Study on the influence of Mach-Zehnder interferometers to the output characteristics of multiwavelength erbium-doped fiber laser

Serving as a frequency selective device, comb filter is a very important component to the multiwavelength erbium-doped fiber laser. There are all kinds of comb filters, among which the Mach-Zehnder interferometer (MZI) is the commonly used one. Since each types of Mach-Zehnder interferometers have its output features, then the study of its influence to the output characteristics of multiwavelength erbium-doped fiber laser is necessary. In this paper, the filtering properties of three basic Mach-Zehnder interferometer are discussed, including single-pass MZI, dual-pass MZI, dual-pass MZI with a optical isolator embedded into the second loop. Furthermore, the working principle and tunable operation of the tunable modified dual-pass MZI are analyzed. Above all, the influence of the four types of MZI to the output characteristics of multiwavelength erbium-doped fiber laser is experimentally studied. The results of this paper are helpful to understand the working principle of these comb filters and improve the output performance of multiwavelength erbium-doped fiber laser.