A Study on the Effects of Dispersion and Nonlinearity in Optical Fiber Communication Systems using DCF

Transcription

1 A Study on the Effet of Dperon and Nonlnearty n Optal Fber Communaton Sytem un DCF Jn Nu 1, Janqao Shen *,, Nu Yubn 3 1 Shool of nformaton Sene & Enneern, Lanzhou Unverty Department of COMPUER & Informaton Sene, Cty Collee of DonGuan Unverty of ehnoloy,donguan 53419, GuanDon, Chna 3 Zhuha Rado & V Unverty,Zhuha, 519, Chna * Correpondn author Janqao Shen, emal: @qq.om Abtrat --- In modern optal fber ommunaton ytem, dperon and nonlnear effet of optal fber are the two man fator of derean ommunaton qualty, epeally n Group Veloty Dperon (GVD). In th paper, we ue nle-mode tranmon fber, Dperon Compenaton Fber (DCF) and erbum-doped fber amplfer (EDFA) to den a dperon ompenaton optal fber ommunaton lnk. In opty oftware, we mulate the 4QAM optal fber ommunaton ytem whh baed on th ommunaton lnk. hrouh the daram of ontellaton of reevn nle, we tudy the nfluene of roup veloty dperon, nonlnear effet, amplfy pontaneou emon (ASE) repetvely, and ther mutual effet to the qualty of the nal n ommunaton ytem. he reult how that dperon ompenaton an only remove the nfluene of roup veloty dperon, but the nonlnear phae noe, whh aued by the mutual effet of nonlnear effet and amplfy pontaneou emon, wll be aumulated a the nrean of fber lenth and nfluenn the qualty of 4QAM optal fber ommunaton ytem. Keyword - Nonlnear Effet, Group Veloty Dperon, Dperon Compenaton Fber, Quadrature Ampltude Modulaton, Nonlnear Phae Noe I. INRODUCION he nfluene to nal tranmon qualty n optal fber ommunaton ytem manly aued by fber lo, dperon and nonlnear effet. However, wth the development and uae of the Erbum Doped Fber Amplfer (EDFA), optal fber ommunaton ytem haned further. Optal amplfer replaed tradtonal photoeletr repeater, and fber lo ha no loner beome the man fator to lmt fber tranmon lenth. A a reult of that, dperon and nonlnear effet beome two hot pot for reearher, and the method to dereae the nfluene of th two fator beome very mportant [1]. Dperon wll aue pule broadenn, reult n the lmt of the ommunaton apaty (produt of BL) of ommunaton ytem, whh wll ultmately affet the qualty of the nal tranmon. For th haratert, the reearher put forward many knd of dperon ompenaton tehn. Fnally the dperon ompenaton fber(dcf) appled wdely beaue of advantae uh a the relatvely matured tehn, utable for lon dtane ompenaton wth ontrollable dperon ompenaton amount, lare bandwdth and tranparent for tranmon format and bt rate. he method of dperon ompenaton fber to add dperon ompenaton fber nto optal fber lnk, to make the total dperon nearly zero, to dereae the nfluene of Group Veloty Dperon (GVD) at leat. he nonlnear effet of the fber aued by the lon tranmon dtane and the mnmum ro-etonal area of lht feld. A a reult, optal fber materal ha obvou nonlnear effet althouh the quartz materal telf doe not have apparent nonlnear effet. Bede, nonlnear effet and amplfer pontaneou emon (ASE) noe wll nterat and aue nonlnear phae noe []. Althouh n the optal ommunaton ytem of ampltude modulaton, phae hane whh aued by nonlnear effet ha no effet on the nal of reevn end. But do very dfferent n oherent optal ommunaton ytem. he mpat of the phae hane obvou. Currently, ampltude modulaton ommunaton ytem tll wdely ued beaue of t advantae of mple, eay to nterate et. But t wll be replaed by the oherent optal ommunaton ytem n the future beaue of t lmted nle hannel bandwdth. So the tudy on the Effet of Fber Dperon and Nonlnearty n 4QAM Dperon Compenaton Optal Fber Communaton Sytem baed on DCF ha ertan nfane. II. PRIOR KNOWLEDGE A. Dperon of Optal Fber 1) he roup veloty and t repreentaton In optal fber tranmon medum, optal nal nlude many dfferent frequeny omponent, and dfferent frequeny omponent tranfer n dfferent velote, o pule broadenn wll aued n the proe of pule tranmon. h phenomenon alled the roup veloty dperon. he roup veloty dperon the dperon of the eond order effet, and the phae veloty dperon the frt order effet. he reult of the roup veloty dperon pule broadenn and the lmtaton of the bt rate dtane produt (BL, ommunaton apaty) n optal fber ommunaton ytem. DOI 1.513/IJSSS.a ISSN: x onlne, prnt

2 Normally dperon manly ome from mode dperon, materal dperon and waveude dperon. Mode dperon refer that the multmode fber n dfferent tranfer mode aue dfferent nal arrve at the end n dfferent tme. Materal dperon beaue there a nonlnear relatonhp between the tranmon wavelenth n and the refratve ndex of fber ore materal λ. h make the roup veloty of a ven pattern depend the wavelenth. V=C/n. he waveude dperon beaue the fber ore and laddn ha mall refratve ndex. When the total refleton happen on the boundary urfae, ome lht o nto the laddn, th part of lht o bak nto the ore after the tranmon n the laddn. h make the dfferent arrval tme of dfferent part of lht, whh mean pule broadenn. Beaue there only one tranfer mode n nle mode fber, reardle of the mode dperon, the two man oure of the roup veloty dperon are materal dperon and waveude dperon. Generally dperon oeffent D() ued to expre the deree of roup veloty dperon ( p / nm km ). he parameter of dperon an be repreent a follow D D W D M.the roup veloty dperon uually repreent a: d d Amon the formula above the β the tranmon ontant. he relatonhp between D and β: D. C Group veloty dperon dvded nto the normal dperon reon( >,D<) and the abnormal dperon reon( <,D>) [3] In the zero dperon wave lenth, Snle-mode fber dperon dd not dappear ompletely, there tll a hh order dperon 3 : 3 d d 3. 3 d d It value ha a relatonhp wth dperon lop S [4,5] : dd 4 S 3. 3 d ) he ba method and prnple of the dperon ompenaton Many ompenaton method of fber dperon are put forward by reearher, uh a dperon ompenaton fber(dcf), hrped fber ratn(cfg), dperon upported tranmon(ds), Spetral Inveron, Chrp and optal oluton tranmon tehn [6]. Amon thee, dperon ompenaton fber wdely ued beaue of t advantae uh a, relatvely mature and mple tehnoloy, tranparent to tranmon format and btrate, table performane and ompatble wth WDM. Normally lnear partal dfferental equaton of optal pule under the aton of roup veloty dperon and hh order dperon: 3 A A A. 3 3 z 6 General oluton obtaned by Fourer hane: 1 ~ 3. A ( L1, t) A(, ) exp[ L1 3L1 t] d 6 here nto, L 1 the lenth of SMF, the term nludn the eond order dperon, the term nludn 3 the thrd order dperon. Compare wth the nfluene aued by,the effet of 3 not obvou. So n the paper, we only onder the nfluene of. Potve dperon beaue that when lht pule nto the materal wth hh refratve ndex from the materal wth low refratve ndex, t veloty delne. When lht pule nto the hh refratve ndex materal from the low one, t veloty nreae. h alled neatve dperon [7]. In atual enneern, SMF ha potve dperon D, whh mean neatve.and DCF ha neatve dperon D, potve. If we nert a lenth of DCF n optal lnk, the dperon effet of DCF wll be mported. In he formula above, an extra term of DCF eond order dperon wll be added nto the term whh nludn SMF eond order dperon. he hane : L L L1 1 1 here nto, L 1 the lenth of SMF, L the lenth of DCF, the term nludn the eond order dperon of 1 SMF, the other term nludn the eond order dperon of DCF. If et the approprate value to make the value of 1L1 L zero, effet to nal ampltude A of eond order dperon an be removed. But n pratal enneern, dperon ompenaton an only aordn to ertan experene to provde a eneral tranmon dtane dperon ompenaton ope, and an't be pree ompenaton. B. Nonlnear effet of optal fber 1) he nonlnear effet of optal fber Fber optal medum polarzaton P hane wth nonlnear eletr feld ntenty E hane. Jut about th led to nonlnear effet. he mnmum order nonlnear effet ome from the thrd-order eletr ueptblty (3). Beaue the eletr polarzaton ntenty ha nonlnear relatonhp( p E ) wth ndent lht ntead of lnear relatonhp.: (1) ( ) ( 3 ) p [ E EE EE...] Althouh the eond order nonlnear polarzaton () an aue frequeny doubln, um frequeny, dfferene frequeny and optal retfaton effet. But () not zero only n the nveron ymmetry moleular truture of medum, and moleular truture of SO ymmetral, therefore, eond order nonlnear effet uually don t how n optal fber ommunaton ytem. he thrd order nonlnear polarzaton (3) wll aue Kerr effet, the two-photon aborpton, ne the foal lenth, the phae modulaton and tmulated Raman attern and tmulated brlloun attern et. here are two knd of effet whh have a reat nfluene on qualty of optal fber ommunaton ytem amon varou knd: One tmulated attern, nludn DOI 1.513/IJSSS.a ISSN: x onlne, prnt

3 Stmulated Raman Sattern (SRS) and Stmulated Brlloun Sattern (SBS). he other the nonlnear refratve ndex modulaton, nludn the elf-phae modulaton, ro phae modulaton and four-wave mxn. In th paper, we manly onder the phae modulaton effet to the ommunaton qualty of ytem. ) Self phae modulaton he nonlnear phae hane whh aued by the nonlnear effet of lht feld alled the elf phae modulaton of lht feld. Nonlnear refratve ndex and optal feld nfluene eah other n ytem, a a reult ondutor tranmon ontant hane and an extra tem added: ' P In the formula, β the tranmon ontant, P the tranmon power, alled the nonlnear fator: k n A eff Here, n alled the nonlnear refratve ndex, A eff the effetve area. After mport the extra tem of tranmon ontant, t phae wll nreae wth the lenth by lnear. Phae devaton dedue by tranmon lenth L a follow: NL L L L ' az ( ) dz p( z) dz pn e dz p the power of ndent lht. n k n L III. DISPERSION AND NONLINEAR EFFECS IN 4QAM OPICAL FIBER COMMUNICAION SYSEM A. Quadrature Ampltude Modulaton (QAM) and Snal Contellaton Daram Quadrature ampltude modulaton: In the M ale dtal modulaton ytem, Maxmum entropy for eah ymbol lo M nbt.in a lmted frequeny band of the hannel, M ale nreae the nformaton tranmon rate, rae the utlzaton rato of the frequeny band. MQAM ompoed of two orthoonal arrer multlevel ampltude hft keyn nal uperpoton. wo of the road of multlevel ampltude equene are ndependent of eah other. MQAM nal expreon a follow: S QAM a o t a n t, 1~ M, t { a },{ a } a et of drete level et. (t) the baeband hapn flter mpule repone. MQAM an be expreed a a lnear ombnaton of two normalzed orthoonal ba funton: 1 f1( t) f ( 1 ~ M ), t wo of the normalzed orthoonal ba funton, t f ( t ) ( t ) o t 1 E A eff eff p n, t f ( t ) ( t ) n t E E 1 f1( t) dt a, 1 ~ M E f( t) dt a, 1 ~ M S he nal waveform of the two-dmenonal vetor expreed a E E [ 1, ] [ a, a ], 1 ~ M E the power of pule (t). So the retanular MQAM nal ontellaton daram a Daram 3.1 a rht. Daram 3.1 the retanular MQAM nal ontellaton daram. h paper ue 4QAM modulaton format, o un the raph M = 4 ontellaton daram. B. 4QAM optal fber ommunaton model baed on dperon ompenaton fber Normally, he dperon ompenaton model baed on optal fber dvded nto the front-end ompenaton, the bak-end ompenaton and the mxed ompenaton. We hooe the bak-end ompenaton model a our example to found our 4QAM optal fber ommunaton ytem model. he optal lnk of model nlude the mple model fber, the bak-end dperon ompenaton fber and the Erbum Doped Fber Amplfer. Our 4QAM optal fber ommunaton ytem model truture a daram 3. a bellow. C. he reearh of the nonlnear effet and the roup veloty dperon n optal fber 1) he nfluene before nertn dperon ompenaton fber In the atual ytem, nal of output end(reevn end) ha a lttle dfferene wth the nal of nput end. Baed on daram 3. model, we mulate the 4QAM optal fber ommunaton ytem n opty oftware. Inorn the effet of dperon ompenaton fber, we ondered the nonlnear effet and the roup veloty dperon of optal fber lnk repetvely. We hooe the 4QAM modulaton mode, lenth 5km, P=5mW, bt rate=4bt/, lo=.db/km, an=1db, at th tme, the tar map of the nput and output end nal a daram 3.3, 3.4,3.5 and. DOI 1.513/IJSSS.a ISSN: x onlne, prnt

4 3.6 a bellow. Daram 3. Our 4QAM optal fber ommunaton. Daram 3.4 he tar map of reevn end nal. Daram 3.3 he tar map of nput end nal Compare daram 3.4 wth daram 3.5, we an ee that before nertn DCF, only ondered the effet of roup veloty dperon D 16 ( p nm km ),the nal of the reevn end erou dtort and the ornal nal an not be dtnuhed. When only ondered the nfluene of the nonlnear Daram 3.5 he tar map of reevn end nal. effet( A eff 8m ),we an ee that t aued the phae hane of the nal. Compare wth the ornal nal, the nfluened nal hane n t phae. DOI 1.513/IJSSS.a ISSN: x onlne, prnt

5 Daram 3.8 he tar map of reevn end nal. Daram 3.6 he tar map of reevn end nal ) he nfluene of the nonlnear effet and the roup veloty dperon after nertn DCF In order to elmnate the reevn nal dtorton aued by dperon, dperon ompenaton fber be ued nert to the ytem n the atual enneern. In our mulaton, we nert the dperon ompenaton fber(lenth 1km dperon=-8p/nm/km effetve area=8um total lenth=6km), the mpat of the dperon n the ytem baally elmnated. In the tar map of daram 3.7, we an ee that after nertn DCF, the ornal nal(tar map a daram 3.4) be reovered, the phae and the ampltude of ornal nal an be dtnuhed learly. But when only ondered the nfluene of the nonlnear effet, the output end nal tll ha a phae hane(daram 3.8) ompared wth ornal nal after DCF ompenaton(daram 3.4). h mean the phae hft aued by nonlnear effet an not be elmnated by nertn dperon ompenaton fber. 3) he aumulaton of nonlnear phae noe After the dperon ompenaton, the output nal ha baally reovered, ee daram 3.9. he nal dtrbuton n ther repetve luter out of order, but dfferent nal luter have no nfluene wth eah other. Beaue of the nonlnear effet aued by the phae hft annot be elmnated, In oherent optal ommunaton ytem, t wll aue the nonlnear phae noe by the nteraton wth Amplfed Spontaneou Emon. he nonlnear phae noe wll be nreaed wth the aumulaton of fber lenth. Daram llutrate the tuaton of th proe. Daram 3.7 he tar map of reevn end nal. Daram 3.9 he tar map of reevn end nal Dperon and nonlnear effet, fber lenth L=6km. DOI 1.513/IJSSS.a ISSN: x onlne, prnt

6 hrouh the tar map above, we an draw a onluon: he nonlnear phae noe, whh an not be elmnated by nertn dperon ompenaton fber, aumulate lowly when the fber not lon enouh. But when the lenth nreae, the dtorton of nal nreae and aue the rotalk of dfferent nal at lat. Daram 3.1 he tar map of reevn end nal Dperon and nonlnear effet, fber lenth L=36km Daram 3.1 he tar map of reevn end nal Dperon and nonlnear effet, fber lenth L=1km Daram 3.13 he tar map of reevn end nal Dperon and nonlnear effet, fber lenth L=1km. Daram 3.11 he tar map of reevn end nal Dperon and nonlnear effet, fber lenth L=4km. DOI 1.513/IJSSS.a ISSN: x onlne, prnt

7 REFERENCES Daram 3.14 he tar map of reevn end nal Dperon and nonlnear effet, fber lenth L=1km. IV. CONCLUSION In th paper we baed on the prnple of the nonlnear effet and dperon of the fber, ued opty oftware a platform, bult 4QAM dperon ompenaton optal fber ommunaton mulaton ytem on dperon ompenaton fber. And tuded the nonlnear effet of the fber( elf phae modulaton) and the dperon effet(roup veloty dperon) of the nal n th ytem. We worked out the tar map of the reevn end n dfferent tuaton, and drew the onluon below throuh the ompare of dfferent tar map: In 4QAM optal ommunaton ytem, the roup veloty dperon wll aue dtorton n tranmon nal ampltude and the nonlnear effet an aue the nal phae hane. he nfluene of roup veloty an be elmnated by dperon ompenaton fber, but the phae hane aued by nonlnear effet an not be reovered. Bede, nonlnear effet and Amplfed Spontaneou Emon aued nonlnear phae noe by ther nteraton. he nonlnear phae noe wll nreae wth the lenth of the fber opt lnk and aumulated radually, and affet the nal tranmon n the oherent lht modulaton ytem eventually. For the optal fber ommunaton ytem of nle ampltude modulaton, the nonlnear effet doen't affet the nal. But for the optal ommunaton ytem of phae modulaton, t a very mportant fator to nfluene the ommunaton qualty. And n the future, oherent lht modulaton bound to replae nle ampltude modulaton. So the reearh on the effet of nonlnear effet wll be the hot of future reearh, and how to elmnate the nfluene of nonlnear effet aued by th problem wll be the man dreton of future reearh. [1] an Xao-hu, Zhan Wen, He Nn, DCF-baed lon-dtane optal fber ommunaton ytem dperon ompenaton, Optal Communaton ehnoloy[j],9, NO.11 [] Guo Janmn, Optal fber nonlnear effet and t nfluene on optal fber ommunaton ytem, Dalan Unverty of ehnoloy[d],.5.3 [3] Wan Ln, EnZe,Zhan Ymo,Ma Xaohon,Yu Jnlon, Chromat Dperon n Fber Opt,Optal Fber Communaton Lab. [J], [4] Wan Guohuan,Lu Chao,Lan Chuqao, Dperon n Hh Btrate Optal Fber Communaton, Modern Eletron ehnoloy[j],,no.6 [5] Zou Lnen, Dperon and Nonlnear Effet n Snal Mode Fber, Study on Optal Communaton[J],1997,NO. 3 [6] A. Braun, S. Kane and. Norr, Compenaton of Self-phae Modu laton n Chrped-pule Amplfaton laer Sytem, Opt. Lett. [J], (1997) [7] R.L.Fork,O.E.Martnez and J.P.Gordon, Neatve Dperon Un par of prm, Opt Letter[J],Volume 9,No.5,1984.3,P.15 [8] Wu Qan,YU Chon-xu,XIN Yu,YAO De-q,XIN xan-jun,hu Yue-hu,WANG Yue-fe,Analy on Dperon Compenaton wth DCF[J],SEMICONDUCOR OPOELECRONICS,4,VOL.4,NO.3 [9] Lu Yunxan,Zhu Yonquan,Ne Xuehun, Applaton of Dperon Compenaton Fber n the Communaton Conveyn Sytem[J],eleommunaton enneern tehnoloy and tandardzaton,4.1 [1] Lu Yan, Effet of four-wave mxn n DWDM ytem omputer mulaton reearh[d], Shandon unverty,4 ACKNOWLEDGEMEN h paper upported by the Youn eaher' Development Fund Projet, ID: 15QJY8 DOI 1.513/IJSSS.a ISSN: x onlne, prnt