A new mechanism of feedback acknowledge is proposed for avoiding loss of data bursts.It is the principle that if failed to establishing end-to-end wavelength path during setting up,the fault core node will send back a acknowledge information (NACK) to the original edge node,once the original edge node receives NACK information before the data burst to be scheduled has not be output,the plan of scheduling the data burst for output will be cancelled and that data burst will be buffered again to be ready for scheduling next time.In such way,a more reliable wavelength path and a less loss may be provided for data burst.