Abstract
In this paper, two printed multiband fractal monopole antennas using the 1(st) and 2(nd) iteration of Minkowski Island geometry are proposed for WLAN communications. The monopole antennas have compact size of 28 x 18 mm(2) and 21.5 x 18 mm(2), respectively. The proposed antennas with different sizes of the ground plane have also been studied through numerical simulations in Ansoft HFSS. It is found that without using any impedance matching method, both of the proposed antennas exhibit good impedance match at both 2.4 and 5.2 GHz band, which is confirmed by the measurement results. It is also observed that the monopole antenna with the geometry of the 1(st) iteration Minkowslci Island can also operate at 3.5 and 5.8 GHz, which means that it almost covers the entire required frequency bands for 802.11a/b/g and WiMAX communications. The simulation shows that both antennas exhibit high radiation efficiency and the measured radiation patterns show that both antennas have similar radiation patterns at each resonant frequency.

Abstract
We assess the performance of a coherent optical system employing a phase estimation algorithm combined with a least mean square decision-directed equalizer in a feedback configuration and compare it to the constant modulus algorithm with an independent carrier phase estimation approach for 16-quadratic-amplitude-modulation transmission. Both series and parallel implementations are discussed. Hardware issues regarding a recursive implementation of the estimation filter are also reported.

Abstract
The options to implement a coherent optical system employing a phase estimation algorithm combined with adaptive linear equalization are investigated. Several carrier phase estimator strategies are discussed, in terms of parallelization, performance and implementation complexity.

Abstract
This article presents the design and fabrication of a simple printed fractal monopole antenna for WLAN USB dongle applications. The proposed antenna uses the combination of meander line and fractal geometry, which is very simple and easy to fabricate, to achieve a multiband operation characteristic. The parameters of this antenna were optimized through numerical simulations in Ansoft HFSS, after which the antenna has been fabricated and characterized. The measurement results show that the proposed antenna has a -10 dB return loss bandwidth of 2.22 to 2.52 GHz and 5.03 to 5.84 GHz, which covers the entire required band for WLAN 802.11a/b/g standards. Moreover, from the simulation results, it is also observed that this proposed antenna exhibits constant gain of 1.8 dBi with 95% radiation efficiency in the lower band and 2.4 dBi with 94% radiation efficiency in the upper band, respectively. ©2009 IEEE.

Abstract
The digital equalization of fibre impairments in coherent optical communications allows for ultimate limits of spectral efficiency to be achieved, while reducing the cost and complexity compared to optical based solutions. Digital backpropagation (BP) was proposed recently as a reduced complexity approach for jointly compensating linear and non-linear impairments in single polarization coherent optical systems. Furthermore, polarization division multiplexed quadrature phase-shift keying (PDM-QPSK) has emerged as a promising format to increase spectral efficiency. Here we assess the performance of the simplified backpropagation equalization in both single channel and multiple channel transmission in combination with polarization multiplexing for different dispersion map configurations. It is shown that polarization multiplexing induces a degradation in performance due to cross-phase modulation polarization scattering, the backpropagation algorithm still overperforming linear equalization.

Abstract
In this paper, we study the performance of OFDM signals in frequency-interleaved WDM radio-over-fiber (RoF) links with optical channel selection made by a uniform Fiber Bragg grating (FBG). The frequency-interleaved signals, transported over 10 km of standard single mode fiber, were transmitted in optical double-sideband (ODSB) format and filtered in optical single-sideband (OSSB) format. The simulations were being performed using the software VPI and the system performance was evaluated in terms of Error Vector Magnitude (EVM). The EVM is kept below 10% in the 100 and 400 Mbits/s for some optical power values and the system performance is limited by the dispersion in the FBG and nonlinearities in the optical modulator.