Cezary Kaczmarek

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.

Fiber Bragg grating differential strain sensor

In the paper a parametric, fiber optic strain sensor with Bragg gratings, in a differential scheme is described. The possibility of compensating the effect of temperature on the accuracy of the strain processing is shown.

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.

Nonlinear propagation of various shape ultrashort pulses in a linearly birefringent single mode optical fiber. Numerical analysis

The results of numerical calculations of propagation of ultrashort hyperbolic secant, Gaussian and super Gaussian pusles in a linearly birefringent single mode fiber with input the polarization angle θ=15° and θ=30° are presented. From the performed calculations it follows, that the threshold amplitude of the initial pulse Ath, after exceeding of which the soliton trapping effect occurs, depends on the shape of the initial pulse and is lowest for the hyperbolic secant pulse and highest for the super Gaussian pulse in the entire range of the birefringence parameter 0.1 < δ < 1.0, with the notion that values of Ath are slightly lower when the polarization angle θ=15°. The calculation results also indicate, that the threshold value of the birefringence parameter δth, which designates the qualitatively different regions of soliton trapping, is dependent on the shape of the initial pulse as well. The highest value of δth was evaluated for the hyperbolic secant pulse, the lowest - for the super Gaussian pulse. The values of δth are very similar for input polarization angles θ=15° and θ=30° for each pulse.

Influence of the input pulse shape on the propagation of the pulse in a birefringent nonlinear optical fiber: unequal excitation of the polarization components

The results of numerical analysis of the influence of the initial pulse shape on the propagation of the pulses in a birefringent nonlinear single mode fiber for the case of unequal excitation of the polarization components are presented in the paper. The following shapes of the initial pulse were investigated: hyperbolic secant, Gaussian, super Gaussian, super Gaussian second order. The analysis was carried out by numerically solving a pair of coupled Nonlinear Schrodinger Equations using the Split Step Fourier Method. The calculations were performed for an optical fiber made of silica glass. The fiber attenuation was not taken into account.

Influence of the input pulse shape on the propagation of the pulse in a birefringent nonlinear single mode fiber

The results of numerical analysis of the influence of the initial pulse shape on the propagation of the pulses in a birefringent nonlinear single mode fiber are presented in the paper. The results are given in form of graphs of the input pulse threshold amplitude as a function of the fibers birefringence. The threshold amplitude is the input pulse amplitude at which the fiber nonlinearity compensates the birefringence and makes the partial pulses travel with the same velocity. The following shapes of the initial pulse were investigated: hyperbolic secant, Gaussian, super Gaussian, super Gaussian second order. The analysis was carried out by numerically solving a pair of coupled Nonlinear Schrodinger Equations using the Split Step Fourier Method. It was assumed that both orthogonal polarization components of the fiber were excited equally. The calculations were performed for an optical fiber made of silica glass. The fiber attenuation was not taken into account.

Soliton stability in a highly birefringent optical fiber different shapes of the initial pulse

In the paper the results of numerical analysis are presented of ultrashort pulse propagation in a highly birefringent optical fiber for hyperbolic secant, Gaussian and super Gaussian initial pulse. It is assumed that the initial pulse is polarized linearly and guided into the fiber at an angle of 45° to its polarization axes. The analysis was carried out by numerically solving a pair of coupled Nonlinear Schrodinger Equations using the Split Step Fourier Method. The calculations were performed for an optical fiber without attenuation.

Investigation of soliton stability in a highly birefringent optical fiber for the case of a Gaussian initial pulse

In the paper the results of numerical analysis are presented of ultrashort pulse propagation in a highly birefringent optical fiber for a Gaussian initial pulse. It is assumed that the initial pulse is polarized linearly and guided into the fiber at an angle of 45° to its polarization axes. The analysis was carried out by numerically solving a pair of coupled Nonlinear Schrodinger Equations using the Split Step Fourier Method. The calculations were performed for an optical fiber without attenuation.

The influence of the initial pulse amplitude on the stability of solitons in a highly birefringent optical fiber

In the paper the results of analysis are presented, of ultrashort pulse propagation in a highly birefringent optical fiber. For the description of soliton propagation the Coupled Nonlinear Schrodinger equations were applied, which were solved numerically using the Split-Step Fourier Method. The analysis was performed for a lossless optical fiber.

Soliton propagation in highly birefringent optical fibers

Numerical approach used to solve Coupled Nonlinear Schrodinger (CNLS) equations is considered. CNLS equations describe propagation of ultrashort optical pulses in highly birefringent nonlinear optical fiber. Numerical results for the case of equal excitement of both modes are presented.