Path average measurements of optical fiber nonlinearity using solitons

This paper experimentally demonstrates a new method to determine the optical nonlinearity of single-mode optical fiber. The technique takes advantage of the well-known nonlinear response of optical fibers and well-developed models for soliton pulse propagation to extract information about the fiber characteristics. Fiber nonlinearity can degrade the performance of communication systems by, for example, causing crosstalk and signal distortions. Measuring the fiber nonlinearity would greatly aid system designers in building and upgrading communication systems. The method is utilized to determine values for n₂/A_eff, where n₂ is the nonlinearity of the glass and A_eff is effective area of the core. On various lengths of Corning SMF-28 fiber and Corning SMF-DS fiber. Experimentally measured propagation results for short (≈2 ps) optical pulses are compared to computer simulated models to determine the fiber nonlinearity. The method finds n₂/A_eff=3.0×10^-10 W^-1 values for short lengths (≈400 m) of Corning SMF-28 fiber and values of 2.7×10^-10 W^-1 for longer lengths (≈6.5 km and ≈20 km). The difference is expected due to the 8/9 polarization scrambling factor, and the values are in agreement with reported literature [1]. The method also determines n₂/A_eff=5.6×10^-10 W^-1 for a ≈12 km Corning dispersion shifted fiber. The method has two major regimes of operation based on the soliton period, a characteristic length for solitons. For few soliton periods (Z/Z₀<N4) the output phase is measured as a function of launched power; for many soliton periods (Z/Z₀>~4) the output pulsewidth is measured as a function of launched power. The method´s major advantage is its capability to measure long lengths of standard fiber, where it uses only standard diagnostic tools such as autocorrelation and optical power measurements. However, the method is only applicable in the soliton regime of fibers