Underwater wireless optical communication (UWOC) with blue-green light is a useful way to transmit data in ocean for short distance application, because it has high speed. In application, the transmitter should have larger divergence angle to make it easier to establish communication link, besides high modulated rate. Laser diode (LD) is suitable to design such transmitter, thanks to its simpler structure and much faster switching speed. However, it is difficult to be widespread used in ocean engineering because of its quite small divergence angle. For this, we present a transmitter based on blue LD and engineered diffuser. It has 100Mbps modulation rate, 80° divergence angle, and 18mW optical power. It could be used to transmit large volume data in short distance underwater communication.
Underwater wireless optical communication (UWOC) is an useful way to transmit date in ocean with short distance, because it has high speed. In application, the first challenge for this technology is establishing optical link underwater. There are two schemes to deal with this issue. The first one is enlarging the angle of divergence of the transmitter, and the field of view of receiver, which reduces the requirement to align the UWOC transmitter and receiver. However, the energy loss is increased in the transmission link. The other method needs a pointing, acquisition, and tracking (PAT) system to establish optical link. The angle of divergence of the transmitter is quite small in this way, which is helpful to reduce energy loss in the transmission link. However, in order to make the optical link stable, the receiver should measure the angle of incident of communication light all the time to provide feedback parameters to PAT system. In this work, a method is presented and demonstrated based on four-quadrant detector (QD) for such issue. It shows that the tested error for pitch angle and azimuth angle is less than 1°, as the communication system could still work with 50Kbps communication rate and 2m distance. It has demonstrated the feasibility of the method.
KEYWORDS: Receivers, Light emitting diodes, Cameras, Optical filters, Light sources and illumination, Photons, Monte Carlo methods, Transmitters, Telecommunications, Signal attenuation
Underwater wireless optical communication (UWOC) is useful for transmitting data short distances in the ocean. In most cases, such devices are placed on underwater vehicles to make it easier to establish a communication link. However, the vehicle often works in dark water. Thus it needs a light emitting diode (LED) as an illuminant for its camera to observe the surroundings, but this is noise to the UWOC system. Although such noise could be eliminated by inserting an optical filter in the UWOC receiver, the effectiveness depends on the incident angle of light into the filter. Because the illumination distribution of LED is quite complicated, there are some special requirements for UWOC systems to eliminate such noise. First, we simulate the incident angle distribution of LED illumination noise into the receivers of a bidirectional UWOC system with the Monte Carlo method. Then we analyze its influence to design an UWOC system. The results show that the wavelength of UWOC should be shorter than that of the LED illuminant to make them work simultaneously. Under the condition that the noise can be eliminated effectively, the spectrum width of the communication signal and the optical filter should be wider to enlarge the receiving field. According to the theoretical conclusion, we experimentally demonstrate a half-duplex UWOC system with an LED illuminant in dark water, where the attenuation coefficient is about 0.20 m − 1. In the system, each terminal has a white LED illuminant with 6.01 W optical power, a blue LED illuminant with 7.72 W optical power, and a UWOC transmitter based on a purple LED with about 1.25 W optical power. The UWOC realized a 27.78 Mbps rate and 19 m distance when the illuminants were open. The proposed UWOC system and its design criteria are useful for UWOC applications.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.