U-suey UNIT-5 Fere Spence Optics FSO Communtcntion System s- — /ftber Ophicat Tx Ophicol Rx In optical Comm unicatron Bystem . Channel. ‘ * OpHeal talineless Communicalron sefeu 4o fonsmigeion 1 unguicled Pxtopagatron medium through the use Of Optical Camsies te. invisibly Infosiecdl GR) & ulbavrokECUY) bands * * Tt 1B Gh Optical Tx and Rx Systm with wine less channel - OWIC 18 also colleclas Fuee Space optical (FSO) Communical'on - Te 1s the | ‘System cohese free space oets as a communscotron channel between Tx* Rx that asie LOS for Successful hransmission of optical Gignals- * Rarig Fs0 kehnalegy dato 1s honsmitted by pesbayaney Ught throush atmospheme os space Communicatron channel , allowing obhical ConnecttViky a r . Te provicles advon togeo of both optical and wineless Bystems « % Thelogs not Hequire Ucense * Te offen veny high band-width- 8 a aa {Ne _Oetves LS “hk Rx ‘ind ction pmpuitieat Photodetecter ee | os Obtics [oem |, Op Signal ig Basic CAiseless Optreal System (Block 01Source I [| Tntensity => fie | aaa | roessinl Yooot Te Rx | Figs Typical Olle System » Te offers high cata sate 4o meet the foremenclous ineseasing demand of bucadband foffic % Te affes much mone ftoribi tly i designing oPtical netwosikk architecture Ot vesty high Sheed|- % FSO eee 1s Affectect by atmosphenic effects, which Limits Bensi Wity andl achievable data sate Lolth acceptoble BER. % FSO Ca ; Nbe used for hoth chart diitane and long Honge communicafton-DIGITAL RECEIVER, PERFORMANCE stl?) Ideally, In a digital yecervest the clecrston cinewit output Serqnal voltage Vout (t) would always exceed the thiteshold ciweusit voltage cohen «1? 14 psesent and would be less than the thueshold shen No pulse was Dent -Due to noises, rhtergymbol theerfeHence and othen disiusbances cleviation I the Ofp voltage May occu Due to the furctuations in Wout Ck) ik & posstble fo have esos in the Ofp bits “The pesformance of aygital Hecery eu Con be evaluated b 2) BER ay Sensmmvity Gy Quantum Laat FROBABIUTY Or ERROR (BER) $~ A simple mea abpsoach to measuse the Hate of CHHOH OccuMence Is to clavicle the Numbes! oP eHHOM occusihg Ovex acestoin Ame intesival hy the numbes Of pulse bans milked clung ams ntosvals- AY numbers of eamion bit wecerved 1 Ne and dotal bit re Ne then BER i defined 7 Ne 0 > BER 18 depending on SNR of Hecervey > OpHeal Hecetvexy has BER songe from 16940 16!, ‘Te Gmpute the BER a \ ER Gt the wecerves, we need to know the PR i : \, 1 Tuobabitty clishibutic CF#€ bignal atthe equalize output, The aistibuttons o faa dotiowing gue " e shown 1m the Teh 3 Pean t Pew) a 5 _.Thmesholel Vot tag ¢ Ww) Few) — ° ehaditive Nojze Pegto) “The puobability that the equalien ofp voltage 1S less than’ U* when o agit Y pulse rs Sent & Riv) = J Poy) dy - @Q -@ Similovily the psiobabi tity that the ofp Yoltoge exceed & when a laghé ‘Oe pent 5 foro) = § Peyfo) by -@ oOHesse Pcyyoo te the puobabitity that the ofp Voltage ia ‘y’ when's’ 15 hransmitted + Ty te thuesholel Woltage 18 Gin then'the estos probability is given by fe= QPiCon)+bRCOn) — @) whexe @ and 'b ave weighting Jactos . Fox unbiased date Q=b=4 , So Re = 4 [ (tin) +Pe (On) J IN genenal dor Gauss dish bution in &4¢«) CEG) = 2 [fe %ay = euson functon in ° Q= 'Sen~ boy = berm bon belt > known ag B-foction Sete - Sant Mor Bin > Thseshotet Voltoge bon Mean of tie Gaussian Ofp Jor a‘ pulse bo Mean of Re Gaussian Op fer a GO bulse Sen > "aMiang of te Gaussian olp for “1? Pu > Varian Of of He Gaussian ofp fr toy The gactou @ i widely used to Specify Hecarver peufoumante, Zinc it 1D Helated to 4Re SNR wequined ‘to achieve Sheerfie Bar. ata] Pe On BER 2 4 € 8 ft Figt. BER vs Q; WSC) RECEIVER Sensitivity > OpHtcal communication gysicm uses BER to speu'ty the Camo srequinement for pastiqulay bonsmrssion fink, (Pow Sone tT iE 8 10" ost eas white Jou gigabit cthesinet it is 15") - "To ochieve @ desised BER AEG given clato sate, a specific minimum avesiqge optical bowess level must GBHYE DE HE photo-cletectos! - The youre of this minimum yetdant bowes# level 18 catled * Rocervesy Sensi levity ”: “The minimum amount of bows sequised to.momtarn speatfic secerves peufoumane Is wenaitevity of Meceven: : Te 18 defined in dBm- {opel med eee) Te gwes a meaguse of the minimum avesiqge owen on OMA needed Maintain a maximum BER ata specific data Hate- Ty 1) 18 the Bignal cusiment fou ¢” pulse and To 1S fhe cuuNent fou ‘0 cpulse and then cossstesponding noise cunnent vaniations ane ST2 OO, sespectvely Ran Q= Ti-To 0) Fit Now if Jor GG? pulse no opheal power Ja incident then Qs ® Di a Now the yececven Bensitvity to mamtarh a specific GER iz ghen Poensi = oa ot FC sensitivity = a [& eee +97 | cohene R= unity gan Mesponsivity R= BW of seceves °F = Theymal nose = Mulhipucation factor ® Ththe ueccives ip highly Bensitive, then it can secetve or cetect Smallest ‘Sensitivity Cel@m) Bignals- “40_Quntrtum, Liaits $- In Case of obHeal communi cation ,the physical bound sJov an obtical 1) cletectox 18 quantum limit: ‘Ty we have an (deal hae. detectou with unity Quantum efffrenc and zero clak cussent, then undes this assum ion it 1 possible fo tind the minimum secerved opHea)’ howe wequised fost a Specitic BER bestformane ina cuigital Aystem « 66 his minimum ececved owes level Jou an tcleal photo: ts known as Quanium lirnit” OR Te isthe minirnum optical eneHgy sequined fo raain tain aggiven BRRJoN optical Hecetvext - Since all the systein parameters ase assumed cdeal and the performance Y limited only hy the photo- detection statistics -cuodEye DIAGRAM i= The eye dragsam 18 a pawestul measurement USC L4) ‘tool acce ssing ‘ the clata hand Ging abraty of a chigttal bansmission - TE 1p an inturtwve gabhical Hebsiesentation of obltcal communicotton Bygnal 2 “The Quatety of HRese Bignals (the amount: of TST, noise, andyittes) can be | Judged from the abpeasrance of eye: . : TE provieles a Bimplo ond usefel tool to Visualize £51 between clata bits Tes dimply a geaphical cesplay oP a Besial data Aignal with Hespect | to time thot shows a pottesin -that Hesembex Qn ye Te 15 Bupertposi- tion of bits. | The Following Measurement Canbe besformed * Distoution * Time vowation at geuocsossing. * SNR * Senstivily of ‘ming using eye slopeo HOW To Draw E: & DINGRAM : Eye fattest 18 Wsuauzed on cro Waltagg/imputude ' Eye Diagram i— time “TY unitineesivet (ot) | Vv © To’ symbol cuxation Te 12 deal eye cktogsiam, © zex10 Distoution om st Buoitem Icleal Eye diogsam WIth Pola R2 x ~ Non Teeal Eye batter with samples ou t- Bide bil/gym>o} duvation. distorted — byt patteen, u Decraron stant Which 18-the point whene We need to Bombe. 1n onetest fo have betiesi eiformon ce 2le neecto Bamble ab a time 1h which wo pulses ane Ja. apart fram: each Othe Sothe time whene these ave Jor apart fo each othest 8 Th/a Te Is called optimal Bampung in6lont * hot is yous plum threshold 2 seb > Tt must be equal to ZeH10 for tho above case Ov ingene’ of thoe tw0 voltage level- a me astho eye opening becomes lage detection TE 13 cleas from +he ,figu: D become efferent , aie necer'ven can clorly Alfferentiate between thaoe +0 poliegs lavel. of LL 40 Re average . Eye Opening justify {he Amount of Ist - Higher the opening towey the TST» \ ening Best Zampung He a B | ites“ - Maximum Signo : | ‘el tage ev) A) Slope (sensttivitye > ® noice | | tetiningtnap SS (eg St) y Distortion at © ie Interval ovesi_, Distortfonct “Ty ‘ EHO Crossing Co) : 1 Coin bi Exe fattesin Reatuses t The eye poten measunemeatysn sl : cat) Que done i time domain allow theeffects of Figt- Simpb fred eye elvaguam oavefosim chistes tron to be shown immediately : onthe display. “the Jollowing information can be obtain‘ec| from the eye “Pattesin : () Glidth of the eye Opening t- timé intexwval ovess which the Hececved distortecl S1gnal can be Bampled with minimum eyso4- The beot time to Rample the Hecervedl waveform 18 ushen the hexght op tho Ye opening 18 laygeot- di Kye Opening dieight ¢- The vertical cis kane beteveenthe topopthe eye Opening Gnd the max. Bignal level gives the claguee Of diétortron . The mone the eve closes the mone diffuse “it 18 to distinguish between 4 4 'g (itt) ‘he hetght of the eye opening at the sbeurred ®ampung time shous the noige Maxigin Tt 18 percentage Hatro of the beak Binal Voltage ij dor totho max: Bignal voltage 2 as measured an altcrnating hit Bequence from threshold level, a vy [noise Mongi Mm) = . Xl00 7. 2(a) Sensittvity of the System timing 3+ Te ts the nate of closuue of eye “Pattesin when yampting tine ig vasied. “the bossibi uty of fining PUMONS incueased as the Slohe become mane hovigontal- (Timing Jitlor anises from noise in the secetves and pulse distortion \n the dhticay fibeu Excessive, jittes con Mesult in bie eMOH, Such jitkess can pucduce uncentaintres ini clecls thing , that will Cause © Meteivess 4o lyse Bynchronigation with incerning bit Sheam phene Py Incousieetly inkespHeking Logie “1? 4°0" pulsto- I] the [Bygnel 1s Dampex In the middie of the time intesival, then the amount of distortion aT atthe threshold level indicate amount of Qiltes- Timing gittest 1s given by TT Cy) = AT. Frrcy= BT ice] (vy “Tuadlitfonaly . the suse time 18 defined as the dime intestva] between +the points cohene the Hising edge of the Bignal sreacheo to y.of tinal value to the time whene it Heacheo gov. of final value- “hese points ane offen chsaisiedl by noise and ities effects: “Inus. the mowe clistinck values at the 207% Gnd Boy. aNe normally measusecl - (vit) Any non-lneas effects ii the channel transfer charactentistiss will cHeate an asymmehy wi the eye pattem -