Incoherent optical frequency domain reflectometry for health monitoring of avionics fiber optics networks

We present a highly sensitive, linear and high spatial resolution approach for the detection of flaws and spurious reflections in avionic optical fiber links based on the technique of incoherent optical frequency domain reflectometry (IOFDR). This approach allows built in test functionality. In particular, we demonstrate the technique of incoherent frequency modulated continuous wave optical frequency domain reflectometry (I-FMCW-OFDR) to detect fiber faults in a 100 m avionic multimode fiber optic link operating at 850 nm. This system can ultimately be engineered to provide diagnosis to the assembly level during line maintenance and provide information useful for preventive maintenance. We demonstrate fault location with accuracy better than 2 mm. We also demonstrate an ultra-high dynamical range approach sufficient for detecting Rayleigh scattering in the multimode fiber. The proposed approach requires very little modification of existing transceivers in present avionic systems, utilizes commercially available digital synthesizer chips, and delivers record performance in terms of sensitivity, dynamic range and spatial resolution for locating the sources of reflection in long fiber optics links. The laser that was used in these measurements is a low cost multimode VCSEL.