《Improved Tuning Accuracy of Fiber Grating Lasers using LVDT》.pdfVIP

Improved Tuning Accuracy of Fiber Grating Lasers using LYPT w. H. Chung12 H. Y. Tam2 M. S. 2 and P. K. A. 2 I Photonics Research Center, The Hong Kong Polytechnic University , Department of Electrical Engineering, The Hong Kong Polytechnic University 3 Department of Electronic and Information Engineering, The Hong Kong Polytechnic University ABSTRACT A microprocessor controlled feedback system using a linear variable differential transformer to measure the compression of a fiber Bragg grating with a view to improve the tuning accuracy of a fiber grating laser is reported. This technique overcomes the large hysteresis of the PZT actuator normally used to compress the grating. A tuning range ofabout 20 nm with a readout wavelength accuracy ofbetter than was achieved. Keywords Fiber lasers, wavelength tuning, fiber Bragg gratings, WDM applications 1. INTRODUCTION Fiber lasers based on fiber Bragg gratings (FBGs) are promising candidates for dense wavelength-division multiplexing (DWDM) systems because of the ease to produce FBG with a highly accurate and repeatable Bragg wavelength that match the ITU wavelength grids. Recently, there has been intense interest in using tunable sources in DWDM systems to use as spare components in order to reduce cost by stocking fewer spare lasers. Tunable fiber grating lasers offer an important advantage in this respect because an FBG can be tuned over a large wavelength range in comparison with a semiconductor lasers which normally can be tuned over just 1 -2 nanometers. FBG tuning is generally achieved by using either thermal or mechanical m