In QPSK modulation, the bit stream of the signal to be transmitted (PCM signal) is previously sampled and decomposed into two binary waves (dibits).

In this paper, the authors are implemented BPSK modulation technique, a subsystem module of digital communication using reversible logic. Later on they have implemented a QPSK modulation technique ...

The QPSK modulation provides double data rate than the BPSK modulation technique. The certain impairments associated with the FSO system are also studied in this paper.

Conclusion A coherent lightwave signal analyzer allows engineers to understand and optimize optical networks that use advanced modulation such as DP-QPSK.