Simplified Hollow-Core Fiber-Based Fabry–Perot Interferometer With Modified Vernier Effect for Highly Sensitive High-Temperature Measurement

Abstract

In this paper, a high-temperature fiber sensor based on an optical fiber Fabry-Perot interferometer is fabricated by splicing a section of simplified hollow-core fiber between two single-mode fibers (SMFs) and cleaving one of the two SMFs to a certain length. With the superposition of three beams of light reflected from two splicing joints and end face of the cleaved SMF, the modified Vernier effect will be generated in the proposed structure and improve the sensitivity of temperature measurement. The envelope of spectrum reflected from the proposed sensor head is modulated by the ambient temperature of the sensor head. By monitoring and measuring the shift of spectrum envelope, the measurement of environment temperature is carried out experimentally, and high temperature sensitivity of 1.019 nm= C for the envelope of the reflected spectrum was obtained. A temperature measurement as high as 1050 C has been achieved with excellent repeatability.

Sensitivity-enhanced fiber interferometric high temperature sensor based on Vernier effect

“…Then, a section of the pure silica tipis formed. Compared with other common IFFPI preparation technologies [3], [15], [16], no additional process is required to splice the third fiber and terminate it at a certain length to form the FP2. Instead, applying a slight arc to the end of HC-PCF effectively simplifies fabrication of the sensor and formation of a pure silica micro-cavity.…”

“…However, the open cavity structure may cause problems in a high temperature sensing environment, because the FP cavities may suffer from disturbances from burning contaminants, which lead to changes in cavity properties. As stated in [3], a section of hollow-core fiber is cascaded by a piece of SMF, and, based on the modified Vernier effect, an amplification factor as high as 133.29 is obtained. However, the maximum temperature of 1050℃ is limited by the doped core of the conventional SMF used in the experiments.…”

“…Using conventional step-index fibers, the maximum temperature measurement may be limited in the doped ions (e.g., ions of germanium, phosphorus, and boron, etc.) inside the core of the fiber [3]- [6]. Compared with traditional coredoped fibers, photonic crystal fibers (PCFs), made from pure silica glass (un-doped single-material), which can withstand temperatures over 1000℃ and has good durability, have been studied intensively [2], [7]- [9].…”

Cascaded-Cavity Fabry-Perot Interferometric Gas Pressure Sensor based on Vernier Effect

“…Among them, diaphragm-based FPI sensors can provide ultra-high sensitivity through minimizing the diaphragm thickness by polishing, wet etching or selecting different diaphragm materials such as grapheme or silver [ 16 , 17 , 18 , 19 ]. An alternative method to obtain high sensitivity is a novel FPI sensors based on the Vernier effect, which is characterized with such qualities as low cost and being easy to implement [ 20 , 21 , 22 , 23 , 24 ].…”

“…The position of the major peak is located at the common resonant wavelength of the two cascaded FPIs. However, the cascaded FPI sensors with Vernier effect are mainly intrinsic which the interference spectrum not available until the sensors are finished [ 20 , 21 , 22 , 23 , 24 ]. So, in fact we are not sure if the sensor has a Vernier effect or the amplification factor of sensitivity is big enough to improve the accuracy.…”