Abstract: A wavelength division multiplexed device is based on a transmission grating spectrometer having at least two diffractive optical elements. The WDM device provides flexible use and may be widely applied in WDM systems. The device is useful for multiplexing and demultiplexing, channel monitoring, for adding and dropping channels, and for controlling the power in individual channels within a multiple channel signal. The device provides for dynamic control of individual channels, and may be advantageous in use as a gain flattening filter.

Abstract: A method and apparatus are presented for aligning a diffractive WDM device that includes i) a multi-channel, light handling device having a selected channel spacing and ii) a multi-channel signal input unit. The method includes adjusting a direction of incidence of an optical signal from the input unit on at least a first diffracting element of the WDM device so as to set an actual optical channel spacing at an output region of the WDM device to be approximately equal to the selected channel spacing of the multi-channel, light handling device. In the apparatus, the orientation of the light input unit is adjustable in a direction parallel to a diffraction plane of the diffractive WDM device so as to select an actual channel spacing at the multi-channel, light handling device that is approximately equal to the selected channel spacing.