Photonic Crystal Fiber–Based Interferometric Sensors

Photonic crystal fibers (PCFs), also known as microstructured optical fibers, are a highlighted invention of optical fiber technology which have unveiled a new domain of manipulating light in engineered fiber waveguides with unparalleled flexibility and controllability. Since the report of the first fabricated PCF in 1996, research in PCFs has resulted in numerous explorations, development and commercialization of PCF-based technologies and applications. PCFs contain axially aligned air channels which provide a large degree of freedom in design to achieve a variety of peculiar properties; numerous PCF-based sensors have been proposed, developed and demonstrated for a broad range of sensing applications. In this chapter, we will review the field of research on design, development and experimental achievement of PCF-based interferometric sensors for physical and biomedical sensing applications

Optical Fibre Long-Period Grating Sensors Operating at and around the Phase Matching Turning Point

Optical fibres have been exploited as sensors for many years and they provide a versatile platform with a small form factor. Long-period gratings (LPGs) operating at and around the phase matching turning point (PMTP) possess some of the highest sensitivities to external perturbations in the family of LPG-based sensor devices. This type of optical fibre grating has been demonstrated as a sensor for use in a wide range of applications. In this review chapter, an overview of PMTP LPGs is presented and the key developments, findings and applications are highlighted. The fabrication considerations and sensor limitations are also discussed

FIELD TRIAL AND NUMERICAL BACK-ANALYSIS OF SUCTION CAISSON EXTRACTION IN HONG KONG

ABSTRACT An in-situ push-out test was carried out on a 3.4m diameter, 12m high trial suction caisson to determine the ultimate uplift capacity and, in particular, the shaft friction that could be generated along the walls of the caisson. The test was performed in the south-eastern waters of Hong Kong in ground conditions comprising soft clay with alluvial sand at the caisson tip. Numerical back-analysis of test reveal that considerable suction was generated at the caisson base due to a combination of the relatively high rate of loading adopted in the test and the silty nature of the alluvium. Inferred friction values generated on the outside wall of the caisson are found to be in line with existing data reported in the literature

Review on photonic crystal fibers with hybrid guiding mechanisms

Photonic crystal fibers (PCFs) with hybrid guiding mechanisms have undergone substantial development in recent years. Due to the co-existence of index-guiding and photonic bandgap (PBG)-guiding mechanisms in this special class of PCFs, many peculiar properties have been investigated and demonstrated as advantageous and favorable in many applications. This review paper provides a comprehensive review of the recent progress of these hybrid guiding PCFs. The first part explains the principles of the hybrid guiding mechanisms in the PCF structures. The hybrid guiding PCFs are realized in three approaches, including polarization-dependent hybrid guiding PCFs, radial hybrid guiding PCFs, and two-core hybrid guiding PCFs. This is followed by a review of various development and applications for each type of hybrid guiding PCFs in the second part, including tunable filters, high power lasers, nonlinear optics, and polarization optics and sensing applications. Finally, the considerations and challenges on the potential applications of the hybrid guiding PCFs are discussed.NRF (Natl Research Foundation, S’pore)MOE (Min. of Education, S’pore)Published versio

Temperature-sensitive photonic liquid crystal fiber modal interferometer

In this paper, we present an experimental investigation of the photonic crystal fiber (PCF) and photonic liquid crystal fiber (PLCF) modal interferometers. The PLCF interferometer is fabricated by infiltrating a liquid crystal (LC) into the PCF and then splicing the effective PLCF between two single-mode fibers (SMF). By heating the PLCF interferometer, we present a possibility to tune optical properties of the propagating light. We also compare PCF- and PLCF-interferometer responses in the presence of changing external temperature conditions

Cascaded photonic crystal fiber interferometers for refractive index sensing

We present a cascaded fiber device based on photonic crystal fiber (PCF) interferometers for refractive index (RI) sensing. The PCF modal interferometers have microbubbles at both sides of the splice regions. The microbubbles act as thick diverging lens that scatter light for efficient excitation of higher order cladding modes and attenuation of the core modes in the transmitted spectrum. Three resonance wavelengths are monitored, and their corresponding RI sensitivities are found to be 252, 187, and 207 nm/refractive index unit (RIU). The results, to our best knowledge, demonstrate that PCF interferometers with microbubbles are repeatable for high RI sensitivity, and the best crosstalk achievable is 0.295 nm/RIU

Design and Analysis of Microfluidic Optical Fiber Device for Refractive Index Sensing

In this letter, the microfluidic optical fiber devices composed of microchannel are modeled and thoroughly analyzed. The microchannel intersecting the fiber core allows direct infusion of surrounding substances for detection. The simulation results suggest that the dimension of the microchannel can significantly affect the detection sensitivity of the device. In addition, the off-center position of the microchannel also plays an important role in shaping the device performance. The optimized microfluidic device can be used for sensitive refractive index sensing and biosensing applications.ASTAR (Agency for Sci., Tech. and Research, S’pore