Tunable U-Band Multiwavelength Brillouin-Raman Fiber Laser with Double Brillouin Frequency Spacing in a Full Open Cavity

A tunable U-band multiwavelength Brillouin-Raman random fiber laser with double Brillouin frequency spacing is demonstrated in a full open cavity utilizing 11 km dispersion compensating fiber (DCF). In this setup, in order to increase the generated Brillouin Stokes lines, optimizing Brillouin and Raman pumps powers with their corresponding wavelengths is necessary. At Brillouin pump wavelength of 1640 nm, with optimized Brillouin and Raman pumps powers, a high number of output channels with high optical signal-to-noise ratio (OSNR) have been attained. In this case, a total of 250 Brillouin Stokes lines of which 152 channels within 3 dB peak power variation are obtained across 26 nm bandwidth at Brillouin and Raman pump powers of 11.8 dBm and 1200mW, respectively. In addition, all the 3 dB-flattened Brillouin Stokes lines (BSLs) exhibit an average OSNR of 29 dB. The laser has a tuning range from 1633 to 1640 nm, translated into 7 nm restricted by the tunable laser source (TLS) maximum wavelength, which can be extended by utilizing TLS with a higher maximum wavelength.