Using Free-Spectral Range of Waveguide Gratings to Compensate for Optical CDMA Spectral Flattenness

• Main Authors: Chung-Chih Hsu, 徐崇智
• Other Authors: Jen-Fa Huang
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/40836367829888439975

碩士 === 國立成功大學 === 電腦與通信工程研究所 === 95 === Spectrum compensation over an arrayed-waveguide grating (AWG)-based optical code-division multiple-access (OCDMA) network coder/decoder (codec) is investigated. Since each network user with different signature address code has different spectral distribution, the sliced spectral power is non-equal that will cause multiple-access interference (MAI) due to the non-flattened spectra of ASE source. Flatness compensation scheme is proposed to solve the MAI effects induced by non-flattened spectra. By arranging the same coding pattern on different coding bands, spectral chips from AWG coder/decoder will incoherently power summed by FSR (free-spectral range) characteristic of AWG in the photo-detectors to approach a more flattened power level. Signal-to- interference ratio (SIR) performances are evaluated with such compensation method for the discussed OCDMA network codec. A realizable technique of spectral flatness compensation (SFC) in spectral-amplitude- coding OCDMA (SAC-OCDMA) system consists of ASE incoherent broadband source, circulators, star couplers, chirped fiber Bragg gratings (chirped-FBGs) and AWGs for encoding/decoding of unipolar M-sequence codes with balanced detection. Based on spectral flatness compensation (SFC), it is experimentally demonstrated that the performance of such system is greater than the conventional system without SFC.