According to the present invention, maintenance data about a plurality of distribution terminal devices which are different from each other in frequency with which they are in use and circumstances under which they are in use are transmitted to a host computer, whereby a lifetime of a semiconductor laser can be predicted and an occurrence of a trouble can be detected without receiving information from a user or shops in which the distribution terminal devices are installed.

 
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> Enhanced link operation of directly modulated lasers using gain-coupled gratings

> Optical lens and optical information recording and reproducing apparatus

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