Abstract: A PAM4 signal generation apparatus is provided. The PAM4 signal generation apparatus includes a DFB, two EA modulators, an SOA, a PSR, a direct-current power source, two electrical-signal generators, and two amplitude-limiting amplifiers. The two electrical-signal generators and the two amplitude-limiting amplifiers are used to generate two NRZ electrical signals respectively, the DFB outputs two optical signals, the SOA amplifies an optical power of one of the optical signals, the two EA modulators use the NRZ electrical signals and the optical signals including “a large signal and a small signal” respectively to generate two NRZ optical signals respectively, and the two NRZ optical signals are multiplexed by the PSR to generate a PAM4 electrical signal. According to this apparatus, a linearity requirement is greatly lowered. PAM4 modulation is performed in an optical domain, and this prevents a PAM4 signal from being generated on an electrical signal.