In this paper

a new static routing and waveband tunnel allocation algorithm suitable for multigranular WDM network is proposed

which is called the balanced-routing and Bidirection-First-fit algorithm.This algorithm is aimed to minimize the total sum of port number over all MG-PXC nodes in the network

and reduce network cosk and control complexity.In the stage of selecting a route

this algorithm manages to keep the balance of link load of the whole network.In the stage of waveband tunnel allocation

it improves the FF algorithm to establish as many waveband passages as possible.The simulation results show that the two characteristics of BBFF reduce the number of wavelength ports needed greatly in the case of certain traffic volume.So much network cost is saved.