CA2178952A1 - Surveillance of optical broad-band connection lines up to a passive interface - Google Patents
Surveillance of optical broad-band connection lines up to a passive interfaceInfo
- Publication number
- CA2178952A1 CA2178952A1 CA 2178952 CA2178952A CA2178952A1 CA 2178952 A1 CA2178952 A1 CA 2178952A1 CA 2178952 CA2178952 CA 2178952 CA 2178952 A CA2178952 A CA 2178952A CA 2178952 A1 CA2178952 A1 CA 2178952A1
- Authority
- CA
- Canada
- Prior art keywords
- signal
- optical
- pseudo
- line unit
- owg
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
- H04B10/071—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using a reflected signal, e.g. using optical time domain reflectometers [OTDR]
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/30—Testing of optical devices, constituted by fibre optics or optical waveguides
- G01M11/31—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter and a light receiver being disposed at the same side of a fibre or waveguide end-face, e.g. reflectometers
- G01M11/3109—Reflectometers detecting the back-scattered light in the time-domain, e.g. OTDR
- G01M11/3118—Reflectometers detecting the back-scattered light in the time-domain, e.g. OTDR using coded light-pulse sequences
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/30—Testing of optical devices, constituted by fibre optics or optical waveguides
- G01M11/39—Testing of optical devices, constituted by fibre optics or optical waveguides in which light is projected from both sides of the fiber or waveguide end-face
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- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- General Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Optical Communication System (AREA)
Abstract
Monitoring optical broadband service cables up to passive interface A pseudo-noise binary signal is transmitted together with the information signal from an OWG line unit, and a small component of the optical signal is branched off at the passive interface and transmitted back to the line unit and fed there to the optoelectric transducer together with the optical signal received from the opposite end; the received electric signal is sub-jected to a correlation with the original pseudo-noise binary signal which has in the meantime been delayed in time, after which the correlation signal amplitude obtained in the process indicates correctly in terms of signal propagation time the occurrence or nonoccurrence of the pseudo-noise binary signal reflected by the passive interface (PNT1).
Description
-/, . . 2 1 78~52 ~GR 93 P 1855 P
~'LE, P~' Tr ~ ~. J~-Foreign version T~:3 T~ r,:_ DQscription Monitoring optical bLua~ d service cahles up to a passive interfacs In accordance with CCITT, an optical B-ISDN
subscriber line is u6ually realized such that at the end of that part of the optic~l subscriber line for which the n~twork provider i8 r~p~n~hle, that i~ to say at the 80-Ca11ed IJB interface, the optical li~e i8 ter~inated by 13 means of a so-called network termination (N~l) (CCITT
~c. I.432).
This NTl network ter ination oompriaes optoelec-tric and alectrooptic transducsrs, correctly t~inAt^~
th~ subscriber lin~ with r~gard to operation, administra-tion and .^-~nt-~n,n. e (OAM) and ~akea available in the direction towards the subscriber a standardized bidirectional broadband interface, the so-aalled TB
interfacQ, also termed the user-network interface (~NI).
The ~ignals in the two transmiasion directions have a gross baud rate of 155.52 Nbit/s in each case both at the ~xchange end of the line t~;nAt ~ ~n NTl (at the ~rB
interfac-) and on the 3ubscriber sidQ (at the TB inter-fac~), and comprise either a seguence of bytswise fra~es in accordance with the ~irst stage STMl (STM T Synchron-OU8 Transport Module) o~ the so-called synchronous digital hierarchy (SD~:), in whose in~ormation-carrying part so-call~d ATM cslls (~x. 149.76 ~bit/s) are trans-mitted with a 53 byte length each (ATM Asynchronous Transfer ~ode), or colq?rise a pure se5~uence o_ ATM cells, ~0 the cell data rats useful for information transmi3sion likewise b~ins 149 . 76 ~bit/s .
Since the NTl line tsrmination is relatively complex and reguire~ space, electric power and relatively expensivQ ~lc~ ytic and optoelectric tr~n~ D~s~
pos~ibly Qven battery _ _ 2 ~ 7 8 9~2 back-up, in order to bridge failures in th- utility grid, proposals have b-en made in thQ CCITT and ETSI to realize optical B-ISDN subscriber lines by means of a so-called "pas~ive NTl", that i8 to say in essence to provide 5 simply an optical connector at the t~l e~ tions interfac~ between th~ network provider and user, up to which the network provider has the r^~F~In~h; 1 ~ ty for acceptable functioning (CCITT COM XVIII No. D.928, D.lll9 and D.1144; ETSI NA5 No. TD90/96; ETSI TM3 No.
1 0 ( I ' _ "_d) ) .
A similar sltuation exists in the TJSA, wher~ by contra~t with the conditions ih 3urope and Japar~ and to the relevant ETSI rs~ Atiora and CCITT re~
tiohs the interfac- between the network provider and user 15 is not the T~ interface but the ~3 interface; the NTl line ter~ination i8 thus - ,let~ly in the po9~ a~r~n of the cohnected subscriber. There are proposals similar to those for the npassiYe NTl~ in the USA, it being assumed that ah optical bus structur~ having taps (a so-called 20 "daisy chainn) is cornected on the subscrib~r side, which per_its the simpl~ realization of LANs (I,ocal Area ~T~
In each case, the subscriber ter~nination must now b~A p~-nDntly _onitored auto_atically with regard to its 25 acceptAble functioning; in modern ~ ~ ~tion retworks, comprehensive, as far a~ possihle Cully automatic perma-n~ent _onitoring is a mandatorY requirenent of the network proYiders. In the case of cos~nection con~igurations which contaih ~ true NTl l~ne termi~ation in the area of 30 respohsibility of the network proYider, this is pcssihle in a comprehensive fashion which is r~latively without problems, since it is poss;hle ih the so-called ~ v~ ' o~E the B-ISDN signal (in bytes, provided for the purpose, in the STM-l frame or, in the casu of cell tr~n~ aion~
35 in O~M c~lls provided for the purpose) to transmit c~nt;n~o~ly a plenitude of relevant ite_s of OAM inform-ation in both directions betweeh the NTl line ter ination and the ~h~ or an appropriate bL~-lL.qnd subscriber li3e u:lit at the 3~twork end~
ANENDED S~EET
¢R 93 P 1~55 P - 3 -and since lt 1B p~pa~hle to for~ suit b~e electric, cptical or aS least logic loops betwoen the outsoin~ and return dlrections ln the N'rl lin~ t~ n-tlnn .
9y contr~st, given r^np^n~Thillty of th- network 5 providcr only for th~ optlcal subscriber line auto2~atlc p~-n~nt ~onitorl~g of thlg optlcal 8~ 'h^ llne i3 no longer directly poE3;hle, even if the subscrlber pos6esses an NTl line ter~in~tlon wlth which the network provider could in princlple ~ t~ in th~ way 10 described above. Sp~n;f;~ ly, the line t~n~t~nn can, for exa~nple, have been swltc~ed off by the subscriber, acd it is then no longer directly po~o;hle for the networ~c provider to ~stabli3h whether there is a ~alfunc-tion ln hls own ar~a of renpnnRih; l; ty, for example 15 becau3e an e~ccavator has damaged the optlcal ~ubscriber llne, or whether the fault is ln the area o~ r~Rpnno;h;l-lty of the subscr~ber. Sinc~, on the other hand, the ~bscriber i8 generally by no means t~hnir~lly capable of judging wheth~r it is the sectlcn of the broadband 20 line in his po~se~o;nn that has falled, or the sectlon at t_e srid end, a plenltude of possibly uTl~ustified co~-plaints c n ari3e, ~d the neSwork provider ust then establi_h by ~eans of relatively expensive neasures whether he is hiTn3elf re3ponsible for the trouble and has 25 to renove the latter, or whether the reTno~ral of the troubl~ is the r~RpnnR;h;~ity of the sub_criber.
It ~aa therefor~ proved to be desirable to be able to nTonltor automatically whether trouble or inter-ruptions occur on optical 3ubscriber line3 in the area of 30 responR;hll; ty of the network provider.
There is already known for this purpose a method for ~onitoring the 3ectlon, situated between an OWG line unit, in particular the subscriber line unit at the exchange end, and a defined passive optic~l interfac-, A.~3ND3D S~EET
2 ~ 78952 GR 93 P 1855 P - 4 ~
of an optical broad'oant service cable, in p~lrticular a broadbaTld gubscriber lin~, to th~ effect t~at a siru-soidal pilot audio signal of le88er amplitude and having a r.~u~i~ which i8 situated outside t_e spectral regio~
5 oc~ ri^~T by the infor3ation oignal to be transmittsd Ls added in thg OWG line u~it to th~ ~lectric drive signal of the optical trsnsmitter ~rovided th^r^, at the passive interfac~ ~ small ~ t of th~ optical aigr~al traTls-mitted ~ro~s t_~ lTn- unit to the subgcriber l8 h~ ar~.h^~7 10 cfC, poasibly ~y refl-^-ction c~used ~ o-~ T~y by mesrs of an optical ~^ t~hl-~ conn-ction provided ~t the passive int~rfac~, ~d led bac~c in the ravers~ directior~
to th~^ line u~it whero it is convertDd, in the optical rGceiver provided t~ers, ~ose~ h~r with the optical sig al 15 received from the subscriber i to an ~l~ctric aignal, and the pilot audio ~ig~al ~o~t~ ^d t~erein ia branched off wit~ the ~id of a fre~ency-~iGlGctive filt3r and ~as it~
a~litud~ aubjGctsd to a ~irgl~ tage. or multistage t_reshold valuG ~ whos^ r~sult for~ ~ measur~ of 20 the quality of the optical aGrvic^ cabl~ between the line unit ard passive int~rfac..; in this case, th~ ~nfo~-ti~
~ignal of or~e t-?~ ti~ direction which is to be transs~itted car. be carrier-bor e ~lectrically before the modulatio:~ of the optical transmitt-^r in JUch ~ way that 25 it i8 convGrtet irto a sp~ctral r_gion not occ~ri^; by the b~n^T~ i irfor~ation . ig al of t_e opposite direc-tion, and a pilot audio signal having a r . ~l.G~-.;y situ-ated outside t~e two spectral regions of thc irfor~atiou ~;g~als can be tran~Tmitted (EP 93113290 6) Furl h. Gt ~or the purpose of ~onitorirg an optical ~road~ard aervice cable it is 3~nown to proceed in such ~ way t~at - an optical downstr~aTs sig~al formed from an inforsation signal to ~e transmitted in the downstraam dirGction over the optical broadba~d ~er~ice cable and a nitoring tiignal in the for~s of a p~eudo-noise binary ~ignal ~ 8 transmitted ~ro~s an OWG lin~ unit, A~DED 5~2 - , ~nto, reflected at F-F-;hle reflection pointa of the optical bL~ '' ' servic~ cable, of the optical downstream signal are transmitted baclc in the upstrean direction to the OWG line unlt and converted i~to an e~lectrlc signal ln the optic^l receiver, provided there, together with a~ optical ~sLLGeu~l signal received oYer the optical broadband servicG cable, - and the reflected monitoring signal, contai~ed therein, is evaluated by virtue of the fact that the said Qlectric signal and the pseudo-noise binary signal, which is dGlayed by a delay time period which co~ ~ c~.,LLds to the signal propagation tine on the ~. ~ a~d service cable between the OWG line unit and reflection point out to and back again, are f ed to a signal correlator, having a ~ultiplier with a downstrea~ integrator, whose output signal anplitude demonstrat~s correctly in terms of signal propagation time the oc.-L G ce of a reflected pseudo-noise bin~ry sicnal f _ ' t (WO92/11710; further ~in Optical Time Domain Reflectometers (OTDR) WO87/07014; l;!r~ CS L3TT~RS 16(1980)16, 629).
In this case, the test code pulse sequence re~auired at the transmitting end can be generated by a first pseudo-noise binary signal generator, and the same code pulsc secuence can be generated, but shi~ted in ti7re, by a second pseudo-noise bi~ary aignal generator operating syTlchronously, the tine shift being effected by a control device to which there are applied the cloc3c signal of the first pseudo-noise binary signal generator and a franing signal irdicating to it the he5;nn;T~ of each test code pul~e secuence, and which, for its part, synchronizes the second pseudo-noise binary signal generator in accordance with the desired tine shift input into it from a PC (WO-92-11710), the time shift being effect~d by a ti~e-delay unit which is situated betweer, the second pseudo-nois~ binary signal generator and the first psGudo-noise binary signal generator (W087/07014), AMENDE D SiIEET
2l 7~952 GR 93 P 1855 P 5~2 or the time shift being effected by a time-delay unit vJa which a synchronous 08cillator directly driving the first pseudo-noiae binary ~ign~l generator drives the second pseudo-noise binary signal generator in a cG-~a~- ~;n~ly delayed fashion (Rr.r--- LElTERS 16 (1980) 16, 629).
~owever, it is rel~tively ~xpensive to producc thc required time shif t by a PC-controlled synchronous control device or by a controllable ti3e-delay unit, and the invention de20nstrates, by contrast, a way of reduc-ing thia cost.
The invention rslatea to a :lethod for 30nitoring the section of an optical broadband service cablQ, in particular ~ broadband sub8criber line, situ~ted betwecn a~ OWG line unit, in particular a sUb3criber line unit at the exchange end and a defined passivc optical interface, to the effect that - an optical down3tream signal for2ed from an infor~ation signal, to be transmitted in the ~'- L~c~ direction over the optical broadband service cablc, and a pseudo-noise binary signal i8 transmitted from the OWG line U~Lit, - a small ~ -nt of the optical downstre~m signal is trans2itted from the passiv~ optlcal intcrface in the upstre~ direction back to the OWG line unit, where it is converted into an electric signal in the optical receiver provided ther~ together with ~ _~nn~nts, possibly reflected at other reflection points of the optical broadba~d service cable, of the optical downstrea3 signal and with ~n optical upstrea2 aignal received via the 3 0 optical broadband service cable, - and the r~flected 20nitoring 8ignal cnnt~ne<? therein is evaluated with regard to it~ reflection at the ~assive optical i~terfacc by providing that the s~id electric .aM3NDED S}~EET
2 1 789~2 signal ~d the pseudo-noi8e binary signal, which i~
delayed by a delay time period which cv ..~.~v~d~ to the sig~al propagation tim~ on the broadband service cable from the OWG line unit to the p~ssive optical int~rface 5 a~ld back again, ~r~ fed to a ~ignal correlator which as a multiplier with ~ downatream integrator and whose output signal amplitud~ is monitored correctly in ter~ns of signal propagation time for the oC.~,L~,. ce of th~
p~eudo-noi~e binary signal _ _ - t reflected from th~
10 pas8ive optical interface; this method is characterized according to the invention in that the pseudo-noise binary signal r~quired at th- transriitting end and the time-delayed pseudo-nois~ binary signal to b~ fed to th~
correlator are generated by two separata pseudo-nois~
15 generators having CO~L~ 1ln~1Y differing starting values .
The i~vention is attended by t~e advantag~ of being able to set the desired delay time dir~ctly by means of al!~Lv~Llately differing prs~etting of t~e two 20 ps~udo-noise generators [generally to bR formed a~ llhift register chains closed to produce a ring in each case~
with the aid o~ ~ microproc~ssor, which is to be provided in any case for the purpose of further processing the corr~lator output signal (integration r~sult), w~thout 25 ther~ being a need ~or a ~upplementary control unit or time-delay unit; it thus renders it pos~ible in the case of the monitoring of an optical broadbard service cable up to a passive interface, the reflection of which i8 utilized, to combat ln a cost-saving way ~
30 caused by additional reflections at other points on the optical service cahle to be ~onitored, or co~Lplications in the evaluation of the desired reflection, and thus r~nders possible in an advantageous way simple ~nd reli~ble nitoring of the optical broadband service 35 cabl~ between the OWG line unit at the excha~gQ e~d and th~ defined passive optlcal interfac~, which may delimit th~ area of resp~n~hility of the networlc provider. The A25ENDED S~T
_ _ _ . _ -2 1 789~2 line unit at th~ exchange end can in thi~ c/Lse ~180 be remote from th~ ~ctual exchang~, and lil~w~5~ ther~ iJ no n~ed for tho pa~JiV~ optical interf~c~ to be provlded directly uJ~_L~ ~ of a subscriber~ statlon.
In order to tran~mit the blnary pseudo-noise r~ndo~ signal, it is po~ih~ ~ in a further ~ t of the invention for the biasing current of a laser dlod~
provided a8 optical transr~itter in the OWG ll~e unit to be ~pliLud~ ted with th~ binary pseudo-noiso r~ndom ~lgnal. AJ ~n alternative to this, it ia ~L180 posslble for the binary p8eudo-noise rando~ signal to be superimposed additively ~n the OWG line unit to the clactric control signal of th~ optical tranamitter provid~d ther~.
In order to avoid i llp9~ hl~ noi8e level3 within the useful bandwidth of the optical 8ignal, it is, f$~ally, also possible ln ~ further ~ ' t of the invention that in the OWG line unit ther~ i8 added to th~
el~ctric drlv~ signal of th~ optic~l tr namitter provlded ther~ ~ pilot audlo signal which i8 Jituated outside th~
frequency range occupied by the information ~ignal to b~
tran~itted and has beerL modulated with the blnary pseudo-nolse random signal; at the recelving end the carrier-borne pseudo-noise hinary slgnal sequencs will then have to he ~ -' lated befor~ the correlatlon.
Further particularitie~ of th~ invention ay be gathered frorL the following description with the aid of the drawlngs, ln which:
AM~21DED S~ T
Eigure 1 shows th~ monitoring of an optical l,~oadbc~d ~ervice csbl~ having only one optical fiber, ~nd Figure 2 shows the monitoring of an optical broadb~d servic- cablo having two separat~ optical fibers for thn two tr~n~r~i^n directions; and Figure 3 shows an exa~ple of a correlation curv~.
Repr~sented diagrammatically in Figure 1 to an extent re~uir~d to underatand the invention i8 a bidirectional OWG (optical waveguide) tel~- ;c?tions system having a ~preferably - '-) OWG s-rvice cable OA~ with only one optical fiber for tran3mitting the optical signals of both tr~nP~; ~Einn directions: this optical fiervic~ cable, which in the exemplary ' ~ t accorting to Figur~ 1 extend3 between a subscriber line u it ~T at the a~ch~ end and a 3ubscriber~ 8 sta-tion TSt, may be r~iuired to be monitored from the ^T~ n~e up to a pas3ive optical interface PNTl.
~n general, various ~odes of operation are F~E;hl~ at a pnEsive optical interface, aa will also b~
~urther illustrated in the following ~ n~ti^n~ such as, for exa~ple, l-fiber wavelength divi3ion multiplex with 1.3~+ and 1. 3 ~L-, and l-fiber wavelength division multiplex with 1.5~L and 1.3~, and 2 - ~iber operation;
~'130 possible is a data 8ignal tr~n~ lnn in one dl rection in the basebar,d ar,d in the other direction in modulated form.
The principle of the invention can be applied independently of the optical con~iguration used and of the type of data tran3mission. Only the attenuation and reflection parametsrs diffar from one another. For this reason, the optical cirouit in Figure l is also to be urderstood only as a diagram of the principle.
In the l ~ t considered, as also i3dicated in Figur~ 1, the passive interface PNTl i3 r~ali~ed by me~n3 of an optical demountable connection ir.
which the optical endfaee of the part of the ~ ' hle eon~ecticn whic}l is ~LL~ ~,1 at thH eYchange Qnd m~y be provided with a ref lecting eoating r At the passive interfae- P~ll, a small fraetio ~
5 of th~ optieal ~ignal transmittet from th~ li3e unit } T
to thY 8 ~hlvQ~--ih~ '~ statio~ TSt is l-- _- - l-or3 off and fed ~c3c in the r~verse direetion to thQ l~nl~ unit LT In th~
1 9 y , t aecording to PlgurQ 1, this is p_L' `1 in sueh a way as to rQfleet at t~e passive 10 ~ntarf~e~ PNTl a portion of the light transm~ tted from the li 8 unit LT T~- optieal signal fed }~aek to t~e line Lnit LT is eorverted there in the optieal reeeiver e\o (a~ th~ e~s~ may ~e, together ~it~ the optieal sig3al r~eaived from t e ~ubscri~er' 8 tatio3 TSt~ into an 15 eleetrie l~ig~al In the ~Y~ a~y ~ ' ' t aeeordi g to Figure 1, aecording to whieh tbe optic~l serv~ co ~able oal has o ~ly one opt~ eal ~ber via which t e optical ~ gnals of ~oth ~ an~; nr ~n dir~etions ~re 20 transmi~ted, tbis t; a~ r~^n c~n proc-Qd i3 ~oth directions in tho ~ame optical ~rindow: Tho wavelength cf t'~e laser transmitter Q/O at t Q ~ y~ end is in t is case, at 1 3 IL, for eYample, ~pproxi2at~ly ~gual to the wavelensth of t~e (not represented in d~tail in Fisur~ 1) 25 #lc_L-~ tical t I nQ~llr~ of the ~lhs~-~h~' s ~tation ~st; in order to prevent mutual intsrf~rence between the two ele_L,~ tieal ~ nQ~ 8 ~ven in eost-optimized syat~s C~t~ 5 no isolator3, a~d to prevent p~Q~hl~
heterodyning (form Ition of ~xed product~ from tl~e 30 d~ffarent signals because of th~ 'nl ~n~ response of the opt ~ cal receiver) - whieh het~r~dynir~g may lead to undesired int~rf erenee ~ot_ with t e useful signal and with ~e pilot audio 9ignal, the wavelengths used ~or t e two tr~n~m; Qsi^n direetions ar~, however, not per~itted 35 to be exactly egual or ne~rly exactly ~cual For this reason, in Pigure 1 the wavelengths are denoted as 1 3 ~-~nd 1 3 ~+ ~owever, inste~d of an opt~ eal l,rindow situ-~ted at 1 3 f~, it is also por~hlL~ to usel a3 optical wi~Ldow 8ituat8d, fo~ oxampl~, ~t 1 55 f~
2 1 78~52 GR 93 P la55 P - g -~ f, in a departure ~ro~ the conditions indicated in Figure 1, the optical signalg or the two tr~ n directicns ar~ trans_itted in dif rereIlt optical windows, for exa_ple at 1.3 ~ in on~ tr~nD--;ssion direction and at 5 l . 55 ~ in the other tr~n~$ ~s~n direction, tb.c reflec-tion point ~t the passive optical interfaco PNT1 can also b~ constructed in a wavelength-selective fashion, with t~e result that it is ~ !''nt~ y only the optical signal w:~ich is trans3litted in th~ direction towards the sub-10 s~riber's 6tation TSt and c~n~ l~n~ the pseudo-noise (PN) binary 3ignal which is parti~lly r2flected.
Represe3t~d diagram~atically in Figure 2 to the extent required to understand the invention is an ~xemp-lary ~ J~ t of a bidir~ction~l OWG tel~. ~c2tions 15 syst2m having a (preferably ~ ) OWG service cable OAI which has a separate optical fiber for each trans-mission direction, it being possible for the optical ~ignals of the two tr~n~m~ ~s1~n directions to be trans-m tted at the game wav~length or at di r rerent wave-20 lengths. This optical service cable OAI" which in the _ l ~ry ~ t according to Figure 2 again extendsb~tween a subscriber line unit ~T ~t the exchange end and a ~ubscriber' 8 station TSt, may, ~gain, need to be monitored ~rom the exchange end up to a passive optical 25 interf~ce PNT1. For this purpose, again a PN binary ~i.gnal is added to tl~e infor~ation signal to be trans-m~ tted o~er the OWG service cable 0~.
At the paEIsive interface PNT1, again, a s_all fracti on of the optical signal transm tted from the line 30 unit 21T to the subscriber TSt is ~ranched off and fed bsck in the reverse d~ rection to the line unit ~T . ~t is indicated in Figure 2 in this regard that couplers V in the fo= of passive optical couplers between which an optical feedbac3c path R extr-nds are provided on the side 35 of the passive optical intarface PNTl facing the lire u~i t LT .
G}~ 93 P 1855 P - 10 _ 2 The optiaal signalg can be ln~n~ and coupled out in this case by means of a ,y -tLlcal passive optical couplers Via the~ feedback path R, a small fraction of the 5 optioal signal tranamitted ~rom the subscriber lin-u~it LT to th~ subscrib~r~ 8 stat~ on TSt passes back in th~ direction towards the subscriber line unit LT where it is convert-d in the optical receiver ~\o provided there into an electric signal togethQr with the optical 10 signal received fro~ the ~ubsoriber TSt It is indicated i3 Figure 1 that a ~odulation circuit M for the information signal to be transmitted and an operati g point control circuit A belong to the laser diode provided as optical tran~mitter Such cir-15 cuita ar~ knowQ i principle (for exa~ple fro~D~-A1-4125075) and do not requirQ further explanation here In th{~ exe2plary -'; t in acco ~c~ with Figur~ 1, the method according to the invention is baaed 20 on the corr-lation betwee~ d paeudo-nois~ (PN) bit 8ecue"ce generated by a generator G and the reflected -~t of an optical signal whose ~ean value was dulated ~y meana of the la~er biasing current ib~ with t~e aame PN bit aec,uence TQe PN bit aequence i8 a pseudo 25 raQdom sequenc~ of binary signal ~le2ents O, 1 (or -1, I 1~ such as can be generated with a period p 2n-1 by means of an n-stage shi~t regiater haviT~g linear feed-bac3c ~he biasing CurreQt i~ " of tQe laser diode at the LT end (LT beiQg the line termination at the subacriber -30 line networX end) ia a2plitude-nodulated u~ins the raQdom sequence of the PN geQerator G WitQ a 8mall raQge of, for example, 10%
The optical dowQatream aigQal, which is modulated by the information sigQal which is to be traQsmitted from 35 the OWG line UQit LT over the optical broadbaQd service cable 0~ L in tQe down~tream direotion, on the one haQd, aQd whose meaQ value is 1 ~te~l using the PN bit sequenc~, on th~ other haQd, is more or less strongly re_lected at all Fo~P;hle reflection points of the optical broadband service cable OA~, and thus al80 at the passive optical interfac~, which effects a deflned (deaired) reflection (for example, with ~ reflection factor of 10%).
The optic~l signal receivced by th~ line unit LT
in the upstrea~ direction cnnt~n~ the TSt ;nforT^-tinn signal ori~;n ~t~ng in the subacriber~8 station TSt, reflected ~ of the LT infor;l~ation signal trans-mitted in the down8trea~ direction, reflected ~
of the PN bi~ary signal and interference (for cxample, noiae) in the receiver input atageg, the levelg ~p-~n~?;n5 on the optical configuration and the type of data trans-fer. Thia aignal is now correlated - as the case ~ay be, amplified but not yet regenerated (in tis~e) - with the PN aeguence, delayed in time by a delay time period r which corresponds to the signal propagation ti~e from the line unit ~T to the passive interface PNT1 and bac3c again, that is to say this signal is 31ultiplied and sub8equently integrated over a plurality of PN s~, r~r~;
the output sig~al resulting fro~ the correlation corres-ponds in amplitude to the reflected aign~ ^nts having an optical aignal propagation ti~e in the region of ~he ti~e delay ~. ~his correlation aignal is finally monitor~d correctly in ter~s of signal propagation ti~e for the DC~u~ ~ c ~ce of the pseudo-noiae binary signal reflect2d from the passive interfacs PNTl, something which can procced in th~ manner of an amplitude threshold value decision. Threshold value ~ ; nn~ are generally ~cnown, and 80 there is no need for any further explan-ations on thia. It may be pointed out in particular in this connection that the correlation signal can alao, as the case nay be, be subjected to not o~ly a single-stage, but alao a ~ultistage threshold value ~c;~n the result of which additionally for 8 a ;lleasure of the guality of 3 5 the optical service cable OAI, between the OWG line unit LT and the pas8ive interface PNTl.
The ti e delay T can be realized ~dvantageously by generating the PN se~ for the biasing current 1 ~t~r A ~in Fisure 1) and for t_e corr~lator S, J (in Figure 1 and Fisur~ 2) by two separatQ PN gen-rators (G, G in Fig-ure 2) formed by means of shift register chains, in which diferent start~ng v~lues ar~ prescribed, from a ~icro-processor I~P, in the form of an ~Lyyl~p lately dlffering pLc~c~ 2 of their shif t resistQr chAins . The ~elec-tion of these starting values det~;n~ th~ tima delay 7 of the PN se~iu~n~ e, fed to th~ correlator X, J (in Figure 1 and Figure 2), with respect to the PN 8-, ~a f~d to the ~ ' lator (A in Fisur~ 1; e/o in Fisure 2).
Interf erence terms ar~ filtered out hy the i tegration downstr~am of the multiplication of the re1ectsd signal and time-delayed sis al. The achievable signal-to-noise ratio of the integrated sisnal, and thus o~ the correlator output sisnal, depends on the param~-tars of the optical signal c ~nta, ~ut al~o essen-tially on the integration time. The correlator output signal (integration result) can ~e subject~d to A/D
converaio3 and further processed in the downstream mi~ ,y OCe~60L ~LP. The distance of the reflection loca-tio~ can be calculated given a known group velocity of the optical signal.
The microprocessor ~P can ~irstly also tak~ over the setting of different time delays 7 in a --1 ;hrat ;~
operation, in order to dete~;~ all the reflection e~n1-~ on the individual route sections. The spati~1 resolution ~1 increases linearly in this case with the clock rate at which the laser biasing current is a=pli-tude-modulated; it is ~1 ~ c/2f, in which c is the ~roup velocity of the optical signal and f the clock fraquency of the pseudo-noise bit sequence. The maxinum ~oritorable route length 13a,~ is also det~;n~d by the temporal length of the PN period; it is 13~ cp/2f, in which p is the period of th~ PN bit sequenca.
Figure 3 shows diagrammatically the characteris-tic of th~ correlator output signal as a function of the time delay r. The measurement points h;~hl ;~hee~' on the correlation curvq have a spacing ,, .
which cu~ u,.ds to the length of ~ individual bit of the PN 8~, r nl~o. The correlatlon curve 2ay be baaed in the exa~nple on a clock rate of 100 k!~z and a paeudo-~oise ~it se~uence having a length of 25-l bits (and thus a period o 310 ~8); the group velocity of the 3ig al 03 the optical rout~ 2ay be 0 . 2 k2/,us . CG~ ". r~; n5 to a forward and return tirle or ti2e delay r of 200 ~8 in the ~xa2ple, is a diatance ~ro2 tha r-flection location of 20 k2; the passiv~- inturfac~ PNTl (in Fisure 1 ~nd Figur~ 2) 2ay bo located at this distzmc~ in the exa2ple.
raki2s account o~ the two-fold ~-~ nn ti2e of the ~ignal to the r~flection locatlon ~nd back aga n, ther~
is a spatial re~olu~ ;nn A1 C 11 k2 and a 20nitorable route lengt~ ", of at 20st 31 km.
~or th~ normal op~-at~ fol~ A'n~J tke calibra-tion operation, a fixed ti2e delay r of 200 ~8 i~ the Qxa2ple is then selected i~ order to ~onitor the part of the optical b ~ nrl ~ervice cable OAI~ (in Pigure 1 and Figur~ 2) ~tuated betweQn the - 20 OWG line unit ~T (in Figur~ 1 and Fisur~ 2) ~d the defined passive optical interface PNTl (in Fisure 1 a~d Figuro 2), in order to 20nitor the o~ ~ca, correctly in t~r~s of ti2e, of the pseudo-roiae ~inary siglal reflectad fro2 the passive int~rfac~ PNTl (in Figure 1 and Figure 2) with the aid of the oc _-C8 of a corr~s-pnrlr~; nrJly high correlator output sig~al a--plitude A, as it is given in accor-l~c~ with Flsure 3 precisely in the case of ~ forward and retur~ t~ ma or delay ti2e r o~
200 IL8 in the exa2ple in accorda~ce with a distane~ of the reflective passive interface PNTl (in P~gur~ 1 a~d Figura 2) of 20 k2. Sinc~ t_e reflQction condit~o~s change in the case of ~m int2rruptios: of t_e optical trans2issioII path, all that is now roquir~d i~ to det2r-2ine ~nd ~valuato deviations of t_Q correlatio~ ~ig~al a~plitude fro2 the valu~ es~hl i ~h~d during the cali-bration operaticn.
A8 may ~o seen fro-- Figurs 3, the ti2e delay r is exps~ ntly sQlectod for nor~al operation ~uch that it is at lQast _ _ . _ , _ _ _ _ .. .. , . ... _ _ _ _ _ _ _ _ approximately equal to the signal propagation time from the OWG line unit LT up to th- passive optical interface PNT1 ~in Figur~ 1 ~nd Figure 2) and b~ck, because then the ~plitude spacing a from the dc - ~ ~nt ucs (~ndesired correlation signal) of th~ corselator output aignal is particul~rly large. This dc _ _ ort is to be 5~"rlhe~, on the one hand, to the fact that in a P~ ~ o ~e the nu~ber of -1 signal ^7~ t~ is not equal to th- nur~ber of tl signal elelsents and, on the other hand, that ;n addition to the r~flection signal origi~at-ing in the passive interfacs PNTl (in Figure 1 and Figure 2) yQt other signals reach the correlator input.
I~: may he noted in this regard that in Figurs 3 increased correlation signal amplitudes are also indicat~d in the le~t-ha d and right-hand edges of the correlatio2 curve, ~d these ~ay be ascribed to reflections at a pA~s;hl~
connector at the LT end. ~owever, this can be neglected for nitoring the oc~ ~LL~ce of the pseudo-noise binary signal reflected by the p~asive intQrface PNT1, becau8e these increased correlation sign~l a~plitudes would occur o~ly in the cas~ of the associated time delays, to be seen in Figur~ 3, of, for exa~ple, O or 310 fi8, _ut not in the case of the o~Te~7~o~ly selected tisle delay of, ~or example, 200 ~8.
If an a~plitude modul~tion of the laser biasing current should not be te~-h~c~ y rDD~ hle, it is also poasible for a COL ~ N a nplitude signal to be superi3lposed additively on t~e electric i3formation signal, as is indicated in Figurs 2. The total signal 3 0 then dulateQ the optical output power of the la~er .
Ii' an amplitude ~odulation of the laser biasing current, or if an additive aignal superimposition should lead to ~rpe~; QQ;hl~ noise levels within the useful b~ndwidth of the optical signal, it is also posaible in the OWG line unit LT to add to the drive signal of the optical trans nitter provided ther~ a pilot audio signal which has been ~ tod with the pseudo-noise binary ~ignal and whose frequency is outsido the GR 93 ~ 1855 P - 15 -freguency ranse occ~ riecl by the infor~ation aignal to be transmitted in the upstream directlon; it i~s then necesa-ary for the carrier-bor~e PN bin~ry aignal 89, ~ -e to be tfi~d again in th~ receiver section before the 5 correlation It i8 r,ot a rsstrictio n of the invention that i~ldividual ~ , OWG line unita (1T ir~ Figure 1 ;~d Figur~ 2) are respectively provided i~ an exchange in each case with a~ individual subscriber optical service 10 cablH (OA~ in Figur- 1 and Ficura a); rather, the ir,ven-tion can al90 bo appli-d i- a passive optical networX ir w~ich a plurality of subscribers or, in general terr~s, of df~central t ~l e~ tiona devices are r~spf ctively cornect~d via a dedicatad optical aervics cable to an lS optical coupler which is connected directly or via at leaat one further optical coupler to a commor, OWG line u~it ~t th- ~cchange end via an optical waveguide bus S~le~ fro3n the exchange f~nd u~8~. ~ of the ju~ctions, thf ra is provided in this cas~ a paasive 20 opt~ cal interfac~ PNT1 witk the aid of which it ia posaible to ~or,itor the optical tr~"f~m; f~f~i~n route fr the exchange end at least up to this interface; the st7<tf tf~ ~nade in relatio~ to Figurs 1 (or in the case of thf~ two- f iber design of Figure 2 ) apply in this ca~;e in a co.~ "g way
~'LE, P~' Tr ~ ~. J~-Foreign version T~:3 T~ r,:_ DQscription Monitoring optical bLua~ d service cahles up to a passive interfacs In accordance with CCITT, an optical B-ISDN
subscriber line is u6ually realized such that at the end of that part of the optic~l subscriber line for which the n~twork provider i8 r~p~n~hle, that i~ to say at the 80-Ca11ed IJB interface, the optical li~e i8 ter~inated by 13 means of a so-called network termination (N~l) (CCITT
~c. I.432).
This NTl network ter ination oompriaes optoelec-tric and alectrooptic transducsrs, correctly t~inAt^~
th~ subscriber lin~ with r~gard to operation, administra-tion and .^-~nt-~n,n. e (OAM) and ~akea available in the direction towards the subscriber a standardized bidirectional broadband interface, the so-aalled TB
interfacQ, also termed the user-network interface (~NI).
The ~ignals in the two transmiasion directions have a gross baud rate of 155.52 Nbit/s in each case both at the ~xchange end of the line t~;nAt ~ ~n NTl (at the ~rB
interfac-) and on the 3ubscriber sidQ (at the TB inter-fac~), and comprise either a seguence of bytswise fra~es in accordance with the ~irst stage STMl (STM T Synchron-OU8 Transport Module) o~ the so-called synchronous digital hierarchy (SD~:), in whose in~ormation-carrying part so-call~d ATM cslls (~x. 149.76 ~bit/s) are trans-mitted with a 53 byte length each (ATM Asynchronous Transfer ~ode), or colq?rise a pure se5~uence o_ ATM cells, ~0 the cell data rats useful for information transmi3sion likewise b~ins 149 . 76 ~bit/s .
Since the NTl line tsrmination is relatively complex and reguire~ space, electric power and relatively expensivQ ~lc~ ytic and optoelectric tr~n~ D~s~
pos~ibly Qven battery _ _ 2 ~ 7 8 9~2 back-up, in order to bridge failures in th- utility grid, proposals have b-en made in thQ CCITT and ETSI to realize optical B-ISDN subscriber lines by means of a so-called "pas~ive NTl", that i8 to say in essence to provide 5 simply an optical connector at the t~l e~ tions interfac~ between th~ network provider and user, up to which the network provider has the r^~F~In~h; 1 ~ ty for acceptable functioning (CCITT COM XVIII No. D.928, D.lll9 and D.1144; ETSI NA5 No. TD90/96; ETSI TM3 No.
1 0 ( I ' _ "_d) ) .
A similar sltuation exists in the TJSA, wher~ by contra~t with the conditions ih 3urope and Japar~ and to the relevant ETSI rs~ Atiora and CCITT re~
tiohs the interfac- between the network provider and user 15 is not the T~ interface but the ~3 interface; the NTl line ter~ination i8 thus - ,let~ly in the po9~ a~r~n of the cohnected subscriber. There are proposals similar to those for the npassiYe NTl~ in the USA, it being assumed that ah optical bus structur~ having taps (a so-called 20 "daisy chainn) is cornected on the subscrib~r side, which per_its the simpl~ realization of LANs (I,ocal Area ~T~
In each case, the subscriber ter~nination must now b~A p~-nDntly _onitored auto_atically with regard to its 25 acceptAble functioning; in modern ~ ~ ~tion retworks, comprehensive, as far a~ possihle Cully automatic perma-n~ent _onitoring is a mandatorY requirenent of the network proYiders. In the case of cos~nection con~igurations which contaih ~ true NTl l~ne termi~ation in the area of 30 respohsibility of the network proYider, this is pcssihle in a comprehensive fashion which is r~latively without problems, since it is poss;hle ih the so-called ~ v~ ' o~E the B-ISDN signal (in bytes, provided for the purpose, in the STM-l frame or, in the casu of cell tr~n~ aion~
35 in O~M c~lls provided for the purpose) to transmit c~nt;n~o~ly a plenitude of relevant ite_s of OAM inform-ation in both directions betweeh the NTl line ter ination and the ~h~ or an appropriate bL~-lL.qnd subscriber li3e u:lit at the 3~twork end~
ANENDED S~EET
¢R 93 P 1~55 P - 3 -and since lt 1B p~pa~hle to for~ suit b~e electric, cptical or aS least logic loops betwoen the outsoin~ and return dlrections ln the N'rl lin~ t~ n-tlnn .
9y contr~st, given r^np^n~Thillty of th- network 5 providcr only for th~ optlcal subscriber line auto2~atlc p~-n~nt ~onitorl~g of thlg optlcal 8~ 'h^ llne i3 no longer directly poE3;hle, even if the subscrlber pos6esses an NTl line ter~in~tlon wlth which the network provider could in princlple ~ t~ in th~ way 10 described above. Sp~n;f;~ ly, the line t~n~t~nn can, for exa~nple, have been swltc~ed off by the subscriber, acd it is then no longer directly po~o;hle for the networ~c provider to ~stabli3h whether there is a ~alfunc-tion ln hls own ar~a of renpnnRih; l; ty, for example 15 becau3e an e~ccavator has damaged the optlcal ~ubscriber llne, or whether the fault is ln the area o~ r~Rpnno;h;l-lty of the subscr~ber. Sinc~, on the other hand, the ~bscriber i8 generally by no means t~hnir~lly capable of judging wheth~r it is the sectlcn of the broadband 20 line in his po~se~o;nn that has falled, or the sectlon at t_e srid end, a plenltude of possibly uTl~ustified co~-plaints c n ari3e, ~d the neSwork provider ust then establi_h by ~eans of relatively expensive neasures whether he is hiTn3elf re3ponsible for the trouble and has 25 to renove the latter, or whether the reTno~ral of the troubl~ is the r~RpnnR;h;~ity of the sub_criber.
It ~aa therefor~ proved to be desirable to be able to nTonltor automatically whether trouble or inter-ruptions occur on optical 3ubscriber line3 in the area of 30 responR;hll; ty of the network provider.
There is already known for this purpose a method for ~onitoring the 3ectlon, situated between an OWG line unit, in particular the subscriber line unit at the exchange end, and a defined passive optic~l interfac-, A.~3ND3D S~EET
2 ~ 78952 GR 93 P 1855 P - 4 ~
of an optical broad'oant service cable, in p~lrticular a broadbaTld gubscriber lin~, to th~ effect t~at a siru-soidal pilot audio signal of le88er amplitude and having a r.~u~i~ which i8 situated outside t_e spectral regio~
5 oc~ ri^~T by the infor3ation oignal to be transmittsd Ls added in thg OWG line u~it to th~ ~lectric drive signal of the optical trsnsmitter ~rovided th^r^, at the passive interfac~ ~ small ~ t of th~ optical aigr~al traTls-mitted ~ro~s t_~ lTn- unit to the subgcriber l8 h~ ar~.h^~7 10 cfC, poasibly ~y refl-^-ction c~used ~ o-~ T~y by mesrs of an optical ~^ t~hl-~ conn-ction provided ~t the passive int~rfac~, ~d led bac~c in the ravers~ directior~
to th~^ line u~it whero it is convertDd, in the optical rGceiver provided t~ers, ~ose~ h~r with the optical sig al 15 received from the subscriber i to an ~l~ctric aignal, and the pilot audio ~ig~al ~o~t~ ^d t~erein ia branched off wit~ the ~id of a fre~ency-~iGlGctive filt3r and ~as it~
a~litud~ aubjGctsd to a ~irgl~ tage. or multistage t_reshold valuG ~ whos^ r~sult for~ ~ measur~ of 20 the quality of the optical aGrvic^ cabl~ between the line unit ard passive int~rfac..; in this case, th~ ~nfo~-ti~
~ignal of or~e t-?~ ti~ direction which is to be transs~itted car. be carrier-bor e ~lectrically before the modulatio:~ of the optical transmitt-^r in JUch ~ way that 25 it i8 convGrtet irto a sp~ctral r_gion not occ~ri^; by the b~n^T~ i irfor~ation . ig al of t_e opposite direc-tion, and a pilot audio signal having a r . ~l.G~-.;y situ-ated outside t~e two spectral regions of thc irfor~atiou ~;g~als can be tran~Tmitted (EP 93113290 6) Furl h. Gt ~or the purpose of ~onitorirg an optical ~road~ard aervice cable it is 3~nown to proceed in such ~ way t~at - an optical downstr~aTs sig~al formed from an inforsation signal to ~e transmitted in the downstraam dirGction over the optical broadba~d ~er~ice cable and a nitoring tiignal in the for~s of a p~eudo-noise binary ~ignal ~ 8 transmitted ~ro~s an OWG lin~ unit, A~DED 5~2 - , ~nto, reflected at F-F-;hle reflection pointa of the optical bL~ '' ' servic~ cable, of the optical downstream signal are transmitted baclc in the upstrean direction to the OWG line unlt and converted i~to an e~lectrlc signal ln the optic^l receiver, provided there, together with a~ optical ~sLLGeu~l signal received oYer the optical broadband servicG cable, - and the reflected monitoring signal, contai~ed therein, is evaluated by virtue of the fact that the said Qlectric signal and the pseudo-noise binary signal, which is dGlayed by a delay time period which co~ ~ c~.,LLds to the signal propagation tine on the ~. ~ a~d service cable between the OWG line unit and reflection point out to and back again, are f ed to a signal correlator, having a ~ultiplier with a downstrea~ integrator, whose output signal anplitude demonstrat~s correctly in terms of signal propagation time the oc.-L G ce of a reflected pseudo-noise bin~ry sicnal f _ ' t (WO92/11710; further ~in Optical Time Domain Reflectometers (OTDR) WO87/07014; l;!r~ CS L3TT~RS 16(1980)16, 629).
In this case, the test code pulse sequence re~auired at the transmitting end can be generated by a first pseudo-noise binary signal generator, and the same code pulsc secuence can be generated, but shi~ted in ti7re, by a second pseudo-noise bi~ary aignal generator operating syTlchronously, the tine shift being effected by a control device to which there are applied the cloc3c signal of the first pseudo-noise binary signal generator and a franing signal irdicating to it the he5;nn;T~ of each test code pul~e secuence, and which, for its part, synchronizes the second pseudo-noise binary signal generator in accordance with the desired tine shift input into it from a PC (WO-92-11710), the time shift being effect~d by a ti~e-delay unit which is situated betweer, the second pseudo-nois~ binary signal generator and the first psGudo-noise binary signal generator (W087/07014), AMENDE D SiIEET
2l 7~952 GR 93 P 1855 P 5~2 or the time shift being effected by a time-delay unit vJa which a synchronous 08cillator directly driving the first pseudo-noiae binary ~ign~l generator drives the second pseudo-noise binary signal generator in a cG-~a~- ~;n~ly delayed fashion (Rr.r--- LElTERS 16 (1980) 16, 629).
~owever, it is rel~tively ~xpensive to producc thc required time shif t by a PC-controlled synchronous control device or by a controllable ti3e-delay unit, and the invention de20nstrates, by contrast, a way of reduc-ing thia cost.
The invention rslatea to a :lethod for 30nitoring the section of an optical broadband service cablQ, in particular ~ broadband sub8criber line, situ~ted betwecn a~ OWG line unit, in particular a sUb3criber line unit at the exchange end and a defined passivc optical interface, to the effect that - an optical down3tream signal for2ed from an infor~ation signal, to be transmitted in the ~'- L~c~ direction over the optical broadband service cablc, and a pseudo-noise binary signal i8 transmitted from the OWG line U~Lit, - a small ~ -nt of the optical downstre~m signal is trans2itted from the passiv~ optlcal intcrface in the upstre~ direction back to the OWG line unit, where it is converted into an electric signal in the optical receiver provided ther~ together with ~ _~nn~nts, possibly reflected at other reflection points of the optical broadba~d service cable, of the optical downstrea3 signal and with ~n optical upstrea2 aignal received via the 3 0 optical broadband service cable, - and the r~flected 20nitoring 8ignal cnnt~ne<? therein is evaluated with regard to it~ reflection at the ~assive optical i~terfacc by providing that the s~id electric .aM3NDED S}~EET
2 1 789~2 signal ~d the pseudo-noi8e binary signal, which i~
delayed by a delay time period which cv ..~.~v~d~ to the sig~al propagation tim~ on the broadband service cable from the OWG line unit to the p~ssive optical int~rface 5 a~ld back again, ~r~ fed to a ~ignal correlator which as a multiplier with ~ downatream integrator and whose output signal amplitud~ is monitored correctly in ter~ns of signal propagation time for the oC.~,L~,. ce of th~
p~eudo-noi~e binary signal _ _ - t reflected from th~
10 pas8ive optical interface; this method is characterized according to the invention in that the pseudo-noise binary signal r~quired at th- transriitting end and the time-delayed pseudo-nois~ binary signal to b~ fed to th~
correlator are generated by two separata pseudo-nois~
15 generators having CO~L~ 1ln~1Y differing starting values .
The i~vention is attended by t~e advantag~ of being able to set the desired delay time dir~ctly by means of al!~Lv~Llately differing prs~etting of t~e two 20 ps~udo-noise generators [generally to bR formed a~ llhift register chains closed to produce a ring in each case~
with the aid o~ ~ microproc~ssor, which is to be provided in any case for the purpose of further processing the corr~lator output signal (integration r~sult), w~thout 25 ther~ being a need ~or a ~upplementary control unit or time-delay unit; it thus renders it pos~ible in the case of the monitoring of an optical broadbard service cable up to a passive interface, the reflection of which i8 utilized, to combat ln a cost-saving way ~
30 caused by additional reflections at other points on the optical service cahle to be ~onitored, or co~Lplications in the evaluation of the desired reflection, and thus r~nders possible in an advantageous way simple ~nd reli~ble nitoring of the optical broadband service 35 cabl~ between the OWG line unit at the excha~gQ e~d and th~ defined passive optlcal interfac~, which may delimit th~ area of resp~n~hility of the networlc provider. The A25ENDED S~T
_ _ _ . _ -2 1 789~2 line unit at th~ exchange end can in thi~ c/Lse ~180 be remote from th~ ~ctual exchang~, and lil~w~5~ ther~ iJ no n~ed for tho pa~JiV~ optical interf~c~ to be provlded directly uJ~_L~ ~ of a subscriber~ statlon.
In order to tran~mit the blnary pseudo-noise r~ndo~ signal, it is po~ih~ ~ in a further ~ t of the invention for the biasing current of a laser dlod~
provided a8 optical transr~itter in the OWG ll~e unit to be ~pliLud~ ted with th~ binary pseudo-noiso r~ndom ~lgnal. AJ ~n alternative to this, it ia ~L180 posslble for the binary p8eudo-noise rando~ signal to be superimposed additively ~n the OWG line unit to the clactric control signal of th~ optical tranamitter provid~d ther~.
In order to avoid i llp9~ hl~ noi8e level3 within the useful bandwidth of the optical 8ignal, it is, f$~ally, also possible ln ~ further ~ ' t of the invention that in the OWG line unit ther~ i8 added to th~
el~ctric drlv~ signal of th~ optic~l tr namitter provlded ther~ ~ pilot audlo signal which i8 Jituated outside th~
frequency range occupied by the information ~ignal to b~
tran~itted and has beerL modulated with the blnary pseudo-nolse random signal; at the recelving end the carrier-borne pseudo-noise hinary slgnal sequencs will then have to he ~ -' lated befor~ the correlatlon.
Further particularitie~ of th~ invention ay be gathered frorL the following description with the aid of the drawlngs, ln which:
AM~21DED S~ T
Eigure 1 shows th~ monitoring of an optical l,~oadbc~d ~ervice csbl~ having only one optical fiber, ~nd Figure 2 shows the monitoring of an optical broadb~d servic- cablo having two separat~ optical fibers for thn two tr~n~r~i^n directions; and Figure 3 shows an exa~ple of a correlation curv~.
Repr~sented diagrammatically in Figure 1 to an extent re~uir~d to underatand the invention i8 a bidirectional OWG (optical waveguide) tel~- ;c?tions system having a ~preferably - '-) OWG s-rvice cable OA~ with only one optical fiber for tran3mitting the optical signals of both tr~nP~; ~Einn directions: this optical fiervic~ cable, which in the exemplary ' ~ t accorting to Figur~ 1 extend3 between a subscriber line u it ~T at the a~ch~ end and a 3ubscriber~ 8 sta-tion TSt, may be r~iuired to be monitored from the ^T~ n~e up to a pas3ive optical interface PNTl.
~n general, various ~odes of operation are F~E;hl~ at a pnEsive optical interface, aa will also b~
~urther illustrated in the following ~ n~ti^n~ such as, for exa~ple, l-fiber wavelength divi3ion multiplex with 1.3~+ and 1. 3 ~L-, and l-fiber wavelength division multiplex with 1.5~L and 1.3~, and 2 - ~iber operation;
~'130 possible is a data 8ignal tr~n~ lnn in one dl rection in the basebar,d ar,d in the other direction in modulated form.
The principle of the invention can be applied independently of the optical con~iguration used and of the type of data tran3mission. Only the attenuation and reflection parametsrs diffar from one another. For this reason, the optical cirouit in Figure l is also to be urderstood only as a diagram of the principle.
In the l ~ t considered, as also i3dicated in Figur~ 1, the passive interface PNTl i3 r~ali~ed by me~n3 of an optical demountable connection ir.
which the optical endfaee of the part of the ~ ' hle eon~ecticn whic}l is ~LL~ ~,1 at thH eYchange Qnd m~y be provided with a ref lecting eoating r At the passive interfae- P~ll, a small fraetio ~
5 of th~ optieal ~ignal transmittet from th~ li3e unit } T
to thY 8 ~hlvQ~--ih~ '~ statio~ TSt is l-- _- - l-or3 off and fed ~c3c in the r~verse direetion to thQ l~nl~ unit LT In th~
1 9 y , t aecording to PlgurQ 1, this is p_L' `1 in sueh a way as to rQfleet at t~e passive 10 ~ntarf~e~ PNTl a portion of the light transm~ tted from the li 8 unit LT T~- optieal signal fed }~aek to t~e line Lnit LT is eorverted there in the optieal reeeiver e\o (a~ th~ e~s~ may ~e, together ~it~ the optieal sig3al r~eaived from t e ~ubscri~er' 8 tatio3 TSt~ into an 15 eleetrie l~ig~al In the ~Y~ a~y ~ ' ' t aeeordi g to Figure 1, aecording to whieh tbe optic~l serv~ co ~able oal has o ~ly one opt~ eal ~ber via which t e optical ~ gnals of ~oth ~ an~; nr ~n dir~etions ~re 20 transmi~ted, tbis t; a~ r~^n c~n proc-Qd i3 ~oth directions in tho ~ame optical ~rindow: Tho wavelength cf t'~e laser transmitter Q/O at t Q ~ y~ end is in t is case, at 1 3 IL, for eYample, ~pproxi2at~ly ~gual to the wavelensth of t~e (not represented in d~tail in Fisur~ 1) 25 #lc_L-~ tical t I nQ~llr~ of the ~lhs~-~h~' s ~tation ~st; in order to prevent mutual intsrf~rence between the two ele_L,~ tieal ~ nQ~ 8 ~ven in eost-optimized syat~s C~t~ 5 no isolator3, a~d to prevent p~Q~hl~
heterodyning (form Ition of ~xed product~ from tl~e 30 d~ffarent signals because of th~ 'nl ~n~ response of the opt ~ cal receiver) - whieh het~r~dynir~g may lead to undesired int~rf erenee ~ot_ with t e useful signal and with ~e pilot audio 9ignal, the wavelengths used ~or t e two tr~n~m; Qsi^n direetions ar~, however, not per~itted 35 to be exactly egual or ne~rly exactly ~cual For this reason, in Pigure 1 the wavelengths are denoted as 1 3 ~-~nd 1 3 ~+ ~owever, inste~d of an opt~ eal l,rindow situ-~ted at 1 3 f~, it is also por~hlL~ to usel a3 optical wi~Ldow 8ituat8d, fo~ oxampl~, ~t 1 55 f~
2 1 78~52 GR 93 P la55 P - g -~ f, in a departure ~ro~ the conditions indicated in Figure 1, the optical signalg or the two tr~ n directicns ar~ trans_itted in dif rereIlt optical windows, for exa_ple at 1.3 ~ in on~ tr~nD--;ssion direction and at 5 l . 55 ~ in the other tr~n~$ ~s~n direction, tb.c reflec-tion point ~t the passive optical interfaco PNT1 can also b~ constructed in a wavelength-selective fashion, with t~e result that it is ~ !''nt~ y only the optical signal w:~ich is trans3litted in th~ direction towards the sub-10 s~riber's 6tation TSt and c~n~ l~n~ the pseudo-noise (PN) binary 3ignal which is parti~lly r2flected.
Represe3t~d diagram~atically in Figure 2 to the extent required to understand the invention is an ~xemp-lary ~ J~ t of a bidir~ction~l OWG tel~. ~c2tions 15 syst2m having a (preferably ~ ) OWG service cable OAI which has a separate optical fiber for each trans-mission direction, it being possible for the optical ~ignals of the two tr~n~m~ ~s1~n directions to be trans-m tted at the game wav~length or at di r rerent wave-20 lengths. This optical service cable OAI" which in the _ l ~ry ~ t according to Figure 2 again extendsb~tween a subscriber line unit ~T ~t the exchange end and a ~ubscriber' 8 station TSt, may, ~gain, need to be monitored ~rom the exchange end up to a passive optical 25 interf~ce PNT1. For this purpose, again a PN binary ~i.gnal is added to tl~e infor~ation signal to be trans-m~ tted o~er the OWG service cable 0~.
At the paEIsive interface PNT1, again, a s_all fracti on of the optical signal transm tted from the line 30 unit 21T to the subscriber TSt is ~ranched off and fed bsck in the reverse d~ rection to the line unit ~T . ~t is indicated in Figure 2 in this regard that couplers V in the fo= of passive optical couplers between which an optical feedbac3c path R extr-nds are provided on the side 35 of the passive optical intarface PNTl facing the lire u~i t LT .
G}~ 93 P 1855 P - 10 _ 2 The optiaal signalg can be ln~n~ and coupled out in this case by means of a ,y -tLlcal passive optical couplers Via the~ feedback path R, a small fraction of the 5 optioal signal tranamitted ~rom the subscriber lin-u~it LT to th~ subscrib~r~ 8 stat~ on TSt passes back in th~ direction towards the subscriber line unit LT where it is convert-d in the optical receiver ~\o provided there into an electric signal togethQr with the optical 10 signal received fro~ the ~ubsoriber TSt It is indicated i3 Figure 1 that a ~odulation circuit M for the information signal to be transmitted and an operati g point control circuit A belong to the laser diode provided as optical tran~mitter Such cir-15 cuita ar~ knowQ i principle (for exa~ple fro~D~-A1-4125075) and do not requirQ further explanation here In th{~ exe2plary -'; t in acco ~c~ with Figur~ 1, the method according to the invention is baaed 20 on the corr-lation betwee~ d paeudo-nois~ (PN) bit 8ecue"ce generated by a generator G and the reflected -~t of an optical signal whose ~ean value was dulated ~y meana of the la~er biasing current ib~ with t~e aame PN bit aec,uence TQe PN bit aequence i8 a pseudo 25 raQdom sequenc~ of binary signal ~le2ents O, 1 (or -1, I 1~ such as can be generated with a period p 2n-1 by means of an n-stage shi~t regiater haviT~g linear feed-bac3c ~he biasing CurreQt i~ " of tQe laser diode at the LT end (LT beiQg the line termination at the subacriber -30 line networX end) ia a2plitude-nodulated u~ins the raQdom sequence of the PN geQerator G WitQ a 8mall raQge of, for example, 10%
The optical dowQatream aigQal, which is modulated by the information sigQal which is to be traQsmitted from 35 the OWG line UQit LT over the optical broadbaQd service cable 0~ L in tQe down~tream direotion, on the one haQd, aQd whose meaQ value is 1 ~te~l using the PN bit sequenc~, on th~ other haQd, is more or less strongly re_lected at all Fo~P;hle reflection points of the optical broadband service cable OA~, and thus al80 at the passive optical interfac~, which effects a deflned (deaired) reflection (for example, with ~ reflection factor of 10%).
The optic~l signal receivced by th~ line unit LT
in the upstrea~ direction cnnt~n~ the TSt ;nforT^-tinn signal ori~;n ~t~ng in the subacriber~8 station TSt, reflected ~ of the LT infor;l~ation signal trans-mitted in the down8trea~ direction, reflected ~
of the PN bi~ary signal and interference (for cxample, noiae) in the receiver input atageg, the levelg ~p-~n~?;n5 on the optical configuration and the type of data trans-fer. Thia aignal is now correlated - as the case ~ay be, amplified but not yet regenerated (in tis~e) - with the PN aeguence, delayed in time by a delay time period r which corresponds to the signal propagation ti~e from the line unit ~T to the passive interface PNT1 and bac3c again, that is to say this signal is 31ultiplied and sub8equently integrated over a plurality of PN s~, r~r~;
the output sig~al resulting fro~ the correlation corres-ponds in amplitude to the reflected aign~ ^nts having an optical aignal propagation ti~e in the region of ~he ti~e delay ~. ~his correlation aignal is finally monitor~d correctly in ter~s of signal propagation ti~e for the DC~u~ ~ c ~ce of the pseudo-noiae binary signal reflect2d from the passive interfacs PNTl, something which can procced in th~ manner of an amplitude threshold value decision. Threshold value ~ ; nn~ are generally ~cnown, and 80 there is no need for any further explan-ations on thia. It may be pointed out in particular in this connection that the correlation signal can alao, as the case nay be, be subjected to not o~ly a single-stage, but alao a ~ultistage threshold value ~c;~n the result of which additionally for 8 a ;lleasure of the guality of 3 5 the optical service cable OAI, between the OWG line unit LT and the pas8ive interface PNTl.
The ti e delay T can be realized ~dvantageously by generating the PN se~ for the biasing current 1 ~t~r A ~in Fisure 1) and for t_e corr~lator S, J (in Figure 1 and Fisur~ 2) by two separatQ PN gen-rators (G, G in Fig-ure 2) formed by means of shift register chains, in which diferent start~ng v~lues ar~ prescribed, from a ~icro-processor I~P, in the form of an ~Lyyl~p lately dlffering pLc~c~ 2 of their shif t resistQr chAins . The ~elec-tion of these starting values det~;n~ th~ tima delay 7 of the PN se~iu~n~ e, fed to th~ correlator X, J (in Figure 1 and Figure 2), with respect to the PN 8-, ~a f~d to the ~ ' lator (A in Fisur~ 1; e/o in Fisure 2).
Interf erence terms ar~ filtered out hy the i tegration downstr~am of the multiplication of the re1ectsd signal and time-delayed sis al. The achievable signal-to-noise ratio of the integrated sisnal, and thus o~ the correlator output sisnal, depends on the param~-tars of the optical signal c ~nta, ~ut al~o essen-tially on the integration time. The correlator output signal (integration result) can ~e subject~d to A/D
converaio3 and further processed in the downstream mi~ ,y OCe~60L ~LP. The distance of the reflection loca-tio~ can be calculated given a known group velocity of the optical signal.
The microprocessor ~P can ~irstly also tak~ over the setting of different time delays 7 in a --1 ;hrat ;~
operation, in order to dete~;~ all the reflection e~n1-~ on the individual route sections. The spati~1 resolution ~1 increases linearly in this case with the clock rate at which the laser biasing current is a=pli-tude-modulated; it is ~1 ~ c/2f, in which c is the ~roup velocity of the optical signal and f the clock fraquency of the pseudo-noise bit sequence. The maxinum ~oritorable route length 13a,~ is also det~;n~d by the temporal length of the PN period; it is 13~ cp/2f, in which p is the period of th~ PN bit sequenca.
Figure 3 shows diagrammatically the characteris-tic of th~ correlator output signal as a function of the time delay r. The measurement points h;~hl ;~hee~' on the correlation curvq have a spacing ,, .
which cu~ u,.ds to the length of ~ individual bit of the PN 8~, r nl~o. The correlatlon curve 2ay be baaed in the exa~nple on a clock rate of 100 k!~z and a paeudo-~oise ~it se~uence having a length of 25-l bits (and thus a period o 310 ~8); the group velocity of the 3ig al 03 the optical rout~ 2ay be 0 . 2 k2/,us . CG~ ". r~; n5 to a forward and return tirle or ti2e delay r of 200 ~8 in the ~xa2ple, is a diatance ~ro2 tha r-flection location of 20 k2; the passiv~- inturfac~ PNTl (in Fisure 1 ~nd Figur~ 2) 2ay bo located at this distzmc~ in the exa2ple.
raki2s account o~ the two-fold ~-~ nn ti2e of the ~ignal to the r~flection locatlon ~nd back aga n, ther~
is a spatial re~olu~ ;nn A1 C 11 k2 and a 20nitorable route lengt~ ", of at 20st 31 km.
~or th~ normal op~-at~ fol~ A'n~J tke calibra-tion operation, a fixed ti2e delay r of 200 ~8 i~ the Qxa2ple is then selected i~ order to ~onitor the part of the optical b ~ nrl ~ervice cable OAI~ (in Pigure 1 and Figur~ 2) ~tuated betweQn the - 20 OWG line unit ~T (in Figur~ 1 and Fisur~ 2) ~d the defined passive optical interface PNTl (in Fisure 1 a~d Figuro 2), in order to 20nitor the o~ ~ca, correctly in t~r~s of ti2e, of the pseudo-roiae ~inary siglal reflectad fro2 the passive int~rfac~ PNTl (in Figure 1 and Figure 2) with the aid of the oc _-C8 of a corr~s-pnrlr~; nrJly high correlator output sig~al a--plitude A, as it is given in accor-l~c~ with Flsure 3 precisely in the case of ~ forward and retur~ t~ ma or delay ti2e r o~
200 IL8 in the exa2ple in accorda~ce with a distane~ of the reflective passive interface PNTl (in P~gur~ 1 a~d Figura 2) of 20 k2. Sinc~ t_e reflQction condit~o~s change in the case of ~m int2rruptios: of t_e optical trans2issioII path, all that is now roquir~d i~ to det2r-2ine ~nd ~valuato deviations of t_Q correlatio~ ~ig~al a~plitude fro2 the valu~ es~hl i ~h~d during the cali-bration operaticn.
A8 may ~o seen fro-- Figurs 3, the ti2e delay r is exps~ ntly sQlectod for nor~al operation ~uch that it is at lQast _ _ . _ , _ _ _ _ .. .. , . ... _ _ _ _ _ _ _ _ approximately equal to the signal propagation time from the OWG line unit LT up to th- passive optical interface PNT1 ~in Figur~ 1 ~nd Figure 2) and b~ck, because then the ~plitude spacing a from the dc - ~ ~nt ucs (~ndesired correlation signal) of th~ corselator output aignal is particul~rly large. This dc _ _ ort is to be 5~"rlhe~, on the one hand, to the fact that in a P~ ~ o ~e the nu~ber of -1 signal ^7~ t~ is not equal to th- nur~ber of tl signal elelsents and, on the other hand, that ;n addition to the r~flection signal origi~at-ing in the passive interfacs PNTl (in Figure 1 and Figure 2) yQt other signals reach the correlator input.
I~: may he noted in this regard that in Figurs 3 increased correlation signal amplitudes are also indicat~d in the le~t-ha d and right-hand edges of the correlatio2 curve, ~d these ~ay be ascribed to reflections at a pA~s;hl~
connector at the LT end. ~owever, this can be neglected for nitoring the oc~ ~LL~ce of the pseudo-noise binary signal reflected by the p~asive intQrface PNT1, becau8e these increased correlation sign~l a~plitudes would occur o~ly in the cas~ of the associated time delays, to be seen in Figur~ 3, of, for exa~ple, O or 310 fi8, _ut not in the case of the o~Te~7~o~ly selected tisle delay of, ~or example, 200 ~8.
If an a~plitude modul~tion of the laser biasing current should not be te~-h~c~ y rDD~ hle, it is also poasible for a COL ~ N a nplitude signal to be superi3lposed additively on t~e electric i3formation signal, as is indicated in Figurs 2. The total signal 3 0 then dulateQ the optical output power of the la~er .
Ii' an amplitude ~odulation of the laser biasing current, or if an additive aignal superimposition should lead to ~rpe~; QQ;hl~ noise levels within the useful b~ndwidth of the optical signal, it is also posaible in the OWG line unit LT to add to the drive signal of the optical trans nitter provided ther~ a pilot audio signal which has been ~ tod with the pseudo-noise binary ~ignal and whose frequency is outsido the GR 93 ~ 1855 P - 15 -freguency ranse occ~ riecl by the infor~ation aignal to be transmitted in the upstream directlon; it i~s then necesa-ary for the carrier-bor~e PN bin~ry aignal 89, ~ -e to be tfi~d again in th~ receiver section before the 5 correlation It i8 r,ot a rsstrictio n of the invention that i~ldividual ~ , OWG line unita (1T ir~ Figure 1 ;~d Figur~ 2) are respectively provided i~ an exchange in each case with a~ individual subscriber optical service 10 cablH (OA~ in Figur- 1 and Ficura a); rather, the ir,ven-tion can al90 bo appli-d i- a passive optical networX ir w~ich a plurality of subscribers or, in general terr~s, of df~central t ~l e~ tiona devices are r~spf ctively cornect~d via a dedicatad optical aervics cable to an lS optical coupler which is connected directly or via at leaat one further optical coupler to a commor, OWG line u~it ~t th- ~cchange end via an optical waveguide bus S~le~ fro3n the exchange f~nd u~8~. ~ of the ju~ctions, thf ra is provided in this cas~ a paasive 20 opt~ cal interfac~ PNT1 witk the aid of which it ia posaible to ~or,itor the optical tr~"f~m; f~f~i~n route fr the exchange end at least up to this interface; the st7<tf tf~ ~nade in relatio~ to Figurs 1 (or in the case of thf~ two- f iber design of Figure 2 ) apply in this ca~;e in a co.~ "g way
Claims (6)
1. A method for monitoring the section of an optical broadband service cable, in particular a broadband subscriber line (OAL), situated between an OWG line unit, in particular the subscriber line unit (LT) at the exchange end and a defined passive optical interface (PNT1), characterized in that together with the information signal to be transmitted over the optical broadband service cable (OAL) in the downstream direction, a pseudo-noise binary signal is also transmitted from the OWF
line unit (LT), in that a small component of the optical downstream signal transmitted from the line unit (LT) is fed back from the passive interface (PNT1) in the upstream direction to the line unit (LT), where it is converted into an electric signal in the optical receiver provided there together with components, possibly reflected at other reflection points of the optical broadband service cable, of the optical downstream signal and with the optical upstream signal received via the optical broadband service cable (OAL), and in that this electric signal and the original pseudo-noise binary signal, which is delayed in time in accordance with the signal propagation time from the line unit (LT) on the broadband service cable (OAL) to the passive interface (PNT1) and back again, are fed to a signal correlator, which has a multiplier (X) with a downstream integrator (J) and whose output signal amplitude is monitored correctly in terms of signal propagation time for the occurrence of the pseudo-noise binary signal reflected from the passive interface (PNT1).
characterized in that the pseudo-noise binary signal required at the transmitting end and the time-delayed pseudo-noise binary signal to be fed to the correlator are generated by two separate pseudo-noise generators having correspondingly differing starting values.
line unit (LT), in that a small component of the optical downstream signal transmitted from the line unit (LT) is fed back from the passive interface (PNT1) in the upstream direction to the line unit (LT), where it is converted into an electric signal in the optical receiver provided there together with components, possibly reflected at other reflection points of the optical broadband service cable, of the optical downstream signal and with the optical upstream signal received via the optical broadband service cable (OAL), and in that this electric signal and the original pseudo-noise binary signal, which is delayed in time in accordance with the signal propagation time from the line unit (LT) on the broadband service cable (OAL) to the passive interface (PNT1) and back again, are fed to a signal correlator, which has a multiplier (X) with a downstream integrator (J) and whose output signal amplitude is monitored correctly in terms of signal propagation time for the occurrence of the pseudo-noise binary signal reflected from the passive interface (PNT1).
characterized in that the pseudo-noise binary signal required at the transmitting end and the time-delayed pseudo-noise binary signal to be fed to the correlator are generated by two separate pseudo-noise generators having correspondingly differing starting values.
2. The method as claimed in claim 1, characterized in that in the OWG line unit (LT) the biasing current of the laser diode provided there as optical transmitter is amplitude-modulated with the pseudo-noise binary signal.
3. The method as claimed in claim 1, characterized in that in the OWG line unit (LT) the electric drive signal of the optical transmitter (e/o) provided there has the pseudo-noise binary signal additively super-imposed on it.
4. The method as claimed in claim 1, characterized in that in the OWG line unit (LT) there is added to the drive signal of the optical transmitter provided there a pilot audio signal which is situated outside the frequency range occupied by theinformation signal to be transmitted in the upstream direction and has been modulated with the pseudo-noise binary signal, and in that at the receiving end the carrier-borne pseudo-noise binary signal sequence received as a function of reflection is demodulated again before the correlation.
5. The method as claimed in one of claims 1 to 4, characterized in that the correlation signal is subjected to a threshold value decision whose result indicates the occurrence or nonoccurrence of the pseudo-noise binary signal reflected from thepassive interface (PNT1).
6. The method as claimed in one of claims 1 to 5, characterized in that the correlation signal is subjected to a multistage threshold value decision whose result additionally forms a measure of the quality of the optical service cable (OAL) between the OWG line unit (LT) and passive interface (PNT1).
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP4342792.8 | 1993-12-15 | ||
| DE19934342792 DE4342792A1 (en) | 1993-12-15 | 1993-12-15 | Monitoring optical wide band subscriber lines |
| DE19944411376 DE4411376A1 (en) | 1994-03-31 | 1994-03-31 | Monitoring optical wide band subscriber lines |
| DEP4411376.5 | 1994-03-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2178952A1 true CA2178952A1 (en) | 1995-06-22 |
Family
ID=25932104
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2178952 Abandoned CA2178952A1 (en) | 1993-12-15 | 1994-12-01 | Surveillance of optical broad-band connection lines up to a passive interface |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0734622A1 (en) |
| JP (1) | JPH09506748A (en) |
| CA (1) | CA2178952A1 (en) |
| RU (1) | RU2115245C1 (en) |
| WO (1) | WO1995017053A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6441937B1 (en) | 2001-07-03 | 2002-08-27 | Infineon Technologies Ag | Optoelectronic transceiver module, and method for receiving optical signals |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2315938B (en) * | 1996-08-01 | 2001-02-28 | Northern Telecom Ltd | Optical transmission system fault analysis |
| US10070695B2 (en) | 2010-04-30 | 2018-09-11 | Boa Technology Inc. | Tightening mechanisms and applications including the same |
| US9118412B2 (en) | 2011-09-27 | 2015-08-25 | Broadcom Corporation | System and method for performing in-band reflection analysis in a passive optical network |
| RU2484521C1 (en) * | 2012-03-27 | 2013-06-10 | Федеральное государственное бюджетное учреждение науки Институт проблем управления им. В.А. Трапезникова РАН | Apparatus for detecting and eliminating faults when transmitting binary signals over two optical channel lines |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62179632A (en) * | 1986-02-03 | 1987-08-06 | Advantest Corp | Optical fiber tester |
| GB2190186B (en) * | 1986-05-09 | 1990-12-19 | Dr Jeremy Kenneth Arth Everard | Greatly enhanced spatial detection of optical backscatter for sensor applications |
| GB9027716D0 (en) * | 1990-12-20 | 1991-02-13 | British Telecomm | Optical communications system |
-
1994
- 1994-12-01 JP JP7516447A patent/JPH09506748A/en active Pending
- 1994-12-01 EP EP95902036A patent/EP0734622A1/en not_active Withdrawn
- 1994-12-01 CA CA 2178952 patent/CA2178952A1/en not_active Abandoned
- 1994-12-01 RU RU96114955A patent/RU2115245C1/en active
- 1994-12-01 WO PCT/DE1994/001424 patent/WO1995017053A1/en not_active Application Discontinuation
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6441937B1 (en) | 2001-07-03 | 2002-08-27 | Infineon Technologies Ag | Optoelectronic transceiver module, and method for receiving optical signals |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0734622A1 (en) | 1996-10-02 |
| JPH09506748A (en) | 1997-06-30 |
| WO1995017053A1 (en) | 1995-06-22 |
| RU2115245C1 (en) | 1998-07-10 |
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