Supervising system, supervising apparatus and supervising method of supervising optical transmission line

A supervising apparatus for supervising optical transmission lines disposed opposite each other, comprising:

• a first optical transmission line which transmits a signal light, a first supervisory light having a different wavelength from that of the signal light, and a second supervisory light having a different wavelength from those of the signal light and the first supervisory light;
• a second optical transmission line disposed opposite the first optical transmission line;
• a first supervisory light transfer unit which cuts off the signal light and the second supervisory light from among lights returned while transmitted in the first optical transmission line, and transfers the first supervisory light transmitted, to the second optical transmission line;
• and
• a second supervisory light transfer unit which cuts off the signal light and the first supervisory light from among lights transmitted in the first optical transmission line, and transfers the second supervisory light transmitted, to the second optical transmission line.

A supervising apparatus for supervising optical transmission lines disposed opposite each other, comprising:

• a first optical transmission line which transmits a signal light, a first supervisory light having a different wavelength from that of the signal light, and a second supervisory light having a different wavelength from those of the signal light and the first supervisory light;
• a second optical transmission line disposed opposite the first optical transmission line;
• first supervisory light transfer means which cuts off the signal light and the second supervisory light from among lights returned while transmitted in the first optical transmission line, and transfers the first supervisory light transmitted, to the second optical transmission line;
• and
• second supervisory light transfer means which cuts off the signal light and the first supervisory light from among lights transmitted in the first optical transmission line, and transfers the second supervisory light transmitted, to the second optical transmission line.

A supervising method of supervising optical transmission lines disposed opposite each other, comprising the steps of:

• transmitting in addition to a signal light, a first supervisory light having a different wavelength from that of the signal light and a second supervisory light having a different wavelength from those of the signal light and the first supervisory light to a first optical transmission line;
• cutting off the signal light and the second supervisory light from among lights returned while transmitted in the first optical transmission line;
• transferring the first supervisory light transmitted, from the first optical transmission line to the second optical transmission line;
• receiving and supervising the first supervisory light transferred to the second optical transmission line;
• cutting off the signal light and the first supervisory light from among lights transmitted in the first optical transmission line;
• transferring the second supervisory light transmitted, from the first optical transmission line to the second optical transmission line;
• and
• receiving and supervising the second supervisory light returned while transmitted in the second optical transmission line.