A high-sensitivity optical fiber temperature sensor based on the vernier sampling of tunable laser was proposed. The sensor contains only one fiber Sagnac interferometer (FSI), and the Vernier effect is achieved by controlling the sampling interval of the tunable narrow-band laser. When the wavelength sampling interval of the tunable laser is close but not equal to the free spectral range (FSR) of the FSI, the spectrum received by the optical power meter will be the envelope generated by the Vernier effect. The experimental results show that for the FSI with an FSR of 2.47 nm, when the sampling interval of 2.78 nm, which is slightly greater than the FSR of the FSI, is selected, an interference spectrum envelope is obtained, and its temperature sensitivity is about 9.1 times that of the FSI. The results prove that vernier sampling is feasible to improve the sensitivity of a single FSI, and its advantage is that the sampling interval can be flexibly controlled to achieve different sensitivity magnifications.

This paper presents a high-sensitivity temperature and humidity synchronous measurement sensor based on virtual Vernier demodulation, designed to overcome the limitations of traditional sensors in high-sensitivity and synchronous measurements. By combining a dual-cavity parallel structure with the Virtual Vernier effect (VVE), two interferometers were designed, with one using a temperature-sensitive material (polydimethylsiloxane, PDMS) and the other using a humidity-sensitive material (polyvinyl alcohol, PVA) for temperature and humidity measurement, respectively. Based on actual interference spectra, a modulation function was used to generate the virtual reference interferometer spectrum, which was then superimposed with the sensing interferometer’s spectrum to form a virtual Vernier envelope. By monitoring the displacement of the envelope, precise measurements of temperature and humidity changes were achieved. Experimental results showed a temperature sensitivity of 5.61 nm/°C and 7.62 nm/°C, a humidity sensitivity of 0 nm/%RH and −3.07 nm/%RH, and average errors of 0.64% and 1.10% for temperature and humidity, respectively, demonstrating the feasibility of the method. The introduction of the virtual interferometer effectively reduces environmental interference with the measurement results and avoids the material loss and errors associated with traditional reference interferometers. More importantly, the VVE enables dynamic adjustment of the envelope magnification, thereby enhancing the sensor’s flexibility and overcoming the structural limitations of traditional interferometers. This sensor provides efficient and reliable technological support for future environmental monitoring and climate change research.

To address the increased demodulation latency and degraded robustness of optical frequency domain reflectometry (OFDR) at millimeter-scale spatial resolution, primarily caused by polarization fading and noise contamination, we propose a fast and robust strain measurement method based on 2D cross-correlation map-guided sparse ridge tracking (CCM-SRT). The proposed approach first performs ridge tracking on a low-resolution 2D cross-correlation map by imposing a physical inertia constraint, thereby converting conventional local peak selection and local peak picking into a global optimal path search, which provides a fading-resilient global guidance trajectory. A Gaussian tunnel is then constructed around the guidance ridge, and a sparsity-based decision mechanism restricts the narrow-band cross-correlation refinement to informative regions only, simultaneously reducing computational load and suppressing spurious peaks. Under stress tests featuring a noise blind zone and severe fading realized with an unbalanced interferometric configuration, both simulations and experiments demonstrate that, at 5 mm spatial resolution and 15% relative noise, CCM-SRT achieves an approximately 2.7× speedup over conventional full-region cross-correlation, while reducing the root-mean-square error (RMSE) from ~500 pm to ~5 pm, markedly improving OFDR applicability in dynamic and complex environments.