TEMPERATURE-DEPENDENCE OF SIGNAL GAIN IN ER-3+-DOPED OPTICAL FIBER AMPLIFIERS

Temperature-dependent signal gain characteristics at signal wavelengths of 1.536 and 1.552-mu-m in Er3+-doped optical fibers with a temperature range of -40 to 80-degrees-C are reported in detail for 0.98 and 1.48-mu-m pumping. The temperature dependences of signal gain strongly depend on fiber length, pump wavelength, and signal wavelength. In particular, the fiber length at which signal gain temperature insensitivity occurs is found for the amplification of a 0.98-mu-m pump-1.536-mu-m signal, a 0.98-mu-m pump-1.552-mu-m signal, and a 1.48-mu-m pump-1.536-mu-m signal. From the measurement results of the absorption and fluorescence spectra at each wavelength band of the signal and pump lights, it is confirmed theoretically that the temperature dependences of the signal gain characteristics result from linear changes in the fluorescence and absorption cross sections at the signal and pump wavelengths, and a shift in the effective pump wavelength. Furthermore, we demonstrate temperature-insensitive optical fiber amplifiers for tuning fibers to their temperature-insensitive lengths for the above three amplifications.