Trace analysis of volatile polar organics by direct aqueous injection gas chromatography

Summary Procedures for the quantitative analysis of industrial effluents which involve concentration by solvent extraction or the purge-and-trap method are time-consuming, labor-intensive, and prone to error. Direct aqueous injection gas chromatography using an electron-capture detector for the analysis of volatile halocarbons at the ppb level is in routine use in many laboratories. We now discuss the development of a similar protocol for the analysis of volatile polar organics such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and tretrahydrofuran using a flame-ionization detector.     

Exploitation of the Fiber Capacity in Optical Networks Using Time, Frequency, and Space Division Multiple Accesses

In this work we investigate how to obtain very high capacity transmissions in optical networks taking into account the limitations due to the physical channel. We consider both the case in which all the users are connected by a star coupler and the case in which the users are directly connected by the network topology. As a reference, we consider a ring network and a Shuffle Multihop Network (SMN). The use of optical systems to implement high-capacity networks is numerically investi gated by means of numerical simulations taking into consideration the channel limitations due to the chromatic dispersion, the Kerr effect, and the amplified spontaneous emission (ASE) noise of the optical amplifiers. In our model, we consider that the signal, during the routing process that is performed at the user position, undergoes only an attenuation. We suppose the use of intensity modulated signals and receivers with direct detection. Packet switching and digital transmission are assumed with soliton and conventional nonreturn to zero signals. Both wave length and time division multiple accesses are considered. The results show that, in the case of the Time Division Multiple Access (TDMA) technique, the use of a star coupler to connect the users reduces the capacity of a network with respect to the case in which a direct connection of the users is used. This is due to the strong power fluctuations that are present during the signal propagation and to the large quantity of accumulated ASE noise. On the other hand, the use of a star coupler shows the advantage to being easily reconfigurable. The Wavelength Divison Multiple Access (WDMA) technique permits us to achieve higher capacities with respect to the TDMA. This is due to the fact that in the propagation conditions, due to the presence of a star coupler, high bit rate signals are strongly degraded. On the other hand, several low bit rate signals operating at different wavelengths can propagate with a low power level, avoiding strong degradation due to the Four Wave Mixing (FWM) effect. Among the topologies considered in this work, the SMN is the one that generally permits us to reach the highest throughput because in the SMN the signal hops in a limited number of Network Interface Units (NIUs) before reaching the final destination.     

10 Gbits−1 optically amplified single-channel systems operating in links encompassing conventional step-index fibres

In this work a numerical investigation is reported on the propagation regimes that allow single-channel systems to obtain the maximum capacity in links with optical amplification encompassing conventional step-index fibres. Solitons and NRZ signals are considered. We show how the periodical introduction of pieces of dispersion compensating fibres can greatly improve the system performance. The polarization properties of the signals are investigated to increase the system performance and     

Reducing Power Consumption in Core Wavelength Division Multiplexing Optical Networks

Abstract

This work proposes some heuristic criteria aiming at saving energy by efficiently switching off optical fibers in generalized multi-protocol label switching-controlled optical networks during low traffic load periods and by taking into account network equipment power consumption. Simulations show that up to 80% of energy can be saved when the traffic is reduced by 20% with respect to its maximum. The impact of network design parameters is also investigated.     

Performance Comparison of Long-Haul Direct Detection Optical Transmission Systems Adopting Dispersion Management with Pre-Compensation

Abstract

This article reports a numerical investigation on the performance of return-to-zero intensity-modulated direct detection, return-to-zero differential phase shifting key, and return-to-zero differential quadrature phase shifting key systems operating in G.652 links adopting dispersion management. Also illustrated are the role and benefits of pre-compensation. For such an aim, the influence of the non-linear Kerr impairments on the in-phase and quadrature components of the signal are studied, along with the consequent degradations in terms of the Q-factor for the different modulation formats. Such an investigation is applied to evaluate the maximum propagation distances for 40- and 80-Gb/s capacities.     

Simulation of Transmissions Through Optical Transport Networks

The introduction of optical technologies in the path layer of the transport network allows the network communication capacity and nodes throughput to be greatly increased. Optical networks covering large geographic areas and information super highways are coming in the not too distant future. For these reasons it is necessary to analyze the transmission of high-speed signals that transport high volumes of traffic throughout large-area networks. Simulation is an effective tool for this analysis, allowing one to take into account the complex nonlinear behavior of the long optical links and of some optical devices as wavelength converters. This article discusses two different approaches to the simulation of transmission through optical networks: the semi-analytical approach and the complete simulation. Advantages and disad vantages of each approach are considered, and the results obtained by different simulation software implementing the two approaches are compared.     

All-optical implementations for high-capacity TDMA networks

In this article we show how optical technology can allow the design of new optical devices that are able to perform some network functions in order to treat very high bit rate signals (100 Gbit/s). The multiplexing technique that we take into account is the Time Division Multiple Access (TDMA), and the network functions we consider are multiplexing, demultiplexing, synchronization, packet decoding, routing, and resolution of packet contention.

In order to show how these new optical devices can improve the network performance we propose two different network topologies: the first concerns a TDMA star network where the signal information is simultaneously broadcast to all users, while the second is a multihop network. The former is useful mainly for circuit switching, while the latter is suitable for packet switching.

Soliton propagation is used in order to avoid the problem of fiber chromatic dispersion.     

Performance evaluation of optical systems operating on long fibre links

We show how to evaluate the performance of optical systems operating in long fibre links, focusing the study on the signal propagation. A comparison between the performance of single- and multichannel systems is reported, considering conventional and soliton signals. A study on the propagation in the presence of polarization mode dispersion is also reported, showing how the Kerr nonlinearity can also compensate this degradation.