An in-ground perimeter security system has been developed by the Naval Undersea Warfare Center Division Newport based upon fiber optic sensor technology. The system, called Blue Rose, exploits the physical phenomenon of Rayleigh optical scattering, which occurs naturally in optical fibers used traditionally for Optical Time Domain Reflectometry techniques to detect sound and vibration transmitted by intruders such as people walking or running and moving vehicles near the sensor. The actual sensor is a single-mode optical fiber with an elastomeric coating that is buried in the ground. A long coherence length laser is used to transmit encoded light down the fiber. Minute changes in the fiber in response to the intrusion produce phase changes to the returning backscattered light signal. The return light signal contains both the actual intrusion sound and the location information of where along the fiber the intrusion has occurred. A digital, in-ground, Blue Rose system has been built and is now operational at NUWC. Due to the low cost of the optical fiber sensor and unique benefits of the system, the Blue Rose system provides an advantage in long perimeter or border security applications and also reduces security manning requirements and therefore overall cost for security.
A remote, aerial, laser-based sonar and communications concept has been demonstrated to direct laser beams from the air onto the water surface to remotely generate and detect underwater sound. This forms the basis for a portable, aerial sonar and communications system for both detecting underwater objects such as vehicles and mines as well as for bi-directional acoustic communication between an in-air platform and a submerged platform operating at speed and depth. Two laser systems are required. The first laser system is a high-energy laser, the opto-acoustic transmitter, whose optical energy is converted to acoustic energy at the water surface. The second laser system is a laser interferometer, the acousto-optic sensor that detects underwater sound by measuring the vibrations of the water surface caused by the incident underwater sound field. Historically, acoustic transmitters and detectors need to be submerged to interact with the underwater environment. This remote, aerial, laser-based sonar and communication system presents a revolutionary change in the way sonar and communications can be realized, by remotely activating and detecting underwater acoustics from the air.
A remote, aerial, laser-based sonar method for detecting and locating underwater targets from the air is discussed. The aerial sonar system combines two independent laser technologies. First, a high power laser is used to remotely generate underwater sound from the air by converting the optical energy into an acoustic pressure wave at the water surface. Second, a low power laser monitors water surface vibrations to detect and localize underwater sound. The aerial (opto-acoustic) generation and (acousto-optic) detection of underwater sound provides a non-contact means for active and passive sonar that does not currently exist. The laser systems could be mounted on an in-air or an above surface platform to search an area to provide intelligence information about the presence and location of underwater objects. Such data could be used for targeting for air-dropped munitions, port defense by monitoring friendly waters, or for area clearance for fleet operations in foreign ports. This transformational capability offers a covert, rapidly deployable, highly distributed, sensor field along the water surface.