| 摘要 |
The disclosed Mach-Zehnder (MZ)-type devices are planar waveguide devices, with interferometer arms of essentially equal length, with a maximum spacing between the arms (e.g., between the waveguide core centers) selected to make possible simultaneous exposure of both arms to refractive index-altering radiation. Exemplarily the maximum spacing is in the range 20-100 mu m. The simultaneous exposure of both waveguides makes it possible to form gratings of essential equal strength, such that typically no individual trimming is required. The resulting devices (typically add-drop filters) are substantially less sensitive to environmental changes (e.g., temperature gradients, mechanical vibrations) than prior art fiber-based devices, and are advantageously used in, for instance, WDM optical communication systems.
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