We report the realization of low-cost in-fiber WDM device function utilizing efficient side-detection of strong radiation mode out-coupling from tilted FBGs. The spatial-to-spectral conversion efficiency as high as 0.32 mm/nm is demonstrated

Bennion, Ian

Simpson, George

Zhang, Lin

Zhou, Kaiming

English

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CTuI 3 Low-cost in-fiber WDM devices using tilted FBGs K. Zhou, G. Simpson, L. Zhang, I. Bennion Photonics Research Group, Electronics Engineering Department, Aston University k.zhouk3aston.ac. uk Abstract: We report the realization of low-cost in-fiber WDM device function utilizing efficient side -detection of strong radiation mode out -coupling from tilted FBGs. The spatial-to-spectral conversion efficiency as high as 0.32mm/nm is demonstrated. 1. Introduction Radiation mode out-coupling from tilted (or blazed) fiber Bragg gratings (FBGs) has been demonstrated for applications in WDM channel monitoring[l], gain flattening of EDFAs[2] and polarization discrimination[3]; there are, however, vely few reports to date on radiati on modes being side detected at the grating's location within the fiber. Side -detection of radiation modes offer many application-specific advantages, for example; in conjunction with the use of CCD array detectors, the function of side-tapping light with high spectral resolution from tilted FBGs may be utilized to implement low cost devices for use in WDM applications. In this paper, we report the realization of in-fiber optical spectrum analyzer function utilizing effective side -detection of strong radiation mode out-coupling from tilted FBGs. 2. Transmission loss profiles of tilted gratings In order to realize strong radiati on mode out-coupling, we fabricated tilted FBGs using both phase-mask and holographic techniques. Figures la and lb  show the trans mission spectra for two sets of tilted gratings fabricated in single-mode fiber by the phase-mask and holographic methods respectively. 4 degree -40 -44 -42  1600 1510 1520 1530 1640 1560 Wavelength Wavelength (4 00) Fig.1 Transmission loss profiles of two sets of tilted FBGs in single-mode fiber fabricated using (a) phase-mask and @) holographic techniques. CTuI3 3. Side-detection If radiation mode out-coupling can be detected from the grating's position within the fiber, an optical spectrum analyzer function may be easily realized. This function is of enormous utility since it can easily implement low -cost WDM devices for applications in telecommunications and optical sensing. To this end, we have developed a system to detect the out -coupled field created by the radiation modes of tilted gratin gs. Acylindrical lens was used to focus the light on to the detector. The radiation field measurement along x-axis was performed using the set -up sketched in Figure 2a. The light from a tunable laser was launched into fiber. A scanning detector mounted on a motorized translation stage was used to measure the spatial distribution of the radiated light side -coupled out from the tilted grating. Figure 2b shows the measured power distribution along the x-axis for different wavelengths. When the wavelength changes, the corresponding focus poi nt on the x-axis moves, giving a clear spatial-to-spectral relationship. The squared curve in Figure 2c plots the peak power position against the wavelength, exhibiting a linear characteristic with a conversion coefficient of 0,17mm/nm. The conversion efficiency as high as 0.32mm/nm was also demonstrated. The top and bottom curves in Figure 2c are the radiation mode out-coupling profiles from side-detection and from end-detection respectively. detector 4 6 8 10 12 (4  W) Postion (mm) Wavelength (nm) ( C )  Fig. 2 (a) Schematic diagram of the side-detection system; (b) radiation power distribution measured using the side-detection technique; (c) plots of spatial-to-spectral relationship (squared curve) and radiation mode out-coupling profiles measured using side-detection (top curve) and end-detection (bottom curve) methods. CTuI 3 4. Conclusions The radiation mode out-coupling of tilted gratings has been effectively measured from the physical grating position within the fiber using the side -detection technique, showing the realization of in -fiber optical spectrum analyzer function. It is fmseeing that in conjunction with the use of CCD detector, the side-detection of the spatial -to-spectral encoded radiati on mode out coupling from tilted FBGs can be exploited to implement low cost WDM devices for applications in t elecommunications and optical sensing. 5. References [I] R.S.Westbrook, K.S.Feder, P.I.Reyes, P.Steinvurre1, BJEggleton, R.G.Ernst, L.A.Reith, and D.M.GiI1. “Application of fiber Bragg grating fdterhp module to a wavelength-locked low-chirp directly-modulated l0Gbis Rz transmitter” OFC 2002, ThGG49 ~ ~ 6 8 0 - 6 8 1  [2] R.Kashyap$.Wyatt and R.J.Campbel1, “Wideband gain flattened erbium fibre amplifier using a photosensitive fibre blazed grating” Electron.Lett., Vo1.29, N0.2, pp154-156(1993) [3] H.Labidi, C.Debams,RLetteron and I.Riant, “Slanted Bragg grating with ultra-low polarization dependant loss” OFC 2002, TuQ5, pp 113 

Low-cost in-fiber WDM devices using tilted FBGs

https://publications.aston.ac.uk/id/eprint/24567/1/01297981.pdf

Low-cost in-fiber WDM devices using tilted FBGs

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