Variable long-period fiber gratings controlled by ND-FE-B permanent magnet for erbium-doped fiber sources

Filter characteristics of long-period fiber gratings are externally controlled by deforming the fiber axis with a Nd-Fe-B permanent magnet. The loss amplitude is tuned from 0 to 15 dB by moving the magnet under the fiber. The loss peak wavelength is changed over a range of 200 nm by stretching the coil spring over the fiber. We apply this device to flatten the amplified spontaneous emission of an Er3+-doped fiber (EDF). We also demonstrate the tunable EDF laser that oscillates from 1532 to 1566 nm.