Giuliano Conforti

A Mixed Method for Measuring the Inner Scale of Atmospheric Turbulence

Abstract A new method for measuring the inner scale and structure constant of atmospheric turbulence is proposed and tested. It utilizes both phase and amplitude fluctuations of laser radiation propagating in the medium. The measured quantities are the intensity variance of a spherical wave and the transverse-displacement variance (wandering) of a narrow laser beam. The method is developed within the limits of geometrical optics. Experimental laboratory results are presented. Values of inner scale of a few millimetres are measured.

Fiber optic vibration sensor for remote monitoring in high power electric machines

A novel fiber optic vibration sensor is presented, based on the motion detection of an elastic cantilever by means of the optical triangulation technique. The sensor was designed to work at a fixed frequency of 100 Hz for applications in high power electrical plants where insulation and EM immunity requirements make fiber optic sensing the most suitable choice. The working linear range reaches a peak amplitude of 0.25 mm; resolution is 0.1 microm; accuracy is better than +/-3%; and sensitivity is 10 mV/microm. Design details and experimental results are reported.

Thermochromic transducer optical fiber thermometer.

A new dielectric thermometer based on multimode optical fibers for light transmission and on a thermochromic solution transducer for temperature sensing is presented. The working principle of the transducer, technical data of the optoelectronic system, and experimental results are described and discussed.

Detector saturation effect on higher-order moments of intensity fluctuations in atmospheric laser propagation measurement

We investigate the influence of the detection-system saturation on the intensity-fluctuation statistics in measurements of optical scintillation induced by atmospheric turbulence. The statistical distribution of the intensity is assumed to be log normal. The values of the nth moments detected by the apparatus are shown to depend on the ratio between the saturation intensity of the detector and the mean intensity of the distribution to be measured.

Strong-scintillation-statistics deterioration due to detector saturation

The deterioration that is due to saturation of a revealing apparatus on high-order moments of intensity is investigated in the case of Furutsu’s distribution. This is a two-parameter distribution and seems suitable for describing intensity fluctuations that are due to atmospheric turbulence in the case of intermediate and strong scintillation. The effect of saturation was shown to depend on only one parameter, αDS, defined as the ratio between the saturation intensity of the system and the mean intensity to be measured, a result already found in the case of a log-normal distribution. An expression of the deteriorated moments is given in terms of αDS and of the two parameters of the distribution. The theoretical results are used to give a qualitative interpretation of measured moments after laser propagation along a 1800-m path above the city of Florence.

Aperture size and bandwidth requirements for measuring strong scintillation in the atmosphere

Irradiance statistics were simultaneously measured with five apertures of four different sizes and also with five different bandwidths under conditions of strong path-integrated turbulence to determine aperture size and bandwidth requirements. The probability density function and the second and third moments are considered. Good measurements of these statistics can be made with detector apertures near the wave coherence length and with bandwidths near the ratio of the transverse wind velocity to the wave coherence length under these conditions.

Fiber-optic thermometric probe utilizing GRIN lenses

A multimode optical fiber thermometer is described, which makes use of a single fiber for light guiding and a thermochromic solution as a differential absorption temperature transducer. The probe has a novel design and utilizes graded-index microlenses to achieve high coupling efficiency between fiber and transducer. Technical data of the electrooptic unit, along with the working principle of the probe are presented, and calibration tests of the thermometer are given.

Measuring inner scale and structure constant of atmospheric turbulence in a simple way

An optical method of measuring inner scale and refractive structure constant of atmospheric turbulence by laser radiation is described and a laboratory test presented. 1 -