Hamed S. Al-Raweshidy

Numerical modeling of a fiber-optic phase modulator using piezoelectric polymer coating

A new approach in analysing an all-fiber phase modulator using a commercially available finite-element software package is presented. A single-mode fiber coated with a radially poled piezoelectric unoriented vinylidene fluoride (73 mol%)/trifluoroethylene (27 mol%) copolymer was successfully modeled using a two-dimensional axi-symmetric approach. The response of the phase modulator was determined over a wide frequency range, from 10 Hz to 50 MHz. Results showed a phase shift of 0.155 rad/V/m in the low-frequency (axially unconstrained) region, and 0.045 rad/V/m in the high-frequency (axially constrained) region. An excellent agreement exists between the simulation results and experimental measurements.

Optical response of an all-fibre acoustooptic phase modulator using aluminium nitride coating

Abstract For the first time we present results on an all-fibre acoustooptic phase modulator using aluminium nitride (AlN) thin film as the piezoelectric coating. Two-dimensional axisymmetric finite element analysis was employed to determine the response of the modulator over a wide frequency range from 10 kHz to 700 MHz. Phase shifts of 0.823 rad/V/m in the low frequency region and 0.374 rad/V/m in the high frequency region were observed. At frequencies higher than 28 MHz the response is dominated by radial resonances of the fibre-coating composite. A theoretical investigation of the acoustic impedance showed that there is good impedance matching between the AlN piezoelectric coating and the glass fibre resulting in a high acoustic energy transfer of ∼82% at the coating–fibre interface.

Phase noise effect on HIPERLAN/2 system performance

The paper analyses the performance of the HIPERLAN/2 system as the phase noise due to a receivers instability is introduced. Signal degradation is looked at by providing graphs of degradation (dB) against the E/sub b//N/sub 0/ (dB). We also look at the effect of phase noise variance on the signal-to-noise ratio of the signal. Some discussion about the oscillator phase noise mask type to be used in HIPERLAN/2 to achieve acceptable signal-to-noise ratio under the phase noise effect is provided. Lastly, the effect on system performance of phase noise due to the fading channel is investigated. All four modulation types (BPSK, QPSK, 16 QAM, 64 QAM) are modelled where the appropriate phase noise is added depending on the modulation scheme used.

Evaluation of user capacity and channel model effect in HiperLAN/2 system

HiperLAN/2 is an upcoming standard, which is being specified by the ETSI/BRAN project. High Performance Radio Local Area Network type 2 (HiperLAN/2) is one of the wireless broadband access networks, shall provide high-speed communications of up to 54 Mbps between mobile terminals and various broadband infrastructure networks. This paper presents an overview of the H/2 standard together with simulated physical layer performance results for each of the transmission mode define in the standard for channel A, C and E as these channels are the most common environments where H/2 will be deployed. Furthermore, the effect on systems throughput as the number of users and number of connections per user increases are also investigated. At the end, some comparison are made between HiperLAN/2 and IEEE 802.11(a) standards as they are two competing systems.

In-building coverage for UMTS using radio over fibre technology

This paper presents a bi-directional optical link for a wireless indoor coverage system operating in the UMTS band, using radio over fibre technology. It shows the feasibility of a dual loop architecture in which only one optical source for both directions and an electroabsorption modulator (EAM) are applied. The EAM is used as a simultaneous receiver as well as transmitter at the remote end of a bi-directional analogue optical fibre link in the UMTS band. On the basis of measurements the distortion performance of the basic dual loop architecture is evaluated. A promising alternative problem solution is demonstrated which may also be cost efficient.

Macrodiversity performance in the uplink of WCDMA with radio over fibre access network

In this paper, the performance of the uplink of a WCDMA radio over fibre (RoF) access network during macrodiversity mode is investigated. We propose a novel macrodiversity scheme in the uplink, based on maximum ratio combining (MRC) of the received symbols by different BS receivers of a WCDMA mobile cellular system with RoF. Our simulation results demonstrate that, for a given service, the coverage efficiency increased by 19%-23% (depending on the channel model and the mobile speed) in the case of MRC as compared to selection combining (SC).

Spread Spectrum Technique to Improve the Performance of Radio over Fibre for Microcellular GSM Networks

This paper presents a GSM-specific assessment of the performance of a radioover fibre link between a remote antenna unit and GSM base station. Theintermodulation distortion (IMD) has been analysed for a system using thesubcarrier multiplexing (SCM). A novel technique using direct sequence spreadspectrum is proposed to minimize the IMD by decreasing the signal amplitudeprior to a direct modulation of a laser diode. The results show that theoptical fibre microcellular is outperforming the full wireless system.

Finite Element Analysis of Piezoelectric Polymer-Coated D-Fiber Intended for Electric Field Sensing

We report, for the first time, the advantage of using a polymer-coated D-fiber over conventional circular fiber as the sensing element in an all-fiber electric field sensor. Finite element analysis has been used to study the strains in a D-fiber subjected to an external electric field. The optical D-fiber carrying a transversely poled piezoelectric poly(vinylidene fluoride) polymer coating was modeled by using three-dimensional stress analysis. The response of the D-fiber electric field sensor was determined over a wide frequency range from 100 Hz to 50 MHz. The modeling predicts that the resulting strains will cause a phase shift of 0.06 rad / V / m in the low-frequency (axially unconstrained) region and 0.002 rad / V / m in the high-frequency (axially constrained) region. An increase in the phase modulation sensitivity by a factor of 3 compared to conventional circular fiber has been achieved by utilizing the unique properties of the D-fiber structure.We report, for the first time, the advantage of using a polymer-coated D-fiber over conventional circular fiber as the sensing element in an all-fiber electric field sensor. Finite element analysis has been used to studythe strains in a D-fiber subjected to an external electric field. The optical D-fiber carrying a transversely poled piezoelectric poly(vinylidene fluoride) polymer coating was modeled by using three-dimensional stress analysis. The response of the D-fiber electric field sensor was determined over a wide frequency range from 100 Hz to 50 MHz. The modeling predicts that the resulting strains will cause a phase shift of 0.06 rad V m in the low-frequency (axially unconstrained) region and 0.002 rad V m in the high-frequency (axially constrained)region. An increase in the phase modulation sensitivity by a factor of 3 compared to conventional circular fiber has been achieved by utilizing the unique properties of the D-fiber structure.

D-Fiber antenna characterization using finite-element analysis

An all-fiber antenna using piezoelectric polymer coated circular core D-fiber has been characterized using finite-element analysis. The response of the D-fiber antenna was determined over a wide frequency range from 1 MHz to 2 GWz. The modeling predicts an electric field induced phase shift of 2.43/spl times/10/sup -6/ rad/(V/m) per meter at 5 MHz. At frequencies higher than 8 MHz, the optical response is dominated by radial resonances of the D-fiber/coating composite. Using the simulation results, a minimum detectable electric field of 41 /spl mu/V/m has been achieved using a 1 km length of coated D-fiber. In addition, a D-fiber antenna network intended for microcellular communications has been analyzed using shot noise limited detection. The D-fiber antenna has potential applications in areas such as electromagnetic compatibility testing and radio-over-fiber networks where it provides a convenient means of optically generating radio signals.

The performance of macrodiversity in the downlink of WCDMA with radio over fibre access network

The performance of a WCDMA radio over fibre access network in macrodiversity mode is investigated. We computed the E/sub b//N/sub 0/ for different cases applying the macrodiversity combining method. Our simulation results demonstrate that, for a given service, the capacity increased by 13%-46% (depending on the channel model and the mobile speed) in the case of the macrodiversity link as compared to the single link.