Fiber Michelson Interferometer Research Articles

Michelson interferometer based on a fiber with a germanium-doped core and inner cladding for high-temperature sensing

We proposed and demonstrated a temperature sensor based on a fiber Michelson interferometer. The Michelson Interferometer contains a special fiber with a germanium-doped core and pure silica inner cladding, so the interference spectrum is formed as a result of interference of the mode of the core and one of the modes of the inner cladding. The existence of inner cladding reduces the number of interacting cladding modes. When annealing the sensor for 300 min at a temperature of 600 °C, no thermal hysteresis of the interference spectrum was observed. The temperature sensitivities of the proposed sensor are 48 pm/°C in the range of 20–250 °C and 78 pm/°C in the range of 250–600 °C. But when the sensor was exposed to a constant temperature of 700 °C and above for a few hours, a shift in the wavelength of the dip of the interference spectrum is observed. This wavelength shift, which occurs even at a fixed temperature, depends on the temperature of annealing. It can be explained by a number of processes occurring in glass at high temperatures: the changing fictive temperature of the glass, diffusion of germanium oxide from the core, and formation of mechanical stresses resulting from the difference in thermal expansion coefficients of the core and cladding, and relaxation of these mechanical stresses at an elevated temperature.

SCF-MMF based Michelson interferometer for ethanol multi-parameter measurements

A optical fiber Michelson interferometer (MI) for multi-parameter ethanol measurements is proposed and experimentally demonstrated. The sensor consists of a brief seven-core fiber (SCF) and a section of multimode fiber (MMF). With the SCF, multiple high-order modes are coupled into MMF, while the core fundamental mode and high-order modes are reflected back by the MMF end face and recoupled to the SMF by the SCF. When the surrounding ethanol changes, the reflection spectrum of the MI shift for the intermodal interference strongly integrates with the surrounding medium. Experimental results show that the sensor has an ethanol concentration sensitivity of −0.041 dB/% over the range of 0–90 %. The level sensitivities are −0.0795 nm/mm and −0.1052 nm/mm in the 0–5 mm range for 5 % and 10 % ethanol solutions, respectively, while in the 5–20 mm range, the sensitivities are −0.2773 nm/mm and −0.2243 nm/mm, respectively. Moreover, the volatilization time and volatilization stability are tested under different concentrations of ethanol, and the volatilization sensitivity is 0.071 dB/% in the range of 0–60 %. Response and recovery time of 1.008 s and 0.514 s for 15 % ethanol volatilization molecules is achieved. This MI has advantages of compact structure, easy fabrication, good stability and dominant ability to achieve multi-parameter ethanol measurement via reflective operation.

Liquid‐level sensor based on Michelson interferometer with double hook structure

AbstractA new type of Michelson interferometer (MI) based on a double hook structure is proposed for measurement of liquid level and temperature. The optical fiber MI based on the double‐hook structure is fabricated using a hydroxide flame heating device. Furthermore, the angle and sensing length of the double‐hook structure can be controlled by a rotating platform. The sensor is fixed on a ruler, which is set vertically on the iron support stand employing a beaker clamp, and the position of the beaker clamp is adjusted so that the double hook structure of the sensor overflows the water surface in the beaker. The temperature and liquid level sensitivities of the sensor are 129.8 pm/°C and −186.2 pm/mm, respectively. The novel optical fiber MI based on the double‐hook structure has the advantages of high sensitivity, low cost and easy fabrication, which has a great market prospect in production and life.

Low-Coherence Homodyne Interferometer for Sub-Megahertz Fiber Optic Sensor Readout.

This study proposes a method for interferometric fiber optic sensor readouts. The method utilizes the advantages of the active homodyne demodulation technique and low-coherence interferometry. The usage of the tandem low-coherence interferometer enables modulating the reference interferometer without any changes to the sensor. This achieves high sensitivity, high stability, and a wide frequency band. A sensitivity of up to 0.1 nm (RMS) in the frequency range of 5 kHz is demonstrated by detecting acoustic signals with a fiber Michelson interferometer as a sensor.

Linewidth narrowing and frequency stabilization of a coin-sized laser module

We demonstrate linewidth narrowing and frequency stabilization of a coin-sized laser module using both a short imbalance path length Michelson fiber interferometer and Doppler-free spectroscopy of molecular iodine. The linewidth of the coin-sized laser is reduced from 2 MHz to 6 kHz, which is now narrower than the Doppler-free spectral linewidth (670 kHz) of molecular iodine. Laser frequency stabilization based on the Doppler-free iodine signal is carried out by directly controlling the imbalance path length of the fiber interferometer. The frequency stability of the hybrid-locked coin-sized laser is 9.8 × 10−13 at 1-s averaging time and reaches 6.8 × 10−14 at 400 s. The hybrid-locked coin-sized laser with linewidth narrowing and frequency stabilization has a long coherence time and known absolute frequency and can be used for precision measurements in either fundamental science or industrial applications.

Highly sensitive torsion sensor based on helical eccentric dual-core fiber Michelson interferometer

An optical fiber torsion sensor was academically put forward and experimentally demonstrated by applying a Michelson interferometer (MI) based on a helical eccentric dual core fiber (HEDCF). The sensor consists of an eccentric dual core fiber (EDCF), a taper, and a helical structure based on the EDCF. Since there is a large interval between a centric core and an eccentric core of the EDCF, the helical structure can greatly improve the torsion sensitivity of the sensor. When the twisting direction is consistent with the pre-twisting direction, the optical path difference (OPD) of MI negative increases during the twisting process, and the spectral resonance wavelength shifts blue. Experimental results show that the greater the degree of helical addition, the higher the torsional sensitivity. The torsion sensitivity can reach as high as −7.01 nm/(rad/m) in clockwise (CW) direction in the range of 0–9.595 rad/m. Moreover, the satisfactory sensitivity, stable structure and small temperature crosstalk, let it a valuable select in torsion sensing domain, and is promising to be useful for broad applications across engineering fields.

High-resolution liquid level sensor utilizing a microwave photonics interrogated multicore fiber interferometer.

We propose and experimentally demonstrate a high-resolution, high-sensitivity liquid level sensor based on a multicore fiber (MCF) Michelson interferometer (MI), where the sensing fiber is securely affixed to a cantilever beam, such that liquid level variations will change the beam's curvature, meanwhile leading to a substantial phase difference between the two interfering arms of the MI, and the sensor is interrogated using a microwave photonics filter (MPF) system, which can provide greatly enhanced measurement resolution compared to the traditional optical wavelength demodulation methods. The angular position of the MCF is precisely calibrated to ensure optimal sensitivity of the MI sensor. As a result, within a measurement range of up to ±14 cm, the proposed liquid level sensor achieves a sensitivity of 10.35 MHz/cm and an impressive resolution of 0.04835 cm. The proposed sensor has unique advantages of high sensitivity, superior resolution, long-term stability, etc.

Temperature Sensor Based on Side-Polished Two-Core Fiber Michelson Interferometer

Temperature Sensor Based on Side-Polished Two-Core Fiber Michelson Interferometer

A relative humidity sensor based on 2-core fiber Michelson interferometer with end-face aluminium mirror

A relative humidity sensor based on 2-core fiber Michelson interferometer with end-face aluminium mirror

Novel design of phase demodulation scheme for fiber optic interferometric sensors in the advanced undergraduate laboratory

Phase modulation depth (PMD) is crucial for the phase demodulation scheme of fiber optic interferometric sensors. The novel design of phase generated carrier differential-cross-multiplying (PGC-DCM) demodulation schemes allows undergraduates to understand the operation principle of the sensors and explore the connection between the PMD and the system performance. The system mainly consists of a laser, a fiber Michelson interferometer (FMI), a data acquisition card and a host computer. The simulation signal is first applied on the sensing arm of the FMI by a piezoelectric transducer and induces the phase difference shift between the two arms. Next the signal-to-noise ratios (SNRs) of the demodulated signals from the PGC-DCM algorithms under different PMD values are tested and an optimum PMD value is found. Thus, a proportion integral differential (PID) module is designed and integrated with the demodulation algorithm to calibrate the PMD to the optimum value. An ellipse fitting algorithm (EFA) is used to estimate the real-time PMD of the system that is then fed into the PID module. The amplitude of the laser modulation signal is controlled by the PID module, which is proportional to the PMD. Moreover, the response linearity, dynamic range, total harmonic distortion and phase resolution of the system are investigated.

Compact Fiber Optic Sensor for Temperature and Transverse Load Measurement Based on the Parallel Vernier Effect

An optical fiber sensor based on the parallel Vernier effect for temperature and transverse load measurement is reported in this paper. The sensor is composed of a novel compact fiber Michelson interferometer (MI) and a closed-cavity Fabry–Perot interferometer (FPI) connected in parallel. The fiber MI consists of a bent single-mode fiber (SMF) structure and a short length of hollow core silicon tube (HCST). A section of HCST is fused between two segments of SMF to form the fiber FPI. Two sensors in parallel can easily measure different physical parameters independently, thus realizing multi-parameter sensing. The fiber MI and FPI are used for temperature and transverse load measurement, respectively. Fiber optic MI and FPI are Vernier effect mutual reference interferometers. When MI is used for temperature sensing, FPI is the reference interferometer. When FPI is used for transverse load sensing, MI is the reference interferometer. It can improve the sensitivity of temperature and transverse load. Two samples were made and the sensing experiment was carried out. Through the sensing experiment, we get the maximum temperature sensitivity of 85.1 pm/°C in the temperature range of 30–80 °C and a transverse load sensitivity of −3.15 nm/N in the temperature range of 0–1.96 N. In addition, the sensor has the advantages of tiny size, low cost, and easy manufacture, which is suitable for temperature and transverse load sensing applications.

A Novel System for Quasi-Continuous THz Signal Transmission and Reception.

This paper presents a novel system for generating and receiving quasi-continuous (QC) TeraHertz (THz) waves. A system design and theoretical foundation for QC-THz signal generation are presented. The proposed QC-THz system consists of commercially available photo-conductive antennas used for transmission and reception of THz waves and a custom-designed QC optical signal generator, which is based on a fast optical frequency sweep of a single telecom distributed-feedback laser diode and unbalanced optical fiber Michelson interferometer used for a high-frequency modulation. The theoretical model for the proposed system is presented and experimentally evaluated. The experimental results were compared to the state-of-the-art continuous-wave THz system. The comparison between the continuous-wave THz system and the proposed QC-THz system showed the ability to transmit and receive QC-THz waves up to 300 GHz. The upper-frequency limit is bounded by the length of the used Michelson interferometer. The presented design of THz signal generation has a potential for industrial application because it is cost-efficient and can be built using commercially available components.

All-optical vector magnetic field sensor based on a side-polished two-core fiber Michelson interferometer.

A magnetic field sensor based on a side-polished two-core fiber (SPTCF)-based Michelson interferometer (MI) has been developed and demonstrated. The magnetic field sensor is composed of a standard single mode fiber (SMF) and a section of tapered TCF. By side-polishing a segment of the TCF, the effective index of the exposed core can be made sensitive to the environmental refractive index (RI). To evaluate its performance, a magnetic fluid is used to cover the polished region with a magnetic field sensitive material, where the sensor then measures the magnetic field intensity by sensing the RI change of the magnetic fluid through the evanescent field in the polished core. The SPTCF MI device developed allows for vector magnetic field sensing because of its asymmetric structure, with its highest directional sensitivity being 55.2 pm/degree. Experimental results obtained show that when the magnetic field is parallel to the side-polished plane, a sensitivity of 1.262 nm/mT can be achieved, operating over the magnetic flux density region of 0-5 mT and over a temperature range of 20∼85 °C, where the device is minimally affected by temperature changes. The sensor is well suited to a variety of potential applications given its low cost, strong anti-interference ability, simple structure and high stability.

非平衡光纤干涉仪的相位稳定方法研究

By using photons to carry quantum information, optical quantum information technology plays an essential role in quantum communication, quantum metrology, and linear optical quantum computing. In recent years, the unbalanced fiber interferometer has been widely applied in preparing, manipulating, and measuring photon qubits. However, the unbalanced fiber interferometer based on fiber devices is sensitive to the environment's thermal, mechanical, and acoustic noise. Thus, phase stabilization based on feedback control is essential in utilizing an unbalanced fiber interferometer. The existing phase stabilization methods typically employ a reference laser combined with optoelectronic detection, thus introducing additional noise to photon qubits. In this paper, we propose and demonstrate a feedback control method to stabilize a phase in an unbalanced fiber interferometer by combining weak coherent reference light and single photon counting. Using theoretical analysis, we realized the phase stabilization of an unbalanced fiber Michelson interferometer with an arm-length difference of about 1 m. The results showed that the jitter of the stabilized phase is less than 0.042 rad, while the visibility of single-photon interference fringes is higher than 99%.

High sensitivity interrogation system of fiber Bragg grating sensor with composite cavity fiber laser

A high sensitivity interrogation system of fiber Bragg grating (FBG) sensor with composite cavity fiber laser is proposed and experimentally demonstrated. The FBG is used as a sensing grating and the chirped fiber Bragg grating (CFBG) is used as a reference grating. Both are placed at the end of the fiber Michelson interferometer (MI) acts as the two arms mirrors and form a composite cavity of the fiber laser. The longitudinal modes generated by the composite cavity fiber laser are superimposed on each other to generate envelopemodulation of the beat frequency signal (BFS) which depends on the optical path difference between the two arms. The wavelength change of the sensor FBG can be obtained by measuring the BFS drift causedby the arm length change of the MI. In our scheme, the wavelength change of sensor FBG is converted into arm length change by using CFBG and finally into fiber laser BFS drift. The system has a simple structure, low cost, and high sensitivity.

Compact all-fiber thermo-optic modulator based on a Michelson interferometer coated with NaNdF4 nanoparticles.

We propose and investigate an all-fiber thermo-optic modulator based on a side-polished twin-core fiber (TCF) Michelson interferometer (MI) coated with NaNdF4 nanoparticles. The MI was fabricated by tapering the splicing point between the TCF and a single mode fiber (SMF). A short suspended core fiber (SCF) is spliced to one core of the TCF to introduce a fixed optical phase difference (OPD). The side-polished core is coated with photo-thermal material NaNdF4. Owing to the ohmic heating of NaNdF4 nanoparticles under 808 nm pump laser, the effective refractive index of the polished core is changed, resulting in a phase shift of the MI. The MI has a significant modulation phase shift with 2.9 π near the wavelength of 1260 nm and can obtain an optical switching with a rise (fall) time of 152 (50) ms. The proposed device will have a great application potential in optical modulators due to compact structure and strong robustness.

Ultrasensitive temperature sensor with Vernier-effect improved fiber Michelson interferometer.

A novel fiber Michelson interferometer (FMI) based on parallel dual polarization maintaining fiber Sagnac interferometers (PMF-SIs) is proposed and experimentally demonstrated for temperature sensing. The free spectral range (FSR) difference of dual PMF-SIs determines the FSR of envelope and sensitivity of the sensor. The temperature sensitivity of parallel dual PMF-SIs is greatly enhanced by the Vernier effect. Experimental results show that the temperature sensitivity of the proposed sensor is improved from -1.646 nm/°C (single PMF-SI) to 78.984 nm/°C (parallel dual PMF-SIs), with a magnification factor of 47.99, and the temperature resolution is improved from ±0.03037°C to ±0.00063°C by optimizing the FSR difference between the two PMF-SIs. Our proposed ultrasensitive temperature sensor is with easy fabrication, low cost and simple configuration which can be implemented for various real applications that need high precision temperature measurement.

The Strain Sensor with Enhanced Sensitivity Based on Improved Optical Fiber Michelson Interferometer

The Strain Sensor with Enhanced Sensitivity Based on Improved Optical Fiber Michelson Interferometer

Silver-coated three-core fiber Michelson interferometer for liquid-level measurement

Abstract The Michelson liquid-level sensor based on silver coated the end face of the three-core fiber reflection structure has been proposed to measure continuous or discrete liquid level. The Michelson interference structure can be obtained by the combination of the single-mode optical fiber and the three-core optical fiber with the silver film coated on the other end face of it. The inter-mode interference can be obtained by the fiber-core mismatch at the fusion joint. The liquid level can be measured by monitoring the dip wavelength shift of the interference spectrum. The results indicate that the sensitivity of the liquid-level sensor will decrease with the increasing sensing length. The sensing length of 30 mm is selected to investigate the performance of the sensor. The sensitivity of water level is reached as high as 392.83 pm/mm with an excellent linearity of 0.99946. Interestingly, the sensitivity of the sensor increases with the liquid refractive index and the sensitivity of the refractive index for NaCl solution is 4410.74 pm/mm/RIU. The performance of the sensor is very stable in the range of 20–90 °C. The maximum drift for temperature is 0.3001 nm. The sensor can be applied to the measurement of the liquid level in different environments.

Parallelized fiber Michelson interferometers with advanced curvature sensitivity plus abated temperature crosstalk.

In this Letter, we proposed a super sensitive optic-fiber curvature sensor with ultra-low temperature crosstalk based on Vernier effect and achieved it experimentally. This sensor composes a pair of parallelized 2CFMIs (2-core-fiber Michelson interferometers) in similar lengths, both of which are involved sensing, but there is a rotation angle between their cross-sections. When the rotation angle approaches 180°, the magnification factor for curvature sensitivity is doubled compared with conventional Vernier effect, while for temperature it is always 1. Therefore, advanced curvature sensitivity and abated temperature crosstalk can be realized simultaneously when demodulating Vernier envelops. The experiment results indicate that the curvature sensitivity of this sensor reached 214.533nm/m-1, and temperature crosstalk was as low as 0.000276m-1/∘C. The fabrication process is extremely flexible and repeatable, and the magnification factor of Vernier effect could be controlled conveniently.