A 1 Mbps Underwater Communication System Using a 405 nm Laser Diode and Photomultiplier Tube

communications;optical;underwater;laser diode;laser;free space optical;PMT;photomultiplier tube

Cox, William Charles, Jr. ; Dr. Brian Hughes, Committee Member,Dr. John Muth, Committee Chair,Dr. Robert Kolbas, Committee Member,Cox, William Charles, Jr. ; Dr. Brian Hughes ; Committee Member ; Dr. John Muth ; Committee Chair ; Dr. Robert Kolbas ; Committee Member

University:North Carolina State University

关键词: communications;    optical;    underwater;    laser diode;    laser;    free space optical;    PMT;    photomultiplier tube;   

Others  :  https://repository.lib.ncsu.edu/bitstream/handle/1840.16/1696/etd.pdf?sequence=1&isAllowed=y

美国|英语

来源: null

【 摘 要 】

Radio frequency communications in seawater are impractical due to high conductivity ofseawater limiting the propagation of electromagnetic waves. Current methods, such asacoustic communication, are limited in bandwidth, and the use of cables, such as fiber optic,are expensive and not practical for autonomous vehicles. Underwater tetheredcommunication systems are also very costly to repair if damaged. Optical wirelesscommunications that exploit the blue/green transparency window of seawater potentiallyoffer high bandwidth, although short range, communications.The goal of this Masters thesis was to build sufficient infrastructure to experimentallyvalidate the performance of underwater optical communication systems under laboratory, buthopefully realistic, water conditions.An optical transmitter based on a 405nm blue laser diode was constructed. Thetransmitter is capable of sourcing 200mA of current to a blue laser diode at speeds of up to200MHz. The receiver was based on a photomultiplier tube. The high gain and blue/greensensitivity of a photomultiplier tube make it ideal for underwater optical communications.Finally, a 1,200 gallon water tank was constructed that allows the water conditions to beappropriately controlled to simulate an ocean environmentExperiments were conducted to validate the design and construction of the receiver,transmitter and water tank. An underwater optical data link was demonstrated that wascapable of transmitting data at 500kpbs in return-to-zero format, or 1Mpbs in non-return-tozeroformat. The transmitted signal could then be optically detected, digitized and stored on aPC for later signal processing.