Optical transmitting device and optical receiving device

1. An optical transmitting device comprising:

a detector to detect a transmission rate of a received transmission signal;

a transmission method selector to select, from among a plurality of transmission methods, a transmission method for the received transmission signal, based on the transmission rate detected by the detector;

a modulation signal generator circuit to generate a modulation signal from the received transmission signal, based on the transmission method selected by the transmission method selector; and

an optical modulator to generate a modulated optical signal from the modulation signal generated by the modulation signal generator circuit,

wherein when the transmission rate of the received transmission signal is less than or equal to a client accommodation rate of a first transmission method, from among the plurality of transmission methods, to which a first modulation method and a single polarization are applied and when the transmission rate of the received transmission signal is less than or equal to a client accommodation rate of a second transmission method, from among the plurality of transmission methods, to which a second modulation method and a dual polarization are applied, the transmission method selector selects the first transmission method.

2. An optical transmitting device comprising:

a detector to detect a transmission rate of a received transmission signal;

a transmission method selector to select, from among a plurality of transmission methods, a transmission method for the received transmission signal, based on the transmission rate detected by the detector;

a modulation signal generator circuit to generate a modulation signal from the received transmission signal, based on the transmission method selected by the transmission method selector; and

an optical modulator to generate a modulated optical signal from the modulation signal generated by the modulation signal generator circuit, the optical modulator includes a first optical modulator and a second optical modulator,

wherein when the transmission rate of the received transmission signal is less than or equal to a client accommodation rate of a first transmission method, from among the plurality of transmission methods, to which a first modulation method and a dual polarization are applied and when the transmission rate of the received transmission signal is greater than a client accommodation rate of the remaining plurality of transmission methods, to which a single polarization are applied, the transmission method selector selects the first transmission method,

the modulation signal generator circuit generates the modulation signal corresponding to the first transmission method,

the first optical modulator and second optical modulator generate a first modulated optical signal and a second modulated optical signal, respectively, from the modulation signal, and

the optical modulator polarization-multiplexes the first modulated optical signal and the second modulated optical signal.

3. The optical transmitting device according to claim 1 , wherein the modulation signal generator circuit includes:

a mapping circuit to assign received transmission signals to one or more transmission frames corresponding to the transmission method selected by the transmission method selector; and

a coder circuit to generate modulation signals from the transmission frames to which the received transmission signals are assigned.

4. The optical transmitting device according to claim 1 , wherein the transmission method selector selects the transmission method, based on the transmission rate and a state of an optical transmission path therefrom to an optical receiving device for receiving the modulated optical signal.

5. The optical transmitting device according to claim 4 , wherein the transmission method selector extracts candidates for the transmission method from the plurality of transmission methods, based on the state of the optical transmission path, and selects the transmission method corresponding to the transmission rate from the candidates for the transmission method.

6. The optical transmitting device according to claim 4 , wherein the transmission method selector receives, from the optical receiving device, transmission path information indicating the state of the optical transmission path.

7. An optical transmission system on which an optical signal is transmitted through an optical transmission path, the optical transmission system comprising:

an optical transmitting device including:

a detector to detect a transmission rate of a received transmission signal;

a transmission method selector to select, from among a plurality of transmission methods, a transmission method for the received transmission signal, based on the transmission rate detected by the detector;

a modulation signal generator circuit to generate a modulation signal from the received transmission signal, based on the transmission method selected by the transmission method selector; and

an optical modulator to generate a modulated optical signal from the modulation signal generated by the modulation signal generator circuit,

wherein when the transmission rate of the received transmission signal is less than or equal to a client accommodation rate of a first transmission method, from among the plurality of transmission methods, to which a first modulation method and a single polarization are applied and when the transmission rate of the received transmission signal is less than or equal to a client accommodation rate of a second transmission method, from among the plurality of transmission methods, to which a second modulation method and a dual polarization are applied, the transmission method selector selects the first transmission method; and

an optical receiving device to receive, from the optical transmitting device, the modulated optical signal.