Using a 1.5-microm DFB InGaAsP laser in a passive ring cavity type fiber gyroscope

It has been demonstrated that a 1.5-microm distributed feedback InGaAsP laser can be used as a coherent light source in a passive ring cavity-type fiber gyroscope. A formula for the detector shot noise-limited sensitivity of detection of rotation was derived for this type of gyroscope. Its value in the present experimental setup was estimated as being 0.8 . tau(-1/2) degree/hour, where tau represents the integration time of measurements. Experiments showed that the uncertainty of the detection of rotation was 1.5 degrees /h at tau = 100 s, which was governed by the slight reflection of light at the AR-coated fiber edges and residual frequency fluctuations of the laser.