Communication arrangements wherein each of ONUs of a first or second PON transmits data toward a connected first or second OLT after a wait time period designated by the connected first or second OLT; the first communication device of the first packet communication network sends a first frame for measuring communication time period, to the second communication device of the second packet communication network through the first PON, and sends a second frame for measuring communication time period, to the second communication device through the second PON; and the second communication device calculates a difference of communication time period between the received first and second frames, and instructs the first or second OLT of the first or second PON, for correcting a wait time period which is set to the one or plural ONUs connected to the first or second OLT, based on the difference between communication time periods.