We successfully improved the output characteristics of a hybrid broadband light source consisting of a cascaded super luminescent diode (SLD) and a Tm3+-doped fiber amplifier (TDFA), which we propose as a candidate 1.7 ∼ 1.8 µm band light source. The achieved bandwidth where the intensity exceeded −40 dBm/0.1 nm was 325 nm (from 1577 to 1902 nm), and the total output power was 16 dBm with a low ripple and a peak-to-peak value of less than 0.14 dB.