CA2245460A1 - Unequal couplers for multimode pumping optical amplifiers - Google Patents
Unequal couplers for multimode pumping optical amplifiers Download PDFInfo
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Abstract
A twin coupler system includes first and second optical couplers that couple a multimode pump fiber into a double-clad active primary fiber. The pump fiber carries multimode pump power from a multimode source. The primary fiber, on the other hand carries optical information signals on the single mode core that are amplified through the pump power. A system and method for manufacturing the twin coupler system constructs the first coupler by preparing first portions of the primary and pump fibers for coupling and performing fusion and tapering operations on the primary and pump fibers at the first portions and constructs the second coupler by preparingsecond portions of the primary and pump fibers for coupling and performing fusion and tapering operations on the primary and pump fibers at the second portions. The fusion and tapering operations at the second portions are dependent upon the fusion and tapering operations performed at the first portions so as to achieve a maximum coupling efficiency of the pump power from the pump fiber to the primary fiber for the entire twin coupler system.
Description
UNEQUAL COUPLERS FOR MULTIMODE PUMPING OPTICAL AMPLIFIERS
FIELD OF THE INVENTION
The present invention relates generally to a high power multimode pumped 5 optical fiber amplifier, and more particularly, to a twin coupler system that increases the pumping ~lTis ~nc~ ot a double-clad optical fiber a"lp!;fier.
BACKGROUND OF THE INVENTION
Conventional optical fiber amplifi~rs include active fibers having a core doped 10 with a rare earth ele."enb Pump power st a chara..1~ri:,tic wavelength for the rare earth elen~ent, when i~e :ted into the actffve fiber, excites the ions of the rare earth elehlehl, leading to gain in the core for an info""alion signal propagc,li.,g along the fiber.
Rare earth elements used for doping typically include Erbium (Er), 15 Neodymium (Nd), Ytterbium (Yb), Samarium (Sm), and Praseodymium (Pr). The particular rare earth eleml~ll used is det~rrnined in a~ordance with the wav¢leng~l, of the input signal light and the v:avelength of the pump light. For example, Er ions would be used for input signal light having a wavelen!Jtl, of ~.55~m and for pump power having a wav¢len.lll, of 1 .48~m or 0.98~1m; codop ng with Er and Yb ions,20 further, allows dil,~rt,nt and broader pump wavelehytl, bands to be used.
Traditional pump sources include single mode laser diodes and multimode broad area lasers coupled t~ the active flber over single mode and multimode pumping fibers, respectively, to provide the pump power. Single mode lasers provide low pump power, typicall~l~ in the order of 100 mW. Broad area lasers, on the other 25 hand, provide high pump power, in the order of 500 mW. These lasers of high output power, however, cannot I fficiently inject light into the small core of a single mode fiber. Consequently, the use of high power broad area lasers requires the use of wide core and multimode fibers for pumping optical amplifiers.
Broad area lasers generale multimode pump power and input the pump power 30 to a non-active pumping ~Fiber. This non-active pumping fiber in tum typically inputs the pump power through a coupler and into the inner cladding of a doubl~clad active fiber, acting as a multimode core for the pump power.
In the amplifier fib,ers, pump power is guided into the inner multimode cladding ,~
of the fiber from which it is transrer~ed into a single mode core doped with an active dopant.
A fused fiber multimode coupler has a ll,eo,~tic~l coupling coefficient directlypropo, lional to the ratio oF the areas of the two fibers constituting the coupler itself. In 5 an ideal case for two ident.cal fibers, the coupling coemcient is app~ oximately 50%.
Typically, the coupling coemcient is in the range of 45~8%. This means that onlyabout 4548% of the total pump power output by the pump souroe into the pumping fib,er actually passes froml the pumping fiber to the inner cladding of the double-clad active fiber, wt~ile the remlaining 52-55% remains in the pumping fiber.
Some systems us~e two optical fibers having differen: did."_ter of mulL",ode cores to i.opr~ the coupling coefficient of the mulli."ode coupler. However, such a,.dr~e",ents often lead to a waste of pclwer due to the difficulty in matching the tapering of two cores of different size.
Fig. 1 is a block ~ ", of a conventional amplifying system containing a multimode pump souroe coupled to a primary fiber via a single traditional coupler.
Primary fiber 1100 is a double-clad fiber. The i.,fo,l,-dtion signal flows through its single mode core. Amplifier 1200, which may take the form of an ErNb doped double-clad active fiber, almplifies the information signal as it propagates through the single mode core of primary fiber 1100.
Mu:timode pump 11300 is coupled into primary hber 1100 via multimode pump fiber 1400 and coupler 15100.
Multimode pump power generated by multimode pump 1300 is coupled into primary fiber 1100 via multi"-ode pump fiber 1400 and coupler 1500. Coupler 1500 is a conventional fused fiber waveleh!JU, division multiplexer (WDM) type coupler. WDM
couplers behave as multimode o ouplers fbr the pump power and t,ansi"it the single mode signal along the primary fiber subat i,ltially without coupling to the pump fiber.
WDM couplers have maximum coupling effi~-~nc es of 50~h forthe pump power, and typically have coupling efficioncies in the range of about 45%.
Multimode pump 1300 may take the form of a broad area laser that outputs pump power of approxi-"i?te'y 450-500 mW. Due to the couplir~ coe~, c-ent of coupler 1500, hol:o~or, only about 45% of this pump power, or appro~i."ately 200-225 mW, enters primary flber 1100. The remaining 55% of the pump power is lost, as it exits from pump fiber 1400.
More recent systems have attempted to recover the lost pump power. Fig. 2 , ~, is a block diagr~." of one of these systems. The primary fiber through which theinformation signal flows includes signal fiber 2100 and signal fiber 2200, which are ",atcl)ed double-clad fibers, and amplifiers 2300 and 2400. Amplifiers 2300 and 2400, which may cGm~, ise ErlYb doped double-clad active fibers, amplify the 5 inf~ rmalion signal as it pl o~wg~tes through the single mode core of the primary fiber.
In this system, mulltimode pump 2500 is coupled into the primary fiber via two idei,lical couplers 2600 and 2700, over pump fiber 2800 and pump fiber 2900, ,~spe~ ely. Pump fibers 2800 and 2900 are mat-ihed multimode fibers, spliced togetl.er at a point betwe~en couplers 26a0 and 2700.
Multimode pump :2500 outputs multimode pump power over pump fiber 2800.
Due to the coupling coeffident of coupler 2600, only about 45% of the pump powerenters signal flber 2100. VVith this ar-dfigen,ent, however, the remaining 55% of the pump power is not lost, but, instead, enbrs pump fiber 2900, which couples into signal fiber 2200 via coupler 2700.
AppJicants have observed that the addition of pump fiber 2900 and coupler 2700, ho.~e,~er, does not significantly improve the total pump power transfer over the one coupler system desc~ d above. There are a few r~asons for this. First, the splice between pump fiber 2800 and pump fiber 2900 results in a loss of pump power.
Second, the first couplin!3 ~t~ een pump fiber 2800 and signal fiber 2100 results in 20 most of the exbemal modes of the pump power being b afi fc rred to signal fiber 2100, leaving only the internal rnodes for the second coupling. This leads to ine~,ienl l.ar,:,fer of the r~"-a;.)ing pump power at coupler 2700. Such a structure dtl~:r"pts to recouple most of the intemal modes of the multimode pump power, those with the poorest coupling efficienc:y. As a result, the coupled pump power and the multimode 25 amplifier's output power clo not change s4, -if~c~rltly over the single coupler system desc,il,ed above.
Several articles in the patent and non-patent literature a~dlt5ss multi."ode coupling technbues but clo not over~Gfi,e the deficiencies of other converltional appruacl.es de~cribed ab~ove. WO 95/10868 d;scloses a fib!er optic amplifier 30 co-"prisi"g a fiber with two concent-ic cores. Pump power provided by multimode sources couples transversely to the outer core of the fiber through multimode fibers and multimode optical couplers. The pump power prop~g,~tes through the outer core and interacts with the inner core to pump active material contained in the inner core.
U.S. Patent No. 5,185,814 di t:'o9es an optical communications network in . ~ . .
which amplifiers amplify optical signals as the optical signals propag,~le along a waveguide. A single optical pump source coupled to the optical fiber pumps the amplifiers.
U.S. Patent No. 5,533,163 disclQses a double-clad optical fiber configuration that includes a core dopeld with an active gain ."atti,ial, an~an inner claddingsurrounding the core. An extemal pump souroe inputs multimode pump energy to theinner cladding. The multimode pump energy in the inner cladding l,dnsfer:i energy into the core through repeated i, llel a~,liGns between the energy and the active dopant within the core.
WO 93J15536 disc'o8es a compound glass fiber that includes an outer c.ad 'i"g, inner dadding, and a single mode central core. The inner cladding has a cross-se~,1ional profile opli"lked to reoeive multimode pumping radiation. The single mode core is located within the inner cla~ding and doped with a lasant ",aterial to maximize l,ari~f~r of the rnultimode pumping IddidtiGn to the single mode doped core.
U.S. Patent No. 5,170,458 disc~Qses an optical fiber light-amplifier that includes an optical fiber with a center core through which signal light propag~les, and a pumping light gel1~r~i-,g device that applies pumping light obliquely to the optical fiber. While the pumping li~ht pro~g~t~ ~ through the fiber, it is absorbed by and excites the oenter core to amplify the signal light propa~Ptecl through the optical fiber.
In Applicants' view, none of the known literature has adequately add~essed Applicants' discovery that conventional s~sle:"~s have failed to recouple sufficient pump power, thereby leadin~ to an inaclequate overall pump power l,ans~er efficiency.
SUMMARY OF THE INVENTION
The present invention adJI~7sses the above pr~blems in a twin coupler system that recouples more multimode pump power to a double~clad optical amplifier thanconventional s~sle",s by using couplers having dissimilar tapel i, .g.
In acct~dance with the invention as c.,.~Qd e ~ and broadly desclil~d herein, 30 the pr~sent invention in one aspect includes a twin coupler system having a signal fiber configured to receive and ll ~nspGl I an optical signal, a pump fibler configured to reoeive and tlanspoi ~ pump power, a first coupler induding the signal and pump fibers fused and tape~d by a first amount to l,dns~r a portion of the pump power from the pump fiber to the signal fiber, and a second ooupler including the signal and pump fibers fused and bpered by a second amount to l-ansfer at least some of a remaining portion of the pump power from the pump fiber to the sbnal fiber. The second amount of tapering is generally depende.~t upon the first amount of tape,ing to achieve a maximurn total coupling ~ffic ency for the twin coupler system.
In another aspect the present in~ntion also includes a method for manufacturing the twin c~upler system. The manufacturing method constructs the first coupler by pr~palil)g first po, lions of the primary and pump fibers for coupling and performing fusbn and tap~, i ,9 ope~Uon~ on the primary and pump fibers at the first po,lions and constructs the second coupler by pr~pa,i"g second portions of the 10 primary and pump fibers Ior coupling and performing fusion and tap~ering oper~lions on the primary and pump fibers at the second portions. The fusion and tapering opcrdtions at the second pG tions are dependent upon the fusion and tapering ope.dtions pe,h,l"-ad at the first polliGns so as to acl,.~\~e a maximum coupling ~ffi~ rnc~ of the pump power from the pump fiber to the primary fiber for the entire 15 twin coupler system.
In an~tl.er aspect the present inv~nlion indudes an apparatus for manufacturing the twin coupler system. The appa- dtUs includes means for prepa. i"g first and second po, lions of both the signal fiber and the pump fiber for coupling and means for pe-f~J.-"ing fusion and stretching operalions on the signal and pump fibers 20 at the first and second portions. The fusion and stretching opei dlions at the first portions form the first coupler and the fu~iion and stretching opcrations at the second po, tions form the second coupler and are dependent upon the fusion and stretching optlations pe, fvl med in fDrming the first coupler.
The present invention further includes an apparatus for manufacturing at least 25 first and second optical couplers of a multiple coupler system for coupling amultimode pump fiber to a double-clad active signal fiber. The apparatus includes means for su~,ply;ng a multimode optical signal to the pump fiber, means for fusing the signal and pump fibers at first and second spaced lo~tions means for tape.il.g the signal and pump fibers at the first and second loc~iions means for monitoring a 30 coupling efficiency based on an amount of the multimode optical power l-al-sfe"t,d from the pump fiber to the signal fiber at the first and second couplers, and means for controlling the fusing and tapering means to heat and stretch the signal and pump fibers at the first locations to produce the first coupler based on the ",on-t~red coupling ~f~c.a~ for the first coupler and for controlling the fusing and tapering .. ~................ . .
means to heat and stretch the signal and pump fibers at the second localions to produce the second coupler based on the coupling emciency for the first coupler and the mon tor~d coupling effidency for the ~econd coupler.
In ar,vtl,er aspect, the present invention includes a n.ethod for manufacturing at least first and second optkal couplers of a multiple coupler system for coupling a double-clad active signal fiber and a multimode pump fiber. The Illetllod includes the steps of supply;. I9 a multimode opticaJ s4nal to the pump fiber, heating and stretching first poi lions of the signal and pump fibers to produce the first coupler, monilo~ ing a coupling effciency for the first coupler based on an amount of the mullimode optical 10 power t-dnsf~l.ed from the pump fiber to the signal fiber at the first coupler, controlling the first poll;ons heating and $tretching step to a~)bvc a maximum value for the coupling efficiency for the first cowpler, heating and stretching second po- lions of the signal and pump fiber6 to produce the second coupler, monitoring a coupling efficiency for the second c oupler based on an amount of the multimode optical power 15 lran~rGI ~ed from the pump fber to the signal fiber at the second coupler, and controlling the second pol1~.s heating and stretching step to ad~.ev~ a maximum total coupling efficiency for the multiple coupler system based on the acl) evedmaximum coupling ~lT; c ~ for the first coupbr and the coupling efficiency for the second coupler.
BRIEF DESCRIPTION OF THE DRAWINGS
The accorllpanyin!3 ~ ings, which are illcGi~ord~d in and constitute a part of this spe~,ific~tion, illustrat- an embodiment of the invention and, tOge~tl er with the desc,iption, explain the ob,ects, advanlages and principles of the invention. In the 25 ~ gs, Fig. 1 is a block ~iay.dm of a conva.lliGnal system containing a mullill,ode pump source coupled to a primary fiber via a single t,aJiliGnal coupler;
Fig. 2 is a block d;~.am of a system that recovers a portion of the lost pump power;
Fig. 3 is a diagrarn of a twin coupbr system consist~nt witn the principles of the present invention;
Fig. 4A is a Jiaglalll depicting a cross-se~;tional view of the primary fiber ofFig. 3;
Fig. 4B is a graph of the difrerenl indexes of refraction of the primary fiber of Fig. 3;
Fig. 5A is a cliagrai" depicting a cross-se.,tional view of the pump fiber of Fig.
3;
Fig. 58 is a graph of the differ~nt i"dexes of rer, a.;lion of the pump fiber of Fig.
5 3;
Figs. 6A~D are flow charts describing a method for manufacturing the twin coupler system consistent wlth the principles of the present inv~ntion;
Fig. 7 is a block dia~lam of a simplified version of the twin coupler system of Fig. 3;
Fig. 8 is a block Jia~a,n of the equipment used for manufacturing a first coupler of Fig. 3;
Figs. 9A and 9B are graphs depicting temperature and speed profiles, respectively, for the fusion and tape. ing ~ralions to produce the first coupler;
Fig. 10 is a block dia~, am of the equipment used for manufacturing a second coupler of Fig. 3; and Figs. 11A and 11 E~ are graphs depicting bh)perature and speed profiles, :spe~ ely, for the fusion alnd tape, i-~g u~Jerdtions to produce the second coupler.
It is to be unde, tood that both the for~gDI.)g g~neral de~ lion and the following detailed descri~,~iGn are e~e."~~ry and are i,-lended to provide further eA~lanation of the invention as claimed.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The folbwing detaibd dascii~ction of the invention refers to the accol-,pat)yingdIL~;n9S~ The same ,ef_r~nce numbers identify the same or similar elements.
The de~cription indudes exemplaly embodiments, other embodiments are possible, and ~ ,anges may be made to the embodiments described without depa. Ii- ,9 from the spirit and scope of the invention. The f~!l..~.ng detailed descri,vtbn does not limit the inventbn. Instead, the scope of the invenlion is defined only by the appended claims.
Systems and m~tl lo~s consistent with the principles of the present invention achieve high l,ar,sf~r ~fi~ e~cy of multimode pumping power to an active, information-carrying, doubb-clad fiber using a twin-coupler sysbm having two dissimilar couplers.
Fig. 3 is a diag, dm of an amplifier system having a twin coupler system consistent with the principles of the present invention. The amplifier sysbm can be coupled as a high power optical amplifier in an optical fiber communication system; in this case input of fiber 3100 and output dF amplifier fiber 3400 are in general spliced to a single mode fiber of the! communication system. The amplifier system may to 5 advantage constitute a power booster amplifier or a line a.n~!;r,er.
The system includes two dmerent types of multimodelsingle mode optical fibers, a primary fiber and a pump fiber, coupled tog~tl,er by two dissimilar couplers.
The primary fiber contains an embedded singb mode core to carry an illfolllldtiGn signal.
The primary fiber includes signal fibers 3100 and 3200 and optical amplifiers 3300 and 3400. Signal fibers 3100 and 3200 are ".atched double clad optical fibers, while optical amplifiers 3300 and 3400 are double-clad ErlYb fibers doped to amplify the ill~ullndtion sbnal as it popag~t~Fs through the primary fiber. Fig. 4A is a diagram depicting a cro6s scctional view of the primary fiber, and Fig. 4B is a graph of the 15 difl_rent i"de:.es of ~eF~d~;ti~) of the prim~ry fiber.
As shown in Figs. 4A and 4B, the primary fiber ~3100, 3200) includes three kinds of glass forming conco.)t ic regions 4100, 4200, and 4300 having di~fer_ntindexes of refraction n1, n2, and n3, tespe_tively, and di1farerlt dia--,eter;i d1, d2, and d3, respectively. In an irnplel"er,tdtion consistent with the principles of the present 20 invention, the primary fiber i~ constructed such that the indexes of refraction have the relationship n1 < n2 < n3, and the dia",oters dl, d2, and d3 of the three concent,ic regions 4100, 4200, and 4300 ach.eve single mode optical pro~ ion for the i"fo, ~"dtion signal in region 4300 and multimode optical propagation for the pump power in region 4200. In other words, region 4300 surrounded by region 4200 forms 25 a single mode core for the ii~for,lldlion signal. Region 4200 surrounded by region 4100, on the other hand, forms a multimode core for the pump power.
In an implemenlation consistent with the principles of the p,~sent invention, the i..dexes of refraction and the diamet6l~ of concent-ic regions 4100, 4200, and 4300 have the fi"ow;.,g relationships:
CA 02245460 l998-08-2l ~(n32 n22) = 019 (1) ~/(n22- n ~2~ = 0 21 (2) d1 = 90~1m (3 d2 = 65~,1m d3 = 4~1m (5) Multimode pump 3500 connect~ to the primary fiber (3100, 3200) via couplers 3600 and 3700 to supply pump power. In an i",Fl~..,entdlion consislenl with the principles of the present invonlion, multimode pump 3500 is a broad area laser that outputs multimode pump power to pump fiber 3800. Pump fiber 3800 is a multimode optical fiber that carries the muHimode pump power. Fig. 5A is a diayl dm depicting a cross-sectional view of pump fiber 3800, and Fig. SB is a graph of the differentindexes of refraction of pump fiber 3800.
As shown in Figs. 5A and 5B, pump fiber 3800 includes two different types of glass ror,.,i"g concentric regions 5100 and 5200 having dfflerent indexes of rer,dction n1' and n2'"~,~pe-,ti~/ely, and different diameters d1' and d2', r~spe..li~/ely. In an implen ,entdtion consist~nt with the principles of the pr ,sent inv~nlion, pump fiber 3800 is constructed such that the i--deAe~ of ~~fld~tion have the ~1.4tionship n1' <- n2'.
The ~Jia",eter~ d1' and d2' of the two concentric regions 5100 and 5200 acl,:~ve15 multimode optical propas~tion for the pump power in region 5200. In other words, region 5200 surrounded by region 5100 forms a multimode core for the pump power.In an implel"enldlion oonsistent with the principles of the p~sent invention, the indexes of refnction and the diameters of concent,ic regions 5100 and 5200 have the f~llc ~:;. ,9 reldtionships:
.
~(n2' )~ - (nl ' )2 = 0. 21 (6) d1' = 90~m (7) d2' = 65~1m (8) Even though the concent- ic regions of pump fiber 3800 have been described as having the same indices of ,~f~a~tion and diar ,ct~ra as the conc~,l,ic regions of the primary fiber (3100, 3200), this need not be the case.
Both the primary fik~r (3100, 3200) and pump fiber 3800 contain a protective plastic coating surrounding the outer conaent,ic region (4100, 5100). In an implementation consistenl with the principles of the pr~sent invention, the protecti~e plastic coating has a thickne~s such that the exter. -al Jiam3tcr of both the primary fiber (3100, 3200) and pump fiber 3800 is appn"-i",ate~ly 25011m . The exter..al.Jiar ,etera may, of course, bo dfflerent vahes, and the CAt~5IIIaIdjarIIetera of the primary fiber (3100, 3200) and pump fiber 3800 need not be the same.
Couplers 3600 and :3700 are dissimilar optical fiber couplers for transferring pump power from pump fiber 3800 to the primary fiber (3100, 3200). In an imple".enbtion consistenl with the principles of the present invention, couplers 3600 and 3700 are manufactur~3d by a fusion k con ~,~' tape,ing technique des~iLed below.
Figs. 6A~D are flow charts describing a method for manufacturing a twin coupler system cons st~ nt with the principles of the p,~5enl invention. Fig. 7 is a simplified block diayIar" of the twin coupler system of Fig. 3. Figs. 8 and 10 are block diay.d",s of equipment use~ for manufaduring the first and second couplers 3600 and 3700 of Fig. 3"~spe.;ti~lely.
Turning first to Fig. 8, equipment usod in a manufacturing method consistent with the principles of the pr~ent invention will be deseriL~d first to facilitate descl iption of the manufacturing method with regard to Figs. 6A~D. The manufacturing equipment cGr"pri~es conv~ntional equipment, including cont,.'ler 8100, multi",oc;e source 8200, mode scrambler 8300, quartz capillary 8400, cylindrical heater 8500""ot~i~ed sbges 8620 and 8640, detect~rs 8720 and 8740 with adapte,~ 8760 and 8780, p~"u"~ct~r 8800, and py-uillJt~,r c~nt,~"er 8900.
Cont..!lYr 8100 may take the form of a personal computer, such as an IBMT~-cGn~pdlible computer. Contl~,ller 8100 cont.ol~ the operdtion of the manufacturing equipment. Multimode source 8200 may be any light souroe, such as a broad area laser, that gen~r~tes a multimode optical signal. In ac~rdance with an 5 imp'2mentation consistent with the principles of the present invention, multimode source 8200 g~nerates a multimode optical signal having a wave'en~th equal to 0.98~m . Mode scrambler 8300, spliced into the output fiber of multimode source 8200, scramb'~s the modes of the multimode optical signal generated by multimodesource 8200.
Quartz capillary 8400 secures signal fiber 3100 and pump fiber 3800 for fusing and tapering. Cylindrical heater 8500 en~".rasses quark capillary 8400 and provides heat for fusing signal fiber 3100 and pump fiber 3800 together to form coupler 3600. Motor~cd stages 8620 and 8640 grip signal fiber 3100 and pump fiber 3800 on either side of cylinJI ioal heater 8500. Moto, i~ed stages 8620 and 8640, under control of controller 8100, stretch signal fiber 3100 and pump fiber 3800 to form coupler 3600.
Detecto,~ 8720 and 8740 are atla~,hed to the end of signal fiber 3100 and pump fiber 3800 oppo~ multimode source 8200 via suitable adaptera 8760 and 8780.
Dete~Aor~ 8720 and 8740 detect the amount of the power signal transfer from pumpfiber 3800 to sbnal fiber 3100 that takes place in coupler 3600 (i.e., the coupling efficiency), and report th0 amount to controller 8100. Pyrometer 8800, in conjunction with pylu",eter contl~"er 8900, monitors the tel.lperdture of the extemal wall of cylindrical heabr 850C during fo~ ation of coupler 3600.
Tuming to Figs. 6A-6~, a manufacturing method consiste~rlt with the principles of the present hvention begins by cutting a double-clad optical fiber (i.e., the primary fiber) to a length arpr~ ately equal to the sum of the expected lengths of signal fiber section 3100A and signal fiber section 3100B (Fig. 7) lstep 6110]. Next, amultimode optical fiber (i.e., pump fiber 3B00) is cut to have a bngth apploAilllately equal to the sum of the e~l ected lengths of se~,tions 3800A, 3800B, and 3800C of pump fiber 3800 (Fig. 7) [step 6110].
Mode sc~ 'er 8300 is spliced into the output fiber of rnultimode source 8200, and pump fiber 3800 is, in tum, spliced into mode scr~i~lb'sr 8300 lstep 6120]. Next, both signal fiber 3100 and pump fiber 3800 are st.i~uped (i.e., the coating is removed) for a length of ~pproximately 4 cm [step 6130]. Signal fiber 3100 is ;,ll i~,ped at a location equal to the length of signal fiber section 3100A and pump fiber 3800 is stripped at a location equal to the length of pump fiber section 3800A. The sl. r p-ng may be made by any conveittional method.
Signal fiber 3100 and pump fiber 3800 are i"se, lad into quartz capillary 8400 which is center~d inside cylindrical heater 8500 lstep 61401. Signal fiber 3100 and pump fiber 3800 are inse~ted in quartz capillary 8400 such that the stripped areas of the fibers are centered in quartz capillary 8400 and signal fiber section 3100A and pump fiber section 3800A are located on the same side of quark capillary 8400.
Signal fiber 3100 and pump fiber 3800 aro then twisted to ensure contact with each 10 other in the sl.i~d areas lstep 6150]. The twisting may be pe,f,""ed by any conventional method Signal fiber 3100 and pump fiber 3800 are then dUdclled to motorized stages 8620 and 8640 at either side of quartz capillary 8400 [step 6210]. The ends of signal fiber 3100 and pump fiber 3800 opposite multimode source 8200 are cleaved and 15 inse. led into detectors 8720 and 8740 through suitable adapt~rs 8760 and 8780 r~spe~;tively lstep 62201.
Multimode source 8200 outputs a multimode optical power signal to mode sc,dr"~'er 8300 [step 6230l. Mode scrambler 8300 scrambles the modes of the power signal and outputs lthe scrambled power signal to pump fiber section 3800A20 lstep 62301. Ddectors 8720 and 8740 monitor the amount of the power signal t,ansferled from pump fiber 3800 to signal fiber 3100 and reports this i"r~r",ation to cont,ullar 8100.
Cont,."er 8100 init;Jtas fusion and tapering oper~tions performed by cylindricalheater 8500 and motorked stages 8620 and 8640, respectively lstep 6240].
FIELD OF THE INVENTION
The present invention relates generally to a high power multimode pumped 5 optical fiber amplifier, and more particularly, to a twin coupler system that increases the pumping ~lTis ~nc~ ot a double-clad optical fiber a"lp!;fier.
BACKGROUND OF THE INVENTION
Conventional optical fiber amplifi~rs include active fibers having a core doped 10 with a rare earth ele."enb Pump power st a chara..1~ri:,tic wavelength for the rare earth elen~ent, when i~e :ted into the actffve fiber, excites the ions of the rare earth elehlehl, leading to gain in the core for an info""alion signal propagc,li.,g along the fiber.
Rare earth elements used for doping typically include Erbium (Er), 15 Neodymium (Nd), Ytterbium (Yb), Samarium (Sm), and Praseodymium (Pr). The particular rare earth eleml~ll used is det~rrnined in a~ordance with the wav¢leng~l, of the input signal light and the v:avelength of the pump light. For example, Er ions would be used for input signal light having a wavelen!Jtl, of ~.55~m and for pump power having a wav¢len.lll, of 1 .48~m or 0.98~1m; codop ng with Er and Yb ions,20 further, allows dil,~rt,nt and broader pump wavelehytl, bands to be used.
Traditional pump sources include single mode laser diodes and multimode broad area lasers coupled t~ the active flber over single mode and multimode pumping fibers, respectively, to provide the pump power. Single mode lasers provide low pump power, typicall~l~ in the order of 100 mW. Broad area lasers, on the other 25 hand, provide high pump power, in the order of 500 mW. These lasers of high output power, however, cannot I fficiently inject light into the small core of a single mode fiber. Consequently, the use of high power broad area lasers requires the use of wide core and multimode fibers for pumping optical amplifiers.
Broad area lasers generale multimode pump power and input the pump power 30 to a non-active pumping ~Fiber. This non-active pumping fiber in tum typically inputs the pump power through a coupler and into the inner cladding of a doubl~clad active fiber, acting as a multimode core for the pump power.
In the amplifier fib,ers, pump power is guided into the inner multimode cladding ,~
of the fiber from which it is transrer~ed into a single mode core doped with an active dopant.
A fused fiber multimode coupler has a ll,eo,~tic~l coupling coefficient directlypropo, lional to the ratio oF the areas of the two fibers constituting the coupler itself. In 5 an ideal case for two ident.cal fibers, the coupling coemcient is app~ oximately 50%.
Typically, the coupling coemcient is in the range of 45~8%. This means that onlyabout 4548% of the total pump power output by the pump souroe into the pumping fib,er actually passes froml the pumping fiber to the inner cladding of the double-clad active fiber, wt~ile the remlaining 52-55% remains in the pumping fiber.
Some systems us~e two optical fibers having differen: did."_ter of mulL",ode cores to i.opr~ the coupling coefficient of the mulli."ode coupler. However, such a,.dr~e",ents often lead to a waste of pclwer due to the difficulty in matching the tapering of two cores of different size.
Fig. 1 is a block ~ ", of a conventional amplifying system containing a multimode pump souroe coupled to a primary fiber via a single traditional coupler.
Primary fiber 1100 is a double-clad fiber. The i.,fo,l,-dtion signal flows through its single mode core. Amplifier 1200, which may take the form of an ErNb doped double-clad active fiber, almplifies the information signal as it propagates through the single mode core of primary fiber 1100.
Mu:timode pump 11300 is coupled into primary hber 1100 via multimode pump fiber 1400 and coupler 15100.
Multimode pump power generated by multimode pump 1300 is coupled into primary fiber 1100 via multi"-ode pump fiber 1400 and coupler 1500. Coupler 1500 is a conventional fused fiber waveleh!JU, division multiplexer (WDM) type coupler. WDM
couplers behave as multimode o ouplers fbr the pump power and t,ansi"it the single mode signal along the primary fiber subat i,ltially without coupling to the pump fiber.
WDM couplers have maximum coupling effi~-~nc es of 50~h forthe pump power, and typically have coupling efficioncies in the range of about 45%.
Multimode pump 1300 may take the form of a broad area laser that outputs pump power of approxi-"i?te'y 450-500 mW. Due to the couplir~ coe~, c-ent of coupler 1500, hol:o~or, only about 45% of this pump power, or appro~i."ately 200-225 mW, enters primary flber 1100. The remaining 55% of the pump power is lost, as it exits from pump fiber 1400.
More recent systems have attempted to recover the lost pump power. Fig. 2 , ~, is a block diagr~." of one of these systems. The primary fiber through which theinformation signal flows includes signal fiber 2100 and signal fiber 2200, which are ",atcl)ed double-clad fibers, and amplifiers 2300 and 2400. Amplifiers 2300 and 2400, which may cGm~, ise ErlYb doped double-clad active fibers, amplify the 5 inf~ rmalion signal as it pl o~wg~tes through the single mode core of the primary fiber.
In this system, mulltimode pump 2500 is coupled into the primary fiber via two idei,lical couplers 2600 and 2700, over pump fiber 2800 and pump fiber 2900, ,~spe~ ely. Pump fibers 2800 and 2900 are mat-ihed multimode fibers, spliced togetl.er at a point betwe~en couplers 26a0 and 2700.
Multimode pump :2500 outputs multimode pump power over pump fiber 2800.
Due to the coupling coeffident of coupler 2600, only about 45% of the pump powerenters signal flber 2100. VVith this ar-dfigen,ent, however, the remaining 55% of the pump power is not lost, but, instead, enbrs pump fiber 2900, which couples into signal fiber 2200 via coupler 2700.
AppJicants have observed that the addition of pump fiber 2900 and coupler 2700, ho.~e,~er, does not significantly improve the total pump power transfer over the one coupler system desc~ d above. There are a few r~asons for this. First, the splice between pump fiber 2800 and pump fiber 2900 results in a loss of pump power.
Second, the first couplin!3 ~t~ een pump fiber 2800 and signal fiber 2100 results in 20 most of the exbemal modes of the pump power being b afi fc rred to signal fiber 2100, leaving only the internal rnodes for the second coupling. This leads to ine~,ienl l.ar,:,fer of the r~"-a;.)ing pump power at coupler 2700. Such a structure dtl~:r"pts to recouple most of the intemal modes of the multimode pump power, those with the poorest coupling efficienc:y. As a result, the coupled pump power and the multimode 25 amplifier's output power clo not change s4, -if~c~rltly over the single coupler system desc,il,ed above.
Several articles in the patent and non-patent literature a~dlt5ss multi."ode coupling technbues but clo not over~Gfi,e the deficiencies of other converltional appruacl.es de~cribed ab~ove. WO 95/10868 d;scloses a fib!er optic amplifier 30 co-"prisi"g a fiber with two concent-ic cores. Pump power provided by multimode sources couples transversely to the outer core of the fiber through multimode fibers and multimode optical couplers. The pump power prop~g,~tes through the outer core and interacts with the inner core to pump active material contained in the inner core.
U.S. Patent No. 5,185,814 di t:'o9es an optical communications network in . ~ . .
which amplifiers amplify optical signals as the optical signals propag,~le along a waveguide. A single optical pump source coupled to the optical fiber pumps the amplifiers.
U.S. Patent No. 5,533,163 disclQses a double-clad optical fiber configuration that includes a core dopeld with an active gain ."atti,ial, an~an inner claddingsurrounding the core. An extemal pump souroe inputs multimode pump energy to theinner cladding. The multimode pump energy in the inner cladding l,dnsfer:i energy into the core through repeated i, llel a~,liGns between the energy and the active dopant within the core.
WO 93J15536 disc'o8es a compound glass fiber that includes an outer c.ad 'i"g, inner dadding, and a single mode central core. The inner cladding has a cross-se~,1ional profile opli"lked to reoeive multimode pumping radiation. The single mode core is located within the inner cla~ding and doped with a lasant ",aterial to maximize l,ari~f~r of the rnultimode pumping IddidtiGn to the single mode doped core.
U.S. Patent No. 5,170,458 disc~Qses an optical fiber light-amplifier that includes an optical fiber with a center core through which signal light propag~les, and a pumping light gel1~r~i-,g device that applies pumping light obliquely to the optical fiber. While the pumping li~ht pro~g~t~ ~ through the fiber, it is absorbed by and excites the oenter core to amplify the signal light propa~Ptecl through the optical fiber.
In Applicants' view, none of the known literature has adequately add~essed Applicants' discovery that conventional s~sle:"~s have failed to recouple sufficient pump power, thereby leadin~ to an inaclequate overall pump power l,ans~er efficiency.
SUMMARY OF THE INVENTION
The present invention adJI~7sses the above pr~blems in a twin coupler system that recouples more multimode pump power to a double~clad optical amplifier thanconventional s~sle",s by using couplers having dissimilar tapel i, .g.
In acct~dance with the invention as c.,.~Qd e ~ and broadly desclil~d herein, 30 the pr~sent invention in one aspect includes a twin coupler system having a signal fiber configured to receive and ll ~nspGl I an optical signal, a pump fibler configured to reoeive and tlanspoi ~ pump power, a first coupler induding the signal and pump fibers fused and tape~d by a first amount to l,dns~r a portion of the pump power from the pump fiber to the signal fiber, and a second ooupler including the signal and pump fibers fused and bpered by a second amount to l-ansfer at least some of a remaining portion of the pump power from the pump fiber to the sbnal fiber. The second amount of tapering is generally depende.~t upon the first amount of tape,ing to achieve a maximurn total coupling ~ffic ency for the twin coupler system.
In another aspect the present in~ntion also includes a method for manufacturing the twin c~upler system. The manufacturing method constructs the first coupler by pr~palil)g first po, lions of the primary and pump fibers for coupling and performing fusbn and tap~, i ,9 ope~Uon~ on the primary and pump fibers at the first po,lions and constructs the second coupler by pr~pa,i"g second portions of the 10 primary and pump fibers Ior coupling and performing fusion and tap~ering oper~lions on the primary and pump fibers at the second portions. The fusion and tapering opcrdtions at the second pG tions are dependent upon the fusion and tapering ope.dtions pe,h,l"-ad at the first polliGns so as to acl,.~\~e a maximum coupling ~ffi~ rnc~ of the pump power from the pump fiber to the primary fiber for the entire 15 twin coupler system.
In an~tl.er aspect the present inv~nlion indudes an apparatus for manufacturing the twin coupler system. The appa- dtUs includes means for prepa. i"g first and second po, lions of both the signal fiber and the pump fiber for coupling and means for pe-f~J.-"ing fusion and stretching operalions on the signal and pump fibers 20 at the first and second portions. The fusion and stretching opei dlions at the first portions form the first coupler and the fu~iion and stretching opcrations at the second po, tions form the second coupler and are dependent upon the fusion and stretching optlations pe, fvl med in fDrming the first coupler.
The present invention further includes an apparatus for manufacturing at least 25 first and second optical couplers of a multiple coupler system for coupling amultimode pump fiber to a double-clad active signal fiber. The apparatus includes means for su~,ply;ng a multimode optical signal to the pump fiber, means for fusing the signal and pump fibers at first and second spaced lo~tions means for tape.il.g the signal and pump fibers at the first and second loc~iions means for monitoring a 30 coupling efficiency based on an amount of the multimode optical power l-al-sfe"t,d from the pump fiber to the signal fiber at the first and second couplers, and means for controlling the fusing and tapering means to heat and stretch the signal and pump fibers at the first locations to produce the first coupler based on the ",on-t~red coupling ~f~c.a~ for the first coupler and for controlling the fusing and tapering .. ~................ . .
means to heat and stretch the signal and pump fibers at the second localions to produce the second coupler based on the coupling emciency for the first coupler and the mon tor~d coupling effidency for the ~econd coupler.
In ar,vtl,er aspect, the present invention includes a n.ethod for manufacturing at least first and second optkal couplers of a multiple coupler system for coupling a double-clad active signal fiber and a multimode pump fiber. The Illetllod includes the steps of supply;. I9 a multimode opticaJ s4nal to the pump fiber, heating and stretching first poi lions of the signal and pump fibers to produce the first coupler, monilo~ ing a coupling effciency for the first coupler based on an amount of the mullimode optical 10 power t-dnsf~l.ed from the pump fiber to the signal fiber at the first coupler, controlling the first poll;ons heating and $tretching step to a~)bvc a maximum value for the coupling efficiency for the first cowpler, heating and stretching second po- lions of the signal and pump fiber6 to produce the second coupler, monitoring a coupling efficiency for the second c oupler based on an amount of the multimode optical power 15 lran~rGI ~ed from the pump fber to the signal fiber at the second coupler, and controlling the second pol1~.s heating and stretching step to ad~.ev~ a maximum total coupling efficiency for the multiple coupler system based on the acl) evedmaximum coupling ~lT; c ~ for the first coupbr and the coupling efficiency for the second coupler.
BRIEF DESCRIPTION OF THE DRAWINGS
The accorllpanyin!3 ~ ings, which are illcGi~ord~d in and constitute a part of this spe~,ific~tion, illustrat- an embodiment of the invention and, tOge~tl er with the desc,iption, explain the ob,ects, advanlages and principles of the invention. In the 25 ~ gs, Fig. 1 is a block ~iay.dm of a conva.lliGnal system containing a mullill,ode pump source coupled to a primary fiber via a single t,aJiliGnal coupler;
Fig. 2 is a block d;~.am of a system that recovers a portion of the lost pump power;
Fig. 3 is a diagrarn of a twin coupbr system consist~nt witn the principles of the present invention;
Fig. 4A is a Jiaglalll depicting a cross-se~;tional view of the primary fiber ofFig. 3;
Fig. 4B is a graph of the difrerenl indexes of refraction of the primary fiber of Fig. 3;
Fig. 5A is a cliagrai" depicting a cross-se.,tional view of the pump fiber of Fig.
3;
Fig. 58 is a graph of the differ~nt i"dexes of rer, a.;lion of the pump fiber of Fig.
5 3;
Figs. 6A~D are flow charts describing a method for manufacturing the twin coupler system consistent wlth the principles of the present inv~ntion;
Fig. 7 is a block dia~lam of a simplified version of the twin coupler system of Fig. 3;
Fig. 8 is a block Jia~a,n of the equipment used for manufacturing a first coupler of Fig. 3;
Figs. 9A and 9B are graphs depicting temperature and speed profiles, respectively, for the fusion and tape. ing ~ralions to produce the first coupler;
Fig. 10 is a block dia~, am of the equipment used for manufacturing a second coupler of Fig. 3; and Figs. 11A and 11 E~ are graphs depicting bh)perature and speed profiles, :spe~ ely, for the fusion alnd tape, i-~g u~Jerdtions to produce the second coupler.
It is to be unde, tood that both the for~gDI.)g g~neral de~ lion and the following detailed descri~,~iGn are e~e."~~ry and are i,-lended to provide further eA~lanation of the invention as claimed.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The folbwing detaibd dascii~ction of the invention refers to the accol-,pat)yingdIL~;n9S~ The same ,ef_r~nce numbers identify the same or similar elements.
The de~cription indudes exemplaly embodiments, other embodiments are possible, and ~ ,anges may be made to the embodiments described without depa. Ii- ,9 from the spirit and scope of the invention. The f~!l..~.ng detailed descri,vtbn does not limit the inventbn. Instead, the scope of the invenlion is defined only by the appended claims.
Systems and m~tl lo~s consistent with the principles of the present invention achieve high l,ar,sf~r ~fi~ e~cy of multimode pumping power to an active, information-carrying, doubb-clad fiber using a twin-coupler sysbm having two dissimilar couplers.
Fig. 3 is a diag, dm of an amplifier system having a twin coupler system consistent with the principles of the present invention. The amplifier sysbm can be coupled as a high power optical amplifier in an optical fiber communication system; in this case input of fiber 3100 and output dF amplifier fiber 3400 are in general spliced to a single mode fiber of the! communication system. The amplifier system may to 5 advantage constitute a power booster amplifier or a line a.n~!;r,er.
The system includes two dmerent types of multimodelsingle mode optical fibers, a primary fiber and a pump fiber, coupled tog~tl,er by two dissimilar couplers.
The primary fiber contains an embedded singb mode core to carry an illfolllldtiGn signal.
The primary fiber includes signal fibers 3100 and 3200 and optical amplifiers 3300 and 3400. Signal fibers 3100 and 3200 are ".atched double clad optical fibers, while optical amplifiers 3300 and 3400 are double-clad ErlYb fibers doped to amplify the ill~ullndtion sbnal as it popag~t~Fs through the primary fiber. Fig. 4A is a diagram depicting a cro6s scctional view of the primary fiber, and Fig. 4B is a graph of the 15 difl_rent i"de:.es of ~eF~d~;ti~) of the prim~ry fiber.
As shown in Figs. 4A and 4B, the primary fiber ~3100, 3200) includes three kinds of glass forming conco.)t ic regions 4100, 4200, and 4300 having di~fer_ntindexes of refraction n1, n2, and n3, tespe_tively, and di1farerlt dia--,eter;i d1, d2, and d3, respectively. In an irnplel"er,tdtion consistent with the principles of the present 20 invention, the primary fiber i~ constructed such that the indexes of refraction have the relationship n1 < n2 < n3, and the dia",oters dl, d2, and d3 of the three concent,ic regions 4100, 4200, and 4300 ach.eve single mode optical pro~ ion for the i"fo, ~"dtion signal in region 4300 and multimode optical propagation for the pump power in region 4200. In other words, region 4300 surrounded by region 4200 forms 25 a single mode core for the ii~for,lldlion signal. Region 4200 surrounded by region 4100, on the other hand, forms a multimode core for the pump power.
In an implemenlation consistent with the principles of the p,~sent invention, the i..dexes of refraction and the diamet6l~ of concent-ic regions 4100, 4200, and 4300 have the fi"ow;.,g relationships:
CA 02245460 l998-08-2l ~(n32 n22) = 019 (1) ~/(n22- n ~2~ = 0 21 (2) d1 = 90~1m (3 d2 = 65~,1m d3 = 4~1m (5) Multimode pump 3500 connect~ to the primary fiber (3100, 3200) via couplers 3600 and 3700 to supply pump power. In an i",Fl~..,entdlion consislenl with the principles of the present invonlion, multimode pump 3500 is a broad area laser that outputs multimode pump power to pump fiber 3800. Pump fiber 3800 is a multimode optical fiber that carries the muHimode pump power. Fig. 5A is a diayl dm depicting a cross-sectional view of pump fiber 3800, and Fig. SB is a graph of the differentindexes of refraction of pump fiber 3800.
As shown in Figs. 5A and 5B, pump fiber 3800 includes two different types of glass ror,.,i"g concentric regions 5100 and 5200 having dfflerent indexes of rer,dction n1' and n2'"~,~pe-,ti~/ely, and different diameters d1' and d2', r~spe..li~/ely. In an implen ,entdtion consist~nt with the principles of the pr ,sent inv~nlion, pump fiber 3800 is constructed such that the i--deAe~ of ~~fld~tion have the ~1.4tionship n1' <- n2'.
The ~Jia",eter~ d1' and d2' of the two concentric regions 5100 and 5200 acl,:~ve15 multimode optical propas~tion for the pump power in region 5200. In other words, region 5200 surrounded by region 5100 forms a multimode core for the pump power.In an implel"enldlion oonsistent with the principles of the p~sent invention, the indexes of refnction and the diameters of concent,ic regions 5100 and 5200 have the f~llc ~:;. ,9 reldtionships:
.
~(n2' )~ - (nl ' )2 = 0. 21 (6) d1' = 90~m (7) d2' = 65~1m (8) Even though the concent- ic regions of pump fiber 3800 have been described as having the same indices of ,~f~a~tion and diar ,ct~ra as the conc~,l,ic regions of the primary fiber (3100, 3200), this need not be the case.
Both the primary fik~r (3100, 3200) and pump fiber 3800 contain a protective plastic coating surrounding the outer conaent,ic region (4100, 5100). In an implementation consistenl with the principles of the pr~sent invention, the protecti~e plastic coating has a thickne~s such that the exter. -al Jiam3tcr of both the primary fiber (3100, 3200) and pump fiber 3800 is appn"-i",ate~ly 25011m . The exter..al.Jiar ,etera may, of course, bo dfflerent vahes, and the CAt~5IIIaIdjarIIetera of the primary fiber (3100, 3200) and pump fiber 3800 need not be the same.
Couplers 3600 and :3700 are dissimilar optical fiber couplers for transferring pump power from pump fiber 3800 to the primary fiber (3100, 3200). In an imple".enbtion consistenl with the principles of the present invention, couplers 3600 and 3700 are manufactur~3d by a fusion k con ~,~' tape,ing technique des~iLed below.
Figs. 6A~D are flow charts describing a method for manufacturing a twin coupler system cons st~ nt with the principles of the p,~5enl invention. Fig. 7 is a simplified block diayIar" of the twin coupler system of Fig. 3. Figs. 8 and 10 are block diay.d",s of equipment use~ for manufaduring the first and second couplers 3600 and 3700 of Fig. 3"~spe.;ti~lely.
Turning first to Fig. 8, equipment usod in a manufacturing method consistent with the principles of the pr~ent invention will be deseriL~d first to facilitate descl iption of the manufacturing method with regard to Figs. 6A~D. The manufacturing equipment cGr"pri~es conv~ntional equipment, including cont,.'ler 8100, multi",oc;e source 8200, mode scrambler 8300, quartz capillary 8400, cylindrical heater 8500""ot~i~ed sbges 8620 and 8640, detect~rs 8720 and 8740 with adapte,~ 8760 and 8780, p~"u"~ct~r 8800, and py-uillJt~,r c~nt,~"er 8900.
Cont..!lYr 8100 may take the form of a personal computer, such as an IBMT~-cGn~pdlible computer. Contl~,ller 8100 cont.ol~ the operdtion of the manufacturing equipment. Multimode source 8200 may be any light souroe, such as a broad area laser, that gen~r~tes a multimode optical signal. In ac~rdance with an 5 imp'2mentation consistent with the principles of the present invention, multimode source 8200 g~nerates a multimode optical signal having a wave'en~th equal to 0.98~m . Mode scrambler 8300, spliced into the output fiber of multimode source 8200, scramb'~s the modes of the multimode optical signal generated by multimodesource 8200.
Quartz capillary 8400 secures signal fiber 3100 and pump fiber 3800 for fusing and tapering. Cylindrical heater 8500 en~".rasses quark capillary 8400 and provides heat for fusing signal fiber 3100 and pump fiber 3800 together to form coupler 3600. Motor~cd stages 8620 and 8640 grip signal fiber 3100 and pump fiber 3800 on either side of cylinJI ioal heater 8500. Moto, i~ed stages 8620 and 8640, under control of controller 8100, stretch signal fiber 3100 and pump fiber 3800 to form coupler 3600.
Detecto,~ 8720 and 8740 are atla~,hed to the end of signal fiber 3100 and pump fiber 3800 oppo~ multimode source 8200 via suitable adaptera 8760 and 8780.
Dete~Aor~ 8720 and 8740 detect the amount of the power signal transfer from pumpfiber 3800 to sbnal fiber 3100 that takes place in coupler 3600 (i.e., the coupling efficiency), and report th0 amount to controller 8100. Pyrometer 8800, in conjunction with pylu",eter contl~"er 8900, monitors the tel.lperdture of the extemal wall of cylindrical heabr 850C during fo~ ation of coupler 3600.
Tuming to Figs. 6A-6~, a manufacturing method consiste~rlt with the principles of the present hvention begins by cutting a double-clad optical fiber (i.e., the primary fiber) to a length arpr~ ately equal to the sum of the expected lengths of signal fiber section 3100A and signal fiber section 3100B (Fig. 7) lstep 6110]. Next, amultimode optical fiber (i.e., pump fiber 3B00) is cut to have a bngth apploAilllately equal to the sum of the e~l ected lengths of se~,tions 3800A, 3800B, and 3800C of pump fiber 3800 (Fig. 7) [step 6110].
Mode sc~ 'er 8300 is spliced into the output fiber of rnultimode source 8200, and pump fiber 3800 is, in tum, spliced into mode scr~i~lb'sr 8300 lstep 6120]. Next, both signal fiber 3100 and pump fiber 3800 are st.i~uped (i.e., the coating is removed) for a length of ~pproximately 4 cm [step 6130]. Signal fiber 3100 is ;,ll i~,ped at a location equal to the length of signal fiber section 3100A and pump fiber 3800 is stripped at a location equal to the length of pump fiber section 3800A. The sl. r p-ng may be made by any conveittional method.
Signal fiber 3100 and pump fiber 3800 are i"se, lad into quartz capillary 8400 which is center~d inside cylindrical heater 8500 lstep 61401. Signal fiber 3100 and pump fiber 3800 are inse~ted in quartz capillary 8400 such that the stripped areas of the fibers are centered in quartz capillary 8400 and signal fiber section 3100A and pump fiber section 3800A are located on the same side of quark capillary 8400.
Signal fiber 3100 and pump fiber 3800 aro then twisted to ensure contact with each 10 other in the sl.i~d areas lstep 6150]. The twisting may be pe,f,""ed by any conventional method Signal fiber 3100 and pump fiber 3800 are then dUdclled to motorized stages 8620 and 8640 at either side of quartz capillary 8400 [step 6210]. The ends of signal fiber 3100 and pump fiber 3800 opposite multimode source 8200 are cleaved and 15 inse. led into detectors 8720 and 8740 through suitable adapt~rs 8760 and 8780 r~spe~;tively lstep 62201.
Multimode source 8200 outputs a multimode optical power signal to mode sc,dr"~'er 8300 [step 6230l. Mode scrambler 8300 scrambles the modes of the power signal and outputs lthe scrambled power signal to pump fiber section 3800A20 lstep 62301. Ddectors 8720 and 8740 monitor the amount of the power signal t,ansferled from pump fiber 3800 to signal fiber 3100 and reports this i"r~r",ation to cont,ullar 8100.
Cont,."er 8100 init;Jtas fusion and tapering oper~tions performed by cylindricalheater 8500 and motorked stages 8620 and 8640, respectively lstep 6240].
2~ Py,u,-,aler 8800, in conjunction with py, u-l.eter cor,t,,"e r 8900, oonstantly monitors the te."perdture of the extemal wall of cylindrical heater 8500 and reports the te",peralure to cGnl,-~l'er 8100.
Cont, Jl'er 8100 regu~n~es the fusion and tapering oper~tions on the basis of the te",perdl~re of cylindrical heater 8~00 as H heats signal fiber 3100 and pump fiber 30 3800 the speed of motoii~d stages 8620 and 8640 as they stretch signal fiber 3100 and pump fiber 3800 and the fusion time before r,,otu,,Lad stages 8620 and 8640 begin stretching. Figs. 9A and 9B are graphs depicting ter"perature and speed prohles for the fusion and tape,ing ope-dti~ns respe~lively during ror",dtion ofcoupler 3600. In an imple"~ntdtion consistent with the principles of the present invention, the va,i '-les t1-t7 (in seconds), T1-T4 (in ~C), V1, and V2 (in ~m /sec) are as follows:
t1 =10 T1 =850 t2=20 T2=1150 t3 = 30 T3 = 1380 t4 = 60 T4 = 900 t5 = 80 V1 = 30 t6=380 V2=20 t7 = 390 Controller 8100 stops the fusion and taperi"g operations once cGnl,."er 8100 deterrnines that coupler 3600 has ach ~v~d a maximum multimode power l,an~rer from pump fiber 3800 to signal fiber 3100, with a minimum amount of power loss.
Controller 8100 makes this determination based on the information received from d~t~lor~ 8720 and 8740. Based on the information from the embodiment provided above, coupler 3600 would have a maximum multimode power t~dnsfer, or coupling efficiency, of 44% and a power loss of 0.29 dB.
When cG~b."er 8100 obtains the maximum coupling ~fi~ ~ncy and minimum power loss for coupler 3600, the structure formed by the fused and tapered fibers is 20 fixed at quartz capillary 8400 by epoxy, ll~reby completing coupler 3600 [step 6250].
Cont,~l'er 8100 records the results to aid in calculating the total coupling ~ n~ of the final twin coupler system ~step 6250].
Once cGnl,~"er 8100 cG~I~pletes coupler 3600, coupler 3700 is formed while keeping the monitoring system online (see Fig. 10). A doub~e-clad optical fiber (j.e., 25 the primary fiber) is cut to a length app,oA;.n.itcly equal to the sum of the expected lengths of signal fiber section 3200A and l;ignal fiber section 3200B (Fig. 7) lstep 63101. Next, both signal fiber 3200 and pump fiber 3800 are sl,i~)ped for a length of approxin~ately 4 cm Istep 6320]. Signal ffber 3200 is st,ipp.;d at a loc~tiGn equal to the length of signal fiber section 3200A, and pump fiber 3800 is sll i~d at a lo~tion 30 equal to the sum of the lengths of pump fiber se~lions 3800A and 3800B from the end connected to multimode source 8200. The st,irp.ng may be mad~e by any convenlional method.
In Fig. 10, signal fiber 3200 and pump fiber 3800 are inserted into quark capillary 8400, which is centered inside cylindrical heater 8500 lstep 6330]. Signal fiber 3200 and pump fiber 3800 are inserted in quark capillary 8400 such that the stripped areas of the fibers are centered in quark capillary 8400, and signal fiber section 3200A and pump fiber section 3800B are located on the same side of quartz capillary 8400. Signal fib*r 3200 and pump fiber 3800 are then twisted to ensure5 contact with each other in the st, ipped areas [step 6340]. The twisting may be performed by any conventional method.
Signal fiber 3200 and pump fiber 3800 are then attached to motorized stages 8620 and 8640 at either side of quartz capillary 8400 [step 63503. The end of signal fiber 3200, o~cF c s ~ multil ,)ode souroe 8200, is cleaved and both signal fiber 3200 and pump fiber 3800 are i!nsel led into det~;tor:j 8720 and 874Q through suitable addptera 8760 and 8780, r~sF~ctively lstep 64101.
Multimode source 8200 outputs a multimode optical power signal to mode scrai"b'er 8300 lstep 6420l. Mode SUdi- t'er 8300 sc~amt'es the modes of the power signal and outputs the scrambled power signal to pump fiber section 3800A
lstep 6420l. Dete~,1Or:, 8720 and 8740 mon't~r the amount of the power signal t, ar,~fer-ed from pump fiber 3800 to signal fiber 3200, and reports this information to cor",."er 8100.
CG,It,.l'er 8100 initiates the fusion and taperi"g operations peiru.--~ed by cy;i.,d,ical heater 8500 and .~lotoii~ed stages 8620 and 8640, respectively lstep 6430l. Pyrometer 8800, in conjunction with py-o,r)eter cGnt-ul'~r 8900, asain .-,onltora the te"~perdl-lre of the e~te.l-al wall of cylindrical heater 8500, and reports the te,.,peralure to conl,u'ler 8100 CGr.I~"er 8100 regulates the fusion and taperi-,g operations on the basis of thetemperature of cylindrical heater 8500 as it heats signal fiber 3200 and pump fiber 3800, the speed of m~,to. i~d stages 8620 and 8640 as they stretch signal fiber 3200 and pump fiber 3800, and the fusion time before i~-oto.i~ed stages 8620 and 8640begin stretching. Figs. 11 A and 11 B are graphs depicting te.nperature and speed profiles for the fusion and tapering operaffons, r~spe~,ti~ely, during fou-.ation of coupler 3700. In an implel..cntation consistent with the principles of the present invention, the variables t1-t8 (in seconds), T1-T5 (in ~C), V1, and V2 (in ~lm /sec) are as follows:
t1 = 10 T1 = 850 t2 = 20 T2 = 1150 t3 = 40 T3 = 1400 t4=60 T4= 1370 t5 = 80 T5 = 900 t6 = 90 V1 = 30 t7=420 V2=20 t8 = 430 The te,nperdlure and speed profiles for forming coupler 3700 are dirft:r~nl than the profiles for forrning coupler 3600. CO ,b."er 8100 tapers coupler 3700 more thancoupler 3600 and with a diffbient shape be~uss the mode distribution of the power signal remaining in pump fibl~r section 3800B after coupler 3600 is dirr~r~nl from the mode distribution of the power signal in pump fiber section 3800A.
CGnb~ller 8100 regulates the fusion and tapering oper~tions to ",ax,",i~e the coupling eM~-,;en-,y as a result of the mode distribution of the power signal remaining after coupler 3~00. The tape. ing of coupler 3700 creates malched mode scrambling of the power signal remaining in pump fiber section 3800B after coupler 3600.
Controller 8100 stops the fusion and tapering oF~rations once cûntl~ller 8100 determines that the operdtions have obtained a maximum total multimode power t~an:,rer from pump fiber 3800 to the primary fiber. Cont,-"er 8100 makes such adetermination based on the information r~ivcd from dete~lola 8720 and 8740 in forming coupler 3700 and the i"rur"~dtion previously ,~corded from the formation of coupler 3600.
Based on the i~fu~mation from the embodiment provided above, the twin coupler system, consistenl with the principles ûf the pr~sent inwntion, would have a total coupling eMdency of 66%, much better than the 50-55% eMc en.,~ acl. ~ed byconwntiol)al systems, total coupled pump power of 300 mW and, by proper seleulion of length and doping of the amplifying fibers, a saturated output power of the amplifier equal to 18.5 dBm. When cGnt~u"er 8100 obtains the maximum total coupling ~:M en.;y, the tructure formed by the fused and tapered fibers is fixed at quartz capillary 8400 by epoxy, thereby completing coupler 3700 ~step 6440].
The systems and mzthods consistent with the principles of the pn:seril invention CA 02245460 l998-08-2l t, dnsfer multimode pump power to an active double-clad fiber with increased coupling ~:f~c en~ over convenlional systems by using a pair of dissimilar couplers.
The ~or~g~ ng derc,i~tion of pr~fe.-ad embodiments of the present invention provides illustration and description, but is not intended to be exhaustive or to limit the 5 inventiGn to the precise form ~isclos4~l Modific~tions and variations are possible in light of the above teachings or may be aoquired from pldc~ice of the invention.
For example, though an amplifying ~ystem for single mode optical signals has been di~closed so far, the skilled in the art may use this invention with an amplifying system for mufflmode signal$ by adopti. ,g, where app, ~,pridte, fibers having a10 multimode signal core instead of a single mode core.
The f ,re~ D;ng description included ~pecific data values obtained through ex~,elilnentalion. These values serve as examples only and the true scope of theinvention is defined only by the claims and their equivalents.
Cont, Jl'er 8100 regu~n~es the fusion and tapering oper~tions on the basis of the te",perdl~re of cylindrical heater 8~00 as H heats signal fiber 3100 and pump fiber 30 3800 the speed of motoii~d stages 8620 and 8640 as they stretch signal fiber 3100 and pump fiber 3800 and the fusion time before r,,otu,,Lad stages 8620 and 8640 begin stretching. Figs. 9A and 9B are graphs depicting ter"perature and speed prohles for the fusion and tape,ing ope-dti~ns respe~lively during ror",dtion ofcoupler 3600. In an imple"~ntdtion consistent with the principles of the present invention, the va,i '-les t1-t7 (in seconds), T1-T4 (in ~C), V1, and V2 (in ~m /sec) are as follows:
t1 =10 T1 =850 t2=20 T2=1150 t3 = 30 T3 = 1380 t4 = 60 T4 = 900 t5 = 80 V1 = 30 t6=380 V2=20 t7 = 390 Controller 8100 stops the fusion and taperi"g operations once cGnl,."er 8100 deterrnines that coupler 3600 has ach ~v~d a maximum multimode power l,an~rer from pump fiber 3800 to signal fiber 3100, with a minimum amount of power loss.
Controller 8100 makes this determination based on the information received from d~t~lor~ 8720 and 8740. Based on the information from the embodiment provided above, coupler 3600 would have a maximum multimode power t~dnsfer, or coupling efficiency, of 44% and a power loss of 0.29 dB.
When cG~b."er 8100 obtains the maximum coupling ~fi~ ~ncy and minimum power loss for coupler 3600, the structure formed by the fused and tapered fibers is 20 fixed at quartz capillary 8400 by epoxy, ll~reby completing coupler 3600 [step 6250].
Cont,~l'er 8100 records the results to aid in calculating the total coupling ~ n~ of the final twin coupler system ~step 6250].
Once cGnl,~"er 8100 cG~I~pletes coupler 3600, coupler 3700 is formed while keeping the monitoring system online (see Fig. 10). A doub~e-clad optical fiber (j.e., 25 the primary fiber) is cut to a length app,oA;.n.itcly equal to the sum of the expected lengths of signal fiber section 3200A and l;ignal fiber section 3200B (Fig. 7) lstep 63101. Next, both signal fiber 3200 and pump fiber 3800 are sl,i~)ped for a length of approxin~ately 4 cm Istep 6320]. Signal ffber 3200 is st,ipp.;d at a loc~tiGn equal to the length of signal fiber section 3200A, and pump fiber 3800 is sll i~d at a lo~tion 30 equal to the sum of the lengths of pump fiber se~lions 3800A and 3800B from the end connected to multimode source 8200. The st,irp.ng may be mad~e by any convenlional method.
In Fig. 10, signal fiber 3200 and pump fiber 3800 are inserted into quark capillary 8400, which is centered inside cylindrical heater 8500 lstep 6330]. Signal fiber 3200 and pump fiber 3800 are inserted in quark capillary 8400 such that the stripped areas of the fibers are centered in quark capillary 8400, and signal fiber section 3200A and pump fiber section 3800B are located on the same side of quartz capillary 8400. Signal fib*r 3200 and pump fiber 3800 are then twisted to ensure5 contact with each other in the st, ipped areas [step 6340]. The twisting may be performed by any conventional method.
Signal fiber 3200 and pump fiber 3800 are then attached to motorized stages 8620 and 8640 at either side of quartz capillary 8400 [step 63503. The end of signal fiber 3200, o~cF c s ~ multil ,)ode souroe 8200, is cleaved and both signal fiber 3200 and pump fiber 3800 are i!nsel led into det~;tor:j 8720 and 874Q through suitable addptera 8760 and 8780, r~sF~ctively lstep 64101.
Multimode source 8200 outputs a multimode optical power signal to mode scrai"b'er 8300 lstep 6420l. Mode SUdi- t'er 8300 sc~amt'es the modes of the power signal and outputs the scrambled power signal to pump fiber section 3800A
lstep 6420l. Dete~,1Or:, 8720 and 8740 mon't~r the amount of the power signal t, ar,~fer-ed from pump fiber 3800 to signal fiber 3200, and reports this information to cor",."er 8100.
CG,It,.l'er 8100 initiates the fusion and taperi"g operations peiru.--~ed by cy;i.,d,ical heater 8500 and .~lotoii~ed stages 8620 and 8640, respectively lstep 6430l. Pyrometer 8800, in conjunction with py-o,r)eter cGnt-ul'~r 8900, asain .-,onltora the te"~perdl-lre of the e~te.l-al wall of cylindrical heater 8500, and reports the te,.,peralure to conl,u'ler 8100 CGr.I~"er 8100 regulates the fusion and taperi-,g operations on the basis of thetemperature of cylindrical heater 8500 as it heats signal fiber 3200 and pump fiber 3800, the speed of m~,to. i~d stages 8620 and 8640 as they stretch signal fiber 3200 and pump fiber 3800, and the fusion time before i~-oto.i~ed stages 8620 and 8640begin stretching. Figs. 11 A and 11 B are graphs depicting te.nperature and speed profiles for the fusion and tapering operaffons, r~spe~,ti~ely, during fou-.ation of coupler 3700. In an implel..cntation consistent with the principles of the present invention, the variables t1-t8 (in seconds), T1-T5 (in ~C), V1, and V2 (in ~lm /sec) are as follows:
t1 = 10 T1 = 850 t2 = 20 T2 = 1150 t3 = 40 T3 = 1400 t4=60 T4= 1370 t5 = 80 T5 = 900 t6 = 90 V1 = 30 t7=420 V2=20 t8 = 430 The te,nperdlure and speed profiles for forming coupler 3700 are dirft:r~nl than the profiles for forrning coupler 3600. CO ,b."er 8100 tapers coupler 3700 more thancoupler 3600 and with a diffbient shape be~uss the mode distribution of the power signal remaining in pump fibl~r section 3800B after coupler 3600 is dirr~r~nl from the mode distribution of the power signal in pump fiber section 3800A.
CGnb~ller 8100 regulates the fusion and tapering oper~tions to ",ax,",i~e the coupling eM~-,;en-,y as a result of the mode distribution of the power signal remaining after coupler 3~00. The tape. ing of coupler 3700 creates malched mode scrambling of the power signal remaining in pump fiber section 3800B after coupler 3600.
Controller 8100 stops the fusion and tapering oF~rations once cûntl~ller 8100 determines that the operdtions have obtained a maximum total multimode power t~an:,rer from pump fiber 3800 to the primary fiber. Cont,-"er 8100 makes such adetermination based on the information r~ivcd from dete~lola 8720 and 8740 in forming coupler 3700 and the i"rur"~dtion previously ,~corded from the formation of coupler 3600.
Based on the i~fu~mation from the embodiment provided above, the twin coupler system, consistenl with the principles ûf the pr~sent inwntion, would have a total coupling eMdency of 66%, much better than the 50-55% eMc en.,~ acl. ~ed byconwntiol)al systems, total coupled pump power of 300 mW and, by proper seleulion of length and doping of the amplifying fibers, a saturated output power of the amplifier equal to 18.5 dBm. When cGnt~u"er 8100 obtains the maximum total coupling ~:M en.;y, the tructure formed by the fused and tapered fibers is fixed at quartz capillary 8400 by epoxy, thereby completing coupler 3700 ~step 6440].
The systems and mzthods consistent with the principles of the pn:seril invention CA 02245460 l998-08-2l t, dnsfer multimode pump power to an active double-clad fiber with increased coupling ~:f~c en~ over convenlional systems by using a pair of dissimilar couplers.
The ~or~g~ ng derc,i~tion of pr~fe.-ad embodiments of the present invention provides illustration and description, but is not intended to be exhaustive or to limit the 5 inventiGn to the precise form ~isclos4~l Modific~tions and variations are possible in light of the above teachings or may be aoquired from pldc~ice of the invention.
For example, though an amplifying ~ystem for single mode optical signals has been di~closed so far, the skilled in the art may use this invention with an amplifying system for mufflmode signal$ by adopti. ,g, where app, ~,pridte, fibers having a10 multimode signal core instead of a single mode core.
The f ,re~ D;ng description included ~pecific data values obtained through ex~,elilnentalion. These values serve as examples only and the true scope of theinvention is defined only by the claims and their equivalents.
Claims (20)
1. An optical amplifier system comprising:
a signal fiber configured to receive and transport an optical signal;
a pump fiber configured to receive and transport pump power;
a first coupler including the signal and pump fibers fused and tapered by a first amount to transfer a portion of the pump power from the pump fiber into the signal fiber; and a second coupler including the signal and pump fibers fused and tapered by a second amount to transfer at least some of a remaining portion of the pump powerfrom the pump fiber to the signal fiber, the second amount being dependent upon the first amount to achieve a maximum total coupling efficiency for the optical amplifier system.
a signal fiber configured to receive and transport an optical signal;
a pump fiber configured to receive and transport pump power;
a first coupler including the signal and pump fibers fused and tapered by a first amount to transfer a portion of the pump power from the pump fiber into the signal fiber; and a second coupler including the signal and pump fibers fused and tapered by a second amount to transfer at least some of a remaining portion of the pump powerfrom the pump fiber to the signal fiber, the second amount being dependent upon the first amount to achieve a maximum total coupling efficiency for the optical amplifier system.
2. The optical amplifier system of claim 1, wherein the signal fiber includes a first double-clad active fiber coupled to the pump fiber via the first coupler, and a second double-clad active fiber coupled to the pump fiber via the second coupler.
3. The optical amplifier system of claim 2, wherein the signal fiber further includes an optical amplifier coupled between the first and second double-clad active fibers, the optical amplifier including an active double-clad fiber doped with a rare earth element.
4. The optical amplifier system of claim 1, wherein the pump fiber includes a multimode pump fiber configured to receive and transport multimode pump power.
5. The optical amplifier system of claim 4, wherein the multimode pump fiber includes a single multimode fiber coupled to the signal fiber via the first and second couplers.
6. The optical amplifier system of claim 1, wherein the total coupling efficiency for the optical amplifier system is approximately 66%.
7. A method of manufacturing an optical amplifier configured in a twin coupler system having first and second optical couplers for coupling a pump fiber, configured to carry pump power, to a primary fiber, configured to carry optical informationsignals, comprising the steps of:
preparing first portions of the primary and pump fibers for coupling;
performing fusion and tapering operations on the primary and pump fibers at the first portions to construct the first coupler;
preparing second portions of the primary and pump fibers for coupling; and performing fusion and tapering operations on the primary and pump fibers at the second portions to construct the second coupler, the fusion and tapering operations at the second portions being dependent upon the fusion and tapering operations performed at the first portions.
preparing first portions of the primary and pump fibers for coupling;
performing fusion and tapering operations on the primary and pump fibers at the first portions to construct the first coupler;
preparing second portions of the primary and pump fibers for coupling; and performing fusion and tapering operations on the primary and pump fibers at the second portions to construct the second coupler, the fusion and tapering operations at the second portions being dependent upon the fusion and tapering operations performed at the first portions.
8. The manufacturing method of claim 7, further including the step of supplying a multimode optical signal to the pump fiber;
wherein the fusion and tapering step for the first coupler further includes the substeps of determining when a maximum transfer of the multimode optical signal from the pump fiber to the primary fiber is obtained during the fusion and tapering operations at the first portions; and discontinuing the fusion and tapering operations at the first portions when it is determined that the maximum multimode optical signal transfer is obtained.
wherein the fusion and tapering step for the first coupler further includes the substeps of determining when a maximum transfer of the multimode optical signal from the pump fiber to the primary fiber is obtained during the fusion and tapering operations at the first portions; and discontinuing the fusion and tapering operations at the first portions when it is determined that the maximum multimode optical signal transfer is obtained.
9. The manufacturing method of claim 8, wherein the fusion and tapering step for the second coupler further includes the substeps of determining when a maximum total transfer of the multimode optical signal from the pump fiber to the primary fiber is obtained during the fusion and tapering operations at the second portions based on the maximum multimode optical signal transfer obtained at the first portions and a maximum multimode optical signal transfer obtained at the second portions, and discontinuing the fusion and tapering operations at the second portions when it is determined that the maximum total multimode optical signal transfer is obtained.
10. The manufacturing method of claim 7, wherein the preparing first portions step includes the substeps of stripping the first portion of the primary fiber, stripping the first portion of the pump fiber, and twisting the primary and pump fibers together at the first stripped portions.
11. The manufacturing method of claim 10, wherein the fusion and tapering step for the first coupler further includes the substep of finalizing the first coupler formed by the fused and tapered fibers.
12. The manufacturing method of claim 7, wherein the preparing second portions step includes the substeps of stripping the second portion of the primary fiber, stripping the second portion of the pump fiber, and twisting the primary and pump fibers together at the second stripped portions.
13. The manufacturing method of claim 12, wherein the fusion and tapering step for the second coupler further includes the substep of finalizing the second coupler formed by the fused and tapered fibers.
14. An apparatus for manufacturing a twin coupler having first and second optical coupling means for coupling a pump fiber to a signal fiber, comprising:
means for preparing first and second portions of both the signal fiber and the pump fiber for coupling; and means for performing fusion and stretching operations on the signal and pump fibers at the first and second portions, the fusion and stretching operations at the first portions forming the first coupling means, and the fusion and stretching operations at the second portions forming the second coupling means and being dependent upon the fusion and stretching operations performed at the first portions.
means for preparing first and second portions of both the signal fiber and the pump fiber for coupling; and means for performing fusion and stretching operations on the signal and pump fibers at the first and second portions, the fusion and stretching operations at the first portions forming the first coupling means, and the fusion and stretching operations at the second portions forming the second coupling means and being dependent upon the fusion and stretching operations performed at the first portions.
15. The apparatus of claim 14, further including multimode source means for supplying a multimode signal to the pump fiber;
and means for determining when a maximum transfer of the multimode signal from the pump fiber to the signal fiber is obtained during the fusion and stretching operations at the first portions, and for discontinuing the fusion and stretching operations at the first portions when it is determined that the maximum multimode signal transfer is obtained.
and means for determining when a maximum transfer of the multimode signal from the pump fiber to the signal fiber is obtained during the fusion and stretching operations at the first portions, and for discontinuing the fusion and stretching operations at the first portions when it is determined that the maximum multimode signal transfer is obtained.
16. The apparatus of claim 15, further including means for determining when a maximum total transfer of the multimode signal from the pump fiber to the signal fiber is obtained during the fusion and stretching operations at the second portions based on the maximum multimode signal transferobtained at the first portions and a maximum multimode signal transfer obtained at the second portions, and for discontinuing the fusion and stretching operations at the second portions when it is determined that the maximum total multimode signal transfer is obtained.
17. The apparatus of claim 14, wherein the preparing means includes means for stripping the first portion of the signal fiber, means for stripping the first portion of the pump fiber, and means for twisting the signal and pump fibers together at the first stripped portions.
18. The apparatus of claim 14, wherein the preparing means includes means for stripping the second portion of the signal fiber, means for stripping the second portion of the pump fiber, and means for twisting the signal and pump fibers together at the second stripped portions.
19. An apparatus for manufacturing at least first and second optical couplers ofa multiple coupler system for coupling a multimode pump fiber to a multimode signal fiber, comprising:
means for supplying a multimode optical signal to the pump fiber;
means for fusing the signal and pump fibers at first and second spaced locations;
means for tapering the signal and pump fibers at the first and second locations;
means for monitoring a coupling efficiency based on an amount of the multimode optical signal transferred from the pump fiber to the signal fiber at the first and second couplers; and means for controlling the fusing and tapering means to heat and stretch the signal and pump fibers at the first locations to produce the first coupler based on the monitored coupling efficiency for the first coupler, and for controlling the fusing and tapering means to heat and stretch the signal and pump fibers at the second locations to produce the second coupler based on the coupling efficiency for the first coupler and the monitored coupling efficiency for the second coupler.
means for supplying a multimode optical signal to the pump fiber;
means for fusing the signal and pump fibers at first and second spaced locations;
means for tapering the signal and pump fibers at the first and second locations;
means for monitoring a coupling efficiency based on an amount of the multimode optical signal transferred from the pump fiber to the signal fiber at the first and second couplers; and means for controlling the fusing and tapering means to heat and stretch the signal and pump fibers at the first locations to produce the first coupler based on the monitored coupling efficiency for the first coupler, and for controlling the fusing and tapering means to heat and stretch the signal and pump fibers at the second locations to produce the second coupler based on the coupling efficiency for the first coupler and the monitored coupling efficiency for the second coupler.
20. A method for manufacturing at least first and second optical couplers of a multiple coupler system for coupling a multimode signal fiber and a multimode pump fiber, comprising the steps of:
supplying a multimode optical signal to the pump fiber;
heating and stretching first portions of the signal and pump fibers to produce the first coupler;
monitoring a coupling efficiency for the first coupler based on an amount of themultimode optical signal transferred from the pump fiber to the signal fiber at the first coupler;
controlling the first portions heating and stretching step to achieve a maximum value for the coupling efficiency for the first coupler;
heating and stretching second portions of the signal and pump fibers to produce the second coupler;
monitoring a coupling efficiency for the second coupler based on an amount of the multimode optical signal transferred from the pump fiber to the signal fiber at the second coupler; and controlling the second portions heating and stretching step to achieve a maximum total coupling efficiency for the multiple coupler system based on the achieved maximum coupling efficiency for the first coupler and the coupling efficiency for the second coupler.
supplying a multimode optical signal to the pump fiber;
heating and stretching first portions of the signal and pump fibers to produce the first coupler;
monitoring a coupling efficiency for the first coupler based on an amount of themultimode optical signal transferred from the pump fiber to the signal fiber at the first coupler;
controlling the first portions heating and stretching step to achieve a maximum value for the coupling efficiency for the first coupler;
heating and stretching second portions of the signal and pump fibers to produce the second coupler;
monitoring a coupling efficiency for the second coupler based on an amount of the multimode optical signal transferred from the pump fiber to the signal fiber at the second coupler; and controlling the second portions heating and stretching step to achieve a maximum total coupling efficiency for the multiple coupler system based on the achieved maximum coupling efficiency for the first coupler and the coupling efficiency for the second coupler.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP97114620.4 | 1997-08-23 | ||
| EP97114620 | 1997-08-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2245460A1 true CA2245460A1 (en) | 1999-02-23 |
Family
ID=8227262
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2245460 Abandoned CA2245460A1 (en) | 1997-08-23 | 1998-08-21 | Unequal couplers for multimode pumping optical amplifiers |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPH11135868A (en) |
| AR (1) | AR016632A1 (en) |
| AU (1) | AU8090398A (en) |
| BR (1) | BR9803158A (en) |
| CA (1) | CA2245460A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6359728B1 (en) * | 1998-09-22 | 2002-03-19 | Pirelli Cavi E Sistemi S.P.A. | Pump device for pumping an active fiber of an optical amplifier and corresponding optical amplifier |
-
1998
- 1998-08-14 BR BR9803158A patent/BR9803158A/en not_active IP Right Cessation
- 1998-08-18 AR ARP980104063 patent/AR016632A1/en unknown
- 1998-08-21 AU AU80903/98A patent/AU8090398A/en not_active Abandoned
- 1998-08-21 CA CA 2245460 patent/CA2245460A1/en not_active Abandoned
- 1998-08-24 JP JP10237161A patent/JPH11135868A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| BR9803158A (en) | 1999-11-03 |
| JPH11135868A (en) | 1999-05-21 |
| AR016632A1 (en) | 2001-07-25 |
| AU8090398A (en) | 1999-03-04 |
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