In this study, two fiber Bragg grating sensors are multiplexed using time division multiplexing. The fiber Bragg gratings are setup in a dual bus configuration and the sensor signals are detected using a transmit-reflect detection system. The results demonstrate that both the transmitted and reflected signals from both fiber Bragg gratings can be resolved when the sensors are separated by a sufficient distance.
In this paper, we report the response of Cobalt-60 gamma irradiation on Photonic Crystal Fibre Bragg gratings (PCFFBGs) and standard commercial FBGs (STD-FBGs). Optical measurements were performed to determine the shift of the Bragg wavelength as a function of accumulated dose and relaxation time. To simulate real time conditions of a radiation dosimeter, the FBGs are examined through three consecutive radiation stages followed by very limited recovery times. We were able to obtain a Bragg wavelength shift with both sets of FBGs. The PCF-FBGs response included strong recovery after each irradiation compared to the STD-FBGs. This makes the PCF-FBGs strong candidates as optical fibre FBG sensors in the area of radiation dosimetry.
In this study, a fibre Bragg grating (FBG) was embedded beneath three common flooring materials acting as a pressure
switch for in-ground intrusion detection. This is achieved using an intensiometric detection system, where a laser diode
and FBG were optically mismatched so that there was a static dc offset from the transmitted and reflected optical power
signals. As pressure was applied, in the form of a footstep, a strain induced wavelength shift occurred that could then be
detected by converting the wavelength shift into an intensity change. The change in intensity caused a significant change
in the DC offset which behaved as on optical switch. This switch could easily be configured to trigger an alarm if
required. The intention is to use the FBG sensor as an in-ground intrusion detection pressure switch to detect an intruder
walking within range of the sensor. This type of intrusion detection system can be applied to both external (in soil, etc)
and internal (within the foundations or flooring of the home) security systems. The results show that a person's footstep
can clearly be detected through solid wood flooring, laminate flooring, and ceramic floor tiles.
In this study, we compare the practical implementation of both silicon and germanium Photovoltaic Power Converters
(PPCs). Simulations have previously shown that silicon PPCs can produce up to 43% optical to electrical power
conversion and germanium PPCs can produce conversion efficiencies as high as 22% when illuminated by 980nm light.
Moreover, germanium can produce conversion efficiencies of up to 36% when illuminated by 1550nm light. Here, we
compare these results to real power conversion efficiencies of off-the-shelf silicon and germanium photodiodes,
producing 9.9% and 8.0% conversion efficiencies, respectively for 980nm. Furthermore, we show germanium produces
conversion efficiencies up to 14.6% under illumination of 1550nm light. A discussion of the limitations is made. The
results show there is a peak efficiency point corresponding to a specific input optical power. We also show that the
power over fibre signal can be successfully combined with communications signals, using wavelength division
multiplexing, and that the multiplexed signals can be separated without significant loss of signal, or power conversion
efficiency. In addition, we investigate the affects of free space problems, such as divergence and misalignment, in both
the lateral and longitudinal directions. As expected, optical alignment plays a significant role in producing maximum
Most automated industrial processes use Distributed Control Systems (DCSs) or Programmable Logic Controllers
(PLCs) for automated control. PLCs tend to be more common as they have much of the functionality of DCSs, although
they are generally cheaper to install and maintain. PLCs in conjunction with a human machine interface form the basis of
Supervisory Control And Data Acquisition (SCADA) systems, combined with communication infrastructure and Remote
Terminal Units (RTUs). RTU's basically convert different sensor measurands in to digital data that is sent back to the
PLC or supervisory system. Optical fibre sensors are becoming more common in industrial processes because of their
many advantageous properties. Being small, lightweight, highly sensitive, and immune to electromagnetic interference,
means they are an ideal solution for a variety of diverse sensing applications. Here, we have developed a PLC Optical
Fibre Sensor Interface Module (OFSIM), in which an optical fibre is connected directly to the OFSIM located next to the
PLC. The embedded fibre Bragg grating sensors, are highly sensitive and can detect a number of different measurands
such as temperature, pressure and strain without the need for a power supply.