Hitachi, Ltd.

Hitachi Communication Technologies, Ltd.

Oclaro Japan, Inc.

Lumentum Japan, Inc.

Lumentumradiant Gmbh

Nobuhiko Kikuchi

Shinya Sasaki

Kohei Mandai

Kenro Sekine

Ryoji Takeyari

Hiroyuki Nakano

Toshiki Sugawara

Tetsuya Uda

Shigenori Hayase

Shigehisa Tanaka

Naohiro Sakakida

Riu Hirai

Takao Fukushima

Yuki Wakayama

Hideaki Kotake

A plurality of optical signals are arranged on optical frequency grids having a frequency spacing of Δf, a wavelength multiplexing optical signal includes at least one specific arrangement signal group, and the specific arrangement signal group includes Q S signal(s) and R P signal(s), where Q is an integer of 1 or more and R is an integer of 1 or more. A frequency difference between any pair of S signals included in the specific arrangement signal group is different from frequency differences between all of other pairs of S signals and frequency differences between all pairs of P signals, and a frequency difference between any pair of P signals included in the specific arrangement signal group is different from frequency differences between all pairs of S signals and frequency differences between all of other pairs of P signals.

Wavelength multiplexing optical transmission system and wavelength multiplexing optical transmitter

Provided are an optical transceiver, an optical transmitter IC, and an optical receiver IC, which can be applied to both a case of coding an optical signal and a case of decoding an optical signal, and can suppress an influence of waveform degradation with an inexpensive circuit. The optical transceiver includes an optical transmitter, an optical receiver, and at least any one of: a first delay circuit included in the optical transmitter and configured to delay an input first multi-level digital signal by a delay time corresponding to an amplitude level of the first multi-level digital signal; and a second delay circuit included in the optical receiver and configured to delay an input second multi-level digital signal by a delay time corresponding to an amplitude level of the second multi-level digital signal.

Optical transceiver, optical transmitter IC, and optical receiver IC

Provided is an optical communication system capable of suppressing the deterioration of an intensity waveform of an optical intensity modulated signal subjected to transformation using SSB modulation and improving a bit error ratio and a receiver sensitivity of the optical intensity modulated signal. The optical communication system includes: an optical transmitter section including: a single-side band modulation circuit configured to subject a double-side band modulated signal to generate a single-side band modulated signal; a correction circuit configured to correct an intensity of the single-side band modulated signal so that the intensity of the single-side band modulated signal becomes closer to an intensity of the double-side band modulated signal; and an optical IQ modulator configured to output an optical modulated signal; and an optical receiver section configured to receive the optical modulated signal to directly detect an intensity component of the optical modulated signal.

Optical communication system and optical transmitter

An optical multilevel transmitter includes a semiconductor quadrature optical modulator configured to separately modulate and output in-phase and quadrature electric field components and a semiconductor nonlinear characteristic compensation circuit configured to generate, from in-phase and quadrature drive signals to be inputted to the semiconductor quadrature optical modulator, two signals for correcting each other and to add the two correcting signals to the corresponding drive signals.

Optical multilevel transmitter and optical transponder

It is provided a polarization multiplexing optical transceiver including a polarization multiplexing optical transceiver, a polarization multiplexing optical receiver, a transmission side polarization state control unit and a reception side polarization state control unit. The polarization multiplexing optical receiver includes: a polarization demultiplexing unit; a plurality of information signal reconstruction units configured to receive the reconstructed polarization component on the transmission side as an input, and reconstruct and extract information signals; and an information signal coupling unit configured to one of couple and select the information signals output by the plurality of information signal reconstruction units and output the resultant under control of the reception side polarization state control unit. The polarization multiplexing optical receiver is configured to control, in the single polarization reception state, the polarization demultiplexing unit and at least a part of the plurality of information signal reconstruction units to transition to a power saving mode.

Polarization multiplexing optical transceiver

In order to reduce the circuit size for a chromatic dispersion pre-equalization operation, an optical multilevel signal pre-equalization circuit is provided with: (1) a plurality of look-up tables in which a string of middle codes utilizing a symmetry of a signal constellation of a multilevel code or a string of middle codes represented by polar coordinates is stored in association with a waveform response component; and (2) one or more operation circuits to which the waveform response component corresponding to a multilevel signal to be transmitted is inputted from the plurality of look-up tables, and which outputs a pre-equalized output waveform corresponding to the multilevel signal by operating the waveform response components outputted from different look-up tables.

Optical multilevel signal pre-equalization circuit, optical multilevel signal pre-equalization transmitter, and polarization-multiplexed pre-equalization transmitter

The optical signal to noise ratio is improved when the polarization multilevel signal light is demodulated. A optical polarization multilevel signal receiving apparatus is provided with a polarization multilevel receiver configured to generate at least one estimation symbol A1 to AN estimating a state of the symbol A by utilizing a polarization state of at least one polarization multilevel symbol received in a past before the symbol A, a past value of a decision variable, and a decision result, average the estimation symbols A1 to AN and the symbol A to calculate a reference symbol Ar, and use the calculated reference symbol Ar in place of the symbol A to calculate a decision variable corresponding to a polarization state change of the received symbol R, where R is a received symbol and A is at least one past symbol used as a reference for a change.

Optical polarization multilevel signal receiving apparatus, optical polarization multilevel signal transmitting apparatus, and optical polarization multilevel signal transmission apparatus

Provided is a wavelength division multiplexing (WDM) optical transmission device which is suitable of performing splitting, wavelength multiplexing, switching, and routing on an optical WDM signal in which optical signals having a spectrum close to a rectangle are arranged with a high density, and efficiency of spectral usage is ultimately high in units of wavelengths. A WDM optical transmission device according to the present invention is configured to cause flat portions of adjacent transmission bands on a wavelength spectrum overlap each other.

Wavelength-multiplexed optical transmission device, wavelength-multiplexed optical transmission system, wavelength-multiplexed optical transmission method

A PDL compensation technique is provided that reduces the number of and the number of types of the PDL compensators even if it is uncertain to determine which of the two polarization principal axes of an optical device has a larger loss. The PDL compensator according to the present invention is configured to, before an optical signal input from a first or a second input/output terminal enters a PDL compensation device, switch between the first polarization principal axis and the second polarization principal axis of the optical signal depending on which of the first and the second polarization principal axes has a larger loss or gain.

PDL compensator optical device, and PDL compensation method

An optical field receiver comprises an optical branching circuit for branching a received optical multilevel signal into first and second optical signals, a first optical delayed demodulator for performing delayed demodulation on the first optical signal at a delay time T (T=symbol time), a second optical delayed demodulator for performing delayed demodulation on the second optical signal at the delay time T with an optical phase difference deviating from the first optical delayed demodulator by 90&#xb0;, first and second optical receivers for converting each of the delayed demodulation signals representing x and y components of complex signals output from the first and second delayed demodulators into first and second electrical signals, and a field processing unit fort generating a first reconstructed signal representing an inter-symbol phase difference or a phase angle of a received symbol from the first and second electrical signals for each symbol time T.

Optical field receiver, optical multilevel signal receiver, and optical transmission system

Optical receiveruses two optical delay detectors(set such that the delay times T are equal to symbol time and the phase differences are zero and 90 degrees) to receive an optical multilevel signaland the output signals are A/D converted, thereafter subjected to retiming processes, and then subjected to a differential phase detection, thereby detecting a differential phase at a symbol center time point. In the receiver, the detected differential phase is integrated for each symbol and thereafter combined with an amplitude component obtained from a separately disposed optical intensity receiver, thereby reproducing an optical electric field. Thereafter, a wavelength dispersion compensation circuit () of a time period T is used to compensate for the wavelength dispersion of the transmission path. Moreover, an electric or optical Nyquist filter may be inserted to perform a band limitation, thereby enhancing the wavelength dispersion compensation effect.

Optical receiver and optical transmission system

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 +&#x394;f and &#x2212;&#x394;f 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 2&#x394;f is supplied to X-polarization and Y-polarization components. A polarization diversity coherent optical receiverreceives 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.

Polarization-multiplexed optical transmission system, polarization-Multiplexed optical transmitter, and polarization-multiplexed optical receiver

In an optical multilevel transmitter (), a polar representation of an optical multilevel signal (r, &#x3c6;) is generated by a polar coordinate multilevel signal generation circuit (), input to an optical amplitude modulator () and a polar coordinate type optical phase modulator (), and output as an optical multilevel modulated signal (). The polar coordinate type optical phase modulator () generates an optical phase rotation proportional to an input voltage, so the modulation distortion of the electric signal is transferred in a linear form to the optical phases of the optical multilevel modulated signal (). In an optical multilevel receiver (), a received signal is input to two sets of optical delay detectors () and balance receivers () and directly demodulated, and a differential phase &#x394;&#x3c6; for the received signal is calculated by arctangent computation from the output signal. In a phase adaptive equalizer (), the modulation distortion of the phase is removed by adaptive equalization of the differential phase &#x394;&#x3c6;. By separately receiving the amplitude components and combining them, the modulation distortion is removed and highly sensitive optical multilevel transmission is achieved.

Optical transmission system

Provided is an optical multilevel transmission system, comprising at least one optical multilevel transmitter for transmitting an optical multilevel signal obtained and an optical multilevel receiver for receiving the optical multilevel signal. The received optical multilevel signal has a larger noise in an angular direction than in a radial direction. The optical multilevel receiver sets, in a symbol decision of the received optical multilevel signal demodulated on the complex plane, for positions of all or some of ideal signal points, a width in the angular direction of a decision area, to which each of the ideal signal points belongs and which is measured along a circumference of a circle centered at an origin and passing through a center of the each of the ideal signal points, larger than a width in the angular direction of a decision area defined based on a Euclidean distance.

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Tokyo, Japan

Nobuhiko Kikuchi