Determination of temperature and strain by a compact optical fiber Mach-Zehnder interferometer (MZI) composed of a single-mode fiber (SMF), seven core fiber (SCF), and multimode fiber (MMF) with a fiber Bragg grating (FBG)

A compact optical fiber Mach-Zehnder interferometer (MZI) sensor is reported for temperature and strain. The MZI sensor consists of a single-mode fiber (SMF), a seven core fiber (SCF) and a multimode fiber (MMF) with a fiber Bragg grating (FBG). The intensity distribution of the sensor is calculated by the beam propagation method. The light is coupled from the lead-in SMF into the SCF through the MMF. The highest transmission efficiency was obtained when the length of MMF is 2 mm with a diameter of 105 μm. The temperature sensitivity is up to 55.06 pm/°C from 130 °C to 250 °C, while the maximum extinction ratio was 27.4 dB. The measurements were divided into two intervals to address cross coupling to provide sensitive temperature and strain measurements.