CA2179920A1 - Optical fiber coil and method of winding - Google Patents
Optical fiber coil and method of windingInfo
- Publication number
- CA2179920A1 CA2179920A1 CA 2179920 CA2179920A CA2179920A1 CA 2179920 A1 CA2179920 A1 CA 2179920A1 CA 2179920 CA2179920 CA 2179920 CA 2179920 A CA2179920 A CA 2179920A CA 2179920 A1 CA2179920 A1 CA 2179920A1
- Authority
- CA
- Canada
- Prior art keywords
- turns
- layer
- segment
- coil
- optical fiber
- 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
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
- G01C19/58—Turn-sensitive devices without moving masses
- G01C19/64—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams
- G01C19/72—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams with counter-rotating light beams in a passive ring, e.g. fibre laser gyrometers
- G01C19/721—Details
Abstract
A fiber optic sensor coil is wound from a length of optical fiber with the mid-point of the optical fiber at the mid-point of the innermost layer of the coil and subsequent layers of the coil each have alternating turns of the two sections of the fiber emanating from the mid-point. The layers of alternating turns are formed by first winding a portion of one segment in such a fashion that adjacent turns are spaced apart by a distance equivalent to the diameter of the optical fiber. The layer is completed by winding a portion of the other segment such that the turns of the other segment are disposed between adjacent turns of the one segment. The number of turns in adjacent layers are unequal such that the turns of a next layer are arranged in grooves formed between two adjacent turns of optical fiber in the previous layer.
Description
2 ~ 79920 OPTIC~ I, FIl~FR ~OIL ~NI) ~li~THQ~ QF WlNnlN~ _ BA~ RQU~ QF TRF, IN~,lYTION
Field of the TnvPution This invention relates to optical fiber coils and to methods of 5 mAmlf~rtnre thereof, and more particularly, to an improved coil pattern.
Des~ " )rofl~Pla~ed,~r~
Fiber optic sensor coils are used, inter alia, in fiber optic ~ylvs~vpcstoprovideanopticaloutputsignalusedindrtl ,lli"i~,grotationofa vehicle (e.g. an airplane) about an axis of rotation. A typical fiber optic 10 gyroscope uses three sensor coils to sense rotation about each of three orthogonal axes. The fiber optic gyroscope is typically configured as a Sagnac interferometer including a light source providing an optical signal, a multi-turn coil of optical fiber, referred to as a fiber optic ring, and electronic read-out and control circuits. The optical signal is first applied to an optical beam 15 splitter/combiner which provides two identical optical output signals, each of which is applied to one end of the fiber optic coil. The two optical signals travel through the coil in opposite directions and are lccvllllJillcd at the beam ~lilleltcollll,illcl. A rotation of the fiber optic coil about its wound, or Ir,nghn~iins31 axis will result in a phase shift between the counter-propagatory20 optical signals traveling through the coil. This phase shift is known as the Sagnac effect phase shift. The Sagnac effect can be explained by relativistic theory which shows that a wave traveling through a rotating coil in the direction of rotation requires more time to traverse the path than a wave traveling opposite to the direction of rotation. This time difference is manifested by phase shift 25 interference pattern of the recombined optical signal. In an optical gyro, the m:lgnitllf~e of the phase shift is determined by analysis of the l~cvlll'vhled signal as applied to an output optical detector. The detector output is translated intoelectrical output signals l.,~ llhlg rotation.
~ 2 1 79920 --2--The phase shift detected at the output detector may be ~ ullsid~l~,.i as consisting of two parts. The first part is the Sagnac effect phase shift. Theother part of the detected phase shift is due to perturbations in the optical fiber caused by cllvhvlllll~ l factors. The Sagnac phase shift which defines the 5 mllgnit~l-le and direction of rotation is relatively small, such that any cignifi~nt phase shift due to ~IIVilUlllllclll~l factors may obscure an accurate reading of the Sagnac effect phase shift. It is therefore desirable to minimize the effect of environmental perturbations on the detected phase shift of the l~culul,ll.cd optical signal.
The two optical signals emanating from the splitter/ combiner in response to the single optical input signal are in phase and are applied at opposite ends of the coiled fiber and traverse the fiber in opposite directions. The undesirable phase shift effects occur when cnvhu~l~u~ l~t~l perturbations affectone of the light signals differently than the other. It is generally It;co~..i,~d that 15 c l~vilulllllell~l perturbations cannot be l~limin~t~orl but that their effect can be inillli ,~ d if these perturbations are applied equally to the counter propagatory light signals. A known approach to reducing the effect of c;llvh u~ul~
perturbations is to build a symmetry in the sensing coils. Known sensing coils include dipole, ~luadl ulJolc, and octupole windings. In these coils the midpoint 20 of a length of optical fiber is placed near one side flange of a spool and the two optical fiber segments emanating from the midpoint, referred to as the forward segment and the reverse segment, are then wound around the coil in opposite directions. In the case of a dipole, the forward and reverse segments are wound on the spool in ~It~rn~ting layers. In the quadruple, a layer of the forward 25 segment is followed by two layers of the reverse segment, followed by two Iayers of the for vard segment, and so on. In an octupole c~-nfi~lrsltion, two layers of the reverse segment are sandwiched between two layers of the forward segment followed by another set of four layers in which two layers of the forward segment are sandwiched between layers of the reverse segment. All of 30 these various c~-nfi~ fions are ~tt~ illg to introduce a symmetry such that an ~ -3 -cllvho~ lc~ l perturbation of the coil will affect the counter-propagating lightsignals in the same manner. However, when the coil is built up of slltt~rn~ting layers or ~lt~rrl~ting pairs of layers of the forward and reverse segments, the forward and reverse segments are not necessarily affected in the same way by the5 cllvhulLlll~ l perturbations. This may be better ~In~l~rstood by c~-nc~ ring the nature of the cllvhvlllllclll~l perturbations.
Ellvhulllll~ l perturbations may be due to mechanical strain, vibration, shock and t~,llly~lalule changes. It is known, that pred~)min~ntly two types of I r~ ,r". 1 " . c perturbations have to be dealt with, namely, those due to 10 radial tclllyclaiulc gradients and those due to axial tcllly~,lalulc gradients. A
third gradient type, transverse to the wound (ll~ngit~ in:ll) axis of the spool, is a less significant problem. As the name implies~ with a radial u "y ~ c gradient, the trl "l~r~ c varies radially such that an optical fiber segment cr~mpricing a portion of innermost layer of the coil is at a different l~ "I' . ~ C
15 than fiber segments in layers which are a distance removed from the core of the coil. An axial gradient extends along the wound axis of the spool. It is therefore desirable to avoid ~isgnifi~S~nt axial and radial distances between segments of the optical fiber which are the same distance from the center point of the length ofthe fiber such that cullc~yon.lillg segments of the forward and reverse segment of 20 the coil C~yCIiGllcC the same cllvilvlllllcllldl pcllLIlbaLio~
SUMMARY QF Tl~TF. ~I~VENTIQN
These and other problems of the prior art are overcome in a~culdallcG with the present invention in a fiber optic sensing coil by cun~ ,lhlg each of the layers of the coil of ~Itrrn~fing turns of the forward and 25 reverse segments. In acculd~lcc with one aspect of the invention, the coil comprises an inner layer wound from opposite ends of the length of fiber. The optical fiber has a midpoint and the midpoint is located at the dyylv~d midpoint of the innermost layer. Advantageously, the positioning of the midpoint of the fiber at the midpoint of the innermost layer allows the coil to be wound in opposite directions from the midpoint and tends to reduce variations due to ~;IIVilUlllll~ perturbations. A snhst:~nti~l reduction in the effects of cl~vilvlllllcll~l perturbations over prior art coils has been observed.
In accv d~ncc with another aspect of the invention, adjacent layers 5 of optical fibers are arranged such that the turns of optical fiber in one layer rest in grooves formed by adjacent turns in the preceding layer. In one l~mho~liml ntof the invention, adjacent layers of optical fibers have unequal numbers of turns to allow fibers ûf a next layer to be disposed in grooves formed by the turns ofthe preceding layer. In another ~ bvdh~l~,lll, adjacent layers have equal numbers 10 of turns with each laterally offset from the previous layer by a distance cllhst~nti~lly equal to one-half fiber diameter, allowing fibers of a next layer to rest in grooves formed by adjacent turns in the preceding layer. Adv~ g.~ùl ~ly~such an arrangement adds stability to the coil and reduces its overall outside diameter.
In one particular embodiment of the invention, the pattern of alternate adjacent segrnents of the fiber is such that the second through the fifth layers of the coil each have a unique pattern with respect to any preceding layer and the patterns of the sixth through ninth layers cu..c~l,vnd individually to the patterns of the second through the fifth layers, .ci~,e~,livcly, with the four-layer 20 pattern conf ~Ir~tiOll repeated in the remaining layers of the coil. In another ci...bodi...ci..l of the invention, even numbered layers have cvll."~ùnv;llg patterns and :llt(~rn:lting odd numbered layers have ~;ollc~,uvll.lhlg patterns. In yet another c...bollill-c~lt of the invention, all layers after the first layer are wound identically.
In a method of winding an optical fiber coil in accu.Jdllcc with the 25 invention, the first layer is formed such that portions of the forward and reverse segments are disposed adjacent opposite side flanges of a spool. The second layer is formed by winding an alternate turns pattern of the forward segment of the fiber on the f rst layer such that adjacent turns of the forward segment arespaced apart by a ~ t~ d distance and then winding a portion of the 30 reverse segment in an alternate turns pattern on the first layer between the 2 ~ 79920 alternate turns pattern of the forward segrnent, thereby forming a layer of :~lt~ ting turns of the forward and reverse segments. In ac~uld~ulce with a particular aspect of the invention, the second and additional layers are formed by winding the next layer such that the turns of the next layer are disposed in 5 grooves formed between turns of the preceding layer.
In a particular ~;.llbod;lll~,lll of the invention, the coil is wound on a spool and is treated with an adhesive to retain the shape of the core. The coil is ,"l,~ ly removed from the spool to advsnt~lgrol~cly realize weight and volume savings and potentially improve coil performance.
In another ~lllI,odi~ ,lll of the invention, the core is provided with a longihl~lin:~l groove to provide an improved first layer of the coil. In yet another embodiment, the core is provided with ~h-;ulllr~l~lll,dlly-extending parallel grooves.
BRIEF Vl; ~Cl~ IPTION Ol~Tl~F l~AWING
The invention is described in detail in the following p~a~ hs with reference to the drawing in which:
FIG. 1 is a schematic l~ cl,ldtion of a cross-section of a portion of sensing coil constructed in acculJa,.~,e with the principles of this invention;
FIGS. 2 through 4 are alternate embodiments of the invention 2û showing alternate coil winding patterns;
FIG. ~ is a schematic representation of apparatus for winding a fiber optic coil in acc~lJallcc with the invention;
FIG. 6 is a side view representation of a spool adapted for winding a fiber optic coil;
FIG. 7 is a side view of a coil would on the core of FIG. 6.
FIG. 8A is an end view of an alternate embodiment of a core;
FIG. 8 is a side view of the core of FIG. 8A; and FIG. 9 is a side view of another alternate embodiment of a core.
-6- 2 ~ 7992C
DETA~F~n DESCR~PTION
FIG. r is a schematic ~ llalion of a cross section of a sensing coil 100 wound on a spool 102 having a core 103 and opposing flanges 104, 106.
The coil is constructed as an optical fiber sensing coil for use, for example, in a 5 fiber optic gyro. The coil consists of a cf ntimlollc flber of a selected length having its midpoint adjacent the core of the spool and its ends exposed. The twooptical fiber segments extending from the midpoint, referred to as the forward segment and the reverse segment, are wound on the spool in opposite directions.
In use, as explained in the background of the invention, two identical optical 10 signals are individually applied to opposite ends of the coil and propagate through the forward and reverse segments in opposite directions.
FIG. I depicts a coil 100 having 28 layers, each layer consisting of a number of turns of oppositely wound fiber segments. For the sake of this description, turns of the forward fiber segment are depicted as extending away 15 from the viewer and identified by X's and turns of the reverse segment are depicted as extending toward the viewer and are referred to as O's. The coil 100shown in FIG. I has a first layer (I) having an odd number of turns, e.g., 99 turns. The turns extend in opposite direction from the midpoint of the fiber, lled by M, toward the opposing flanges 104, 106. The next layer (2) has 20 an even number of alternate, oppositely directed turns of the optical fiber. The outermost turns of that layer are preferably displaced from each of the flanges 104, 106 by a distance of d~)~lU~illla~ one-half of the diameter of the fiber such that the second layer has one fewer turn than the first layer. This arrangement of layers is repeated such that all even numbered layers have one 25 fewer turn than the odd numbered layers. This allows the fiber turns of the next layer to be positioned in the naturally formed grooves between adjacent turns ofthe previous layer. This ~ ng~... ,.. ,l of layers lends stability to the coil. It also tends to reduce the overall coil diameter, which is important in space craft andother applications with s~lt st:lnfi:'l space limit~tinn~ Adjacent turns may be 2 1 7q92~
spaced apart by a selected distance to form more pronounced and deeper grooves for the turns of the next layer.
As depicted in FIG. 1, the first layer, layer 1, consists of half of each of the forward and reverse segments. After the first layer, a particular 5 pattern of forward and reverse segment turns is developed. The paKern of turnsin the layers shown in FIG. l is such that it is repeated every fourth layer. The pattern of turns in each of the layers 2 through 5 is unique with respect to any of the preceding layers. After layer 5, however, the pattern of turns in layers 2 through 5 is repeated in y~ e~ groups of four layers. Thus, layer 6 has the 10 same paKern of turns as layer 2. The other layers shown in FIG. 1, layer 28, has the same pattern as layer 4.
Other patterns of ~lltPrn~fing turns of the forward and reverse segment may be created. In the paKern shown in FIG. 2, the even rows, e.g. 2, 4,6, all have the same turns paKern, whereas the odd numbered layers, i.e., 3, 5, 7, 15 and 9 have ~ltPrn~ting turns patterns. Thus the pattern of layer 3 is repeated in layers 7, I l, etc., and the pattern of layer 5 is repeated in layers 9, 13, etc. Other patterns, besides those shown in FIG. I and FIG. 2 can be readily envisioned.
The pattern shown in FIG. I and FIG. 2 are for an arrangement in which the firstlayer adjacent to the core 103 has an odd number of turns. FIG. 3 shows an 20 arrangement wherein the first layer, layer 1, has an even number of turns. In that c-~nfigl-r:~tinn, the odd numbered layers, i.e., 3, 5, etc., have the same turnspattern and the even numbered layers, i.e., 2, 4, 6, etc., have an alternate pattern.
These turns patterns are repeated in every fourth layer. Thus, layer 6 has the same paKern as layer 2, layer 8 has the same pattern as layer 4, and so on. The 25 formation of the turns patterns in the layers is a function of the method of winding the coil 100.
It is also possible that the fiber has different diameters in different areas. For example, a depolarizer may be inserted at various positions in the fiber. This may result in differing numbers of turns of the fiber in certain layers.
2 ~ 7992û
FIG.4 is a cross-sectional schematic ~ . a~ llL;lLion of a part of a sensing coil 100 wound in a fashion such that all layers have the same number ofturns while the fiber turns of adjacent layers are laterally displaced from eachother by a distance a~lu~h.lately equal to one-half of the fiber diameter. In this 5 particular configuration, the even numbered layers have ~ Oll. a~Jolldillg configurations of forward and reverse segment turns and the odd numbered layers, beginning with the third layer, have ~ollca~)ulldillg confi~-r~tions of forward and reverse segment turns. The total number of turns in each layer may be even or odd. In the sl r:lngement of FIG.4, the first layer is displaced from the 10 right flange 104 by a distance snbstontiolly equal to one-half fiber diameter. A
spacer 105, having a lateral dimension of approximately one-half the fiber diameter, may be provided adjacent to core 103 and the right flange 104 to provide the desired spacing of the right most turn of the first layer from the right flange 104. Layer 2 is displaced from the left flange 106 by a distance 15 sl-hst~nti~lly equal to one-half the fiber diameter with turns of the second layer disposed in the grooves formed by the turns of the first layer. ~l ~hac~ layers are alternately spaced away from the right flange 104 and the left ilange 106 tomaintain the one-half fiber diameter offset between adjacent layers.
FIG. S is a schematic lc~ lLaLion of an apparatus for winding 20 the coil 100. As shown in FIG.5, the spool 102 is mounted on a drive shaft 204 driven by a drive motor 203. When a fiber is to be wound around the spool I OZ, the fiber is first wound, starting with opposite ends of the fiber, on two separate supply spools 209 and 223. The supply spools 209 and 223 are mounted on left and right support brackets 207 and 221, l~al,e- LiYC;Iy. In apreferred method of25 winding the coil 100, the length of fiber on one of the supply spools, e.g. the right supply spool 209, is equal to one-half of the total length of the fiber plus the length co l~ lldi.lg to one half of the first layer, layer I . The midpoint between the two supply spools may be placed adjacent one of the flanges, for example, the left flange 106 and wound across to the right flange 104. The 30 midpoint of the length of fiber will then be positioned substantially in alignment 2~ 79920 ~ g with the midpoint of the spool 102, as depicted in FIG. 1. Thereafter, the remainder of the coil 100 is wound from the two supply spools 209 and 223 .
The left and right support brackets 221 and 207 are attached to the c~ apulldillg lefl and right shaft sections 204 and 205, respectively. Clutches 215 and 216 are provided to selectively engage shaft sections 204 and 205, ~,a~c~liv~;ly, with drive shaft 203 for rotation with the spool 102. The opticalfiber from supply spool 209 on bracket 207 is fed via a roller 213 to the spool 102. The roller 213 is supported by means of a bracket 211 attached to the bracket 207. In a similar fashion, bracket 225 connected to bracket 221 supportsa roller 226 to guide the optical fiber from spool 223 on bracket 221 to the spool 102. When the coil 100 is to be wound from supply spool 209 mounted on the right bracket 207, the left clutch 215 is engaged to lock the left shaft section 204 andbracket221 todriveshaft203 forrotationwiththespool 102. Theright clutch is ~1ic~-ng~lged from drive shaft 204 and is held in a fixed position.
Similarly, when the soil 100 is to be wound from supply spool 223 on bracket 221, clutch 216 is engaged to lock the right shaft section 205 and bracket 207 to drive shafi 203 for rotation with the spool 102. Clutch 215 is ~ ngagrd and bracket221 isheldstationary. Motor201 isreversibletoallowcoil lOOtobe turned in either the clockwise or counterclockwise direction.
The procedure for winding the coil 100 to obtain the pattern shown in FIG. 1, using the apparatus l1~L~s~ d in FIG. 5, is described further below.
In the following description, the spool 223 will be referred to as the X spool, ,a~lllhlg the forward segment, and the spool 209 will be referred to as the O
spool, ~ Ca~llLil.g the reverse segment of the optical fiber sensing coil 100. As 25 shown in FIGS. I through 4, the turns in adjacent layers are offset from eachother. This facilitates the winding process, as outlined below, by causing turnsof a next layer to follow grooves provided in the preceding layer. This is especially helpful in forming a spaced-apart turns pattern wherein adjacent turns ~ -10-are spaced apart by a distance equal to or slightly greater than the diameter of the fiber, as described further below.
The procedure for winding a coil on a spool in the configuration as shown in FIG. I comprises the following steps:
1. Winding the reverse segment O, supply spool with a length of fiber cul~.,a~Olldillg to one-half of the total length of the fiber plus the length required to form one-half of the first layer of the coil on the spool 102, and mark the endpoint of that segment.
2. Winding the remainder of the optical fiber on the forward 10 segment X, supply spool.
Field of the TnvPution This invention relates to optical fiber coils and to methods of 5 mAmlf~rtnre thereof, and more particularly, to an improved coil pattern.
Des~ " )rofl~Pla~ed,~r~
Fiber optic sensor coils are used, inter alia, in fiber optic ~ylvs~vpcstoprovideanopticaloutputsignalusedindrtl ,lli"i~,grotationofa vehicle (e.g. an airplane) about an axis of rotation. A typical fiber optic 10 gyroscope uses three sensor coils to sense rotation about each of three orthogonal axes. The fiber optic gyroscope is typically configured as a Sagnac interferometer including a light source providing an optical signal, a multi-turn coil of optical fiber, referred to as a fiber optic ring, and electronic read-out and control circuits. The optical signal is first applied to an optical beam 15 splitter/combiner which provides two identical optical output signals, each of which is applied to one end of the fiber optic coil. The two optical signals travel through the coil in opposite directions and are lccvllllJillcd at the beam ~lilleltcollll,illcl. A rotation of the fiber optic coil about its wound, or Ir,nghn~iins31 axis will result in a phase shift between the counter-propagatory20 optical signals traveling through the coil. This phase shift is known as the Sagnac effect phase shift. The Sagnac effect can be explained by relativistic theory which shows that a wave traveling through a rotating coil in the direction of rotation requires more time to traverse the path than a wave traveling opposite to the direction of rotation. This time difference is manifested by phase shift 25 interference pattern of the recombined optical signal. In an optical gyro, the m:lgnitllf~e of the phase shift is determined by analysis of the l~cvlll'vhled signal as applied to an output optical detector. The detector output is translated intoelectrical output signals l.,~ llhlg rotation.
~ 2 1 79920 --2--The phase shift detected at the output detector may be ~ ullsid~l~,.i as consisting of two parts. The first part is the Sagnac effect phase shift. Theother part of the detected phase shift is due to perturbations in the optical fiber caused by cllvhvlllll~ l factors. The Sagnac phase shift which defines the 5 mllgnit~l-le and direction of rotation is relatively small, such that any cignifi~nt phase shift due to ~IIVilUlllllclll~l factors may obscure an accurate reading of the Sagnac effect phase shift. It is therefore desirable to minimize the effect of environmental perturbations on the detected phase shift of the l~culul,ll.cd optical signal.
The two optical signals emanating from the splitter/ combiner in response to the single optical input signal are in phase and are applied at opposite ends of the coiled fiber and traverse the fiber in opposite directions. The undesirable phase shift effects occur when cnvhu~l~u~ l~t~l perturbations affectone of the light signals differently than the other. It is generally It;co~..i,~d that 15 c l~vilulllllell~l perturbations cannot be l~limin~t~orl but that their effect can be inillli ,~ d if these perturbations are applied equally to the counter propagatory light signals. A known approach to reducing the effect of c;llvh u~ul~
perturbations is to build a symmetry in the sensing coils. Known sensing coils include dipole, ~luadl ulJolc, and octupole windings. In these coils the midpoint 20 of a length of optical fiber is placed near one side flange of a spool and the two optical fiber segments emanating from the midpoint, referred to as the forward segment and the reverse segment, are then wound around the coil in opposite directions. In the case of a dipole, the forward and reverse segments are wound on the spool in ~It~rn~ting layers. In the quadruple, a layer of the forward 25 segment is followed by two layers of the reverse segment, followed by two Iayers of the for vard segment, and so on. In an octupole c~-nfi~lrsltion, two layers of the reverse segment are sandwiched between two layers of the forward segment followed by another set of four layers in which two layers of the forward segment are sandwiched between layers of the reverse segment. All of 30 these various c~-nfi~ fions are ~tt~ illg to introduce a symmetry such that an ~ -3 -cllvho~ lc~ l perturbation of the coil will affect the counter-propagating lightsignals in the same manner. However, when the coil is built up of slltt~rn~ting layers or ~lt~rrl~ting pairs of layers of the forward and reverse segments, the forward and reverse segments are not necessarily affected in the same way by the5 cllvhulLlll~ l perturbations. This may be better ~In~l~rstood by c~-nc~ ring the nature of the cllvhvlllllclll~l perturbations.
Ellvhulllll~ l perturbations may be due to mechanical strain, vibration, shock and t~,llly~lalule changes. It is known, that pred~)min~ntly two types of I r~ ,r". 1 " . c perturbations have to be dealt with, namely, those due to 10 radial tclllyclaiulc gradients and those due to axial tcllly~,lalulc gradients. A
third gradient type, transverse to the wound (ll~ngit~ in:ll) axis of the spool, is a less significant problem. As the name implies~ with a radial u "y ~ c gradient, the trl "l~r~ c varies radially such that an optical fiber segment cr~mpricing a portion of innermost layer of the coil is at a different l~ "I' . ~ C
15 than fiber segments in layers which are a distance removed from the core of the coil. An axial gradient extends along the wound axis of the spool. It is therefore desirable to avoid ~isgnifi~S~nt axial and radial distances between segments of the optical fiber which are the same distance from the center point of the length ofthe fiber such that cullc~yon.lillg segments of the forward and reverse segment of 20 the coil C~yCIiGllcC the same cllvilvlllllcllldl pcllLIlbaLio~
SUMMARY QF Tl~TF. ~I~VENTIQN
These and other problems of the prior art are overcome in a~culdallcG with the present invention in a fiber optic sensing coil by cun~ ,lhlg each of the layers of the coil of ~Itrrn~fing turns of the forward and 25 reverse segments. In acculd~lcc with one aspect of the invention, the coil comprises an inner layer wound from opposite ends of the length of fiber. The optical fiber has a midpoint and the midpoint is located at the dyylv~d midpoint of the innermost layer. Advantageously, the positioning of the midpoint of the fiber at the midpoint of the innermost layer allows the coil to be wound in opposite directions from the midpoint and tends to reduce variations due to ~;IIVilUlllll~ perturbations. A snhst:~nti~l reduction in the effects of cl~vilvlllllcll~l perturbations over prior art coils has been observed.
In accv d~ncc with another aspect of the invention, adjacent layers 5 of optical fibers are arranged such that the turns of optical fiber in one layer rest in grooves formed by adjacent turns in the preceding layer. In one l~mho~liml ntof the invention, adjacent layers of optical fibers have unequal numbers of turns to allow fibers ûf a next layer to be disposed in grooves formed by the turns ofthe preceding layer. In another ~ bvdh~l~,lll, adjacent layers have equal numbers 10 of turns with each laterally offset from the previous layer by a distance cllhst~nti~lly equal to one-half fiber diameter, allowing fibers of a next layer to rest in grooves formed by adjacent turns in the preceding layer. Adv~ g.~ùl ~ly~such an arrangement adds stability to the coil and reduces its overall outside diameter.
In one particular embodiment of the invention, the pattern of alternate adjacent segrnents of the fiber is such that the second through the fifth layers of the coil each have a unique pattern with respect to any preceding layer and the patterns of the sixth through ninth layers cu..c~l,vnd individually to the patterns of the second through the fifth layers, .ci~,e~,livcly, with the four-layer 20 pattern conf ~Ir~tiOll repeated in the remaining layers of the coil. In another ci...bodi...ci..l of the invention, even numbered layers have cvll."~ùnv;llg patterns and :llt(~rn:lting odd numbered layers have ~;ollc~,uvll.lhlg patterns. In yet another c...bollill-c~lt of the invention, all layers after the first layer are wound identically.
In a method of winding an optical fiber coil in accu.Jdllcc with the 25 invention, the first layer is formed such that portions of the forward and reverse segments are disposed adjacent opposite side flanges of a spool. The second layer is formed by winding an alternate turns pattern of the forward segment of the fiber on the f rst layer such that adjacent turns of the forward segment arespaced apart by a ~ t~ d distance and then winding a portion of the 30 reverse segment in an alternate turns pattern on the first layer between the 2 ~ 79920 alternate turns pattern of the forward segrnent, thereby forming a layer of :~lt~ ting turns of the forward and reverse segments. In ac~uld~ulce with a particular aspect of the invention, the second and additional layers are formed by winding the next layer such that the turns of the next layer are disposed in 5 grooves formed between turns of the preceding layer.
In a particular ~;.llbod;lll~,lll of the invention, the coil is wound on a spool and is treated with an adhesive to retain the shape of the core. The coil is ,"l,~ ly removed from the spool to advsnt~lgrol~cly realize weight and volume savings and potentially improve coil performance.
In another ~lllI,odi~ ,lll of the invention, the core is provided with a longihl~lin:~l groove to provide an improved first layer of the coil. In yet another embodiment, the core is provided with ~h-;ulllr~l~lll,dlly-extending parallel grooves.
BRIEF Vl; ~Cl~ IPTION Ol~Tl~F l~AWING
The invention is described in detail in the following p~a~ hs with reference to the drawing in which:
FIG. 1 is a schematic l~ cl,ldtion of a cross-section of a portion of sensing coil constructed in acculJa,.~,e with the principles of this invention;
FIGS. 2 through 4 are alternate embodiments of the invention 2û showing alternate coil winding patterns;
FIG. ~ is a schematic representation of apparatus for winding a fiber optic coil in acc~lJallcc with the invention;
FIG. 6 is a side view representation of a spool adapted for winding a fiber optic coil;
FIG. 7 is a side view of a coil would on the core of FIG. 6.
FIG. 8A is an end view of an alternate embodiment of a core;
FIG. 8 is a side view of the core of FIG. 8A; and FIG. 9 is a side view of another alternate embodiment of a core.
-6- 2 ~ 7992C
DETA~F~n DESCR~PTION
FIG. r is a schematic ~ llalion of a cross section of a sensing coil 100 wound on a spool 102 having a core 103 and opposing flanges 104, 106.
The coil is constructed as an optical fiber sensing coil for use, for example, in a 5 fiber optic gyro. The coil consists of a cf ntimlollc flber of a selected length having its midpoint adjacent the core of the spool and its ends exposed. The twooptical fiber segments extending from the midpoint, referred to as the forward segment and the reverse segment, are wound on the spool in opposite directions.
In use, as explained in the background of the invention, two identical optical 10 signals are individually applied to opposite ends of the coil and propagate through the forward and reverse segments in opposite directions.
FIG. I depicts a coil 100 having 28 layers, each layer consisting of a number of turns of oppositely wound fiber segments. For the sake of this description, turns of the forward fiber segment are depicted as extending away 15 from the viewer and identified by X's and turns of the reverse segment are depicted as extending toward the viewer and are referred to as O's. The coil 100shown in FIG. I has a first layer (I) having an odd number of turns, e.g., 99 turns. The turns extend in opposite direction from the midpoint of the fiber, lled by M, toward the opposing flanges 104, 106. The next layer (2) has 20 an even number of alternate, oppositely directed turns of the optical fiber. The outermost turns of that layer are preferably displaced from each of the flanges 104, 106 by a distance of d~)~lU~illla~ one-half of the diameter of the fiber such that the second layer has one fewer turn than the first layer. This arrangement of layers is repeated such that all even numbered layers have one 25 fewer turn than the odd numbered layers. This allows the fiber turns of the next layer to be positioned in the naturally formed grooves between adjacent turns ofthe previous layer. This ~ ng~... ,.. ,l of layers lends stability to the coil. It also tends to reduce the overall coil diameter, which is important in space craft andother applications with s~lt st:lnfi:'l space limit~tinn~ Adjacent turns may be 2 1 7q92~
spaced apart by a selected distance to form more pronounced and deeper grooves for the turns of the next layer.
As depicted in FIG. 1, the first layer, layer 1, consists of half of each of the forward and reverse segments. After the first layer, a particular 5 pattern of forward and reverse segment turns is developed. The paKern of turnsin the layers shown in FIG. l is such that it is repeated every fourth layer. The pattern of turns in each of the layers 2 through 5 is unique with respect to any of the preceding layers. After layer 5, however, the pattern of turns in layers 2 through 5 is repeated in y~ e~ groups of four layers. Thus, layer 6 has the 10 same paKern of turns as layer 2. The other layers shown in FIG. 1, layer 28, has the same pattern as layer 4.
Other patterns of ~lltPrn~fing turns of the forward and reverse segment may be created. In the paKern shown in FIG. 2, the even rows, e.g. 2, 4,6, all have the same turns paKern, whereas the odd numbered layers, i.e., 3, 5, 7, 15 and 9 have ~ltPrn~ting turns patterns. Thus the pattern of layer 3 is repeated in layers 7, I l, etc., and the pattern of layer 5 is repeated in layers 9, 13, etc. Other patterns, besides those shown in FIG. I and FIG. 2 can be readily envisioned.
The pattern shown in FIG. I and FIG. 2 are for an arrangement in which the firstlayer adjacent to the core 103 has an odd number of turns. FIG. 3 shows an 20 arrangement wherein the first layer, layer 1, has an even number of turns. In that c-~nfigl-r:~tinn, the odd numbered layers, i.e., 3, 5, etc., have the same turnspattern and the even numbered layers, i.e., 2, 4, 6, etc., have an alternate pattern.
These turns patterns are repeated in every fourth layer. Thus, layer 6 has the same paKern as layer 2, layer 8 has the same pattern as layer 4, and so on. The 25 formation of the turns patterns in the layers is a function of the method of winding the coil 100.
It is also possible that the fiber has different diameters in different areas. For example, a depolarizer may be inserted at various positions in the fiber. This may result in differing numbers of turns of the fiber in certain layers.
2 ~ 7992û
FIG.4 is a cross-sectional schematic ~ . a~ llL;lLion of a part of a sensing coil 100 wound in a fashion such that all layers have the same number ofturns while the fiber turns of adjacent layers are laterally displaced from eachother by a distance a~lu~h.lately equal to one-half of the fiber diameter. In this 5 particular configuration, the even numbered layers have ~ Oll. a~Jolldillg configurations of forward and reverse segment turns and the odd numbered layers, beginning with the third layer, have ~ollca~)ulldillg confi~-r~tions of forward and reverse segment turns. The total number of turns in each layer may be even or odd. In the sl r:lngement of FIG.4, the first layer is displaced from the 10 right flange 104 by a distance snbstontiolly equal to one-half fiber diameter. A
spacer 105, having a lateral dimension of approximately one-half the fiber diameter, may be provided adjacent to core 103 and the right flange 104 to provide the desired spacing of the right most turn of the first layer from the right flange 104. Layer 2 is displaced from the left flange 106 by a distance 15 sl-hst~nti~lly equal to one-half the fiber diameter with turns of the second layer disposed in the grooves formed by the turns of the first layer. ~l ~hac~ layers are alternately spaced away from the right flange 104 and the left ilange 106 tomaintain the one-half fiber diameter offset between adjacent layers.
FIG. S is a schematic lc~ lLaLion of an apparatus for winding 20 the coil 100. As shown in FIG.5, the spool 102 is mounted on a drive shaft 204 driven by a drive motor 203. When a fiber is to be wound around the spool I OZ, the fiber is first wound, starting with opposite ends of the fiber, on two separate supply spools 209 and 223. The supply spools 209 and 223 are mounted on left and right support brackets 207 and 221, l~al,e- LiYC;Iy. In apreferred method of25 winding the coil 100, the length of fiber on one of the supply spools, e.g. the right supply spool 209, is equal to one-half of the total length of the fiber plus the length co l~ lldi.lg to one half of the first layer, layer I . The midpoint between the two supply spools may be placed adjacent one of the flanges, for example, the left flange 106 and wound across to the right flange 104. The 30 midpoint of the length of fiber will then be positioned substantially in alignment 2~ 79920 ~ g with the midpoint of the spool 102, as depicted in FIG. 1. Thereafter, the remainder of the coil 100 is wound from the two supply spools 209 and 223 .
The left and right support brackets 221 and 207 are attached to the c~ apulldillg lefl and right shaft sections 204 and 205, respectively. Clutches 215 and 216 are provided to selectively engage shaft sections 204 and 205, ~,a~c~liv~;ly, with drive shaft 203 for rotation with the spool 102. The opticalfiber from supply spool 209 on bracket 207 is fed via a roller 213 to the spool 102. The roller 213 is supported by means of a bracket 211 attached to the bracket 207. In a similar fashion, bracket 225 connected to bracket 221 supportsa roller 226 to guide the optical fiber from spool 223 on bracket 221 to the spool 102. When the coil 100 is to be wound from supply spool 209 mounted on the right bracket 207, the left clutch 215 is engaged to lock the left shaft section 204 andbracket221 todriveshaft203 forrotationwiththespool 102. Theright clutch is ~1ic~-ng~lged from drive shaft 204 and is held in a fixed position.
Similarly, when the soil 100 is to be wound from supply spool 223 on bracket 221, clutch 216 is engaged to lock the right shaft section 205 and bracket 207 to drive shafi 203 for rotation with the spool 102. Clutch 215 is ~ ngagrd and bracket221 isheldstationary. Motor201 isreversibletoallowcoil lOOtobe turned in either the clockwise or counterclockwise direction.
The procedure for winding the coil 100 to obtain the pattern shown in FIG. 1, using the apparatus l1~L~s~ d in FIG. 5, is described further below.
In the following description, the spool 223 will be referred to as the X spool, ,a~lllhlg the forward segment, and the spool 209 will be referred to as the O
spool, ~ Ca~llLil.g the reverse segment of the optical fiber sensing coil 100. As 25 shown in FIGS. I through 4, the turns in adjacent layers are offset from eachother. This facilitates the winding process, as outlined below, by causing turnsof a next layer to follow grooves provided in the preceding layer. This is especially helpful in forming a spaced-apart turns pattern wherein adjacent turns ~ -10-are spaced apart by a distance equal to or slightly greater than the diameter of the fiber, as described further below.
The procedure for winding a coil on a spool in the configuration as shown in FIG. I comprises the following steps:
1. Winding the reverse segment O, supply spool with a length of fiber cul~.,a~Olldillg to one-half of the total length of the fiber plus the length required to form one-half of the first layer of the coil on the spool 102, and mark the endpoint of that segment.
2. Winding the remainder of the optical fiber on the forward 10 segment X, supply spool.
3. Placing the X spool on the left feed bracket 221 and placing the O spool on the right feed bracket 207.
4. Starting with the marked position of the optical fiber adjacent the left flange 106 of spool 100, winding the first layer from the O
supply spool in the counterclockwise direction, moving from left to right, to complete the first layer.
supply spool in the counterclockwise direction, moving from left to right, to complete the first layer.
5. Winding one revolution in the counterclockwise direction from the O supply spool, adjacent the right flange 104, as part of the second layer.
6. Winding a spaced-apart alternate turns pattern in the clockwise direction from the X supply spool, moving from left to right.
7. Interchanging the X and O supply spools by moving the O
supply spool from the right bracket 207 to the left bracket 221 and moving the Xspool from the left bracket 221 to the right bracket 207.
supply spool from the right bracket 207 to the left bracket 221 and moving the Xspool from the left bracket 221 to the right bracket 207.
8. Winding an alternate turns pattern in the counterclockwise direction from the O supply spool between the turns of the ~Itl~nulting pattern of X fiber, moving from right to left, to complete the second layer.
9. Winding a spaced-apart alternate turns pattern in the clockwise direction from the X supply spool, moving from right to left.
21 7992~
21 7992~
10. I.lt~l.,hangillg the X and O supply spools by moving the X
supply spool to the left bracket 221 and the O supply spool to the right bracket207.
supply spool to the left bracket 221 and the O supply spool to the right bracket207.
11. Winding an alternate turns pattern between the alternate 5 turns of X fiber in the counterclochwise direction from the O supply spool, moving from left to right, to complete the third layer.
12. Winding a spaced-apart alternate turns pattern in the clochwise direction from the X supply spool, moving from left to right.
13. Interchanging the X and O supply spools by moving the X
10 supply spool to the right bracket 207 and the O supply spool to the left bracket 221.
10 supply spool to the right bracket 207 and the O supply spool to the left bracket 221.
14. Winding an alternate turns pattern between the alternate turns of X fiber in the counterclochwise direction from the O supply spool, moving from right to left, to complete the fourth layer.
15. Winding a spaced-apart alternate turns pattern in the countcl.,lo.,hwi~e direction from the O supply spool, moving left to right.
16. I..t~l~,Ld~-~ il-g the X and O supply spools by moving the X
supply spool to the left bracket 221 and the O supply spool to the right bracket207.
supply spool to the left bracket 221 and the O supply spool to the right bracket207.
17. Winding an alternate turns pattern between the alternate turns of the O fiber in the clockwise direction from the X spool, moving from right to left, to complete the fifth layer.
18. Repeating steps 5 through 17 for each of the groups of 4 layers (6) through (9), (10) through (13), etc., until the coil is completed.
As outlined above, the optical fiber sensing coil 100 is formed by winding an optical fiber on a spool 102 in the manner described herein. The completed coil 100 may be retained on the spool 102 and installed or used as an integrated assembly. Alt~ , the coil 100 may be removed from the spool 102 and installed or used as a ~ I;.,g coil. In a certain applications it is desirable to remove the spool 102 to reali~e weight and volume savings and 2~ 79920 ~ --12-potentially improve p~. r(" ".~ of the coil. The rLeP~ - ,.1",g coil may be formed by applying a bonding agent to the fiber segments to bond adjacent turns and adjacent layers together in order to form a cohesive coil 100, wherein the windings of the fiber segments will be retained in proper relationship to each S other. The process of bonding may be accomplished in a variety of methods which are well known in the art. A preferred method is to use optical fiber which has been pretreated with a bonding agent which possesses no adhesive properties until subjected to a curing process. Ideally, the bonding agent will not adhere to the spool on which the coil is wound during construction of the coil.
10 The spool may also be treated with a release coating or agent to reduce or prevent adherence. Once a coil has been formed on a spool in the winding process outlined earlier herein, the combination of the coil 100 and the spool 102 is subjected to a curing process to activate a bonding agent thereby bonding adjacent layers of turns of the fiber to each other. After curing, either one or15 both of the spool flanges 104, 106 can be removed from the spool 102 and the coil 100 can then be removed from the core 103 to yield a fl~ "li"g coil. As an alternative, a potting compound may be used. Instead of fiber segments provided with a bonding agent, a potting compound may be applied to the completed coil 100 and induced in spaces between the turns of optical fiber in a20 known manner. Once the potting compound cures, the coil 100 may be removed from the spool 102 in the manner described above. Another alternative is to apply an adhesive bonding agent during the winding process that can be cured as part of winding each layer or in the completed coil.
A procedure for winding a coil in the configuration shown in FIG.
25 1 is described above. The following procedure may be used to obtain a frePct~n-iing fiber optic coil. In addition to steps I through 18 outlined above, the following steps may be executed:
Prior to the first step, step 1, of the procedure for winding a coil on a spool outlined above, the total length of the fiber is coated with an adhesive coating and after the last step, step 18 of the above procedure, the following additional steps may be executed:
l. Curing the completed fiber coil to activate the adhesive coating and bond individual turns of the fiber together.
2. Removingthe flanges 104, 106.
3. Removing the completed coil from the spool core 103.
Alt~ la~ ly, a bonding agent may be applied to the fiber during the winding process and cured on a layer-by-layer basis or after several layers or the the entire coil have been wound.
FIG. 6 is a ~ lcs~ tion of a spool 202 comprising a spool core 203 and opposing side flanges 204 and 205. The core 203 is particularly adapted for the winding of a fiber optic sensing coil of the type described earlier herein.
As stated earlier herein, in accordance with the present invention the midpoint of the optical fiber is located at the a~ v~hlla~ midpoint of the innermost layer. In lS the embodiment shown in and described with respect to FIGS. I through 4, the coil is wound by starting the first layer along one side and placing successive turnsi",.,...ii,,t.1yadjacenteachother. Furthermore,thefirstlayerofacore, such as depicted in FIGS. l through 4, has a plurality of adjacent turns of fiber of one direction on one side of the center and a plurality of adjacent turns of the20 other direction on the other side of the center line.
FIG. 6 shows a spool 302 having a core 303 provided with a groove 3 lO extending between the opposing flanges 302,304 and parallel to the center line of the core. In winding the core, the midpoint of the optical fiber is placed in the groove at the midpoint of the groove, i.e., equal distant from the25 flanges 302 and 304. The first layer of the coil to be formed on the core is formed by winding the portion adjacent one of the two flanges 302, 304 in the clockwise direction and winding the portion of the fiber adjacent the other of the two flanges in the opposite direction. The two portions are wound toward opposite sides with successive turns being spaced apart such that windings of the 30 forward and reverse fiber sections are j u~taposed in the first layer in the same ~ -14- 2 1 79920 manner as other layers of the coil. The second and additional layers are wound in the same manner as described earlier with respect to FIGS. I through 4.
Accordingly, Altrrnq.~ing direction turns are disposed in juxtaposition in all layers, thereby further enhancing p~,. rO~ allce of the coil.
A common difficulty in winding the first layer of fibers on a spool such as a spool 102 is to maintain the fibers in proper spaced relationship to each other. FIG. 6 shows a plurality of circumferentially extending grooves in the surface of the core 303. Such core grooves may be formed by mqehining, or grinding, or etching. The grooves are preferably parallel rather than helical and 10 may be formed, for example, by electronic discharge mqrhining by introducing a coll.lu.,live wire in tangential contact with the core and rotating the core. With the first layer of the core formed in the parallel grooves, adjacent turns of the optical fiber forming the innermost layer are parallel for essentially one complete revolution and then are displaced to one side by a distance equivalent to one 15 diameter of the fiber. This concept is illustrated in FIG. 7 which is a side view of an optical fiber 305 wound on the core of FIG. 6, showing the area of di~l~ldc~.llle.lL of the adjacent turns. The ~ plq~Pment to one side may be facilitated by the formation of a flat area 312 on the surface of the core wherein the grooves have been removed from the core by machine processing as depicted 20 in FIGS. 8A and 8B. Alternatively, the di~lacc;lllc;lll may be formed in the surface of the core by electronic discharge mq~hining, or the like, in a manner such as depicted in FIG. 9.
It will be lln-lPr~tood that the above-described ArrqngPnnPn~ is merely illustrative of the application of the principles of the invention and that 25 numerous other arrqngemen~ may be devised by those skilled in the art without departing from the spirit and scope of the invention.
As outlined above, the optical fiber sensing coil 100 is formed by winding an optical fiber on a spool 102 in the manner described herein. The completed coil 100 may be retained on the spool 102 and installed or used as an integrated assembly. Alt~ , the coil 100 may be removed from the spool 102 and installed or used as a ~ I;.,g coil. In a certain applications it is desirable to remove the spool 102 to reali~e weight and volume savings and 2~ 79920 ~ --12-potentially improve p~. r(" ".~ of the coil. The rLeP~ - ,.1",g coil may be formed by applying a bonding agent to the fiber segments to bond adjacent turns and adjacent layers together in order to form a cohesive coil 100, wherein the windings of the fiber segments will be retained in proper relationship to each S other. The process of bonding may be accomplished in a variety of methods which are well known in the art. A preferred method is to use optical fiber which has been pretreated with a bonding agent which possesses no adhesive properties until subjected to a curing process. Ideally, the bonding agent will not adhere to the spool on which the coil is wound during construction of the coil.
10 The spool may also be treated with a release coating or agent to reduce or prevent adherence. Once a coil has been formed on a spool in the winding process outlined earlier herein, the combination of the coil 100 and the spool 102 is subjected to a curing process to activate a bonding agent thereby bonding adjacent layers of turns of the fiber to each other. After curing, either one or15 both of the spool flanges 104, 106 can be removed from the spool 102 and the coil 100 can then be removed from the core 103 to yield a fl~ "li"g coil. As an alternative, a potting compound may be used. Instead of fiber segments provided with a bonding agent, a potting compound may be applied to the completed coil 100 and induced in spaces between the turns of optical fiber in a20 known manner. Once the potting compound cures, the coil 100 may be removed from the spool 102 in the manner described above. Another alternative is to apply an adhesive bonding agent during the winding process that can be cured as part of winding each layer or in the completed coil.
A procedure for winding a coil in the configuration shown in FIG.
25 1 is described above. The following procedure may be used to obtain a frePct~n-iing fiber optic coil. In addition to steps I through 18 outlined above, the following steps may be executed:
Prior to the first step, step 1, of the procedure for winding a coil on a spool outlined above, the total length of the fiber is coated with an adhesive coating and after the last step, step 18 of the above procedure, the following additional steps may be executed:
l. Curing the completed fiber coil to activate the adhesive coating and bond individual turns of the fiber together.
2. Removingthe flanges 104, 106.
3. Removing the completed coil from the spool core 103.
Alt~ la~ ly, a bonding agent may be applied to the fiber during the winding process and cured on a layer-by-layer basis or after several layers or the the entire coil have been wound.
FIG. 6 is a ~ lcs~ tion of a spool 202 comprising a spool core 203 and opposing side flanges 204 and 205. The core 203 is particularly adapted for the winding of a fiber optic sensing coil of the type described earlier herein.
As stated earlier herein, in accordance with the present invention the midpoint of the optical fiber is located at the a~ v~hlla~ midpoint of the innermost layer. In lS the embodiment shown in and described with respect to FIGS. I through 4, the coil is wound by starting the first layer along one side and placing successive turnsi",.,...ii,,t.1yadjacenteachother. Furthermore,thefirstlayerofacore, such as depicted in FIGS. l through 4, has a plurality of adjacent turns of fiber of one direction on one side of the center and a plurality of adjacent turns of the20 other direction on the other side of the center line.
FIG. 6 shows a spool 302 having a core 303 provided with a groove 3 lO extending between the opposing flanges 302,304 and parallel to the center line of the core. In winding the core, the midpoint of the optical fiber is placed in the groove at the midpoint of the groove, i.e., equal distant from the25 flanges 302 and 304. The first layer of the coil to be formed on the core is formed by winding the portion adjacent one of the two flanges 302, 304 in the clockwise direction and winding the portion of the fiber adjacent the other of the two flanges in the opposite direction. The two portions are wound toward opposite sides with successive turns being spaced apart such that windings of the 30 forward and reverse fiber sections are j u~taposed in the first layer in the same ~ -14- 2 1 79920 manner as other layers of the coil. The second and additional layers are wound in the same manner as described earlier with respect to FIGS. I through 4.
Accordingly, Altrrnq.~ing direction turns are disposed in juxtaposition in all layers, thereby further enhancing p~,. rO~ allce of the coil.
A common difficulty in winding the first layer of fibers on a spool such as a spool 102 is to maintain the fibers in proper spaced relationship to each other. FIG. 6 shows a plurality of circumferentially extending grooves in the surface of the core 303. Such core grooves may be formed by mqehining, or grinding, or etching. The grooves are preferably parallel rather than helical and 10 may be formed, for example, by electronic discharge mqrhining by introducing a coll.lu.,live wire in tangential contact with the core and rotating the core. With the first layer of the core formed in the parallel grooves, adjacent turns of the optical fiber forming the innermost layer are parallel for essentially one complete revolution and then are displaced to one side by a distance equivalent to one 15 diameter of the fiber. This concept is illustrated in FIG. 7 which is a side view of an optical fiber 305 wound on the core of FIG. 6, showing the area of di~l~ldc~.llle.lL of the adjacent turns. The ~ plq~Pment to one side may be facilitated by the formation of a flat area 312 on the surface of the core wherein the grooves have been removed from the core by machine processing as depicted 20 in FIGS. 8A and 8B. Alternatively, the di~lacc;lllc;lll may be formed in the surface of the core by electronic discharge mq~hining, or the like, in a manner such as depicted in FIG. 9.
It will be lln-lPr~tood that the above-described ArrqngPnnPn~ is merely illustrative of the application of the principles of the invention and that 25 numerous other arrqngemen~ may be devised by those skilled in the art without departing from the spirit and scope of the invention.
Claims (32)
1. A substantially symmetrically wound coil of optical fiber comprising:
a plurality of turns of a first segment of optical fiber wound in a clockwise direction and a plurality of turns of a second segment of optical fiber wound in the counterclockwise direction;
the turns of the first segment and of the second segment together forming a plurality of layers of turns of optical fiber; and at least one of the layers comprising alternate, adjacent turns of the first and second segments of optical fiber.
a plurality of turns of a first segment of optical fiber wound in a clockwise direction and a plurality of turns of a second segment of optical fiber wound in the counterclockwise direction;
the turns of the first segment and of the second segment together forming a plurality of layers of turns of optical fiber; and at least one of the layers comprising alternate, adjacent turns of the first and second segments of optical fiber.
2. The coil in accordance with claim 1 and further comprising an inner layer having opposite ends and wherein the first and second segments each terminate in an end point and are joined at a midpoint of the optical fiber substantially equidistant from the end points and wherein the midpoint of the optical fiber is disposed between the opposite ends of the inner layer and substantially equidistant from the opposite ends of the inner layer.
3. The coil in accordance with claim 2 and comprising an inner layer having a plurality of turns of the first segment and of the second segment and second, third and fourth layers each having alternate, adjacent turns of the first and second segments and wherein the position of the turns of the first segment and of the second segment in the fourth layer, correspond directly to the position of the turns of the first and second segments in the second layer.
4. The coil in accordance with claim 2 and further comprising second, third, fourth and fifth layers of alternate, adjacent turns of the first and second segments and wherein the position of the turns of the firstsegment in the fifth layer correspond to the position of turns of the second segment in the third layer and wherein the position of turns of the second segment in the fifth layer corresponds to the position of turns of the first segment in the third layer.
5. The coil in accordance with claim 2 and further comprising a second and a third layer and a plurality of additional layers of alternate, adjacent turns of the first and second segments and wherein turns of the first and second segments in even numbered layers correspond in position directly to the position of turns of the first and second segments in the secondlayer and wherein turns of the first and second segments in odd numbered layers correspond in position directly to the positions of turns of the first and second segments of the third and fifth layers.
6. The coil in accordance with claim 5 wherein the inner layer comprises an even number of turns of the optical fiber.
7. A substantially symmetrically wound coil of optical fiber of substantially uniform circular cross-section, the coil comprising:
a plurality of turns of a first segment of the optical fiber wound in a clockwise direction and a plurality of turns of a second segment of the optical fiber wound in the counterclockwise direction;
the turns of the first segment and of the second segment together forming a plurality of layers of the optical fiber and grooves are formed between immediately adjacent turns in a layer;
the turns of each layer of the optical fiber partially disposed in the grooves formed in an adjacent layer.
a plurality of turns of a first segment of the optical fiber wound in a clockwise direction and a plurality of turns of a second segment of the optical fiber wound in the counterclockwise direction;
the turns of the first segment and of the second segment together forming a plurality of layers of the optical fiber and grooves are formed between immediately adjacent turns in a layer;
the turns of each layer of the optical fiber partially disposed in the grooves formed in an adjacent layer.
8. The coil in accordance with claim 7 wherein adjacent layers have alternating odd and even numbers of turns.
9. The coil in accordance with claim 7 and comprising laterally spaced-apart sides and wherein adjacent layers have equal numbers of turns and each layer is laterally displaced from one of the sides by a distance of substantially equal to one-half the diameter of the circular cross-section.
10. A method of forming an optical fiber sensing coil comprising a plurality of layers by winding an optical fiber of predetermined length and diameter on a spool having axially spaced apart side flanges, the fiber having a forward segment and a reverse segment, the method comprising the steps of:
forming a first layer by winding a portion of the fiber on the spool such that portions of the forward and reverse segments are disposed adjacent opposite side flanges;
forming a second layer by winding a portion of the forward segment in an alternate turns pattern on the first layer such that adjacent turns of the forward segment are spaced apart by a distance substantially equal to the diameter of the optical fiber and winding a portion of the reverse segment in an alternate turns pattern on the first layer between the turns of the alternate turns pattern of the forward segment.
forming a first layer by winding a portion of the fiber on the spool such that portions of the forward and reverse segments are disposed adjacent opposite side flanges;
forming a second layer by winding a portion of the forward segment in an alternate turns pattern on the first layer such that adjacent turns of the forward segment are spaced apart by a distance substantially equal to the diameter of the optical fiber and winding a portion of the reverse segment in an alternate turns pattern on the first layer between the turns of the alternate turns pattern of the forward segment.
11. The method in accordance with claim 10 wherein the spool comprises a spool midpoint disposed axially equidistant from the side flanges and the fiber has opposite ends and a fiber midpoint substantially equidistant from the opposite ends and the forward and reverse segments extend in opposite directions from the fiber midpoint, and wherein the step of forming the first layer comprises winding the first layer such that the fiber midpoint is in substantial alignment with the spool midpoint.
12. The method in accordance with claim 10 and further comprising the step of forming additional layers with each comprising alternate turns of the forward segment and of the reverse segment.
13. The method in accordance with claim 12 wherein the steps of forming the second layer and the additional layers comprises forming a coil of adjacent layers with alternating odd and even numbers of turns.
14. The method in accordance with claim 13 wherein the steps of forming the second layer and the additional layers comprises winding a next layer such that the turns of the next layer are disposed in grooves formed between turns of the immediately preceding layer.
15. The method in accordance with claim 10 wherein the steps of forming the second layer comprises winding the turns of the forward segment in a first rotational direction and winding the turns of the reverse segment in a second rotational direction, opposite to the first rotational direction.
16. The method in accordance with claim 10 and further comprising the step of winding an additional turn of the reverse segment adjacent one of the flanges to form a turn of a second layer before the step of forming the second layer.
17. The method in accordance with claim 10 wherein the step of forming the first layer comprises forming an odd number of turns of the optical fiber in the first layer and the step of forming the second layer comprises forming an even number of turns of the optical fiber in the second layer.
18. The method in accordance with claim 10 and further comprising the step of forming a third layer of alternate turns of the forward segment and of the reverse segment and the step of forming a fourth layer of alternating turns of the forward and reverse sections such that the section of the turns of the forward and reverse segments in the fourth layer, relative to the side flanges, correspond directly in position to the turns of the second layer, relative to the side flanges.
19. The method in accordance with claim 18 and further comprising the step of forming a fourth layer of alternate turns of the forward segment and the reverse segment such that the position of the turns of the forward segment of the fourth layer, relative to the side flanges, correspond to the position of the turns of the reverse segment of the second layer, relative to the side flanges, and the position of the turns of the reverse segment of thefourth layer, relative to the side flanges, corresponds to the position of the turns of the forward segment of the of the second layer, relative to the side flanges.
20. The method in accordance with claim 19 and further comprising the step of forming a fifth layer such that the position of the turnsof the forward segment of the fifth layer, relative to the side flanges, correspond to the position of the turns of the reverse segment of the third layer, relative to the side flanges and the position of the turns of the reversesegment of the fifth layer, relative to the flanges, correspond the position of the turns of the forward segment of the third layer, relative to the flanges.
21. The method in accordance with claim 20 and further comprising the steps of forming sixth, seventh, eighth and ninth layers of alternate turns of the forward and reverse segments such that the positions of the turns of the forward and reverse sections of the sixth layer, relative to the side flanges, correspond to the position of the turns of the forward and reverse segments of the second layer, relative to the side flanges, and the positions of the turns of the forward and reverse segments of the seventh layer, relative to the side flanges, correspond to the positions of the turns ofthe forward and reverse segments of the third layer and the positions of the turns of the forward and reverse segments of the eighth layer, relative to the side flanges, correspond to the positions of the turns of the forward and reverse segments of the fourth layer, relative to the side flanges, and the positions of the turns of the forward and reverse segments of the ninth layer, relative to the side flanges, correspond to the position of the burns of the forward and reverse segments of the fifth layer, relative to the side flanges.
22. The coil in accordance with claim 1 wherein the coil has an axis of rotation and a greater part of each turn of the plurality of turns ofthe optical fiber has a tangential component extending perpendicular to the axis of rotation.
23. A spool for supporting a sensing coil formed of a plurality of turns of an optical fiber, the spool comprising a cylindrically shaped core having an axis of rotation and an outer surface and a longitudinally extending groove in the outer surface extending parallel to the longitudinally axis.
24. The spool in accordance with claim 23 and further comprising a plurality of parallel, circumferentially extending grooves in the outer surface, the grooves each extending perpendicularly to the axis of rotation and formed to receive a portion of the optical fiber.
25. A method of forming an optical fiber sensing coil comprising a plurality of layers by winding an optical fiber of predetermined length on a spool having a core with axially spaced apart opposite ends, the core having an axis of rotation and an outer surface and a longitudinally extending groove in the outer surface extending between the opposite ends and parallel to the longitudinally axis, the groove having a midpoint substantially equidistant from the opposite ends of the core, the fiber having opposite ends and a fiber midpoint substantially equidistant from the opposite ends of the fiber and a forward segment disposed on one side of the midpoint of the fiber and a reverse segment disposed on another side of the midpoint of the fiber, the method comprising the steps of:
placing portion of the fiber in the groove such that the mid point of the fiber is disposed in substantial alignment with the midpoint of the groove and such that a portion of the forward segment and a portion of the reverse segment are disposed adjacent opposite ends of the core;
forming a first layer by winding a portion of the forward segment in one direction in an alternate turns pattern on the surface of the core such that adjacent turns of the forward segment are spaced apart by a distance substantially equal to the diameter of the optical fiber and winding a portion of the reverse segment in a direction opposite the one direction in an alternate turns pattern on the core and between the turns of the alternate turnspattern of the forward segment.
placing portion of the fiber in the groove such that the mid point of the fiber is disposed in substantial alignment with the midpoint of the groove and such that a portion of the forward segment and a portion of the reverse segment are disposed adjacent opposite ends of the core;
forming a first layer by winding a portion of the forward segment in one direction in an alternate turns pattern on the surface of the core such that adjacent turns of the forward segment are spaced apart by a distance substantially equal to the diameter of the optical fiber and winding a portion of the reverse segment in a direction opposite the one direction in an alternate turns pattern on the core and between the turns of the alternate turnspattern of the forward segment.
26. The method in accordance with claim 25 and further comprising the step of forming additional layers with each additional layer comprising alternate turns of the forward segment and of the reverse segment.
27. The method in accordance with claim 26 wherein the steps of forming the second layer and the additional layers comprises winding a next layer such that the turns of the next layer are disposed in grooves formed between turns of the immediately preceding layer.
28. The method in accordance with claim 10 wherein the fiber is coated with a bonding agent requiring a curing process for proper activation and wherein the method further comprising the step of applying a bonding process after the step of forming the second layer, thereby bonding adjacent layers of the coil together, and the step of removing the coil from thespool.
29. The method in accordance with claim 10 and further comprising the step of applying a potting compound to the coil and the step of curing the compound and the step of removing the coil from the core after the step of curing.
30. The spool in accordance with claim 24 and further comprising a substantially flat portion on the outer surface extending parallel to the axis of rotation to provide an area for lateral displacement of optical fiber to be wound on the spool.
31. The spool in accordance with claim 24 and comprising opposing sides and wherein the grooves each comprise a portion displaced toward one of the sides of the spool to facilitate the winding of a coil of fiber having a section displaced toward the one of the sides of the spool.
32. The method in accordance with claim 10 wherein the turns of the fiber are bonded in place with a bonding agent during the bonding process.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2179920 CA2179920A1 (en) | 1996-06-25 | 1996-06-25 | Optical fiber coil and method of winding |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2179920 CA2179920A1 (en) | 1996-06-25 | 1996-06-25 | Optical fiber coil and method of winding |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2179920A1 true CA2179920A1 (en) | 1997-12-26 |
Family
ID=4158481
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2179920 Abandoned CA2179920A1 (en) | 1996-06-25 | 1996-06-25 | Optical fiber coil and method of winding |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2179920A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114993283A (en) * | 2022-08-02 | 2022-09-02 | 武汉利科夫科技有限公司 | Optical fiber winding method capable of accurately controlling turn-changing area of optical fiber loop |
-
1996
- 1996-06-25 CA CA 2179920 patent/CA2179920A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114993283A (en) * | 2022-08-02 | 2022-09-02 | 武汉利科夫科技有限公司 | Optical fiber winding method capable of accurately controlling turn-changing area of optical fiber loop |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5841932A (en) | Optical fiber coil and method of winding | |
| US7477806B2 (en) | Crossover-free fiber optic coil sensor and winding method | |
| JPS61296211A (en) | Method of forming coil for optical-fiber gyroscope and optical fiber coil formed through said method | |
| EP0616196B1 (en) | A fibre optic gyroscope sensing coil | |
| EP0624777B1 (en) | Method for tuning fiber optic sensor coils | |
| US5351900A (en) | Method of manufacture of quadrupole-wound fiber optic sensing coil | |
| EP0736189B1 (en) | Optical fiber coil and method of winding | |
| CA2179920A1 (en) | Optical fiber coil and method of winding | |
| JPH07103771A (en) | Flange-support type sensor coil for fiber-optic gyroscope | |
| EP0699892B1 (en) | Multilayer fiber optic coil | |
| JP2727030B2 (en) | Optical fiber winding trimming | |
| US5506923A (en) | Apparatus and method for trimming of fiber optic winding | |
| EP0874219A3 (en) | Fiber optic gyroscope | |
| CA2236884C (en) | Negative trimming of fiber optic winding | |
| EP1123486B1 (en) | Winding pattern for fiber optic coils | |
| EP1141752A2 (en) | Support structure for fiber optic coil | |
| JP2000503765A (en) | Negative trimming of optical fiber windings |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |