The cost of using WDM to expand local area optical network is analyzed. In the case of shorter distances between the loop nodes
the cost of network expansion through WDM isn’t be less than that of expansion through installation of new cables. But with fixed distances between nodes
the cost will decrease with the increase of number of optical paths.In addition
it will be difficult to save cost if the price of WDM equipments can’t decrease simultaneously with that of optical cables.