Polarization insensitive detection of optical phase modulation via two-wave mixing in Er-doped fiber with saturable absorption

Dynamic population gratings in rare-earth-doped optical fibres

“…Figure 17 shows the relative amplitude of the TWM signal observed in response to the square-wave phase modulation as a function of the input polarization angle θ of one recording wave, when polarization of the other wave was kept along one proper axis of the birefringent fibre. Recent experiments (Garcia Casillas and Stepanov 2008) have also shown that recording of dynamic grating by two waves of crossed polarizations is quite general for EDF, no matter whether it is birefringent or not, and is observed through the whole absorption spectrum of Er +3 ions (from 1492 to 1567 nm).…”

“…As was proposed in García Casillas and Stepanov (2008), such adaptive beam splitters can also be realized in a polarization insensitive form, i.e. can resolve another (in addition to the stabilization of the operation point) most important problem of potentially highly sensitive interferometric fibre sensors (Dandridge 1991).…”