe4 crystal. The Cu2HgSnSe4 crystal is characterized in that the Cu2HgSnSe4 crystal belongs to a tetragonal system; the space group of the crystal is (No. 121); and a conduction band and a valence band of the Cu2HgSnSe4 crystal are asymmetric in an energy band structure diagram, only Dirac fermion exists in the conduction band, and Schrodinger fermion and the Dirac fermion coexist in the valence band. If Fermi energy is located in the conduction band, transport properties are mainly derived from the Dirac fermion. Such a system is helpfulfor people to obtain relatively clean transportation experiment data, so the novel transportation property of a topological quantum state can be explored. Meanwhile, the linear dispersion relation ofelectrons near a Dirac point is always kept within the energy range of about 400 mV, and a Dirac cone energy band structure of linear dispersion has large-range frequency nonlinear response to lightwaves. The crystal has important academic value and potential application prospect.

A method for nonlinearity compensation for an optical transmission link includes determining a dispersion effect of a transmission link; applying a phase conjugation to the transmission link, the phase conjugation responsive to an input wave over the transmission link and providing a conjugated version of the input wave; and configuring an optimum equivalent link responsive to the phase conjugation after the transmission link to compensate for a non-linear dispersion effect from said transmission link

The invention discloses a double-grating spectrometer system capable of detecting three-phase-state water Raman spectral signals simultaneously. The system comprises a signal feed-in unit, an optical dispersion unit and a signal detection unit. The signal feed-in unit uses a fiber in the core diameter of 0.6mm and numerical aperture of 0.12 to feed conducted signal light into the optical dispersion unit; the optical dispersion unit comprises two cascaded grating dispersion systems of quasi-Littrow structural layout, can transmit and disperse passband signal light in the range 393.0-424.0nm in the focal plane efficiently in the linear dispersion rate of 1.0mm nm <-1>, and generates inhibition superior to 6 magnitude orders for outband light near 354.8nm; and the signal detection unit can distinguish and record the passabnd signal light after dispersion in the spectral precision of 0.8nm. In 354.8nm UV laser radiation, vibration-rotation Raman spectral regions of gas-sate, liquid-state and solid-state water correspond to the ranges of 395-409nm, 396-410nm and 401-418nm respectively; the passband spectral range covers the vibration-rotation Raman spectral regions of the three-phase-state water, the three-phase-state water Raman spectral signals are detected simultaneously, and substantial inhibition is generated for optical signals near 354.8nm.