The Reconfigurable Optical Add/Drop Multiplexer（ROADM）is a core device for building a large-scale all-optical switching network.At present

most of the commercially available ROADMs support the colorless and directionless features;however

the unblocking feature still cannot be widely applied because of its high cost.Therefore

it is a problem at present demanding prompt solution to effectively reduce the blocking probability of the optical communication traffics.As the existing ROADM nodes have multiple add/drop port modules

this paper proposes three different Routing and Wavelength Assignment（RWA）algorithms.Simulation results show that the Plane-Wave Algorithm（PWA）with the awareness of add/drop port availability at the source and destination nodes can effectively reduce the blocking probability of the optical channel traffics as compared with those without such awareness.