Multi-wavelength Er–Yb-doped fibre ring laser using a double-pass Mach–Zehnder interferometer with a Sagnac interferometer

•Performance of switchable multi-wavelength laser using DMZI–SI filter is presented.•The laser output can be switched in the 1532–1546 nm wavelength range (C-band).•A side-mode suppression ratio is more than 28 dB was obtained.•Proposed laser demonstrates high stability in power and wavelength emissions.•It is suitable in optical sensing, communication systems, and microwave generation.