Systems and Methods for Adaptive Interference Cancellation

In one embodiment a communications system includes an RF receiver that receives a desired signal and the interference signal, a first phase modulator that receives the desired signal and the interference signal from the RF receiver and generates a resulting optical signal, a second phase modulator that generates a modulated optical signal relative to an inverse interference signal and transmits the modulated optical signal to the first phase modulator, and a detector that receives the resulting optical signal from the first phase modulator and detects the desired signal, wherein the resulting optical signal comprises a modulated optical signal generated by the first phase modulator relative to the desired signal and the interference signal received from the RF receiver and relative to the modulated optical signal received from the second phase modulator

Systems for Extending WDM Transmission into the O Band

Method, apparatus and systems for a wavelength division multiplexing system operating at 0-Band. The system includes a transmitter for wavelength division multiplexing digital 0-band optical channels into a multiplexed optical signal, amplifying and transmitting the multiplexed optical signal, a fiber transmission span using constant intensity modulation and semiconductor optical amplification, and a receiver for receiving and amplifying the transmitted multiplexed optical signal and restoring the individual digital 0-band optical signals. In an embodiment, the transmission span is a single mode fiber transmission span and in another embodiment includes an optical amplifier module coupled into the fiber transmission span. In another embodiment, the transmission span includes a length of 0- band dispersion compensating fiber to reduce four-wave mixing. In another embodiment the system uses wavelength division multiplexing in combination with polarization interleaving. In another emb

All Optical Regeneration

All optical regeneration methods and systems can be realized through an exponential amplifier and a limiting amplifier, which could be two independent devices (one piece of fiber with parametric amplification and a semiconductor optical amplifier operating at saturation state) or one single device (one piece of fiber). The signal quality and the extinction ratio after regeneration are significantly improved compared with the degraded incoming data using a parametric amplifier with the data signal to be regenerated as the pump. The regenerated data has an extinction ratio as high as 14 dB, an extinction ratio enhancement of approximately 5 dB and an approximately 5 dB negative power penalty. This regeneration schemes are format transparent (RZ and NRZ), and provide noise reduction both for bit 1s and bit 0s of the data sequence. The regeneration method and apparatus that just utilizes fibers has the additional capability of ultrafast response speed (several femtoseconds due to the Ker

Joint Fiber and SOA Impairment Compensation Using Digital Backward Propagation

An electronic scheme for joint postcompensation of fiber and semiconductor optical amplifier (SOA) impairments based on coherent detection and digital backward propagation is proposed and demonstrated. A 10-GBd amplitude-phase-modulated transmission system was demonstrated experimentally using semiconductor optical amplification. The Q-factor of the received signal was improved by 5 dB with simultaneous fiber and SOA impairment compensation in the electrical domain

Electronic Compensation of Nonlinear Effects ofSemiconductor Optical Amplifiers

An electrical post-compensation scheme for semiconductor optical amplifier (SOA) impairments has been proposed. An on-off keying (OOK) transmission over 100 km standard single mode fiber (SSMF) and three SOAs was demonstrated experimentally with SOA impairment compensation. An 8dB improvement in Q-factor has been achieved

Nonlinear Impairment Compensation for Polarization-Division Multiplexed WDM Transmission Using Digital Backward Propagation

It is shown experimentally that impairments induced by dispersion and Kerr nonlinearity can be compensated digitally for polarization-division multiplexed wavelength division multiplexing (WDM) transmission. The method of digital backward propagation based on solving the Manakov equation can be used to efficiently compensate for the nonlinear interactions between orthogonally polarized channels

Systems and Methods of Polarization Time Coding for Optical Communications

Systems and methods of polarization-time coding are disclosed. One method includes encoding information in orthogonal polarizations of light and correlated information in multiple time slots, and transmitting the information using the orthogonal polarizations in the time slots. Another method includes receiving a first input pair which specifies a first polarization state and a second input pair containing which specifies a second polarization state; transforming each input pair according to a matrix specifying a conjugate operation to produce four output pairs. The method further includes transmitting at a first time the first output pair using the first polarization state and the third output pair using the second polarization state. The method further includes transmitting at a second time the second output pair using the first polarization state and the fourth output pair using the second polarization state

Noise statistics of and BER estimation using demodulated signals for direct detection differential polarization-phase-shift keying

The noise statistics of optically demodulated signal of the recently proposed modulation format, namely differential polarization-phase-shift keying, are analyzed. It is found that, in the linear regime, the Gaussian approximation is reasonably accurate in estimating the BER. In the nonlinear regime, the noise of the demodulated signal is dominated by the effect of nonlinear phase noise and obeys chi-squared statistics with a degree of freedom of one. Gaussian approximation underestimates the BER in the nonlinear regime. A two-step BER estimation method accounting for both linear beat noise and nonlinear phase noise is proposed. The effectiveness of this two-step BER estimation method at all power levels has been established by comparison with direct error counting

Waveguides Configured to Simultaneously Guide Electromagnetic Waves of Different Wavelengths

Optical fibers are often used to transmit electromagnetic signals. As a result of the geometry of such fibers, each fiber is typically configured to guide electromagnetic waves within only a limited range of wavelengths. In situations in which electromagnetic signals having significantly different wavelengths (e.g., signals from opposite ends of the electromagnetic spectrum) are to be transmitted, multiple fibers are typically required, one for each wavelength. The need for multiple fibers increases the complexity of the systems in which the fibers are used. It would therefore be desirable to have optical fibers or other waveguides that can transmit both relatively short and relatively long wavelength electromagnetic signals