The nonlinear coefficient (nLc) is the ratio of the Kerr nonlinear refractive index@ n2@ and the effective area@ Aeff (see FOTP-132)@ as: The nonlinear coefficient is related to the following nonlinear optical distortion effects as a combined parameter: Self-phase modulation (SPM) Cross-phase modulation (XPM) Four-wave mixing (FWM) Other fiber attributes@ such as chromatic dispersion@ also influence the transmission. Two methods are given@ with details specific to each in normative annexes. They are: Method A Continuous-wave dual-frequency Method B Pulsed single-frequency Both methods require injecting very high powers (5 dBm or more) into the fiber@ measurement of this power (absolute)@ and measurement of the output spectrum - which is modified by nonlinear effects. Both methods use calculations that combine these measured results with those derived from other measurements such as attenuation (FOTP-61 or FOTP-78) and chromatic dispersion (FOTP- 168@ FOTP-169@ or FOTP-175). Both methods have limitations on the length of fiber that can be measured - in a relationship with the chromatic dispersion at the wavelength being measured.