An optical switch (10) comprising: input ports (12, 14) arranged to receive optical signals from directions D1 to Dn; output ports (16, 18) arranged to output optical signals to the said directions; drop ports (20); add ports (22); a first switch array (24) arranged to receive from a first said input port (12) optical signals at a plurality of wavelengths, and comprising switch elements (26) each arranged to selectively direct optical signals to a respective drop port. The optical switch (10) further comprising optical filters (28), each arranged to receive from the first input port optical signals having bypass wavelengths, each optical filter arranged to transmit to a respective one of the output ports (18) optical signals at different bypass wavelengths; and a second switch array (30) arranged to receive from the other input ports (14) optical signals at some of said wavelengths, the second switch array comprising a plurality of switch elements (32) arranged to selectively add optical signals received from the add ports at others of said wavelengths.