Intracavity spectral control and full temperature range stability optimization of a superfluorescent fiber source for the high-precision fiber optic gyroscope

To meet the requirements for a high-precision FOG light source with a stable mean wavelength and a near-Gaussian spectrum over a wide temperature range, this study proposes a novel intracavity filtering technique, to the best of our knowledge. A saddle-shaped grating filter is embedded into the light source structure to achieve near-Gaussian spectral characteristics and enhanced mean-wavelength stability. To obtain a highly stable wavelength output, a temperature-insensitive filter packaged in a bimetallic structure is integrated into a double-pass forward superfluorescent fiber source (SFS) to suppress thermally induced spectral drift. Based on the rate-equation theory, the source configuration was simulated and iteratively optimized using the OptiSystem software. The simulation results confirm that the embedded saddle-shaped grating enables near-Gaussian spectral shaping. Experimentally, a broadband saddle-shaped grating was designed via a reverse design strategy based on the stacked grating principles and fabricated using the excimer laser phase mask method. The encapsulated filter was then integrated into the light source for the experimental validation, with optimization of the pump power and the erbium-doped fiber length. A near-Gaussian output with a power of 11.25 mW and a spectral bandwidth of 18.4 nm was achieved. Over the temperature range of -45^∘<i>C</i> to 70°C, the light source exhibits a mean wavelength stability of 0.84 ppm/°C and an output power variation with temperature of 8.22×10^-3<i>m</i><i>W</i>/^∘<i>C</i>. These results meet the application requirements for high-precision FOG light sources and offer a technical pathway for further improving gyroscope accuracy.