Improved Vernier Effect Scheme Based on a Single Interferometer With Unique Wavelength and Compact Structure

The optical Vernier effect scheme has proven to be a powerful tool for significantly enhancing the sensitivity of the interferometric sensors by combining two interferometers, provided that the free spectral range (FSR) of each interferometer closely matches that of the other. However, the fabrication of a reference cell that precisely aligns with the sensing interferometer (SI) to meet the Vernier condition can be challenging. In this article, we propose a novel Vernier effect scheme consisting of only one interferometer. The single interferometer functions as both the SI and reference interferometer (RI), where the reference spectrum can be achieved by inverting the sensing spectrum along its wavelength axis. By combining the sensing spectrum and reference spectrum, the resulting Vernier envelope features a unique wavelength (UW), breaking the periodicity seen in the conventional envelope. The sensitivity enhancement principle of the proposed Vernier effect has been theoretically investigated and its effectiveness has been validated experimentally in a temperature measurement. This study offers the advantages of simplicity and cost-effectiveness, with promising potential to improve the performance of Vernier effect-based sensors. It paves the way for achieving higher sensitivity with a more compact sensor configuration, which is highly beneficial for practical sensing applications.