VW Unt Ophal Technolopies Whavelenghs Division Multiplexing (wom) -— ~ Optical signals vA diffecent evaveleyg ty (1300 — 1600 nm) ‘can propagate atthout interfering Colt each other. The scheme of combiniy a numbes esavelengths over @ single jibe 7s called esavelenphh, division multiplexing (wom) Each ip is generaled by a _sepaxate optical source evith a unigue wavelength. An aptical multiplexer couples Light from individual source te -the transmittin jibe. At the xeceivirg station, an optical dernultplerer is xepuived te separate the cliffecent carriers before photodetection of individual ignols. Fig. shows simple Wom scheme. id) At Postemplifier In-line i] anplifies Span Tunable. k a Souxces Receivers (could include ophical jilfecs) To prevent spucious signals te enter tte receiv; the demultiplexer must have narver spectval cpecation eit sharp esaveleryty cut-offs. The acceptable Limit gf Crosstalk Ls ~30d8. ng channel:Featuses of WDM :— Important adlvanteges or ea features ¥ WOM ase as mentoned belocer: — @ Capacity Upgrade !— The classical application of Wom hae been to upgiade the cxpacily of existing point —te- point fibex ophic hansmission lik. Since each evarclengt, supports indeperclent daly vate in gigabits per second (Gps). @ Peanspasercy I An important aspect of bIDr1 is that each optical channel can caxx any transmussion geomet. WDM can cass. fot asynchronous Slees synchronous synchronous analeg and digital dat © CO) Hlawelenght outing — Link enpaetly avd fleriiity cxavelenptl. Can be increased! by wsieg multiple @ Weweleng tr _sesitehing $— Wp can add ox dkep en multiplexers, Cwoss connects and ccavelengite converters. Passtve COMPONENTS — for implementing Wom vauous passive and achive component: ase xegucced fe combine, dishibule, isolate and te amelify optical pores at diffecent erovelengh,. . Passive component’ ace mainly used be split a+ combine optical signals . these component: opexale tn apical domains. Passive components don't need extemal contre! for her apexation. Passive Componente axe fabriceted by using optical fibers or by planas epheal evsaveguides. Commonly xegucied passive Componente arc! O NXN couplers ® Pocrer Splitters @ fosex taps @ Star couplecsSTAR COUPLER -— Stax couple. ts mainly used foe combining optical posers from N- inpuds and divide them equally al M-ap ports. Techvigues a creating Starx couplers Tnelude fused fibers, geting, maicso - ophe tecvologies and trtegrated - optics schemes . The fibex fusion technigue is pepulacly used fe Producing Nx N Stax couplecs . AY. sheers 4 4x4 fused hex couples . fe The optical poexer pul tule any port en ene side gf couplec is egually chivided among tre cufpul- ports Ports en Same side of coupler. ace tiolated, from each olbes Total loss in stax coupler #< constituted y ‘Splittigg loss and excess loss . Excess loss = to Jeg E keoe = tout8X8 STAR COUPLER :— An 8x8 ste couple. can be formed by inteccennecting 2x2 couplecs. $+ xeguixes teelve 2x2 couplers 8Xe Couplex Excess Jess in dB fs ghen as [ Excess loss = -10 ‘a(r™*) ere, Fy ts peach es i “ ee ts fxachon of poorer avecsing each couple, splitting less = 40 ley w Tetal Loss = Splithisg less + Excess loss = 10 (1 3.32 Jey Fr) dog TH shows Hat the loss increase Aegaitlomicelly eit N_Isolatow i— An isolator to a passive non- ae vice . dt allocss transrussion # and blecks all ensriission eciprocal oe in one disection through in otbex direction. _Isalator Axe used in csystrs before ophieal amplifies ard lesecs mainly t prevent elections fiom evtecirg these devices othexcsise pesforrrance exill depeacle _Smpertank pasametecs af an tsolater axe its tnsedion loss (in Jonsacd disechon) and tsolation (tn wxeveate dlixection) . The insection loss should be as “small as possible cobile isolation should be as tage as possible. the typical insection loss ts axound LAB and. tsolation ts axound 40 t 5048. Principle of Operation :— “Ysolator exsorks an the principle of of. polasization n_ (SP) of Hight faa ingle mode fibexs. “the Lalete of polaxtzation Crop) Adfers te the orientations ils electric field vector on a plane hak is ovtrogenal ty its ditection of propagation. the electric’ field canbe expressed As diveax. combination of to ovthagenal Uineax. pelacizelien supported y probacdiecetion jibe. These -teso polanization modes ase borizental ard vediital modes qe principle of opexation ts iMuttrated in fry. FawadaY stale Stole 9 polasization ce Oo oO @ Q ‘LL. Reflected Light BB 0 a 0 le aes PolaxizesLet inpule Light aigral tas vetical stale of polacization (sor) and blocks enespy in tevizorrtal SOP. Te pebuze ts Jollecsed by Faxadoay xolalor. Fasaday cxotater is an asymmetric device ebich wdtale the S0P clockesite by 4s" fn bot direction of propagation. the polarizer after Fosaday xatator pastes only Sops eith 4S" orientation. $n Hs eay bt signal from deft & ght is passed Hworgh tre Gevice eottheut- any less. pies Lig evden He device from ci aoflechenr, exith came 45° sop pais hang Ava ad another 45° by the Favaday cotator and blacked by the next polaxizer. i * ivelator in fio Q. lato 2 A three past circu I Civcul Signals gy diffecert cravelengths ace enteced at a port and sends them out fl civculator ak next port. All the ecovelensths os ise port-2. I) pert 2 absorbs any wpecyfic ewavelength then xernaiving coavelengths lecled and sends them tb next ace passed te Ji coolest AAAs pet-3. Circulators axe used te implement clemultiplexer. using 3 fibex Bragg gating for extracting a desixed evavelengte The eravelength setigpying the Bragg condition of grating gelf ofleckel and exits at next pork. Fig @ Mustrates the concept of demultiplexer F9-O vveulator- Arya Ay fat Crete Fibex junchon using a a cents l beg aati fibec eating “and Mi /AaA3, 4 : Aya an ephtal cixculator. Hexe, fiom all the Pat 3 . ; Aa ts wh evavelengths erly Aa Dropped covery th be extracted 63-@) dsThe cixculator takes fous esaveleagths A, Ay Ax and Ay fom tp port -1 and sends them % port-2. All evavelengths except Ax pass theegh grating because Az satisfy the Bragg condition of grating tence gele rgflecled and exist at pert -3. TUNABLE FELTERS (— The fleribility of wor netesork fnexeases cath 4 tunable optical fibex. Mest tunable Jitter opexalés on -similax principle as passive devices. $t cpealés ove. a uarge of uencies and can be tuned at only one optical frequency to pass through BH. Ay. iMustrales concept of tunable. filtec neo oPcal ifr , Selected optical sl) frequencies Se gp fepuency crac leav-of Tuning conto! CElectrical cx trecmal) The system pasamelecs ; ao tunable opal filtecs ae O Tuning aarge Cav) — @) channel spacivg Sv O Mex” ro of charmele (nN) @ Tanteg speed O Tuning Rayge ing — the vange ovex vsbuch filler can be tuned is called tuning xange. Mast commen csaveleryt trancrussion esindecs is 1200 and 1S0onm then 25 THz (or AWA= 200nm) bs xeasenable hurts : @ C hannel Spacing (Sw) 3 tug ange . — The minimum FY: —sepasation beteseen channels de minimus crosstalk. The Crosctalk from acyacent channel should be 30d for desirable pesfermance.QO Moximum no. gf Channel (ni) -~ _4¢ fe maximum yo ual ed channels that can be packecl in’ 4 eee mointeinicy am adeguatily Joes level gp css Kk betreen adjacent channEe. $f is defired as He xatio of the total faring ange AV to channel spacing sv a OY, =\cpn @ Tuning Speed *— Tanisy speed wepecified toes Butkly Pikec can be cca Jrom one freguency to anther, TUNAGLE FILTER Trees -— Tunable fillecs cstth fixed jeguency —apacth esith channel Len that axe multiples of Lost (Sv < LooGte) axe used tn WIM syckms. Follocoing types ae used ar His purpose — ® Tunable 2x2 directional coupler. @ Tunable Mach - Zehnder interfecomelecs @ Fiber Fabry - pecot filters @ Turable xvoveguide acays © Liguid cxystal Fabry - pecot filerc © Tunable. rrultigcating filters O route phe ell pte CAOTF:)OPTICAL AMPLIFIER Mast optical amplifiers amplified Pncident Light through stimulated emission. An optical ampliper ts nothing bub a Sacer coitroul- feedback. Optical goin is achieved when the amplifier is pumped optically or electrically te achieve population invexsion. Optical amplification deperds on :— — Freguency (or exavelengh) oy tneident sional. — Local beam intensity. Genexal applications optical amplifiers axe: — Inline optical hype ri — Pre- amplifies — foesex amplifies Basic Opesction of an Optical Amplifier a P' Aroplified optical ofp So The extecnal pump suxce enex ry is absorbed by the electrons th the active meolium. the electrons —sbypts tr the biyhe enegy devel producing population rnvecsien. plo Photons of incomirgg signal triggecc these excited electrens to focrer evel thxcugh 4 stimulated erussion process, preduciag amplified optical signal. All optical anplifies jncxease -the poeres Mevel of inciclent Lyle through sirleted emission ree loys oup-TIL an coup (phosphorus Gelli, Srdiuen, 1 eka) coenicontuche Sake ote the achve medium.Applications of optical Amplifices — Fy. -chovas geneal applicatians o the folloming three Laster of “ephial amplifices Fibec Lines _ ~ ‘eat | ILI ortieal QO) nn pl Om apc In Line amp daw tev) Ficanpifeg | ropa UIUL (pM ana . ' Link exer. (boastes)amplifiee fro 1 Lief SUL Stations peo m pM gia? LAN booster Arapliffer, fiz A) @ In-Line Optical Amplifiers I tn a cingle - fibec Link, re the effeck of fibec dispersion may be small so thal- Hee main a Limitation Lo Aepeatex spacing is piber attenuation, Since such a dink does vot necessaxily Keguie a complelé ageresation the yral , simple amplification of te optical sjynal is sufficient. Thus an apheal amplifie. can be used to Compensate for transmission loss and increase he distance betereen xegeneratie xepecters as fy) illusheates(2) Preamplifier — Fig tb) -shors an optical amplifier being used as a dont—end preamplfiex for an ophical receiver. Tere by, a eeak optical signal ts amplified before phalodelection eo thal- He —sigial to noise xatio dexadation caused by themal noite in the aeceiver electronics can be suppressed Compared exith other front ~ end devices such as avalanche photodiodes ev ophical helecedme detectors, an optical preamplifiec provides a dage gain factor and @ broader bandesidh,. G foeser Areplifier :— Reeser ov boother amplifice = applications inchide placing He device inmediatly after an aphtal transmitter & beat the transmitted pore, as fj. (¢) shows. Ths senest increase thre. transmission distance by 1o-— 100 km deperding on the amplifiex gain and pibex tess. As an example using Hws beoshing technigue syetrex est. an optical preamplifics ab He -eceiving end can enable xepeatedess undersea transmission Distance o 200-250 km. One con also employ an ophcol amplifiec in a Socal area neteoork as 4 booster amplifier to compensate for couples insection loss and pocsex —plitting boss. fi.) shows an example dee boosting tre optical! signal in front of a shox coupler Amplifier Tyres 2 The ophical amplifiecs can be Classified ints “beso main types O Semiconductor ophizol amplifiex (SoA) @ Dored fiber amplifier (DFa) Bott the types Shrulaled emission process , @ Semiconductor Optical Amplifier (SoA) :— ng SOR Fa Mose dite cottboul- ond wn and colt, avdivsflecton coating coupled to bots fic je Light coming in ether Pibex “i's amplified bya ingle pass through the lesec diade. SoA te an alternative to EDFA.Active medium consists of alley serriconductor (P, Ga, Tn hs). SOA eoxks tn beth los atenvation evindbert ice. 1300nm and 1ss0nm. The 3d6 bandevidth ts aboul- Jonm because o very broad gain spectrum. SOA Consumes less poerer and has Jecsec componente. Toso mq jor 4ypes ¢ SOA axe j— @) Fabry - Faxct amplifier (FPA) (cs) Travelling crave amplifier (TWA) SoA Las vapiel gain Hesperia Lest odne, @ Exbium Doped Fiber Amplifier (Evea) -— The. achive medium ti an optical fibex amplifie. consists of 4 rominally Lo to 30m engi, optical hex thal has been Liybtly cloped exit a Kae eat element sud as Lebsum (Ex) Yilecbium (Y%,) , Necdymium (Na) ov Peaseodyraium (B). the best pibex mateual can be ether standard xilica a fluoride - based glass or a multicomponent Ges. The operat gions of these devices depends on the test material and the ay ing elemenk. Fluovoziveonale glasses doped exit Por Ny axe used for opexction ithe 1300nm evindows, since neithec of these ions can amplify 1300 nm stynals eehen embedded fn silica Glass. The most populax material fer dong boul telecommunication applications is a silica fbex doped esith exbium , cohich is knoon as Erbium” coped fibex amplifier or EDFA Tee operation of an EDFA by itself rowmelly is limited 6 the 1530 4 Lsgo nm Agen