Marcin Swillo

Compact optical fiber refractive index differential sensor for salinity measurements

Design and initial tests of a compact differential refractometer of deviation type are described. The use of optical fiber instrumentation for detection of the beam deviation profited in a compact device for remote sensing. For the industrial application a reflection type of type differential refractometer was designed. The laser is launched into the refractometer cell through the single mode fiber and SELFOC to illuminate a detector in form of a gaussian beam. The detection system consists of the in-line arranged multimode fibers. The deviation of the beam due to salinity of water is evaluated from light intensifies detected by four sequentially arranged fibers. Analog digital conversion and numerical computation of the signal results in the accuracy in determination of salinity better than 0.5%. The salinity measurement range starts from the lowest concentrations through seawater up to coal mine salt water.

Dynamic strain measurements by use of the polarimetric fiber optic sensors

Polarimetric fier optic sensing is based on measurements of polarization changes of tight transmitted inside sin& mode fiber affected by external phenomena Polarimetric optic sensors are mainly used for static mearuremrnts of strain, stress and high pressure. In tlie paper the res& of dytuimic strain masuremenis of a steel rain by use of the polarimetric f ier optic sensors are presented We can observe a quick response of optical f i er memuring +em for changes of strain in the rail for &ierent frequencies as well as wide range of dynamic amplitude chmges

Fiber optic salinity sensor: temperature influence on salinity measurement

The temperature influence on salinity measurement by optical fiber salinity sensor has been investigated. Study of the sensor sensitivity with temperature change in range of temperatures 20 - 80 degree(s)C is presented. The construction of the sensor has followed the example of differential refractometer. As a result of this construction and high sensitivity of sensor on salinity, temperature changes have not deformed salinity measurements with the use of this sensor.

Optoelectronic mammoscope for breast cancer diagnosis

The aim of this paper is to introduce an optoelectronic mammoscope that has been developed at Warsaw University of Technology for early breast cancer detection. The idea of the mammoscope is based on a direct comparison of light transmission spectra through breast tissue obtained for two selected wavelengths: 670 nm and 810 nm. As light sources, two types of laser diode are used. The optoelectronic mammoscope is equipped with a specially designed optoelectronic head which decreases light path throughout the breast tissue under examination and, simultaneously increases intensity of the light transmitted through the tissue. At the output, a CCD camera coupled to the IBM PC/486 computer is used for detection of shadow images created by the transmitted light at both wavelengths.

Fiber optic salinity sensor alarm

The modification of salinity sensor was achieved in such a way that it is possible to perform salinity measurement and directly to send the data about an exceeding of salinity level for the purpose of quick intervention permitted by National Environmental Standards. The designed system of a network of central controllable sensors may be useful to automatic monitoring of an environment.

Vortex flowmeter with polarimetric sensing

The paper presents initial studies of the fiber flowmeter realized by polarimetric sensing with highly birefringent polarization-maintaining optical fibers. In the studied system one fiber is applied as the both bluff body and sensing element. The flow velocity is evaluated from the amplitude modulated signal of the frequency of vortex shedding. The polarimetric sensing based on polarization interference presents the advantage of sensitivity compared to the interferometry measurement but without the expense of its complex arrangement.

Polarimetric optical fiber sensor with compensated birefringence for dynamic strain measurement

Polarimetric fiber optic sensors belong to phase sensors, in which phase shift between two electric field components of beam passing through a high birefringent optical fibers responsible for a change in polarization state of the light. The paper presents polarimetric fiber sensor for dynamic strain measurements. In order to measure the strain in several points of the rail a relatively long, of length of few meters, measuring fiber was used. It causes problems with coherence of light passing through the fiber and hence the compensation of the birefringence was introduced.

Liquid crystalline fiber optic colorimeter for hydrostatic pressure measurement

This paper presents results of tests performed on a fiber optic system of liquid crystalline transducer for hydrostatic pressure monitoring based on properties of colorimetry. The system employs pressure-induced deformations occurring in liquid crystalline (LC) cells configured in a homogeneous Frederiks geometry. The sensor is compared of a round LC cell placed inside a specially designed pressure chamber. As a light source we used a typical diode operating at red wavelength and modulated using standard techniques. The pressure transducer was connected to a computer with a specially designed interface built on the bas of advanced ADAM modules. Results indicate that the system offers high response to pressure with reduced temperature sensitivity and, depending on the LC cell used, can be adjusted for monitoring of low hydrostatic pressures up to 6 MPa. These studies have demonstrated the feasibility of fiber optic liquid crystal colorimeter for hydrostatic pressure sensing specially dedicated to pipe- lines, mining instrumentation, and process-control technologies.

Polarimetric vortex flow investigation

The paper presents initial studies of potential application of polarimetric sensing in flow control by the effect of vortex shedding (vosh). Discussion on geometrical factors of the flow tube for arising of a turbulence and oversimplified analysis of the response of the high birefringent (Hi-Bi) fiber on the flow are presented. Some features of the polarimetric sensing of the fluid flow are exemplified.

Structural optical nonlinearity in chiral nematics

Interaction of intense laser light with chiral nematic structure was examined by use of a reflected-probe-beam experimental technique. The technique is sensitive to structural changes in periodic media and appears to be as valuable for chiral nematics (CHNs) investigation as roentgenographic diffraction for crystal lattices. The probe-beam reflexes for various pitch-to-pump-laser- wavelength ratio including the selective reflection region, various glancing angles of the probe beam, and various CHN- layer thicknesses are presented. In the experiment a great care was taken to distinguish optical nonlinearity of the collective nature from that of thermal or photochemical origin. The results we have obtained point out the optical field-CHN structure coupling rather than the non-collective mechanism of observed effects.