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Characterizing Multimode Fibers and Sources for Gigabit Ethernet Applications

Michael J. Hackert Corning, Inc.

Chair, '1IA FO-2.2.1 - Moclal Dependcnce of Multimode Fiber Bandwidth (IEEE Senior Meinbcr)

Abstract

Low cost 850 nm vertical cavity sui-lace ernittirig laser (VCSEL) technology has caused renewed interest in multimode fiber. for high specd data cominunication. Gigabit per second (Gbps) or faster performance sucli as this had prcviously been left to single-mock fi ber based system solutions. This paper reviews the hxnsceiver lauilch condition and Irber rriodal tuning devclopmerit completed to achieve this performance.

Introduction

l 'hc information revolution is driving the need lor ever increasing bandwidth. The challenge is to provide this bandwidth at ever tlcct-easing costs. Tlic advent of low cost, short wavelength (850 nm) VCSEL Iascr technology has caused renewed interest in inultirnode fiber for high speed (Gbps and beyond) data communication applications.

There is a n iclcal rnaniagc between multimode fihcr and VCSELs since iniiltirnode Itber c m be tuned to operate with high txindwidtli at this wavelength arid VCSIXs couple lots of power irito rriultirnotle' fi bci. at high specd. Multiinodc fibcl- can also take advantage of low cost connection technology simx the lnrgcr cores of multiriiotic Lihci. require looser tolerances (meaning lower cost) than singe-inode fiber. Also, standard singlc-iriodc i'ibcr (clcsignctl to operate at 1310 nrn) is bi-moded at 850 nm. This iiiakes it cl'fcctively iiioperable with thcsc VCIS1;I.s (i.e. very low bandwidth or very high niotlal noise).

1)evelopment Progress -

Developmcnt began during the work by IEliE 1 o n

802.3 to establish a 1 Gigabit Etheinet slantlard.' .08

Once complete, this group bcgati work OII the I

next increment in specd - I0 (?lips. 'l'lic . , I

information carcyiiig capacity of iiiultimoclc - 1 6

i'iher, namely bandwidth, is laiinch tlependeiit.

> " 6

z 1.2

This laiirich dcpenclcrice quickly bccamc cvitlcrit during the 1 Gbps tlcvcloprnent. The tradiLional way of charnctcrizinc the launch clcliendciicc ot'

Figul-c I . - UMI) a1 1300 iiin i i w 6%.5 pin F i lm will, (:cl,Lcl.lir,c nl.l,~,l. -

multilnotle fiber is tlic di1l'crenti;d niotlal delay (l>Ml)).2 By scanning ;i sinal1 spot 01' light ;icross the core, the tuning of the fiber's rnodes (cflcctivcly delay elerneiits) tail tic tlctermincd. While providing ;I thorough charactciizatioti of thc fiber's modal ttiniiig, it is in ipc t ica l for high

0-7803-5947-X/00/$10.0002000 IEEE 472

volume tcsling (or low cost iriariul'rictui.iiig) sincc thc i i i c ; i s t~~~~nc i i t is leiigtliy.

I'M IX-2.2. 1 has recently ariivcd itt ail agi-cciiiciil on ii iricthodology 10 achieve irnpiwctl 1 Gbps systern pcrfoimarice ovci' 62.5 piii fi lw. 'l'ticic ai'c two cleniciits to the solution. Iiii,st, thc cxtcrit o f the lauricli cotiditioii ptoduccc! t q ihc timsinittcr. ncccls to bc lirnitctl. This is doiic by use of the eiicir.clct1 1'1ux mcasuicnierit. Scconcl, the imgc o f the 1)MD in the ceritcr of the fibcl. must be limited. 'I'his is cloiic by ttic iisc 01. i t rcsti-ictcd i n o ~ l c Iauiich Imiitlwirlth mcasureincnt. The group has stantlarclizccl hotti iiie:isIii-cirierits.'i 1X-2.2. I is cui-icntly working oil the solution for 50 pin fihcr which will :allow i t to pci~loriri ai IO Ghps at 300 m. Hoih the incthoclology and the i.ecoinmentlation wil I bc prcscntecl.

Acknowlledgments

The author woiild like to express his appreciation to the iiitlividuals i d organizatioiis participatiiig iii '1'1.4 PO-2.2. I . H e woitlcl like to cxprcss special tliuiiks to thc following organizations husiIicsses thal liavc contribiitcd I'ibcr, calilc, wansccivcrs a n c l testing iri suppol-i of this efiori: Agilcrit, Rlcatel, AMP, Cielo, Coming, h j i k i i i x , Iioneywcll, IBM, I ,uccnt, Mettiode, Molex, NET, l'icolight, Plasnia, Siecoi., Siemens, Spcctran, Unisys, aiitl Vixcl.

References

I IEET: b"802.k Specification for 602.3 1'dI Uuplcx Operation Supplcnieni L o Carrier Sense Multiple Access with Collision Detection (CXMNCD) Access Metliod and Physical Tiiyer Spccification lor 1000 Mh/s O p e d o n .

Ilackert, Michael J ., "Chaiactcrizing Multiinode Fiber I~andwitlth for. Gigabit Etlieriiet Applications", Symposimn on Optical Fiber Measurements, September, 1998.

TIA KeCerences: Fiber Optic l'cst l'rocctlurcs (FOlPs) - 1'111-455, Optical Fiber System Test Procedures

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