Optical Fiber Telecommunication Systems Research Articles

Periodic and quasi-periodic compensation strategies of extreme outages caused by polarization mode dispersion and amplifier noise

Effect of birefringent disorder on the Bit Error Rate (BER) in an optical fiber telecommunication system subject to amplifier noise may lead to extreme outages, related to anomalously large values of BER. We analyze the Probability Distribution Function (PDF) of BER for various strategies of Polarization Mode Dispersion (PMD) compensation. A compensation method is proposed that is capable of more efficient extreme outages suppression, which leads to substantial improvement of the fiber system performance.

Fixed focus: Adjustable lenses from liquid droplets

These lenses may cut the price of the assemblies of laser chips and lightmanipulating components in fiberoptic telecommunications systems, says chemist Shu Yang, a member of the Lucent team. Currently, installing such assemblies requires a technician to use an expensive micromanipulator to make time-consuming alignments of tiny, hard lenses. The droplet strategy may offer an easy-to-tweak alternative, Yang says.

Optics and Information Technology

How optical scientists work and what they can make has changed profoundly with the information technology revolution of the past 50 years. The software packages developed to aid in the traditional activities of lens and coating design are now several generations old. New programs capable of tackling increasingly sophisticated optical problems are emerging: examples include optimization packages for non-imaging optics in illumination and programs to model the complex physics of multichannel, multiwavelength, fiber-optic telecommunications systems.

Low-loss polymeric materials for passive waveguide components in fiber optical telecommunication

With fiber optical telecommunication systems penetrating into metropolitan and access networks, planar waveguide technology is increasingly being considered a solution to the bottleneck of cost-effective manufacture of passive components. Being recognized for their high thermo-optical coefficients, ease of fabrication, cost-effectiveness, and compatibility with other materials, polymers as a platform technology for waveguide devices are gaining more and more commercial acceptance. Fully exploiting the potentials of the polymeric materials demands comprehensive understanding of both the specific device applications and various polymer systems. The right choice of materials is often the key to the success of component development. Unfortunately, since extensive study of polymeric materials and devices operating at 1.55 μm began just recently, few ideal materials have so far been made commercially available. From the polymer chemistry point of view, it is possible to tailor the materials to meet specific and strict requirements for optical waveguide devices. This is a review of the most promising fluorinated polymers and silicone resins and their demonstrated device applications. The paper is designed to provide a guide to both polymer scientists who want to develop novel high-performance materials for waveguide applications, and optical engineers who need to gain insight into the materials.

Nonlinear interactions in wavelength-multiplexed optical fibre telecommunication systems

This paper reports on an investigation of optical crosstalk caused by nonlinear interactions in short- and long-haul wavelength division multiplexion transmission systems called inter-domain interfaces. These investigations are based on numerical simulations of multichannel optical transmission systems, using specialist software: Gigabit Optical Line Designer v.2.0 from Virtual Photonics. The nonlinear phenomena in fibres that have to be taken into account include four-wave mixing, self-phase modulation, cross-phase modulation, stimulated Raman scattering, stimulated Brillouin scattering and nonlinear interactions in erbium-doped fibre amplifiers.

High Speed Resonant-Cavity InGaAs/InAlAs Avalanche Photodiodes

The evolution of long-haul optical fiber telecommunications systems to bit rates greater than 10 GB/s has created a need for avalanche photodiodes (APDs) with higher bandwidths and higher gain-bandwidth products than are currently available. It is also desirable to maintain good quantum efficiency and low excess noise. At present, the best performance (f3dB ~ 15 GHz at low gain and gain-bandwidth product ~ 150 GHz) has been achieved by AlInAs/InGaAs(P) multiple quantum well (MQW) APDs. In this paper we report a resonant-cavity InAlAs/InGaAs APD that operates near 1.55 μm. These APDs have achieved very low noise (k equivalent to 0.18) as a result of the very thin multiplication regions that were utilized. The low noise is explained in terms of a new model that accounts for the non-local nature of impact ionization. A unity-gain bandwith of 24 GHz and a gain-bandwidth-product of 290 GHz were achieved.

HIGH SPEED RESONANT-CAVITY InGaAs/InAlAs AVALANCHE PHOTODIODES

The evolution of long-haul optical fiber telecommunications systems to bit rates greater than 10 GB/s has created a need for avalanche photodiodes (APDs) with higher bandwidths and higher gain-bandwidth products than are currently available. It is also desirable to maintain good quantum efficiency and low excess noise. At present, the best performance (f3dB ~ 15 GHz at low gain and gain-bandwidth product ~ 150 GHz) has been achieved by AlInAs/InGaAs(P) multiple quantum well (MQW) APDs. In this paper we report a resonant-cavity InAlAs/InGaAs APD that operates near 1.55 μm. These APDs have achieved very low noise (k equivalent to 0.18) as a result of the very thin multiplication regions that were utilized. The low noise is explained in terms of a new model that accounts for the non-local nature of impact ionization. A unity-gain bandwith of 24 GHz and a gain-bandwidth-product of 290 GHz were achieved.

Theoretical investigation of threshold properties of purely and partly gain-coupled distributed-feedback semiconductor lasers with stepwise constant coupling coefficients

A basic analysis of complex-coupled distributed-feedback semiconductor lasers with stepwise constant coupling coefficients κ is derived. Solving coupled-wave equations at threshold reveals that the longitudinal distribution of κ as well as the relative amount of index and gain coupling plays a decisive role in the modal and spatial (internal fields) properties of complex-coupled structures. The standing-wave effect, extended to multisection devices, and the concept of apparent absorption induced by spatially dependent κ can explain the discrepancies between uniformly and nonuniformly complex-coupled structures. The complex-coupling profile is also discussed with respect to its influence on spatial hole burning and threshold gain margin, the usual criteria for optimizing sources in optical fiber telecommunication systems.

The packaging of large spot-size optoelectronic devices

The demand for more bandwidth to the home is starting to drive optical fiber telecommunication systems further into the access network. For fiber systems to reach directly into customer premises the cost of the optoelectronic receivers and transmitters have to be significantly reduced. The major cost of producing these components is the active alignment step to couple an optical fiber to the semiconductor device. This paper details how by matching the output radiation pattern of the device to the input radiation pattern of an optical fiber low-cost passive alignments processes can be utilized.

Bandgap engineering of electro-optical modulators and switches

Bandgap engineering of advanced optoelectronic devices is a natural and desired outcome of the basic studies of semiconductor quantum well structures. This is first illustrated with the problem of the polarization sensitivity of guided-wave devices. It is shown that tensile-strained quantum wells near the light- and heavy-hole degeneracy provide almost equal absorption spectra and nearly identical electroabsorption curves in the TE and TM modes, which are necessary features for on-line applications in optical fibre telecommunication systems. In the second part, the ultimate performances of photovoltaic bistable devices based on the Wannier - Stark effect are discussed. It is shown that the commutation energy of today's silicon MOSFETs can be challenged by usable optical devices.

On the design of polarization-insensitive optoelectronic devices

We examine theoretically the problem of the polarization dependence of guided-wave devices. We show that tensile-strained quantum wells near the light-and heavy-hole degeneracy provide almost equal absorption spectra and nearly identical electroabsorption curves in the TE and TM modes, which are necessary features for on-line applications such as signal amplification and pulse reshaping in optical fibre telecommunication systems.

Some exact algebraic expressions for the reliability of multipath switching networks

Abstract Some optical-fiber telecommunication systems have multipath switching designs that do not lend themselves to reliability evaluation using conventional methods for series and parallel components. Efficient and exact numerical procedures for reliability evaluation of such systems are described in previous publications of the authors but no exact algebraic results have been reported. Exact algebraic expressions for reliabilities of multipath systems are generally intractable, except possibly by means of computerized symbol manipulation. In this article, exact algebraic expressions for the reliabilities of several simple multipath systems are derived. The results are useful in their own right but also for the theoretical insight that they provide. In spite of the difficulty posed by their initial derivation, once discovered, the expressions have a surprising simplicity. The derivation is based on an eigensystem analysis of the Markov transition matrices involved in the reliability evaluation.

Principles of modern optical systems

Theoretical and applications aspects of optoelectronics technology are examined in an introduction for engineering students and practicing engineers. Chapters are devoted to the fundamental principles of optics and optoelectronics, optical coherence and polarization, semiconductor light sources, optical fibers, nonlinear effects in optical fibers, optical-fiber cables and connectors, and fiber-optic components. Consideration is given to integrated optics, fiber-optic telecommunication systems, fiber sensors and sensor networks, optical remote sensing, optical information processing, guided-wave signal processing, and optical-disk storage systems.

Photodétectors for 1.3 μln - 1.55 μnl fiber optic transmissions: State of the art

In the optical fiber telecommunication systems, the emission and reception modules contain optoelectronic components such as laser diodes and photodiodes. Beside the laser whose task and complexity are obvious, the photodiode, the mechanism of which is quite straightforward, becomes a sophisticated device when optimized for 1.3–1.55 µm fiber window. For photodetection, the photodiode is always associated to a preamplifier obtained from a transistor. For a given link, the performances of the receiver straightly depend on those of the photodiode and of the transistor. Different types of photodetectors are suitable for 1.3 µm and 1.55 µm transmissions. This paper surveys the different semiconductors materials and device structures encountered nowadays, pointing out the respective merits of each solution. Comparisons between photoreceivers outline the importance of matching the photodiode to the transistor, whether dealing with hybrid or monolithic circuits.

CMT: The material for fiber optical communication devices

Over many years, Hg 1 - x Cd x Te ternary alloys have been widely investigated, principally in the mercury-rich composition range, mainly for far infrared military applications. However, recent developments of fiber optical telecommunication systems have led to a great interest in near infrared transmission links at 1.3 and 1.55 μm or higher. Cadmium mercury telluride (CMT) alloys in the cadmium-rich composition range have proved to be good candidates for the detection of these wavelengths. Besides excellent basic characteristics, the resonance between spin-orbit coupling and bandgap values makes this material exceptionally attractive for the manufacture of low noise avalanche photodiodes. Recent metallurgical progress has enabled us to grow high quality ingots up to 40 mm diameter using the Travelling Heater Method with a homogeneity better than 0.2% for x values around 0.7. A highly reproducible planar technology has been developed to manufacture high sensitivity (0.8 A/W)n + -n-p photodiodes with an active area up to 5 mm diameter and a very low reverse current. The high hole-to-electron multiplication coefficient ratio leads to high gain avalanche photodiodes with an excess noise factor lower than 0.5. These CMT components are currently being manufactured on an industrial basis for optical receiver equipments and for laser feedback photodiodes now in field use.

Laser Transmitter Design for Optical Fiber Systems

The need for high performance sources for optical fiber telecommunications systems has resulted in the development of laser transmitters that incorporate high efficiency coupling optics, sophisticated control electronics, and high-speed modulation circuits. Present thinking on system development indicates the need for transmitters to have, in addition, much improved spectral characteristics. This paper reviews the present status of laser transmitters and describes likely future trends.