Photonic crystal fibers are a kind of fiber optics that present a diversity of new and improved features beyond what conventional optical fibers can offer. Due to their unique geometric structure, photonic crystal fibers present special properties and capabilities that lead to an outstanding potential for sensing applications. A review of photonic crystal fiber sensors is presented. Two different groups of sensors are detailed separately: physical and biochemical sensors, based on the sensor measured parameter. Several sensors have been reported until the date, and more are expected to be developed due to the remarkable characteristics such fibers can offer.

/pdf/photonic-crystal-fibers-for-sensing-applications-3479q9acwh.pdf

Photonic crystal fibers for sensing applications

Optical fiber sensors have attracted considerable attention for marine environment and marine structural health monitoring, owing to advantages including resistance to electromagnetic interference, durability under extreme temperature and pressures, light weight, high transmission rate, small size and flexibility. In this paper, the optical fiber sensors employed for marine environment and marine structural health monitoring are summarized for the understanding of their basic sensing principles, and their various sensing applications such as physical parameters, chemical parameters and structural health monitoring. This review paper shows the feasibility of using optical fiber sensing technology for marine application and, due to the aforementioned advantages, it is possible to envisage a widespread use in this research field in the next few years.

Optical fiber sensing for marine environment and marine structural health monitoring: A review

5G communications require a multi Gb/s data transmission in its small cells. For this purpose millimeter wave (mm-wave) RF signals are the best solutions to be utilized for high speed data transmission. Generation of these high frequency RF signals is challenging in electrical domain therefore photonic generation of these signals is more studied. In this work, a photonic based simple and robust method for generating millimeter waves applicable in 5G access fronthaul is presented. Besides generating of the mm-wave signal in the 60 GHz frequency band the radio over fiber (RoF) system for transmission of orthogonal frequency division multiplexing (OFDM) with 5 GHz bandwidth is presented. For the purpose of wireless transmission for 5G application the required antenna is designed and developed. The total system performance in one small cell was studied and the error vector magnitude (EVM) of the system was evaluated.

Towards 5G: A Photonic Based Millimeter Wave Signal Generation for Applying in 5G Access Fronthaul.

Nowadays, optical devices and circuits are becoming fundamental components in several application fields such as medicine, biotechnology, automotive, aerospace, food quality control, chemistry, to name a few. In this context, we propose a complete review on integrated photonic sensors, with specific attention to materials, technologies, architectures and optical sensing principles. To this aim, sensing principles commonly used in optical detection are presented, focusing on sensor performance features such as sensitivity, selectivity and rangeability. Since photonic sensors provide substantial benefits regarding compatibility with CMOS technology and integration on chips characterized by micrometric footprints, design and optimization strategies of photonic devices are widely discussed for sensing applications. In addition, several numerical methods employed in photonic circuits and devices, simulations and design are presented, focusing on their advantages and drawbacks. Finally, recent developments in the field of photonic sensing are reviewed, considering advanced photonic sensor architectures based on linear and non-linear optical effects and to be employed in chemical/biochemical sensing, angular velocity and electric field detection.

/pdf/recent-advances-in-integrated-photonic-sensors-55fdkscba6.pdf

Recent advances in integrated photonic sensors.

Optical measurement of mechanical parameters is gaining significant commercial interest in different industry sectors. Torsion, twist and rotation are among the very frequently measured mechanical parameters. Recently, twist/torsion/rotation sensors have become a topic of intense fiber-optic sensor research. Various sensing concepts have been reported. Many of those have different properties and performances, and many of them still need to be proven in out-of-the laboratory use. This paper provides an overview of basic approaches and a review of current state-of-the-art in fiber optic sensors for measurements of torsion, twist and/or rotation.Invited Paper.

Fiber-Optic Sensors for Measurements of Torsion, Twist and Rotation: A Review

A highly sensitive torsion sensor, which can measure the torsion angle and determine the torsion direction simultaneously, is proposed and demonstrated based on Sagnac interferometer by incorporating a segment of novel side-leakage photonic crystal fiber (SLPCF). The SLPCF was designed by introducing an elliptical Ge-doped core and a symmetrical linear side-leakage defect. The experimental results show that the proposed sensor has different torsion sensitivities at different valley wavelengths and in different twist directions. The achieved maximum torsion sensitivity is about 0.9354 nm/°, which is much higher than that of the previously reported torsion sensors. In order to eliminate the temperature effect and obtain an accurate value of the torsion angle, the matrix method is adopted.

Highly Sensitive Torsion Sensor Based on Sagnac Interferometer Using Side-Leakage Photonic Crystal Fiber

Switchable multi-wavelength fiber ring laser with an in-fiber Mach-Zehnder interferometer incorporated into the ring cavity serving as wavelength-selective filter at room temperature is demonstrated. The filter is formed by splicing a section of few-mode photonic crystal fiber (PCF) and two segments of single mode fiber (SMF) with the air-holes on the both sides of PCF intentionally collapsed in the vicinity of the splices. By adjusting the states of the polarization controller (PC) appropriately, the laser can be switched among the stable single-, dual- and triple-wavelength lasing operations by exploiting polarization hole burning (PHB) effect.

Switchable multi-wavelength fiber ring laser based on a compact in-fiber Mach-Zehnder interferometer with photonic crystal fiber

A switchable multi-wavelength fiber ring laser is proposed and experimentally demonstrated with a novel side-leakage photonic crystal fiber (SLPCF) based filter incorporated into the ring cavity at room temperature. Stable multi-wavelength laser operations can be achieved due to the spatial mode beating, polarization hole burning and spectral hole burning effects. By adjusting the polarization controller appropriately, the laser can be switched among the single-, dual- and triple-wavelength lasing oscillations whose signal-to-noise ratio is up to 50 dB. In addition, the lasing wavelength can be also tuned and switched by applying the strain to the filter.

Switchable multi-wavelength fiber ring laser using a side-leakage photonic crystal fiber based filter

In-fiber modal interferometer based on dual-concentric-core photonic crystal fiber and its strain, temperature and refractive index characteristics

Single-polarization single-mode (SPSM) fiber can efficiently eliminate polarization mode coupling, polarization mode dispersion, and polarization-dependent loss. Up to now, most single-polarization fibers have been designed based on form birefringence, which would result in a non-Gaussian field distribution and a small effective mode field area. In this paper, a novel structure of SPSM photonic crystal fibers based on the resonant coupling phenomena is proposed and analyzed by using a full-vector finite-element method with a second-order transparent boundary condition. From the numerical results it is confirmed that this fiber has a near-Gaussian mode field within the wavelength range from 1.46 to 2.2μm, where only one polarized mode exists effectively, and the mode field area is about 79μm2 at the wavelength of 1.55μm, matching that of the conventional single-mode fiber.

Weiguo Chen

Papers

Highly Sensitive Torsion Sensor Based on Sagnac Interferometer Using Side-Leakage Photonic Crystal Fiber

Switchable multi-wavelength fiber ring laser based on a compact in-fiber Mach-Zehnder interferometer with photonic crystal fiber

Switchable multi-wavelength fiber ring laser using a side-leakage photonic crystal fiber based filter

In-fiber modal interferometer based on dual-concentric-core photonic crystal fiber and its strain, temperature and refractive index characteristics

Design of a single-polarization single-mode photonic crystal fiber with a near-Gaussian mode field and wide bandwidth