Study on the Actual Mean Wavelength of the Interferometric Fiber Optic Gyroscope

Scale factor stability is a critical parameter determining the precision of the interferometric fiber optic gyroscope (IFOG), with current advanced high-precision IFOGs requiring scale factor stability at the level of several parts per million (ppm). This study investigates the relationship between the IFOG scale factor and the mean wavelength (MWL) of light, focusing on the mean wavelength in the wavenumber domain (k-MWL) and the mean wavelength in the wavelength domain (λ-MWL) to identify the key indicator and core mechanism determining the optical scale factor stability of the IFOG. The results demonstrate that, compared to the λ-MWL, the k-MWL exhibits a more direct and fundamental mathematical and physical relationship with the IFOG interference fringes. The k-MWL can be considered the actual MWL that reflects the properties of the interference fringes and determines the IFOG scale factor. Additionally, a quantitative discrepancy exists between the k-MWL and λ-MWL, with variations ranging from tens of picometers to several nanometers across different spectral bands and bandwidths of light sources. Even under the same light source, spectral perturbations can induce variations in this discrepancy at the picometer level. This magnitude of discrepancy variation suggests that using the λ-MWL as the metric for evaluating the IFOG's MWL may misguide the reference standard and optimization direction for the high-precision IFOG scale factor, potentially hindering the achievement of ppm level stability. This study innovatively investigates the physical properties of interference fringes, combining clear mathematical derivations to establish k-MWL as the actual mean wavelength determining the optical scale factor of the IFOG from the fundamental physical perspective of the interference process. It reveals the intrinsic relationship between high-precision IFOG scale factor stability and the k-domain MWL, optimizes the optical model of the IFOG, effectively reduces scale factor error terms, and establishes a more accurate reference standard for optimizing scale factor stability in the high-precision IFOG.