Frequency response of thermo-optic tuning mechanism of planar silica optical multiplexer.

The thermo-optic mechanism provides a simple means of tuning the wavelength of interferometric optical multiplexers constructed from planar silica waveguides upon a silicon substrate. Frequencydomain measurements of the tuning response permit an understanding of the tuning mechanism that is relevant to the design of components for applications in which wavelength-tracking error and cross-talk penalty are important. Measurements on a prototype device have shown a primary low-pass breakpoint at 360 Hz but have also highlighted the possibility of secondary mechanisms affecting the low-frequency response. A continually increasing phase lag at higher frequencies has also been detected and must be allowed for in control-circuit design.