High Resolution Short Response Time Fiber-Optic Temperature Sensor
High resolution, high sensitivity, and fast temperature sensing are critical across various fields, including atmospheric studies, biomedicine, environmental monitoring, aeronautics, defense, and industrial process control. Many applications often require temperature sensors to work in gaseous environments. To obtain realistic data in these challenging environments, the sensors should be compact and have low mass, high sensing resolution, low thermal conductivity, and limited heat capacity.
Conventional temperature sensors often face challenges in environments requiring fast and accurate temperature measurements. This work presents a highly responsive fiber-optic temperature sensor that leverages the unique properties of silicon to overcome these limitations. The proposed sensor has a resolution of about 5 millikelvin and a response time of 4 milliseconds. Its compact, all-silica design makes it suitable for operations in a broad temperature range. This also ensures immunity to electromagnetic interference, inertness to chemical exposure, and corrosive environments. These properties make it well-suited for monitoring in dynamic and challenging environments where both short response time and high sensitivity are essential.
The optical sensor presented herein utilizes a micro-wire based, femto-second laser micromachined Fabry–Perot interferometer (FPI) formed on the tip of the optical fiber. Within this configuration, temperature-induced variations due to the thermo-optic effect alter the optical path length of a short microwire forming the interferometer. These changes result in measurable phase shifts in the spectrum of a reflected optical signal, which can be extracted using spectral or phase-sensitive interrogation techniques.
Unlike conventional fiber-optic sensors, which typically exhibit longer thermal response times due to larger thermal mass and less efficient heat exchange, the presented configuration of the sensor demonstrates a bandwidth of 38 Hz (corresponding to a time constant of 4 ms) when tested in still air. This performance is enabled by sensing microwire diameter of about 11 μm, cylindrical geometry, and overall low heat capacity of the sensor.
The proposed sensor demonstrated a resolution of about 5 mK. This performance was validated experimentally through dynamic testing, including controlled periodic gas compression experiments. Achieved resolution and dynamic performance make the sensor particularly well-suited for applications requiring real-time monitoring of small temperature fluctuations in the atmosphere, such as atmospheric turbulence characterization, biomedical diagnostics, and other high-resolution thermal sensing applications.
The sensor’s all-silica design also provides inherent immunity to electromagnetic interference and chemical inertness, enabling reliable operation in harsh or corrosive environments. High-temperature tests demonstrated operation up to 600 °C over an extended time duration, with no observable degradation in signal quality.
The proposed sensor developed using fabrication methods established in photonic technologies integrates high-resolution, exceptional sensitivity, improved temperature detection, ultra-fast response time, and environmental robustness in a compact fiber-optic sensor design. This sensor offers a suitable pathway toward advanced temperature monitoring in dynamic environments by overcoming limitations in response time and resolution commonly associated with conventional thermal sensors. The device has been experimentally proven to be quick and reliable for real-time temperature monitoring, exhibiting high measurement resolution and operational stability, enabling its practical implementation and future integration in various applications.