“…The synthetic-wave absolute-distance interferometric measurement is a kind of high-accuracy no-guideway ranging technology based on the fraction-coincident method of the interference fringes, which provides an effective way to solve the technical problems of precision measurement and ultra-precision measurement of large-dimension workpieces. At present, the dual-frequency lasers [ 1 , 2 ] and optical-frequency combs [ 3 , 4 , 5 , 6 ] are normally used as the light sources for synthetic-wave absolute-distance interferometric systems, in which dual-frequency lasers have attracted great attention and strong research interests of scholars worldwide due to the advantages of simple structure and low cost. As the typical representatives of dual-frequency lasers, the Zeeman dual-frequency He-Ne laser at 632.8 nm [ 7 ], the two-longitudinal-mode He-Ne laser at 632.8 nm [ 8 ], and the birefringent dual-frequency He-Ne laser at 632.8 nm [ 9 ] have been successfully applied to the synthetic-wave absolute-distance interferometric system.…”