Sensitivity-improved microwave photonic fiber-ring temperature sensor with the self-Vernier effect

A microwave photonic (MWP) fiber-ring (FR) temperature sensor that enhances sensitivity with the assistance of the self-Vernier effect is proposed and demonstrated. By using a fiber-ring interferometer combined with a delay fiber, the Vernier effect can be generated through the superposition of the interferometer's intrinsic spectrum with its time-delayed counterpart. The method eliminates the need to integrate two separate interferometers and to precisely control their slightly different optical path differences (OPDs). Microwave photonic technology converts spectrum shifts of the interferometer caused by temperature variations into frequency shifts of the notch point in the frequency domain, and the self-Vernier effect further amplifies this frequency changes, enhancing the sensitivity. The sensitivity of the proposed simple microwave photonic fiber-ring temperature sensor constructed in the experiment reached -392.317 kHz/℃, representing approximately 15 times higher than that without the self-Vernier effect.