Patent ID: 8059959
Filing Date: 2011-11-15
Classification: H04B

Abstract:
1. An apparatus comprising: a correction level calculator that calculates a correction level, which is an input signal light level necessary to meet an optical signal-to-noise ratio at a maximum level of an optical noise; a threshold-value setting unit that compares the correction level with an initial threshold value to set a loss-of-light detection threshold value used in detection of loss of signal light based on the comparison result; and a loss-of-light detector that compares a level of an input optical signal with the loss-of-light detection threshold value to determine that loss of signal light is caused when the level of the input optical signal is lower than the loss-of-light detection threshold value, wherein the threshold-value setting unit sets the correction level as the loss-of-light detection threshold value when the correction level is higher than the initial threshold value and sets the initial threshold value as the loss-of-light detection threshold value if the correction level is lower than the initial threshold value.