We demonstrate a novel device that comprises a pair of broadband and narrowband long-period gratings written in specially designed few-mode fibers to achieve in-fiber bandpass filtering. This device configuration opens the possibility of using long-period gratings for complex spectral shaping in a band-selection as opposed to the conventional band-rejection configuration. The devices are low loss (<0.5dB) as well as tunable over large spectral ranges (26 nm). We demonstrate, for the first time to our knowledge, that the unique dispersive properties of long-period gratings allow for constructing dispersion-free bandpass filters with arbitrarily sharp spectral profiles.
© 2002 Optical Society of America
(060.2280) Fiber optics and optical communications : Fiber design and fabrication
(060.2340) Fiber optics and optical communications : Fiber optics components
(060.4510) Fiber optics and optical communications : Optical communications
Siddharth Ramachandran, Samir Ghalmi, Zhiyong Wang, and Man Yan, "Band-selection filters with concatenated long-period gratings in few-mode fibers," Opt. Lett. 27, 1678-1680 (2002)