Path average measurements of optical fiber nonlinearity using solitons

This paper experimentally demonstrates a new method to determine the optica l nonlinearity of single-mode optical fiber. The technique takes advantage of the well-known nonlinear response of optical fibers and well-developed m odels for soliton pulse propagation to extract information about the fiber characteristics. Fiber nonlinearity can degrade the performance of communic ation systems by, for example, causing crosstalk and signal distortions, Me asuring the fiber nonlinearity would greatly aid system designers in buildi ng and upgrading communication systems, The method is utilized to determine values for n(2)/A(eff), where n(2) is the nonlinearity of the glass and A( eff) is effective area of the core, on various lengths of Coming SMF-28 fib er and Coming SMF-DS fiber. Experimentally measured propagation results for short (approximate to 2 ps) optical pulses are compared to computer simula ted models to determine the fiber nonlinearity. The method finds n(2)/A(eff ) = 3.0 x 10(-10) W-1 values for short lengths (approximate to 400 m) of Co ming SMF-28 fiber and values of 2.7 x 10(-10) W-1 for longer lengths (appro ximate to 6.5 km and approximate to 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 n(2)/A(eff) = 5.6 x 10(-10) W-1 for a approximate to 12 km Coming dispersion shifted fiber. T he method has two major regimes of operation based on the soliton period, a characteristic length for solitons, For few soliton periods (Z/Z(0) < simi lar to 4) the output phase is measured as a function of launched power; for many soliton periods (Z/Z(0) > similar to 4) the output pulsewidth is meas ured as a function of launched power. The method's major advantage is its c apability to measure long lengths of standard fiber, where it uses only sta ndard diagnostic tools such as autocorrelation and optical pow er measureme nts. However, the method is only applicable in the soliton regime of fibers .