Digital Twin technology as an idea of implementing simulation models of particularly every physical entity became universally adopted in the last five years thanks to a huge leap in computer hardware performance and software tools evolution. The early pioneers of Fiber Optic Current Sensors (FOCS) technology in the late 90-th had no access to such an advanced research tool as digital twin of the product being developed. As a result, nowadays FOCS remain undervalued due to its legacy problems including the lack of stability and high cost. However, the Connected World, Industrial Internet of Things open the great opportunities for new metering technologies in power grid. The modern computer simulation approaches helped us in this challenge to bypass the caveats of FOCS, to understand and improve this technology making it more accurate, robust and more competitive in its field.