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We describe the first wide-band tellurite-based fiber Raman amplifier (T-FRA) for application to seamless ultra-large-capacity dense wavelength-division multiplexing (WDM) systems. First, we confirmed that the Raman scattering characteristics of the tellurite-based fiber has so large a gain coefficient and Stokes shift that we can achieve a wide-band tellurite-based fiber Raman amplifier with a shorter fiber length than when using silica-based fiber. Second, we investigated the small signal gain and the signal transmission characteristics for a high gain and high output power operation with a single-stage amplifier. Focusing on double Rayleigh scattering, we compared the high gain limit of tellurite- and silica-based fibers. We then studied the impact of nonlinear effects by measuring the bit error rate (BER) when using a two-stage amplifier with a high output power of 18.8 dBm in which we simultaneously amplified eight channel signals in the L-band located on the ITU 100-GHz grid. Finally, we designed a wide-band tellurite-based fiber Raman amplifier with a multiwavelength band pumping scheme. We constructed this amplifier with a tellurite-based fiber only 250 m in length pumped by four-wavelength-channel laser diodes, and it provided a 160-nm bandwidth with a gain of over 10 dB and a noise figure below 10 dB from 1490 to 1650 nm. We also measured the BER to confirm the transmission characteristics of the amplifier for single channel operation over the whole signal wavelength range of 160 nm. We thus confirmed that the amplifier could be employed in ultra-high-capacity WDM systems.