Roy Francis Navea et al., International Journal of Emerging Trends in Engineering Research, 8(6), June 2020, 2266 - 2270 2266 ABSTRACT Visible light communication (VLC) is a type of data communications which uses the visible light spectrum in the 350-800nm wavelength range. Light signals are converted into electrical pulses to indicate a specific information which in this case, diving instructions. In this study, VLC is used in an underwater communication system for recreational diving activities in order to reinforce the conventional hand signaling protocols. Wearable LED-based transmitter and phototransistor-based receiver were used. The hand-held transmitter was used to emit different light pulses corresponding to 16 commands in which 13 are standard scuba diving hand signals. The goggle receiver process and translates these pulses into an audio signal which can be heard by the diver through waterproof earphones. The VLC system developed was able to achieve an average signal reception accuracy of at least 97.0% on a series of tests conducted underwater with a maximum transmitter-to-receiver distance of 5m using white LEDs. Key words: Visible light communication, light emitting diodes, light pulses, underwater, scuba diving 1. INTRODUCTION Visible light is the portion of the electromagnetic spectrum seen by the human eye. A typical human eye can respond to wavelengths from 380nm to 750nm which has an equivalent frequency of 790THz - 400THz. This spectrum consists of the basic colors Magenta, Red, Red Orange, Orange, Yellow Orange, Yellow, Green Yellow, Green, Cyan, Blue, Blue Violet, and Violet [1]. Visible light has been a research interest in the development of underwater visible light communication systems which are used for tourism and in the protection of under the ocean conditions in the Okinawa Region, a popular Diving spot in Japan [2]. Light emitting diodes (LED) are commonly utilized as light sources as they offer a number of potential advantages over conventional lighting technologies taking the lead in low power consumption. LED light beam can project up to a maximum of 20m. More than this, its luminous energy will be scattered away [3]. Recreational scuba diving or sports diving is a professional underwater that requires skills and familiarity with the usage of scuba diving equipment. This also requires a high level of training and a certain number or hours of diving experience in order to be aware of the different hazards and conditions associated on how it is conducted. Divers Alert Network (DAN) is the largest diving industry association that focuses on scuba diving safety. In 2015, DAN reported 127 scuba diving fatalities around the world and most of these cases are due to the loss of communication between the divers or between the lead and the distress diver [4]. The conventional way of communication in recreational diving is through the Recreational Scuba Training Council (RSTC) approved hand signals which can be flawed when panic and low visibility situation occur under water [5]. With this, an alternative method of communication is proposed by this study. The channels used for underwater wireless communication may differ as compared to those used in radio and tv broadcast [6]. Unused frequencies in this spectrum may not be useful due to underwater wave behavior like diffraction, Doppler Shifts and spreads to name a few. Communication under water is usually through ultrasonic communication but has not been deployed in recreational diving. Ultrasonic waves experience noise due to the water surface reflections and this is not easy to use since this mode of communication could confuse divers in identifying the speaker when there are several divers are present in the same area [2]. This study presents a developmental design of a visible light communication (VLC) system for recreational diving by integrating electronic communication devices as part of scuba diving equipment. This could give divers not just a flexible bidirectional communication system but also an alternative mean of relaying information underwater. 2. METHODS As in a typical communication system, the proposed VLC system is composed of a transmitter and a receiver equipped with transmission and reception protocols. Standard hand signals are assigned in keypad buttons which when pressed, transmits unique light patterns for the receiver to decode [7]. The transmitter light source is a specialized flashlight with a Design and Development of Visible Light Communication-based Underwater Communication System for Recreational Scuba Diving Roy Francis Navea 1 , Mervin Japer Claveria 2 1 De La Salle University, Philippines, roy.navea@dlsu.edu.ph 2 De La Salle University, Philippines, merv245@gmail.com ISSN 2347 - 3983 Volume 8. No. 6, June 2020 International Journal of Emerging Trends in Engineering Research Available Online at http://www.warse.org/IJETER/static/pdf/file/ijeter10862020.pdf https://doi.org/10.30534/ijeter/2020/10862020