Maritime Sensing
Maritime Sensing (in lasers and photonics) refers to the use of laser- and light-based (photonic) technologies to detect, measure, map, image, or monitor objects, surfaces, water properties, and environments in maritime settings—aboard ships, coastal areas, the sea surface, or underwater.
It primarily involves active optical sensing systems such as LiDAR (Light Detection and Ranging), laser rangefinders, single-photon detectors, fiber-optic sensors, and related photonic integrated systems, often operating in wavelengths optimized for air or water propagation (e.g., near-infrared ~1550 nm for atmospheric/surface use, or blue-green ~520–532 nm for water penetration).
Technical Information:
Maritime sensing systems typically emit short laser pulses and analyze the backscattered or returned light (via time-of-flight, intensity, Raman scattering, or photon counting) to extract range, 3D geometry, material properties, or environmental parameters.
Key elements include:
Transmitter: Pulsed lasers (solid-state, diode, or fiber lasers). Eye-safe 1550 nm is common for shipborne surface sensing; blue-green wavelengths enable bathymetry and subsurface profiling due to lower attenuation in water.
Receiver/Detectors: Photodiodes, avalanche photodiodes (APDs), or highly sensitive single-photon avalanche diodes (SPADs)/InGaAs detectors. Single-photon LiDAR enables longer ranges and lower power by detecting individual photons.
Scanning & Processing: Mechanical or solid-state scanning for 3D point clouds; advanced algorithms for denoising (e.g., in fog, waves, or high ambient light), target extraction, and fusion with other sensors (radar, cameras, IMU/GNSS).
Platforms: Shipborne, airborne, spaceborne (e.g., photon-counting systems), or underwater/in-situ. Challenges include dynamic range (bright sea surface vs. faint returns), wave motion, turbidity, fog/rain attenuation, and biofouling.
Related photonics: Fiber-optic sensors (FBG, distributed acoustic/temperature sensing) for structural health or ocean parameters; free-space optical links; microwave photonics for radar enhancement; silicon photonic optical gyroscopes for inertial navigation in GPS-denied environments.
Performance examples include shipborne single-photon LiDAR detecting targets at ~1.6–3.2 km (depending on conditions) and underwater photon-counting systems profiling >50 m or operating to depths of hundreds of meters.
Applications:
Navigation & Situational Awareness: Obstacle detection (small boats, containers, ice, people), collision avoidance, dynamic positioning (e.g., laser PRS systems with retro-reflectors), berthing/unberthing, and support for autonomous surface vessels (ASVs). Provides higher resolution than radar for near-to-medium range and works in low light/night.
Bathymetry & Hydrography: Mapping seafloor, coastal zones, and shallow-water depths (airborne or satellite photon-counting LiDAR can reach tens of meters in clear water).
Environmental Monitoring & Ocean Science: Water-column profiling (optical properties, attenuation), oil-spill detection/characterization (via Raman or elastic returns), phytoplankton/particulate sensing, and long-term ocean observation (temperature, salinity, currents via fiber sensors or distributed sensing).
Defense & Security: Maritime domain awareness, night vision/single-photon imaging for long-range observation, target classification/tracking, and resilient navigation.
Port/Terminal Operations & Vessel Efficiency: Container handling precision, structural health monitoring of ship components (via photonic sensors on winches/rotating parts), and laser rangefinders integrated with multi-spectral cameras.
Emerging Uses: Support for unmanned/autonomous systems, free-space optical communications at sea, and fusion with AI for real-time perception.
These technologies complement radar and cameras by offering superior spatial resolution and direct ranging, while photonics advances (compact lasers, single-photon detectors, integrated photonics) improve size, power, cost, and robustness for harsh marine environments.