Broadband power division in fused-fiber couplers using long-period gratings

Rene Ghosh; Xavier Daxhelet; Suzanne Lacroix

doi:10.1117/12.333758

21 December 1998 Broadband power division in fused-fiber couplers using long-period gratings

Rene Ghosh, Xavier Daxhelet, Suzanne Lacroix

Proceedings Volume 3542, Doped Fiber Devices II; (1998) https://doi.org/10.1117/12.333758
Event: Photonics East (ISAM, VVDC, IEMB), 1998, Boston, MA, United States

Abstract

Index gratings written in fused-fiber couplers have been shown to make promising WDM devices featuring good wavelength selectivity. Reflection gratings especially show a narrowband wavelength response. Codirectional gratings, however, can exhibit broadband behavior under certain circumstances, such as when coupled modes of a waveguide have similar effective indices, the coupling length is short or the grating is strongly chirped. We propose a device that effects 2 X 2 power division over a large wavelength band through the fused coupler supermode coupling effected using a long period grating inscribed in the coupler waist. Coupling from one branch of the coupler to the other is null without the grating due to a strong coupler asymmetry, thus preventing the overall wavelength response from being too oscillatory. The variation of the supermode beat lengths in the coupler inducing an intrinsic chirp and the convergence at a certain coupler waist diameter of the effective indices of the two lower-order supermodes representing power transfer from one branch to the other facilitate the process of obtaining a broadband response. Though the device shown is a 2 X 2 coupler, the concept can be easily transposed to couplers having more branches than in this case.

Citation Download Citation

Rene Ghosh, Xavier Daxhelet, and Suzanne Lacroix "Broadband power division in fused-fiber couplers using long-period gratings", Proc. SPIE 3542, Doped Fiber Devices II, (21 December 1998); https://doi.org/10.1117/12.333758

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