Demonstration of optical de-aggregation of a single 10-Gbit/s QPSK signal to two 5-Gbit/s OOK signals using nonlinear wave mixing and constellation biasing.

Optical data format de-aggregation enables the conversion from a single higher-order phase-encoded data channel coming from a high-bandwidth network into two amplitude-modulated signals that may be commonly used in lower-bandwidth local information systems. We experimentally demonstrate the optical de-aggregation of a 10-Gbit/s quadrature phase-shift keyed (QPSK) signal into two 5-Gbit/s on-off keyed (OOK) signals. Using wave mixing in a highly nonlinear fiber (HNLF), we apply two optical effects simultaneously to the input signal: (a) constellation squeezing, in which the 10-Gbit/s QPSK signal is de-aggregated into two different 5-Gbit/s binary phase-shift keying (BPSK) signals, and (b) constellation biasing, in which the coherent addition of a continuous-wave (CW) bias and the two BPSK signals shifts the data constellation points, resulting in only amplitude modulation and two different 5-Gbit/s OOK signals.

Demonstration of an 8-Gbit/s quadrature-phase-shift-keying coherent underwater wireless optical communication link using coherent heterodyne detection under scattering conditions.

In this paper, we experimentally demonstrate an 8-Gbit/s quadrature-phase-shift-keying (QPSK) coherent underwater wireless optical communication (UWOC) link under scattering conditions at 532 nm. At the transmitter, we generate the 532-nm QPSK signal using second-harmonic generation (SHG), where the 1064-nm signal modulated with four phase levels of an 8-phase-shift-keying (8-PSK) format is phase doubled to produce the 532-nm QPSK signal. To enhance the receiver sensitivity, we utilize a local oscillator (LO) at the receiver from an independent laser source.