A method, a system, and an apparatus for transmitting data information by using optical signals are disclosed. The method includes: selecting at least two optical carriers, where the at least two optical carriers correspond to at least two optical frequency slots, and a vacant optical frequency slot or an optical frequency slot occupied by other optical signals exists between the two optical frequency slots; modulating data information onto the at least two optical carriers to form a channel of optical signals, so that the channel of optical signals occupies the at least two optical frequency slots, and a vacant optical frequency slot or an optical frequency slot occupied by other optical signals exists between the two optical frequency slots; and sending the channel of optical signals.