Distributed optical fiber sensors by using Brillouin optical time-domain analysis (BOTDA) have been developed extensively by many researchers. Coding pulsed pump light of the BOTDA is an effective way to improve the signal-to-noise ratio (SNR). This article reports a new way to configure electrical signals that are amplified by an AC-coupled highspeed amplifier and then fed into an electro-optic modulator to generate coded pump light. The new configuration caused little distortion of the amplified electrical signals and consequently produced coded pump light with a good waveform with the modulator. The optical SNR of the coded BOTDA signals achieved by the new configuration was about 1dB better than that by a conventional way for 32 bit-length code.