Telecom Components Research Articles

From quantum cloning to quantum key distribution with continuous variables: a review (Invited)

Quantum information processing with continuous variables is a paradigm that has attracted a growing interest over the past years, partly as a consequence of the prospects for high-rate quantum communication systems based on standard optical telecommunication components. In this overview article, we introduce the concept of quantum continuous variables in optics and then turn to the fundamental impossibility of cloning continuous-variable light states, a result that lies at the heart of quantum key distribution. Then we present state-of-the-art quantum key distribution systems relying on continuous variables, focusing mainly on the protocols using Gaussian-modulated coherent light states and emphasizing the current experimental demonstration of these systems. Finally, we briefly review recent security proofs of these cryptographic protocols.

Neither Fish Nor Fowl: New Strategies for Selective Regulation of Information Services

This paper will examine whether and how the FCC can support a campaign to deregulate or treat as outside its jurisdiction many next generation network services while at the same time imposing financially burdensome requirements and regulatory duties on some ventures that fit within the information service provider classification. The FCC has erected a regime largely predisposed to treat next generation services as information services free of interconnection, unbundling, tariffing, line sharing and other requirements Title II of the Communications requires the FCC to impose. To support its deregulatory mission the FCC has found ways to subordinate the telecommunications components in a service that blends telecommunications transmission of bits with information services. For example, in reclassifying DSL from a telecommunications service to an information service the FCC combined the need for deregulatory parity with a new finding that the once stand alone telecommunications service characteristic of DSL had become inextricably integrated with information services with the latter predominating. Notwithstanding the urge to deregulate, either on rational or doctrinal grounds, the Commission has had to confront the fact that competition alone will not ensure the achievement of all Congressionally mandated, or FCC identified public interest objectives. Even with actual or prospective competition, the wholesale abdication of regulatory oversight leaves the FCC in a precarious legal position, if and when it needs to reassert regulatory oversight as has occurred on four separate occasions for VoIP services and once for all types of broadband Internet access information services.

Evaluation of glued-diaphragm fibre optic pressure sensors in a shock tube

Glued-diaphragm fibre optic pressure sensors that utilize standard telecommunications components which are based on Fabry–Perot interferometry are appealing in a number of respects. Principally, they have high spatial and temporal resolution and are low in cost. These features potentially make them well suited to operation in extreme environments produced in short-duration high-enthalpy wind tunnel facilities where spatial and temporal resolution are essential, but attrition rates for sensors are typically very high. The sensors we consider utilize a zirconia ferrule substrate and a thin copper foil which are bonded together using an adhesive. The sensors show a fast response and can measure fluctuations with a frequency up to 250 kHz. The sensors also have a high spatial resolution on the order of 0.1 mm. However, with the interrogation and calibration processes adopted in this work, apparent errors of up to 30% of the maximum pressure have been observed. Such errors are primarily caused by mechanical hysteresis and adhesive viscoelasticity. If a dynamic calibration is adopted, the maximum measurement error can be limited to about 10% of the maximum pressure. However, a better approach is to eliminate the adhesive from the construction process or design the diaphragm and substrate in a way that does not require the adhesive to carry a significant fraction of the mechanical loading.

Focus on photonics and imaging

Focus on photonics and imaging

The influence of pressure during solidification of high pressure die cast aluminium telecommunications components

The effects of process variables on the quality of high-pressure die cast components was determined with the aid of in-cavity pressure sensors. In particular, the effects of set intensification pressure, delay time, and casting velocity have been investigated. The in-cavity pressure sensor has been used to determine how conditions within the die-cavity are related to the process parameters regulated by the die casting machine, and in turn the effect of variations in these parameters on the integrity of the final part. Porosity was found to decrease with increasing intensification pressure and increase with increasing casting velocity. The delay time before the application of the intensification pressure was not observed to have a significant effect on porosity levels.

Nortricarbocyanine dyes as suitable long wavelength pH indicators for chemical sensing

New norcyanine dyes were characterised for their use as long wavelength chromoionophores in optodes. Different membrane compositions were formulated for pH determination in water and their response in terms of sensitivity, linear range, response time and reversibility was examined with the aim to apply them in planar optochemical sensors. Their absorbance maxima are located in the NIR region (785–830 nm), which is very appropriate for applications using common low cost telecommunication components. The characterised optodes showed good analytical features. Hence, fully reversible, reproducible, fast, and sensitive bulk optodes were obtained. The photostability of dyes in the plasticised matrices and their tendency to leach from the membrane phase were also evaluated at different conditions.

Integrable optical-fiber source of polarization-entangled photon pairs in the telecom band

We demonstrate an optical-fiber-based source of polarization-entangled photon pairs with improved quality and efficiency, which has been integrated with off-the-shelf telecom components and is, therefore, well suited for quantum communication applications in the 1550-nm telecom band. Polarization entanglement is produced by simultaneously pumping a loop of standard dispersion-shifted fiber with two orthogonally polarized pump pulses, one propagating in the clockwise and the other in the counterclockwise direction. We characterize this source by investigating two-photon interference between the generated signal-idler photon pairs under various conditions. The experimental parameters are carefully optimized to maximize the generated photon-pair correlation and to minimize contamination of the entangled photon pairs from extraneously scattered background photons that are produced by the pump pulses for two reasons: (i) spontaneous Raman scattering causes uncorrelated photons to be emitted in the signal and idler bands and (ii) broadening of the pump-pulse spectrum due to self-phase modulation causes pump photons to leak into the signal and idler bands. We obtain two-photon interference with visibility $>90%$ without subtracting counts caused by the background photons (only dark counts of the detectors are subtracted), when the mean photon number in the signal (idler) channel is about 0.02/pulse, while no interference is observed in direct detection of either the signal or idler photons.

Networkcentric healthcare operations: the telecommunications structure

Healthcare globally is failing to meet its objectives of delivering appropriate medical attention to patients. We suggest that by adopting a networkcentric approach healthcare operations and delivery will be dramatically enhanced with the ultimate beneficiary being the patient. Underlying the networkcentric doctrine of healthcare is the use of IC2T. As discussed in the paper, all the essential network and telecommunication components already exist. We must now focus on how to combine them so that network centric healthcare can in fact become a reality.

Controlling excess noise in fiber-optics continuous-variable quantum key distribution

We describe a continuous-variable coherent-states quantum-key distribution system working at $1550\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$, and entirely made of standard fiber optics and telecommunications components, such as integrated-optics modulators, couplers and fast InGaAs photodiodes. The setup is composed of an emitter randomly modulating a coherent state in the complex plane with a doubly Gaussian distribution, and a receiver based on a shot-noise limited time-resolved homodyne detector. By using a reverse reconciliation protocol, the device can transfer a raw key rate up to $1\phantom{\rule{0.3em}{0ex}}\mathrm{Mbit}∕\mathrm{s}$, with a proven security against Gaussian or non-Gaussian attacks. The dependence of the secret information rate of the present fiber setup is studied as a function of the line transmission and excess noise.

A frequency-doubled laser system producing ns pulses for rubidium manipulation

We have constructed a pulsed laser system for the manipulation of cold 87Rb atoms. The system combines optical telecommunications components and frequency doubling to generate light at 780 nm. Using a fast, fibre-coupled intensity modulator, we sliced output from a continuous laser diode into pulses with a length between 1.3 and 6.1 ns and a repetition frequency of 5 MHz. These pulses are amplified using an erbium-doped fibre amplifier, and frequency-doubled in a periodically poled lithium niobate crystal, yielding a peak power up to 12 W. Using the resulting light at 780 nm, we demonstrate Rabi oscillations on the F=2,mF=+2↔F′=3, m′ F=+3-transition of a single 87Rb atom.

Chaos-based communications at high bit rates using commercial fibre-optic links

Chaotic signals have been proposed as broadband information carriers with the potential of providing a high level of robustness and privacy in data transmission. Laboratory demonstrations of chaos-based optical communications have already shown the potential of this technology, but a field experiment using commercial optical networks has not been undertaken so far. Here we demonstrate high-speed long-distance communication based on chaos synchronization over a commercial fibre-optic channel. An optical carrier wave generated by a chaotic laser is used to encode a message for transmission over 120 km of optical fibre in the metropolitan area network of Athens, Greece. The message is decoded using an appropriate second laser which, by synchronizing with the chaotic carrier, allows for the separation of the carrier and the message. Transmission rates in the gigabit per second range are achieved, with corresponding bit-error rates below 10(-7). The system uses matched pairs of semiconductor lasers as chaotic emitters and receivers, and off-the-shelf fibre-optic telecommunication components. Our results show that information can be transmitted at high bit rates using deterministic chaos in a manner that is robust to perturbations and channel disturbances unavoidable under real-world conditions.

Tuneable Femtosecond Fiber Lasers – Ultra-short laser pulses from green to IR

There is a wealth of applications for ultra-short, pulsed lasers in many areas of science and technology, material processing and also in medicine. However, their widespread use is severely hampered by the size and cost of these lasers, both in terms of acquisition and maintenance. This implies that there could be a large market for affordable, turn-key femtosecond lasers (1 fs = 10–15 s). A technical solution is now possible with a new generation of fiber lasers, which are made of standard telecom components. These fiber lasers are compact (A4 size) and scalable in cost and performance. They can also be produced in large volumes. They render water cooling methods and large power supplies obsolete.

Optoelectronic phase chaos generator for secure communication

An optoelectronic chaos phase generator is reported, which involves conventional integrated optics and optical telecommunication components. Fast chaotic behavior of the optical phase with a constant optical power is experimentally demonstrated over multi-GHz bandwidth. Application to secure optical communications using chaos is discussed, as well as generation of high-purity rf oscillations, depending on the parameter settings. © 2005 Optical Society of America

Manufacture of high pressure die-cast radio frequency filter bodies

The manufacture of a radio frequency filter box using high pressure die casting (HPDC) is compared to the traditional high speed machining route. This paper describes an industrial exercise that concluded HPDC to be an economical and appropriate method to produce larger volumes of thin-walled telecommunications components. Modifications to the component design were made to make the component suitable for the HPDC process. Development of the die design through simulation modelling is described. The wrought alloy was replaced by near-eutectic Al–Si die casting alloy that was found to give better temperature stability performance. Apart from the economic benefits, HPDC was found to give lower filter efficiency losses through better surface finish. The effects of HPDC process variables, such as intensification pressure and injection piston velocity, on component quality, particularly porosity levels, were investigated. The pressure was analysed in terms of HPDC machine set pressure and the pressure measured in the die cavity by pressure sensors. Porosity was found to decrease with increased pressure and slightly increase with higher casting velocities.

Development of an All-Fiber Coherent Laser Radar for Precision Range and Velocity Measurements

AbstractAn all-fiber coherent laser radar system capable of high-resolution range and line of sight velocity measurements is under development with a goal to aid NASA's new Space Exploration initiative for manned and robotic missions to the Moon and Mars. Precision range and velocity data are key parameters to navigating planetary landing pods to the pre-selected site and achieving autonomous safe soft-landing. By employing a combination of optical heterodyne and linear frequency modulation techniques [1-3] and utilizing state-of-the-art fiber optic technologies, highly efficient, compact and reliable laser radar suitable for operation in a space environment is being developed.The all-fiber coherent laser radar has several important advantages over more conventional pulsed laser altimeters or range finders. One of the advantages of the coherent laser radar is its ability to directly measure the platform velocity by extracting the Doppler shift generated by the platform motion. The Doppler velocity measurement is about two orders of magnitude more accurate than the velocity estimates obtained by laser altimeters using the rate of change in range [4]. Another advantage is continuous-wave operation that allows the use of highly efficient and reliable commercial off-the-shelf fiber optic telecommunication components. This paper will describe the design and operation of this laser radar sensor and discuss its projected performance. A laboratory breadboard system has already been developed as a step toward a flight prototype. The experimental data representing the potentials of this laser radar system will be reported.

Rapid measurement of cavity ringdown absorption spectra with a swept-frequency laser

A novel cavity ringdown spectrometer, incorporating a miniature continuous-wave swept-frequency laser that is widely tunable, requires less than 1 s to record wide-ranging absorption spectra with high sensitivity in a single rapid sweep of the laser frequency. The free spectral range of the ringdown cavity defines a sampling grid to measure absorbance-dependent ringdown times at successive cavity-resonance frequencies. The spectrometer has a single-ended transmitter-receiver configuration based on retro-reflected optical-heterodyne detection and exploiting fibre-optical telecommunications components. This swept-frequency approach to cavity ringdown spectroscopy yields a simple, low-cost, compact, rugged, versatile instrument for efficient sensing of gases. The performance of the spectrometer is demonstrated by measuring weak near-infrared rovibrational spectra of carbon dioxide gas within the 1.5–1.6 μm wavelength range.

Insertion loss comparison of microcollimators used to propagate light in and out of single-mode fibers

Most telecom components use lenses to collimate the beam emerging from a single-mode fiber and again, after some manipulation of the beam, to focus the beam back into an output fiber. In response to the drive for smaller components, collimator lenses have shrunk and a number of new microcollimator types been introduced. Several of the newer collimator types involve lenses that are fused to the fiber. Optical software was used to model six different types of microcollimators divided into three different size categories. Because not all of the six types were applicable in all three of the size categories, a total of eleven different collimator systems were modeled. A collimator system consists of an input collimator and an identical output collimator. Each collimator includes a single-mode fiber and a collimating lens. In order to achieve equivalence, all of the collimators in the same size category produce an intermediate waist with the same mode field diameter and distance from the lens surface to the intermediate waist. An algorithm is presented to determine the necessary physical parameters (lengths and radii) for a collimator to produce the appropriate beam criteria for a given size category. Once the physical parameters for the collimator systems were determined, all of the collimator systems were examined for insertion loss in their ideal configuration as well as in the presence of fabrication and alignment errors. All of the insertion loss analyses were performed using coherent field propagation starting from the fundamental fiber mode of the input fiber, through the collimating lenses, and finishing with the calculation of the overlap integral of the field inside the output fiber with the fundamental fiber mode. No thin lens or paraxial propagation assumptions are made...The results indicate that the collimator types involving lenses that are fused to the fiber are less sensitive to longitudinal fiber and collimator shifts than the components with the fiber and lens not in direct contact.

Cavity ringdown strain gauge.

Biconical tapered single-mode fiber, which is common in many telecommunications components, offers an alternative sensor to typical optical fiber strain gauges that are susceptible to temperature and pressure effects and require expensive and sophisticated signal acquisition systems. Cavity ringdown spectroscopy, a technique commonly applied to high-sensitivity chemical analysis, offers detection sensitivity advantages that can be used to improve strain measurement with biconical tapers. Combining these two technologies in a spatially extended resonator, we demonstrate a minimum detectable change in ringdown time of 0.08%, corresponding to a minimum detectable displacement of 4.8 nm, and a sensitivity to strain as small as 79 n epsilon/square root(Hz) over a 5-mm taper length.

박막 광학 필터 디바이스의 패키징시 솔더 조인트의 피로 신뢰성 해석

Plastic and creep deformations of solder joints during thermal cycling are the main factors of misalignments and power losses in optical telecommunication components. Furthermore, the increased mismatch between solder joint-areas may cause severe failure in the components. Darveaux's creep model was implemented into a finite element program (ABAQUS) to simulate creep response of solder. Based on the finite element results, thermal fatigue reliability was predicted by using various fatigue life prediction models. Also, the effects of ramp conditions, dwelling time. and solder joint-embedding materials on the reliability were investigated under the thermal cycling conditions of the Telcordia schedule (-40~75.C).<br/>

Packaging Multiple Active and Passive Elements in a Hybrid Optical Platform

The commercial market for telecom components has had an increasing demand for laser transmitter packages with higher functionality and smaller form factor. These higher levels of integration require an optical bench platform that can incorporate multiple active and passive elements and withstand stringent reliability requirements. Furthermore, the laser package must be compatible with high-volume manufacturing. We have developed an optical platform for building hybrid (multiple active elements) optoelectronic devices in a stable, hermetically sealed package. Two novel approaches to optical packaging have been developed: a localized laser soldering process and a flexure-based lens mount with large dynamic range. We present the optical bench and component design and the results of engineering reliability testing of the assembled package.