Polarization-sensitive interference spectrum of long-period fiber grating pair separated by erbium-doped fiber

The authors investigate the polarization dependency of the transmission spectrum of cascaded long-period fiber gratings between which an erbium-doped fiber (EDF) is inserted. Due to the birefringence of the EDF, the device has a much greater spectral polarization dependency than the normal cascaded long-period fiber gratings have. The authors use this polarization dependency to modulate the transmission spectrum of the proposed device. This modulation capability suggests that this device based on cascaded long-period fiber grating is a promising one for use as a simple interleaved signal-gating apparatus in wavelength-division-multiplexed optical communication systems.