Experimental Study of Hollow-Core Photonic Crystal Fiber Optical Switching Effect in Liquid Nitrogen Environment

In this study, the hollow-core photonic crystal fiber (HC-PCF) optical switching effect in liquid nitrogen (LN
₂
) environment is demonstrated and experimentally investigated. Turning off the light transmission is realized by the liquefaction of air present in the airholes of the HC-PCF when the fiber is immersed in LN
₂
, and turning on the light transmission is realized by the evaporation of air when the fiber is taken out of LN
₂
. The extinction ratio of the optical switching effect is found to be ~50 dB; furthermore, the turn-on and turn-off time of the optical switching effect can reach ~8 s and ~3 s, respectively. Thus, optical switching effect in a HC-PCF in LN
₂
environment can be easily realized, which is beneficial in building all-fiber in-line low-frequency optical-switching systems that can be potentially applied in areas such as fiber sensors.