52 m/9 Gb/s PAM4 Plastic Optical Fiber- Underwater Wireless Laser Transmission Convergence with a Laser Beam Reducer

Autor: Pei-Hsien Chew, 周沛賢
Rok vydání: 2018
Druh dokumentu: 學位論文 ; thesis
Popis: 106
Underwater wireless laser transmission (UWLT), a promising provider of high-speed underwater links, has obtained considerable interest over the past few years. Some recent works have shown that high-speed UWLTs can be achieved over finite underwater links. Transmissions of several gigabit per second (Gb/s) with limited underwater links have been implemented using different water types with attenuation characteristics, which is a com-bination of absorption and scattering. Nevertheless, transmissions of several Gb/s with long-reach underwater links have not been realized. For the real implementation of high-speed UWLTs, constructing a long-reach underwater link is amajor concern of system designers. Many applications of UWLTs have been proposed for environmental monitoring, disaster precaution, offshore exploration, and underwater oil pipe investigation. To meet the demands of different applications, a high-speed UWLT with a long-reach underwater link is required. A new transmissionmediumdifferent from the aquatic medium is required to realize a long-reach underwater link. A graded-index (GI) plastic optical fiber (POF) has been developed with good features, such as large core diameter, small bending radius, high bandwidthdistance product, and low transmission loss. The GI-POF can enhance the coverage of UWLT and, thus, can be effectively utilized as an underwater extender of UWLT. As a result, a long-reach underwater link can be practicably constructed by adopting a POF-UWLT convergence. In this Letter, a 9 Gb/s four-level pulse amplitude modulation (PAM4) POF-UWLTconvergence with a laser beam reducer for reducing the collimated beam diameter over a 50 m GI-POF transmission with a 2 m clear ocean water link is proposed. For the first time, to the authors’ knowledge, a 52 m/9 Gb/s PAM4 POFUWLT convergence is practically demonstrated with the application of a laser beam reducer to reduce the collimated beam diameter. For reducing the collimated beam diameter, the laser beam reducer converts a large collimated beam diameter into a small one. The laser beam reducer has been adopted in free-space optical (FSO) communications to improve the performances of FSO links. However, it has not been adopted as the performance improvement scheme in POF-UWLT convergence. POF-UWLT convergence presents several similarities compared to FSO links due to the fact that they utilize optical wavelengths to deliver data signals between dedicated point-to-point links. A laser beam reducer, which can reduce the collimated beam diameter, is thereby expected to improve the performances of PAM4 POF-UWLT convergence. The performances of PAM4 POF-UWLT convergence in view of bit error rate (BER) and eye diagrams improve with the decrease of the collimated beam diameter because of the lower amounts of light absorbed by clear ocean water. Competent BER and clear eye diagrams (three independent eye diagrams) are acquired at a 50 m GI-POF operation with a 2 m clear ocean water link. Our novel proposal reveals a more prominent one than those of UWLTs with short-reach and low-speed characteristics. This proposed 52 m/9 Gb/s PAM4 POF-UWLT convergence is demonstrated to be superior over the prior UWLTs, given its feasibility for long-reach and high-speed underwater links.
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