Single-Mode Fiber Refractive Index Sensor Based on Core-Offset Attenuators

Abstract

Mach-Zehnder and Michelson interferometers using core-offset attenuators were demonstrated. As the relative offset direction of the two attenuators in the Mach-Zehnder interferometer can significantly affect the extinction ratio of the interference pattern, single core-offset attenuator-based sensors appear more robust and repeatable. A novel fiber Michelson interferometer refractive index (RI) sensor was subsequently realized by a single core-offset attenuator and a layer of 500-nm gold coating. The device had a minimum insertion loss of 0.01 dB and maximum extinction ratio over 9 dB. The sensitivity (0.333 nm) of the new sensor to its surrounding RI change (0.01) was found to be comparable to that (0.252 nm) of an identical long period gratings pair Mach-Zehnder interferometric sensor, and its ease of fabrication makes it a low-cost alternative to existing sensing applications.

High sensitivity refractive index sensor based on a tapered small core single-mode fiber structure

“…The maximum sensitivities for S-18.8, S-15.0, and S-12.5 are 4722.9 nm∕RIU (RI 1.4249-1.4319), 8353.6 nm∕RIU (RI 1.4256-1.4312), and 19212.5 nm∕RIU (RI 1.4304-1.4320), respectively. Taking into account that the OSA has a wavelength resolution of 0.01 nm, the RI sensor based on S-12.5 has an RI resolution of 5.025 × 10 −7 which, to the best of our knowledge, is significantly higher than previously reported [16][17][18][19][20]. It is noted that, in this Letter, the central wavelength of the spectral dip is determined as the 3 dB mean wavelength, which is a more reliable parameter compared to the central peak wavelength.…”

Recent Developments in Micro-Structured Fiber Optic Sensors

“…Offset splicing is another technique for manufacturing the mode mismatched micro-structure fiber optic sensors. MZI and MI could be realized by making two offset splicing and one offset splicing combined with fiber end-face coating [272]. The offset splicing deliberately introduces a core offset between the two sections of fibers, leading to that part of the energy in the core mode from the Offset splicing is another technique for manufacturing the mode mismatched micro-structure fiber optic sensors.…”

“…The offset splicing deliberately introduces a core offset between the two sections of fibers, leading to that part of the energy in the core mode from the Offset splicing is another technique for manufacturing the mode mismatched micro-structure fiber optic sensors. MZI and MI could be realized by making two offset splicing and one offset splicing combined with fiber end-face coating [272]. The offset splicing deliberately introduces a core offset between the two sections of fibers, leading to that part of the energy in the core mode from the lead-in fiber will be spread out to the cladding region of the lead-out fiber.…”

Single-mode fiber refractive index sensor with large lateral offset fusion splicing between two abrupt tapers

“…There are many methods for constructing in-fiber RI sensors, including fiber Bragg grating (FBG), 1 long-period grating (LPG), 2 photonic crystal fiber (PCF), 3 and single mode-multimode-single mode fiber structure. 4 Recently, many kinds of Mach-Zehnder interferometer (MZI) structures have been applied to the design and fabrication of in-fiber RI sensors, such as the two-taper MZI, 5 core-offset attenuators, 6 LPG pairs, 7,8 an improved sandwiched-taper MZI, 9 and PCF-based MZI structure.…”