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Characterization of erbium doped fibers

University of British Columbia

In this thesis the theory of operation of single-mode erbium-doped fiber amplifiers pumped at 980 nm is described. Details of the derivation of the general rate equation for the propagation of signal, pump, and amplified spontaneous emission are provided. Based on this equation, and McCumber's theory of phonon-terminated optical masers, two closed form expressions are derived. In one of them, the fluorescence spectrum of an erbium-doped fiber is related to its spectral absorption coefficient. Based on this expression, a rigorous basis for the assessment of the applicability of McCumber's theory to the study of [sup 4]I[sub 13/2] ⇔ [sup 4]I[sub 15/2] transitions in erbium-doped fibers has been established. For the cases of five silica-based erbiumdoped fibers, experiments were performed and the results were used to validate this expression. Another important benefit of this expression is that it does not require a measurement of silica-based fiber's fluorescence spectrum, as it can be simply calculated from the spectral absorption coefficient, simplifying fiber characterization. The other closed form expression, provides a simple means for calculating absorption and emission cross-sections of erbiumdoped fibers using the easily measured spectral absorption coefficient, the gain coefficient at one particular wavelength, and the fluorescence lifetime. Also, based on this expression, an analytical method for the simple determination of the erbium ion concentration inside the fiber core is proposed. Experiments were performed to evaluate the cross-sections of an erbium-doped fiber over the wavelength range 1400-1650 nm. To check the accuracy of the calculated cross-sections,saturation powers at the wavelengths 1530 nm and 1550 nm were measured and results compared with the ones calculated from the cross-sections, obtaining agreements within 6%. Problems and difficulties associated with the conventional techniques for the measurement of the spectral fluorescence and of the fluorescence lifetime are described. Also new experimental setups were designed to simplify the measurement of these parameters. Furthermore, experimental techniques for the measurement of other fiber parameters such as, spectral absorption coefficient, gain coefficient, and signal saturation power are described. The new theoretical and experimental techniques presented in this thesis can provide a much simpler and more accurate means for characterizing erbium-doped fibers, improving the accuracy of the numerical models commonly used for modeling erbium-doped fiber amplifiers.

Thesis/Dissertation

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2009-02-11

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http://hdl.handle.net/2429/4483

Electrical and Computer Engineering

University of British Columbia

UBCV

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