Keith J. Blow

Radio range adjustment for energy efficient wireless sensor networks

In wireless ad hoc sensor networks, energy use is in many cases the most important constraint since it corresponds directly to operational lifetime. Topology management schemes such as GAF put the redundant nodes for routing to sleep in order to save the energy. The radio range will affect the number of neighbouring nodes, which collaborate to forward data to a base station or sink. In this paper we study a simple linear network and deduce the relationship between optimal radio range and traffic. We find that half of the power can be saved if the radio range is adjusted appropriately compared with the best case where equal radio ranges are used.

Soliton dynamics in the presence of phase modulators

Abstract The evolution of a solitons parameters under the influence of a phase modulator are investigated theoretically and numerically. It is shown that one of the two extrema of the modulation cycle is unstable with respect to small shifts in the timing position of the soliton. The other position exhibits superior suppression of Gordon-Haus jitter in comparison to an amplitude modulator. The formation of continuum dispersive waves is also discussed.

All-optical binary counter

We experimentally demonstrate an all-optical binary counter composed of four semiconductor optical amplifier based all-optical switching gates. The time-of-flight optical circuit operates with bit-differential delays between the exclusive-OR gate used for modulo-2 binary addition and the AND gate used for binary carry detection. A movie of the counter operating in real time is presented.

All-optical passive 2R regeneration for N×40 Gbit/s WDM transmission using NOLM and novel filtering technique

We propose a passive all-optical 2R regeneration method for WDM (N×40 Gbit/s) dispersion-managed RZ transmission based on specially designed WDM guiding filters and in-line nonlinear optical loop mirrors. By system optimisation, the feasibility of 150 GHz-spaced × 16 channel 25000 km transmission over standard fibre is numerically demonstrated.

Analysis of energy conservation in sensor networks

In this paper we use the Erlang theory to quantitatively analyse the trade offs between energy conservation and quality of service in an ad-hoc wireless sensor network. Nodes can be either sleeping, where no transmission or reception can occur, or awake where traffic is processed. Increasing the proportion of time spent in the sleeping state will decrease throughput and increase packet loss and delivery delay. However there is a complex relationship between sleeping time and energy consumption. Increasing the sleeping time does not always lead to an increase in the energy saved. We identify the energy consumption profile for various levels of sensor network activity and derive an optimum energy saving curve that provides a basis for the design of extended-life ad hoc wireless sensor networks.

Study of the operating regime for all-optical passive 2R regeneration of dispersion-managed RZ data at 40 Gb/s using in-line NOLMs

In this letter, we numerically demonstrate that the use of inline nonlinear optical loop mirrors in strongly dispersion-managed transmission systems dominated by pulse distortion and amplitude noise can achieve all-optical passive 2R regeneration of a 40-Gb/s return-to-zero data stream. We define the tolerance limits of this result to the parameters of the input pulses.

Average soliton dynamics in strongly perturbed systems

Abstract We advance the average soliton concept to include averaging of the pulse shape in addition to the pulse energy. A simple prescription is presented for the optimum launch position of a bandwidth-limited sech( t ) pulse, relative to the periodic cycle. We identify how this result can also be obtained from the Lie algebra approach by Hasegawa and Kodama (Optics Lett. 15 (1990) 1443). Improved stability and reduced pulse distortion is demonstrated in a numerical example. Application of this result will enhance the performance of some strongly perturbed, soliton-based, amplified optical communication systems.

Time domain all-optical signal processing at a RZ optical receiver

We propose a new all-optical signal processing technique to enhance the performance of a return-to-zero optical receiver, which is based on nonlinear temporal pulse broadening and flattening in a normal dispersion fiber and subsequent slicing of the pulse temporal waveform. The potential of the method is demonstrated by application to timing jitter- and noise-limited transmission at 40Gbit/s.

Suppression of soliton interactions by periodic phase modulation.

We study analytically and numerically the interaction of adjacent solitons under the influence of a phase modulator. Above a critical value, a bifurcation takes place and the interaction-free lengths are considerably increased.

Bit Error Rate Estimation Methods for QPSK CO-OFDM Transmission

Coherent optical orthogonal frequency division multiplexing (CO-OFDM) is an attractive transmission technique to virtually eliminate intersymbol interference caused by chromatic dispersion and polarization-mode dispersion. Design, development, and operation of CO-OFDM systems require simple, efficient, and reliable methods of their performance evaluation. In this paper, we demonstrate an accurate bit error rate estimation method for QPSK CO-OFDM transmission based on the probability density function of the received QPSK symbols. By comparing with other known approaches, including data-aided and nondata-aided error vector magnitude, we show that the proposed method offers the most accurate estimate of the system performance for both single channel and wavelength division multiplexing QPSK CO-OFDM transmission systems.