I have a problem with the ray tracing in a CAD object.

The structure I want to simulate is a spire plastic optical fiber, as the one depicted in the image below. As I don’t know how to generate this object in Zemax (is it posible?), I designed it in SolidWorks, both cladding and core. However, in such a closed loop (2mm radius), there is no light propagation, and I achieve a high transmission. In order to verificate, the simulation is incorrect I put all the structure in a rectangular volume of the same refractive index as the cladding (1.4). In consequence, when the light escapes core and reach cladding, total internal reflection should no occur. The ray should be propagated to the volumen, as there is no RI difference. In the image below, it can be seen it does not happen as predicted.

I suppose the problem is related with the render of the 3D object, but is there any solution to this?

Thank you in advance.