The fourth-order pulse amplitude modulation signal requires high linearity and a small dispersion tolerance in an optoelectronic device. The bandwidth limitation of the 10G-class optics device severely degrades system performance. This study describes a 50 Gbit/s non-return zero (NRZ) signal transmission scheme using commercial 25G-class optical components. Herein, for a back-to-back and 25-km standard single-mode fiber transmission, the maximum likelihood sequence estimation and decision feedback equalization based on the least mean square algorithm are used for decoding. A comparison of the bit error rate performances under different received optical power conditions proves that the 50 Gbit/s NRZ signal transmission based on the 25G-class optics device can act as a single-wavelength 50 Gbit/s candidate solution.