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Optical diffraction tomography (ODT) applied to measurement of optical microelements is limited by low dynamic range, i.e., only objects with small deviations of refractive-index distribution can be measured. Therefore in this paper the limitations and errors of ODT are investigated throughout extensive numerical experiments. It is shown that these errors can be reduced by introduction of additional numerical focusing in the tomographic reconstruction algorithm. Additionally, new tomographic reconstruction algorithm using back propagation in reference medium for optical microelements measurement with known design is proposed. This hybrid reconstruction algorithm allows significant extension of ODT applicability in measurement of elements having large deviations of refractive-index distribution.

Microinterferometric tomography method for determination of 3D refractive index distribution in phase elements is described. . Applications ofthis method to measurement of gradient index fibers, fiber splices and single mode fiber are presented. Initial results ofholey fiber testing are given and future trends in development ofthis method ( applications to photonic structures ) are discussed.

In the paper we present method for three-dimensional measurement of birefringence distribution in photonics components. The tool we used in this work is automated digital photoelasticity combined with tomography, namely photoelastic tomography. Till now the photoelasticity procedures have been applied for objects with significant dimensions and therefore the diffraction phenomena could be neglected. In this paper we verify the correctness of this method for measurement of small objects. In order to identify this error we simulate the measurement process starting from integrated retardation determination and ending on 3D distribution evaluation. Computations are performed using full vectorial propagation method based on Maxwell-curl equations (finite difference time domain method FDTD). The results of simulations are compared with actual measurement results derived from physical setup. The result of experimental and numerical analysis allow optimizing the measurement setup and minimizing the errors. The correctness of the photoelastic tomography for analysis of microobjects has been proven on an example of birefringent optical fibers.

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