We present a spectrum broadening technique to improve the signal-to-noise ratio of spectrum sliced incoherent light sources using the fiber four-wave mixing effect which occurs in a nonlinear loop mirror located at the receiver. The initial transmission channel bandwidth of 0.92 nm was increased to 1.62 nm in the nonlinear loop mirror at the optical receiver, which enhances the signal-to-noise ratio to a desired value. Using this technique, we have demonstrated the transmission of a 2.5 Gb/s NRZ signal with the 0.92 nm bandwidth through a 80 km dispersion-shifted fiber. The measured transmission penalty was less than 0.2 dB at $1{imes}10^{-10}$ BER.