Ultralong Raman Fiber Lasers as Virtually Lossless Optical Media

By transforming the optical fiber span into an ultralong cavity laser, we experimentally demonstrate quasilossless transmission over long (up to 75 km) distances and virtually zero signal power variation over shorter (up to 20 km) spans, opening the way for the practical implementation of integrable nonlinear systems in optical fiber. As a by-product of our technique, the longest ever laser (to the best of our knowledge) has been implemented, with a cavity length of 75 km. A simple theory of the lossless fiber span, in excellent agreement with the observed results, is presented.

Figure 1

Schematic depiction of the system.

Figure 2

Signal power excursion for two different transmission lengths. The solid lines correspond to the experimental results, whereas the dashed line shows the theoretical prediction.

Figure 3

Top: Total required pump power in the primary pumps vs input signal power. Solid line—numerics; dashed line—analytics. Bottom: Idem vs span length for a 1 mW (0 dBm) signal.

Figure 4

Lower (dashed) and upper (solid) limits for the lasing threshold vs length of the fiber link for a 1 mW (black) and a 100 mW (gray) input signal