248results about "Optical code multiplex" patented technology

A system for bidirectional communication of digital data between a central unit and a remote unit wherein the need for tracking loops in the central unit has been eliminated. The central unit transmitter generates a master carrier and a master clock signal which are used to transmit downstream data to the remote units. The remote units recover the master carrier and master clock and synchronize local oscillators in each remote unit to these master carrier and master clock signals to generate reference carrier and clock signals for use by the remote unit receiver. These reference carrier and clock signals are also used by the remote unit transmitters to transmit upstream data to the central unit. The central unit receiver detects the phase difference between the reference carrier and clock signals from the remote units periodically and adjusts the phase of the master carrier and master clock signals for use by the central unit receiver to receive the upstream data.

An optical device includes, a first Mach-Zehnder modulator that produces a first output, and a second Mach-Zehnder modulator which produces a second output. A splitter couples the first and second Mach-Zehnder modulators. A combiner combines the first and second outputs. A phase shifter is coupled to the first and second Mach-Zehnder modulators. The first Mach-Zehnder modulator, second Mach-Zehnder modulator, splitter, combiner and the phase shifter are each formed as part of a single chip made of electro-optical material. Such two similar optical device integrated together with polarization combiner provide a two-polarization performance.

A system for optical communication send optical signals over a plurality of wavelength channels. Each wavelength channel comprises a number of orthogonal subchannel frequencies which are spaced apart from one another by a predetermined amount. Each of the subchannel frequencies is modulated with data from a data stream. The data modulation scheme splits a subchannel frequency code into H and V components, and further processes the components prior to modulation with data. The various data-modulated subchannels are then combined into a single channel for transmission. The received signals are detected and demodulated with the help of a symbol timing recovery module which establishes the beginning and end of each symbol. A polarization mode distortion compensation module at the receiver is used to mitigate the effects to polarization more distortion in the fiber.

The present invention relates to a communication system and method that allows a transmitter segment (ground end of uplink segment) to dynamically combine power from plurality of propagation channels (transponders) in order to improve power levels of signals being transmitted, without affecting the receiver segment (user end of downlink segment) and the propagation segment (space segment), and without modifying the configuration of the propagation apparatus (satellite). Specifically, the transmitter segment generates mixtures of input signals by using Wavefront-Multiplexing and transmits the wavefront-multiplexed (WFM) signals through propagation channels to a receiver segment that coherently separates the mixtures of received WFM signals by using adaptive equalization and Wavefront-De-Multiplexing. The WFM signal mixtures allow an operator, or automated system, at the transmitter segment to dynamically allocate equivalent channel (transponder) powers according to continuously changing market demands by dynamically including change of relative input powers into ratios of the WFM signal mixtures being transmitted.

An optical fiber communications system using spread spectrum code division multiple access techniques to achieve better bandwidth utilization. A transmitting user in the system encodes the optical signal using a first coding mask, and a receiving user decodes the received signal using two decoding masks, all of the masks having lengths N. The first mask is divided into two sections of lengths N/2 each, one of the sections defining a first sub-code of length N/2, while the other section blocks light. Each of the second and third masks is also divided into two sections, which correspond to the two sections of the first mask. The section of the second mask corresponding to the coded section of the first mask has a second code that is identical to the first code, and the section of the second mask corresponding to the blocked section of the first mask is also blocked. The section of the third mask corresponding to coded section of the first mask has a third code that is complementary to the first code, and the section of the third mask corresponding to the blocked section of the first mask is also blocked. Some users on the system have masks in which the first of the two sections are blocked and the second of the two sections are coded, while other users have masks in which the second of the two sections are blocked and the first of the two sections are coded. The first codes used to code the encoding masks are selected from a set of unipolar codes that are derived from a set of balanced bipolar orthogonal codes.

Apparatus and system for transmitting and receiving optical code division multiple access data over an optical network. The apparatus comprises a spectral phase decoder for decoding the encoded optical signal to produce a decoded signal, a time gate for temporally extracting a user signal from the decoded signal, and a demodulator that is operable to extract user data from the user signal. The system preferably comprises a source for generating a sequence of optical pulses, each optical pulse comprising a plurality of spectral lines uniformly spaced in frequency so as to define a frequency bin, a data modulator associated with a subscriber and operable to modulate the sequence of pulses using subscriber data to produce a modulated data signals and a Hadamard encoder associated with the data modulator and operable to spectrally encode the modulated data signal to produce an encoded data signal.

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.

A communication system has lighting equipment that has transmitter comprising multiple light-emitting elements that each emit light of different wavelengths and terminal equipment that has light-receiver comprising multiple light-receiving elements that receive optical signals for each of the different wavelengths.

An optical communications system includes a receiver subsystem with at least two heterodyne receivers. The receiver subsystem receives a composite optical signal having two or more subbands of information and corresponding tones. An optical splitter splits the composite optical signal into optical signals. Each optical signal includes a subband(s) and corresponding tone. Each heterodyne receiver receives an optical signal. The receiver includes a heterodyne detector coupled to a signal extractor. The heterodyne detector mixes the optical signal with an optical local oscillator to produce an electrical signal which includes a frequency down-shifted version of the subband and the tone of the optical signal. The signal extractor mixes the frequency down-shifted subband with the frequency down-shifted tone to produce a frequency component containing the information.

A high efficiency, low cost, nondispersive optical multiplexing arrangement for optical beams, used a technique denominated “Reverse Laser Scanning.” In the Reverse Laser Scanning operation, different laser beams angularly meet on the rotational axis of a galvanometer-mounted mirror or the like. Upon reflection from the mirror, each of the laser beams is propagated along one defined direction by appropriate angular positioning of the galvanometer mirror. The process enables several useful deployments, including multi-chemical detection using several lasers in the same sensor, remotely operated laser switching for medical surgery and diagnosis where multiple lasers may be used, and wavelength, code, and time division multiplexing in communication systems, among others.

An object of the present invention is to provide an OCDM transceiver with which the reduction amount of the intensity of the correlation waveform signal is smaller than that of a conventional device of the same type in the decoding step that comprises a time gate processing step. Hence, in the OCDM transceiver of the present invention that comprises an encoding portion and a decoding portion, the decoding portion is constituted comprising a decoder, clock extractor, and time gate. The decoder decodes an encoded optical pulse signal and separates the encoded optical pulse signal into a clock signal extraction signal and an optical pulse signal playback signal. The clock extractor extracts a clock signal from the clock signal extraction signal. Further, the time gate removes only the auto-correlation waveform component from the optical pulse signal playback signal. The auto-correlation waveform component is converted to an electrical signal by means of an optical receiver and generated as a reception signal.

The present invention relates to a method for transmitting data. An optical pulse stream comprising a plurality of return-to-zero optical pulses is prepared by modulating a phase of light output by an optical source to thereby encode data from a data source. The light of the optical pulse stream has a wavelength. The optical pulse stream is transmitted along an optical fiber of an optical network. Optical pulse streams of the invention enhance transmission performance at least in part by reducing noise at the receiver caused by fiber non-linearities.

A two-dimensional wavelength/time optical CDMA system employing balanced-modified pseudo random noise (PN) matrix codes is provided. Through an inverse-exclusive OR operation of a pair of modified PN code, the balanced codes are generated as optical CDMA codes in the form of a new matrix. When the codes are applied to an optical CDMA system to perform encoding and decoding, if the same number of channels as the number (M−1) of subgroups of the codes are connected, the system becomes an MAI-free system, and even if the number of channels connected is twice the number of the subgroups, an error-free system can be established. Accordingly, the number of channels that can be used simultaneously is doubled compared to the prior art method such that the economical efficiency of the optical CDMA system improves.

In an Optical Transport Network (OTN) system, methods and devices are provided for communicating rate-adaptive OTUk frames. One method determines channel statistics for a fiber span connecting a transmitter to a receiver. A client input data rate is determined that is sufficient to meet a minimum communication threshold, and a rate-adaptive OTUk frame format is determined sufficient to carry the client input data rate. The format comprises a set of (n) allocated slots of client input data in a rate-adaptive OTUk frame comprising (m) slots, where (n) is less than or equal to (m). The method then fills the rate-adaptive OTUk frame, including (m−n) unallocated slots, using one of two processes. The first process fills the rate-adaptive OTUk frame with parity bits computed from client input data. The second process fills at least a portion of the rate-adaptive OTUk frame with and dummy bits.

A data storage system is disclosed that includes a recirculating loop storing data in motion. The data may be carried by a signal via the loop including one or more satellites or other vessels that return, for example by reflection or regeneration, the signals through the loop. The loop may also include a waveguide, for example an optical fiber, or an optical cavity. Signal multiplexing may be used to increase the contained data. The signal may be amplified at each roundtrip and sometimes a portion of the signal may be regenerated.

System and method for transmitting and receiving encoded signals over a network along with one or more additional signals transported within a spectral gap created by the coded signals.

An optical CDMA encoder-decoder is constructed by combining arrayed-waveguide gratings, matrix optical switches, and delay lines, otherwise by combining arrayed-waveguide gratings and variable delay lines, thus providing an encoding process that a wavelength change with respect to time in optical pulses.

A high data rate optical signal is inverse multiplexed into a multitude of lower-rate tributaries, each of which is coded by its unique OCDM code, and the combined coded tributaries are injected into a common phase scrambler. Coherent summation of these optically encoded tributaries pass through a shared phase or phase and frequency scrambler before exiting the secure location. The setting of the scrambler acts as the key. The authorized recipient with the correct key retrieves the ones and zeros of the several decoded signals.

A method and device are provided for automatically generating a key and a conjugate key to be used in an optical code division multiple access system. The method comprises applying a down conversion process to pump input light to thereby produce down converted broadband signal and idler fields that are complex conjugates of each other. The signal and idler fields thus serve as the key and its conjugate. Also provided according to the invention is a method for use in coding/decoding a signal in an optical code division multiple access system.

A method and apparatus for enhancing the receiving and information identification functions of multiple access communications systems by employing one or more optical processors configured as a bank of 1-D correlators. The present invention is particularly useful in a DS/SS CDMA communications system, resulting in a multiuser CDMA system that approaches carrier to noise performance (C/N) as opposed to being limited by multiple access interference (MAI). The correlators are arranged in parallel to detect and/or demodulate the received signal, in conjunction with one or more complex algorithms to perform near-optimum multiuser detection, perform multipath combining and/or perform carrier Doppler compensation. An improved receiver in accordance with the present invention comprises means for receiving a plurality of signals transmitted through a communications channel; signal conversion means for converting the received signals into a form suitable for input to the multichannel correlator; a multichannel optical correlator for identifying the presence of particular waveforms and estimating the relative time delay or delays, carrier frequency offset from expected, RF amplitude and RF phase for each received spread spectrum waveform present in the received plurality of signals; a controller for determining and providing to the optical correlator the appropriate set of reference hypotheses; and one or more receiver algorithms depending on the exact receiver function to be performed.

A communication system and method for a deep space spacecraft receiver to perform post-processing to dynamically combine received signal power coherently for pre-processed signal streams radiated non-coherently from a distributed, multiple element, Ka-band transmitting array via multiple concurrent propagation paths. Mutually orthogonal data and pilot signals travel though the multiple propagation paths. A pre-processor utilizing wavefront multiplexing restructures signal streams on the ground into multi-channel wavefrom structures along with injections of pilot signals for diagnostic and probing purposes. These restructured, or “wavefront multiplexed” (WFM) signals are transmitted through propagation channels to a receiver on the spacecraft, wherein adaptive equalization and wavefront de-multiplexing coherently separates the mixtures of received WFM signals. Transmitting power can be dynamically allocated for the multiple concurrent data streams, radiated to different spacecraft within the same field of view according to continuously changing demand by changing the relative input power ratios of the WFM signal mixtures.