Anthony J. Ruggiero

Characterization of Gigabit Ethernet Over Highly Turbulent Optical Wireless Links

We report on the performance characterization and issues associated with using Gigabit Ethernet (GigE) over a highly turbulent 1.3 km air-optic lasercom links. Commercial GigE hardware is a cost-effective and scalable physical layer standard that can be applied to air-optic communications. We demonstrate a simple GigE hardware interface to a single-mode fiber-coupled, 1550 nm, WDM air-optic transceiver. TCP/IP serves as a robust and universal foundation protocol that has some tolerance of data loss due to atmospheric fading. Challenges include establishing and maintaining a connection with acceptable throughput under poor propagation conditions. The most useful link performance diagnostic is shown to be scintillation index, where a value of 0.2 is the maximum permissible for adequate GigE throughput. Maximum GigE throughput observed was 49.7% of that obtained with a fiber jumper when scintillation index is 0.1. Shortcomings in conventional measurements such as bit error rate are apparent. Prospects for forward error correction and other link enhancements will be discussed.

Mini-AM DIAL system

Summary form only given. We have developed a compact optical remote sensing system prototype for short-range detection of gaseous effluents. The sensor system leverages recent advances in photonics and modulation-based detection technologies to make multiple-wavelength differential-absorption-lidar (DIAL) measurements with low power diode lasers.

Energy transfer dynamics and impact sensitivity

In this paper we focus on the relation between impact sensitivity and energy transfer rates. When a crystal receives an impact, low frequency lattice vibrations (called phonons) are excited. Typical phonon frequencies are 0-200 cm[sup [minus]1]. This energy must then be converted to vibron frequencies (1000--2000 cm[sup [minus]1]) before bond breaking can occur. We derive a simple formula for the energy transfer rate in terms of the density of vibrational states and the vibron-phonon coupling. We are able to estimate the phonon upconversion rate in widely varying energetic materials such as TATB, HMX, and Pb styphnate by examining existing inelastic neutron scattering data. We find that the estimated energy transfer rates in pure unreacted material are strongly correlated with impact sensitivity.

Horizontal path laser communications employing MEMS adaptive optics correction

Horizontal path laser communications are beginning to provide attractive alternatives for high-speed optical communications. In particular, companies are beginning to sell fiberless alternatives for intranet and sporting event video. These applications are primarily aimed at short distance applications (on the order of 1 km pathlength). There exists a potential need to extend this pathlength to distances much greater than a 1km. For cases of long distance optical propagation, atmospheric turbulence will ultimately limit the maximum achievable data rate. In this paper, we propose a method of improved signal quality through the use of adaptive optics. In particular, we show work in progress toward a high-speed, small footprint Adaptive Optics system for horizontal path laser communications. Such a system relies heavily on recent progress in Micro-Electro-Mechanical Systems (MEMS) deformable mirrors as well as improved communication and computational components. In this paper we detail two Adaptive Optics approaches for improved through-put, the first is the compensated receiver (the traditional Adaptive Optics approach), the second is the compensated transmitter/receiver. The second approach allows for correction of the optical wavefront before transmission from the transmitter and prior to detection at the receiver.

Characterization of FibreChannel over highly turbulent optical wireless links

We report on the performance characterization and issues associated with using Fibre Channel (FC) over a highly turbulent free-space optical (FSO) link. Fibre Channel is a storage area network standard that provides high throughput with low overhead. Extending FC to FSO links would simplify data transfer from existing high-bandwidth sensors such as synthetic aperture radars and hyperspectral imagers. We measured the behavior of FC protocol at 1 Gbps in the presence of synthetic link dropouts that are typical of turbulent FSO links. Results show that an average bit error rate of less than 2E-8 is mandatory for adequate throughput. More importantly, 10 ns dropouts at a 2 Hz rate were sufficient to cause long (25 s) timeouts in the data transfer. Although no data was lost, this behavior is likely to be objectionable for most applications. Prospects for improvements in hardware and software will be discussed.

Modeling of Long-Range Atmospheric Lasercom Links Between Static and Mobile Platforms

We describe modeling and simulation of long-range terrestrial laser communications links between static and mobile platforms. Atmospheric turbulence modeling, along with pointing, tracking and acquisition models are combined to provide an overall capability to estimate communications link performance.

Optical frequency conversion using nondegenerate four-wave mixing in broad-area angled grating (/spl alpha/-DFB) lasers

Summary form only given.Four-wave mixing techniques are of great interest as a mechanism for wavelength conversion applications in multiple wavelength telecommunications systems. Angled-distributed feedback (/spl alpha/-DFB) lasers are ideal device structures for frequency conversion via intracavity four-wave mixing. Lateral grating confinement in the broad area multimode waveguide results in stable single longitudinal and transverse modes. Narrow frequency bandwidths of less than 10 MHz can be obtained in a fundamental spatial mode with output powers on the order of 1 watt from a 300 micron aperture device. Using the correspondingly intense intracavity laser beams to pump the four-wave mixing (FWM) process, all that is needed is an external probe beam to be injected into the cavity for efficient frequency conversion. A probe beam at frequency /spl omega//sub /spl mu// injected into the laser cavity with intracavity beams at /spl omega//sub /spl mu// will generate a conjugate beam at 2/spl omega//sub 2/-/spl omega//sub 1/. In this case, the nonlinear susceptibility involved in the FWM process is strongly enhanced by the optical gain and the cavity feedback.

MWIR lidar systems and multiline DIAL techniques

This paper reports on recent progress made in developing rapidly tunable MWIR lidar system for the detection and identification of multiple trace atmospheric molecules. The lidar systems and multiline DIAL approach are described in detail. The unique advantages of the lidar system and multiline DIAL measurement technique are demonstrated with results from field measurements.