Using an ytterbium-doped fiber optic amplifier, we have improved the signal-to-noise ratio (SNR) of a terahertz (THz) pulse detection obtained by upconversion to an infrared (NIR) signal in a nonlinear lithium niobate crystal. This demonstration was carried out with a THz transmitter using a photoconductive antenna (PCA) and a femtosemcond laser oscillator. The geometrical separation between the signal and the optical pump easily enables unique amplification of the NIR signal to achieve an order-of-magnitude improvement in SNR.