We report on the transmission over a wide frequency range (from the far infrared through the visible) ofudpristine and hole-doped, free-standing carbon nanotube films at temperatures between 50 and 300 K. Opticaludconstants are estimated by Kramers-Kronig analysis of the transmittance. We see evidence in the far infraredudfor a gap below 10 meV. Hole doping causes a shift of spectral weight from the first interband transition intoudthe far infrared. Temperature dependence in both the doped and undoped samples is restricted to the farinfraredudregion.
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