The feasibility of self-tuning WDM technique has been experimentally evaluated and demonstrated on planar lightwave circuits. This techniques utilizes only one optical window a simple filter operated as not only WDM-MUX/DMUX but also a tuning gauge, and adopts no designation of specific emission wavelength. It is applicable for both DFB-LD and FP-LD to be the optical source of high-bit-rate transmission systems by designating appropriately the free spectrum range of the WDM filter. Proposed tuning control algorithm with a master/slave scheme secures the stable operation under a wide range of environmental temperature variation including various aging effects. A highlight of this paper is the proposed WDM system's capability to settle the defects of conventional WDM systems.