Mach-Zehnder Interferometer Structure Research Articles

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

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.

Mode insensitive switch for on-chip interconnect mode division multiplexing systems.

A mode insensitive switch is proposed and experimentally demonstrated on a silicon-on-insulator platform using a balanced Mach-Zehnder interferometer structure with a mode insensitive phase shifter for on-chip mode division multiplexing interconnects. Switching the first three quasi-transverse electric (TE) modes, consuming less than 40 mW power is demonstrated. The whole system exhibits approximately $ - {2},\;{ - 3.7}$-2,-3.7, and $ - {5.2}\;{\rm dB}$-5.2dB insertion loss for the TE0, TE1, and TE2 modes at 1550 nm, respectively. The corresponding crosstalk is less than $ - {8.6}\;({\rm - 9}), {- 8} ({ - 10.3})$-8.6(-9),-8(-10.3), and $ - {10}\;{\rm dB}$-10dB ($ - {10.3}\;{\rm dB}$-10.3dB) within the wavelength range of 40 nm (1535-1575 nm) for the cross (bar) states, respectively. The extinction ratios (ERs) for the cross (bar) states are 20.1 (19.5), 22.8 (33.7), and 15.4 dB (18.1 dB) for the TE0, TE1, and TE2 modes at 1550 nm, respectively. The payload transmission is also conducted using non-return-to-zero pseudorandom binary sequence (PRBS)-31 data signals at 10 Gb/s for single-mode transmission and simultaneous three-mode transmissions. For all the scenarios, open eyes are observed.

High-temperature sensor based on a special thin-diameter fiber

We proposed and experimentally demonstrated a novel compact high temperature sensor, based on a special thin-diameter fiber (TDF) sandwiched between two segments multimode fibers (MMFs). The TDF is specially designed with 20μm cladding radius and 3.5μm core radius, which is pliable to fabricate a robust all fiber high temperature Mach–Zehnder interferometer (MZI). The clear interference spectrums of TDF-MZI structures with TDF length at 5 mm, 10 mm and 27 mm, are obtained in our experiments and analyzed in spatial frequency domain. The transmission characteristics of the light propagating in the TDF based MZI structure, with the MMFs connected or not, are researched and compared in experiments and theoretical simulations. A theoretical comparative study on the fiber thermal expansion between 40μm fiber and 125μm fiber is given, under the temperatures varying from 100 °C to 1000 °C, and the simulation results show that the TDF-MZI suffers a relatively larger thermal stress than that of the normal diameter fiber (typically 125μm). Experimental results also demonstrated that the TDF-MZI has a relatively high temperature sensitivity of 0.088 nm/°C, 0.150 nm/°C and 0.285 nm/°C, in the range of 100–650 °C, 650–850 °C and 900–1000 °C, respectively. The TDF-MZI device is straightforwardly fabricated by only fiber fusion splicing, which make it simple, reproducible and low cost, and have potential for practical applications in various industrial processes

Compact and broadband 2 × 2 optical switch based on hybrid plasmonic waveguides and curved directional couplers

In this paper, a compact, broadband, and CMOS compatible ${2} \times {2}$2×2 optical switch based on hybrid plasmonic waveguides (HPWs) and curved directional coupler is presented. The proposed coupler consists of a combination of straight and curved hybrid plasmonic waveguides. By using the ability of HPWs for confining the light wave in a sub-wavelength scale and the curved structure to decrease the wavelength dependence of the directional coupler, a 3 dB power splitter with a ${3}\,\,\textrm{dB} \pm 0.5$3dB±0.5 bandwidth of about 410 nm and a footprint of ${7.6}\,\,\unicode{x00B5}\textrm{m} \times {2}\,\,\unicode{x00B5}\textrm{m}$7.6µm×2µm is achieved. By exploiting this optimal power splitter in a Mach-Zehnder interferometer structure, a ${2} \times {2}$2×2 electro-optic switch with a broad bandwidth of 400 nm and a small footprint of ${33}\,\,\unicode{x00B5}\textrm{m} \times {2.5}\,\,\unicode{x00B5}\textrm{m}$33µm×2.5µm is realized, which denotes the widest bandwidth compared to the previously reported similar structures. The three-dimensional finite-difference time-domain simulation results show a switching speed of 0.15 THz for the proposed optical switch, while the extinction ratio, power consumption, and insertion loss are 20 dB, 95.2 fJ/bit, and 4 dB, respectively, at the central wavelength of 1550 nm.

RETRACTED: Apprehension of parity generator through array of Mach–Zehnder modulation process

Abstract Optical communication relies on electro optic effect for switching and modulation processes for various purposes. In order to achieve this, Mach-Zehnder interferometer (MZI) structure is utilized to achieve influential optical switching based on the function of electro-optic effect. This function is widely investigated in this paper and the same is implemented in a parity generator/checker for obtaining electro-optic effect by using MZI structure. Simulation is devised in a computer by applying a Titanium (Ti) in-diffused lithium niobate profile of MZI. Basic 2 × 2 switch is transformed as MZI for the design of parity device over a functional wavelength range of 1.3 µm to 1.65 µm. This simulated design is analyzed with different Ti LiNbO3 stripe thicknesses, in order to attain the optimum Ti-LiNbO3 stripe thickness and also to improve the performance of the switch on its cross talk, power imbalance, extinction ratio and transition losses. Opti BPM and Optisystem software is the tool used to design, implement and investigate the outputs obtained. The result set has proved to be efficient than all previous standards.

Recent advances in key elements of spin-wave logic gates

Traditional charge-based device development is approaching the limit of Moores law, thus, there is a desperate need for new information processing principles or architectures. Replacing traditional charge-based devices with non-charge-based devices for information processing shows promise. Spin waves, which are generated from the collective precession of electron spins, are thought to be an important information carrier for the transmission and processing of information in a beyond-Moore era. Spin-wave logic gates possess incomparable advantages over traditional logic devices in energy consumption, device scale, application frequency, and logical operation, among other factors. This article explains the operating principles of spin-wave logic gates based on a Mach-Zehnder interferometer structure, and then analyzes the realization theory of key spin-wave logic gate elements at a device level. Recent advances in these key elements are also reviewed systematically. Lastly, future prospects of spin-wave logic gates are discussed.

On-Chip Electro-Optic Modulator With Loss Compensation Based on Polymeric Active-Integrated Waveguides

In this paper, an on-chip electro-optic (EO) modulator with loss compensation based on polymeric active-integrated waveguides was demonstrated. An erbium-doped waveguide amplifier was investigated and integrated with the EO modulator to compensate for signal loss. Polymeric active-integrated waveguides were based on the Mach-Zehnder interferometer structure, which consists of an amplified waveguide formed by two symmetric Y-junction branches and an EO waveguide formed by two decoupled waveguide arms. The dimensions of the polymeric active-integrated waveguides and the modulator were carefully designed and simulated. Moreover, a six-level spectroscopic model pumped at 980 nm was presented. The rate equations and propagation equations were solved, and the gain characteristics were simulated. The internal gain of 4.65 dB was achieved when the signal power was 0.1 mW at 1550 nm, the pump power was 100 mW at 980 nm, the Er 3+ concentration was $9.3\times 10^{25}/\text{m}^{3}$ , and the Yb 3+ concentration was $8.6\times 10^{26}/\text{m}^{3}$ in one Y-junction branch with a length of 1.5 cm. With the integrated waveguide amplifier, the loss of the EO modulator can be compensated at 9.3 dB in the two symmetric Y-junction branches. The light output intensity was also statistically presented. The proposed device with active-integrated waveguides could be used in polymer-based photonics integrated circuits.

All-optical devices based on two-dimensional materials

The leap in communication technology in recent years has brought new challenges to the compactness, modulation speed, working bandwidth and control efficiency of modulation equipment. The discovery of graphene has led the two-dimensional materials to develop rapidly, and a series of new materials have continuously emerged, such as MXene, black phosphorus, transition metal sulfides, etc. These new two-dimensional materials have excellent nonlinear optical effects, strong light-matter interaction, and ultra-wide working bandwidth. Using their thermo-optic effect, nonlinear effect and the combination with optical structure, the needs of ultra-fast modulation in optical communication can be met. Compact, ultra-fast, and ultra-wide will become the tags for all-optical modulation of two-dimensional materials in the future. This article focuses on all-optical devices based on thermo-optical effects and non-linear effects of two-dimensional materials, and introduces fiber-type Mach-Zehnder interferometer structures, Michelson interferometer structures, polarization interferometer structures, and micro-ring structures. In this paper, the development status of all-optical devices is discussed from the perspectives of response time, loss, driving energy, extinction ratio, and modulation depth. Finally, we review the latest developments, analyze the challenges and opportunities faced by all-optical devices, and propose that all-optical devices should be developed in the direction of ring resonators and finding better new two-dimensional materials. We believe that all-optical devices will maintain high-speed development, acting as a cornerstone to promote the progress of all-optical systems.

High resolution measurement of refractive index with resistance to temperature crosstalk through an all fiber MZI-PMF structure

A simple cascaded structure composed of all-fiber Mach-Zehnder interferometer (MZI) and polarization-maintaining fiber (PMF) is proposed and experimentally demonstrated for simultaneous refractive index (RI) and temperature measurement. By splicing a section of thin no-core fiber (TNCF) between two conventional no-core fibers (NCFs) with large lateral offset, a part of the light in the MZI structure can interact directly with the external environment to obtain a high RI sensitivity. A Panda-type PMF is cascaded with the MZI to eliminate temperature crosstalk in the RI measurement. The experimental results show that the RI sensitivity of MZI is as high as −13862 nm/RIU, and the temperature sensitivities of MZI and PMF are −0.4 nm/℃ and 1.47 nm/℃, respectively. With the help of a sensitivity matrix, the change of RI and temperature can finally be demodulated. The RI and temperature resolutions of the cascaded structure can achieve 1.83 × 10−6 RIU and 0.014 ℃ respectively, to the best of our knowledge, which are the highest among all fiber structures without special materials coating or filling for simultaneous measurement. This structure presents outstanding advantages of easy fabrication, low cost and less sample consumption, which has great potential for integrated biochemical analysis systems.

Dual Mach–Zehnder Interferometer Based on Side-Hole Fiber for High-Sensitivity Refractive Index Sensing

A unique type of refractive index (RI) sensor is proposed using a dual Mach-Zehnder interferometer (MZI) structure based on side-hole fibers (SHFs). The MZI structure contains two single-mode fibers (SMFs), two coreless fiber (CLF) sections and an SHF section, which are spliced together in the order of SMF-CLF-SHF-CLF-SMF. The SMFs and the CLFs enable light lead in/out and beam splitting/combining, respectively. As a special feature of the structure, one hole of SHF is exposed for liquid filling and to form two MZIs as well. Three types of sensors are fabricated, namely S1, S2 and S3. Numerical simulation and experimental studies have been conducted to characterize the sensing performance. The RI sensitivity of the S1 using the ∼550 μm long SHF section reaches 14,000 nm/RIU. When a shorter SHF section is used in S2, the detectable RI range is broadened due to larger FSR. When the closed hole of SHF in S3 is filled with liquid to introduce the Vernier effect, the sensitivity can be further enhanced to over 44,000 nm/RIU (i.e., Refractive Index Unit), which corresponds to the detection limit at the level of 1.0 × 10−5 RIU. This sensor design is original and easy to package, which gives it potential for label-free biochemical analyses.

Dispersed-Monolayer Graphene-Doped Polymer/Silica Hybrid Mach-Zehnder interferometer (MZI) Thermal Optical Switch with Low-Power Consumption and Fast Response.

This article demonstrates a dispersed-monolayer graphene-doped polymer/silica hybrid Mach–Zehnder interferometer (MZI) thermal optical switch with low-power consumption and fast response. The polymer/silica hybrid MZI structure reduces the power consumption of the device as a result of the large thermal optical coefficient of the polymer material. To further decrease the response time of the thermal optical switch device, a polymethyl methacrylate, doped with monolayer graphene as a cladding material, has been synthesized. Our study theoretically analyzed the thermal conductivity of composites using the Lewis–Nielsen model. The predicted thermal conductivity of the composites increased by 133.16% at a graphene volume fraction of 0.263 vol %, due to the large thermal conductivity of graphene. Measurements taken of the fabricated thermal optical switch exhibited a power consumption of 7.68 mW, a rise time of 40 μs, and a fall time of 80 μs at a wavelength of 1550 nm.

Accelerated secure key distribution based on localized and asymmetric fiber interferometers.

We propose and experimentally demonstrate an approach to generate and distribute secret keys over optical fiber communication infrastructure. Mach-Zehnder interferometers (MZIs) are adopted for key generation by transferring the environmental noise to random optical signals. A novel combination of wideband optical noise and an asymmetric MZI structure enables the secret keys to be securely transmitted and exchanged over public fiber links without being detected. We experimentally demonstrate this system and show reliable performance: keys are generated at the rate of 502 bit/s, and are successfully exchanged between two parties over a 10 km optical fiber with a bit error of ∼ 0.3%. System security analysis is performed by corroborating our experimental findings with simulations. The results show that our system can protect the key distribution under different attacks, attributed to wideband optical noise and asymmetric MZI structures. Compared to the previous schemes based on distributed MZIs, our scheme exploits localized MZI which provides twofold advantages. Firstly, the key generation rate can be increased by a factor of 5.7 at a negligible additional cost. Secondly, the system becomes robust to, in particular, active intrusion attack. The proposed system is a reliable and cost-effective solution for key establishment, and is compatible with the existing optical fiber communication infrastructure.

Array of Mach Zehnder Modulators for Realization of Parity Generator/Checker

The electro-optic effect is one of the most important techniques for modulation and switching purpose in optical communication. The Mach–Zehnder interferometer (MZI) structure functioning on the principle of electro-optic effect behaves as the influential optical switching device. This paper contains discussion of electro-optic effect based MZI structure and its efficient application to construct parity generator and checker. Titanium (Ti) in-diffused lithium niobate profile of MZI through computer simulation has been used for this purpose. Basic 2*2 switch is transformed as MZI for the design of parity device over a functional wavelength range of 1.3 µm to 1.65µm. This simulated design is analyzed with different Ti-LiNbO3 stripe thicknesses, in order to attain the optimum Ti-LiNbO3 stripe thickness and also to improve the performance of the switch on its crosstalk, power imbalance, extinction ratio and transition losses. The simulation model of proposed optical parity device has been implemented using the OptiBPM and OptiSystem softwares have been used for suitable verification of the discussed schemes.

High-resolution and fast-response optical waveguide temperature sensor using asymmetric Mach-Zehnder interferometer structure

We propose and demonstrate a high-resolution and fast-response optical waveguide temperature sensor based on asymmetric Mach-Zehnder interferometer (MZI) structure. The sensing region is composed of an asymmetric MZI structure, which consists of two different kinds of cores formed with commercial polymer materials EpoClad and Norland optical adhesive 73 (NOA 73), respectively, in the two arms. Due to the higher thermo-optic coefficient of NOA 73, the phase changes of the two MZI arms are different with the temperature which in turn induces output optical power variations, enabling simple and real-time temperature detection. The sensor exhibits a large sensitivity of −1.685 °C−1, high resolution of 1.48 × 10−3 °C and fast response time of about 510 μs. The advantages of high sensitivity and resolution, low-cost, competent integration and compatible with most biological assays make the designed sensor potential application in temperature detections of molecular analysis, biotechnology and chemical synthesis.

Polarization influence and its mitigation on laser frequency noise measurement by a short-delayed self-homodyne interference method.

This paper investigated how a polarization state influences frequency noise measurement accuracy of the short-delayed self-homodyne interference method. An autopolarization control method was demonstrated to mitigate polarization-induced fading (PIF) in a 120-deg phase difference Mach-Zehnder Interferometer (MZI). This method used a feedback adjustment with simulated annealing algorithm, which had the advantages of a short control period, high accuracy, and easy implementation. Frequency fluctuations' power spectral density and linewidth results measured by the improved MZI were consistent with the results of the Michelson interferometer, which used the Faraday rotator mirrors (FRMs) to overcome PIF. The novel MZI structure is unrestricted to FRMs and can extend the capability of the short-delayed self-homodyne interference technique for many special bands' laser frequency noise measurements such as visible bands.

C-Band and O-Band Silicon Photonic Based Low-Power Variable Optical Attenuators

We propose and experimentally demonstrate low-power and broadband variable optical attenuators (VOAs) on the silicon photonics platform. The VOAs are based on a Mach–Zehnder interferometer structure. Different variations were fabricated using electron beam lithography using different input and output couplers, heater length and width, operating wavelength, and substrate undercut. Experimental results for the C-band VOA show that, including the substrate undercut, a 3X improvement can be achieved in the power consumption, at the expense of a reduction in electrical bandwidth, where 5- and 20-dB attenuation can be achieved using only 5.5 and 8 mW. Moreover, the VOA can operate over more than 80-nm optical bandwidth with ripples below 1 dB. Furthermore, we study the impact of the heater dimensions on the optical attenuation and VOA bandwidth. Finally, we present similar results for an O-band VOA design.

A Compact Graphene Modulator Based on Localized Surface Plasmon Resonance with a Chain of Metal Disks

Most graphene electro-optic modulators based on the electro-refractive modulation are composed of Mach-Zehnder interferometer or microring resonator structures and have a relative compact size comparing with dielectric ones. To further shrink the footprint, we use the localized surface plasmon resonance of a chain of three metal disks to realize a submicron graphene modulator, whose length can be reduced to less than 1 μm. The proposed graphene modulator has an extinction ratio of 5.5 dB with a length of only 740 nm. And the insertion loss, 3-dB bandwidth, and power consumption of the modulator are 1.9 dB, 83.4 GHz, and 8.55 fJ/bit respectively.

Energy efficient photonic millimeter-wave generation using cascaded polarization modulators

A filter-less millimeter-wave generation scheme consisting of four polarization modulators in series, each followed by a polarizer is proposed to achieve optoelectronic frequency octupling. The cascade of polarization modulator and polarizer provides an intensity modulator whose biasing condition can be set by the polarizer angle and polarization state of the input light to each polarization modulator. A theoretical analysis of the architecture is performed using a transfer function method and validated by industry-standard software simulation tools. The circuit shows high potential in achieving desired performance with lower input RF power when compared to the another configuration based on a generalized Mach–Zehnder interferometer structure. Although the operating range in terms of applied RF drive becomes narrow, low RF input operation can be achieved by this circuit. The effect of imbalances in the key circuit parameters is also investigated in terms of electrical side harmonic suppression ratio.

High Temperature (Up to 950 °C) Sensor Based on Micro Taper In-Line Fiber Mach–Zehnder Interferometer

A high temperature (up to 950 °C) sensor was proposed and demonstrated based on a micro taper in-line fiber Mach–Zehnder interferometer (MZI) structure. The fiber MZI structure comprises a single mode fiber (SMF) with two micro tapers along its longitudinal direction. An annealing at 1000 °C was applied to the fiber sensor to stabilize the temperature measurement. The experimental results showed that the sensitivity was 0.114 nm/°C and 0.116 nm/°C for the heating and cooling cycles, respectively, and, after two days, the sensor still had a sensitivity of 0.11 nm/°C, showing a good stability of the sensor. A probe-type fiber MZI was designed by cutting the sandwiched SMF, which has good linear temperature responses of 0.113 nm/°C over a large temperature range from 89 to 950 °C. The probe-type fiber MZI temperature sensor was independent to the surrounding refractive index (RI) and immune to strain. The developed sensor has a wide application prospect in the fields of high temperature hot gas flow, as well as oil and gas field development.

Mach-Zehnder Interferometer Cascaded With FBG for Simultaneous Measurement of Magnetic Field and Temperature

A kind of composite structure consisting of Mach–Zehnder interferometer (MZI) cascaded with fiber Bragg grating (FBG) is proposed for simultaneous measurement of magnetic field and temperature. The MZI structure consists of a pair of up-tapered joints, which are used to excite high order modes and re-couple them to the fiber core. The structure is immersed in magnetic fluid to make it magnetically sensitive. The cascaded FBG is employed for temperature compensation. Simultaneous measurement of magnetic field and temperature can be achieved by monitoring the transmission spectra of MZI and FBG. The magnetic field sensitivity of the proposed sensing structure can be up to 407.82 pm/mT in the range of 0–25 mT. The advantages of the proposed sensing structure lie in low cost, simple structure, easy manufacture, and strong robustness, which make it attractive in the field of magnetic field sensing.