A demonstration of the simple optical fiber filter in visible and near-infrared wavelengths from green laser and red laser pointers

Abstract

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 prev ious 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, t he 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 (2 nd harmonic component), 808 nm (pump wavelength), and 1,064 nm (fundamental component) an d 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 ou t 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. Keywords: Optical fiber filter; Mode coup ling; Filtered wavelength , Red diode laser, Green solid state laser .