When a fiber Bragg grating (FBG) is fabricated with the proximity side-writing technique using a phase shifted phase mask, the phase shifts in the phase mask are split into two half-amplitude phase shifts. In this paper, we investigate the effects of the phase shift-split on the DFB grating, which has a single π-phase shift at mid-length. The split of the phase shift produces a slight blue-shift of the transmission peak of the DFB grating and creates spectral asymmetry errors. We model the split-phase shifted FBG as two cascaded and tightly coupled grating-based Fabry-Perot filters, and obtain a compact expression of the reflectivity spectrum with the transfer-matrix approach. The theory is able to describe the spectral asymmetry errors and the shift of the transmission peak and to show that the effects of the phase shift-split decrease with increasing FBG length and become negligible for gratings more than a few millimeters long.

Date Published: 8 September 2006
PDF: 6 pages
Proc. SPIE 6343, Photonics North 2006, 634343 (8 September 2006); doi: 10.1117/12.707930

Published in SPIE Proceedings Vol. 6343:
Photonics North 2006
Pierre Mathieu, Editor(s)