Berendt, Martin Ole

Hübner, Jörg

Kristensen, M.

Lauridsen, Vibeke Claudia

Palsdottir, B.

Philipsen, Jacob Lundgreen

Povlsen, Jørn Hedegaard

Varming, Poul

Online Research Database In Technology

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Downloaded from orbit.dtu.dk on: Dec 17, 2017Polarisation Control Mechanism of DFB Fibre LasersVarming, Poul; Philipsen, Jacob Lundgreen; Berendt, Martin Ole; Lauridsen, Vibeke Claudia; Povlsen,Jørn Hedegaard; Hübner, Jörg; Kristensen, M.; Palsdottir, B.Published in:Lasers and Electro-Optics Europe, 1998. 1998 CLEO/Europe. Conference onPublication date:1998Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Varming, P., Philipsen, J. L., Berendt, M. O., Lauridsen, V. C., Povlsen, J. H., Hübner, J., ... Palsdottir, B. (1998).Polarisation Control Mechanism of DFB Fibre Lasers. In Lasers and Electro-Optics Europe, 1998. 1998CLEO/Europe. Conference on IEEE.Tuesday / 62 12.15 CTuFG Single-polarisation operation of injection locked fibre DFB lasers Shmji Yamashila and Gregory J .  Cawle Optoelectronics llesearrh Centre. i:niuetsiiy of Southanpton Soutliampton SO17 IBJ ,  UK Tel +44-1703-553139 Fax C44-1703-593142 Ernal. ~ y ~ m ~ ~ ~ ~ . l . ~ - t ~ k , ~ . a i j p  Optical Rbre dimibuted-feedhack (DFB) l a e r s  using UV-written fibre Biagg gratings on E+:ubs+ glo-firqueocy operation, lhus &re a promiang technology for applications in optical fibre [I]. Most fibre DFB lases, however a~tuall3' operate i s  two orthogonal polansacions as a resvit of polarisation independence i~ the  fibre DFB r e ~ m ~ t o r .  which ir not denirable for these Lpplicairunr. In I l l i s  paper, we q o r t  smgle-polariration operations of fibre DFB I a e m  u m g  injeruon locking techniques, whiih are similar to those used for polarisation sroltching in He-Ne lasers(?1. The configuration of the mjection locked libre DTB Iaer is shonn in Fig.1. The fibre DFB laser is pumped Rich a 580nm pump l a m  diode (LD) thraiigh 8 WDM coupler, and the l a i n &  light is  output through the \VUM coupler and m isolator. A single-frequency (f,), siingle~polansation signal from R tunahlr 1.u is fed LD another end of the  DFB l a m  Lhrough a poiarisatian controller (PC) and an kolator Wilhout in j~r l ian ,  the DFB 1h.w operated al. 1548.fnm, and in two palsrirntions (denoted by I aiid v )  af diffnmt frequrncm (f= and I,) separated by 0 8GHz. Figure 2 shows the RF spectra obmned by direct deteciian of the 1ae1 output. In Fig.?(&). the  light m a  Injected but the UI'U Iaer  u , a  not locked. A line a t  0.BGHr i s  a beat between fz and f v ,  and lines I I  0 l G H z  ana 0 . K H z  are beak beLween f, and f* and hetrcen f, and f,, respettively. \Vhen f, w a  ret cI01er to f,, t h e  DFB IMC~ via in~edion  locked, i.c. fs i v a  locked to f., and the beats between fs and f, and hetiwen f, and f, disappeared. a s h o w n  in Fig 2 ( h j ,  which means that the y-polarisafian sa suplmssed h> mjection lacking U'+ coufiriiied using a polarisation analyzer that, when j. w a  locked f, the avfput h_ 11) ~-p01arisacions. regardless a i  the polarisation ~ 1 s t ~  of injected bght, That  wes o true when f ,  wm lacked to f.. The injection locking rauge w&i found to be around IOblHz at tho e r t w  power of U.2mW. which 18 very n m m  compared with that of DFB LDs (typicall: B few CHa), babl) due t o  much longer length of tile fibre DFB larsi(-5cm]. As the locking range w a  belou' the iiequenq As si:Tlpler and mox .table rnelliod to achieve single-palariaation opemttlon, we triad the sclf- mjecnon locking technique. iii r h i r h  one of two polaiiaatian is feedback to the DFB I a e r ,  as shown in ~ ~ g . 3 .  I polariz~r and i r n ~ r r m  arc u r d  and two PCs m e  inserted between the DFB imei and the polarizer IPCI!. and between the  polaiiaer and the mirror (PC2) iespectiveiy U% m i  select either of the two poiamations to be lacked b? dJurling Lhe PCI. r igu rp  4 rhoas the R? spectra ohtaned by licterodyne derectmv of tbe laser output r l t h  B light from t h e  runnblc LD Without sdf~iojection, two beat liner W C ~ P  observed cormpoading to  I= and I, hr 4.h(:H1. az shown in Fig.l(a).  WLth %eIf~i+t im only f. xvas locked and f, was suppressed (ng..l(b!l. Br adjusting the PCl. we could also select f, Wc iouod that this operation WM very stable. Rcfcrencer [I] \\'. H Loh, et  al., J. Lighlwave Te~linol.. vol.16. no 1, pp.114-118, Jan. 1558. 121 S. T .  ~ ~ ~ , i ~ ~ .  et ai., o p t .  Lett., voi 7, n0.8, pp.:j56-36n. A U ~  m a  of injected ihgiib, the locking beharior WB- u r ~ t e b l e .  P"mP I Fig I injection locked fibre UFB lase?. Fig.2 Kf spectra. (a) Unlocked (b) locked (f, =/,I P " W  Fig 3 s d f . ~ j ~ ~ t m  locked fibre DFB 1-r F ig4  RF beat spectra (a) No injection (b) locked to f. ~ ~ ~~ ~~ 12.30 CTuF7 Polarisation control mechanism ofDFB fibre lasers P Vmmn$. 1 L Philipsen. M. 0. Bcrmdl. V. C. Lauridrm. 1. H Po\ l a ,  I. HUbnFr., M. Knlcnnn', B P P i ~ o m r . ~  Dmanmcnl olEl~tramalncl ic  S)sLms,  Technical Unitwsh) ofDtnmark. Building 348. DK.78W L>ngb), Dmrnarilr *M!kMIekImnik Cearrt. Technical Uniutrrity ofDrnrnarl. Budding 34Ss. DK-2800 Lyngby. Dromari Lvrmt Technologies Denmark. Pnor@m 680. DK-lhOJ Brondh). D m a r i  Since the introduction a i  single-made DFB fibre l a ~ n  with U V  induced phase-shifr, there lasier~ have found many applications withm optical ~ommunication [I] .  Single polarisation operaiion of the I s e r  could be amihuld to a polariralion dependence of either the p i i n g  reflecliviry. background 10x3. erbium gain, m the pbsse-nhifi. It has been shown that a birefringent distributed phae-h i f i  C ~ U S C I  a ~nr idcrablc  difference in the magnitude of the phase-shifi experienced by the Two polarbarion$ [21. H O W ~ V C T ,  until now it has not been clarified which polarisation dependent effect is dominating in awining single polariratmn aperation. In $his paper. we p r c ~ c m  rxpmrhanlal evidence hat a birefringent dimibu8Edphawshifi is  !he Aominatsg effect. A Bragg grating 181 winen in an erbium doped fibre using a KrF e x i m e r  laser. The UV lnduccd birefringence was around 2 10'. A dimbuied phase-shin was i n d u d  by exposing :he ccnnc pan of the Bragg grating 10 addilional UV pulner through a 4 mm apsmre. ARer 1500 pulses of this UV Post-procerSing (UVPP). ~inglc polarisanan lasing was obtained when the Brag8 grating was pumped by B diode 11111. Continuing the UVPP. the lasing was s h i e d  Lrre  tMes bswcm orthogomi polarIration 11atss G shown in Rg. I .  The rcvcrriblc behaviow indicates chat the lasing polarisation mode is not ronuolled by B polarisation dependent IOPI mcrbanism. Single longitudinal m d e  operation *as obrervcd throughout the experimanl using a scanning FabryPeioc inlerfecromelrr. The lasing pdarisalion m d e r  were relafed to the mnsmislion praki in the Bragg grating ssuird by thr phase-shift The phase-rhin ii polarisation dependant and the diffcrrncr is CORIIOI IE~  by tho birefringence of be UV-induced index change. An index change of2 10' in the 4 mm phase-rhifi region is required fm obraining B gming phe- rh i f i  of T. Throughout the UVPP we observed cr~cllmt ~greement b m v m  the position of the Iranrmission peaks and the p w i r  of the eomspanding laring polarirarion model. Single palariratran lasing wm ablcrvtd whm only one plariialion peak was positiancd near be centre of the Bragg grating. In  E O ~ ~ ~ U $ I D ~  se have demonsmted that the palani~m ofa  single-mode DFB fibre laser can be connolled by the birefnngence of rhe UV induced phase-rbifr 0 4  0 2  ;L--.- 0 0  0 L 5000 10000 15000 20000 25000 30000 [I] J .  Hilbner. P. V m i n g  and M K r i s ~ c ~ s e o ,  '"Fivc\~avslength DFB fibre 18sr murce for WDM systcm~" EleruonicrLoners,Volume 33, Numbeil .  Pager l39.140,1997. 121 11. s tow,  B. Sahlgren and R. Srubbe, "Single planration fibre DFB 1 % ~ ' ' .  Eleclronicr Lenrrr, Volume 33, Number I, Pqes56-57.1997. Authorized licensed use limited to: Danmarks Tekniske Informationscenter. Downloaded on June 01,2010 at 14:36:58 UTC from IEEE Xplore.  Restrictions apply. 

Polarisation Control Mechanism of DFB Fibre Lasers

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Polarisation Control Mechanism of DFB Fibre Lasers

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