Thin film filters have been a basic building block of many wavelength division multiplexed (WDM) systems providing the means by which a signal, defined by a center wavelength, can be separated from a group of WDM signals. In an effort to maintain the same performance over a range of operating temperatures, thin film filters have been coated onto specially designed substrates, which expand and contract with the change in temperature to counteract the effects that the temperature change has on the thin film filters. Unfortunately, only very few materials provide the necessary thermal expansion characteristics to counteract the shift in center wavelength. Moreover, the application of a force onto only one side of the filter causes the thin film filter to bend or curve. Accordingly, the present invention solves the aforementioned problems by providing a thin film filter sandwiched between a substrate and a superstrate, which apply equal forces to each side of the filter. The present invention also includes an actively tunable thin film filter assembly, which utilizes stress applying devices, e.g. heaters or piezo-electric crystals, to adjust signal characteristics, such as the bandwidth, the group delay, and the chromatic dispersion, as desired.

An integrated optical communications receiver/alignment system and method. In one embodiment, a method and an apparatus are disclosed in which a semiconductor substrate includes a plurality of outer optical detectors disposed in the substrate. An optically transparent center region such as for example an optical waveguide or an optical fiber is integrated in the semiconductor substrate in a central location relative to the plurality of outer optical detectors. The optically transparent center region is optically coupled to receive an optical communications beam and the plurality of outer optical detectors are employed for alignment and/or tracking purposes.