Experimental analysis of phase conjugation properties of four-wave mixing in an SOA after probe broadening due to fibre dispersion

Experimental results are presented which analyze the phase conjugation properties of four-wave mixing signals generated due to the beating between probe pulses broadened by a length of fibre and narrow pump pulses. This results in four-wave mixing pulses significantly narrower than the injected probe pulses albeit with reduced phase conjugation properties, which are examined. The pulses are completely characterized using the second-harmonic generation frequency resolved optical gating technique. The probe pulse is initially broadened due to propagation through 40 in of dispersion compensating fibre. This causes the probe pulse to be much wider than the injected pump pulse, in contrast to previously reported results. The four-wave mixing signal is therefore both wavelength converted and compressed, due to the gating properties of four-wave mixing, with respect to the initial probe signal. The phase conjugation properties of the converted signal are discussed and this signal is then passed through a second length of dispersion compensating fibre in order to further compress the pulse and to examine in more detail the phase conjugation properties. (C) 2007 Elsevier B.V. All rights reserved.