Abstract

Very high speed modulation of guided light has been reported using directional coupler switches (ref. |1, 2|) or Mach-Zehnder interferometers (ref |3, 4, 5, 6|). In some applications base band operation is not necessary and band pass type modulators around a given frequency may be preferred. Such resonance has been predicted in ref |7| where switching diagrams of Y-fed directional couplers have been investigated. A Y-fed coupler as reported in ref |8|, appears to be the combination of a directional coupler switch and of a Y junction through which light is launched. This results in - 3 dB built-in optical bias and makes the device free of any electrical DC drift which is regarded to be a problem in most cases for long term operation. Those considerations lead to consider Y-fed directional couplers as very good candidates for very high speed and band pass operation as it will be discussed in the following.

© 1988 Optical Society of America