a slight time difference and to control errors as will be noted from fig5 in comparison with fig1 a source node apparatus 1 is provided with optical cross connects 16 for controlling the number of optical delay lines inserted at an upstream stage of an optical buffer 12 31 or 12 32 that receives packets from a router 31 or 32 a traffic monitor 14 monitors the traffic in a plurality of the access lines at the upstream of the optical cross connects 16 in case that additional paths must be added at substantially the same time for two or more access lines the traffic monitor 14 will notify to add the additional paths to the optical cross connects 16 in response to the notification the optical cross connects 16 insert an optical delay line so as to make a time interval for adding the respective additional paths thus the additional paths are not added at substantially the same time for the two or more access lines and a time interval for adding the respective additional paths can be extended furthermore according the embodiment shown in fig5 at the upstream of the optical cross connects 16 and at the downstream of a connection point to the traffic monitor 14 for measuring the traffic one optical delay line 15 31 or 15 32 is provided for each router this optical delay line gives a delay larger than a time period.