The dependence of the output pulse characteristics of a Mamyshev fiber oscillator on cavity parameters is investigated in detail. We analyze the change in pulse spectrum bandwidth, pulse duration, dechirped pulse duration and chirp with the change in fiber group velocity dispersion, fiber nonlinearity, gain, and filters by putting forward a numerical model. In particular, as one of the most important components, the effect of filters bandwidth and the central wavelength interval between them is discussed. The passive fibers are classified into two kinds according to their locations in the cavity, which are the one before the gain fiber and the one after the gain fiber. Numerical simulation results show that a wide spectrum can be obtained by increasing the nonlinearity of the second passive fiber, while the change in nonlinearity of the first passive fiber has a weak effect on spectrum broadening. A wide spectrum could also be obtained by increasing the nonlinearity or the small-signal gain coefficient of the gain fiber. A Yb-doped Mamyshev fiber oscillator is demonstrated. The results show the increase in pump power, which agrees reasonably well with the numerical simulation results.

An interference filter is designed by cascading two Mach-Zehnder interferometers (MZIs), which is then utilized in the construction of a wavelength interval adjustable dual-wavelength Erbium-doped fiber laser (EDFL). Each MZI consists of two 3 dB optical couplers (OCs) connected in series. The input light is split into two arms at the first OC and recombined at the second OC. The first MZI (MZI 1) has a smaller free spectral range (FSR) and is used for selecting the output wavelength of the laser. The second MZI (MZI 2) has a larger FSR and forms an envelope structure on the comb-like spectrum of MZI 1. By adjusting the optical path difference between the two arms of MZI 2, the FSR of the envelope can be changed, thereby altering the interval of the output wavelengths. The implemented filter is inserted into the EDFL to achieve stable dual-wavelength output. By stretching one arm of MZI 2, the interval of the dual-wavelength can be adjusted from 4.64 to 13.94 nm, with the side-mode suppression ratio of over 44 dB for all wavelengths.