I don't understand if the OOK IMDD VLC use only modulated signal and not the carrier signal.
for example: if i have a LED with flashing frequencies of 10Mhz i don't use a carrier signal to translate frequencies to high value. Is this phrase correct?
If the previous is correct, why i don't use carrier?
On off keying is indeed intensity modulation. There is no modulated carrier. There is instead a lot of incoherent light, and all you care about is the aggregate intensity.
Why not use a carrier? You can, but for that you will need a coherent light source, such as laser. With laser, you can pretty much use the same techniques as you use in RF modulation schemes. But if you have an incoherent light source such as LED, intensity modulation is your best bet.
Light has its own frequency, which you can use as a carrier. But it is impossible to do if the light source is incoherent because you will get mixed readings.