306 results about "Single-sideband modulation" patented technology

A method and system for generating and transmitting optical signals with only one sideband. Single-sideband optical signal transmission reduces the signal impairment effects associated with dispersion. Such transmission also increases the spectral efficiency of optical transmission systems. Single-sideband modulation also makes possible electrical compensation for optical link dispersion during transmission. Single-sideband modulation is generated using the modulating data signal and its Hilbert transform, which is approximated by a tapped-delay time filter. Line coding is used to remove the low-frequency content in the modulating data signal, avoiding the inefficiencies of tapped-delay-line filter approximated Hilbert transformers at low frequencies. Line coding can also help optical single side band signal generation and transmission using a simple optical filter instead of Hilbert transformers.

An optical carrier notch filter includes an optical coupler with at least first, second and third ports. The first port is configured to receive an output that includes an optical carrier and interleaved optical single sideband signals. An optical bandpass filter is coupled to a port of the optical coupler. The optical bandpass filter separates the output into a transmitted signal that contains the optical carrier, and a reflected signal that includes the interleaved optical single sideband signals. The reflected signal is reflected from the optical bandpass filter to the third port of the optical coupler.

The invention discloses an optical device measuring method and device based on double sideband modulation, which belongs to the technical fields of optical device measuring and microwave photonics. An optical double sideband modulation method is used to modulate a radio frequency signal to a first optical carrier signal, so as to generate a double sideband modulation signal. The double sideband modulation signal passes through an optical device to be measured to carry out beam combining with a second optical carrier signal. Frequency difference is between the second optical carrier signal and the first optical carrier signal. A photoelectric detector is used to carry out beat frequency on the signals after beam combining. The amplitude information of a +1 order sideband signal and a -1 order sideband signal in the beat frequency signals is extracted. The frequency of the radio frequency signal is scanned, so as to acquire the broadband amplitude frequency response of the optical device to be measured. The invention further discloses an optical device measuring device based on double sideband modulation. According to the invention, the system complexity and the cost are reduced; the measuring range and the measuring efficiency are greatly improved; and more importantly, a new direction is opened up for an optical device measuring technology.

With the normal modulation method, it is difficult to construct a Hilbert transform device because it is complicated. To solve the problem, a single sideband modulated optical pulse train is generated by driving a Mach-Zehnder optical modulator for optical pulse generation with a laser source's sine wave clock signals that have been rendered 90 degrees out of phase from each other. The generated pulse train is applied to an optical modulator, modulated with an NRZ (nonreturn-to-zero) data signal, and filtered by a narrow-band optical filter to obtain one of two sidebands.

The invention belongs to the technical field of fiber communication and optical network transmission signal equalization treatment, and particularly discloses a single-sideband modulated single carrier frequency-domain equalization technology-based fiber communication system. In a transmission system of fiber communication, by using a DSP equal high-speed digital signal processing mode, single-sideband modulated electrical signals received by direct detection are transformed to a frequency domain from a time domain by adopting FFT transformation, an equalization module designed aiming at a transmission link is adopted for performing equalization compensation in the frequency domain, and finally the signals processed by the equalization module are transformed to the time domain from the frequency domain through IFFT to acquire the final equalization signal. The fiber communication system can improve the transmission quality of the signals, and has the signal equalization compensation capacity of the self-adaptive fiber transmission link.

The invention discloses a microwave photon mixing method and system based on local oscillator frequency doubling, and belongs to the fields of optical communication and microwave photonics. The microwave photon mixing system based on local oscillator frequency doubling is formed by utilizing a double-polarization double-parallel mach-zehnder modulator through combination with devices such as a laser, a front polarization controller, a microwave 90-degree coupler, a rear polarization controller, an optical fiber polarizer, an adjustable optical band-pass filter, an erbium-doped fiber amplifier,a photoelectric detector and the like. The system adopts second-order local oscillator sideband and first-order radio frequency sideband beat frequencies, and mixing processing based on local oscillator frequency doubling can be realized; on one hand, the frequency requirement of a mixing system on a local oscillator signal is reduced, and on the other hand, due to the fact that a single-sidebandmodulation mode is adopted, stray signals can be effectively reduced. In addition, the mixing method can realize switching of up conversion and down conversion by changing a direct current bias voltage, and can be used for time-sharing transmitting and receiving of radio frequency.

The invention discloses a microwave signal phase shifting method based on polarized light interference technique in the technical field of microwave photonics. Photonic microwave signals generated by modulating a single sideband are transmitted by a polarization maintaining fiber and generate a group of optical carrier with locked phase and vertical polarization in a polarization manner by using the high birefringence characteristics and an appointed fusion angle. The input vertically-polarized optical carriers can generate different phase shift under the bias voltage of a phase modulator according to the polarization relativity of the modulation efficiency of the phase modulator, so that the phase difference among the optical carriers can be changed by adjusting the bias voltage. Then, the optical carriers are received by an analyzer with an appointed polarization angle to generate a group of parallel-polarized phase-shifting optical carriers. A photoelectrical detector can generate an electrical domain microwave phase-shifting signals after receiving beat frequency and isolating DC components, wherein the phase shifting magnitude depends on the bias voltage of the phase modulator. The invention further lowers the complexity of the microwave phase shifting system, and improves the phase shifting accuracy.

The invention relates to the technical field of fiber sensing, and especially to a pre-pumped pulse and Gray code based BOTDA instrument. The BOTDA instrument comprises a narrow-linewidth semiconductor sensor, a coupler, a first erbium doped fiber amplifier, a first polarization controller, a single sideband modulator, a microwave source, an optical isolator, a sensing fiber, an optical annular device, a second erbium doped fiber amplifier, a polarization scrambler, an electro-optical intensity modulator, a second polarization controller, an arbitrary waveform generator, an optical filter, a photoelectric detector and a signal collecting and processing system. On the premise that the high spatial resolution of a BOTDA system is maintained, the BOTDA instrument ensures the sensing distance and the measuring precision of the system, and improves the sensing performance of the system.

The invention discloses a fiber laser static-state strain beat frequency demodulation system based on single-sideband frequency sweep modulation. The system comprises a pumped source, a coupler, a first wavelength division multiplexer, a second wavelength division multiplexer, a first polarization controller, a second polarization controller, a sensing fiber laser, a reference fiber laser, a first isolator, a second isolator, a first beam combiner, a second beam combiner, a first broadband photoelectric detector, a second broadband photoelectric detector, a control processor, a narrow linewidth laser light source, a third isolator, a third polarization controller, a third beam combiner, a suppressed carrier single-sideband modulator, a fourth beam combiner, a frequency sweep signal generator, a phase modulator, a radio frequency signal generator, a frequency stabilization source and a photoelectric detector. The system provided by the invention realizes high-precision static-state strain measurement of the fiber lasers and solves the problems of incapacity of realizing high-precision static-state strain measurement, influences exerted by tunable laser frequency sweep non-linearity on demodulation precision, and the like by use of a conventional fiber laser demodulation technology.

The invention discloses an optical single-side band modulation based optical device measuring method. By substituting a narrow linewidth laser with fixed output wavelength in an original measuring device by two tunable narrow linewidth lasers which are connected in parallel and utilizing the method of controlling the two lasers to operate alternatively, the measuring range of the optical single-side band measuring technology is widened from 0.4nm to 40nm or above, and accordingly, testing of response of optical devices to any wavelength in a certain wave band is realized. The invention further discloses an optical single-side band modulation based optical device measuring device and a using method thereof. Compared with existing single-side band measuring technology, measuring range of the measuring device is widened greatly.

The invention discloses a distributed type optical fiber sensing device which comprises a frequency stabilized laser, a single side band modulator, an optical pulse generator, an optical amplification unit, a scrambling unit, an optical circulator or optical coupler, a sensing optical fiber, a light splitting unit, a first optical detector, a second optical detector, a third optical detector, a high-speed data collecting unit and a system control and data processing unit. The system control and data processing unit is respectively and electrically connected with the frequency stabilized laser and the optical pulse generator, and the system control and data processing unit is electrically connected with the single side band modulator through a microwave generator. The distributed type optical fiber sensing device has the advantages that a high-stability laser light source is adopted to be combined with microwave frequency modulation, and temperature, strain and vibration can be simultaneously measured through the unique control and data processing process.

The invention belongs to the technical field of optical fiber communication and wireless communication convergence, in particular to a system for generating an optical cable-carried terahertz signal based on two-stage single-side band modulation. The system consists of three parts: an optically inhibited carrier double-side band signal generating part, a two-stage single-side band modulation partand a terahertz wave transmitting and receiving part. The two-stage single-side band modulation part which is the core part of the system of the invention selects one side band of a carrier-inhibiteddouble-side band to perform a primary stage signal-band data modulation and uses base band signal-side band modulation technology in the data modulation process again so as to generate the two-stage cascade single-band modulation. The system has the advantages of simple structure, low cost, low element requirements, compatibility with the prior core net system, and the like.

The invention discloses a microwave photon full-band radar detection method. The microwave photon full-band radar detection method comprises the steps that suppression carrier single sideband modulation is carried out on an optical carrier with a frequency of fL by using an intermediate frequency chirp signal to obtain a linear frequency swept first-order sideband optical signal; a single comb signal is selected from optical frequency comb signals with frequency distribution fOC=fL+/-Nfc to combine beams with the linear frequency swept first-order sideband optical signal, wherein N=0, 1, 2, 3... L, and L is a positive integer; the obtained combined beam optical signal is converted into an electrical signal, and the electrical signal is transmitted to a target as a radar detection signal; and the combined beam optical signal is taken as a reference optical signal, a target reflected electrical signal is subjected to optical domain frequency conversion and deskewing processing to obtainan intermediate frequency signal carrying target information, and the target information is extracted from the intermediate frequency signal. The invention further discloses a microwave photon full-band radar. The microwave photon full-band radar detection method and the microwave photon full-band radar can quickly and conveniently adjust the working wave band of the radar and the radar signal parameters in the full wave band range, the structure is simple, and the detection efficiency is high.

The invention discloses an optical device measuring method which comprises the following steps that A, a microwave signal with fixed frequency and phase is modulated to a light carrier which is output by a light source through an optical frequency comb modulator, so as to generate an optical frequency comb; a plurality of continuous comb teeth of the optical frequency comb are filtered in sequence by a photonic filter; B, each filtered comb tooth serves as the light carrier, and the transmission functions of an optical device to be measured in a frequency band which corresponds to the comb tooth are measured through the optical device measuring method based on the unilateral modulation of light; and C, the broadband transmission functions of the optical device to be measured in the frequency bands which correspond to a plurality of continuous comb teeth are obtained according to the transmission functions in the frequency bands which correspond to all the comb teeth. The invention also discloses an optical device measuring device which adopts the method. According to the optical device measuring method and the measuring device, the optical frequency comb modulator works together with the photonic filter in a cooperate mode based on the optical device measuring method of the unilateral band modulation of light in the prior art, so that the measuring scope is greatly expanded.

The invention discloses an optical device measuring method based on optical single side band modulating. The optical device measuring method includes the steps of making improvements on the basis of an optical device measuring technology based on optical single side band modulating in the prior art, dividing optical single side band swept-frequency signals into two paths during photovoltaic conversion, filtering carrier waves of one of the two paths, adjusting the length of optical path of the other path, in the end using a balance photoelectric detector to conduct balance photoelectric detection of two optical signal paths, and obtaining electrical signals after conversion. The invention further discloses an optical device measuring device based on the optical single side band modulating. Compared with the prior art, the optical device measuring method eliminates errors introduced into the measuring results due to beat frequencies of numerous high-order side bands and residual first-order side bands of optical single side band modulating signals through the method of balance photoelectric detection and obtains the measuring results of higher accuracy.

From an real valued OFDM signal (S₀(t)) is a baseband signal (S_B(t)) derived and converted into a complex single sideband modulation signal (n(t)). This is modulated onto an optical carrier (f_OC) to generate a SSB transmission signal (S_OT) having a small bandwidth an carrying the information in the envelope or in the power of the envelope. According to the modulation direct detection is possible. Only a small bandwidth is necessary for the transmission.

Provided are methods and systems for receiving and processing optical signals are provided. A dual single side band (SSB) modulation scheme is utilized to take advantage of given wavelengths' bandwidth. Modulation schemes are employed that modulate each SSB with their In-phase (I) and Quadrature (Q) components. The methods and systems discussed perform MIMO de-multiplexing algorithms to remove any imaging components of the left and right SSBs provided by the modulators. Various algorithms can be employed, including but not limited to inserting time interleaved training sequences into the channels of the right and left SSB signals or by employing a constant-modulus-algorithm (CMA) de-multiplexing.

The invention discloses a device and method for realizing microwave frequency conversion by utilizing a double-drive DPMZM, relates to the technical field of microwaves and the technical field of optical communication, and is mainly used for frequency conversion of a microwave signal. The method comprises a light source, a radio-frequency signal source, an intrinsic signal source, an electric shunt device, a phase shifter, the double-drive DPMZM and a photoelectric detector (as drawing show). Double-sideband modulation of a radio-frequency signal and a single-sideband modulation of an intrinsic signal are respectively realized by utilizing the double-drive DPMZM; an optical carrier of an output signal of the double-drive DPMZM can be inhibited by reasonably setting a parameter; and, a frequency conversion signal can be obtained after the frequency of the output signal of the double-drive DPMZM is beaten through the photoelectric detector. The scheme has relatively high conversion efficiency; and furthermore, the power periodic fading due to optical fibre dispersion in a signal transmission process can be avoided.

The invention discloses an optical fiber sensing method, an optical fiber sensing device and a using method of the optical fiber sensing device. In the optical fiber sensing method disclosed by the invention, a transmission function curve of an optical fiber grating is obtained by adopting a method for ensuring an optical single side band sweep frequency signal modulated by a microwave sweep frequency signal to pass through the optical fiber grating. The optical fiber sensing device disclosed by the invention comprises a microwave sweep frequency source, a narrow linewidth laser, a broadband single side band modulator, a narrow-band optical fiber grating sensor, an optical detector, a microwave amplitude-phase information extraction module, a data processing control module and a display module. The invention also discloses the using method of the optical fiber sensing device. Compared with the prior art, the optical fiber sensing method and the optical fiber sensing device have high sensing accuracy and large measurement range and the distributed sensing can be implemented by adopting a mode that a plurality of narrow-band optical fiber gratings with different stop-band center wavelengths are cascaded.

The present invention relates to a single side band modulator for splitting a signal into a first split signal and a second split signal 90 degrees out of phase with the first split signal. A first double balanced mixer modulates the first split signal and includes a transformer, a modulating signal input, and a first diode ring. The transformer connects the first diode ring to a quadrature hybrid. A second double balanced mixer modulates the second split signal and includes a transformer, a modulating signal input, and a second diode ring. The transformer of the second double balanced mixer connects the second diode ring to the quadrature hybrid. The first and second diode rings are connected in parallel and are connected to a third transformer which performs the function of a power combiner.

The invention discloses a photon upconversion method and system based on microwave frequency quadruplication and belongs to the field of microwave photonics. Optical carriers generated by a laser areinput into a first double-parallel Mach-Zehnder modulator. An upper arm submodulator is modulated through utilization of local oscillator signals. Through adjustment of direct current bias of the modulator, the modulator is enabled to work a carrier suppressed maximum transmission point. Modulated optical signals enter a fiber bragg grating through an optical circulator. Through utilization of wavelength selectivity of the fiber bragg grating, positive second-order optical sidebands of a local oscillator are transmitted and are taken as carriers to enter a second double-parallel Mach-Zehnder modulator. Negative second-order optical sidebands of the local oscillator are reflected and are collected through utilization of the optical circulator. Intermediate frequency signals are loaded to the second double-parallel Mach-Zehnder modulator through utilization of a 90-dgree electric bridge, and carrier suppressed single-sideband modulation is realized through utilization of the direct current bias. Two optical paths are combined, power amplification is carried out on the optical signals, and insertion losses of the modulator are compensated. Frequency beating is carried out through utilization of a photoelectric detector, thereby obtaining frequency quadruplicated upconversion signals.

The present invention provides an optical carrier suppression-based optical fiber distribution system and method of photo-produced microwave signals. The optical carrier suppression-based optical fiber distribution system of the photo-produced microwave signals includes a photo-produced microwave signal module, a phase detection module, a phase compensation module and a system output module; the photo-produced microwave signal module generates signal light which is required to be transmitted to a remote end and local light which serves as reference; the phase detection module detects phase jitter caused by optical fiber link jitter and obtains corresponding phase information; the phase compensation module controls the output of a voltage-controlled oscillator according to the phase information, and performs single-sideband modulation on the microwave signals outputted by a microwave signal generator through the output signals of the voltage-controlled oscillator, and then generates compensation signals; and the system output module outputs signals light which has been subjected to phase compensation. With the system and method of the invention adopted, phase detection sensitivity is increased to a magnitude order of light wavelength; technical difficulty in live operation-based high-frequency microwave mixing can be eliminated; a phase-locked loop is adopted to carry out feedback control on obtained phase error signals; and a phase compensation mechanism is fast and accurate, and is not limited in compensation scope.

The invention discloses an optical equipment measurement method and belongs to the technical field of optical equipment measurement and microwave photonics. According to the method, on the basis of existing optical equipment measurement methods based on optical single-sideband modulation, two single-sideband detection signals (namely single-sideband detection signals including carriers and carrier suppression) are combined; accordingly, measurement errors caused by beat frequency between adjacent high-order sidebands in the optical single-sideband detection signals are eliminated, and measurement accuracy and dynamic range of the measurement system are increased greatly. The invention further discloses the optical equipment measurement system. The optical equipment measurement method and system has the advantages that optical equipment can be measured finely and accurately and the optical equipment measurement technology based on single-sideband modulation can be practical.