This application report discusses the design of non-invasive Optical plethysmography
also called as pulsoximeter using the MSP430FG437 Microcontroller (MCU). The
pulsoximeter consists of a peripheral probe combined with the MCU displaying the
oxygen saturation and pulse rate on a LCD glass. The same sensor is used for both
heart-rate detection and pulsoximetering in this application. The probe is placed on a
peripheral point of the body such as a finger tip, ear lobe or the nose. The probe
includes two light emitting diodes (LEDs), one in the visible red spectrum (660nm) and
the other in the infrared spectrum (940nm). The percentage of oxygen in the body is
worked by measuring the intensity from each frequency of light after it transmits
through the body and then calculating the ratio between these two intensities.
Optical communication technology has been extensively developed over the
last 50 years, since the proposed idea by Kao and Hockham [1]. However, only
during the last 15 years have the concepts of communication foundation, that
is, the modulation and demodulation techniques, been applied. This is pos-
sible due to processing signals using real and imaginary components in the
baseband in the digital domain. The baseband signals can be recovered from
the Optical passband region using polarization and phase diversity tech-
niques, as well as technology that was developed in the mid-1980s.
Free Space Optical Communication (FSOC) is an effective alternative technology to
meet the Next Generation Network (NGN) demands as well as highly secured (mili-
tary) communications. FSOC includes various advantages like last mile access, easy
installation, free of Electro Magnetic Interference (EMI)/Electro Magnetic Compatibil-
ity (EMC) and license free access etc. In FSOC, the Optical beam propagation in the
turbulentatmosphereisseverelyaffectedbyvariousfactorssuspendedinthechannel,
geographicallocationoftheinstallationsite,terraintypeandmeteorologicalchanges.
Therefore a rigorous experimental study over a longer period becomes significant to
analyze the quality and reliability of the FSOC channel and the maximum data rate
that the system can operate since data transmission is completely season dependent.
Optical wireless communication is an emerging and dynamic research and development
area that has generated a vast number of interesting solutions to very complicated
communication challenges. For example, high data rate, high capacity and minimum
interference links for short-range communication for inter-building communication,
computer-to-computer communication, or sensor networks. At the opposite extreme is
a long-range link in the order of millions of kilometers in the new mission to Mars
and other solar system planets.
The roots of this book were planted about a decade ago. At that time, I became
increasingly convinced that wide-area and metropolitan-area networks, where much
of my group’s research has been centered at that time, were in good shape. Although
research in these fields was (and still is) needed, that’s not where the networking
bottleneck seemed to be. Rather, the bottleneck was (and still is in many places) in
the access networks, which choked users’ access to information and services. It was
clear to me that the long-term solution to that problem has to involve Optical fiber
access networks.
Since the advent of Optical communications, a great technological effort has
been devoted to the exploitation of the huge bandwidth of Optical fibers. Start-
ing from a few Mb/s single channel systems, a fast and constant technological
development has led to the actual 10 Gb/s per channel dense wavelength di-
vision multiplexing (DWDM) systems, with dozens of channels on a single
fiber. Transmitters and receivers are now ready for 40 Gb/s, whereas hundreds
of channels can be simultaneously amplified by Optical amplifiers.
The use of light to send messages is not new. Fires were used for signaling in
biblical times, smoke signals have been used for thousands of years and flashing
lights have been used to communicate between warships at sea since the days of
Lord Nelson.
The idea of using glass fibre to carry an Optical communications signal originated
with Alexander Graham Bell. However this idea had to wait some 80 years for
better glasses and low-cost electronics for it to become useful in practical
situations.
