This article describes a significant advancement in the design of fiber-coupled THz time-domain spectrometers using an Er-doped fiber laser with 70 mW average output power and 45 fs pulse duration, and a Fe-doped InGaAs THz emitter with a 50 µm photoconductive gap to prevent saturation of the THz emission. Based on these improvements, the THz emitter delivers up to 958 µW radiated THz power at 60 kV/cm bias field and 56.5 mW excitation power, enabling a record-breaking dynamic range of 137 dB, with up to 117 dB in 60 s acquisition time.