Kerr nonlinearity of Thulium-doped fiber near 2 um

The nonlinear coefficient and group velocity dispersion of a thulium-doped fiber near 2μm are evaluated via four-wave mixing. Nonlinearity of thulium-doped fiber can be used for the design of doped-fiber lasers in this spectral region

Lake Imaging and Monitoring Aerial Drone

We describe the development of a BVLOS (Beyond Visual Line-Of-Sight) model aircraft (UAV). The broad design requirements included (i) fuselage capable of accommodating an imaging package or other instrumentation, (ii) suitability for over-lake BVLOS authorization in Switzerland, (iii) capability of land or water take-offs/landing, (iv) at least 90-min flight autonomy, (v) modularity of the imaging package and (vi) real-time IR/RGB imagery. Requirement (i) was to ensure an aircraft amenable to future developments. Requirements (ii)-(iv) were driven by the goal of improving estimates of lake surface energy fluxes, since such fluxes have a major impact on long-term lake temperatures and hence ecological status. Requirement (v), in conjunction with (i), allows the UAV to be adapted to other imaging applications. The real-time imagery requirement (vi) permits modifications of on-going missions to map areas of specific interest as they are detected. The prototype UAV produced to satisfy these characteristics was built on the twin-motor My Twin Dream (MTD) aircraft, which has a 1.8-m wing span airframe and a spacious fuselage. The legal authorization necessitated, where feasible, hardware redundancy as well as installation of a parachute system. Continuous communication between the ground station and UAV is provided by the LTE cellular telephone network. The UAV communication is handled by an on-board Linux computer, which is also responsible for control of the imagery package. The avionics involved modifications of the open-source APM autopilot software and the associated ground control station. A key modification was to support a custom-built emergency recovery system, which is triggered by loss of a heartbeat signal from the autopilot. The MTD airframe was modified to accommodate the system electronics and imaging hardware. Results from test flights over Lake Geneva demonstrate the ability of the aircraft to produce imagery data

A BVLOS UAV for Lake Surface Imagery

We describe the development of a BVLOS (Beyond Visual Line-Of-Sight) model aircraft (UAV). The broad design requirements included: 1. BVLOS Legal authorization by the Swiss Federal Aviation authority 2. Suitable for land and water take-offs/landing 3. More than 60 minutes flight autonomy 4. Modularity of the imaging package 5. Real-time IR/RGB imagery Requirements 1 to 3 are driven by the goal of improving estimates of lake surface energy flux, since such fluxes have a major impact on long-term lake temperatures and hence ecological status. Requirement 4 allows the UAV to be readily adapted to other applications. The need for real-time imagery permits modifications of on-going missions to map areas of specific interest as they are detecte

A low-cost, autonomous mobile platform for limnological investigations, supported by high-resolution mesoscale airborne imagery

Two complementary measurement systems – built upon an autonomous floating craft and a tethered balloon – for lake research and monitoring are presented. The autonomous vehicle was assembled on a catamaran for stability, and is capable of handling a variety of instrumentation for in situ and near-surface measurements. The catamaran hulls, each equipped with a small electric motor, support rigid decks for arranging equipment. An electric generator provides full autonomy for about 8 h. The modular power supply and instrumentation data management systems are housed in two boxes, which enable rapid setup. Due to legal restrictions in Switzerland (where the craft is routinely used), the platform must be observed from an accompanying boat while in operation. Nevertheless, the control system permits fully autonomous operation, with motion controlled by speed settings and waypoints, as well as obstacle detection. On-board instrumentation is connected to a central hub for data storage, with real-time monitoring of measurements from the accompanying boat. Measurements from the floating platform are complemented by mesoscale imaging from an instrument package attached to a He-filled balloon. The aerial package records thermal and RGB imagery, and transmits it in real-time to a ground station. The balloon can be tethered to the autonomous catamaran or to the accompanying boat. Missions can be modified according to imagery and/or catamaran measurements. Illustrative results showing the surface thermal variations of Lake Geneva demonstrate the versatility of the combined floating platform/balloon imagery system setup for limnological investigations

Lake imaging and monitoring aerial drone

We describe the development of a BVLOS (Beyond Visual Line-Of-Sight) model aircraft (UAV). The broad design requirements included (i) fuselage capable of accommodating an imaging package or other instrumentation, (ii) suitability for over-lake BVLOS authorization in Switzerland, (iii) capability of land or water take-offs/landing, (iv) at least 90-min flight autonomy, (v) modularity of the imaging package and (vi) real-time IR/RGB imagery. Requirement (i) was to ensure an aircraft amenable to future developments. Requirements (ii)–(iv) were driven by the goal of improving estimates of lake surface energy fluxes, since such fluxes have a major impact on long-term lake temperatures and hence ecological status. Requirement (v), in conjunction with (i), allows the UAV to be adapted to other imaging applications. The real-time imagery requirement (vi) permits modifications of on-going missions to map areas of specific interest as they are detected. The prototype UAV produced to satisfy these characteristics was built on the twin-motor My Twin Dream (MTD) aircraft, which has a 1.8-m wing span airframe and a spacious fuselage. The legal authorization necessitated, where feasible, hardware redundancy as well as installation of a parachute system. Continuous communication between the ground station and UAV is provided by the LTE cellular telephone network. The UAV communication is handled by an on-board Linux computer, which is also responsible for control of the imagery package. The avionics involved modifications of the open-source APM autopilot software and the associated ground control station. A key modification was to support a custom-built emergency recovery system, which is triggered by loss of a heart-beat signal from the autopilot. The MTD airframe was modified to accommodate the system electronics and imaging hardware. Results from test flights over Lake Geneva demonstrate the ability of the aircraft to produce imagery data. Keywords: 4G network, Mobile, Streaming, Telemetry, UAV, Imagery, Autonomous aircraft, LIMONAD, Infrared, RGB, Parachute, BVLOS, I