Temperature sensing based on multimodal interference in polymer optical fibers: Room-temperature sensitivity enhancement by annealing

Abstract

To date, we have developed a temperature sensor based on multimodal interference in a polymer optical fiber (POF) with an extremely high sensitivity. Here, we experimentally evaluate the influence of annealing (heat treatment) of the POF on the temperature sensitivity at room temperature. We show that the temperature sensitivity is enhanced with increasing annealing temperature, and that, by annealing the POF at 90°C, we can achieve a temperature sensitivity of +2.17 nm/°C, which is 2.9 times larger than that without annealing (+0.75 nm/°C).

Multimodal Interference in Perfluorinated Polymer Optical Fibers: Application to Ultrasensitive Strain and Temperature Sensing

“…In addition to these achievements, we have found that the strain and temperature sensitivities do not largely depend on the length of the MMF [25], that the temperature sensitivity at room temperature can be enhanced by annealing [33] and that the modal interference in partially chlorinated GI POFs is potentially applicable to high-sensitivity temperature measurement with low strain sensitivity [34]. Future tasks include clarification of the critical wavelength dependence on fiber properties [15] (which will be a useful guideline for the researchers who search for new materials with high sensitivities), extremely large strain sensing with plastic deformation [35], clarification of the shortest length of the MMF, clarification of cross effect of strain and temperature [36], and discriminative (not distributed) sensing of strain, temperature, and some other parameters by combined use of FBG and/or Brillouin scattering.…”

Observation of multimodal interference in millimeter-long polymer optical fibers

“…If a higher sensitivity is preferable, the dip nearest to C should be used; while if a wider strain/temperature dynamic range is preferable, it may not be the best dip to be selected. To date, when the MMF is a PFGI-POF, a dip around 1350 nm has been often used for its higher sensitivity [16,19,20].…”

“…Sensing technology of strain and temperature using optical fibers has been an active area of research for many decades, and a wide variety of configurations have been developed thus far. They operate based on fiber Bragg gratings [1,2,3], long-period gratings [4,5], Brillouin scattering [6,7,8,9], Raman scattering [10,11], optical interference [12,13,14,15,16,17,18,19,20,21,22,23,24], and many others. Among numerous types of interference-based sensors, those based on intermodal interference in multimode fibers (MMFs) have recently attracted a considerable attention owing to their system simplicity and cost efficiency.…”

“…Of all the multimodal-interference-based sensors previously developed, which are well summarized in Table 1 in Ref. [12], the most widely used configuration is what is called a "single-mode-multimode-single-mode" (SMS) structure [13,14,15,16,17,18,19,20], in which two single-mode fibers (SMFs) sandwich an MMF.…”

“…However, the propagation loss of PMMA-based POFs at telecom wavelength is extremely high ()1 Â 10 5 dB/km). To tackle this issue, we have recently implemented SMS-based strain and temperature sensors using perfluorinated (PF) GI-POFs [16,17,18,19,20,21,22], which are the only POFs with a relatively low propagation loss even at telecom wavelength (∼250 dB/km at 1550 nm; ∼50 dB/km at 1300 nm). Using a PFGI-POF with a length of 1.0 m and a core diameter of 62.5 µm, we obtained a strain sensitivity of −111.8 pm/µε and a temperature sensitivity of +49.8 nm/°C at 1300 nm [16]; these large absolute values suggest that PFGI-POFbased SMS sensors are extremely sensitive to strain and temperature compared with other SMS sensors composed of silica MMFs or PMMA-POFs.…”