SUB-STATION DEVICE, MASTER STATION DEVICE, CONTROL DEVICE, OPTICAL COMMUNICATION SYSTEM AND BAND ALLOCATION CONTROL METHOD

PROBLEM TO BE SOLVED: To obtain a sub-station device capable of actualizing highly accurate band allocation with a reduced time required for the inquiry of the band allocation.SOLUTION: An ONU 10-1 constituting a PON system and an OLT 1 includes: a GW function unit 16 for detecting the start and end of communication; a communication type determination unit 17 for detecting a communication type of communication when the GW function unit 16 detects the start of the communication; and a band request unit 111 for transmitting a communication start notification, in which the determined communication type is stored, to the OLT 1, and for transmitting a band allocation cancellation notification to the OLT 1 when the GW function unit 16 detects the end of the communication.