Takahisa Harayama

Experimental investigation of Sagnac beat signals using semiconductor fiber-optic ring laser gyroscope (S-FOG) based on semiconductor optical amplifier (SOA)

We are conducting research to confirm the performance of a semiconductor fiber-optic ring laser gyroscope (S-FOG) featuring a semiconductor in its laser cavity. This S-FOG consists of a semiconductor optical amplifier (SOA) as a gain medium, a polarization-maintaining fiber to make a ring cavity, and a directional coupler to take part of the optical power out of the cavity. One of the advantages of the S-FOG is the adaptability of the laser cavity, which allows us to examine many cases of S-FOG applications easily. In the first case, we observed that the S-FOG generated Sagnac beat signals whose peak frequency was proportional to the rotation rate when it rotated. In the second case, we changed the area surrounded by the ring cavity (the fiber) and its perimeter and maintained a near-fixed oscillation wavelength of the ring laser. In this case, all of our experimental results were in good agreement with theoretical calculations, within a few percent. In the third case, we changed the oscillation wavelength and fixed the shape of the ring cavity. In this case, our results were also in good agreement with theoretical calculations. In the fourth case, we examined the Sagnac beat spectrum generated by the S-FOG in detail. The linewidth of the Sagnac beat spectrum increases as the area bounded by the optical path in the ring cavity becomes smaller, or as the length of the cavity becomes shorter. Our experimental results show that the S-FOG works as a gyro and that there exists practical potential for a semiconductor ring laser gyro.

Sagnac Beat Signals Observed in Semiconductor Fiber-Optic Ring Laser Gyroscope

A semiconductor fiber-optic ring laser gyroscope, which consist of a semiconductor optical amplifier as a gain medium and polarization-maintaining fiber to form a ring resonator, generate Sagnac beat signals demonstrating good agreement with theoretical calculations.

Improvement of accuracy of angular velocity detection in semiconductor fiber-optic ring laser gyroscope

A semiconductor fiber-optic ring laser gyroscope (S-FOG) consists of a semiconductor optical amplifier (SOA) and optical fiber to form a ring cavity. The fiber ring cavity enables larger sizes and smaller scattering, while the SOA gain is shared by the clockwise (CW) and counterclockwise (CCW) propagating modes. When the S-FOG is rotated, a new beat signal called the Sagnac beat frequency is observed. We investigated the effect of the fiber ring cavitys length on detection characteristics. Detection sensitivity was not dependent on the number of laps of fiber ring cavity. However, when the cavity length became longer, the linewidth of Sagnac beat became narrower, and then accuracy of angular velocity detection improved. The relation between the linewidth Δ ν of the Sagnac beat and cavity length P was proved to be Δ ν ≈ P-1.86.

Earth's rotation rate detection using an extremely large semiconductor fiber optic gyroscope extending over 10,000 m2

We detect the Earths rotation rate using a semiconductor fiber optic gyroscope (S-FOG), which is an active ring laser gyroscope that consists of a semiconductor optical amplifier (SOA) and a fiber optic ring resonator. Four different optical fiber layouts with different scale factors in rotation rate measurement are configured and measured. Expected Sagnac beat signals proportional to the scale factors are observed. The maximum layout of S-FOG is extended over 10,898 m2, which, to our knowledge, is the largest active ring laser gyroscope ever built.