Troubleshooting fiber Bragg grating fabrication with modeling

Transcription

1 Troubshooting fibr Bragg grating fabrication with moding Assandra Chiari Fibr Otics & Ectronics Coaborators: Jim Brnnan (TSD), Dwayn LaBrak (TSD), Chars Haggans

2 Abstract Svra aroachs ar avaiab for moding fibr Bragg gratings, ach having thir own strngths and waknsss. In this tak, w wi discuss how diffrnt tchniqus for soving coud mod thory quations can rovid commntary information that is not asiy attainab by using on tchniqu aon. This work is articuary aicab to vry ong ngth fibr Bragg gratings.

3 Motivation Outin What is a fibr Bragg grating Rviwing chromatic disrsion FGB as disrsion comnsator W mad on and it dos not ook good Using moding to undrstand why and to st fabrication torancs Concusion

4 Tcommunications has a bandwidth robm disrsion comnsation WDM bandwidth rbium dod fibrs for fibr amifirs

5 Introduction Rfctivity Wavngth (nm) Signa In Rfction 1558 Fibr Cor Otica Fibr L Indx Moduation Transmission Transmissivity Wavngth (nm) Rfctivity Wavngth (nm) 1558 Cor Rfractiv Indx 1.46 Λ = 2n b Fibr Axis -5-2 n = 10 to 10

6 Phas Mask: Dirct Imrinting UV Bam +1 ordr Phas Mask Otica Fibr -1 ordr

7 Bragg Gratings:Basic Dfinitions n n Uniform Profi : Uniform Bragg Grating Priod (tyica). Chir : Non-Uniform Bragg Grating Priod. n n Aodization : Taiord Satia Exosur. Aodization : Taiord Satia Exosur.

8 Chromatic Disrsion Probm Otica Fibr > 400 km Dtction Schm Dos Not Rsov Puss Otica Fibr > 400 km

9 Disrsion Comnsation Th Probm Standard sing-mod fibr has zro disrsion at th 1310nm transmission band. It is not corrctd at th 1550nm band. Disrsion broadns otica uss as thy trav in sing-mod fibr, imiting th utimat data rat suortd by fibr. A Soution Rcomrss th otica uss using chird gratings. Inut: Long λ ags short λ Long λ Dcrasing grating riod (Chir) Outut: Comrssd Pus Short λ

10 Fibr Bragg Grating Disrsion Comnsator

11 Disrsion Comnsator Goa to comnsat th arg bandwidth λ of rbium fibr amifirs for ong distancs of fibr inks L f with disrsion D 1550 nm) DL f L n g 2 = c ff D - disrsion r unit ngth L f - fibr ink ngth L g - grating ngth n ff - ffctiv indx c - sd of ight λ - grating bandwidth For a 80 km ink, nd to comnsat 1360 s/nm For a bandwidth of 7 nm, nd about 1 m granting

12 Aroach to FBG Sctrum Simuation: coud-mod thory Good quantitativ rdictor of diffraction fficincy and sctra dndnc of fibr gratings Cou Mod amitud quations ()()()() dr izrzizsz ds izszizrz dz =+ = Whr R and S ar th forward and backward roagating mods, rsctivy, and σ and κ ar couing cofficints

13 Som Soution Aroachs Dirct numrica intgration of coud mod qs. advantag - can rsov ffct of sma sca fabrication rrors disadvantag - not fast Transfr matrix (icwis-uniform aroach) advantag - rasonab simuation tims for ong gratings disadvantag - smast sction must b about 50 riods in ngth

14 Main Moding Paramtrs Inut fibr gomtry (dimnsion, rfractiv indics,hotosntivity) grating ngth cntra riod chir/bandwidth grating strngth aodization has shifts Outut rfction transmission day (ri factor) disrsion

15 d ( n o i t c f r What is an ida disrsion comnsating grating sctrum? wavngth (m) d a y ( s )

16 Grating showing instabiity in fabrication rocss

17 Anaysis Rsut dirct numrica intgration Masurmnt in bu & Simuation in Rd

18 Anothr fabricatd DCG: why d ( n 0 o i -5 t c f -20 r th fuzz? dviation from inar day is cad day ri wavngth (nm) d a y ( s )

19 Transfr Matrix icwis-uniform aroach W imosd stochastic has shifts and studid thir ffct on grating sctra as w varid thir max. amitud and thir frquncy aong th grating.

20 d ( n 0 o i -5 t c f -20 r wavngth (nm) Figur of mrit d a y ( s ) Ri standard dviation ( i r y a d wavngth (nm)

21 Anaysis Rsut transfr matrix aroach Day ri amitud as a function of... d u t i m a i r...random has maximum amitud has shift amitud (dgrs)... numbr of random has shifts aong th grating ngth u t i m a i r numbr of has shifts, N Th simuation rsuts (circs) foow a owr aw rationshi (in).

22 Day ri Day ri for chird FBG with riodic has shifts across its ngth is shown bow. Th ri incrass with th otica ath ngth through th grating. Th wavngths on th aunch sid show th ast amount of ri both in th u t i 200 m150 A i R Wavngth (nm) simuations and masurmnts. ( i r y a d wavngth (nm) simuation: day ri across chird FBG with ight aunchd into ong wavngth sid masurmnt: day ri across chird FBG with ight aunchd into ong wavngth sid.

23 Concusion A varity of moding & comutationa toos is ndd to gt th work don.