An optical cross connect architecture is provided in which the density of spectral bands on optical signals through the cross connect may vary. The general functionality of such variable-density optical cross connect is to receive input optical signals that each have multiple spectral bands and to transmit output optical signals each having one or more of the spectral bands. A concentrator redistributes the spectral bands from the input optical signals among a smaller number of first intermediate optical signals. A core cross connect redistributes the spectral bands on the first intermediate optical signals among second intermediate optical signals. An expander redistributes the spectral bands on the second intermediate optical signals among a greater number of output optical signals.