Phase regeneration of phase encoded signals by hybrid optical phase squeezer

All-optical regenerator of multi-channel signals

One of the main reasons why nonlinear-optical signal processing (regeneration, logic, etc.) has not yet become a practical alternative to electronic processing is that the all-optical elements with nonlinear input–output relationship have remained inherently single-channel devices (just like their electronic counterparts) and, hence, cannot fully utilise the parallel processing potential of optical fibres and amplifiers. The nonlinear input–output transfer function requires strong optical nonlinearity, e.g. self-phase modulation, which, for fundamental reasons, is always accompanied by cross-phase modulation and four-wave mixing. In processing multiple wavelength-division-multiplexing channels, large cross-phase modulation and four-wave mixing crosstalks among the channels destroy signal quality. Here we describe a solution to this problem: an optical signal processor employing a group-delay-managed nonlinear medium where strong self-phase modulation is achieved without such nonlinear crosstalk. We demonstrate, for the first time to our knowledge, simultaneous all-optical regeneration of up to 16 wavelength-division-multiplexing channels by one device. This multi-channel concept can be extended to other nonlinear-optical processing schemes.

Nonlinear optical processing devices are not yet fully practical as they are single channel. Here the authors demonstrate all-optical regeneration of up to 16 channels by one device, employing a group-delay-managed nonlinear medium where strong self-phase modulation is achieved without nonlinear inter-channel crosstalk.

Optimization of a degenerate dual-pump phase-sensitive optical parametric amplifier for all-optical regenerative functionality

We present a thorough investigation aimed at the optimization of a phase-sensitive optical parametric amplifier capable of simultaneous phase and amplitude regeneration. The regeneration potential, quantified in terms of the phase-sensitive extinction ratio, has been carefully assessed by a scalar model involving high-order waves associated with high-order four-wave mixing processes, going beyond the usual three-wave approach. Additionally, this model permits to unveil the physics involved in the high-order waves assisted regeneration. This permits a multi-dimensional and comprehensive optimization that fully exploits the underlying regenerative capability and expedites the design of a transparent regenerator, showing the potential to act as basic building block in future all-optical processing. We also compare different strategies when such regenerators are configured in concatenation. The approach can be readily applied to virtually any similar applications for different all-optical processing functionalities.

Experimental demonstration of phase-sensitive regeneration of a binary phase-shift keying channel without a phase-locked loop using Brillouin amplification

All-optical phase regeneration of a binary phase-shift keying signal is demonstrated at 10-30 Gb/s without a phase-locked loop in a phase-sensitive amplification-based system using Brillouin amplification of the idler. The system achieves phase noise reduction of up to 56% and up to 11 dB OSNR gain at 10^-5 bit error rate for the 10 Gb/s signal. The system's sensitivity to different parameters and stability is also evaluated.

Signal phase regeneration through multiple wave coherent addition enabled by hybrid optical phase squeezer

A newly proposed concept, which is called hybrid optical phase squeezer (HOPS), achieves multi-level optical phase quantization through coherent addition of two (dual-wave scheme) or three (triple-wave scheme) optical waves exploiting optical parametric processes and electro-optic modulation. The triple-wave scheme enables signal phase regeneration free from phase-to-amplitude noise transfer, which is inevitable in the dual-wave scheme. By using HOPS in the dual-wave scheme, 3-fold phase-noise reduction was achieved for 24-Gb/s QPSK signals with a slight increase of amplitude noise. On the other hand, HOPS in the triple-wave scheme allowed phase regeneration of 12-Gb/s BPSK signal with a suppression of phase-to-amplitude noise transfer.