Optical Wireless Data Transfer Through Biotissues
Light has been used in many medical applications to monitor health status and diagnose diseases. Examples include optical sensing through nearinfrared (NIR) spectroscopy, optical coherence tomography, and pulse oximetry. In this article, we propose and demonstrate digital communications through biological tissues using near-infrared light. There are many possible uses to an optical system transmitting information across tissues. In current practices, implants predominantly use radio frequency (RF) radiation for communication. However, molecular biology restricts use of the RF in terms of power, frequency etc., while interference and security issues represent technological challenges in RF communication. In this paper, we demonstrate a novel way of employing NIR light for wireless transmission of data through biological tissues. A phantom mimicking a biological tissue is illuminated with a NIR 810 nm wavelength light-emitting diode (LED), and a light detector with line-of-sight alignment is placed on receiving end. An experimental testbed for Optical Communications through Biotissue (OCBT) was designed and implemented using mostly off-the-shelf components. Measurements for different levels of optical output power and thicknesses were carried out. Transmission rates as high as several tens of kilobits-per-second across several millimeters of tissues were achieved. Hardware limitations in modulating the baseband signal prevented achieving higher data rates. In addition, a high-resolution picture was successfully transmitted through biotissue. The communication system as well as details of the testbed implementations are presented in this paper. Moreover, initial performance measures as well as suggestions for potential use of this optical communication system are also presented and discussed.