  We introduce an all-glass, vacuum tight, fiber-integrated and alkali
compatible spectroscopy device consisting of two conventional optical fibers
spliced to each end of a capillary. This is mainly realized through a
decentered splicing method allowing refilling of the capillary and controlling
the vapor density inside. We analyze the light guidance of the setup through
simulations and measurements of the transmission efficiency at different
wavelengths and show that filling it with highly reactive alkali metals is
possible, and that the vapor density can be controlled reliably.
