KR20020057717A - In-line type variable fiber-optic attenuator - Google Patents

In-line type variable fiber-optic attenuator Download PDF

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Publication number
KR20020057717A
KR20020057717A KR1020010000704A KR20010000704A KR20020057717A KR 20020057717 A KR20020057717 A KR 20020057717A KR 1020010000704 A KR1020010000704 A KR 1020010000704A KR 20010000704 A KR20010000704 A KR 20010000704A KR 20020057717 A KR20020057717 A KR 20020057717A
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South Korea
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voltage
light
thin film
attenuator
electrode layer
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KR1020010000704A
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Korean (ko)
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KR100400890B1 (en
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정치섭
김광호
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정치섭
김종혁
김광호
주식회사 엠텍월드
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Priority to KR10-2001-0000704A priority Critical patent/KR100400890B1/en
Priority to PCT/KR2002/000015 priority patent/WO2002054138A2/en
Priority to AU2002219681A priority patent/AU2002219681A1/en
Publication of KR20020057717A publication Critical patent/KR20020057717A/en
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Publication of KR100400890B1 publication Critical patent/KR100400890B1/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
    • 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
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/2804—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers
    • G02B6/2821—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using lateral coupling between contiguous fibres to split or combine optical signals
    • G02B6/2826—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using lateral coupling between contiguous fibres to split or combine optical signals using mechanical machining means for shaping of the couplers, e.g. grinding or polishing
    • G02B6/283—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using lateral coupling between contiguous fibres to split or combine optical signals using mechanical machining means for shaping of the couplers, e.g. grinding or polishing couplers being tunable or adjustable
    • 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
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/2804—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers
    • G02B6/2852—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using tapping light guides arranged sidewardly, e.g. in a non-parallel relationship with respect to the bus light guides (light extraction or launching through cladding, with or without surface discontinuities, bent structures)
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/011—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  in optical waveguides, not otherwise provided for in this subclass
    • G02F1/0115—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  in optical waveguides, not otherwise provided for in this subclass in optical fibres
    • G02F1/0118—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  in optical waveguides, not otherwise provided for in this subclass in optical fibres by controlling the evanescent coupling of light from a fibre into an active, e.g. electro-optic, overlay
    • 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
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/2804—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers
    • G02B6/2821—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using lateral coupling between contiguous fibres to split or combine optical signals
    • G02B6/2826—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using lateral coupling between contiguous fibres to split or combine optical signals using mechanical machining means for shaping of the couplers, e.g. grinding or polishing
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F2203/00—Function characteristic
    • G02F2203/48—Variable attenuator

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Nonlinear Science (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
  • Optical Couplings Of Light Guides (AREA)
  • Optical Integrated Circuits (AREA)
  • Light Guides In General And Applications Therefor (AREA)

Abstract

PURPOSE: An inline type variable optical attenuator and a method for fabricating the same are provided to lower driving voltage, reduce power consumption and a loss of insertion by using an electro optic effect. CONSTITUTION: A substrate(20) is formed by a quartz block or a silicon wafer. An optical fiber(30) is adhered along a groove on the substrate(20) by using an epoxy or an adhesive. The optical fiber(30) includes a core(40) and a cladding(50). A plurality of overlay layers(60,70,80,90) including electrode layers is laminated on the substrate(20). Namely, the first electrode layer(60) is deposited on the substrate(20). The ferroelectric overlay layer(70) is deposited on the first electrode layer(60) by using a sputtering method. A leakage prevention layer(80) for preventing current leakage is deposited on the ferroelectric overlay layer(70). An ITO layer(90) is deposited thereon.

Description

인-라인 형 가변 감쇄기와 그의 구동방법 및 제조방법{In-line type variable fiber-optic attenuator}In-line type variable attenuator, driving method thereof and manufacturing method {In-line type variable fiber-optic attenuator}

본 발명은 광섬유 또는 광전송로를 통해 전달되는 광 신호의 감쇄에 이용되어지는 인-라인형 가변 광 감쇄기 와 그의 구동방법 및 제조방법에 관한 것이다.The present invention relates to an in-line variable optical attenuator used for attenuating an optical signal transmitted through an optical fiber or an optical transmission path, a driving method thereof, and a manufacturing method thereof.

광 감쇄기는 기본적으로 광섬유 또는 광전송로를 통해 전달되는 광 세기를 감쇄 시키는 장치로, 광통신상의 출력의 조절이 필요한 모든 경우에 있어, 광감쇄기는 광증폭기와 함께 필수 불가결한 구성요소 이다. 광감쇄기의 용도는 시스템 또는 소자의 광세기에 대한 특성분석 등에서부터, 최근의 파장분할다중(wave-length division multiplex, 이하WDM이라 칭함) 기반 광 교차접속(cross connect)에 이르기까지 다양하다. 특히 EDFA(Erbium Doped Fiber Amplifier)에서의 이득 평탄화, DWDM(Danced Wavelength Division Multiplexing) 상의 channel equalization, 기타 광출력 측정 system 에서의 가변 광쇄기의 역할은 필수적이다.An optical attenuator is basically a device for attenuating the light intensity transmitted through an optical fiber or an optical transmission path. In all cases where the control of optical output is required, the optical attenuator is an essential component together with the optical amplifier. Applications of optical attenuators range from the characterization of the light intensity of a system or device, to the recent wave-length division multiplex (WDM) based optical cross connect. In particular, gain flattening in Erbium Doped Fiber Amplifier (EDFA), channel equalization on DWDM (Danced Wavelength Division Multiplexing), and the role of variable optics in other optical power measurement systems are essential.

상기한 가변형 감쇄기에 있어서는 크게 구별해서 (A)광화이버를 절단해서 그 단면 사이의 광감쇄량을 변화시키는것(B) 1개의 광화이버를 이용하여 그 화이버의 곡률반경 변화나 휨 응력변화에 의해 광감쇄량을 변화시키는 것 (C) 매질의 온도에 따라 달라지는 굴절률 변화 (열광학효과)를 이용한 감쇄기등을 들 수 있다.In the above-described variable type attenuator, (A) cutting the optical fiber and changing the amount of light attenuation between its cross sections (B) by using one optical fiber, the optical fiber can be changed by the change in curvature radius or bending stress of the fiber. Changing the attenuation amount (C) Attenuators using a refractive index change (thermo-optical effect) which varies depending on the temperature of the medium may be mentioned.

(A)의 예로서는 단면사이의 거리를 조절함으로써 광감쇄량을 변화시키는것(특개평 4-133005호), 단면사이의 광축을 겹치치 않게 함으로써 광감쇄량을 변화시키는 것 (특개평 4-166803호), 단면사이에 가변감쇄판을 삽입하여 광감쇄량을 변화시키는 것 (특개평 3-225312호) 등이 있으며, 상기한 발명들의 결점은 (1)광화이버 단면사이의 광축을 정밀하게 제어할 필요가 있기 때문에 구조가 복잡해지고 또한그러므로써 고가화된다는점(2)광화이버 단면이나 광감쇄판의 공기 계면에서 광의 반사가 발생하여 발생한 반사광이 광원으로 되돌아가서 영향을 준다는 점이다.As an example of (A), the amount of light attenuation is changed by adjusting the distance between end faces (Japanese Patent Laid-Open No. 4-133005), and the amount of light attenuation is made by not overlapping the optical axes between the end faces (Japanese Patent Laid-Open No. 4-166803). In addition, there is a change in the amount of light attenuation by inserting a variable attenuating plate between the cross-sections (Japanese Patent Application Laid-Open No. 3-225312). As a result, the structure becomes complicated and therefore expensive. (2) Reflected light generated by reflection of light at the optical fiber cross section or at the air interface of the light attenuating plate returns to and affects the light source.

(B)의 예로서는 광화이버의 일부를 변형시킴으로써 광손실을 일으켜 광감쇄량을 변화시키는 것이 있다.As an example of (B), some of the optical fibers are deformed to cause light loss and to change the amount of light attenuation.

이것은 구조가 간단하고 제조도 용이하지만 광화이버는 본래 약간 휘어져도 손실이 발생되기 어렵게 설계되어있기 때문에 원하는 감쇄량을 얻기 위해서는 광화이버를 권취한 루프로 해야하지만 이 때문에 광화이버 감쇄기의 구성에서는 길이가 긴 화이버가 필요로 하여 감쇄기 자체도 커지게 된다. 또 루프상으로 하지않은 경우는 필요한 화이버의 길이는 짧아지게 되지만 곡률반경을 작게 하지 않으면 광감쇄기로써 필요로 하는 레벨의 감쇄량을 구하지 못함과 동시에 가변범위도 아주 작아지게 된다.It is simple in structure and easy to manufacture, but since optical fiber is designed to be hard to lose even if it is slightly bent, in order to obtain a desired amount of attenuation, it is required to use a loop wound with optical fiber. The need for fiber also increases the attenuator itself. If the loop is not formed, the required fiber length will be shorter, but if the radius of curvature is not reduced, the amount of attenuation required by the optical attenuator will not be obtained and the variable range will be very small.

그리고 곡률반경을 작게하려고 하면 화이버가 절선된다든지 하는 문제가 생긴다.Attempting to reduce the radius of curvature causes the fiber to be cut off.

(C)의 경우로 Mach-Zehnder 형, Y 분지형, 열판 내장형등 다양한 형태들로 개발되고 있다. 모든 경우에서 공통적으로 사용되는 개념은 온도에 따라 굴절률이 변한다는 열광학효과를 이용한다는 것이다. 따라서 열 확산 및 느린 반을속도등 근본적 문제를 극복할 수 없으며, 더우기 도파로 구조를 사용할 경우 높은 삽입손실을 감수하여야한다는 점들이 문제로 제기되고 있다.In the case of (C), it is developed in various forms such as Mach-Zehnder type, Y branch type, and hot plate embedded type. A common concept in all cases is to take advantage of the thermooptic effect of changing the refractive index with temperature. Therefore, it is not possible to overcome fundamental problems such as heat diffusion and slow half speed, and moreover, the use of waveguide structures requires high insertion loss.

본 발명의 목적은 본 발명에서는 기본적으로 전기광학효과를 사용하므로써낮은 구동전압, 낮은 전력손실, 낮은 삽입손실을 만족하면서도 간단한 구조를 가지면서 고속전송이 가능함과 동시에 WDM 전송용에 적합한 가변 감쇄기를 제공함을 과제로 한다.An object of the present invention is to provide a variable attenuator suitable for WDM transmission while enabling high-speed transmission while satisfying low driving voltage, low power loss, and low insertion loss by using electro-optical effects. Make it a task.

도 1은 본 발명의 실시 예에 따르는 측면연마 광섬유를 이용한 가변 광 감쇄기의 시스템 개요도1 is a system schematic diagram of a variable optical attenuator using side polished optical fiber according to an embodiment of the present invention

도 2은 본 발명의 실시 예에 따르는 측면연마 광섬유를 이용한 가변 광감쇄기의 횡 단면도2 is a cross-sectional view of a variable optical attenuator using a side polished optical fiber according to an embodiment of the present invention.

도3는 도 2의 2-2 선을 따라 절단된 단면도3 is a cross-sectional view taken along the line 2-2 of FIG.

도4는 본 발명의 실시 예에 따르는 횡축전가인가방법의 측면연마 광섬유를 이용한 가변 광감쇄부의 횡 단면도Figure 4 is a cross-sectional view of the variable light attenuation portion using the side polished optical fiber of the method of applying the transverse axial charge in accordance with an embodiment of the present invention

도5는 본 발명의 실시 예에 따르는 채널드롭곡선 및 오버레이의 두께 또는 굴절률변화에 따르는 채널드롭곡선의 이동5 is a view showing a shift of a channel drop curve according to a change in thickness or refractive index of a channel drop curve and an overlay according to an exemplary embodiment of the present invention.

도6은 본 발명에서 오버레이 로 사용되는 강유전체 박막에서의 P-E 이력 곡선(hysteresis loop).6 is a P-E hysteresis loop in a ferroelectric thin film used as an overlay in the present invention.

도7은 본 발명의 가변 광감쇄기중 광감쇄부를 제조하기 위한 공정을 설명하기 위한 공정 흐름도이다.7 is a process flowchart for explaining a process for manufacturing the light attenuator in the variable light attenuator of the present invention.

상기 목적을 달성하기 위해 본 발명에서는 삽입손실이 극히 적은 측면연마광섬유(side polished fiber: 이하SPF라 칭함)구조로 이루어져 입력광을 감쇄를 실현하는 광감쇄부와 상기한 광감쇄부에 필요전압을 인가하는 전압인가부 와 상기한 광감쇄부에서 출력된 광을 수신하여 전압 기준으로 모니터링하는 감쇄광 수신수단과 상기한 감쇄광 수신수단에서 검출된 전압과 사용자의 감쇄요구량에 비례하는 전압을 비교하여 차이를 검출하는 비교수단으로 이루어지는 감쇄량 비교부와 상기한 감쇄량 비교부에서 검출한 차이를 상기한 전압인가부로 궤환시키는 궤환부로 이루어진다. 또한 상기한 본 발명의 광감쇄부는 스퍼터링(sputtering)시 연마 면에 수직한 방향의 강유전성을 가지는 강유전체 박막을 포함하고 있다. 상기한 강유전체 박막은 박막의 굴절률로부터 광신호 파장의 부근에서 효과적인 모드결합이 이루어지는 특정두께로 되어있으며, 전압 인가시 변화되는 굴절률은 모드결합파장의 이동을 유발시키며 이로 인해 투과 광의 세기가 변화 되도록 하였다.In order to achieve the above object, the present invention has a side polished fiber structure having a very low insertion loss (hereinafter referred to as a SPF) structure to provide a necessary voltage to the light attenuating part and the light attenuating part to realize attenuation of input light. By comparing the voltage applied to the applied voltage and the attenuated light receiving means for receiving the light output from the light attenuator and monitoring the voltage reference and the voltage detected by the attenuated light receiving means and the voltage proportional to the attenuation requirements of the user Attenuation amount comparison section comprising a comparison means for detecting a difference and a feedback section for returning the difference detected by the attenuation amount comparison section to the voltage application section described above. In addition, the optical attenuator of the present invention includes a ferroelectric thin film having ferroelectricity in a direction perpendicular to the polishing surface during sputtering. The ferroelectric thin film has a specific thickness at which the mode coupling is effective in the vicinity of the optical signal wavelength from the refractive index of the thin film, and the refractive index changed when voltage is applied causes the mode coupling wavelength to be shifted, thereby changing the intensity of transmitted light. .

이하, 첨부된 도면을 참조하여 본 발명의 바람직한 실시 예를 설명한다.Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

도1은 본 발명의 실시 예에 따르는 가변형 광 감쇄기의 전체구조도로 전압가변감쇄기에 입력되는 광신호는 인가된 전압과 상기원리에 의해 감쇄되어 출력된다. 출력광의 일부는 탭(tap)에 의해 분기되며 분기된 추력광은 감쇄량비교부의 수신수단에 수신되어 상기한 출력광의 광세기에 해당하는 전압으로 변환된 후,비교수단에 의해 수요자가 지정한 광세기의 전압과 비교된다.상기한 감쇄량비교부의 비교부에서 차이가 발생되면, 즉 출력광의 세기가 수요자가 요구하는 세기와 다르면, 궤환부에서 이에 해당하는 전압을 전압인가부에서 인가하게 하는 궤환 기능을 하게 되므로 궁극적으로는 출력광의 세기가 수요자가 원하는 광세기와 같아지게 된다.1 is an overall structure of a variable optical attenuator according to an embodiment of the present invention, the optical signal input to the voltage variable attenuator is attenuated and output by the applied voltage and the principle. A part of the output light is branched by a tap, and the branched thrust light is received by the receiving means of the attenuation comparison part and converted into a voltage corresponding to the light intensity of the output light, and then, by the comparing means, If a difference occurs in the comparison unit of the attenuation comparison unit, that is, the intensity of the output light is different from the intensity required by the consumer, the feedback unit causes the voltage applying unit to apply a corresponding voltage. Ultimately, the intensity of the output light becomes the same as the light intensity desired by the consumer.

도2는 본 발명의 실시 예에 따르는 가변형 광 감쇄기의 횡단면도이며, 도3는 도2의 B-B 선을 따라 절단한 단면도이다. 본 발명의 광감쇄기(10)는 석영블록(quartz block) 이나 실리콘 웨이퍼(silicon wafer)로 만들어진 기판(20)과, 상기기판(20)에 소정의 곡률(R)을 갖도록 형성된 홈을 따라 에폭시(epoxy) 또는 유사한 접착제로 심어진 광섬유(30)를 포함한다. 또한 상기한 광섬유(30)는 코아(40)와 클래딩(50)을 포함한다. 클래딩(50)의 한 단면(65)은 일반연마 또는 화학적역학적 연마법으로 연마된 면을 도시한 것이다. 이때 남은 클래딩의 두께는 광섬유를 통과하는 1.3μm 또는 1.5μm의 파장이 오버레이층과 소산파 결합이 가능한 5μm 이내로 하였으며, 상기 두께는 리퀴드 드롭(liquid drop) 방법으로 측정된다. 또한 상기한 기판(20)위에는 전극층을 포함한 오버레이층 (60,70,80,90)이 적층되어 있다. 기판(20)위에는 리튬나이오베이트(LiNbO3) 등 강유전특성을 가지는 오버레이(overlay) 층(70)을 구성하되, 전극으로서 기능을 하는 제1전극층(60)을 먼저 적층한 후, 순차적으로 오버레이(overlay)층인 강유전체 박막(70)을 스퍼터링(sputtering)하여 적층시킨다. 이때 층(60)은 빛이 통과 할 수 있는 투명전극으로 하되 100nm 이하로 얇게 한다. 층(70)의 두께는 2-3μm 이내로 하되 주어진 입사레이저 파장 부근에서 채널드롭 곡선이 일치되도록 한다. 층(70) 위에는 전극 형태에 따라 전류누설을 방지하기 위한 Si:N등의 누설 방지막(80)을 올리고 마지막으로 또 하나의 전극층(IT0)(90)을 적층시킨다.FIG. 2 is a cross-sectional view of a variable light attenuator according to an embodiment of the present invention, and FIG. 3 is a cross-sectional view taken along line BB of FIG. 2. The optical attenuator 10 of the present invention includes a substrate 20 made of a quartz block or a silicon wafer, and an epoxy along a groove formed to have a predetermined curvature R in the substrate 20. epoxy) or a similar optical fiber 30. In addition, the optical fiber 30 includes a core 40 and a cladding 50. One cross section 65 of the cladding 50 shows a surface polished by general polishing or chemical mechanical polishing. At this time, the thickness of the remaining cladding was within 5μm wavelength 1.3μm or 1.5μm passing through the optical fiber is possible to combine the overlay layer and the dissipation wave, the thickness is measured by the liquid drop method (liquid drop). In addition, overlay layers 60, 70, 80, and 90 including electrode layers are stacked on the substrate 20. An overlay layer 70 having ferroelectric properties, such as lithium niobate (LiNbO 3 ), is formed on the substrate 20, but the first electrode layer 60 serving as an electrode is first stacked, and then sequentially overlayed. The ferroelectric thin film 70, which is an overlay layer, is sputtered and stacked. At this time, the layer 60 is a transparent electrode through which light can pass, but is made thinner than 100 nm. The thickness of layer 70 should be within 2-3 μm so that the channel drop curves match around a given incident laser wavelength. On the layer 70, a leakage preventing film 80 such as Si: N is prevented to prevent current leakage according to the shape of the electrode, and finally, another electrode layer (IT0) 90 is laminated.

강유전 오버 레이(overlay)층에 전압을 인가하는 전극의 형태는 도2,도3과 같은 종 전극 형태도 가능하며, 또한 도4 처럼 횡 전극 형태도 가능하다. 다만 횡전극형태 에서는 상기한 누설방지막(80)이 필요없으며, 이때 전극(60)의 간격은 광섬유의코아직경에 준하게 하므로서 굴절률변화가 효과가 최대가 되도록 한다.An electrode that applies a voltage to the ferroelectric overlay layer may have a vertical electrode form as shown in FIGS. 2 and 3, and a horizontal electrode form as shown in FIG. 4. However, in the transverse electrode type, the above-described leakage preventing film 80 is not necessary. In this case, the gap of the electrode 60 is made to conform to the core diameter of the optical fiber, so that the refractive index change is maximized.

도5는 광섬유를 통해 전송되는 백색광(넓은 영역의 파장폭을 가지는 광원으로, 예를 들면 할로겐 램프 등)을 광원으로 하였을 때 출력특성을 나타내는 채널드롭을 보여주고 있다. 오버레이(overlay)층의 두께를 변화시키거나, 전장을 인가하여 굴절률 변화 시킬 때 그림과 같이 실선의 채널드롭곡선은 점선의 채널드롭 곡선쪽으로 이동하게 된다. 입사광을 백색광 대신 단일한 파장의 빛을 방출하는 레이저로 하고, 이 빛의 파장을 도5의 λ라 한다면, 전압을 인가하지 않았을 때 광섬유를 통해 출력되는 광 세기는 전혀 감쇄 되지 않으나( λ파장에서 실선값(A) ), 전압을 인가할 때 그림에서 보여주듯 감쇄 ( λ파장에서 점선값(B) )이 된다. 그림에서 실선과 점선사이의 폭은 인가된 전장의 크기에 따라 달라지기 때문에 전장에 따른 가변감쇄의 기능이 실현된다.FIG. 5 shows a channel drop showing output characteristics when white light (a light source having a wide wavelength wavelength, for example, a halogen lamp) transmitted through an optical fiber is used as a light source. When changing the thickness of the overlay layer or changing the refractive index by applying the electric field, the channel drop curve of the solid line moves toward the channel drop curve of the dotted line as shown in the figure. If the incident light is a laser that emits light of a single wavelength instead of white light, and the wavelength of the light is λ of FIG. 5, the light intensity output through the optical fiber is not attenuated at all when no voltage is applied (at λ wavelength). The solid line value (A)), and attenuation (dashed line value (B) at λ wavelength) as shown in the figure. In the figure, the width between the solid line and the dotted line depends on the size of the applied electric field, so the function of variable attenuation according to the electric field is realized.

한편 도6은 본 발명의 가변 광감쇄기에 사용되는 강유전체 박막의 P-E 이력곡선(hysterisis loop)을 보여준다. 상기한 가변감쇄기에서 사용되는 강유전체 박막에서의 중요점은 도(6)에서 제시한 점선으로 특징지워지는 P-E이력곡선을 가지는 강유전체 박막을 이용하며 (K.H.Kim, Appl. Phy.Lett.,vol 19, No.6, 204,1998), 상기한 박막의 P-E이력곡선중의 사면을 이용한다는 점이다. 사면의 기울기가 클수록 작은 인가전압의 변화에도 큰 편극의 변화가 가능하며 이에 따라 큰 굴절률의 변화가 가능하므로 편극곡선은 가능한 사면의 기울기가 선형적이면서도 큰 것이 바람직하다. 도(6)에서 횡축은 인가전압이고, 횡축은 이에 따라 형성되는 편극을 보여준다. 이때 편극은 낮은 주파수에서 측정된 결과이나, 광 주파수(∼1014Hz)의 반응에 대해서는 매질의 굴절률과 직접적 관계 n=(1+χ)1/2를 가진다. 상기식에서 n은 굴절률, 그리고 χ는 편극률을 나타낸다. 따라서 오버레이에 인가된 전장은 오버레이의 굴절률을 변화시키며, 이는 다시 채널드롭이 일어나는 주파수를 파장축에서 이동시킨다. 본 발명에서 광 감쇄기는 주어진 입사레이저 파장에서, 인가된 전압에 따라 달라지는 채널드롭의 크기 즉 투과광량을 변화시킬수 있도록 고안되어 있다.6 shows a PE hysterisis loop of the ferroelectric thin film used in the variable optical attenuator of the present invention. An important point in the ferroelectric thin film used in the variable attenuator is a ferroelectric thin film having a PE history curve characterized by a dotted line shown in Fig. 6 (KHKim, Appl. Phy. Lett., Vol 19, No. .6, 204,1998), using the slope of the above-described PE history curve of the thin film. As the slope of the slope is larger, a large polarization can be changed even with a small change in the applied voltage, and thus a large refractive index can be changed. Accordingly, it is preferable that the slope of the polarization curve is linear and large. In Fig. 6, the horizontal axis shows applied voltage, and the horizontal axis shows polarization formed accordingly. In this case, the polarization is measured at a low frequency, but has a direct relation n = (1 + χ) 1/2 with the refractive index of the medium for the response of the optical frequency (˜10 14 Hz). Where n represents the refractive index and χ represents the polarization index. The electric field applied to the overlay thus changes the refractive index of the overlay, which in turn shifts the frequency at which the channel drop occurs on the wavelength axis. In the present invention, the optical attenuator is designed to change the size of the channel drop, that is, the amount of transmitted light, depending on the applied voltage at a given incident laser wavelength.

도7은 본 발명의 가변 광감쇄기중 광감쇄부를 제조하기 위한 공정을 설명하기 위한 공정 흐름도이다. 실리콘 웨이퍼(silicon wafer)또는 석영블록(quartz block)의 측면에 곡률(R)을 가진 홈을 에칭 또는 줄연마로 형성하는 단계(110), 상기한 홈에 광섬유(30)을 심은 다음, 접착제를 사용하여 광섬유를 홈에 부착하는 단계(112),상기한 광섬유가 부착된 기판(20)의 상부를 연마하여 광섬유의 클래딩을 특정두께로 하는 단계(114),상기한 기판 위에 전장을 인가하기 위한 제1전극층(ITO)을 특정두께로 증착하는 단계(116), 상기한 제1전극층위에 리튬나이오베이트(LiNbO3) 등의 강유전체 박막을 증착하는 단계(118),필요에따라 강유전체 박막에서의 전류누설을 방지하기위한 전류누설방지막을 상기한 강유전체 박막 위에 적층시키는 단계(120),마지막으로 전장을 인가하기 위한 제2전극층을 증착시키는 단계(122)로 제조공정이 이루어진다.7 is a process flowchart for explaining a process for manufacturing the light attenuator in the variable light attenuator of the present invention. Etching or stirring grooves with curvature R on the sides of silicon wafers or quartz blocks (110), planting an optical fiber 30 in the grooves, and then applying an adhesive Attaching the optical fiber to the groove using the step 112; polishing the upper part of the substrate 20 to which the optical fiber is attached to make the cladding of the optical fiber a specific thickness 114; for applying an electric field on the substrate. Depositing a first electrode layer (ITO) to a specific thickness (116), depositing a ferroelectric thin film such as lithium niobate (LiNbO3) on the first electrode layer (118), the current in the ferroelectric thin film as needed The manufacturing process is performed by depositing a current leakage prevention film for preventing leakage on the ferroelectric thin film 120 and finally depositing a second electrode layer for applying an electric field.

한편, 여기에서는 본 발명의 실시 예에 대하여 도시하고 설명하였지만, 통상의 지식을 가진 자에 의하여 변형과 변경이 가능할 것이다. 따라서 이하 특허 청구범위는 본발명의 본질과 범위를 벗어나지 않는 한 그러한 모든 변경과 변경을 포함하는 것으로 간주한다.Meanwhile, although illustrated and described with respect to embodiments of the present invention, modifications and changes may be made by those skilled in the art. Therefore, the following claims are intended to cover all such alterations and modifications without departing from the spirit and scope of the invention.

본 발명에서 전기광학효과를 이용하여 가변광감쇄기를 구현함에 따라 낮은 구동전압, 낮은 전력손실, 낮은 삽입손실을 만족하면서도 간단한 구조로서 외부에서 감쇄량을 자동으로 제어하 수 있게 되었을 뿐만아니라 고속전송이 가능함과 동시에 WDM 시스템에서 광감쇄기의 제반문제를 해결하였다.By implementing the variable optical attenuator using the electro-optic effect in the present invention, it is possible to automatically control the amount of attenuation from the outside as well as to satisfy the low driving voltage, low power loss, and low insertion loss, and to enable high-speed transmission. At the same time, we solved the problems of optical attenuator in WDM system.

Claims (8)

기판에 소정의 곡률을 갖고서 설치되어, 광 신호를 전송하는 코아와 클래딩을 포함하는 광섬유와,An optical fiber provided with a predetermined curvature on the substrate, the optical fiber including core and cladding for transmitting an optical signal; 상기 클래딩의 일측면을 연마하여 설치되며, 전압인가에 의해 굴절율변화를 일으키는 강유전체 박막과 상기 박막에 전압을 인가하는 전극층으로 이루어지는 광감쇄부와,An optical attenuator formed by polishing one side of the cladding, the ferroelectric thin film generating a refractive index change by applying a voltage and an electrode layer applying a voltage to the thin film; 상기한 광감쇄부에 전압을 인가하는 전압인가부와,A voltage applying unit for applying a voltage to the light attenuating unit; 상기한 광감쇄부에서 출력된 광을 전압 기준으로 모니터링하는 감쇄광 수신수단과,Attenuated light receiving means for monitoring the light output from the light attenuating unit on a voltage basis; 상기한 감쇄광 수신수단에서 검출된 전압과사용자의 감쇄요구량에 비례하는 전압을 비교하여 차이를 검출하는 비교수단으로 이루어지는 감쇄량 비교부 및 상기한 전압차이를 상기한 전압인가부로 궤환시키는 궤환부를 포함하여 이루어짐을 특징으로 하는 인-라인형 가변 광감쇄기.Attenuation amount comparison unit comprising a comparison means for comparing the voltage detected by the attenuation light receiving means with a voltage proportional to the attenuation requirement of the user and detecting a difference, and a feedback unit for returning the voltage difference to the voltage applying unit. In-line variable optical attenuator, characterized in that made. 제1항에 있어서,The method of claim 1, 상기한 광감쇄부의 강유전체 박막은 리튬나이오베이트 (LiNbO3), 리튬탄탈레이트(LiTaO3), 전기광학 폴리머 등의 강유전체로 이루어짐을 특징으로 하는 인-라인(in-line)형 가변 광감쇄기.The ferroelectric thin film of the light attenuating unit is an in-line type variable optical attenuator, characterized in that the ferroelectric made of lithium niobate (LiNbO 3 ), lithium tantalate (LiTaO 3 ), electro-optic polymer and the like. 제1항에 있어서,The method of claim 1, 상기한 전극층은 종형또는 횡형으로 설치됨을 특징으로 하는 인-라인(in-line)형 가변 광감쇄기.The in-line variable optical attenuator, characterized in that the electrode layer is installed in the vertical or horizontal type. 제3항에 있어서,The method of claim 3, 상기한 종형전극층은 제1전극층, 제2전극층으로 이루어짐을 특징으로 하는 인-라인(in-line)형 가변 광감쇄기.The vertical electrode layer is an in-line variable optical attenuator, characterized in that the first electrode layer, the second electrode layer. 제4항에 있어서,The method of claim 4, wherein 상기한 제1전극층은 투명전극임을 특징으로 하는 인-라인(in-line)형 가변 광감쇄기.The first electrode layer is an in-line variable light attenuator, characterized in that the transparent electrode. 제1항에 있어서,The method of claim 1, 상기한 기판은 석영 블록(quartz block) 또는 실리콘 웨이퍼(silicon wafer)임을 특징으로 하는 인-라인(in-line)형 가변 광감쇄기.The substrate is an in-line variable light attenuator, characterized in that the quartz block (quartz block) or silicon wafer (silicon wafer). 기판에 소정의 곡률을 갖고서 설치되어, 광 신호를 전송하는 코아와 클래딩을 포함하는 광섬유와 상기 클래딩의 일측면을 연마하여 설치되며, 전장인가에 의해 굴절율변화를 일으키는 강유전체 박막과 상기 박막에 전압을 인가하는 전극층으로 이루어지는 광감쇄부와 상기한 광감쇄부에 전압을 인가하는 전압인가부와 상기한 광감쇄부에서 출력된광을 전압을 기준으로 모니터링한 후, 요구값과 비교하여 차이를 검출하는 감쇄량 비교부 및 상기한 차이를 상기한 전압인가부로 궤환시키는 궤환부를 포함하여 이루어지는 인-라인형 가변 광감쇄기에 있어서,It is installed on the substrate with a predetermined curvature, and is installed by polishing an optical fiber including a core and a cladding for transmitting an optical signal and one side of the cladding, and applying a voltage to the ferroelectric thin film and the thin film that cause a refractive index change by application of electric field. After monitoring the light attenuator comprising an electrode layer to be applied, the voltage applying unit applying voltage to the light attenuating unit, and the light output from the light attenuating unit based on the voltage, the difference is detected by comparing with the required value. In the in-line variable optical attenuator comprising attenuation comparison unit and a feedback unit for returning the difference to the voltage applying unit, 상기한 강유전체 박막에 인가된 전압에 따르는 분극도의 변화를 나타내는 P-E이력곡선의 사면기울기에 대응하는 전압을 변화시켜 상기 강유전체 박막의 굴절율을 변화시키는 것에 의하여 상기 강유전체 박막을 통하여 전파되는 입력 광 신호를 감쇄하는 것을 특징으로 하는 광감쇄기기의 구동방법.By changing the refractive index of the ferroelectric thin film by changing the voltage corresponding to the slope of the PE history curve showing a change in polarization degree according to the voltage applied to the ferroelectric thin film, the input optical signal propagated through the ferroelectric thin film A driving method of an optical attenuating device, characterized in that the attenuation. 실리콘 웨이퍼(silicon wafer) 또는 석영블록(quartz block)의 일측면에 소정의곡률(R)을 가진 홈을 에칭 또는 줄연마로 형성하는 단계,Etching or row polishing grooves having a predetermined curvature R on one side of a silicon wafer or a quartz block; 상기한 홈에 광섬유(30)을 심은 다음, 접착제를 사용하여 광섬유를 홈에 부착하는 단계,Planting the optical fiber 30 in the groove, and then attaching the optical fiber to the groove using an adhesive, 상기한 광섬유가 부착된 기판(20)의 상부를 연마하여 광섬유의 클래딩을 특정두께로 하는 단계,Polishing the upper part of the substrate 20 to which the optical fiber is attached to make the cladding of the optical fiber a specific thickness; 상기한 기판위에 전장을 인가하기위한 제1전극층(IT0)을 특정두께로 증착하는 단계,Depositing a first electrode layer IT0 having a specific thickness on the substrate to apply an electric field; 상기한 제1전극층위에 리튬나이오베이트(LiNbO3 등의 강유전체 박막을 증착하는 단계,Depositing a ferroelectric thin film such as lithium niobate (LiNbO3) on the first electrode layer; 필요에 따라 강유전체 박막에서의 전류누설을 방지하기위한 전류누설방지막을 상기한 강유전체 박막위에 증착시키는 단계,If necessary, depositing a current leakage prevention film on the ferroelectric thin film for preventing current leakage in the ferroelectric thin film; 최종적으로 전압을 인가하기 위한 제2전극층을 증착시키는 단계로 광감쇄부가 제작되어짐을 특징으로 하는 인-라인(in-line)형 가변 광감쇄기의 제조방법.A method of manufacturing an in-line variable optical attenuator, characterized in that a light attenuator is manufactured by depositing a second electrode layer for applying a voltage.
KR10-2001-0000704A 2001-01-05 2001-01-05 Variable optical attenuator of in-line type and fabrication method thereof KR100400890B1 (en)

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KR100709038B1 (en) * 2005-04-01 2007-04-20 정치섭 In-line type variable optical coupler using symmetrically etched fiber
KR100714758B1 (en) * 2002-12-10 2007-05-07 인터내셔널 비지네스 머신즈 코포레이션 Apparatus and methods for remakeable connections to optical waveguides

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KR100608632B1 (en) 2004-04-12 2006-08-08 엘지전자 주식회사 Optical attenuator for optical communication and fabrication method thereof
GB2550401A (en) * 2016-05-19 2017-11-22 Airbus Operations Ltd Limiting optical power in aircraft ignition risk zones

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JP3283772B2 (en) * 1996-11-13 2002-05-20 日本電気株式会社 Waveguide type variable optical attenuator
JP3337629B2 (en) * 1997-10-30 2002-10-21 エヌティティエレクトロニクス株式会社 Waveguide type optical variable attenuator
JP2000227581A (en) * 1999-02-05 2000-08-15 Sumitomo Osaka Cement Co Ltd Waveguide type optical modulator

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Publication number Priority date Publication date Assignee Title
KR100714758B1 (en) * 2002-12-10 2007-05-07 인터내셔널 비지네스 머신즈 코포레이션 Apparatus and methods for remakeable connections to optical waveguides
KR100709038B1 (en) * 2005-04-01 2007-04-20 정치섭 In-line type variable optical coupler using symmetrically etched fiber

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