Oil and gas (O&G) explorations moving into deeper zones for enhanced oil and gas recovery are causing serious safety concerns across the world. The sensing of critical multiple parameters like high pressure, high temperature (HPHT), chemicals, etc., are required at longer distances in real-time. Traditional electrical sensors operate less effectively under these extreme environmental conditions and are susceptible to electromagnetic interference (EMI). Hence, there is a growing demand for improved sensors with enhanced measurement capabilities and also sensors that generates reliable data for enhanced oil and gas production. In addition to enhanced oil and gas recovery, the sensing technology should also be capable of monitoring the well bore integrity and safety. The sensing requirements of the O&G industry for improved sensing in deeper zones include increased transmission length, improved spatial coverage and integration of multiple sensors with multimodal sensing capability. This imposes problems like signal attenuation, crosstalks and cross sensitivities. Optical fibre-based sensors are expected to provide superior sensing capabilities compared to electrical sensors. This review paper covers a detailed review of different fibre-optic sensing technologies to identify a feasible sensing solution for the O&G industry.

Photonic crystal fibre (PCF)–fibre bragg grating (FBG) integration opens up new possibilities in multi-parameter fibre-optic sensing, owing to their active control over light characteristics and mode confinements. Their integration results in a mismatch in their mode field diameters (MFDs), which in turn causes various types of losses such as confinement loss, scattering loss, etc. This paper primarily investigates the effect of geometrical parameters on fibre parameters such as confinement loss and MFD, which plays a significant role in long distance fibre-optic remote sensing. Liquid crystal PCFs (LCPCFs) are utilized in the sensor configuration, exploiting their optical properties for photonic bandgap based tighter mode confinements and wavelength tunability. Furthermore, the LCPCF–FBG combo enables multi-parameter fibre-optic sensing which can be effectively utilized in oil and gas sensing applications. Theoretical study conducted on the fibre sensor revealed that confinement loss and MFD can be reduced by properly optimizing their structural parameters.

A Radio Over Fiber has the special characteristic feature of having both a fiber optic link and a free space radio path. Fiber based wireless (Fi-Wi) access facilitates high-capacity multimedia services in a real-time basis. The simulation model developed using Optisystem 10 have integrated systems for both RF wireless and optical fiber whereby, the ROF network model consists of a central station, a remote access unit and an optical fiber link model that uses the commercially available parameters. We also investigates the variations in Q factor, BER and eye opening with respect to the wavelength, bit rate and fiber length using the simulation software.

Condition monitoring of offshore structures is an indispensable task in the oil and gas industry. Fibre Bragg Grating (FBG) is the key technology used down-hole in order to sense different physical parameters such as strain, vibration, etc. This paper investigates the effect of FBG sensor positions on its reflected signal, in order to optimise the sensor positioning plan in structural health monitoring of subsea structures. Theoretical and experimental study was carried out on FBG sensors, to evaluate its strain sensitivities with varying positions. In addition, micro-displacement based strain analysis of FBG was carried out using a cantilever setup, in order to identify the effects of tensile and compressive strain under various load conditions. Furthermore, the effect of different grating parameters on FBG sensing signal were also analyzed. Theoretical modeling and simulation of FBG was conducted in MATLAB using the coupled mode theory.

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We investigate a linear light propagation mechanism in the photonic crystal fibers infiltrated with nematic liquid crystals which is used for Radio over Fiber (ROF) applications. PCF core region consists of soft glass and has nematic liquid crystal filled holes in the cladding region. Using the designed hexagonal solid core liquid crystal PCF, the wavelength dependent fundamental optical characteristics of single mode photonic crystal fibers (SMPCFs) such as birefringence, effective area, confinement loss and dispersion are numerically investigated. The effects of dispersion in an ROF communication are also analysed in detail. Coding and simulation of the problem have been done using MATLAB and COMSOL softwares.