Source: http://www.google.com/patents/US5160522?dq=6377161
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Patent US5160522 - Method for producing preform for polarization retaining optical fiber - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA preform for a polarization retaining optical fiber is produced by making at least two bores symmetrically around a center axis of a preform comprising a core part and a cladding part which surrounds the core part, decreasing a diameter of one end of each bore, or connecting a glass tube to one end...http://www.google.com/patents/US5160522?utm_source=gb-gplus-sharePatent US5160522 - Method for producing preform for polarization retaining optical fiberAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS5160522 APublication typeGrantApplication numberUS 07/741,043Publication dateNov 3, 1992Filing dateAug 6, 1991Priority dateAug 9, 1990Fee statusPaidAlso published asCA2048745A1, CA2048745C, DE69102599D1, DE69102599T2, EP0470591A1, EP0470591B1Publication number07741043, 741043, US 5160522 A, US 5160522A, US-A-5160522, US5160522 A, US5160522AInventorsMasahiro Takagi, Hiroshi Suganuma, Hiroo KanamoriOriginal AssigneeSumitomo Electric Industries, Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (8), Referenced by (6), Classifications (7), Legal Events (5) External Links: USPTO, USPTO Assignment, EspacenetMethod for producing preform for polarization retaining optical fiber
US 5160522 AAbstract
A preform for a polarization retaining optical fiber is produced by making at least two bores symmetrically around a center axis of a preform comprising a core part and a cladding part which surrounds the core part, decreasing a diameter of one end of each bore, or connecting a glass tube to one end of the preform, the glass tube having a part with a smaller inner diameter near its end which is connected to the preform, inserting a first glass rod, a stressing member and a second glass rod in this order from the other end of each bore or from an end of each bore which is remote from the connected glass tube, contacting the first glass rod to the diameter-decreased end of each bore or to the part with a smaller inner diameter of the glass tube, and heating and fusing the second glass rod to the preform.
1. A method for producing a preform for a polarization retaining optical fiber which comprises steps of:making at least two bores positioned symmetrically around a center axis of a preform comprising a core part and a cladding part which surrounds the core part, connecting one end of a glass tube to one end of said preform, said glass tube having a part with a smaller inner diameter near its one end which is connected to said preform, inserting a first glass rod, a stressing member and a second glass rod in this order into each bore through the end of each bore which is remote from said connected glass tube having said smaller diameter part, contacting said first glass rod to said part of said glass tube with a smaller inner diameter, and heating and fusing said second glass rod to said preform to thereby form said preform for a polarization retaining optical fiber. 2. The method according to claim 1, wherein said glass tube having a part with a smaller inner diameter is formed by heating a part of said glass tube, softening said part and then pressing said softened part.
3. The method according to claim 1, wherein said glass tube having a part with a smaller inner diameter is formed by connection of a pair of glass tubes each having a larger inner diameter with both ends of a glass tube having a smaller inner diameter.
As a method for producing a preform for a polarization retaining optical fiber, Japanese Patent Kokai Publication No. 155535/1985 discloses a method comprising boring at least two bores which are symmetrically arranged around a center axis of a preform for use in the fabrication of an optical fiber, smoothening inner surfaces of the bores, and inserting and fixing a stressing members having a different coefficient of thermal expansion from that of a core and cladding parts of the preform in the bores. The stressing member is fixed in the bore by making an outer diameter of one end of the bore larger than an inner diameter of the bore and inserting and fixing said one end of the stressing member to an end opening of the bore.
In general, since a material of the stressing member has a very much different coefficient of thermal expansion from that of the material of the preform for the optical fiber, the stressing member deforms much larger than the preform material when they are heated to integrate them together.
In the above conventional fixing manner, since the whole stressing member is not completely fixed to the preform though the one end of the stressing member is inserted in the bore, an unfixed part of the stressing member deforms largely, so that the stressing member moves during the integration of the stressing member and the preform and drawing of the preform having the stressing members. As the result, a desired stress is not achieved in the drawn fiber and no good polarization retaining property is realized because of the decrease of the diameter of the stressing member or deformation of the stressing member.
An object of the present invention is to provide a method for producing a preform for a polarization retaining optical fiber, by which both ends of a stressing member can be fixed to a respective bore made in the preform, whereby the deformation of the stressing member during the integration step is minimized and the desired stress is achieved in a finally fabricated polarization retaining optical fiber.
In a second embodiment, a glass tube is connected to one end of the preform, and this glass tube has a part with a smaller inner diameter near its end which is connected to the preform. Then, from an end of each bore which is remote from the preform end to which the glass tube is connected, the first glass rod, the stressing member and the second glass rod are inserted in this order.
The part with the smaller inner diameter may be formed by heating this part of the glass tube, stretching this part and then pressing the stretched part, whereby the inner diameter of the part is decreased while the outer diameter of the part is made substantially the same as the outer diameter of the rest of the glass tube. Alternatively, to both ends of a short glass tube having a smaller inner diameter, glass tubes having a larger inner diameter than and the same outer diameter as the short glass tube are connected to form the glass tube having the smaller diameter part.
According to the present invention, the stressing member is sandwiched by the first and second glass rods, and the both ends of the stressing member are fixed by the glass rods. Therefore, the deformation of the stressing members can be minimized during heating for integrating the stressing members and the preform together. When the resulting preform is heated and drawn to fabricate the polarization retaining optical fiber, the fabricated optical fiber has better accuracy since the both ends of the stressing member are fixed.
For fixing the ends of the stressing member, it may be contemplated to insert the stressing member in the bore and then the glass rods are connected to the respective ends of the preform. However, in the connection step, an interior space of the bore is contaminated with impurities so that the fabricated optical fiber tends to have decreased strength.
It may be also contemplated to integrate the stressing member and the preform in the step of the formation of the preform. However, the integrated preform may be cracked due to large difference of the coefficient of thermal expansion between the preform glass and the stressing member.
According to the present invention, since the core can be passed through after the insertion of the stressing member and the glass rods, the impurities can be removed from the bore even after the insertion of the stressing member and the glass rods. Since the stressing member and the preform are not integrated together, the final preform does not tend to be cracked.
To prevent the deformation of the stressing member during the integration step and the drawing of the preform, the first and the second glass rods have a softening point which is substantially the same as or higher than that of the glass to be used for the formation of the cladding.
FIG. 1 is a cross sectional view of an example of the preform to be produced by the first embodiment of the method according to the present invention. In FIG. 1, a preform 1 for an optical fiber contains a first glass rod 2, a stressing member 3 and a second glass rod. To one end of the preform, a glass tube 5 is connected for easy handling.
First, in the preform 1 from one end to a position before the other end of the preform, at least two bores each having an inner diameter slightly larger than an outer diameter of the stressing member 3 are formed, and from the above position to the other end, a bore having a smaller inner diameter than the outer diameter of the stressing member 3 is formed. After fusing the glass tube 5 to the other end of the preform, the glass rod 2, the stressing member 3 and the second glass rod 4 are inserted in each bore from the one end thereof. The first glass rod is pressed against the bore part having the smaller diameter and fixed. To the glass tube 5, a vacuum connector may be attached.
FIG. 2 is a cross sectional view of another example of the preform to be produced by the first embodiment of the method according to the present invention. In this example, a part of the bore near the other end of the preform is narrowed down. Such bore can be formed by forming a bore having the same inner diameter from the one end to the other of the preform 1 and the part to be narrowed down is heated and softened while slightly pressing the preform in its longitudinal direction. Other features in this example are the same as explained above.
The narrow part 5a may be formed by fusing the glass tube 5 to the preform, heating only the part 5a, stretching it and then pressing the softened part 5a. Alternatively, the glass tube 5 having the narrow part 5a may be connected to the preform.
Thereafter, from the other end of the preform, the first glass rod 2, the stressing member 3 and the second glass rod 4 are inserted in each bore. The first glass rod 2 is pressed against the narrow part 5a of the glass tube 5 having the smaller diameter and fixed. To the glass tube 5, a vacuum connector may be attached.
Alternatively, as shown in FIG. 4, the narrow part 5a can be formed by connecting, to both ends of a short glass tube 5c having a smaller inner diameter, glass tubes 5b and 5d each having a larger inner diameter than and the same outer diameter as the short glass tube 5c to form the glass tube 5 having the smaller diameter part 5c. The glass tubes 5b, 5c and 5d may be connected to the preform 1 in this order.
Through a preform 1 for an optical fiber which consisted of a core part made of GeO2 --SiO2 glass and a cladding part made of SiO2 glass and had an outer diameter of 25 mm and a length of 300 mm, two bores each having an inner diameter of 8 mm and center axis apart from each other by 5.0 mm were formed in parallel with the center axis of the preform 1 till a point which was 280 mm apart from one end of the preform 1. From this point, bores each having an inner diameter of 3 mm and a length of 20 mm were formed.
After polishing inner surfaces of the bores having the inner diameter of 8 mm, to each end of the preform 1, a quartz tube 5 having an outer diameter of 25 mm and an inner diameter of 23 mm was respectively connected. Since FIG. 1 shows the fused preform, the right end of the preform has no glass tube 5.
From a free end of each bore having the inner diameter of 8 mm, a first quartz rod 2 having an outer diameter of 7.8 mm and a length of 20 mm, a stressing member 3 made of B2 O3 --SiO2 glass and having an outer diameter of 7.8 mm and a length of 200 mm and a second quartz glass rod 4 having an outer diameter of 7.8 mm and a length of 60 mm were inserted in each bore in this order.
After removing impurities from the interiors of the bores, the second quartz rod 4 and the preform 1 were heated with a flame and stretched to integrate them together to fix the second quartz rod 4 to the preform 1, whereby the end of each bore was sealed. Then, the interiors of the bores were evacuated and the free end of the glass tube 5 was fused and sealed to obtain a preform for a polarization retaining optical fiber.
The produced preform was heated with a resistance furnace and drawn to fabricate an optical fiber having an outer diameter of 125 μm while integrating the stressing member with the cladding part.
The cross sectional structure of the fabricated optical fiber was measured to find that the outer diameter of the stressing member was 41 μm which was substantially the same as a designed size. The optical fiber had a good birefringence of 5×10-4 at a wavelength of 0.85 μm. In addition, a cross talk per 1 km was -25 dB at a wavelength of 0.85 μm.
Through a preform 1 for an optical fiber which of a core part made of GeO2-- SiO2 glass and a cladding part made of SiO2 glass and had an outer diameter of 25 mm and a length of 300 mm, two bores each having an inner diameter of 8 mm and center axis apart from each other by 5.0 mm were formed in parallel with the center axis of the preform 1 throughout the preform. After polishing inner surfaces of the bores, one end of the preform was heated, stretched and then shrunk to decrease the inner diameter of a part of each bore to about 4 mm.
From a free end of each bore, a first quartz rod 2 having an outer diameter of 7.7 mm and a length of 20 mm, a stressing member 3 made of B2 O3 --SiO2 glass and having an outer diameter of 7.8 mm and a length of 200 mm and a second quartz glass rod 4 having an outer diameter of 7.7 mm and a length of 60 mm were inserted in each bore in this order.
The cross sectional structure of the fabricated optical fiber was measured to find that the outer diameter of the stressing member was 39 μm which was substantially the same as a designed size. The optical fiber had a good birefringence of 5×10-4 at a wavelength of 0.85 μm. In addition, a cross talk per 1 km was -27 dB at a wavelength of 0.85 μm.
Through a preform 1 for an optical fiber which consisted of a core part made of GeO2--SiO 2 glass and a cladding part made of SiO2 glass and had an outer diameter of 25 mm and a length of 300 mm, two bores each having an inner diameter of 8 mm and center axis apart from each other by 5.0 mm were formed in parallel with the center axis of the preform 1 throughout the preform.
After polishing inner surfaces of the bores having the inner diameter of 8 mm, to each end of the preform 1, a quartz tube 5 having an outer diameter of 25 mm and an inner diameter of 23 mm was respectively connected. Since FIG. 3 shows the fused preform, the right end of the preform has no glass tube 5.
From an end of each bore on the side of the glass tube an inner diameter was not reduced, a first quartz rod 2 having an outer diameter of 7.8 mm and a length of 60 mm, a stressing member 3 made of B2 O3 --SiO2 glass and having an outer diameter of 7.8 mm and a length of 200 mm and a second quartz glass rod 4 having an outer diameter of 7.8 mm and a length of 60 mm were inserted in each bore in this order.
The cross sectional structure of the fabricated optical fiber was measured to find that the outer diameter of the stressing member was 40 μm which was the same as a designed size. The optical fiber had a good birefringence of 5×10-4 at a wavelength of 0.85 μm. In addition, a cross talk per 1 km was -26 dB at a wavelength of 0.85 μm.
Through a preform 1 for an optical fiber which consisted of a core part made of GeO2 --SiO2 glass and a cladding part made of SiO2 glass and had an outer diameter of 25 mm and a length of 300 mm, two bores each having an inner diameter of 8 mm and center axis apart from each other by 5.0 mm were formed in parallel with the center axis of the preform 1 throughout the preform.
After flame polishing inner surfaces of the bores having the inner diameter of 8 mm, to one end of the preform 1, a quartz tube 5 consisting of a quartz tube 5c having an outer diameter of 25 mm and an inner diameter of 10 mm and a pair of quartz tubes 5b, 5d each having an outer diameter of 25 mm and an inner diameter of 23 mm which were connected to the both sides of the tube 5c was connected, and to the other end of the preform 1, a quartz tube 5 having an outer diameter of 25 mm and an inner diameter of 23 mm was connected.
From an end of each bore on the side of the single piece glass tube 5, a first quartz rod 2 having an outer diameter of 7.7 mm and a length of 70 mm, a stressing member 3 made of B2 O3 --SiO2 glass and having an outer diameter of 7.8 mm and a length of 200 mm and a second quartz glass rod 4 having an outer diameter of 7.7 mm and a length of 60 mm were inserted in each bore in this order.
The second quartz rod 4 and the preform 1 were heated with a flame and stretched to integrate them together to fix the second quartz rod 4 to the preform 1, whereby the end of each bore was sealed. Then, the interiors of the bores were evacuated and the free end of the glass tube 5d was fused and sealed to obtain a preform for a polarization retaining optical fiber.
The produced preform was heated with a resistance furnace and drawn to fabricate an optical fiber having an outer diameter of 125 μm while integrating the stressing members with the cladding part.
When the cross sectional structure of the fabricated optical fiber was measured to find that the outer diameter of the stressing member was 39 μm which was substantially the same as a designed size. The optical fiber had a good birefringence of 5×10-4 at a wavelength of 0.85 μm. In addition, a cross talk per 1 km was -27 dB at a wavelength of 0.85 μm.
Through a preform 1 for an optical fiber which consisted of a core part made of GeO2 --SiO2 glass and a cladding part made of SiO2 glass and had an outer diameter of 25 mm and a length of 300 mm, two bores each having an inner diameter of 8 mm and center axis apart from each other by 5.0 mm were formed in parallel with the center axis of the preform 1 till a point which was 250 mm apart from one end of the preform 1. That is, the bores did not open at the other end of the preform as shown in FIG. 5.
From a free end of each bore having the inner diameter of 8 mm, a stressing member 3 made of B2 O3 --SiO2 glass and having an outer diameter of 7.8 mm and a length of 200 mm with one end having a large diameter of 9 mm was inserted in each bore and fixed to the preform by using the one end having the large diameter as shown in FIG. 5.
The cross sectional structure of the fabricated optical fiber was measured to find that the outer diameter of the stressing member was 20 μm which was much smaller than a designed size of 40 μm.
The fabricated optical fiber had a birefringence of 3×10-4 at a wavelength of 0.85 μm. In addition, a cross talk per 1 km was -12 dB at a wavelength of 0.85 μm. These results are not satisfactory as the polarization retaining optical fiber.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS4698084 *Apr 17, 1986Oct 6, 1987U.S. Philips CorporationMethod of manufacturing a passive fiber optic componentUS4810277 *Feb 23, 1988Mar 7, 1989Siemens AktiengesellschaftMethod for fastening a glass fiber to a light wave guide componentUS4812154 *Oct 13, 1987Mar 14, 1989Sumitomo Electric Industries, Ltd.Method for producing glass preform for optical fiberEP0147225A2 *Dec 21, 1984Jul 3, 1985Corning Glass WorksMethod of forming an optical fiberJPH01153551A * Title not availableJPS5836941A * Title not availableJPS53144348A * Title not availableJPS60246236A * Title not available* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS6360565 *Jun 4, 1997Mar 26, 2002Corning IncorporatedMethod of making polarization retaining fiberUS6405566 *Aug 22, 1994Jun 18, 2002Samsung Electronics Co., Ltd.Method and device for over-cladding an optical fiber primary preformUS6584808 *Feb 17, 2000Jul 1, 2003Pirelli Cavi E Sistemi S.P.A.Method of manufacturing an optical fiber preform by collapsing a tube onto a rodUS6587624Dec 11, 2001Jul 1, 2003Corning IncorporatedPolarization retaining fiberUS20020118938 *Feb 19, 2002Aug 29, 2002Takemi HasegawaOptical fiber and optical fiber transmission line, and manufacturing method thereforUS20140186645 *Jan 2, 2013Jul 3, 2014Ofs Fitel, LlcManufacture of bend insensitive multimode optical fiber* Cited by examinerClassifications U.S. Classification65/411, 65/412, 385/11International ClassificationC03B37/012Cooperative ClassificationC03B37/01217, C03B2203/31European ClassificationC03B37/012B2BLegal EventsDateCodeEventDescriptionAug 6, 1991ASAssignmentOwner name: SUMITOMO ELECTRIC INDUSTRIES, LTD., JAPANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:TAKAGI, MASAHIRO;SUGANUMA, HIROSHI;KANAMORI, HIROO, YOKOH;REEL/FRAME:005809/0932Effective date: 19910729Oct 19, 1993CCCertificate of correctionApr 23, 1996FPAYFee paymentYear of fee payment: 4Apr 24, 2000FPAYFee paymentYear of fee payment: 8Apr 8, 2004FPAYFee paymentYear of fee payment: 12RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services