Description:
OBJECTIVE: Identify the major issues limiting the mechanical strength and power transmittance of the As2S3 chalcogenide infrared fiber and develop manufacturing technology for long length (>ten meters) applications and increased mechanical strength and optical transmission. DESCRIPTION: The As2S3 fibers are critical to the implementation of a new design for a Directed InfraRed CounterMeasure system (DIRCM). DIRCM systems are essential to defeating the new generations of infrared guided missile threats to tactical aircraft. Utilizing these fibers allows a system design that can achieve the performance required of a DIRCM system, including the stringent weight limits, size and power levels acceptable for the H-1 series helicopters deployed by the Navy and Marine Corps. The fiber-based system design has also been demonstrated as effective for use on the larger H-60 series and V-22 aircraft operational in the Navy and Marine Corps. Alternative DIRCM system designs are considerably heavier, more expensive and do not allow for Open System Architecture, whereby the laser and pointer are separately replaceable units. The major issue with fabrication of the As2S3 fiber-based system with long length fibers, lengths exceeding 10 meters, is loss of laser power during transmission. Losses are due to various impurities in the As2S3 materials, including absorbed contaminants in the fiber and imperfections introduced in the drawing process. The major impurities such as hydrogen sulfide (HS) are difficult to reduce to the extremely low levels (sub-ppm) required. The imperfections introduced during drawing can include but are not limited to, non-uniformity of the acrylate coating, off-center positioning of the core within the cladding, defects in the fiber [1], and induced loss due to environmental factors such as humidity and temperature. A second issue is the mechanical strength of the fiber. Embedded particulates and imperfections are a known cause of fiber failures under stress. Measurements of the tensile strengths of chalcogenide, including As2S3, fibers show values considerably lower than the theoretical value [2]. The program objectives of this topic are for the fibers to be manufactured in lengths exceeding 10 meters and for them to pass a tensile proof test of at least 20kpsi and possess an optical loss of<0.15dB/m. The Navy will only fund proposals that are innovative, address materials and manufacturing R&D and involve technical risk. PHASE I: Identify the impurity levels needed for producing low-loss fibers and develop concepts for manufacturing processes to provide suitably pure materials. Define the bounds of the environmental conditions necessary for producing fibers of consistent quality as well as the methods for controlling the conditions. Identify the critical steps and components of the fiber drawing process and equipment and define a manufacturing process for drawing low-loss, high tensile strength fibers. PHASE II: Build or assemble a prototype IR fiber drawing system capable of delivering high quality fiber with high yield. Demonstrate the operation of the system including measurements to verify the quality of the fiber produced. PHASE III: Transition the process for creating a manufacturing capability for producing the IR fibers in quantity by providing a detailed description of how high quality fibers can be produced with high yield. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The IR fibers transmit in the infrared fingerprint region and so would be suitable for remote chemical sensing and other commercial applications.
