You can use http://www.arcgis.com/home/item.html?id=b59665cb906a435da3f8c45332d7cfdf
ArcGIS Pro 2.1 introduced a geoprocessing tool that will also convert densified lines into one or more separate circular arcs by fitting circular arcs to the straight-line segment sequences. This new gp tool can be found in the Editing toolbox and is called Simplify By Straight Lines And Circular Arcs. http://pro.arcgis.com/en/pro-app/tool-reference/editing/simplifybystraightlinesandcirculararcs.htm