Design of all-optical strain and temperature sensor by micrometer high-birefringence fiber loop mirror

High-birefringence fiber loop mirrors (Hi-Bi FLM) are interested in a variety of applications such as temperature and strain sensors, but their serious limitation is their structure length, in the order of several meters, for application in optical integrated devices. In this paper, we have used electromagnetically induced transparency (EIT) phenomena to reduce the length of Hi-Bi FLM to below 50 μm, where 3-level nanocrystals (QDs) are doped in Hi-Bi FLM to realize EIT conditions. EIT phenomenon amplifies refractive index differences of slow and fast axes of Hi-Bi FLM, so that the length of FLM to obtain required phase difference is reduced. This proposed sensor can measure temperature and strain simultaneously with 62.5 pm/°C and 0.3 μm, respectively.