A method of communication through a network, executed by a communication apparatus that performs transmission by selecting a transmission mode, the method includes determining whether to transmit the data in either a first mode or a second mode when transmitting data; transmitting the data using a predetermined number of kinds of optical signals having different levels in light intensity when determined to transmit in the first mode; and transmitting the data using a fewer number of kinds of optical signals having different levels in light intensity than the predetermined number when determined to transmit in the second mode.