Nathaniel J. C. Libatique

Single-longitudinal-mode tunable WDM-channel-selectable fiber laser.

We report operation of a single-longitudinal-mode WDMchannel-selectable fiber laser. The use of a tunable fiber Bragg grating and a linewidth narrowing saturable absorption filter in conjunction with an intracavity etalon enabled single-frequency emission and discretely tunable WDM channel operation without the need for external wavelength locking modules. Side mode suppression ratios (SMSRs) > 50 dB have been demonstrated with ~ 3 dBm individual channel output powers for 8 channel (f = 50 GHz) operation of this WDM source.

A broadly tunable wavelength-selectable WDM source using a fiber Sagnac loop filter

In this letter, we describe a new discretely wavelength-selectable 1.5-/spl mu/m source based on the use of a fiber Sagnac loop filter leading to the possibility of an efficient all-fiber source. The filter has an /spl sim/1.6-dB insertion loss, 14-dB peak-to-valley transmission ratios, and can be tuned to a very precise match with the International Telecommunications Union-wavelength-division-multiplexing grid. We demonstrate 25-channel outputs with precise 50-GHz channel spacings and very large (65 dB) output signal to background noise ratios.

UAV aerial imaging applications for post-disaster assessment, environmental management and infrastructure development

This paper discusses the use of a low-cost unmanned aerial vehicle (UAV)-based remote sensing system for different applications, namely post-disaster assessment, environmental management and monitoring of infrastructure development. A collaborative research consortium was established to promote the acquisition, post processing, analysis and sharing of UAV-based aerial imagery. A streamlined workflow - flight planning and data acquisition, post-processing, data delivery and collaborative sharing - was created in order to deliver acquired images and orthorectified maps to various stakeholders within this consortium. Various use case examples of UAV aerial imagery work are still in ongoing development. Initial experience shows that the combination of aerial surveys, ground observations and collaborative sharing with domain experts results in richer information content and a more effective decision support system.

Precisely and rapidly wavelength-switchable narrow-linewidth 1.5-μm laser source for wavelength division multiplexing applications

We report the design and demonstration of a novel narrow-linewidth fiber laser that is switchable (at microsecond speeds) to precise predesignated wavelengths. This simple multiwavelength source, based on off-the-shelf components (fiber Bragg gratings (FBGs) and fiber Fabry-Perot filters), appears very promising for wavelength-division multiplexing.

Design of a tropical rain - Disaster alarm system: A new approach based on wireless sensor networks and acoustic rain rate measurements

This paper discusses the design of a broadband wireless network infrastructure which itself is a rain measurement platform for applications such as disaster alarm and sudden hazard decision management systems. A sensor testbed is setup which consists of a hybrid broadband wireless network in conjunction with real-time acoustic rain rate point sensors and complementary rain gauges. The testbed simulates the commercial deployment of a line-of-sight wireless backbone (implemented via a 26 GHz line of sight link) and broadband wireless access network at 5 GHz and 2.4 GHz. Combined wireless signal fade, acoustic power and tipping bucket rain rate measurements over a several month span indicate the feasibility of using rain-induced attenuation and fade durations to trigger imminent-hazard alerts.

Near-IR tunable laser with an integrated LiTaO3 electro-optic deflector.

We report the successful demonstration of a near-IR tunable laser (1525.4-1558.2 nm) that uses an integrated LiTaO3 deflector in combination with a reflection grating as an electronically tunable filter. The electro-optic deflector is a unique integrated optical device and consists of a horn-shaped array of electro-optic prisms in series. The almost 33 nm of tuning covers a wavelength region of high interest to the communications industry (1527-1550 nm).

A compact diode-pumped passively Q-switched mid-IR fiber laser

A compact cladding-pumped Er:ZBLAN mid-infrared pulsed fiber laser using a liquefying gallium mirror as a saturable absorber is demonstrated for the first time. Preliminary results give pulse widths of 7 µs and energies of 38 nJ.

Deployment of a wireless sensor network for aquaculture and lake resource management

We describe the ongoing deployment of a wireless network system for monitoring aquaculture applications and managing a lake resource in one of the Seven Lakes in San Pablo, Laguna, Philippines. Field servers are deployed to measure water quality parameters such as dissolved oxygen and temperature. In addition, a novel floating platform field server is developed to gather data in the middle parts of the lake. Cameras are also deployed to monitor different aspects of the area. A knowledge management system allows dissemination of these data and other information that would be of interest to stakeholders and the local community.

Low cost sensor system for wave monitoring

Most wave monitoring buoys and systems conventionally rely on the direct acquisition of wave height data. This paper introduces an alternate wave monitoring method that uses acceleration and angular deviation data. A threshold level crossing counting scheme is used as a means for data compression and as a basis for an alarm system. The sensor modules pre-process data at predetermined sampling periods before sending out telemetry to more efficiently manage power. The MEMS based sensors used provide a smaller footprint lower cost alternative to direct wave height measurement systems.

CdTe/InSb/α-Sn heterostructures grown by molecular beam epitaxy

Abstract MBE-grown CdTe/InSb/CdTe single quantum wells were characterized by TEM, FTIR and photoconduction. Even in the presence of In, Te related compounds and CdTe buffer-width dependent Fabry-Perot interference, a step-like quantum size effect was observed in the SQW FTIR data. The photocurrent peaks are also attributable to quantum well intersubband transitions due to higher subband energy levels. With the improvement of the CdTe/InSb interface in mind, we studied the characteristics of α-Sn layers grown on top of CdTe. TEM pictures show that the propagation of dislocation planes originating from the CdTe buffer layer is stopped at the α-Sn/CdTe heterointerface.