Microfiber Mach-Zehnder Interferometer Research Articles

Robust Strain Sensor with High Sensitivity Based on Polymer-Encapsulated Microfiber Mach-Zehnder Interferometer.

A robust strain sensor is demonstrated based on a microfiber Mach-Zehnder interferometer (MMZI) encapsulated by the polymer polydimethylsiloxane (PDMS). Benefiting from the low Young's modulus of PDMS, both a robust structure and high sensitivity can be realized based on three different encapsulations. In the experiment, the proposed sensors are fabricated and tested with strain sensitivities ranging from -20.95 pm/με to 127.00 pm/με within the wavelength range of 1200-1650 nm. Compared with the bare MMZI sensor, at least one order of magnitude higher sensitivity is reached. To further evaluate the performance of the sensor, the dependences of sensitivity on probing wavelength and the different types and quantities of polymers used in encapsulation are discussed. Results show that the sensitivity of the sensor will increase with the probing wavelength. The type and quantity of polymer used are also very critical to sensitivity. Additionally, a response time of 24.72 ms can be reached. Good recoverability and repeatability of the sensor are also demonstrated by repeated experiments. The strain sensor demonstrated here shows the advantages of simple fabrication, robust structure, high and tunable sensitivity, fast response, good recoverability and repeatability.

Ocean exploration-oriented temperature and salinity sensor based on bend-insensitive microfiber Mach-Zehnder interferometer.

Ocean exploration-oriented temperature and salinity (TS) sensor based on bend-insensitive microfiber Mach-Zehnder interferometer (MMZI) is proposed and demonstrated in a marine environment. To solve the demodulation problem induced by the narrow waveband of the spectrometer used in the sea trial, a MMZI sensor is calibrated and demodulated by machine learning method. Results show that even if the wavelength range used in demodulation is as small as tens of nanometers, a relatively accurate demodulation can still be achieved. Then a sea trial is performed based on the design of the test system on board. Compared with commercial conductivity-temperature-depth systems, mean relative errors of 2.28% and 2.29% for TS measurement are obtained. In addition, the influence of spectral range on the demodulation result and response of the spectrum to fiber bending is discussed. Repeatability and stability of the sensor are proved in repeated sea trials. The sensor demonstrated here provides a new optical method for measuring TS in seawater with the advantages of multi-parameter measurement, low cost, easy deployment, and high accuracy, which will hopefully become a useful complement to the existing electrical method used in ocean exploration.

Fast and accurate prediction of interference spectra of non-adiabatic tapered microfiber Mach-Zehnder interferometer in liquid

Microfiber Mach-Zehnder interferometer (MMZI) is a widely used optical device. To solve the problems of large difference between the theoretical and experimental spectrum, low calculation efficiency, poor universality in spectrum calculation of MMZI, a fast and accurate calculation method for predicting the interference spectrum of MMZI used in liquid is proposed. In calculations, phase accumulated in transition region of the taper is considered to reach a good agreement between theoretical and experimental spectrum. To further improve the computational efficiency, dependence of the phase accumulation on wavelength is developed by linear fitting, and a non-linear fitting of difference of effective refractive index (∆neff) on fiber diameter, wavelength, temperature and salinity of the surrounding is obtained by the data from commercial software. In addition, a visual interface for displaying the predicted spectrum is established, by which one accurate spectral calculation can be realized within only two or three seconds. Finally, effects of LP03 mode and shape of transition region on transmission spectrum are discussed and the accuracy of this method is also verified by sensitivity. The calculation method demonstrated here provides an accurate and fast spectral prediction method for MMZI, and will afford important reference for sensor design and optimization.

Experimental Demonstration of an Angle Laser Sensor Based on an Optical Thinned Microfiber Mach-Zehnder Interferometer

Experimental Demonstration of an Angle Laser Sensor Based on an Optical Thinned Microfiber Mach-Zehnder Interferometer

Temperature and Curvature Microfiber Mach-Zehnder Interferometer Sensor Based on Double Peanut-Shaped Structures and Tapered Coreless Fiber

Temperature and Curvature Microfiber Mach-Zehnder Interferometer Sensor Based on Double Peanut-Shaped Structures and Tapered Coreless Fiber

Ultrasensitive measurement of tactile force based on a PDMS-embedded microfiber Mach-Zehnder interferometer.

This study investigates the utilization of an in-fiber interferometer embedded in polydimethylsiloxane (PDMS) to develop a highly sensitive tactile sensor. The tapered mode-field mismatch structure is more conducive to stimulating strong high order modes to promote the sensitivity of the sensor. Experimental investigations are conducted to study the sensing performance of the sensor, resulting in a sensitivity of 23.636 nm/N and a detection limit of 0.746 mN. The experiments demonstrate that employing fast Fourier transform (FFT) and inverse FFT (IFFT) methods to filter weak high order modes significantly improves the repeatability of the sensor, resulting in a repeatability error of less than 1%.

An acoustic sensor based on balloon-shaped microfiber Mach-Zehnder interferometer

An acoustic sensor based on balloon-shaped microfiber Mach-Zehnder interferometer

Highly sensitive temperature and curvature sensor based on seven-core fiber

A high sensitivity temperature and curvature micro-fiber Mach-Zehnder interferometer (MMZI) sensor is proposed and demonstrated. A peanut structure is fused by a section of seven-core fiber (SCF) and a section of single-mode fiber (SMF). Then the SCF is connected to another SMF and tapered. Finally, the composite structure with the tapered SCF and the SCF-SMF peanut structure is fabricated. The coupling efficiency can be significantly improved, and more high-order modes can be stimulated via the new sensor structure. The experimental results demonstrated that the maximum temperature sensitivity is 836.67 pm/ °C in the range of 35 °C to 40 °C, which is the highest temperature sensitivity of the peanut-shaped MMZI sensor to the best of our knowledge. Furthermore, the sensor can be used for curvature measurement. When the curvature changes from 0 m−1 to 0.0522449 m−1, the sensitivity can achieve 93.33664 nm/m−1. The proposed sensor not only provides a novel method to fabricate a high-sensitivity sensor by combining different types of fibers, but it also has a meaningful application prospect in the fields of biological detection and environmental monitoring.

High sensitivity curvature sensor based on a double-sphere tapered no-core fiber Mach–Zehnder interferometer

A micro-fiber Mach–Zehnder interferometer (MMZI) based on a double-sphere tapered no-core fiber (DST-NCF) for curvature sensing is proposed and experimentally demonstrated. The sensor is composed of the DST-NCF sandwiched to two single-mode fibers (SMF). The DST-NCF is tapered from a double-sphere structure which is fused by no-core fiber (NCF). When light passes through the DST-NCF from SMF, higher-order modes will be excited, which will improve the sensing performance of the MMZI. This proposed structure achieves a significant improvement in curvature sensitivity for the first time by combining the characteristics of NCF, spherical format, and MMZI. When the central waist region is 2.07 mm, the maximum curvature sensitivity of the sensor is −224.64 nm/m−1, which is the highest curvature sensitivity in the MZI structure based on the spherical structure or the NCF as we have known. In addition, the maximum temperature sensitivity is −5.79 pm/℃ in the range of 40 ℃ − 90 ℃. It shows that this sensor has the characteristics of being insensitive to temperature and avoids the cross-sensitivity effect between temperature and curvature.

Multi-parameter demodulation for temperature, salinity and pressure sensor in seawater based on the semi-encapsulated microfiber Mach-Zehnder interferometer

Semi-encapsulated microfiber Mach-Zehnder interferometer is designed and developed for temperature, salinity and pressure (TSP) sensing in seawater. Based on the theoretical analysis, sensing experiment is performed with typical sensitivities of −2312 pm/℃, 631 pm/‰, and 3775 pm/MPa, respectively. To demodulate the signal with cross-sensitivity, sensitivity matrix method (SMM) and machine learning method (MLM) are used, respectively. By 25 tests under arbitrary TSP, relatively low errors of about 19.14 %, 4.01 % and 15.75 % are obtained based on the support vector regression (SVR) model. In addition, non-linear dependence of sensitivity on surrounding, SMM accuracy on sensing dips, stability of prediction and influence of the dataset used in training are also investigated. Finally, combination of SMM and MLM is realized, which shows relatively good performance for TSP measurement with errors of 10.67 %, 5.25 % and 16.76 %, respectively.

High Sensitivity Temperature and Curvature Sensor Based on Mach-Zehnder Interferometer With Tapered Two Peanut-Shaped Structures

A high-sensitivity temperature and curvature microfiber Mach-Zehnder interferometer (MMZI) with two peanut-shaped structures is proposed and demonstrated for the first time. The interferometer consists of a section of microfiber and two peanut-shaped structures. The microfiber can be easily affected by the external environment due to its strong evanescent field on the surface and the peanut-shaped structure is conducive to excite fundamental mode to high-order mode, which is beneficial to realize high-sensitivity sensing detection. The experimental results show that the maximum temperature sensitivity of &#x2212;678.67 pm<inline-formula> <tex-math notation="LaTeX">$/$ </tex-math></inline-formula>&#x00B0;C is obtained in the range of 30 &#x00B0;C to 42 &#x00B0;C, which is the highest temperature sensitivity we have known in the peanut-shaped structure sensor. Furthermore, the sensor is also used for curvature measurements. The curvature sensitivity can be up to &#x2212;79.09 nm<inline-formula> <tex-math notation="LaTeX">$/\text{m}$ </tex-math></inline-formula>^&#x2212;1 from 0.10188 m^&#x2212;1 to 0.20374 m^&#x2212;1. Therefore, the proposed sensor will have good application prospects in the field of biological detection and environment monitoring due to the advantage of high temperature sensitivity.

High-Sensitive Acoustic Sensor Based on Microfiber Mach–Zehnder Interferometer with Tapered Polarization-Maintaining Fiber

ABSTRACT We propose a high sensitive acoustic sensor based on a microfiber Mach-Zehnder interferometer (MMZI) with tapered polarization-maintaining fiber (PMF). The optical tapering technology is used to taper the PMF. Then, the MMZI is attached to a wood pulp diaphragm (WPD) to form an acoustic sensor, whose curvature will change with the vibration of the diaphragm. Two sensors with different waist diameters are made for performance comparison. Experimental results show that the acoustic sensor can achieve a wideband frequency response range from 200 Hz to 4000 Hz. The responses are flat at frequencies ranging from 200 Hz to 1500 Hz. Moreover, we find that the sensing performance of the acoustic sensor improves with the decrease in its waist diameter. When the waist diameter is 25.72 μm, the response sensitivity of the sensor can reach 42.4 mV/kPa at 2000 Hz, and the minimum detection pressure is 1.24 Pa/√Hz. It provides an effective way to fabricate an acoustic sensor, with low cost, easy integration, and high sensitivity.

Multi-Parameter Sensing and Demodulation of Temperature, Salinity and Pressure in Seawater Based on the Semi-Encapsulated Microfiber Mach-Zehnder Interferometer

Multi-Parameter Sensing and Demodulation of Temperature, Salinity and Pressure in Seawater Based on the Semi-Encapsulated Microfiber Mach-Zehnder Interferometer

Magnetic-ionic-liquid-integrated microfiber Mach-Zehnder interferometer for simultaneous measurement of magnetic field and temperature

A microfiber Mach-Zehnder interferometer (MMZI) integrated with magnetic ionic liquid (MIL) for simultaneous measurement of magnetic field and temperature is proposed and experimentally demonstrated. The MMZI-based sensor is fabricated by splicing a section of microfiber between two segments of single- mode fibers with pre-designed lateral offset, and then encapsulating the sensor structure into a capillary tube filled with MIL. By monitoring the wavelength shifts of two interference dips in the transmission spectrum at the same time, magnetic field and environmental temperature can be simultaneously measured. Experimental results show that the magnetic field and temperature sensitivities reach 25.5 pm/Oe and −4.63 nm/°C for the magnetic field and temperature ranges of 0 Oe to 375 Oe and 30 °C to 42 °C, respectively. In order to resolve the temperature cross sensitivity, a sensor matrix is set up by employing different magnetic field as well as temperature sensitivities of the two selected transmission dips. Our proposed MMZI sensor has several desirable merits such as compact structure, ease of fabrication, and low cost, which make it a good candidate for magnetic field/temperature dual-parameter sensing and related applications.

A High Sensitivity Curvature Sensor Based on Microfiber Mach-Zehnder Interferometer With Tapered Seven-Core Fiber

A Microfiber Mach-Zehnder interferometer (MMZI) based on tapered seven-core fiber (SCF) for curvature measurement has been reported and demonstrated. The tapered SCF promoted the light coupling efficiency from the single-mode fiber (SMF) to the SCF, which results in the transmission spectrum with a low loss and high extinction ratio. In the process of curvature measurement, the sensitivity can reach up to 174.02957 nm/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> , which is the highest curvature sensitivity in the MZI with SCF as best as we have known. Furthermore, the maximum temperature sensitivity is 0.00956 nm/°C when the temperature changes from 30 °C to 140 °C. It shows that this sensor is naturally insensitive to temperature, which has a good performance in avoiding the cross-sensitivity effect between the temperature and curvature.

Encapsulation Research of Microfiber Mach-Zehnder Interferometer Temperature and Salinity Sensor in Seawater

Encapsulation of microfiber Mach-Zehnder interferometer (MMZI) sensor for temperature and salinity sensing in seawater is developed. It includes a C-shape metal tube with a slit on the bottom and polymer adhesive with large elasticity modulus, by which a more robust sensor with relatively fast response can be obtained. To evaluate the performance of sensor after encapsulation, effects of different polymer adhesives on tension withstanding, temperature and salinity sensitivities are evaluated, and dependence of response time on shape of metal tube is investigated. Results show that sensitivities of the sensor in temperature and salinity sensing can reach to be about −1.77 nm/°C and 1.18 nm/ ‰, and response times are about 219.0 ms and 12.5 ms, respectively. By comparing temperatures and salinities measured by sensor with those measured by commercial device, accuracy of the sensor after encapsulation is proved. In addition, cross-sensitivities of strain/pressure and short/long-term stability after encapsulation are also evaluated. Finally, based on the basic structure, further improvements are attempted, such as double encapsulation with stainless steel mesh and complex encapsulation with two kinds of polymer. Encapsulations of MMZI demonstrated here show advantages of low cost, improved robustness, relatively fast response, long-term stability and easy expandability, which will not only afford a critical support for optical sensors operated in the ocean, but also offer some useful references for microfiber sensors used in other sensing applications.

Highly sensitive vibration sensor based on the dispersion turning point microfiber Mach-Zehnder interferometer.

In the present work, we introduced a highly sensitive vibration sensor, which is based on the dispersion turning point (DTP) microfiber Mach-Zehnder interferometer. The axial strain and vibration sensing characteristics of the microfiber Mach-Zehnder interferometer were investigated. First, we theoretically analyzed the spectrum evolution characteristics of the microfiber Mach-Zehnder interferometer caused by axial strain. Second, the microfiber with different diameters was fabricated using the electrode discharge and fused taper method, and the axial strain experiments were conducted; the maximum sensitivity of the DTP microfiber with a diameter of ∼2.2 µm reached -45.55 pm/µɛ at ∼1550 nm. Finally, based on the axial strain principle of the microfiber, we designed a highly sensitive vibration sensor using a DTP microfiber integrated into a rectangular through-hole cantilever beam. The 30-3500 Hz vibration signal monitoring could be realized, the maximum signal-to-noise ratio (SNR) was ∼75 dB at 52 Hz, and the acceleration sensitivity reached as high as 0.764 V/g at 45Hz. These results suggested the high performance of the microfiber in axial strain and micro-vibration sensing fields.

Temperature Sensing Characteristics of an MKR in a Microfiber Taper Based on Mechanisms of Interference and Resonance with Vernier Effect

In this work, spectral characteristics and temperature sensing characteristics of an in-line microfiber Mach-Zehnder interferometer (MZI) with an embedded microfiber knot resonator (MKR) is investigated. The microfiber MZI with an MKR (MZIKR) has a dual-effect composite spectrum with comb-like spectrum of the MKR loaded on the dominant interference spectrum. Vernier effect is generated by the MKR via superposition of resonant spectra with three resonant modes circulating in the MKR. This is the first time that Vernier effect is generated in a single MKR, which has advantages of easy fabrication and compact structure compared to the traditional resonant structures with Vernier effect such as two cascaded MKRs. Fast Fourier transform (FFT) and FFT filter are used to analyze and extract the different components of the transmission spectrum of the MZIKR. Temperature sensing characteristics of the different components of the polydimethylsiloxane-coated MZIKR are studied, showing that the interference dip of the MZI spectrum and the envelope dip of the MKR Vernier spectrum achieve a high temperature sensitivity of about -1.8 nm/ °C and about -3.5 nm/ °C, respectively. The proposed sensor has the advantages of easy fabrication, robust structure, and high sensitivity in temperature measurement. The MZIKR with dual-effect composite spectrum may have potential in two-parameter measurement and narrow-band filtering.

A Novel Optical Fiber Sensor Based on Microfiber Mach-Zehnder Interferometer With Two Spindle-Shaped Structures

A microfiber Mach-Zehnder interferometer (MMZI) with two spindle-shaped structures was reported for measuring temperature and curvature. Due to the core-separated structure, the MMZI could excite more high-order modes, which improves the sensitivity more efficiently. When the central waist region is 4 μm, the sensitivities for temperature and curvature were 1290.4pm /°C and 56.1947 nm/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , respectively. Furthermore, the sensitivity could be improved effectively by increasing the length of the central waist region. Increasing the length of central waist region to 6 μm, the temperature sensitivity of the sensor could up to 1756.3 pm/°C, which was the highest temperature sensitivity we have known in MMZI.

Simultaneous Measurement of Pressure and Temperature in Seawater with PDMS Sealed Microfiber Mach-Zehnder Interferometer

Simultaneous measurement of pressure and temperature in seawater is realized based on polydimethylsiloxane (PDMS) sealed microfiber Mach–Zehnder interferometer (MZI). Benefitting from the high thermal-optic coefficient and large elasticity of PDMS, high sensitivity and robust structure can be obtained. In theoretical modeling, significant enhanced pressure response in fiber is observed clearly, and pressure or temperature sensitivities are calculated theoretically. In experiment, PDMS sealed MZI is fabricated by a two-step sealing method. Using this MZI, sensitivity of 13.31 nm/MPa for pressure sensing and −7.41 nm/°C for temperature sensing are demonstrated, respectively, which are about one order higher than bare fiber MZIs (without PDMS sealing). To verify the accuracy of sensor, several tests under arbitrarily pressure and temperature are performed with average errors of 4.38% and 1.44%, respectively. In addition, effects of encapsulation on avoiding cross-sensitivity with salinity, PDMS thickness on pressure sensitivity, response time, repeatability, time stability, and polarization of the sensor are also evaluated by experiment. Sensors demonstrated here show advantages of low cost, simple fabrication, robust and compact structure, high-pressure resistance, high sensitivity, good repeatability, and long-term stability.