A network node, comprising: a plurality of network degree interfaces (220 1. 220 2, 220 3, 220 4) that each direct WDM optical signals onto, and receive WDM optical signals from, a different optical transmission path of a optical transmission network, each of the network degree interfaces being optically coupled to one another so that any one or more wavelength components of a WDM optical signal received on any one of the network degree interfaces is directable to any other of the network degree interfaces; an add/drop interface that includes a drop wavelength selective switch WSS and an add WSS, the drop WSS having a plurality of inputs each being optically coupled to receive wavelength components from a different one of the network degree interfaces (220 1. 220 2, 220 3, 220 4) and a plurality of outputs, the add WSS having a plurality of outputs each being optically coupled to direct wavelength components to a different one of the network degree interfaces (220 1. 220 2, 220 3, 220 4) and a plurality of inputs, wherein the add and drop WSSs (260, 250) are each configured to selectively direct any subset of the wavelength components received at any of its inputs to a different one of its optical outputs, provided that the wavelength components of optical beams received by any two of the inputs cannot be simultaneously directed to a common one of the outputs; a plurality of transponder ports each being optically coupled to a different output of the drop WSS and a different input of the add WSS; wherein at least one of the add or drop WSSs (260, 250, 100) comprises a wavelength dispersion element for spatially separating optical beams into a plurality of wavelength components and a switching arrangement (106, 109, 304) for receiving the plurality of wavelength components of the optical beams and selectively directing the wavelength components between the inputs (101 1, 101 2,..., 101 n) and the outputs (112 1, 112 2,..., 112 n); and wherein the switching arrangement (106, 109, 301) includes at least one optical beam steering arrangement (106, 109) having a first region onto which the spatially separated wavelength components are directed and a second region onto which each of the selectively directed subset of wavelength components are directed after the wavelength components in each of the subsets are spatially recombined with one another, the at least one optical beam steering arrangement (106, 109) selectively directing each of the subsets of the plurality of wavelength components to a different one of the outputs (112 1, 112 2,..., 112 n), characterized in that the add and drop WSSs (260, 250, 100) are each further configured to selectively direct only a single one of the wavelength components to any given one of the outputs (112 1, 112 2,..., 112 n) at any given time. a plurality of network degree interfaces (220 1. 220 2, 220 3, 220 4) that each direct WDM optical signals onto, and receive WDM optical signals from, a different optical transmission path of a optical transmission network, each of the network degree interfaces being optically coupled to one another so that any one or more wavelength components of a WDM optical signal received on any one of the network degree interfaces is directable to any other of the network degree interfaces; an add/drop interface that includes a drop wavelength selective switch WSS and an add WSS, the drop WSS having a plurality of inputs each being optically coupled to receive wavelength components from a different one of the network degree interfaces (220 1. 220 2, 220 3, 220 4) and a plurality of outputs, the add WSS having a plurality of outputs each being optically coupled to direct wavelength components to a different one of the network degree interfaces (220 1. 220 2, 220 3, 220 4) and a plurality of inputs, wherein the add and drop WSSs (260, 250) are each configured to selectively direct any subset of the wavelength components received at any of its inputs to a different one of its optical outputs, provided that the wavelength components of optical beams received by any two of the inputs cannot be simultaneously directed to a common one of the outputs; a plurality of transponder ports each being optically coupled to a different output of the drop WSS and a different input of the add WSS; wherein at least one of the add or drop WSSs (260, 250, 100) comprises a wavelength dispersion element for spatially separating optical beams into a plurality of wavelength components and a switching arrangement (106, 109, 304) for receiving the plurality of wavelength components of the optical beams and selectively directing the wavelength components between the inputs (101 1, 101 2,..., 101 n) and the outputs (112 1, 112 2,..., 112 n); and wherein the switching arrangement (106, 109, 301) includes at least one optical beam steering arrangement (106, 109) having a first region onto which the spatially separated wavelength components are directed and a second region onto which each of the selectively directed subset of wavelength components are directed after the wavelength components in each of the subsets are spatially recombined with one another, the at least one optical beam steering arrangement (106, 109) selectively directing each of the subsets of the plurality of wavelength components to a different one of the outputs (112 1, 112 2,..., 112 n), characterized in that the add and drop WSSs (260, 250, 100) are each further configured to selectively direct only a single one of the wavelength components to any given one of the outputs (112 1, 112 2,..., 112 n) at any given time.