High-Sensitivity Mach-Zehnder Interferometer for Precise Seawater Temperature Measurements Using No-Core and Seven-Core Fibers

The high-precision measurement of seawater temperature is crucial for resource development, environmental protection, and climate monitoring. A Mach-Zehnder interferometer (MZI) for highly sensitive seawater measurements is proposed and demonstrated using a sandwich structure of no-core fiber (NCF) and seven-core fiber (SCF) spliced in single-mode fiber (SMF). By observing the shifts in various resonance peaks in the transmission spectrum of the interferometer, temperature measurements can be achieved as the temperature of seawater change. The results show a linear temperature response in the range of 30.7°C to 32.0°C, with a maximum sensitivity of approximately 3.158 nm/°C. The proposed MZI sensor demonstrates capabilities for potential applications in seawater temperature monitoring.