Wavelength division multiplexing device, an optical leakage prevention method, and a wavelength division multiplexing communication system

An optical leakage prevention method for a wavelength division multiplexing device, comprising the steps of:

• receiving an optical signal, adjusting an optical power level of the input optical signal, and outputting the level-adjusted optical signal;
• analyzing the optical power level of the output optical signal;
• controlling the optical power level of the output optical signal at a constant level;
• controlling a transition to an “off-state” to take place when the optical power level of the output optical signal becomes less than a predetermined disconnection-detection threshold, and providing a predetermined amount of attenuation to the input optical signal;
• and
• transitioning from the “off-state” when the optical power level of the output optical signal becomes greater than a predetermined recovery threshold, and when an upstream wavelength division multiplexing device is not in the “off-state”.

A wavelength division multiplexing communication system that includes a plurality of wavelength division multiplexing devices, each wavelength division multiplexing device comprising:

• a level adjusting unit for receiving an optical signal, for adjusting an optical power level of the received optical signal, and for outputting the level-adjusted optical signal;
• and
• a controlling unit for analyzing the optical power level of the optical signal output from the level adjusting unit, for controlling the level adjusting unit so that the optical power level of the output optical signal stays at a constant level, and for transitioning to an “off-state” when the optical power level of the output optical signal becomes less than a predetermined disconnection-detection threshold so that the level adjusting unit gives a predetermined attenuation to the input optical signal;
• wherein the controlling unit control transitions from the “off-state” when the optical power level of the output optical signal is greater than a predetermined recovery threshold, and an upstream wavelength division multiplexing device is not in the “off-state”.