Optics & Laser Technology 33 (2001) 285–291 www.elsevier.com/locate/optlastec Opticalberswithlownonlinearityandlowpolarization-mode dispersionforterabitcommunications J.A.Baghdadi a ,A.Safaai-Jazi b; ∗ ,H.T.Hattori c a Fiber-To-The-Home, APON, Systems & Technology, Advanced Systems, Alcatel USA, 2912 Wake Forest Rd., Raleigh, NC 27609, USA b Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0111, USA c Department of Electrical Engineering, Instituto Technologico de Aeronautica-CTA, Sao Jose dos Campos, SP Brazil 12228-900 Received 15 February 2000; received in revised form 15 December 2000; accepted 23 December 2000 Abstract Refractive-indexnonlinearitieshavenegligibleeectontheperformanceofshort-haulber-opticcommunicationlinksutilizingelectronic repeaters. However, in long links, nonlinearities can cause severe signal degradations. To mitigate nonlinear eects, a new generation of bers,referredtoaslargeeective-areabers,havebeenintroducedinrecentyears.Thispaperreviewsthelatestresearchanddevelopment work on these bers conducted by several research groups around the world. Attention is focused on a class of large eective-area bers that are based on a depressed-core multiple-cladding design. Another important issue in long-haul and high capacity ber optic systems is the polarization-mode dispersion (PMD) which has been recognized as a serious limiting factor. In this paper, an improved ber design is proposed which, in addition to providing large eective-area and low bending loss, eliminates PMD due to elliptical deformation in the single-mode wavelength region. Furthermore, this design is allowed to provide a small chromatic dispersion about few ps= nmkm,in order to overcome four-wave mixing eects. c 2001 Elsevier Science Ltd. All rights reserved. Keywords: Fiber optics; Optical communications; Optical bers 1. Introduction The unprecedented success of information technology in recent years ushers an explosive growth in demand for the Internet access in the 21st century. Ultra-wideband trans- mission media are needed in order to provide high-speed communications for a much larger number of users. A promising solution to the capacity crunch can come from wavelength-division-multiplexed optical ber communica- tionsystemsthatareshowntoprovideenormouscapacities ontheorderofterabitpersecondoverlongdistances.These systems utilize single-mode bers, in conjunction with erbium-dopedberampliers,asthetransmissionmedium. Until recently, only ber attenuation and dispersion were regarded as major sources of signal degradation. However, * Corresponding author. Tel.: +1-540-231-4538; fax: +1-540-231- 3306. E-mail address: ajazi@vt.edu (A. Safaai-Jazi). the much higher power level due to simultaneous transmis- sion of multiplexed channels and propagation over much longer distances made possible with the utilization of ber ampliers, cause the otherwise weak and negligible ber nonlinearities to aect the signal transmission signicantly. With the exception of soliton transmission where the inter- playofbernonlinearityanddispersionresultsindistortion freetransmission,thenonlinearitieshaveundesirableeects ontheinformationsignalandlimittheinformation-carrying capacity of the ber-optic system. The eects of ber nonlinearities on pulse propagation and on the capacity of ber-optic communication sys- tems have been studied extensively by many researchers. Chraplyvy [1] has examined the nature and severity of system degradation due to several nonlinear eects, in- cluding stimulated Raman scattering, stimulated Brillouin scattering and the refractive-index nonlinearity. Marcuse [2] has carried out an in-depth study of pulse propagation in bers with refractive-index nonlinearity. He has shown 0030-3992/01/$-see front matter c 2001 Elsevier Science Ltd. All rights reserved. PII:S0030-3992(01)00019-6