Multi-band programmable gain Raman amplifier

Optical communication systems, operating in C–band, are reaching their theoretically achievable capacity limits. An attractive and economically viable solution to satisfy the future data rate demands is to employ the transmission across the full low–loss spectrum encompassing O, E, S, C, and L band of the single mode fibers (SMF). Utilizing all five bands offers a bandwidth of up to $\sim$ 53.5 THz (365 nm) with loss below 0.4 dB/km. A key component in realizing multi–band optical communication systems is the optical amplifier. Apart from having an ultra–wide gain profile, the ability of providing arbitrary gain profiles, in a controlled way, will become an essential feature. The latter will allow for signal power spectrum shaping which has a broad range of applications such as the maximization of the achievable information rate × distance product, the elimination of static and lossy gain flattening filters (GFF) enabling a power efficient system design, and the gain equalization of optical frequency combs. In this paper, we experimentally demonstrate a multi–band (S+C+L) programmable gain optical amplifier using only Raman effects and machine learning. The amplifier achieves $>$ 1000 programmable gain profiles within the range 3.5 to 30 dB, in an ultra–fast way and a very low maximum error of $1.6 \cdot 10^{-2}$  dB/THz over an ultra–wide bandwidth of 17.6–THz (140.7–nm).