Interference Arm Research Articles

Design of a magnetic field and temperature fiber sensor based on Fabry–Pérot interferometer and OAM interrogation

We have designed a Fabry–Pérot interferometric fiber sensor based on the principal component analysis (PCA) assisted orbital angular momentum (OAM) interrogation for simultaneous measurement of magnetic field intensity and temperature. A hollow core fiber sandwiched between two segments of single mode fiber serving as the sensing probe, is introduced to the Gaussian interference arm. Encapsulated with magnetic fluid, the intensity and phase of Gaussian beam are highly sensitive to the variations of magnetic field and temperature, exerting a modulation on the intensity and rotation angle of OAM interferograms. A dual-parameter sensing matrix to discrimination the cross-sensitivity could be established via the PCA-assisted OAM interrogation. The minimum sensing resolutions of magnetic field and temperature are calculated as 0.06 G and 0.0079 °C, respectively.

Investigation of an inline fiber Mach-Zehnder interferometer based on hybrid joints of core-offset and peanut-shape for refractive index sensing

An inline fiber Mach-Zehnder Interferometer (MZI) that consisted of a standard single-mode fiber sandwiched between a core-offset and a peanut-shape joint is fabricated for the purpose of refractive index (RI) sensing. After one of the core-offset joints is replaced by a peanut-shape joint in an inline fiber MZI with the core-offset pair, the influence of the interference performance caused by the relative offset direction of the two core-offsets is avoided. The RI sensing characteristics under different core-offset displacement and interference arm length are studied. After bending the inline fiber MZI, the interference spectra become more stable, and the RI sensing performance is markedly improved. The RI sensitivity of −167.27 nm/RIU with a resolution of 2.39 × 10-4 RIU is achieved within the measured RI range of 1.333–1.373.

Fiber-Optic Interferometry and Phase Generation-Based Micro-Vibration Estimating System

This research presents a novel contactless micro-vibration estimating system that combines a Michelson fiber-optic interferometer and phase generation carriers based on calculation of the arc tangent. The system utilizes a narrow-band light source, a coupler, and a non-equilibrium Michelson fiber-optic interferometer to measure micro-vibrations on the surface of an object. One path of the light irradiates the object's surface vertically using an optical-fiber self-focusing lens, while the other path is reflected by a device at the reference arm's optical fiber. The light paths are then coupled, detected by a photoelectric coupler (PD), and processed by a data processing module. Additionally, the data processing module generates carrier waves to control a phase modulator on the interference arm. The resulting measurements are obtained using a phase demodulation technique based on the calculation of arc tangent (ARCTAN). The proposed system exhibits high flexibility, excellent response, and is unaffected by light intensity and visibility drifting, enabling online measurements of contactless micro-vibrations.

Design of a Mach-Zehnder Interferometric Fiber Sensing System Based on PCA-Assisted OAM Interrogation for Simultaneous Measurement of Refractive Index and Temperature

We propose and numerically design a Mach-Zehnder interferometric sensing system using principal-component-analysis-based orbital angular momentum (OAM) interrogation for simultaneous measurement of refractive index (RI) and temperature. A capillary-assisted Mach-Zehnder interferometer (CAMZI) encapsulated into a microfluidic channel serves as the sensor probe, which is introduced in the Gaussian interference arm of the sensing system. Temperature-sensitive liquid and RI sample are respectively loaded inside and outside the silica capillary to discriminate the cross sensitivity between refractive and temperature. As the output light of the CAMZI carrying intensity and phase information in response to the variations in RI and temperature interferes with the OAM beam, the intensity and rotation angle of the spiral interferogram would change accordingly. And by performing principal component analysis (PCA) on these interference patterns, RI and temperature variations could be retrieved. The proposed sensing system based on PCA-assisted OAM interrogation is anticipated to resolve cross-sensitivity for dual-parameter sensing, and moreover it paves new way toward developing OAM-related photonic devices.

High Sensitivity Optical Fiber Mach-Zehnder Refractive Index Sensor Based on Waist-Enlarged Bitaper.

A Mach–Zehnder fiber optic sensor with high refractive index response sensitivity was developed. By fabricating a waist-enlarged bitaper structure on the interference arm of a single mode–multimode–single mode (SMS) Mach–Zehnder interferometer (MZI), the spectral contrast and response sensitivity were improved. Subsequently, the response sensitivity was further improved by etching the interference arm. When a beam of light was introduced into the sensor, due to the structural mismatch between the multimode fiber and the normal transmission light, the difference between the low-order mode and the high-order mode was generated in the fiber core and the fiber cladding. In the process of transmission in the sensing arm, due to the different refractive indices of the core and cladding, the optical path difference of the high-order mode and the low-order mode was different, which eventually generated interference fringes. The experimentally measured response sensitivity of SMS MZI in the range of 1.351 RIU to 1.402 RIU is 57.623 nm/RIU; the response sensitivity of a single mode–multimode–bitaper–multimode–single mode (SMBMS) MZI is 61.607 nm/RIU; and the response sensitivity of the etched SMBMS (ESMBMS) MZI is 287.65 nm/RIU. The response sensitivity of the new ESMBMS MZI is three times higher than that of the original SMS MZI. The sensor has the characteristics of compact structure, high sensitivity, easy manufacture, and a wide range of refractive index measurements, and can be used in food processing, pharmaceutical manufacturing and other fields.

Fiber Bending Sensor With Turning Point in a Multimode Fiber Peanut-Like Structure

In this paper, we experimentally demonstrated a bending sensor based on Michelson interferometer (MI). The sensor was fabricated by fusion splicing single-mode fiber (SMF) and multimode fiber (MMF) spheres. The improved end-face packaging scheme was adopted to realize the measurement of bending. The advantage of MMF numerical aperture increases the mode field diameter and the number of modes. Fiber bending induces transition between modes, resulting in the generation and fade of fiber modes, achieving the emergence of bending turning points (BTPs). The BTP is defined as the point where the direction of interference dip shift changes due to fiber bending. By observing the direction of interference dip shift during bending, the degree of bending can be intuitively estimated. The simulation results verify the generation and fade of excited modes in the bending MMF peanut-like structure, which are in good agreement with the experimental results. When the sensor is installed in parallel and titled ways, due to the uneven force of the plate in the bending state, it shows the differences in sensitivity, BTP and initial bending response. Further, the BTP can be roughly adjusted by the MMF core diameter, and the deviation of the sensitivity is reflected in the length of the interference arm. Besides, compact size, low cost and low hysteresis make the sensor more competitive in harsh environment applications.

Design and modeling of a graphene-based composite structure optical pressure sensor.

In this paper, a novel graphene-based composite structure optical pressure sensor is designed and built with the aid of modeling. A PDMS force-sensitive structural mechanics model is established to optimize the size of the pyramid array distributed on the PDMS layer so that to support high levels of sensitivity and stability. Meanwhile, a graphene waveguide optical model is established to obtain the optimized interference length (L), arm spacing (H) and core width (W), with the objectives of advanced sensitivity, low propagation loss, high resolution. The experimental results show that the pressure sensitivity of the proposed sensor is 17.86 nm/kPa and the maximum pressure that can be detected is 3.40 kPa, which is consistent with the theoretical analysis and verifies the feasibility of the design, also the modeling methods of the graphene-based composite structure optical pressure sensor.

Interference and frequency-to-time mapping based high anti-jamming and anti-interception frequency hopping receiving.

We have proposed an interference and frequency-to-time mapping based high anti-jamming and anti-interception frequency hopping receiving scheme. By changing the delay difference between the interference arms through high-speed switchable delay lines and using electrooptical sampling, fast and large-range frequency hopping signals can be received. Benefited from the high shaping resolution for using the interference as the spectral shaping method, more receiving passbands in high frequency bands can be available to enhance the anti-jamming and anti-interception performance. By fast pulse shaping through switchable delay lines, the bandwidth of the electric end, the sampling rate, and the number of frequencies in the frequency hopping pattern are decoupled, and the bandwidth of the electric end can be reduced to improve the receiving selectivity. In experiments, the signal hopping from 15.2 GHz to 35.4 GHz with the switching time up to that of the used optical switch is received. Utilizing a switchable delay line in the interference arm with the tuning step of 2.5 ps, eight available receiving passbands within 25 GHz to 42 GHz are generated. The receiving selectivity is also improved from 18.3 to 43.7 in terms of Q factor by decreasing the electric end's bandwidth in experiments.

DPSK modulation and demodulation system based on a novel Mach-Zehnder interference structure

As the conventional fiber Mach-Zehnder (M−Z) interference structure being sensitive to temperature variation and mismatching of arm length in Differential Phase Shift Keying (DPSK) system, we proposed a modulation and demodulation system of DPSK based on novel M−Z interference structure. This novel M−Z interference structure has some advantages of higher temperature stability, better robustness and lower restriction of laser linewidth. A detailed discussion of the working principle is presented and demonstrated, the influences of the delay induced by arm mismatching and temperature variation on the Q factor of DPSK system are analyzed. Experimental results as well as simulations show that the delay length mismatching corresponding to descent point of 3dB increases from [0.925,1.124] to [0.536,1.31], which reduces the requirement for the length accuracy of the interference arm, and the demodulation effect of the novel structure is better under the same deviation. The Q factor of the system keeps fluctuation within a narrow range when the temperature variation in the range of 20°C–120°C, and the demodulation effect of the system is almost unaffected by the variation of ambient temperature.

Preliminary simulation analysis of the temperature fluctuation effect on Taiji-1 Laser interferometer

Space-borne gravitational wave detection imposes a demanding requirement on the sensitivity of the laser interferometer. Among all disturbances that affect the measurement accuracy of the laser interferometer, temperature fluctuations contribute significantly. In this paper, the structure model and the interference path design of Taiji-1 laser interferometer have been used to conduct a preliminary simulation analysis of the temperature fluctuation noise through the finite element method. The temperature, the displacement and the optical path difference fluctuations have been obtained and theoretically analyzed. The preliminary simulation results are consistent with the theoretical analysis, which shows that the thermal–structural–optical simulation scheme adopted in this paper is reasonable. With the preliminary simulation results and the actual temperature control of Taiji-1 laser interferometer, we estimate that in Taiji-1 laser interferometer system, the temperature fluctuation is below the order of mK, the node displacement is within [Formula: see text][Formula: see text]pm, and the interference arm length difference fluctuation amplitude of the laser interferometer is also within [Formula: see text][Formula: see text]pm.

High-Performance Bending Sensor Based on Fiber Microspheres Array Michelson Interferometer

A compact, high-performance bending sensor based on fiber microspheres array (FMA) Michelson interferometer (MI) was experimentally proved. The sensor consists of a refractive index modulation region (RIMR) fused by three microspheres, interference arm and end face protection. The RIMR acts as a modal coupling device between core and cladding modes. Due to the different stress for the RIMR in the middle (lowest point) of the stepper motor or the side (high point) during the bending process, the mode field distribution excited to the cladding is inconsistent which shows a discrepancy in sensitivity. The results show that the bending sensitivity at the lowest point is lower than the high point, which is consistent with the theory. Meanwhile, the variable range method is used to realize the repeatability verification of the sensor. Besides, the relative sensitivity (the ratio of wavelength sensitivity to intensity sensitivity) is defined to realize the resolution of strain and bending.

Performance Optimization of Fiber Optic Interferometric Accelerometer Based on Phase Noise Analysis

The phase noise of a Michelson interferometer-based fiber optic accelerometer is analyzed to determine the optimal modulation depth of the laser light frequency and the length difference between the interference arms. The output intensity fluctuation of the interferometer, originating from the phase noise of the modulated laser source, is examined theoretically, revealing that both the interference intensity noise power and the phase modulation depth of the interferometer are proportional to the frequency modulation depth of the laser and the interference arm length difference. In addition, it is determined experimentally that the laser linewidth, or equivalently, the laser phase noise, varies approximate linearly with the light frequency. As the optimum phase modulation depth is a constant, the interference intensity noise power has a minimum value, when the light frequency modulation depth is at its maximum. The proposed theory is demonstrated experimentally, with results showing that a high-performance broadband fiber optic interferometric accelerometer achieves the lowest noise level when the light frequency modulation depth of the source laser is at its maximum value.

Highly Sensitive Refractive Index Sensor Based on an In-Fiber Droplet-Shape Air-Cavity

We present a highly sensitive refractive index (RI) sensor based on an ultra-compact in-fiber Mach–Zehnder interferometer (MZI) with a droplet-shape air-cavity. The droplet-shape air-cavity is fabricated by fusion splicing and single-side fused tapering. The fabricated MZI is with a very short interference arm of $\sim 330\mu \text{m}$ and the taper waist diameter of $\sim 40\mu \text{m}$ . The interference happens between the silica-cladding mode and the air-core mode. The trough wavelength of the interference with specific order in the transmission spectrum shifts with the change of surrounding refractive index. The experimental results show that this sensor offers high sensitivity (up to 2803.6 nm/RIU at RI∼1.42) for RI measurement in the range of 1.3164–1.4270, which match well with the theoretical analysis. High RI sensitivity, high-spatial resolution, temperature insensitivity, easy fabrication, and low-cost make it a competitive RI sensor in the biochemical and physical sensing fields.

Zoom into picometer: a picoscale equivalent phase-difference-generating method for testing heterodyne interferometers without ultraprecision stages

A simple and low-budget method aiming to generate phase difference equivalent to picoscale-measured displacements of heterodyne interferometers is proposed. By changing the length of an interference arm in an interferometer-like optical configuration, a small phase difference between the two wavelengths is generated for creating the same effect as a picoscale-measured displacement of the heterodyne interferometer. It is derived and experimentally demonstrated that the zoom factor, defined as the ratio of displacements in a heterodyne interferometer and the proposed method leading to the same phase difference, is proportional to the beat frequency and generally in a scale of 10 − 9. Thus, instead of ultraprecision piezo-stages, only a commercial linear guide rail is equipped in the method, and rigorous vibrating isolation is not necessary. The method has been already used to evaluate signal-processing electronics of a heterodyne grating interferometer.

A Novel Mach-Zehnder Interferometer Using Eccentric-Core Fiber Design for Optical Coherence Tomography.

A novel Mach-Zehnder interferometer using eccentric-core fiber (ECF) design for optical coherence tomography (OCT) is proposed and demonstrated. Instead of the commercial single-mode fiber (SMF), the ECF is used as one interference arm of the implementation. Because of the offset location of the eccentric core, it is sensitive to directional bending and the optical path difference (OPD) of two interference arms can be adjusted with high precision. The birefringence of ECF is calculated and experimentally measured, which demonstrates the polarization sensitivity of the ECF proposed in the paper is similar to that of SMF. Such a structure can replace the reference optical delay line to form an all-fiber passive device. A mirror is used as a sample for analyzing the ECF bending responses of the system. Besides, four pieces of overlapping glass slides as sample are experimentally measured as well.

Majorana box qubits

Quantum information protected by the topology of the storage medium is expected to exhibit long coherence times. Another feature is topologically protected gates generated through braiding of Majorana bound states (MBSs). However, braiding requires structures with branched topological segments which have inherent difficulties in the semiconductor–superconductor heterostructures now believed to host MBSs. In this paper, we construct quantum bits taking advantage of the topological protection and non-local properties of MBSs in a network of parallel wires, but without relying on braiding for quantum gates. The elementary unit is made from three topological wires, two wires coupled by a trivial superconductor and the third acting as an interference arm. Coulomb blockade of the combined wires spawns a fractionalized spin, non-locally addressable by quantum dots used for single-qubit readout, initialization, and manipulation. We describe how the same tools allow for measurement-based implementation of the Clifford gates, in total making the architecture universal. Proof-of-principle demonstration of topologically protected qubits using existing techniques is therefore within reach.

采用可调Mach-Zehnder滤波的波长可切换掺铒光纤激光器

In order to realize a highly stable and tunable laser output, an Er3+-doped fiber laser based on Mach-Zehnder filter structure and grating array made by femtosecond laser was proposed, and an optical delay line(ODL) was set into one interference arm to tune the interference interval flexibly. In the designed configuration, one 976 nm laser diode (LD) was used for pumping; an Er3+-doped fiber (EDF) of 6 m length was selected as the gain medium; The grating array will selete the femtosecond light reflection loop cavity specific wavelength oscillation form; the M-Z structure, which was used as comb filter, was adopted to select the wavelength reflected by the grating array; Tuning laser output can be realized by adjusting the ODL. In the experiment, when the pump power was 100 mW, a stable and tunable single, dual and triple wavelength output laser was observed. The single wavelength tunable interval was 2 nm within 1 570-1 596 nm, and the side-mode suppression ratios (SMSRs) of all were more than 50 dB.

Optical security validation using Michelson interferometer

We propose an improved interference-based encoding that is suitable for security validation application. Two random phase masks are designed by a specific iterative phase retrieval algorithm; they serve as the system phase lock and the authentication key. In the validation process, two-beam interference is implemented using the two masks with a classical Michelson interferometer; the phase lock is fixed on one interference arm, and the authentication key is presented on another moveable arm, which can output two recognizable images by moving a certain distance. Without the correct authentication key, the secret image cannot be recognized even knowing the system lock. As a result, the validation result can be simply determined by checking the interference outputs. Numerical simulations are performed to demonstrate the validity and security of the proposed optical validation method.

Reconfigurable and ultra-sensitive in-line Mach-Zehnder interferometer based on the fusion of microfiber and microfluid

A reconfigurable Mach-Zenhnder interferometer (MZI) based on a microfluidic cavity (MFC) constructed by embedding a microfiber between two segments of single-mode fibers with pre-designed lateral offset has been proposed and experimentally demonstrated. The MFC serves as an interference arm with an eccentric annular cross section and allows convenient sample (gas or liquids) replacement procedure. The microfiber works as the other interference arm that provides the proposed device with ease of reconstruction and also enhances the force sensitivity. The re-configurability and the ultra-wide tuning sensitivity range are demonstrated by immersing the MZI constructed with a 484 μm-long-MFC and a microfiber 44 μm in diameter in different droplets. Ultrahigh sensitivities of 34.65 nm/°C (∼88 380 nm/RIU) and −493.7 nm/N (∼−590 pm/με) are experimentally achieved using a droplet with a refractive index of ∼1.44.

Compact magnetic-field sensor based on optical microfiber Michelson interferometer and Fe3O4 nanofluid

We report a magnetic-field sensor by merging the advantages of optical fiber Michelson interferometers with that of magnetic fluid. Compact and low-cost optical fiber Michelson interferometers were first fabricated by a high-frequency CO(2) laser, and then they were inserted into glass capillaries with water-based Fe(3)O(4) magnetic fluid as sensing elements. The sensing characteristics have been investigated and the experimental results show that the reflective spectrum of the fiber-magnetic sensor linearly shifted with the change of the magnetic-field strength that is perpendicular to the axial of the devices. The fiber-magnetic sensor with interference arm's diameter of 50 μm is most sensitive to the external magnetic field, and the sensitivity is up to 64.9 pm/mT, which is 20 times higher than that of 125 μm diameter.