# Frequency-Stable Low-Threshold SBS-OEO for Precision Temperature Sensing in Electromagnetically Harsh Environments

## TL;DR

A new low-power, high-precision temperature sensor was developed using a stable optoelectronic oscillator with improved environmental resistance and reduced energy needs.

## Contribution

A dual-pass SBS interaction using a Faraday rotation mirror reduces the power threshold and enhances environmental robustness in SBS-OEO temperature sensing.

## Key findings

- The FRM-based system reduced the SBS power threshold by 2.7 dB compared to conventional systems.
- The sensor achieved a sensitivity of 1.0609 MHz/°C with an R² of 0.999 over a 67 °C range.
- Long-term stability of ±0.004 °C was achieved, surpassing existing SBS-OEO schemes.

## Abstract

What are the main findings?

Threshold Reduction and Environmental Robustness

Introduced a Faraday rotation mirror (FRM) to enable dual-pass SBS interaction, reducing the SBS power threshold by 2.7 dB compared to conventional systems.

The FRM’s polarization rotation inherently suppresses polarization-induced fluctuations and vibration noise, eliminating the need for active polarization control.

Record-Breaking Performance

Sensitivity: 1.0609 MHz/°C (R2 = 0.999) over a 67 °C range (30–97 °C).

Stability: ±0.004 °C long-term precision, surpassing existing SBS-OEO schemes.

Power Efficiency: Operates at 13.6 dBm pump power.

What is the implication of the main finding?

For threshold reduction and environmental robustness: The dual-pass SBS interaction enabled by FRM provides a feasible technical path to lower the energy consumption of SBS-based systems, while the inherent suppression of polarization fluctuations and vibration noise simplifies the system structure (avoiding complex active polarization control modules), reducing the difficulty of system integration and maintenance costs.

For record-breaking performance: The high sensitivity (1.0609 MHz/°C, R2 = 0.999) over a 67 °C range allows the system to achieve high-precision temperature sensing in scenarios requiring wide-temperature-range monitoring (e.g., industrial equipment thermal management, environmental temperature tracking). The ±0.004 °C long-term precision surpasses existing SBS-OEO schemes, making it suitable for high-stability application scenarios such as precision instrument calibration and quantum sensing auxiliary temperature control. Additionally, the low pump power (13.6 dBm) enhances the system’s portability and energy efficiency, laying a foundation for its practical application in field detection or battery-powered devices.

In this research, precision temperature sensing for electromagnetically harsh environments was achieved utilizing a low-threshold frequency-stable optoelectronic oscillator (OEO) leveraging stimulated Brillouin scattering (SBS). The sensing mechanism relied on the temperature-dependent frequency shift in the SBS-induced notch filter. By embedding this filter in the OEO feedback loop, the oscillator’s output frequency was locked to the difference between the optical carrier frequency and the SBS notch center frequency. The temperature variations were translated into microwave frequency shifts through OEO oscillation, which was quantified with heterodyne detection. To suppress environmental perturbations, a Faraday rotation mirror (FRM) was integrated at the fiber end, creating a dual-pass SBS interaction that simultaneously enhanced the vibration immunity and reduced the SBS power threshold by 2.7 dB. The experimental results demonstrated a sensitivity of 1.0609 MHz/°C (R2 = 0.999) and a long-term stability of ±0.004 °C. This innovative scheme demonstrated significant advantages over conventional SBS-OEO temperature sensing approaches, particularly in terms of threshold reduction and environmental stability enhancement.