Sensitive Mach-Zehnder interferometric sensor based on a grapefruit microstructured fiber by lateral offset splicing

Detection limit analysis of optical fiber sensors based on interferometers with the Vernier-effect

Vernier-effect has been widely employed in interferometer-based optical fiber sensors to improve the sensitivities greatly. However, the influence of the Vernier-effect on detection limit (DL) that is more important for evaluating the actual performance of the sensor has not been discussed. Two gas pressure fiber sensors (a typical Fabry-Perot interferometer-based sensor and a Vernier sensor) are used to compare the DL of them by experiments. Both the theoretical analysis and the experimental results show that, though the Vernier-effect magnifies the spectrum shift sensitivity, it also magnifies the value of the smallest detectable wavelength shift. As a result, the actual DL of the sensor is not improved by employing the Vernier-effect. If the contrast ratio of the Vernier envelope is not optimized enough for most of the reported sensors, the DL can even degenerate greatly.

Hybrid sensor based on a hollow square core fiber for temperature independent refractive index detection

In this work, a hybrid sensor based on a section of hollow square core fiber (HSCF) spliced between two single mode fibers is proposed for the measurement of refractive index of liquids. The sensor, with a length of a few millimeters, operates in a transmission configuration. Due to the HSCF inner geometry, two different interferometers are generated. The first, a Mach-Zehnder interferometer, is insensitive to the external refractive index, and presents a sensitivity to temperature of (29.2 ± 1.1) pm/°C. The second one, a cladding modal interferometer, is highly sensitive to the external refractive index. An experimental resolution of 1.0 × 10^-4 was achieved for this component. Due to the different responses of each interferometer to the parameters under study, a compensation method was developed to attain refractive index measurements that are temperature independent. The proposed sensor can find applications in areas where refractive index measurements are required and the control of room temperature is a challenge, such as in the food and beverage industry, as well as in biochemical or biomedical industries.

Robust and low cost in-fiber acousto-optic Mach-Zehnder interferometer and its application in a dual-wavelength laser

A robust in-fiber tunable acousto-optic Mach-Zehnder interferometer with a taper-shaped sandwich-like fiber structure is proposed and characterized experimentally, based on which tunable dual-wavelength lasers are demonstrated. The fiber structure was prepared by two-step etching methods, which could be used to fabricate either a symmetric structure for a continuous tuning dual-wavelength laser or an asymmetric structure for a switchable one. The proposed structure has advantages of low cost, low driving power, and robustness. The method for preparing the fiber structure is agile, which paves the way for its applications.

In-Fiber Interferometric-Based Sensors: Overview and Recent Advances

In-fiber interferometric-based sensors are a rapidly growing field, as these sensors exhibit many desirable characteristics compared to their regular fiber-optic counterparts and are being implemented in many promising devices. These sensors have the capability to make extremely accurate measurements on a variety of physical or chemical quantities such as refractive index, temperature, pressure, curvature, concentration, etc. This article is a comprehensive overview of the different types of in-fiber interferometric sensors that presents and discusses recent developments in the field. Basic configurations, a brief approach of the operating principle and recent applications are introduced for each interferometric architecture, making it easy to compare them and select the most appropriate one for the application at hand.