Performance evaluation of multiple-beam free space optics in tropical rainy weather

Free space optics (FSO) has the potential to replace optical fiber as a solution for the last mile problem. FSO is favored because of its cheap maintenance costs and quick deployment time as compared to other communication system such as fiber optics. Atmospheric attenuation is a problem for FSOs with classic single beam systems, especially when it rains heavily specially in tropical region like Malaysia. As a result, a multibeam FSO transceiver system has become popular as a solution to this problem. The purpose of this study is to compare the standard single beam FSO system with the suggested multibeam FSO system. At a bit error rate (BER) of 10-9, the comparison is made in terms of received optical power, channel distance, and geometrical losses. Rain intensity data is gathered over a six-month period. To evaluate the performance of both systems, the average rain attenuation is calculated from this data and exposed to single beam and multibeam FSO systems. The multibeam FSO approach was found to increase the system's performance. The results show that employing up to four beams improves the quality of received power and increases the channel distance to 1150 m when compared to a single beam FSO system with a channel distance of only 830 m

Investigation of high voltage polymeric insulators performance under wet pollution

In this paper, a unique approach based on electrical characteristics observed from measurements of contaminated polymeric insulators was established to calculate the electric field distribution over their surfaces. A case study using two different 33 kV polymeric insulator geometric profiles was performed to highlight the benefits of the proposed modeling approach. The conductance of the pollution layer was tested to establish a nonlinear field-dependent conductivity for pollution modeling. The leakage current (LC) of the polluted insulator was measured in a laboratory under clean and wet conditions. Then, using the finite element method (FEM), the electric field and current density distributions along the insulator were computed. The results showed that the insulators experienced an increase in the electric field (EF) magnitude ranging from 0.3 kV/cm to 3.6 kV/cm for the insulator with similar sheds (type I) and 2.2–4.5 kV/cm for the insulator with alternating sheds (big and small, type II) under the high rain condition with a flow rate of 9 L/h. Meanwhile, the highest electric field under fog was 1.74 kV/cm for the insulator with similar sheds and 2.32 kV/cm for an insulator with alternating sheds. Due to the larger diameter on the big shed and the longer leakage distance on the insulator with alternating sheds, the EF on the insulator with alternating sheds is higher than the EF on the insulator with similar sheds. The proposed modeling and simulation provided a detailed field condition estimation around the insulators. This is critical for forecasting the emergence of dry bands and the commencement of flashover on the surfaces of the insulators

Pollution flashover characteristics of coated insulators under different profiles of coating damage

Based on experiments and numerical analysis techniques, this paper aims to investigate the influence of the four different coating damage profiles on the performance of coated 33 kV porcelain insulator strings under polluted and clean surface conditions. The performance of the insulators coated with room temperature vulcanizing (RTV) under partial coating damage and undamaged coating was evaluated. The influence of humidity on pollution flashover was taken into consideration. The ring-shaped, fan-shaped, and random-shaped coating was applied following coating damage. The results showed that the flashover characteristic of the RTV-coated insulators had a significant difference as compared to the normal insulators. Electrical characteristics such as the flashover voltage, critical current, and surface resistance were significantly affected by coating damage distribution and humidity level on the insulators’ surface. The electric field and potential difference were analyzed as well using the finite element method (FEM). The initiation of the arc was observed to appear at the area of insulators where the electric field was the highest. It was also observed that different coating distributions of pollution and humidity levels resulted in a change in the surface pollution layer resistance and an uneven distribution of the electric field. This indicates that the coated insulators’ parameters are directly related to the coating damage distribution on the insulator surface, particularly in the presence of humidity

Characteristics of free space optics communication link in an unusual haze

The connectivity and presence of free space optics (FSO) systems dependent on weather conditions especially in unusual haze have been studied. The attenuation and visibility have been analyzed using different formulas and compared with the experimental study. In an unusual haze condition, the attenuation of signal follows the same pattern as obtained from the theoretical analysis. Attenuation due to scattering, which has been expressed as a function of the link distance, wavelength and meteorological visibility, has been calculated from the visibility data collected at Senai airport in Malaysia. Maximum attenuation about 20 dB/km has been observed due to the unusual haze in Malaysia

Millimeter-wave propagation measurements and models at 28 GHz and 38 GHz in a dining room for 5G wireless networks

To meet 5G requirements, industries are looking forward to a new set of frequency allocation in the millimeter spectrum space, where there is huge amount of bandwidth for wireless gigabit communications. In this paper, the statistics of large-scale path loss and time dispersion parameters are investigated based on ultra-wideband measurements using a steerable directional horn antenna at transmitter (Tx) and omni-directional antenna at the receiver (Rx). The measurement was conducted in a dining room line-of-sight (LOS) scenario, which represents a typical closed-plan for in-building communication. The single-frequency, multi-frequency directional and omni-directional large-scale path loss models are evaluated at 28 GHz and 38 GHz bands based on data acquired from unique Tx and Rx antennas with combination pointing angles. The results show that the large-scale path loss models for indoor propagation developed in this paper is less complex, and yet more physically-based than those used in the third-generation partnership project (3GPP) systems, which involve additional model parameters but yield less accurate results. The time dispersion statistics for mmWave systems using directional antennas and omni-omni antennas configuration at both Tx and Rx are presented for co-polarization scenarios. We show that the multipath root mean square delay spread can be reduced when Tx and Rx antenna are pointed to each other, which results in the strongest received power

New RoF-PON architecture using polarization multiplexed wireless MIMO signals for NG-PON

Next-generation access networks require provision of wireless services and high data rate to meet the huge demands for mobility and multiple services. Moreover, reusing the currently deployed optical distribution networks (ODNs) is highly beneficial and cost effective for providing the new high data rate wireless demands. In this paper, bidirectional radio over fiber passive optical network (RoF-PON) capable of handling multiple-input-multiple-output (MIMO) streams at low cost, high spectral efficiency and backward compatibility with currently deployed PON, is proposed. To the best of our knowledge, all the existing RoF MIMO solutions have not considered compatibility with currently deployed ODNs. Eight laser diodes (LDs) at the central office (CO) are enough for the whole system, instead of having LD or optical transmitter at each remote antenna unit (RAU), which makes a colorless and cost-effective RAU. Twenty four wavelengths are generated using optical comb technique. Each two 16-QAM MIMO signals that have the same carrier frequency in the downstream (DS) transmission are optically combined using polarization-division-multiplexing (PDM), where each two upstream (US) MIMO signals are time division multiplexed. The PDM configuration doubles spectral efficiency with a power penalty of only 1.5 dB. The proposed architecture is a bidirectional asymmetric RoF-PON with total 40/10 Gb/s for DS/US transmission. Even after transmission over 20 km SMF and splitting ratio of 32, acceptable transmission performance and widely separated constellation diagrams for the 16-QAM signals are achieved, with bit error rate (BER) of 10-6 for DS signals and 10-3 for the US signals which can be reduced down to 10-6 by using forward error correction (FEC)

Characteristics of free space optics communication link in an unusual haze

The connectivity and presence of free space optics (FSO) systems dependent on weather conditions especially in unusual haze have been studied. The attenuation and visibility have been analyzed using different formulas and compared with the experimental study. In an unusual haze condition, the attenuation of signal follows the same pattern as obtained from the theoretical analysis. Attenuation due to scattering, which has been expressed as a function of the link distance, wavelength and meteorological visibility, has been calculated from the visibility data collected at Senai airport in Malaysia. Maximum attenuation about 20 dB/km has been observed due to the unusual haze in Malaysia

Single and multiple transceiver simulation modules for free-space optical channel in tropical Malaysian weather

Free space optics (FSO) is an optical communication technology that uses light propagating in free space to transmit data for telecommunications or computer networking, and is exposed to atmospheric attenuation, like absorption and scattering. These types of attenuations seriously degrade the strength of transmitted signal, especially when single beam FSO system is used. So to overcome this problem, a multiple beam FSO transceiver system has become dominance and is usually used. In this paper simulation models are obtained by using average rain attenuation which is evaluated from the five months collected rain intensity data. These models are obtained to demonstrate the results concerning link distance and received optical power of using multiple beam FSO system and comparing it with single beam FSO system. Comparison is carried out in terms of signal to noise ratio (SNR), geometrical losses, atmospheric losses, and bit error rate (BER). From the results it is clear that, by using up to four beams has improved geometrical loss, sensitivity of the receiver, SNR, and link distance

Scalability analysis of hybrid optical wireless access network (HOWAN)

The hybrid optical wireless access network (HOWAN) is a prestigious architecture for next generation (NG) access network. NG access networks are proposed to provide high data rate, broadband multiple services, scalable bandwidth, and flexible communication for manifold wireless end-users (WEUs). In the proposed HOWAN, the optical backhaul and the wireless front-end are implemented by using wavelength division multiplexing/time division multiplexing passive optical network (WDM/TDM PON), and WiFi wireless access technique respectively. In this paper, the scalability of the optical backhaul in terms of the number of supported APs and link reach range are analyzed. The scalability of the optical backhaul based on maximum split ratio of 1/32 for each wavelength channel and a fiber length around 23 km from the central office (CO) to the access point (AP) is analyzed with bit error rate (BER) of 10-9

Cost-effective 2.5 gb/s bidirectional WDM pon using single optical source at the central office

Nowadays, the bandwidth demand of the telecommunication network is growing rapidly due to the increasing number of technology-intelligent users. Optical broadband access networks have emerged to address two issues: (1) channel capacity sharing fairly to the customers, and (2) adequate capacity assignment according to service requirements. The wavelength division multiplexing passive optical network (WDM PON) is a promising solution to provide high data rate, excellent scalability, good protocol transparency and easy upgradability. In this paper, a cost-effective bidirectional WDM PON is proposed to provide symmetrical 2.5 Gb/s by using just single optical laser diode (LD) at the central office (CO). The optical frequency upconversion (OFU) technique is used to implement the proposed network. At the optical network unit (ONU), the reflective semiconductor optical amplifier (RSOA) reuses and amplifies the downlink wavelength to modulate the upstream data. The bit error rate (BER) performance and eye diagrams of the designed system are investigated