| Summary: | 碩士 === 國立中山大學 === 光電工程學系研究所 === 97 === 100Gbit/s transmission data rate is very attractive for the next generation Ethernet
transport systems, and this kind of high-speed channel based WDM systems is very
attractive for constructing cost-effective optical transport networks. However, it is
quite difficult to achieve such high bit-rate by using the conventional amplitude shift
keying (ASK) technology. For the subcarrier modulation of the orthogonal frequency
division multiplexing (OFDM) scheme, it is possible to use various modulation
formats. It is relatively easy to use such an advanced format in the microwave domain
compared to the optical domain. Therefore, it is possible to increase the spectral
efficiency relatively easily by using the OFDM technology. In this master thesis, 100
Gbit/s WDM system with OFDM is discussed. The performance of 8 channels
100Gbit/s OFDM system was evaluated. The simulation result showed that the BER
of all channels were below 10-3 after 500 km transmission, and the performance could
be improved by using the FEC. This result shows the possibility of 100Gbit/s
transmission system using the OFDM technology.
The major concern of WDM-PON system is the cost. For WDM-PON system, it
needs several light sources for downstream signals and upstream signals. For the
practical implementation of WDM-PON, it is essential to develop a low-cost light
source in the optical network unit (ONU). In order to develop a simple efficient ONU,
a promising solution is re-modulated the downstream signal from central office (CO)
as the upstream signal at ONU using reflective semicounductor optical amplifier
(RSOA) so that there is no need to setup an additional light source at the ONU side.
For the conventional fiber-to-the-home (FTTH) system, the modulation format for
both downstream signal and upstream signal is intensity modulation with direct
detection (IM/DD). The demerit of the IM/DD scheme for the FTTH system is that
the performance of the re-modulated upstream signal is limited by the interference of
the downstream signal. In order to overcome this issue, the IM/DD format of
downstream should be replaced by some different formats such as differential phase
shift keying (DPSK). As there is no amplitude modulation for the DPSK downstream
signal, the re-modulated signal will not be affected by the downstream signal.
Therefore, this master thesis is focusing on comparing the re-modulated signal quality
for both IM/DD downstream and DPSK downstream. The experimental results shows
that the upstream signal of the DPSK downstream case shows better performance than
the IM/DD downstream case, and the performance difference of the re-modulated
signal is 17dB.
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