687 results about "Intensity modulator" patented technology

An optical transmitter for an optical fiber transmission system is described. The optical transmitter includes an optical source that generates an optical signal having a wavelength at an output. An optical intensity modulator modulates the optical signal with an electrical modulation signal to generate a modulated optical signal at an output. At least one parameter of the optical intensity modulator is chosen to suppress at least one of phase and sideband information in the modulated optical signal. An optical fiber is coupled to the output of the optical intensity modulator. The suppression of the at least one of the phase and the sideband information in the modulated optical signal increases an effective modal bandwidth of the optical fiber.

Methods and apparatus for reducing the coherence of an optical signal that is used to interrogate optical interferometric sensors are disclosed. The optical field phasor of the interrogation source is modulated in a controlled manner to produce a broadened optical source power spectrum at the output of the source unit. The output from the source unit is launched into an optical sensor network, comprising a multiple of optical pathways from its input to the detection unit, where pairs of optical pathways form sensor interferometers. A compensating interferometer with delay difference similar to the sensor delay difference may be arranged in a serially coupled manner with the optical sensor network, either before or after the network. The optical output power from the source unit may either be continuous or pulsed with a pulse duration similar to the sensor delay. The coherence modulation may be performed through direct modulation of the source or through external modulation of the light with piezoelectric ring modulator, a Lithium niobate phase or intensity modulator, or an acoustooptic modulator.

In a quantum cryptographic transmitter (11), a phase modulator (1103, 1104) and an LN intensity modulator (1105) apply optical phase modulation and light intensity modulation to an optical signal based on desired data to generate a desired optical signal to be transmitted to a quantum cryptographic receiver (13). Based on the number of photons detected from the desired optical signal, a bias control circuit (1108) controls an operating point in light intensity modulation of the LN intensity modulator (1105).

The invention discloses a broadband tunable single-passband microwave photon filter generating system. The system comprises a laser, an optical coupler, a polarization modulator, a dispersion displacement optical fiber, a photoelectric detector, a vector network analyzer, a strength modulator and an optical fiber; the laser is used for providing continuous light signals; the optical coupler is used for dividing the continuous light signals into the first path of light signals and the second path of light signals; the polarization modulator is used for modulating the polarization state of the first path of light signals; the dispersion displacement light fiber is used for performing stimulated Brillouin scattering on the detection light signals under the induction effect of pump light signals; the photoelectric detector is used for receiving the detection light signals which are processed in a stimulated Brillouin scattering mode and output by the dispersion displacement optical fiber and generating microwave signals; the vector network analyzer is used for receiving microwave signals output by the photoelectric detector, performing measurement frequency response on the microwave signals, and outputting the microwave signals to the a first polarization modulator at the same time; the strength modulator is used for modulating the polarization state of the first path of light signals and outputting the first path of light signals which are modulated; the optical fiber is used for filtering the first path of light signals which are modulated, and the first path of light signals serve as the pump light signals.

The invention discloses a control system of bias voltage of an IQ optical modulator and a control method of the bias voltage of the IQ optical modulator. The control system comprises a laser optical source, a polarization controller, the IQ optical modulator, an optical coupler, a photoelectric detector and a data processing module, which are connected in sequence, wherein the output of the IP optical modulator is divided by the optical coupler, and then is connected to the photoelectric detector; the output of the IP optical modulator is connected with the input of the data processing module; three outputs of the data processing module are respectively sent to the direct current bias voltage input ports of three subsidiary modulators of the IQ optical modulator. The control method comprises the steps of optimizing the bias voltage of a subsidiary phase modulator by measuring the maximum value and the adjacent minimum value of an output optical power, loading the minimum value of search optical power of a path of low-frequency square signal onto two subsidiary intensity modulators in sequence to optimize the bias voltages of the two subsidiary intensity modulators on that basis, and finally realizing the control and locking on each subsidiary modulator working point of the IQ optical modulator. By applying the control system and the control method, the perfect bias point of the IQ optical modulator can be rapidly and automatically controlled.

An optical transmission system in which a transmitting station and a plurality of receiving stations are connected via an optical splitter, wherein the transmitting station includes: a controller configured to determine whether to perform intensity modulation or phase modulation on optical signals based on information on transmission distances to the receiving stations and modulation bands; an intensity modulator configured to perform intensity modulation on an optical signal; and a phase modulator configured to perform phase modulation on an optical signal, and wherein one of an intensity modulation signal and a phase modulation signal is transmitted from the transmitting station to each of the receiving stations.

The invention discloses a microwave signal optical fiber stationary phase transmission system based on a microwave phase shifter. The system comprises a central station, a far end and a single-mode optical fiber. The central station is connected with the far end through the single-mode optical fiber. The central station is composed of a semiconductor laser device, a dual-drive Mach-Zehnder modulator, a microwave signal source, a first power divider, a first optical filter, an erbium-doped optical fiber amplifier, an optical coupler, a first array waveguide grating, a first photoelectric detector, a frequency eliminator, a second power divider, an optical source, a strength modulator, a second optical filter, an optical circulator, a second photoelectric detector, a first electric mixer, a band-pass filter, a second electric mixer, a low-pass filter and a linear voltage amplification circuit. The far end is composed of a second array waveguide grating, a third photoelectric detector and a Faraday polariscope. According to the invention, the advantage of low building and maintenance cost can be realized; and the phase jitter of microwave signals can be extracted and fed back on a real-time basis.

The invention discloses a high bandwidth tunable double-passband microwave photon filter, belongs to the field of microwave photonics, and relates to the high bandwidth tunable double-passband microwave photon filter based on high non-linear optical fiber excited brillouin scattering effects and multiple pumping signals. The filter consists of a first laser, a first phase modulator, an opto-isolator, a vector network analyzer, a high non-linear optical fiber, a second laser, a strength modulator, a microwave signal source, a second phase regulator, a pulse code generator, an erbium-doped optical fiber amplifier, an optical circulator and a photoelectric detector. The filter is based on phase modulation and excited brillouin scattering effects caused by two pumping signals, and thus double-passband output of the microwave photon filter is achieved. By changing the frequency of the two pumping signals, the frequency of two passband centers can be randomly modulated within a certain frequency range. Through binary phase shift keying modulation on the pumping signals, the bandwidth of the pumping signals can be changed, and thus adjustment on the output bandwidth of the filter is achieved.

The invention discloses a monitoring method for a continuous-variable quantum key distribution system. The method is used for monitoring a quantum channel between a sender and a receiver of the continuous-variable quantum key distribution system. The receiver comprises a balanced homodyne detector. The balanced homodyne detector comprises a 50:50 BS and an AM. According to the non-ideality of relevance between the transmittance and the wave length of the 50:50 BS of the balanced homodyne detector, two kinds of de-noising light are introduced besides spurious signal light and spurious local oscillation light, and therefore the extra noise caused by acquiring and resending behaviors of a monitor is eliminated.

The invention provides a high non-linear optical fiber excited Brillouin scattering effect and amplitude ratio based microwave frequency measurement method and device and belongs to the technical field of microwave photonics. The device provided by the invention is composed of a tunable laser, a coupler, a phase modulator, a strength modulator, a vector network analyzer, an opto-isolator, a high non-linear optical fiber, a circulator, an erbium-doped optical fiber amplifier, a microwave signal source, a DC voltage stabilizing power source and a photoelectric detector. The frequency range of to-be-detected microwave signals can be enlarged through increasing bandwidths of the strength modulator and the phase modulator and enlarging the scanning range of the vector network analyzer and measurement precision can be improved through reducing noise in optical links and increasing the magnitude of energy transfer of excited Brillouin scattering effect. According to the invention, an amplitude ratio function curve is constructed based on the high non-linear optical fiber excited Brillouin scattering effect and a frequency value of to-be-detected microwave signals is obtained through the amplitude ratio function curve. Therefore, the measurement precision is improved.

The invention discloses terahertz wave generating device and method based on optical four-wave mixing effect, which belong to the technical field of microwave photonics. The method comprises the following steps of: driving an intensity modulator by a microwave source signal through electric frequency multiplication by using optical carrier suppression modulation of the external intensity modulator and the four-wave mixing effect in a nonlinear device, forming a carrier suppression signal with only two first-order side bands, then forming two new side bands through the nonlinear device, filtering the original first-order side bands by an optical filter, only retaining two new side bands and carrying out beat frequency on the two new side bands in a PD (Photo Detector) to generate a terahertz wave frequency with six frequency multiplications. The invention lowers the requirements of the microwave modulation signal frequency and the modulator band width and reduces the cost of a system, the generating device has simple structure and favorable portability and the generated terahertz wave has very high stability.

The invention discloses a coherent Brillouin optical time-domain analysis sensing system based on phase modulation probe light. In the system, an electro-optic intensity modulator is driven by an electric pulse signal to externally modulate light carrier waves to generate pump light, the electro-optic intensity modulator working at a carrier wave inhibition point is driven by a microwave signal to externally modulate light carrier waves to generate local light, the local light is externally modulated through an electro-optic phase modulator to generate symmetric side bands as the probe light, and the electro-optic phase modulator is driven by a frequency-adjustable radio-frequency signal. Two components of the probe light scan a Brillouin gain area and a loss area of the pump light respectively at the same time, and losses of the pump light can be dynamically compensated so that non-local effects can be reduced while amplitude modulation is carried out on the pump light by a Brillouin gain spectrum. Frequency beating is carried out on the probe light and the local light through a photoelectric detector, information of the Brillouin gain spectrum is loaded to GHz high-frequency carrier waves to avoid base band noise damage, and meanwhile the signal-to-noise ration of the whole system is improved through coherent detection.

A time-multiplexed waveform generator includes a wavelength splitter that receives an input optical signal and spectrally separates the input optical signal into a plurality of frequency components. A plurality of intensity modulators receives each of the frequency components and passes each of the frequency components for a selective time period, and then extinguishes that frequency for the remainder of a chirp time, the plurality of intensity modulators producing a plurality of first output signals. A plurality of adjustable delay lines is positioned after the intensity modulators and receives the first output signals. Each of the adjustable delay lines enables phase control of each of the frequency components associated with the first output signals for compensating any relative drifts of the path lengths and phase coherently stitching a plurality of sub-chirps together. The adjustable delay lines produce a plurality of second output signals. A wavelength combiner receives the second output signals and recombines the output signals to produce a stair-step waveform output signal.

The invention discloses a device and a method for measuring the chirp parameter frequency response characteristics of an electro-optic intensity modulator, and relates to the technical fields of electronics. The device comprises a tunable laser, a polarization controller, a modulator for electro-optic intensity to be measured, a microwave signal source, a first optical connector, a second optical connector, a single mold optical fiber, an optical power meter, a photoelectric detector, a microwave power meter, a data collecting card and a computer, wherein the tunable laser, the polarization controller, the modulator for electro-optic intensity to be measured, the first optical connector, a dispersion optical fiber group, the second optical connector and the photoelectric detector are sequentially connected through optical paths, and the photoelectric detector, the microwave power meter, the data collecting card, the computer and the microwave signal source are sequentially connected through circuits. The device and the method have the advantages that the measurement precision is high, and the operation is convenient. The device and the method have important application prospects in aspects of optical fiber communication systems, electro-optic intensity modulator analysis and optical signal processing.

The invention discloses a dynamic distributed Brillouin optical fiber sensing device and method. The dynamic distributed Brillouin optical fiber sensing device comprises a narrow linewidth laser, a polarization-maintaining coupler, a coupler, a first electro-optic intensity modulator, a pulse signal generator, a frequency shifter, an optical amplifier, a polarization scrambler, an optical circulator, a polarization controller, a second electro-optic intensity modulator, a microwave signal source, a sensing optical fiber, a 3dB coupler, a balanced photoelectric detector and a data acquisition and processing module. Two technologies including a Brillouin gain spectrum dual-slope frequency point assisted method and a coherent detection technology are adopted at the same time. The coherent detection technology can increase the signal-noise ratio of a system, improve the measurement precision and increases the sensing distance; the Brillouin gain spectrum dual-slope frequency point assisted method solves a problem of influence of optical power fluctuation of a pumping pulse on the measurement precision in a conventional Brillouin gain spectrum slope frequency point assisted method. Therefore, the dynamic distributed Brillouin optical fiber sensing device and method can realize dynamic event measurement with relatively high measurement precision while guaranteeing that the Brillouin optical fiber sensing system has relatively long sensing distance.

The invention provides a long-distance distributed type large-measuring-range rapid response optical fiber dynamic strain sensing device. The device comprises a phase modulator, a multi-frequency signal generating module, an intensity modulator, a microwave switch, an electric pulse generating module, a microwave signal generating module and other components. The signal generating module comprising multi-frequency components is used for modulating the phase of detection continuous light, so that multi-light-frequency components are generated in the detection continuous light, and corresponding Brillouin gain spectrum amplitudes are adjusted through controlling the amplitudes of all the light-frequency components in the detection continuous light. A Brillouin gain spectrum of a needed spectrum width and a spectrum type is obtained through splicing, and the dynamic strain measuring range is greatly enlarged under the condition that the signal-to-noise ratio and the response speed of a system are not destroyed. The frequency difference between two light beams generating a Brillouin amplification effect is fixed in the middle of a beveled edge linear region of the spliced Brillouin gain spectrum, drifting of the spliced Brillouin gain spectrum is converted into power fluctuation of the detection light, and long-distance distributed type large-measuring-range high response speed quantitative measuring on optical fiber dynamic strain and optical fiber static strain is achieved.

A coherent optical link includes a laser master oscillator operative to generate an amplitude- and phase-stable narrow linewidth optical carrier, a first programmable read-only memory (PROM) having an input for receiving and encoding an M-ary data word, a first digital-to-analog (D/A) converter operative to obtain the amplitude-encoded M-ary data word and output a corresponding analog signal, a Mach-Zehnder intensity modulator that obtains the analog signal and intensity-modulates the carrier based on the analog signal, an optical phase modulator having an input, and an optical waveguide that connects the Mach-Zehnder intensity modulator to the input of the optical phase modulator. The Mach-Zehnder intensity modulator and optical phase modulator may be formed into a single package. A modulation method includes modulating an intensity of an optical signal using a Mach-Zehnder intensity modulator, and then modulating the phase of the intensity-modulated optical signal.

The invention provides a 60GHz millimeter wave-based optical wireless fusion video transmission system and method. According to the system, at a junction center, a single-arm Mach-Zehnder intensity modulator is adopted to generate optical millimeter waves through an optical carrier suppression manner, wherein the frequency of the optical millimeter waves is twice of that of radio frequency signals; then, downlink baseband data signals, i.e. high-definition television data stored in a DVD (Digital Video Disk), are modulated to the optical millimeter waves by using another electro-optical Mach-Zehnder modulator; the downlink signals are transmitted to a base station unit through an optical fiber link, and 60GHz electrical millimeter waves are generated from optical-millimeter-wave signals by a high-speed photolectric transducer, are amplified, and then are sent out by an antenna; and the optical-millimeter-wave signals received through the antenna by a user unit are reconstructed into downlink video baseband data signals by using coherent demodulation. According to the system, the radio frequency signals with the frequency of 29GHz are adopted to generate the optical millimeter waves with the frequency of 58GHz, the video transmission rate is 500Mb/s, the transmission distance for data in a downlink in monomode optical fiber at the transmission rate of 500Mb/s is 200m, and the wireless transmission distance can reach 5m.