Showing papers on "Mach–Zehnder interferometer published in 2020"

Conventional/phase Shift Dual Drive Mach-Zehnder Modulation Measured Type Based Radio Over Fiber Systems

Abstract: This work clarified the conventional/phase shift dual Mach–Zehnder modulation measured technique for upgrading radio over fiber (ROF) systems. Four levels of pulse amplitude modulation and non-return to zero code scheme are employed in different previous studies for upgrading ROF systems. The possible transmission distance is extended to 150 km and a bit rate of 40 Gb/s for achieved acceptable max. Q factor of 13.7498 and minimum bit error rates of 1.82×10–43. The total optical received power is measured at fiber cable length for maximum distance. Also, in the same way, the signal power levels are measured after fiber optic cable and avalanche photo detector optical receiver. The proposed model has presented the enhancement percentage ratio of 13.654% over the previous models in signal quality enhancement.

Mid Infrared Optical Gas Sensor Using Plasmonic Mach-Zehnder Interferometer.

Abstract: In this work, we propose an optimized design for on-chip gas sensor using metal-insulator (MI) plasmonic waveguide in the mid infrared range and utilizing a Mach-Zehnder Inetrferometer (MZI). The MI waveguide utilizes a high index dielectric layer on top of the metal to enhance the sensitivity of the sensor. The thickness and the refractive index of this layer are optimized to achieve high sensitivity. Using this layer, a design that exhibits high performance for both wavelength and intensity interrogation schemes is achieved. In addition, another one that furtherly enhances the sensor performance for intensity interrogation is also proposed. This design also minimizes the sensor sensitivity to wavelength variations. Intensity interrogation scheme has the advantage of eliminating the size and cost needed by wide wavelength band measurements including either spectrometer or tunable laser in wavelength interrogation. The first design sensitivity has reached 10000 nm/RIU with wavelength interrogation figure of merit (FOMλ) of 133RIU-1 and intensity interrogation FOMI of 239RIU-1. While the second one exhibit FOMI of 363RIU-1, both with length of 250 µm around 4.6 µm wavelength. Finally, these structures are cheap, compact, and easy to fabricate.

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

Abstract: 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.

Humidity sensor based on a graphene oxide-coated few-mode fiber Mach-Zehnder interferometer.

Abstract: A relative humidity sensor based on a graphene oxide-coated few-mode fiber Mach-Zehnder interferometer (MZI) is proposed in this paper. The MZI was made by splicing a segment of the few-mode fiber (FMF) between two segments of a no-core fiber (NCF) and two segments of a single mode fiber (SMF) located outside the two NCFs. The core and cladding of the FMF acted as interferometric arms, while the NCFs acted as couplers for splitting and recombining light due to mismatch of mode field diameter. The cladding of the FMF was corroded with hydrofluoric acid, and a layer of graphene oxide (GO) film was coated on the corroded cladding of FMF via the natural deposition method. The refractive index of GO varied upon absorption the water molecules. As a result, the phase difference of the MZI varied and the wavelength of the resonant dip shifted with a change in the ambient relative humidity (RH). High humidity sensitivity of 0.191 and 0.061 nm/%RH in the RH range of 30-55% and 55-95%, respectively, were achieved experimentally. The high sensitivity, compact size, and simple manufacturing of the proposed sensor could offer attractive applications in fields of chemical sensors and biochemical detection.

Temperature-Independent Curvature Sensor Based on In-Fiber Mach–Zehnder Interferometer Using Hollow-Core Fiber

Abstract: An in-fiber Mach–Zehnder Interferometer (MZI), based on hollow core fiber (HCF), for measuring curvature is fabricated and experimentally demonstrated. The sensing part was fabricated by splicing a section of HCF between two sections of multimode fiber (MMF), and different HCF lengths were investigated in order to achieve the highest curvature sensitivity. These devices were tested in a transmission configuration using lead-in and lead-out single mode fibers (SMF). The sensor was attached to a steel sheet by using the polymer Polydimethylsiloxane (PDMS) for accurate control of the applied curvature. The modal analysis was carried out using a commercial software based on finite element method (FEM) and by incorporating some of the experimental data, it was feasible to determine the two dominant modes that interfere in this sensor. The devices were characterized by measuring the fringe contrast variations due to the curvature changes. The interferometer fabricated with a HCF 2.5 mm in length HCF showed the highest curvature sensitivity, −17.28 ± 2.30 dB/m−1, in a range from 1.84 m−1 to 2.94 m−1. Moreover, the sensor that exhibited a better performance was fabricated with a HCF length of 1 mm, combining the most extensive curvature range (from 0.95 m−1 to 2.68 m−1) and an adequate sensitivity (−11.80 ±1.30 dB/m−1). The analysis of the interferometric signal of this device in Fourier domain, allows us to establish a one to one relationship between the contrast and the curvature in a broader range (from 0 m−1 to 2.94 m−1). Moreover, the fringe contrast showed a very low dependency on temperature (from 30 °C to 90 °C), depicting that this device was not affected by temperate fluctuation.

Folded-tapered multimode-no-core fiber sensor for simultaneous measurement of refractive index and temperature

Abstract: In this paper, a refractive index (RI) and temperature sensor based on a folded-tapered multimode-no-core (FTMN) fiber structure is proposed and experimentally demonstrated. The FTMN has an additional Mach-Zehnder interferometer (MZI), which is introduced in the folded-tapered multimode (FTM) fiber. And with the inherent multimode interference (MMI) and the previously mentioned MZI as foundation, a composite interference is successfully established. This synthetic composite interference greatly improves the performance of traditional optical fiber RI sensing in the low RI range. The experimental results demonstrate that a maximum sensitivity of 1191.5 nm/RIU within a linear RI ranging from 1.3405 to 1.3497 can be achieved, which is greater than the traditional modal interferometer structure. Furthermore, the temperature sensitivities at interference dips A and B are 0.0648 nm/°C and 0.0598 nm/°C, respectively. By monitoring the wavelength shifts of interference dips A and B, the sensor can simultaneously measure RI and temperature to overcome the temperature induced cross-sensitivity.

Proposal for an ultra-broadband polarization beam splitter using an anisotropy-engineered Mach-Zehnder interferometer on the x-cut lithium-niobate-on-insulator

Abstract: We propose and theoretically demonstrate an integrated polarization beam splitter on the x-cut lithium-niobate-on-insulator (LNOI) platform. The device is based on a Mach-Zehnder interferometer with an anisotropy-engineered multi-section phase shifter. The phase shift can be simultaneously controlled for the TE and TM polarizations by engineering the length and direction of the anisotropic LNOI waveguide. For TE polarization, the phase shift is −π/2, while for TM polarization, the phase shift is π/2. Thus, the incident TE and TM modes can be coupled into different output ports. The simulation results show an ultra-high polarization extinction ratio of ∼47.7 dB, a low excess loss of ∼0.9 dB and an ultra-broad working bandwidth of ∼200 nm. To the best of our knowledge, the proposed structure is the first integrated polarization beam splitter on the x-cut LNOI platform.

High-Performance Ultrafast Humidity Sensor Based on Microknot Resonator-Assisted Mach-Zehnder for Monitoring Human Breath.

Abstract: Monitoring the dynamic humidity requires sensors with fast response and anti-electromagnetic interference, especially for human respiration. Here, an ultrafast fiber-optic breath sensor based on the humidity-sensitive characteristics of gelatin film is proposed and experimentally demonstrated. The sensor consists of a microknot resonator superimposed on a Mach-Zehnder (MZ) interferometer produced by a tapered single-mode fiber, which has an ultrafast response (84 ms) and recovery time (29 ms) and a large dynamic transmission range. The humidity in dynamic ambient causes changes in the refractive index of gelatin coating, which could trigger spectral intensity transients that can be explicitly distinguished between the two states. The sensing principle is analyzed using the traditional transfer-matrix analysis method. The influence of coating thickness on the sensor's trigger threshold is further investigated. Experiments on monitoring breath patterns indicate that the proposed breath sensor has high repeatability, reliability, and validity, which enable many other potential applications such as food processing, health monitoring, and other biomedical applications.

Switchable and tunable multi-wavelength fiber laser based on a core-offset aluminum coated Mach-Zehnder interferometer

Abstract: In this work, a switchable and tunable multi-wavelength erbium-doped fiber laser based on a core-offset aluminum coated Mach-Zehnder interferometer (ACMZI) is presented. The ACMZI is fabricated by core-offset fusion splicing a single-mode fiber segment between two lengths of single mode fiber and then by coating it with aluminum using the thermal evaporation technique. The ACMZI is used as a wavelength selective filter in the proposed ring cavity design. Experimental results show that the laser emission can be switched among a single, double, and triple emission lines by carefully adjusting a polarization controller. Furthermore, the laser lines can be tuned by changing the temperature of the ACMZI. The laser can emit in a single-longitudinal mode and has a single-mode suppression ratio of about 55 dB, a linewidth of 0.05 nm and an efficiency slope of 0.29%. Finally, the laser arrangement is compact, robust, and requires a relatively simple fabrication procedure.

Bias-drift-free Mach–Zehnder modulators based on a heterogeneous silicon and lithium niobate platform

Abstract: Optical modulators have been and will continue to be essential devices for energy- and cost-efficient optical communication networks. Heterogeneous silicon and lithium niobate modulators have demonstrated promising performances of low optical loss, low drive voltage, and large modulation bandwidth. However, DC bias drift is a major drawback of optical modulators using lithium niobate as the active electro-optic material. Here, we demonstrate high-speed and bias-drift-free Mach–Zehnder modulators based on the heterogeneous silicon and lithium niobate platform. The devices combine stable thermo-optic DC biases in silicon and ultra-fast electro-optic modulation in lithium niobate, and exhibit a low insertion loss of 1.8 dB, a low half-wave voltage of 3 V, an electro-optic modulation bandwidth of at least 70 GHz, and modulation data rates up to 128 Gb/s.

Multimode Interference of Bloch Surface Electromagnetic Waves

Abstract: Integrated photonics aims at on-chip controlling light in the micro- and nanoscale ranges utilizing the waveguide circuits, which include such basic elements as splitters, multiplexers, and phase s...

Large measurement range and high sensitivity temperature sensor with FBG cascaded Mach-Zehnder interferometer

Abstract: A high sensitivity and wide measurement range temperature sensor with Mach-Zehnder interferometer (MZI) and fiber Bragg grating (FBG) cascaded is proposed and experimentally implemented. The proposed MZI is fabricated by inserting a section of single mode fiber between two sections of single mode fibers with 62 μm core-offset, where the length of the inserted fiber is 300 μm. Polydimethylsiloxane (PDMS), as a kind of thermo-sensitive material, is covered on core-offset region. Meanwhile, FBG is adopted to enlarge the measurement range. Temperature experiment results turn out to be fruitful for improving the performance of sensitivity and measurement range, and the sensitivity of proposed sensor is up to 10.389 nm/°C from 10 °C to 59.4 °C with good linearity. Moreover, the exhaustively comparison with other optical fiber interferometers reveals that the proposed sensor is simple making, miniature size, good reproducibility, high sensitivity and large measurement range, which has tempting commercial prospect.

A Design of Taper-Like Etched Multicore Fiber Refractive Index-Insensitive a Temperature Highly Sensitive Mach-Zehnder Interferometer

Abstract: We propose and demonstrate Mach-Zehnder interferometer (MZI), which is the refractive index (RI) insensitive and temperature highly sensitive based on etched multi-core fiber (MCF) structure. The MCF and Fiber Bragg Grating (FBG) are used as hybrid sensing elements. The fabrication of the interferometer is provided a new taper-like structure by etching the MCF to further expose the side cores to the surroundings. The interferometer has produced a sensitivity of 103.2pm/°C within the ambient temperature up-to 70°C. Moreover, the superior temperature sensitivity is 89.19pm/°C, 66.64pm/°C, 56.42pm/°C in the range of 24°C to 130°C, and RI-insensitive in the range of 1.34 to 1.38, for different waists of etched seven-core fiber interferometers (E7CFIs) $\sim ~84.70\mu \text{m}$ , $93.10\mu \text{m}$ , $108.67\mu \text{m}$ , respectively. Compared with the conventional FBGs, the sensitivity of the interferometer is significantly improved by 8 times. E7CFI’s novel and advantageous features can easily be distinguished other devices. Besides, the proposed sensing architecture is compact, easy to fabricate, highly sensitive, easy to reproduce, and makes it an inexpensive fiber optic device.

Adapting Mach–Zehnder Mesh Equalizers in Direct-Detection Mode-Division-Multiplexed Links

Abstract: A Mach–Zehnder mesh (MZM), which is comprised of a network of tunable $2\times 2$ Mach–Zehnder interferometers and embedded photodetectors (PDs), can be used to perform arbitrary unitary matrix multiplications in the optical domain and compensate modal crosstalk in short-reach mode-division-multiplexed (MDM) links that use direct detection (DD). MZMs can be adapted using a self-configuration method, proposed by Miller, where multiple low-speed and low-power code sequences are superimposed on parallel high-speed information streams. We show that self-configuration in its original form is a sub-optimal equalization method for high-speed data transmission because adaptation based on detected code strengths is adversely impacted by low measurement signal-to-noise ratios and interference from the high-speed information streams. These impairments prevent the method from accurately tracking the millisecond-timescale modal dynamics of short-reach DD-MDM channels. We propose small modifications to the self-configuration method that can enable the MZM to track up to $10^8$ -fold faster channel dynamics. In particular, we show that replacing continuous equalization of low-power code sequences by periodic equalization of full-power training signals and using special optimization methods can yield faster MZM tuning. We also discuss the tradeoffs between MZM architectures that embed PDs inside the mesh and those that have PDs at the output ports only. Our results indicate that optimally designed MZMs and their associated control methods can increase the information capacity of short-reach multimode optical fiber links.

Mach-Zehnder silicon photonic modulator assisted by phase-shifted Bragg gratings

Abstract: We experimentally demonstrate a silicon photonic Mach-Zehnder modulator (MZM) assisted by phase-shifted Bragg gratings. Coupled resonators are inserted in the Bragg grating structure to significantly enhance the phase modulation efficiency, while maintaining a wide optical bandwidth compared to other resonator-based modulators. Fabricated using a CMOS-compatible foundry process, the device achieved a small-signal V π × L of 0.18 V.cm, which is seven times lower than a conventional silicon MZM fabricated with the same process. The device has a compact footprint, with a length of only 162 μm, and shows a modulation bandwidth of 28 GHz at a reverse bias of 1 V. Non-return-to-zero modulation is demonstrated at 30 Gb/s with a bit-error-rate (BER) below the 7%-overhead forward error correction (FEC) threshold over a bandwidth of 3.5 nm. This bandwidth should translate into an operating temperature range greater than 40 °C.

Design Rule of Mach-Zehnder Interferometer Sensors for Ultra-High Sensitivity.

Abstract: A design rule for a Mach-Zehnder interferometer (MZI) sensor is presented, allowing tunable sensitivity by appropriately choosing the MZI arm lengths according to the formula given in this paper. The present MZI sensor designed by this method can achieve an ultra-high sensitivity, which is much higher than any other traditional MZI sensors. An example is given with silicon-on-insulator (SOI) nanowires and the device sensitivity is as high as 106 nm/refractive-index -unit (or even higher), by choosing the MZI arms appropriately. This makes it possible for one to realize a low-cost optical sensing system with a detection limit as high as 10-6 refractive-index-unit, even when a cheap optical spectrum analyzer with low-resolution (e.g., 1 nm) is used for the wavelength-shift measurement.

Optical fiber temperature sensor based on a Mach-Zehnder interferometer with single-mode-thin-core-single-mode fiber structure.

Abstract: A Mach-Zehnder interferometer for measurement of temperature is proposed and experimentally demonstrated, which consists of two sections of single mode fiber (SMF) and a section of thin core fiber spliced between the two SMFs. The two welding areas are heated and stretched to improve the split and recombination of light. The wavelength of the resonant dip will shift when temperature varies due to the thermo-optic and thermal expansion effect. The experimental results show that a temperature sensitivity of 65 pm/°C with a linear correlation coefficient of 0.996 can be achieved in a temperature range from 25 °C to 80 °C. Due to its ease of manufacture, low cost, and high sensitivity, the fiber optic temperature sensor is suitable for temperature measurement applications.

GHz-clocked teleportation of time-bin qubits with a telecom C-band quantum dot

Abstract: Teleportation is a fundamental concept of quantum mechanics with an important application in extending the range of quantum communication channels via quantum relay nodes. To be compatible with real-world technology such as secure quantum key distribution over fibre networks, such a relay node must operate at GHz clock rates and accept time-bin encoded qubits in the low-loss telecom band around 1550 nm. Here, we show that InAs/InP droplet epitaxy quantum dots with their sub-Poissonian emission near 1550 nm are ideally suited for the realisation of this technology. To create the necessary on-demand photon emission at GHz clock rates, we develop a flexible pulsed optical excitation scheme, and demonstrate that the fast driving conditions are compatible with a low multiphoton emission rate. We show further that, even under these driving conditions, photon pairs obtained from the biexciton cascade show an entanglement fidelity close to 90\%, comparable to the value obtained under cw excitation. Using asymetric Mach Zehnder interferometers and our photon source, we finally construct a time-bin qubit quantum relay able to receive and send time-bin encoded photons, and demonstrate mean teleportation fidelities of $0.82\pm0.01$, exceeding the classical limit by nearly 10 standard deviations.

Investigation of a Side-Polished Fiber MZI and Its Sensing Performance

Abstract: A novel all-fiber Mach–Zehnder interferometer (MZI), which consists of lateral core fusion splicing of a short section of side-polished single mode fiber (SMF) between two SMFs was proposed and demonstrated. A simple fiber side-polished platform was built to control the side polished depth through a microscope. The sensitivity of the fiber MZI structure to the surrounding refractive index (RI) can be greatly improved with the increase of the side-polished depth, but has no effect on the temperature sensitivity. The sensor with a polished depth of $44.2~\mu \text{m}$ measured RI sensitivity up to −118.0 nm /RIU (RI unit) in the RI range from 1.333 to 1.387, which agrees well with simulation results by using the beam propagation method (BPM). In addition, the fiber MZI structure also can achieve simultaneous measurement of both RI and temperature. These results show its potential for use in-line fiber type sensing application.

Simultaneous Curvature and Temperature Sensing Based on a Novel Mach-Zehnder Interferometer

Abstract: A novel fiber inline Mach-Zehnder interferometer (MZI) is proposed for simultaneous measurement of curvature and temperature. The sensor composes of single mode-multimode-dispersion compensation-multimode-single mode fiber (MMF-DCF-MMF) structure, using the direct fusion technology. The experimental results show curvature sensitivities of −12.82 nm/m−1 and −14.42 nm/m−1 in the range of 0–0.65 m−1 for two resonant dips, as well as temperature sensitivities of 57.6 pm/°C and 74.3 pm/°C within the range of 20 °C–150 °C. In addition, the sensor has unique advantages of easy fabrication, low cost, high fringe visibility of 24dB, and high sensitivity, which shows a good application prospect in dual-parameters of sensing of curvature and temperature.

Hollow-Core Photonic Crystal Fiber Mach–Zehnder Interferometer for Gas Sensing

Abstract: A novel and compact interferometric refractive index (RI) point sensor is developed using hollow-core photonic crystal fiber (HC-PCF) and experimentally demonstrated for high sensitivity detection and measurement of pure gases. To construct the device, the sensing element fiber (HC-PCF) was placed between two single-mode fibers with airgaps at each side. Great measurement repeatability was shown in the cyclic test for the detection of various gases. The RI sensitivity of 4629 nm/RIU was demonstrated in the RI range of 1.0000347–1.000436 for the sensor with an HC-PCF length of 3.3 mm. The sensitivity of the proposed Mach–Zehnder interferometer (MZI) sensor increases when the length of the sensing element decreases. It is shown that response and recovery times of the proposed sensor inversely change with the length of HC-PCF. Besides, spatial frequency analysis for a wide range of air-gaps revealed information on the number and power distribution of modes. It is shown that the power is mainly carried by two dominant modes in the proposed structure. The proposed sensors have the potential to improve current technology’s ability to detect and quantify pure gases.

A Novel Optical Fiber Mach–Zehnder Interferometer Based on the Calcium Alginate Hydrogel Film for Humidity Sensing

Abstract: A novel optical fiber humidity sensor based on a Mach–Zehnder Interferometer (MZI) is proposed and experimentally demonstrated. The MZI is fabricated by three sections of single mode fiber (SMF) and two sections of multimode fiber (MMF), where the two MMFs are spliced among the three SMFs. To obtain an excellent sensor, two sections of MMF are etched with hydrofluoric acid, then sodium alginate is coated on the corroded areas and immersed in calcium chloride solution to form calcium alginate (CaAlg) hydrogel by fully crosslinking sodium alginate with calcium ions. While humidity is between 15%~80%, the sensitivity of the sensor can reach 0.48346 dB/%RH. In addition, the proposed sensor shows good performances in the repeatability, stability, response and recovery time, which can be potentially used in the medical storage field.

Distributed fiber-optic sensor for location based on polarization-stabilized dual-Mach-Zehnder interferometer.

Abstract: A novel distributed fiber-optic sensor is proposed and demonstrated, in which two Mach-Zehnder interferometers are used to detect the interference signals with different wavelengths, and one 3 × 3 coupler is deployed to demodulate the time-varying phase change caused by vibration. The novel dual Mach-Zehnder interferometer (DMZI) is composed of two wavelength division multiplexers. Then, a time delay estimation algorithm is designed to construct two related signals using the phase difference, and the two constructed signals are used to obtain vibration position through cross-correlation. Experimental results show that the sensing distance can reach 100 km and the location error is within ±25 m.