Zdzislaw Kaczmarek

Fiber Bragg grating impulsive pressure sensor

A new impulsive pressure sensor based on the elastic bar, is presented in this paper. As the elastic bar a piece of single mode optical fiber with photo-inscribed Bragg gratings is used. The grating is an optical strain gauge that converts the stress waves in the fiber into the changes of the Bragg wavelength. Experimental setup for the proposed sensor is demonstrated. The sensor was used to measure the pressure produced by an electric discharge in water.

Modified fiber Bragg grating pulse pressure sensor

A new fiber optic, pulse pressure sensor with a Bragg grating, in the structure of which the operating principle of the Hopkinson bar is applied, is presented in the paper. The delivery of the measured pressure to the sensor is realized by means of a measuring head with truncated cone, made of silica glass and fusion-spliced to the gratings fiber. The optical and the electronic setup of the sensor is given. The sensor was employed to measure pulse pressure generated by an electric discharge in water. The obtained measurement results and the conclusions arising from them are presented.

Optical wavelength discriminator with an apodized, uniform fiber Bragg grating

In the paper the results of simulation and experimental investigation are presented of an optical frequency discriminator with an apodized, fiber Bragg grating of a constant period, cooperating with an identical grating of the sensor. Assuming the nonlinearity of the discriminators conversion characteristic not greater than 1%, a conversion range of 0.30 nm was achieved, for gratings with a 3 dB bandwidth of 0.45 nm. Discriminators of such a type can be useful in many problems of dynamic measurements of mechanical quantities. Their certain inconvenience is the necessity of using an optical circulator, which is more expensive than a fiber optic coupler.

Work of fiber Bragg grating with linear changeable period as an impulsive strain transducer

The article presents the influence of the length of fiber Bragg grating with linear changeable period on processing accuracy of impulsive excitations acting along the longitudinal fiber axis. Using transfer matrix method the power reflectivity spectrums caused by impulsive strains are obtained. On this basis, assuming that gratings output signal is of centroidal frequency, the mean square error was evaluated as a function of the ratio of the length of the grating to the length of impulse, for different shapes of impulsive strains.

A modified impulsive force and pressure sensor intended for waveform reconstruction purposes

The correction of the effect of dispersion on the accuracy of processing in a Hopkinson bar type mechanical transducer enables extension of its application in measurements of impulsive force and pressure of short duration onto the dispersive operating range. In the experimental methods of correction two point processing of the strain inside the bar is usually applied. This way the dispersive characteristic of the bar is determined, and also the process of reconstructing waveforms is carried out. In the paper a sensor of impulsive force and pressure with one-point processing of the strain inside the bar is presented, in which the incident wave as well as the first reflected one, generated by the input function are utilised. Temporal restrictions of the input function and spatial restrictions of mounting strain gauges on the bar, preventing the superposition of the incident and the first reflected pulses in the strain gauges are given. The non-superposition of these pulses is the condition of the sensor functioning correctly. The way to use the sensor in a transformation reconstruction method of impact force waveform, is demonstrated. The advantage of the described sensor is the reduction in the complexity of the amplification circuit and the output signal processing circuit and also the improved processing accuracy.

Elastic Bar Transfer Function Determination Using Two-Point Strain Measurements

This paper presents an experimental method of determining the elastic bars transfer functions in the form of formulas. The method is based on the two-point measurement of the elastic strain waves propagating inside the bar, the spectral analysis of these waves, and making use of the general solution of the equation of movement of the bar in the frequency domain. The determined transfer functions of the bar are used for impulsive strain waveform reconstruction by means of deconvolution in the frequency domain and for the validity check of the reconstruction. The application of this method to the reconstruction of impact pressure waveforms is presented.

Polarimetric fiber optic strain sensor

In the paper a polarimetric fiber optic strain sensor is presented, built with the use of a polarization maintaining optical fiber. The sensor was constructed in two version without compensation and with the compensation of the ambient temperature. Results of the test trials are given for both versions of the sensor.

Sensor systems for equipment for determination of stochastic electromagnetic field

A sensor system for equipment used for the determination of stochastic electromagnetic field parameters is considered. The system is intended for underwater electromagnetic probing on the sea shelf. New highly sensitive induction sensors elaborated for this purpose are described. A new procedure for determining the orientation of sensors at the sea bottom is proposed.