160 research outputs found
The behavior of fatty acids in the blood plasma of monkeys following exposure to short term stresses
Monkeys exposed to short term stresses (immobilization, jealousy) were found to develop hyperlipacidemia with a rise in concentration of unsaturated fatty acids in blood plasma, especially of oleic acid, and a relative decrease of saturated free fatty acids, chiefly of palmitinic acid. This finding was more pronounced under immobilization stress than in the jealousy situation. Meanwhile, the composition of triglycerides did not change essentially under the conditions used
Deterministic Raman crosstalk effects in amplified wavelength division multiplexing transmission
We study the deterministic effects of Raman-induced crosstalk in amplified
wavelength division multiplexing (WDM) optical fiber transmission lines. We
show that the dynamics of pulse amplitudes in an N-channel transmission system
is described by an N-dimensional predator-prey model. We find the equilibrium
states with non-zero amplitudes and prove their stability by obtaining the
Lyapunov function. The stability is independent of the exact details of the
approximation for the Raman gain curve. Furthermore, we investigate the impact
of cross phase modulation and Raman self and cross frequency shifts on the
dynamics and establish the stability of the equilibrium state with respect to
these perturbations. Our results provide a quantitative explanation for the
robustness of differential-phase-shift-keyed WDM transmission against Raman
crosstalk effects.Comment: 34 pages and 12 figures. Revised paper. Submitted to Optics
Communication
Fiber nonlinearity mitigation of WDM-PDM QPSK/16-QAM signals using fiber-optic parametric amplifiers based multiple optical phase conjugations
We demonstrate fiber nonlinearity mitigation by using multiple optical phase conjugations (OPCs) in the WDM transmission systems of both 8 Ă— 32-Gbaud PDM QPSK channels and 8 Ă— 32-Gbaud PDM 16-QAM channels, showing improved performance over a single mid-span OPC and no OPC in terms of nonlinear threshold and a best achievable Q2 factor after transmission. In addition, after an even number of OPCs, the signal wavelength can be preserved after transmission. The performance of multiple OPCs for fiber nonlinearity mitigation was evaluated independently for WDM PDM QPSK signals and WDM PDM 16-QAM signals. The technique of multiple OPCs is proved to be transparent to modulation formats and effective for different transmission links. In the WDM PDM QPSK transmission system over 3600 km, by using multiple OPCs the nonlinear threshold (i.e. optimal signal launched power) was increased by ~5 dB compared to the case of no OPC and increased by ~2 dB compared to the case of mid-span OPC. In the WDM PDM 16-QAM transmission system over 912 km, by using the multiple OPCs the nonlinear threshold was increased by ~7 dB compared to the case of no OPC and increased by ~1 dB compared to the case of midspan OPC. The improvements in the best achievable Q2 factors were more modest, ranging from 0.2 dB to 1.1 dB for the results presented
Theory of quantum frequency translation of light in optical fiber: application to interference of two photons of different color
We study quantum frequency translation and two-color photon interference
enabled by the Bragg scattering four-wave mixing process in optical fiber.
Using realistic model parameters, we computationally and analytically determine
the Green function and Schmidt modes for cases with various pump-pulse lengths.
These cases can be categorized as either "non-discriminatory" or
"discriminatory" in regards to their propensity to exhibit high-efficiency
translation or high-visibility two-photon interference for many different
shapes of input wave packets or for only a few input wave packets,
respectively. Also, for a particular case, the Schmidt mode set was found to be
nearly equal to a Hermite-Gaussian function set. The methods and results also
apply with little modification to frequency conversion by sum-frequency
conversion in optical crystals
Phase shift keyed systems based on a gain switched laser transmitter
Return-to-Zero (RZ) and Non-Return-to-Zero (NRZ) Differential Phase Shift Keyed (DPSK) systems require cheap and optimal transmitters for widespread implementation. The authors report on a gain switched Discrete Mode (DM) laser that can be employed as a cost efficient transmitter in a 10.7 Gb/s RZ DPSK system and compare its performance to that of a gain switched Distributed Feed-Back (DFB) laser. Experimental results show that the gain switched DM laser readily provides error free performance and a receiver sensitivity of -33.1 dBm in the 10.7 Gbit/s RZ DPSK system. The standard DFB laser on the other hand displays an error floor at 10(-1) in the same RZ DPSK system. The difference in performance, between the two types of gain switched transmitters, is analysed by investigating their linewidths. We also demonstrate, for the first time, the generation of a highly coherent gain switched pulse train which displays a spectral comb of approximately 13 sidebands spaced by the 10.7 GHz modulation frequency. The filtered side-bands are then employed as narrow linewidth Continuous Wave (CW) sources in a 10.7 Gb/s NRZ DPSK system
Generation of 1.024-Tb/s Nyquist-WDM phase-conjugated twin vector waves by a polarization-insensitive optical parametric amplifier for fiber-nonlinearity-tolerant transmission
One-to-six WDM multicasting of DPSK signals based on dual-pump four-wave mixing in a silicon waveguide
Spectrally-efficient 17.6-Tb/s DWDM optical transmission system over 678 km with pre-filtering analysis
Ellipsometry with an undetermined polarization state
We show that, under the right conditions, one can make highly accurate
polarization-based measurements without knowing the absolute polarization state
of the probing light field. It is shown that light, passed through a randomly
varying birefringent material has a well-defined orbit on the Poincare sphere,
which we term a generalized polarization state, that is preserved. Changes to
the generalized polarization state can then be used in place of the absolute
polarization states that make up the generalized state, to measure the change
in polarization due to a sample under investigation. We illustrate the
usefulness of this analysis approach by demonstrating fiber-based ellipsometry,
where the polarization state of the probe light is unknown, and, yet, the
ellipsometric angles of the investigated sample ( and ) are
obtained with an accuracy comparable to that of conventional ellipsometry
instruments by measuring changes to the generalized polarization state.Comment: 6 pages, 4 figures, 1 tabl
- …