Cascaded Mach-Zehnder Interferometer Research Articles

Ultra-sensitive optical fiber ethanol gas sensor based on Vernier effect in cascaded Mach-Zehnder interferometer and Sagnac interferometer

Optical fiber-based sensors, which show the merits of high sensitivity, real-time, and rapid detection, have important research value in the detection of volatile organic compounds (VOCs). In this paper, a novel ethanol gas sensor was experimentally investigated based on the cascaded optical fiber-based Sagnac interferometer and Mach-Zehnder interferometer. The Sagnac interferometer was constructed with an anisotropic nematic liquid crystal (NLC) film which acted as the reactor with ethanol gas. A tapered single-mode fiber (SMF) was used to build the Mach-Zehnder interferometer (MZI). The two interferometers were parallelly and tandemly cascaded respectively to achieve the magnification of measurement sensitivity. Experimental results showed that the sensitivities were 8.561 pm/ppm with a magnification factor of 3.76 for the parallel cascaded structure and 7.924 pm/ppm with a magnification factor of 3.48 for the tandemly cascaded structure. The designed optical fiber-based ethanol gas sensor, showing the advantages of compact structure, high sensitivity, small size, and low cost, could be a competitive candidate for the detection of ethanol gas leakage.

Ultra-sensitive fiber optic sensor for glucose concentration measurement based on Vernier effect in cascaded Mach–Zehnder interferometers

In this paper, a fiber optic glucose concentration sensor based on cascaded Mach–Zehnder interferometers (CMZIs) was proposed and experimentally verified. Two single-mode fibers (SMFs) with slightly different tapering lengths and as well free spectral ranges (FSRs) were obtained through the melt-drawn cones technique and then were cascaded together to achieve the Vernier effect (VE). Experimental results showed that the measurement sensitivity of glucose concentration based on a single tapered SMF was 0.0494 nm (mmol l−1)−1. Furthermore, the measurement sensitivity based on the cascaded tapered SMFs was enhanced by 4.86 times to an ultra-high level of 0.2402 nm (mmol l−l)−1. The resolution reached 0.083 mmol l−1. The refractive index sensitivity reached 9066 nm/RIU. The resolution reached 2.21 × 10−6 RIU. In addition, the proposed glucose concentration sensor based on CMZIs shows good hysteresis. In conclusion, the designed sensor, showing the merits of easy to fabricate, high sensitivity, and high detection resolution, could be used to monitor the tiny variation in glucose concentration.

Ultra-compact and high-performance four-channel coarse wavelength-division (de)multiplexing filters based on cascaded Mach-Zehnder interferometers with Bezier-shape directional couplers

Using cascaded Mach-Zehnder interferometers (CMZIs) provides an attractive option for realizing coarse wavelength-division (de)multiplexing (CWDM) filters with low losses, low crosstalk, flat tops, and high scalability. However, they usually have large footprints and insufficient fabrication tolerances, due to the inferior performance of conventional directional couplers (DCs) used for MZIs. Here, a four-channel CMZI wavelength-division (de)multiplexer based on novel Bezier-shape DCs with compact footprints, broad bandwidths and decent fabrication tolerances. For the fabricated (de)multiplexer with 20-nm channel spacing, the excess loss is less than 0.5 dB and the crosstalk is lower than −19.5 dB in the 1-dB bandwidth of 12.8 nm. For the case with a core-width deviation of ±20 nm, the device still performs very well with low losses and low crosstalk. Compared to the state-of-the-art MZI-based CWDM filters, the present device has slightly high performances and a footprint of 0.012 mm2 shrunk greatly by ∼3-folds. This work can be extended for more channels and other material platforms.

Multimode optical switch based on cascaded Mach-Zehnder interferometer waveguides.

We present a 1 × 1 multimode optical switch for E11, E21, E12, and E22 modes based on cascaded Mach-Zehnder interferometer (MZI) waveguides, where the primary MZI is used to split E11, E21, E12, and E22 modes into E11 or E12 mode and then couple back to the original mode at the output, and the secondary MZIs are the modulation arms of the primary MZI. In addition, the secondary MZIs are designed to be mode-insensitive for switching E11 and E12 modes simultaneously. As a proof of concept, we fabricate the device with polymer material to achieve thermo-optic switching for the four modes. Our experimental device exhibits the extinction ratios of larger than 10.2 dB with a power consumption of 5.5 mW and response times of less than 1.28 ms for each mode. The presented device can be widely applied in mode-division multiplexing (MDM) systems where multimode switching is needed.

Real-time reconfigurable on-chip photonic frequency decoder.

A group-delay-unit-based integrated silicon photonic integrated circuit (PIC) is employed as a reconfigurable analog radio frequency decoder, which provides a real-time temporal and spectral analysis of any arbitrary multi-tone signal in the micro- and mm-wave range. The circuit is based on cascaded Mach-Zehnder interferometer embedded silicon microring resonators as variable delay units. The temporal decoding of the multi-tone input signal is demonstrated by tuning the signal with respect to the ring resonator delay and resonance. A one-to-one conformal time-to-frequency mapping provides real-time spectral decoding of the signal under test without additional digital signal processing. The idea is validated by several experimental results with single-tone and two-tone input signals in a compact, low-power, silicon PIC. The proposed real-time temporal analog frequency decoder may be very intriguing for high-speed, low-latency wireless applications, such as autonomous driving and 6G.

A dual-parameter sensing system for temperature and curvature based on Nano-EYDF and in-line cascaded Mach-Zehnder interferometer

Based on the self-developed erbium ytterbium co-doped fiber, a sensing system consisting of an amplified spontaneous emission (ASE) source and an optical fiber sensor is introduced. The spectrum test results and stability of ASE source are given. A dual-parameter sensor for temperature and curvature based on in-line cascaded Mach-Zehnder interferometer (MZI) is demonstrated theoretically and experimentally. The proposed sensor is mainly composed of single-mode fiber (SMF) and Nano-Erbium-Ytterbium co-doped fiber (Nano-EYDF) to form a symmetrical sensing structure. MZI is formed due to the mode field mismatch between EYDF and SMF. The sensor displays different response to temperature and curvature. By demodulating the wavelength shifts of different peaks or dips, the sensitivity coefficient matrix method can be used to measure the temperature and curvature simultaneously. The experimental results show that, in the range of 25 ∼ 100 °C, the maximum temperature sensitivity is 94.70 pm/ °C and in the curvature range of 0 ∼ 1.03 m−1, the maximum curvature sensitivity is −9.48 nm/m−1. And the power output of ASE source is stable, the spectral unevenness is less than 2.5 dB in the range of 1530 ∼ 1580 nm. The sensor has the advantages of good repeatability, high sensitivity and compact structure. It can be used in 3D reconstruction, robot shape detection, human medicine and other fields.

Pseudo noise sequence generator based on cascaded Mach–Zehnder interferometer

Abstract An optical pseudo noise sequence generator based on Mach–Zehnder interferometer (MZI) is proposed. The device consists of MZI and a feedback line. Operability of the proposed device is simulated for continuous wave signals of 1.5 micrometer wavelength. The simulated results shows that all possible sequences of four bit pseudo noise sequence can be generated using proper arrangement of the MZI structures. The operation is numerically analysed and simulated results are discussed. Moreover, various parameters affecting performance of the device are also discussed. The proposed sequence generator can be utilized for different applications in optical wireless communication technology.

Ultra-high sensitivity gas pressure sensor based on cascaded Mach-Zehnder interferometer and Sagnac interferometer

A highly sensitive optical fiber gas pressure sensor based on Vernier effect of cascaded optical fiber Sagnac interferometer (SI) and Mach Zehnder interferometer (MZI) is proposed, and the sensing characteristics are verified. The SI consists of a 3 dB coupler and a section of panda fiber, and SI is used as a filter. As the sensing part, MZI has high sensitivity and good stability. It is composed of single-mode fiber, multimode fiber and quartz capillary. By controlling the length of two interferometers, their free spectrum ranges (FSR) are similar but not equal. Therefore, the cascade structure produces the Vernier effect, which can amplify the gas pressure sensitivity of the sensor. The experimental results show that the gas pressure sensitivity of a single MZI is only − 7.75 nm/MPa. The cascade structure can amplify the sensitivity to − 211.9 nm/MPa, and the magnification factor is 27.3, which is consistent with the theoretical analysis results. In addition, the proposed sensor has excellent repeatability and stability.

Wideband and Channel Switchable Mode Division Multiplexing (MDM) Optical Power Divider Supporting 7.682 Tbit/s for On-Chip Optical Interconnects.

Silicon photonics (SiPh) are considered a promising technology for increasing interconnect speed and capacity while decreasing power consumption. Mode division multiplexing (MDM) enables signals to be transmitted in different orthogonal modes in a single waveguide core. Wideband MDM components simultaneously supporting wavelength division multiplexing (WDM) and orthogonal frequency-division multiplexing (OFDM) can significantly increase the transmission capacity for optical interconnects. In this work, we propose, fabricate and demonstrate a wideband and channel switchable MDM optical power divider on an SOI platform, supporting single, dual and triple modes. The switchable MDM power divider consists of two parts. The first part is a cascaded Mach-Zehnder interferometer (MZI) for switching the data from their original TE0, TE1 and TE2 modes to different modes among themselves. After the target modes are identified, mode up-conversion and Y-branch are utilized in the second part for the MDM power division. Here, 48 WDM wavelength channels carrying OFDM data are successfully switched and power divided. An aggregated capacity of 7.682 Tbit/s is achieved, satisfying the pre-forward error correction (pre-FEC) threshold (bit-error-rate, BER = 3.8 × 10-3). Although up to three MDM modes are presented in the proof-of-concept demonstration here, the proposed scheme can be scaled to higher order modes operation.

Sensitivity enhanced fiber optic temperature sensor based on optical carrier microwave photonic interferometry with harmonic Vernier effect

A sensitivity enhanced fiber optic temperature sensor based on optical carrier microwave interferometry (OCMI) with harmonic Vernier effect is proposed and experimentally demonstrated. The sensor is composed of two cascaded Mach–Zehnder interferometers (MZIs) with different optical length differences. Harmonic Vernier effect in microwave frequency domain is generated due to the free spectral range (FSR) difference in the microwave frequency response. Temperature sensing is realized by detecting the intersection of the inner envelopes of the measured frequency response curve. Experimental results demonstrate that sensitivity up to 580.45kHz/°C has been obtained by employing the harmonic Vernier effect, whose sensitivity amplification factor is up to 18.61. Through the application of harmonic Vernier effect in microwave domain, the amplification factor can be easily adjusted with much higher manufacturing tolerance and alleviate the measurement range restriction induced by the periodic frequency response.

Silicon photonic flat-top WDM (de)multiplexer based on cascaded Mach-Zehnder interferometers for the 2 µm wavelength band: publisher's note.

This publisher's note contains a correction to [Opt. Express30, 28232 (2022)10.1364/OE.467473].

Silicon photonic flat-top WDM (de)multiplexer based on cascaded Mach-Zehnder interferometers for the 2 µm wavelength band.

The 2 µm wavelength band has proven to be a promising candidate for the next communication window. Wavelength-division multiplexing (WDM) transmission at 2 µm can greatly increase the capacity of optical communication systems. Here, we experimentally demonstrate a high-performance silicon photonic flat-top 8-channel WDM (de)multiplexer based on cascaded Mach-Zehnder interferometers for the 2 µm wavelength band. A three-stage-coupler scheme is utilized to provide passbands and reduce channel crosstalk, and 11 thermo-optic phase shifters have allowed active compensation of waveguide phase errors. The fabricated device shows low insertion loss (< 0.9 dB), channel crosstalk (< 20.6 dB) and 1-dB bandwidth of 2.3 nm for operating wavelength ranging from 1955nm to 1985nm. The demonstrated (de)multiplexer could potentially be used for WDM optical data communication in the 2 µm spectral band.

Eight-Channel LAN WDM (De)Multiplexer Based on Cascaded Mach–Zehnder Interferometer on SOI for 400GbE

In this paper, we design and experimentally demonstrate an eight-channel cascaded Mach–Zehnder interferometer (MZI) based Local Area Network (LAN) Wavelength Division Multiplexing (WDM) (de)multiplexerwith channel spacing of 800 GHz on a silicon-on-insulator. By cascading a three-stage MZI, eight target wavelengths are (de)multiplexed. The length difference of the third-stage MZI delay arms is adjusted so that the output channels skip the guard band. In order to keep the central wavelength of each channel from shifting, we utilize a wide waveguide for the phase delay arm in MZI to achieve large fabrication tolerance, and the multi-mode interference (MMI) couplers as power splitters with weak dispersions. The measurement results of the fabricated device show the precise wavelength alignment over the whole working wavelength range.

Comparison of Silicon Lattice-Filter-Based O-Band 1×8 (De)Multiplexers With Flat and Gaussian-Like Passbands

Based on cascaded Mach-Zehnder interferometer (MZI) lattice filters, we demonstrate and compare silicon O-band 8-channel (de-)multiplexers with flat and Gaussian-like passbands for the 400 GBASE-LR8 norm. The 1×8 (de-)multiplexer with flat passbands exhibit insertion loss less than 2.5 dB, channel crosstalk lower than −11 dB, and 3 dB bandwidths of ∼3.9 nm. In contrast, the maximum insertion loss, the worst channel crosstalk, and 3 dB bandwidths of the 1×8 (de-)multiplexer with Gaussian-like passbands are 1.1 dB, −13 dB, and ∼2.9 nm, respectively. The comparison result indicates that the latter is more advisable choice. A theoretical calculation based on measured coupling ratios of stand-along directional couplers (DC) indicates that the performance deteriorations of practical filtering curves are mainly caused by dispersions and fabrication errors of the DCs.

Highly Sensitive Magnetic Field Measurement With Taper-Based In-Line Mach-Zehnder Interferometer and Vernier Effect

A taper-based in-line Mach-Zehnder interferometer (MZI) coated with the magnetic fluids (MFs) is designed and experimentally verified for the highly sensitive magnetic field measurement. The effect of waist diameter on the characteristic parameters of transmission modes is numerically analyzed by the finite element method (FEM). The sensing MZI (S-MZI) with a waist diameter of &#x223C;8.92 &#x03BC;m is fabricated, in which the multi-mode interference occurs between the fundamental mode (HE₁₁) and cladding modes (HE₂₁ and TM₀₁ modes). The S-MZI has the average sensitivities of 1.180 and 1.305 nm&#x002F;mT near 1550 nm as the magnetic field increases and decreases in the range of 10.15&#x223C;30.44 mT. In order to further improve the measurement sensitivity of the magnetic field, a cascaded MZI (C-MZI) based on the Vernier effect is proposed, which is composed of a reference MZI (R-MZI) without MFs connected in series with the above S-MZI. An evident envelope and shift influenced by the external magnetic field is observed in the transmission spectra of the C-MZI, resulting in the sensitivity being elevated by an amplification factor. The C-MZI shows the average sensitivities of &#x2212;5.148 and &#x2212;5.782 nm&#x002F;mT near 1500 nm, respectively, being &#x223C;4.77 and 4.83 times of those in the single S-MZI. Therefore, the proposed device may have broad applications in the magnetic field measurement in view of the advantages of high sensitivity, low cost, small volume, and simple fabrication.

High-speed programmable photonic circuits in a cryogenically compatible, visible\u2013near-infrared 200\u2009mm CMOS architecture

Recent advances in photonic integrated circuits have enabled a new generation of programmable Mach–Zehnder meshes (MZMs) realized by using cascaded Mach–Zehnder interferometers capable of universal linear-optical transformations on N input/output optical modes. MZMs serve critical functions in photonic quantum information processing, quantum-enhanced sensor networks, machine learning and other applications. However, MZM implementations reported to date rely on thermo-optic phase shifters, which limit applications due to slow response times and high power consumption. Here we introduce a large-scale MZM platform made in a 200 mm complementary metal–oxide–semiconductor foundry, which uses aluminium nitride piezo-optomechanical actuators coupled to silicon nitride waveguides, enabling low-loss propagation with phase modulation at greater than 100 MHz in the visible–near-infrared wavelengths. Moreover, the vanishingly low hold-power consumption of the piezo-actuators enables these photonic integrated circuits to operate at cryogenic temperatures, paving the way for a fully integrated device architecture for a range of quantum applications.

1 × 4 optical demultiplexer of the second band in a hole-type silicon photonic crystal

A 1 × 4 optical demultiplexer (OD) based on the self-collimation (SC) effect in hole-type silicon photonic crystal (PC) was proposed, and its performance was numerically demonstrated. The 1 × 4 OD consists of two cascaded Mach–Zehnder interferometers and an independent mirror. It has a total of four splitters and five mirrors. The simulation results indicate that by selecting the correct optical path length, the input SC beam with four evenly spaced frequencies can be demultiplexed into four output ports in the 1 × 4 OD. If the center working wavelength is 1550 nm, the free spectral range of the 1 × 4 OD is about 23 nm, which almost covers the whole optical communication C-band window. The size of the structure is on the order of 50 μm. Because of its simple structure, small size, and single material, it has potential application value in future photonic integrated circuits.

Parity–time symmetric optical neural networks

Optical neural networks (ONNs), implemented on an array of cascaded Mach–Zehnder interferometers (MZIs), have recently been proposed as a possible replacement for conventional deep learning hardware. They potentially offer higher energy efficiency and computational speed when compared to their electronic counterparts. By utilizing tunable phase shifters, one can adjust the output of each of MZI to enable emulation of arbitrary matrix–vector multiplication. These phase shifters are central to the programmability of ONNs, but they require a large footprint and are relatively slow. Here we propose an ONN architecture that utilizes parity–time (PT) symmetric couplers as its building blocks. Instead of modulating phase, gain–loss contrasts across the array are adjusted as a means to train the network. We demonstrate that PT symmetric ONNs (PT-ONNs) are adequately expressive by performing the digit-recognition task on the Modified National Institute of Standards and Technology dataset. Compared to conventional ONNs, the PT-ONN achieves a comparable accuracy (67% versus 71%) while circumventing the problems associated with changing phase. Our approach may lead to new and alternative avenues for fast training in chip-scale ONNs.

In-Line Mach-Zehnder Interferometers Based on a Capillary Hollow-Core Fiber Using Vernier Effect for a Highly Sensitive Temperature Sensor.

In this paper, we propose a highly sensitive temperature sensor based on two cascaded Mach–Zehnder interferometers (MZIs) that work using the Vernier effect. The all-fiber MZIs were assembled by splicing a segment of capillary hollow-core fiber (CHCF) between two sections of multimode fibers (MMFs). This cascaded configuration exhibits a temperature sensitivity of 1.964 nm/°C in a range from 10 to 70 °C, which is ~67.03 times higher than the sensitivity of the single MZI. Moreover, this device exhibits a high-temperature resolution of 0.0153 °C. A numerical analysis was carried out to estimate the devices’ temperature sensitivity and calculate the magnification of the sensitivity produced by the Vernier effect. The numerical results have an excellent agreement with the experimental results and provide a better insight into the working principle of the MZI devices. The sensor’s performance, small size, and easy fabrication make us believe that it is an attractive candidate for temperature measurement in biological applications.

Ultra-Broadband Polymer 1 × 2 Thermo-Optic Mode Switch

Optical mode switch is a key device for reconfigurable mode-division-multiplexing (MDM) technique. Here, an ultra-broadband 1×2 mode switch based on cascaded Mach-Zehnder interferometer and asymmetric Y-branch is proposed. The input E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</sub> or E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode will be converted to E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</sub> mode and switched between two output ports by changing the working state of electrode. When E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</sub> mode is launched, the measured insertion loss of fabricated switch is 3.3 dB (off-state)/3.4 dB (on-state), and corresponding crosstalk is -18.8 dB (off-state)/-16.1 dB (on-state) at 1550 nm, respectively. Due to the adoption of polymer with high thermo-optic coefficient as the waveguide material, the measured switching power is 10.3 mW. The captured far-field output mode patterns prove the wavelength independence of proposed mode switch within the range from 1500 to 1630 nm. This broadband operation mode switch has potentials in wavelength-division-multiplexing & MDM complex systems, as well as cost-effective low-end switching applications.