A dual wavelength erbium-doped random fiber laser with tunable wavelength separation

A dual wavelength erbium-doped random fiber laser, based on a micro air cavity, is experimentally demonstrated. The proposed random fiber laser has a lower threshold of about 15 mW and a high optical signal to noise ratio of over 40 dB. Changing the length of air cavity realizes a stable dual wavelength output with a variable and controllable separation from 2.5 nm to 20.2 nm. The measured fluctuation of lasing wavelengths and the output powers are smaller than 0.005 % and 2.25 %, respectively, which are proved to be very highly stable with such a relatively simple structure. It is expected to meet the growing demand of applications including optical communication, lidars, fiber sensing, and so on.