Field demonstration of in-line all-optical wavelength conversion in a WDM dispersion managed 40-Gbit/s link

The development of WDM all-optical transport networks is an interesting solution to increase the capacity of long-haul transmission systems and to solve the route-exhaust problems of metropolitan networks, driving down the cost of that traffic. Routing can be achieved using a transparent device able to select and interchange wavelengths, such as an all-optical wavelength converter. In this letter an optical transport network over an embedded link located between Rome and Pomezia in Italy is emulated. The transmission has been realized along a WDM, 5x100 km long, dispersion managed link at 40 Gb/s. The in-line rerouting process has been controlled by means of an all-optical wavelength converter realized with a periodically poled lithium niobate waveguide. Moreover, a polarization-independent scheme for the converter has been exploited to allow the in-line signal processing. This scheme is based on the counter-propagation of TE and TM signal components along the same guide and results extremely compact. In the paper is demonstrated that wavelength conversion and rerouting add no penalty with respect to the simple transmission along the embedded cable. This result seems to be another step toward the feasibility of true all-optical networks.