Nested-Ring Mach–Zehnder Interferometer in Silicon-on-Insulator

For the first time, a nested-ring Mach-Zehnder interferometer (MZI) on silicon-on-insulator is realized using a complementary metal-oxide-semiconductor-based process. In this letter, we verify that the device operates in two modes: the inner-loop resonance dominant mode due to strong build-up inside the inner-ring, and the double-Fano resonances mode due to strong light interaction with the outer loop. The results show that the inner-loop resonance is highly sensitive to the MZI arm imbalance compared to the double-Fano resonance mode. Based on these considerations, we obtain a good fit between theory and experiment.     

Resonance Enhancement in Silicon-on-Insulator-Based Two-Ring Mach–Zehnder Interferometer

We propose and demonstrate a two-ring coupled Mach–Zehnder interferometer (2RMZI) device that exhibits a sharp resonance with background suppression to give both high finesse and modulation depth. The combination of MZI and the two-ring structure leads to more complete destructive interference that effectively removes the unwanted background envelope effect found in the transmission spectrum of a simple two-ring-two-bus (2R2B) system. The projected finesse enhancement of 2RMZI relative to one-ring coupled MZI and 2R2B is discussed based on best-fit parameter values that match the fabricated devices.      

Ultracompact Intrinsic Micro Air-Cavity Fiber Mach–Zehnder Interferometer

A compact intrinsic fiber Mach–Zehnder interferometer (MZI) is proposed and experimentally demonstrated by incorporating a micro air-cavity ablated by femtosecond laser irradiation. A short cavity of length $sim$10 $muhbox{m}$ along the single-mode fiber core provided two optical paths: one propagating through the air and the other guided along the ring-shaped silica cladding. A spectral analysis confirmed MZI in a good agreement with experimental results. Temperature-dependent spectral shifts were measured and analyzed.      

Polarization-Insensitive Operation of Lithium Niobate Mach–Zehnder Interferometer With Silica PLC-Based Polarization Diversity Circuit

We demonstrate the polarization-insensitive operation of a Mach-Zehnder interferometer (MZI)-based lithium niobate switch with a silica waveguide polarization beam splitter. The splitter is composed of an MZI with a half wave plate installed in one arm, and exhibits a polarization extinction ratio of more than 15 dB. The switch functions for both polarizations with an extinction ratio of more than 20 dB, a polarization-dependent loss of 0.1 dB and a switching speed of 40 ps.     

High-Temperature Sensing Using Miniaturized Fiber In-Line Mach–Zehnder Interferometer

A miniaturized single fiber in-line Mach-Zehnder interferometer is proposed for high-temperature sensing. The interferometer has a microcavity in one of its arms, formed by removing part of the fiber core and cladding, while the other arm remains in the fiber core. Because the fiber core exhibits a temperature coefficient of refractive index which is different from that of air, the interferometer is sensitive to temperature variation. The microcavity structured interferometer also has excellent sustainability to high temperatures up to 1100°C . The system is compact, reliable and can detect the temperature at precise location.     

Fiber Grating Sensor Interrogation Using a Double-Pass Mach–Zehnder Interferometer

We propose an advanced quadrature sampling method for a fiber grating sensor interrogation. A Mach–Zehnder interferometer output is sampled at internal triggers which are generated at the zero-crossing points of a double-pass Mach–Zehnder interferometer output. Due to the phase relationship, the internal trigger signals assure a 90$^{circ}$ phase difference between the sampled signals even in the presence of environmental disturbances. Also, no parameter adjustment is required when the frequency and/or shape of the phase modulation signal changes, which makes it a very practical technique for fiber grating sensor demodulation. From the preliminary experiments, we could obtain a measurement resolution of $sim $ 8 pm.      

Demonstration of 20-Gb/s DQPSK With a Single Dual-Drive Mach–Zehnder Modulator

Using a single, dual-drive Mach-Zehnder modulator and high-speed electronics, differential quadrature phase-shift keying modulation and detection are demonstrated for a bit rate of 20 Gb/s. Back-to-back system performance is measured, and the receiver sensitivity is found to be -32.25 dBm.     

A High-Performance Ultracompact Optical Interleaver Based on Double-Ring Assisted Mach–Zehnder Interferometer

We present an ultracompact and high-performance optical interleaver based on a microring assisted Mach-Zehnder interferometer using an ultrahigh-index-contrast waveguide (17% Delta). The device, a 100/200-GHz interleaver at 1.55-mum region, exhibits flat and nearly square passband and better than -30-dB stopband extinction ratio. Fiber-to-fiber loss is -2.2 dB. Passband bandwidth is 90 and 121 GHz at -1 and -20 dB, respectively. The dimension of this interleaver chip is 12times1 mm. Design optimization is also discussed for further performance improvement.     

Coherence Multiplexing System Based on Asymmetric Mach–Zehnder Interferometers for Faraday Sensors

An optical coherence multiplexing system for Faraday sensors is proposed. With an asymmetric Mach-Zehnder (M-Z) interferometer, the linearly polarized light from a Faraday sensor is decomposed into two orthogonal modes, which are interrogated by a path-scanning Michelson interferometer at different path positions. The variations in the intensities of these two modes are utilized to deduce the rotation of the polarization plane, which is related to the measurand tested by the Faraday sensor. By employing multiple asymmetric M-Z interferometers with arm-lengths carefully controlled, the sensing signals of the multiplexed Faraday sensors are obtained and well separated in one scan of the Michelson interferometer.     

Proposal to Produce Coupled Resonator-Induced Transparency and Bistability Using Microresonator Enhanced Mach–Zehnder Interferometer

We propose a microresonator scheme for a Mach-Zehnder interferometer in which a microresonator is side coupled to one arm and the other is inserted in the other arm, to produce coupled resonator-induced transparency (CRIT) and absorption (CRIA) effects. In this system, CRIT and CRIA effects with one effect next to another over a frequency range when two microresonators are identical and Fano-resonance line shape when the sizes of two microresonators are unequal are achieved. We also theoretically investigate the improving optical bistability characteristic based on CRIT.     

Proposal for All-Optical Generation of Ultra-Wideband Impulse Radio Signals in Mach–Zehnder Interferometer With Quantum-Dot Optical Amplifier

We developed a theoretical analysis of a novel method of ultra-wideband impulse radio signals all-optical generation based on cross-phase modulation and cross-gain modulation in a nonsymmetric integrated Mach-Zehnder interferometer (MZI) containing quantum-dot semiconductor optical amplifier. The proposed method is promising due to the advantages of compact, easily controlled, and low energy integrated MZI structures as compared to optical fiber systems.     

Cascaded Mach–Zehnder Interferometers Assembled by Submicrometer PTT Wires

A single bow-shaped Mach–Zehnder interferometer (MZI) and two-cascaded MZIs were assembled by flexible submicrometer polymer wires, which were directly drawn from poly(trimethylene terephthalate) melt. The size of the cascaded MZIs is tens to hundreds of micrometers and their path-length differences can be dynamically adjusted by micromanipulation under an optical microscope. Experimental results show that the cascaded MZIs have a large extinction ratio (25 dB) with a flat-top transmission over a wavelength range of 1.3–1.6 $mu$m. The insertion losses of the cascaded MZIs with two and three bow-shaped MZIs are 1.1–1.8 and 1.5–2.3 dB, respectively.      

Tunable Optical Dispersion Compensator With Increased Bandwidth via Connection of a Mach–Zehnder Interferometer to an Arrayed-Waveguide Grating

We propose and demonstrate a novel colorless tunable optical dispersion compensator (TODC) consisting of a Mach-Zehnder interferometer (MZI) connected to an ar- rayed-waveguide grating with a thermooptic lens. The MZI approximately doubles the magnitude bandwidth at large dispersion settings. We demonstrate compensation of a 43-Gb/s nonreturn-to-zero signal dispersed over a range of -844 to + 1700 ps/nm. To our knowledge, +1700 ps/nm is the largest demonstrated dispersion compensation amount of a 40-Gb/s signal with a single TODC.     

InP-Based Mach–Zehnder Modulator With Capacitively Loaded Traveling-Wave Electrodes

InP-based Mach-Zehnder modulators with capacitively loaded traveling-wave electrodes (CL-TWEs), which have segmented structures along the optical waveguides, are presented. Devices with various structural parameters for gap length (the length between adjacent segmented phase modulators) and total active length were fabricated and investigated both optically and electrically. Excellent characteristics such as characteristic impedance matching to 50 Omega and low electrical propagation losses were obtained. Using the optimum structures, 40- and 10-Gb/s large signal operations were successfully performed with peak-to-peak driving voltages of 3.0 and 1.2 V, respectively. The effects of structural parameters, such as gap length and total active length on electrical and optical modulation properties, are discussed.     

All-optical NAND gate using integrated SOA-based Mach–Zehnder interferometer

An all-optical NAND gate using integrated SOA-based Mach–Zehnder interferometer is proposed and demonstrated for the first time. Numerical analysis shows the switching window of the proposed NAND gate, which is synchronous with the dynamic gain experienced by the probe pulses. The effects of the SOA and input data parameters on the switching performance are discussed. The operation of the proposed NAND gate with 10 Gb/s RZ pseudorandom bit sequences is simulated and the results demonstrate its effectiveness. This NAND gate could provide a new possibility for all-optical routing in future all-optical networks.     

Simple Rules for Optimizing Asymmetries in SOA-Based Mach–Zehnder Wavelength Converters

In this paper, we present an analysis of semiconductor optical amplifier (SOA)-based differential Mach–Zehnder wavelength converters with a specific focus on optimizing performance through intentional asymmetries in optical power splitting, SOA bias, and interferometer phase bias. By introducing a simple conceptual framework for understanding the amplifier pulse dynamics, two simple yet effective design rules are derived. These design rules are validated using pseudorandom code in a comprehensive computer model, demonstrating the performance penalties that result when attempting optimization using only unequal SOA biasing or phase biasing. This work illustrates that dramatic improvements in extinction and eye margin can be achieved with optimized splitter asymmetries, and have significant implications for improved network performance and converter cascadability.      

双Mach Zehnder光纤干涉仪中的遗传偏振控制算法

Mach-Zehnder光纤传感系统在实际应用中受偏振相位偏移现象影响,使得信号相关性不稳定,造成定位时出现粗大误差,甚至无法定位的问题。为解决这一问题,提出了一种基于双臂检测信号相关系数的遗传偏振控制算法。利用偏振控制器对输入光的偏振态进行实时控制,在系统信号相关性恶化时,通过改变输入偏振态,恢复信号的相关性。实验证明,该算法可使检测信号维持良好的相关性,系统的稳定性得到较大提高。     

In-Line Abrupt Taper Optical Fiber Mach–Zehnder Interferometric Strain Sensor

A Mach–Zehnder interferometer with two abrupt single-mode fiber tapers is simulated, constructed, and demonstrated. The interferometer has an insertion loss of 5 dB and an extinction ratio over 15 dB. The interferometer is tested as a strain sensor based on the maximum attenuation wavelength shift with a comparable sensitivity (slope: 2000 nm/ $varepsilon, R^{2} =0.996$) with long-period-grating-type sensor and promises low fabrication cost.      

Ultracompact Asymmetric Mach–Zehnder Interferometers with High Visibility Constructed from Exciton Polariton Waveguides of Organic Dye Nanofibers

Manipulation of light using subwavelength waveguides is a key technology in the development of miniaturized photonic circuits, which possess various advantages over their electronic counterparts. The novel approach presented for such waveguiding involves the propagation of exciton polaritons (EPs), which are quasi‐particles formed by strong exciton–photon coupling, along organic dye nanofibers. A self‐assembled nanofiber of thiacyanine (TC) with a width of ≈200 nm propagates the EPs created by an optical excitation over a submillimeter‐scale distance and passes through a bend with a micrometer‐scale radius with low bending loss. To demonstrate the remarkable potential of EP‐based miniaturized photonic circuits, asymmetric Mach–Zehnder interferometers (AMZIs) are fabricated with TC nanofibers by micromanipulation. The AMZIs with a footprint of ≈20 μm × 20 μm exhibit a visibility of nearly unity and function as channel drop filters with the considerably high extinction ratio of up to ≈15 dB. Such high‐performance and ultracompact channel drop filters operating in the visible wavelength region have rarely been developed with other waveguide technologies. The coherent properties of the EPs in the nanofibers are investigated using time‐resolved experiments. The coherent properties provide useful information for designing EP‐based photonic circuits and for understanding EP dynamics in a nanofiber.     

Wideband, Low Driving Voltage Traveling-Wave Mach–Zehnder Modulator for RF Photonics

We report the design, fabrication, and testing of a traveling-wave Mach-Zehnder modulator on a GaAs substrate. Operating at 870-nm wavelength, we obtained an extremely low driving voltage of 0.45 V and a high measurement-instrument-limited small-signal modulation bandwidth of 18 GHz, projected to an estimated bandwidth of 50 GHz. We have also monolithically integrated photodetectors with an impulse response of 8-ps full-width at half-maximum, and a saturation power of 330 mW, giving a flexible high-performance platform for RF photonics.