An example reconfigurable optical add/drop multiplexer includes: optical fibers, X first wavelength selective switches, and Y wavelength add/drop modules. The X first wavelength selective switches correspond to W directions. The W directions include a first direction and a second direction. The first direction corresponds to P first wavelength selective switches among the X first wavelength selective switches. The second direction corresponds to Q first wavelength selective switches among the X first wavelength selective switches, where P+Q is less than or equal to X. A first wavelength add/drop module is connected to A of the P first wavelength selective switches by using one or more first optical fibers, and connected to B of the Q first wavelength selective switches by using one or more second optical fibers, where the first wavelength add/drop module is one of the Y wavelength add/drop modules, A is less than P.