Error compensation in Brillouin optical correlation-domain reflectometry by combining bidirectionally measured frequency shift distributions

In standard single-end-access Brillouin optical correlation-domain reflectometry (BOCDR), the systematic error caused by the phase difference between amplitude modulation (AM) and frequency modulation (FM) in the light source can be up to tens of megahertz, causing considerable errors in strain and temperature measurement. In this letter, we develop a new concept of two-end-access BOCDR, in which light is injected into each end of a sensing fiber in turn and the measured results of the Brillouin frequency shift distributions are combined. We numerically show that this configuration can suppress the systematic error caused by the AM-FM phase difference by approximately 90%.