Determination of the coupling length in directional couplers from spectral response

A novel technique to determine the coupling length as a function of wavelength in directional couplers, especially in the case of weakly coupled, symmetrical directional couplers is described. The technique is illustrated by using Ag/sup +/-Na/sup +/ ion-exchanged directional couplers in BK7 glass. Application of this technique to asymmetrical directional couplers is also addressed.<
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