Coupler Based On Erbium-doped Fiber Laser

The fiber laser is the key device in high-speed, large-capacity optical fiber communication systems due to its high power, low noise, tunable range, good compatibility with the common fiber, high coupling efficiency, resistance to electromagnetic interference, high surface area-volume ratio, stability, usability etc, played an increasingly important role in high-precision spectroscopy, fiber sensor, laser medical, automotive, military etc as well.Firstly, the background and components (erbium-doped fiber, resonator, pump laser) of the erbium-doped fiber laser are introduced, then we describe main optoelectronic devices including polarization controller, high birefringence fiber loop, fiber isolator and circulator.The variable wavelength erbium-doped fiber laser based on over-coupler is proposed. By optimizing the fiber coupler, coupling ratio of coupler is sensitive to wavelength, a novel fiber loop mirror which is composed of polarization controller (PC) and an over-coupler are investigated. The notch depths and positions of loops' reflection spectrum can be changed by adjusting the PC in the loops. The linear cavity of the L-band variable wavelength fiber laser consists of high-birefringence fiber loop and the over-coupler fiber loop. The reflectivity of various wavelengths and the laser gain are controlled by changing the states of the polarization controllers in the cavity. In the experiment the stable output of wavelength can be changed from 1564nm to 1592nm, over 28nm tuning range, within this range the 3dB line-width is less than 0.2nm and the side mode suppression ratio (SMSR) is more than 40dB; A simple concept of switchable multi-wavelength erbium-doped fiber laser is successfully proposed and demonstrated. The multi-wavelengths are specified by a cascaded fiber Bragg gratings. The wavelength switching can be achieved due to the polarization dependence loss induced by proper adjustment of polarization controller in ring cavity; The notch depths and positions of the reflection or transmission spectrum of fiber loop mirror that matches the gain spectrum of EDFA can be changed by adjusting the PC in the loop. The experimental results show that the spectrum can be flattened in the L-band range with ripples within±0.6dB.