[20p-P6-1~3] 3.16 Optics and Photonics English Session

▲ [20p-P6-3] Effect of pump wavelength on Brillouin gain spectra in optical fibers

〇(M1)李 熙永¹、林 寧生¹、水野 洋輔¹、中村 健太郎¹ (1.東工大精研)

キーワード：Brillouin scattering,Optical fibers,Erbium-doped fiber amplifiers

Over the past few decades, optical fiber sensors based on Brillouin scattering have been extensively studied owing to their ability to measure strain and temperature distribution. Brillouin scattering is one of the nonlinear phenomena in optical fibers; higher-power pump light induces even higher-power scattered light, leading to a high signal-to-noise ratio (SNR) of the sensing system. In addition, such higher-power pump light provides narrower Brillouin linewidth, resulting in a high-precision measurement. Therefore, Brillouin sensors have been mainly implemented using lasers at the telecom wavelength, where relatively inexpensive erbium-doped fiber amplifiers (EDFAs) have been used. The typical wavelengths of lasers at the telecom wavelength are 1510, 1530, and 1550 nm. To date, no reports have been provided as to which wavelength is the most suitable for Brillouin observation, because the Brillouin gain spectrum (BGS) is known not to be largely dependent on the wavelength of the pump light in this range. However, the BGS observed by using a practical setup containing an EDFA for preparing the Brillouin pump light should exhibit optical wavelength dependence if we consider the wavelength dependence of the gain of the EDFA. In this work, we investigate the optical wavelength dependence of the BGS in a silica single-mode fiber (SMF) using an experimental setup containing an EDFA in the Brillouin pump path. The driving current of the 980-nm pump laser in the EDFA is constant. As a result, the Brillouin peak power and linewidth exhibited a clear dependence on the pump wavelength, the trend of which corresponded well with the wavelength dependence of the EDFA gain. Thus, we showed that, to practically obtain a higher Brillouin peak power and narrower linewidth at the telecommunication wavelength, the unique wavelength dependence of the gain of the EDFA used in the system should be carefully considered. We anticipate that this result will be a practically useful guideline for selecting suitable light sources for developing strain and temperature sensors based on Brillouin scattering with a high SNR and high precision.