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

Coherent optical communication using polarization multiple-input-multiple-output

Polarization-division multiplexed (PDM) optical signals can potentially be demultiplexed by coherent detection and digital signal processing without using optical dynamic polarization control at the receiver. In this paper, we show that optical communications using PDM is analogous to wireless communications using multiple-input-multiple-output ( MIMO) antennae and thus algorithms for channel estimation in wireless MIMO can be ready applied to optical polarization MIMO (PMIMO). Combined with frequency offset and phase estimation algorithms, simulations show that PDM quadrature phase-shift keying signals can be coherently detected by the proposed scheme using commercial semiconductor lasers while no optical phase locking and polarization control are required. This analogy further suggests the potential application of space-time coding in wireless communications to optical polarization MIMO systems and relates the problem of polarization-mode dispersion in fiber transmission to the multi-path propagation in wireless communications

Phase-and-amplitude regeneration of differential phase-shift keyed signals using a phase-sensitive amplifier

DPSK phase- and- amplitude regeneration with a NOLM- based phase- sensitive amplifier is demonstrated experimentally. For a highly degraded input signal, maximum differential phase errors were reduced from 82 degrees to 41 degrees, while the SNR was improved by more than 5- dB. Differential phase Q- factor improvement was better than 6- dB. The PSA was operated free of excess noise due to stimulated Brillouin scattering by using a binary phase modulated pulse train as the pump. The impact of pump fluctuations on regeneration performance is clarified. The regenerated signal was characterized by measurement of the constellation diagram by linear optical sampling, giving the first directly measured evidence of DPSK phase regeneration

2-Amino-4-[4-(dimethyl­amino)­phen­yl]-5-oxo-5,6,7,8-tetra­hydro-4H-chromene-3-carbonitrile

In the title mol­ecule, C18H19N3O2, the fused cyclo­hexenone and pyran rings adopt sofa conformations. Inter­molecular N—H⋯N and N—H⋯O hydrogen bonds link mol­ecules into corrugated layers parallel to the bc plane

WDM transmission over 320 km EDFA-amplified SSMF using 30 Gb/s return-to-zero optical differential 8-level phase-shift keying (OD8PSK)

Fiber transmission of optical differential 8- level phase- shift keying ( OD8PSK) signals is demonstrated for the first time. Co- polarized 8 WDM channels of 10 Giga- symbol/ s or 30 Gb/ s return- to- zero ( RZ) OD8PSK signals with a channel spacing of 50 GHz were transmitted over 320 km of standard single mode fiber ( SSMF) with an EDFA spacing of 80 km. The BER of the worst WDM channel after transmission of 320 km was 2.3 x 10(-5)

2-Amino-4-(2-chloro­phen­yl)-5-oxo-5,6,7,8-tetra­hydro-4H-chromene-3-carbonitrile ethanol monosolvate

In the title compound, C16H13ClN2O2·C2H6O, the fused cyclo­hexene and pyran rings adopt envelope and flattened boat conformations, respectively. In the crystal, N—H⋯O and O—H⋯O hydrogen bonds link the chromene and ethanol solvent mol­ecules into infinite chains along the c axis, and N—H⋯N hydrogen bonds link these chains into a three-dimensional framework. Weak C—H⋯π inter­actions are also present