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  • 专利说明
  • 权利要求
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    • 专利摘要:
    The present invention relates to a temperature compensated long period optical fiber grating filter, the core having a long period grating; Cladding surrounding the core; A coating portion surrounding the cladding of the portion where the long period lattice is not formed; And coated with a material that surrounds the cladding of the long period lattice and increases the refractive index with increasing temperature, so that the coupling wavelength shift due to the increased refractive index occurs in the opposite direction to the coupling wavelength shift due to the refractive index difference between the core and the cladding. It characterized in that it comprises a coating. According to the present invention, by compensating the long-period lattice with a material whose refractive index increases with increasing temperature, temperature compensation is more easily achieved without the need to adjust the refractive index in the filter or to add a material that does not change the refractive index with temperature. It is possible.
    公开号:KR20000060201A
    申请号:KR1019990008332
    申请日:1999-03-12
    公开日:2000-10-16
    发明作者:장주녕
    申请人:윤종용；삼성전자 주식회사；
    IPC主号:
    专利说明:

    Temperature-compensated long period optical fiber grating filter
    The present invention relates to a temperature compensation long period optical fiber grating filter.
    In general, a long-period fiber grating filter is a device that couples a core mode, which proceeds to the core of an optical fiber, to a cladding mode, and is not a reflection type. There is a big advantage to gain leveling.
    The long-period grating filter is manufactured by injecting ultraviolet rays into the core of the optical fiber which is sensitive to ultraviolet rays to give a change in refractive index periodically. That is, the portion exposed to ultraviolet rays increases in the refractive index, but the portion that is not exposed to the ultraviolet rays does not change, causing periodic refractive index changes. At this time, the coupling occurs when the phase matching condition is satisfied.
    Here, β co is a propagation constant of core mode, Is the propagation constant of the m-th cladding mode, and Λ is the grating period.
    However, when β = 2πn / λ (where n is a refractive index and λ is a wavelength) in Equation 1, the difference in refractive index between core mode and cladding mode is Becomes Therefore, in order to change the light of a certain wavelength into the cladding mode, the grating period Λ and the refractive index difference ( ).
    The refractive index difference can be obtained by appropriately exposing an ultraviolet laser to an optical fiber sensitive to ultraviolet rays. That is, when masking an ultraviolet-sensitive optical fiber with a mask having a specific period Λ, and scanning an ultraviolet laser on the mask, the photosensitive optical fiber reacts to increase the refractive index of the core. As the refractive index increases, the coupling wavelength increases toward the longer wavelength. In order to obtain the desired long-period fiber grating filter spectrum, that is, the desired coupling wavelength and extinction ratio, it is necessary to precisely adjust the mask period to scan the UV laser for a proper time.
    The coupling wavelength of the long-period fiber grating thus manufactured is also affected by temperature. The shift of the coupling wavelength with temperature changes is determined by the change in refractive index with the temperature change and the thermal expansion of the length with the temperature change. This is expressed as the following equation.
    Here, T represents temperature.
    When a long period grating is manufactured on a general communication optical fiber or a dispersion shifted fiber, the right side term 2 is not considered because the value according to the right side term 1 in Equation 2 is several times larger than the value according to the right side term 2 . For example, in the case of Corning's Flexcor 1060, the coupling wavelength shifts by about 5nm per 100 ° C. In typical distributed compensation optical fibers, the coupling wavelength shifts by length expansion about 0.3nm per 100 ° C, whereas the shift of coupling wavelength due to the change of refractive index is about 5nm. However, the gain flattening filter, which is one of the applications of long-period fiber gratings in practical applications, requires temperature stability of about 0.3nm per 100 ° C.
    For this temperature compensation, conventionally, The refractive index in the filter was adjusted so that the part had a negative value. Another method is to select a higher order cladding mode by shortening the period of the long period fiber grating. Another way is to use Equation 2 There is a way to add B 2 O 3 to zero the term.
    However, these methods are complicated by the need to adjust the refractive index in the filter or to add a substance that does not change the refractive index with temperature.
    The technical problem to be achieved by the present invention is to provide a long-period optical fiber grating coated with a material of a material whose refractive index changes with temperature to move the coupling wavelength in the opposite direction to compensate for the shift of the coupling wavelength according to the temperature change. It is.
    1A is a structural diagram of a long period optical fiber grating filter.
    FIG. 1B illustrates an operation in which a core mode is coupled to a cladding mode in the long period grating filter illustrated in FIG. 1A.
    2A to 2D illustrate a phenomenon in which coupling peaks move according to refractive index conditions outside the cladding.
    3 shows the coupling wavelength shift with respect to the cladding external refractive index.
    4 shows the shift of the coupling wavelength according to the external refractive index of the cladding.
    5A to 5D show the temperature compensation mechanism of the long period grating filter.
    6 is a structural diagram of a temperature compensation long period optical fiber grating filter according to the present invention.
    In order to achieve the above technical problem, the present invention is a core formed with a long period lattice; A cladding surrounding the core; A coating portion surrounding the cladding of the portion where the long period lattice is not formed; And coated with a material that surrounds the cladding of the long period lattice and increases the refractive index with increasing temperature, so that the coupling wavelength shift due to the increased refractive index is opposite to the coupling wavelength shift due to the refractive index difference between the core and the cladding. It characterized in that it comprises a recording portion to occur in the direction.
    Hereinafter, the operation of the present invention will be described in detail with reference to the accompanying drawings. 1A is a structural diagram of a long period optical fiber grating filter. The long-period fiber grating filter shown in FIG. 1A includes a core 102 having a long period grating 100, a cladding 104 surrounding the long period grating 100 and the core 102, and a coating 106 wrapping the cladding 104. It is composed.
    The long period grating 100 is formed by removing the coating 106 of the ultraviolet-sensitive optical fiber and inducing a periodic refractive index change in the optical fiber core 102 by passing an amplitude mask (not shown) that transmits the ultraviolet laser at predetermined intervals. .
    FIG. 1B illustrates an operation in which a core mode is coupled to a cladding mode in the long period grating filter illustrated in FIG. 1A. Fundamental guided mode 110, which proceeds to core 102, is scattered upon encountering refractive index variation 112. As the scattered light 114 is coupled to the cladding 104, light of a wavelength satisfying the phase matching condition is coherently reinforced. As light having this wavelength exits the cladding, the long period grating filter acts as a wavelength-dependent attenuator. As can be seen, the basic waveguide mode decreases in intensity as it passes through the changing portion 112 of the refractive index, and the intensity of light having a wavelength coupled to the cladding 104 increases gradually.
    The external condition of the cladding when manufacturing such a long period grating filter has a refractive index of 1 as air. After fabrication of the long-period grating, when the cladding is coated with a material having a refractive index of n, the coupling conditions are changed and thus the coupling wavelength is shifted to a long or short wavelength.
    2A to 2D illustrate a phenomenon in which coupling peaks move according to refractive indices outside the cladding. Figure 2a shows the light transmission characteristics when the refractive index of the cladding outside of the long period grating is 1. When the extinction ratio is 0dB, it is transmitted without loss. FIG. 2B illustrates transmission characteristics when the cladding external refractive index of the long period grating is 1.400. As shown, it can be seen that the extinction ratio was increased, and the coupling wavelength was shifted by about 4.8 nm toward the shorter wavelength. 2C shows the transmission characteristics when the external refractive index is 1.448, and it can be seen that the coupling wavelength has shifted toward the short wavelength by about 16.5 nm. 2D illustrates the transmission characteristics when the external refractive index is 1.484, and it can be seen that the coupling wavelength is shifted toward the longer wavelength and the extinction ratio is reduced than when the external refractive index is 1.
    As shown, based on the case where the cladding external refractive index is 1, as shown in FIG. 2B or 2C, when the cladding external refractive index increases but is smaller than the refractive index of the cladding, the coupling wavelength moves to a short wavelength. However, it can be seen that when the external refractive index of the cladding increases and becomes larger than the refractive index of the cladding, the coupling wavelength moves to a long wavelength as shown in FIG. 2D. If the cladding external refractive index is equal to the cladding refractive index, the total reflection condition is broken and the coupling peak disappears.
    3 shows the shift of the coupling wavelength with respect to the cladding external refractive index. As the external refractive index of the cladding increases from 1.0, the coupling wavelength shifts to a shorter wavelength, and when the same as the refractive index of the cladding, the coupling peak disappears.
    In order to change the external refractive index of the cladding, in the present invention, the coating of the portion where the long period grating is formed is peeled off, and the stripped portion is coated with a material whose refractive index changes with temperature. For this coating material, a material in which the refractive index increases with increasing temperature but smaller than the refractive index of the cladding is appropriate. As the refractive index increases, the coupling wavelength of the long period grating shifts to a shorter wavelength.
    If the coating is made of a material whose refractive index decreases with increasing temperature, the coupling wavelength of the long period grating shifts to the long wavelength. For example, Corning's Flexcore 1060 shows a temperature sensitivity of 5nm / 100 ° C without the coating, but 10nm / 100 ° C when the silicone resin is coated. In addition to the phenomenon that the coupling wavelength is shifted to the long wavelength by the right side term of Equation 2 above, the long wavelength shifting effect of the coupling wavelength appears because the refractive index of the silicone resin used as the recording material decreases with increasing temperature. Because.
    Therefore, a desired temperature compensation effect can be obtained by using a coating material whose refractive index increases with temperature as a coating material. The characteristics required for the coating material of such a temperature compensation long period lattice filter are as follows. The initial refractive index value should be smaller than the refractive index of the cladding material, that is, silica (pure silica), and the refractive index increases as the temperature is increased to have a characteristic of shifting the coupling wavelength to a short wavelength.
    4 shows the shift of the coupling wavelength according to the external refractive index of the cladding. LP 0l to LP 0p are the mode orders of the optical signal passing through the long period grating, and the mode orders increase along the vertical axis of the graph. As shown, it can be seen that the coupling wavelength is shifted to the short wavelength according to the external refractive index in each mode order.
    5A to 5D show the temperature compensation mechanism of the long period grating filter. Figure 5a shows the refractive index change characteristic of the coating material with respect to temperature. As shown, it can be seen that the refractive index increases with increasing temperature. Figure 5b shows the shift of the coupling wavelength with respect to the external refractive index of the cladding. It can be seen that the coupling wavelength shifts to a shorter wavelength as the external refractive index increases. 5c shows the shift of the coupling wavelength with temperature. It can be seen that the refractive index of the recording material increases as the temperature increases, and the coupling wavelength shifts to the shorter wavelength as the refractive index increases.
    Figure 5d shows the temperature compensation effect of the long period lattice with temperature. Reference numeral 500 shows the wavelength shift with temperature of the coating material. 502 illustrates the coupling wavelength shift due to the refractive index difference between the core and the clad with temperature. It can be seen that 504 does not shift the coupling wavelength even when the temperature is increased by compensating 500 and 502 with each other.
    6 is a structural diagram of a temperature compensation long period optical fiber grating filter according to the present invention. Reference numeral 600 is a long period lattice, 602 is a core, 604 is a long period lattice and cladding surrounding the core, 606 is a coating portion and 608 is a coating portion surrounding the cladding of the long period lattice is formed. As described above, the material of the coating unit 608 may be a material whose refractive index is smaller than that of the cladding 604 and increases with increasing temperature.
    According to the present invention, by shifting the long-period grating with a material whose refractive index increases with increasing temperature, it is possible to compensate the shift of the coupling wavelength with increasing temperature. Therefore, temperature compensation can be performed more easily without the trouble of adjusting the refractive index in the filter or adding a substance which does not change the refractive index with temperature.
    权利要求:
    Claims (2)
    [1" claim-type="Currently amended] Cores with long period lattice formed;
    A cladding surrounding the core;
    A coating portion surrounding the cladding of the portion where the long period lattice is not formed; And
    It is coated with a material that covers the cladding of the long period grating is formed and the refractive index increases with increasing temperature, so that the coupling wavelength shift due to the increased refractive index is opposite to the coupling wavelength shift due to the refractive index difference between the core and the cladding. A long period optical fiber grating filter, characterized in that it comprises a recording to cause.
    [2" claim-type="Currently amended] According to claim 1, wherein the material of the coating portion
    The refractive index increases with increasing temperature, the long period optical fiber grating filter, characterized in that the material having a refractive index less than the refractive index of the cladding.
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    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    1999-03-12|Application filed by 윤종용, 삼성전자 주식회사
    1999-03-12|Priority to KR1019990008332A
    2000-10-16|Publication of KR20000060201A
    2002-02-04|Application granted
    2002-02-04|Publication of KR100322136B1
    优先权:
    申请号 | 申请日 | 专利标题
    KR1019990008332A|KR100322136B1|1999-03-12|1999-03-12|Temperature-compensated long period optical fiber grating filter|
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