Broadband quantum-correlated photon-pairs in the O-band generated from a dispersion-engineered silicon waveguide

Multiplexing both quantum key distribution (QKD) and Internet channels in the C-band requires tight time-and-spectral filtering in order to suppress four-wave mixing (FWM) and spontaneous Raman scattering (SRS) noise [1, 2]. In addition, one needs to carefully select the wavelengths of Internet channels and limit their launched optical power. This requires QKD service providers to have authority over Internet channels. Another option is to operate QKD in the O-band [3]. FWM and SRS crosstalk from C-band channels would be negligible in this case. Although higher fiber loss in the O-band limits the range to <;40 km [2], this dual-band scheme is attractive because it does not affect existing Internet services and can be readily implemented in cities such as Singapore.