OOK to QPSK modulation format conversion based on two gain transparent SOAs

In this paper, the system scheme of on–off keying (OOK) to quadrature phase-shift keying (QPSK) format conversion is proposed, which is based on two gain-transparent semiconductor optical amplifiers (GTSOA). GT-SOA is used as a simple all-optical phase modulator, which is no effects of cross g