A system and method for maintaining alignment between a source and router in a Wavelength Division Multiplexed (WDM) fiber optic network. In a preferred embodiment, a narrow band of the wavelengths emitted by the WDM source is designated as a monitor channel. The monitor channel is matched in wavelength to a fiber grating that is located in the optical path between the source and router so that the grating reflects the monitor channel light while allowing all other source light to pass through unimpeded. By monitoring the reflected light and adjusting the source wavelengths to maximize the amount of reflected light, alignment between the source and router is maintained.