A package accommodates an LD device for emitting laser light with the center
wavelength
of which is in a range of 1300 to 1440 nm and airtight seals a light path extending
from the LD device to an incident end of an optical fiber. The package is filled
with a nitrogen gas at a standard atmospheric pressure with the amount of moisture
limited to a value lower than 100000 ppm by volume or less. Therefore, the amount
of moisture in the light path for laser light within the package is limited to
100000 ppm by volume or less.
