Suppression of Stimulated Brillouin Scattering by Intentionally Induced Periodical Residual-Strain in Single-Mode Optical Fibers

Akira WADA  Tetsuo NOZAWA  Tak-On TSUN  Ryozo YAMAUCHI  

IEICE TRANSACTIONS on Communications   Vol.E76-B   No.4   pp.345-351
Publication Date: 1993/04/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Optical Fiber Cables and Related Technologies)
optical fiber,  stimulated Brillouin scattering (SBS),  brillouin threshold,  residual strain,  

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Single-mode fibers with intentionally induced periodical residual strains (IIPRS) along the fiber length are proposed for the suppression of the stimulated Brillouin scattering (SBS). A change of the residual strain along a fiber will change the Brillouin frequency shift, resulting in a broadening of the Brillouin gain profile. Such an increase of the line-width of the gain profile will cause a decrease of the gain coefficient which will raise the threshold power of the stimulated Brillouin scattering in optical fibers. Two types of the IIPRS fibers were fabricated. The residual strain of one IIPRS fiber is modified rectangularly while that of the other is changed triangularly. The measured spectra of the SBS are compared with that of a fiber with a constant strain. Using a novel mathematical model presented in this report, the possible improvements of the threshold powers for these two IIPRS fibers over the constant-strain fiber can be assessed through the SBS spectra. Finally, the achieved improvements are confirmed with the experimental results. The estimated improvement of the threshold for the IIPRS fiber with the rectangular profile is 2.9dB while the measured is 2.4dB. In case of the IIPRS fiber with a triangular profile, the improvement of the threshold is 5.4dB by estimation and is 5.1dB by experiment. While the limit of the threshold improvement for rectangular IIPRS fibers is 3dB, the threshold improvement for triangular IIPRS fibers is limited only by the allowable deviation of the tension applied during the drawing of fibers. It is estimated that a 5dB improvement is not difficult to realize.