| 摘要 |
<p>In order to identify a cause of a power fluctuation in a light signal being monitored, this light-monitoring circuit is equipped with: a light branching means whereby the light power of one of two rays of light, which are branched from input light due to a temperature increase, is increased and the light power of the other of the two rays of light is reduced by the same amount as the increase in the first-mentioned light power; light detection means for respectively detecting the light powers of the two branched rays of light; and an arithmetic means that determines a cause of light power fluctuations in the two branched rays of light on the basis of whether absolute values of the respective amounts of increase in the light powers that are detected of the two branched rays of light by the light detection means are the same or not and on the basis of whether or not one of the two branched rays of light has been increased while the other has been reduced, and outputs a signal in accordance with the determination result.</p> |
