Brillouin spectroscopy of Nd–Ge co-doped silica fibers

Single-frequency ytterbium doped photonic bandgap fiber amplifier at 1178 nm

“…This small peak was originated from cladding acoustic modes, because the Yb-PBGF has Gedoped rods with the slower sound velocity [20,21] in the clad. Hence some acoustic antiguiding effect [17,20] exists and causes the 1.8 dB suppression in the Brillouin gain.…”

Dynamics of the Stokes pulse in a Brillouin amplifier

“…(5), are shown by dashed curves 3. We have found that for each G the calculated curves 2 and 3 give the best fit with the experimental data at τ 4 ns, which is ∼1.8 times lower that the expected decay of the acoustic wave in fused silica due to viscosity [13]. Analysis of possible reasons for this difference has shown that most probably it is due to the diffraction losses of the acoustic wave which is induced in the fiber core [14].…”

“…(1) and (2) are fully relevant to our experiment. In this experiment we investigated a standard fiber sample with NA 0.12 and estimated τ ≅ 7.5 ns [13].…”

The Acoustic Velocity of Ge‐Doped Silica Fibers: A Comparison of Two Models

“…Both models for the acoustic velocity will be compared with the data for the Ge‐doped fibers obtained in Dragic 18 . There are data available from four fibers, Corning SMF‐28 ™ (Nufern, East Granby, CT), Corning HI‐1060 ™ , an INO fiber (HIGe, Quebec City, Quebec, Canada), and finally a Nufern UHNA ™ fiber (Corning, NY), listed in order of ascending Ge concentration.…”

“…The acoustic velocities were calculated from measurements of the spontaneous Brillouin spectra via a microwave heterodyne approach. This experimental setup is described in more detail elsewhere 18 and summary descriptions of both the RIP and Brillouin measurement systems will be provided later in the paper.…”