US Patent 10892822 Optical fiber event location

An optical network including a processing device configured to receive from photodetectors, information indicative of a time period between loss of light received through a first optical fiber and loss of light received through a second optical fiber. The first optical fiber has a first latency and the second optical fiber has a second latency. The first optical fiber and the second optical fiber extend along a common path through the optical network: a first end of the path being defined by the photodetectors and a second end of the path being defined by a second location in the optical network. The processor is configured to calculate, based on the timing information and a difference in latency between the first optical fiber and the second optical fiber, a distance along the common path from the photodetectors to an event resulting in the losses of light.