All-optical 100-Gbit/s word packet time-division-multiplexed access node in a looped-back configuration: enabling technologies for sequential add-drop functionality

We experimentally demonstrate the adding, dropping, and passing through of 100-Gbit/s word packets in a looped-back all-optical time-division-multiplexed (TDM) access node. Packets are routed with a 17-dB contrast ratio and demultiplexed with a 20-dB contrast ratio. This node uses short 100-Gbit/s words to demonstrate its potential to process data packets from multiple sources and to perform packet switching in a multinode ring network configuration. The ability to tolerate timing jitter as well as varying input signal characteristics is essential to an all-optical access node in a multinode network. For 2-ps input pulses, the header processor has a timing window of ~5 ps, and the demultiplexer has a timing window of ~5.5 ps. This allows for tolerance to bit-to-bit timing jitters or to an increase in the pulse width of as much as 3 ps. Packet-to-packet timing jitter is detected and compensated by the technique used to synchronize the local source to each packet. The key enabling technologies of an all-optical TDM packet add-drop multiplexer are discussed, including an erbium-doped fiber laser, a nonlinear optical loop mirror logic gate, self-synchronization to incoming packets with a fast-saturation/slow-recovery gain element followed by an intensity discriminator, a two-wavelength nonlinear optical loop mirror demultiplexer, and synchronization of new packets to the network packet rate with a phase-locked loop. The local source is automatically synchronized to the incoming packet, because it uses an extracted pulse from the packet, which has a contrast ratio of >20 dB to the rest of the packet. Finally, new packets are added by use of a local laser and a synchronization method, which gives a timing jitter of ~1 ps. Using a statistical method of measuring Q value with picosecond resolution, we show that a header processor with two cascaded logic gates has a Q value of 7.1 with a 95% confidence level.     

Antifungal properties of some herb decoctions

The antifungal activities of four spice decoctions (sage, wild thyme, oregano and savory) which grow wild in Turkey against six moulds (Fusarium oxysporum f. sp. phaseoli, Macrophomina phaseoli, Botrytis cinerea, Rhizoctonia solani, Alternaria solani and Aspergillus parasiticus) were tested for fungistatic and fungicidal activity in vitro. Decoctions were added at 5% and 10% levels to 250 ml culture medium. The results showed that the decoctions investigated varied in their antifungal activity. Sage had weak activity, whilst wild thyme, oregano and savory were active against all moulds tested. All test fungi were completely inhibited by both of the concentrations of wild thyme and the 10% level of oregano decoctions in all the incubation periods. It was concluded that some decoctions may be useful as mould inhibitors at food additive levels.     

Demonstration and performance analysis for the off-ramp portion ofan all-optical access node

Ultrafast processing of packets is demonstrated and the performance analyzed for the off-ramp portion of an all-optical access node. The off-ramp consists of synchronized fiber lasers driving an all-optical header processor that includes nonlinear optical loop mirrors (NOLM), electrooptic router, and demultiplexer in the form of a two-wavelength NOLM. We achieve switching contrasts of 10:1 for the header processor and demultiplexer with switching energies of 10 pJ and 1 pJ, respectively. Also, a proposed measurement technique to obtain eye diagrams is used to analyze the all-optical header processor using the synchronized lasers. Using this technique, we obtain an eye diagram with a Q value of 7.1±0.36, which corresponds to a worst case BER value of 8.8×10^-12 for a 95% confidence level. Finally, simulation models are used to verify and compare the experimental results, and we find good agreement. We also use the model to study the various causes for the degradation of the Q value through our system     

Fiber parametric amplifiers for wavelength band conversion

By using a loop configuration formed by a polarization beam splitter, we experimentally demonstrate that the existing wavelength-division multiplexing (WDM) sources in C-band can be wavelength converted to the S-band with low polarization sensitivity and low crosstalk. Using a fiber parametric amplifier as a band converter, we achieve experimentally <0.65-dB polarization sensitivity and >4.7-dB conversion efficiency over 30-nm conversion bandwidth in 315 m of fiber. Compared to the conventional straight fiber wavelength conversion scheme, a more than 2-dB improvement in polarization sensitivity is measured. In addition to the polarization insensitivity, channel crosstalk is measured to be <-27 dB in 315 m of high nonlinearity fiber. In a detailed experimental study, the pattern of crosstalk in longer fiber lengths and the coupling between the polarization sensitivity and crosstalk are measured. For example, with a 430-m fiber length, we measure the degradation in polarization sensitivity to be ~4 dB for 12-dB increased signal power. The experimental results are also confirmed by theoretical calculations. Moreover, in a 32 channels systems simulation, the signal-to-noise ratio (SNR) of the converted signals after 800-km propagation is calculated to be only 0.8-dB degraded compared to using laser diodes with the same initial SNR values. Furthermore, we calculate the effect of pump noise and show that the relative intensity noise of the pump is transferred to the converted signals with an additional 8-dB/Hz degradation     

Inhibition of phytopathogenic fungi by essential oil, hydrosol, ground material and extract of summer savory (Satureja hortensis L.) growing wild in Turkey

The antifungal activities of the essential oil, hydrosol, ground material and extract of summer savory (Satureja hortensis L.) on mycelial growth of Alternaria mali Roberts and Botrytis cinerea Pers. were determined. All doses of extract inhibited 100% the mycelial growth of both fungi, and exhibited a fungicidal effect. The 15% level of hydrosol and the 1.0% level of ground material had a 100% effect on B. cinerea. The other doses showed weak inhibition on mycelial growth of the fungi, and antifungal activity of the essential oil varied depending on concentrations. While the levels of essential oil show fungistatic effect, the increasing doses of hydrosol and ground material showed a fungicidal effect against B. cinerea and A. mali. While the ground material had not showed any fungicidal activity against mycelial growth of A. mali, the 1% and 1.5% levels of the ground material exhibited a fungicidal effect on B. cinerea. The results obtained from this study may contribute to the development of environmentally safer alternatives to protect the spoilage of food products from pathogenic and saprophytic fungi.     

Information fusion for robust ‘context and driver aware’ active vehicle safety systems

Although there is currently significant development in active vehicle safety (AVS) systems, the number of accidents, injury severity levels and fatalities has not reduced. In fact, human error, low performance, drowsiness and distraction may account for a majority in all the accident causation. Active safety systems are unaware of the context and driver status, so these systems cannot improve these figures. Therefore, this study proposes a ‘context and driver aware’ (CDA) AVS system structure as a first step in realizing robust, human-centric and intelligent active safety systems. This work develops, evaluates and combines three sub-modules all employing a Gaussian Mixture Model (GMM)/Universal Background Model (UBM) and likelihood maximization learning scheme: biometric driver identification, maneuver recognition, and distraction detection. The resultant combined system contributes in three areas: (1) robust identification: a speaker recognition system is developed in an audio modality to identify the driver in-vehicle conditions requiring robust operation; (2) narrow the available information space for fusion: maneuver recognition system uses estimated driver identification to prune the selection of models and further restrict search space in a novel distraction detection system; (3) response time and performance: the system quickly produces a prediction of driver’s distracted behaviour for possible use in accident prevention/avoidance. Overall system performance of the combined system is evaluated on the UTDrive Corpus, confirming the suitability of the proposed system for critical imminent accident cases with narrow time windows.     

Duty-ratio control of nonlinear phase noise in dispersion-managed WDM transmissions using RZ-DPSK modulation at 10 Gb/s

The authors compare analytical and numerical estimates, showing that the nonlinear phase noise of short optical pulses associated with the coupling between amplified spontaneous emission noise and fiber nonlinearity may be controlled by adjusting the duty cycle of the return-to-zero (RZ) signal modulation format. The impact of this effect in the optimization of the performance of 10-Gb/s dispersion-managed wavelength division multiplexed (WDM) systems using RZ-differential phase-shift keying (DPSK) modulation is discussed. By extensive numerical simulations, it is shown that the transmission quality of ultradense WDM systems using the RZ-DPSK modulation format may be significantly enhanced by optimizing the duty cycle of the RZ pulses.