Passively mode-locked laser using an entirely centred erbium-doped fiber

This paper describes the setup and experimental results for an entirely centred erbium-doped fiber laser with passively mode-locked output. The gain medium of the ring laser cavity configuration comprises a 3 m length of two-core optical fiber, wherein an undoped outer core region of 9.38 μm diameter surrounds a 4.00 μm diameter central core region doped with erbium ions at 400 ppm concentration. The generated stable soliton mode-locking output has a central wavelength of 1533 nm and pulses that yield an average output power of 0.33 mW with a pulse energy of 31.8 pJ. The pulse duration is 0.7 ps and the measured output repetition rate of 10.37 MHz corresponds to a 96.4 ns pulse spacing in the pulse train

Evaluating the performance impact of protocol parameters on ad-hoc network routing protocols

Routing protocols are used to discover, maintain, and repair routes between pairs of nodes in wireless ad-hoc networks. In order to handle dynamic network topologies caused by node mobility, many routing protocols are designed with multiple features and parameters to effectively discover routes and to quickly detect link breaks. In this paper, we compare the performance of four popular routing protocols, AODV, DYMO, OLSR and HWMP, in terms of the Packet Delivery Ratio (PDR) metric, and analyse the various reasons for packet loss in scenarios where nodes are mobile. We also explore key protocol parameters and how their choice impacts the protocol performance. Based on our simulation results, we find that the way in which protocols detect link breaks is critical for overall network performance. We therefore specifically explore how the choice of link break detection parameters can improve protocol performance. We further explore other protocol variations and features and their potential for performance improvements

Evaluation of parameterised route repair in AODV

One of the key challenges for routing protocols in wireless multi-hop networks is to deal with link failures, and to repair the routes in these situations. In the Ad-hoc On Demand Distance Vector (AODV) protocol, routes can either be repaired by re-establishing a new route from scratch starting from the source node (Source Repair), or they can be locally repaired by the node that detects the link break along the end-to-end path (Local Repair). In some situations Source Repair will lead to better performance, in other situations Local Repair will be the more appropriate choice. In this work, we explore a flexible, parameterised approach in deciding on which of these two route repair strategies to use in the event of a link break. We define a Local Repair Threshold parameter that determines how far along the end-to-end path that a link break needs to occur in order to initiate Local Repair, as opposed to Source Repair. Our simulation results show that the optimal choice of the Local Repair Threshold, in terms of Packet Delivery Ratio, depends on the network load. We show that a flexible, parameterised and adaptive approach to choosing the Local Repair Threshold, can improve the Packet Delivery Ratio by up to 37% (in absolute terms), compared to the approach employed by standard AODV. We also show a significant potential improvement of up to 18% over the route repair strategy employed by the Dynamic On demand MANET (DYMO) routing protocol, which is based on AODV

Generation of four-wave mixing with highly sharp idlers using 2 mm home-made side-polished fiber deposited by ZnO nanorod

A side-polished fiber with embedded zinc oxide nanorods (ZnO-NRs) is proposed, fabricated, and tested to generate four-wave-mixing (FWM). The side-polished fiber is manufactured by polishing a conventional single mode fiber to completely remove 2 mm of its cladding and its core partially, after which the fiber is simply immersed into a solution consisting of ZnO-NRs and allowing it to dry. A pump and a signal wavelength of 1550 and 1551 nm are injected into the fiber and generate idlers at 1549 and 1552 nm which agree well with theoretical values. Our experimental results show that the optimum FWM range is determined to be a 6 nm shifted away from the pump wavelength and occurs in the pump and wavelength spacing as narrow as 0.1 nm. The proposed system allows for the easy integration of optically active materials into a fiber