We present a dual-channel inline coherent imaging system for laser machining monitoring using a single spectrometer. Sensitivity enhancement due to the added signal of the two input channels is demonstrated with a maximum sensitivity of 99 dB at a 73 kHz acquisition rate. We also treat, theoretically and experimentally, dual-channel detection in the case of signal saturation. A method to mitigate saturation artifacts while maintaining high signal-to-noise ratio is shown.