H THNG THNG TIN QUANG COHERENTBai 2:H THNG IM/DD

NOI DUNGCu trc h thng IM/DDMy pht quang iu ch cng Nguyn l pht quang Ngun quangiu ch tn hiu quangS khi my pht quang iu ch cng .iu khin - n nh ngun quang.My thu quang tch sng trc tipNguyn l thu quang tch sng trc tipS khi my thu quang.B tin khuch i - Khi phc tn hiu sNhiu - nh gi cht lng h thng IM/DD

CU TRC H THNG IM/DD

CU TRC H THNG IM/DD

THIET B THU

THIET B PHAT

Tn hieu quang

Tn hieu ien

Tn hieu ien

Si quang

K

Phuc hoi

tn hieu

Linh kien

thu quang

Nguon

quang

Mach

kch thch

MY PHT QUANGIU CH CNG Nguyn l pht quang Ngun quangCu to ca my pht quang:Ngun quang: thnh phn chnhB iu ch: chuyn i d liu t tn hiu in thnh tn hiu quangiu ch trc tipiu ch ngai tng tnh n nh ngun pht s dng trong cc h thng thng tin tc caoModule ghp si: a tn hiu quang t cng pht vo trong si quangMch in t: cung cp dng cho ngun quangxem phn 3.3 Thit k thit b pht quang, trang 140-146, H Thng Thng Tin Quang, tp 1, V Vn San, NXB Bu in, H Ni, 2003

MY THU QUANGTCH SNG TRC TIPNguyn l tch sng quang Linh kin thu quangMy thu quang tch sng trc tip: v tr sau cng ca h thng truyn dn quang nhn mi c tnh tc ng trn tan tuyn a ti lin quan n cht lng tan b h thng truyn dnBin i tn hiu quang thu c thnh tn hiu inTch sng trc tip DD (Direct Detection): PIN hoc APD

THIET B THU

Tn hieu quang

Tn hieu ien

Si quang

K

Phuc hoi

tn hieu

Linh kien

thu quang

MY THU QUANGTCH SNG TRC TIPYu cu ca my thu quang: nhy thu caop ng nhanhNhiu thpGi thnh hBo m c tin cy cao

NHIU TRONG TCH SNG QUANGCc ngun nhiu trong b tch sng quang PIN:Nhiu lng t: Do bn cht thng k ca qu trnh bin i photon thnh in tIp: dng photoBe: bng tn inNhiu nhit: lin quan n cc mch khuch i in trong b thuIp: dng photoFn: hs nhiu .c kRL: in tr tiNhiu dng ti: Id: dng tiNhiu dng r b mt photodiode:Il: dng r

NHIU TRONG TCH SNG QUANGCng sut nhiu tng ca b tch sng quang PIN:

Cng sut nhiu tng ca b tch sng quang APD:

Vi FA l h s nhiu tri ca APD ph thuc vo M lin quan n bn cht ngu nhin ca qu trnh thc l(0 < x < 1)

NHIU TRONG TCH SNG QUANGT s tn hiu trn nhiu:

SNR ca b thu quang PIN:

Trong gii hn nhiu nhit (s > T):Trong cc b thu quang thc t s dng PIN, nhiu tri l nhiu nhit iT

NHIU TRONG TCH SNG QUANGSNR ca b thu quang APD:

Trong gii hn nhiu nhit:

SNRAPD tng ln bi h s M2 so vi SNRPIN

Trong gii hn nhiu lng t:

SNRAPD gim i bi h s FA so vi SNRPIN,

NHY CA B THU QUANGLa mc cong suat quang trung bnh thap nhat ma b thu quang co the hat ng c vi mot t s SNR hc ty so bit loi (BER) nhat nhnh gi kh nng v cht lng ca h thng thng tin si quangChu tc ng trc tip t SNR ca b tch sng quangSNR cng cao th b thu quang cng c c nhy thu cao hn mc cng sut thu c cng nh i vi cng mt ch tiu cht lng truyn dn

NHY CA B THU QUANGCc h thng thng tin s: t s bit li BERGi tr BER ty thuc vo cc yu cu v cht lng ca tng h thng truyn dn (ITU-T Recommendations):PDH: 1x10-6 n 1x10-9STM-1, STM-4, STM-16: 1x10-10STM-64: 1x10-12

G.691

NHY CA B THU QUANG+ Nu p(0) = p(1):vi

NHY CA B THU QUANGCng sut nhiu tng trong b tch sng quang PIN:

Xc sut li tng ng vi bit 0 v bit 1:

NHY CA B THU QUANGThay th ( ) v ( ) vo biu thc ( ) ta c:

BER ph thuc vo mc quyt nh ID Chn ID sao cho BER t gi tr nh nht?

t v

BER nh nht khi ID c chn sao cho Q1=Q0=Q

NHY CA B THU QUANGThay th ( ) v ( ) vo biu thc ( ) ta c:

Hm li (error function):

Hm li ph:

NHY CA B THU QUANGThay ( ) vo biu thc ( ) ta c:

NHY CA B THU QUANG nhy b thu quang s dng tch sng quang PIN:Gi thit: bit 0 khng mang cng sut P0=0, =0Cng sut quang trung bnh thu c:

Cng sut trung bnh ng vi bit 1:

Tng qut: Vi cc gi thit nu trn, ta c: (Id=0)

NHY CA B THU QUANG nhy b thu quang s dng tch sng quang PIN:H s Q:

nhy ca b thu quang:

i vi b thu quang PIN, nhiu nhit thng l tri (s

NHY CA B THU QUANG nhy b thu quang s dng tch sng quang APD:Gi thit: bit 0 khng mang cng sut P0=0, =0Cng sut trung bnh ng vi bit 1:

H s Q:

Vi

nhy ca b thu quang:

NHY CA B THU QUANGSo snh nhy b thu quang APD vi b thu quang PIN:Nhiu lng t tng ln vi h s FANhiu nhit gim i M lnThnh phn nhiu lng t v nhiu nhit cn c xc nh khi xc nh nhiu trong b thu quang APD nhy tng 6-8 dB so vi b thu PIN nhy thng gim nhanh hn khi tc bit B tng ??? c tnh chung cho cc b thu c gii hn nhiu lng t

CC THAM S NH HNG N NHY THU QUANGGii hn lng t:L mc cng sut quang thu c nh nht c yu cu i vi c tnh t s bit li xc nh khi hiu sut lng t =1 v khng c dng tii vi b tch sng l tng, 0=0 v nhiu lng t trit tiu khi khng c cng sut quang ti ngng quyt nh ~0 bit 1 c th c nhn bit ngay c ch c mt photonGi Np l trung bnh cc photon trong tng bit 1. Xc xut pht ra m cp in t - l trng c cho bi phn b Poisson:

P(1/0)=0 v m=0 khi Np=0 P(0/1)=exp(-Np) c xc nh khi m=0

CC THAM S NH HNG N NHY THU QUANGGii hn lng t:T s bt li: BER = exp(-Np)/2Vi BER

CC THAM S NH HNG N NHY THU QUANGT s phn bit:

H s Q:

Khi nhiu nhit tri: 1 0 T, nhy thu:

S mt mt cng sut:

CC THAM S NH HNG N NHY THU QUANGT s phn bit:

Bi TpCho 1 tuyn truyn dn quang IM/DD im ni im truyn tn hiu quang vi tc 2.5Gb/s. Bit:Cng sut pht ca my pht PT = 1mWSi quang c suy hao 0.4dB/km ti bc sng 1310nm.Cch 2 km li c mt mi hn vi suy hao 0.1dB/mh. Ti mi trm s dng 1 connector c suy hao 0.5dB/connector kt ni cp quang v thit b.My thu s dng PIN c h/s lng t =0.5; in tr ti RL=1k; h s nhiu c khuch i Fn=2; hat ng nhit 27oC.Hy xc nh:a.p ng ca PIN ti bc sng 1310nm?b. nhy ca my thu tuyn quang c th hat ng c vi t s bit li BER 10-10 ?c.Khang cch lp t ti a ca tuyn quang trn m khng s dng trm lp khi BER 10-10 ?d.T s bit li BER nu tuyn quang c chiu di L=40km?

Bi TpMt tuyn truyn dn quang s hat ng bc sng 850nm vi t s BER = 10-9.a.Hy xc nh nng lng ca dng photon chiu ti my thu s dng PIN trong gii hn lng t? Gi s hiu st lng t =1b.Xc nh cng sut quang thu nh nht t c BER=10-9 tc d liu 10Mb/s?