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conferenceseries
.com
Volume 4, Issue 4 (Suppl)
J Laser Opt Photonics, an open access journal
ISSN: 2469-410X
Optics 2017
November 15-17, 2017
November 15-17, 2017 | Las Vegas, USA
8
th
International Conference and Exhibition on
Lasers, Optics & Photonics
The influence of constant-envelope signals in coherent-detection optical OFDM systems
Jair Adriano Lima Silva
Federal University of Espírito Santo, Brazil
T
he resilience towards fiber dispersion is the main attractive feature of orthogonal frequency division multiplexing (OFDM) signal
processing in optical communications systems. Coherent-detection optical OFDM (CO-OFDM) posses many benefits that are
critical for high data rate fiber transmission systems. It is extremely robust against chromatic and polarization mode dispersions at the
same time that it improves spectral efficiency eliminating the need for a guard band between the optical carrier and the information-
bearing signal. Furthermore, adaptive data rates with different subcarrier mapping levels can be supported using software-defined
solutions. However, large peak-to-average power ratio (PAPR) of the inherent multicarrier signals is one of the main drawbacks in
CO-OFDM systems, as it not only limits the resolution of digital-to-analog converters and power amplifiers, but also reduces the
tolerance to the nonlinearities introduced by Mach-Zehnder (MZM) optical modulators and optical fibers. Several PAPR reduction
techniques such as coding, tone reservation, clipping, peak windowing and partial transmit sequence, have been proposed in the
literature. These distinctly techniques provide different degrees of effectiveness and tradeoffs that may include increased complexity,
reduced spectral efficiency and performance degradation. Recently, we proposed a PAPR reduction scheme based on constant
envelope (CE) signals to improve the tolerance towards MZM modulators and fiber nonlinearities in direct-detection optical OFDM
systems. As a power efficient technique, it reduced the PAPR to 3 dB using electrical phase modulation (PM). After a successful
experimental demonstration in direct-detection optical systems, this CE-OFDM technique was introduced in coherent detection
systems as a suitable solution to the aforementioned problems. Unlike the approaches evaluated in the literature, the intermediate
electrical constant-envelope signals of this solution were used tomodulate the continuous wave laser source, employing a conventional
one-branch MZMmodulator. The influence of the electrical phase modulation index
h
in the performance of CE-OFDM in coherent
detection optical systems was treated analytically and its range of validity examined by simulations. A compromise between
h
and
subcarrier mapping was identified according to differences in sensitivity related to non-linearities inserted by the MZM. We showed
that the proposed scheme outperforms conventional coherent detection OFDM systems.
Biography
Jair Adriano Lima Silva received his BS, MS and PhD degrees in Electrical Engineering from the Federal University of Esp´ rito Santo (UFES), Vitória, Brazil in 2003, 2006
and 2011 respectively. In 2012, he joined the Department of Electrical Engineering of UFES. His research interest include optical fiber communication, radio-over-fiber,
orthogonal frequency division multiplexing, passive optical communication network, visible light and powerline communiactions.
jair.silva@ufes.brJair Adriano Lima Silva, J Laser Opt Photonics 2017, 4:4 (Suppl)
DOI: 10.4172/2469-410X-C1-017