This paper addresses the problem of efficient communication in unreliable multi-hop optical networks supported by Wavelength Division Multiplexing (WDM). We first define a new cost model for routing in (optical) WDM networks that is more general and realistic than the existing models. Our model takes into consideration not only the cost of wavelength access and conversion but also the cost for wavelength switching when several optical channels of the same wavelength arriving at the same node. We then propose a set of efficient algorithms in both reliable and unreliable WDM networks on the new cost model respectively for each of three important communication patterns --- multiple point-to-point routing, multicast and multiple multicast.