| Patent application number | Description | Published |
|---|
| 20090074415 | PMD INSENSITIVE DIRECT-DETECTION OPTICAL OFDM SYSTEMS USING SELF-POLARIZATION DIVERSITY - A self-polarization diversity technique to combat PMD in a direct-detection optical OFDM system. This technique does not require any dynamic polarization control, and can simultaneous compensate PMD in a WDM system with one device. Simulation results show that this technique virtually completely eliminates the PMD impairments in direct-detection optical OFDM systems. | 03-19-2009 |
| 20090324224 | System, method and apparatus to suppress inter-channel nonlinearities in WDM systems with coherent detection - For optical communications, apparatus and methods are provided for performing dispersion compensation management that suppresses intra-channel nonlinearities, inter-channel cross-phase modulation (XPM) and/or nonlinear polarization scattering. In optical communication, in which wavelength division multiplexed (WDM) channels are modulated, detecting and measuring channels with coherent detection is complicated due to impairments caused by neighboring channels. Apparatus and methods are provided which reduce the effect of impairments by performing in-line Periodic Group Delay (PGD) dispersion compensation on a WDM signal so as to enable detection of individual channels without severe degradation of system performance. Preferably the PGD dispersion compensator has within a channel a chromatic dispersion substantially similar to a DCF and between channels the group delay is substantially similar. | 12-31-2009 |
| 20100034541 | PMDC FEEDBACK SIGNAL FOR ALTERNATE POLARIZATION DPSK SYSTEM - A feedback signal indicative of the average RF power of an APol-DPSK optical signal is used by a PMD compensator to adjust the amount of compensation applied to the optical signal. | 02-11-2010 |
| 20100103505 | POLARIZATION-INDEPENDENT FOUR-WAVE MIXING IN A BIREFRINGENT FIBER - A two-pump optical parametric device (OPD) having a nonlinear birefringent fiber, in which various four-wave mixing (FWM) processes can occur. The OPD applies, to the nonlinear birefringent fiber, two pump waves, each polarized at about 45 degrees with respect to a birefringence axis of the fiber, and a polarized input signal. A relevant FWM process couples the pump waves and the signal to cause the fiber to generate a desired output signal. In one configuration, the relevant FWM process is inverse modulational interaction, which causes the desired output signal to be generated through amplification or attenuation of the input signal. In another configuration, the relevant FWM process is phase conjugation, which causes the desired output signal to be generated through amplification of the input signal. In yet another configuration, the relevant FWM process is Bragg scattering, which causes the desired output signal to be generated as a corresponding idler signal. | 04-29-2010 |
| 20100150555 | Automatic polarization demultiplexing for polarization division multiplexed signals - Method and apparatus are provided for polarization demultiplexing for a Polarization Division Multiplexed (PDM) signal stream in the optical domain. The optical PDM signal stream includes a first channel representing a first data stream and a second channel representing a second data stream, a time delay between the first channel and the second channel. A Polarization Beam Splitter (PBS) demultiplexes an optical PDM signal into the first channel and the second channel. An associated processing block obtains one of the channels and provides a Polarization Controller with for a control signal corresponding to the power level of the low frequency portion of the RF spectrum of the channel obtained. Based on the control signal, the Polarization Controller adjusts a state of polarization of the optical PDM signal stream that is provided to the PBS for demultiplexing. | 06-17-2010 |
| 20100150559 | Time-interleaved polarization-division-multiplexed transmission systems and transmitters - A WDM system having at least two channels, each of which employs two polarizations, is arranged so that the start times of symbols carried by one polarization of a channel are displaced in time from the start times of symbols carried by the other polarization of that channel, e.g., the start time for each symbol on one polarization is not substantially synchronized with the closest-in-time symbol start time on the other polarization of that channel. Preferably, the data signals are modulated using a return-to-zero (RZ) format and the start times of the symbols of the data signal carried by one polarization of a channel is offset from the start time of the symbols data signal carried by the other polarization of that channel by between 20% to 80%—preferably 50%—of the symbol period of the data signals, when the data signals have the same symbol period. | 06-17-2010 |
| 20100247109 | PMDC FEEDBACK ARRANGEMENT FOR APOL-DPSK - Methods and apparatus are provided for optical polarization mode dispersion compensator (PMDC) feedback control for APol-DPSK signals. A feedback signal generator includes a delay-line-interferometer (DLI), with a differential delay line delay (D) different from one bit period (Tb). In an exemplary embodiment, the DLI delay is in the range of 0.5 Tb| 09-30-2010 | |
| 20110052196 | Narrow-band DPSK apparatus, system, method - System, apparatus and methods are provided for optical communication which tolerates the tight filtering effects from concatenation of reconfigurable optical add drop multiplexers (ROADMs). An exemplary system includes a receiver configured to receive a Narrow-Band Differential-Phase-Shift-Keyed (NB-DPSK) optical signal. The receiver includes a Delay Line Interferometer (DLI) with a path length difference of less than approximately one bit period and a detector for detecting DLI output to form an electrical signal. The bandwidth of the NB-DPSK optical signal is less than approximately one-half of a first bit rate of a transmitter from which the NB-DPSK optical signal is received. The electrical signal is processed to decode transmitted data. A corresponding transmitter amplifies a first input signal having a first bit rate; and drives a DPSK modulator after amplification to generate the NB-DPSK optical signal, which has a bandwidth less than approximately one-half of the first bit rate. | 03-03-2011 |
| 20110142449 | Method And Apparatus For Polarization-Division-Multiplexed Optical Coherent Receivers - The singularity problem of the constant modulus algorithm (CMA) equalizer may be overcome by implementing the CMA equalizer as a two-stage equalizer, with the first stage being a modified version of a CMA equalizer and the second stage being a conventional CMA equalizer. The first stage may be made up of four sub-equalizers, of which only two of the sub-equalizers are independent, i.e., uncorrelated to each other. This first stage equalizer may compensate for PMD. The second stage equalizer is a conventional CMA equalizer made up of four sub-equalizers that are adjusted independently. This second stage equalizer may compensate for polarization-dependent loss (PDL) and any residual CD that is not fully compensated for by a CD compensator before the two-stage equalizer. Advantageously, as the determinant of the first stage never approaches zero, the singularity problem of a conventional CMA single-stage-only equalizer is avoided by the two-stage equalizer. | 06-16-2011 |
