Abstract
This paper presents the design of a single feed multiband printed monopole antenna array using the 2nd generation of the Minkowski fractal geometry. The multiband operation is achieved by a suitable chosen of the size and iteration of the fractal geometry, which is optimized using the EM simulation tool Ansoft HFSS. During this work, it is found that adding a rectangular stub on the ground plane, the impedance match of the antenna can be improved with little influence on the original resonant frequencies. This finding has been confirmed by both simulation and measurement results. Meanwhile, the antenna array on a PDA size substrate was also designed and fabricated. The experimental results show that it can operate from 2.32 to 2.49 and from 5.1 to 5.88 GHz, which covers the required bands for IEEE 802.11a/b/g (2.41-2.48 GHz, 5.15-5.35 GHz and 5.725-5.875 GHz) applications. Measurements indicate that the maximum gain of this printed monopole array can reach 2.3 dBi at lower band and 5.6 dBi at upper band. The simulation results show that the radiation efficiency of this antenna array is 86% at 2.4 GHz, 82% at 5.2 GHz and 89% at 5.8 GHz. ©2010 IEEE.

Abstract
In this paper, we study the effect of uplink wise on the optimality of the receiver structure proposed in [1][2]. This optimum receiver is composed by a demodulator that extracts a set of sufficient statistic, and by an ML detector that uses the demodulator output to estimate the original data, We concentrate on Intensity Modulation/Direct Detection (IM/DD) Radio-over-Fiber (RoF) uplink system when OFDM signals suffer from noise generated by the antenna and photodiode and from nonlinear distortion. The results show that for small and medium modulalion index values, the uplink noise maintains its Gaussian distribution and the optimum receiver still outperforms the conventional.

Abstract
A statistical model linking the probability of detecting photons in a photon counting experiment to the average number of input photons is used to analytically derive an error distribution of the estimates of the average number of photons in coherent input pulses. The estimates distribution determines the required number of experimental count runs required for an acceptable measurement error, for any value of the average number of input photons. An expression for the minimum detectable power by photon counting is obtained, fully capturing the effect of the photon counting statistics thereby completing an earlier analysis.

Abstract
We show experimental results of clock recovery from return-to-zero (RZ) format data by using injection locking of a free-running optoelectronic oscillator (OEO) circuit, which consists of a resonant tunneling diode (RTD) oscillator integrated circuit with both a detector and optical source. Error free extraction of a clock signal from the RTD-OEO is shown under both optical and electrical injection. The clock recovery performance at similar to 1.25 Gb/s is analyzed in terms of timing jitter, phase noise and locking bandwidth.

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.