QPSK is widely used as a modulation technique in RF and wireless communication. DP-QPSK, on the other hand, is used in optical communication to represent laser output into symbols for transmission, aiming to reduce bandwidth in information transmission. This article breaks down what DP-QPSK is, why it's so crucial, and how it powers the optical. QPSK stands for Quadrature Phase Shift Keying, while DP-QPSK stands for Dual Polarization Quadrature Phase Shift Keying. 2 specifications are separated into three parts: ◦ Optical interface specification @ single-channel Tx output. ◦ The DWDM network in between Tx and Rx, containing optical multiplexers & demultiplexers, optical amplifier(s), single-mode optical fibres and OADMs. Interfaces with popular design tools.