Rapid reinforcement for fusion mass-spliced fibers usinglow-power induction heating
Toshiaki Katagiri, Norio Murata, and Masao Tachikura
A rapid reinforcement method using low-power induction heating is developed. The reinforcement of amass-spliced fiber ribbon unit comprising five graded-index multimode fibers was completed in 30 sec withgood performance by supplying 30 W of electric power.
1. Introduction
Some reinforcement is necessary for spliced fibers tosuppress the strength degradation of the spliced portionand prevent optical loss from changing at the splice.Furthermore, to splice fibers quickly, a short rein-forcement time is required. A mass-splice reinforce-ment technique for fiber ribbon units comprising fivegraded-index multimode fibers1 had been developedpreviously, but the total reinforcement time with thismethod was 5 mins, and there is a need to shorten thereinforcement time because of the thermal resistancebetween the heaters and the glass-ceramic substrates.On the other hand, the induction heating operation forsingle-splice reinforcement has been done using a re-modeled cooking machine curently on the market.2 Itis true that the induction heating method is promising,but it has the disadvantage of using high electric powerof the order of 1 kW. There has been no small induc-tion heating device using low electric power of the orderof 10 W. This paper presents a new rapid reinforcementmethod using low-power induction heating. The re-inforcement machine, analysis of the transient tem-perature distribution of the heated substrate, and re-sulting reinforcement performance are described.
11. Reinforcement Method
The basic construction of the mass-splice reinforce-ment method using induction heating is illustrated inFig. 1. The reinforcing assembly has two substratesmade of clear glass-ceramics and (36Ni) Permalloy withhot-melt adhesive films 0.4 and 0.5 mm thick, respec-tively. The linear expansion coefficient of the Per-malloy is so small (1.2 X 10- 6/deg) that splice loss sta-
The authors are with NTT baraki Electrical CommunicationLaboratory, Tokai, Ibaraki-ken 319-11, Japan.
bility can be maintained against surrounding temper-ature change because little thermal stress occurs. Theelectric circuit for induction heating consists of seveninduction coils with 3-3-4-5-4-3-3 turns of wire, acondenser, switching transistor, and dc power source.The seven coils are excited when dc power is suppliedto the resonance circuit (L = 7 ,uH, C = 0.9 AF) throughthe switching transistor whose switching frequency isregulated to the resonance frequency of the circuit. Atthis time, each portion of the Permalloy substrate,which is opposite the four open magnetic cores, is in achanging magnetic field where joule's heat occurs. Thetransmissible power from the dc power source to thePermalloy substrate was approximately half of thesupplied electric power, which was obtained by ana-lyzing the measured voltage and current wave forms atboth the dc power source and induction coils.
Ill. Thermal Design
To improve the adhesive property by melting theadhesive films at a high temperature without meltingthe fiber's nylon coat, a thermal gradient from themiddle to the ends must be given to the Permalloysubstrate by designing the number of turns of each in-duction coil. Eddy current loss W as mentioned belowis proportional to the square of the magnetic field in-tensity, in other words, to the square of the number ofturns of the induction coil when the electric current isconstant. The transient temperature distribution ofthe Permalloy substrate in the longitudinal directionis estimated by the following 1-D heat conductionequation:
OT a2T W aP
d = a - +-- - (T - Tr),at Ox2 PC PCs(1)
where T is the temperature, t the time, x the coordinate,a the thermal diffusivity, W the eddy current loss perunit volume and time, p the specific weight, c the spe-cific heat, P the surface area per unit length of thePermalloy substrate, S the cross-sectional area of thePermalloy substrate, ae the equivalent heat transfer
Press Spliced bare fiberFiber's nylon coat Xunit _0
= | T~~~~hermal
Magnetic Induction coils (t=0.4mm)core -
Condenser Switching
]DC power transistor
1 Glass-ceramics substrate (70x 5mm, t=1 .5mm)
2 Hot-melt adhesive film
3 Permalloy substrate (70X 5mm, t=0.5mm)
Fig. 1. Basic construction of mass-splice reinforcement method usinginduction heating.
300
0
I-
I-
20
10
0 15 30
TIME (sec)
Fig. 2. Temperature rise characteristic of the Permalloy substrate.
0.10
w
':
: 0.05z
0-j0 L-75 -50 0 30
TEMPERATURE (C)
Fig. 3. Optical loss increase at low temperature for fiber with fivereinforced splice portions.
coefficient characterized by this system, and Tr thesurrounding temperature.
Numerical methods3 can be used by changing thepartial differential equation (1) into a finite differenceequation and giving a boundary condition with regardto heat transfer from the surface of the Permalloysubstrate. The temperature rise characteristic at themiddle and end of the Permalloy substrate when 30-Wdc electric power is supplied is shown in Fig. 2. Thesolid and dashed curves represent the measured results,the open circles and triangles represent the computersimulation results obtained by giving the physicalconstants and dimensions of the Permalloy substrateto Eq. (1) assuming c to be 0.000105 J/(mm 2 s deg)and letting the eddy current loss W not vary withtime.
It can be seen from Fig. 2 that the measured resultsagreed approximately with the simulation results for thetemperature rise characteristic. The difference be-tween the measured and simulated results is believedto be caused strictly by the fact that the actual eddycurrent loss W changes a little with time, which is dueto the decrease in the magnetic permeability of thePermalloy substrate with its temperature rise. Thereinforcement procedure takes -30 sec, the sum of theheating and cooling times; both times were approxi-mately the same. The reinforcement time becameone-tenth of that required by the conventional electri-cal-resistance heating method.1 This short reinforce-ment time was achieved by heat generation in the Per-malloy substrate itself and heat transfer from the Per-malloy substrate which has small thermal capacity.Because the proper thermal gradient was given to thePermalloy substrate, the adhesive films melted at a hightemperature of 2000 C without melting the fiber's nyloncoat.
IV. Reinforcement Performance
The low-temperature dependence of optical loss forfive reinforced portions located every 2 m is shown inFig. 3. There are five splice points at each reinforcedportion because a fiber ribbon unit comprises five fibersof GI 50/125 type. The loss increase was measured foreach fiber which was spliced at five reinforced points.The loss change was plotted relative to the loss at 200C.It was found that the average loss increase for the sumof the five reinforced portions was <0.05 dB in thetemperature range of 20'C to -70'C, so that the aver-age loss increase for a reinforced splice portion was-0.01 dB in its temperature range. It was also experi-mentally shown that there was no loss increase of thefiber unit itself in its temperature range. For this rea-son, the loss increase mentioned above was caused onlyby reinforcement. On the other hand, a heat cycle testwith 3 cycles/day between -30 and 60'C was examinedfor 56 cycles. The maximum loss change for the fivereinforced portions was <0.05 dB during the test.Moreover, the average tensile strength increase betweenthe unreinforced and reinforced mass-splice was -3.5kgf, which is comparable with that of the conventionalreinforcement method.1
A new reinforcement method using induction heatingfor a mass-spliced fiber ribbon unit comprising fivegraded-index multimode fibers has been developed.The reinforcement time was one-tenth of that requiredby the conventional electrical-resistance heatingmethod. The adhesive property is improved by meltingthe adhesive films at 200'C without melting the fiber'snylon coat, which is achieved by giving the properthermal gradient to the Permalloy substrate. The av-erage and maximum loss changes for the sum of the fivereinforced portions are <0.05 dB in both the low-tem-perature test (+20 - -70'C) and heat cycle test (-30
+600C). Moreover, the tensile strength of the rein-forced mass-splice was comparable with that of theconventional reinforcement method.
The advantage of this method is to be able to useelectric power supplied by a battery.
The authors would like to thank Shinya Kojima,Naoya Uchida, Masamitsu Tokuda, and Ryosuke Ari-oka for their helpful suggestions and encouragement.
References1. M. Tachikura and N. Kashima, "Fusion Mass-Splices for Optical
Fibers Using High-Frequency Discharge," IEEE/OSA J. Light-wave Technol. LT-2, (1984).
2. N. Murata, M. Hoshino, and S. Yamakawa, "High-Speed FusionSplice Packages Using Internal Heat Sources," Electron. Lett. 20,1025 (1984).
3. H. W. Emmons, "The Numerical Solution of Partial DifferentialEquations," Q. Appl. Math. 173 (1944).
Meetings Calendar continued from page 1707
1986February
13-14 Optical Fiber Sensors, OSA Top. Mtg., San DiegoOSA Mtgs. Dept., 1816 Jefferson Pl., N.W., Wash.,D.C. 20036
24-26 Optical Fiber Communication Conf., Atlanta OSAMtgs. Dept., 1816 Jefferson Pl., N.W., Wash., D.C.20036
26-28 Integrated & Guided-Wave Optics Top. Mtg., Atlan-ta OSA Mtgs. Dept., 1816 Jefferson Pl., N.W.,Wash.,D.C. 20036
March
9-14 Microlithography Conf., Santa Clara SPIE, P.O. Box 10,Bellingham, Wash. 98227
4,483,617 20 Nov. 1984 (Cl. 356-350)Optical gyroscope with large propagation constant differ-ence.H. MATSUMURA, T. KATSUYAMA, and T. SUGANUMA. As-signed to Hitachi, Ltd. Filed 3 Mar. 1982.
This patent describes a fiber-optic gyroscope of conventional design withlinear polarized input beams. The optical fiber develops orthogonal principalaxes in the fiber optic by a design that comprises at least three concentric layersof a core, clad, and jacket with the clad layer having an elliptic contour whichhas major and minor axes corresponding to the orthogonal principal axes.
W.N.P.
4,485,473 27 Nov. 1984 (Cl. 371-18)Mode locking of travelling wave ring laser by amplitude mod-ulation.C. L. TANG, N. A. OLSSON, and J.-M. HALBOUT. Assigned toCornell Research Foundation, Inc. Filed 29 Apr. 1982.
This patent describes an amplitude modulator for a tunable ring cavity dyelaser. The modulator is operated in time synchronization with the laser pumpand is located asymmetrically within the ring to attenuate dye laser pulses inone direction while passing pulses in the opposite direction, thereby producinga mode-locked unidirectional traveling wave. The use of a low dispersionelectrooptical modulator in a dye laser yields subpicosecond optical pulses withwide tunability. W.N.P.
4,487,472 11 Dec. 1984 (Cl. 350-3.71)Light beam scanning apparatus.E. ASANO. Assigned to Minolta Camera K. K. Filed 2 July1982.
This patent describes use of a prism to correct the curve scan line from aholographic disk scanner. The curve scan line is the result of change in thedeflection angle of the laser beam both in the scanning direction and also normalto the scanning direction. With a prism having a vertex angle of 600 and averageincidence angle of 60.16752°, the variation of the deflection angles emergingfrom the prism is greatly minimized. In an example worked out in the patent,the deviation between the center of the scan line to the end of the scan line isonly 0.0132 mm over a 310-mm scan length. W.-H.L.
4,487,476 11 Dec. 1984 (Cl. 350-162.13)Method of multivariant intraclass pattern recognition.C. F. HESTER and D. P. CASASENT. Assigned to U.S.A. as rep-resented by Secretary of the Air Force. Filed 28 Apr. 1981.
The title, abstract, and discussion of this invention relate to some of the au-thors' work on the design of appropriate filters for use in optical pattern rec-ognition. I have often wondered how such designs can be patented. The in-teresting observation is that the claims appear to barely describe this methodand embrace many other preceding and following methods. What is claimedis "a multiclass reference function" or "an average filter of said multiclass ref-erence function." My basic question remains unanswered. H.J.C.
4,488,041 11 Dec. 1984 (Cl. 250-231 GY)Device for measuring the coordinates of a rotating sphere andprocess for manufacturing part of this device.J.-J. BAUDOT. Assigned to Societe Anonyme de Telecommunica-tions. Filed 14 May 1982 (in France 18 May 1981).
This patent describes a method used to monitor rotation of a spherical solid(such as a gyroscopic spinner) about the axes of a Cartesian coordinate systemcentered at the spherical center. The spherical surface is prepared to be ap-propriately patterned for absorption and reflection so as to absorb and reflectelectromagnetic radiation as the sphere spins and thus provide signals to de-tectors which can be analyzed to determine axes orientation. In some caseswhere geometry prohibits their use, the need for angle encoders can therebybe avoided. The figure represents one possible embodiment for such asphere. R.L.A.
+ x max
-xmax , flll liii}
4,488,039 11 Dec. 1984 (Cl. 250-216)Imaging system having vari-focal lens for use in endoscope.M. SATO, N. ARAI, Y. SUNAGA, and M. INUIYA. Assigned to FujiPhoto Film Co., Ltd. and Fuji Photo Optical Co., Ltd. Filed 3 Sept.1982.
This patent describes an electromechanical means for adjusting the positionof the distal optics of a flexible endoscope. The movable optics either changethe magnification of a zoom system or focus on a chosen object plane. Thesystems described in the claims use a solid-state imaging device at the distalend of the endoscope. D.C.L.
4,458,980 10 July 1984 (Cl. 350-3.73)Optical reproducing head.H. OHKI and C. KOJIMA. Assigned to Sony Corp. Filed 23 Sept.1980.
This patent describes the use of a holographic lens to generate a focused beamfor use in an optical data recording system. R.A.B.
4,491,394 1 Jan. 1985 (Cl. 350-414)
Image-forming lens system.M. MATSUBARA. Assigned to Olympus Optical Co., Ltd. Filed25 May 1982 (in Japan 26 May 1981).
Three embodiments are given of an imaging system for use following a mi-croscope objective that has been designed to yield a parallel beam. Ordinarilysuch an image former consists of a cemented or airspaced doublet, while in thepresent invention the system contains three, four, or five elements to give im-proved aberration correction. In each case the pupil (i.e., the microscope ob-jective) is at 40 or 50 mm to the left, while the final image is at -65 mm to theright. R.K.
4,491,395 1 Jan. 1985 (Cl. 350-427)Zoom lens system.S. OKUDAIRA. Assigned to Asahi Kagaku Kogyo K.K. Filed 16Feb. 1982 (in Japan 16 Feb. 1981).
Two examples are given of a conventional zoom lens for 8-mm cameras ora home VTR camera. In each example the front positive component containsthree or four elements, the negative variator contains three elements, the neg-ative compensator one element, and the fixed rear component eight or ten el-ements. The design is controlled by five conditions. The two examples are:
4,493,217 15 Jan. 1985 (Cl. 73-861.27)Process and apparatus for measuring travel time differencesof ultrasonic pulses for the determination of flow fields.R. ENGLER and R. WULF. Assigned to Deutsche Forschungs- undVersuchsanstalt fur Luft- und Raumfahrt. Filed 17 Aug 1982 (in Fed.Rep. Germany 18 Aug. 1981).
This patent describes the use of optical schlieren systems to determine thetimes of arrival of an ultrasonic pulse at various points in a gaseous medium.The intent is to determine the velocity of the pulse as a measure of velocitycomponents of the medium, and wind tunnels are mentioned as a particularapplication. No data are presented on the expected signal or noise levels.
13 Nov. 1984 (Cl. 250-201) 4,496,223Optical sensor for focusing control.J.-P. LACOTTE, B. FICHOT, and G. TROUDE. Assigned toThomson-CSF. Filed 22 Mar. 1982.
This patent describes a simplified optical system using one prism to producethe required optical beam which generates an error signal for focus control inan optical data recording system. R.A.B.
4,493,536 15 Jan. 1985 (Cl. 350-462)Inverted telephoto type lens system.Y. KUDO. Assigned to Minolta Camera K.K. Filed 25 Mar. 1982(in Japan 31 Mar. 1981).
Four examples are given of a 28-mm lens with aperture f/2.8 and a back focaldistance of 36 mm. The design consists of a large negative meniscus elementin front and four airspaced elements in order (+-++) behind, elements twoand three being quite thick. The design is controlled by eight conditions.
R.K
4,494,819 22 Jan. 1985 (Cl. 350-1.4)Telescope objective system for the infrared range.M. 0. LIDWELL. Assigned to Barr & Stroud, Ltd. Filed 29 Dec.1983. Continuation of Ser. 234,439 abandoned.
A family of infrared telephoto lenses is described consisting of three elements,the front element being of germanium and at least one of the others being ofchalcogenide glass. These lenses are achromatic over the 8-13-pum range andare compensated for shifts in the focal plane caused by ambient temperaturevariations. With only spherical surfaces, near-diffraction-limited performanceis claimed at 10 Am with a flat focal plane and 6° field for relative apertures off/2 to f/3. By making one surface of the first element aspheric, the same per-formance can be achieved at f/1.5. R.A.
4,494,828 22 Jan. 1985 (Cl. 350-427)Zoom lens system of relatively high zoom ratio ranging to wideangle photography.H. MASUMOTO and S. OGINO. Assigned to Minolta Camera K.K.Filed 8 Apr. 1982 (in Japan Apr. 1981 and Jan. 1982).
Seventeen embodiments are disclosed of a zoom lens intended for use on anSLR camera, the shortest focal length being 35 mm and the aperture f/3.5 tof/4.5. Although the main plan is conventional with a positive focusing memberin front, a negative variator, a compensator, and a fixed positive relay system,the various embodiments include relative movements between portions of thesefour members aimed at improving the aberration correction over a long rangeof focal lengths, the maximum varying from 82 to 195 mm. The number of el-ements varies from twelve to seventeen in the different embodiments. R.K.
4,494,829 22 Jan. 1985 (Cl. 350-464)Curved field photographic objective.G. H. AKLIN, deceased, and M. M. AKLIN. Filed 20 Sept. 1982.
A complex f/2.8 objective covering +25' is described intended to be con-structed in a 6-in. focal length having a slightly inward-curving field with vir-tually no astigmatism. The lens contains ten elements, and the aberrationsare exceptionally well corrected. The refractive indices of the glasses rangefrom 1.65 to 1.81. R.K.
4,497,534 5 Feb. 1985 (Cl. 350-3.72)Holographic optical head.G. T. SINCERBOX. Assigned to International Business MachinesCorp. Fil6d 28 Feb. 1983.
This patent describes a holographic optical head for imaging a laser diodefor optical data storage applications. The optical head consists of four holo-grams. Three holograms are used for imaging purposes. One volume hologramis used as a polarization beam splitter. In a preferred embodiment of this in-vention, the optical head is integrated to contain the laser diode, detector, andnecessary holograms. The integrated optical head would be small and lightweight and move as one unit during focus servoing. W.-H.L.
68,
80-
64 66 (62
Compact afocal attachment for use with photographic objec-tives.J. G. BAKER. Assigned to Polaroid Corp. Filed 4 Nov. 1981.
A low cost f/10 convertible lens system is described consisting of a fixedmeniscus element convex toward the front made of molded plastic material witha rear aspheric surface and a rear stop. To increase the focal length by a factorof 1.3X, an afocal Galilean system can be moved in front of the main lens. Thisconsists of one or two positive menisci and a negative meniscus. These elementsmay be of plastic material with one or more aspheric surfaces or of glass withspherical surfaces. R.K.
4,497,546 5 Feb. 1985 (Cl. 350-410)Wide-field eyepiece.Y. KOBAYASHI. Assigned to Olympus Optical Co., Ltd. Filed 8Apr. 1983 (in Japan 19 Apr. 192).
Four embodiments are given of a 25-mm (lOX) microscope eyepiece coveringan apparent field of ±261/2h. The eyepiece consists of a positive cementeddoublet located some 13 mm ahead of the internal real image followed by afurther space of 8 mm, then a negative cemented doublet and two thin positiveelements. The eyepiece has an unusually long eye relief of 19-20 mm, and itis exceptionally well corrected for spherical aberration of the exitpupil. R.K.
Three embodiments are given of a conventional four-component zoom lenscovering 50-135mm atf/3.5. The front positive component has three elements,the negativ&variator has three elements, the negative compensator has one ortwo elements, and the fixed rear relay has eight elements, making fifteen orsixteen elements in all. The design is controlled by eight conditions. R.K.
4,498,729 12 Feb. 1985 (Cl. 350-3.69)Method and apparatus for making achromatic holograms.S. A. BENTON. Assigned to Polaroid Corp. Filed 13 Aug. 1979.
This patent describes a method for making achromatic holographic imagesof an object. The achromatization is done by using a diffraction grating madewith multiple light sources. To produce the desired hologram one first makesa conventional hologram of an object on a photographic plate. A second ho-logram is then made from the image reconstructed from a narrow strip of thefirst hologram. The reconstructed image is projected onto the second hologramthrough the multiple-beam diffraction grating. The principle behind this re-cording method is discussed in details with many illustrations. W.-H.L.
~42 \-H Z L
Io .j 4
1 en H '
68 60
74
78
4,498,741 12 Feb. 1985 (Cl. 350-427)Compact, wide magnification-variable zoom lens.S. ISHIYAMA. Assigned to Konishiroku Photo Industry Co., Ltd.Filed 1 Apr. 1982 (in Japan 3 Apr. 1981).
Seven examples are given of a complex zoom system in which five componentsall move during a zoom. The components are, in order, a positive with threeelements, a negative with four elements, a positive with three elements, a neg-ative with three elements, and a rear positive with five elements, making eigh-teen elements in all. The focal length ranges from 29 or 36 to 100 or 133 mmat f/3.8 to f/4.2, and the back focus varies by a small amount during a zoom.The design is controlled by eight conditions. R.K.
