High bandwidth optical links over multimode fibre

A Fabry-Perot laser source operating at 1300 nm was modulated at 2.5 Gb/s with a 27-1 pseudo-random bit sequence. Three techniques were examined for increasing the bandwidth of optical links using multimode fiber (MMF). With an offset launch of 14 μm, the eye remained open after the 2 km link of 50 μm core MMF containing seven connectors and three splices. An approximate four-fold bandwidth improvement was obtained using the offset launch with a bandwidth-length product of 7.5 Gb/s.km and a bit error rate below 10-10. The bandwidth enhancement was stable against environmental influences on the fiber link, such as mechanical agitation. Detailed simulations demonstrated that the technique allows enhanced operating bandwidths in over 99% of existing link.

10-Gbits/s all-optical 3R regeneration and format conversion using a gain-switched DFB laser

A strain-compensated multiple quantum well device is used as a DFB laser, this has been optimized for low jitter gain switched operation at 10 GHz. The signal is transmitted down 80 km of standard fiber then amplified, filtered and polarization controlled before being injected into a DFB laser. The purpose of this regeneration process is to gain switch the DFB with the extracted clock signal in order to retime the converted signal. This process also simultaneously converts the input NRZ format to an output RZ data to format and results in a signal whose optical power and extinction ratio are considerably improved by the regeneration process.

Low-cost, scalable optical packet switching networks with multi-wavelength labels

We propose a self-forwarding packet-switched optical network with bit-parallel multi-wavelength labels. We experimentally demonstrate transmission of variable-length optical packets over 80 km of fiber and switching over a 1×4 multistage switch with two stages. © 2007 Optical Society of America.

Design of carbon nanotubes based microwave applications employing mechanical resonance analysis

Carbon nanotubes (CNTs) have good mechanical properties and unique structural, electronic, thermal, and optical characteristics. In this work, we present the results of our investigations of a resonator device based on embedded vertical CNT arrays. The device's design is based on the mechanical resonance of the tubes. CoventorWare FEA tools have been used to simulate the mechanical resonance frequencies of the vertical nanotubes arrays integrated on a silicon substrate. ©2008 IEEE.

Application of the fractional Fourier transform to the design of LCOS based optical interconnects and fiber switches

It is shown that reflective liquid crystal on silicon (LCOS) spatial light modulator (SLM) based interconnects or fiber switches that use defocus to reduce crosstalk can be evaluated and optimized using a fractional Fourier transform if certain optical symmetry conditions are met. Theoretically the maximum allowable linear hologram phase error compared to a Fourier switch is increased by a factor of six before the target crosstalk for telecom applications of -40 dB is exceeded. A Gerchberg-Saxton algorithm incorporating a fractional Fourier transform modified for use with a reflective LCOS SLM is used to optimize multi-casting holograms in a prototype telecom switch. Experiments are in close agreement to predicted performance. © 2012 Optical Society of America.

Ferroelectric liquid crystal mixture integrated into optical waveguides

We report an on-chip integrated ferroelectric liquid crystal (FLC) waveguide structure suitable for telecommunication applications. Single gaps with different widths of 5, 10, and 20 μ m inside individual silica waveguides were filled with an FLC mixture. The waveguide devices operate as a binary switch or an attenuator in a temperature range from 30 °C to 60 °C. The FLC mixture exhibited a good alignment quality in these gaps without alignment layers. A good extinction ratio of up to 33.9 dB and a low insertion loss of <4.3 dB at λ = 1550 nm were observed. Switching times of <100 μs were obtained for the low electric fields applied in this experiment. © 2012 IEEE.

Comparisons between 28 Gb/s NRZ, PAM, CAP and optical OFDM systems for datacommunication applications

Theoretical investigations have been performed to analyze and compare the link power budget and power dissipation of a 28 Gb/s datacommunication system for data center switch scenarios using NRZ, PAM-4, CAP-16 and 16-QAM-OFDM modulation schemes. © 2012 IEEE.

Coexistence of high-bit-rate quantum key distribution and data on optical fiber

Quantum key distribution (QKD) uniquely allows distribution of cryptographic keys with security verified by quantum mechanical limits. Both protocol execution and subsequent applications require the assistance of classical data communication channels. While using separate fibers is one option, it is economically more viable if data and quantum signals are simultaneously transmitted through a single fiber. However, noise-photon contamination arising from the intense data signal has severely restricted both the QKD distances and secure key rates. Here, we exploit a novel temporal-filtering effect for noise-photon rejection. This allows high-bit-rate QKD over fibers up to 90 km in length and populated with error-free bidirectional Gb/s data communications. With high-bit rate and range sufficient for important information infrastructures, such as smart cities and 10 Gbit Ethernet, QKD is a significant step closer towards wide-scale deployment in fiber networks.

A non-intrusive in situ method of optical beam profiling in LCOS-based optical fiber switches

This paper proposed a non-intrusive method of measuring the optical beam profile at the surface of the liquid crystal on silicon (LCOS) device in an optical fiber switch. This method is based on blazed grating and can be employed in situ (on-line) for two-dimensional beam profiling in the LCOS-based optical fiber switches without introducing additional components or rearranging the system. The measured beam radius was in excellent agreement with that measured by the knife-edge technique. © 2013 Elsevier Ltd.

A numerical simulation of AFR switch of SI engines

A novel mechanical method of achieving a rapid switch between stoichiometric and lean conditions for SI engines is explored. Two and three throttle configurations, a switch strategy which employs a standard intake manifold and an assembly of pipes and throttle(s), are investigated numerically by using a one-dimensional engine simulation program based on the method of characteristics. The results indicate that it is possible to achieve rapid AFR switch without a torque jump, i.e. unperceptible to the driver. © 1998 Society of Automotive Engineers, Inc.

A printable optical time-temperature integrator based on shape memory in a chiral nematic polymer network

An optical and irreversible temperature sensor (e.g., a time-temperature integrator) is reported based on a mechanically embossed chiral-nematic polymer network. The polymer consists of a chemical and a physical (hydrogen-bonded) network and has a reflection band in the visible wavelength range. The sensors are produced by mechanical embossing at elevated temperatures. A relative large compressive deformation (up to 10%) is obtained inducing a shift to shorter wavelength of the reflection band (>30 nm). After embossing, a temperature sensor is obtained that exhibits an irreversible optical response. A permanent color shift to longer wavelengths (red) is observed upon heating of the polymer material to temperatures above the glass transition temperature. It is illustrated that the observed permanent color shift is related to shape memory in the polymer material. The films can be printed on a foil, thus showing that these sensors are potentially interesting as time-temperature integrators for applications in food and pharmaceutical products. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Scalable, low-energy hybrid photonic space switch

A scalable monolithically integrated photonic space switch is proposed which uses a combination of Mach-Zehnder modulators and semiconductor optical amplifiers (SOAs) for improved crosstalk performance and reduced switch loss. This architecture enables the design of high-capacity, high-speed, large-port count, low-energy switches. Extremely low crosstalk of better than -50 dB can be achieved using a 2 × 2 dilated hybrid switch module. A 'building block' approach is applied to make large port count optical switches possible. Detailed physical layer multiwavelength simulations are used to investigate the viability of a 64 × 64 port switch. Optical signal degradation is estimated as a function of switch size and waveguide induced crosstalk. A comparison between hybrid and SOA switching fabrics highlights the power-efficient, high-performance nature of the hybrid switch design, which consumes less than one-third of the energy of an equivalent SOA-based switch. The significantly reduced impairments resulting from this switch design enable scaling of the port count, compared to conventional SOA-based switches. © 1983-2012 IEEE.

Optical trapping and manipulation of nanostructures

Optical trapping and manipulation of micrometre-sized particles was first reported in 1970. Since then, it has been successfully implemented in two size ranges: the subnanometre scale, where light-matter mechanical coupling enables cooling of atoms, ions and molecules, and the micrometre scale, where the momentum transfer resulting from light scattering allows manipulation of microscopic objects such as cells. But it has been difficult to apply these techniques to the intermediate-nanoscale-range that includes structures such as quantum dots, nanowires, nanotubes, graphene and two-dimensional crystals, all of crucial importance for nanomaterials-based applications. Recently, however, several new approaches have been developed and demonstrated for trapping plasmonic nanoparticles, semiconductor nanowires and carbon nanostructures. Here we review the state-of-the-art in optical trapping at the nanoscale, with an emphasis on some of the most promising advances, such as controlled manipulation and assembly of individual and multiple nanostructures, force measurement with femtonewton resolution, and biosensors.

Electro-optic integration of liquid crystal cladding switch with multimode passive polymer waveguides on PCB

Optical switching functionality is demonstrated in PCB integrated multimode passive polymer waveguides using a localised liquid-crystal cladding structure. Waveguide switching contrast of 15 dB is achieved with only 0.5 dB of on-state excess loss. © 2009 OSA.