Norman E. Farr

Optical modem technology for seafloor observatories

Regional cabled observatories will bring broadband Internet to the seafloor around areas that include hydrothermal vent sites and other scientifically interesting features. The ideal platform for exploring these sites in response to episodic events is a remotely-piloted, autonomous underwater vehicle (AUV) that is capable of sending back high-quality video or other high-rate sensor data. The combined requirement of remote command/control and high data rates argues for a bi-directional optical communications link capable of streaming data at 1-10 Mbit per second rates. In this paper, we present a preliminary design for an optical modem system based on an omnidirectional source and receiver. The functional requirements and system constraints driven by use case scenarios are first reviewed. This is followed by a discussion of the optical transmission properties of seawater and the resulting impact on detection in high-rate communications, including coding considerations. A link budget and the data rate versus range relationship are developed. Validation results in a test tank and in the ocean will then be reviewed

Diffuse high-bandwidth optical communications

High speed underwater optical communications has at least three distinct advantages over acoustic communications. The data rates achievable are high (1 to 10 Mbps), the latency from when data is sent to when data is received is low, and there is no acoustic noise associated with transmission. Of course one of the biggest limitations of an optical approach underwater is the rapid attenuation of optical signals due to spreading loss, scattering, and absorption. Nonetheless, communication signals have been broadcast, received, and decoded over distances of 100 to 200 meters. High data rates and low latency make optical communications an attractive human interface to underwater systems, such as wireless control of underwater vehicles. Underwater optical communications is generally well-suited to multiple platform environments, where acoustic silence and limited range avoids interference between platforms. High data rates are advantageous in data retrieval applications, where, for one example, wireless data retrieval would make deployment and recovery of certain systems more economical. Recent engineering developments and accompanying experimental data are put forth in this paper, and the implications for future development are discussed.

Fiberoptic Balloon Catheter Ablation of Pulmonary Vein Ostia in Pigs Using Photonic Energy Delivery with Diode Laser

LEMERY, R., et al.: Fiberoptic Balloon Catheter Ablation of Pulmonary Vein Ostia in Pigs Using Photonic Energy Delivery with Diode Laser. Circumferential lesions to the pulmonary vein (PV) ostia to cause conduction block at the junction of the PV and left atrium could offer a new approach during catheter ablation of patients with paroxysmal (focal) atrial fibrillation. Diode laser can deliver energy through diffusing or ring fiber tips. In three pigs weighing between 60 and 65 kg, transseptal puncture was performed and a fiberoptic balloon catheter with a collapsed profile of 10 Fr was advanced through a sheath under fluoroscopic guidance to the ostium of the right and left PVs. The balloon was inflated with a 3‐cc mixture of D2O (deuterium oxide) and contrast to deliver circumferential lesions with a 15‐mm diameter × 3‐mm ring width of light. Applications consisted of 3.2 to 3.8 W/cm for 120 seconds; the animals were sacrificed 3 hours after ablation for pathological examination. Photonic energy was delivered successfully to the ostium of five of the five targeted PVs, and was well tolerated hemodynamically in each animal without ectopy. Gross inspection revealed endocardial lesions at the ostium of four of five PVs, confined to the atrium in each and circumferential in three of five PVs. Microscopically, transmural coagulation necrosis of the atrium was present at the ostium of three of five PVs, and extended into the myocardial sleeves of two PVs. Photonic energy delivery using a fiberoptic balloon catheter can create circumferential lesions to the PV ostia, suggesting that this new form of energy delivery may be therapeutically advantageous for pulmonary vein ablation with need to pursue chronic studies.

Field Tests of a New Camera/LED Strobe System

Two Hybrid ROV (HROV) subsystems were recently tested together in the deep sea using the Jason 2 ROV as a host. The first system is a new standards-based architecture for digital still camera control and telemetry; the second is a prototype LED array. The camera was used to trigger the strobe system while operating in 2300 m of water at the Juan de Fuca Vent Field. Several thousand images were collected under a range of varying conditions, validating several of the assumptions made in the development process, and guiding future development efforts

Bright blue: Advanced technologies for marine environmental monitoring and offshore energy

Major programs such as the Ocean Observatories Initiative (OOI) seek to increase societal understanding of subsurface marine environments. This interest has arisen because of environmental concerns related to degradation of marine habitats, climate change, as well as the globally increasing demand for marine natural resources, particularly food and energy. These pressures now affect marine systems at scales that require active management of marine environments. Nevertheless, our ability to monitor and perform even relatively simple operations in subsurface environments remains limited and costly because of technological limitations. This paper provides an overview of advanced platform, power generation, communications, and sensing technologies that are intended to enable high-resolution environmental monitoring, real-time field surveillance, subsea infrastructure operation and maintenance, and unattended robotic intervention for event response.

Evaluation of laser-induced breakdown spectroscopy (LIBS) as a new in situ chemical sensing technique for the deep ocean

Present day expeditionary oceanography based on short term ship and submersible deployments is beginning to shift to an ocean observatory mode where long term temporally focused studies become feasible. As a result, a greater need for in situ chemical and biological sensors is evolving. Laser-induced breakdown spectroscopy (LIBS) possesses many of the characteristics required for such in situ chemical sensing, and is a promising technique for field measurements in extreme environments. LIBS has many possible applications in the ocean, including the analysis of rocks, sediments, and hydrothermal vent fluids. Although many LIBS researchers have focused their work on solids, very little attention has been paid to bulk liquid analysis, and especially on the effect of oceanic pressures on LIBS signals. In this work, preliminary laboratory experiments are presented to validate the technique in a simulated deep ocean environment; more specifically, the focus is on using LIBS to study hydrothermal vent fluids

Infrared techniques for detecting carbonization at onset of device failure

We describe the design, and development of an infrared detection system which detects the onset of carbonization of fluoropolymers in the presence of up to 60 watts of 1.06 micrometer laser energy. This system is used to shut down a therapeutic laser system before significant damage is done to a laser delivery device and patient. Black body radiation emitting from the diffusion tip is transmitted, backwards, through the same optical fiber as the therapeutic wavelength. Using a high power 1.06 micrometer laser mirror at 45 degrees, most of the 1.06 micrometer light is reflected while the black body radiation is passed to a holographic notch filter which further filters the signal. Still more filtering was needed before the 1.1 to 2 micrometer signal could be detected within the presence the therapeutic light using an extended indium gallium arsenide photodetector. There was still a significant detected offset which increased with laser power which necessitated a means to automatically null the offset for different laser power settings. The system is designed to be used with any unmodified laser system. It interfaces directly to or in series with most common external safety interlocks and can be used with various diffusing tips, probes or bare fibers.

Development of Synthetic Fiber-Reinforced Electro-Optical-Mechanical Cables for Use With Moored Buoy Observatories

We consider an alternative to traditional high-modulus synthetic electro-optical-mechanical (EOM) mooring cables that are being used in single-point moorings for deep-ocean observatories. The alternative cable design is based on using low-modulus nylon or polyester fibers as the strength member. High-modulus EOM cables such as those that use Vectran fibers as the strength member are usually constructed with the conductors and optical fibers in the core and the strength member on the outside. The key aspect of the new design is that the strength member is placed in the center of the cable and the conductors and fibers are wrapped around the outside at a high helix angle to accommodate stretching of the center-strength-member. A comparison of the static and dynamic responses of moorings constructed with nylon, polyester, and Vectran EOM cables (for mooring scopes of 1.1 and 1.2 and deployment depths of 1800, 3000, and 5000 m) shows that the maximum total tensions of moorings made with nylon EOM cables are lowest under all conditions. Differences between the nylon and the Vectran EOM cable moorings are due principally to the differences in the dynamic tensions. Differences between the nylon and the polyester EOM cable moorings are due mainly to differences in static tensions caused by the higher specific gravity of polyester fibers. Reduction in the scope of all the moorings from 1.2 to 1.1 resulted in significantly higher tensions for the polyester and Vectran EOM cable moorings but only slightly higher tensions for the nylon EOM cable moorings

High-power diffusing-tip fibers for interstitial photocoagulation

A line of optical fiber based diffusing tips has been designed, developed, and tested that are capable of distributing tens of watts of cw laser power over lengths ranging from two millimeters to over 10 cm. The result is a flexible non-stick diffuser capable of coagulating large volumes of tissue in reasonably short exposures of 3 - 5 minutes. Sub-millimeter diameter devices have a distinct effect on reducing the force needed to insert the applicator interstitially into tissue. Utilizing our design approach, we have produced diffusers based on 200 micrometer core fiber that has delivered over 35 watts of Nd:YAG energy over diffusion lengths as short as 4 mm. These applicators are being tested for applications in oncology, cardiology, electrophysiology, urology and gynecology.