 | Superstructure Fiber Bragg Gratings (SSFBG’s) for DWDM Systems
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| | Shinji Yamashita1)3) and Yusuke Nasu2)3) |
| 1) Dept. of Frontier Informatics, Univ. of Tokyo
2) Dept. of Electronic Eng., Univ. of Tokyo
3) CREST, JST |
| | Fiber Bragg gratings (FBG’s) are essential optical devices for both telecommunication and sensor applications. Superstructure FBG’s (SSFBG’s), or sampled FBG’s, are especially attractive for WDM systems because of their comb filter response. The comb-like filter response of SSFBG’s originates in multiple FBG’s in their structures (Fig.1). The channel spacing Δf of reflection spectrum is inversely proportional to the period of respective FBG’s Lg. Therefore, to halve the channel spacing to Δf/2, the FBG period have to be doubled to be 2×Lg (Fig. 1). Thus, the total SSFBG length is doubled. In the same way, the total length becomes 3 times to realize Δf/3 (Fig. 1). The sections between each FBG’s in the SSFBG are left unused, therefore the fiber and the phase mask are not used efficiently in the conventional SSFBG’s. |
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