when {HEAD ~ the service} is provisioned for {TAIL ~ the service} receiving side device, searching, by the service provider according to the service transmission rate and the topology scenario parameter that are provided by the service receiving side device, the power spectral density template to determine a corresponding power spectral density 
when { HEAD ~ the service } is provisioned for { TAIL ~ the service } receiving side device , searching , by the service provider according to the service transmission rate and the topology scenario parameter that are provided by the service receiving side device , the power spectral density template to determine a corresponding power spectral density
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH