Fabry-Perot Interferometric Temperature Sensor Research Articles

Polymer-coated fiber-optic Fabry-Perot interferometer-based temperature sensor with high sensitivity

In this paper, a highly sensitive temperature sensor based on polymer-coated Fabry-Perot interferometer (FPI) is proposed and demonstrated. The FPI temperature sensor consists of the end face of single-mode fiber (SMF) and the Polydimethylsiloxane (PDMS) cap on the end face. By varying the number of coatings, the thickness of the PDMS cap can be flexibly controlled to obtain FPI sensors with different cavity lengths. The temperature sensitivity is studied experimentally from −30 °C to 85 °C, and it is found that the sensor shows different sensitivity in different temperature intervals, up to 0.698 nm/°C. Compared to similarly constructed sensors, the sensor in this paper has a large temperature range while maintaining a high sensitivity. In addition, the performance of the sensor is tested by experiments and the results show that the sensor possesses the advantages of good stability, fast response time and good repeatability.

In-fiber Fabry-Perot temperature sensor using silicone-oil-filled the quartz capillary tube

In this study, a highly sensitive temperature sensor based on a Fabry–Perot interferometer (FPI) filled with the silicone oil was designed and demonstrated. The FPI temperature sensor comprised an in-line sandwiched structure, i.e., single mode fiber – capillary – single mode fiber. A microchannel was processed on the capillary wall with a femtosecond laser. The capillary was filled with the silicone oil through the microchannel using the immersing method. Through theoretical analysis, the sensitivity of FPI temperature sensor is mainly determined by the thermo-optical coefficient of silicone oil. Owing to the high TOC of the silicone oil, the optical path difference (OPD) in the FP cavity varied strongly with temperature, which consequently induced a drastic wavelength shift of the reflection spectrum. Thus, FPI temperature sensor has high sensitivity. The temperature response, repeatability and stability of the sensor are studied experimentally. The results show that the temperature sensitivity of FPI sensor filled with silicon oil reaches −0.4102 nm/°C, which is about 205.1 times compared to that of the FPI sensor unfilled with silicon oil. The proposed sensor has the advantages of simple manufacturing, good robustness and stability. In addition, the total length of the sensor head is small, which is compact size and can be used flexibly in limited space and harsh environment.

Highly sensitive PDMS-filled Fabry–Perot interferometer temperature sensor based on the Vernier effect

A highly sensitive temperature sensor is demonstrated experimentally, which is fabricated based on a Fabry-Perot interferometer (FPI) filled with polydimethylsiloxane (PDMS). The sensor's sensitivity is -0.653 nm/°C by utilizing the thermal expansion effect of PDMS, which has been greatly improved compared to that of the traditional FPI temperature sensor. Moreover, in order to further improve the sensitivity, a scheme where two parallel FPI structures are used to form the Vernier effect is proposed, which are a sensing FPI and reference FPI, respectively. Such a temperature sensor based on the FPI filled with PDMS and the Vernier effect exhibits a high temperature sensitivity of 17.758 nm/°C. Meanwhile, the proposed sensors show the advantages of high sensitivity, simplicity, and low cost.

Process Monitoring of a Thermosetting Resin Using Optical-Fiber Sensors in a Microwave Environment

Conventional means of curing thermosetting resins used in advanced fiber-reinforced composites involves heating the sample in an oven or autoclave where heat is transferred to the sample through conduction and convection. In general, the cure schedules that are used can be time consuming and expensive. Hence, significant attempts are being made to improve the processing efficiency and productivity of this class of material. Microwave-based processing has been claimed to offer the advantage of a significantly faster processing time. In this study, two remote (noncontact) sensor systems were designed and developed to facilitate spectral-based quantitative process monitoring inside a custom-modified commercial microwave oven. The two fiber-optic sensor systems were 1) a noncontact optical-fiber reflectance probe and 2) a reusable transmission probe assembly. Spectroscopic data were obtained using the fiber-optic probes at specified microwave power levels. Since conventional metal-based temperature monitoring devices cannot be used in the microwave oven, a low-cost disposable fiber-optic probe was developed. This design was based on an optical fiber-based extrinsic Fabry-Perot interferometer (FPI). The extrinsic FPI temperature sensor demonstrated an accuracy of /spl plusmn/0.5/spl deg/C over the range from ambient to 300/spl deg/C. The temperature of the resin system was also measured simultaneously, along with the spectral data, to monitor the progress of the chemical reaction (curing).