Fiber Mach-Zehnder Interferometer Research Articles

A MMF-TSMF-MMF Structure Coated Magnetic Fluid for Magnetic Field Measurement

An optical fiber Mach-Zehnder interferometer (MZI) coated by magnetic fluid (MF) is fabricated for magnetic field measurement. The interferometer is composed of multimode fiber-taper single mode fiber-multimode fiber (MTSM). The two MMFs play the role of a beam splitter and a coupler. The TSMF induces the generation of high-order cladding mode and enhances the re-coupling ability of the interferometer. The transmission spectrum and cladding modes with different taper waist diameter are theoretically analyzed. Interference dips are sensitive to the alteration of magnetic field intensity when the taper waist diameter of interferometer is 34 μm. The highest sensitivity is up to -0.81 nm/mT at the magnetic field range of 8-17 mT.

Refractometer based on fiber Mach-Zehnder interferometer composed of two micro bending cores

In this paper, a novel refractometer based on Mach-Zehnder Interferometer (MZI) is proposed and experimentally investigated. The MZI is composed of 2 micro bending cores (MBCs), one of which excites the cladding modes and the other couples the modes back. This structure is formed by high-frequency CO2 laser polishing and oxyhydrogen flame heating. With the unique deformation method, the interaction between the fiber core and the external status gets enhanced, moreover, higher modes in the cladding are excited, which leads to a high refractive index (RI) sensitivity. Due to the high temperature of the oxyhydrogen flame, the core of CO2 polished fiber is modulated, furthermore, the cladding shape of MBC tends to be circular. Hence, relatively small modulating regions of 500 μm can form for interference. In the experiment, 2 transmission dips are chosen for RI measuring, which possesses the wavelength of 1530.4 nm and 1600.8 nm, respectively. The RI sensitivities of the 2 transmission dips are -271.7 nm/RIU and -333.8 nm/RIU with the RI range of 1.33-1.42. The temperature characteristic is also experimentally analyzed and the temperature sensitivities of which are 0.121 nm/℃ and 0.171 nm/℃ in the range of 34℃-154℃. By solving the matrix equation, the proposed sensor can be applied for simultaneous measurement of RI and temperature.

Ultrasensitive Refractive Index Sensor Based on Mach–Zehnder Interferometer and a 40μm Fiber

An ultra-high sensitivity refractive index (RI) sensor, based on an in-line fiber Mach-Zehnder interferometer (MZI) and utilizing a special 40 μm fiber which has been specifically designed for the purpose, supporting only the LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> and LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> modes propagating in the fiber, has been proposed and numerically demonstrated in this work. The all-fiber MZI, based on LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> and LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode interference, was fabricated by utilizing a special design with two gradually tapered joints at both sides of this multi-clad thin diameter fiber (TDF). When the TDF diameters varied from 40 μm to 5 μm, a sudden change in the direction of the wavelength shift in the transmission spectrum of the TDF-MZI devices was observed both in liquid RI and air relative humidity (RH) monitoring experiments, as the surrounding RI or RH was seen to increase monotonically. Ultra-high sensitivity values of 5942.8nm/RIU (1.335-1.342) and 21292.2nm/RIU (1.4000-1.4025) were obtained in the experiments carried out, through the use of a tapered TDF-MZI device with TDF diameters of ~5 μm and ~9 μm, respectively. The maximum RH sensitivity of 1.084nm/%RH was obtained by the use of the TDF-MZI device with a TDF diameter of ~12 μm. A compact all-fiber TDF-MZI sensor was thus created with an overall sensing length of <; 4mm, showing the advantages of high sensitivity, low loss, and flexibility in the tunable monitoring direction of the wavelength shift. This design is well suited to various applications, where the high sensitivity RI and RH measurements are required at precise locations.

Research on NCF-PCF-NCF Structure Interference Characteristic for Temperature and Relative Humidity Measurement

A novel structure of photonic crystal fiber (PCF) Mach-Zehnder interferometer (MZI) for temperature and relative humidity measurement is proposed. The novel structure is composed of two sections of no core fiber (NCF) with a piece of PCF. The sensitivity of the proposed sensor is enhanced by adopting NCF coupling method. The results show that the sensitivities of temperature are 0.059 nm/°C, 0.074 nm/°C and 0.130 nm/°C in the range of 25 °C to 70 °C, and the sensitivities of relative humidity are 0.020 nm/%RH, 0.027 nm/%RH and 0.036 nm/%RH in the range of 30%RH to 70%RH. The sensor has the advantages of high stability, good linearity fit and simple structure, which indicates that the sensor has the potential of making an important contribution to the field of biology, chemistry, and medical.

Cascaded fiber MZIs for simultaneous measurement of pressure and temperature

A hybrid cascade structure composed of two Mach–Zehnder interferometers (MZI) is proposed and demonstrated to measure gas pressure and temperature, simultaneously. The key sensing components of the two MZIs are all based on a tapered single mode fiber (TSMF) spliced between two multimode optical fibers. The difference is that one of the TSMFs is covered with PDMS material, while the other one is exposed to air. Because of the large changes in the refractive index versus air pressure and the high thermo-optic coefficient of PDMS, the MZI covered with PDMS has a high sensitivity to gas pressure and temperature. While the MZI exposed to air has only high gas pressure sensitivity because the air is directly involved in the sensing as a signal of interferometer and the effective refractive index of air varies with the pressure. Experimental results show that the gas pressure and temperature sensitivities of the MZI filled with PDMS can be as high as 78.553 nm/MPa and 8.455 nm/°C, respectively, and another MZI can obtain −8.405 nm/MPa and 0.038 nm/°C, respectively. Therefore, the simultaneous measurement can be achieved by utilizing two MZIs with different gas pressure and temperature sensitivities.

Trace copper detection using in-line optical fiber Mach-Zehnder interferometer combined with an optoelectronic oscillator.

We experimentally demonstrate a novel optical fiber chemosensor for trace Cu2+ ions detection that is implemented by using an in-line optical fiber Mach-Zehnder interferometer (MZI) in conjunction with an optoelectronic oscillator (OEO). The MZI is fabricated by lateral offset splicing a section of D-shaped fiber between two single-mode fibers. It splices the broadband optical source into a sinusoidal-shaped light, which can form a single passband microwave photonic filter (MPF) by combining the Mach-Zehnder modulator, a segment of fiber and a photodetector. The center frequency of the MPF, determined by the free spectra range of MZI, is affected by the solution concentration. Incorporating the MPF in the OEO sensor, the oscillation frequency is determined by the solution concentration. Therefore, we can estimate the solution concentration by measuring the microwave frequency change. We carry out a proof to concept experiment. High sensitivity Cu2+ ions concentration sensing with sensitivity of 13 Hz/(μM/L) is achieved. The maximum measurement error of concentration obtained is within 1.38 μM/L. The proposed sensor has merits of high interrogation speed, simple operation, high sensitivity and accuracy, offering the potentials in a wide range of biological application scenarios.

High-sensitivity optical fiber temperature sensor of cascaded FSI and MZI based on Vernier effect

A high-sensitivity optical fiber temperature sensor based on the Vernier effect of cascaded fiber Sagnac interferometer (FSI) and Mach-Zehnder interferometer (MZI) is proposed and experimentally demonstrated. The FSI is composed of a 3 dB four-port coupler and a section of polarization maintaining fiber, which has high sensitivity and good stability as the sensing part. As the filtering part, MZI is made up of two three-port couplers by controlling the length of the two arms. The free spectral range (FSR) of these two interferometers is similar but not equal, so the cascade system can effectively amplify the temperature sensing sensitivity based on the vernier effect. The experimental results show that the temperature sensitivity of a single FSI is only −1.68 nm/°C, and the cascade system can amplify it to 14.30 nm/°C with a gain coefficient of 8.51, which is consistent with the theoretical results.

Application of the principal components analysis technique to optical fiber sensors for acetone detection

Generally, the data analysis of sensors based on spectral measurements, for instance, fiber Bragg gratings (FBG), long period fiber gratings (LPFG) is performed observing the shift or attenuation of a single wavelength. However, sometimes such spectrum variations are not evident or clearly perceptible; therefore, it becomes necessary to use other analysis techniques. One of them is principal components analysis (PCA) which allows to explore the behavior of the complete transmission spectrum pattern. In this work, we show the application of PCA to the response of fiber optical sensors for acetone detection. Two kinds of acetone sensors based upon single long period fiber gratings (LPFG) and Mach-Zehnder fiber interferometers (MZI), formed with a pair of cascaded LPFGs, coated with polydimethylsiloxane (PDMS) were developed. The sensor response was measured inside a Teflon chamber injecting a liquid acetone sample. The transmission spectrum variations at the devices output were measured with an optical spectrum analyzer, stored in a computer and analyzed by PCA. A comparison between the performance of both kinds of sensors was carried out and it was found that the sensitivity was increased up to 13 times (from 0.7 × 10−4 ppm−1 to 9.4 × 10−4 ppm−1) for the MZI sensors compared with that of single LPFG ones, which means, at best, a limit of detection (LOD) of 170 ppm.

Ultrasensitive measurement of gas refractive index based on cascaded Mach–Zehnder interferometers and Vernier effect

An ultrasensitive gas refractive index (RI) sensor based on fiber Mach–Zehnder interferometers (MZIs) and Vernier effect is proposed and demonstrated. The sensor consists of two cascaded fiber MZIs, one of which serves as a reference unit and is fabricated by fusion splicing a section of symmetrical side-hole fiber in between two short pieces of multi-mode fiber (MMF); the other acts as a sensing unit, which is composed of a section of tapered single-mode fiber sandwiched between two sections of MMF. The two MZIs are designed to have similar free spectral range for generating optical Vernier effect. Because the two MZIs have different responses to external RI, the RI-related Vernier effect can be obtained and the RI sensitivity can be improved, while there is no temperature sensitivity enhancement because the two MZIs have the same response to temperature. Thus the structure has low temperature crosstalk when obtaining high RI sensitivity. Experimental results show that the gas RI sensor has an ultrahigh sensitivity of 4.2 × 104 nm RIU−1 (RI unit). At the same time, the temperature cross-sensitivity is only 2.2 × 10−6 RIU °C−1. Therefore, the proposed sensor has potential applications for modern gas concentration monitoring in a large dynamic range.

Fiber Mach–Zehnder interferometers fabricated by nanosecond pulses and applications in refractive index sensing

A novel and simple microfabrication method for in-line micro-cavity based fiber Mach–Zehnder interferometers (FMZIs) is proposed and demonstrated by nanosecond (ns) pulsed fibers lasers for the first time. Instead of using high-end femtosecond laser for the fabrication process, only conventional ns-pulsed fiber lasers of modest optical powers are required in our approach. Such fabricated fiber MZ interferometer has exhibited a high sensitivity of −20048 nm/RIU (refractive index unit) for the index sensing application. The achieved index sensitivity is in good agreement with the theoretical estimation.

Efficient 2D Optical Beamforming Network With Sub Partitioning Capability Based on Raised Cosine Chirped Fiber Grating and Mach-Zehnder Delay Interferometer

In this paper, a two-dimensional true time delay optical beamforming network (OBFN) has been proposed with sub partitioning capability for 3X3 phased array antenna (PAA) with operating frequency in X-Band. The architecture is based on raised cosine apodised chirp fiber Bragg grating (CFBG) and Mach-Zehnder delay interferometer (MZDI). Compared to unapodised CFBG, raised cosine apodization drastically reduces the ripple as well as sidelobes and gives a flat response in the passband of reflection spectrum. Multiwavelength optical signals with a wavelength difference of 0.3 nm are used to steer 10 GHz RF signal in elevation and azimuth direction. Further, broad angular control of beam radiation due to sub partitioned PAA is also demonstrated. The RF signal beam is steered in elevation at -62.2,-31.9, and-10.8 degrees, and in azimuth at 123.6 and 55.9 degrees. Theoretical analysis of the OBFN has been presented and validated with the experimental results. At the best of our knowledge, delay characteristics of raised cosine apodised CFBG have been theoretically explored for the first time with mathematical formulation and a comparative discussion is given with the measured data.

Approaching quantum-limited phase tracking with a large photon flux in a fiber Mach–Zehnder interferometer

Approaching quantum-limited phase tracking with a large photon flux in a fiber Mach–Zehnder interferometer

Phase noise of the near-infrared single-mode fiber Mach–Zehnder interferometer and its stabilization technology

We present an estimation method and an investigation on the phase-noise stabilization for a near-infrared fiber Mach–Zehnder interferometer (MZI) using a laser diode at 1530 nm as the light source. Based on the theoretical analysis, the phase noise is mainly produced by the tiny fluctuations of external temperature, whose amplitude is proportional to the optical path difference (OPD) between two arms of optical fibers in the interferometer. By minimizing the length difference between two fibers in the MZI and specifying the compensation signal applied to the piezoelectric transducer (PZT) modulator actively, the interferometer worked stably at different phase differences. When the interferometer was working at the 90° phase difference, which is usually necessary for practical application, the RMS noise was minimized to 0.47°. By quantitative analysis, the magnification ratio of noise amplitude at room temperature per unit OPD of the MZI was 132.29°/m ( = 0.73 r a d / m ). In this experiment, a good linear correlation between the initial OPD and the phase signal intensity was successfully observed. Using this estimation method, an optical fiber interferometer of different wavelengths can be built more conveniently in practical engineering applications.

Determination of temperature and strain by a compact optical fiber Mach-Zehnder interferometer (MZI) composed of a single-mode fiber (SMF), seven core fiber (SCF), and multimode fiber (MMF) with a fiber Bragg grating (FBG)

A compact optical fiber Mach-Zehnder interferometer (MZI) sensor is reported for temperature and strain. The MZI sensor consists of a single-mode fiber (SMF), a seven core fiber (SCF) and a multimode fiber (MMF) with a fiber Bragg grating (FBG). The intensity distribution of the sensor is calculated by the beam propagation method. The light is coupled from the lead-in SMF into the SCF through the MMF. The highest transmission efficiency was obtained when the length of MMF is 2 mm with a diameter of 105 μm. The temperature sensitivity is up to 55.06 pm/°C from 130 °C to 250 °C, while the maximum extinction ratio was 27.4 dB. The measurements were divided into two intervals to address cross coupling to provide sensitive temperature and strain measurements.

In-Fiber Mach–Zehnder Interferometer Sensor Based on Er Doped Fiber Peanut Structure in Fiber Ring Laser

A novel temperature sensor based on rare earth fiber peanut (REFP) shape structure in fiber ring laser (FRL) is proposed and demonstrated. A single-mode rare earth doped fiber is used to fabricate a peanut structure to produce Mach-Zehnder interferometer (MZI). Benefited from the strong thermo-optic effect of rare earth ions in fiber, high sensitivity measurement of temperature is exploited to realize. More importantly, there is no need for additional filters compared to traditional fiber laser sensors. The sensitivity of refractive index (RI) was measured to further verify the sensing performance of MZI. The experimental results show that compared with the external sensing unit, the Er-doped fiber peanut (EDFP) structure has higher thermo-optic effect coefficient and superior temperature sensitivity. The temperature and RI sensitivity of the EDFP is 0.158 nm/°C and -19.55 nm/RIU, respectively. The optical fiber MZI sensor based on the EDFP has the advantages of high sensitivity, good repeatability, simple fabrication, and compact structure. It has good application prospects in biomedicine, aerospace, and marine development.

Effect of hygroscopic polymer-coatings on the performance of relative humidity sensor based on macro-bend single-mode fiber

In this paper, we present an investigation on the sensing performance of a relative humidity (RH) sensor based on macro-bending structure-induced fiber Mach-Zehnder interferometer (MZI). The macro-bending structure was formed by bending a section of single-mode fiber (SMF) into a droplet-shape without any splicing. By properly adjusting the bending diameter of the droplet-shaped fiber section, interference has been achieved between the whispering gallery mode (WGM) and the core mode. Four sensing probes based ondifferent SMFs were fabricated and compared to investigate the effect of polymer coatings on the sensing properties towards RH variation ranges from 35% to 95%; namely, probe A composed of a bare SMF with its original protective polymer coating, probe B based on polymer jacket stripped SMF, probe C based on polyethylene oxide (PEO)-coated SMF, and probe D based on polyvinyl‐alcohol (PVA)-coatedSMF. The sensitivity increased after the deposition of PEO and PVA coating on the macro-bending structures. Through a comparative investigation, experimental results revealed that sensor D performed better than other probes and possessed an improved sensitivity of −0.6 nm/RH% and an ultrafast response time of 1.33 ms. To the best of our knowledge, this is the first time that two main roles of the original polymer jacket of the SMF and the deposited polymer coatings on the SMF have been investigated in fabricating and optimizing the RH sensing performance of a droplet-like interferometer.

基于氧化石墨烯涂层的侧抛光纤马赫-曾德尔干涉仪温湿度传感器

基于氧化石墨烯涂层的侧抛光纤马赫-曾德尔干涉仪温湿度传感器

A CONCATENATED UP AND DOWN TAPERED FIBER FOR SIMULTANEOUS MEASUREMENT OF STRAIN AND TEMPERATURE

A novel fiber optical sensor based on in-line fiber Mach-Zehnder interferometer for simultaneous measurement of strain and temperature is proposed and demonstrated experimentally. The interferometer is simple, extremely robust and highly sensitive and consists of two concatenated parts; one is a down-tapered fiber (DTF) and the other is an up-tapered fiber (UTF). UTF and DTF sections of the sensor are fabricated by using a commercial fiber splicer and a non-commercial setup based on heating and stretching a portion of a standard single-mode fiber, respectively. While UTF section behaves as a beam splitter to decompose the injected light into core and cladding modes, DTF section provides evanescent field to access the surrounding environment. Experimental results indicate that the resolutions of 0.83 °C and 45.80 micro-epsilon were achieved in temperature and strain, respectively, for simultaneous measurement with a 10 pm of wavelength resolution.

Multiple interference components in a fiber Mach–Zehnder interferometer sensor and their influence on wavelength shift tracing

In this paper, multiple interference components in a fiber Mach–Zehnder interferometer sensor and their influence on wavelength shift tracing were studied, based on which a frequency filtering method followed by inverse Fourier transform was proposed to improve the sensor’s response accuracy. Firstly, multiple interference components in the transmission spectrum of a fiber MMF-SMF-MMF structure were simulated, and environmental response discrepancy in different components was calculated. Then, Fourier transform was performed on the transmission spectrum followed by frequency filtering to pick out the dominant interference component. An inverse Fourier transform was then carried out to obtain the wavelength shift which was undisturbed by minor interference components. The method was demonstrated by temperature and ambient refractive index (RI) calibration experiments as well as verification tests. The deviation between temperature sensitivity obtained with and without frequency filtering was 39%. The verification test at 80 °C was carried out and the measurement error was three times lower due to frequency filtering. For RI sensing, the deviation between sensitivity obtained with and without filtering was 19%. Measurement errors at 1.3706 of RI were seven times decreased after frequency filtering. Due to its simplicity and efficiency, the proposed method is believed to have extensive application prospects in sensing fields, especially when high-precision temperature and RI sensing are desired.

Optical fiber curvature sensor based on polydimethylsiloxane encapsulated Mach–Zehnder interferometer

An all-optical fiber curvature sensor is proposed, which is composed of a polydimethylsiloxane elastic material encapsulated all-optical fiber Mach–Zehnder interferometer, and its bending characteristics are demonstrated. Our experimental results show that the output spectrum of the sensor is sensitive to the curvature of the bend angle with a result of interferent dip wavelength drift with it. The curvature sensitivity of the sensor presents 205.36 nm/cm − 1 with 98.27% linearity in the curvature range from 0.03 to 0.08 cm − 1. The temperature sensitivity is 0.1235 nm / ° C in 35°C to 105°C range. This sensor structure also has the advantages of small size, low cost, and easy fabrication, which means it has potential applications in robots, artificial intelligence, aerospace, and so on.