WO2016114514A1 - Ribbon optical fiber comprising compact single-mode optical fibers - Google Patents

Ribbon optical fiber comprising compact single-mode optical fibers Download PDF

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Publication number
WO2016114514A1
WO2016114514A1 PCT/KR2015/014476 KR2015014476W WO2016114514A1 WO 2016114514 A1 WO2016114514 A1 WO 2016114514A1 KR 2015014476 W KR2015014476 W KR 2015014476W WO 2016114514 A1 WO2016114514 A1 WO 2016114514A1
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optical fiber
optical
ribbon
cladding
mode
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PCT/KR2015/014476
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French (fr)
Korean (ko)
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정윤철
장준호
김훈
오치환
정창현
조형수
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한국과학기술원
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Priority claimed from KR1020150187846A external-priority patent/KR101788628B1/en
Application filed by 한국과학기술원 filed Critical 한국과학기술원
Publication of WO2016114514A1 publication Critical patent/WO2016114514A1/en

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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
    • G02B6/44—Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables

Definitions

  • the present invention relates to a method for increasing transmission capacity per unit area, and more particularly, to a miniaturized single mode optical fiber and a ribbon optical fiber design for optical communication.
  • the transmission capacity to be handled in the optical communication network is greatly increased.
  • the amount of information that needs to be processed in data centers is increasing, it is expected that the use of additional fibers in the near future will soon be required.
  • installing new fiber and installing related equipment in a limited space such as a data center can be difficult in terms of space utilization and cost. Therefore, technologies for maximizing transmission capacity while using minimal space have been attracting attention.
  • the spatial multiplexing technique based on multicore optical fibers or multimode optical fibers can significantly increase the transmission capacity per unit area.
  • the transmission capacity of the optical fiber can be increased in proportion to the number of cores.
  • new connectors, amplifiers, and splitters, which are suitable for multicore optical fibers are required to be used. Therefore, it is expected to be difficult to apply to a real system.
  • the multimode optical fiber has an advantage of increasing the transmission capacity in proportion to the number of modes by using the orthogonality of each mode.
  • various new components and elements are required and the complexity of the transmitting and receiving end is required. Has the disadvantage of greatly increasing. In order to overcome these shortcomings and to be used in actual systems, it is necessary to improve the maturity of the industry, and it is expected to take considerable time in the future.
  • miniaturizing a single mode optical fiber which is currently widely used, has been proposed. Since it has a similar shape and characteristics to the existing single-mode fiber, the manufacturing method is simple, and the structure and various parts and elements of the system that are already installed can be utilized as it is. Of course, new types of devices such as optical connectors may be required for compatibility with existing optical fibers, but the complexity is relatively insignificant compared to the method using a multicore optical fiber or a multimode optical fiber. Therefore, miniaturized single-mode fiber can be an excellent alternative for building a space-efficient system in the near future before multicore fiber or multimode fiber can be utilized.
  • This method has less space efficiency gain than the method using multi-core fiber or multi-mode fiber, but the manufacturing method is relatively simple and the structure, various parts and elements of the system already installed can be used as it is. Can be.
  • the miniaturized single-mode fiber is used in the form of a ribbon, it is expected that the space efficiency can be significantly increased compared to the use of multiple strands of the conventional fiber.
  • Ribbon optical fiber refers to a form in which several optical fibers are arranged in parallel and grouped together using a matrix material.
  • Various optical cables used today have many forms in which the optical fiber in the form of a ribbon is closely arranged, and has the advantage of being high in space efficiency and easy to handle at the same time.
  • multiple fibers included in the ribbon fiber can be cut and connected at one time for convenient maintenance.
  • each of the fibers constituting the ribbon fiber must be significantly smaller than the conventional single mode fiber.
  • Existing optical fiber has a diameter of 125 ⁇ m of the cladding and 250 ⁇ m of the diameter including the coating, and thus it is necessary to reduce the thickness of the cladding or coating to manufacture a miniaturized optical fiber. For example, if the diameter of the optical fiber including the coating is reduced to 200 ⁇ m, a space efficiency increase of 36% may be obtained.
  • each fiber constituting the ribbon should have similar optical transmission characteristics as the conventional single mode fiber. Light transmission characteristics include light loss, mode field diameter (MFD), cutoff wavelength, refractive loss characteristics, and the like.
  • the design of the optical fiber and ribbon having the minimum cross-sectional area is required based on the analysis.
  • the present invention has been proposed to solve the above-mentioned conventional problems, and the object of the optical fiber ribbon optical fiber composed of a miniaturized single-mode optical fiber according to the present invention, compared to the conventional single-mode optical fiber, the transmission quality of the optical signal, mechanical
  • the present invention provides a means for maximizing transmission capacity per unit area without significantly different reliability and splicing characteristics.
  • each optical fiber has a refractive index of the core n 1 and a refractive index of n it includes 2 naegwak cladding, and a refractive index n 3 of the outer cladding,
  • the diameter d 2 of the inner cladding of each optical fiber is 40 ⁇ m to 50 ⁇ m
  • ⁇ 2 / ⁇ 1 The value of ⁇ 2 / ⁇ 1 is greater than 0 and less than 0.7
  • the diameter of each optical fiber including the cladding is 85 ⁇ m or less
  • ⁇ 1 (n 1 -n 3 ) / n 3 as a difference in refractive index between the core and the outer cladding
  • ⁇ 2 is a difference in refractive index between the inner cladding and the outer cladding
  • ⁇ 2 (n 2 -n 3 ) / n 3 .
  • each optical fiber is covered with one or more layers of coating, the number of optical fibers included in the ribbon optical fiber is N, the diameter of each optical fiber When referred to as d ⁇ m, the size of the ribbon optical fiber may not exceed (d ⁇ N + 60) ⁇ (N + 60) ⁇ m 2 .
  • the core diameter (d 1 ) of each optical fiber is 8 ⁇ m to 10 ⁇ m, and the refractive index difference ⁇ 1 between the core and the outer cladding may be 0.35% to 0.41%.
  • each optical fiber is covered with one or more coatings, the total diameter of each optical fiber including the coating may be 190 ⁇ m or less.
  • each optical fiber has a value of less than 0.4 dB / km in the wavelength band of 1310 nm, in the wavelength band of 1550 nm It may have a value less than 0.35 dB / km.
  • the mode field diameter of each optical fiber may be 8.6 ⁇ m to 9.5 ⁇ m in the wavelength band of 1310 nm.
  • the cable blocking wavelength of each optical fiber may have a value of 1300 nm or less.
  • the tensile strength of each optical fiber may have a value of at least 0.69 GPa.
  • each optical fiber the optical loss of 0.5 dB or less in the 1625 nm wavelength band when rotated 100 times in a state of bending radius 37.5 mm Can have
  • each optical fiber has a color dispersion of 20 ps / nm / km or less in the wavelength band of 1550 nm, 0.07 ps / nm 2 / It may have a change rate of chromatic dispersion according to the wavelength of less than km.
  • the optical fiber ribbon optical fiber composed of a miniaturized single-mode optical fiber according to the present invention is an optical fiber suitable for large-capacity optical transmission, and in particular, it is possible to provide an effective transmission capacity increasing method by maximizing the transmission capacity per unit area. have. In addition, it can relieve the burden of freeing up space in costly data centers.
  • 1 is a graph showing the change in bending loss with cladding thickness of single-mode fiber and the requirements of ITU-T G.652.
  • FIG. 2 is a structural diagram illustrating a structure of an optical fiber having a depressed cladding index profile according to an embodiment of the present invention.
  • 3 (a) and 3 (b) are graphs showing changes in bending loss and cable cutoff wavelength of an optical fiber according to an inner cladding diameter
  • FIG. 5 is a graph showing the change in minimum cladding thickness required to satisfy the bending loss conditions specified in ITU-T G.652, according to the structure of the optical fiber.
  • FIG. 6 is a graph showing the optical fiber structure required to satisfy the mode field diameter condition specified in ITU-T G.652.
  • Figure 7 is a schematic view showing the structure and design of the optical fiber ribbon optical fiber consisting of a miniaturized optical fiber according to an embodiment of the present invention.
  • miniaturized single-mode optical fiber suitable for optical communication must have optical transmission characteristics similar to the conventional single-mode optical fiber to be practical.
  • the size of the conventional single mode optical fiber has a cladding diameter of 125 ⁇ m and a coating diameter of 250 ⁇ m.
  • Various requirements have been established for single-mode fiber, and the standards for the most commonly used fiber optics for communications are specified in ITU-T G.652.
  • the main items of the above standards are optical loss, mode field diameter, cable cut-off wavelength, bending loss, and tensile strength. Satisfying these conditions is the most important part of fiber design.
  • a method for reducing the cross-sectional area of the optical fiber is a method for reducing the thickness of the cladding and coating.
  • the refractive index of the cladding is designed to be lower than the refractive index of the core, allowing light to travel through the core.
  • the progress of light intensity does not only exist in the core but also in the cladding, so as the thickness of the cladding decreases, the probability of exiting the cladding increases. That is, this may increase the light loss.
  • the optical fiber is bent, the distribution of light is directed to the outside of the optical fiber, so the thinner the cladding, the more susceptible it is to light loss due to the bending. FIG.
  • ⁇ (n 1 -n 2) / n 2.
  • a method for suppressing the bending loss of the optical fiber is to increase the difference between the refractive index of the core and the refractive index of the cladding. If the core-cladding refractive index difference is ⁇ , the larger the ⁇ , the more the light propagating through the optical fiber is toward the core, so that the light does not escape to the outside of the cladding. However, if ⁇ is increased, the mode field diameter is greatly reduced.
  • the mode field diameter represents the extent to which light propagates through an optical fiber, and the ITU-T G.652 standards specify that it should have a value of 8.6 to 9.5 ⁇ m at a 1310 nm wavelength.
  • the mode field diameter is important because of its compatibility with existing optical fibers.
  • Equation 1 The splice loss occurring when two optical fibers having different mode field diameters are connected is represented by Equation 1 below.
  • W 1 and W 2 are the mode field diameters of the respective optical fibers, and d is the optical fiber connection offset.
  • connection loss occurs when the mode field diameter of each optical fiber is different, and as the difference increases, the connection loss increases. Since the optical transceivers and various optical devices currently used are connected to optical fibers having a mode field diameter of 8.6 to 9.5 ⁇ m at a wavelength of 1310 nm, miniaturized single mode optical fibers should be designed to have similar mode field diameters.
  • a depressed cladding index profile was used instead of a step index.
  • 2 shows the structure of a depressed cladding index profile.
  • the cladding is divided into an inner cladding (i) and an outer cladding (o), and a refractive index of the inner cladding (i) is lower than that of the outer cladding (o).
  • a lower bending loss can be obtained for the same mode field diameter as compared to the step index profile.
  • the cladding In the case of a typical step index profile, the cladding consists of pure silica and the core portion increases refractive index through germanium doping. However, due to the difference in doping, the hardness and other properties are different, and thus two materials having different properties are adjacent to each other and thus have properties that are vulnerable to external stress. However, if the outer cladding uses pure silica and the inner cladding is a small amount of doping such as fluorine, the above problems can be alleviated. In addition, since the doping concentration of the core can be relatively lower than that of the step index, it is advantageous to obtain low light loss.
  • n 3 ) / n 3 and ⁇ 2 (n 2 -n 3 ) / n 3 .
  • 3 (a) shows the bending loss of the optical fiber with respect to the inner cladding diameter d 2 .
  • d 1 , d 3, and ⁇ 1 + ⁇ 2 were set to 9 ⁇ m, 80 ⁇ m, and 0.44%, respectively, and the value of ⁇ 2 / ⁇ 1 was considered 0.1 or 0.7.
  • the bending radius was set to 17.5 mm, much smaller than the recommended 37.5 mm of ITU-T G.652.
  • the wavelength was assumed to be 1625 nm.
  • the bending loss decreases as d 2 increases, and when the value of ⁇ 2 / ⁇ 1 is 0.1, the bending loss of 0.001 dB / turn or less is obtained when d 2 is 40 ⁇ m or more. Can be.
  • the wavelength band to be used must be longer than the blocking wavelength of the optical fiber.
  • LP11 mode as well as LP01 mode exist, so the signal dispersion can seriously distort the signal. Therefore, when designing a miniaturized single-mode fiber, various design parameters should be determined so that the blocking wavelength is sufficiently low.
  • the cable cutoff wavelength is defined as the shortest wavelength at which LP11 mode losses of more than 19.3 dB occur when light is transmitted through a 22 m long fiber.
  • the 22 m long optical fiber consists of an optical fiber part wound twice in the state of bend radius 40 mm and the remaining optical fiber part wound in the state of bend radius 140 mm.
  • the cable blocking wavelength increases. This is because the wider the inner cladding region, the less leakage of higher-order modes such as LP11 mode is suppressed.
  • d 2 should be set to 50 ⁇ m or less in order to obtain a cable cutoff wavelength shorter than 1300 nm. In this embodiment, a low bending loss and a short cable cutoff wavelength are simultaneously obtained. D 2 was set to 45 ⁇ m.
  • d 1 and ⁇ 1 on the bending loss were examined for various d 3 .
  • 4 shows the minimum d 3 required to obtain a bending loss of 0.001 dB / turn or less.
  • the bend radius was set here to 17.5 mm, less than the recommended 37.5 mm of ITU-T G.652. This is to consider the effect of reducing the bending radius due to errors that may occur in the manufacturing and processing. It was found that the larger the d 1 and the larger the value of ⁇ 1 , the more satisfied the bending loss condition for the thinner cladding. 5 also shows the effect of d 1 and ⁇ 1 on the cable blocking wavelength.
  • the blocking wavelength increases, because higher light gathers toward the core, higher order modes such as LP11 mode can be guided at relatively higher wavelengths.
  • the blocking wavelength increases. Therefore, it is advantageous to design small values of d 1 and ⁇ 1 to obtain a short cutoff wavelength.
  • FIG. 6 shows values of d 1 and ⁇ 1 such that the mode field diameter is from 8.6 ⁇ m to 9.5 ⁇ m in the wavelength band of 1310 nm.
  • This range is the range of the mode field diameters of a typical single mode fiber, which improves the compatibility between the fibers.
  • the diameter (d 3 ) of the outer cladding can be made 80 ⁇ m or less
  • the cable cut-off wavelength is 1300 nm or less
  • d 1 which can satisfy the requirements of the mode field diameter simultaneously
  • ⁇ 1 values are present in the range of 8 ⁇ m ⁇ d 1 ⁇ 10 ⁇ m, 0.35% ⁇ d 1 ⁇ 0.41%.
  • the core has a diameter of about 9.0 ⁇ m and ⁇ 1 is about 0.4%, and the outer cladding diameter at this time may be reduced to 80 ⁇ m or less.
  • the mode field diameter (@ 1550 nm) of the optical fiber having this design value was 10.3 ⁇ m, which is almost similar to the mode field diameter of a general single mode optical fiber.
  • the coating consisted of dual-layer acrylate and had a refractive index of about 1.51 to 1.53, which is higher than the refractive index of the cladding.
  • the characteristics of the fabricated fiber and its comparison with the ITU-T G.652 standards are summarized in Table 1.
  • the macro bending loss is the value at the bending radius of 16 mm for the measurement and at the bending radius of 32.5 mm for the ITU-T G.652 standards. Even in more severe bending conditions, bending losses lower than 0.005 dB / turn, the tolerances specified in the ITU-T G.652 standards, were obtained. It can be seen that the size of the optical fiber is reduced by about 40% compared to a single mode optical fiber having a typical 250 ⁇ m coating diameter. At the same time, it was confirmed that all items except the cable cut-off wavelength met the ITU-T G.652 standards. Cable blocking wavelengths nevertheless have values less than 1300 nm, allowing broadband optical transmission.
  • a ribbon optical fiber By arranging the single-mode optical fibers with a smaller cross-sectional area in a row, a ribbon optical fiber can be usefully used for optical cables and various connectors.
  • Four, eight and twelve optical fiber-based ribbons are available.
  • 5 illustrates a design value of a ribbon optical fiber based on twelve optical fibers as an example.
  • the ribbon jacket for attaching each optical fiber was designed to have a thickness of about 25 ⁇ m. This is set in consideration of the situation that the optical fibers are not evenly arranged.
  • the size of the optical fiber ribbon fabricated in this form was measured to be 2320 ⁇ m in width and 240 ⁇ m in length, and the cross-sectional area was about 556,800 ⁇ m 2 .

Abstract

A ribbon optical fiber comprising compact single-mode optical fibers, according to an embodiment of the present invention, is a ribbon optical fiber for increasing a transmission capacity per unit area. Each optical fiber that constitutes the ribbon optical fiber is made considerably compact, compared with an existing optical fiber so that the cross-sectional area thereof can be reduced to about 40% or more of that of the existing optical fiber, thereby increasing the transmission capacity of an optical transmission network while minimizing the securing of additional space that costs a lot. The optical fibers have an optical transmission property, mechanical reliability, and the like that are similar to those of the existing optical fiber and can be easily connected to each other, thereby achieving excellent compatibility. Although a depressed cladding index profile, which is relatively simply manufactured, is used, various types of properties of the optical fibers are appropriate for an optical communication network through the optimization of each numerical value, and it is possible to maximize the effect of a transmission capacity increase while using various types of devices and optical elements, used in the existing optical communication network, as they are.

Description

소형화된 단일모드 광섬유로 구성된 리본 광섬유 Ribbon fiber consisting of miniaturized single-mode fiber
본 발명은 단위 면적 당 전송용량을 증대시키기 위한 방안에 관한 것으로, 특히 소형화된 단일모드 광섬유와 이로 구성된 광통신용 리본 광섬유 설계에 관한 것이다.The present invention relates to a method for increasing transmission capacity per unit area, and more particularly, to a miniaturized single mode optical fiber and a ribbon optical fiber design for optical communication.
최근 각종 데이터 수요의 급증으로 인해 광통신망에서 감당해야 하는 전송용량이 크게 증가하고 있다. 특히 데이터 센터에서 처리해야 하는 정보의 양이 점차 증가하면서, 기존에 포설되어 있는 광섬유 외에 추가적인 광섬유의 사용이 조만간 요구될 것으로 예상된다. 하지만 데이터 센터와 같은 한정된 공간에서 새롭게 광섬유를 포설하고 관련 설비를 설치하는 것은 공간 활용과 비용 문제에 있어서 어려움이 있을 수 있다. 따라서 최소한의 공간을 사용하면서 전송용량을 극대화시키기 위한 기술들이 주목받고 있다. 대표적인 예로, 멀티코어 광섬유나 멀티모드 광섬유 기반의 공간 다중화 기법을 사용하면 단위면적 당 전송용량을 크게 증가시킬 수 있음이 확인되었다. 멀티코어 광섬유의 경우, 한 가닥의 광섬유 내에 다수의 코어가 설치되어 있으며 각 코어를 통해 서로 다른 신호가 전송되므로 코어 개수에 비례하여 광섬유의 전송용량을 증가시킬 수 있다. 하지만 멀티코어 광섬유에 적합한 커넥터, 증폭기, 분기기 등의 사용이 새롭게 요구되므로 실제 시스템에 적용하기에는 적지 않은 어려움이 있을 것으로 예상된다. 또한 멀티모드 광섬유의 경우는 각 모드의 직교성을 이용하여 모드의 개수에 비례하여 전송용량을 증가시킬 수 있는 장점이 있으나, 멀티코어 광섬유와 마찬가지로 각종 새로운 부품 및 소자들이 요구될 뿐만 아니라 송수신단의 복잡도가 크게 증가한다는 단점이 있다. 이러한 단점들이 극복되고 실제 시스템에 사용되기 위해서는 산업의 성숙도의 개선이 필수적이며, 앞으로도 상당한 기간이 소요될 것으로 예상된다. Recently, due to the rapid increase in the demand for various data, the transmission capacity to be handled in the optical communication network is greatly increased. In particular, as the amount of information that needs to be processed in data centers is increasing, it is expected that the use of additional fibers in the near future will soon be required. However, installing new fiber and installing related equipment in a limited space such as a data center can be difficult in terms of space utilization and cost. Therefore, technologies for maximizing transmission capacity while using minimal space have been attracting attention. As a representative example, the spatial multiplexing technique based on multicore optical fibers or multimode optical fibers can significantly increase the transmission capacity per unit area. In the case of a multicore optical fiber, since a plurality of cores are installed in a single optical fiber and different signals are transmitted through each core, the transmission capacity of the optical fiber can be increased in proportion to the number of cores. However, new connectors, amplifiers, and splitters, which are suitable for multicore optical fibers, are required to be used. Therefore, it is expected to be difficult to apply to a real system. In addition, the multimode optical fiber has an advantage of increasing the transmission capacity in proportion to the number of modes by using the orthogonality of each mode. However, like the multicore optical fiber, various new components and elements are required and the complexity of the transmitting and receiving end is required. Has the disadvantage of greatly increasing. In order to overcome these shortcomings and to be used in actual systems, it is necessary to improve the maturity of the industry, and it is expected to take considerable time in the future.
따라서 그에 대한 대안으로 현재 널리 사용되고 있는 단일모드 광섬유를 소형화하는 방법이 제안되고 있다. 이는 기존의 단일모드 광섬유와 유사한 형태 및 특성을 가지고 있기 때문에 제조방법이 간단하고, 현재 이미 포설되어 있는 시스템의 구조 및 각종 부품 및 소자의 상당부분을 그대로 활용할 수 있다. 물론 기존 광섬유와의 호환을 위해 새로운 형태의 광커넥터 등의 소자들이 요구될 수 있지만, 멀티코어 광섬유나 멀티모드 광섬유를 사용하는 방법에 비하면 그 복잡도의 증가가 상대적으로 미미하다. 따라서 소형화된 단일모드 광섬유는 멀티코어 광섬유나 멀티모드 광섬유가 활용되기에는 이른 가까운 미래에 공간효율이 높은 시스템 구축을 위한 훌륭한 대안이 될 수 있다. 이러한 방법은 멀티코어 광섬유나 멀티모드 광섬유를 사용하는 방법에 비해 공간 효율의 이득이 적지만, 제조방법이 상대적으로 간단할 뿐만 아니라 이미 포설되어 있는 시스템의 구조 및 각종 부품 및 소자를 많은 경우 그대로 사용할 수 있다. 특히 이러한 소형화된 단일모드 광섬유를 리본 형태로 만들어서 사용하면 기존의 광섬유를 여러 가닥 사용할 때에 비해 공간효율을 상당히 증가시킬 수 있을 것으로 예상된다. 리본 광섬유는 여러 개의 광섬유를 평행하게 나열하고 매트릭스 재료 (matrix material)을 사용해 하나로 묶은 형태를 말한다. 현재 사용되는 각종 광 케이블에는 이러한 리본 형태의 광섬유가 촘촘히 배치된 형태가 많으며, 높은 공간효율과 동시에 다루기 쉽다는 장점을 가지고 있다. 또한 리본 광섬유에 포함된 여러 개의 광섬유를 한 번에 절단 및 접속할 수 있어 유지 보수에 편리하다. Therefore, as an alternative, a method of miniaturizing a single mode optical fiber, which is currently widely used, has been proposed. Since it has a similar shape and characteristics to the existing single-mode fiber, the manufacturing method is simple, and the structure and various parts and elements of the system that are already installed can be utilized as it is. Of course, new types of devices such as optical connectors may be required for compatibility with existing optical fibers, but the complexity is relatively insignificant compared to the method using a multicore optical fiber or a multimode optical fiber. Therefore, miniaturized single-mode fiber can be an excellent alternative for building a space-efficient system in the near future before multicore fiber or multimode fiber can be utilized. This method has less space efficiency gain than the method using multi-core fiber or multi-mode fiber, but the manufacturing method is relatively simple and the structure, various parts and elements of the system already installed can be used as it is. Can be. In particular, when the miniaturized single-mode fiber is used in the form of a ribbon, it is expected that the space efficiency can be significantly increased compared to the use of multiple strands of the conventional fiber. Ribbon optical fiber refers to a form in which several optical fibers are arranged in parallel and grouped together using a matrix material. Various optical cables used today have many forms in which the optical fiber in the form of a ribbon is closely arranged, and has the advantage of being high in space efficiency and easy to handle at the same time. In addition, multiple fibers included in the ribbon fiber can be cut and connected at one time for convenient maintenance.
한편, 위와 같이 소형화된 리본 광섬유가 효용성이 있으려면 다음과 같은 사항들이 고려되어야 한다. 먼저 리본 광섬유를 구성하고 있는 각각의 광섬유들이 기존의 단일모드 광섬유와 비교해서 확연히 작아야 한다. 기존의 광섬유는 클래딩의 직경이 125 ㎛, 코팅을 포함한 직경이 250 ㎛이므로 클래딩이나 코팅의 두께를 줄여 소형화된 광섬유를 제작할 수 있어야 한다. 예를 들어 코팅을 포함한 광섬유의 직경을 200 ㎛로 감소시키면 36%의 공간효율 증대효과를 얻을 수 있다. 둘째로 리본을 구성하고 있는 각각의 광섬유는 기존의 단일모드 광섬유와 유사한 광전송 특성을 가져야 한다. 광전송 특성에는 광 손실, 모드필드 직경(mode field diameter, MFD), 차단 파장, 굴절손실 특성 등이 포함된다. 셋째로 기존의 단일모드 광섬유와 유사한 기계적 신뢰도(mechanical reliability)가 요구된다. 마지막으로 기존 단일모드 광섬유 및 단일모드 광섬유 기반 각종 광소자들과의 호환을 위해서 기존 125 ㎛의 클래딩을 가지는 광섬유와의 접속(splicing)이 용이해야 한다. On the other hand, in order for the miniaturized ribbon optical fiber to be effective, the following matters should be considered. First, each of the fibers constituting the ribbon fiber must be significantly smaller than the conventional single mode fiber. Existing optical fiber has a diameter of 125 μm of the cladding and 250 μm of the diameter including the coating, and thus it is necessary to reduce the thickness of the cladding or coating to manufacture a miniaturized optical fiber. For example, if the diameter of the optical fiber including the coating is reduced to 200 μm, a space efficiency increase of 36% may be obtained. Second, each fiber constituting the ribbon should have similar optical transmission characteristics as the conventional single mode fiber. Light transmission characteristics include light loss, mode field diameter (MFD), cutoff wavelength, refractive loss characteristics, and the like. Third, mechanical reliability similar to that of a conventional single mode fiber is required. Finally, in order to be compatible with the existing single-mode optical fiber and various optical elements based on the single-mode optical fiber, splicing with the optical fiber having the existing 125 μm cladding should be easy.
위와 같은 조건들을 충족시키는 광섬유를 제작하기 위해서는 광섬유의 클래딩 및 코팅 두께의 감소가 광섬유의 특성에 미치는 영향을 분석하여야 한다. 또한, 광섬유 굴절률 프로파일에 따른 각종 광전송 특성 변화에 대한 조사가 필요하다. 최종적으로 이와 같이 분석한 내용을 바탕으로 최소한의 단면적을 가지는 광섬유 및 리본의 설계가 요구된다.In order to fabricate the optical fiber satisfying the above conditions, it is necessary to analyze the effect of the reduction of the cladding and coating thickness of the optical fiber on the characteristics of the optical fiber. In addition, it is necessary to investigate the various optical transmission characteristics change according to the optical fiber refractive index profile. Finally, the design of the optical fiber and ribbon having the minimum cross-sectional area is required based on the analysis.
본 발명은 상기와 같은 종래의 문제점을 해결하기 위하여 제안된 것으로, 본 발명에 따른 소형화된 단일모드 광섬유로 구성된 광통신용 리본 광섬유의 목적은, 기존 단일모드 광섬유와 비교하여 광신호의 전송품질, 기계적 신뢰도, 접속(splicing) 특성이 크게 다르지 않으면서 단위 면적 당 전송 용량을 극대화할 수 있는 수단을 제공하는데 있다.The present invention has been proposed to solve the above-mentioned conventional problems, and the object of the optical fiber ribbon optical fiber composed of a miniaturized single-mode optical fiber according to the present invention, compared to the conventional single-mode optical fiber, the transmission quality of the optical signal, mechanical The present invention provides a means for maximizing transmission capacity per unit area without significantly different reliability and splicing characteristics.
상기 과제를 해결하기 위한 본 발명의 일 실시예에 의한 소형화된 단일모드 광섬유로 구성된 리본 광섬유는, 일렬로 배치되어 있는 복수개의 광섬유를 포함하는 리본 광섬유에 있어서,In the ribbon optical fiber composed of a miniaturized single-mode optical fiber according to an embodiment of the present invention for solving the above problems, in a ribbon optical fiber comprising a plurality of optical fibers arranged in a line,
상기 각 광섬유는 굴절률이 n1인 코어와, 굴절률이 n2인 내곽 클래딩, 및 굴절률이 n3인 외곽 클래딩을 포함하고,And wherein each optical fiber has a refractive index of the core n 1 and a refractive index of n it includes 2 naegwak cladding, and a refractive index n 3 of the outer cladding,
상기 각 광섬유의 내곽 클래딩의 직경(d2)은 40 ㎛ 내지 50 ㎛ 이며,The diameter d 2 of the inner cladding of each optical fiber is 40 μm to 50 μm,
Δ2/Δ1의 값은 0보다 크고 0.7보다 작고,The value of Δ 2 / Δ 1 is greater than 0 and less than 0.7,
클래딩을 포함한 상기 각 광섬유의 직경은 85 ㎛ 이하이며,The diameter of each optical fiber including the cladding is 85 μm or less,
상기 Δ1은 상기 코어와 외곽 클래딩의 굴절률 차이로 Δ1=(n1-n3)/n3로 정의되고, 상기 Δ2는 상기 내곽 클래딩과 외곽 클래딩의 굴절률 차이로 Δ2=(n2-n3)/n3로 정의된다.Δ 1 is defined as Δ 1 = (n 1 -n 3 ) / n 3 as a difference in refractive index between the core and the outer cladding, and Δ 2 is a difference in refractive index between the inner cladding and the outer cladding Δ 2 = (n 2 -n 3 ) / n 3 .
본 발명의 일 실시예에 의한 소형화된 단일모드 광섬유로 구성된 리본 광섬유에 있어서, 상기 각 광섬유는 한 층 이상의 코팅으로 덮여 있고, 상기 리본 광섬유에 포함된 광섬유의 개수를 N, 상기 각 광섬유의 직경을 d ㎛라 할 때, 상기 리본 광섬유의 크기는 (d × N + 60) × (N + 60) ㎛2을 넘지 않을 수 있다.In the ribbon optical fiber composed of miniaturized single-mode optical fiber according to an embodiment of the present invention, each optical fiber is covered with one or more layers of coating, the number of optical fibers included in the ribbon optical fiber is N, the diameter of each optical fiber When referred to as d μm, the size of the ribbon optical fiber may not exceed (d × N + 60) × (N + 60) μm 2 .
또한 본 발명의 일 실시예에 의한 소형화된 단일모드 광섬유로 구성된 리본 광섬유에 있어서, 상기 각 광섬유의 코어 직경(d1)은 8 ㎛ 내지 10 ㎛ 이며, 상기 코어와 외곽 클래딩의 굴절률 차이(Δ1)는 0.35% 내지 0.41%일 수 있다.In addition, in the ribbon optical fiber composed of a miniaturized single-mode optical fiber according to an embodiment of the present invention, the core diameter (d 1 ) of each optical fiber is 8 ㎛ to 10 μm, and the refractive index difference Δ 1 between the core and the outer cladding may be 0.35% to 0.41%.
또한 본 발명의 일 실시예에 의한 소형화된 단일모드 광섬유로 구성된 리본 광섬유에 있어서, 상기 각 광섬유는 한 층 이상의 코팅으로 덮여 있고, 상기 코팅을 포함한 상기 각 광섬유의 총 직경은 190 ㎛ 이하일 수 있다.In addition, in the ribbon optical fiber composed of a miniaturized single-mode optical fiber according to an embodiment of the present invention, each optical fiber is covered with one or more coatings, the total diameter of each optical fiber including the coating may be 190 ㎛ or less.
또한 본 발명의 일 실시예에 의한 소형화된 단일모드 광섬유로 구성된 리본 광섬유에 있어서, 상기 각 광섬유는 광 손실이 1310 ㎚의 파장 대역에서 0.4 dB/km 보다 작은 값을 가지고, 1550 ㎚의 파장 대역에서 0.35 dB/km 보다 작은 값을 가질 수 있다.In addition, in the ribbon optical fiber composed of miniaturized single-mode optical fiber according to an embodiment of the present invention, each optical fiber has a value of less than 0.4 dB / km in the wavelength band of 1310 nm, in the wavelength band of 1550 nm It may have a value less than 0.35 dB / km.
또한 본 발명의 일 실시예에 의한 소형화된 단일모드 광섬유로 구성된 리본 광섬유에 있어서, 상기 각 광섬유의 모드 필드 직경은 1310 ㎚의 파장 대역에서 8.6 ㎛ 내지 9.5 ㎛ 일 수 있다.In addition, in the ribbon optical fiber composed of miniaturized single-mode optical fiber according to an embodiment of the present invention, the mode field diameter of each optical fiber may be 8.6 ㎛ to 9.5 ㎛ in the wavelength band of 1310 nm.
또한 본 발명의 일 실시예에 의한 소형화된 단일모드 광섬유로 구성된 리본 광섬유에 있어서, 상기 각 광섬유의 케이블 차단 파장은 1300 ㎚ 이하의 값을 가질 수 있다.In addition, in the ribbon optical fiber composed of a miniaturized single-mode optical fiber according to an embodiment of the present invention, the cable blocking wavelength of each optical fiber may have a value of 1300 nm or less.
또한 본 발명의 일 실시예에 의한 소형화된 단일모드 광섬유로 구성된 리본 광섬유에 있어서, 상기 각 광섬유의 인장 강도는 최소 0.69 GPa의 값을 가질 수 있다.In addition, in the ribbon optical fiber composed of a miniaturized single-mode optical fiber according to an embodiment of the present invention, the tensile strength of each optical fiber may have a value of at least 0.69 GPa.
또한 본 발명의 일 실시예에 의한 소형화된 단일모드 광섬유로 구성된 리본 광섬유에 있어서, 상기 각 광섬유는, 구부림 반경이 37.5 ㎜인 상태에서 100회 회전 시, 1625㎚ 파장 대역에서 0.5 dB 이하의 광 손실을 가질 수 있다.In addition, in the ribbon optical fiber composed of a miniaturized single-mode optical fiber according to an embodiment of the present invention, each optical fiber, the optical loss of 0.5 dB or less in the 1625 nm wavelength band when rotated 100 times in a state of bending radius 37.5 mm Can have
또한 본 발명의 일 실시예에 의한 소형화된 단일모드 광섬유로 구성된 리본 광섬유에 있어서, 상기 각 광섬유는, 1550 ㎚ 파장 대역에서 20 ps/㎚/㎞ 이하의 색분산을 갖고, 0.07 ps/㎚2/㎞ 이하의 파장에 따른 색분산 변화율을 가질 수 있다.In addition, in the ribbon optical fiber composed of miniaturized single-mode optical fiber according to an embodiment of the present invention, each optical fiber has a color dispersion of 20 ps / ㎚ / km or less in the wavelength band of 1550 nm, 0.07 ps / ㎚ 2 / It may have a change rate of chromatic dispersion according to the wavelength of less than km.
이상에서 설명한 바와 같이, 본 발명에 따른 소형화된 단일모드 광섬유로 구성된 광통신용 리본 광섬유는 대용량 광전송에 적합한 광섬유로, 특히 단위면적 당 전송용량을 극대화시킴으로써 효과적인 전송용량 증대 방안을 제공할 수 있는 효과가 있다. 이뿐 아니라, 많은 비용이 소요되는 데이터 센터 등의 주변 공간 확보에 대한 부담을 덜어줄 수 있다. As described above, the optical fiber ribbon optical fiber composed of a miniaturized single-mode optical fiber according to the present invention is an optical fiber suitable for large-capacity optical transmission, and in particular, it is possible to provide an effective transmission capacity increasing method by maximizing the transmission capacity per unit area. have. In addition, it can relieve the burden of freeing up space in costly data centers.
또한, 본 발명에 의한 리본 광섬유를 사용하면, 기존의 광전송 시스템에서 사용되던 각종 장치들이 그대로 호환 가능하기 때문에, 새로운 종류의 광소자 및 장비를 구비할 필요 없이 추가적인 광전송 시스템을 경제적으로 구축할 수 있는 효과가 있다.In addition, when using the ribbon optical fiber according to the present invention, since the various devices used in the conventional optical transmission system is compatible as it is, it is possible to economically build an additional optical transmission system without having to provide a new kind of optical elements and equipment It works.
도 1은 단일모드 광섬유의 클래딩 두께에 따른 구부림 손실의 변화 및 ITU-T G.652의 요구조건을 나타낸 그래프.1 is a graph showing the change in bending loss with cladding thickness of single-mode fiber and the requirements of ITU-T G.652.
도 2는 본 발명의 일 실시예에 따른 depressed cladding index profile을 가진 광섬유의 구조를 설명하기 위한 구조도.2 is a structural diagram illustrating a structure of an optical fiber having a depressed cladding index profile according to an embodiment of the present invention.
도 3의 (a) 및 (b)는 내곽 클래딩 직경에 따른 광섬유의 구부림 손실과 케이블 차단 파장의 변화를 나타낸 그래프.3 (a) and 3 (b) are graphs showing changes in bending loss and cable cutoff wavelength of an optical fiber according to an inner cladding diameter;
도 4는 광섬유의 구조에 따른 차단파장의 변화를 나타낸 그래프.4 is a graph showing the change in the blocking wavelength according to the structure of the optical fiber.
도 5는 ITU-T G.652에 명시된 구부림 손실 조건을 만족하기 위해 요구되는 최소 클래딩 두께의 변화를 광섬유의 구조에 따라 나타낸 그래프.5 is a graph showing the change in minimum cladding thickness required to satisfy the bending loss conditions specified in ITU-T G.652, according to the structure of the optical fiber.
도 6은 ITU-T G.652에 명시된 모드 필드 직경 조건을 만족하기 위해 요구되는 광섬유 구조를 나타낸 그래프.6 is a graph showing the optical fiber structure required to satisfy the mode field diameter condition specified in ITU-T G.652.
도 7은 본 발명의 일 실시예에 따른 소형화된 광섬유로 이루어진 광통신용 리본 광섬유의 구조 및 설계치를 나타내는 설계도.Figure 7 is a schematic view showing the structure and design of the optical fiber ribbon optical fiber consisting of a miniaturized optical fiber according to an embodiment of the present invention.
이하, 본 발명의 일 실시예에 따른 소형화된 단일모드 광섬유로 구성된 리본 광섬유를 실시하기 위한 구체적인 내용을 설명하면 다음과 같다. Hereinafter, a detailed description for implementing a ribbon optical fiber composed of a miniaturized single-mode optical fiber according to an embodiment of the present invention.
먼저 광통신에 적합한 소형화된 단일모드 광섬유가 실용성이 있으려면 기존의 단일모드 광섬유와 유사한 광전송 특성을 가져야 한다. 기존 단일모드 광섬유의 크기는 클래딩 직경이 125 ㎛, 코팅 직경이 250 ㎛을 가진다. 단일모드 광섬유는 용도에 따라 다양한 요구사항이 확립되어왔으며, 특히 가장 일반적으로 사용되는 광통신용 광섬유에 대한 표준(standards)이 ITU-T G.652에 명시되어 있다. 위의 ㅍ표준(standards)의 주요 항목으로는 광 손실, 모드필드 직경, 케이블 차단파장, 구부림 손실, 인장 강도가 있으며 이와 같은 조건을 만족시키는 것이 광섬유 설계에 있어서 가장 중요한 부분이다. First, miniaturized single-mode optical fiber suitable for optical communication must have optical transmission characteristics similar to the conventional single-mode optical fiber to be practical. The size of the conventional single mode optical fiber has a cladding diameter of 125 μm and a coating diameter of 250 μm. Various requirements have been established for single-mode fiber, and the standards for the most commonly used fiber optics for communications are specified in ITU-T G.652. The main items of the above standards are optical loss, mode field diameter, cable cut-off wavelength, bending loss, and tensile strength. Satisfying these conditions is the most important part of fiber design.
광섬유의 단면적을 줄이기 위한 방법으로는 클래딩 및 코팅의 두께를 감소시키는 방법이 있다. 클래딩의 굴절률은 코어의 굴절률보다 낮게 설계되기 때문에 빛이 코어를 통해 진행할 수 있도록 한다. 하지만 진행하는 빛의 세기는 코어에만 존재하는 것이 아니라 클래딩에도 일정부분 존재하기 때문에 클래딩의 두께가 감소할수록 클래딩 바깥으로 빠져나갈 확률이 증가하게 된다. 즉, 이로 인해 광 손실이 증가할 수 있다. 특히 광섬유가 구부러진 경우 빛의 분포가 광섬유의 외곽으로 쏠리기 때문에, 클래딩이 얇아질수록 구부러짐으로 인한 광 손실에 더욱 취약해질 수 있다. 도 1은 코어-클래딩 굴절률 차이 Δ=0.35%, 코어의 직경이 9 ㎛ 인 스텝 인덱스(step index) 프로파일의 광섬유를 가정했을 때, 클래딩 두께에 따른 구부림 손실의 변화를 나타낸 것이다. 여기서, 코어-클래딩 굴절률 차이(Δ)는 코어의 굴절률을 n1, 클래딩의 굴절률을 n2라 할 때, Δ=(n1-n2)/n2로 정의된다. 도 1의 결과를 통해 구부림 반경이 감소할수록 구부림 손실이 클래딩의 크기와 관계없이 증가함을 확인할 수 있다. 또한 클래딩의 직경이 감소할수록 작은 구부림에도 손실이 크게 나타났다.A method for reducing the cross-sectional area of the optical fiber is a method for reducing the thickness of the cladding and coating. The refractive index of the cladding is designed to be lower than the refractive index of the core, allowing light to travel through the core. However, the progress of light intensity does not only exist in the core but also in the cladding, so as the thickness of the cladding decreases, the probability of exiting the cladding increases. That is, this may increase the light loss. In particular, when the optical fiber is bent, the distribution of light is directed to the outside of the optical fiber, so the thinner the cladding, the more susceptible it is to light loss due to the bending. FIG. 1 shows a change in bending loss according to cladding thickness when a fiber having a step index profile having a core-cladding refractive index difference Δ = 0.35% and a core diameter of 9 μm is illustrated. Here, the core-cladding refractive index difference (Δ) is when the refractive index n 2 d of n 1, a cladding the refractive index of the core, defined as Δ = (n 1 -n 2) / n 2. As can be seen from the results of FIG. 1, the bending loss increases regardless of the size of the cladding as the bending radius decreases. In addition, as the diameter of the cladding decreased, the loss was large even at small bends.
광섬유의 구부림 손실을 억제하기 위한 방법으로는 코어의 굴절률과 클래딩의 굴절률 차이를 높이는 것이 있다. 코어-클래딩 굴절률 차이를 Δ라 하면, Δ가 클수록 광섬유를 진행하는 빛이 코어 쪽으로 더 응집되기 때문에 클래딩 외부로 빛이 잘 빠져나가지 않게 된다. 하지만 Δ를 증가시키는 경우 모드 필드 직경이 크게 감소하는 단점이 있다. 모드 필드 직경은 광섬유를 진행하는 빛이 퍼진 정도를 나타내는 것으로 ITU-T G.652 표준(standards)에는 1310 ㎚ 파장에서 8.6 ~ 9.5 ㎛ 의 값을 가져야된다고 명시되어 있다. 모드 필드 직경이 중요한 이유는 기존의 광섬유와의 호환성 때문이다. 서로 다른 모드 필드 직경을 가지는 두 개의 광섬유를 접속할 때 발생하는 접속 손실은 다음의 [수학식 1]로 나타난다. A method for suppressing the bending loss of the optical fiber is to increase the difference between the refractive index of the core and the refractive index of the cladding. If the core-cladding refractive index difference is Δ, the larger the Δ, the more the light propagating through the optical fiber is toward the core, so that the light does not escape to the outside of the cladding. However, if Δ is increased, the mode field diameter is greatly reduced. The mode field diameter represents the extent to which light propagates through an optical fiber, and the ITU-T G.652 standards specify that it should have a value of 8.6 to 9.5 μm at a 1310 nm wavelength. The mode field diameter is important because of its compatibility with existing optical fibers. The splice loss occurring when two optical fibers having different mode field diameters are connected is represented by Equation 1 below.
Figure PCTKR2015014476-appb-M000001
Figure PCTKR2015014476-appb-M000001
여기서 W1, W2는 각 광섬유의 모드 필드 직경, d는 광섬유 접속 오프셋이다. W 1 and W 2 are the mode field diameters of the respective optical fibers, and d is the optical fiber connection offset.
수학식 1에 나타난 바와 같이, 각 광섬유의 모드 필드 직경이 상이한 경우 접속 손실이 발생하며, 그 차이가 커질수록 접속 손실이 증가함을 확인할 수 있다. 현재 사용되는 광 송수신단 및 각종 광소자는 1310 ㎚ 파장에서 8.6 ~ 9.5 ㎛ 의 모드필드 직경을 가지는 광섬유로 연결되어 있기 때문에, 소형화된 단일 모드 광섬유도 유사한 모드 필드 직경을 갖도록 설계되어야 한다.As shown in Equation 1, connection loss occurs when the mode field diameter of each optical fiber is different, and as the difference increases, the connection loss increases. Since the optical transceivers and various optical devices currently used are connected to optical fibers having a mode field diameter of 8.6 to 9.5 μm at a wavelength of 1310 nm, miniaturized single mode optical fibers should be designed to have similar mode field diameters.
위와 같은 목적에 적합한 광섬유의 인덱스 프로파일(index profile)로 스텝 인덱스(step index)가 아닌 디프레스드 클래딩 인덱스 프로파일(depressed cladding index profile)을 사용하였다. 도 2는 디프레스드 클래딩 인덱스 프로파일(depressed cladding index profile)의 구조를 나타낸 것이다. 도 2를 참조하면, 클래딩은 내곽 클래딩(i)과 외곽 클래딩(o)으로 나뉘며 내곽 클래딩(i)의 굴절률이 외곽 클래딩(o)의 굴절률보다 낮은 것이 특징이다. 이러한 구조를 사용하면 스텝 인덱스 프로파일(step index profile)과 비교했을 때, 동일한 모드 필드 직경에 대해 더 낮은 구부림 손실을 얻을 수 있다. 또한 단면적이 소형화된 광섬유가 겪을 수 있는 기계적 신뢰도에 있어서도 디프레스드 클래딩 인덱스 프로파일(depressed cladding index profile)을 사용하면 이득이 존재한다. 일반적인 스텝 인덱스 프로파일(step index profile)의 경우, 클래딩은 순수한 실리카(pure silica)로 구성되어 있고 코어 부분은 게르마늄(germanium) 도핑을 통해서 굴절률을 증가시킨다. 하지만 이러한 도핑의 차이로 인해 경도 등의 특성이 다르게 되고, 이렇게 특성이 다른 두 개의 물질이 인접하고 있기 때문에 외부 스트레스(stress)에 취약한 성질을 갖게 된다. 하지만 외곽 클래딩은 순수한 실리카(pure silica)를 사용하고 내곽 클래딩은 소량이나마 불소(fluorine) 등의 도핑을 하게 되면 위와 같은 문제점을 완화할 수 있다. 그뿐만 아니라 코어의 도핑 농도를 스텝 인덱스(step index)의 경우보다 상대적으로 낮출 수 있기 때문에 낮은 광 손실을 얻기에도 유리하다. 하지만 주의해야할 부분은 내곽 클래딩의 두께가 충분하지 않으면 내곽 클래딩으로 진행하는 일부분의 빛이 외곽 클래딩 쪽으로 쉽게 빠져나갈 수 있다는 점이다. 이는 외곽 클래딩의 굴절률이 내곽 클래딩의 굴절률보다 높아서 생기는 현상으로 특히 광섬유가 구부러졌을 때 쉽게 발생할 수 있다. 따라서 먼저 굴절률 프로파일에서 내곽 클래딩 직경(d2)의 최적화를 수행하였다. 본 실시예에서는 도 2에 표시된 것과 같이 코어(c)-외곽 클래딩(o) 굴절률 차이를 Δ1, 내곽 클래딩(i)-외곽 클래딩(o) 굴절률 차이를 Δ2라 하면 Δ2=0.1×Δ1가 만족하도록 하였다. 여기서, Δ1와 Δ2는 코어(c)의 굴절률이 n1, 내곽 클래딩(i)의 굴절률이 n2, 외곽 클래딩(o)의 굴절률이 n3일 때, 각각 Δ1=(n1-n3)/n3와 Δ2=(n2-n3)/n3로 정의된다. 도 3의 (a)는 내곽 클래딩 직경(d2)에 대한 광섬유의 구부림 손실을 나타낸다. 여기서 d1, d3, Δ1+Δ2는 각각 9 ㎛, 80 ㎛, 0.44%로 설정하였고, Δ2/Δ1의 값은 0.1이나 0.7인 경우를 고려하였다. 구부림 반경은 ITU-T G.652의 권고치인 37.5 ㎜보다 훨씬 작은 17.5 ㎜로 설정하였다. 또한, 파장은 1625 ㎚로 가정하였다. 먼저 Δ2/Δ1의 값이 0.7인 경우를 살펴보면, 모든 d2의 값에 대해 0.001 dB/turn 보다 작은 구부림 손실을 얻을 수 없었다. 하지만 Δ2/Δ1의 값이 0.7보다 작은 경우에는 특정 d2 값들에 대해서 0.001 dB/turn 이하의 구부림 손실을 얻을 수 있다. 특히 구부림 손실은 d2가 증가할수록 감소하는 것을 볼 수 있으며, Δ2/Δ1의 값이 0.1일 때를 보면 d2가 40 ㎛ 이상일 때 0.001 dB/turn 이하의 구부림 손실을 얻을 수 있음을 확인할 수 있다.As the index profile of the optical fiber suitable for the above purpose, a depressed cladding index profile was used instead of a step index. 2 shows the structure of a depressed cladding index profile. Referring to FIG. 2, the cladding is divided into an inner cladding (i) and an outer cladding (o), and a refractive index of the inner cladding (i) is lower than that of the outer cladding (o). Using this structure, a lower bending loss can be obtained for the same mode field diameter as compared to the step index profile. In addition, there is a gain in using a depressed cladding index profile in terms of the mechanical reliability that a small optical fiber can experience. In the case of a typical step index profile, the cladding consists of pure silica and the core portion increases refractive index through germanium doping. However, due to the difference in doping, the hardness and other properties are different, and thus two materials having different properties are adjacent to each other and thus have properties that are vulnerable to external stress. However, if the outer cladding uses pure silica and the inner cladding is a small amount of doping such as fluorine, the above problems can be alleviated. In addition, since the doping concentration of the core can be relatively lower than that of the step index, it is advantageous to obtain low light loss. It should be noted, however, that if the inner cladding is not thick enough, a portion of the light that proceeds to the inner cladding can easily escape to the outer cladding. This is caused by the refractive index of the outer cladding being higher than the refractive index of the inner cladding, which can easily occur especially when the optical fiber is bent. Therefore, the optimization of the inner cladding diameter d 2 in the refractive index profile was first performed. In the present embodiment, as shown in FIG. 2, when the difference between the refractive index of the core (c) -outer cladding (o) is Δ 1 and the difference between the inner cladding (i) and the outer cladding (o) is Δ 2 , Δ 2 = 0.1 × Δ 1 was satisfied. Here, Δ 1 and Δ 2 are Δ 1 = (n 1 −, respectively) when the refractive index of the core c is n 1 , the refractive index of the inner cladding i is n 2 , and the refractive index of the outer cladding o is n 3. n 3 ) / n 3 and Δ 2 = (n 2 -n 3 ) / n 3 . 3 (a) shows the bending loss of the optical fiber with respect to the inner cladding diameter d 2 . Here, d 1 , d 3, and Δ 1 + Δ 2 were set to 9 μm, 80 μm, and 0.44%, respectively, and the value of Δ 2 / Δ 1 was considered 0.1 or 0.7. The bending radius was set to 17.5 mm, much smaller than the recommended 37.5 mm of ITU-T G.652. In addition, the wavelength was assumed to be 1625 nm. First, when the value of Δ 2 / Δ 1 is 0.7, bending loss of less than 0.001 dB / turn was not obtained for all d 2 values. However, if the value of Δ 2 / Δ 1 is less than 0.7, bending loss of less than 0.001 dB / turn can be obtained for specific d 2 values. In particular, it can be seen that the bending loss decreases as d 2 increases, and when the value of Δ 2 / Δ 1 is 0.1, the bending loss of 0.001 dB / turn or less is obtained when d 2 is 40 μm or more. Can be.
한편, 광섬유가 단일 모드로 동작하기 위해서는 사용하고자 하는 파장 대역이 광섬유의 차단파장보다 길어야 한다. 차단파장보다 낮은 파장대역에서는 LP01 모드뿐만 아니라 LP11 모드도 존재하기 때문에 모드 분산으로 인해 신호가 심각하게 왜곡될 수 있다. 따라서 소형화된 단일모드 광섬유를 설계할 때는 차단파장이 충분히 낮도록 각종 설계 변수를 정해주어야 한다. On the other hand, in order for the optical fiber to operate in a single mode, the wavelength band to be used must be longer than the blocking wavelength of the optical fiber. In the wavelength band lower than the cut-off wavelength, LP11 mode as well as LP01 mode exist, so the signal dispersion can seriously distort the signal. Therefore, when designing a miniaturized single-mode fiber, various design parameters should be determined so that the blocking wavelength is sufficiently low.
도 3의 (b)는 Δ2/Δ1의 값이 0.1인 경우, d2에 따른 케이블 차단 파장의 변화를 나타낸다. 이때의 각종 변수들의 값은 도 3의 (a)의 결과를 얻기 위해 사용된 값과 동일하다. 케이블 차단 파장은 22 m 길이의 광섬유를 통해 빛이 전송되었을 때, 19.3 ㏈ 이상의 LP11 모드 손실이 발생하는 최단 파장으로 정의된다. 여기서 22 m 길이의 광섬유는 구부림 반경 40 ㎜ 상태에서 2회만큼 감겨있는 광섬유 부분과 구부림 반경 140 ㎜ 상태에서 감겨있는 나머지 광섬유 부분으로 이루어져 있다고 가정한다. d2가 증가할수록 케이블 차단 파장도 증가하는 것을 확인할 수 있다. 이는 내곽 클래딩 영역이 넓어질수록 LP11 모드와 같은 고차모드들의 유실 (leakage)이 억제되기 때문이다. 도 3의 (b)의 결과를 바탕으로 1300 ㎚ 보다 짧은 케이블 차단 파장을 얻기 위해서는 d2를 50 ㎛ 이하로 설정해주어야 함을 확인하였으며, 본 실시예에서는 낮은 구부림 손실과 짧은 케이블 차단 파장을 동시에 얻기 위해 d2를 45 ㎛ 로 설정해 주었다.3 (b) shows the change in the cable cut-off wavelength according to d 2 when the value of Δ 2 / Δ 1 is 0.1. At this time, the values of the various variables are the same as the values used to obtain the result of FIG. The cable cutoff wavelength is defined as the shortest wavelength at which LP11 mode losses of more than 19.3 ㏈ occur when light is transmitted through a 22 m long fiber. Here, it is assumed that the 22 m long optical fiber consists of an optical fiber part wound twice in the state of bend radius 40 mm and the remaining optical fiber part wound in the state of bend radius 140 mm. As d 2 increases, the cable blocking wavelength increases. This is because the wider the inner cladding region, the less leakage of higher-order modes such as LP11 mode is suppressed. On the basis of the result of FIG. 3 (b), it was confirmed that d 2 should be set to 50 μm or less in order to obtain a cable cutoff wavelength shorter than 1300 nm. In this embodiment, a low bending loss and a short cable cutoff wavelength are simultaneously obtained. D 2 was set to 45 μm.
다음으로 d1와 Δ1이 구부림 손실에 미치는 영향을 다양한 d3에 대해 살펴보았다. 도 4는 0.001 dB/turn 이하의 구부림 손실을 얻기 위해 요구되는 최소 d3를 나타낸다. 여기서 구부림 반경은 ITU-T G.652의 권고치인 37.5 ㎜ 보다 작은 17.5 ㎜로 설정하였다. 이는 제작 및 공정 상에서 발생할 수 있는 오차로 인한 구부림 반경의 감소 효과를 감안하기 위함이다. d1이 커질수록, Δ1의 값이 증가할수록 더 얇은 클래딩에 대해서 구부림 손실 조건을 만족하는 것으로 나타났다. 또한 도 5는 d1과 Δ1이 케이블 차단 파장에 미치는 영향을 보여준다. Δ1이 증가할수록 차단 파장이 증가하는 것을 볼 수 있으며, 이는 빛이 강하게 코어 쪽으로 모일수록 LP11모드 같은 고차모드들이 상대적으로 높은 파장에서도 도파될 수 있기 때문이다. 또한 d1이 커질수록 차단 파장도 증가함을 확인할 수 있다. 따라서 짧은 차단 파장을 얻기 위해서는 d1과 Δ1의 값을 작게 설계하는 것이 유리하다.Next, the effects of d 1 and Δ 1 on the bending loss were examined for various d 3 . 4 shows the minimum d 3 required to obtain a bending loss of 0.001 dB / turn or less. The bend radius was set here to 17.5 mm, less than the recommended 37.5 mm of ITU-T G.652. This is to consider the effect of reducing the bending radius due to errors that may occur in the manufacturing and processing. It was found that the larger the d 1 and the larger the value of Δ 1 , the more satisfied the bending loss condition for the thinner cladding. 5 also shows the effect of d 1 and Δ 1 on the cable blocking wavelength. As Δ 1 increases, the blocking wavelength increases, because higher light gathers toward the core, higher order modes such as LP11 mode can be guided at relatively higher wavelengths. In addition, as d 1 increases, the blocking wavelength increases. Therefore, it is advantageous to design small values of d 1 and Δ 1 to obtain a short cutoff wavelength.
도 6은 모드 필드 직경이 1310 ㎚의 파장 대역에서 8.6 ㎛ 내지 9.5 ㎛ 이 되도록 하는 d1과 Δ1의 값들을 나타낸다. 이 범위는 일반적인 단일모드 광섬유의 모드 필드 직경의 범위이므로 광섬유 간 호환성을 향상시킨다. 도 4, 도 5 및 도 6의 결과로부터 외곽 클래딩의 직경 (d3)을 80 ㎛ 이하로 만들 수 있으며, 케이블 차단 파장이 1300 ㎚ 이하이고, 모드 필드 직경의 요구치를 동시에 만족시킬 수 있는 d1 및 Δ1값은 8 ㎛ ≤ d1 ≤ 10 ㎛ , 0.35% ≤ d1 ≤ 0.41% 의 범위 내에 존재함을 확인할 수 있다.FIG. 6 shows values of d 1 and Δ 1 such that the mode field diameter is from 8.6 μm to 9.5 μm in the wavelength band of 1310 nm. This range is the range of the mode field diameters of a typical single mode fiber, which improves the compatibility between the fibers. From the results of Figs. 4, 5 and 6, the diameter (d 3 ) of the outer cladding can be made 80 μm or less, the cable cut-off wavelength is 1300 nm or less, and d 1, which can satisfy the requirements of the mode field diameter simultaneously, And Δ 1 values are present in the range of 8 μm ≦ d 1 ≦ 10 μm, 0.35% ≦ d 1 ≦ 0.41%.
본 실시예에서는 코어의 직경이 약 9.0 ㎛, Δ1이 약 0.4%인 경우을 고려하였고, 이때의 외곽 클래딩 직경은 80 ㎛ 이하로 작아질 수 있다. 또한 이 설계치를 가지는 광섬유의 모드 필드 직경(@1550 ㎚)은 일반적인 단일모드 광섬유의 모드 필드 직경과 거의 비슷한 10.3 ㎛임을 확인하였다.In the present embodiment, the core has a diameter of about 9.0 μm and Δ 1 is about 0.4%, and the outer cladding diameter at this time may be reduced to 80 μm or less. In addition, it was confirmed that the mode field diameter (@ 1550 nm) of the optical fiber having this design value was 10.3 μm, which is almost similar to the mode field diameter of a general single mode optical fiber.
이러한 설계치를 기반으로 단면적이 소형화된 광섬유를 제작하였다. 코팅은 듀얼 레이어 아크릴레이트(dual-layer acrylate)로 구성되었으며 굴절률은 약 1.51~1.53으로 클래딩의 굴절률보다 높게 제작되었다. 제작된 광섬유의 특성 및 ITU-T G.652 표준(standards)과의 비교가 표 1에 정리되어 있다.Based on these designs, an optical fiber with a smaller cross-sectional area was produced. The coating consisted of dual-layer acrylate and had a refractive index of about 1.51 to 1.53, which is higher than the refractive index of the cladding. The characteristics of the fabricated fiber and its comparison with the ITU-T G.652 standards are summarized in Table 1.
측정치Measure ITU-T G.652 표준ITU-T G.652 Standard
Core diameterCore diameter 9.04 ㎛9.04 μm --
Cladding diameterCladding diameter 82.49 ㎛82.49 μm 125.00 ㎛125.00 μm
Primary coating diameterPrimary coating diameter 156.80 ㎛156.80 μm --
Secondary coating diameterSecondary coating diameter 188.43 ㎛188.43 μm 250.00 ㎛250.00 μm
Attenuation (㏈/㎞)Attenuation (㏈ / km) 0.225 (@1550 ㎚)0.345 (@1310 ㎚)0.225 (@ 1550 nm) 0.345 (@ 1310 nm) <0.350 (@1550 ㎚)<0.400 (@1310 ㎚)<0.350 (@ 1550 nm) <0.400 (@ 1310 nm)
Mode field diameter (@1310 ㎚)Mode field diameter (@ 1310 nm) 9.325 ㎛9.325 μm 8.6 ~ 9.5 ㎛8.6 to 9.5 μm
Cable cutoff wavelengthCable cutoff wavelength 1290.89 ㎚1290.89 nm <1260.00 ㎚<1260.00 nm
Macro bending loss (@1625 ㎚)Macro bending loss (@ 1625 nm) ~0.002 dB/turn~ 0.002 dB / turn <0.005 dB/turn<0.005 dB / turn
Tensile strengthTensile strength ~2.5 kgf (4.58 GPa)~ 2.5 kgf (4.58 GPa) >0.69 GPa> 0.69 GPa
위의 표에서 매크로 구부림 손실은 측정치의 경우 16 ㎜의 구부림 반경에서의 값이며, ITU-T G.652 표준(standards)의 경우 32.5 ㎜의 구부림 반경에서의 값이다. 더 심한 구부림 환경에서도 ITU-T G.652 표준(standards)에 명시된 허용치인 0.005 dB/turn 보다 더 낮은 구부림 손실을 얻을 수 있었다. 광섬유의 크기는 일반적인 250 ㎛ 코팅 직경을 가지는 단일모드 광섬유와 비교하여 약 40% 감소하였음을 볼 수 있다. 이와 동시에 케이블 차단파장을 제외한 모든 항목에서 ITU-T G.652 표준(standards)을 만족함을 확인하였다. 케이블 차단파장의 경우는 그럼에도 불구하고 1300 ㎚ 보다 작은 값을 가지므로 광대역 광전송이 가능하다. In the table above, the macro bending loss is the value at the bending radius of 16 mm for the measurement and at the bending radius of 32.5 mm for the ITU-T G.652 standards. Even in more severe bending conditions, bending losses lower than 0.005 dB / turn, the tolerances specified in the ITU-T G.652 standards, were obtained. It can be seen that the size of the optical fiber is reduced by about 40% compared to a single mode optical fiber having a typical 250 μm coating diameter. At the same time, it was confirmed that all items except the cable cut-off wavelength met the ITU-T G.652 standards. Cable blocking wavelengths nevertheless have values less than 1300 nm, allowing broadband optical transmission.
위와 같은 단면적이 소형화된 단일모드 광섬유를 일렬로 배치하여 광케이블 및 각종 커넥터에 유용하게 사용될 수 있는 리본 광섬유를 만들 수 있다. 일반적으로 사용되는 4개, 8개, 12개 광섬유 기반의 리본이 제작 가능하다. 도 5은 한 가지 예로 12개 광섬유 기반의 리본 광섬유의 설계치를 나타낸 것이다. 각 광섬유를 부착시키기 위한 리본 재킷의 두께는 약 25 ㎛가 되도록 설계하였다. 이는 광섬유가 균일하게 배치되는 않은 상황을 감안하여 설정된 것이다. 이러한 형태로 제작된 광섬유 리본의 크기는 가로 2320 ㎛, 세로 240 ㎛로 측정되었으며, 단면적은 약 556,800 ㎛2로 나타났다. 일반적으로 사용되는 상용 12가닥 광섬유 리본의 단면적은 약 976,500 ㎛2임을 감안하면, 제작된 광섬유 리본을 사용함으로써 약 75% (=976,500÷556,800-1)의 공간효율 이득을 얻을 수 있다.By arranging the single-mode optical fibers with a smaller cross-sectional area in a row, a ribbon optical fiber can be usefully used for optical cables and various connectors. Four, eight and twelve optical fiber-based ribbons are available. 5 illustrates a design value of a ribbon optical fiber based on twelve optical fibers as an example. The ribbon jacket for attaching each optical fiber was designed to have a thickness of about 25 μm. This is set in consideration of the situation that the optical fibers are not evenly arranged. The size of the optical fiber ribbon fabricated in this form was measured to be 2320 μm in width and 240 μm in length, and the cross-sectional area was about 556,800 μm 2 . Considering that the cross-sectional area of a commercially available 12-strand optical fiber ribbon is about 976,500 μm 2 , a space efficiency gain of about 75% (= 976,500 ÷ 556,800-1) can be obtained by using the manufactured fiber ribbon.
이상 본 발명의 실시예로 설명하였으나 본 발명의 기술적 사상이 상기 실시예로 한정되는 것은 아니며, 본 발명의 기술적 사상을 벗어나지 않는 범주에서 다양한 단면적이 소형화된 광섬유 및 이로 구성된 광통신용 리본 광섬유가 구현될 수 있다.Although the embodiments of the present invention have been described above, the technical idea of the present invention is not limited to the above embodiments, and various optical fibers having a small cross-sectional area and a ribbon optical fiber for optical communication including the same may be implemented without departing from the technical idea of the present invention. Can be.

Claims (10)

  1. 일렬로 배치되어 있는 복수개의 광섬유를 포함하는 리본 광섬유에 있어서,In the ribbon optical fiber comprising a plurality of optical fibers arranged in a line,
    상기 각 광섬유는 굴절률이 n1인 코어와, 굴절률이 n2인 내곽 클래딩, 및 굴절률이 n3인 외곽 클래딩을 포함하고,And wherein each optical fiber has a refractive index of the core n 1 and a refractive index of n it includes 2 naegwak cladding, and a refractive index n 3 of the outer cladding,
    상기 각 광섬유의 내곽 클래딩의 직경(d2)은 40 ㎛ 내지 50 ㎛ 이며,The diameter d 2 of the inner cladding of each optical fiber is 40 μm to 50 μm,
    Δ2/Δ1의 값은 0보다 크고 0.7보다 작고,The value of Δ 2 / Δ 1 is greater than 0 and less than 0.7,
    클래딩을 포함한 상기 각 광섬유의 직경은 85 ㎛ 이하이며,The diameter of each optical fiber including the cladding is 85 μm or less,
    상기 Δ1은 상기 코어와 외곽 클래딩의 굴절률 차이로 Δ1=(n1-n3)/n3로 정의되고, 상기 Δ2는 상기 내곽 클래딩과 외곽 클래딩의 굴절률 차이로 Δ2=(n2-n3)/n3로 정의되는, 소형화된 단일모드 광섬유로 구성된 리본 광섬유.Δ 1 is defined as Δ 1 = (n 1 -n 3 ) / n 3 as a difference in refractive index between the core and the outer cladding, and Δ 2 is a difference in refractive index between the inner cladding and the outer cladding Δ 2 = (n 2 Ribbon fiber consisting of miniaturized single-mode fiber, defined as -n 3 ) / n 3 .
  2. 제1항에 있어서,The method of claim 1,
    상기 각 광섬유는 한 층 이상의 코팅으로 덮여 있고, 상기 리본 광섬유에 포함된 광섬유의 개수를 N, 상기 코팅을 포함한 상기 각 광섬유의 직경을 d ㎛라 할 때, 상기 리본 광섬유의 크기는 (d × N + 60) × (N + 60) ㎛2을 넘지 않는, 소형화된 단일모드 광섬유로 구성된 리본 광섬유.Each optical fiber is covered with one or more layers of coating, and when the number of optical fibers included in the ribbon optical fiber is N and the diameter of each optical fiber including the coating is d μm, the size of the ribbon optical fiber is (d × N + 60) Ribbon optical fiber consisting of miniaturized single-mode optical fibers not exceeding (N + 60) μm 2 .
  3. 제1항에 있어서,The method of claim 1,
    상기 각 광섬유의 코어 직경(d1)은 8 ㎛ 내지 10 ㎛ 이며, 상기 코어와 외곽 클래딩의 굴절률 차이(Δ1)는 0.35% 내지 0.41%인, 소형화된 단일모드 광섬유로 구성된 리본 광섬유.The core diameter (d 1 ) of each optical fiber is 8 μm to 10 μm, wherein the refractive index difference Δ 1 between the core and the outer cladding is 0.35% to 0.41%.
  4. 제1항에 있어서,The method of claim 1,
    상기 각 광섬유는 한 층 이상의 코팅으로 덮여 있고, 상기 코팅을 포함한 상기 각 광섬유의 총 직경은 190 ㎛ 이하인, 소형화된 단일모드 광섬유로 구성된 리본 광섬유.Wherein each optical fiber is covered with one or more layers of coatings, wherein the total diameter of each of the optical fibers including the coatings is equal to or less than 190 μm.
  5. 제1항에 있어서,The method of claim 1,
    상기 각 광섬유는 광 손실이 1310 ㎚의 파장 대역에서 0.4 dB/km 보다 작은 값을 가지고, 1550 ㎚의 파장 대역에서 0.35 dB/km 보다 작은 값을 갖는, 소형화된 단일모드 광섬유로 구성된 리본 광섬유.Wherein each optical fiber has a light loss value less than 0.4 dB / km in a wavelength band of 1310 nm and a value less than 0.35 dB / km in a wavelength band of 1550 nm.
  6. 제1항에 있어서,The method of claim 1,
    상기 각 광섬유의 모드 필드 직경은 1310 ㎚의 파장 대역에서 8.6 ㎛ 내지 9.5 ㎛ 인, 소형화된 단일모드 광섬유로 구성된 리본 광섬유.And the mode field diameter of each of the optical fibers is a miniaturized single mode optical fiber, which is 8.6 µm to 9.5 µm in a wavelength band of 1310 nm.
  7. 제1항에 있어서,The method of claim 1,
    상기 각 광섬유의 케이블 차단 파장은 1300 ㎚ 이하의 값을 갖는, 소형화된 단일모드 광섬유로 구성된 리본 광섬유.And a cable blocking wavelength of each of the optical fibers has a value of 1300 nm or less.
  8. 제1항에 있어서,The method of claim 1,
    상기 각 광섬유의 인장 강도는 최소 0.69 GPa의 값을 갖는, 소형화된 단일모드 광섬유로 구성된 리본 광섬유.And wherein the tensile strength of each of said optical fibers has a value of at least 0.69 GPa.
  9. 제1항에 있어서,The method of claim 1,
    상기 각 광섬유는, 구부림 반경이 37.5 ㎜인 상태에서 100회 회전 시, 1625㎚ 파장 대역에서 0.5 dB 이하의 광 손실을 갖는, 소형화된 단일모드 광섬유로 구성된 리본 광섬유.Wherein each optical fiber has a light loss of 0.5 dB or less in a wavelength band of 1625 nm when rotated 100 times with a bending radius of 37.5 mm.
  10. 제1항에 있어서,The method of claim 1,
    상기 각 광섬유는, 1550 ㎚ 파장 대역에서 20 ps/㎚/㎞ 이하의 색분산을 갖고, 0.07 ps/㎚2/㎞ 이하의 파장에 따른 색분산 변화율을 갖는, 소형화된 단일모드 광섬유로 구성된 리본 광섬유.Each optical fiber has a color dispersion of 20 ps / nm / km or less in a wavelength band of 1550 nm, and a ribbon optical fiber composed of miniaturized single mode optical fibers having a chromatic dispersion change rate according to a wavelength of 0.07 ps / nm 2 / km or less. .
PCT/KR2015/014476 2015-01-12 2015-12-30 Ribbon optical fiber comprising compact single-mode optical fibers WO2016114514A1 (en)

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