62 results about "Beat noise" patented technology

Methods and systems for processing communication signals in an Orthogonal Frequency Division Multiple Access (OFDMA)-Passive Optical Network (PON) are disclosed. An optical carrier at a wavelength generated at an optical line terminal (OLT) may be reused by optical network units (ONUs) in the network for upstream transmission of data signals to the OLT. In addition, each ONU may perform carrier suppression to avoid broadband beating noise resulting from the simultaneous transmission of upstream data signals on the same wavelength. Further, the optical source at the OLT used to generate the optical carrier may be reused as a local oscillator for coherent detection of received upstream signals to minimize any frequency offsets.

The invention aims at reducing the beating noise generated from motors of equipments placed in a galley unit of an aircraft. A galley unit 1 of an aircraft includes a cabinet 10 formed of honeycomb panels and the like. The cabinet 10 has a counter 50 for cooking, and a compartment 20 formed under the counter 50 for storing service carts 30. A plurality of ovens 100 for heating warm dishes are provided above the counter 50. Each oven 100 has a fan motor for making the inner heat even. If all the fan motors of the ovens are driven at the same rotation frequency, a beating noise will be generated from the motor and amplified through the compartment 20. Therefore, the rotation frequencies of the fan motors are slightly varied.

PCT No. PCT/GB94/01149 Sec. 371 Date Jan. 22, 1996 Sec. 102(e) Date Jan. 22, 1996 PCT Filed May 27, 1994 PCT Pub. No. WO94/28648 PCT Pub. Date Dec. 8, 1994In an optical network through which data is transmitted as a stream of bits during successive bit periods by an optical source with a given optical center frequency, to a receiver for detecting a frequency baseband, interferometric noise power, in particular incoherent beat noise power, is minimized by causing a variation in the center frequency of the source such as to cause a redistribution of the incoherent beat noise power from the baseband to higher frequencies, thereby reducing the noise in the baseband.

The invention discloses an optical code demultiplexing/multiplexing sending and receiving method and device based on electric domain encoding/decoding. Different spread spectrum codons are used for digital signals of different users, spread spectrum encoding is carried out by an electric domain encoder, electric encoding signals of all the users are multiplexed, and all the encoding signals are modulated on one group of optical signals with different wave lengths for transmission. Wavelength demultiplexing and photoelectric conversion are first carried out on received optical signals by a wave demultiplexer/multiplexer at a receiving end, and data signals of target users can be recovered as long as corresponding decoder structures are used for the electric signals with different wavelengths. Compared with a traditional incoherent optical code demultiplexing/multiplexing system, the method has the advantages that influence brought by beating noise and multiple access interference can be better eliminated, and better system transmission performance is obtained.

The invention relates to a method for forming a two-dimensional optical orthogonal code with a zero correlation window, and the method comprises following steps of constructing a first sequence with the zero correlation window; constructing a second sequence; and mapping the first sequence and the second sequence to form the two-dimensional optical orthogonal code with the zero correlation window. The invention also relates to a device for realizing the method. The method and the device for forming the two-dimensional optical orthogonal code with the zero correlation window have following beneficial effects that the two-dimensional orthogonal code is completely orthogonal, i.e. the autocorrelation limit of the code is zero, cross-correlation limit of the code is also zero, and thus the multi-address interference and beat noise can be completely eliminated, the near-far effect of a two-dimensional optical code division multiple access (OCDMA) system also can be eliminated; therefore, the two-dimensional OCDMA system with large capacity can be realized, and the two-dimensional OCDMA system can be applied to an optical access network, an optical local area network, an optical code mark switching network, an optical fiber sensor network and the like.

A novel Q-switch device enables significant quality and value improvement for a Q-switched laser system by achieving a significant reduction of mode-beating noise during the pulsed output. The origin of mode-beating noise in a Q-switched laser is a result of high gain availability and amplification of competing standing-waves in formation, whose optical frequency is a product of natural selection via spatial hole burning in the gain medium. The novel Q-switch device employs an active, electro-optics or acousto-optics, Q-switch in combination with a saturable absorber device, to provide an optimized soft opening of the optical path and a controlled timing of a Q-switched laser. This novel combination offers larger modulation loss than otherwise possible with the active modulator alone, and it allows for higher gain build-up and energy extraction efficiency. Specifically, it will enable a low-voltage modulator (<100 V) for high gain (small-signal gain >10) and Q-switched operation at high repetition rate (>10 kHz). The combination is devised to slow down the signal build-up and to sweep the fundamental longitudinal mode frequency at least within the free spectral range of the resonator, such that it varies adiabatically during the Q-switched pulse formation. A laser geometry amenable to high gain and high power is proposed for use in conjunction with the proposed novel Q-switch device. The invention will enable the deployment of cost-effective Q-switched lasers operating in both single-longitudinal and single-transverse (TEM₀₀) mode.

A vehicle (1, 17) includes an electric drive motor (5, 19), an inverter (4) that provides a drive current to the electric motor (5, 19) and a controller (13) that controls the inverter (4). The controller (13) functions as a beat noise generation system that creates beat noise by generating a second operating noise containing a component an order of which is very close to a value representing an order of an operating noise generated in proportion to a rotation speed of the electric motor (5, 19) so as to create desirable traveling noise corresponding to an accelerating state while the vehicle accelerates.

The invention discloses a frequency hopping period optical coding and decoding method, which is used for monitoring optical fiber links of a passive optic network. According to the frequency hopping period optical coding and decoding method, the coding and decoding are simultaneously performed in time domains and frequency domains; and optical code words are periodically coded and decoded in the time domains and are coded and decoded in a frequency hopping way in the frequency domains. The invention also discloses an optical coder decoder for realizing the coding and decoding method and a method for monitoring the optical fiber links of the passive optic network. The optical coder decoder consists of a plurality of optical fiber Bragg optical gratings which are connected in series through optical fiber delay lines; the optical fiber delay lines among the optical gratings have the same length, and the length depends on the period values of the frequency hopping period optical code words and the width of the time domains of detection optical pulse; and the center reflection wavelength of each optical grating depends on frequency hopping sequences on the frequency domains. In the method for monitoring the optical fiber links, the frequency hopping period optical coding and decoding method is adopted. According to the methods, code word capability of the optical code words can be improved, related distance of the optical code words can be reduced, the multi-user interference and beating noise can be effectively restrained, and the system monitoring performance can be improved.

Systems and methods are disclosed for a filter-less coherent receiving system with a filter-less coherent receiver frontend; a signal-signal beat-noise detector coupled to the filter-less coherent receiver frontend; and a real-time processor coupled to the filter-less coherent receiver frontend and the signal-signal beat-noise detector to reject signal-signal interference.

Conventionally, a non-conductive period is provided in a region in the vicinity of zero of an AC power voltage via a voltage detection circuit 14 to turn off reliably. The FET 17 maintains the ON state within several switching cycles after the non-conductive interval to rapidly restore the magnetizing coil current, so that the magnetizing coil current rapidly increases. An object is to suppress beat noise in the electromagnetic device. Within a prescribed interval following the non-conductive interval, a partial voltage at a resistor 19 of an output V2 of a mono-stable circuit 20 is added as a bias voltage to a detection voltage of a magnetizing coil current at a resistor 18, and is detected by the IC 11. The IC 11 drives a FET 17 with a constant switching period after the non-conductive interval, thereby preventing the increase in the magnetizing coil current and resolving the problem.

The invention discloses a metal zipper. The metal zipper comprises two symmetrically arranged fixed cloth strips, zipper teeth, terminal-end limiting codes, a zipper head and a pull tab, wherein the zipper teeth respectively and correspondingly arranged on the two fixed cloth strips; the zipper head is connected between the fixed cloth strips on the two sides by virtue of the zipper teeth; the pull tab is connected to the zipper head; the terminal-end limiting codes are arranged on the bottom of the fixed cloth strips; the zipper teeth are made of steel, and the zipper head is made of steel; a magnet is fixedly arranged on the bottom of the pull tab; a magnetic adhesive tape is attached on the surface of each terminal-end limiting code. Through the way above and according to the metal zipper, the pull tab is absorbed on the zipper teeth under the action of the magnet after the zipper is closed, so that the pull tab is not easy to swing to result in beating noise; the zipper head is absorbed at the terminal-end limiting codes under the action of the magnetic adhesive tapes after the zipper is separated, so that upward and downward sliding is reduced, and the metal zipper is good in quietness.

A differential delay detection system and method includes an optical splitter to split an incoming optical signal between a first path and a second path. The first path includes a cross-polarization interferometer configured to separately generate polarization independent outputs using split paths and to generate cross-polarization interference outputs, balanced photodetectors to aid in removing cross-polarization beating noise, and a polarization demultiplexer configured to combine the polarization independent outputs and the cross-polarization interference outputs from the cross-polarization interferometer with updated coefficients received from the second path to remove the cross-polarization mixed signals. The second path includes a training signal receiver configured to compute the updated coefficients and output the updated coefficients to the polarization demultiplexer.

The invention provides a method and system for constructing a no-hit-zone bipolar frequency hopping code. The method for constructing the no-hit-zone bipolar frequency hopping code includes the steps that first, a no-hit-zone frequency hopping sequence NHZ is constructed; second, a Walsh sequence is constructed; third, the no-hit-zone frequency hopping sequence NHZ and the Walsh sequence are combined to form the no-hit-zone bipolar frequency hopping code. The method and system for constructing the no-hit-zone bipolar frequency hopping code have the advantages that according to the constructed no-hit-zone bipolar frequency hopping code, all codons are totally orthogonal as long as the delay between users is within a zero correlation zone, so that multi-site interference and beat noise of a two-dimensional coherent OCDMA system will be completely eliminated, and the near-far effect of the two-dimensional coherent OCDMA system can also be eliminated. Therefore, by means of the no-hit-zone bipolar frequency hopping code constructed through the method and system, a high-capacity two-dimensional coherent OCDMA system can be achieved, and the no-hit-zone bipolar frequency hopping code can be applied to an optical access network, an optical local area network, an optical code label switching network, an optical fiber sensor network and the like.

The invention provides a constructing method and system for the two-dimensional bipolar code of a zero-correlation region in time/frequency domain. The constructing method comprises the steps that A a time domain zero-correlation region spread-spectrum sequence LA with the zero-correlation region is constructed; B a single coincidence sequence in frequency domain is constructed; C a Walsh sequence is constructed; D the time domain zero-correlation region spread-spectrum sequence of the zero-correlation region is combined with the single coincidence sequence in frequency domain are combined to form a time/frequency domain zero-correlation region two-dimensional optical orthogonal code; and E the time/frequency domain zero-correlation region two-dimensional optical orthogonal code is combined with the Walsh sequence to form the two-dimensional bipolar code of the zero-correlation region in time/frequency domain. The method and the system have the advantages that multi-site interference and beat noise of a two-dimensional coherent OCDMA system are completely eliminated; the near-far effect of the two-dimensional coherent OCDMA system can be eliminated; the large-capacity two-dimensional coherent OCDMA system can be realized; and the method and the system can be applied to an optical access network, an optical local area network, an optical code tag switching network, a fiber optic sensor network and the like.

The invention provides a method and system for adopting colourless and nonluminous optical network units in an optical access network. The method comprises the steps that a binary downlink original signal and an uplink seed signal orthorhombic with the downlink original signal are overlapped together on an optical line terminal and modulated to a light carrier, then the modulated downlink combined optical signal is transmitted to the optical network units, and the optical network units do not comprise a light source; the optical network units receive the downlink combined optical signal, the signal is processed, and the downlink original signal is obtained; a binary uplink original signal is modulated to the downlink combined optical signal through the optical network units, and the modulated uplink modulation signal is transmitted to the optical line terminal; the optical line terminal receives the uplink modulation signal from the optical network units, and then the uplink original signal is restored. The same wavelength light source is adopted in the downlink signal and the uplink signal. The downlink signal does not need to be wiped, and when the uplink signal is received, frequency beating noise caused by rayleigh scattering can be eliminated.

A correlation optical time domain reflectometer (OTDR) provides a correlation sequence that is continuously transmitted along a fiber for testing the fiber for anomalies. Such continuous transmission can result in beat noise that degrades the quality of the measured returns. In this regard, each sample is composed of backscatter returns from many points along the fiber that arrive at the OTDR at the same time. When a subset of these returns have frequency differences that appear in the passband of the OTDR receiver, the constructive and destructive interference of these returns at the OTDR receiver can cause significant low-frequency beat noise in the OTDR signal. An optical transmitter is configured to transmit the correlation sequence through the fiber using a wideband optical signal such that the beat noise is suppressed within the passband of the OTDR receiver, thereby improving the quality of the returns measured by the OTDR.

The invention relates to a method of setting a colorless optical network unit uplink optical wavelength based on beat noise. In a colorless ONU (105), a low bandwidth photoelectric detector used for generating beat noise is accessed; a microwave power meter transmits detected beat noise power to a control unit (1053) in real time; the control unit (1053) determines whether a current output optical wavelength of a tunable laser or a tunable optical transmitter is consistent with the wavelength of a downlink optical signal, and if yes, the operating wavelength of the tunable laser or the tunable optical transmitter is set as a current optical wavelength or a specified optical wavelength, otherwise the control unit (1053) controls the tunable laser or the tunable optical transmitter to continuously perform optical wavelength polling. According to the method, a colorless ONU based on a tunable laser or a tunable optical transmitter can independently set an upward optical wavelength by no means of an OLT, and thereby the method can be widely applied to the wavelength division multiplexing passive optical network technical field.