Abstract
Wavelength conversion is a key WDM function which is used to avoid wavelength blocking, thus allowing greater flexibility in the network design. Wavelength conversion of an intensity modulated signal can be simply achieved by employing cross-phase modulation (XPM) on a CW beam placed at the desired wavelength, normally followed by a band-pass filter and a narrowband notch filter to reject the pump and the carrier frequency respectively. The notch filter in particular has to be precisely tuned to the CW wavelength and be extremely narrowband in order to avoid any distortions on the spectral envelope of the converted signal (see e.g. [1]). This extra complexity could be avoided using conventional band-pass filters only to select a single sub-carrier band, but this usually implies non optimal CW extinction and thus some extra power penalties as compared to the original signal. In this paper we investigate the use of pulse shaping of the signal to be converted into a saw-tooth waveform (i.e. a pulse with leading/trailing edges of a constant intensity gradient), to improve the performance of the converted signal. Due to their linear gradient, when saw-tooth pulses are used as the XPM pump, they induce a constant frequency shift to the signal [2, 3]. These new frequency components are highly spectrally confined and discretely separated from the CW carrier, thus allowing most of the wavelength converted signal energy to pass through the subsequent offset filters, thereby improving the overall optical signal to noise ratio (OSNR) and the overall system performance. Similarly, self-phase modulation (SPM) of saw-tooth pulses is more confined, giving more flexibility on the choice of the pump and signal wavelength allocations.
© 2009 IEEE
PDF ArticleMore Like This
Ken Kashiwagi, Azusa Hasegawa, and Takashi Kurokawa
NW3A.2 Nonlinear Optics (NLO) 2013
Ken Kashiwagi
JTh2A.25 CLEO: Applications and Technology (CLEO:A&T) 2014
Ken Kashiwagi, Azusa Hasegawa, and Takashi Kurokawa
CTh4H.7 CLEO: Science and Innovations (CLEO:S&I) 2013