Tunable wavelength division multiplexing channel isolation filter based on dual chirped long-period fiber gratings

We propose and demonstrate a wavelength tunable wavelength division multiplexing channel isolation filter based on two concatenated chirped long-period fiber gratings (LPGs). An intergrating space (IGS), deliberately introduced between the two gratings, provides an extra phase difference between the core and cladding modes. Changing this phase by heating the IGS without affecting the gratings tunes the channels. A theoretical account of the filter action is also presented and the results are found to be in excellent agreement with the experiments. Unlike the filters based on normal concatenated chirped LPGs without an IGS, the current filter shows a linear tuning over an increased spectral range.     

Lavandulifolioside B: a new phenylethanoid glycoside from the aerial parts of Stachys lavandulifolia Vahl

Reversed-phase preparative HPLC analyses of the methanol extract of the aerial parts of Stachys lavandulifolia afforded a new phenylethanoid glycoside, 4,3',4'-trimethoxy-lavandulifolioside A, named lavandulifolioside B, together with three other known phenylethanoid glycosides, lavandulifolioside A, verbascoside and leucosceptoside A, and an iridoid glycoside 5-O-β-allopyranosyloxy-aucubin (5-O-β-allopyranosyl-monomelittoside). While the structures of the known compounds, except the iridoid glycoside, were established by direct comparison of their spectroscopic data with respective literature data, lavandulifolioside B and 5-O-β-allopyranosyloxy-aucubin were identified comprehensively by extensive 1D and 2D NMR analyses. The distribution of the isolated compounds within the genus Stachys has been discussed.