Optical transmission/reception device, optical communication system and optical transmission/reception method

1. An optical transmission/reception device comprising:

optical output unit which outputs light;

optical split unit splitting which splits the light from the optical output unit into a first split light and a second split light;

optical power adjustment unit which adjusts the optical power of the first split light and the optical power of the second split light;

optical transmission unit which modulates the first split light whose optical power is adjusted, and outputs the modulated first split light as a first optical signal;

optical reception unit which receives the second split light whose optical power is adjusted and a second optical signal given from an outside by causing the second split light and the second optical signal to be interfered with each other; and

control unit which controls the optical power adjustment unit in accordance with an optical property of the light which is output from the optical output unit.

2. The optical transmission/reception device according to claim 1 , wherein the optical output unit is a wavelength variable light source, and the control unit controls the optical power adjustment unit in accordance with a wavelength of an output light which is output from the wavelength variable light source.

3. The optical transmission/reception device according to claim 1 , wherein the optical power adjustment unit includes one or both of a first optical attenuation unit for attenuating the optical power of the first split light and a second optical attenuation unit for attenuating the optical power of the second split light, and the control unit controls the optical power adjustment unit by controlling the attenuation quantity of the first or the second optical attenuation unit.

4. The optical transmission/reception device according to claim 1 further comprising:

an optical switch for outputting the second optical signal given from an outside to any one of the optical reception unit and the split units,

wherein when an abnormality occurs in the optical output unit, the control unit switches an output destination of the optical switch from the optical reception unit to the split unit, and the split unit treats the input second optical signal as the first split light.

5. The optical transmission/reception device according to claim 4 , wherein the optical reception unit performs reception in accordance with a reception method of any one of a direct detection and a coherent detection which receives the second optical signal which is input from the outside by causing the second optical signal to be interfered with the second split light,

when an abnormality occurs in the optical output unit, the control unit switches the reception method of the optical reception unit from the coherent detection to the direct detection, and thereafter, the output destination of the optical switch is switched to the split unit on the basis of input timing of the second optical signal received by the optical reception unit in accordance with the direct detection.

6. An optical communication system comprising:

a terminal-side device including the optical transmission/reception device according to claim 1 ; and

a station-side device capable of transmitting and receiving a coherent optical signal to and from the terminal-side device.

7. The optical communication system according to claim 6 , wherein in a case where the station-side device cannot receive the coherent optical signal from the terminal-side device for a period equal to or more than a predetermined period, a continuous optical signal is transmitted instead of the coherent optical signal, and

when an abnormality occurs in the optical output unit, the terminal-side device uses the received continuous optical signal as the first split light.

8. The optical communication system according to claim 7 , wherein in a case where the station-side device cannot receive the coherent optical signal from the terminal-side device for a period equal to or more than a predetermined period, a pilot signal is transmitted for the predetermined period, and thereafter, transmission of the continuous optical signal is started, and

the terminal-side device achieves a synchronization by using the received pilot signal, thus receiving the continuous optical signal.

9. An optical transmission/reception method comprising:

outputting light;

splitting the output light into a first split light and a second split light;

respectively adjusting the optical power of the first split light and the optical power of the second split light in accordance with the optical property of the output light;

modulating the first split light obtained by adjusting the optical power, and outputting the modulated first split light as a first optical signal; and

receiving the second split light obtained by adjusting the optical power and a second optical signal given from an outside by causing the second split light and the second optical signal to be interfered with each other.

10. The optical transmission/reception method according to claim 9 comprising:

monitoring the output light;

changing a reception method of the input second optical signal from a coherent detection to a direct detection when light is not output; and

using the second optical signal by receiving the direct detection as the first split light.