Q: Is there a way to extend this distance to 100 meters ?
A: No, there is not a way to extend the CLink2 interface more than what is documented in the HDX Integrator's Guide.
Q: Does anyone know why there is such a limitation (audio attenuation, power supply for the mic, other ...) ?
A: The Clink2 interface is a digital communications interface and the reliablity of the communications is not acceptable beyond the documented distances.
Q: Does anyone know the kind of signal transmitted for Audio from Polycom mic ?
A: Answered above.
Q:Is there another solution (like with repeater or other) than cables only, to integrate microphone with HDX over such a distance that were already implemented ?
A: The solutions would be to used analog micorphones and run them back to the SoundStructure co-located with the HDX and to use the CLink2 between the SoundStructure and the HDX.