Fast-Light Enhanced Brillouin Laser Based Active Fiber Optic Sensor for Simultaneous Measurement of Rotation and Strain

We have developed a conceptual design for an active fast light fiber optic sensor (AFLIFOS) that can perform simultaneously or separately as a gyroscope (differential mode effect) and as a sensor for strain and other common mode effects. Two Brillouin lasers in opposite directions and separated in frequency by several free spectral ranges are used for this sensor. By coupling two auxiliary resonators to the primary fiber resonator, we produce superluminal effects for the two laser modes. We develop a detailed theoretical model for optimizing the design of the AFLIFOS, and show that the enhancement factor of the sensitivity is ~8.2 x 10
³
, under the optimized condition, when the effective change in the length of the primary fiber resonator is 0.1 pm, corresponding to a rotation rate of 1.4 x 10
^-3
deg/sec. With this enhancement factor, the minimum detectable rotation rate is 2.4 x 10
^-11
deg/sec when the output power is 1 mW and the measurement time is 1 s, which is ~8.2 x 10
³
times better than that of the passive version with the same parameters. The minimum measurable strain is 1.4 x 10
^-2
fε/VHz when 1/4 of the primary resonator is sensitive to strain and the linewidth of the master laser is taken to be 200 Hz. It may be possible to get much higher enhancement by adjusting parameters such as the length of the laser loops and the coupling coefficients.