WO2025028628A1 - 偏波保持ファイバ - Google Patents

偏波保持ファイバ Download PDF

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Publication number
WO2025028628A1
WO2025028628A1 PCT/JP2024/027623 JP2024027623W WO2025028628A1 WO 2025028628 A1 WO2025028628 A1 WO 2025028628A1 JP 2024027623 W JP2024027623 W JP 2024027623W WO 2025028628 A1 WO2025028628 A1 WO 2025028628A1
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Prior art keywords
polarization
less
maintaining fiber
core
stress
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English (en)
French (fr)
Japanese (ja)
Inventor
達 松永
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Fujikura Ltd
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Fujikura Ltd
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Priority to JP2025537520A priority Critical patent/JPWO2025028628A1/ja
Priority to CN202480050180.6A priority patent/CN121620722A/zh
Publication of WO2025028628A1 publication Critical patent/WO2025028628A1/ja
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/024—Optical fibres with cladding with or without a coating with polarisation maintaining properties

Definitions

  • the present invention relates to polarization-maintaining fiber.
  • Patent Document 1 An example of a polarization-maintaining fiber is described in the following Patent Document 1.
  • the present invention therefore aims to provide a polarization-maintaining fiber that suppresses degradation of macrobend loss characteristics even when a user applies the polarization-maintaining fiber to the optical device.
  • aspect 1 of the present invention is a polarization-maintaining fiber comprising a core, a pair of stress-applying parts arranged at positions sandwiching the core, and a cladding containing the core and the pair of stress-applying parts, the stress-applying parts having a twisted section in which they permanently rotate in a spiral around the core, the spiral twist of the stress-applying parts in the twisted section is within one turn per 47.1 mm of fiber length, the mode field diameter at a wavelength of 1.55 ⁇ m is 10.6 ⁇ m or less, and the cutoff wavelength when the fiber length is 2 m and the bending radius is 140 mm is 1.24 ⁇ m or more and less than 1.55 ⁇ m.
  • the light confinement force can be increased due to the smaller mode field diameter compared to when the mode field diameter at that wavelength is greater than 10.6 ⁇ m. Also, by having a cutoff wavelength of 1.24 ⁇ m or more when the fiber length is 2 m and the bending radius is 140 mm, the light confinement force can be increased compared to when the cutoff wavelength is smaller than 1.24 ⁇ m. This makes it possible to suppress the loss of light propagating through the core.
  • this polarization-maintaining fiber has the above-mentioned mode field diameter and cutoff wavelength configuration, it can increase the light confinement force as described above. Therefore, compared to a polarization-maintaining fiber that does not have this configuration, it can suppress light leakage even in the twist section with the above-mentioned number of twist rotations, and for example, even when a user applies the polarization-maintaining fiber to the optical device, it can suppress deterioration of macrobend loss characteristics.
  • the present invention it is possible to provide a polarization-maintaining fiber that suppresses deterioration of macrobend loss characteristics even when a user applies the polarization-maintaining fiber to the optical device.
  • FIG. 1 illustrates a polarization-maintaining fiber according to an embodiment of the present invention.
  • FIG. 2 illustrates a twisted section of polarization-maintaining fiber.
  • FIG. 13 is a diagram showing the distribution of relative refractive index difference along the fast axis direction.
  • FIG. 13 is a diagram showing the distribution of the relative refractive index difference along the slow axis direction.
  • FIG. 1 is a diagram showing a polarization-maintaining fiber according to this embodiment.
  • (a) is a cross-sectional view showing the transverse section of the polarization-maintaining fiber according to this embodiment
  • (b) is a diagram showing the refractive index distribution along line A-A of the cross section shown in (a) of FIG. 1.
  • the transverse section is a cross section perpendicular to the central axis C of the polarization-maintaining fiber 1.
  • the polarization-maintaining fiber 1 includes a core 11, a pair of stress-applying portions 12a, 12b arranged on either side of the core 11, and a cladding 13 that contains the core 11 and the pair of stress-applying portions 12a, 12b.
  • the polarization-maintaining fiber 1 may also include a coating that covers the cladding 13.
  • a polarization-maintaining fiber 1 configured in this manner may be referred to as a PANDA (Polarization-maintaining AND Absorption-reducing) fiber. In other words, it may be referred to as a PANDA-type polarization-maintaining fiber.
  • the relative refractive index difference ⁇ 11 of the core 11 with respect to the cladding 13 is preferably 0.32% or more.
  • the relative refractive index difference ⁇ 11 is more preferably 0.33% or more.
  • the relative refractive index difference ⁇ 11 of 0.33% or more the light confinement force to the core 11 can be increased and the leakage of light from the core 11 can be suppressed compared to when the relative refractive index difference ⁇ 11 is less than 0.33%.
  • the relative refractive index difference ⁇ 11 is preferably 0.40% or less. It is possible to suppress the mode field diameter of the light propagating through the core 11 from becoming too small, and to suppress the loss of light at the connection point with another optical fiber or optical device. Therefore, the relative refractive index difference ⁇ 11 is preferably 0.32% or more and 0.40% or less in order to balance the light confinement power and the light loss at the connection point, and more preferably 0.33% or more and 0.40% or less.
  • optical device examples include, for example, (1) telecom optical devices such as transceivers for intercity networks and submarine networks, or optical devices for datacom such as CPO (Co-packaged Optics) modules (CPO switch modules, etc.) and pluggable transceivers (coherent optical transceivers, etc.), (2) optical devices for amplifiers, and (3) optical devices for sensors.
  • CPO Co-packaged Optics
  • pluggable transceivers coherent optical transceivers, etc.
  • optical devices for amplifiers examples include, for example, (1) telecom optical devices such as transceivers for intercity networks and submarine networks, or optical devices for datacom such as CPO (Co-packaged Optics) modules (CPO switch modules, etc.) and pluggable transceivers (coherent optical transceivers, etc.), (2) optical devices for amplifiers, and (3) optical devices for sensors.
  • the “optical device” described below is used to include the optical devices in (1) to (3) above.
  • the cross-sectional shape of the core 11 in this embodiment is generally circular.
  • the cross-sectional shape of the core 11 is not limited to circular, and may be, for example, elliptical, crescent, or noncircular.
  • the cross-sectional shape of the core 11 here refers to the shape of a cross section perpendicular to the central axis C of the polarization-maintaining fiber 1.
  • the radius of the core is preferably 4.4 ⁇ m or less.
  • the radius of the core 11 is preferably 4.1 ⁇ m or more.
  • the radius of the core 11 is more preferably 4.1 ⁇ m or more and 4.4 ⁇ m or less.
  • the radius of the core 11 is, for example, half the size of the average value of the diameter of the core 11 in the direction perpendicular to the central axis C.
  • the radius of the core 11 is not particularly limited as long as the cutoff wavelength described later satisfies any one of the preferable conditions for the cutoff wavelength that satisfies ⁇ Condition 2> or (3) or (4) described later.
  • the pair of stress-applying parts 12a, 12b have a columnar shape extending along the central axis C, but may have a shape other than a columnar shape. As described later, the pair of stress-applying parts 12a, 12b may have at least a part of a twisted section along the longitudinal direction that permanently rotates in a spiral around the core 11. The pair of stress-applying parts 12a, 12b may have a twisted section along the longitudinal direction that permanently rotates in a spiral around the core 11 over the entire longitudinal area of the polarization-maintaining fiber 1. In this embodiment, the refractive index n12 of the stress-applying parts 12a, 12b is lower than the refractive index n13 of the cladding.
  • the stress-applying parts 12a, 12b are made of, for example, quartz glass to which a down dopant such as boron oxide (B 2 O 3 ) is added.
  • the cross-sectional shape of the stress-applying parts 12a, 12b may be an isosceles trapezoid with the upper base (shorter base) facing the core 11.
  • one or both of the upper and lower bases (longer bases) of the stress-applying parts 12a, 12b may be an arc shape bulging in a direction away from the core 11.
  • a polarization-maintaining fiber 1 in which the stress-applying parts 12a, 12b have an isosceles trapezoid shape is sometimes called a "bow-tie type polarization-maintaining fiber.”
  • the polarization-maintaining fiber 1 is not limited to the above-mentioned PANDA type polarization-maintaining fiber, and may be a bow-tie type polarization-maintaining fiber.
  • the cross-sectional shape of the stress applying parts 12a and 12b in this embodiment is generally circular as shown by the solid line in FIG. 1, or generally elliptical with the arrangement direction of the stress applying parts 12a and 12b as the minor axis direction as shown by the dashed line.
  • the cross-sectional shape of the stress applying parts 12a and 12b is not limited to circular or elliptical, and may be, for example, crescent or noncircular.
  • the cross-sectional shape of the stress applying parts 12a and 12b here refers to the shape of a cross section perpendicular to the central axis C of the polarization-maintaining fiber 1.
  • the diameter t of the stress applying parts 12a and 12b along the S-axis direction is preferably 24.8 ⁇ m or more, and more preferably 30.0 ⁇ m or more. This allows sufficient stress to be applied to the core 11, and as a result, the polarization-maintaining function can be preferably realized. Also, the diameter t is preferably 40.0 ⁇ m or less, more preferably 38.0 ⁇ m or less, and more preferably 34.4 ⁇ m or less. This allows the stress applying parts 12a and 12b to be suitably arranged inside the cladding 13, which has a diameter of 125 ⁇ m ⁇ 1 ⁇ m.
  • the diameter t is preferably 24.8 ⁇ m or more and 40.0 ⁇ m or less, preferably 24.8 ⁇ m or more and 38.0 ⁇ m or less, preferably 24.8 ⁇ m or more and 34.4 ⁇ m or less, preferably 30.0 ⁇ m or more and 40.0 ⁇ m or less, preferably 30.0 ⁇ m or more and 38.0 ⁇ m or less, and preferably 30.0 ⁇ m or more and 34.4 ⁇ m or less.
  • the diameter of the cladding 13 described below is 80 ⁇ m ⁇ 1 ⁇ m
  • the diameter t of the stress applying portions 12a, 12b along the S-axis direction is 22.0 ⁇ m or more. This allows sufficient stress to be applied to the core 11, and as a result, the polarization maintaining function can be suitably realized.
  • the diameter t is 27.0 ⁇ m or less. This allows the stress applying portions 12a, 12b to be suitably arranged inside the cladding 13, which has a diameter of 80 ⁇ m ⁇ 1 ⁇ m.
  • the diameter of the cladding 13 is 80 ⁇ m ⁇ 1 ⁇ m
  • the diameter t is 22.0 ⁇ m or more and 27.0 ⁇ m or less.
  • the stress applying portions 12a and 12b are each spaced apart from the core 11. This reduces the possibility that the core 11 will be subjected to unexpected deformation due to stress from the stress applying portions 12a and 12b when the polarization-maintaining fiber 1 is manufactured by melt drawing.
  • the core 11 is in contact with the stress applying portions 12a and 12b, and boron oxide is added to the stress applying portions 12a and 12b, the boron oxide may cause a deterioration in transmission loss.
  • this deterioration in transmission loss can be suppressed.
  • the interval between the stress applying portion 12a and the stress applying portion 12b is 2a, and the distance from the central axis C of the core 11 to the stress applying portion 12a, 12b is a.
  • this distance a refers to the distance from the center of the core 11 to the point included in the stress applying portion 12a that is closest to the core 11, or the distance from the center of the core 11 to the point included in the stress applying portion 12b that is closest to the core 11.
  • This distance a is preferably 10 ⁇ m or less.
  • the stress applying portions 12a, 12b which have a lower refractive index than the cladding 13, are closer to the core 11 than when the distance a is greater than 10 ⁇ m.
  • the function of the stress applying portions 12a, 12b as a low refractive index layer in the S-axis direction can be improved, and the leakage of light from the core 11 can be further suppressed.
  • the ratio of the distance a to the radius of the mode field diameter MFD (a/(MFD/2)) is 1.05 or more.
  • the stress-applying parts 12a and 12b are disposed outside the mode field, so that the deterioration of the transmission loss caused by boron oxide when the boron oxide is added to the stress-applying parts 12a and 12b can be suppressed.
  • the distance between the core 11 and the stress-applying parts 12a and 12b is preferably 1 ⁇ m or more.
  • the size of the diameter t described above is not particularly limited as long as the distance a satisfies any of the conditions (1), (2), (3), or (4) described below.
  • the cladding 13 has a columnar shape extending along the direction of the central axis C. As described above, the refractive index n13 of the cladding 13 is lower than the refractive index n11 of the core 11 and higher than the refractive index n12 of the stress applying portions 12a and 12b.
  • the cladding 13 is made of, for example, quartz glass.
  • the cross-sectional shape of the cladding 13 in this embodiment is generally circular.
  • the cross-sectional shape of the cladding 13 is not limited to this, and may be, for example, elliptical, crescent, or noncircular.
  • the cross-sectional shape of the cladding 13 here refers to the shape of a cross section perpendicular to the central axis C of the polarization-maintaining fiber 1.
  • the diameter b of the cladding 13 is preferably 125 ⁇ m ⁇ 1 ⁇ m, i.e., 124 ⁇ m or more and 126 ⁇ m or less, and more preferably 125 ⁇ m.
  • a polarization-maintaining fiber of approximately the same diameter as optical fibers commonly used in communication infrastructure can be realized.
  • the optical characteristics and mechanical characteristics of the optical fiber will be approximately the same as when the cladding diameter is 80 ⁇ m or 125 ⁇ m, or the variation will be within the margin of error, and will not have a significant effect on the optical characteristics and mechanical characteristics of the optical fiber.
  • the cladding diameter of ⁇ 1 ⁇ m is the same as the tolerance value of the cladding diameter specified in the optical fiber standard (ITU-T).
  • the cladding diameter of ⁇ 1 ⁇ m in an optical fiber with a cladding diameter of 80 ⁇ m may also correspond to the above tolerance value.
  • the diameter of the cladding 13 may be 79 ⁇ m or more and 126 ⁇ m or less.
  • the diameter b of the cladding 13 is, for example, the average diameter of the cladding 13 in a direction perpendicular to the central axis C.
  • the center of the circle that constitutes the outer periphery of the core 11 coincides with the center of the circle that constitutes the outer periphery of the clad 13, but this is not limited thereto, and the center of the circle that constitutes the outer periphery of the core 11 may be included in the center of the clad 13. Therefore, when the diameter of the clad 13 is 79 ⁇ m or more and 126 ⁇ m or less, the center of the circle that constitutes the outer periphery of the core 11 may be included in the center of the clad 13.
  • the center of the clad 13 refers to the inner region of a circle with a radius of 0.6 ⁇ m, whose center coincides with the center of the circle that constitutes the outer periphery of the clad 13.
  • the fiber length of the polarization-maintaining fiber 1 is preferably less than 50 m, may be less than 10 m, or may be 300 mm or less.
  • the fiber length of the polarization-maintaining fiber 1 is preferably 47.1 mm or more, and may be, for example, 2 m or more.
  • the polarization-maintaining fiber 1 When used for a sensor, it may be often used for a length of 50 m or more as a polarization-maintaining fiber that is generally available commercially. This is because the longer the polarization-maintaining fiber, the better the measurement resolution of the sensor.
  • a polarization-maintaining fiber for a sensor is used for several meters, the measurement resolution may decrease, making it difficult to use it as a sensor.
  • high measurement resolution is not required like a polarization-maintaining fiber for a sensor.
  • the length is less than 50 m as described above.
  • the fiber length when the polarization-maintaining fiber is connected in a wound state, the fiber length may be not only less than 50 m, but may also be a single digit value of more than 300 mm and less than 10 m in consideration of storage in various optical devices, and when the polarization-maintaining fiber is connected without being wound, the fiber length may be 300 mm or less, and it is preferable to determine the fiber length according to the connection state. Therefore, the fiber length does not need to be as long as 50 m or more, and by being less than 50 m, the polarization-maintaining fiber may be less likely to interfere with various optical devices.
  • the fiber length of the polarization-maintaining fiber 1 is preferably 23.55 mm or more and less than 50 m, preferably 23.55 mm or more and less than 10 m, preferably 23.55 mm or more and less than 300 mm, preferably 31.4 mm or more and less than 50 m, preferably 31.4 mm or more and less than 10 m, preferably 31.4 mm or more and less than 300 mm, preferably 47.1 mm or more and less than 50 m, preferably 47.1 mm or more and less than 10 m, preferably 47.1 mm or more and less than 300 mm, preferably 2 m or more and less than 50 m, preferably 2 m or more and less than 10 m, and preferably greater than 300 mm and less than 10 m.
  • the polarization-maintaining fiber 1 also has a twisted section along the longitudinal direction in which the stress-applying portions 12a and 12b permanently rotate in a spiral around the core 11.
  • Figure 2 shows the twisted section 1A of the polarization-maintaining fiber 1.
  • the stress-applying portions 12a and 12b are generally parallel to each other in a spiral shape centered on the central axis C of the core 11.
  • the helical twist of the stress-applying sections 12a and 12b per 50 m of the fiber length of the polarization-maintaining fiber 1 is greater than one rotation.
  • the twist is greater than 1/25 rotation per 1 m of the fiber length.
  • the longitudinal scale of the polarization-maintaining fiber 1 has been changed from the actual scale to make the figure easier to understand.
  • the stress applying portions 12a, 12b per 1 m of fiber length in the twisted section 1A When the helical twist of the stress applying portions 12a, 12b per 1 m of fiber length in the twisted section 1A is greater than 1/50 rotation, the stress applying portions 12a, 12b rotate helically, which can prevent light propagating through the core from concentrating in only a specific bending direction, such as the F-axis direction, from leaking out, thereby preventing the macrobend loss from becoming extremely large. In this way, it is possible to prevent the macrobend loss from becoming strongly dependent on the bending direction, which can eliminate the need to pay attention to the bending direction when using the polarization-maintaining fiber 1, and can make handling easier than when the fiber is twisted within 1/50 rotation per 1 m.
  • the polarization-maintaining fiber 1 since the other twisted sections are twisted in the opposite direction to the twisted section 1A, when no external force is applied to the polarization-maintaining fiber 1, the polarization-maintaining fiber 1 may be slightly curved in the other twisted section in the opposite direction to the slight curvature of the twisted section 1A.
  • the polarization-maintaining fiber 1 by having the polarization-maintaining fiber 1 with the twisted section 1A and the other twisted sections, when no external force is applied to the polarization-maintaining fiber 1, the polarization-maintaining fiber 1 can approach a straight line as a whole, compared to a case in which the polarization-maintaining fiber 1 has only the twisted section 1A. Therefore, it is preferable that the lengths of the twisted section and the other twisted sections are approximately the same, and it is preferable that they are the same.
  • the absolute value of the amount of helical twist of the stress-applying sections 12a, 12b per unit length is approximately the same in the twisted section 1A and the other twisted sections, and it is preferable that they are the same. It is also preferable that the twisted section 1A and the other twisted sections are provided alternately. The twist period may be different between the twisted section 1A and the other twisted sections. Furthermore, even if the polarization-maintaining fiber 1 has the twisted section 1A and the other twisted section, if the twisted section 1A and the other twisted section are arranged at the same period, they can be considered to have equivalent configurations when the optical characteristics are measured. Therefore, the optical characteristics, such as macrobend loss, of the polarization-maintaining fiber 1 having the twisted section 1A and the polarization-maintaining fiber 1 having the other twisted section can be roughly equivalent to each other.
  • the amount of helical twist can be found, for example, by immersing the polarization-maintaining fiber 1 in matching oil and observing the side of the polarization-maintaining fiber 1, or by observing both end faces of the polarization-maintaining fiber 1. In the latter case, the amount of helical twist can be found by observing the positions of the stress-applying portions 12a, 12b at both end faces of the polarization-maintaining fiber 1, respectively, and estimating the number of twist rotations from the amount of relative positional deviation of the two stress-applying portions.
  • the polarization-maintaining fiber 1 configured as above satisfies the following conditions 1 and 2.
  • the mode field diameter at a wavelength of 1.55 ⁇ m is smaller than when the mode field diameter is greater than 10.6 ⁇ m, and the light confinement effect can be improved accordingly.
  • the cutoff wavelength is 1.24 ⁇ m or more and less than 1.55 ⁇ m. Note that the cutoff wavelength here refers to the cutoff wavelength of light in the LP11 mode when the fiber length is 2 m and the bending radius is 140 mm.
  • a cutoff wavelength of 1.24 ⁇ m or more can improve the light confinement effect compared to a cutoff wavelength of less than 1.24 ⁇ m. Furthermore, if the above mode field diameter satisfies condition 1 and the cutoff wavelength satisfies condition 2, the refractive index distribution can be determined naturally.
  • the cutoff wavelength is less than 1.55 ⁇ m
  • single-mode optical transmission can be achieved when the wavelength used is 1.55 ⁇ m or more.
  • the polarization-maintaining fiber 1 satisfies at least one of the following (1) and (2) by having ⁇ Condition 1> and ⁇ Condition 2>.
  • macrobend loss is sometimes called bending loss.
  • the bending radius is 7.5 mm, and the macrobend loss at a wavelength of 1.55 ⁇ m is 0.67 dB/turn or less.
  • the bending radius is 10 mm, and the macrobend loss at a wavelength of 1.55 ⁇ m is 0.16 dB/turn or less.
  • a fiber length of 47.1 mm is the fiber length when one turn is made with a bending radius of 7.5 mm
  • a fiber length of 62.8 mm is the fiber length when one turn is made with a bending radius of 10 mm.
  • “one turn” refers to winding the polarization-maintaining fiber one turn around a mandrel with a diameter of 7.5 mm, or winding the polarization-maintaining fiber one turn around a mandrel with a diameter of 10 mm.
  • one turn is synonymous with one turn.
  • the polarization-maintaining fiber 1 can be realized to suppress the macrobend loss value to the loss tolerance required by the optical device, etc., even when, for example, a user applies the polarization-maintaining fiber to the optical device under the condition that the bending radius required as one of the target values of the optical device such as a coherent optical transceiver is about 7.5 mm or more.
  • the case where the user applies the polarization-maintaining fiber to the optical device which will be described later, can be, for example, the case where the polarization-maintaining fiber 1 is stored in various optical devices, etc.
  • the above-mentioned loss tolerance can be, for example, a value that can be applied to various optical devices. Also, as long as the above conditions 1 and 2 are satisfied, the measurement can be performed under the condition of 0.5 turns in the above condition 3 (1), and in this case, the fiber length of the above-mentioned polarization-maintaining fiber 1 can be less than 47.1 mm (for example, 23.55 mm), and in this case, the above-mentioned macrobend loss value can be a value proportional to 0.5 times.
  • the polarization-maintaining fiber 1 satisfy the above condition (2), it is possible to realize a polarization-maintaining fiber that can suppress the macrobend loss value to a loss tolerance value required by the optical device, etc., even when a user applies the polarization-maintaining fiber to the optical device under conditions where the bending radius required as a guideline for an integrated form with a bending radius larger than about 7.5 mm is about 10 mm or more.
  • the measurement may be performed under the condition of 0.5 turns in the above condition 3 (2), in which case the fiber length of the above polarization-maintaining fiber 1 may be less than 62.8 mm (e.g., 31.4 mm), in which case the above macrobend loss value may be a value proportional to 0.5 times.
  • the light confinement force can be made greater than when the diameter t is smaller than 24.8 ⁇ m, making it easier to satisfy at least one of the above conditions (1) and (2).
  • the cutoff wavelength when the polarization-maintaining fiber has a fiber length of 2 m and is wound around a diameter of 280 mm is referred to as the fiber cutoff wavelength.
  • the fiber cutoff wavelength was measured based on IEC 60793-1-44 as the wavelength at which the higher mode attenuates by 19.3 dB when the polarization-maintaining fiber 1 cut to a fiber length of 2 m is wound around a mandrel having a diameter of 280 mm.
  • the polarization-maintaining fiber was wound around the mandrel so that the slow axis of the polarization-maintaining fiber was perpendicular to the surface of the mandrel.
  • the mandrel is a rod-shaped jig with a perfectly circular cross section.
  • the polarization-maintaining fiber 1 is wound around the mandrel so that the slow axis of the polarization-maintaining fiber 1 is perpendicular to the surface of the mandrel.
  • R indicates the radius of the mandrel.
  • ⁇ Cladding diameter> The cladding diameter was measured by the transmitted near-field method based on IEC 60793-1-20.
  • the relative refractive index difference ⁇ 11 is the relative refractive index difference of the core with respect to the cladding.
  • FIG. 3 is a diagram showing the distribution of the relative refractive index difference along the fast axis direction.
  • the relative refractive index difference ⁇ 11 was obtained as the average of the relative refractive index difference in a region of 90% or more of the maximum value of the relative refractive index difference of the core with respect to the cladding by the following method.
  • the refractive index distribution of the core in the fast axis direction of the polarization-maintaining fiber was obtained by measurement using an interference method, the relative refractive index difference distribution on the fast axis was calculated, and the maximum value of the relative refractive index difference of the core with respect to the cladding was obtained, and then the relative refractive index difference was obtained as the average of the relative refractive index difference in a region of 90% or more of the maximum value of the relative refractive index difference of the core with respect to the cladding.
  • the relative refractive index difference ⁇ 12 is the relative refractive index difference of the stress-applying part with respect to the cladding.
  • FIG. 4 is a diagram showing the distribution of the relative refractive index difference along the slow axis direction.
  • the relative refractive index difference ⁇ 12 was obtained as the average of the relative refractive index differences in the region (from the region corresponding to 0.5 ⁇ 12 min to the region corresponding to ⁇ 12 min in FIG. 3) that satisfies 50% or less of the minimum value of the refractive index distribution in the slow axis direction of the stress-applying part, similar to the relative refractive index difference ⁇ 11 of the core.
  • the refractive index distribution of the stress-applying part in the slow axis direction of the polarization-maintaining fiber was obtained by measurement using an interference method, the relative refractive index difference distribution on the slow axis was calculated, and the minimum value of the relative refractive index difference of the stress-applying part with respect to the cladding was obtained, and then the average of the relative refractive index difference in the region that satisfies 50% or less of the minimum value of the refractive index distribution in the slow axis direction of the stress-applying part was obtained.
  • the distance from the central axis of the core to the stress applying portion was obtained by measuring the fiber end face with an optical microscope.
  • Stress applying part diameter was obtained by measuring the fiber end face with an optical microscope.
  • macrobend loss the bending loss of light with a wavelength of 1.55 ⁇ m per turn when the polarization-maintaining fiber is wound around a mandrel with a radius of 7.5 mm or 10 mm.
  • the polarization-maintaining fiber 1 when the polarization-maintaining fiber 1 is wound once so that the slow axis is perpendicular to the surface of a mandrel with a radius of 7.5 mm or 10 mm (when the bending radius is 7.5 mm or 10 mm), the power of the light in the LP01 mode from the light source at that time and the power of the light in the LP01 mode from the light source in a state before winding as a reference are measured, and the bending loss per turn was calculated from the difference between the above two powers.
  • the mandrel is a rod-shaped jig with a cross-sectional shape that is a perfect circle. In the table below, R indicates the radius of the mandrel.
  • the bending loss was measured when the polarization-maintaining fiber was not twisted and was wound around a mandrel with a bending radius of 10 mm one turn, and when the same winding was used to apply one twist per 62.8 mm of fiber length per turn.
  • the bending loss was measured for these polarization-maintaining fibers when the polarization-maintaining fiber was not twisted and was wound around a mandrel with a bending radius of 7.5 mm one turn, and when the same winding was used to apply one twist per 47.1 mm of fiber length per turn.
  • the bending loss of light per turn at a wavelength of 1.55 ⁇ m was measured when the bending radius was 7.5 mm and the twist was one turn per 47.1 mm of fiber length
  • the bending loss of light per turn at a wavelength of 1.55 ⁇ m was measured when the bending radius was 10 mm and the twist was one turn per 62.8 mm of fiber length.
  • the polarization-maintaining fibers of Examples 1 to 12 and Comparative Examples 1 to 3 do not have the twisted section 1A.
  • the configuration in which the polarization-maintaining fiber is twisted as described above and the configuration having the twisted section 1A in which the stress-applying parts 12a and 12b permanently rotate helically around the core 11 can be regarded as equivalent to each other. Therefore, the former polarization-maintaining fiber can have approximately the same optical characteristics as the latter polarization-maintaining fiber 1.
  • Tables 1 to 3 the refractive index profile of the core relative to the cladding in the polarization-maintaining fibers of Examples 1 to 12 and Comparative Examples 1 to 3 is step-like.
  • Examples 1 to 12 satisfy Condition 1 and Condition 2. Specifically, by satisfying Condition 1, the mode field diameter of these polarization-maintaining fibers can be smaller than when the mode field diameter at a wavelength of 1.55 ⁇ m is greater than 10.6 ⁇ m, and the light confinement effect can be improved accordingly. Furthermore, by satisfying Condition 2, these polarization-maintaining fibers can improve the light confinement effect compared to when the cutoff wavelength is less than 1.24 ⁇ m. By improving the light confinement effect in this way, bending loss is suppressed. Furthermore, when these polarization-maintaining fibers satisfy Condition 3, the macrobend loss value can more reliably satisfy the allowable range in an optical device such as a coherent optical transceiver.
  • the allowable range is, for example, a range in which the deterioration of the macrobend loss characteristics can be suppressed to a degree that allows a user to apply the polarization-maintaining fiber to the optical device, even when the user applies the polarization-maintaining fiber to the optical device.
  • the polarization-maintaining fiber of Comparative Example 1 has a large mode field diameter and does not satisfy Condition 1. Furthermore, this polarization-maintaining fiber does not satisfy Condition 3, and compared to the polarization-maintaining fibers of Examples 8 and 12, which have the largest macrobend loss among Examples 1 to 12, the macrobend loss of Condition 3 (1) is approximately 3.7 times that of the polarization-maintaining fibers of Examples 8 and 12, which have the largest macrobend loss among Examples 1 to 12, the macrobend loss of Condition 3 (2) is approximately 3.0 times that of the polarization-maintaining fiber of Comparative Example 1. For this reason, it may be difficult to use the polarization-maintaining fiber of Comparative Example 1 in optical devices that satisfy the above-mentioned tolerance range, such as coherent optical transceivers.
  • the relative refractive index difference ⁇ 11 of the core with respect to the cladding is smaller than the relative refractive index differences ⁇ 11 of the polarization-maintaining fibers of Examples 1 to 12. Therefore, the relative refractive index difference ⁇ 11 of the core 11 with respect to the cladding 13 is preferably 0.32% or more, as described above, and more preferably 0.33% or more. Also, the relative refractive index difference ⁇ 11 is preferably 0.40% or less, as described above.
  • the polarization-maintaining fiber of Comparative Example 3 has a small cutoff wavelength and does not satisfy Condition 2. Furthermore, this polarization-maintaining fiber does not satisfy Condition 3, and compared to the polarization-maintaining fibers of Examples 8 and 12, which have the largest macrobend loss, the macrobend loss of Condition 3 (1) is approximately 1.9 times that of the polarization-maintaining fibers of Examples 8 and 12, which have the largest macrobend loss, and the macrobend loss of Condition 3 (2) is approximately 1.6 times that of the polarization-maintaining fiber of Comparative Example 3. For this reason, it may be difficult to use the polarization-maintaining fiber of Comparative Example 3 in optical devices such as coherent optical transceivers.
  • the mode field diameter at a wavelength of 1.55 ⁇ m in the polarization-maintaining fiber 1 is 10.3 ⁇ m or less. Further, from Tables 1 to 3, it is more preferable that the mode field diameter at a wavelength of 1.55 ⁇ m is 9.6 ⁇ m or less. In this case, as is clear from each example, macrobend loss can be further suppressed.
  • the mode field diameter is 8.9 ⁇ m or more in order to reduce the connection loss to a level that can be used when applied to the optical transceiver.
  • the mode field diameter of the optical waveguide at the connection destination of the actual polarization-maintaining fiber is often 8.9 ⁇ m or more and 9.6 ⁇ m or less. This is because the mode field diameter of the single mode fiber connected to the above-mentioned optical waveguide is often 8.9 ⁇ m or more and 9.6 ⁇ m or less.
  • the mode field diameter is 8.9 ⁇ m or more and less than 10 ⁇ m in terms of the balance between the connection loss with the optical element for converting the mode field diameter and the miniaturization of the optical element for converting the mode field diameter.
  • the cutoff wavelength of the polarization-maintaining fiber 1 is 1.24 ⁇ m or more and 1.39 ⁇ m or less.
  • the cutoff wavelength may shift to the long wavelength side when the fiber length is short, for example, 1 m or less. Therefore, in order to reduce the possibility that the cutoff wavelength exceeds the wavelength used due to a shift of the cutoff wavelength to the long wavelength side caused by the fiber length, making single-mode transmission at the wavelength used difficult, it is preferable that there is a certain margin between the upper limit of the cutoff wavelength when the fiber length is measured at 2 m and the wavelength used.
  • the cutoff wavelength is, for example, 1.24 ⁇ m or more and 1.39 ⁇ m or less as described above, even if the cutoff wavelength shifts to the long wavelength side when the fiber length is short as described above, the cutoff wavelength can be prevented from exceeding the wavelength used. Therefore, it is possible to reduce the possibility that single-mode transmission at the wavelength used becomes difficult.
  • the cutoff wavelength of the polarization-maintaining fiber 1 may be greater than 1.39 ⁇ m and less than 1.55 ⁇ m.
  • the cutoff wavelength can be brought closer to the wavelength band in use, and the light confinement effect can be improved compared to when the cutoff wavelength is 1.39 ⁇ m or less. Therefore, for example, even when a user applies the polarization-maintaining fiber to the optical device, the macrobend loss value can be reduced compared to when the cutoff wavelength is 1.39 ⁇ m or less.
  • the cutoff wavelength is 1.36 ⁇ m or more and less than 1.55 ⁇ m.
  • an appropriate balance can be maintained between the high light confinement effect compared to when the cutoff wavelength is less than 1.36 ⁇ m, and the effect of reducing the possibility that single-mode transmission will become difficult at the wavelength used compared to when the cutoff wavelength is greater than 1.39 ⁇ m and less than 1.55 ⁇ m.
  • the cutoff wavelength of the polarization-maintaining fiber 1 is 1.36 ⁇ m or more and 1.39 ⁇ m or less. In this case, a proper balance can be maintained between the high light confinement effect and the effect of reducing the possibility of single-mode transmission becoming difficult at the wavelength used, compared to when the cutoff wavelength is less than 1.36 ⁇ m. Also, compared to when the cutoff wavelength is greater than 1.39 ⁇ m, the possibility of single-mode transmission becoming difficult at the wavelength used can be reduced.
  • the diameter of the cladding 13 is 124 ⁇ m or more and 126 ⁇ m or less
  • the mode field diameter at a wavelength of 1.55 ⁇ m is 10.2 ⁇ m or more and 10.6 ⁇ m or less
  • the cutoff wavelength is 1.33 ⁇ m or more and 1.39 ⁇ m or less
  • the relative refractive index difference ⁇ 11 of the core 11 with respect to the cladding 13 is 0.32% or more and 0.34% or less.
  • the diameter of the cladding 13 is 79 ⁇ m or more and 81 ⁇ m or less
  • the mode field diameter at a wavelength of 1.55 ⁇ m is 8.9 ⁇ m or more and 9.6 ⁇ m or less
  • the cutoff wavelength is 1.24 ⁇ m or more and 1.39 ⁇ m or less
  • the relative refractive index difference ⁇ 11 of the core 11 with respect to the cladding 13 is 0.33% or more and 0.40% or less.
  • the mode field diameter at a wavelength of 1.55 ⁇ m is greater than 9.2 ⁇ m and less than 10.6 ⁇ m, and the cutoff wavelength is greater than or equal to 1.26 ⁇ m and less than 1.55 ⁇ m.
  • the polarization-maintaining fiber 1 satisfies any one of the following (A) to (C).
  • A) The mode field diameter at a wavelength of 1.55 ⁇ m is 9.6 ⁇ m or less, and the cutoff wavelength is 1.24 ⁇ m or more and less than 1.55 ⁇ m.
  • B) The mode field diameter at a wavelength of 1.55 ⁇ m is greater than 9.6 ⁇ m and less than 10.5 ⁇ m, and the cutoff wavelength is greater than or equal to 1.33 ⁇ m and less than 1.55 ⁇ m.
  • the mode field diameter at a wavelength of 1.55 ⁇ m is greater than 10.5 ⁇ m and less than 10.6 ⁇ m, and the cutoff wavelength is greater than or equal to 1.36 ⁇ m and less than 1.55 ⁇ m.
  • At least one of (1) and (2) of condition 3 can be more reliably satisfied.
  • the cutoff wavelength range that satisfies at least one of (1) and (2) of condition 3 is 1.36 ⁇ m or more and less than 1.55 ⁇ m.
  • the mode field diameter is less than 10.6 ⁇ m, the light confinement effect can be improved more than when the mode field diameter is 10.6 ⁇ m.
  • the cutoff wavelength range that satisfies at least one of (1) and (2) of condition 3 when the mode field diameter is 10.6 ⁇ m is satisfied, at least one of (1) and (2) of condition 3 can be necessarily satisfied in the cutoff wavelength range even when the mode field diameter is less than 10.6 ⁇ m.
  • the cutoff wavelength range is 1.24 ⁇ m or more, at least one of (1) and (2) of condition 3 can be satisfied even if the cutoff wavelength is less than 1.36 ⁇ m.
  • the polarization-maintaining fiber 1 satisfies the following (3) instead of (1) or (2).
  • (3) The bending radius is 7.5 mm, and the macrobend loss at a wavelength of 1.55 ⁇ m is 0.27 dB/turn or less.
  • the mode field diameter is 10.3 ⁇ m or less. Furthermore, it is preferable that the mode field diameter is greater than 9.6 ⁇ m. Therefore, it is more preferable that the mode field diameter is greater than 9.6 ⁇ m and less than 10.3 ⁇ m. Furthermore, when (3) is satisfied, it is preferable that the cutoff wavelength is greater than 1.36 ⁇ m and less than 1.55 ⁇ m.
  • the ITU-T standard G657.A2 for low bending loss single mode optical fiber that is required to support access networks and general transport networks, and that requires strict macrobend loss conditions.
  • This standard specifies that the bending radius is 7.5 mm at a wavelength of 1.55 ⁇ m, and the macrobend loss value when wrapped around a mandrel once is 0.5 dB.
  • the polarization-maintaining fiber 1 can achieve a value equal to or less than the standard value, even though it has a twisted section 1A.
  • the polarization-maintaining fiber 1 satisfies the following (4) instead of (1) or (2).
  • the bending radius is 10 mm, and the macrobend loss at a wavelength of 1.55 ⁇ m is 0.07 dB/turn or less.
  • the ITU-T standard G657.A2 specifies that the macrobend loss is 0.1 dB when the fiber has a wavelength of 1.55 ⁇ m, a bending radius of 10 mm, and is wound around a mandrel once.
  • the polarization-maintaining fiber 1 can obtain a value equal to or less than the value of the ITU-T standard, even though it has a twisted section 1A.
  • the ITU-T standard G657.B3 which specifies conditions for macrobend loss that are stricter than those of the ITU-T standard G657.A2, specifies that the macrobend loss is 0.08 dB when the fiber has a wavelength of 1.55 ⁇ m, a bending radius of 10 mm, and is wound around a mandrel once.
  • the polarization-maintaining fiber 1 can obtain a value equal to or less than the value of the standard, even though it has a twisted section 1A.
  • the polarization-maintaining fiber satisfies at least one of (3) and (4) of Condition 3
  • the macrobend loss can be small enough to support an access network, a general transport network, and the like.
  • Aspect 1 of the present invention is a polarization-maintaining fiber comprising a core 11, a pair of stress-applying portions 12a, 12b arranged at positions sandwiching the core 11, and a cladding 13 containing the core 11 and the pair of stress-applying portions 12a, 12b, and characterized in that the stress-applying portions have a twisted section in which they permanently rotate helically around the core, and in the twisted section, the helical twist of the stress-applying portions per 47.1 mm of fiber length is within one turn, the mode field diameter at a wavelength of 1.55 ⁇ m is 10.6 ⁇ m or less, and the cutoff wavelength when the fiber length is 2 m and the bending radius is 140 mm is 1.24 ⁇ m or more and less than 1.55 ⁇ m.
  • the light confinement force can be increased compared to when the mode field diameter at that wavelength is greater than 10.6 ⁇ m.
  • the light confinement force can be increased compared to when the cutoff wavelength at that wavelength is smaller than 1.24 ⁇ m. Therefore, the loss of light propagating through the core can be suppressed.
  • single-mode optical transmission can be realized when the wavelength used is 1.55 ⁇ m or more.
  • a polarization-maintaining fiber that is particularly applicable to coherent optical transceivers with a wavelength of about 1.55 ⁇ m and optical fibers and optical devices with a wavelength of 1.55 ⁇ m or more can be realized. Also, since the polarization-maintaining fiber 1 has the mode field diameter and cutoff wavelength as described above, the light confinement force can be increased as described above. Therefore, even in the twisted section with the number of twist rotations as described above, it is possible to suppress light leakage, and for example, even if the user can apply the polarization-maintaining fiber to various optical devices, the deterioration of the macrobend loss characteristics can be suppressed.
  • the cutoff wavelength is a wavelength value measured at a fiber cutoff wavelength with a fiber length of 2 m, but if the method of calculating the loss per unit length of each wavelength in the LP11 mode from the refractive index structure in the following document is used, it is possible to calculate the cutoff wavelength at any length even if the fiber length is less than 2 m. Therefore, since the polarization-maintaining fiber 1 of this embodiment can measure the cutoff wavelength, it can be used even if the fiber length is less than 2 m. 16th Opto-Electronics and Communications Conference “LP11 mode attenuation behavior of optical fibers with trench-cladding”
  • Aspect 2 of this embodiment is a polarization-maintaining fiber according to Aspect 1, characterized in that in the twisted section, the helical twist of the stress-applying portion is within one turn per 62.8 mm of fiber length.
  • Aspect 3 of this embodiment is a polarization-maintaining fiber according to aspect 1 or 2, characterized in that the relative refractive index difference of the core with respect to the cladding is 0.32% or more.
  • Aspect 4 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 3, characterized in that the relative refractive index difference of the core with respect to the cladding is 0.33% or more.
  • Aspect 5 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 4, characterized in that the relative refractive index difference of the core with respect to the cladding is 0.40% or less.
  • Aspect 6 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 5, characterized in that the distance from the central axis of the core to the stress-applying portion is 10 ⁇ m or less.
  • Aspect 7 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 6, characterized in that the relative refractive index difference of the stress-applying portion with respect to the cladding is -0.78% or less.
  • Aspect 8 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 7, characterized in that the mode field diameter is 10.3 ⁇ m or less.
  • Aspect 9 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 8, characterized in that the mode field diameter is 9.6 ⁇ m or less.
  • Aspect 11 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 10, characterized in that the cutoff wavelength is 1.24 ⁇ m or more and 1.39 ⁇ m or less.
  • Aspect 12 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 11, characterized in that the cutoff wavelength is greater than 1.39 ⁇ m and less than 1.55 ⁇ m.
  • Aspect 13 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 12, characterized in that the cutoff wavelength is 1.36 ⁇ m or more and less than 1.55 ⁇ m.
  • Aspect 14 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 13, characterized in that the cutoff wavelength is 1.36 ⁇ m or more and 1.39 ⁇ m or less.
  • Aspect 15 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 14, characterized in that in the twisted section, the helical twist of the stress-applying portion per meter of fiber length is greater than 1/50 rotation.
  • Aspect 16 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 15, characterized in that the diameter of the cladding is 124 ⁇ m or more and 126 ⁇ m or less, the mode field diameter is 10.2 ⁇ m or more and 10.6 ⁇ m or less, the cutoff wavelength is 1.33 ⁇ m or more and 1.39 ⁇ m or less, and the relative refractive index difference of the core with respect to the cladding is 0.32% or more and 0.34% or less.
  • Aspect 17 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 16, characterized in that the diameter of the cladding is 79 ⁇ m or more and 81 ⁇ m or less, the mode field diameter is 8.9 ⁇ m or more and 9.6 ⁇ m or less, the cutoff wavelength is 1.24 ⁇ m or more and 1.39 ⁇ m or less, and the relative refractive index difference of the core with respect to the cladding is 0.33% or more and 0.40% or less.
  • An eighteenth aspect of the present invention is the polarization-maintaining fiber of any one of the first to seventeenth aspects, which satisfies any one of the following (A) to (C):
  • (A) The mode field diameter is 9.6 ⁇ m or less, and the cutoff wavelength is 1.24 ⁇ m or more and less than 1.55 ⁇ m.
  • (B) The mode field diameter is greater than 9.6 ⁇ m and less than 10.5 ⁇ m, and the cutoff wavelength is greater than or equal to 1.33 ⁇ m and less than 1.55 ⁇ m.
  • C The mode field diameter is greater than 10.5 ⁇ m and not greater than 10.6 ⁇ m, and the cutoff wavelength is greater than or equal to 1.36 ⁇ m and less than 1.55 ⁇ m.
  • Aspect 19 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 18, characterized in that the bending radius is 7.5 mm and the macrobend loss at a wavelength of 1.55 ⁇ m is 0.67 dB/turn or less.
  • Aspect 20 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 19, characterized in that the bending radius is 10 mm and the macrobend loss at a wavelength of 1.55 ⁇ m is 0.16 dB/turn or less.
  • Aspect 21 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 20, characterized in that the mode field diameter is less than 10 ⁇ m.
  • Aspect 22 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 21, characterized in that the mode field diameter is greater than 9.6 ⁇ m.
  • Aspect 23 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 22, characterized in that the fiber length is 47.1 mm or more.
  • Aspect 24 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 23, characterized in that the fiber length is less than 50 m.
  • Aspect 25 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 24, characterized in that the fiber length is less than 10 m.
  • Aspect 26 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 25, characterized in that the fiber length is less than 300 mm.
  • Aspect 27 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 26, characterized in that the refractive index profile of the core relative to the cladding is step-like or GI-type profile.
  • Aspect 28 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 27, characterized in that the diameter of the stress-applying portion is 24.8 ⁇ m or more.
  • Aspect 29 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 28, characterized in that the diameter of the stress-applying portion is 38.0 ⁇ m or less.
  • Aspect 30 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 29, characterized in that the diameter of the stress-applying portion is 34.4 ⁇ m or less.
  • Aspect 31 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 30, characterized in that the radius of the core is 4.4 ⁇ m or less.
  • Aspect 32 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 31, characterized in that the radius of the core is 4.1 ⁇ m or more.
  • Aspect 33 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 32, characterized in that the relative refractive index difference of the stress-applying portion with respect to the cladding is -1.0% or more.
  • Aspect 34 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 33, characterized in that the ratio of the distance from the central axis of the core to the stress-applying portion to the radius of the mode field diameter is 1.05 ⁇ m or more.
  • Aspect 35 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 34, characterized in that the diameter of the cladding is 79 ⁇ m or more and 126 ⁇ m or less.
  • Aspect 36 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 35, characterized in that the diameter of the cladding is 124 ⁇ m or more and 126 ⁇ m or less.
  • Aspect 37 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 36, characterized in that the diameter of the cladding is 79 ⁇ m or more and 81 ⁇ m or less.
  • Aspect 38 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 37, characterized in that it has the twisted section and another twisted section, and the twist period of the other twisted section is different from that of the twisted section.
  • Aspect 39 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 38, characterized in that the length of the twisted section and the other twisted section are approximately the same.
  • Aspect 41 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 40, characterized in that in the twisted section, the helical twist of the stress-applying portion per meter of fiber length is greater than 1/25 rotation.
  • Aspect 42 of the present invention is a polarization-maintaining fiber according to any one of aspects 1 to 41, characterized in that the center of the circle that constitutes the outer periphery of the core is included in the center of the cladding, the center of the cladding is a circle with a radius of 0.6 ⁇ m, and the center of the circle is an inner region of the circle that coincides with the center of the circle that constitutes the outer periphery of the cladding.
  • a polarization-maintaining fiber can be provided in which the deterioration of macrobend loss characteristics is suppressed even when the user can apply the polarization-maintaining fiber to the optical device, and it is expected that the fiber will be used as a polarization-maintaining fiber for communications in fields such as optical communications, a polarization-maintaining fiber for amplifiers in fields such as amplifiers, and a polarization-maintaining fiber for sensors in fields such as measurement.

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JP2018512618A (ja) * 2015-03-20 2018-05-17 コーニング インコーポレイテッド 偏波保持光ファイバ
CN112147739A (zh) * 2019-06-26 2020-12-29 上海康阔光智能技术有限公司 光纤陀螺用抗弯抗扭光纤及使用该光纤的传感光纤环和光纤陀螺
WO2023119925A1 (ja) * 2021-12-24 2023-06-29 住友電気工業株式会社 屈曲光ファイバ、屈曲光ファイバの製造方法、および光接続部品

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JP2003337238A (ja) * 2002-03-15 2003-11-28 Fujikura Ltd 偏波保持光ファイバ
JP2006124219A (ja) * 2004-10-27 2006-05-18 Furukawa Electric Co Ltd:The 光ファイバの線引方法及び線引装置
JP2012113234A (ja) * 2010-11-26 2012-06-14 Furukawa Electric Co Ltd:The 光ファイバモジュール
JP2015184371A (ja) * 2014-03-20 2015-10-22 株式会社フジクラ 偏波保持光ファイバ
JP2018512618A (ja) * 2015-03-20 2018-05-17 コーニング インコーポレイテッド 偏波保持光ファイバ
US20170235049A1 (en) * 2016-02-12 2017-08-17 Institut National D'optique Optical fiber assembly with enhanced filtering of higher-order modes
CN112147739A (zh) * 2019-06-26 2020-12-29 上海康阔光智能技术有限公司 光纤陀螺用抗弯抗扭光纤及使用该光纤的传感光纤环和光纤陀螺
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