Wind turbine blade with optical sensor system

Wind turbine blade extending along a longitudinal axis from a root end to a tip end and in a transverse plane perpendicular to the longitudinal axis, the transverse plane having a main axis extending through an elastic center point, the wind turbine blade comprising a blade shell forming a profiled contour including a pressure side and a suction side, as well as a leading edge and a trailing edge with a chord having a chord length extending there between, the main axis being parallel to the chord, the wind turbine blade comprising a sensor system with an optical path comprising a first optical sensor fiber, a second optical sensor fiber and a patch optical fiber, the first optical sensor fiber including a first core with a first core diameter, wherein the first optical sensor fiber extends from a first end to a second end and comprising at least one sensor, the second optical sensor fiber including a second core with a second core diameter, wherein the second optical sensor fiber extends from a first end to a second end and comprising at least one sensor, the patch optical fiber including a patch core with a patch core diameter, wherein the patch optical fiber extends from a first end to a second end and connects the first optical sensor fiber and the second optical sensor fiber, wherein the first core diameter is the same as the patch core diameter.