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In this article, we propose and numerically demonstrate a novel dual-phase modulated time-delay signature (TDS) concealed communication system. The proposed system addresses the fatal disadvantage of conventional electro-optic chaotic systems in that TDS is vulnerable to detection. Combined with the dispersive devices ahead, which significantly expands the complexity of the signal, the scheme perturbs the transmitted data with the mutual injection of the feedforward and feedback branches in the phase, strengthening the nonlinear effect of the system considerably. In addition, the key space of the system against illegal users’ exhaustive attack within reasonable parameters reaches 1019, which is 14 orders of magnitude larger than that of the classical electro-optic system. A confidential 32 G/s OOK signal was transmitted over 100 km and successfully recovered. Numerical results demonstrate that the chaotic system can tolerate minor parameter mismatches which are controllable in practice, proving that the system can be used for secure communication.

Graphene silicon devices have attracted significant attention due to their outstanding electronic and optical properties. By electrically tuning the Fermi level of the monolayer graphene sheet, electro-optic (EO) modulators have been widely analyzed. Despite significant progress has been achieved on high-speed modulation with integrated graphene silicon waveguides, it remains challenging to realize a high modulation efficiency since the light absorption in graphene is limited. Here, we propose and experimentally demonstrate a high efficiency EO modulator using a graphene-assisted tapered silicon ring resonator, where the tapered zone is covered by a graphene/graphene capacitor. This graphene-assisted tapered zone strongly enhances the graphene-light interaction that the achieved static and dynamic modulation (1KHz) depths are up to 26 dB and 12 dB, respectively. Physical mechanism of the modulation based on this nanostructure is also discussed in detail. The proposed nanostructure provides a promising alternative method for high-performance EO modulator, which is essential for the on-chip optical communication, optical computing and optical signal processing.

A graphene-coated two-layer dielectric loaded surface plasmon polariton (GTDLSPP) rib waveguide is designed. The mode characteristics and electro-optic (EO) modulation performances of the four hybrid plasmonic modes (HPMs) in the designed waveguide are simulated by using the finite element method. The simulation results show that a 103 mm-scale propagation length and an effective mode field area of ~λ2/1333 are obtained by adjusting the bias voltage. The EO wavelength tunings are -68.6, -42.0, -49.7, and -11.1 nm/V for the HPM 1, HPM 2, HPM 3, and the peak 2 of HPM 4, which are two orders of magnitude larger than those of other EO modulation structures. For the peak 1 of the HPM 4, the EO wavelength tuning is the piecewise linear. For a 150-μm long waveguide, the modulation depths of ~98.7, ~87.9, and 99.5%, and FWHMs of ~450, ~100, and ~42 nm can be achieved for the HPM 1, HPM 2, and HPM 3. For the HPM 4, there are two peaks in the transmission spectrum. The modulation depths are ~97.3 and 75.2%, and FWHMs are ~92 and ~34 nm for the peaks 1 and 2. There is a tradeoff between the modulation depth and FWHM for different waveguide lengths. The GTDLSPP rib waveguide designed has small size, high modulation depth, broad bandwidth, and compatibility with the CMOS technology, soit has potential applications in the EO tunable devices, optical interconnects, and optical switches.

An optical phase shifter based on narrow-core hollow waveguide is proposed. The light is guided in an air core between the top and bottom reflectors made up of silicon and indium tin oxide (ITO) gratings. The proposed narrow-core hollow structure is able to guide slow light mode with a low loss of 0.2 dB/cm and a high group index of 64 in 0.8 μm thick air core. The presence of ITO enables electrically controlled phase shifting. In order to realize phase shifting, a p-i-n junction in ITO is used around the air core and in the top and bottom gratings. The geometry is optimized for enhanced interaction between the free charge carriers injected in the intrinsic region of ITO and the propagating optical mode. The proposed device shows a phase shifting of 180° for a 71-μm long device resulting from the slow-light effect.

Resonator-enhanced electro-optic (RE-EO) frequency comb generators produce broad combs by coupling an optical field to a resonator containing a phase modulator driven at a harmonic of the resonator free spectral range (FSR). Recent advances in integration technologies have opened up the possibility of fabricating low-loss, efficient, and tunable ring-based RE-EO comb generators. In this work, we analyze the properties of a canonical ring-based RE-EO comb generator and propose a new dual-ring comb generator to increase comb conversion efficiency, an especially important characteristic for comb-based optical communications systems. After a brief review of RE-EO comb generator properties in the case of resonant operation, i.e., when the optical frequency and the modulation frequency are harmonics of the resonator FSR, we analyze the effect of input optical phase noise and modulation phase noise on the resulting comb. Additionally, we show analytically that in non-resonant operation the optical frequency offset and the modulation frequency offset can be much larger than the linewidth of the resonator, increasing the tolerance to fabrication errors. Then, we develop and validate numerical models to predict the output spectrum in the presence of dispersive waveguides, which cannot be modeled analytically. Using these accurate models, we analyze a dual-ring RE-EO comb generator that uses a small coupling ring to increase the conversion efficiency to 32%, compared to the 1.3% efficiency of a single-ring RE-EO comb generator. We then analyze a point-to-point inter-data center optical link and determine that a dual-ring RE-EO comb generator can support high-capacity coherent links at 20 Tb/s per fiber. [ABSTRACT FROM AUTHOR]

An optical phase shifter based on narrow-core hollow waveguide is proposed. The light is guided in an air core between the top and bottom reflectors made up of silicon and indium tin oxide (ITO) gratings. The proposed narrow-core hollow structure is able to guide slow light mode with a low loss of 0.2 dB/cm and a high group index of 64 in 0.8 μm thick air core. The presence of ITO enables electrically controlled phase shifting. In order to realize phase shifting, a p-i-n junction in ITO is used around the air core and in the top and bottom gratings. The geometry is optimized for enhanced interaction between the free charge carriers injected in the intrinsic region of ITO and the propagating optical mode. The proposed device shows a phase shifting of 180° for a 71-μm long device resulting from the slow-light effect. [ABSTRACT FROM AUTHOR]

To enhance the functionality of the standard silicon photonics platform and to overcome its limitations, in particular for light emission, ultrafast modulation, and nonlinear applications, integration with novel materials is being investigated by several groups. In this paper, we will discuss, among others, the integration of silicon waveguides with ferroelectric materials such as lead zirconate titanate (PZT) and barium titanate (BTO), with electro–optically active polymers, with 2-D materials such as graphene and with III–V semiconductors through epitaxy. We discuss both the technology and design aspects. [ABSTRACT FROM AUTHOR]

We demonstrate 100 GBd operation of an optical transmitter module including a distributed feedback laser monolithically integrated with aMach-Zehnder modulator (DFBMZM), to the best of our knowledge for the first time. Combining high-speed optics and electronics with digital signal processing (DSP), different schemes for intensitymodulation and direct detection at 100, 200, and 300 Gbit/s are analyzed, using electrical signals from a 100 GSa/s BiCMOS DAC. Due to close-to-zero transmitter chirp, 100 Gbit/s NRZ transmission over 1.8 km and 200 Gbit/s PAM4 transmission over 1.2 km at 1550 nm with a bit error rate (BER) below the 7% overhead forward error correction (FEC) threshold (3.8 × 10-3) is achieved. At 200 Gbit/s PAM4, the DFBMZM module consumes only 0.85 pJ/bit, making it a promising device for attractive dual-lane 400 Gbit/s systems.We also achieve 300 Gbit/s PAM8 transmission over 1.2 km with a BER below the 20% overhead FEC threshold (1.9 × 10-2) by implementing advanced DSP based on a pattern-dependent lookup table tomitigate the electrical and optical device bandwidth limitations. [ABSTRACT FROM AUTHOR]

Dynamic control of the electromagnetic properties of metamaterials requires wide modulation bandwidth. Tunable metamaterials with large tunability and fast speed are thus highly desirable. Due to the small dimensions, subwavelength meta-atoms or resonant elements that constitute a metamaterial in the mid-to-near-infrared (IR) wavelength range are often not easy to be tuned at a high rate of several tens of megahertz (MHz). Here, we report on a nanoelectromechanical systems (NEMS)-based tunable IR metamaterial realized by unique embedding of nanocantilevers into complementary split ring resonators (c-SRRs) suspended over individual wells. The optical field confined in the air gap of the c-SRR is strongly influenced by electrostatically induced mechanical deflection of the nanocantilever, thus modulating the reflection spectrum of the metamaterial. With the easy-to-implement tunable meta-atom design, the IR metamaterial with 800-nm-long cantilevers provides an ultrahigh mechanical modulation frequency of 32.26 MHz for optical signal modulation at a wavelength of 2.1 \mu \textm , and is rather easy to manufacture and operate. We envision a compact, efficient, and high-speed electrooptic modulation platform in the IR region using this NEMS tunable metamaterial technology. [2017–0012] [ABSTRACT FROM PUBLISHER]

Compact lithium niobate polarization-independent electrooptic modulators using integration of polarization splitters and mode converters are presented. Experimental results show polarization-dependent loss as low as 0.04 dB can be achieved for devices fabricated on Z-cut substrates with an applied voltage of 26 V. The electrode lengths required for electrooptic modulation are 10 and 6 mm for TE and TM modes, respectively, and the total device length is only 1.6 cm. Moreover, only one diffusion step is required that greatly simplifies the fabrication process. [ABSTRACT FROM PUBLISHER]

This paper studies integrated silicon light emitter implemented in standard CMOS technologies. A new MOS-like structure utilizing deep p-well is presented, and compared with conventional planar p-n junction diode at visible wavelength and avalanching bias conditions. Prototype light emitter is fabricated in a 3- \mu \textm standard CMOS technology, and its dc, phase shift, and direct modulation frequency response with nanowatt power level are characterized, with experimental results for a reverse-bias region showing light modulation with the simulated maximum modulation frequency around $\sim 45$ GHz being reported. [ABSTRACT FROM PUBLISHER]

A digital coherent radio-over-fiber (RoF) system comprising a microwave photonic integrated circuit (MPIC) as the main building block is proposed. The multifunction MPIC circuit is analyzed to operate as a single-sideband (SSB) modulator and as an in-phase and quadrature modulator (IQM) of a baseband signal in the RoF downlink. The circuit is also analyzed in the uplink as an SSB of a 60-GHz frequency-shifted input. The performance of the MPIC is assessed through numerical simulations, computing the harmonic distortions in the SSB, as well as the error vector magnitude in the IQM and coherent RoF system. Obtained results illustrate the advantage of the proposed MPIC for heterodyne mixing by providing the upper and lower sidebands spatially located in distinct ports. Moreover, simulation results yield insights into the feasibility of the circuit as an IQM of both baseband and low-power intermediate frequency signals. A comparison of an orthogonal frequency division multiplexing system and a single carrier system employing the proposed circuit in the end-to-end transport of high data rate is presented through error vector magnitude calculations. [ABSTRACT FROM PUBLISHER]

An optical transmitter incorporating a monolithically integrated laser and a traveling wave electrode in-phase and quadrature modulator is presented. A co-designed SiGe differential driver was co-packaged for highest quality push-pull modulation. With only 0.1-dB coupling loss between the laser and the modulator, and a low modulator switching voltage the transmitter power consumption was 1.1 W, which fits the CFP4 (analog coherent optics) ACO module overall budget of 6 W. Without DSP for precompensation, FEC or equalization, 32 GBd QPSK with 3 V pp driving voltage and an error vector magnitude of <10% are presented. Operation with an optical signal-to-noise ratio larger than 14 dB is achieved before breaking the hard decision forward error correction threshold (3.8 × 10−3). [ABSTRACT FROM PUBLISHER]

We present a transmitter optical subassembly consisting of an InP-based travelling wave electrode Mach–Zehnder modulator monolithically integrated with a distributed feedback laser. At 56-Gb/s non-return-to-zero ON/OFF keying (NRZ-OOK), we achieve 3.5-km transmission before breaking the hard decision forward error correction threshold (3.8 ×10−3). 9-km transmission is achieved at 71.6-Gb/s 4-pulse–amplitude modulation (PAM4) and 5 km at 107.4 Gb/s PAM8. The modulation voltage is between 1.5 and 2 V, leading to overall power consumption of 171 mW for the NRZ-OOK case and 206 mW at PAM4 and PAM8. [ABSTRACT FROM PUBLISHER]

We propose an analytical time-domain model for microring and microdisk modulators, which considers both their electrical and optical properties. Theory of the dynamics of microring/microdisk is discussed, and general solutions to the transfer matrix representation are presented. Both static and dynamic predictions from the model are compared to measurement results to demonstrate the accuracy of our model. Static predictions and measurements are presented for power and phase responses, whereas dynamic predictions and measurements are presented for small-signal and large-signal operations. The model verifies that the chirping and modulation bandwidth of the modulators depend on the detuning state. Finally, the accuracy and scalability of several techniques employed in the model are discussed. [ABSTRACT FROM PUBLISHER]

Injection-type silicon electro-optic modulators are widely used in on chip optical interconnections due to its high modulation efficiency. However, as the modulator dimension approaches the wavelength limit, it becomes hard to improve the modulator speed by shrinking the device. A new approach to further scale down the dimension of an intrinsic device in injection-type electrooptic modulators without suffering from sub-wave-length confinement problem is proposed. The device consists of stacked PN or PiN cells connected by tunneling structures to enable current conduction. The diffusion capacitance is reduced due to the reduction of quasi-neutral region width in each device. In this paper, a detail study is given to the case of a two-cell modulator. A twofold of capacitance reduction and speed improvement are observed. Further speed improvement is expected by splitting the modulator into more cells, and the simulation approach for the tunneling structures in such an optical device is also discussed in details. [ABSTRACT FROM AUTHOR]

This study deals with an electromagnetic compatibility (EMC) problem of fiber cable in disturbing electric field. Lightwaves that emerge from the output endface of the fiber are intensity modulated, phase shifted, or modulation frequency multiplied under special conditions. In this paper, theoretical investigation of the effect of interfering electric fields on the bit error rate of digital signals propagating originally in an optical fiber is presented for the EMC evaluation. Theoretical analysis and specific numerical examples show that depending on the required EMC level, the unshielded fiber may not be immune to interference of electromagnetic fields. [ABSTRACT FROM AUTHOR]

High-resolution spectrometers are nowadays achievable in compact devices using integrated optics. The approach developed here consists in obtaining a static interferogram by means of a Fresnel reflection at the waveguide output (Lippmann interference between forward and backward beams) and then sample the fringes by periodically etching the waveguide with transverse nanogrooves, that will collect a negligible part of the flux. We present the first SWIFTS-Lippmann interferometer in the near and mid-infrared, thanks to high form factor grooves obtained by focused ion beam in lithium niobate, which opens the way to electrooptic modulation of the interferogram and thus, sampling on-chip, without any moving part. Possible applications are high-resolution spectroscopy and accurate measurement of effective refractive index of a waveguide. A measurement of the effective group refractive index of the guided mode is presented. [ABSTRACT FROM PUBLISHER]

In this paper, we present a new type of photonic interface that is capable of conveying a receive signal from an antenna while simultaneously conveying a transmit signal to the same antenna. We call this interface a TIPRx, which is short for transmit-isolating photonic receiver. We first present the TIPRx theory of operation, and then focus on the key figures of merit: the degree of suppression of the transmit signal at the receive port, which is known as the transmit-to-receive (Tx/Rx) isolation, and the bandwidth over which this isolation is achieved. For a TIPRx using a conventionally designed Mach-Zehnder modulator that has a constant interaction between the modulator electrodes and the optical waveguides, we find that the Tx/Rx isolation has a sin(x)x response. We then show that the Tx/Rx isolation can be significantly enhanced, at only a modest decrease in receive noise figure, by tapering the interaction between the modulator electrodes and optical waveguides. Finally, we report on experimental results of some TIPRx prototypes, which have achieved better than -30 dB of Tx/Rx isolation from 2.5-20 GHz and better than -40 dB from roughly 10-20 GHz. [ABSTRACT FROM PUBLISHER]

We present experimental results on magnification dependent power penalty studied with a novel resonator-based time-stretch analog-to-digital converter. Exploiting the potential of variable magnification inherent to the resonator-based concept the dispersion penalty dependency on dispersion length and magnification factor is measured and compared to numerical calculations. [ABSTRACT FROM PUBLISHER]

Interest in photonic crystal nanocavities is fueled by advances in device performance, particularly in the development of low-threshold laser sources. Effective electrical control of high-performance photonic crystal lasers has thus far remained elusive due to the complexities associated with current injection into cavities. A fabrication procedure for electrically pumping photonic crystal membrane devices using a lateral p-i-n junction has been developed and is described in this study. We have demonstrated electrically pumped lasing in our junctions with a threshold of 181 nA at 50 K—the lowest threshold ever demonstrated in an electrically pumped laser. At room temperature, we find that our devices behave as single-mode light-emitting diodes (LEDs), which when directly modulated, have an ultrafast electrical response up to 10 GHz corresponding to less than 1 fJ/bit energy operation—the lowest for any optical transmitter. In addition, we have demonstrated electrical pumping of photonic crystal nanobeam LEDs, and have built fiber taper coupled electro-optic modulators. Fiber-coupled photodetectors based on two-photon absorption are also demonstrated as well as multiply integrated components that can be independently electrically controlled. The presented electrical injection platform is a major step forward in providing practical low power and integrable devices for on-chip photonics. [ABSTRACT FROM PUBLISHER]

Lowering the operating voltage of electro-optic modulators is desirable for a variety of applications, most notably in analog photonics and digital data communication. In particular for digital systems such as CPUs, it is desirable to develop modulators that are both temperature-insensitive and compatible with typically sub-2 V CMOS electronics; however, drive voltages in silicon-based Mach–Zehnder interferometers (MZIs) currently exceed 1.8 V. Here, we show an MZI modulator based on an electro-optic polymer-clad silicon slot waveguide, with a halfwave voltage of only 0.69 V (corresponding to a 0.62 V\left(\cdot\right)cm modulation figure of merit), and a bandwidth of 500 MHz. We also show that there are paths to significantly improve both the bandwidth and drive voltage. [ABSTRACT FROM PUBLISHER]

Two different techniques were used to extend the dynamic range of analog optical links operating at microwave frequencies. The link noise figure was reduced by adjusting the bias point of an external Mach-Zehnder intensity modulator. The link distortion was reduced by linearizing the transfer function of the intensity modulator. Frequency conversion was implemented using an additional optical modulator and electrical local oscillator rather than a conventional electronic mixer. A microwave frequency signal transport link was demonstrated with a spur-free dynamic range (SFDR) of 71 dB in a 500-MHz noise bandwidth. A link with down-conversion from a microwave frequency to an intermediate frequency was demonstrated with an SFDR of 64 dB in a 500-MHz noise bandwidth. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

This paper describes advanced lithium niobate (LiNbO3) optical modulators for broadband optical communications. It includes 40-Gb/s ultralow voltage modulators, compact modulators and modulators for frequency comb generator and short pulse generation [ABSTRACT FROM PUBLISHER]

In this paper, we describe the experimental approaches to understand the microdischarge physics of an alternating current plasma display panel (ac PDP) cell. We discuss the experimental techniques to explore the major parameters to understand the operation of ac PDP such as the vacuum ultra violet (VUV) emission and wall charge variation. Regarding the discharge dynamics, the detailed VUV emission characteristics were measured and explained by the gas reaction modeling and the microdischarge characteristics during the ramp reset period were compared with the simulation result. The wall voltage and wall charge distribution were measured by laser induced fluorescence (LIF) and electro-optic modulation method. The slight increase of the wall voltage by Xe addition to pure He discharge gas was observed by LIF. And the existence of self-erasing discharge results in the drastic decrease of wall charge near discharge gap. [ABSTRACT FROM PUBLISHER]

A novel analog optical technique for multipath interference cancellation of broadband signals is proposed. Multiple optical compensation branches are utilized to replicate wireless multipath channel effects. The duplicated signal is subtracted from the total received signal to recover the signal of interest while suppressing interference. The proposed architecture achieved 40 dB of cancellation over 200 MHz and 50 dB over 10 MHz. The depth and broadband nature of the cancellation demonstrates the precision of optical components and the validity of our interference cancellation scheme. [ABSTRACT FROM PUBLISHER]

The performance of orthogonal frequency division multiplexing ultra wideband (UWB) radio signals distribution in long-reach passive optical networks (LR-PONs) using conventional chirp-less Mach Zehnder (MZ) and linearized (L) Y-fed directional couplers electro-optic modulators (EOMs) is compared. Particularly, the optimum modulation index and the corresponding minimum optical signal-to-noise ratio (OSNR) required to achieve a bit error probability of 10-12 are evaluated through numerical simulation for systems operating with single and three UWB sub-bands and different standard single-mode fiber (SSMF) distances indicated for LR-PONs. Both modulators are characterized experimentally and theoretical model parameters are adjusted to correctly describe the power and chirp characteristics of the electro-optic conversion in the simulation process. It is shown that the optimum modulation index and the tolerance to modulation index variations, considering either single or multi band UWB operation, is approximately two times higher for systems employing L-EOM than MZ-EOM. Additionally, with MZ-EOM, the required OSNR may increase considerably when the fiber length increases due to the power fading induced by fiber chromatic dispersion, achieving a penalty of almost 3 dB for systems with 100 km of SSMF and single UWB sub-band operation. Instead, with L-EOM, the required OSNR penalty (when compared with the back-to-back case) is lower for fiber lengths up to 100 km than it is for systems employing the MZ-EOM modulator due to the combined effect of the chirp generated by the modulator and the chromatic dispersion. [ABSTRACT FROM AUTHOR]