We present an analytical tool to enhance the blocking performance in the circuit-switched wide-area optical wavelength division multiplexed (WDM) networks with no wavelength conversion at the nodes. Given any network of arbitrary topology, the aim is to see if one can achieve the wavelength conversion (optimal) performance by using wavelength reassignment techniques in no conversion networks. If there is significant performance deviation, the tool identifies the critical points in the network which prevents the reassignment to totally remove wavelength continuity constraint (wcc) blocking. Once the critical points are identified, the tool appropriately modifies the routing such that the wavelength reassignment can achieve the optimal performance. © 2007 IEEE.