Ascorbate enhances iron uptake into intestinal cells through formation of a FeCl3–ascorbate complex

It has been well documented that ascorbate enhances iron uptake, with a proposed mechanism based on reduction to the more absorbable ferrous form. We have performed a study on the effects of ascorbate on ferric iron uptake in the human epithelial Caco-2 cell-line. Ascorbate increased uptake in a concentration-dependent manner with a significant difference between iron uptake and reduction. Uptake kinetics are characteristic of a non-essential activator and the formation of an Fe³⁺–ascorbate complex. This investigation provides evidence that ascorbate enhances the apical uptake of ferric iron into Caco-2 cells through the formation of a Fe³⁺–ascorbate complex.     

Transmission surveillance and self-restoration against fibre fault for time division multiplexing using passive optical network

This study proposes a practical transmission surveillance and self-protection scheme for time division multiplexing using passive optical network (TDM-PON) with centralised monitoring and self-restorable apparatus. Troubleshooting a TDM-PON involves locating and identifying the source of an optical problem in what may be a complex optical network topology that includes several optical line terminals (OLTs), optical splitters, fibres and optical network units (ONUs). Since most components in the network are passive, a large part of the issues are due to dirty/damaged/misaligned connectors or breaks/macrobends in optical fibre cables. These will affect one, some or all subscribers in the network, depending on the location of the problems. The proposed scheme is able to prevent and detect the occurrence of fibre faults in a network system through centralised monitoring and remotely operate from a central office via Ethernet connection. Even with fibre fault prevention mechanisms, failures will still occur. Therefore fibre fault detection is required in order to detect potential faults and precisely localise the exact failure location.Whenever any failure occurs on the primary entity, the proposed system can protect and switch the failure line to the protection line to ensure that traffic flows continuously. Meanwhile, the failure information will be delivered to field engineers for taking appropriate recovery action to treat the fibre fault and failure link. One suggestion in point-to-multipoint (P2PM) applications has been proposed with the experimental results as the feasibility approach. This approach has bright prospects for improving the survivability and reliability as well as increasing the efficiency and monitoring capabilities in TDM-PON.     

High Efficiency of PON Network Monitoring and Management

This paper presents a transmission surveillance and protection-based approach for failures/faults over the passive optical network (PON) with an excellent combination of Smart Access Network _ Testing, Analyzing and Database (SANTAD) and Smart Drop Protection Scheme (SDPS). SANTAD is an optical monitoring and management system tool that focused on optical testing and line’s status monitoring in PON with some excellence features added, while SDPS is implemented in the drop region to provide self-protection capabilities against fiber cuts. A tapper circuit is designed to allow the optical time domain reflectometer (OTDR) testing signal to bypass the optical splitter for distant monitoring when emitted in downstream direction. With the assistance of fourth window region at 1,625 nm and de(multiplexing) capabilities of wavelength selective coupler, the status of each fiber link can be displayed onto computer screen. Access Control System (ACS) is function to control the OTDR troubleshooting signals and activate the SDPS restoration scheme according to the type of failure in the drop region of PON. The implementation of the excellent combination in PON shows its contributions on obtains the high accuracy in detecting any occurrence of failures/faults and recovery the failure links within 15 s.     

Access network survivability: an architecture approach for monitoring, protection and restoration in FTTH application

This paper presented a simple monitoring, protection switching, and fast restoration approach for fiber to the home passive optical network (FTTH-PON) using Access Control System (ACS). ACS is developed for centralized monitoring and failure detection from central office (CO) in downstream direction (from CO towards customer sides). The proposed system architecture incorporating low cost and enable the network service providers and field engineers to remotely control the testing module from anywhere in the world and automatically identify any fiber fault and address the failure location in the fiber field. Another unique function of ACS is to provide the activation for optical switching in a restoration scheme which implemented at the drop region of FTTH-PON. A protection device named Customer Protection Device that comprises of programmable optical switches will be employed at the customer sides, just before the optical network unit, for rerouting the disrupted signals to the protection line when failure occurs in the working line to ensure continuous service delivery to customers.     

Development of monitoring system for FTTH‐PON using combined ACS and SANTAD

This paper proposes a design of Access Control System (ACS) for fiber‐to‐the‐home passive optical network (FTTH‐PON). Our design works on a standard local area network using a specially designed hardware interfaced with a microcontroller integrated Ethernet to monitor the status of optical signals flow and provides the restoration against fiber failures/faults in FTTH‐PON. We also introduce the centralized troubleshooting system by means of Smart Access Network Testing, Analyzing, and Database (SANTAD). ACS is the subsystem that controls the troubleshooting mechanism carried out by SANTAD. This design will be implemented together with optical line terminal (OLT) at central office (CO) to centralized monitoring and for controlling each optical fiber line's status as well as detecting any failure that occurs in the network system downwardly from CO toward multiple optical network units at different customer residential locations. The scope of this discussion highlighted only the monitoring and controlling instead of the restoration scheme offered. Copyright © 2009 John Wiley & Sons, Ltd.