SOA-based, idler-free phase quantiser

Energy consumption, system complexity and potential for integration are important factors when considering the suitability of all-optical processing, and depend upon both the scheme used and the medium in which it is performed. We have recently proposed a simple, wavelength-converting phase quantising scheme based on an idler-free phase-sensitive amplifier, notable for its flexibility of operating power and relative compactness [1]. We have demonstrated its performance for QPSK regeneration using an operating power of 24 dBm in 300 m of highly nonlinear fibre (HNLF). Despite offering low loss and high net nonlinearity, the size and geometry of the HNLF do not make it suitable for integration in a photonic device. Semiconductor optical amplifiers (SOAs) on the other hand, offer a particularly compact medium for nonlinear signal processing, combining an amplifier and nonlinear medium in one device. BPSK phase regeneration has been demonstrated in SOAs [2]; in this paper we experimentally demonstrate, to our knowledge, the first realisation of QPSK phase regeneration in SOAs, making use of the above idler-free scheme to realise a compact and more easily integrated QPSK regenerator