It is theoretically demonstrated that the recently reported quantum-noise-limited sensitivity of the squeezed-light-enhanced German-British gravitational wave detector GEO 600 is exceedingly close to the fundamental theoretical bound, given the present amount of optical loss. Furthermore, it is proven that the employed combination of a bright coherent state and a squeezed vacuum state is generally the optimum practical approach for phase estimation with high precision on absolute scales. [Demkowicz-Dobrzanski et al, Phys. Rev. A 88, 041802(R) (2013)]