A coupling including a main body, a first hub at a first end of the main body and a second hub at a second end of the main body opposite the first end is provided. The first hub includes a first inner bore configured to receive a first shaft and a pair of aligned first and second through holes extending through opposite walls of the first hub. The first through hole and the second through hole are in optical communication with the first inner bore.

A displacement compensating coupling comprises a first coupling member, a second coupling member and connecting elements for connecting the coupling members. The coupling members are each made in one piece from composite material and have a first flange portion for attachment to one of the drive elements, a diaphragm portion that extends radially outwardly from the first flange portion, a second flange portion and a tube portion extending from an outer circumference of the diaphragm portion to the second flange portion. Each of the tube portions has two or more recesses that are spaced from each other in circumferential direction. In a first relative position of the coupling members, the recesses of the first coupling member face the recesses of the second coupling member, and in a second relative position the recesses of the first coupling member and of the second coupling member are offset in circumferential direction.