The essence of OPSK modulation is to select four possible values on the phase of the optical field so as to reduce the baud rate of the optical signal by half without reducing the line rate. This…

The essence of OPSK modulation is to select four possible values on the phase of the optical field so as to reduce the baud rate of the optical signal by half without reducing the line rate. This multiplexing method can reduce the spectral bandwidth of the optical signal by half, making multi- wavelength ULH transmission with 50GH interval and 40G line rate possible.