423 results about "Polarization multiplexed" 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.

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.

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.

An optical mixer that, in one embodiment, has a single optical hybrid optically coupled to a single polarization beam splitter. The optical hybrid mixes a polarization-multiplexed optical communication signal and a local-oscillator signal to generate four mixed signals, each corresponding to a different relative phase shift between the communication and local-oscillator signals. The polarization beam splitter separates each of the mixed signals into two polarization components, subsequent processing of which enables an optical receiver employing the optical mixer to recover the data carried by the communication signal.

There is a need to prevent two receivers from converging on a state of receiving the same polarization state, fast start receivers, and ensure highly reliable operations. A polarization-multiplexed transmitter previously applies frequency shifts of frequencies +Δf and −Δf to X-polarization and Y-polarization digital information signals to be transmitted. Optical field modulators modulate and polarization-multiplex the signals. As a result, a frequency difference of 2Δf is supplied to X-polarization and Y-polarization components. A polarization diversity coherent optical receiver 215 receives the signal. A frequency estimation portion in a digital signal processing circuit detects a frequency difference signal in both polarization components. This signal is used to a polarization splitting circuit in the digital signal processing circuit.

A high capacity optical transmitter implemented on a photonic integrated circuit chip comprises a single light source which supplies a continuous wave having a particular wavelength to a plurality of modulators to form modulated optical information signals. A phase shifter is coupled to at least one of the modulators and is used to shift the phase of the corresponding modulated optical information signal associated with a particular modulator. A polarization beam combiner receives each of the modulated optical information signals from the modulators and the modulated optical information signal from the phase shifter and combines each of these signals to form a polarization multiplexed differential quadrature phase-shift keying signal. The light source, the plurality of modulators, the phase shifter and the polarization beam combiner are all integrated on the chip.

The present invention discloses a system for signalling within optical or combined optical/electronic networks wherein a first transmission node executes polarization multiplexing on transmitted traffic, and at one or more intermediate nodes one or more of the following processes are carried out on the sent traffic: demultiplexing by polarization and/or polarization and/or SOP-alignment. Further a method for packet handling within optical packet switched networks where, at a first transmission node carries out polarisation demultiplexing of transmitted traffic, and at one or a number of intermediate nodes carries out one or more of the following processes on the transmitted traffic; demultiplexing by polarisation, and/or polarisation and/or SOP-alignment. Said separation into states of polarisation is used in separation of QoS-classes.

A method is provided for detecting the skew between parallel light signals generated from a serial data stream. The method can be used with polarization multiplexed signal, as well as with wavelength division multiplexed signals, spatial division multiplexed signals, phase modulated signals, or intensity modulated signals. The method can be used with direct detection schemes as well as with coherent detection schemes. The method is provided with: imprinting dips between a fixed number of transmitted symbols of the parallel signals; detecting an electrical signal related to the dips for each parallel signal; and comparing the electrical signals in delay.

The invention discloses a multi-channel vector holographic polarization multiplexing method based on a birefringent medium metasurface, and belongs to the technical field of micro-nano optics and holographic multiplexing application. The method comprises the following steps that: the metasurface for achieving the holographic polarization multiplexing is composed of nano column arrays with rectangular cross sections and different geometric dimensions and different azimuth angles; by changing the geometric size and azimuth angles of the nano column unit, the phase and polarization state of the emergent light beam are randomly regulated and controlled by the metasurface; holograms corresponding to different mutually independent original images are obtained by using a GS algorithm; according to the obtained holograms, the geometric size and azimuth angles of the nano column unit are determined by coding so as to generate a processing file of a corresponding medium metasurface structure; the metasurface of the transmission-type medium is processed by adopting a micro-nano processing process of electron beam etching; through the selection of the polarization states of the incident lightbeam and emergent light beam, the combination and multiplexing of seven different polarization images of twelve different polarization channels are achieved.

The invention discloses a single-fiber bidirectional transmission system based on mode division multiplexing. The single-fiber bidirectional transmission system based on the division multiplexing mainly comprises two optical signal input units, two optical signal output units and a mode division multiplexing and demultiplexing unit, wherein the mode division multiplexing and demultiplexing unit comprises two mode-type multiplexers which are connected through few-mode fiber. Polarization multiplexing optical signals are generated by the signal input units, the polarization multiplexing optical signals are enabled to be coupled into a mode field of the few-mode fiber by the mode-type multiplexer to finish the mode division multiplexing, the polarization multiplexing optical signals carried by the mode field are sent to the other mode-type multiplexer through the few-mode fiber, the received polarization multiplexing optical signals are enabled to be coupled into single-mode fiber by the other mode-type multiplexer and sent to the optical signal output units through the single-mode fiber, polarization diversity, mixing and balance detection are carried out on the received optical signals by the signal output units, then the received optical signals are changed into electric signals and then changed into digital signals. According to the single-fiber bidirectional transmission system based on the mode division multiplexing, the few-mode fiber is used for overcoming Rayleigh backward scattering effect, single-fiber bidirectional transmission is achieved, and use efficiency of optical fiber and wavelength resources is improved.

A polarization multiplexing transmitter which generates polarization-multiplexed signals which are arbitrarily polarization-scrambled at high speed, without adding a polarization modulator and a polarization scrambler. In the transmitter, an orthogonally polarized signal generator includes two optical modulators which modulate the electric fields of optical signals and generate two optical signals with mutually orthogonal polarized waves. The transmitter includes electric field mappers which convert two data strings into electric field signals, polarization mappers which give different polarized waves to the two signals, polarization rotators which rotate the polarized waves of the signals uniformly, a polarization multiplexer which multiplexes the two polarization-rotated signals, a polarization demultiplexer which demultiplexes the multiplexed signal into polarized wave components of optical signals generated by the orthogonally polarized signal generator, and a driver. The optical modulators are driven to make the two demultiplexed electric field signals consistent with the electric fields of optical signals modulated by the modulators.

The invention provides a method for performing polarization state tracking and balancing on a received signal in a coherent optical communication system. The method is based on linear Kalman filtering, and comprises the following steps: performing depolarization on an electrical signal input into a filter according to a state vector predicted value to obtain a Kalman measurement predicated value; finding a point which is closest to the measurement predicated value on a circle formed by the rotation of an ideal constellation point for serving as a Kalman practical measured value; subtracting the measurement predicated value from the practical measured value to obtain a measurement allowance, and inputting the measurement allowance into a Kalman updating process; and putting an updated state vector into a next iteration. A highest polarization state rotating speed which can be tracked is about 100 times those of a constant modulus algorithm and a multi-modulus algorithm; the depolarization cost is lowered; the calculation complexity is low; and the calculation amount is small. Moreover, the method is suitable for phase shift keying (PSK) and quadrature amplitude modulation (QAM) polarization multiplexed signals of each order.

A method and system for averaging the effects of polarization distortions across a multitude of transmitted data streams in a dual polarization multiplexed optical communications system. Data streams are interleaved amongst each other in accordance with a predetermined pattern. The interleaved data streams are symbol mapped and modulated to provide a pair of optical signals. The pair of optical signals are orthogonally polarized, and multiplexed for transmission across an optical fibre. A receiver circuit receives the transmitted signal and extracts the interleaved data streams. The interleaved data streams are de-interleaved to generate the original data streams. While the data streams can be interleaved and transmitted via a single wavelength optical signal, the data streams can be interleaved and transmitted over two or more different wavelength optical signals to further mitigate the effects of polarization distortions.

Systems and methods for optical communication that use a transmitter/receiver. The systems and methods include receiving a modulated, encoded input stream. Channel memory is reduced using coarse digital backpropagation and other channel impairments are removed using turbo equalization. Symbols are detected in the input stream that conform to a non-uniform, polar constellation having a Gaussian source distribution to produce a stream of encoded data. The stream of encoded data is decoded with one or more low density parity check (LDPC) decoders.

The present disclosure provides systems and methods for the compensation of signal distortion in fiber optic communication systems and the like. More specifically, the present disclosure provides an orthogonal polarization detection and broadband pilot (OPDBP) technique for the compensation of nonlinear cross polarization (i.e. nonlinear cross polarization modulation) (XPolM) induced noise and nonlinear nonlinear cross phase modulation (XPM) induced noise in a high data rate polarization multiplexed (PM) multilevel-quadrature amplitude modulated (M-QAM) channel due to neighboring channels. This approach allows for the compensation of both XPolM and XPM simultaneously, providing several dBs of optical reach extension. The approach uses a pilot tone based orthogonal polarization detection scheme with broadband (i.e. a few GHz wide) filtering of the pilot tones.

There is provided a system and a method for determining an in-band noise parameter representative of the optical noise contribution (such as OSNR) on a polarization-multiplexed optical Signal-Under-Test (SUT) comprising two polarized phase-modulated data-carrying contributions and an optical noise contribution. For each of a multiplicity of distinct polarization-analyzer conditions, the SUT is analyzed to provide at least one polarization-analyzed component of the SUT and the polarization-analyzed component is detected with an electronic bandwidth at least ten times smaller than the symbol rate of the SUT to obtain a corresponding acquired electrical signal; for each acquired electrical signal, a value of a statistical parameter is determined from the ac component of the acquired electrical signal, thereby providing a set of statistical-parameter values corresponding to the multiplicity of distinct polarization-analyzer conditions; and, from the set of statistical-parameter values, the in-band noise parameter is mathematically determined.

A simplified optical receiver architecture capable of tracking and demultiplexing polarization-multiplexed signals, dynamically compensating for PMD using a variety of polarization controller technologies, and reducing the number of delay line demodulators by two for both DPSK and DQPSK modulation is illustrated. Once polarization is stabilized at the first stage of the cascaded system of the present invention, subsequent stages can be simplified and cost reduced.