Optical module and optical communication system

1. An optical module comprising:

a photoelectric converter configured to:

receive an optical signal having an intensity that changes at one of a first frequency or a second frequency that is higher than the first frequency, and

convert the optical signal into a current signal corresponding to the intensity of the optical signal;

a signal processor configured to:

acquire, when the optical signal has the intensity that changes at the first frequency, wavelength information set on a transmitting side based on a ratio between a plurality of signal intensities included in the current signal relating to the optical signal having the intensity that changes at the first frequency; and

a decoder configured to:

generate, when the optical signal has the intensity that changes at the second frequency, communication data from the current signal relating to the optical signal having the intensity that changes at the second frequency.

2. The optical module of claim 1 , further comprising:

an optical transmitter configured to transmit an optical signal having a wavelength corresponding to wavelength information based on the wavelength information acquired by the signal processor.

3. The optical module of claim 1 ,

wherein the current signal relating to the optical signal having the intensity that changes at the first frequency includes signal intensities having at least ternary values, and

wherein the signal processor is configured to acquire the wavelength information based on the ratio between the signal intensities having at least ternary values.

4. The optical module of claim 1 , wherein the optical module is configured to start to extract the communication data from the current signal relating to the optical signal having the intensity that changes at the second frequency when the wavelength information is acquired based on the ratio between the plurality of signal intensities.

5. The optical module of claim 1 , wherein the first frequency is from 1 Hz to 250 Hz.

6. The optical module of claim 1 , wherein the second frequency is 1 GHz or higher.

7. The optical module of claim 1 , wherein:

the optical signal having the intensity that changes at the first frequency is used during a wavelength setting mode, and

the optical signal having the intensity that changes at the second frequency is used during an operation mode.

8. An optical module comprising:

a photoelectric converter configured to output a current signal corresponding to an intensity of a first optical signal;

an optical transmitter configured to transmit a second optical signal having an intensity that changes at one of a first frequency or a second frequency higher than the first frequency; and

a signal processor configured to:

cause, under a state before the photoelectric converter receives the first optical signal, the optical transmitter to transmit the second optical signal including wavelength information at the first frequency with a wavelength indicated by the wavelength information;

cause, when the photoelectric converter receives the first optical signal through a path that allows only an optical signal having the wavelength corresponding to the wavelength information to pass therethrough, the optical transmitter to stop transmitting the second optical signal including the wavelength information; and

transmit the second optical signal having the wavelength indicated by the wavelength information and including communication data at the second frequency.

9. The optical module of claim 8 , further comprising:

storage configured to store information indicating a ratio between a plurality of signal intensities included in the current signal relating to the second optical signal having the intensity that changes at the first frequency and the wavelength information in association with each another.

10. The optical module of claim 9 , wherein the signal processor is further configured to cause, under the state before the photoelectric converter receives the first optical signal, the optical transmitter to transmit the second optical signal based on the ratio.

11. The optical module of claim 8 , wherein the signal processor is further configured to cause, when the photoelectric converter receives no optical signal, the optical transmitter to sequentially transmit the second optical signal on another wavelength at the second frequency.

12. The optical module of claim 8 , wherein the first frequency is from 1 Hz to 250 Hz.

13. The optical module of claim 8 , wherein the second frequency is 1 GHz or higher.

14. The optical module of claim 8 ,

wherein the current signal includes signal intensities having at least ternary values, and

wherein the signal processor is configured to acquire the wavelength information based on a ratio between the signal intensities having at least ternary values.

15. The optical module of claim 8 , wherein

the second optical signal having the intensity that changes at the first frequency is used during a wavelength setting mode, and

the second optical signal having the intensity that changes at the second frequency is used during an operation mode.

16. An optical communication system comprising:

a first optical module comprising:

a photoelectric converter configured to receive a first optical signal having an intensity that changes at one of a first frequency or a second frequency higher than the first frequency and convert the first optical signal into a current signal corresponding to the intensity of the first optical signal;

a first signal processor configured to acquire, when the first optical signal has the intensity that changes at the first frequency, wavelength information set on a transmitting side based on a ratio between a plurality of signal intensities included in the current signal relating to the first optical signal having the intensity that changes at the first frequency; and

a first optical transmitter configured to transmit a second optical signal having a wavelength corresponding to the wavelength information based on the wavelength information acquired by the first signal processor; and

a second optical module comprising:

a second photoelectric converter configured to output a current signal indicating a change in intensity of a third optical signal;

a second optical transmitter configured to transmit a fourth optical signal having an intensity that changes at one of the first frequency and the second frequency; and

a second signal processor configured to:

cause, under a state before the second photoelectric converter receives the third optical signal, the second optical transmitter to transmit the fourth optical signal including the wavelength information at the first frequency with the wavelength indicated by the wavelength information; and

cause, when the second photoelectric converter receives the third optical signal through a path that allows only an optical signal having the wavelength corresponding to the wavelength information to pass therethrough, the second optical transmitter to stop transmitting the fourth optical signal including the wavelength information and transmit a fifth optical signal having the wavelength indicated by the wavelength information and including communication data at the second frequency.

17. The optical communication system of claim 16 , further comprising:

a multiplexer including:

a plurality of input terminals, to which optical signals having mutually different wavelengths are to be input; and

an output terminal, from which an optical multiplex signal obtained by multiplexing a plurality of optical signals having mutually different wavelengths is to be output.

18. The optical communication system of claim 17 , further comprising:

a demultiplexer including:

an input terminal to which the optical multiplex signal is to be input; and

a plurality of output terminals, from which optical signals having mutually different wavelengths included in the optical multiplex signal are to be output,

wherein the first optical transmitter is coupled to one of the plurality of input terminals included in the multiplexer, and

wherein the second photoelectric converter is coupled to one of the plurality of output terminals included in the demultiplexer.

19. The optical communication system of claim 16 , wherein:

the first frequency is from 1 Hz to 250 Hz, and

the second frequency is 1 GHz or higher.

20. The optical communication system of claim 16 , wherein:

the first optical signal having the intensity that changes at the first frequency is used during a wavelength setting mode, and

the first optical signal having the intensity that changes at the second frequency is used during an operation mode.