Six-Wavelength-Switchable SLM Thulium-Doped Fiber Laser Enabled by Sampled FBGs and 3 × 3 Coupler Based Dual-Ring Compound Cavity Filter

Abstract

A switchable and tunable six-wavelength single-longitudinal mode (SLM) thulium-doped fiber laser in the 2050 nm band is proposed and experimentally demonstrated. Two cascaded sampled fiber Bragg gratings (SFBGs), acted as an integrated six-channel reflector, are to define the lasing wavelength channels in a multi-wavelength switchable fiber laser for the first time. The switchability of the fiber laser was realized by polarization-dependent loss modulation. SLM lasing in each channel was guaranteed by a novel passive dual-ring compound cavity (DRCC), composed of two symmetric 3 × 3 optical couplers (OCs). Six single-wavelength operations are easily obtained and switched, with the high optical signal-to-noise ratios of >71 dB, >72 dB, >62 dB for λ 11 -λ 13 and > 65 dB, >61 dB, >59 dB for λ 21 -λ 23, respectively. The maximum power and wavelength fluctuations are as low as 0.56 dB and 0.01 nm, respectively. The measured laser linewidths ranged from 7.5 to 9.2 kHz, calculated by the β-separation line method based on the measured frequency noise spectra. Nine switchable dual-wavelength operations with different wavelength intervals and two triple-wavelength operations were also obtained. Our proposed fiber laser has great potential in free-space optical communication.

Tuning of laser frequency spacing output by lasers via fiber ring filter banks

“…The longer cavity length of the ring cavity allows for the flexible insertion of tuning and filtering components, which expands the tuning range and results in a narrower laser linewidth. Currently, prominent wavelength-selective devices include Fabry-Perot filters [7] , fiber Sagnac ring filters [8] , fiber Lyot filters [9] , Mach-Zehnder interferometer filters [10][11] , and multi-fiber ring-structure filters [12][13] , among others. This paper investigates the filtering characteristics of fiber ring filters.…”

Thulium-doped fiber laser with switchable single-wavelength output using polarization-dependent loss

“…However, PDL can be easily induced by inserting a polarization controller and an in-line polarizer that are compatible with the fiber structure of the laser cavity. In fact, however, using PDL to realize switchable output in TDFL has rarely been reported [33][34][35].…”

Refractive index sensing of melting tapered fiber coupler based on dual-port input

“…Fiber coupler is a new type of optical passive device used for the proportional distribution and synthesis of optical power based on micro-nano fiber [1][2][3] . With the rapid development of optical fiber communication, and fiber network, the fiber coupler studied by domestic and foreign scholars gradually deepened, thereby making fiber coupler in many high-tech fields more and more widely used [4][5][6] .…”