Abstract
The optical fiber filter can be used to reject the noise or unwanted spectrum in the optical communication system. In this study, the performance of the optical fiber filter in visible and near-infrared wavelengths is studied. The working principle of the filter is based on the cladding mode coupling to the high order mode introduced by perturbation on a short section of single-mode (SM) fiber with a specific cut-off wavelength. In the previous study, the filtered wavelengths from the SM-fibers with the cut-off wavelength of 600 nm are 547 nm and near IR range (980-1,100 nm). The filtered wavelength from the SM-fiber with the cut-off wavelength of 800 nm is 666 nm. Also, the magnitude of the filtered wavelengths can be controlled by the magnitude of the applied perturbation force. In this study, the green solid state laser with the wavelength of 532 nm (2nd harmonic component), 808 nm (pump wavelength), and 1,064 nm (fundamental component) and the red diode laser with the wavelength of 668 nm are launched into the SM-fiber with the cut-off wavelength of 600 and 800 nm, respectively. The experimental results clearly show that the harmonic wavelength of 1,064 nm of green laser can be filtered out by the fiber with cut-off wavelength of 600 nm up to 66% with the perturbation force 60 N. The fiber with cut-off wavelength of 800 nm can reject the red laser spectrum up to 50% with the perturbation force 80 N.
