CA2008909A1 - Method of determining optical losses at the ends and end joints of fiber light guides - Google Patents
Method of determining optical losses at the ends and end joints of fiber light guidesInfo
- Publication number
- CA2008909A1 CA2008909A1 CA 2008909 CA2008909A CA2008909A1 CA 2008909 A1 CA2008909 A1 CA 2008909A1 CA 2008909 CA2008909 CA 2008909 CA 2008909 A CA2008909 A CA 2008909A CA 2008909 A1 CA2008909 A1 CA 2008909A1
- Authority
- CA
- Canada
- Prior art keywords
- losses
- light guide
- light guides
- light
- output end
- 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
Links
Classifications
-
- 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
Abstract
A METHOD OF DETECTING OPTICAL LOSSES AT THE END AND
END JOISTS OF FIBER LIGHT GUIDES
Abstract The aim of the invention, improving the resolution by increasing the maximum possible distance to the test joint and expanding the range of applications by allowing the finish qua-lity of the ends, and their parallel and coaxial alignment to be determined, is achieved by successively sending probing light pulses into the light guides being joined, measuring the total power of reflection from the ends and end joints, and de-termining optical losses in these portions from mathematical formulae. Bibliog. 2, 2 illustrations.
END JOISTS OF FIBER LIGHT GUIDES
Abstract The aim of the invention, improving the resolution by increasing the maximum possible distance to the test joint and expanding the range of applications by allowing the finish qua-lity of the ends, and their parallel and coaxial alignment to be determined, is achieved by successively sending probing light pulses into the light guides being joined, measuring the total power of reflection from the ends and end joints, and de-termining optical losses in these portions from mathematical formulae. Bibliog. 2, 2 illustrations.
Description
X0089~)9 Field of the Inventlon ~' The ~resent invention relates to Eiber optics and can be used for deternlining the e~tent oE radiation attenuation at the joints of lisht gui~es devoid of air gaps in municipal and trunk communication networks built on the basis of fiber light ~uide3. . . .
Industrial Applicability The present invention can be used durin~ assembly, repairs, ' and maintenance oE trun~ networks of optical fiber light c3uides, -and also in studying various kinds of ~oints between fiber light guides.
Background of the Invention ICnown in the art is a r.lethod of measuring optical losses in riber light guides in reflecte~ light (ref. USSR Application 1;io.42~4727, with a decision to issue an Inventor's Certificats pL~Sr-~d on J.lay 3~, 1938), co~prising a proking radiation pulse into a test light guide throu~-h a klank liyht cJuide, the len~th of ~hich is e~ual to nalf thr-~ len~h o~ the esta'~lishe-! ~.or~e _istri~ution fcr the ~ en tyl:e of li3-ht ~uice, ..:easuriil; the energ~ L.1 of a ;~uls-e rerlecte~l ~~ro~ the outp-ut encl o~ the }:lank ~ ht luie, ;.leasurin~ the ener~ly ~1~ of a -i~ulse reElected from 7~" ~ :
20~189~)9 the o-~tput end of the ~lan~ li(,~ht ~Juide anc' t~le inri~ end of the test li~ht guicle locate-' at a ~i~imull distarlcs fror eac o~her, ,m~asurin, tihe ener~3y i~3 o. a pulse reflected from the output end of the -test liyht guide and deterrLiining optical loss-es ~ per unit length of the test light cJuide.
This prior art method is disadvantageous in that it cannot be used for determining optical losses at the radiation input and output of the test light guide, i.e., at the output end of the blank light guide and at the input and output ends of the test light guide, and also in the air ~ap between the joined light guides because of the non-parallel alignment of their ends and the non-co~Yial alignment of their cores.
Also known in the art is a method of determining optical losses in joints of light guides according to scattered radiat-ion propagating in the backward direction (ref. Shiketants, D., "Theory of ~easurement by Backward Scattering ~ethod in Light Guides" in Zarubezhnaya Radioelektronika, 1981, ~o.6, pp.87-94), comprising sendiny radiation into the light guides being joined, measuring the intensity of radiation scattered in the light yuides upstream and downstream of the joint, and determining op-tical losses in the joint of the light guides.
As the closest prior art of the present method in tech-nical essence, this method has been selected as the prototype.
A drawback of the prior art method is the low intensitv of the scattered radiation, which limits the maxim~m possible dis tance in the light guide line to the test joint.
The need exists, however, and its importance rises with an increase in the length of trunk light guid~ communication cables, the length of which presently reaches 30 to 40 kilometers or more, and which are accessed by measuring devices fro~ one ~,, ,. : : , .. . .
a~.
. , . ' ' ~ ~, . ' . .
f X0089~)9 side onlv.
Su~marv of the Invention The ~resent invention is aimed at expandiny t~e ranc;e of applications by determining the finishing quality of the end fac~s, and their parallel and coaxial ali~nment.
Another aim of the invention is to improve the resolution by increasing the maximurn possible distance to the test joint, as a result or which the dynamic range of measure~.ents is ex-panded.
The first of these aims is achieved by tnat a prior art me-thod co~prising successively sending a probing radiation pulse into the fiber light guides being joined and then determining optical losses at their joint according to the radiation pro-pagating in the backward direction, further co~,prises rneasuring the energy or total power N1 of pulses reflected from the output end of the first test light guide, determining losses K1=
10log(N1max/N1) at the output end of the first light guide from the difference between the value of N1 and the maximum N1maX~
measurin~ the energy or total power N2 of pulses reflected from the ends of the first and second light guides interconnected at :
a measured air gap, determining losses X2= 10log(N2max/~2)-Kl at the lnput en~ of the secona light guide from the difference between the values of N2 and ~2max and ~1 and N1max' .. ~
ing losses R//= 1olog~ 2/N1)max/(N2/N1)J due to non-parallel ~
alignment of the joined ends from the difference between the ~ ~-rat~o `L~2/~1 and the maximum 1~2 ( +1)2 (~1)max n2 + 1 measuring the energy or total power i~l3i of pulses which have passed through the test joint and have been re~lected from the ~ , . . . . .
~"''', ~ ' '' ~ " ' '" ,'. ' " '; ;: , ~:~,,,' ,,, , , , -,. . . . . .
1 ~ . . . .
Industrial Applicability The present invention can be used durin~ assembly, repairs, ' and maintenance oE trun~ networks of optical fiber light c3uides, -and also in studying various kinds of ~oints between fiber light guides.
Background of the Invention ICnown in the art is a r.lethod of measuring optical losses in riber light guides in reflecte~ light (ref. USSR Application 1;io.42~4727, with a decision to issue an Inventor's Certificats pL~Sr-~d on J.lay 3~, 1938), co~prising a proking radiation pulse into a test light guide throu~-h a klank liyht cJuide, the len~th of ~hich is e~ual to nalf thr-~ len~h o~ the esta'~lishe-! ~.or~e _istri~ution fcr the ~ en tyl:e of li3-ht ~uice, ..:easuriil; the energ~ L.1 of a ;~uls-e rerlecte~l ~~ro~ the outp-ut encl o~ the }:lank ~ ht luie, ;.leasurin~ the ener~ly ~1~ of a -i~ulse reElected from 7~" ~ :
20~189~)9 the o-~tput end of the ~lan~ li(,~ht ~Juide anc' t~le inri~ end of the test li~ht guicle locate-' at a ~i~imull distarlcs fror eac o~her, ,m~asurin, tihe ener~3y i~3 o. a pulse reflected from the output end of the -test liyht guide and deterrLiining optical loss-es ~ per unit length of the test light cJuide.
This prior art method is disadvantageous in that it cannot be used for determining optical losses at the radiation input and output of the test light guide, i.e., at the output end of the blank light guide and at the input and output ends of the test light guide, and also in the air ~ap between the joined light guides because of the non-parallel alignment of their ends and the non-co~Yial alignment of their cores.
Also known in the art is a method of determining optical losses in joints of light guides according to scattered radiat-ion propagating in the backward direction (ref. Shiketants, D., "Theory of ~easurement by Backward Scattering ~ethod in Light Guides" in Zarubezhnaya Radioelektronika, 1981, ~o.6, pp.87-94), comprising sendiny radiation into the light guides being joined, measuring the intensity of radiation scattered in the light yuides upstream and downstream of the joint, and determining op-tical losses in the joint of the light guides.
As the closest prior art of the present method in tech-nical essence, this method has been selected as the prototype.
A drawback of the prior art method is the low intensitv of the scattered radiation, which limits the maxim~m possible dis tance in the light guide line to the test joint.
The need exists, however, and its importance rises with an increase in the length of trunk light guid~ communication cables, the length of which presently reaches 30 to 40 kilometers or more, and which are accessed by measuring devices fro~ one ~,, ,. : : , .. . .
a~.
. , . ' ' ~ ~, . ' . .
f X0089~)9 side onlv.
Su~marv of the Invention The ~resent invention is aimed at expandiny t~e ranc;e of applications by determining the finishing quality of the end fac~s, and their parallel and coaxial ali~nment.
Another aim of the invention is to improve the resolution by increasing the maximurn possible distance to the test joint, as a result or which the dynamic range of measure~.ents is ex-panded.
The first of these aims is achieved by tnat a prior art me-thod co~prising successively sending a probing radiation pulse into the fiber light guides being joined and then determining optical losses at their joint according to the radiation pro-pagating in the backward direction, further co~,prises rneasuring the energy or total power N1 of pulses reflected from the output end of the first test light guide, determining losses K1=
10log(N1max/N1) at the output end of the first light guide from the difference between the value of N1 and the maximum N1maX~
measurin~ the energy or total power N2 of pulses reflected from the ends of the first and second light guides interconnected at :
a measured air gap, determining losses X2= 10log(N2max/~2)-Kl at the lnput en~ of the secona light guide from the difference between the values of N2 and ~2max and ~1 and N1max' .. ~
ing losses R//= 1olog~ 2/N1)max/(N2/N1)J due to non-parallel ~
alignment of the joined ends from the difference between the ~ ~-rat~o `L~2/~1 and the maximum 1~2 ( +1)2 (~1)max n2 + 1 measuring the energy or total power i~l3i of pulses which have passed through the test joint and have been re~lected from the ~ , . . . . .
~"''', ~ ' '' ~ " ' '" ,'. ' " '; ;: , ~:~,,,' ,,, , , , -,. . . . . .
1 ~ . . . .
2(~89~)9 ide~lly finislled output end OL the second light guide, deter-mining the losses an= 1010cJ(`I~3max/`.~3i) due to non-coaxial aliyn-ment of the joint Ero~ the difference between the value of ::i3i and the maxi~um level, measuring the energy or total power ;~T3 of pulses reflected from the output end of the second test light guide, determinins the losses X3= 1010g(M3i/3i) at the output end of the second light guide from the difference between the values of `13 and -'~3i' evaluating the total losses R~s in the test joint of the light guides from the ormula:
~ s K// + Xn, and evaluating the total losses K~T at all the three ends of the light guides fro~ the formula:
X2T= ~1 + K2 + K3.
To attain the second aim of the invention, the method pro-vides for measuring the energy or power N1 of a pulse which has passed through the ends of the light guides joined at a mini-mum air gap, has been reflected from the output end of the se-cond light guide, and returned to the input end of the Eirst :::
light guide, connecting the first and second light guides, mea-suring the energy or power ï~2 or a pulse which has passed through the joint and been reflected from the output end of the result-ing integral light guide, and determining the optical losses K
at the joint from the formula:
KldB¦ = lOloy2n - 1010g(n2+1) + 510gN2 - 51o5~1 (1) wherein n is the group refraction inde~ of the cores Oc the light guides being joine~
The claimed combination of features has not ~een used any~
where previously and, therefore, meets the world novelty inven-tive criterion.
The method of determining losses depending on the rinisning ~,:, . . :
~- ' ' , '' , . ' ' ' " ', .:
4. , . :, . -: :
5:: . ', . ' - ,,,:, .
. .
- 5 - 20~89~)9 q`1a1itY OL the endc, co~.~rises the follo~inc, se~iucnce cf ln-terrelated steps:
~ iation ~ulses (~ulse~ are sent into the first test light gui~e;
2. The ener~y (total power) Nl or pulses reflec~ed from the ideally L inished output end of sai~l light guide and propag-ating in the '~ackward direction is measured;
~ s K// + Xn, and evaluating the total losses K~T at all the three ends of the light guides fro~ the formula:
X2T= ~1 + K2 + K3.
To attain the second aim of the invention, the method pro-vides for measuring the energy or power N1 of a pulse which has passed through the ends of the light guides joined at a mini-mum air gap, has been reflected from the output end of the se-cond light guide, and returned to the input end of the Eirst :::
light guide, connecting the first and second light guides, mea-suring the energy or power ï~2 or a pulse which has passed through the joint and been reflected from the output end of the result-ing integral light guide, and determining the optical losses K
at the joint from the formula:
KldB¦ = lOloy2n - 1010g(n2+1) + 510gN2 - 51o5~1 (1) wherein n is the group refraction inde~ of the cores Oc the light guides being joine~
The claimed combination of features has not ~een used any~
where previously and, therefore, meets the world novelty inven-tive criterion.
The method of determining losses depending on the rinisning ~,:, . . :
~- ' ' , '' , . ' ' ' " ', .:
4. , . :, . -: :
5:: . ', . ' - ,,,:, .
. .
- 5 - 20~89~)9 q`1a1itY OL the endc, co~.~rises the follo~inc, se~iucnce cf ln-terrelated steps:
~ iation ~ulses (~ulse~ are sent into the first test light gui~e;
2. The ener~y (total power) Nl or pulses reflec~ed from the ideally L inished output end of sai~l light guide and propag-ating in the '~ackward direction is measured;
3. The ideally finished inpu-t end of the second test light suide is attached to the output encl of the first lisht guide pa-rallel thereto and ~t a minimum air gap therebetween;
4- The energy (total power) I~12~aX of pulses reflected from the ideally joined ends is measured;
5. Light pulses are sent into t'ne second test light yuide ideally coaYial with the first light guide;
6. The energy (total ?ower) .~.13max of ~ulses reflected from the ideally finished output end of the second light guide is measured;
7. The output end of the first test light guide is treated;
8. The energy (total power) N1 of pulses reElected from the realistically finished output end of the fir.st light guide is measured;
9. The losses K1= 10log(il1max/~1) at the output end of the irst light guide are determined;
10. The realistically finished end of the second light guide is attached at a realistic air gap to the output end of the ~irst light guide;
11. The energy (total power) N2 of pulses reflected fror.
the ends of the first and second light guides connected at test air gap is measured;
the ends of the first and second light guides connected at test air gap is measured;
12 Optical losses K = 101og(-~T /'~T ) - K at the input . . .
~s,,, i, :-Z0089~19 e~ OL the seconl light guide and losses IC//= 1~)log[(.~2/.~ a~c/
(.~2/~ due to non-parallel alignment of the joined ends are deter~.ined;
~s,,, i, :-Z0089~19 e~ OL the seconl light guide and losses IC//= 1~)log[(.~2/.~ a~c/
(.~2/~ due to non-parallel alignment of the joined ends are deter~.ined;
13. The rirst and the second test light guides are joinea in a realistic coaxial alignment;
14. The eneray (total power) ~3i of pulses which have t~.~ice passed through the test joint and have ~een reflected from the ideally finished output end of the second light guide is meas-ured;
n 1log(~3max/N3i) due to non-coaxial ali~nment of the test joint are determined;
16. The output end of the second test light guide is treated;
17. The energy (total power) N3 of pulses reflected from the ~ :
realistically finished output end of the second light guide is measured;
13. Optical losses K3= 10log(N3i/M3) at the output end of the second test light guide are determined, and 19. The total optical losses K~s in the measured joint are evaluated from the formula K~s= R~ + Rn, and the total loss-es R~T at all the three test joints are found from the formula:
sT 1 2 3 The method of determining optical losses at the end joints of the light guide.s for a maximum ~ossible dis-tance to the test end comprises the following sequence of inter-related steps~
1. Sendins a probing light pulse into the light guides be- ;
ing joined;
2. .~!easuring the energv or power L~1 o. a pulse which has passed throu~h the ends of the liyht guides joined at a minimum air gap and prepared for subsequent connection, has been reflect-''''',~' ' ' . . ~, ' ' . ~ " ;, i:', ' , ~....................... . .
i -:,, .
~,',,, ' , , .
", , ~ - , , Z0(~89~)9 ed from the output end of the second li~ht guide an retùrned to the input end of the first light guide alony the previous path;
3. Connecting the first and second light guides;
4. Ieasuring the energy or power ~2 of a pulse whicn has passed through the joint along the previous path and has been re-flected from the outnut end of t~e resulting integral light ~uide, and 5. Determining optical losses K at the joint from the for-mula: :
K~dB~ = 1010g2n - 1010g(n2 + 1) + 510y~2 - 510gi~
An advantage of the present measurement method is that owing to the closer relation between the amount of reflected radiat-ion and the condition of the end faces of the light guides and the extra pure quartz glass from which they are drawn compared ~ ;
to the radiation passing through the same ends,as well as on ac-count of the reflection fror,l the ends being several orders higher in comparison with the radiation scattere~-1 by the light guides, the sensitivity of mèasurements in the reflected light to the con-dition of the end faces, their ~arallel alignment, optical loss-es in the air gap between the ends, and the coaxial relation between the fiber light guides, which determines mode mismatch losses, is considerably greater than the sensitivity to similar losses in passiny radiation or radiation scattered by the light guides, and also that measurements are made in the light reflect-ed from the equivalent ends of the light guides, rather than in the light scattered by the different portions of the light guides being joined, the intensity of reflected light being several orders higher than tha~ of the scattered light, as a result OL
which the dynamic range of measurements and, there~ore, the dis-tance to the test joint of the light guides can be increased a ,~ . , . , ~
~ , ... ..
~ "',: ' ' , .
~ ~ , Z0~89~)9 corresponcin~ num~er o. tir~es.
~rief ~escriptior of tne ,~ra~ings ~hc invention is illustr~ted in the accom?allyinc- drawings, ~herein:
~ ig. 1 shows a de~Jics for ?erformin~-j the method of measurin~~
losses de?endin~ on the finish ~ualit~ Or the erd faces o-f the 'i~er li7ht quides, ~nd Fig.2 shows a device for perfor.--ing the inethod of measur~
ing losses at the end joints of jcined light guides. ~ -The device comprises a radiation source 1, a s litter 2 for incident and reElected radiation, a reLlected pulse receiver 3, a first light guide 4 and a second light yuide 5 to be joined to the first light guide.
Description of the Preferred Em~odiment The method is performed as follows: 2~ radiation pulse rrom the source 1 is sent through the splitter 2 into the first light guide 4 and the radiation reflected from its output end reaches through the same s~litter 2 the rsflected light receiver 3 (view a). A signal N1 separated by corresponding time sampling and caused by the pulse reflected from the output end is equal to: .
N1= const ~1 2(1~~)exP(-u4~4)~exp( ~U4~4)(1 ~)~2,3 = const-~1 2 ~2 3(1-p)2exp(-2~4!~4)p , (2) wherein the factor const characterizes the spectral response of the receiver 3 and the radiation flux of the source 1, ~1 2 and ~2 3 are transmission factors of the splitter 2 during propasat-ion o~ light from the source 1 to the receiver 2, (1-~) is the transmission factor cf the input end of the light guide 4, ~ is the reflection factor OL the output end, and ~4 and 24 are a radiation attenuation factor and the length of the light guide 4.
Two factors in the fonnula (2) characterize the condition ~ , . . .
~ ~'',' ~ ' ' :
~,, , 20~89~)9 of ti1e end sur~aces of the light guide~ ) is tl1e in~ut surface and ~ is the output surface.
I'he relative changes in the signal ~ 1 following from the formula (2) are equal (only in the function of changes of sai~
two factors).
N 1 ~ ( 1 ~ P
Since in the case of optical (quartz) glass rrom wnich the lignt guiaes are uraws~, lt may be assumed that p - 0.035 and accordingly l-f ~- 0.965, changes in ~ at the input end and in p at the output end by + 10% will result in changes 2~p(1-p) =
+ 2 x 0.0~35/(1-0.035 - 0.0035) = +0.007/0.9615 = + 0.0073 =
+0.7% and ~n changes a~/p= + O C335 = + 0.1 = + 10~
In other words, as a result of the same chanyes in the op-tical condition of the input and output surfaces changes ~.J1/
in the signal reflected from the output end of the light guide being joined are 13 times, i.e., more than an order, more sensi-tive to the condition of the output end than to the condition of the input end. Similarly, it may be demonstrated that during studies in scattered light propagating in a backward path throuyh the test joint surface, changes in the condition OL the surface are also equal to 2~p/(1-p), rather than ~p/p.
Therefore, measurement of the energy (power) i~J1 for differ-ent shear surraces of the output end of the light guide 4 and determination of the ratio OL N1 to the maximum value of M1~aX at tained on an ideal shear surface, which can be checked visually, with the help of ~icroscope, make it possible to evaluate most truthfully, at the greatest sensitivity to existing derects, the finish ~uality of the output end of the _irst light yuide of the joint. The lossss K1 at this end are, in decibels:
' ' '. '' .
~" ::
X0089~)9 i1 = l Clo'~ a,X/~
~ iext, the inut end or the second light guide 5 is treated and arfixed to the ou.put end of the first light suide ~ (~ie~7 b) at a corres~onding air gap, ~hich appears opti-nal to the ob- -server. The same receiver 3 measures the energy or total po~er i~2 of pulses reflected from the realistically joined ends of the light guides 4 and 5.
2 t 1,2 ~2,3(~ exP~-2~4~4)r~ + (1-~)2~ +
+ (1_~2)~3... = const ~~ )2exp(-2u4Y4)~ (1+ 1+p) =
const 71 2 ~2 3(1-~)2eXP(-2\u4~4) 1+fp (3) It is to be seen from formula (3) that changes in the op-tical condition of the joined end surfaces have twice as high an effect on changes in the signal N2: N2/N2 because of the fac-tor ~ 2 ~ . Therefore, the lo~ quality of the shear surface, ;~
the non-parallel alignment of the end aces and the additional optical losses in them have a maximum effect on chanc3es in the signal AN2/N2 recorded by the receiver 3.
As a result, the ratio of N2 to l~2maX, correspondins to the idealcondition of the end faces and their parallel alignment at a minimum air ga~ that does not disturb the radiation mode dis-tribution in the light guides, characterizes the total radiation losses in the air gap produced by the joint. Therefore, with the ~ -losses X1 at the first end kno~m from the formula (2), the loss-es ~2 contributed to the joint by the second end, i.e., the in-put end oE the light guide 5, are determined:
2 g(~2max/~2) 10log(~J1~ax/~11) - 1lCJ(!~2m /~2) ~ ~<1 In order to isolate the losses due to non-Farallel align-ment of the ends of the light guides being joined out o~~ the to-tal losses in the air gap, use is made of the following formula:
~;, '- '~: ' '" ' ' ' ~,~,, " ", ~' ,. . : ;
~' ' -1.~./, . - .
"~",, - ~ ' . ', ' .
~,,, ~ , : , , , ~"~
.'~ " -'-- . - , ' , , zoo~9~9 ::
~ 1 1 +~ ~4) the ma:~imum value of ~hich, given the ideal condition of the end faces and their parallel alignment, and in the absence oE ad~
ditional losses, is equal to:
(L~2) = ~ n~+1 wherein n is the group refraction index of the light guide cores.
Therefore, the difference between the formula (4) and formula (5) determines optical losses in the joint due to the lo~ finish-ing quality of the end faces (in particular, the input end of the second light guide, since the condition of the output end of the first light guide is already determined), the non-parallel alignment of the surfaces, and the total optical losses in the air gap. Losses caused by non-parallel ali~Jnment of the joined ends expressed in decibels are: Kt/= 10log[N2/l~1)max/(i12/~1)] .
In all the above-mentioned losses of the useful signal in the resulting joint of the light guides, no account was taken of the losses due to the non-coaxial alignment of the cores of the light yuiaes Delng ~olnea, because reflectlon ~rom the input end of the second li~ht guide actually provides no idea about the accuracy of connection of the cores themselves, because the reflection factor of the sheath of a hi-h ~ualitv 10~'7 mode light guide liffers very little _rom the reflection factsr of the cores. ~herefore, in determining losses caused by the non-co-axial alignment of the cores, it is essential to send radiation into the light glide beinq attached and then determine losses due to non-coaxial alignment.
To determine real losses due to non-coaxial alignment, the light ~uides 4 and 5 being joined are centered, a pulse (~ulses) of radiation from the source 1 is sent into the light guide 5 '- - , ~:''' " ' ' :.
~, ' -, ' :, 20~89~19 (view b i~ the drawiilg), the s~ ling inter~al OL the receiver 3 is changed so as to record only oulses reflected from t~le output end OL the light guide 5, and the energv or total power ~3i ' the rerlected pulses is measured, provided said end is ideally finished as its ideal condition is monitored, for example, vis-ually with the help of a microscope.
i= const-~1,2 ~2,3(1-~) e~p(-2~u4~4) [ ~ ¦ eXp(-2~us~s~
1,2 2,3(1 P) (1+p) exp(-2~u4e4 - 2u ~ )~ (6) wherein (1_~)/(1+~)2 is a squared transmission factor of the air gap between the joined light guides, and ~i is the reflection factor of the ideally finished out~ut end.
By analogy ~,rith the determination or deviations in ~N1/i~l, it follows from the formula (6) that the value of ~13 depends strongly on changes in ~p/~ of the condition of the output end of the second light guide and only little on the conditions of the other ends and the air gap. Since~ however, the formula (6) is derived on the assurnption that all the radiation emerging frorn the first light guide enters fully the second light guide and vice versa, because of the geometric matching of their cores, a mismatch (misalignment) of the cores causes the formula (6) to be transformed into:
N3i=const.l1 2-~2 3(1-~)2(11+p)2(1- ~n)2exp(-2~4e4- 2~u5~5)~i,(7) wherein Kn designates optical losses due to non-coaxial alignrnent because of the geometric mismatch of the light gui~le cores. Ob~i-ously, unliXe the forr..ula (7), a mismatch of the light guide core does not cause an appreciable change in the formula (3), becau3e the reflection factor of the sheath occupving the ~osition of the core should the latter be orfset mav differ only slightly from the reflection factor of the core.
20(~89~)9 ~ hereLore, in accordarce witll the for.lulae (6) and (7), t'ne signal ~3 is Ir.ost sensi-~ive to the condi.tion or the output end of the seconu li~ht guide and the mismatch or the light gui~e cores.
After losses due to non-coaxial ali~n?rent have been deter-mined, the output end oE the second light guide is trea-ted and, without dis~urking the connection, the energy (total power) N3 of pulses reflected from the realistically finished output end of the second light guide at a factor y is measured:
N3= const~1 2 ~2 3(1-f)2(11+P)2(1-~n)exp(-21u4e4 -2u5eS) ~ (8) The losses X3 at the output end of the second light yui~e are cletermined in dB from the foF~mulae (7) and (8) ~3/-~4 ~ ~/Pi ~3 = 11g(~3i/i~3) (9) Since all the kinds of losses at the ends and in the joint of the test light guides have been-determined separately in the course of the akove operations, the total losses ~T at the ends of the light guides and X~s in the joint can ~e assessed. Lo~se~
at the ends are found from the formula:
RsT= R1 + K2 + 3 (10) and in the joint, from the formula:
K~s = X// + Kn (11) LO detennine optical losses in the end face joints of the fi~er light guides, a radiation pulse (pulses) from the source 1 is sent successively through the splitter 2 into the first liyht gui~e 4 and the second light yuide 5 bein~s connected. r~fter the cores OL tlle light suides have keen joined wltil the help of any adjustin~ device so that they are coaxial with each other and with the s~litter, and the air yaps are r,.inil.~al and do not dis-turb the stationary mode distrikution of the rroking radiation, the receiver 3 ~easures the pO~Jer or energy or the pulse reflecte~
~, . . .
~' ' " '''i~'' ' '""' '' nt ,...................... " . .
,, . , - , , from the output end OL the second ligllt Guid2 5 (v~e~ a in riy.2). rrhe receiver siqnal .11 is in this case equal to:
1,2~2 4 e~;P(~2`~nen).4 5 e~p(-2~5~5) ~2 5=
n 1~ 2 2,3 ~2~ se~p(-2~nen)ex-p(-2u5~5)~ (12) .
whereln K is the proportionality factor;
~n is the ra~iation flux or eneray of the source 1;
~1 2; ~2 3 are transmission factors of the liaht flu~;
from the source to the splitter and from the splitter to the receiver;
~2 4;~4 5 are transmission factors of the air gap bet-ween the splitter 2 and the first light guide 4 and between the two light yuides 4 and 5 being joined, and ,U4; ~U5; ~4; ~5 are attenuation factors and lengths of the light guides 4 and 5.
After the light guides 4 and 5 have been connected without an air gap, the energy or maximum power of the pulse reflected is measured from the output end of the now integral light guide 4-5 (view b)~
In this case, the signal ~N2 of the receiver 3 is equal to:
2 ~n 1,2 '2,3, t2,4eXP~~2~4~4)K exp(-2~u5~5)~ =
n 1,2 2,3 2,4K p eXp(-2~u4e4)exp(-2u ~ ) and the ratio of the signals is:
N2 = 2 ~T~ ~,5 (14) Since, in accordance with Fresnel formulae, in view of mul-tiple reflections, the transmission factor ~4 5 of the air gap ~ .
between the joined light guid2s is equal to: : :
~ )2 1 = ~ = 2n (15) ~ ~ :
wherein ~ is the reflection factor of the end, n is the refrac-tion index, the formula (14) can be transformed to:
~,, - . , X0(~89~)9 ~; n2 + 1 V ~, (16) The rinal optical losses at the connecting point of the light guides, ex~ressed in deci~els, are determined from the - formula:
-l~ = 10log 2n - 1Clog(n2 + 1) + 5logi~2 - 5N~ (17J
~ ince the refraction index of the light guides is known or can be determined with an accuracy of at least ~n = +(1.10 3 to 1.10 4), the indefinite value of the reflection factor of the enZ of the light guide made of an extra pure quartz glass does not exceed ~p~ + 0.0025 x 0.00347718 c + 1.10 ~, and the value cf ~/l~ + 2.10 4, i.e., a change in the transmission factor or one end compared to the computed value does not exceed +0.001 dB and ~ of the air gap + 0.001 dB. Therefore, the accuracy of measurements according to the formula (7), with the known values of the rerraction index substituted therein, is considerably higher than the accuracy achieved in measurements according to the prototype with the help of reflectometers in scattered light and equal to +~.01 dB even for the most precise instruments.
Therefore, the ~resent method of measuring losses in fiber light guides in reflected light makes it possible to determine, with the highest attainable sensitivity, the finish quality and parallel alignment of the end faces, the coaxial relationship and optical losses in the area where the fiber light guides are joined at an air gap.
~loreover, these measurenents help deter~ine not only loss -es at the joint of light guides connected at an air gap, but also mini.n~ pos.sible losses durincJ sub.,equent splicing of the light csuides, because losses in the ends characterize losses ~,.. . . . .
,~, - . . .
~, ' ' ' ' ", ~ , ' ' '' '.. :" ' "," ~
XOOR9~)9 throaysl ~efects in s~.ear surfaces, asso~hin(J films, etc.,;/hich are ~ot c'etec'ed by other measur~.ents (ref. analysis o~ relat-ive sersitivitics iil passin-. and re~lectecl liyhts). Cimilarly, the rossibility o- losses bein;j deter~inea at the output end presupposes the possioility o~ losses beiny deter;nined at any successive joint of the second lisht guide with the tnird, or with the first, when their mutual position is chan~ed.
An advantage of the measurerment method described herein lies not only in that it expands the dynarnic range of measurements and enhances their accuracy by carrying out measurements, not in scattered radiation but in a significantly more intensive radiation, but also in that it simplifies and accelerates con-siderakly the cycle or optical loss measurements at the joint cor,lpared to the rulti-point method used in optical reflectometry, which comprises, rirst, measuring the scattering factor in the first liyht yuide, then in the second light guide, then measur-ing the distance to the joint, and when it is possible, after all these procedures, to determine with su~ficient accuracy the losses in the joint or splice. Accordingly, the ~ossibility oE
chanaes in the signal at the splicing point being monitored dur-ing measurements according to the present method allows ref-lected signals to be measured, while the possibility of loss~
es at the test splicing noint heing determined quantitatively is ensured by the combination of measurement steps described hereinabove.
~, . ', ' ', . ' '; " ' " '.'.':
~- ; . ' ,'. ' . '.,, ' .
~,, ' , ', ', ' ' ' ' ' " ' "' "'"' '
n 1log(~3max/N3i) due to non-coaxial ali~nment of the test joint are determined;
16. The output end of the second test light guide is treated;
17. The energy (total power) N3 of pulses reflected from the ~ :
realistically finished output end of the second light guide is measured;
13. Optical losses K3= 10log(N3i/M3) at the output end of the second test light guide are determined, and 19. The total optical losses K~s in the measured joint are evaluated from the formula K~s= R~ + Rn, and the total loss-es R~T at all the three test joints are found from the formula:
sT 1 2 3 The method of determining optical losses at the end joints of the light guide.s for a maximum ~ossible dis-tance to the test end comprises the following sequence of inter-related steps~
1. Sendins a probing light pulse into the light guides be- ;
ing joined;
2. .~!easuring the energv or power L~1 o. a pulse which has passed throu~h the ends of the liyht guides joined at a minimum air gap and prepared for subsequent connection, has been reflect-''''',~' ' ' . . ~, ' ' . ~ " ;, i:', ' , ~....................... . .
i -:,, .
~,',,, ' , , .
", , ~ - , , Z0(~89~)9 ed from the output end of the second li~ht guide an retùrned to the input end of the first light guide alony the previous path;
3. Connecting the first and second light guides;
4. Ieasuring the energy or power ~2 of a pulse whicn has passed through the joint along the previous path and has been re-flected from the outnut end of t~e resulting integral light ~uide, and 5. Determining optical losses K at the joint from the for-mula: :
K~dB~ = 1010g2n - 1010g(n2 + 1) + 510y~2 - 510gi~
An advantage of the present measurement method is that owing to the closer relation between the amount of reflected radiat-ion and the condition of the end faces of the light guides and the extra pure quartz glass from which they are drawn compared ~ ;
to the radiation passing through the same ends,as well as on ac-count of the reflection fror,l the ends being several orders higher in comparison with the radiation scattere~-1 by the light guides, the sensitivity of mèasurements in the reflected light to the con-dition of the end faces, their ~arallel alignment, optical loss-es in the air gap between the ends, and the coaxial relation between the fiber light guides, which determines mode mismatch losses, is considerably greater than the sensitivity to similar losses in passiny radiation or radiation scattered by the light guides, and also that measurements are made in the light reflect-ed from the equivalent ends of the light guides, rather than in the light scattered by the different portions of the light guides being joined, the intensity of reflected light being several orders higher than tha~ of the scattered light, as a result OL
which the dynamic range of measurements and, there~ore, the dis-tance to the test joint of the light guides can be increased a ,~ . , . , ~
~ , ... ..
~ "',: ' ' , .
~ ~ , Z0~89~)9 corresponcin~ num~er o. tir~es.
~rief ~escriptior of tne ,~ra~ings ~hc invention is illustr~ted in the accom?allyinc- drawings, ~herein:
~ ig. 1 shows a de~Jics for ?erformin~-j the method of measurin~~
losses de?endin~ on the finish ~ualit~ Or the erd faces o-f the 'i~er li7ht quides, ~nd Fig.2 shows a device for perfor.--ing the inethod of measur~
ing losses at the end joints of jcined light guides. ~ -The device comprises a radiation source 1, a s litter 2 for incident and reElected radiation, a reLlected pulse receiver 3, a first light guide 4 and a second light yuide 5 to be joined to the first light guide.
Description of the Preferred Em~odiment The method is performed as follows: 2~ radiation pulse rrom the source 1 is sent through the splitter 2 into the first light guide 4 and the radiation reflected from its output end reaches through the same s~litter 2 the rsflected light receiver 3 (view a). A signal N1 separated by corresponding time sampling and caused by the pulse reflected from the output end is equal to: .
N1= const ~1 2(1~~)exP(-u4~4)~exp( ~U4~4)(1 ~)~2,3 = const-~1 2 ~2 3(1-p)2exp(-2~4!~4)p , (2) wherein the factor const characterizes the spectral response of the receiver 3 and the radiation flux of the source 1, ~1 2 and ~2 3 are transmission factors of the splitter 2 during propasat-ion o~ light from the source 1 to the receiver 2, (1-~) is the transmission factor cf the input end of the light guide 4, ~ is the reflection factor OL the output end, and ~4 and 24 are a radiation attenuation factor and the length of the light guide 4.
Two factors in the fonnula (2) characterize the condition ~ , . . .
~ ~'',' ~ ' ' :
~,, , 20~89~)9 of ti1e end sur~aces of the light guide~ ) is tl1e in~ut surface and ~ is the output surface.
I'he relative changes in the signal ~ 1 following from the formula (2) are equal (only in the function of changes of sai~
two factors).
N 1 ~ ( 1 ~ P
Since in the case of optical (quartz) glass rrom wnich the lignt guiaes are uraws~, lt may be assumed that p - 0.035 and accordingly l-f ~- 0.965, changes in ~ at the input end and in p at the output end by + 10% will result in changes 2~p(1-p) =
+ 2 x 0.0~35/(1-0.035 - 0.0035) = +0.007/0.9615 = + 0.0073 =
+0.7% and ~n changes a~/p= + O C335 = + 0.1 = + 10~
In other words, as a result of the same chanyes in the op-tical condition of the input and output surfaces changes ~.J1/
in the signal reflected from the output end of the light guide being joined are 13 times, i.e., more than an order, more sensi-tive to the condition of the output end than to the condition of the input end. Similarly, it may be demonstrated that during studies in scattered light propagating in a backward path throuyh the test joint surface, changes in the condition OL the surface are also equal to 2~p/(1-p), rather than ~p/p.
Therefore, measurement of the energy (power) i~J1 for differ-ent shear surraces of the output end of the light guide 4 and determination of the ratio OL N1 to the maximum value of M1~aX at tained on an ideal shear surface, which can be checked visually, with the help of ~icroscope, make it possible to evaluate most truthfully, at the greatest sensitivity to existing derects, the finish ~uality of the output end of the _irst light yuide of the joint. The lossss K1 at this end are, in decibels:
' ' '. '' .
~" ::
X0089~)9 i1 = l Clo'~ a,X/~
~ iext, the inut end or the second light guide 5 is treated and arfixed to the ou.put end of the first light suide ~ (~ie~7 b) at a corres~onding air gap, ~hich appears opti-nal to the ob- -server. The same receiver 3 measures the energy or total po~er i~2 of pulses reflected from the realistically joined ends of the light guides 4 and 5.
2 t 1,2 ~2,3(~ exP~-2~4~4)r~ + (1-~)2~ +
+ (1_~2)~3... = const ~~ )2exp(-2u4Y4)~ (1+ 1+p) =
const 71 2 ~2 3(1-~)2eXP(-2\u4~4) 1+fp (3) It is to be seen from formula (3) that changes in the op-tical condition of the joined end surfaces have twice as high an effect on changes in the signal N2: N2/N2 because of the fac-tor ~ 2 ~ . Therefore, the lo~ quality of the shear surface, ;~
the non-parallel alignment of the end aces and the additional optical losses in them have a maximum effect on chanc3es in the signal AN2/N2 recorded by the receiver 3.
As a result, the ratio of N2 to l~2maX, correspondins to the idealcondition of the end faces and their parallel alignment at a minimum air ga~ that does not disturb the radiation mode dis-tribution in the light guides, characterizes the total radiation losses in the air gap produced by the joint. Therefore, with the ~ -losses X1 at the first end kno~m from the formula (2), the loss-es ~2 contributed to the joint by the second end, i.e., the in-put end oE the light guide 5, are determined:
2 g(~2max/~2) 10log(~J1~ax/~11) - 1lCJ(!~2m /~2) ~ ~<1 In order to isolate the losses due to non-Farallel align-ment of the ends of the light guides being joined out o~~ the to-tal losses in the air gap, use is made of the following formula:
~;, '- '~: ' '" ' ' ' ~,~,, " ", ~' ,. . : ;
~' ' -1.~./, . - .
"~",, - ~ ' . ', ' .
~,,, ~ , : , , , ~"~
.'~ " -'-- . - , ' , , zoo~9~9 ::
~ 1 1 +~ ~4) the ma:~imum value of ~hich, given the ideal condition of the end faces and their parallel alignment, and in the absence oE ad~
ditional losses, is equal to:
(L~2) = ~ n~+1 wherein n is the group refraction index of the light guide cores.
Therefore, the difference between the formula (4) and formula (5) determines optical losses in the joint due to the lo~ finish-ing quality of the end faces (in particular, the input end of the second light guide, since the condition of the output end of the first light guide is already determined), the non-parallel alignment of the surfaces, and the total optical losses in the air gap. Losses caused by non-parallel ali~Jnment of the joined ends expressed in decibels are: Kt/= 10log[N2/l~1)max/(i12/~1)] .
In all the above-mentioned losses of the useful signal in the resulting joint of the light guides, no account was taken of the losses due to the non-coaxial alignment of the cores of the light yuiaes Delng ~olnea, because reflectlon ~rom the input end of the second li~ht guide actually provides no idea about the accuracy of connection of the cores themselves, because the reflection factor of the sheath of a hi-h ~ualitv 10~'7 mode light guide liffers very little _rom the reflection factsr of the cores. ~herefore, in determining losses caused by the non-co-axial alignment of the cores, it is essential to send radiation into the light glide beinq attached and then determine losses due to non-coaxial alignment.
To determine real losses due to non-coaxial alignment, the light ~uides 4 and 5 being joined are centered, a pulse (~ulses) of radiation from the source 1 is sent into the light guide 5 '- - , ~:''' " ' ' :.
~, ' -, ' :, 20~89~19 (view b i~ the drawiilg), the s~ ling inter~al OL the receiver 3 is changed so as to record only oulses reflected from t~le output end OL the light guide 5, and the energv or total power ~3i ' the rerlected pulses is measured, provided said end is ideally finished as its ideal condition is monitored, for example, vis-ually with the help of a microscope.
i= const-~1,2 ~2,3(1-~) e~p(-2~u4~4) [ ~ ¦ eXp(-2~us~s~
1,2 2,3(1 P) (1+p) exp(-2~u4e4 - 2u ~ )~ (6) wherein (1_~)/(1+~)2 is a squared transmission factor of the air gap between the joined light guides, and ~i is the reflection factor of the ideally finished out~ut end.
By analogy ~,rith the determination or deviations in ~N1/i~l, it follows from the formula (6) that the value of ~13 depends strongly on changes in ~p/~ of the condition of the output end of the second light guide and only little on the conditions of the other ends and the air gap. Since~ however, the formula (6) is derived on the assurnption that all the radiation emerging frorn the first light guide enters fully the second light guide and vice versa, because of the geometric matching of their cores, a mismatch (misalignment) of the cores causes the formula (6) to be transformed into:
N3i=const.l1 2-~2 3(1-~)2(11+p)2(1- ~n)2exp(-2~4e4- 2~u5~5)~i,(7) wherein Kn designates optical losses due to non-coaxial alignrnent because of the geometric mismatch of the light gui~le cores. Ob~i-ously, unliXe the forr..ula (7), a mismatch of the light guide core does not cause an appreciable change in the formula (3), becau3e the reflection factor of the sheath occupving the ~osition of the core should the latter be orfset mav differ only slightly from the reflection factor of the core.
20(~89~)9 ~ hereLore, in accordarce witll the for.lulae (6) and (7), t'ne signal ~3 is Ir.ost sensi-~ive to the condi.tion or the output end of the seconu li~ht guide and the mismatch or the light gui~e cores.
After losses due to non-coaxial ali~n?rent have been deter-mined, the output end oE the second light guide is trea-ted and, without dis~urking the connection, the energy (total power) N3 of pulses reflected from the realistically finished output end of the second light guide at a factor y is measured:
N3= const~1 2 ~2 3(1-f)2(11+P)2(1-~n)exp(-21u4e4 -2u5eS) ~ (8) The losses X3 at the output end of the second light yui~e are cletermined in dB from the foF~mulae (7) and (8) ~3/-~4 ~ ~/Pi ~3 = 11g(~3i/i~3) (9) Since all the kinds of losses at the ends and in the joint of the test light guides have been-determined separately in the course of the akove operations, the total losses ~T at the ends of the light guides and X~s in the joint can ~e assessed. Lo~se~
at the ends are found from the formula:
RsT= R1 + K2 + 3 (10) and in the joint, from the formula:
K~s = X// + Kn (11) LO detennine optical losses in the end face joints of the fi~er light guides, a radiation pulse (pulses) from the source 1 is sent successively through the splitter 2 into the first liyht gui~e 4 and the second light yuide 5 bein~s connected. r~fter the cores OL tlle light suides have keen joined wltil the help of any adjustin~ device so that they are coaxial with each other and with the s~litter, and the air yaps are r,.inil.~al and do not dis-turb the stationary mode distrikution of the rroking radiation, the receiver 3 ~easures the pO~Jer or energy or the pulse reflecte~
~, . . .
~' ' " '''i~'' ' '""' '' nt ,...................... " . .
,, . , - , , from the output end OL the second ligllt Guid2 5 (v~e~ a in riy.2). rrhe receiver siqnal .11 is in this case equal to:
1,2~2 4 e~;P(~2`~nen).4 5 e~p(-2~5~5) ~2 5=
n 1~ 2 2,3 ~2~ se~p(-2~nen)ex-p(-2u5~5)~ (12) .
whereln K is the proportionality factor;
~n is the ra~iation flux or eneray of the source 1;
~1 2; ~2 3 are transmission factors of the liaht flu~;
from the source to the splitter and from the splitter to the receiver;
~2 4;~4 5 are transmission factors of the air gap bet-ween the splitter 2 and the first light guide 4 and between the two light yuides 4 and 5 being joined, and ,U4; ~U5; ~4; ~5 are attenuation factors and lengths of the light guides 4 and 5.
After the light guides 4 and 5 have been connected without an air gap, the energy or maximum power of the pulse reflected is measured from the output end of the now integral light guide 4-5 (view b)~
In this case, the signal ~N2 of the receiver 3 is equal to:
2 ~n 1,2 '2,3, t2,4eXP~~2~4~4)K exp(-2~u5~5)~ =
n 1,2 2,3 2,4K p eXp(-2~u4e4)exp(-2u ~ ) and the ratio of the signals is:
N2 = 2 ~T~ ~,5 (14) Since, in accordance with Fresnel formulae, in view of mul-tiple reflections, the transmission factor ~4 5 of the air gap ~ .
between the joined light guid2s is equal to: : :
~ )2 1 = ~ = 2n (15) ~ ~ :
wherein ~ is the reflection factor of the end, n is the refrac-tion index, the formula (14) can be transformed to:
~,, - . , X0(~89~)9 ~; n2 + 1 V ~, (16) The rinal optical losses at the connecting point of the light guides, ex~ressed in deci~els, are determined from the - formula:
-l~ = 10log 2n - 1Clog(n2 + 1) + 5logi~2 - 5N~ (17J
~ ince the refraction index of the light guides is known or can be determined with an accuracy of at least ~n = +(1.10 3 to 1.10 4), the indefinite value of the reflection factor of the enZ of the light guide made of an extra pure quartz glass does not exceed ~p~ + 0.0025 x 0.00347718 c + 1.10 ~, and the value cf ~/l~ + 2.10 4, i.e., a change in the transmission factor or one end compared to the computed value does not exceed +0.001 dB and ~ of the air gap + 0.001 dB. Therefore, the accuracy of measurements according to the formula (7), with the known values of the rerraction index substituted therein, is considerably higher than the accuracy achieved in measurements according to the prototype with the help of reflectometers in scattered light and equal to +~.01 dB even for the most precise instruments.
Therefore, the ~resent method of measuring losses in fiber light guides in reflected light makes it possible to determine, with the highest attainable sensitivity, the finish quality and parallel alignment of the end faces, the coaxial relationship and optical losses in the area where the fiber light guides are joined at an air gap.
~loreover, these measurenents help deter~ine not only loss -es at the joint of light guides connected at an air gap, but also mini.n~ pos.sible losses durincJ sub.,equent splicing of the light csuides, because losses in the ends characterize losses ~,.. . . . .
,~, - . . .
~, ' ' ' ' ", ~ , ' ' '' '.. :" ' "," ~
XOOR9~)9 throaysl ~efects in s~.ear surfaces, asso~hin(J films, etc.,;/hich are ~ot c'etec'ed by other measur~.ents (ref. analysis o~ relat-ive sersitivitics iil passin-. and re~lectecl liyhts). Cimilarly, the rossibility o- losses bein;j deter~inea at the output end presupposes the possioility o~ losses beiny deter;nined at any successive joint of the second lisht guide with the tnird, or with the first, when their mutual position is chan~ed.
An advantage of the measurerment method described herein lies not only in that it expands the dynarnic range of measurements and enhances their accuracy by carrying out measurements, not in scattered radiation but in a significantly more intensive radiation, but also in that it simplifies and accelerates con-siderakly the cycle or optical loss measurements at the joint cor,lpared to the rulti-point method used in optical reflectometry, which comprises, rirst, measuring the scattering factor in the first liyht yuide, then in the second light guide, then measur-ing the distance to the joint, and when it is possible, after all these procedures, to determine with su~ficient accuracy the losses in the joint or splice. Accordingly, the ~ossibility oE
chanaes in the signal at the splicing point being monitored dur-ing measurements according to the present method allows ref-lected signals to be measured, while the possibility of loss~
es at the test splicing noint heing determined quantitatively is ensured by the combination of measurement steps described hereinabove.
~, . ', ' ', . ' '; " ' " '.'.':
~- ; . ' ,'. ' . '.,, ' .
~,, ' , ', ', ' ' ' ' ' " ' "' "'"' '
Claims (2)
1. A method of determining optical losses at the ends and end joints of fiber light guides, comprising successively send-ing a probing light pulse into the fiber light guides being joined and subsequently determining optical losses at their joints, wherein, in order to expand the range of applications by allowing the finish quality of the ends, and their parallel and coaxial alignment to be determined, the method comprises measuring the energy or total power N1 of pulses reflected from the output end of the first test light guide, determining loss-es K1= 10log(N1max/N1) at the output end of the first light guide from the difference between the value of N1 and maximum N1max, measuring the energy or total power N2 of pulses reflect-ed from the ends of the first and second light guides connected at a test air gap, determining losses K2= 10log(N2max/N2)-K1 at the input end of the second light guide from the difference between the values of N2 and N2max and between N1 and N1max, de-termining losses K//= 10log [(N2/N1)max/(N2/N1)] due to non-pa-rallel alignment of the joined ends from the difference bet-ween the ratio N2/N1 and the maximum:
, wherein n is the group refraction index of the cores of the light guides, measuring the energy or total power N3i of pulses which have passed through the test joint and been reflected by the ideally finished output end of the second light guide, determin-ing losses Kn= 10log(N3max/N3i) due to non-coaxial configuration of the joint from the difference between the value of N3i and maximum N3max, measuring the energy or total power N3 of pulses reflected from the output end of the second test light guide, determining losses K3= 10log(N3i/N3) at the output end of the second light guide from the difference between the values of N3 and N3i, evaluating the total losses K.SIGMA.s in the test joint of the light guides from the formula:
K.SIGMA.s= K// + Kn, and measuring the total losses K.SIGMA.T at all the three test ends of the light guides from the formula:
K.SIGMA.T= K1 + K2 + K3.
, wherein n is the group refraction index of the cores of the light guides, measuring the energy or total power N3i of pulses which have passed through the test joint and been reflected by the ideally finished output end of the second light guide, determin-ing losses Kn= 10log(N3max/N3i) due to non-coaxial configuration of the joint from the difference between the value of N3i and maximum N3max, measuring the energy or total power N3 of pulses reflected from the output end of the second test light guide, determining losses K3= 10log(N3i/N3) at the output end of the second light guide from the difference between the values of N3 and N3i, evaluating the total losses K.SIGMA.s in the test joint of the light guides from the formula:
K.SIGMA.s= K// + Kn, and measuring the total losses K.SIGMA.T at all the three test ends of the light guides from the formula:
K.SIGMA.T= K1 + K2 + K3.
2. A method of determining optical losses at the ends and end joints of fiber light guides according to claim 1, wherein, in order to improve the resolution by increasing the distance to the test end joint, it comprises measuring the energy or power N? of a pulse which has passed through the ends of the light guides joined at a minimum gap, has been reflected from the output end of the second light guide and returned to the input end of the first light guide, joining the first and second light guides, measuring the energy or power N? of a pulse which has passed through the joint and has been reflected from the output end of the resulting integral light guide, and determin-ing the optical losses K at the joint from the formula:
K[dB]= 10log2n - log(n2 + 1) + 5logN? - 5logN?, wherein n is the group refraction index of the cores of the light guides being joined.
K[dB]= 10log2n - log(n2 + 1) + 5logN? - 5logN?, wherein n is the group refraction index of the cores of the light guides being joined.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SU4688092 | 1989-02-01 | ||
| SU4688092 | 1989-02-01 | ||
| SU4688480 | 1989-02-01 | ||
| SU4688480 | 1989-02-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2008909A1 true CA2008909A1 (en) | 1990-08-01 |
Family
ID=26666208
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2008909 Abandoned CA2008909A1 (en) | 1989-02-01 | 1990-01-30 | Method of determining optical losses at the ends and end joints of fiber light guides |
Country Status (10)
| Country | Link |
|---|---|
| EP (1) | EP0380981A3 (en) |
| JP (1) | JPH02278136A (en) |
| CN (1) | CN1046390A (en) |
| AU (1) | AU4897890A (en) |
| BR (1) | BR9000411A (en) |
| CA (1) | CA2008909A1 (en) |
| CS (1) | CS43790A2 (en) |
| ES (1) | ES2020419A6 (en) |
| FI (1) | FI900391A0 (en) |
| HU (1) | HUT57435A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU666382B2 (en) * | 1992-05-01 | 1996-02-08 | Nippon Telegraph & Telephone Corporation | Method for identifying optical line |
-
1990
- 1990-01-19 EP EP19900101087 patent/EP0380981A3/en not_active Withdrawn
- 1990-01-24 HU HU25790A patent/HUT57435A/en unknown
- 1990-01-25 FI FI900391A patent/FI900391A0/en not_active Application Discontinuation
- 1990-01-30 CA CA 2008909 patent/CA2008909A1/en not_active Abandoned
- 1990-01-30 CS CS90437A patent/CS43790A2/en unknown
- 1990-01-31 ES ES9000283A patent/ES2020419A6/en not_active Expired - Lifetime
- 1990-01-31 BR BR9000411A patent/BR9000411A/en unknown
- 1990-02-01 JP JP2360490A patent/JPH02278136A/en active Pending
- 1990-02-01 AU AU48978/90A patent/AU4897890A/en not_active Withdrawn
- 1990-02-01 CN CN 90101162 patent/CN1046390A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPH02278136A (en) | 1990-11-14 |
| FI900391A0 (en) | 1990-01-25 |
| CS43790A2 (en) | 1991-06-11 |
| EP0380981A2 (en) | 1990-08-08 |
| CN1046390A (en) | 1990-10-24 |
| HU900257D0 (en) | 1990-03-28 |
| ES2020419A6 (en) | 1991-08-01 |
| HUT57435A (en) | 1991-11-28 |
| AU4897890A (en) | 1990-08-09 |
| EP0380981A3 (en) | 1991-10-30 |
| BR9000411A (en) | 1991-01-15 |
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