Widely interval-adjustable multiwavelength erbium-ytterbium doped fiber laser based on micro-air cavity

•Multiwavelength fiber laser is based on a micro-air cavity (MAC).•The MAC comprises of two opposite flat fiber-end facets with adjustable distance.•Wavelength interval can be continuously tuned via the adjustment of MAC length. We propose a widely interval-adjustable multiwavelength erbium-ytterbium doped fiber laser (EYDFL) based on a micro-air cavity (MAC). The fabricated MAC functions as a selective channel filter for multiwavelength generation with adjustable wavelength interval. By adjusting the MAC length from 0.10 to 2.40 mm, the wavelength interval can be continuously tuned from 8.61 to 0.47 nm, respectively. When the MAC length is set at 2.40 mm and erbium-ytterbium doped fiber amplifier at 300 mW, 12 multiple wavelength lasers with 0.47 nm spacing are obtained. The generated channels have an average optical signal-to-noise ratio of 40 dB and an average peak power of −35 dBm. The proposed laser introduces the advantages of a relatively simple structure and ease of operation at any wavelength band for potential applications including optical communication systems and sensing.