GB2116744A - Optical fiberguide - Google Patents

Optical fiberguide Download PDF

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Publication number
GB2116744A
GB2116744A GB08306443A GB8306443A GB2116744A GB 2116744 A GB2116744 A GB 2116744A GB 08306443 A GB08306443 A GB 08306443A GB 8306443 A GB8306443 A GB 8306443A GB 2116744 A GB2116744 A GB 2116744A
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United Kingdom
Prior art keywords
n4
fiber
gt
cladding
dispersion
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Granted
Application number
GB08306443A
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GB8306443D0 (en
GB2116744B (en
Inventor
Leonard George Cohen
Wanda Lee Mammel
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Western Electric Co Inc
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Western Electric Co Inc
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Priority to US35705382A priority Critical
Application filed by Western Electric Co Inc filed Critical Western Electric Co Inc
Publication of GB8306443D0 publication Critical patent/GB8306443D0/en
Publication of GB2116744A publication Critical patent/GB2116744A/en
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Publication of GB2116744B publication Critical patent/GB2116744B/en
Application status is Expired legal-status Critical

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Classifications

    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS, OR APPARATUS
    • G02B6/00Light guides
    • G02B6/02Optical fibre with cladding with or without a coating
    • G02B6/02214Optical fibre with cladding with or without a coating tailored to obtain the desired dispersion, e.g. dispersion shifted, dispersion flattened
    • G02B6/02219Characterised by the wavelength dispersion properties in the silica low loss window around 1550 nm, i.e. S, C, L and U bands from 1460-1675 nm
    • G02B6/02223Dual window fibres, i.e. characterised by dispersion properties around 1550 nm and in at least another wavelength window, e.g. 1310 nm
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS, OR APPARATUS
    • G02B6/00Light guides
    • G02B6/02Optical fibre with cladding with or without a coating
    • G02B6/02214Optical fibre with cladding with or without a coating tailored to obtain the desired dispersion, e.g. dispersion shifted, dispersion flattened
    • G02B6/02219Characterised by the wavelength dispersion properties in the silica low loss window around 1550 nm, i.e. S, C, L and U bands from 1460-1675 nm
    • G02B6/02228Dispersion flattened fibres, i.e. having a low dispersion variation over an extended wavelength range
    • G02B6/02233Dispersion flattened fibres, i.e. having a low dispersion variation over an extended wavelength range having at least two dispersion zero wavelengths
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS, OR APPARATUS
    • G02B6/00Light guides
    • G02B6/02Optical fibre with cladding with or without a coating
    • G02B6/02214Optical fibre with cladding with or without a coating tailored to obtain the desired dispersion, e.g. dispersion shifted, dispersion flattened
    • G02B6/02219Characterised by the wavelength dispersion properties in the silica low loss window around 1550 nm, i.e. S, C, L and U bands from 1460-1675 nm
    • G02B6/02266Positive dispersion fibres at 1550 nm
    • G02B6/02271Non-zero dispersion shifted fibres, i.e. having a small positive dispersion at 1550 nm, e.g. ITU-T G.655 dispersion between 1.0 to 10 ps/nm.km for avoiding nonlinear effects
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS, OR APPARATUS
    • G02B6/00Light guides
    • G02B6/02Optical fibre with cladding with or without a coating
    • G02B6/036Optical fibre with cladding with or without a coating core or cladding comprising multiple layers
    • G02B6/03616Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference
    • G02B6/03661Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference having 4 layers only
    • G02B6/03666Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference having 4 layers only arranged - + - +

Abstract

To broaden the range of wavelengths over which an optical fiber has low loss and low chromatic dispersion, four optically active cladding (22, 23, 24, 25) layers are employed. The relative refractive indices and radii of the core and claddings are advantageously selected (e.g. as shown) such that the chromatic dispersion curve has three zero crossings. <IMAGE>

Description

SPECIFICATION Optical fiberguide This invention relates to optical fibers and preferably to low-loss, low-dispersion fibers.

In ourcopending application Serial No. 299,213, filed September 3, 1981,there is disclosed a double-clad, single-mode optical fiber comprising a core region surrounded by a thin inner cladding and a thicker outer cladding. By the suitable selection of radii and refractive indices, low chromatic dispersion can be realized over the range of wavelengths between 1.3 and 1.55 um. However, as the wavelength increases, losses due to radiation through the cladding layers become significant. In particular, in the vicinity of the fundamental mode cut-off wavelength, a small change in signal wavelength causes the fundamental mode to change from a guided wave to a leaky wave that radiates through the claddings. The result is high loss at the upper end of the low dispersion range.

According to the present invention there is provided an optical fiber comprising: a core region having a refractive index nc and a radius Rc, surrounded by four cladding layers having refractive indices and radii (n1, R1), (n2, R2,), (n3, R3,) and (n4, R4), respectively.

In accordance with the preferred embodiment of the present invention, the above-described loss mechanism is displaced away from the desired wavelength region of low chromatic dispersion and, in addition, the low dispersion band is broadened. This is accomplished in a lightguide comprising a core region surrounded by four cladding layers. Designating the refractive indices of the core and the successive cladding layers as nc, n1, n2, n3, and n4, respectively, the indices are advantageously proportioned such that nC > n2 > n4 > n3 > n,.

By the appropriate selection of indices and radii, the chromatic dispersion curve can be made to have three zero crossings, as compared to the two possible crossings for the prior art doube-clad fiber, and to cover the desired range of wavelengths which includes 1.3 and 1.55 lim.

For a better understanding of the invention, reference is made to the accompanying drawing, in which: Figure 1 shows a prior art double-clad (DC) optical fiber; Figure 2 shows a typical chromatic dispersion curve for a double-clad fiber; Figure 3 shows a quadruple-clad (QC) fiber in accordance with an embodiment of the present invention; Figure 4 shows the variations in the group index in DC and OC fibers; and Figure 5 shows chromatic dispersion curves for quadruple-clad fibers of different sizes; and Figure 6 shows dispersion curves for single, double and quadruple clad fibers.

Referring to the drawing, Figure 1 shows a cross section of a prior art double-clad (DC) optical fiber 10 comprising a core region 11 surrounded by a relatively thin first inner cladding 12 and a thicker, second outer cladding 13. Designating the refractive index of the outer cladding as nO, the refractive index nc of the core is equal to nO (1 + Ac), and the refractive index n1 of the inner cladding is equal to nO (1 + A), where Ac and As are the fractional differences between the refractive indices of the core and outer cladding, and between the inner and the outer claddings.The index profile of such a fiber is the so-called "W-profile", also illustrated in Figure 1, wherein the several indices are shown as a function of the fiber radius normalized with respect to the inner cladding radius a.

For a fiber composed of a germanium-doped silica core, a fluorine-doped inner cladding, and a pure silica outer cladding, Rc is advantageously about 0.7, and the ratio A/ Ac is advantageously equal to 2. For such a fiber, the total chromatic dispersion is low over the desired wavelength region between 1.3 m and 1.55 Fm.

Figure 2, included for purposes of explanation, shows a set of typical dispersion curves for a DC fiber including a material dispersion curve 15, a wavelength dispersion curve 16, and the resulting total chromatic dispersion curve 17, obtained by summing curves 15 and 16. In general, the total dispersion curve for a DC fiber can have two zero crossings at wavelengths X, and X2. For this particular illustrative fiber these occur at X, = 1.35 um and p2 = 1.63 Zm. Because of the large material dispersion at the longer wavelength, the X2 zero crossing is associated with a correspondingly large waveguide dispersion that occurs near the fundamental mode cut-off wavelength h,,, approximately equal to 1.7 lim. This is the wavelength at which the effective refractive index becomes less than n O. At this wavelength, the signal wave is no longer guided by the fiber but, instead, radiates through the claddings and is lost.

In order to insure low-loss operation, pcO should be more than 0.1 um larger than the longest wavelength of interest. Based upon this criteria, the total chromatic dispersion characteristics obtainable with currently available double-clad fibers designed to have low dispersion over the range between 1.3 and 1.55 um are only marginally acceptable for operation near 1.55 um.

To avoid the above-described limitations and disadvantages of the prior art double-clad fiber, two additional claddings are added, in accordance with the present invention, to form the quadruple-clad fiber 20 illustrated in Figure 3. This fiber comprises a core region 21 surrounded by four cladding layers 22, 23, 24 and 25, where layer 22 is the first, innermost cladding, and layer 25 is the fourth, outermost cladding.Designating the refractive index n4 of the outermost cladding 25 as nO, the refractive indices of the core nc, and the indices n1, n2 and n3 of the respective claddings 22, 23 and 24 are given by nc = nO (1 + Ac) n1 = nO (1 n2= nO (1 + 2) and n3=n0(1-A3) where Ac, A1, A2 and A3 are the fractional differences between the indices of the respective portions of the fiber and that of the outermost cladding.

The index profile for the QC fiber is shown in Figure 3 as a function of the fiber radius normalized with respect to the radius R1 of the innermost cladding 22. As can be seen, the relative magnitudes of the indices are such that nC > n2 > n4 > n3 > n,.

As explained hereinabove, in the vicinity of the fundamental mode cut-off, a small change in wavelength causes the signal to change from a guided mode into a leaky mode that radiates into the second cladding.

The reason for this can be explained with reference to Figure 4 which shows the effective group index, n9, as a function of wavelength, X, for both the DC and QC fibers. At the shorter wavelengths, the signal is primarily guided by an inner lightguide formed by the core 21 and the first cladding 22. Accordingly, the effective group index at the shorter wavelengths, given by curve portion 43, is shown to be larger than the core index, given by curve 40. At the longer wavelengths, more of the signal field extends into the first cladding and beyond. The effect is to decrease the effective group index. In the DC fiber, the group index eventually becomes less than the outermost (i.e., second cladding) and the guide becomes cut-off.This is indicated by curve portion 44 which approaches cut-off at h,,.

By contrast, in the OC fiber, the wave energy that radiates out of the fiber core is trapped in an outer lightguide formed by the second cladding 23 and the surrounding first and third claddings 22 and 24. The light thus trapped is not lost through radiation but continues to be guided, albeit in a different portion of the fiber. The effective group index, given by curve portion 45, is seen to change from a value greater than no to a value that approaches that of the second cladding given by curve 41.As can be seen, the resulting index curve for the OC fiber has three turning points at wavelengths X 2 and k3. Inasmuch as the total chromatic dispersion characteristic is proportional to the slope of the group index curve, the chromatic dispersion can have three zero points, at wavelengths k" 2 and R3, as illustrated in Figure 5.

In the design of a QC fiber, there are nine independent parameters Ac, A 2, A3, Rc, R1, R2, R3 and a. The radius of the outermost cladding is not critical and, typically, is is made relatively large for reasons to be explained hereinbelow. A generalized method for calculating the total chromatic dispersion characteristic for any arbitrary index profile is described in a paper by L.G.Cohen et al., entitled "Correction Between Numerical Predictions and Measurements of Single-Mode Fiber Dispersion Characteristics", published in the June 15, 1980 issue of Applied Optics, Vol. 19, pp.2007-2010. Using this method for the OC fiber, the illustrative series of curves shown in Figures are obtained. These particular curves are calculated for the four different values of 2a shown, and Ac = 0.3% Rc = 0.7 A1 = 0.6% R1 = 1.0 2 = 0.06% R2=1.7 A3=0.12% R3=2.0.

A comparison with the dispersion curve for the DC fiber, shown in Figure 2, illustrates that low dispersion for the QC fiber occurs over a much broader band of wavelengths. In particular, the inclusion of the two additional claddings has the effect of adding an additional zero crossing at the high wavelength end of the curves, thus significantly increasing the low dispersion interval. The improvement in the loss characteristic is also evident. For the DC fiber, cut-off occurs at about 1.7 um whereas cut-off for the QC fiber (indicated by the ends of the dispersion curves) occurs above 1.9 Fm. Finally, the curves illustrate that the dispersion characteristics are relatively stable with respect to changes in fiber parameters. Compare, for example, the curves for 2a equal to 13.1, and 2a equal to 13.9.

The invention is of particular interest in connection with single mode fibers and dual mode fibers. (See Chapter 3 of Optical Fiber Telecommunications edited by S.E. Miller and A.G. Chynoweth, Academic Press, 1979, and the article by L.G. Cohen, et al., entitled "Propagation Characteristics of Double-Mode Fibers," published in the July-August issue of the Bell System Technical Journal, Vol. 59, No. 6, pp. 1061-1072 for discussions of such fibers). Therefore, the requirements of such fibers must also be taken into consideration in the design of a QC fiber. For example, if either 2 or R2-R1 is made too large, the fiber will not remain single-mode. If A3 or R3-R2 is too small, the dispersion curve at the longer wavelengths will not turn around enough to obtain the desired zero crossing at the high end of the band. In this regard one can define a function <img class="EMIRef" id="027138996-00030001" />

which must be greater than unity if a zero at the longer wavelength is to be obtained.

An additional advantage of the invention is that bending losses in a OC fiber are less than in a DC fiber.

Fibers, in accordance with the present invention, can be drawn from preforms manufactured by many of the well known techniques such as, for example, the modified chemical vapor deposition (MCVD) process.

Similarly, any appropriate index-modifying dopants, or combination of dopants can be used. Exemplary dopants are F (fluorine), Ge (germanium) and P (phosphorous). In preferred embodiments, the outermost cladding consists of silica (SiO2) with the core and second cladding being silica that is lightly doped with an index-increasing dopant (i.e., germanium, and/or phosphorus in those cases where it is desired to move the first zero crossing to a shorter wavelength) and the first and third cladding being silica that is lightly doped with an index-decreasing dopant (i.e., fluorine).

In addition to the four active, waveguiding cladding layers, there may be additional layers of material which are by-products of the method of manufacture, or are included for reasons unrelated to the waveguiding function of the fiber. Unlike the four optically active claddings, which are designed to have very low losses at the wavelengths of interest, such additional layers may be lossy at these wavelengths. For example, if the MCVD process is employed, theoutermost cladding will be surrounded by the preform starting tube which, while made of silica, typically has high losses. Other layers may include a barrier layer prevent migration of OH-radicals into the core region.However, by making the fourth cladding layer thick enough, these additional claddings do not affect the lightguide characteristics of the fiber and can be ignorec for the purposes of the present invention.

In summary, to broaden the range of wavelengths over which an optical fiber has low chromatic dispersion (less than 5 ps/km-nm) and low loss (less than 1 dB/km), four optionally active cladding layers are employed. A principle advantage of the invention is that low dispersion and low loss are obtained over a range which includes 1.3 and 1.55 Fm. Figure 6, included for purposes of comparison, shows the dispersion curves 60, 61 and 62 for a representative step-index single mode fiber, a typical double-clad fiber, and a quadruple-clad fiber. As can be readily seen, the low dispersion bandwidth of the OC fiber is considerably broader than that of the other fibers.

Claims (4)

1. An optical fiber comprising: a core region, having a refractive index nc and a radius Rc, surrounded by four cladding layers having refractive indices and radii (n1, R), (n2, R2,), (n3, R3,) and (n4, R4), respectively.
2. The fiber according to claim 1,wherein: R4 > R3 > R2 > R1 and nc > n2 > n4 > n3 > n1
3. The fiber according to claim 2, wherein: <img class="EMIRef" id="027138997-00030002" />
where n4 - n, 1 = n4 - n1 n4 A2 n4 - n2 n4 A3 = n4 - n3 n4 and n4 - nc.
Ac = n4
4. Afiber according to claim 1, and substantially as herein described with reference to Figure 3,4,5 or 6 of the accompanying drawing.
GB08306443A 1982-03-11 1983-03-09 Optical fiberguide Expired GB2116744B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US35705382A true 1982-03-11 1982-03-11

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GB8306443D0 GB8306443D0 (en) 1983-04-13
GB2116744A true GB2116744A (en) 1983-09-28
GB2116744B GB2116744B (en) 1987-01-21

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JP (1) JPS6237361B2 (en)
CA (1) CA1248386A (en)
DE (1) DE3307874C2 (en)
FR (1) FR2523316B1 (en)
GB (1) GB2116744B (en)
NL (1) NL8300880A (en)

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0127408A1 (en) * 1983-05-20 1984-12-05 Corning Glass Works Optical waveguide fiber
WO1986004689A1 (en) * 1985-02-08 1986-08-14 American Telephone & Telegraph Company Single mode optical fiber
EP0224282A1 (en) * 1985-09-26 1987-06-03 Philips Electronics N.V. Optical transmission system comprising a radiation source and a multiple-clad monomode optical transmission fibre with a negative-step index profile
EP0341427A2 (en) * 1988-04-12 1989-11-15 Schott Glaswerke Single mode light-guiding fibre, and method for its production
EP0413387A1 (en) * 1989-08-16 1991-02-20 Philips Electronics N.V. Polarisation-maintaining single-mode optical fibre
EP0721119A1 (en) * 1994-12-27 1996-07-10 Corning Incorporated Controlled dispersion optical waveguide
US5675690A (en) * 1995-07-07 1997-10-07 Alcatel Submarcom Dispersion-flattened single-mode optical waveguide with large effective mode surface area
US5878182A (en) * 1997-06-05 1999-03-02 Lucent Technologies Inc. Optical fiber having a low-dispersion slope in the erbium amplifier region
WO2000063732A1 (en) * 1999-04-16 2000-10-26 Sumitomo Electric Industries, Ltd. Optical fiber and optical transmission line comprising the same
WO2000065386A1 (en) * 1999-04-23 2000-11-02 Massachusetts Institute Of Technology All-dielectric coaxial waveguide
US6317549B1 (en) 1999-05-24 2001-11-13 Lucent Technologies Inc. Optical fiber having negative dispersion and low slope in the Erbium amplifier region
WO2002021172A2 (en) * 2000-09-01 2002-03-14 Sumitomo Electric Industries, Ltd. Negative-dispersion optical fiber and optical transmission line incorporating the same
US6363196B1 (en) 1998-08-13 2002-03-26 Alcatel Single mode dispersion-shifted optical fiber with external refractive index ring
US6614975B2 (en) 1998-07-03 2003-09-02 University Of Southampton Optical fiber and optical fiber device
US6856738B2 (en) * 1999-12-13 2005-02-15 Sumitomo Electric Industries, Ltd. Optical fiber and optical transmission system
US7203407B2 (en) * 2004-10-21 2007-04-10 Corning Incorporated Rare earth doped single polarization double clad optical fiber and a method for making such fiber
US7321711B2 (en) 2002-02-13 2008-01-22 The Furukawa Electric Co., Ltd. Optical fiber and optical transmission line and optical communication system including such optical fiber
USRE44288E1 (en) 2004-02-20 2013-06-11 Corning Incorporated Optical fiber and method for making such fiber

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5361319A (en) * 1992-02-04 1994-11-01 Corning Incorporated Dispersion compensating devices and systems
JP2005031581A (en) * 2003-07-11 2005-02-03 Sumitomo Electric Ind Ltd Optical fiber, optical fiber transmission line and optical transmission system
JP4953097B2 (en) * 2008-06-12 2012-06-13 市光工業株式会社 Vehicle lighting

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GB2002535A (en) * 1977-08-12 1979-02-21 Corning Glass Works Multiple mode waveguides
GB2012066A (en) * 1977-12-29 1979-07-18 Int Standard Electric Corp Water resistant high strength fibres
EP0034670A1 (en) * 1980-02-12 1981-09-02 The Post Office A glass optical fibre and a method of coating a plastic coated glass fibre with metal
GB1602052A (en) * 1977-06-20 1981-11-04 Int Standard Electric Corp Optical fibre manufacture
WO1982001543A1 (en) * 1980-11-03 1982-05-13 Aircraft Co Hughes Multiply coated metallic clad fiber optical waveguide
GB2104241A (en) * 1981-08-18 1983-03-02 Hitachi Cable Single polarization optical fibres
GB2104239A (en) * 1981-08-19 1983-03-02 Hitachi Cable Single polarization optical fibers and process for fabrication of same

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AU504423B2 (en) * 1975-11-14 1979-10-11 International Standard Electric Corporation Optical fibre
GB2067781B (en) * 1979-10-29 1983-09-01 Standard Telephones Cables Ltd Optical fibres
CA1205307A (en) * 1981-12-07 1986-06-03 Venkata A. Bhagavatula Low dispersion, low-loss single-mode optical waveguide

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GB1602052A (en) * 1977-06-20 1981-11-04 Int Standard Electric Corp Optical fibre manufacture
GB2002535A (en) * 1977-08-12 1979-02-21 Corning Glass Works Multiple mode waveguides
GB2012066A (en) * 1977-12-29 1979-07-18 Int Standard Electric Corp Water resistant high strength fibres
EP0034670A1 (en) * 1980-02-12 1981-09-02 The Post Office A glass optical fibre and a method of coating a plastic coated glass fibre with metal
WO1982001543A1 (en) * 1980-11-03 1982-05-13 Aircraft Co Hughes Multiply coated metallic clad fiber optical waveguide
GB2104241A (en) * 1981-08-18 1983-03-02 Hitachi Cable Single polarization optical fibres
GB2104239A (en) * 1981-08-19 1983-03-02 Hitachi Cable Single polarization optical fibers and process for fabrication of same

Cited By (28)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0127408A1 (en) * 1983-05-20 1984-12-05 Corning Glass Works Optical waveguide fiber
WO1986004689A1 (en) * 1985-02-08 1986-08-14 American Telephone & Telegraph Company Single mode optical fiber
US4641917A (en) * 1985-02-08 1987-02-10 At&T Bell Laboratories Single mode optical fiber
EP0224282A1 (en) * 1985-09-26 1987-06-03 Philips Electronics N.V. Optical transmission system comprising a radiation source and a multiple-clad monomode optical transmission fibre with a negative-step index profile
US4784466A (en) * 1985-09-26 1988-11-15 U.S. Philips Corp. Optical transmission system comprising a radiation source and a multipleclad monomode optical transmission fibre with a negative-step index profile
EP0341427A2 (en) * 1988-04-12 1989-11-15 Schott Glaswerke Single mode light-guiding fibre, and method for its production
US5013131A (en) * 1988-04-12 1991-05-07 Schott Glaswerke Single-mode optical, fiber and process for its production
EP0341427A3 (en) * 1988-04-12 1991-02-27 Carl-Zeiss-Stiftung trading as SCHOTT GLASWERKE Single mode light-guiding fibre, and method for its production
EP0413387A1 (en) * 1989-08-16 1991-02-20 Philips Electronics N.V. Polarisation-maintaining single-mode optical fibre
US5067793A (en) * 1989-08-16 1991-11-26 U.S. Philips Corporation Polarization-maintaining single-mode optical fibre and method of making same
EP0721119A1 (en) * 1994-12-27 1996-07-10 Corning Incorporated Controlled dispersion optical waveguide
US5675690A (en) * 1995-07-07 1997-10-07 Alcatel Submarcom Dispersion-flattened single-mode optical waveguide with large effective mode surface area
US5878182A (en) * 1997-06-05 1999-03-02 Lucent Technologies Inc. Optical fiber having a low-dispersion slope in the erbium amplifier region
US6614975B2 (en) 1998-07-03 2003-09-02 University Of Southampton Optical fiber and optical fiber device
US6424775B1 (en) * 1998-08-13 2002-07-23 Alcatel Single mode dispersion-shifted optical fiber comprising an external refractive index ring
US6363196B1 (en) 1998-08-13 2002-03-26 Alcatel Single mode dispersion-shifted optical fiber with external refractive index ring
WO2000063732A1 (en) * 1999-04-16 2000-10-26 Sumitomo Electric Industries, Ltd. Optical fiber and optical transmission line comprising the same
US6556758B2 (en) 1999-04-16 2003-04-29 Sumitomo Electric Industries, Ltd. Optical fiber and optical transmission line including the same
US6573813B1 (en) 1999-04-23 2003-06-03 Massachusetts Institute Of Technology All-dielectric coaxial waveguide with annular sections
WO2000065386A1 (en) * 1999-04-23 2000-11-02 Massachusetts Institute Of Technology All-dielectric coaxial waveguide
US6317549B1 (en) 1999-05-24 2001-11-13 Lucent Technologies Inc. Optical fiber having negative dispersion and low slope in the Erbium amplifier region
US6856738B2 (en) * 1999-12-13 2005-02-15 Sumitomo Electric Industries, Ltd. Optical fiber and optical transmission system
WO2002021172A3 (en) * 2000-09-01 2003-05-01 Sumitomo Electric Industries Negative-dispersion optical fiber and optical transmission line incorporating the same
WO2002021172A2 (en) * 2000-09-01 2002-03-14 Sumitomo Electric Industries, Ltd. Negative-dispersion optical fiber and optical transmission line incorporating the same
US7321711B2 (en) 2002-02-13 2008-01-22 The Furukawa Electric Co., Ltd. Optical fiber and optical transmission line and optical communication system including such optical fiber
US7505659B2 (en) 2002-02-13 2009-03-17 The Furukawa Electric Co., Ltd. Optical fiber and optical transmission line and optical communication system including such optical fiber
USRE44288E1 (en) 2004-02-20 2013-06-11 Corning Incorporated Optical fiber and method for making such fiber
US7203407B2 (en) * 2004-10-21 2007-04-10 Corning Incorporated Rare earth doped single polarization double clad optical fiber and a method for making such fiber

Also Published As

Publication number Publication date
CA1248386A (en) 1989-01-10
DE3307874A1 (en) 1983-09-22
CA1248386A1 (en)
NL8300880A (en) 1983-10-03
FR2523316A1 (en) 1983-09-16
DE3307874C2 (en) 1991-01-10
JPS6237361B2 (en) 1987-08-12
GB2116744B (en) 1987-01-21
JPS58168004A (en) 1983-10-04
FR2523316B1 (en) 1987-11-27
GB8306443D0 (en) 1983-04-13

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