In this paper, the coupling between circular parallel dielectric waveguides of unequal radii and of different permittivities is analyzed with various coupling criteria such as the coupling coefficient, the transmitted power and the supermodes propagation coefficients. A method due to Arnaud is used to evaluate the coupling coefficient because it is simple and tractable. The results we have obtained have been found to be in good agreement with those obtained by other authors. Graphs of the coupling have been given as a function of the normalized frequency and as a function of the permittivity for equal and for unequal radii. Physical interpretations have been proposed for same results.

A method devised by Arnaud for evaluating the coupling between two parallel dielectric waveguides has been extended to an arbitrary number of guides. Expressions for the propagation coefficients of the system have been found and calculated numerically for six identical guides uniformly distributed in a circular structure with and without a central core. A good measure of agreement has been found between the results obtained by this method and those obtained by other methods. This method is simple because it requires the evaluation of a line integral outside the guides, instead of a surface integral over their cross-section, as in most other methods. It is general because it applies to any configuration, any geometry and any refractive index of the guides, provided their fields can be calculated.

The coupling between two parallel identical circular open chirowaveguides has been investigated. The coupling coefficient has been evaluated and its variation with different parameters such as chirality admittance, normalized frequency, relative permittivity and normalized separation has been studied. It has been found that the coupling variation with chirality or frequency presents a peak. Increasing the chirality admittance enhances the peaks of the coupling which occur at lower and lower frequencies with smaller and smaller bandwidths. These characteristics seem to point out that the chirowaveguides have more flexibility and are more advantageous than their dielectric counterparts.

A method devised by Arnaud to evaluate the transverse coupling between dielectric waveguides has been successfully applied with a step-like approximation to two skew rectangular dielectric waveguides lying in different parallel layers, and tractable analytical expressions, which can be very useful in the analysis and the design of the waveguides, have been obtained. The mode power along one of the guides when the other is excited has been calculated and the results compared with experimental results appearing in the literature. The agreement is in general quite satisfactory.