Redhwan Q. Shaddad

A survey on access technologies for broadband optical and wireless networks

The bandwidth demand of telecommunication network is growing rapidly due to the increasing number of technology-intelligent end-users. The emerging optical and wireless access networks are continuously competing with each other to provide these requirements for the end-users. The optical access networks provide huge data rate and long-distance link, but it is less ubiquitous. The wireless access networks provide flexible and ubiquitous communication with a low deployment cost. However, its deployment scalability is limited by the spectrum and range limitations. The hybrid wireless optical broadband access network (WOBAN) is a powerful combination of optical backhaul and wireless front-end to contribute to a good scalability, cost effective and flexible communication system. This paper reviews the key enabling access technologies and progress advancements of these networks. The emerging optical and wireless access technologies are also presented and compared.

Evaluation of a 1 Gb/s Free Space Optic system in typical Malaysian weather

Free Space Optical (FSO) communication is increasingly growing type of communication around the world because it has capability similar to fiber optic in terms of speed and bandwidth. But FSO is more preferred compared to fiber optics communication from the point of view of time and cost of deployment. FSO can transmit data from point to point at speed of light through space and requires no licensing. Since FSO is a line of sight communication so it is vulnerable to atmospheric attenuation, so to overcome this immense problem it is necessary to precisely study the channel characteristics present between the transmitter and receiver, especially for tropical climate region like Johor Bahru (JB) Malaysia, where rain and haze attenuation are the main concern. Many studies have been carried out in the temperate climate region where the attenuation due to snow and fog are the two major problems in the placement of FSO. The study in this paper concentrates on performance of single beam FSO system under heavy rain events for a period of four months from the point of view of attenuation and BER versus link distance L. The study is based on simulation and other atmospheric losses are not included. The results from the analysis have shown that under average of maximum rain rate intensities for the period of four months in typical Malaysian weather, single beam FSO system can successfully operate for a link distance of 830m with 19 dB/km attenuation and BER of 10-9. It is also clear from this study that link distance is inversely proportional to rain intensity.

Performance assessment of a 2 Gb/s hybrid optical-wireless access network

The hybrid optical-wireless access network (HOWAN) is a promising architecture for future access networks. It is an optimal combination of an optical backhaul and a wireless front-end for an efficient access network. The HOWAN is proposed that can provide blanket coverage of broadband and flexible connection for end-users. In this paper, the HOWAN architecture is designed based on a WDM / TDM PON at the optical backhaul and a WiFi technology at the wireless front-end. We report performance analysis in terms of the bit-error-rate (BER), eye diagram, and signal-to-noise ratio (SNR) of the HOWAN system. It is accommodating an 8 wavelength channels × 32 optical access network / wireless access points (ONU / APs). Our simulations successfully demonstrate that downstream and upstream of 2 Gb/s can be achieved at optical backhaul for each wavelength channel, within a total distance 20 km and at a data rate of 54 Mb/s per ONU / APs along a 100 m outdoor wireless link.

Capacity improvement of TWDM-PONs exploiting the 16-QAM technique for downstream side with a nonlinearity effect study for upstream DML

Currently, the main goal of developing time-wavelength- division multiplexing passive optical networks (TWDM-PONs) is to acquire capacity improvement in a scalable and cost-effective manner. In response to the challenge, this paper demonstrates a full-system TWDM-PON through physical layer simulation that provides 56 Gb/s downstream and 40 Gb/s upstream bandwidths. We propose a simple and cost-effective scheme to improve the capacity of the downstream signal by utilizing highly spectrally efficient 16 quadrature amplitude modulation (QAM) with 20 GHz radio-over-fiber signal distribution using a single sideband signal that is generated by an optical dual-arm modulator. In addition, we study the effect of nonlinearity on a directly modulated laser (DML) as the upstream laser of an optical network unit. The outcomes obtained revealed good transmission quality in both directions, where bit error ratios of 10-6 and 10-5 are obtained for the downstream and upstream transmissions, respectively. This leads to the ability to support up to 128 users over 40 km of single-mode fiber.

Simultaneous provision of two MIMO wireless and baseband wired services in a single wavelength

Next-generation access networks require simultaneous provision of wired and wireless services and high data rate to meet the huge demands for mobility and multiple services. In this paper, we propose a spectral efficient radio over fiber scheme to simultaneously provide two spatial multiplexed multiple input multiple output (MIMO) wireless signals with baseband (BB) signal in one wavelength using a centralized light source. The proposed scheme can be applicable in wavelength division multiplexed passive optical network (WDM-PON). The BB signal is modulated at low extinction ratio. Using the same modulated light, the two MIMO signals that have the same career frequency are combined optically using polarization-division-multiplexing (PDM). The BER performance of 10-9 is achieved for the three signals after transmission of 20 km single mode fiber (SMF).

Upgrade of an optical network unit in a 40 Gb/s time and wavelength-division multiplexed passive optical network using an upstream tunable colorless laser

Abstract. A high data transmission rate is the main requirement for next-generation telecommunication networks. A design for a 40  Gb/s time and wavelength-division multiplexed passive optical network (TWDM-PON) for next-generation passive optical network stage 2 is presented. The use of a modulated grating Y-branch (MG-Y) laser is proposed as an upstream tunable colorless laser source to upgrade the optical network unit. The electronically tuned MG-Y externally modulated laser with a 10  Gb/s modulation rate is applied to a TWDM-PON and presented across a 3.2-nm tuning range. The performance of the proposed laser is analyzed in terms of bit error rate, eye diagram, and optical signal-to-noise ratio. The proposed TWDM-PON achieved an aggregated data rate of 40  Gb/s along 40 km of bidirectional fiber at a 1:128 splitting ratio without amplification and dispersion compensation.