Patent ID: 8718097

Claim:
A method implemented in a communications system and comprising the steps of: obtaining, by a processor, a first data rate in a flexible wavelength division multiplexing FWDM network; and applying, by the processor, a recursive rate selection for determining a given data rate from the obtained first data rate such that a required spectrum over said network for said given data rate is minimized, said first data rate being lower than said given data rate; wherein said recursive rate selection comprises recursively determining a spectrum and a set of channels required for data rate n using said spectrum and set of channels required for a data rate n′, where n′<n, wherein if an optimal said spectrum and set of channels are known for each data rate n′<n, then said optimal spectrum for said data rate n being obtainable as follows: X n =0 if n≦ 0 X n =min lEL [x l +X n-1 ] if n> 0, where l denotes a channel line rate, n′=n−l, X n being a total required spectrum for data rate n, x l being a required spectrum for a channel operating at a line rate lεL.