Can I use Cat6 ethernet cable to connect switches to Fibaro binary sensors
Cat6 is good for low-frequency signals too and especially with properly grounded shields using a 1nF cap to earth ground to shield termination prevent line ground loop noise if present.

RC snubbers can also improve signal noise rejection.

Interference near Triac dimmers or brushed motors are typical issues on long cables.
Ethernet cards use Common mode chokes and isolation transformer to improve signals.

Cat6 cables have designated pairs, so use those. Using parallel wires may extend the useful length due to lower inductance since this is high impedance and may improve signal integrity.

I think the 1 wire communication is rated for 30m if there is no extreme interference. Even then, a 330 Ohm + 0.01uF series snubber across the analog signal can suppress this noise.

The datasheet says...


  Do not connect other sensors than DS18B20 to the 1-wire line (terminals TP and TD).
  It is prohibited to connect the TP and TD lines to devices that are not compatible with the 1-wire protocol. Unused lines should be left insulated.
  Use conductors made from a single wire with a length of up to 30 meters in order to connect the DS18B20 sensors