Showing papers on "Mach–Zehnder interferometer published in 2012"

High-speed low-voltage single-drive push-pull silicon Mach-Zehnder modulators

Abstract: We demonstrate a single-drive push-pull silicon Mach-Zehnder modulator (MZM) with a π-phase-shift voltage of 3.1 V and speed up to 30 Gb/s. The on-chip insertion loss is 9 dB due to the use of a 6 mm-long phase shifter. Higher switching speed up to 40-50 Gb/s is also demonstrated in devices with shorter phase shifters which require higher drive voltages but have lower insertion losses.

Refractive index sensor using microfiber-based Mach-Zehnder interferometer.

Abstract: A simple and robust refractive index (RI) sensor based on a Mach–Zehnder interferometer has been demonstrated. A section of optical microfiber drawn from silica fiber is employed as the sensing arm. Because of the evanescent field, a slight change of the ambient RI will lead to the variation of the microfiber propagation constant, which will further change the optical length. In order to compensate the variation of the optical length difference, a tunable optical delay line (ODL) is inserted into the other arm. By measuring the delay of the ODL, the ambient RI can be simply demodulated. A high RI sensitivity of about 7159 μm/refractive index unit is achieved at microfiber diameter of 2.0 μm.

Enhancement of the phase-measurement sensitivity beyond the standard quantum limit by a nonlinear interferometer

Abstract: A nonlinear interferometer uses nonlinear elements as beam splitters to split and to recombine optical waves for interference. As a result, the interference fringe size has a nonlinear dependence on the intensity of the field for phase sensing and leads to an enhanced phase signal. In this paper, a practical scheme of nonlinear interferometry for precision phase measurement is analyzed with parametric amplifiers as the nonlinear beam splitters. It is found that the signal due to phase shift is enhanced by a factor of the amplification gain as compared to a linear interferometer with the same phase-sensing light intensity while the quantum noise is kept at the vacuum level, thus, effectively increasing the signal-to-noise ratio (SNR) beyond the standard quantum limit. Furthermore, the scheme is not as sensitive to the detection loss as the linear scheme with a squeezed state for noise reduction. However, losses inside the interferometer limit the enhancement factor in SNR. We apply the concept to a Michelson interferometer but with parametric amplifiers involved for gravitational-wave detection. We find that effective power is increased by the gain of the amplifiers without actually increasing the cycling power inside the interferometer. Furthermore, the full benefits with squeezed input and variational output or the combination of a quantum nondemolition interferometer for sensitivity beyond the standard quantum limit apply here with even better results. Such a nonlinear interferometer will find wide applications in precision measurements.

Fiber-optic bending vector sensor based on Mach–Zehnder interferometer exploiting lateral-offset and up-taper

Abstract: A simple, compact, and highly sensitive optical fiber directional bend sensor is presented. This device consists of a lateral-offset splicing joint and an up-taper formed through excessive fusion splicing method. The lateral-offset splicing breaks the cylindrical symmetry of the fiber and defines a pair of directions along which the bending response of the Mach-Zehnder interferometer transmission spectrum is different and thus could be used for bending vector measurement. For a curvature range from -3 to 3 m(-1), the bending sensitivities at 1463.86 nm and 1548.41 nm reach 11.987 nm/m(-1) and 8.697 nm/m(-1), respectively.

Compact Polarization Beam Splitter Using an Asymmetrical Mach–Zehnder Interferometer Based on Silicon-on-Insulator Waveguides

Abstract: A compact polarization beam splitter based on an asymmetrical Mach-Zehnder interferometer (MZI) on a sub-micron silicon-on-insulator platform is demonstrated experimentally. The present MZI polarization beam splitter (PBS) is fabricated with a double-etching process and the deeply-etched region includes the MZI arms and the multimode- interference (MMI) couplers. In this way, the birefringence of the MZI arms and the power splitting ratio of the MMI coupler become insensitive to the etching depth, which makes the fabrication easier. The 2×2 MMI couplers are optimized to be polarization-insensitive and have a balanced ratio (50:50) for both polarizations. The measured extinction ratio of the fabricated MZI PBS is higher than 10 dB in the wavelength range from 1.54 to 1.58 μm.

Microwave Photonic Downconverter With High Conversion Efficiency

Abstract: A high conversion efficiency microwave photonic frequency downconverter based on an integrated dual-parallel Mach Zehnder modulator (DPMZM) and optical phase shifter configuration, is presented. This structure features the advantages of high conversion efficiency, robust operation, and ability to function over a very wide frequency range. The introduction of a novel phase shifter that is incorporated within the structure enables a high rejection of over 45 dB of the local oscillator (LO) to be achieved. The integrated DPMZM based photonic mixer also has a lower noise figure and a higher spurious free dynamic range compared to the conventional dual-series modulator based photonic mixer. Experimental results demonstrate a significant improvement of 23.7 dB in the conversion efficiency compared to the conventional dual-series modulator based photonic mixer for the same optical power into the photodetector.

Quantum interference and manipulation of entanglement in silicon wire waveguide quantum circuits

Abstract: Integrated quantum photonic waveguide circuits are a promising approach to realizing future photonic quantum technologies. Here, we present an integrated photonic quantum technology platform utilizing the silicon-on- insulator material system, where quantum interference and the manipulation of quantum states of light are demonstrated in components orders of magnitude smaller than previous implementations. Two-photon quantum interference is presented in a multi-mode interference coupler, and the manipulation of entanglement is demonstrated in a Mach-Zehnder interferometer, opening the way to an all-silicon photonic quantum technology platform.

All Single-Mode Fiber Mach–Zehnder Interferometer Based on Two Peanut-Shape Structures

Abstract: A peanut-shape fiber structure that can realize the coupling and recoupling between the fiber core mode and the cladding modes is proposed in this paper. Based on the structure, a simple and low-cost Mach-Zehnder interferometer (MZI) formed by cascading two peanut-shape structures in the single-mode fiber is demonstrated. The theory and the experimental results show that the first peanut-shape structure can couple the light energy of the core mode into the cladding modes and the second peanut-shape structure can recouple the light in the cladding modes into the core mode. A high-quality interference spectrum with a fringe visibility of about 13 dB is observed. Moreover, it has very good mechanical strength compared with the MZIs based on the tapers or the offset structures. When the interferometer length L = 22 mm, the temperature sensitivity of the device is ~ 46.8 pm/°C and the strain sensitivity is ~ 14 pm/μe. Such kind of interferometer would find potential applications in communication and sensing fields.

Polarization-dependent curvature sensor based on an in-fiber Mach-Zehnder interferometer with a difference arithmetic demodulation method

Abstract: A curvature sensor based on a polarization-dependent in-fiber Mach-Zehnder interferometer (MZI) is proposed. The MZI is fabricated by core-offset fusion splicing one section of polarization maintaining fiber (PMF) between two single mode fibers (SMFs). Two independent interference patterns corresponding to the two orthogonal polarization modes for the PMF are obtained. The couple efficiency between the core mode and the cladding mode decreased with the increasing of the bending on the MZI part. The curvature variation on the MZI part can be obtained by detecting the fringe visibility of the interference patterns. A difference arithmetic demodulation method is used to reduce the effects of the light source power fluctuations and temperature cross-sensitivity. Experimental results show that maximal sensitivity of −0.882 dB/m−1 is obtained under a measurement range of 0.1 to 0.35 m−1 for the curvature sensor. With the use of difference arithmetic demodulation method, the temperature-curvature cross-sensitivity and light source power fluctuations effects on the proposed sensor are decreased by 94% and 91%, respectively.

Ultra-low-power carrier-depletion Mach-Zehnder silicon optical modulator.

Abstract: We demonstrate a 26 Gbit/s Mach-Zehnder silicon optical modulator. The doping concentration and profile are optimized, and a modulation efficiency with the figure of merit (VπL) of 1.28 V·cm is achieved. We design an 80-nm-wide intrinsic silicon gap between the p-type and n-type doped regions to reduce the capacitance of the diode and prevent the diode from working in a slow diffusion mode. Therefore, the modulator can be driven with a small differential voltage of 0.5 V with no bias. Without the elimination of the dissipated power of the series resistors and the reflected power of the electrical signal, the maximum power consumption is 3.8 mW.

Miniaturized fiber in-line Mach-Zehnder interferometer based on inner air cavity for high-temperature sensing.

Abstract: We demonstrate a miniaturized fiber in-line Mach–Zehnder interferometer based on an inner air cavity adjacent to the fiber core for high-temperature sensing. The inner air cavity is fabricated by femtosecond laser micromachining and the fusion splicing technique. Such a device is robust and insensitive to ambient refractive index change, and has high temperature sensitivity of ∼43.2 pm/°C, up to 1000°C, and low cross sensitivity to strain.

Switchable multiwavelength fiber laser by using a compact in-fiber Mach?Zehnder interferometer

Abstract: We propose a simple and compact method for implementing an in-fiber Mach–Zehnder interferometer, which is constructed with two optical paths, propagating through the core and the ring-shaped silica cladding modes in the double-cladding fibers. Strong cladding-mode resonance across the thin inner cladding is used to excite the cladding modes. The measured spectra fringe presents high-contrast interference from cascading a pair of well-overlapped resonant spectra dips. In combination with the nonlinear polarization rotation (NPR) technique, switchable and tunable multi-channel laser outputs are experimentally demonstrated with a fluctuation of less than 0.1 dB.

A heterodyne interferometer with periodic nonlinearities smaller than ±10 pm

Abstract: The PTB developed a new optical heterodyne interferometer in the context of the European joint research project ?Nanotrace?. A new optical concept using plane-parallel plates and spatially separated input beams to minimize the periodic nonlinearities was realized. Furthermore, the interferometer has the resolution of a double-path interferometer, compensates for possible angle variations between the mirrors and the interferometer optics and offers a minimal path difference between the reference and the measurement arm. Additionally, a new heterodyne phase evaluation based on an analogue to digital converter board with embedded field programmable gate arrays was developed, providing a high-resolving capability in the single-digit picometre range. The nonlinearities were characterized by a comparison with an x-ray interferometer, over a measurement range of 2.2 periods of the optical interferometer. Assuming an error-free x-ray interferometer, the nonlinearities are considered to be the deviation of the measured displacement from a best-fit line. For the proposed interferometer, nonlinearities smaller than ?10 pm were observed without any quadrature fringe correction.

Photonic Crystal Fiber Strain Sensor Based on Modified Mach–Zehnder Interferometer

Abstract: In this paper, a novel strain sensor is proposed and demonstrated by employing a modified photonic crystal fiber (PCF)-based Mach-Zehnder interferometer, in which a collapsed region is introduced at the middle point of the PCF to improve the extinction ratio. Experimental results show that this proposed structure has a high sensitivity of 11.22 over a range of 1.28 and high-temperature stability.

Demonstration of electrooptic modulation at 2165nm using a silicon Mach-Zehnder interferometer

Abstract: We demonstrate electrooptic modulation at a wavelength of 2165nm, using a free-carrier injection-based silicon Mach-Zehnder modulator. The modulator has a Vπ∙L figure of merit of 0.12V∙mm, and an extinction ratio of −23dB. Optical modulation experiments are performed at bitrates up to 3Gbps. Our results illustrate that optical modulator design methodologies previously developed for telecom-band devices can be successfully applied to produce high-performance devices for a silicon nanophotonic mid-infrared integrated circuit platform.

Photonic crystal fiber Mach-Zehnder interferometer for refractive index sensing.

Abstract: We report on a refractive index sensor using a photonic crystal fiber (PCF) interferometer which was realized by fusion splicing a short section of PCF (Blaze Photonics, LMA-10) between two standard single mode fibers. The fully collapsed air holes of the PCF at the spice regions allow the coupling of PCF core and cladding modes that makes a Mach-Zehnder interferometer. The transmission spectrum exhibits sinusoidal interference pattern which shifts differently when the cladding/core surface of the PCF is immersed with different RI of the surrounding medium. Experimental results using wavelength-shift interrogation for sensing different concentrations of sucrose solution show that a resolution of 1.62 × 10−4–8.88 × 10−4 RIU or 1.02 × 10−4–9.04 × 10−4 RIU (sensing length for 3.50 or 5.00 cm, respectively) was achieved for refractive indices in the range of 1.333 to 1.422, suggesting that the PCF interferometer are attractive for chemical, biological, biochemical sensing with aqueous solutions, as well as for civil engineering and environmental monitoring applications.

Ultrafast All-Optical Half Adder Using Quantum-Dot Semiconductor Optical Amplifier-Based Mach-Zehnder Interferometer

Abstract: Interferometric devices have drawn a great interest in all-optical signal processing for their high-speed photonic activity. Quantum-dot semiconductor optical amplifier (QD-SOA)-based gate has added a new momentum in this field to perform all-optical logic and algebraic operations. In this paper, a new and alternative scheme for all-optical half adder using two QD-SOA-based Mach-Zehnder interferometers is theoretically investigated and demonstrated. The proposed scheme is driven by the pair of input data streams for one switch between which the Boolean xor function is to be executed to produce sum-bit. Then the output of the first switch and one of the input data are utilized to drive the second switch to produce carry-bit. The impact of the peak data power as well as of the QD-SOAs current density, small signal gain, and QD-SOAs length on the ER and Q-factor of the switching outcome are explored and assessed by means of numerical simulation. The operation of the system is demonstrated with 160 Gbit/s.

High-Sensitive Fiber-Optic Refractometer Based on a Core-Diameter-Mismatch Mach–Zehnder Interferometer

Abstract: An in-fiber Mach-Zehnder interferometer (MZI) for high-sensitive refractive index (RI) measurement is proposed and experimentally demonstrated. The sensing head is formed by a single-mode fiber (SMF) sandwiched between two short sections of thin-core fibers (TCFs), i.e., TCF-SMF-TCF MZI configuration with a length of 9 mm. A well-defined interference pattern is obtained as the result of fiber-core mismatch and core-cladding modes interference. The selected interference dip is extremely sensitive to ambient RI, providing a stable RI response with sensitivity up to 159 nm/RIU for water-based solutions close to the RI of 1.33, making it a good candidate for bio-chemical measurements.

On the design of ultrafast all-optical NOT gate using quantum-dot semiconductor optical amplifier-based Mach–Zehnder interferometer

Abstract: The feasibility of implementing an ultrafast NOT gate by means of a two-input Mach–Zehnder interferometer (MZI) that employs quantum-dot semiconductor optical amplifiers (QD-SOAs) is theoretically explored and shown. For this purpose a numerical treatment is conducted by modeling the propagation of strong pulses through a QD-SOA and the resultant change of the QD-SOA gain dynamics. This procedure allows to evaluate the impact of the critical parameters on the MZI complementary output port and find which is the most appropriate way to be selected and combined. The analysis of the simulation results reveals that with the non-data driven QD-SOA constantly held in the linear gain regime, the other QD-SOA, which is perturbed by the data to be logically inverted, must be operated in a nonlinear regime. This is defined by the drop of the specific QD-SOA gain by approximately 5.5 dB from its unsaturated value, which is caused by a data peak power being 4 dB higher than its saturation input power. Moreover, in order for the design to be complete, both QD-SOAs must be of medium length, provide a maximum modal gain such that their net gain exceeds by two orders of magnitude that at transparency, be biased at moderate current density and exhibit an electron relaxation time from the excited state to the ground state as fast as possible. Provided that these conditions are satisfied then a more than adequate extinction ratio can be obtained, which ensures that Boolean NOT logic is executed at 160 Gb/s both with logical correctness and high quality using QD-SOAs in a structurally simple, power efficient and operationally flexible version of the MZI.

On the feasibility of ultrafast all-optical NAND gate using single quantum-dot semiconductor optical amplifier-based Mach–Zehnder interferometer

Abstract: The feasibility of implementing an all-optical NAND gate for 160 Gb/s return-to-zero data pulses using a single quantum-dot semiconductor optical amplifier (QD-SOA)-based Mach–Zehnder interferometer is theoretically investigated and demonstrated. The proposed scheme exploits a modified Fredkin gate simultaneously driven by the pair of data streams between which the Boolean NAND function is to be executed, a sequence of continuous pulses and the complement of the first data input. The impact of the peak data power as well as of the QD-SOAs current density, small signal gain and electron relaxation time from the excited state to the ground state on the amplitude modulation of the switching outcome is explored and assessed by means of numerical simulation. The interpretation of the obtained results allows to specify the conditions under which the QD-SOAs must be biased to operate so that the defined performance metric becomes acceptable. By following the extracted guidelines whose satisfaction is technologically feasible and making a suitable choice for the critical parameters the NAND gate can be realized both with logical correctness and high quality at the target ultrafast data rate while being cascadable and scaleable for constructing more complex all-optical circuits.

Low-voltage, high-extinction-ratio, Mach-Zehnder silicon optical modulator for CMOS-compatible integration

Abstract: We demonstrate a carrier-depletion Mach-Zehnder silicon optical modulator, which is compatible with CMOS fabrication process and works well at a low driving voltage. This is achieved by the optimization of the coplanar waveguide electrode to reduce the electrical signal transmission loss. At the same time, the velocity and impedance matching are both considered. The 12.5 Gbit/s data transmission experiment of the fabricated device with a 2-mm-long phase shifter is performed. The driving voltages with the swing amplitudes of 1 V and 2 V and the reverse bias voltages of 0.5 V and 0.8 V are applied to the device, respectively. The corresponding extinction ratios are 7.67 and 12.79 dB.

Silicon Photonic Switches Hybrid-Integrated With CMOS Drivers

Abstract: This paper describes the design and measured performance of three different silicon photonic switches: a 2×2 switch, a 1×2 switch, and a 4×4 switch. All of the devices have been hybrid integrated with a corresponding custom 90-nm CMOS driver. The 2×2 switch is based on a wavelength-insensitive Mach-Zehnder interferometer (WIMZ) and the 1×2 is based on a two-ring resonator. The power dissipation of the 2×2 WIMZ switch was 2 mW from a 1.0-V supply, with measured transition time of 3.9 ns. The 4×4 switch, composed of six 2×2 Mach-Zehnder interferometer (MZI) switches was demonstrated to route 3×40 Gb/s WDM data with BER <; 10-12, with less than -10-dB crosstalk and 7-dB loss.

Ring-Assisted Mach–Zehnder Interferometer Silicon Modulator for Enhanced Performance

Abstract: A high-speed ring-assisted Mach-Zehnder interferometer (RAMZI) silicon modulator is reported and experimentally demonstrated. The RAMZI optical structure relaxes the optimum coupling condition of the ring without degrading the modulator performance, which therefore improves the modulator robustness against fabrication deviations and could eventually lead to an enhanced modulation bandwidth. Hence, our RAMZI silicon modulator, based on carrier depletion in a pipin active structure, exhibits a 3 dB electro-optical bandwidth of 19 GHz, enabling up to 20 Gbit/s data transmission over a RF/optical interaction length of only ~200 μm.

Mid-infrared photonic crystal waveguides in silicon.

Abstract: We demonstrate the design, fabrication and characterization of mid-infrared photonic crystal waveguides on a silicon-on-insulator platform, showing guided modes in the wavelength regime between 29 and 39 µm The characterization is performed with a proprietary intra-cavity Optical Parametric Oscillator in a free space optical setup and with a fibre coupled setup using a commercial Quantum Cascade Laser We discuss the use of an integrated Mach-Zehnder interferometer for dispersion measurements and report a measured group velocity of up to a value of ng = 12, and determine the propagation loss to be 20 dB/cm

In-line fiber Mach–Zehnder interferometer for simultaneous measurement of refractive index and temperature based on thinned fiber

Abstract: In this letter, we propose and demonstrate a novel and simple method for simultaneous measurement of refractive index and temperature using all-fiber in-line single-mode-multimode-thinned-single-mode (SMTS) fiber structures based on a small core and cladding diameters thinned fiber Mach–Zehnder interferometer (MZI). The principle of operation relies on the strong effect of the core and cladding mode interference of the thinned fiber through the employing of a multimode fiber. By measuring the shifts of the attenuation peak wavelengths of the two arbitrarily selected interference orders in the transmission spectrum, we can simultaneously measure the refractive index and temperature surrounding the sensor. Results indicate that the selected two interference orders have sensitivities of −2.85 × 10 −3 RIU with 3.49 × 10 −1 °C, and −1.12 × 10 −3 RIU with 4.07 × 10 −1 °C respectively at RI range from 1.3325 to 1.3715 and temperature range from 24 °C to 84 °C. The fabrication is easy, safe and cost effective, and includes only the fusion splicing, making the device properly attractive for physical, biological and chemical sensing in practical applications.

Spectral Interferometry-Based Chromatic Dispersion Measurement of Fibre Including the Zero-Dispersion Wavelength

Abstract: We report on a simple spectral interferometric technique for chromatic dispersion measurement of a short length optical fibre including the zero-dispersion wavelength. The method utilizes a supercontinuum source, a dispersion balanced Mach-Zehnder interferometer and a fibre under test of known length inserted in one of the interferometer arms and the other arm with adjustable path length. The method is based on resolving one spectral interferogram (spectral fringes) by a low-resolution NIR spectrometer. The fringe order versus the precise wavelength position of the interference extreme in the recorded spectral signal is fitted to the approximate function from which the chromatic dispersion is obtained. We verify the applicability of the method by measuring the chromatic dispersion of two polarization modes in a birefringent holey fibre. The measurement results are compared with those obtained by a broad spectral range (500-1600 nm) measurement method, and good agreement is confirmed.

Femtosecond laser fabricated micro Mach-Zehnder interferometer with Pd film as sensing materials for hydrogen sensing.

Abstract: In this paper, a femtosecond laser fabricated fiber inline micro Mach-Zehnder interferometer with deposited palladium film for hydrogen sensing is presented. Simulation results show that the transmission spectrum of the interferometer is critically dependent on the microcavity length and the refractive index of Pd film and a short microcavity length corresponds to a high sensitivity. The experimental results obtained in the wavelength region of 1200-1400 nm, and in the hydrogen concentration range of 0-16%, agree well with that of the simulations. The developed system has high potential in hydrogen sensing with high sensitivity.

Mach–Zehnder Interferometer Based on a Sandwich Fiber Structure for Refractive Index Measurement

Abstract: A novel refractive-index (RI) sensor based on Mach-Zehnder interferometer composed of an uncoated single-mode fiber section sandwiched between two short sections of multimode fiber is proposed and experimentally demonstrated. A clear interference spectrum is obtained and the dip wavelength shifts as a function of surrounding RI. An estimated resolution of 7.1 × 10-5 within the linear sensing range from 1.33 to 1.40 and a maximum up to 6.4 × 10-6 at indexes around 1.44 have been achieved for the cost-effective RI measurement.