An optical receiver for use in an Optical Network (ON) such as a WPON based on an SCMA scheme. The optical receiver apparatus for use in a Central Office contained in an ON includes: an optical power divider for dividing an input optical signal into first and second optical signals; a frequency generator for generating a oscillation frequency; a phase shifter for shifting a phase of the oscillation frequency; a first optical modulator for modulating the first optical signal with the oscillation frequency; a second optical modulator for modulating the second optical signal with the oscillation frequency phase-shifted; a first photodiode for converting the optical signal modulated by the first optical modulator into a first RF signal; a second photodiode for converting the optical signal modulated by the second optical modulator into a second RF signal; and a differential amplifier for differentially amplifying the first RF signal and the second RF signal.