CA2037216A1 - Testing of optical fiber by introducing multiple simulated peel location bends - Google Patents
Testing of optical fiber by introducing multiple simulated peel location bendsInfo
- Publication number
- CA2037216A1 CA2037216A1 CA002037216A CA2037216A CA2037216A1 CA 2037216 A1 CA2037216 A1 CA 2037216A1 CA 002037216 A CA002037216 A CA 002037216A CA 2037216 A CA2037216 A CA 2037216A CA 2037216 A1 CA2037216 A1 CA 2037216A1
- Authority
- CA
- Canada
- Prior art keywords
- optical fiber
- mandrel
- bending
- light
- bending mandrel
- 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
-
- 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
- G01M11/33—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face
-
- 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
- G01M11/08—Testing mechanical properties
- G01M11/088—Testing mechanical properties of optical fibres; Mechanical features associated with the optical testing of optical fibres
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- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Testing Of Optical Devices Or Fibers (AREA)
- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
- Light Guides In General And Applications Therefor (AREA)
Abstract
TESTING OF OPTICAL FIBER BY INTRODUCING
MULTIPLE SIMULATED PEEL LOCATION BENDS
ABSTRACT OF THE DISCLOSURE
The optical characteristics of an optical fiber (28) are studied by simultaneously introducing multiple small-radius bends into a short length of the optical fiber (28). Since there is a small loss of light associated with each bend, those losses are added and made easier to measure and analyze when multiple bends are used. The optical fiber (28) is wound over a mandrel (10, 50) that is shaped to include at least two simulated peel location bends of the optical fiber (28) wound onto the mandrel (10, 50), and, preferably, four or more simulated peel location bends per turn of optical fiber (28) around the mandrel (10, 50).
MULTIPLE SIMULATED PEEL LOCATION BENDS
ABSTRACT OF THE DISCLOSURE
The optical characteristics of an optical fiber (28) are studied by simultaneously introducing multiple small-radius bends into a short length of the optical fiber (28). Since there is a small loss of light associated with each bend, those losses are added and made easier to measure and analyze when multiple bends are used. The optical fiber (28) is wound over a mandrel (10, 50) that is shaped to include at least two simulated peel location bends of the optical fiber (28) wound onto the mandrel (10, 50), and, preferably, four or more simulated peel location bends per turn of optical fiber (28) around the mandrel (10, 50).
Description
TESTING OF OPTICAL FIBER BY INTRODUCING
MULTIPLE SIMULATED PE~L LOCATION BENDS
BACKGROUND OF THE INVENTION
This inventlon relates to the testing of optical fibers, and more partlcularly, to bend testing of such fibers.
Optical fibers are strands of glass fiber processed so that light transmitted therethrough is subJect to total lnternal reflection. A large fractlon of the incident lntenslty of light directed into the fiber is received at the other end of the fiber, even though the flber may be hundreds of meters long. Optlcal fibers have shown great promise in communications applications, because a high density of informatlon may be carried along *he fiber and because the quality of the signal ls less sub~ect to external interferences of various types than are electrlcal signals carried on metallic wires. Moreover, the glass fibers are light in weight and made from a hlghly plentiful substance, silicon dioxide.
Glass fibers are fabricated by preparing a preform of glasses of two dlfferent optlcal ind~ces of refraction, one inside the other, and processing the preform to a flberO The optical fiber is coated with a polymer layer termed a buffer to protect the glass from scratching and other types of damage. As an e~ample of the dimensions, in one configuration the diameter of the glass optical fiber is about 125 micrometers, and the diameter of the fiber plus the polymer buffer is about 250 micrometers (approximately 0.010 lnches).
For such very fine fibers, the handling of the optlcal fiber to avoid damage that might reduce 2~7~1~
its light transmisslon properties becomes an important consideration. The flbers may be wound onto a cylindrical or tapered cylindrlcal bobbln with many turns adJacent to each other in a side by side fashion. After one layer is complete, another layer of flber ls lald on top of the first layer, and so on. The final assembly of the bobbln and the wound layers of flber is termed a canister, and the mass of wound flber is termed the fiber pack. When the optical flber ls later to be used, the flber ls pald out from the canlster in a direction parallel to the a~ls of the cyllnder.
It has been found by e~perlence that, where the fiber ls to be pald out from the canister ln a rapid fashion, as for example over a hundred meters per second, the turns of optlcal fiber must be held in place on the canister with an adhesive. The adhesive holds each turn of fiber in place on the fiber pack as ad~acent turns and layers are initially wound onto the canister, and also as ad~acent turns and layers are pald out. Without the use of an adhesive, payout of the fibers may not be uniform and regular, leading to snarls or snags of the fibers that damage them or cause them to break as they are paid out.
When the optlcal fiber is paid out from the canister ln a dlrectlon parallel to the cyllndrical axis of the canlster, the optlcal fiber ls bent through an angle, called the peel angle, w~th a relatlvely small bend radius as lt ls pulled away from the fiber pack to which it is adhesively bonded. The peel angle may var~ dependlng upon the peel tenslon and the geometr~ of the peellng, but is typlcally about 30-~0 degrees. It is known that bending of the fiber, such as that e~perienced during payout, reduces the transmission of light through the fiber, and can cause it to fail mechanically.
The processing of optlcal fibers has progressed to the point that the loss of light energy resulting from a peel bend can be as small as 0.1 decibel (db) or less. It is lmportant to measure such small energy losses in order to fully characterize the flber, but such measurements can be dlfflcult due to a variety of effects. There ls a need for an approach to the testing of optical flbers that permlts small bend losses of the optical flbers to be rellably measured. The present invention fulfllls this need, and further provldes related advantages.
SUMMARY OF THE INVENTION
The present inventlon provides a testing procedure that permits optical loss from bends of small radlus to be measured more reliably and accurately than has heretofore been posslble. The process is implemented using e2isting light measurement apparatus, and a specialized testing fixture. The method is reliable and easily used.
In accordance with the lnvention, a process for testing an optlcal fiber comprises the steps of provlding a bending mandrel having at least two simulated peel point bendlng locations disposed such that an optical fiber wound around the mandrel passes over the bending locations, each peel point bending location bending the optical flber in a manner simulating the bending that an optical fiber undergoes when paid out from a fiber canister; and winding the optical fiber over the bending mandrel, thereby simultaneously applying multiple slmulated peel point bends to the length of the optical fiber in contact with the mandrel. In the preferred --0s -approach, the process ls used ln con~unctlon with light transmisslon measurement apparatus to determine the light loss due to a slngle bend ln the optical fiber.
The design of the bending mandrel i~ selected so that the optical fiber is bent through an angle that simulates the peel angle at which the optical fiber is pald out from the canister, at each of several loc~tlons. That angle ls typically about 10 30-bO degrees. In one design of bending mandrel, the mandrel is formed by machining flat surfaces on each side of a cyllndrical rod, each flat surface being perpendicular to the same cylindrical diameter. By selectlng a particular depth of the 15 material removed to form the flat surfaces, the angle between the cur~ed face and the flat face is determined to simulate the peel angle. It has been determined empirically that a distan e between the flat faces of about 1/2 the cylindrical dlameter 20 produces four simulated peel bends of about 30 degrees each and four simulated peel bends of about degrees each, per turn of optlcal fiber around the mandrel.
With this design of bending mandrel, each 25 turn of the optical fiber around the portlon having flat surface produces eight simulated peel point bending locations within a length of optical fiber of less than four inches. A second turn produces another eight simulated peel point bendlng 30 locations, and so on. Wlth the appllcatlon of th0 proper tension to the free ends of the optlcal fiber, the 30 and 60 degree peel beh~vlor ls well simulated, so that the optical loss per peel bend may be more readily measured.
Another design of bending mandrel has an equilateral trlangular prism section configuration about which the optlcal fiber is wound. Each turn 2~37215 of the optical fiber about the mandrel produces slx simulated 60 degree peel polnt bends because of the equllateral trlangular deslgn of the mandrel. The equllateral trlangular prlsm mandrel produces two preclsely equal peel conflguratlons at each corner, and the high degree of symmetry coupled with the three point contact simplify calculation of the e~act curvature of the optlcal fiber.
After lt is wound around the mandrel wlth a precisely applied fiber tenslon, the optlcal fiber may be tested for optlcal, mechanical, or other types of propertles. In the test presently of most interest, an optical signal ls introduced lnto the optical flber on one side of the portion wound around the mandrel, passed through the portion of the optical flbPr that læ wound around the mandrel, and received on the other slde of the portlon wound around the mandrel. The attenuatlon of the slgnal due to the multlple slmulated peel point bends ls determlned, and the attenuation dlvlded by the number of simulated peel polnt bends to obtaln the attenuatlon per bend. This determinatlon achleves greater accuracy than posslble b~ meaæurement of only a s~ngle peel polnt bending location.
T~e approach o~ the invention also e~tends to an apparatus useful in performlng the nptlcal testing of the optlcal flber. In accordance with this aspect of the invention ? apparatus for testing optical transmission of an optical fiber comprises a bendlng mandrel havlng at least two slmulated peel point bendlng locatlons thereon; and means for sendlng a beam of llght through an length of an optical fiber wound over the bending mandrel, for recelvlng that portlon of the beam of light transmltted through the length of the optical fiber wound over the bending mandrel, and for comparing the lntensities of the light received and the light sent. The apparatus also preferably lncludes means for applylng a tension to the optical flber, and further means for ensuring that the tension applled to the optical fiber is substantially the same at 5 each of the bendlng locations.
The present invention provides an advance in the art of testing an optical fiber to be dispensed from canisters or the like. It allows careful testing of properties of the optical fiber in payout 10 configuration, without the necessity for developing measurement techniques to be used durlng rapid payout. Other features and advantages of the invention will be apparent from the following more detailed description of the preferred embodiment, 15 taken in con~unction with the accompanying drawings, which illustrste, by way of e~ample~ the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of one bending 20 mandrel of the invention, with two turns of optical fiber thereon Figure 2 is an end elevational view of the bending mandrel of Figure 1;
Figure 3 is a schematic vlew of the apparatus 25 for measuring peel point bending loss from an optical flber Figure 4 is a perspective view of an equilateral triangular prism bending mandrel;
Flgure 5 ls an end elevatlonal view of the 30 bending mandrel of Figure 4;
Figure 6 is a schematic plan view of the peel point bénding conflguration of an optical fiber belng paid out from a canister; and Figure 7 is an elevational view of an 20372~S
~7--apparatus for applying preclsely controlled and dlstrlbuted tension to an optical flber wound around a bendlng mandrel.
DETAILED DESCRIPTION OF TEE INVENTION
_ In accordance with one preferred embodiment of the invention, a process for testing an optlcal flber comprises the steps of providing a bending mandrel formed from a cylinder havlng two flat surfaces thereln perpendicular to a cyllndrical diameter; and windlng an optlcal fiber around the bendlng mandrel.
Referrlng to Flgure 1, a bendlng mandrel 10 is formed from a cylindrical piece 12. One end of the piece 12 is left cylindrical. At the other end, two flat surfaces 14 are machlned into the cylinder. As shown ln Figure 2, the flat surfaces 14 lie perpendlcular to, and at the opposite ends of what was, before machlning, a cyllndrical diameter 16. The flat surfaces 14 are symmetrical ln the sense that they lie the same distance from a cylindrical axis 18 of the mandrel 10.
In the preferred embodiment, the piece 12 ls stainless steel cylindrlcal stock, havlng a diameter of about 1 lnch and a length of about 2 lnches. The flat surfaces 14 are about 1 lnch long ln the dlrection parallel to the cylindrlcal axls 18. The distance 20 between the flat surfaces 14 ls about one-half the cyllndrical dlameter 16, or about one-half inch ln the preferred case. Thls dlmensloning of the mandrel 10 produces an angle between the plane of the flat surface 14 and a tangent 24 to a cyllndrlcal surface 26 of about 60 degrees, as illustrated in Flgure 2. Each corner 22 between one of the flat surfaces 14 and the curved 20372~
surface of the cyllndrlcal piece 12 ls made sharp (i.e., not bevelled or broken) but also free of burrs that might snag the optical fiber.
In practiclng the invention, an optlcal fiber 28 ls wound around the portion of the mandrel 10 having the flat surfaces 14 thereon. A slmulated payout tenslon is applled to each of the free ends of the optical fiber 28, the tenslon typically being about 50 grams. At each corner 22, the optical fiber 28 is bent around the corner. In the preferred embodiment, the total bending angle is about 90 degrees at each corner 22. ~owever, this total bendlng angle is equlvalent to two symmetrical and 60 degree simulated peel point bends. (The analysls of slmulated peel polnt bends is dlscussed ln greater detall in relation to Flgures 5 and ~.) Since there are four corners 22, one turn of the optical fiber 28 around the portion of the mandrel having the flat surfaces 14 results in four well-controlled and stable simulated peel polnt bends of 30 degrees each, and four well-controlled and stable simulated peel polnt bends of 60 degrees each. There are therefore eight slmulated peel point bending locatlons per turn. In the illustratlon of Figure 1, the optlcal fiber 28 is wound around the mandrel 10 twice, the two turns produclng a total of eight slmulated peel point bending locations of 30 degrees bending each, and eight simulated peel point bending locations of 60 degrees bendlng each, for a total of slxteen simulated bending locations. Additlonal turns would produce eight more simulated bending locatlons per turn.
The bending mandrel 10 ~ust described is used to test optical properties of the optical flber 28, using an apparatus 2~ such as that illustrated in Figure 3. At one free end of the optical fiber 28, 2~372~
_9_ a light source ~0 of known intensit~, such as a laser, directs light lnto the optlcal fiber 28 through an optical coupler ~2. The light is transmitted through the optical flber 28, includlng the simulated peel point bending locatlons, which number sixteen in the illustration of Figure 3.
Light leaves the other end of the optical fiber 28 through another optlcal coupler ~4 and is detected by a detector 3~. All of the components 30, 32, 34, and ~6 are well known in the art. An alternative approach to lntroducing light into the optical fiber 28 and extractlng llght from the optical fiber 28 during the peel polnt bending test is transversel~
through the sides of the optical flber when lt is bent. This in~ection/extraction technique ls well known in other contexts.
The input light lntensity and the output light intensity are compared b~ a comparator 38, whlch calculates the light loss due to the si~teen simulated peel point bends. (Normally, the llght loss due to losses in the apparatus and the unbent optical fiber is prevlously determined by conducting the measure.ment Just described prior to the optical fiber being wound around the mandrel. The remaining llght loss when the optlcal fiber ls wound around the mandrel is due to the simulated peel point bends.) Since there are slxteen simulated bends in the illustrated embodiment, the loss determined in the comparator ~8 is dlvided by 16 ln an arithmetic divider 40, to yield an attenuation loss per bend, numeral 42. In a typical circumstance, the energy loss per peel point bend is about 0.1 db, which ls difflcult to measure accurately. Wlth si~teen simulated bends, the total loss is about 1.6 db, which may be measured more easily and accurately.
The apparatus 29 can be used either for stationary measurements of ths optlcal fiber 28 ln the manner Just described, or for movlng measurements. In the latter case, the mandrel 10 ls mounted in an apparatus such as wlll be dlscussed in relatlon to Figure 7. In thls approach, the optical fiber may be fed from a spool and taken up by a spool, and rotating optlcal couplers are used.
In accordance wlth another preferred embodiment of the lnventlon, a process for testing an optical fiber comprises the steps of providing a bending mandrel formed with a portlon thereof being an equilateral triangular prism; and winding an optical fiber around the equilateral triangular prism portion of the bending mandrel.
Figures 4 and 5 illustrate such a triangular prism bending mandrel 50. The mandrel 50 includes a cylindrlcal portion 52 and a prism portion 54 that has the shape of an equilateral trlangle when viewed in end view, Figure 5. The optical fiber 28 is wound around the prism portlon 54, with two turns being illustrated in Figure 4. Each turn has si~
simulated peel polnt bends of 60 degrees each, two at each corner 56 of the prism portlon 54. Two complete turns results in twelve slmulated peel point bends, as compared with si~teen simulated peel point bends for the mandrel 10. Addltlonal turns of the optical fiber 28 around the prism portion 54 can yield more slmulated peel point bends, lf such is required to obtain accurate results in subsequent measurements.
The total bending angle through which the optical fiber 28 is bent at each corner 56 is greater than for the case of the mandrel 10, and is 120 degrees as illustrated in Figure 5. The bending produced by the mandrel 50 has the sdvantage of being precisely the same at each corner, in the sense that the optlcal flber extends around the corner 56 from flat face to flat face. (In the 20372~
mandrel 10 the optlcal fiber extends around the corner from flat face to curved face on two corners per turn of fiber, and from curved face to flat face at the other two corners per turn.) The mandrel 50 is used in a measurement apparatus 29 identical to that lllustrated ln Figure 3, e~cept that an appropriate divider 40 is used (i.e., division by 12 in the case of two turns of optical fiber around a triangular mandrel).
The mechanics of the bending of the optical fiber ~8 over the mandrel 50 are lllustrated in Figures 5 and 6. Figure 6 is a schematic plan view illustration of the payout of the optical flber 28 from a fiber pack 60 on a canister 62. The individual optical fiber 28 is separated from the fiber pack 60 at a peel point 64, whlch is typically a short length but can be ldealized as a point of separation. The peel point bending angle A depends upon the geometry of the peel separation and the tension applied to the optical fiber 28. As lndlcated, the angle A is typically from about 30 to about 60 degrees, and normally is about 60 degrees.
The radius of bending at the peel polnt ls lndicated as R, and ls typlcally about 0.060 inches.
Flgure 5 lllustrates how the triangular bending mandrel 60 slmulates the bending conditions of Figure 6, twice for each corner 56 and six tlmes for each turn of the optlcal fiber 28 about the prlsm portlon 54. As illustrated ln Flgure 5 at the 30 upwardly polnting corner 56, the optlcal flber 28 ls bent through a first 60 degree simulated peel point bend 66 from one flat face to the corner 56, and through a second 60 degree simulated peel point bend 68 from the corner 56 to the ne~t flat face, for a total bending around the corner 54 of 120 degrees.
The tenslon on the optlcal flber 28 is selected to yleld a bendlng radlus R comparable to that 20372~
e~perlenced during the peellng operatlon of Fi~ure 7, or about 0.060 inches ln the typlcal case. The comblnatlon of prlsm geometry and applled tension determlnes the bendlng radlus of the mandrel 50. A
one-lnch face dlmension and 50 grams of tension results in a bending radius of about 0.060 lnches, through two simulated 60 degree peel point bends per corner, in the embodiment of Flgure 5. These dimensions and tenslons can be varled as requlred to slmulate varlous peellng condltions.
The present inventlon also extends to other configuratlons of the bendlng mandrel, and should not be vlewed as belng llmlted to the mandrel 10 and the mandrel 50. The mandrel may, for example, be made in the form of a square prism, or ln other forms to provide other bendlng angles.
Application of the proper tensloning to the optical flber during the slmulated peel polnt bending is lmportant to achieve the proper bend geometry and for reproduclbility. A tensloning apparatus 80 that produces such tensloning is lllustrated ln Figure 7. The mandrel, here lllustrated .as the trlangular prism mandrel 50, is mounted to a mandrel stand 82 by a rotational bearing 84, that permits the mandrel 50 to rotate freely about its prlsm axis. In the illustrated embodiment, the prlsm axls is in the horizontal plane. The mandrel stand 82 is mounted to a base 86 on a slidlng track 88, whlch permlts the mandrel stand 82, and thence the mandrel 50, to slide in the dlrection parallel to the lengths of the optlcal flber 28 that e~tend from the mandrel 50.
The optical fiber 28 ls secured near one end ~n a spllt rubber block 90 against longitudinal or transverse movement. Light is in~ected into the optical flber 28 with the llght source 30 discussed previously in relation to Figure 3.
203721~
~13-On the other slde of the mandrel stand 82, the optical fiber 28 passes over a pulley 92 havlng a radius much larger than the radius R of curvature at the peel point. The optical fiber 28 extends downwardly from the pulley 92 to a rubber block 94 ln whlch lt is secured and thence to the detector 36. A wcight 96 is hung from the rubber block 94, so that the total weight of the rubber block 94 and the weight 96 applies a tension to the optical fiber 28.
If the optical fiber 28 were simply wound around the mandrel and the tension applied, the optical flber at various locations around the mandrel 50 would experience highly variable tensions. The tension can be equalized by moving the mandrel stand 82 back and forth along the track 88 while the tension is applied. Since the mandrel freely rotates in the bearing 84, undue stress is not placed upon the optical fiber 2~. The movement aids in ensuring that the tension applied to the optical flber 28 at the varlous corners 56 around the mandrel become substantially equal to the tension produced by the total force of the weight 96 and the rubber block 94. This tenslonlng apparatus also permits the measurement of the light loss at a range of locations along the length of the optical fiber 28.
The tensioning apparatus 80 is preferably used in conJunction wlth the light measurement apparatus 29 and circultry illustrated ln Figure 3.
The present invention provldes an approach for measuring peel point bending losses of an optical fiber accurately. Although partlcular embodiments of the invention have been described in detail for purposes of illustration, various modifications may be made without departing from the spirit and scope of the lnvention. Accordingly, the 203721~
inventlon is not to be limited except as by the appended claims.
MULTIPLE SIMULATED PE~L LOCATION BENDS
BACKGROUND OF THE INVENTION
This inventlon relates to the testing of optical fibers, and more partlcularly, to bend testing of such fibers.
Optical fibers are strands of glass fiber processed so that light transmitted therethrough is subJect to total lnternal reflection. A large fractlon of the incident lntenslty of light directed into the fiber is received at the other end of the fiber, even though the flber may be hundreds of meters long. Optlcal fibers have shown great promise in communications applications, because a high density of informatlon may be carried along *he fiber and because the quality of the signal ls less sub~ect to external interferences of various types than are electrlcal signals carried on metallic wires. Moreover, the glass fibers are light in weight and made from a hlghly plentiful substance, silicon dioxide.
Glass fibers are fabricated by preparing a preform of glasses of two dlfferent optlcal ind~ces of refraction, one inside the other, and processing the preform to a flberO The optical fiber is coated with a polymer layer termed a buffer to protect the glass from scratching and other types of damage. As an e~ample of the dimensions, in one configuration the diameter of the glass optical fiber is about 125 micrometers, and the diameter of the fiber plus the polymer buffer is about 250 micrometers (approximately 0.010 lnches).
For such very fine fibers, the handling of the optlcal fiber to avoid damage that might reduce 2~7~1~
its light transmisslon properties becomes an important consideration. The flbers may be wound onto a cylindrical or tapered cylindrlcal bobbln with many turns adJacent to each other in a side by side fashion. After one layer is complete, another layer of flber ls lald on top of the first layer, and so on. The final assembly of the bobbln and the wound layers of flber is termed a canister, and the mass of wound flber is termed the fiber pack. When the optical flber ls later to be used, the flber ls pald out from the canlster in a direction parallel to the a~ls of the cyllnder.
It has been found by e~perlence that, where the fiber ls to be pald out from the canister ln a rapid fashion, as for example over a hundred meters per second, the turns of optlcal fiber must be held in place on the canister with an adhesive. The adhesive holds each turn of fiber in place on the fiber pack as ad~acent turns and layers are initially wound onto the canister, and also as ad~acent turns and layers are pald out. Without the use of an adhesive, payout of the fibers may not be uniform and regular, leading to snarls or snags of the fibers that damage them or cause them to break as they are paid out.
When the optlcal fiber is paid out from the canister ln a dlrectlon parallel to the cyllndrical axis of the canlster, the optlcal fiber ls bent through an angle, called the peel angle, w~th a relatlvely small bend radius as lt ls pulled away from the fiber pack to which it is adhesively bonded. The peel angle may var~ dependlng upon the peel tenslon and the geometr~ of the peellng, but is typlcally about 30-~0 degrees. It is known that bending of the fiber, such as that e~perienced during payout, reduces the transmission of light through the fiber, and can cause it to fail mechanically.
The processing of optlcal fibers has progressed to the point that the loss of light energy resulting from a peel bend can be as small as 0.1 decibel (db) or less. It is lmportant to measure such small energy losses in order to fully characterize the flber, but such measurements can be dlfflcult due to a variety of effects. There ls a need for an approach to the testing of optical flbers that permlts small bend losses of the optical flbers to be rellably measured. The present invention fulfllls this need, and further provldes related advantages.
SUMMARY OF THE INVENTION
The present inventlon provides a testing procedure that permits optical loss from bends of small radlus to be measured more reliably and accurately than has heretofore been posslble. The process is implemented using e2isting light measurement apparatus, and a specialized testing fixture. The method is reliable and easily used.
In accordance with the lnvention, a process for testing an optlcal fiber comprises the steps of provlding a bending mandrel having at least two simulated peel point bendlng locations disposed such that an optical fiber wound around the mandrel passes over the bending locations, each peel point bending location bending the optical flber in a manner simulating the bending that an optical fiber undergoes when paid out from a fiber canister; and winding the optical fiber over the bending mandrel, thereby simultaneously applying multiple slmulated peel point bends to the length of the optical fiber in contact with the mandrel. In the preferred --0s -approach, the process ls used ln con~unctlon with light transmisslon measurement apparatus to determine the light loss due to a slngle bend ln the optical fiber.
The design of the bending mandrel i~ selected so that the optical fiber is bent through an angle that simulates the peel angle at which the optical fiber is pald out from the canister, at each of several loc~tlons. That angle ls typically about 10 30-bO degrees. In one design of bending mandrel, the mandrel is formed by machining flat surfaces on each side of a cyllndrical rod, each flat surface being perpendicular to the same cylindrical diameter. By selectlng a particular depth of the 15 material removed to form the flat surfaces, the angle between the cur~ed face and the flat face is determined to simulate the peel angle. It has been determined empirically that a distan e between the flat faces of about 1/2 the cylindrical dlameter 20 produces four simulated peel bends of about 30 degrees each and four simulated peel bends of about degrees each, per turn of optlcal fiber around the mandrel.
With this design of bending mandrel, each 25 turn of the optical fiber around the portlon having flat surface produces eight simulated peel point bending locations within a length of optical fiber of less than four inches. A second turn produces another eight simulated peel point bendlng 30 locations, and so on. Wlth the appllcatlon of th0 proper tension to the free ends of the optlcal fiber, the 30 and 60 degree peel beh~vlor ls well simulated, so that the optical loss per peel bend may be more readily measured.
Another design of bending mandrel has an equilateral trlangular prism section configuration about which the optlcal fiber is wound. Each turn 2~37215 of the optical fiber about the mandrel produces slx simulated 60 degree peel polnt bends because of the equllateral trlangular deslgn of the mandrel. The equllateral trlangular prlsm mandrel produces two preclsely equal peel conflguratlons at each corner, and the high degree of symmetry coupled with the three point contact simplify calculation of the e~act curvature of the optlcal fiber.
After lt is wound around the mandrel wlth a precisely applied fiber tenslon, the optlcal fiber may be tested for optlcal, mechanical, or other types of propertles. In the test presently of most interest, an optical signal ls introduced lnto the optical flber on one side of the portion wound around the mandrel, passed through the portion of the optical flbPr that læ wound around the mandrel, and received on the other slde of the portlon wound around the mandrel. The attenuatlon of the slgnal due to the multlple slmulated peel point bends ls determlned, and the attenuation dlvlded by the number of simulated peel polnt bends to obtaln the attenuatlon per bend. This determinatlon achleves greater accuracy than posslble b~ meaæurement of only a s~ngle peel polnt bending location.
T~e approach o~ the invention also e~tends to an apparatus useful in performlng the nptlcal testing of the optlcal flber. In accordance with this aspect of the invention ? apparatus for testing optical transmission of an optical fiber comprises a bendlng mandrel havlng at least two slmulated peel point bendlng locatlons thereon; and means for sendlng a beam of llght through an length of an optical fiber wound over the bending mandrel, for recelvlng that portlon of the beam of light transmltted through the length of the optical fiber wound over the bending mandrel, and for comparing the lntensities of the light received and the light sent. The apparatus also preferably lncludes means for applylng a tension to the optical flber, and further means for ensuring that the tension applled to the optical fiber is substantially the same at 5 each of the bendlng locations.
The present invention provides an advance in the art of testing an optical fiber to be dispensed from canisters or the like. It allows careful testing of properties of the optical fiber in payout 10 configuration, without the necessity for developing measurement techniques to be used durlng rapid payout. Other features and advantages of the invention will be apparent from the following more detailed description of the preferred embodiment, 15 taken in con~unction with the accompanying drawings, which illustrste, by way of e~ample~ the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of one bending 20 mandrel of the invention, with two turns of optical fiber thereon Figure 2 is an end elevational view of the bending mandrel of Figure 1;
Figure 3 is a schematic vlew of the apparatus 25 for measuring peel point bending loss from an optical flber Figure 4 is a perspective view of an equilateral triangular prism bending mandrel;
Flgure 5 ls an end elevatlonal view of the 30 bending mandrel of Figure 4;
Figure 6 is a schematic plan view of the peel point bénding conflguration of an optical fiber belng paid out from a canister; and Figure 7 is an elevational view of an 20372~S
~7--apparatus for applying preclsely controlled and dlstrlbuted tension to an optical flber wound around a bendlng mandrel.
DETAILED DESCRIPTION OF TEE INVENTION
_ In accordance with one preferred embodiment of the invention, a process for testing an optlcal flber comprises the steps of providing a bending mandrel formed from a cylinder havlng two flat surfaces thereln perpendicular to a cyllndrical diameter; and windlng an optlcal fiber around the bendlng mandrel.
Referrlng to Flgure 1, a bendlng mandrel 10 is formed from a cylindrical piece 12. One end of the piece 12 is left cylindrical. At the other end, two flat surfaces 14 are machlned into the cylinder. As shown ln Figure 2, the flat surfaces 14 lie perpendlcular to, and at the opposite ends of what was, before machlning, a cyllndrical diameter 16. The flat surfaces 14 are symmetrical ln the sense that they lie the same distance from a cylindrical axis 18 of the mandrel 10.
In the preferred embodiment, the piece 12 ls stainless steel cylindrlcal stock, havlng a diameter of about 1 lnch and a length of about 2 lnches. The flat surfaces 14 are about 1 lnch long ln the dlrection parallel to the cylindrlcal axls 18. The distance 20 between the flat surfaces 14 ls about one-half the cyllndrical dlameter 16, or about one-half inch ln the preferred case. Thls dlmensloning of the mandrel 10 produces an angle between the plane of the flat surface 14 and a tangent 24 to a cyllndrlcal surface 26 of about 60 degrees, as illustrated in Flgure 2. Each corner 22 between one of the flat surfaces 14 and the curved 20372~
surface of the cyllndrlcal piece 12 ls made sharp (i.e., not bevelled or broken) but also free of burrs that might snag the optical fiber.
In practiclng the invention, an optlcal fiber 28 ls wound around the portion of the mandrel 10 having the flat surfaces 14 thereon. A slmulated payout tenslon is applled to each of the free ends of the optical fiber 28, the tenslon typically being about 50 grams. At each corner 22, the optical fiber 28 is bent around the corner. In the preferred embodiment, the total bending angle is about 90 degrees at each corner 22. ~owever, this total bendlng angle is equlvalent to two symmetrical and 60 degree simulated peel point bends. (The analysls of slmulated peel polnt bends is dlscussed ln greater detall in relation to Flgures 5 and ~.) Since there are four corners 22, one turn of the optical fiber 28 around the portion of the mandrel having the flat surfaces 14 results in four well-controlled and stable simulated peel polnt bends of 30 degrees each, and four well-controlled and stable simulated peel polnt bends of 60 degrees each. There are therefore eight slmulated peel point bending locatlons per turn. In the illustratlon of Figure 1, the optlcal fiber 28 is wound around the mandrel 10 twice, the two turns produclng a total of eight slmulated peel point bending locations of 30 degrees bending each, and eight simulated peel point bending locations of 60 degrees bendlng each, for a total of slxteen simulated bending locations. Additlonal turns would produce eight more simulated bending locatlons per turn.
The bending mandrel 10 ~ust described is used to test optical properties of the optical flber 28, using an apparatus 2~ such as that illustrated in Figure 3. At one free end of the optical fiber 28, 2~372~
_9_ a light source ~0 of known intensit~, such as a laser, directs light lnto the optlcal fiber 28 through an optical coupler ~2. The light is transmitted through the optical flber 28, includlng the simulated peel point bending locatlons, which number sixteen in the illustration of Figure 3.
Light leaves the other end of the optical fiber 28 through another optlcal coupler ~4 and is detected by a detector 3~. All of the components 30, 32, 34, and ~6 are well known in the art. An alternative approach to lntroducing light into the optical fiber 28 and extractlng llght from the optical fiber 28 during the peel polnt bending test is transversel~
through the sides of the optical flber when lt is bent. This in~ection/extraction technique ls well known in other contexts.
The input light lntensity and the output light intensity are compared b~ a comparator 38, whlch calculates the light loss due to the si~teen simulated peel point bends. (Normally, the llght loss due to losses in the apparatus and the unbent optical fiber is prevlously determined by conducting the measure.ment Just described prior to the optical fiber being wound around the mandrel. The remaining llght loss when the optlcal fiber ls wound around the mandrel is due to the simulated peel point bends.) Since there are slxteen simulated bends in the illustrated embodiment, the loss determined in the comparator ~8 is dlvided by 16 ln an arithmetic divider 40, to yield an attenuation loss per bend, numeral 42. In a typical circumstance, the energy loss per peel point bend is about 0.1 db, which ls difflcult to measure accurately. Wlth si~teen simulated bends, the total loss is about 1.6 db, which may be measured more easily and accurately.
The apparatus 29 can be used either for stationary measurements of ths optlcal fiber 28 ln the manner Just described, or for movlng measurements. In the latter case, the mandrel 10 ls mounted in an apparatus such as wlll be dlscussed in relatlon to Figure 7. In thls approach, the optical fiber may be fed from a spool and taken up by a spool, and rotating optlcal couplers are used.
In accordance wlth another preferred embodiment of the lnventlon, a process for testing an optical fiber comprises the steps of providing a bending mandrel formed with a portlon thereof being an equilateral triangular prism; and winding an optical fiber around the equilateral triangular prism portion of the bending mandrel.
Figures 4 and 5 illustrate such a triangular prism bending mandrel 50. The mandrel 50 includes a cylindrlcal portion 52 and a prism portion 54 that has the shape of an equilateral trlangle when viewed in end view, Figure 5. The optical fiber 28 is wound around the prism portlon 54, with two turns being illustrated in Figure 4. Each turn has si~
simulated peel polnt bends of 60 degrees each, two at each corner 56 of the prism portlon 54. Two complete turns results in twelve slmulated peel point bends, as compared with si~teen simulated peel point bends for the mandrel 10. Addltlonal turns of the optical fiber 28 around the prism portion 54 can yield more slmulated peel point bends, lf such is required to obtain accurate results in subsequent measurements.
The total bending angle through which the optical fiber 28 is bent at each corner 56 is greater than for the case of the mandrel 10, and is 120 degrees as illustrated in Figure 5. The bending produced by the mandrel 50 has the sdvantage of being precisely the same at each corner, in the sense that the optlcal flber extends around the corner 56 from flat face to flat face. (In the 20372~
mandrel 10 the optlcal fiber extends around the corner from flat face to curved face on two corners per turn of fiber, and from curved face to flat face at the other two corners per turn.) The mandrel 50 is used in a measurement apparatus 29 identical to that lllustrated ln Figure 3, e~cept that an appropriate divider 40 is used (i.e., division by 12 in the case of two turns of optical fiber around a triangular mandrel).
The mechanics of the bending of the optical fiber ~8 over the mandrel 50 are lllustrated in Figures 5 and 6. Figure 6 is a schematic plan view illustration of the payout of the optical flber 28 from a fiber pack 60 on a canister 62. The individual optical fiber 28 is separated from the fiber pack 60 at a peel point 64, whlch is typically a short length but can be ldealized as a point of separation. The peel point bending angle A depends upon the geometry of the peel separation and the tension applied to the optical fiber 28. As lndlcated, the angle A is typically from about 30 to about 60 degrees, and normally is about 60 degrees.
The radius of bending at the peel polnt ls lndicated as R, and ls typlcally about 0.060 inches.
Flgure 5 lllustrates how the triangular bending mandrel 60 slmulates the bending conditions of Figure 6, twice for each corner 56 and six tlmes for each turn of the optlcal fiber 28 about the prlsm portlon 54. As illustrated ln Flgure 5 at the 30 upwardly polnting corner 56, the optlcal flber 28 ls bent through a first 60 degree simulated peel point bend 66 from one flat face to the corner 56, and through a second 60 degree simulated peel point bend 68 from the corner 56 to the ne~t flat face, for a total bending around the corner 54 of 120 degrees.
The tenslon on the optlcal flber 28 is selected to yleld a bendlng radlus R comparable to that 20372~
e~perlenced during the peellng operatlon of Fi~ure 7, or about 0.060 inches ln the typlcal case. The comblnatlon of prlsm geometry and applled tension determlnes the bendlng radlus of the mandrel 50. A
one-lnch face dlmension and 50 grams of tension results in a bending radius of about 0.060 lnches, through two simulated 60 degree peel point bends per corner, in the embodiment of Flgure 5. These dimensions and tenslons can be varled as requlred to slmulate varlous peellng condltions.
The present inventlon also extends to other configuratlons of the bendlng mandrel, and should not be vlewed as belng llmlted to the mandrel 10 and the mandrel 50. The mandrel may, for example, be made in the form of a square prism, or ln other forms to provide other bendlng angles.
Application of the proper tensloning to the optical flber during the slmulated peel polnt bending is lmportant to achieve the proper bend geometry and for reproduclbility. A tensloning apparatus 80 that produces such tensloning is lllustrated ln Figure 7. The mandrel, here lllustrated .as the trlangular prism mandrel 50, is mounted to a mandrel stand 82 by a rotational bearing 84, that permits the mandrel 50 to rotate freely about its prlsm axis. In the illustrated embodiment, the prlsm axls is in the horizontal plane. The mandrel stand 82 is mounted to a base 86 on a slidlng track 88, whlch permlts the mandrel stand 82, and thence the mandrel 50, to slide in the dlrection parallel to the lengths of the optlcal flber 28 that e~tend from the mandrel 50.
The optical fiber 28 ls secured near one end ~n a spllt rubber block 90 against longitudinal or transverse movement. Light is in~ected into the optical flber 28 with the llght source 30 discussed previously in relation to Figure 3.
203721~
~13-On the other slde of the mandrel stand 82, the optical fiber 28 passes over a pulley 92 havlng a radius much larger than the radius R of curvature at the peel point. The optical fiber 28 extends downwardly from the pulley 92 to a rubber block 94 ln whlch lt is secured and thence to the detector 36. A wcight 96 is hung from the rubber block 94, so that the total weight of the rubber block 94 and the weight 96 applies a tension to the optical fiber 28.
If the optical fiber 28 were simply wound around the mandrel and the tension applied, the optical flber at various locations around the mandrel 50 would experience highly variable tensions. The tension can be equalized by moving the mandrel stand 82 back and forth along the track 88 while the tension is applied. Since the mandrel freely rotates in the bearing 84, undue stress is not placed upon the optical fiber 2~. The movement aids in ensuring that the tension applied to the optical flber 28 at the varlous corners 56 around the mandrel become substantially equal to the tension produced by the total force of the weight 96 and the rubber block 94. This tenslonlng apparatus also permits the measurement of the light loss at a range of locations along the length of the optical fiber 28.
The tensioning apparatus 80 is preferably used in conJunction wlth the light measurement apparatus 29 and circultry illustrated ln Figure 3.
The present invention provldes an approach for measuring peel point bending losses of an optical fiber accurately. Although partlcular embodiments of the invention have been described in detail for purposes of illustration, various modifications may be made without departing from the spirit and scope of the lnvention. Accordingly, the 203721~
inventlon is not to be limited except as by the appended claims.
Claims (21)
1. A process for testing an optical fiber, comprising the steps of:
providing a bending mandrel having at least two simulated peel point bending locations disposed such that an optical fiber wound around the mandrel passes over the bending locations, each peel point bending location bending the optical fiber in a manner simulating the bending that an optical fiber undergoes when paid out from a fiber canister; and winding the optical fiber over the bending mandrel, thereby simultaneously applying multiple simulated peel point bends to the length of the optical fiber in contact with the mandrel.
providing a bending mandrel having at least two simulated peel point bending locations disposed such that an optical fiber wound around the mandrel passes over the bending locations, each peel point bending location bending the optical fiber in a manner simulating the bending that an optical fiber undergoes when paid out from a fiber canister; and winding the optical fiber over the bending mandrel, thereby simultaneously applying multiple simulated peel point bends to the length of the optical fiber in contact with the mandrel.
2. The process of claim 1, wherein the bending mandrel is a cylindrical rod having opposing flat surfaces symmetrically formed therein along a cylindrical diameter.
3. The process of claim 1, wherein the bending mandrel is an equilateral triangular prism.
4. The process of claim 1, wherein the optical fiber is bent through a total angle of from about 60 degrees to about 120 degrees at each of the bending locations.
5. The process of claim 1, further including the additional step of applying a tension to the optical fiber while it is wound over the bending mandrel.
6. The process of claim 5, further including the additional step of ensuring that the tension is applied substantially equally at each of the bending locations.
7. The process of claim 1, further including the additional step of measuring the transmission of light through the optical fiber while it is wound over the bending mandrel.
8. A process for testing an optical fiber, comprising the steps of:
providing a bending mandrel formed from a cylinder having two flat surfaces therein perpendicular to a cylindrical diameter and winding an optical fiber around the bending mandrel.
providing a bending mandrel formed from a cylinder having two flat surfaces therein perpendicular to a cylindrical diameter and winding an optical fiber around the bending mandrel.
9. The process of claim 8, wherein the optical fiber is wound around the bending mandrel at least twice.
10. The process of claim 8, wherein tension is applied to the optical fiber while it is wound around the mandrel.
11. The process of claim 8, wherein the spacing between the flat surfaces is about one-half the diameter of the cylinder.
12. The process of claim 8, wherein the cylindrical diameter of the mandrel is about 1 inch.
13. The process of claim 8, further including the additional step of measuring the transmission of light through the optical fiber while it is wound over the optical fiber.
14. A process for testing an optical fiber, comprising the steps of:
providing a bending mandrel formed with a portion thereof being an equilateral triangular prism; and winding an optical fiber around the equilateral triangular prism portion of the bending mandrel.
providing a bending mandrel formed with a portion thereof being an equilateral triangular prism; and winding an optical fiber around the equilateral triangular prism portion of the bending mandrel.
15. The process of claim 14, wherein the optical fiber is wound around the bending mandrel at least twice.
16. The process of claim 14, wherein tension is applied to the optical fiber while it is wound around the mandrel.
17. The process of claim 14, further including the additional step of measuring the transmission of light through the optical fiber while it is wound over the optical fiber.
18. Apparatus for testing optical transmission of an optical fiber, comprising:
a bending mandrel having at least two simulated peel point bending locations thereon; and means for sending a beam of light through an length of an optical fiber wound over the bending mandrel, for receiving that portion of the beam of light transmitted through the length of the optical fiber wound over the bending mandrel, and for comparing the intensities of the light received and the light sent.
a bending mandrel having at least two simulated peel point bending locations thereon; and means for sending a beam of light through an length of an optical fiber wound over the bending mandrel, for receiving that portion of the beam of light transmitted through the length of the optical fiber wound over the bending mandrel, and for comparing the intensities of the light received and the light sent.
19. The apparatus of claim 18, further including:
means for applying a tension to the optical fiber wound over the bending mandrel.
means for applying a tension to the optical fiber wound over the bending mandrel.
20. The apparatus of claim 18, further including:
means for manipulating the optical fiber wound over the mandrel to ensure that the tension in the optical fiber at all simulated peel point bending locations is substantially the same.
means for manipulating the optical fiber wound over the mandrel to ensure that the tension in the optical fiber at all simulated peel point bending locations is substantially the same.
21. The apparatus of claim 18, wherein the bending mandrel is mounted on a support that permits the mandrel to rotate about its axis.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/500,623 US5039218A (en) | 1990-03-28 | 1990-03-28 | Testing of optical fiber by introducing multiple simulated peel location bends |
| US500,623 | 1990-03-28 | ||
| AU76356/91A AU626497B2 (en) | 1990-03-28 | 1991-05-02 | Testing of optical fiber by introducing multiple simulated peel location bends |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2037216A1 true CA2037216A1 (en) | 1991-09-29 |
Family
ID=25638318
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002037216A Abandoned CA2037216A1 (en) | 1990-03-28 | 1991-02-27 | Testing of optical fiber by introducing multiple simulated peel location bends |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US5039218A (en) |
| EP (1) | EP0449491B1 (en) |
| JP (1) | JPH04223245A (en) |
| KR (1) | KR940009539B1 (en) |
| AU (1) | AU626497B2 (en) |
| CA (1) | CA2037216A1 (en) |
| DE (1) | DE69105576T2 (en) |
| EG (1) | EG19137A (en) |
| TR (1) | TR25962A (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE9301883L (en) * | 1993-06-02 | 1994-10-31 | Telia Ab | Method and apparatus for determining the life of a fiber |
| US5895417A (en) * | 1996-03-06 | 1999-04-20 | Cardiac Pathways Corporation | Deflectable loop design for a linear lesion ablation apparatus |
| US6721086B2 (en) * | 2001-05-10 | 2004-04-13 | International Business Machines Corporation | Optical fiber emulator |
| US6821293B2 (en) * | 2002-10-25 | 2004-11-23 | Medinol Ltd. | Mandrel and method for making stents |
| US9036137B2 (en) * | 2012-05-07 | 2015-05-19 | Fluke Corporation | Optical light source with controlled launch conditions |
| KR101876317B1 (en) * | 2018-03-05 | 2018-07-09 | 주식회사 한국종합건축사사무소 | Beam Clamp |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1596757A (en) * | 1977-05-12 | 1981-08-26 | Int Standard Electric Corp | Apparatus for and method of measuring the optical properties of an optical fibre while it is being drawn |
| US4468117A (en) * | 1982-02-22 | 1984-08-28 | General Dynamics | Integrated optical fiber testing device |
| AU573924B2 (en) * | 1984-02-13 | 1988-06-23 | Sumitomo Electric Industries, Ltd. | Measuring cut-off wavelength of a single-mode optical fibre |
| JPH073488B2 (en) * | 1986-02-24 | 1995-01-18 | 三菱レイヨン株式会社 | Processing method for plastic optical fiber |
| GB2196735B (en) * | 1986-10-30 | 1991-01-23 | Babcock & Wilcox Co | Strain gauges |
| DE3643525A1 (en) * | 1986-12-19 | 1988-06-30 | Philips Patentverwaltung | METHOD AND DEVICE FOR MEASURING THE ADDITIONAL DAMPING RESULTING FROM CURVES IN A FOC |
| FR2622696B1 (en) * | 1987-11-04 | 1990-01-12 | Peugeot | DEVICE FOR MEASURING THE RESULT OF AERODYNAMIC FORCES ACTING ON A MOTOR VEHICLE |
| US4957364A (en) * | 1989-04-18 | 1990-09-18 | Hughes Aircraft Company | Helical bend proof testing of optical fibers |
-
1990
- 1990-03-28 US US07/500,623 patent/US5039218A/en not_active Expired - Lifetime
-
1991
- 1991-02-27 CA CA002037216A patent/CA2037216A1/en not_active Abandoned
- 1991-03-20 DE DE69105576T patent/DE69105576T2/en not_active Expired - Fee Related
- 1991-03-20 EP EP91302401A patent/EP0449491B1/en not_active Expired - Lifetime
- 1991-03-27 KR KR1019910004819A patent/KR940009539B1/en active IP Right Grant
- 1991-03-27 TR TR91/0275A patent/TR25962A/en unknown
- 1991-03-27 EG EG17091A patent/EG19137A/en active
- 1991-03-28 JP JP3090021A patent/JPH04223245A/en active Pending
- 1991-05-02 AU AU76356/91A patent/AU626497B2/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04223245A (en) | 1992-08-13 |
| TR25962A (en) | 1993-11-01 |
| KR940009539B1 (en) | 1994-10-14 |
| EG19137A (en) | 1994-12-30 |
| AU626497B2 (en) | 1992-07-30 |
| EP0449491A1 (en) | 1991-10-02 |
| DE69105576D1 (en) | 1995-01-19 |
| US5039218A (en) | 1991-08-13 |
| DE69105576T2 (en) | 1995-04-13 |
| AU7635691A (en) | 1991-11-14 |
| EP0449491B1 (en) | 1994-12-07 |
| KR910017182A (en) | 1991-11-05 |
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