| Summary: | 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.
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