An optical conversion node scheme for direct detection of complex modulation format is proposed to bridge long-haul transmissions and short-reach interconnects. A noisy 10G Baud quadrature phase shift keying signal is converted into a 10G Baud normal 4-level pulse amplitude modulation (PAM4) signal by the node. The conversion node is realized mainly relies on four-wave mixing-based phase-sensitive amplifiers. The power ratio and constellation shape of the converted PAM4 both can be flexibly designed based on network demands and five kinds of uniform or non-uniform PAM4s are generated to verify the shaping functionality. With the input optical signal-to-noise ratio range of (10 dB∼30 dB), the key indicators of the signals went through every part are measured, includes constellations, eye diagrams, error vector magnitudes, bit error rates, normalized impact factors of phase and amplitude. The proposed node scheme has great application potential in intermediate nodes for bridging long-haul transmissions and short-reach interconnects, hierarchical modulation and flexible constellations design for advanced format signals.