Chng 7. Phn Loi OFDM QUANG7.1.Gii thiu.Ghp knh phn chia theo tn s trc giao OFDM c ng dng rt nhiu trong cc cng ngh hin nay.Trong cc h thng khng dy, OFDM c tch hp trong cc mng ni b khng dy (LAN; IEEE 802.11a/g, nh l Wi-Fi), mng WAN khng dy (IEEE 802.16e, nh l WiMAX), v k thut v tuyn s/h thng video (DAB/DVB) c p dng hu ht cc khu vc ca th gii.Trong cc h thng cp RF, OFDM c p dng vo cng ngh ADSL v VDSL thng qua h thng ng dy cp ng hay ng dy in. S a dng ny l nh u im ca qu trnh iu ch OFDM, bao gm rng tn sc, kh nng c lng knh, hiu sut ph cao, lu lng bit v ti. C nhiu sut khc nhau cho ng dng OFDM nhm t c nhiu li ch t h thng OFDM mang li. Mc d thc t l OFDM c nghin cu rng ri trong lnh vc h thng RF, nhng tht ng ngc nhin l vo nm 1996 mi xut hin ti liu nghin cu u tin v OFDM; Pan v Green1 phn tch su thc hin lai ghp AM/OFDM bng ghp knh SCM trong h thng cp quang. S thiu ch trng n h thng OFDM trong qu kh l do h thng x l tn hiu silicon khng t c nh khi s dng h thng OFDM trong mt mch tch hp CMOS (IC).Trong chng ny, chng ta phn loi OFDM theo tng k thut v ng dng c bn. Phn 7.2 v 7.3 phn tch v nguyn tc c bn ca OFDM trong qu trnh tch sng kt hp v trc tip. Mc d tch sng kt hp tr thnh cng c chnh trong h thng vin thng trong hai thp k qua, nhng nhng tin b trong cng ngh ch ra rng tch sng trc tip mi l cng ngh ch cht ca tng lai. Phn 7.4 minh ha vn tt cc ng dng khc nhau cho hai h thng tch sng trn.7.2 Kt hp OFDM quang mch lcOFDM quang hc kt hp ( CO -OFDM ) i din cho hiu sut cui cng trong thu nhy, hiu qu quang ph , v mnh m chng li phn cc phn tn , nhng n i hi s phc tp cao nht trong thit k thu pht . Trong cc ti liu m , CO -OFDM ln u tin bi Shieh v Athaudage 2 v cc khi nim v mch lc quang u ra angten khng dy xut OFDM c chnh thc ha bi Shieh 3 Cc th nghim CO -OFDM u c thc hin bi Shieh 4 cho mt tiu chun 1000 km cp quang n mode (SSMF ) truyn ti 8 Gb / s v Jansen 5 cho 4160 truyn km SSMF ti 20 Gb / s. Mt pht trin th v v quan trng l xut v trnh din ca khng c bo v khong CO -OFDM bi Yamada 6 trong OFDM quang c xy dng s dng sng mang con quang hc m khng c mt nhu cu cho cc tin t tun hon . Tuy nhin, c bn nguyn tc ca CO -OFDM vn ging nhau: t c hiu sut ph cao bi chng cho ph sng mang con trong khi trnh can thip bng cch s dng pht hin mch lc v tn hiu b trc giao . Trong phn ny, chng ti m t cc nguyn tc chi tit ca CO -OFDM , bao gm phn tch truyn v nhn thit k.7.2.1 Nguyn tc ca CO-OFDMVic phi hp gia truyn thng quang hc cht ch v OFDM c hai mt. OFDM mang n cho h thng cht ch hiu qu tnh ton v d knh v giai on d ton. Cc h thng mch lc mang OFDM mt tuyn tnh rt cn thit trong RF n quang (RTO) ln chuyn i v quang n RF ( OTR ) xung chuyn i. Do , mt bin i tuyn tnh l cha kha mc tiu thc hin OFDM. Mt h thng OFDM quang hc chung nh m t trong hnh 7.1 c th c chia thnh nm khi chc nng : (1) RF OFDM truyn , (2) RTO xung chuyn i,

Hnh 7.1: Mt h thng CO -OFDM trong kin trc (a) ch o ln / xung chuyn i v (b) kin trc tn s trung gian .(3) knh quang hc, (4) OTR xung chuyn i, v (5) RF OFDM nhn. cc chi tit kin trc cho RF OFDM truyn / nhn c th hin trong hnh 2.2 , to ra phc hi tn hiu OFDM trong c hai baseband hay ban nhc RF . Gi s mt si quang tuyn tnh knh ni phi tuyn si khng c xem xt. R rng l nhng thch thc cho thc hin CO -OFDM l c c mt RTO ln chuyn i v tuyn tnh OTR xung- tuyn tnh Chuyn i . N c xut v phn tch, xu hng ca cc b m ha Mach Zehnder ( MZMs ) vo thi im null, mt chuyn i tuyn tnh gia cc tn hiu RF v tn hiu lnh vc quang hc c th t c .2,7 Chng ti s tip tc x l vn quan trng ny (khng ) tuyn tnh ca RTO ln chuyn i ti mc 7.2.4 . N cng c ch ra rng bng cch s dng pht hin mch lc, mt bin i tuyn tnh t tn hiu lnh vc quang hc RF (hoc in ) tn hiu c th t c , 2,7-9 c tho lun ti mc 7.2.6. Bng cch to ra mt h thng hn hp nh trn v RF lnh vc quang hc, 2,4,5 mt knh tuyn tnh c th c xy dng trong OFDM c th thc hin n tt nht (v d , knh gim thiu s phn tn suy gim ) trong c hai lnh vc RF v min quang . Trong chng ny, chng ti s dng thut ng min RF v min in thay th cho nhau .7.2.2 Thit k pht quang cho CO -OFDMNh tho lun ti mc 7.2.1 , mc tiu thit k chnh cho CO -OFDM l xy dng mt tuyn tnh h thng chuyn i. Do , iu tra ca cc phi tuyn ca mt CO-OFDM my pht l c tm quan trng sng cn .7,10,11 c im MZM c rng ri iu tra bi Auracher v Keil.12 Cc phi tuyn ca MZM v vic thc hin h thng cc h thng pht hin trc tip c nghin cu k lng .13,14 N c ch ra rng i vi thng thng h thng pht hin trc tip cc im thin v ti u l ti cu phng v mt tn hiu ln s thm phi tuyn suy gim cc h thng . y, chng ti tp trung vo cc phi tuyn t OFDM chuyn i ln RTO . Chng ti u tin trnh by cc la chn kin trc cho mt h thng CO -OFDM chung .Sau chng ti xy dng cc i din phi tuyn hai tng mu cho RTO chuyn i ln m thc hin vic chuyn i tuyn tnh t in p in n lnh vc quang hc.7.2.3 Ln / Xung- Chuyn i thit k la chn cho h thng CO OFDM

Hnh 7.1a v 7.1b cho thy , tng ng, mt h thng CO -OFDM s dng trc tip ln / xung kin trc v chuyn i tn s trung gian (IF) kin trc . Trong thng trc tip kin trc chuyn i trong hnh 7.1a , my pht quang s dng mt I quang hc / Q iu bin m bao gm hai MZMs ln chuyn i thc / phn o ca OFDM phc tp tn hiu s (t) trong phng trnh . (2.1) t min RF lnh vc quang hc; c ngha l, mi MZM l tng ng thc y bi s tht hay phn o ca s (t) . Trong trc tip xung chuyn i kin trc, thu quang OFDM s dng hai cp ca my thu cn v mt quang 90 lai thc hin ti quang / pht hin Q . Nhn RF t OFDM thc hin OFDM x l bng tn c s phc hi d liu . Nhng li th ca mt trc tip chuyn i nh vy kin trc l: (1 ) loi b mt nhu cu cho mt b lc loi b hnh nh trong c hai b truyn v nhn v (2) gim ng k bng thng in yu cu cho c truyn v nhn . Trong kin trc chuyn i IF ln trong hnh 7.1b , tn hiu bng tn c s OFDM l ln u tin ln chuyn i sang mt tn s trung gian trong lnh vc in v sau cc tn hiu OFDM IF l tip tc ln chuyn i sang lnh vc quang hc vi mt MZM . Trong h thng chuyn i xung -IF , tn hiu OFDM quang l ln u tin chuyn xung n mt tn s trung gian v sau l in I / Q pht hin c thc hin.Bi v cc my pht c th l trc tip hoc IF ln kin trc chuyn i, v ngi nhn c th l trc tip hoc IF xung chuyn i kin trc , c bn la chn thit k cho mt h thng CO -OFDM ( ch c hai c th hin trong hnh 7.1). Hn na, vo cui nhn , ch o xung chuyn i ng ngha vi pht hin homodyne , v IF chuyn i xung ng ngha vi pht hin phch . Tuy nhin, cc iu khon trc tip chuyn i v nu chuyn i c s dng trong chng ny bao gm cc kin trc c hai truyn v nhn kt thc.7.2.4 H thng quang I/Q chuyn i ln RF.

Phn tch hai tng mu c s dng rng ri m t thnh phn RF v h thng phi tuyn .Trong phn ny, chng ti s dng phn tch hai tng mu xuyn tng t nh nghin cu I / Q iu bin quang hc phi tuyn trn chuyn i RF -to- quang cho mt my pht CO -OFDM . Cc kt qu thu c y nn p dng cho cc h thng a sng analog mch lc. i vi kin trc thng / xung chuyn i trc tip (hnh 7.1a ) , hai tng mu sng mang phc tp ti v c p dng cho u vo ca b iu bin quang hc I / Q . V li ch ca s n gin , chng ti ch phn tch hiu sut phi tuyn cho kin trc thng / xung chuyn i trc tip. Cc tn hiu quang ti u ra ca ch s IQ quang iu bin l

(7.1)

trong A l hng s t l. Tt c cc hng s tng xng s c b qua trong phn cn li ca chng ny. Cc lnh vc quang hc E (t) c vit bng mt hnh thc, mt thc t ph bin phc tp trong in 18 nhng lnh vc in ng nn c xem xt nh l mt phn thc s ca E (t). v l phn thc v phn o ca tn hiu a RF phc tp mi MZM, th hin l; trong l thin v DC in p ca cc chuyn i; l in p chuyn mch na bc sng; v l tn s / giai on cho laser pht. Sau khi sp xp li n gin, cc tn hiu u ra ca b iu bin quang hc IQ tr thnh

(7.2)

(7.3)

trong c nh ngha l ch s iu ch, l mt giai on chuyn i tnh (im thin v), v l c s ban nhc tng ng (hoc tn s chuyn xung) phin bn ca lnh vc quang hc E (t). Cc ch s iu ch xc nh M bng ch s iu ch quang hc ca cc tn hiu quang hc nu b iu bin quang hc c thin v ti cu phng trong mt h thng pht hin trc tip. Cc ch s iu ch M c xc nh y c s dng m t bin ca in p a, v sau n khng c gii hn trn ca 1 l ch s iu ch quang hc thng thng. Chng ti thc hin cc phn tch trn v li ch ca s n gin bi v n l mt bn dch tn s n gin ca lnh vc quang hc E (t). Cc phi tuyn c ngun gc biu hin cho s p dng cho lnh vc quang hc E (t).M rng hn cosin trong phng trnh (7.3) bng cch s dng chc nng Bessel, cc thnh phn c bn u ra vi tn s c th c th hin nh

(7.4)

Th hai u ra xuyn vi tn s c th c th hin nh

(7.5)

Th ba xuyn vi tn s s c

(7.6) Chng ti s dng th n im nh chn tiu chun (IPN) m t b iu bin phi tuyn 13 c bit, IP2 (IP3) l im m phn m rng tuyn tnh ca cc bc hai (th ba) cng sut u ra xuyn ct cc phn m rng tuyn tnh ca cc c bn sn lng in. Cc im chn c a ra trong cc iu khon ca cng sut u ra c bn. IP2 v IP3 c tnh ton t phng trnh. (7.4) - (7.6) v c th c th hin nh

(7.7)

(7.8)Cc im nh chn tng ng tham chiu ti u vo ca b iu bin quang hc I / Q l ch s iu ch c a ra bi

(7.9)

(7.10)N c th c ch ra rng phng trnh. (7.8) v (7.9) cng c gi tr kin trc IF, nhng phi tuyn bc hai l trnh cho kin trc IF.

Hnh 7.2: Cc bc nht, th hai, v u ra th ba nh l mt hm ca ch s iu ch M (dB)=20logM ti cc im thin v ca (a) v (b) .

Phng trnh (7.8) cho thy rng khi b iu bin c thin v ti khng u ra (), IP3 c gi tr ti a, hoc t nht l phi tuyn, c ngha l cc im thin v ti u nn p,v im ca b iu bin quang hc. Hnh 2.2a v 2.2b cho thy nhng c im ca s xuyn bc nht, th hai, v th ba l mt hm ca ch s iu ch M (dB) cho mt im thin v ti v gi tr v vung gc tng ng. C th thy rng ti cc C th thy rng ti sai lch v im , u ra c bn l ti a trong khi cc sn phm xuyn iu th hai c loi b trong so snh vi cc im thin v cu phng. Trong h thng CO-OFDM, bt k cp ca cc sng mang con s to ra sn phm xuyn hai v th ba. H thng hnh pht do I / Q iu bin quang hc phi tuyn trong iu kin thin v khc nhau l hon ton tho lun trong Tang "7".

Trong iu kin v thin v ti u , gi nh rng VI v VQ l nh v phi tuyn l khng ng k. Phng trnh (7.1) tr thnh (7.11)

trong l tn hiu bng tn OFDM phc tp. N sau lnh vc quang ti u ra ca b iu ch IQ E (t) v c bn l mt bn sao tuyn tnh ca cc tn hiu bng tn S (t) up-chuyn i sang tn s trung tm ca .

7.2.5 Cuc tho lun v cc im sai lch trong h thng CO-OFDMCc im thin v cu phng c p dng rng ri cho c analog v k thut s trc tip h thng pht hin. Cc im sai lch cho CO-OFDM ln chuyn i c ngha mt s khc bit c bn gia iu ch cng quang hc v iu ch lnh vc quang hc. V d, trong h thng pht hin mch lc, vic chuyn i gia cc in p in v lnh vc quang hc l mi quan tm, trong khi cc h thng pht hin trc tip thng thng vic chuyn i gia cc in p in v quang in l mi quan tm.

Hnh 7.3: Chuyn chc nng cho cng quang hc v cc lnh vc quang hc chng li in p a.Hnh 7.3 cho thy cc chc nng chuyn giao cho c cng quang hc v cc lnh vc quang hc (phn I / Q) so vi in p. Trong hnh 7.3, chng ti gi nh khng giai on u b p gia hai cnh tay ca MZM in p bng khng thin v. Cc chc nng chuyn giao cho cc pht hin trc tip l cng quang hc chng li cc in p, trong khi chuyn giao chc nng pht hin mch lc l I hoc Q thnh phn ca lnh vc quang hc chng li cc in p. R rng t hnh 7.3 rng s thin v MZM ti u cho iu ch cng quang l im vung gc, trong khi thin v ti u cho iu ch lnh vc quang hc l im rng.

Lu rng cc kt lun ca cc b iu ch ti u im sai lch v gi tr cho RTO ln chuyn i v c bn l c lp vi dng sng chi tit ca ; c ngha l, c th l bt k dng sng ty , khng nht thit phi gii hn ca CO-OFDM. V d, pht hin trc tip OFDM quang hc, n vn l ti u thin v b iu bin ti v im gim thiu RTO ln phi tuyn chuyn i. Tuy nhin, thch thc l lm th no lp li cc tu sn bay quang hc chnh, m b mt do s sai lch im rng. Chng ti d on rt nhiu n lc nghin cu ban u tn dng li th ca bin i tuyn tnh gia cc lnh vc quang hc v in p in trong cc h thng mch lc hoc khng mch lc, k thut s hoc tng t.7.2.6 Pht hin mch lc cho tuyn xung chuyn i v ngn chn ting nNh trong hnh 7.4, pht hin mch lc c th c su cng 90 lai quang hc v mt cp cn bng hnh nh d. Mc ch chnh ca pht hin mch lc l (i) phc hi tuyn tnh ca ti v Q thnh phn ca tn hiu n, v (ii) ngn chn hoc hy b ch ting n thng thng. S dng mt su cng 90 lai pht hin tn hiu v phn tch c thc hnh trong lnh vc RF trong nhiu thp k XV-XVI v ng dng ca n i vi h thng quang hc cht ch sng mang n cng c th c tm thy Ly-Gagnon v Savory 8,9. Sau minh ha nguyn tc lm vic ca mnh, chng ti s thc hin mt phn tch chuyn i xung thng qua pht hin cht ch gi nh iu kin l tng cho mi thnh phn trong hnh 7.4.

Mc ch ca bn cng u ra ca 90 quang lai l to ra mt 90 giai on chuyn i cho cc thnh phn I v Q, v 180 giai on chuyn i cho cn bng pht hin. B qua s mt cn bng v mt lai quang hc, cc tn hiu u ra c th c th hin nh

(7.12)

ni v l, tng ng, tn hiu n v dao ng trong (LO) tn hiu. Chng ti tip tc phn hy cc tn hiu u vo thnh hai thnh phn: (i) cc tn hiu nhn c l khi khng c ting n khuch i t pht (ASE), Er (t) v (ii) cc ting n ASE, n(t), c th l

(7.13)

u tin chng ta nghin cu cch cc thnh phn I ca quang pht hin hin ti c to ra, v Q thnh phn c th c bt ngun cho ph hp. Cc thnh phn ti thu c bng cch s dng mt cp ca hnh nh pht hin, PD1 v PD2 trong hnh 7.2, c dng quang c th c m t nh

(7.14)

(7.15)

(7.16)

(7.17)

ni m v l cng sut trung bnh v ting n cng tng i (RIN) ca LO laser, v "Re" hoc "Im" biu th phn thc hay tng tng ca mt tn hiu phc tp. v n gin, quang nhy pht hin c thit lp nh mt n v y. Ba iu kin bn tay phi ca (7.16) i din cho tn hiu-to-tn hiu nh bi ting n, tn hiu ASE nh bi ting n, v ASE ASE nh bi ting n. Bi v vic pht hin cn bng, s dng (7.14) v (7.15), cc thnh phn I ca dng quang tr thnh

(7.18)By gi c ch c ch ting n tr nn kh r rng bi v ba thut ng ting n trong (7.16) v ting n RIN trong (7.17) t mt my d n l hon ton hy b thng qua pht hin cn bng. Tuy nhin, n c hin th m pht hin mch lc c th c thc hin bng cch s dng mt nh pht hin duy nht, nhng vi s hy sinh ca gim phm vi hot ng.Trong mt cch tng t, thnh phn Q t cp khc ca my d cn bng c th c bt ngun nh

(7.19)S dng kt qu (7.18) v (7.19), cc I(t) dng quang phc tp bao gm c hai thnh phn I v Q tr thnh

(7.20)T (7.9), qu trnh tuyn tnh xung chuyn i thng qua pht hin mch lc tr nn kh d thy: cc dng quang I(t) phc tp l trong bn cht mt bn sao tuyn tnh ca cc tn hiu phc tp n l tn s chuyn xung bi mt tn s dao ng a phng. Tuyn tnh ny xung chuyn i c tm quan trng i vi iu ch OFDM trong gi nh tuyn tnh trong mi giai on ca x l tn hiu.7.2.7 nhy ca my thu cho CO-OFDM

Cc m hnh knh ca (5.8) cho

(7.21)

ni m l biu tng thng tin nhn, l giai on biu tng OFDM hoc chung li giai on, l chc nng chuyn giao min tn s knh, v l ngu nhin ting n. Tm thi b qua cc ch s "i" v "k", chng ta c th thy rng mi knh sng mang con v c bn l mt knh tuyn tnh vi mt ting n Gaussian trng ph gia. B qua hnh pht t li knh v giai on lp d ton c tho lun trong chng 4, vic thc hin l tng ca h thng vi bc bn giai on chuyn kha (QPSK) iu ch CO-OFDM l nh vy, c a ra bi

(7.22)

(7.23)

trong g l tn hiu ting n t l; v l phng sai cho cc tn hiu nhn c v ting n, tng ng; v erfc l hm li. y l bi hc vit mt cch r rng. Trong b tch sng coherent, nhiu s nh hng bi tn hiu khuch i t pht (ASE). Tng ng vi t s li bt (BER),hm Q, t s tn hiu quang trn nhiu (OSNR) v ca h thng ca h thng CO-OFDM s dng k thut iu ch QPSK c xc nh bi iu kin sau:

Vi B0 l bng thng nhiu ASE s dng tnh ton OSNR (~12.5GHz ca 0.1nm bng thng); l tc pht i k hiu tng ca h thng hoc bng thng ca tn hiu OFDM, v Nsc v l s lng sng mang con v khong cch gia cc sng mang con.7.3. iu ch trc tip tn hiu quang OFDM7.3.1. nh x tuyn tnh DDO-OFDM

Hnh 7.5: H thng LM-DDO-OFDM, ti ph ca tn hiu OFDM tng t nh ph ca tn hiu bng gc OFDM.Nh th hin trn hnh 704, ph quang ca mt tn hiu LM-DDO-OFDM ti u ra ca pha pht O-OFDM l m phng tuyn tnh ca ph RF-OFDM thm vi mt sng mang con, chnh l 50% ca ton b cng sut. V tr ca sng mang quang c th l ph bng rng OFDM hoc ph OFDM. DDO-OFDM c m t nh sau:

(7.27)

Ti s(t) l tn hiu quang OFDM, f0 l tn s sng mang quang chnh. l khong bng bo v gia sng mang quang v bng OFDM, l h s m rng c m t bi di bng OFDM. SB(t) l tn hiu bng gc OFDM c xc nh bi:

(7.28)Ti ck v fk tng ng l k hiu thng tin OFDM v tn s ca sng mang con th k. n gin hn, mt k hiu OFDM c biu din trn cng thc 7.28. Sau khi tn hiu i quan ng dn quang cng vi nh hng ca tn sc, tn hiu quang OFDM c xc nh xp x:

(7.29)

(7.30)

Ti l ph tr trong sut thi gian tn sc ca sng mang con th k, Dt c tch ly bi tn sc bi i lng pico giy trn mi pico mt (ps/pm). F0 l tn s trung tm ca ph quang OFDM, c l tc t nh sang. Ti pha nhn, photoditector c th c biu din:

(7.31)Giai on u tin l kt hp cc thnh phn DC c th c a ra u ra b lc. Giai on 2 l giai on c bn gm cc sng mang con OFDM. Giai on 3 l giai on cp 2 phi tuyn cn loi b.Theo nh cc cch tip cn c th c s dng ti thiu ha phi tuyn: dc ca SSB-OFDM Tn hiu quang bng gc SSB-OFDM an xen cc sng mang Gim tn scC rt nhiu u im v nhc im trong 4 cch trn. V d nh cch th 2 c u im l hiu sut ph tt hn nhng nhy pha nhn s b mt. Cch th 4 c u im l hiu sut ph v nhy nhng cha ti trng phc tp.

7.3.1.1. dc SSB-OFDM dc OFDM c gi s bi Lowery. Chng th hin DDO-OFDM c th gim nh tn sc xung 5000 km vi si quang SSMF. Hnh 7.6 th hin h thng c doccs OFDM trong m phng. H thng m phng l 10Gb/s cng vi iu ch 4-QAM v rng bng thng xp x l 5Ghz, pha pht min in OFDM, tn hiu OFDM c nng tn ln 7.5Ghz. u ra ph tn hiu quang c 2 pha OFDM l h thng i xng thng quang cc sng mang quang.

Hnh 7.6 H thng thng tin quang DDO-OFDMTn hiu quang ti b lc c s dng u ra b lc. Tn hiu cc di bin (SSB) c m bo gii hn l vic nh x tn hiu RF OFDM v tn hiu quang OFDM. Ti pha thu, b photoditector c s dng. Ph RF ca photoditector hin ti c m t trn hnh 7.6. N c th c s dng iu ch trong mc 2, Giai on 3 trong cng thc (7.31).Hnh 7.7 th hin hm Q pha nhn trong h thng back to back nh mt hm ca sng mang. su iu ch c xc nh thng qua lch tiu chuaanrcuar tn hiu in iu khin nh phn trm in p yu cu n b iu ch t 0% n 100% . B khuch i quang nhiu ASE c thm vo t c OSNR l 12.9 dB. S dng xc nh su iu ch, iu chnh di mc 20%, dng sng OFDM s t nh ti 0% v 100%, hoc ch s iu ch quang s t mc 100%.

Hnh 7.7: Hiu nng ca h thng da vo vic loi b dc DDO-OFDM

Hnh 7.8: Hm Q so vi cng sut ban u ti mi knh bin thin

Vic ct xn loi b ti a hm Q xung di mc gii hn ca nhiu. Mt khc, b iu ch iu khin cc mc (