RSoft Application Gallery Note: Coherent PM-QPSK versus RZ-DQPSK and DPSK for high bitrate systems

Tool Used: OptSim

This example shows that coherent PM-QPSK offers a 2 dB sensitivity improvement over RZ-DQPSK and 1.3 dB improvement over DPSK systems.

The figure below depicts the layout for coherent PM-QPSK:

layout for coherent PM-QPSK

The figure below depicts the layout for RZ-DQPSK:

layout for RZ-DQPSK

The figure below depicts the layout for DPSK:

layout for DPSK

The figure below compares OSNR sensitivites of coherent and non-coherent systems as above. As can be seen, coherent PM-QPSK offers a 2 dB sensitivity improvement over RZ-DQPSK and hence can be a viable solution for high bitrate systems.

OSNR sensitivites of coherent and non-coherent systems