High Resolution Distributed Optical Fiber Sensing Using Time-Expanded Phase-Sensitive Reflectometry

We have demonstrated a novel scheme for distributed optical fiber sensing based on the use of a dual frequency comb, which enables the development of a high-resolution (in the cm range) distributed sensor with significantly relaxed electronic requirements compared with previous schemes. This approach offers a promising solution for real time structure monitoring in a variety of fields, including transportation, manufacturing or mechatronics. In this work, we review the principle of operation of the technique, recent advances to improve its performance and different experimental tests.

Multi-gas leakage synchronous monitoring system based on the distributed optical fiber sensing technology

In the process of long-distance transportation of different gas, the remote pipeline plays an irreplaceable role in energy transmission. When the pipeline is laid in remote areas for a long distance, it is easy to be influenced by geological disasters and complex working conditions, which may lead to corrosion and leakage. therefore, it is necessary to conduct pipeline gas real-time safety monitoring. An optical fiber gas leakage synchronous monitoring system was proposed and demonstrated based on distributed optical sensing technology for simultaneous multi-gas measurements. In this study, we discuss that the principle of multi-gas leakage synchronous monitoring system is investigated and then validated by the theoretical simulation experiments. Furthermore, gas concentration and leakage location discrimination tests are also conducted in laboratory. The experimental results show that the output intensity values increased obviously along with the gas concentration changes, and the response time of the sensor system is about 40 seconds, and it’s concluded that the multi-gas leakage synchronous monitoring system based on distributed optical fiber sensing technology exhibited good sensing and location discrimination performance.

Calculation of Bandwidth of Multimode Step-Index Polymer Photonic Crystal Fibers

By solving the time-dependent power flow equation, we present a novel approach for evaluating the bandwidth in a multimode step-index polymer photonic crystal fiber (SI PPCF) with a solid core. The bandwidth of such fiber is determined for various layouts of air holes and widths of Gaussian launch beam distribution. We found that the lower the NA of SI PPCF, the larger the bandwidth. The smaller launch beam leads to a higher bandwidth for short fibers. The influence of the width of the launch beam distribution on bandwidth lessens as the fiber length increases. The bandwidth tends to its launch independent value at a particular fiber length. This length denotes the onset of the steady state distribution (SSD). This information is useful for multimode SI PPCF applications in telecommunications and optical fiber sensing applications.

Switchable and tunable linear cavity erbium-doped fiber laser based on FBGs embedded in Sagnac rings

A switchable and tunable erbium-doped fiber laser with a linear cavity based on fiber Bragg gratings embedded in Sagnac rings is proposed and experimentally verified. Due to the stress birefringence effect and the polarized hole burning effect, which are introduced into the single-mode fiber in the polarization controllers (PCs) by the PCs, the designed laser can achieve seven kinds of laser-states output including three kinds of single-wavelength laser states, three kinds of dual-wavelength laser states and one kind of triple-wavelength laser state. The optical signal-to-noise ratios of the output wavelengths are all higher than 52 dB, and the wavelength shifts are all less than 0.04 nm. Furthermore, the temperature tuning of the wavelength range is also researched, which is about 1.2 nm. Due to advantages, such as low cost, simple structure, easy switching and multiple laser states, the designed laser has great application potential in laser radar, optical fiber sensing and so on.

Application of Fiber Optics in Bio-Sensing

The unique properties of optical fibers such as small size, immunity to electromagnetic radiation, high sensitivity with simpler sensing systems have found their applications from structural monitoring to biomedical sensing. The inclusion of optical transducers, integrated electronics and new immobilization methods, the optical fibers have been used in industrial process, environmental monitoring, food processing and clinical applications. Further, the optical fiber sensing research has also been extended to the area of detection of micro-organisms such as bacteria, viruses, fungi and protozoa. The validation of optical fibers in bio-sensing applications can be observed from the growing number of publications. This chapter provides a brief picture of optical fiber biosensors, their geometries including the necessary procedure for their development. This chapter could be a milestone for the young researchers to establish their laboratory.