A transceiver unit (140, 150) for receiving an optical input signal and transmitting an amplitude modulated optical output signal and, comprising: a first coupler configured to power split said optical input signal comprising a modulated optical signal and an unmodulated optical signal to a receiver and to a second coupler, said receiver being configured to convert said modulated optical signal and an said unmodulated optical signal to an electrical output signal; said second coupler being configured to split said optical input signal from said first coupler to a first Semiconductor Optical Amplifier, SOA, and a second SOA, said first SOA being configured to saturation to erase amplitude modulation of the optical input signal; said transceiver unit (140, 150) further comprising phase modulation means connected to said first SOA configured to phase modulate a first saturated optical input signal from said first SOA based on data information to be transferred; first reflection means connected to the phase modulation means configured to reflect a phase modulated first saturated optical input signal from the phase modulation means back into said phase modulation means; said second SOA being configured to saturation to erase amplitude modulation of the optical input signal from the second coupler; said transceiver unit (140, 150) further comprising; second reflection means connected to said second SOA configured to reflect a second saturated optical input signal from the second SOA back into said second SOA, said second SOA being further configured to further erase amplitude modulation of said second saturated optical input signal, and said first SOA being further configured to further erase amplitude modulation of the phase modulated first saturated optical input signal; said second coupler being yet further configured to create the amplitude modulated optical output signal by adding a first output signal from said first SOA and a second output signal from the second SOA. a first coupler configured to power split said optical input signal comprising a modulated optical signal and an unmodulated optical signal to a receiver and to a second coupler, said receiver being configured to convert said modulated optical signal and an said unmodulated optical signal to an electrical output signal; said second coupler being configured to split said optical input signal from said first coupler to a first Semiconductor Optical Amplifier, SOA, and a second SOA, said first SOA being configured to saturation to erase amplitude modulation of the optical input signal; said transceiver unit (140, 150) further comprising phase modulation means connected to said first SOA configured to phase modulate a first saturated optical input signal from said first SOA based on data information to be transferred; first reflection means connected to the phase modulation means configured to reflect a phase modulated first saturated optical input signal from the phase modulation means back into said phase modulation means; said second SOA being configured to saturation to erase amplitude modulation of the optical input signal from the second coupler; said transceiver unit (140, 150) further comprising; second reflection means connected to said second SOA configured to reflect a second saturated optical input signal from the second SOA back into said second SOA, said second SOA being further configured to further erase amplitude modulation of said second saturated optical input signal, and said first SOA being further configured to further erase amplitude modulation of the phase modulated first saturated optical input signal; said second coupler being yet further configured to create the amplitude modulated optical output signal by adding a first output signal from said first SOA and a second output signal from the second SOA.