Fiber lasers in the field of optical fiber communication

Fiber lasers in the field of optical fiber communication

The Fiber Laser refers to a laser that uses rare earth-doped glass fibers as the gain medium. Fiber lasers can be developed based on fiber amplifiers, and their working principle is: take a longitudinally pumped fiber laser as an example. A section of fiber doped with rare earth metal ions is placed between two mirrors with selected reflectivity. The pump light couples into the fiber from the left mirror. The left mirror transmits all the pump light and reflects the laser completely, so as to effectively utilize the pump light and prevent the pump light from resonating and causing unstable output light. The right endoscope allows the laser part to pass through in order to form the feedback of the laser beam and obtain the laser output. Photons at the pump wavelength are absorbed by the medium, forming ion number inversion, and finally generate stimulated emission in the doped fiber medium to output laser.

Characteristics of fiber lasers: High coupling efficiency because the laser medium itself is the waveguide medium. High conversion efficiency, low threshold and good heat dissipation effect; It has a wide coordination range, good dispersion and stability. Fiber lasers can also be understood as an efficient wavelength converter, that is, converting the wavelength of the pump light into the lasing wavelength of the doped rare earth ions. This lasing wavelength is precisely the output light wavelength of the fiber laser. It is not controlled by the pump wavelength and is determined only by the rare earth doping elements in the material. Therefore, semiconductor lasers of different short wavelengths and high power corresponding to the absorption spectra of rare earth ions can be utilized as pump sources to obtain laser outputs of different wavelengths.

Fiber laser classification: There are numerous types of fiber lasers. According to the gain medium, they can be classified as: rare earth doped fiber lasers, nonlinear effect fiber lasers, single crystal fiber lasers, and plastic fiber lasers. According to the fiber structure, they can be classified into: single-clad fiber lasers and double-clad fiber lasers. According to the doped elements, they can be classified into more than ten types such as erbium, neodymium, praseodymium, etc. According to the pumping method, it can be classified as: optical fiber end face pumping, micro prism side optical coupling pumping, ring pumping, etc. According to the structure of the resonant cavity, they can be classified as: FP cavity fiber lasers, annular cavity fiber lasers, “8″ shaped cavity lasers, etc. According to the working mode, they can be classified as: pulsed optical fiber and continuous laser, etc. The development of fiber lasers is accelerating. Currently, various high-power lasers, ultrashort pulse lasers, and narrow-linewidth tunable lasers are emerging one after another. Next, fiber lasers will continue to develop in the directions of higher output power, better beam quality, and higher pulse peaks.