An extremely sensitive and simple fiber loop-cavity ringdown spectroscopy (FL-CRDS) setup has been designed based on a turn-key nanosecond pulse laser source operating at 1535 nm. The system sensitivity is demonstrated to be approximately 0.01 dB after extracting the characteristic macrobend loss curve of a standard single mode fiber (SMF-28). The experiment demonstrated that the oscillatory behavior in the rapid loss due to the increasing curvature could be seen for single turn bare fibers with radii of curvature from 10-20 mm. Since the wavelength of laser lies in the range of the conventional window, known as C-band, the demonstrated scheme may suggest the use of these techniques in versatile applications where quick results are necessary without the system complexity. (C) 2013 Elsevier B.V. All rights reserved.