JP3781925B2 - Dispersion compensating optical fiber and optical fiber type dispersion compensator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dispersion-compensating optical fiber and an optical fiber-type dispersion compensator, and more particularly to a dispersion-compensating optical fiber and an optical fiber-type dispersion compensator that can be miniaturized while compensating for a dispersion slope for wavelength division multiplexing transmission. is there.
[0002]
[Prior art]
With the advent of erbium (Er) doped optical fiber amplifiers, systems using optical amplifiers such as ultra-long-distance non-regenerative repeaters and optical subscriber multi-distribution networks in the 1.55 μm band are being actively studied for practical use. Yes.
Assuming high-speed transmission, it is desirable to use a 1.55 μm dispersion-shifted fiber that has a wavelength dispersion value of 1.55 μm and a chromatic dispersion value that is small for these transmission lines. When transmission is performed in the 1.55 μm wavelength band, a large chromatic dispersion occurs and the optical signal deteriorates. Therefore, technical means for suppressing this chromatic dispersion is necessary when transmission is performed in the 1.55 μm wavelength band using a 1.3 μm band single mode optical fiber. As one of the technical means, there is a method of compensating a chromatic dispersion value in a wavelength of 1.55 μm band by using a dispersion compensating optical fiber having a wavelength dispersion having a sign opposite to that of a 1.3 μm band single mode optical fiber.
[0003]
In addition, when performing WDM transmission using a 1.55 μm band dispersion-shifted fiber, if the chromatic dispersion in the operating wavelength band is small, a phenomenon of four-wave mixing, which is one of nonlinear effects, occurs, and transmission characteristics deteriorate. Problems arise. In order to suppress this non-linear effect, a transmission method for transmitting 1.55 μm using a 1.3 μm band single mode optical fiber and a dispersion compensating optical fiber has been proposed from the beginning.
Dispersion compensation methods using optical fiber include a dispersion compensation optical fiber with a single-peak structure with a large relative refractive index difference, and dispersion compensation with a double clad refractive index profile structure that enables dispersion slope compensation. Several proposals, such as a method using an optical fiber, have been made.
This dispersion-compensating optical fiber is incorporated into the device in use, like a rare-earth-doped optical fiber for optical amplification that compensates for transmission path loss, so it is usually a small coil wound around a small reel. Used as a module.
[0004]
[Problems to be solved by the invention]
However, this dispersion-compensating optical fiber needs to be designed where the bending is relatively weak (where the dispersion slope value is small) in order to increase the dispersion value per unit length and take a large dispersion slope on the minus side. is there. In particular, in order to obtain a large dispersion slope compensation on the minus side, the refractive index distribution structure is very weak against bending. This dispersion compensating optical fiber having a high dispersion slope compensation effect has a small transmission loss when it is not bent to a small radius of curvature. However, when it is wound around a small reel for modularization, there is a problem that the transmission loss becomes large. It will be. For this reason, it has been extremely difficult to manufacture a dispersion compensating optical fiber that has a high dispersion slope compensation effect and that does not cause deterioration in transmission loss characteristics even when wound on a small reel. For this reason, it is conceivable that the coil body diameter is increased and the coil is wound with a diameter that does not cause deterioration of the bending loss characteristics. However, since the winding volume is increased, there is a problem that it is difficult to reduce the size of the module. Become.
[0005]
The dispersion compensating optical fiber and the optical fiber type dispersion compensator of the present invention have been made in view of the above circumstances, and have the following objects.
That is, an object of the present invention is to provide a dispersion compensating optical fiber and an optical fiber type dispersion compensator that have a high dispersion slope compensation effect and that do not cause deterioration in transmission loss characteristics even when they are wound into a small coil.
[0006]
[Means for Solving the Problems]
  The dispersion compensating optical fiber and the optical fiber type dispersion compensator of the present invention employ the following means in order to solve the above problems. That is, the dispersion compensating optical fiber according to claim 1 is wound in a small coil shape and used as an optical fiber type dispersion compensator.BecauseUse wavelength band selected from 1.53 to 1.61 μmInChromatic dispersion is -80 ps / nm / km or less, and dispersion slowIs0 ps / nm²/ Km or less, and has a cut-off wavelength capable of substantially single-mode propagation over the length of use.Comprising a single dispersion compensating optical fiberLongitudinal directionInDistributed throwIs0 to -1.0ps / nm²In the range of / kmThe dispersion slope is wound in the small coil shape so as to decrease from the radially inner side to the outer side.It is characterized by that.
[0007]
A dispersion compensating optical fiber according to claim 2 is the dispersion compensating optical fiber according to claim 1, wherein the center core, a side core having a lower refractive index than the center core, and a lower refractive index are provided on the outer periphery of the center core. And a refractive index distribution shape including a clad having a lower refractive index than the center core and a higher refractive index than the side core.
[0008]
The dispersion compensating optical fiber according to claim 3 is the dispersion compensating optical fiber according to claim 1, wherein the center core, a side core having a lower refractive index than the center core, and a lower refractive index are provided on the outer periphery of the center core. A ring layer having a higher refractive index than that of the center core and a refractive index lower than that of the center core, and a refractive index lower than that of the center core and the ring layer and higher than that of the side core. It has a refractive index distribution shape provided with a clad of refractive index.
[0009]
  The dispersion compensating optical fiber according to claim 4.Manufacturing methodIsA dispersion compensating optical fiber wound as a small coil and used as an optical fiber type dispersion compensator, and having a wavelength dispersion of −80 ps / nm / km or less in a used wavelength band selected from 1.53 to 1.61 μm Yes, and dispersion slope is 0ps / nm ² / Dispersion-compensating optical fiber having a cut-off wavelength that can be propagated in a single mode substantially in its use length, and the dispersion slope in the longitudinal direction is 0 to −1.0 ps / nm ² In the dispersion compensating optical fiber wound in the small coil shape so that the dispersion slope decreases from the radially inner side to the outer side, and the base material is uniform in the longitudinal direction. It is characterized by comprising at least a step of drawing the base material into a tapered shape after manufacturing and then drawing so as to form a constant optical fiber diameter.
  Furthermore, the dispersion compensating optical fiber manufacturing method according to claim 5 is a dispersion compensating optical fiber that is wound in a small coil shape and used as an optical fiber type dispersion compensator, and is selected from 1.53 to 1.61 μm. The chromatic dispersion in the used wavelength band is -80 ps / nm / km or less and the dispersion slope is 0 ps / nm. ² / Dispersion-compensating optical fiber having a cut-off wavelength that can be propagated in a single mode substantially in its use length, and the dispersion slope in the longitudinal direction is 0 to −1.0 ps / nm ² In the dispersion compensating optical fiber wound in the small coil shape so that the dispersion slope decreases from the radially inner side to the outer side, and the base material is uniform in the longitudinal direction. At least a step of changing the outer diameter of the optical fiber at the time of drawing after manufacture is provided. Dispersion compensating optical fiber manufacturing method.
[0010]
  Also,Claim 6The described optical fiber type dispersion compensator,smallIn an optical fiber type dispersion compensator having a dispersion compensating optical fiber wound in a coil shape,ReportThe dispersion compensating optical fiber is used in a wavelength band selected from 1.53 to 1.61 μm.InChromatic dispersion is -80 ps / nm / km or less, and dispersion slowIs0 ps / nm²/ Km or less, and has a cut-off wavelength capable of substantially single-mode propagation over the length of use.Comprising a single dispersion compensating optical fiberLongitudinal directionInDistributed throwIs0 to -1.0ps / nm²In the range of / kmThe dispersion slope is wound in the small coil shape so that the dispersion slope decreases from the inner side to the outer side in the radial direction.The residual wavelength component in the used wavelength band selected from 1.53 to 1.61 μm when connected to a single mode optical fiber for 1.3 μm band transmission.Scatter-8 to +8 ps / nm / km, and residual dispersion slope is -0.03 to +0.03 ps / nm²/ Km.
[0011]
  The dispersion compensating optical fiber according to claim 1 andClaim 6According to the optical fiber type dispersion compensator, the dispersion compensating optical fiber is, MinutesScattered throwIsThe larger one is more resistant to bending,MinScattered throwIsThe smaller one is vulnerable to bending, so the dispersion throw is relatively strong against bending.IsThe larger one is the winding start part with a smaller bending diameter, and the dispersion throw is relatively weak against bending.IssmallNoThis is wound as an outer peripheral portion having a larger bending diameter. This makes it possible to configure a small coil with a single optical fiber while maintaining the dispersion slope compensation rate.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the dispersion compensating optical fiber of the present invention and an optical fiber type dispersion compensator provided with the same will be described, but the present invention is of course not limited thereto.
[0013]
The dispersion compensating optical fiber of the present embodiment is used as an optical fiber type dispersion compensator by being wound in a small coil shape, and has a 1.55 μm band (a used wavelength band selected from 1.53 to 1.61 μm). Chromatic dispersion at -80 ps / nm / km or less and a dispersion slope value of 0 ps / nm²/ Km or less, and has a refractive index distribution (refractive index distribution shown in FIGS. 1 and 2 to be described later) structure having a cutoff wavelength that can propagate substantially in a single mode in the use length, and in the longitudinal direction. Dispersion slope value of 0 to -1.0 ps / nm²The structure which changes in the range of / km is adopted. Furthermore, when winding the dispersion compensating optical fiber, a winding method is adopted in which the dispersion slope value is reduced to a small coil shape so that the dispersion slope value decreases from the radially inner side to the outer side.
[0014]
That is, the dispersion compensating optical fiber of the present embodiment has a dispersion slope value of 0 to −1.0 ps / nm in the longitudinal direction in at least one wavelength in the 1.55 μm band, that is, in the range of 1.53 μm to 1.61 μm.²A dispersion compensating optical fiber that is changing in the range of / km is manufactured, and the part that starts to be wound around the body is made a part having a relatively low dispersion slope compensation effect and a strong bending characteristic, and the part toward the outer periphery has a relatively bending characteristic. A dispersion compensating optical fiber that is weak and has a high dispersion slope compensation effect to achieve a high dispersion slope compensation effect as a whole is intended to be realized by a single optical fiber instead of a plurality of connections.
[0015]
As a means for changing the characteristics in the longitudinal direction, as in Example 1 to be described later, before drawing, the base material is processed into a tapered shape and then drawn with a constant optical fiber diameter. A base material having a constant outer diameter may be drawn so that the diameter changes in a tapered shape. That is, even if the refractive index distribution shape is the same, it is possible to change the dispersion slope together with the chromatic dispersion by changing the core diameter. In this case, since the bending loss is larger when the dispersion slope is smaller, that is, when the core diameter is smaller, it is preferably used on the fiber outer peripheral side where the bending diameter can be naturally increased when coiled. As a method of changing the core diameter, after manufacturing a uniform base material in the longitudinal direction, the processing described in the first embodiment is performed, and then the core diameter is drawn with a constant diameter so that the outer diameter is constant and the core An optical fiber having a changed diameter can be manufactured. It can also be produced by manufacturing a uniform base material in the longitudinal direction and then changing the outer diameter of the fiber during drawing.
[0016]
  In addition, as an optical fiber type dispersion compensator including such a dispersion compensating optical fiber, a dispersion compensating optical fiber wound in a small coil shape is connected to a 1.3 μm band single mode optical fiber, Use wavelength band selected from 1.53 to 1.61 μmInResidual wavelengthScatter-8 to +8 ps / nm / km, and residual dispersion slope is -0.03 to +0.03 ps / nm²/ Km is preferable from the viewpoint of achieving both a reduction in the size of the dispersion compensator and an improvement in transmission characteristics in a wide band.
[0017]
By adopting the configuration described above, it is possible to easily manufacture a dispersion compensating optical fiber that has a high dispersion slope compensation effect and does not cause deterioration in transmission loss characteristics even when it is wound into a small coil.
Therefore, by adopting a dispersion compensating optical fiber that has a high dispersion slope compensation effect and does not cause deterioration of transmission loss characteristics even if it is wound in a small coil shape, an optical fiber type dispersion compensator that can be reduced in size can be easily obtained. It can also be manufactured.
[0018]
Embodiments of the present invention will be described below with reference to the drawings.
1 is a graph showing the refractive index distribution of the dispersion compensating optical fiber used in Example 2, FIG. 2 is a graph showing the refractive index distribution of Example 1, FIG. 4 is Example 1 and FIG. FIG. 5 is a dispersion characteristic diagram when the core diameter of the dispersion compensating optical fiber is changed, FIG. 5 is an explanatory diagram of a tapered rod used in the first embodiment, and FIG. 6 is used in the first and second embodiments. It is a schematic explanatory drawing of an extending | stretching apparatus.
[0019]
[Example 1]
The dispersion compensating optical fiber 1 according to the first embodiment satisfies the conditions of the dispersion compensating optical fiber described above. The manufacturing method is shown below.
First, GeO is obtained by the VAD method.₂Addition core-SiO₂A porous body having a cladding structure was produced. The porous body was dehydrated with He and a chlorine-based gas in an atmosphere of about 1000 ° C., and then 5 l / min He and 1000 cc / min SiF._FourIn the atmosphere, fluorine addition and transparent vitrification were simultaneously performed. This rod is stretched to form a core base material around which SiO2 is used for cladding.₂1 is attached to the outside, dehydrated with He and a chlorine-based gas in an atmosphere of approximately 1000 ° C., and further converted into transparent glass in the He atmosphere to have a profile (refractive index distribution) as shown in FIG. Type dispersion compensating optical fiber preform was fabricated.
[0020]
  Referring to FIG. 1, this W-type dispersion compensating optical fiber preform 1 (or a dispersion compensating optical fiber manufactured using the same) is provided on the outer periphery of the center core 1a and the center core 1a and is lower than this. The refractive index profile has a refractive index side core 1b and a cladding 1c provided on the outer periphery of the side core 1b and having a lower refractive index than the center core 1a and a higher refractive index than the side core 1b. The symbol r1 is a radius from the axis of the center core 1a (accordingly, twice the r1 is the outer diameter of the center core 1a), and the symbol r2 is from the coaxial line.ofThe radius of the side core 1b (accordingly, twice the r2 is the outer diameter of the side core 1b), Δ2 is the cladding1cRelative refractive index difference between the core and the side core 1b, Δ1 is the cladding1cAnd the relative refractive index difference between the center core 1a. In FIG. 1, the higher the refractive index is, the higher the direction of the paper is. FIG. 3 is a graph in which a ratio obtained by dividing the inner radius r2 of the side core 1b by the radius r1 of the center core 1a is plotted in a graph in which the horizontal axis represents the core radius and the vertical axis represents the chromatic dispersion and the dispersion slope. Note that the chromatic dispersion and dispersion slope in FIG. 3 all indicate values at a wavelength of 1550 nm. In the first embodiment, as described in FIG. 3, Δ1 = 2.3% and Δ2 = −0.40%. It can also be seen that if the ratio r2 / r1 is in the range of 2.5 to 4.5, the above-mentioned characteristics can be obtained satisfactorily.
[0021]
This W-type dispersion compensating optical fiber preform 1 is processed into a taper shape as shown in FIG. 5, and then drawn with a drawing device 3 as shown in FIG. 6 to have the same fiber outer diameter of 125 μm. (Not shown). At this time, the core diameter (r2 × 2) at one end was 4.3 μm, and the core diameter (r2 × 2) at the other end was 4.05 μm. In FIG. 6, reference numeral 4 is a dummy rod, reference numeral 5 is an upper chuck, reference numeral 6 is a lower chuck, reference numeral 7 is a heating furnace, and reference numeral 8 is a furnace core tube.
[0022]
  The produced dispersion-compensating optical fiber has a total length of 7.35 km, a transmission loss at a total length of 1.55 μm of 0.45 dB / km, a chromatic dispersion of −125 ps / nm / km, and a dispersion slow.Is-0.40ps / nm²/ Km. This has a chromatic dispersion of +17 ps / nm / km and a dispersion slope of +0.06 ps / nm.²/ Km 1.3μm bandFor transmissionWhen used in connection with a single mode optical fiber 54 km, the chromatic dispersion in the entire transmission line is substantially zero, and the dispersion slope is 0.30 ps / nm in the entire transmission line.²+ 0.005ps / nm in terms of unit length²/ Km and a low dispersion slope transmission line can be constructed.The. In addition, this dispersion compensating optical fiber is wound around an aluminum reel having a body diameter of 60 mm and wound into a small coil shape. At this time, since the core diameter is large and the winding characteristic is strong, the bending loss characteristic is not deteriorated. The bending loss characteristics of the coil itself did not deteriorate. Therefore, 1.3μm in the 1.55μm bandBand transmissionWhen dispersion compensation is performed at a wavelength of 1.55 μm by connecting to a single-mode optical fiber, the dispersion is almost zero in a wide band of wavelengths from 1.53 μm to 1.61 μm, low loss, and dispersion in a wide band is small Therefore, good transmission could be performed.
[0023]
[Example 2]
GeO by VAD method₂Addition core-SiO₂A porous body having a cladding structure was produced. The porous body was dehydrated with He and a chlorine-based gas in an atmosphere of about 1000 ° C., and then 5 l / min He and 1000 cc / min SiF._FourIn the atmosphere, fluorine addition and transparent vitrification were simultaneously performed. This rod is stretched to be a core base material, and a ring portion is formed around it.₂-SiO₂Made of porous material and SiO for cladding₂A porous body made of the above is sequentially attached, dehydrated with He and a chlorine-based gas in an atmosphere of about 1000 ° C., and further formed into a transparent glass in a He atmosphere to have a profile (refractive index distribution) as shown in FIG. A dispersion-compensating optical fiber preform was prepared.
Referring to FIG. 2, the dispersion compensating optical fiber preform 2 is provided on the outer periphery of the center core 2a, the side core 2b having a lower refractive index than the center core 2a, and on the outer periphery of the side core 2b. A ring layer 2c having a higher refractive index than the center core 2a and a lower refractive index than the center core 2a and the ring layer 2c and having a higher refractive index than the side core 2b. It has a refractive index profile with a cladding 2d.
The symbol r21 is a radius from the axis of the center core 2a (accordingly, twice the radius r21 is the outer diameter of the center core 2a), and the symbol r22 is the radius of the side core 2b from the coaxial line (accordingly, twice the r22 is the radius of the side core 2b). The outer diameter of the ring layer 2c is the same as the outer diameter of the ring layer 2c. Therefore, Δ21 is the relative refractive index difference between the clad 2d and the center core 2a. Δ22 represents a relative refractive index difference between the clad 2d and the side core 2b, and Δ23 represents a relative refractive index difference between the clad 2d and the ring layer 2c. In FIG. 2, the higher the refractive index is, the higher the direction of the paper is.
FIG. 4 is a graph in which the ratio obtained by dividing the inner radius r22 of the side core 2b by the radius r21 of the center core 2a is plotted in a graph in which the horizontal axis represents the core radius and the vertical axis represents the chromatic dispersion and the dispersion slope. Note that the wavelength dispersion and dispersion slope in FIG. 4 all indicate values at a wavelength of 1550 nm. In the second embodiment, as described in FIG. 4, Δ21 = 2.3%, Δ22 = −0.40%, Δ23 = 0.4%, r23−r22 = 2r21. Moreover, r22 / r21 was 4.5. Furthermore, it can be seen from FIG. 4 that the above-mentioned characteristics can be obtained satisfactorily when r22 / r21 is in the range of 2.5 to 4.5.
[0024]
The dispersion-compensating optical fiber preform 1 is processed into a tapered shape as shown in FIG. 5 of the first embodiment, and then drawn by the drawing device 3 so as to have a fiber outer diameter of 125 μm (not shown). ) At this time, the core diameter (r23 × 2) at one end was 5.1 μm, and the core diameter (r23 × 2) at the other end was 5.3 μm.
[0025]
  The produced dispersion compensating optical fiber has a total length of 4.0 km, a transmission loss of 0.45 dB / km at a total length of 1.55 μm, a chromatic dispersion of −135 ps / nm / km, and a dispersion slow.Is-0.44ps / nm²/ Km. This has a chromatic dispersion of +17 ps / nm / km and a dispersion slope of +0.06 ps / nm.²/ Km 1.3μm bandFor transmissionWhen used in connection with a single mode optical fiber of 31.8 km, the chromatic dispersion in the entire transmission line is substantially zero, and the dispersion slope is 0.15 ps / nm in the entire transmission line.²+ 0.004ps / nm in terms of unit length²/ Km and a low dispersion slope transmission line could be constructed. In addition, this dispersion compensating optical fiber is wound around an aluminum reel having a body diameter of 60 mm and wound into a small coil shape. At this time, since the core diameter is large and the winding characteristic is strong, the bending loss characteristic is not deteriorated. The bending loss characteristics of the coil itself did not deteriorate. Therefore, 1.3μm in the 1.55μm bandBand transmissionWhen dispersion compensation is performed at a wavelength of 1.55 μm by connecting to a single-mode optical fiber, the dispersion is almost zero in a wide band of wavelengths from 1.53 μm to 1.61 μm, low loss, and dispersion in a wide band is small Therefore, good transmission could be performed.
[0026]
[Comparative Example 1]
Similar to Example 1 above, GeO was obtained by the VAD method.₂Addition core-SiO₂A porous body having a cladding structure was produced. The porous body was dehydrated with He and a chlorine-based gas in an atmosphere of about 1000 ° C., and then 5 l / min He and 1000 cc / min SiF._FourIn the atmosphere, fluorine addition and transparent vitrification were simultaneously performed. This rod is stretched to form a core base material around which SiO2 is used for cladding.₂A porous body made of the above is externally attached, dehydrated with He and a chlorine-based gas in an atmosphere of about 1000 ° C., and further transparently vitrified in an He atmosphere to have the same profile (refractive index distribution) as in Example 1. W-type dispersion compensating optical fiber preform (not shown) was prepared.
[0027]
  This W-type dispersion compensating optical fiber preform was drawn so as to have a core diameter = 4.3 μm and a fiber outer diameter = 125 μm to obtain a dispersion compensating optical fiber. The produced dispersion-compensating optical fiber has a transmission loss of 0.45 dB / km, a chromatic dispersion of −100 ps / nm / km, a dispersion slow at 1.55 μm.Is-0.13ps / nm²/ Km, the same 1.3 μm as in Example 1.Band transmissionResidual dispersion slope is +0.032 ps / nm when dispersion compensation is performed at a wavelength of 1.55 μm when connected to a single mode optical fiber²Since about / km remained, dispersion compensation for each wavelength was further required. Further, even when this dispersion compensating optical fiber is wound around an aluminum reel having a body diameter of 60 mm and a small coil is used, the bending loss characteristics are not deteriorated.
[0028]
[Comparative Example 2]
Similar to Example 1 above, GeO was obtained by the VAD method.₂Addition core-SiO₂A porous body having a cladding structure was produced. The porous body was dehydrated with He and a chlorine-based gas in an atmosphere of about 1000 ° C., and then 5 l / min He and 1000 cc / min SiF._FourIn the atmosphere, fluorine addition and transparent vitrification were simultaneously performed. This rod is stretched to form a core base material around which SiO2 is used for cladding.₂Another W-type dispersion compensation light having the same profile as that of Example 1 is obtained by externally attaching a porous body made of the above, dehydrating with He and a chlorine-based gas in an atmosphere of approximately 1000 ° C., and further forming a transparent glass in the He atmosphere. A fiber preform (not shown) was produced.
[0029]
  This W-type dispersion compensating optical fiber preform was drawn so as to have a core diameter = 4.1 μm and a fiber outer diameter = 125 μm to obtain a dispersion compensating optical fiber. The manufactured dispersion compensating optical fiber is 1.55 μm.KickTransmission loss is 0.45dB / km, chromatic dispersion is -133ps / nm / km, dispersion slowIs-0.42ps / nm²/ Km, the same 1.3 μm as in Example 1.Band transmissionWhen dispersion compensation is performed at a wavelength of 1.55 μm when connected to a single-mode optical fiber, the dispersion is almost zero over a wide band from 1.53 μm to 1.61 μm, and the dispersion slope per unit length of the entire transmission line Converted to + 0.006ps / nm²/ Km and low dispersion slope, and good transmission could be performed. However, when this dispersion-compensating optical fiber is wound on an aluminum reel having a body diameter of 60 mm to form a small coil, the bending loss characteristic deteriorates rapidly, and the bending loss characteristic of the coil itself deteriorates. As a result, good transmission cannot be performed.
[0030]
[Comparative Example 3]
GeO by VAD method₂Addition core-SiO₂A porous body having a cladding structure was produced. The porous body was dehydrated with He and a chlorine-based gas in an atmosphere of about 1000 ° C., and then 5 l / min He and 1000 cc / min SiF._FourIn the atmosphere, fluorine addition and transparent vitrification were simultaneously performed. This rod is stretched to be a core base material, and a ring portion is formed around it.₂-SiO₂Made of porous material and SiO for cladding₂The dispersion-compensating optical fiber preform having the same profile as that of Example 2 is obtained by sequentially attaching a porous body made from the above, dehydrating with He and a chlorine-based gas in an atmosphere of approximately 1000 ° C., and further forming a transparent glass in the He atmosphere. Was made.
[0031]
  This W-type dispersion compensating optical fiber preform was drawn so as to have a core diameter = 5.15 μm and a fiber outer diameter = 125 μm to obtain a dispersion compensating optical fiber. The manufactured dispersion-compensating optical fiber has a total length of 4.0 km, a transmission loss of 0.45 dB / km at a total length of 1.55 μm, a chromatic dispersion of −135 ps / nm / km, and a dispersion slow.Is-0.44ps / nm²/ KmWas. This is the same 1.3 μm band as in Example 2.For transmissionWhen used in connection with a single mode optical fiber, the chromatic dispersion in the entire transmission line is substantially zero, and the dispersion slope is 0.15 ps / nm in the entire transmission line.²+ 0.004ps / nm in terms of unit length²/ Km and a low dispersion slope transmission line could be constructed. However, when this dispersion-compensating optical fiber is wound on an aluminum reel having a body diameter of 60 mm to form a small coil, the bending loss characteristic deteriorates rapidly, and the bending loss characteristic of the coil itself deteriorates. As a result, good transmission cannot be performed.
[0032]
Therefore, as described above, the dispersion compensation optical fiber of Comparative Example 1 requires further dispersion compensation for each wavelength, and the dispersion compensation optical fibers of Comparative Example 2 and Comparative Example 3 are small in size. When this coil was used, the bending loss characteristics deteriorated rapidly, and the bending loss characteristics of the coil itself deteriorated. On the other hand, in the dispersion compensating optical fiber according to the above-described embodiment having the configuration of the present invention, even if it is wound around a small coil, the bending loss characteristic does not deteriorate, and the bending loss characteristic of the coil itself does not deteriorate. . As a result, even when connected to a 1.3 μm single-mode optical fiber in the 1.55 μm band, it is possible to obtain excellent performance such that broadband and almost zero dispersion, low loss, and good transmission can be achieved. It became.
[0033]
【The invention's effect】
  As described above, claims 1 to 1 of the present invention.5Dispersion compensating optical fiber as describedAnd its manufacturing methodAccording to the wavelength band selected from 1.53 to 1.61 μmInChromatic dispersion is -80 ps / nm / km or less, and dispersion slowIs0 ps / nm²/ Km or less, and has a cut-off wavelength capable of substantially single-mode propagation over the length of use.Comprising a single dispersion compensating optical fiberLongitudinal directionInDistributed throwIs0 to -1.0ps / nm²Change in the range of / kmAnd the dispersion slope is wound in the small coil shape so as to decrease from the radially inner side to the outer side.Adopting the configurationByIt has become possible to easily manufacture a dispersion compensating optical fiber that has a high dispersion slope compensation effect and that does not deteriorate transmission loss characteristics even when it is wound into a small coil.
[0034]
  In addition, the above claims6According to the described optical fiber type dispersion compensator, it is possible to reduce the size of the optical fiber by adopting the dispersion compensating optical fiber that has a high dispersion slope compensation effect and that does not cause deterioration of transmission loss characteristics even if it is wound around a small coil. Type dispersion compensator can be easily manufactured.
[Brief description of the drawings]
FIG. 1 is a graph showing a refractive index distribution of a dispersion compensating optical fiber used in Example 1 of the present invention.
FIG. 2 is a graph showing a refractive index distribution of a dispersion compensating optical fiber used in Example 2 of the present invention.
FIG. 3 is a dispersion characteristic diagram when the core diameter of the dispersion compensating optical fiber of Example 1 is changed.
FIG. 4 is a dispersion characteristic diagram when the core diameter of the dispersion compensating optical fiber of Example 1 is changed.
FIG. 5 is a view showing a tapered rod used in Example 1, and is a cross-sectional view taken along a cross section along an axis.
6 is a schematic explanatory diagram of a stretching apparatus used in Example 1 and Example 2. FIG.
[Explanation of symbols]
1a, 2a ... center core, 1b, 2b ... side core, 1c, 2d ... clad, 2c ... ring layer

Claims (6)

A dispersion compensating optical fiber wound as a small coil and used as an optical fiber type dispersion compensator ,
Wavelength dispersion in the used wavelength band selected from 1.53~1.61μm is not more than -80 ps / nm / miles, and the dispersion slope is not more 0ps / ^nm 2 / km or less, and substantially in the used length Single-mode propagation can be configured to cut-off wavelength from one of the dispersion compensating optical fiber for chromatic, varies in the range of the dispersion slope is 0~-1.0ps / nm 2 / ^km in the longitudinal direction, the dispersion The dispersion compensating optical fiber , wherein the slope is wound in the small coil shape so that the slope becomes smaller from the inside in the radial direction toward the outside . The dispersion compensating optical fiber according to claim 1, wherein
A center core (1a), a side core (1b) provided on the outer periphery of the center core and having a lower refractive index than the center core, and a lower refractive index provided on the outer periphery of the side core than the center core and having a higher refractive index than the side core. A dispersion-compensating optical fiber having a refractive index distribution shape including a clad (1c). The dispersion compensating optical fiber according to claim 1, wherein
A center core (2a), a side core (2b) provided on the outer periphery of the center core and having a lower refractive index than the center core, and a higher refractive index provided on the outer periphery of the side core and lower than the center core. A refractive index profile comprising: a ring layer (2c); and a center core and a clad (2d) having a lower refractive index than that of the ring layer and a higher refractive index than that of the side core. A dispersion compensating optical fiber characterized by comprising: A dispersion compensating optical fiber wound as a small coil and used as an optical fiber type dispersion compensator, and having a wavelength dispersion of −80 ps / nm / km or less in a used wavelength band selected from 1.53 to 1.61 μm Yes, and dispersion slope is 0ps / nm ² / Dispersion-compensating optical fiber having a cut-off wavelength that can be propagated in a single mode substantially in its use length, and the dispersion slope in the longitudinal direction is 0 to −1.0 ps / nm ² In the method of manufacturing a dispersion compensating optical fiber that changes in the range of / km and is wound in the small coil shape so that the dispersion slope decreases from the radially inner side to the outer side,
A dispersion-compensating optical fiber comprising at least a step of drawing a base material uniform in the longitudinal direction and then drawing the base material so as to have a constant optical fiber diameter after processing the base material into a tapered shape in advance. Production method. A dispersion compensating optical fiber wound as a small coil and used as an optical fiber type dispersion compensator, and having a wavelength dispersion of −80 ps / nm / km or less in a used wavelength band selected from 1.53 to 1.61 μm Yes, and dispersion slope is 0ps / nm ² / Dispersion-compensating optical fiber having a cut-off wavelength that can be propagated in a single mode substantially in its use length, and the dispersion slope in the longitudinal direction is 0 to −1.0 ps / nm ² In the method of manufacturing a dispersion compensating optical fiber that changes in the range of / km and is wound in the small coil shape so that the dispersion slope decreases from the radially inner side to the outer side,
A method for producing a dispersion-compensating optical fiber comprising at least a step of changing an outer diameter of an optical fiber at the time of drawing after producing a base material uniform in the longitudinal direction. In an optical fiber type dispersion compensator having a dispersion compensating optical fiber wound in a small coil shape,
Before SL minute dispersion compensating optical fiber is a chromatic dispersion -80 ps / nm / miles or less in the used wavelength band selected from 1.53～1.61Myuemu, and dispersion slope is 0ps / ^nm 2 / km or less There, and is composed of one of the dispersion compensating optical fiber to have a substantially single-mode propagation cutoff wavelength in the used length, dispersion slope in the longitudinal direction 0~-1.0ps / nm ² / km, and the dispersion slope is wound in the small coil shape so as to decrease from the radially inner side to the outer side ,
In a state of being connected to 1.3μm band single mode optical fiber for transmission, dispersion remaining wavelengths in the use wavelength band selected from 1.53~1.61μm is a -8~ + 8ps / nm / km, and optical fiber dispersion compensator you characterized in that the residual dispersion slope is a ^{-0.03~ + 0.03ps / nm 2 / km} .

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