The present invention realizes an Optical Line Terminal (OLT) in an optical access network and a data signal sending method for the optical access network in which the reliability of the network can be assured without increasing the cost of facility investment. The OLT comprises a multiplex control unit for providing a communication path to be used commonly for transmitting data signals for subscriber terminals to communicate with the network, a plurality of optical network interface units, each accommodates the subscriber terminals and provides either a first path connected to the network for transmitting the data signals individually or a second path connected to the multiplex control unit for transmitting the data signals to the network commonly with data signals from other subscriber terminals accommodated in other optical network interface unit, and a path selection control section, which determines for every optical network interface unit to select either the first path or the second path on the basis of path class information in a path management table in which respective path class information for every optical network interface unit have been predetermined and set.