A Numerical Tool for Spectral Analysis of Fiber Bragg Gratings written in Few-Mode Excited Optical Fibers

P. Pogorzelskia, A. Anuszkiewicza, b, R. Buczyńskib, c, T. Osucha, d aFaculty of Electronics and Information Technology, Institute of Electronic Systems, Warsaw University of Technology, Nowowiejska 15/19, 00-665 Warsaw, Poland bInstitute of Microelectronics and Photonics, Łukasiewicz Research Network, Lotników 32/46, 02-668 Warsaw, Poland cFaculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland dNational Institute of Telecommunications - National Research Institute, Szachowa 1, 04-894 Warsaw, Poland

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This paper focuses on the spectral analysis of fiber Bragg gratings written in nanostructured large mode area and few-mode fibers when fundamental and higher mode(s) are simultaneously excited. For this purpose, an advanced numerical tool was developed and validated. A method for modal decomposition and superposition was proposed, which overcomes the limitations of commercial software. In the presented approach, the intermodal coupling as a consequence of non-ideal fringe pattern spatial distribution in fiber Bragg gratins is also considered. The numerical tool increases the versatility of fiber Bragg grating spectral analysis, especially taking into account the unconventional optical fibers having independent photosensitivity and refractive index profiles and few-mode operation.

DOI:10.12693/APhysPolA.146.490 topics: fiber Bragg grating (FBG), large mode area fibers, intermodal coupling, few-mode fiber