Control of the group-velocity differences between two distinct modes in a few-mode fiber can be used to define the spectral characteristics of long-period gratings written in them. Using this effect, we report the demonstration of strong mode conversion (>99%) with long-period fiber gratings over what is believed to be a record bandwidth of 63 nm. These novel spectra are obtained from gratings written in specially designed few-mode fibers in which the grating phase-matching condition is satisfied over a large spectral range. We show that the bandwidths of such mode converters can be tailored by suitably altering the design of the few-mode fibers. The polarization-dependent coupling for the mode converters varies by less than 0.004% over the entire spectrum.
© 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
(350.2770) Other areas of optics : Gratings
Siddharth Ramachandran, Zhiyong Wang, and Man Yan, "Bandwidth control of long-period grating-based mode converters in few-mode fibers," Opt. Lett. 27, 698-700 (2002)