Availability of wavelength resource in backbone transport network of Indonesian telecom nowadays is the most critical issue. This coused by role of wavelength to transmit data frome one to other node. Moreover, that reasons supported from current condition of backbone area which has so many routes and on thr opponent side, limited wavelength resource that Indonesian telecom has. In this paper, we propose a new method called modified transport unique lambda to optimize wavelength in backbone transport network of Indonesian telecom and make minimum cost of operational expenditure (opex) in operating dense wavelength division multiplexing (DWDM) devices. For simulation purpose, we also develop a tool in web based called AGENCY (Advance guidancetool for Engineering of central frequency).