Built-In Test in Fiber Optic Links - Enabling Technology for a Network-Centric Future

Modern aerospace avionics systems demand both an increased use of networks and an increase in the capacity of such networks. It is quite common today to find links of 1 gigabit-per-second (Gbps) or higher being designed into aircraft. At these rates, the transmission medium of choice is generally fiber optics since copper media at such rates generally perform poorly at lengths of more than a few tens of feet.

While fiber optics use proliferates and improves in a number of important ways, in one respect important to the aerospace industry, it remains stuck in the 70's. That aspect has to do with the way a link is diagnosed when it has problems. Troubleshooting a fiber optic link generally requires the intervention of a skilled technician, sometimes requiring the use of sophisticated diagnostic equipment.

This paper describes the features needed to provide self-diagnosis capability to fiber optics transceivers. Such transceivers would be capable of determining which component within a fiber optic link was bad and, in the case of a broken fiber, would be able to locate the fault to within inches. All such features are thought to be within the capability of current, low-cost technology and are being developed at this time.