An optical detection apparatus comprising: a first optical splitting unit configured to split a seed lightwave, and configured to output the seed lightwave split by the first optical splitting unit to an optical network unit and a second optical splitting unit; the second optical splitting unit configured to split the seed lightwave inputted by the first optical splitting unit, and configured to output the seed lightwave split by the second optical splitting unit to an optical coupling and signal conversion unit (212, 215, 218) and a signal detection unit; a third optical splitting unit configured to split upward signal light transmitted from the optical network unit, based on the seed lightwave, and configured to output the split upward signal light to the optical coupling and signal conversion unit and the signal detection unit; a first control unit configured to control polarizations of the split seed lightwaves based on a first electrical signal; a second control unit configured to control phases of the split seed lightwaves based on a second electrical signal; the optical coupling and signal conversion unit configured to couple the seed lightwaves, of which the polarization and phase are controlled, and the split upward signal light, convert the coupled optical signals into the first and second electrical signals, and transfer the first and second electrical signals to the first and second control units, respectively; and the signal detection unit configured to couple the seed lightwave, of which the polarization and phase are controlled, and the split upward signal light, convert the coupled signals into an optical signal, and detect an upward signal corresponding to the upward signal light. a first optical splitting unit configured to split a seed lightwave, and configured to output the seed lightwave split by the first optical splitting unit to an optical network unit and a second optical splitting unit; the second optical splitting unit configured to split the seed lightwave inputted by the first optical splitting unit, and configured to output the seed lightwave split by the second optical splitting unit to an optical coupling and signal conversion unit (212, 215, 218) and a signal detection unit; a third optical splitting unit configured to split upward signal light transmitted from the optical network unit, based on the seed lightwave, and configured to output the split upward signal light to the optical coupling and signal conversion unit and the signal detection unit; a first control unit configured to control polarizations of the split seed lightwaves based on a first electrical signal; a second control unit configured to control phases of the split seed lightwaves based on a second electrical signal; the optical coupling and signal conversion unit configured to couple the seed lightwaves, of which the polarization and phase are controlled, and the split upward signal light, convert the coupled optical signals into the first and second electrical signals, and transfer the first and second electrical signals to the first and second control units, respectively; and the signal detection unit configured to couple the seed lightwave, of which the polarization and phase are controlled, and the split upward signal light, convert the coupled signals into an optical signal, and detect an upward signal corresponding to the upward signal light.