1：Experimental Design and Method Selection:

The experiment involves designing and fabricating a switchable multi-wavelength figure eight EDF laser with LP beam generation in the C-band region. The methodology includes the use of spatial-mode beating due to multi-mode interference in a weakly-coupled FMF and the creation of a bandpass filter by incorporating a weakly-coupled FMF with a Sagnac fiber loop.

2：Sample Selection and Data Sources:

The samples include a customized weakly-coupled step-index fiber with specific core and cladding diameters, and a core-cladding index difference. Data sources include measurements of mode intensity profiles, OSNRs, and slope efficiencies.

3：List of Experimental Equipment and Materials:

Equipment includes a 980 nm laser diode, wavelength division multiplexer, optical isolator, polarization controller, single-mode EDF, optical couplers, optical switch, mode MUX/DEMUX, and a CCD camera. Materials include the designed FMF and SMF.

4：Experimental Procedures and Operational Workflow:

The procedure involves adjusting the polarization state of the travelling light, using a Sagnac fiber loop as an optical filter, and switching LP modes with an optical switch. The workflow includes measuring lasing outputs and stabilities for different modes.

5：Data Analysis Methods:

Data analysis includes measuring the OSNRs, slope efficiencies, and stabilities of the lasing outputs for different modes.