Graphene-deposited photonic crystal fibers for continuous refractive index sensing applications

© 2015 Optical Society of America. We present a pilot demonstration of an optical fiber based refractive index (RI) sensor involving the deposition of graphene onto the surface of a segment of a photonic crystal fiber (PCF) in a fiber-based Mach-Zehnder Interferometer (MZI). The fabrication process is relatively simple and only involves the fusion splicing of a PCF between two single mode fibers. The deposition process relies only on the cold transfer of graphene onto the PCF segment, without the need for further physical or chemical treatment. The graphene overlay modified the sensing scheme of the MZI RI sensor, allowing the sensor to overcome limitations to its detectable RI range due to free spectral range issues. This modification also allows for continuous measurements to be obtained without the need for reference values for the range of RIs studied and brings to light the potential for simultaneous dual parameter sensing. The sensor was able to achieve a RI sensitivity of 9.4 dB/RIU for the RIs of 1.33-1.38 and a sensitivity of 17.5 dB/RIU for the RIs of 1.38-1.43. It also displayed good repeatability and the results obtained were consistent with the modeling

Continuous refractive index sensing based on carbon-nanotube-deposited photonic crystal fibers

We present a carbon nanotubes (CNTs) deposited photonic crystal fiber (PCF) featuring a Mach-Zehnder interferometer configuration for refractive index (RI) sensing applications. The high RI of the CNTs deposited on the surface of the PCF not only enhances the interaction of the evanescent waves of the cladding modes with the ambient environment around the fiber, but also modifies the sensing scheme to that of intensity variations. Such a modification makes the sensor susceptible to power fluctuations from the optical source but allows the sensor to gain immunity to free spectral range limitations which is commonly found in PCF-based sensors. As such continuous and repeatable measurements can be obtained for the range of RIs being measured. The sensor registered a sensitivity of 19.4 dB/RIU within the RI range of 1.33 to 1.38 and a sensitivity of 24.2 dB/RIU within the RI range of 1.38 to 1.42. Since there is no mechanical modification of the overall structure of the sensing element, the fiber retains its mechanical strength which makes it viable for practical applications. The experimental results are found to be consistent with the modeling of the sensor's behavior. © 2014 Elsevier B.V

Optical Environmental Sensing in Wireless Smart Meter Network

In recent years, the traditional power grid is undergoing a profound revolution due to the advent and development of smart grid. Many hard and challenging issues of the traditional grid such as high maintenance costs, poor scalability, low efficiency, and stability can be effectively handled and solve in the wireless smart grid (WSG) by utilizing the modern wireless sensor technology. In a WSG, data are collected by sensors at first and then transmitted to the base station through the wireless network. The control centre is responsible for taking actions based on this received data. Traditional sensors are failing to provide accurate and reliable data in WSG, and optical fiber based sensor are emerging as an obvious choice due to the advancement of optical fiber sensing technology, accuracy, and reliability. This paper presents a WSG platform integrated with optic fiber-based sensors for real-time monitoring. To demonstrate the validity of the concept, fresh water sensing of refractive index (RI) was first experimented with an optical fiber sensor. The sensing mechanism functions with the reflectance at the fiber’s interface where reflected spectra’s intensity is registered corresponding to the change of RI in the ambient environment. The achieved sensitivity of the fabricated fiber sensor is 29.3 dB/RIU within the 1.33–1.46 RI range. An interface between the measured optical spectra and the WSG is proposed and demonstrated, and the data acquired is transmitted through a network of wireless smart meters