Multiple coupling length nonlinear directional couplers with variable coupling coefficient

Multiple coupling length nonlinear directional couplers (NLDCs) with variable coupling coefficient (VCC) are investigated. As examples, two kinds of VCC NLDCs, exponential and Gaussian VCC NLDCs, are numerically simulated. Both couplers show multiple-switching feature and have eminent digital switching characteristic. In addition, the Gaussian VCC NLDC exhibits equi-power-interval-switching characteristic.