Tunable full waveband- and adjustable spacing multi-wavelength erbium-doped fiber laser based on controlling cavity losses through bending sensitive interferometric filter

In this work, tunable full waveband and adjustable spacing multi-wavelength erbium-doped fiber laser (EDFL) based on the interferometric filtering performance of a bent single-mode fiber (SMF) is experimentally demonstrated. The tunable full waveband EDFL operation with a wide wavelength-tunable range of 11.9 nm was realized by gradually varying the bent diameter of the interferometric filter structure, formed by bending a standard SMF into a balloon shape. Also, when the launched diode pump power was enhanced from 110 to 195 mW, the central wavelength of the EDFL was shifted from 1562.9 nm to 1559.5 nm. Moreover, by adjusting the polarization state inside the cavity, the wavelength operation was switched from a single to multi-wavelength operation. Dual-, triple-, and quadruple- wavelength emissions were achieved. To the best of our knowledge, this is the first time that a bending SMF into a balloon-like MZI has been employed as an all-fiber filter to manipulate the spectral output characteristic of EDFL. The proposed EDFL output characteristics of tunability and switchability can provide great potential in diverse photonics applications.