7901results about "Electromagnetic receivers" patented technology

A method and system of coherent detection of optical signals. The system utilizes a digital signal processor to recover an incoming optical signal. The system employs a local oscillator, which does not need to be phase locked to the signal. The signal may be consistently recovered, even when the polarization state varies over time. Additionally, the signal may be recovered when it comprises two channels of the same wavelength that are polarization multiplexed together. In addition, any impairment to the signal may be reversed or eliminated.

A redundently modulated multicarrier protocol known as Carrier Interference Multiple Access (CIMA) is used in an optical-fiber network having wireless links at network nodes. CIMA is a protocol that can be used to create wireless protocols (such as TDMA and CDMA) having enhanced capacity and reduced system complexity. A CIMA optical-fiber network uses dispersion to enhance signal quality and facilitate switching. CIMA achieves both diversity benefits and capacity enhancements by providing redundancy in at least one diversity parameter while providing orthogonality in another diversity parameter. This basic operating principle of CIMA may be combined with multi-user detection to achieve frequency reuse and improved power efficiency. In the wireless link, diversity may be used to reduce the effects of small-scale fading on interferometry multiplexing.

Techniques for directly converting an electrical signal into an optical signal by using a whispering gallery mode optical resonator formed of a dielectric material that allows for direct modulation of optical absorption by the electrical signal.

A device including an input port configured to receive an input signal is described. The device also includes an output port and a structure, which structure includes a tunneling junction connected with the input port and the output port. The tunneling junction is configured in a way (i) which provides electrons in a particular energy state within the structure, (ii) which produces surface plasmons in response to the input signal, (iii) which causes the structure to act as a waveguide for directing at least a portion of the surface plasmons along a predetermined path toward the output port such that the surface plasmons so directed interact with the electrons in a particular way, and (iv) which produces at the output port an output signal resulting from the particular interaction between the electrons and the surface plasmons.

A system and method providing for the detection of an input signal by distributing the input signal into independent signal components that are independently amplified. Detection of an input signal comprises generating from the input signal a plurality of spatially separate elementary charge components, each having a respective known number of elementary charges, the number of the plurality of spatially separate elementary charge components being a known monotonic function of the magnitude of said input signal; and independently amplifying each of the plurality of spatially divided elementary charge components to provide a respective plurality of signal charge packets, each signal charge packet having a second number of elementary charges greater than the respective known number by a respective amplification factor.

The present disclosure provides a polarization multiplexed transceiver, including: a transmitter; a receiver; circuitry within the transmitter configured to insert pilot tones as a reference state of polarization for a polarization multiplexed signal; and circuitry within the receiver configured to de-multiplex the polarization multiplexed signal using the pilot tones. The transmitted signal is constructed in such a manner as to facilitate the division of the receiver processing between the analog and digital domains such that the implementation may be simultaneously both highly spectrally efficient and power efficient.

A wireless communication system transmits data on multiple carriers simultaneously to provide frequency diversity. Orthogonality is provided by carrier interference, which causes a narrow pulse in the time domain corresponding to each transmitted data symbol. Selection of the frequency separation and phases of the carriers controls the timing of the pulses. Equivalently, pulse waveforms may be generated from an appropriate selection of polyphase sub-carrier codes. Time division of the pulses and frequency division of the carriers may be employed for multiple access. Received signals are processed by combining frequency-domain components corresponding to a desired user's allocated carriers. Individual data symbols are processed by providing polyphase decoding, matched filtering, or time-domain shifting the received carriers. Carrier Interferometry components may be used to build various signals corresponding to other transmission protocols.

Apparatuses, systems, and methods are disclosed that provide for an agile coherent optical modem that can generate agile RF waveforms and data rates on a generic opto-electronic hardware platform. An “agile coherent optical modem” [ACOM] approach to optical communications by employing a software configurable and adaptive technologies to the transport system. The ACOM generate agile RF waveforms and data rates on a generic opto-electronic hardware platform. By employing advanced communication techniques to the optical domain such as wavelength agility, waveform agility, and symbol rate agility, it is possible to enable robust optical communications. The ACOM allows for the transport capacity of a communications link to be varied, thereby accommodating variations in transport conditions, range, opacity, etc.

An optical communications network includes a terminal which can simultaneously receive and modulate an optical signal. The terminal includes an optical modulator which is controlled by varying the bias voltage applied to it.

A switchable bandwidth optical receiver is implemented in a front-end of the receiver in at least one of three ways. A switchable impedance may be provided at the input to a preamplifier of the front end, the preamplifier of the front-end may have a switchable impedance therein, and / or a switchable filter may be provided at an output of the preamplifier.

A method is provided for an equalization strategy for compensating channel distortions in a dual-polarization optical transport system wherein the received signal includes a complex signal of a first transmitted polarization component and a complex signal of a second transmitted polarization component. In a first step, a blind self-recovery mode used a blind adaptation algorithm in calculating and modifying multiple complex equalizer transfer function coefficients to enable recovery of only the complex signal of the first transmitted polarization component. By recovering only a single polarization component in the first step the degenerate case of recovering only a single transmitted signal at both polarization component outputs of an equalizer is prevented. In a second step, equalization is performed in a training mode for calculating and modifying the multiple complex equalizer transfer function coefficients to enable recovery of the complex signals of the first and second transmitted polarization components. In a third step, equalization is performed in a data directed mode for continuing to calculate and modify the multiple complex equalizer transfer function coefficients to ensure continued recovery of the complex signals of the first and second transmitted polarization components. The method is suited for a digital signal processing implementation in a coherent receiver when a modulation scheme used on a transmitted signal is quadriphase-shift keying (QPSK). In other embodiments, the method can be used with modulation schemes such as binary PSK, M-ary PSK where M>4, or Quadrature Amplitude Modulation (QAM).

A phase shift unit provides a prescribed phase difference (π / 2, for example) between a pair of optical signals transmitted via a pair of arms constituting a data modulation unit. A low-frequency signal f0 is superimposed on one of the optical signals. A signal of which phase is shifted by π / 2 from the low-frequency signal f0 is superimposed on the other optical signal. A pair of the optical signals is coupled, and a part of which is converted into an electrical signal by a photodiode. 2f0 component contained in the electrical signal is extracted. Bias voltage provided to the phase shift unit is controlled by feedback control so that the 2f0 component becomes the minimum.

A ultra high speed photonic Analog to Digital Converted (ADC) for sampling and quantizing an electrical voltage signal, internally enabled by photonics uses coherent optical detection architectures for photonic quantization. Coherent light is phase modulated by the test signal. Using an interferometer, or an array of interferometers the phase of modulated light is compared with a reference light. Flash ADC, successive approximation ADC and delta-sigma ADC configurations are presented.

There is provided a visible light control apparatus including: a modulation unit (corresponding to a PPM signal generation circuit, a subcarrier generation circuit, and a first AND circuit) that modulates a subcarrier and thereby generates a modulated signal; a visible light control unit (corresponding to a driving circuit) that controls blinking of visible light which contains information based on the modulated signal modulated by the modulation unit and allows the visible light to be emitted at a predetermined emission time ratio; and an emission time ratio control unit (corresponding to a dimming signal generation circuit, an inverting circuit, a second AND circuit, and an OR circuit) that changes the predetermined emission time ratio and allows the visible light to be emitted at the changed emission time ratio.

An information reception device comprising an imaging portion; a light reception portion for light reception of optional information subjected to optical modulation; a specification portion for specifying an optical modulation region contained in a capture angle of the imaging portion; a decoding portion for controlling the light reception portion in order to carry out light reception of the optical modulation region specified by the specification portion and decoding the optional information from the optical modulation content contained in the region; and a reproduction portion for reproducing the optional information decoded by the decoding portion. By acquiring a region essential for detection of optical modulation, acceleration of the information decoding process is achieved. Furthermore, position adjustment of the optical modulation region is easily accomplished.

A method of carrier recovery from a high speed optical signal received through an optical communications network. A stream of multi-bit digital samples of the optical signal is processed to generate a multi-bit estimate X′(n) of each one of a plurality of transmitted symbols. A phase of each symbol estimate X′(n) is rotated, and a respective symbol phase error Δφ(n) of the rotated symbol estimate determined.

A method and system for initializing a coherent optical receiver. Upon detection of an optical signal, a multi-bit digital sample stream of the optical signal is digitally processed to initialize each one of a plurality of adaptive control blocks of the coherent optical receiver. The adaptive control blocks include at least a dispersion compensation block and a clock recovery block. The dispersion compensation block is initialized before initializing the clock recovery block.

An information reception device comprising an imaging portion; a light reception portion for light reception of optional information subjected to optical modulation; a specification portion for specifying an optical modulation region contained in a capture angle of the imaging portion; a decoding portion for controlling the light reception portion in order to carry out light reception of the optical modulation region specified by the specification portion and decoding the optional information from the optical modulation content contained in the region; and a reproduction portion for reproducing the optional information decoded by the decoding portion. By acquiring a region essential for detection of optical modulation, acceleration of the information decoding process is achieved. Furthermore, position adjustment of the optical modulation region is easily accomplished.

There is provided a transmission device including an optical signal generation section configured to generate an optical signal formed by arranging one or more of each of a plurality of kinds of same-color light beams each having different phase, and a transmission section configured to transmit the optical signal generated by the optical signal generation section.

By using low-frequency signals, an optical transmitting unit modulates one of a wavelength, a transmission timing, and an intensity of light as a carrier wave. A polarization multiplexer synthesizes the output light signals, modulated by the optical transmitting unit, in polarization states orthogonal to each other and generates polarization-multiplexing signals. A polarization splitter splits by extracting two orthogonal polarization components from the polarization-multiplexing signals. The polarization states of the polarization-multiplexing signals are controlled by a polarization controller in an optical receiving unit. A band-pass filter extracts components transmitting through passbands from output signals of the optical receiving unit and outputs an intensity of the components. Based on the intensity output from the filter, a controlling circuit generates feedback control signals for maximizing a ratio of the components of the low-frequency signals and by using the feedback control signals, the polarization controller controls the polarization states of the optical multiplexing signals.

A method comprising splitting a received optical signal into split optical signals, the split optical signals being at least initially orthogonally polarized, coherently detecting at least one of the split optical signals and generating an electrical signal indicative thereof, and processing said electrical signal, the processing being adapted for received optical signals with orthogonal frequency division multiplexing (OFDM) modulation. A transmission system, a transmitter and a receiver are also provided.

An optical fiber radio transmission system is provided which is capable of considerably improving the received dynamic range of radio signals and, in addition, is capable of optically transmitting radio signals while preventing the deterioration of transmission performance and the loss of linearity of an input signal more easily. A received level detection section 111 detects which one of predetermined levels, i.e., Level I, Level II, and Level III, the received level of a radio signal received by an antenna 400 falls under. A signal control section 112 performs an amplification / attenuation process on the radio signal in accordance with the detected level. A control information sending section 113 superimposes control information indicating the detected level on a primary signal obtained after the amplification / attenuation process. This signal is converted to an optical signal and transmitted. An optical to electrical conversion section 211 converts the optical signal received from a transmitting unit to an electrical signal. A control information extraction section 212 extracts the level from the control information, which has been superimposed on the primary signal. A signal control section 213 performs an amplification / attenuation process on the primary signal in accordance with the extracted level.

An access point in an optical fiber-based high-speed optical wireless network is disclosed. The access point includes an antenna for receiving communication requirement signals, a switch for selectively outputting a corresponding signal according to the communication requirement signals, a bias control unit for selectively outputting bias current with variable intensity according to whether an output of the signal from the switch exists or not, on the basis of a threshold current; a bias operation unit for outputting input signals to the antenna when an input bias current is smaller than the threshold current and for outputting signals received by the antenna when an input bias current is larger than the predetermined threshold current, and a semiconductor optical amplifier for selectively performing an optical detection function of converting optical signals, which have been received through a first optical fiber from an central station, into electrical signals and sending the converted electrical signals to the bias operation unit, when a current smaller than the threshold current is input to the bias operation unit, and an optical modulation function of transmitting signals output from the bias operation unit through a second optical fiber to the central station, when a current larger than the threshold current is input to the bias operation unit.

A reader / writer is provided which is capable of speedily recognizing a correspondence between one end and the other end of a fiber-optic cable when a plurality of fiber-optic cables is laid. The reader / writer according to the present invention reads, on receiving through the fiber-optic cable a signal that is an instruction to read data from a RF tag mounted to an end of the fiber-optic cable, data from the RF tag through radio communication, and transmits the read data through the fiber-optic cable. Also, on receiving through the fiber-optic cable a signal that is an instruction to write data into the RF tag and a signal indicating the write data, the reader / writer writes the write instruction and the write data into the RF tag through radio communication.

A controller for controlling the reverse-bias voltage of an avalanche photodiode in a transceiver or receiver. The controller includes memory for storing information related to the avalanche photodiode, and analog to digital conversion circuitry for receiving an analog signal corresponding to the temperature of the avalanche photodiode, converting the received analog signal into a digital value, and storing the digital value in a predefined location within the memory. Control circuitry in the controller controls the operation of the avalanche photodiode in accordance with the digital value corresponding to the temperature of the avalanche photodiode and a temperature lookup table stored in the memory. A serial interface is provided to enable a host device to read from and write to locations within the memory. The invention is also implemented as a method for controlling the reverse-bias voltage of an avalanche photodiode in a transceiver or receiver and a method for calibrating a transceiver or receiver having an avalanche photodiode.

A method, apparatus and system for providing clock and data recovery in a receiver for receiving a high speed coherent polarization division multiplexed optical signal using a digital signal processing block including a spectral domain spatial combiner are provided.

A method is provided for correcting a quadrature angle error that exists in the coherent receiver hardware of a dual-polarization optical transport system. The receiver hardware that causes the quadrature angle error is a 90 degree optical hybrid mixing device. The method involves generating an estimate of the quadrature angle error and compensating for the quadrature angle error by multiplying the first and second detected baseband signals by coefficients that are a function of the estimate of the quadrature angle error. The method is robust to severe channel distortion encountered within an optical fiber transmission channel as well as temperature effects and ageing of the 90 degree optical hybrid. The method is suited for a digital signal processing implementation in the coherent receiver when a modulation scheme used on a transmitted signal is quadriphase-shift keying (QPSK). In other embodiments, the method can be used to correct for quadrature angle error in modulation schemes such as binary PSK, M-ary PSK where M>4, or Quadrature Amplitude Modulation (QAM). The method can be implemented by an application-specific integrated circuit(ASIC).

Provided is a pre-equalized optical transmitter, comprises: a laser source; a duo-binary pre-coder circuit; a pre-equalization circuit for applying an inverse function of chromatic dispersion; at least two D / A converters; and an optical field modulator comprising at least two input terminals for an electric signal. The pre-equalized optical transmitter: converts, by the duo-binary pre-coder circuit, a digital information signal of a predetermined symbol time to be transmitted into a digital complex signal including one sampling point per symbol; equalizes, by the pre-equalization circuit, degradation in transmission of the digital complex signal; converts, by the D / A converters, the equalized digital complex signal into an analogue signal; suppresses an analogue signal leaking outside a Nyquist bandwidth by at least 23 dB; modulates, by the optical field modulator, light output from the laser source with the analogue signal to generate a modulated optical field signal; and transmits the modulated optical field signal.

The present invention relates to a method for optical fiber transmission which can increase a transmission distance. A first optical fiber having dispersion is first provided. An optical signal is next supplied to the first optical fiber so that the optical signal is compressed on the time axis as propagating in the first optical fiber. In the case that the dispersion is normal dispersion, for example, prechirping is performed so that the optical signal has down-chirp. A compressed optical signal output from the first optical fiber is supplied to an optical device having a saturated gain. According to this method, the transmission distance can be increased by the effective combination of compression of the optical signal and waveform shaping by the optical device.