The invention relates to a reconfigurable optical switching system for selectively coupling one or more frequencies of first and second input wavelength division multiplex signals (WDM1, WDM2) consisting of N channels to first and second output ports (O1, O2). The invention also relates to a variable and reconfigurable optical delay circuit comprising said optical switching system associated with an optical delay loop. The input frequency division multiplex optical spectra (WDM1, WDM2) are therefore divided by a first demultiplexer (Demux) to a plurality of interleaved stages of optical switches (D, C, A and B) which selectively feed a plurality of input ports (Mi) of a multiplexer (Mux), which then uses its routing properties to implement in particular the complex reconfigurable multiple 2×2 frequency switching function.