WO2020014814A1 - 双向光纤光栅的制作方法、双向追踪器及无源网络 - Google Patents

双向光纤光栅的制作方法、双向追踪器及无源网络 Download PDF

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WO2020014814A1
WO2020014814A1 PCT/CN2018/095774 CN2018095774W WO2020014814A1 WO 2020014814 A1 WO2020014814 A1 WO 2020014814A1 CN 2018095774 W CN2018095774 W CN 2018095774W WO 2020014814 A1 WO2020014814 A1 WO 2020014814A1
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grating
chirped grating
optical fiber
chirped
mask
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PCT/CN2018/095774
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English (en)
French (fr)
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侯丹
黄舒
邱建军
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深圳太辰光通信股份有限公司
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Priority to PCT/CN2018/095774 priority Critical patent/WO2020014814A1/zh
Publication of WO2020014814A1 publication Critical patent/WO2020014814A1/zh

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/18—Diffraction gratings
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems

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  • the invention relates to the technical field of optical fiber communication, in particular to a method for manufacturing a bidirectional fiber grating, a bidirectional tracker based on a bidirectional fiber grating, and a passive network.
  • OTDR Optical Time Domain Reflectometer
  • a chirped grating is widely deployed because it has the characteristics of having a small impact on the communication band.
  • a chirped grating can be made into a tracker for OTDR detection of an optical link according to the packaging method of a related patent (Chinese Patent Application No. 201210358287.6).
  • the so-called chirped grating refers to a fiber grating formed by a period in which the refractive index of a core of a fiber changes (that is, a grating period) gradually changes along the fiber axis. Incident light of different wavelengths can be reflected at different positions of the chirped grating axis, so that the chirped grating has a large reflection bandwidth.
  • chirped gratings have a large wavelength end and a small wavelength end: when an optical signal passes through, there are two cases where light is incident from the large wavelength end and incident from the small wavelength end. In both cases, the chirped grating has a distinct reflection spectrum. When light is incident from the small wavelength end of the chirped grating, a flat reflection spectrum can be obtained within the required bandwidth; when light is incident from the large wavelength end of the chirped grating, the reflection spectrum obtained is not flat.
  • the spectrum of the chirped grating will limit the direction used by the tracker, that is, only the OTDR detection light will pass from the small wavelength end of the chirped grating. Incidence can get a flat reflection spectrum in the required wavelength range. Conversely, when the OTDR detection light is incident from another direction, the reflection spectrum obtained is not flat.
  • the uneven reflection spectrum means that the reflectance of the fiber grating to the incident detection light of different wavelengths will be greatly different, which will affect the final detection result of the optical link.
  • the purpose of the present invention is to solve the technical problem that the reflectance of the optical fiber grating in the two incident directions with respect to the incident detection light of different wavelengths is greatly different in the prior art.
  • a method for manufacturing a bidirectional fiber grating and a bidirectional fiber grating-based method are provided. Two-way trackers, and passive networks.
  • the present invention adopts the following technical solutions:
  • the manufacturing method of bidirectional fiber grating includes:
  • the grating period of the first chirped grating and the grating period of the second chirped grating are symmetrically distributed on the optical fiber.
  • the mask region includes a first mask region and a second mask region; and the laser is irradiated onto the first mask region and the second mask region simultaneously to The first chirped grating and the second chirped grating are made simultaneously.
  • the phase mask includes a first mask and a second mask spliced together, the first mask region is located on the first mask, and the second mask A region is located on the second mask.
  • the lengths of the first mask region and the second mask region are both L ′, and the distance between the first mask region and the second mask region is d ′.
  • the present invention provides a two-way fiber grating-based two-way tracker, including a mounting component and a fiber grating provided on the mounting component.
  • the fiber grating includes a first chirped grating and a second chirped grating.
  • the first chirped grating and the second chirped grating have the same center wavelength and the same chirp ratio, and the grating period of the first chirped grating gradually increases from small at one end of the optical fiber to the other end of the optical fiber.
  • the grating period of the second chirped grating is gradually increased from small at the other end of the optical fiber to one end of the optical fiber, and the grating period of the first chirped grating is equal to that of the second chirped grating Periods are symmetrically distributed on the fiber.
  • the mounting assembly includes a first ferrule, a second ferrule, and a connector, and the first ferrule and the second ferrule are respectively inserted into two ends of the connector; the first A ferrule is provided with a first cavity, and the second ferrule is provided with a second cavity.
  • the length of the first cavity is D1
  • the length of the second cavity is D2.
  • the D ⁇ 16 mm.
  • the ⁇ ratio is greater than or equal to 10 nm / cm, and the d ⁇ 2 mm.
  • the present invention also provides a passive network, in which an optical line terminal, an optical splitter, and an optical network unit are sequentially arranged on an optical path, and further includes the above-mentioned two-way tracker, wherein the two-way tracker is disposed on the On an optical splitter and / or on the optical network unit.
  • the reflectance of the bidirectional tracker to the incident detection light of different wavelengths is basically the same.
  • the directionality of the tracker is eliminated, and the flexibility and operability of optical link detection are increased.
  • FIG. 1 is a schematic structural diagram of a fiber grating of the present invention
  • FIG. 2 is another schematic structural diagram of a fiber grating of the present invention.
  • FIG. 3 is a schematic structural diagram of a bidirectional tracker of the present invention.
  • FIG. 4 is a schematic structural diagram of a modification of the bidirectional tracker of the present invention.
  • FIG. 6 is a reflection spectrum obtained using a tracker of a comparative example
  • Figure 7 is another reflection spectrum obtained using a tracker of a comparative example
  • FIG. 9 is another reflection spectrum obtained using a tracker of another comparative example.
  • FIG. 10 is a reflection spectrum obtained by using the bidirectional tracker with d ⁇ 0mm according to the present invention.
  • FIG. 11 is a reflection spectrum obtained by using a bidirectional tracker of 0 ⁇ d ⁇ 1 mm according to the present invention.
  • FIG. 12 is a reflection spectrum obtained by using the two-way tracker with d ⁇ 2mm of the present invention.
  • FIG. 13 is a schematic structural diagram of a mask used in a method for manufacturing a bidirectional fiber grating of the present invention.
  • FIG. 14 is a schematic structural diagram of another mask plate used in a manufacturing method of a bidirectional fiber grating of the present invention.
  • FIG. 15 is a schematic structural diagram of a third mask used in the method for manufacturing a bidirectional fiber grating of the present invention.
  • FIG. 16 is a schematic structural diagram of a passive network according to the present invention.
  • a two-way fiber grating-based bidirectional tracker 100 includes a mounting component 1 and a fiber grating 2.
  • the mounting component 1 is used to fix the fiber grating 2, that is, the fiber grating 2 is disposed on the mounting component 1.
  • the fiber grating 2 is a chirped grating and is made of an optical fiber.
  • the fiber grating 2 includes a first chirped grating 21 and a second chirped grating 22, and the first chirped grating 21 and the second chirped grating 22 have the same center wavelength and the same chirp rate.
  • the grating period of the first chirped grating 21 is gradually increased from small at one end 10A of the optical fiber 10 to the other end 10B of the optical fiber 10, and the grating period of the second chirped grating 22 is at the other end 10B of the optical fiber 10 toward the optical fiber.
  • 10A at one end of 10 gradually increases from small.
  • the first chirped grating 21 and the second chirped grating 22 are provided with light and dark stripes.
  • the light chirped stripes 211 and dark stripes 212 of the first chirped grating 21 Is gradually widened; at the other end 10B of the optical fiber 10 in the direction 102 along the axial direction of the optical fiber, the light fringe 221 and the dark fringe 222 of the second chirped grating 22 also gradually widen.
  • the direction of the first chirped grating 21 is from a small wavelength to a large wavelength; at the other end 10B of the optical fiber 10 In the direction 102 along the fiber axis, the direction of the second chirped grating 22 is also from a small wavelength to a large wavelength.
  • the grating period of the first chirped grating 21 and the grating period of the second chirped grating 22 are symmetrically distributed on the optical fiber 10. That is, the first chirped grating 21 and the second chirped grating 22 are two identical chirped gratings, and they are symmetrically distributed on the optical fiber 10.
  • the detection light is incident from one end 10A of the optical fiber 10.
  • the detection light may be the detection light emitted by the OTDR, which is reflected back at the first chirped grating 21 and the second chirped grating 22, and one can be obtained on the spectrometer.
  • Reflection spectrum when the detection light emitted by the OTDR is incident from the other end 10B of the optical fiber 10, it is reflected back at the second chirped grating 22 and the first chirped grating 21, and another reflection spectrum can be obtained on the spectrometer.
  • the two reflection spectra are basically consistent, the left and right sides of the reflection spectrum are basically symmetrical, and the top of the reflection spectrum is flat.
  • the wavelength of the detection light emitted by the OTDR is about 1650 nm.
  • the reflectance of the two-way tracker 100 to the detection light of different wavelengths is basically the same.
  • the reflectivity of the two-way tracker to detection light having a wavelength of 1645 nm to 1655 nm is substantially the same. In this way, almost the same flat reflection spectrum can be obtained. In this way, by using two cascades of chirped gratings with opposite directions, the directionality of the manufactured tracker is eliminated, and the flexibility and operability of optical link detection are increased.
  • the grating period of the first chirped grating 21 decreases from large at one end 10A of the optical fiber 10 to the other end 10B of the optical fiber 10, and the grating period of the second chirped grating 22 is at the other end 10B of the optical fiber 10 toward one end 10A of the optical fiber 10 From big to small.
  • the two reflection spectra obtained are basically consistent, the top of the reflection spectrum is undulating and cannot be used to detect the optical link.
  • the grating period of the first chirped grating 21 decreases from large at one end 10A of the optical fiber 10 to the other end 10B of the optical fiber 10, and the grating period of the second chirped grating 22 is at the other end 10B of the optical fiber 10 toward one end 10A of the optical fiber 10 From small to large.
  • the obtained two reflection spectra are greatly different.
  • One of the reflection spectra has a undulating top and the other reflection spectrum has a flat top.
  • Such a tracker has directivity.
  • the grating period of the first chirped grating 21 is gradually increased from small at one end 10A of the optical fiber 10 to the other end 10B of the optical fiber 10, and the grating period of the second chirped grating 22 is at the other end 10B of the optical fiber 10 toward one end of the optical fiber 10.
  • 10A gradually changes from large to small, the same is true, the tracker also has directionality.
  • the invention can also be implemented as follows:
  • the mounting assembly 1 of the two-way tracker 100 is provided with a cavity 14. Positions other than the cavity 14 in the mounting assembly 1 are used to fix the optical fiber 10.
  • the optical fiber 10 is fixed with the encapsulation glue at these positions.
  • the optical fiber grating 2 is made of the optical fiber 10, that is, the optical fiber grating 2 is a section on the optical fiber 10.
  • the optical fiber 10 is installed on the mounting assembly 1, the optical fiber grating 2 is located in the cavity 14, and the optical fiber 10 of this section, that is, the optical fiber grating 2 is in a free state.
  • the length of the cavity 14 is D
  • the length of the first chirped grating 21 and the second chirped grating 22 is L
  • the distance between the first chirped grating 21 and the second chirped grating 22 is d
  • the mounting assembly 1 includes a first ferrule 11, a second ferrule 12, and a connecting member 13, and the first ferrule 11 and the second ferrule 12 are respectively inserted into the connecting member 13. Both ends.
  • the first ferrule 11 is provided with a first cavity 110
  • the second ferrule 12 is provided with a second cavity 120.
  • the length of the first cavity 110 is D1
  • the length of the second cavity 120 is D2.
  • the first ferrule 11 and the second ferrule 12 fix the optical fiber 10 so that the first chirped grating 21 and the second chirped grating 22 are substantially located in the first cavity 110 and the second cavity 120, respectively.
  • the specific way of fixing the optical fiber 10 by the first ferrule 11 and the second ferrule 12 is: the first ferrule 11 is provided with a first front inner hole 111, the second ferrule 12 is provided with a second front inner hole 121, and the optical fiber 10 One end 10A is fixed in the first front-end inner hole 111 through the sealing glue, and the other end 10B of the optical fiber 10 is fixed in the second front-end inner hole 121 through the sealing glue.
  • the outer diameters of the first ferrule 11 and the second ferrule 12 are in the millimeter level, and the inner diameters of the first front inner hole 111 and the second front inner hole 121 are in the micron level; for example, the first ferrule 11 and the The outer diameter of the second ferrule 12 is 1 mm to 5 mm, and the inner diameters of the first front-end inner hole 111 and the second front-end inner hole 121 are 100 ⁇ m to 200 ⁇ m. Such a size can meet the requirements of various applications.
  • the length of the first chirped grating 21 and the second chirped grating 22 is L
  • the distance between the first chirped grating 21 and the second chirped grating 22 is d
  • the distance d between the first chirped grating 21 and the second chirped grating 22 will affect the overall reflection spectrum:
  • the length of the chirped grating is usually L ⁇ 8mm.
  • the wavelength of the detection light emitted by the existing OTDR has a certain distribution range around its nominal value, which is about 10nm. That is, the reflection spectrum is required to have a certain reflection bandwidth.
  • the reflection bandwidth ⁇ rate ⁇ ⁇ length of the grating ⁇ core refractive index, where the core refractive index is determined by the type of fiber used in the grating, such as 1.448, so that the tracker has sufficient reflection bandwidth
  • the chirp rate of the chirped grating is required to be greater than or equal to 10 nm / cm.
  • the package size of the tracker is less than 22mm. Due to the limitation of the ferrule processing technology, when the cavity 14 is too deep, the concentricity of the inner hole at the front end of the ferrule and the outer diameter of the ferrule cannot be guaranteed. The degree of concentricity will affect the alignment of the ferrule when it is docked, which will affect the insertion loss of the entire device. Therefore, in order to reduce the insertion loss, the size of the cavity 14 is limited, that is, D ⁇ 16mm or D1 + D2 ⁇ 16mm, that is, D1 and D2 are both 8mm or less, such as 6mm.
  • the present invention provides a method for manufacturing a bidirectional fiber grating.
  • the manufacturing method can be used for manufacturing the above-mentioned fiber grating 2 and can also be used for manufacturing other fiber gratings.
  • a laser beam is irradiated onto a mask region 30 of the phase mask 3, and the laser beam is exposed through the mask region 30 to the optical fiber 10 to form a first chirped grating 21 and a second chirped grating on the optical fiber 10. twenty two.
  • the mask area 30, that is, the mask pattern, can be designed as required. After the laser beam is used to expose the optical fiber 10 through the mask region 30, light and dark stripes can be formed on the optical fiber 10.
  • the center wavelengths of the first chirped grating 21 and the second chirped grating 22 are made the same and the chirp ratios are the same; the grating period of the first chirped grating 21 is at one end 10A of the optical fiber 10 Towards the other end 10B of the optical fiber 10 is gradually increased from small; the grating period of the second chirped grating 22 is gradually increased from the other end 10B of the optical fiber 10 to one end 10A of the optical fiber 10; The grating period and the grating period of the second chirped grating 22 are symmetrically distributed on the optical fiber 10.
  • the outer diameters of the first ferrule 11 and the second ferrule 12 are millimeter-level, such as 2.5 mm, and the inner diameters of the first front-end inner hole 111 and the second front-end inner hole 121 are micron-level, such as 125 ⁇ m.
  • the exposure time of the laser light to the optical fiber 10 is increased to obtain a higher reflectance.
  • the invention can also be implemented as follows:
  • the mask region 30 includes a first mask region 31 and a second mask region 32; a laser is irradiated on the first mask region 31 and the second mask region 32 at the same time to simultaneously fabricate a first chirped grating 21 and the second chirped grating 22, which can improve the production efficiency.
  • the phase mask 3 includes a first mask 3A and a second mask 3B spliced together.
  • the first mask area 31 is located on the first mask 3A
  • the second mask area 32 is located on the second mask. 3B.
  • the phase mask 3 may also be an integrated mask, and the first mask region 31 and the second mask region 32 are provided thereon.
  • the distance d ′ between the first mask region 31 and the second mask region 32 is approximately equal to the distance d between the first chirped grating 21 and the second chirped grating 22.
  • the pitch d 'must also be greater than or equal to 0mm.
  • the first mask plate 3A and the second mask plate 3B are mask plates having a thickness of the same thickness.
  • the thickness tolerance of the first mask plate 3A and the second mask plate 3B will not only affect the generation of the chirp effect, but also affect the quality of the two reflection spectra.
  • the thickness tolerance of the first mask plate 3A and the second mask plate 3B is within ⁇ 0.05 mm.
  • the size affects the length of the cavity of the ferrule. As mentioned earlier, to reduce the insertion loss, S' ⁇ 16mm.
  • the present invention also provides a passive network.
  • the passive network is provided with an optical line terminal 4, an optical splitter 5, and an optical network unit 6 in this order on an optical path.
  • the optical splitter 5 is multi-stage. For example, a two-stage optical splitter 5 is provided. Correspondingly, the number of optical network units 6 is multiple.
  • the optical signal enters from the optical line terminal 4, passes through the two-stage optical splitter 5, and finally enters a plurality of optical network units 6.
  • the passive network also includes the bidirectional tracker 100 described above.
  • the bidirectional tracker 100 is disposed on the optical splitter 5 and / or the optical network unit 6.
  • the two-way tracker 100 will have different connection methods at different locations:
  • the optical fiber is disposed on the adapter port left on the panel of the distribution box, and the two-way tracker 100 is reversely installed on the adapter port.
  • the optical fiber is disposed on the adapter port on the optical network unit 6, and the two-way tracker 100 is installed on the adapter port in a forward direction.
  • the above are typical locations and scenarios where the two-way tracker 100 is installed. In actual use, there may be installation methods according to different situations of network deployment.
  • the present invention allows the two-way tracker 100 to be installed at any position on the network in any direction, increasing the flexibility and operability of network detection and maintenance.

Abstract

双向光纤光栅的制作方法、双向追踪器及无源网络。该双向光纤光栅的制作方法包括将激光照射在相位掩模板的掩模区上，使激光通过所述掩模区对所述光纤(10)进行曝光，以在所述光纤(10)上形成第一啁啾光栅(21)和第二啁啾光栅(22)；使所述第一啁啾光栅(21)和所述第二啁啾光栅(22)的中心波长相同、啁啾率相同；使所述第一啁啾光栅(21)的光栅周期在所述光纤(10)的一端(10A)向所述光纤(10)的另一端(10B)由小逐渐变大；使所述第二啁啾光栅(22)的光栅周期在所述光纤(10)的另一端(10B)向所述光纤(10)的一端(10A)由小逐渐变大；使所述第一啁啾光栅(21)的光栅周期与所述第二啁啾光栅(22)的光栅周期在所述光纤(10)上对称分布。本发明增加了光链路检测的灵活性和可操作性。

Description

双向光纤光栅的制作方法、双向追踪器及无源网络 技术领域
本发明涉及光纤通信技术领域，特别涉及双向光纤光栅的制作方法、基于双向光纤光栅的双向追踪器、以及无源网络。
背景技术
在光接入网中，常使用OTDR(Optical Time Domain Reflectometer，光时域反射仪)技术对网络实施检测，以便及时诊断网络中出现的故障。在这样的检测方法中，通过在光链路末端使用追踪器，可以实现对存在分支的光链路进行检测，从而提高网络的运维能力。
啁啾光栅因其具有对通信波段影响小的特点，在实际应用中作为优选的方案制作成上述追踪器，被广泛部署。啁啾光栅可按照相关专利(中国专利申请号201210358287.6)的封装方法，做成用于光链路OTDR检测的追踪器。
所谓啁啾光栅，是指光纤的纤芯折射率变化的周期(也即光栅周期)沿光纤轴向逐渐变化形成的一种光纤光栅。在啁啾光栅轴向不同位置可反射不同波长的入射光，使得啁啾光栅具有较大的反射带宽。
也正因为如此，啁啾光栅具有大波长端和小波长端：在光信号经过时，存在光从大波长端入射和从小波长端入射两种情形。在这两种情形下，啁啾光栅具有截然不同的反射光谱。光从啁啾光栅的小波长端入射时，可以在所需带宽内得到平坦的反射光谱；光从啁啾光栅的大波长端入射时，得到的反射光谱是不平坦的。由于OTDR发出的检测光的波长和标称值会具有偏差，分布在一定范围内，那么啁啾光栅的光谱就会限定追踪器使用的方向，即只有OTDR检测光从啁啾光栅的小波长端入射，才可以在所需波长范围内得到平坦的反射光谱。反之，当OTDR检测光从另一方向入射时，得到的反射光谱是不平坦的。反射光谱的不平坦意味着，光纤光栅对不同波长的入射检测光的反射率会有较大差异，进而影响光链路的最终检测结果。
发明内容
本发明的目的是为了解决现有技术中光纤光栅在两个入射方向上对不同波长的入射检测光的反射率有较大差异的技术问题，提出双向光纤光栅的制作方法、基于双向光纤光栅的双向追踪器、以及无源网络。
为解决上述技术问题，本发明采用以下技术方案：
双向光纤光栅的制作方法，包括：
将激光照射在相位掩模板的掩模区上，使激光通过所述掩模区对所述光纤进行曝光，以在所述光纤上形成第一啁啾光栅和第二啁啾光栅；
使所述第一啁啾光栅和所述第二啁啾光栅的中心波长相同、啁啾率相同；
使所述第一啁啾光栅的光栅周期在所述光纤的一端向所述光纤的另一端由小逐渐变大；
使所述第二啁啾光栅的光栅周期在所述光纤的另一端向所述光纤的一端由小逐渐变大；
使所述第一啁啾光栅的光栅周期与所述第二啁啾光栅的光栅周期在所述光纤上对称分布。
在一些优选的实施方式中，所述掩模区包括第一掩模区和第二掩模区；使所述激光同时照射在所述第一掩模区和所述第二掩模区上以同时制作所述第一啁啾光栅和所述第二啁啾光栅。
在进一步优选的实施方式中，所述相位掩模板包括拼接在一起的第一掩模板和第二掩模板，所述第一掩模区位于所述第一掩模板上，所述第二掩模区位于所述第二掩模板上。
在进一步优选的实施方式中，所述第一掩模区与所述第二掩模区的长度均为L'，所述第一掩模区与所述第二掩模区的间距为d'，光纤光栅的长度为S'，S'＝2L'+d'，S'≤16mm。
在另一方面，本发明提供基于双向光纤光栅的双向追踪器，包括安装组件和设置在所述安装组件上的光纤光栅，所述光纤光栅包括第一啁啾光栅和第二啁啾光栅，所述第一啁啾光栅和所述第二啁啾光栅的中心波长相同、啁啾率相同，所述第一啁啾光栅的光栅周期在光纤的一端向所述光纤的另一端由小逐渐变大，所述第二啁啾光栅的光栅周期在所述光纤的另一端向所述光纤的一端由小逐渐变大，所述第一啁啾光栅的光栅周期与所述第二啁啾光栅的光栅周期在所述光纤上对称分布。
在一些优选的实施方式中，所述安装组件设有空腔，所述空腔的长度为D，所述第一啁啾光栅与所述第二啁啾光栅的长度为L，所述第一啁啾光栅与所述第二啁啾光栅的间距为d，所述光纤光栅的长度为S，S＝2L+d且S ≤D。
在进一步优选的实施方式中，所述安装组件包括第一插芯、第二插芯和连接件，所述第一插芯和所述第二插芯分别插入连接件的两端；所述第一插芯设有第一空腔，所述第二插芯设有第二空腔，所述第一空腔的长度为D1，所述第二空腔的长度为D2，所述空腔包括所述第一空腔和所述第二空腔且D1+D2＝D。
在进一步优选的实施方式中，所述D≤16mm。
在进一步优选的实施方式中，所述啁啾率大于等于10nm/cm，所述d≥2mm。
在另一方面，本发明还提供一种无源网络，在光路上依次设有光线路终端、光分路器和光网络单元，还包括上述的双向追踪器，所述双向追踪器设置在所述光分路器上和/或所述光网络单元上。
与现有技术相比，本发明的有益效果有：
检测光无论从双向追踪器(光纤光栅)的哪一端入射，双向追踪器对不同波长的入射检测光的反射率基本相同。消除了追踪器的方向性，增加了光链路检测的灵活性和可操作性。
附图说明
图1为本发明的光纤光栅的结构示意图；
图2为本发明的光纤光栅的另一结构示意图；
图3为本发明的双向追踪器的结构示意图；
图4为本发明的双向追踪器的一种变型方式的结构示意图；
图5为使用本发明的双向追踪器的所得到的反射光谱；
图6为使用一个对比例的追踪器的所得到的一个反射光谱；
图7为使用一个对比例的追踪器的所得到的另一个反射光谱；
图8为使用另一个对比例的追踪器的所得到的一个反射光谱；
图9为使用另一个对比例的追踪器的所得到的另一个反射光谱；
图10为使用本发明d＜0mm的双向追踪器所得到的反射光谱；
图11为使用本发明0≤d≤1mm的双向追踪器所得到的反射光谱；
图12为使用本发明d≥2mm的双向追踪器所得到的反射光谱；
图13为本发明的双向光纤光栅的制作方法使用的一种掩模板的结构示意图；
图14为本发明的双向光纤光栅的制作方法使用的另一种掩模板的结 构示意图；
图15为本发明的双向光纤光栅的制作方法使用的第三种掩模板的结构示意图；
图16为本发明的无源网络的结构示意图。
具体实施方式
以下对本发明的实施方式作详细说明。应该强调的是，下述说明仅仅是示例性的，而不是为了限制本发明的范围及其应用。
参考图3，基于双向光纤光栅的双向追踪器100，包括安装组件1和光纤光栅2，安装组件1用于固定光纤光栅2，也就是说光纤光栅2设置在安装组件1上。
参考图1，光纤光栅2为啁啾光栅，由光纤制作而成。光纤光栅2包括第一啁啾光栅21和第二啁啾光栅22，第一啁啾光栅21和第二啁啾光栅22的中心波长相同、啁啾率相同。
参考图1，第一啁啾光栅21的光栅周期在光纤10的一端10A向光纤10的另一端10B由小逐渐变大，第二啁啾光栅22的光栅周期在光纤10的另一端10B向光纤10的一端10A由小逐渐变大。第一啁啾光栅21和第二啁啾光栅22均设有明暗相间的条纹，在光纤10的一端10A沿光纤轴向的方向101上，第一啁啾光栅21的明条纹211和暗条纹212是逐渐变宽的；在光纤10的另一端10B沿光纤轴向的方向102上，第二啁啾光栅22的明条纹221和暗条纹222也是逐渐变宽的。或者说，由于光栅周期对应光的波长，那么，在光纤10的一端10A沿光纤轴向的方向101上，第一啁啾光栅21的方向为从小波长到大波长；在光纤10的另一端10B沿光纤轴向的方向102上，第二啁啾光栅22的方向也为从小波长到大波长。
参考图1，第一啁啾光栅21的光栅周期与第二啁啾光栅22的光栅周期在光纤10上对称分布。也就是说，第一啁啾光栅21和第二啁啾光栅22是两个相同的啁啾光栅，两者在光纤10上对称分布。
参考图1，检测光从光纤10的一端10A入射，检测光可以是由OTDR发出的检测光，在第一啁啾光栅21和第二啁啾光栅22处被反射回来，在光谱仪上可得到一个反射光谱；当OTDR发出的检测光从光纤10的另一端10B入射，在第二啁啾光栅22和第一啁啾光栅21处被反射回来，在光谱仪上可得到另一个反射光谱。参考图5，这两个反射光谱是基本一致的， 反射光谱的左右两边基本对称，且反射光谱的顶部是平坦的。
根据上述可知，OTDR发出的检测光的波长在1650nm左右，检测光无论从双向追踪器(光纤光栅)的哪一端入射，双向追踪器100对不同波长的入射检测光的反射率基本相同。参考图5，双向追踪器对波长为1645nm至1655nm的检测光的反射率基本相同。如此，可以得到几乎相同的平坦的反射光谱。这样，通过两段方向相反的啁啾光栅级联(cascade)，消除了所制作的追踪器的方向性，增加了光链路检测的灵活性和可操作性。
发明人曾经也尝试过制作如下的追踪器：
第一啁啾光栅21的光栅周期在光纤10的一端10A向光纤10的另一端10B由大逐渐变小，第二啁啾光栅22的光栅周期在光纤10的另一端10B向光纤10的一端10A由大逐渐变小。参考图6和图7，所得到的两个反射光谱虽然是基本一致的，但是反射光谱的顶部是起伏的，无法用于检测光链路。
第一啁啾光栅21的光栅周期在光纤10的一端10A向光纤10的另一端10B由大逐渐变小，第二啁啾光栅22的光栅周期在光纤10的另一端10B向光纤10的一端10A由小逐渐变大。参考图8和图9，所得到的两个反射光谱相差很大，其中一个反射光谱的顶部是起伏的，另一个反射光谱的顶部是平坦的，这样的追踪器具有方向性。对于第一啁啾光栅21的光栅周期在光纤10的一端10A向光纤10的另一端10B由小逐渐变大，第二啁啾光栅22的光栅周期在光纤10的另一端10B向光纤10的一端10A由大逐渐变小，其情况也是一样，追踪器也具有方向性。
本发明还可以这样实现：
参考图3，双向追踪器100的安装组件1设有空腔14。安装组件1中除空腔14之外的位置用于固定光纤10，比如在这些位置用封装胶将光纤10固定。光纤光栅2是由光纤10制作而成的，也即光纤光栅2是光纤10上的一段。光纤10安装在安装组件1上，光纤光栅2位于空腔14中，且这一段的光纤10也即光纤光栅2处于自由状态。空腔14的长度为D，第一啁啾光栅21与第二啁啾光栅22的长度为L，第一啁啾光栅21与第二啁啾光栅22的间距为d，光纤光栅2的长度为S，S＝2L+d且S≤D。这就使得光纤光栅2全部位于空腔14中，避免光纤光栅2被用于固定光纤10，可避免用于固定光纤10的封装胶流到光纤光栅2上，从而避免光谱的变化，可保证光谱的质量。
参考图4，安装组件1的一种形式为：安装组件1包括第一插芯11、第二插芯12和连接件13，第一插芯11和第二插芯12分别插入连接件13的两端。第一插芯11设有第一空腔110，第二插芯12设有第二空腔120，第一空腔110的长度为D1，第二空腔120的长度为D2。空腔14包括第一空腔110和第二空腔120且D1+D2＝D，也就是说第一空腔110和第二空腔120组合起来形成空腔14。
参考图4，第一插芯11和第二插芯12固定光纤10，使得第一啁啾光栅21和第二啁啾光栅22分别大致位于第一空腔110和第二空腔120中。第一插芯11和第二插芯12固定光纤10的具体方式是：第一插芯11设有第一前端内孔111，第二插芯12设有第二前端内孔121，光纤10的一端10A通过封装胶固定在第一前端内孔111中，光纤10的另一端10B则通过封装胶固定在第二前端内孔121中。通常而言，第一插芯11和第二插芯12的外径为毫米级别，第一前端内孔111和第二前端内孔121的内径为微米级别；示例的，第一插芯11和第二插芯12的外径为1毫米至5毫米，第一前端内孔111和第二前端内孔121的内径为100微米至200微米，这样的尺寸可满足各个应用场合的需求。
参考图2，第一啁啾光栅21与第二啁啾光栅22的长度为L，第一啁啾光栅21与第二啁啾光栅22的间距为d，光纤光栅2的长度为S，S＝2L+d且S≤D1+D2。因为光纤10的两端是分别固定在第一插芯11和第二插芯12上的，光纤光栅2的长度为S≤D1+D2，防止封装胶流到光纤光栅2上从而可保证光谱的质量。
第一啁啾光栅21与第二啁啾光栅22的间距d会对整体的反射光谱产生影响：
参考图10，当间距d＜0mm，即两段啁啾光栅有部分重叠，反射光谱的顶端会有较大波动。参考图11，当0≤d≤1mm时，反射光谱的大波长端的边坡会出现较大波动，但其顶部是平坦的。参考图12，当间距d≥2mm时，反射光谱的两端边坡的波形都比较理想，且顶部是平坦的。
在实际应用中，考虑到追踪器的封装，通常啁啾光栅的长度L≤8mm，现有的OTDR发出的检测光的波长在其标称值附近具有一定分布范围，多见为10nm左右，这也就要求反射光谱具有一定的反射带宽。对于光纤光栅而言，反射带宽＝啁啾率×啁啾光栅的长度×纤芯折射率，其中，纤芯折射率由光栅所用光纤类型决定，比如为1.448，为使追踪器具有足够的反射带 宽，且采用常规尺寸对追踪器进行封装，就要求啁啾光栅的啁啾率大于等于10nm/cm。
通常追踪器的封装尺寸小于22mm，由于插芯加工工艺的限制，当空腔14过深时，插芯前端内孔与插芯外径的同芯度会无法得到保证。同芯度会影响插芯对接时的对准，从而影响整个器件的插入损耗。因此，为减少插入损耗，空腔14的尺寸有一定的限制，即D≤16mm或D1+D2≤16mm，也即D1和D2均小于等于8mm，比如均为6mm。
在另一方面，本发明提供双向光纤光栅的制作方法，该制作方法可用于制作上述的光纤光栅2，也可用于制作其它光纤光栅。
参考图13，将激光照射在相位掩模板3的掩模区30上，使激光通过掩模区30对光纤10进行曝光，以在光纤10上形成第一啁啾光栅21和第二啁啾光栅22。掩模区30也即掩模图形，可按要求进行设计。激光通过掩模区30对光纤10进行曝光后，可在光纤10上形成明暗相间的条纹。
参考图1，在制作的过程中：使第一啁啾光栅21和第二啁啾光栅22的中心波长相同、啁啾率相同；使第一啁啾光栅21的光栅周期在光纤10的一端10A向光纤10的另一端10B由小逐渐变大；使第二啁啾光栅22的光栅周期在光纤10的另一端10B向光纤10的一端10A由小逐渐变大；使第一啁啾光栅21的光栅周期与第二啁啾光栅22的光栅周期在光纤10上对称分布。
如此，得到的光纤光栅2，无论光从光纤10的哪一端入射，光纤光栅2对不同波长的入射检测光的反射率基本相同。
如前所述，第一插芯11和第二插芯12的外径为毫米级别比如2.5mm，第一前端内孔111和第二前端内孔121的内径为微米级别比如125μm，这样的尺寸给光纤光栅2的封装增加了难度，比如要避免用于固定光纤10端面的封装胶流到光纤光栅2上，从而获得较高的反射率。为了减小加工难度，在制作光纤光栅时，增加激光对光纤10的曝光时间，从而获得较高的反射率。
本发明还可以这样实现：
参考图14，掩模区30包括第一掩模区31和第二掩模区32；使激光同时照射在第一掩模区31和第二掩模区32上以同时制作第一啁啾光栅21和第二啁啾光栅22，这样可提高制作效率。
参考图15，相位掩模板3包括拼接在一起的第一掩模板3A和第二掩 模板3B，第一掩模区31位于第一掩模板3A上，第二掩模区32位于第二掩模板3B上。当然，相位掩模板3还可以是一个整体的掩模板，其上设有第一掩模区31和第二掩模区32。
参考图14，第一掩模区31与第二掩模区32的间距d’大约等于第一啁啾光栅21与第二啁啾光栅22的间距d，为获得光谱顶部平坦的反射光谱，间距d’也要大于等于0mm。
第一掩模板3A和第二掩模板3B是具有厚度的掩模板，两者的厚度相同，其厚度公差不仅会影响啁啾效应的产生，而且还会影响两个反射光谱的质量，因此，第一掩模板3A和第二掩模板3B厚度公差在±0.05mm之内。
参考图14，第一掩模区31与第二掩模区32的长度均为L’，光纤光栅长度S’＝2L’+d’，光纤光栅长度S’也就是前述的S，S’的大小影响插芯的空腔的长度，如前所述，为减少插入损耗，S’≤16mm。
在另一方面，本发明还提供一种无源网络，参考图16，该无源网络在光路上依次设有光线路终端4、光分路器5和光网络单元6。光分路器5为多级，比如设置两级光分路器5，相应的，光网络单元6的数量为多个。光信号从光线路终端4进入，经过两级光分路器5，最终进入多个光网络单元6。
该无源网络还包括上述的双向追踪器100，双向追踪器100设置在光分路器5上和/或光网络单元6上。
在该无源网络中，双向追踪器100在不同的位置会具有不同的连接方式：
在分路器5处，光纤设置在配线箱面板上留出的适配器端口上，双向追踪器100反向安装在适配器端口上。
在光网络单元6处，光纤设置在光网络单元6上的适配器端口上，双向追踪器100正向安装在适配器端口上。
以上为双向追踪器100安装的典型位置和场景。实际使用中，根据网络部署的不同情况还会有安装方式。本发明允许将双向追踪器100以任意方向安装在网络的任意位置，增加了网络检测和维护的灵活性和可操作性。
以上内容是结合具体/优选的实施方式对本发明所作的进一步详细说明，不能认定本发明的具体实施只局限于这些说明。对于本发明所属技术领域的普通技术人员来说，在不脱离本发明构思的前提下，其还可以对这些已描述的实施方式做出若干替代或变型，而这些替代或变型方式都应当 视为属于本发明的保护范围。

Claims (10)

  1. 双向光纤光栅的制作方法，其特征在于包括：
    将激光照射在相位掩模板的掩模区上，使激光通过所述掩模区对所述光纤进行曝光，以在所述光纤上形成第一啁啾光栅和第二啁啾光栅；
    使所述第一啁啾光栅和所述第二啁啾光栅的中心波长相同、啁啾率相同；
    使所述第一啁啾光栅的光栅周期在所述光纤的一端向所述光纤的另一端由小逐渐变大；
    使所述第二啁啾光栅的光栅周期在所述光纤的另一端向所述光纤的一端由小逐渐变大；
    使所述第一啁啾光栅的光栅周期与所述第二啁啾光栅的光栅周期在所述光纤上对称分布。
  2. 根据权利要求1所述的制作方法，其特征在于：所述掩模区包括第一掩模区和第二掩模区；使所述激光同时照射在所述第一掩模区和所述第二掩模区上以同时制作所述第一啁啾光栅和所述第二啁啾光栅。
  3. 根据权利要求2所述的制作方法，其特征在于：所述相位掩模板包括拼接在一起的第一掩模板和第二掩模板，所述第一掩模区位于所述第一掩模板上，所述第二掩模区位于所述第二掩模板上。
  4. 根据权利要求2或3所述的制作方法，其特征在于：所述第一掩模区与所述第二掩模区的长度均为L’，所述第一掩模区与所述第二掩模区的间距为d'，光纤光栅的长度为S’，S’＝2L’+d’，S’≤16mm。
  5. 基于双向光纤光栅的双向追踪器，包括安装组件和设置在所述安装组件上的光纤光栅，其特征在于：所述光纤光栅包括第一啁啾光栅和第二啁啾光栅，所述第一啁啾光栅和所述第二啁啾光栅的中心波长相同、啁啾率相同，所述第一啁啾光栅的光栅周期在光纤的一端向所述光纤的另一端由小逐渐变大，所述第二啁啾光栅的光栅周期在所述光纤的另一端向所述光纤的一端由小逐渐变大，所述第一啁啾光栅的光栅周期与所述第二啁啾光栅的光栅周期在所述光纤上对称分布。
  6. 根据权利要求5所述的双向追踪器，其特征在于：所述安装组件设有空腔，所述空腔的长度为D，所述第一啁啾光栅与所述第二啁啾光栅的长度为L，所述第一啁啾光栅与所述第二啁啾光栅的间距为d，所述光 纤光栅的长度为S，S＝2L+d且S≤D。
  7. 根据权利要求6所述的双向追踪器，其特征在于：所述安装组件包括第一插芯、第二插芯和连接件，所述第一插芯和所述第二插芯分别插入连接件的两端；所述第一插芯设有第一空腔，所述第二插芯设有第二空腔，所述第一空腔的长度为D1，所述第二空腔的长度为D2，所述空腔包括所述第一空腔和所述第二空腔且D1+D2＝D。
  8. 根据权利要求6或7所述的双向追踪器，其特征在于：所述D≤16mm。
  9. 根据权利要求6所述的双向追踪器，其特征在于：所述啁啾率大于等于10nm/cm，所述d≥2mm。
  10. 无源网络，其特征在于：在光路上依次设有光线路终端、光分路器和光网络单元，还包括根据权利要求5至9任一项所述的双向追踪器，所述双向追踪器设置在所述光分路器上和/或所述光网络单元上。
PCT/CN2018/095774 2018-07-16 2018-07-16 双向光纤光栅的制作方法、双向追踪器及无源网络 WO2020014814A1 (zh)

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CN107246931A (zh) * 2017-07-11 2017-10-13 中国矿业大学 一种光纤光栅横向受力应变传感器及检测方法
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EP0897124A1 (en) * 1997-08-12 1999-02-17 Photonics Research Ontario Design of complex optical fiber filters using long-period gratings
CN1328648A (zh) * 1998-08-19 2001-12-26 三星电子株式会社 长周期纤维光栅的制造装置和用其制造双波段长周期纤维光栅的装置
GB2381083A (en) * 2001-10-18 2003-04-23 Fujitsu Network Communications Optical distributed chirped grating with reflection symmetry
CN103940360A (zh) * 2014-04-23 2014-07-23 鲁东大学 一种基于级联啁啾光纤光栅的应变监测装置
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