Microwave photonic interrogation of real-time gas vacuum sensor

A real-time gas vacuum sensor interrogated based on a microwave photonic method at high speed and high resolution is proposed and demonstrated. The sensor is a microfiber Mach-Zehnder interferometer (mMZI) with its wavelength sensitive to the gas concentration. Instead of detecting the wavelength shift of the mMZI spectrum in the optical domain, we convert the mMZI spectrum to the time domain by spectral shaping and wavelength-to-time (SS-WTT) mapping and apply a digital signal processor (DSP) to realize the cross-correlation to estimate the wavelength shift of the mMZI. The sensitivity and resolution of the proposed gas vacuum sensor are -0.586 ps/ppm and 34.13 ppm with a concentration range from 0 to 1.4x10(4) ppm, respectively.