Effects of fabrication conditions on the double-peak structure observed in fiber Bragg gratings at harmonics of the Bragg wavelength were investigated, showing that slight variations in the alignment of the phase mask can affect the grating spectra significantly. A single peak occurs only when the incident beam direction is perfectly normal with respect to the fiber.

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http://dx.doi.org/10.1364/JOSAA.29.001597DOI Listing

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