OFDR-Based Distributed Sensing and Fault Detection for Single-and Multi-Mode Avionics Fiber-Optics

Short-length optical communications networks such as those employed in avionics and aerospace applications are in need of frequent assessment of link health. Precise localization and identification of cracks and breaks, as well as an accurate assessment of loss due to fiber bends, splices, and connectors is critical to maintaining signal integrity along the link. Traditionally, optical time domain reflectometry (OTDR) is employed for installationand maintenance-based inspection of fiber systems. However, in many respects traditional OTDR is not well-suited for avionics applications, which are typically dominated by short runs of optical fiber (less than 100 m). This is due to the technological limitations of launch and event dead-zone inherent to OTDR, which can be a significant percentage of the total link length for the short-run networks encountered in avionics. Likewise alternate techniques, such as optical low-coherence reflectometry (OLCR), have limited applicability to avionics fiber-optics. Herein we introduce an optical frequency domain reflectometry (OFDR) technique and its applications in singleand multi-mode avionics fiber-optics. Multiple measurement examples within the avionics field not currently supported by conventional test tools or methods are provided, including high-resolution fault detection and distributed sensing along unaltered standard telecommunications grade optical fiber with millimeter spatial resolution. The utility of this technique as a health monitoring tool for existing and new avionics fiber-optic networks is discussed.