Optical Access Points Research Articles

Spectral and spatial characterization of perfluorinated graded-index polymer optical fibers for the distribution of optical wireless communication cells.

In this paper, the characterization of a perfluorinated graded-index polymer optical fiber (PF-GIPOF) for a high-bitrate indoor optical wireless system is reported. PF-GIPOF is used here to interconnect different optical wireless access points that distribute optical free-space high-bitrate wireless communication cells. The PF-GIPOF channel is first studied in terms of transmission attenuation and frequency response and, in a second step, the spatial power profile distribution at the fiber output is analyzed. Both characterizations are performed under varying restricted mode launch conditions, enabling us to assess the transmission channel performance subject to potential connectorization errors within an environment where the end users may intervene by themselves on the home network infrastructure.

Scheduling for indoor visible light communication based on graph theory.

Visible light communication (VLC) has drawn much attention in the field of high-rate indoor wireless communication. While most existing works focused on point-to-point VLC technologies, few studies have concerned multiuser VLC, where multiple optical access points (APs) transmit data to multiple user receivers. In such scenarios, inter-user interference constitutes the major factor limiting the system performance. Therefore, a proper scheduling scheme has to be proposed to coordinate the interference and optimize the whole system performance. In this work, we aim to maximize the sum rate of the system while taking into account user fairness by appropriately assigning LED lamps to multiple users. The formulated scheduling problem turns out to be a maximum weighted independent set problem. We then propose a novel and efficient resource allocation method based on graph theory to achieve high sum rates. Moreover, we also introduce proportional fairness into our scheduling scheme to ensure the user fairness. Our proposed scheduling scheme can, with low complexity, achieve more multiplexing gains, higher sum rate, and better fairness than the existing works.

Load Adaptive and Fault Tolerant Framework for Energy Saving in Fiber–Wireless Access Networks

Energy saving (ES) in telecommunication networks is an important criterion when planning access networks. In fiber-wireless (FiWi) access networks the ES potential is high, when compared with other architectures, because different routes and optical access points can be used by routers at the wireless section. Although some proposals to increase energy efficiency in these architectures have been presented, these are not approaches that can adapt to variations in traffic load or distribution of traffic across the network. Here we fill this gap and propose a load adaptive and fault tolerant framework for ES in FiWi access networks. This framework allows optical network units (ONUs) to enter long-standing sleep mode under low traffic conditions, reducing energy waste, permitting fast reaction to ONU or fiber failures, and allowing quality of service (QoS) to be kept at a certain level. Results show that significant ES can be achieved under low to medium traffic loads while maintaining QoS and fault tolerance.

Determining of Velocity Fields During Real and Experimental Simulated Beer Fermentations by UDV and LDA

AbstractBeer fermentation is a very complex process, especially in the fluid‐mechanical and the biochemical point of view. Our aim is to optimize the fermentation by flow control, which requires quantities of data. The applied velocity measuring techniques should be non‐invasive to ensure that neither the flow nor the fermentation in the green beer gets influenced. Therefore, an Ultrasonic Doppler Velocimetry (UDV) system is used to determine velocity fields with 128 measuring points. It works in the turbid fluid with the existing yeast cells as tracer particles and can be applied easily to the industrial scale.For the validation of CFD‐codes and the better understanding of measurements and flow processes, model fluids are used. They can be adapted to real fluid properties like density and viscosity and allow measurements with Laser Doppler Anemometry (LDA). Another advantage over the real fluid is their fixed composition, which leads to negligible natural variations. All experiments are performed in a 270 litre fermenter. Besides the real process, measurements through optical access points and the simulation of fermentations with CO2 and heat emission are enabled. Eight individually controllable cooling zones are used as thermal actors. Resulting changes in boundary conditions induce temperature gradients and hence allow to control the flow inside the tank.This work deals with the experimental set‐up and the results on the one hand and a comparison between real and simulated fermentations on the other hand. Special attention is given to investigations of the multi‐phase flow inside the vessel and the effects of changing constraints. The usability of UDV measurement techniques is the key benefit in this case, because it can be used in green beer and model fluids and does not influence the flow. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Research of Communication Technology on IOT for High-Voltage Transmission Line

This paper presents a three layered network construction of Internet of Things (IOT) communication method for high-voltage transmission line which involves the wireless self-organized sensor network (WSN), optical fiber composite overhead ground wire (OPGW), general packet radio service (GPRS) and the Beidou (COMPASS) navigation satellite system (CNSS). The function of each layer of network, application deployment and management of energy consumption are studied. The method can meet the needs of interconnection between the monitoring center and terminals, reduce the terminals’ GPRS and CNSS configuration and OPGW optical access points, and ensure the on-line monitoring data transmission real-time and reliable under the situation of remote region, extreme weather and other environmental conditions.

Design of millimeter-wave fiber-wireless downlink with remote local-oscillator delivery by using dual-electrode Mach–Zehnder modulators configured for optical single-sideband modulations

An optical fiber-wireless system operating in millimeter-wave (MMW) bands may include numerous optical remote access points (RAPs) of which the cost is critical to implement such systems in real market. In this paper, we design an optical fiber communication system for MMW optical fiber downlink transmission with remote MMW local-oscillator (LO) delivery for intermediate frequency (IF) fiber uplink transmission. The new design is based on two dual-electrode Mach–Zehnder modulators in parallel both configured for optical single-sideband modulations. By using the proposed design, a conventional RAP can be simplified in structure to reduce the cost. Our numerical results show that, with the proposed design, 1-Gbit/s binary-phase-shift-keying (BPSK) data at a 42-GHz sub-carrier frequency can be transmitted over a 20-km standard single-mode optical fiber followed by a wireless transmission of several kilometers. Moreover, a MMW LO at 37-GHz frequency can be remotely delivered over tens of kilometers of a standard single-mode fiber with acceptable deterioration in the LO phase noise for IF uplink fiber transmission.

Modeling and performance analysis of IP access interface in optical transmission networks with packet switching

The article analyzes the influence of the Internet Protocol (IP) access interface on the packet loss probability and delay times in the optical packet switched network. The network and node model have been proposed, and the structure of the IP access interface, including assembler and holder, have been included in the analysis. It has been shown that the increase of the maximum optical packet sizes, as well as use of the holding feature as contention resolution mechanism, decrease the packet loss probability, but introduce delays at the optical network access points. Modeling and analysis were based on the discrete event simulation assuming self-similar traffic sources. IP packet lengths were modeled using empirical data.