A channel establishment method, for providing hierarchical management of the frequency spectrum in an optical network, characterized in that the method comprises: establishing a media channel between a first node and a second node, wherein the first node is a source node of the media channel, the second node is a destination node of the media channel, the media channel passes a frequency slot matrix of one or more intermediate nodes between the first node and the second node and an optical fiber between any two nodes, among the first, intermediate and second nodes, and the media channel supports at least one optical channel, forming, after the media channel is successfully established, a traffic engineering link between the first node and the second node in an upper layer signal network, which is corresponding to a lower layer media network where the media channel exists, said traffic engineering link supporting at least one signal channel and the available frequency spectrum of which is the same as the frequency spectrum of the media channel; establishing a signal channel between a third node and a fourth node after the media channel is established, wherein the third node is a source node of the signal channel, the fourth node is a destination node of the signal channel, and the signal channel passes a frequency slot matrix of one or more intermediate nodes between the third node and the fourth node and the traffic engineering link and allocating frequency spectrum to the signal channel from available frequency spectrum of the traffic engineering link, wherein the frequency spectrum allocated comprises a plurality of distributed 50GHz frequency slots, each of which bears one optical channel and each of which only comprises a single optical carrier; wherein the media channel supports a plurality of signal channels which directly support an optical channel signal, and wherein the frequency slot is a fixed or flexible grid. establishing a media channel between a first node and a second node, wherein the first node is a source node of the media channel, the second node is a destination node of the media channel, the media channel passes a frequency slot matrix of one or more intermediate nodes between the first node and the second node and an optical fiber between any two nodes, among the first, intermediate and second nodes, and the media channel supports at least one optical channel, forming, after the media channel is successfully established, a traffic engineering link between the first node and the second node in an upper layer signal network, which is corresponding to a lower layer media network where the media channel exists, said traffic engineering link supporting at least one signal channel and the available frequency spectrum of which is the same as the frequency spectrum of the media channel; establishing a signal channel between a third node and a fourth node after the media channel is established, wherein the third node is a source node of the signal channel, the fourth node is a destination node of the signal channel, and the signal channel passes a frequency slot matrix of one or more intermediate nodes between the third node and the fourth node and the traffic engineering link and allocating frequency spectrum to the signal channel from available frequency spectrum of the traffic engineering link, wherein the frequency spectrum allocated comprises a plurality of distributed 50GHz frequency slots, each of which bears one optical channel and each of which only comprises a single optical carrier; wherein the media channel supports a plurality of signal channels which directly support an optical channel signal, and wherein the frequency slot is a fixed or flexible grid.