Marine Optical Communications
Kendall Carder
The many applications in the field of Optics have grown, and continue to grow, “at the
speed of light”. Fiber-optic communications networks, “Blue-ray” DVDs, laserreshaping of the human eye, high-definition televisions, ultra-fast chemical fluorescence
detection and analysis, night-vision devices, and remote sensing of the earth’s surface are
but a few of the rapidly increasing applications.
This rapid growth in the importance and benefits of exploiting the nature of light is also
true in the application of optical techniques in ocean water, which covers over 70% of our
planet’s surface.
Red-tide, for example, can have devastating economic impacts but also has a unique
optical signature. Detection of red-tide (and its precursors) is now possible but
complicated because red-tide develops at depth, far below the surface. Unmanned gliders
designed to detect algal blooms are being put into use, but high-speed, high-bandwidth
communication with the vehicles remains extremely difficult.
Similar concerns and challenges for the State of Florida involve the automatic
environmental monitoring by Autonomous Underwater Vehicles (AUVs) of the effluents
released near the sea bed during off-shore oil and natural gas drilling operations. For
Homeland Security AUVs monitor our ports, harbors, and infrastructure (e.g., bridges,
ship channels). Optical methodologies can address many important aspects of the above
applications and would be greatly enhanced with high data-rate communications among
AUVs, aircraft, and surface vessels.
An obvious technique for these communications is to use light. However, the only
wavelengths of light that penetrate the ocean effectively are in the visible or ultraviolet
ranges. Longer wavelengths of like, like infrared and microwave ranges cannot be used
for monitoring shallow water habitats from air or spacecraft or for communication
through the air-sea interface. Even sonar, which is a well-established use of sound for
submarine observation and acoustical communication, cannot effectively propagate from
sea to air and vice versa.
Thus any effort to communicate with autonomous underwater vehicles from the air would
appear to be impossible. This fact is especially troubling because, if the preprogrammed
route of such a vehicle needs updating based upon the data being collected by the vehicle
and by other platforms (e.g. moorings and remote sensing), two-way communication
between an autonomous underwater vehicle (AUV) or submarine or an aircraft is often
the most practical way. Thus, use of AUVs is expanding rapidly. AUV gliders are
presently traveling for many hundreds of kilometers under the sea, and AUVs are planned
for port waterway monitoring for suspicious packages that might contain explosives. A
method for communicating with AUVs must be found!
Even using light at visible wavelengths does not always work. Remote sensing of marine
habitats has been successful for viewing features large enough that wave-refraction
effects are relatively small. However, imaging smaller features such as coral heads from
aircraft can only be accomplished for calm conditions. So even at visible wavelengths,
surface waves are very disruptive, and surface ocean waves are usually present.
However, there is a very good prospect for meeting the above-mentioned communication
needs. Sub-aerial optical communication is now being performed for corporations with
needs for extremely high data rates. Very high data rates, in the form of “bandwidth
gains,” are made possible by using fiber optics. For rapid, flexible access to fiber-optic
communication hubs, sub-aerial optical communication can fill the void. No FCC license
is needed since, if the light is properly modified (collimated), its use in point-to-point
communication does not interfere with other communication needs. As long as fog or
high rain rates are not present, the only requirement is that care be taken to correct for or
avoid scintillation (e.g. star-like twinkle to the light being used). The main difficulties in
sub-aerial communication are under control. Purchase of an optical communication
system and devices for measuring various interfering environmental factors (e.g.
turbulence effects on gradients in the profile of refractive indices and wind, temperature,
and water-vapor profiles) will permit researchers to understand the sub-aerial effects on
optical communications before the air-sea interface and marine environment are
considered.
The Marine Optical Communications initiative will revolutionize our ability to
communicate among aircraft, submerged vehicles, and moorings. By taking the approach
used to mitigate scintillation effects in the atmosphere (e.g. multiple sources and multiple
pathways), communication through both submarine turbulence and wave effects should
be practical. We are requesting instrumentation to do the following: 1) measure
environmental optical properties; 2) measure meteorological properties; 3) measure
turbulence and its effect on scintillation; 4) measure effectiveness of multiple pathways
on sub-aerial communication; 5) measure effectiveness of multiple pathways on
communication through wave fields; 6) measure effectiveness of multiple pathways on
submarine communication (AUV to AUV to boat). The effectiveness of various pathway
strategies can then be optimized. An existing ROV can be enhanced to simulate an AUV.
BUDGET
1)
Flight Apex 2.5 GHz, 1.55 micron, bi-directional, optical
communication link
2)
Boundary layer scintillometer (turbulence, heat flux, cross-wind)
3)
ITT-GEN-III ultra blue intensified, digitally controlled scientific
camera (IDG-750)
4)
ITT-GEN-II UV intensified, digitally controlled scientific camera
(IDG-750)
5)
High-performance, Laser power meter (UV-Vis-NIR)
6)
Quartz lenses 25 mm, 78 mm, 105 mm 6
7)
Narrow band-pass, long-pass, short-pass and neutral density filter
kits (1” and 2”)
104,000
100,000
32,000
32,000
3,000
10,300
12,000
8)
9)
10)
11)
12)
13)
14)
15)
16)
17)
18)
19)
20)
21)
22)
23)
24)
Total
Real-time, full-resolution (lossless), digital video recorder 2
Hamamatsu PMT module (UV) and power supply
Hamamatsu PMT module (Vis-NIR) and power supply
Meteorological towers (10m and 20m) with wind, T, RH, P
Above and sub-surface spectral irradiance/radiance meters 3 sets
@ 17K
Spectral radiometers 2@ 15K
In situ absorption and attenuation meters, >9 wavelengths
Laboratory spectrophotometer with integration sphere
Diode lasers (375 nm 8 mW; 405 nm 150 mW)
1-D Wave gauge 3
ROV upgrades:
Navigation
a.
Doppler velocity log (speed, course over ground)
b.
Ring-laser gyro
c.
Auto-pilot system
Umbilical 1000 ft.
APAS optical design package (ray tracing)
Optical tables (4’x 8’; 2’ x16’) anti-vibration base
Micro-positioning stages
Calibration sphere (30 cm), constant source
Oscilloscope and test electronics
Backscattering meter (3 angle, 3 wavelengths)
20,000
3,000
3,000
18,000
51,000
30,000
25,000
35,000
10,800
12,000
26,000
95,000
30,000
10,000
6,000
24,000
8,000
20,000
10,000
16,000
754,800
Satellite Remote Sensing of the Coastal Environment
Frank Muller-Karger and Chuanmin Hu
Florida has coastal resources of critical significance to our nation and to neighboring
countries. Considering the potential for human food supply, recreation, and regulation,
estuaries provide a socio-economic value estimated at ~$1,469 ha–1 y-1, but this does not
highlight the importance of estuaries in navigation, maritime commerce, oil and gas, and
urban development. Using the same criteria, coral reefs contribute about $5,978 ha–1 y-1.
Tourism alone generates about $2.5 billion per year in Florida’s reefs.
Our beaches, estuaries, and coastal ocean may be impacted by natural or
anthropogenic discharges from the land, oil spills, harmful algal blooms (red tides),
various extractive activities (fishing, mining for oil, sand, or gravel), or storm and surge
events. For example, the estuaries of Tampa Bay and Florida Bay have suffered
significant ecosystem changes over the past 40 years, including contamination and
eutrophication caused by nutrient inputs from nonpoint sources, habitat alterations (e.g.
mining, construction, dredge and fill operations), and an increased frequency and
magnitude of salinity anomalies. Many estuaries or adjacent areas are affected by
hypoxia (low oxygen in water), similar to what is observed off the Mississippi Delta.
Evidence of the diminishing ecological quality of coastal zones are the large amounts of
debris washing up on shores, beach closures due to trash, bacteria, or red tide, reduced
water clarity and quality, and consumption advisories due to contaminated fish. There are
negative effects on shrimp, shellfish, or other fisheries, and marked increases in
phytoplankton abundance and turbidity. Seagrass beds are lost and bare sand has
increased.
Public awareness of these problems has been slow in coming, in part because coastal
resources are hidden beneath a surface that is for most purposes impervious to the
attention and the senses of people. Resource managers in local, State, and Federal
agencies don’t have the right environmental monitoring tools, and information on
indicators of stress is not readily available. However, these difficulties may be
circumvented by real-time remote sensing technologies.
Indeed, modern satellites provide unprecedented capability to monitor our coastal
environment because of the repeated, synoptic, accurate, and timely information they can
provide. In the past decades significant advances have been made in data collection,
calibration, processing, archiving, and distribution. These have greatly helped identify red
tides, oil spills, anomaly events, coral reef decline, and other bethic habitat degradation.
The examples shown in Figures 1 and 2 clearly demonstrate the advantage of the satellite
remote sensing technology.
Despite the recent progresses, however, there are several technical and scientific
issues that need immediate work, as identified by various groups including researchers,
coastal resource managers, fishing community, and the general publish. These include:
- Medium and low resolution MODIS satellite-derived images as georeferenced
images.
Jan. 21, 2005
MODIS
Fluorescence
Tampa
Bay
Red
Tide
Figure 1. Satellite imagery shows dark water along the northwest Florida coast and red tide patch near
Tampa Bay. Left: SeaWiFS RGB composite. The dark band along the coast is due to strong absorption of
blue light by colored dissolved organic matter (CDOM) and/or phytoplankton in the water; Right, MODIS
fluorescence line height. Only phytoplankton has a strong signal in the fluorescence detector, therefore this
image unambiguously isolates the red tide patch (confirmed by water sample analysis) from the extensive
dark band.
SeaWiFS
March 21, 2002
50 km
“black water”
July 14,
2001
August 13,
2002
Figure 2. The early 2002 “black water”, as indicated in the SeaWiFS image and lasted for > 3 months near
the Florida Keys, was thought to cause the subsequent benthic decline, including growth of benthic algae
and mortality of sponge.
- High resolution images and habitat maps (e.g. beaches, mangroves, seagrass, coral
reefs) derived from Landsat, Ikonos, and other coastal data.
- In situ and remote sensing observations in real-time and as historical time-series.
These include salinity indicators, temperature, and color, information on nearshore
phytoplankton blooms (e.g. warning of red tide potential), and other estimates of
water quality.
- Selectable overlays (grids, circulation, other satellite data).
- GIS compatible and customized output.
- Meteorological information (local and synoptic winds, precipitation)
- Spatial patterns, patch location, and front detection.
- Animation of customized products (assessment of movement and change
visualization).
- Detect and quantify anomalies (color/turbidity, temperature, motion).
- Access to input datasets.
- Access to metadata.
- Online access.
- Security and access control to protect customized application and products.
L-band
Antenna
Processing cluster
http://imars.usf.edu
Workstation
X-band
Antenna
Figure 3. Schematic of satellite data receiving, processing, archiving, and online broadcasting at the
Institute for Marine Remote Sensing, College of Marine Science, University of South florida.
The USF remote sensing group (Institute for Marine Remote Sensing, IMaRS,
http://imars.usf.edu) has established the framework of the above-outlined tasks using
external funding (mostly from federal agencies, see Figure 3 for the schematic), yet
substantial work is required to fully implement them. In particular, field equipment is
requested to develop/improve the satellite data processing algorithms and to validate the
satellite data products. Therefore, the following budget is requested.
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
Total
Satellite data storage (8 TB)
30000.00
Antenna Maintanence (hardware)
10000.00
Antenna Maintanence (software)
10000.00
Data processing license
5000.00
Submersible optical profiler
50000.00
Slocum Glider, with built-in sensor package96000.00
Glider battery pack
16000.00
Laser particle counter
25000.00
Optical sensors (6) to be mounted on buoys42000.00
Fast processing workstations
12000.00
296000.00