Application of Carrier-Less Amplitude-Phase Modulation in Short-Reach Optical Interconnection with 850-nm VCSELs and Multimode Fiber

• Main Authors: Ting-Wei Zhou, 周庭瑋
• Other Authors: Chia-Chien Wei
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/6c3wy5

碩士 === 國立中山大學 === 光電工程學系研究所 === 106 === This dissertation studies the application of carrier-less amplitude phase modulation (CAP) in short-reach MMF transmission. In addition to two different modulation orders (i.e., CAP-16 and CAP-32), we adopted two kinds of filters in CAP modulation, which are named by Filter 1 and Filter 2. The frequency responses of two data paths in Filter 1 are root raised cosine functions multiplied by sine and cosine, and this scheme is not only inter symbol interference- (ISI-) free but also maintains orthogonality between two paths. As to Filter 2, the root raised cosine function and its Hilbert transform are directly used as the frequency responses of two data paths. Although higher spectral efficiency can be achieved by Filter 2, the orthogonality between two paths does not hold unless the roll-off factor is zero. We used the Volterra and decision feedback equalizer (DFE) to equalize the CAP signals, and the corresponding improvement can demonstrate the characteristics of the used filters. First of all, we experimentally compared the CAP signals based on the two filters at optical back-to-back. When the symbol rate is low, Filter 1 can outperform due to the orthogonality. However, when the symbol rate increases, Filter 2 can perform better due to its better spectral efficiency. In particular, when the system bandwidth was reduced after 200- or 500-m MMF transmission, the highest data rate of CAP-16 was achieved by Filter 2. Nonetheless, if CAP-32 was used, the highest data rate was accomplished by Filter 1 because symbol rate was low to meet the requirement of higher SNR. Since CAP-16 can achieve higher data rate compared to CAP-32, this work demonstrates that Filter 2 is a potential candidate for future high-capacity short-reach MMF transmission.