Most studies about Optical Burst Switched (OBS) networks have assumed availability of full wavelength conversion throughout the network. In an optical network with full wavelength conversion capability, every output on each node is provided with a wavelength converter, resulting in the lowest bound for blocking probability. However, full wavelength conversion capability requires a large number of wavelength converters, which is, and will remain, quite expensive in the foreseeable future. Therefore, it is expected that conversion capability will be limited and only sparsely deployed. In this work we apply to OBS networks the main architectures for wavelength conversion proposed for circuit switched networks. These architectures operate with limited wavelength conversion capability. We also investigate the cost benefit and the gain factor related to full complete wavelength conversion for each architecture. In addition, we propose a new methodology to define the number of wavelength converters in order to achieve the best cost benefit, regardless of the traffic load. ©2008 IEEE. 939942Qiao, C., Yoo, M., Optical burst switching (OBS) - a new paradigm for an optical internet (1999) Journal of High Speed Networks, 8 (1), pp. 69-84Teng, J., Rouskas, G.N., A detailed analysis and performance comparison of wavelength reservation schemes for optical burst switched networks (2005) Photonic Network Communication, 9 (3), pp. 311-335Rosberg, Z., Le, H., Zukerman, M., White, J., Performance analysis of optical burst-switching networks IEEE Journal on Selected Areas in Communications, 21 (7)Dolzer, K., Gauger, C., Sp̈ath, J., Bodamer, S., Evaluation of reservation mechanisms for optical burst switching (2001) International Journal of Electronics ans Communications, 55 (1)Lee, K.-C. and Li, V. . K. (1993). A wavelength-convertible network. Journal of Lightwave Technology, 11(5/6):962-970Soares, A., Maranhão, J., Giozza, W., Cunha, P., Wavelength converter placement scheme for optical network with sparse-partial wavelength conversion capability (2006) 13th International Conference on TelecommunicationsXi, K., Arakawa, S., Murata, M., (2005) How many wavelength converters do we need? Optical Network Design and Modeling, 2005, pp. 347-358Wei, J.Y., McFarland, R.I., Just-in-time signaling for wdm optical burst (2000) Journal of Lightwave Technology, 18 (12)