A new annular-core optical fiber is useful, inter alia, for stabilizing the behavior of an optical attenuator based on a Long Period Grating against fluctuations in the polarization of the fundamental optical signal. The update notifications may be push notifications or pull notifications. When the dozer chassis pitches forwards, the blade begins to tilt forward and to drop closer to the ground. The liquid water product is discharged via an outlet along the length of the chamber and a dried and pyrolysed solid product is discharged from a downstream outlet in the chamber.