Near-IR photoluminescence at the photon level in a silica fiber patch cable

We measure the spectral fluorescence emitted by commercial pure-silica core and germanium-doped core fibers in the range of 760-860 nm and find that the broadband fluorescence that exists in the Ge-doped fiber can be avoided by adopting the pure-silica core fiber. Most importantly, we present a narrowband (∼1 nm FWHM) emission line characteristic of zirconia ferrules used in both commercial Ge-doped and pure-silica core fiber patch cables. The results of this work are significant to many applications in the fields of quantum optics and fluorescence spectroscopy, where strong pump light co-propagates with signals at the photon level.