Modeling and Investigation of High-Power Optical-Fiber Transmitters for Lidar Applications

Abstract

In this work, we develop a high-power optical-fiber transmitter for lidar applications. The device can be utilized for measurements of the methane concentration and determination of the parameters of methane absorption line at wavelengths near 1,650 nm. The transmitter is based on a fiber Raman amplifier with an active fiber length converting the pumping radiation with a wavelength of 1,540 nm to the desired wavelength region of about 1,650 nm. We conduct the theoretical modeling of the Raman amplifier operation and demonstrate the advantage of the two-stage amplifier design over the single-stage design. In the modeling, the total power of a single Raman amplifier in the twostage design is 4.5 W with a pumping power of 5 W and an active fiber length of 1,000 m. Then we experimentally investigate the developed single Raman amplifier and demonstrate a satisfactory agreement between its parameters and the results of the theoretical modeling. The achieved average power of the transmitter at the output stage is over 7 W with two single Raman amplifiers joined in parallel. The distributed-feedback (DFB) master laser utilized in the transmitter is modulated by a linear-frequency signal with simultaneous application of a nonsynchronous high-frequency signal to eliminate the noise due to stimulated Brillouin scattering.