WO2015081761A1 - 反射式光衰减器及对光波的功率进行衰减的方法 - Google Patents

反射式光衰减器及对光波的功率进行衰减的方法 Download PDF

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WO2015081761A1
WO2015081761A1 PCT/CN2014/089013 CN2014089013W WO2015081761A1 WO 2015081761 A1 WO2015081761 A1 WO 2015081761A1 CN 2014089013 W CN2014089013 W CN 2014089013W WO 2015081761 A1 WO2015081761 A1 WO 2015081761A1
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optical
optical attenuator
wave
light wave
reflective optical
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PCT/CN2014/089013
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English (en)
French (fr)
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陈定康
李朝阳
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四川飞阳科技有限公司
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Publication of WO2015081761A1 publication Critical patent/WO2015081761A1/zh

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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
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/264—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting
    • G02B6/266—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting the optical element being an attenuator

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  • the present invention relates to the field of optical fiber communication technologies, and more particularly to a reflective optical attenuator and a method for attenuating the power of optical waves.
  • optical receivers are very sensitive to optical power overload.
  • the input power must be controlled within the input range of the optical receiver to prevent saturation. Before the optical amplifier The balance between the input powers of different channels prevents excessive input power of one or some channels and saturation of the optical amplifier gain.
  • the optical attenuator can attenuate the optical signal as expected by the user.
  • the optical attenuator includes a mechanical optical attenuator, a magneto-optical attenuator, a micro-electromechanical system optical attenuator, a thermo-optic attenuator, an acousto-optic attenuator, and the like, wherein the MEMS optical attenuator can be further divided into a reflective type. And light blocking type.
  • the input fiber and the output fiber of the reflective optical attenuator are coupled by a mirror, and the optical power is attenuated by rotating the mirror to change the angle.
  • the reflective optical attenuator generates WDL (Wavelength Dependent Loss) due to light wave dispersion, and the WDL problem is more serious especially when the optical power attenuation is large.
  • the measure for reducing the WDL of the reflective optical attenuator is mainly to compensate the WDL by increasing the dispersion to change the angle of the light of different wavelengths.
  • the above measures will make it difficult for the coating (the anti-reflection coating on the glass slope for increasing the dispersion) and deteriorate the PDL (Polarize Dependent Loss) index.
  • the invention provides a reflective optical attenuator and a method for attenuating the power of light waves, so as to reduce the WDL index in the process of optical power attenuation without increasing the difficulty of coating and deteriorating the PDL index.
  • the present invention provides the following technical solutions:
  • a reflective optical attenuator comprising: an input fiber, a lens, a mirror, and an output fiber, the reflective optical attenuator further comprising: an aperture between the lens and the mirror, the aperture For partially blocking the light wave, the light of the longer wavelength of the light wave is blocked by more light than the shorter wavelength, so as to reduce the purpose of the reflective optical attenuator WDL.
  • the side of the aperture that blocks the light wave is a straight edge.
  • the vertical distance between the center of the spot formed by the light wave and the side of the stop blocking the light wave is 4 ⁇ m to 8 ⁇ m, including the end point value.
  • the vertical distance between the center of the spot formed by the light wave and the side of the stop blocking the light wave is 6 ⁇ m.
  • the light wave passes through the aperture only once on the optical path from the input fiber to the output fiber.
  • the aperture is located on an optical path before the light wave is reflected by the mirror.
  • the aperture is located on an optical path after the light wave is reflected by the mirror.
  • the central axis of the input fiber, the central axis of the output ray, and the optical axis of the lens are parallel to each other.
  • the distance between the central axis of the input fiber and the optical axis of the lens is equal to the distance between the central axis of the output fiber and the optical axis of the lens.
  • the present invention also provides a method for attenuating the power of a light wave, comprising: adjusting a diaphragm of the reflective optical attenuator of any of the above to a preset position; using the reflective optical attenuator for the light wave The power is attenuated such that the pupil portion at the predetermined position obscures the light wave to reduce the wavelength dependent loss of the reflective optical attenuator.
  • the technical solution provided by the present invention has at least the following advantages:
  • the reflective optical attenuator provided by the present invention and the method for attenuating the power of the optical wave by providing a pupil between the lens and the mirror of the optical attenuator, shielding a part of the light wave by the aperture to make the longer wavelength
  • the light wave is blocked by more light than the shorter wavelength light, so that when the lighted and attenuated light wave reaches the end face of the output fiber, the coupling efficiency of the longer wavelength light wave and the shorter wavelength light wave will be close to or equal. Since WDL is the absolute value of the difference between the maximum coupling efficiency and the minimum coupling efficiency in the operating wavelength range, the absolute value of the difference between the coupling efficiency of the longest wavelength light wave and the coupling efficiency of the shortest wavelength light wave can be simplified.
  • the apparatus and method provided by the invention reduce the WDL index and achieve effective compensation for the WDL. Moreover, since the present invention avoids the method of increasing the dispersion, the method of diaphragm occlusion is used to compensate the WDL, thereby avoiding the problem of coating difficulty and PDL increase caused by the method of increasing dispersion, so that the present invention can Under the premise of increasing the difficulty of coating and deteriorating the PDL index, the WDL index in the process of optical power attenuation is reduced.
  • FIG. 1 is a basic structural diagram of a reflective optical attenuator in the prior art
  • FIG. 2 is a schematic diagram showing attenuation of a reflective optical attenuator in the prior art
  • FIG. 3 is a basic structural diagram of a reflective optical attenuator according to an embodiment of the present invention.
  • FIG. 4 is a schematic diagram of a light block partially blocking light waves in a reflective optical attenuator according to an embodiment of the present invention
  • FIG. 5 is a schematic diagram of attenuation of a reflective optical attenuator according to an embodiment of the present invention.
  • FIG. 6 is a schematic diagram of WDL changing with IL when the optical attenuator is not provided with an aperture
  • FIG. 7 is a schematic diagram of WDL variation with IL of an optical attenuator according to an embodiment of the present invention.
  • the reflective optical attenuator of the prior art has a problem of WDL.
  • the light wave enters the optical attenuator through the input optical fiber 101, and passes through the collimation of the lens 102 to reach the mirror 103.
  • the mirror 103 rotates at different tilt angles to cause different degrees of attenuation of the light wave, and then again.
  • the cross section of the output fiber 104 is reached and output through the output fiber 104.
  • the process of attenuating the optical wave by the mirror 103 is accompanied by the generation of WDL.
  • the spot of the light wave on the end face of the output fiber 104 is as shown in FIG. 2. It is known from the optical fiber that the mode field radius of the fiber is different at different wavelengths, and the shorter wavelength light The longer wavelength light is more closely confined to the center of the fiber, and the radius of the long wave mode field 202 is greater than the radius of the short wave mode field 203.
  • the light wave When the light wave reaches the end face of the output fiber 104 and is in an attenuated state (ie, the spot is laterally mismatched with the output fiber end face), assuming a distance between the center of the spot and the center of the core 201 is the same, the light wave coupling efficiency of the longer wavelength (ie, The degree of overlap of the long-wavelength spot 204 with the core 201 is higher than the light-wave coupling efficiency of the shorter wavelength (i.e., the degree of overlap of the shorter-wavelength spot 205 with the core 201), causing a WDL problem.
  • the light waves are separated at an angle according to the wavelength, so that the spots on the end faces of the fibers are deflected at different angles, and the concentric spots become non-concentric spots, so that the spots of different wavelengths fall on the core.
  • the degree of overlap between the spot of the shorter wavelength and the core is close to or equal to the degree of overlap of the spot of the longer wavelength with the core, thereby achieving compensation to the WDL to some extent.
  • the embodiment provides a reflective optical attenuator, which has the structure shown in FIG. 3, and includes an input optical fiber 301, a lens 302, a mirror 303, and an output optical fiber 304.
  • the reflective optical attenuator further include:
  • the stop 301 is used to partially block light waves, so that longer wavelength light waves are blocked by the shorter wavelengths than the shorter wavelengths In order to achieve the purpose of reducing the reflective optical attenuator WDL.
  • the working process of the reflective optical attenuator is: using the input optical fiber 301 to emit light waves containing light wave components of different wavelengths, collimating the light waves by the lens 302, and receiving the light waves passing through the lens 302 by using the mirror 303, and transmitting the light waves.
  • the reflection is performed so that the light wave finally enters the output fiber 304, and the attenuation value of the light wave is controlled by rotating the mirror 303 at different tilt angles, and the light wave attenuated by the mirror 303 is focused by the lens 302 to cause the light wave to enter the output fiber 304, and finally Light waves are emitted using output fiber 304.
  • the light wave propagates between the lens 302 and the mirror 303, a portion of the light wave is blocked by the aperture 305 to reduce the WDL of the optical attenuator.
  • the reflective optical attenuator in this embodiment can reduce the WDL generated during the optical wave attenuation process, and the specific principle is: when the optical attenuator does not add an aperture, the optical wave is transmitted through the optical fiber, and the beam waist radius ⁇ (unit: um ) is related to the wavelength ⁇ (unit: nm).
  • the insertion loss formula of the attenuated light wave ie, the laterally mismatched circular Gaussian beam
  • the wavelength-dependent loss WDL
  • WDL
  • the variation of the wavelength dependent loss WDL with the insertion loss IL can be calculated, as shown in Fig. 6, where the horizontal axis represents the middle of the operating wavelength range. The insertion loss of the wavelength, and the vertical axis represents the wavelength-dependent loss when the pupil is not added.
  • the optical attenuator When the optical attenuator is provided with an aperture, it is assumed that the light wave is partially blocked by the aperture 305 before reaching the mirror 303 after being collimated by the lens 302. As shown in FIG. 4, if the centers of the spots of the wavelengths in the light wave overlap, The longer wavelength spot 401 has a larger radius than the shorter wavelength spot 402, so the ratio of the blocked energy is different. The power of the longer wavelength is blocked and the power of the shorter wavelength is blocked.
  • the radius of the long-wave mode field 502 is greater than the radius of the short-wave mode field 503.
  • the light wave is attenuated by the mirror and reaches the end face of the output fiber, it is assumed to be longer wavelength.
  • the light is the same as the lateral mismatch ⁇ of the shorter wavelength light.
  • the longer wavelength spot 401 and the long wave mode field The overlapping portion of 502 is close to or equal to the overlapping portion of the shorter wavelength spot 402 and the short wave mode field 503, that is, the insertion loss of the longer wavelength light is close to or equal to the insertion loss of the shorter wavelength light, and the difference therebetween As the value becomes smaller, the value of the wavelength dependent loss WDL becomes smaller, and effective compensation for the WDL is realized.
  • the edge of the aperture 305 blocking the light wave is a straight edge
  • the distance from the center of the spot to the straight edge blocked by the aperture 305 is assumed to be m.
  • the formula of the insertion loss becomes:
  • WDL can be calculated.
  • the insertion loss IL changes, as shown in Fig. 6, the horizontal axis represents the insertion loss of the intermediate wavelength in the operating wavelength range, and the vertical axis represents the wavelength dependent loss when the aperture is added. Compared with the change of the WDL with the insertion loss IL when no aperture is added, it can be concluded that the WDL is reduced by about 0.2 dB after the addition of the aperture.
  • the degree to which the aperture 305 blocks the spot can also be calculated according to the actual situation, combined with the attenuation value of the required optical power, to correspondingly set the position of the aperture 305.
  • the vertical distance between the center of the light spot formed by the light wave and the side of the light occlusion of the light wave may preferably be 4 ⁇ m to 8 ⁇ m, including the end point value, and more preferably It is 6 ⁇ m.
  • the optical wave from the input fiber 301 to the output fiber 304 preferably passes through the aperture 305 only once; and the aperture 305 is located before the light wave is reflected by the mirror 303.
  • the optical path 305 is located on an optical path or the like after the light wave is reflected by the mirror 303.
  • the central axis of the input fiber 301, the central axis of the output ray 304, and the optical axis of the lens 302 may be parallel to each other.
  • the distance between the central axis of the input fiber 301 and the optical axis of the lens 302 is equal to the distance between the central axis of the output fiber 304 and the optical axis of the lens 302.
  • the embodiment further provides a method for attenuating the power of the light wave, comprising:
  • the preset position of the pupil is calculated by simulation.
  • the reflected optical attenuator is used to attenuate the power of the optical wave to partially block the optical wave at the preset position to reduce the wavelength dependent loss of the reflective optical attenuator.
  • the reflective optical attenuator and the method for attenuating the power of the optical wave provided by the embodiment have a pupil disposed between the lens and the mirror, so that the pupil partially blocks the optical wave, and the mode field radius of the optical wave is different according to different wavelengths.
  • the portion where the longer wavelength light wave is blocked is larger than the portion where the shorter wavelength light wave is blocked, so that the occluded light wave reaches the spot of the output light end face, and the overlapping portion of the longer wavelength spot and the long wave mode field
  • the overlap of the shorter wavelength spot and the short wave mode field is close or equal, which makes the insertion loss of the longer wavelength light wave and the shorter wavelength light wave close or equal, thereby realizing the compensation of the wavelength dependent loss WDL and reducing The WDL indicator.
  • the WDM is compensated by the method of setting the pupil to block part of the light wave
  • the method of increasing the dispersion in the prior art is used to compensate the problem of the coating difficulty caused by the WDL and the increase of the PDL index, thereby realizing the problem.
  • the WDL index in the process of optical power attenuation is reduced.

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  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Couplings Of Light Guides (AREA)

Abstract

一种反射式光衰减器，包括：输入光纤（301）、透镜（302）、反射镜（303）和输出光纤（304），还包括：位于透镜（302）与反射镜（303）之间的光阑（305），光阑（305）用于部分遮挡光波，使光波中较长波长的光波被遮挡的能量多于较短波长的光波，从而使长波与短波的耦合效率接近或相等，实现对WDL的有效补偿，以达到减小光衰减器WDL的目的。并且，由于避免采用增加色散的方法，因此也就避免了随之引起的镀膜难度和PDL增加的问题，从而能够在不增加镀膜难度和恶化PDL指标的前提下，减小光功率衰减过程中的WDL指标。

Description

反射式光衰减器及对光波的功率进行衰减的方法
本申请要求于2013年12月02日提交中国专利局、申请号为201310640021.5、发明名称为“反射式光衰减器及对光波的功率进行衰减的方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及光纤通信技术领域，更具体地说，涉及一种反射式光衰减器及对光波的功率进行衰减的方法。
背景技术
在光纤通信系统中，有许多场景需要减少光信号的功率，如：光接收机对光功率的过载非常灵敏，必须将输入功率控制在光接收机的输入范围内，防止其饱和；光放大器前的不同信道输入功率间的平衡，可防止某个或某些信道的输入功率过大和光放大器增益饱和。
光衰减器可按照用户的要求将光信号进行预期的功率衰减。光衰减器包括机械式光衰减器、磁光衰减器、微机电系统光衰减器、热光衰减器、声光衰减器等多种类型，其中，微机电系统光衰减器又可分为反射式和挡光式两种。
反射式光衰减器的输入光纤和输出光纤通过反射镜实现耦合，通过反射镜旋转改变角度实现光功率衰减。但是，反射式光衰减器由于光波色散会产生WDL(Wavelength Dependent Loss，波长相关损耗)，特别是在光功率衰减较大时，WDL问题更加严重。
现有技术中，减小反射式光衰减器的WDL的措施主要是：通过增加色散改变不同波长的光的角度，实现对WDL的补偿。但是，上述措施会给镀膜(用于增加色散的玻璃斜面上镀有增透膜)带来难度，并恶化PDL(Polarize Dependent Loss，偏振相关损耗)指标。
发明内容
本发明提供了一种反射式光衰减器及对光波的功率进行衰减的方法，以在不增加镀膜难度和恶化PDL指标的前提下，减小光功率衰减过程中的WDL指标。
为实现上述目的，本发明提供了如下技术方案：
一种反射式光衰减器，包括：输入光纤、透镜、反射镜和输出光纤，所述反射式光衰减器还包括：位于所述透镜与所述反射镜之间的光阑，所述光阑用于部分遮挡光波，使所述光波中较长波长的光波被遮挡的能量多于较短波长的光波，以达到减小所述反射式光衰减器WDL的目的。
优选的，所述光阑遮挡所述光波的边为一条直边。
优选的，所述光波所呈的光斑的中心与所述光阑遮挡所述光波的边的垂直距离为4μm～8μm，包括端点值。
优选的，所述光波所呈的光斑的中心与所述光阑遮挡所述光波的边的垂直距离为6μm。
优选的，所述光波从所述输入光纤至所述输出光纤的光路上仅经过所述光阑一次。
优选的，所述光阑位于所述光波被所述反射镜反射前的光路上。
优选的，所述光阑位于所述光波被所述反射镜反射后的光路上。
优选的，所述输入光纤的中轴线、所述输出光线的中轴线和所述透镜的光轴三者相互平行。
优选的，所述输入光纤的中轴线与所述透镜的光轴的距离等于所述输出光纤的中轴线与所述透镜的光轴的距离。
本发明还提供了一种对光波的功率进行衰减的方法，包括：将以上任一项所述反射式光衰减器的光阑调整至预设位置；利用所述反射式光衰减器对光波的功率进行衰减，使位于所述预设位置的光阑部分遮挡所述光波，以减小所述反射式光衰减器的波长相关损耗。
与现有技术相比，本发明所提供的技术方案至少具有以下优点：
本发明所提供的反射式光衰减器及对光波的功率进行衰减的方法，通过在光衰减器的透镜和反射镜之间设置光阑，利用光阑遮挡部分光波，使较长波长 的光波被遮挡的能量多于较短波长的光波，从而当经过光阑的、衰减后的光波到达输出光纤端面时，较长波长的光波与较短波长的光波的耦合效率会接近或相等，由于WDL为工作波长范围内最大耦合效率和最小耦合效率差值的绝对值，可简化成最长波长的光波的耦合效率和最短波长的光波的耦合效率的差值的绝对值，因此，采用本发明所提供的装置和方法使WDL指标减小，实现了对WDL的有效补偿。并且，由于本发明避免采用增加色散的方法，而是采用光阑遮挡的方法补偿WDL，因此也就避免了由增加色散的方法而引起的镀膜难度和PDL增加的问题，从而本发明能够在不增加镀膜难度和恶化PDL指标的前提下，减小光功率衰减过程中的WDL指标。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为现有技术中反射式光衰减器的基本结构图；
图2为现有技术中反射式光衰减器的衰减示意图；
图3为本发明实施例所提供的反射式光衰减器的基本结构图；
图4为本发明实施例所提供的反射式光衰减器中光阑部分遮挡光波的示意图；
图5为本发明实施例所提供的反射式光衰减器的衰减示意图；
图6为光衰减器不增设光阑时WDL随IL变化的示意图；
图7为本发明实施例所提供的光衰减器的WDL随IL变化的示意图。
具体实施方式
为使本发明的上述目的、特征和优点能够更加明显易懂，下面结合附图对本发明的具体实施方式做详细的说明。
在下面的描述中阐述了很多具体细节以便于充分理解本发明，但是本发明还可以采用其他不同于在此描述的其它方式来实施，本领域技术人员可以在不违背本发明内涵的情况下做类似推广，因此本发明不受下面公开的具体实施例的限制。
其次，本发明结合示意图进行详细描述，在详述本发明实施例时，为便于说明，表示器件结构的剖面图会不依一般比例作局部放大，而且所述示意图只是示例，其在此不应限制本发明保护的范围。此外，在实际制作中应包含长度、宽度及深度的三维空间尺寸。
正如背景技术所述，现有技术中反射式光衰减器存在WDL的问题。如图1所示，光波通过输入光纤101进入光衰减器中，经过透镜102的准直作用，到达反射镜103，反射镜103通过旋转不同的倾斜角，使光波产生不同程度的衰减，然后再次经过透镜102的聚焦作用，到达输出光纤104的断面，经输出光纤104输出。
反射镜103对光波进行衰减的过程伴随产生WDL，光波在输出光纤104的端面的光斑如图2所示，由光纤光学可知，光纤不同波长的模场半径是不一样的，较短波长的光比较长波长的光被更加紧密的限制于光纤的中心，长波模场202的半径大于短波模场203的半径。光波到达输出光纤104的端面并处于衰减状态(即光斑与输出光纤端面侧向失配)时，假设光斑中心与纤芯201中心之间的距离相同，则较长波长的光波耦合效率(即较长波长的光斑204与纤芯201的重叠程度)高于较短波长的光波耦合效率(即较短波长的光斑205与纤芯201的重叠程度)，引起WDL问题。
而如果采用增大色散的方法，根据波长的不同将光波在角度上进行分离，使光纤端面的光斑产生不同角度的偏离，由同心光斑变为非同心光斑，使不同波长的光斑落在纤芯201的不同位置，达到较短波长的光斑与纤芯的重叠程度接近或等于较长波长的光斑与纤芯的重叠程度的目的，从而实现在一定程度上对WDL的补偿。
但是，发明人研究发现，该方法只有在光波具有较大的入射角度时才能实 现对WDL的有效补偿，这就引起在增加色散的玻璃斜面上镀膜难度的增大；另一方面，由于PDL的产生主要是由横波和纵波在两介质交界处的透射率或反射率不同所引起的，横波和纵波在入射角为0度或接近90度的时候最小，对应的PDL最小，在0度到90度之间有一个角度差异最大，此时对应PDL最大，因此在光波的入射角度较大时，入射角度不可能为0度，也不可能为90度或接近90度，会引起PDL指标的恶化。
针对上述问题，本实施例提供了一种反射式光衰减器，其结构如图3所示，包括：输入光纤301、透镜302、反射镜303和输出光纤304，所述反射式光衰减器还包括：
位于所述透镜302与所述反射镜303之间的光阑301，所述光阑301用于部分遮挡光波，使所述光波中较长波长的光波被遮挡的能量多于较短波长的光波，以达到减小所述反射式光衰减器WDL的目的。
本实施例所提供的反射式光衰减器的工作过程为：利用输入光纤301发射包含不同波长光波成分的光波，利用透镜302准直该光波，利用反射镜303接收经过透镜302的光波，将光波进行反射，使光波最终能够进入输出光纤304，并通过使反射镜303旋转不同倾斜角控制光波的衰减值，利用透镜302对经过反射镜303衰减的光波进行聚焦，使光波进入输出光纤304，最后利用输出光纤304将光波发射出去。在光波在透镜302与反射镜303之间传播时，利用光阑305遮挡部分光波，以减小光衰减器的WDL。
本实施例中的反射式光衰减器能够减小光波衰减过程中产生的WDL，其具体原理为：当光衰减器不增设光阑时，光波经光纤传输后，束腰半径ω(单位：um)跟波长λ(单位：nm)是相关的。在波长范围较小(如：光纤通信上使用的C-Band，约1530nm到1570nm)时，束腰半径ω与波长λ之间的函数关系式可近似写成：ω(λ)＝ω0+a×(λ-λ0)(其中，a为常系数，λ0是整个波长范围内的最小波长，ω0为最小波长对应的束腰半径)。
光衰减器处于衰减状态时，衰减后的光波(即侧向失配的圆形高斯光束)的插入损耗公式为：
Figure PCTCN2014089013-appb-000001
(其中，Δ为衰减后光波中心与纤芯之间的距离，即光波侧向失配的值)，将该公式化简后得到：
Figure PCTCN2014089013-appb-000002
从化简后的公式可以看出，在光不同波长的光斑侧向失配相同的情况下，不同波长的光的插入损耗不同，产生WDL问题。
定义波长相关损耗为工作波长范围内最大插入损耗和最小插入损耗之间的差值，结合以上公式可知，在侧向失配Δ时波长相关损耗WDL＝|IL(λmin)-IL(λmax)|，(其中，λmin和λmax分别表示工作波长范围内的最小波长和最大波长)。
假设工作波长范围为1530nm(即λ0)到1570nm，二者在光纤中传输时的束腰半径分别为5.14μm和5.26μm，根据ω(λ)＝ω0+a×(λ-λ0)，则可得到a＝0.003，进一步得到ω(λ)＝ω0+0.003×(λ-λ0)，代入
Figure PCTCN2014089013-appb-000003
中，利用WDL＝|IL(λmin)-IL(λmax)|，可以计算出波长相关损耗WDL随插入损耗IL的变化情况，如图6所示，图中横轴表示工作波长范围内中间波长的插入损耗，纵轴表示不增设光阑时的波长相关损耗。
当光衰减器增设光阑时，假设光波在被透镜302准直过后，到达反射镜303之前，被光阑305部分遮挡，如图4所示，若光波中各波长的光斑中心重叠，则由于较长波长的光斑401半径大于较短波长的光斑402的半径，因此二者被遮挡住的能量的比例不同，较长波长的光被遮挡的功率比较短波长的光被遮挡的功率高。
如图5所示，在输出光纤的纤芯501中，长波模场502的半径大于短波模场503的半径。当光波被反射镜衰减后到达输出光纤端面时，假设较长波长的 光与较短波长的光的侧向失配Δ相同，由于较长波长的光斑401被遮挡的功率高于较短波长的光斑402被遮挡的功率，则较长波长的光斑401和长波模场502的重叠部分与较短波长的光斑402和短波模场503的重叠部分接近或相等，即较长波长的光的插入损耗与较短波长的光的插入损耗接近或相等，二者的差值变小，从而波长相关损耗WDL的值变小，实现了对WDL的有效补偿。
具体的，若光阑305遮挡光波的边为一条直边，则假设光斑的中心到光阑305遮挡的直边的距离为m，此时，插入损耗的公式变为：
Figure PCTCN2014089013-appb-000004
按照波长范围为1530nm到1570nm，二者在光纤中传输时的束腰半径分别是5.14μm和5.26μm，即a＝0.003。当m＝6时(若m的值太大，优化WDL的效果不明显；若m的值太小，挡掉的光能量太多，会恶化未衰减时光波的耦合效率)，可以计算出WDL随插入损耗IL的变化情况，如图6所示，图中横轴表示工作波长范围内中间波长的插入损耗，纵轴表示增设光阑时的波长相关损耗。与不增设光阑时WDL随插入损耗IL的变化情况相比，可以得出，增设光阑后WDL减小约0.2dB。
侧向失配Δ＝0，即光衰减器处于不衰减状态时，IL(λmin)＝0.0917dB，对插入损耗没有明显恶化。
需要说明的是，本实施例仅以所述光阑305遮挡所述光波的边为一条直边为例进行说明，光阑305遮挡光波也可以为其它形式，在此并不进行限定。
另外，光阑305对光斑遮挡的程度也可根据实际情况，结合所需要的光功率的衰减值进行计算，以相应的设置光阑305的位置。当光阑305遮挡光波的边为一条直边时，所述光波所呈的光斑的中心与所述光阑遮挡所述光波的边的垂直距离可优选为4μm～8μm，包括端点值，更优选为6μm。
并且，在本发明的通过增设光阑305遮挡部分光波以补偿WDL值的核心 思想的基础上，本实施例对光阑305在光衰减器中的具体设置情况并不限定，其可以有多种变形。如：使所述光波从所述输入光纤301至所述输出光纤304的光路上优选的仅经过所述光阑305一次；使所述光阑305位于所述光波被所述反射镜303反射前的光路上；使所述光阑305位于所述光波被所述反射镜303反射后的光路上等。
本实施例中，所述输入光纤301的中轴线、所述输出光线304的中轴线和所述透镜302的光轴三者可相互平行。所述输入光纤301的中轴线与所述透镜302的光轴的距离等于所述输出光纤304的中轴线与所述透镜302的光轴的距离。
与上述装置相对应的，本实施例还提供了一种对光波的功率进行衰减的方法，包括：
将本实施例所述的反射式光衰减器的光阑调整至预设位置；
其中，光阑的预设位置是经过仿真模拟计算的来的。
利用所述反射式光衰减器对光波的功率进行衰减，使位于所述预设位置的光阑部分遮挡所述光波，以减小所述反射式光衰减器的波长相关损耗。
本实施例所提供的反射式光衰减器及对光波的功率进行衰减的方法，通过在透镜和反射镜之间设置光阑，使光阑部分遮挡光波，根据不同波长的光波模场半径不同，使较长波长的光波被遮挡掉的部分大于较短波长的光波被遮挡的部分，使被遮挡后的光波到达输出光线端面时的光斑中，较长波长的光斑与长波模场的重叠部分和较短波长光斑与短波模场的重叠部分接近或相等，这也就使较长波长的光波与较短波长的光波的插入损耗接近或相等，从而实现了对波长相关损耗WDL的补偿，减小了WDL指标。
并且，由于本实施例是利用设置光阑遮挡部分光波的方法补偿WDL的，因此也就避免了现有技术中采用增加色散的方法补偿WDL所引起的镀膜难度和PDL指标增加的问题，从而实现了在不增加镀膜难度和恶化PDL指标的前提下，减小光功率衰减过程中的WDL指标。
虽然本发明已以较佳实施例披露如上，然而并非用以限定本发明。任何熟悉本领域的技术人员，在不脱离本发明技术方案范围情况下，都可利用上述揭 示的方法和技术内容对本发明技术方案作出许多可能的变动和修饰，或修改为等同变化的等效实施例。因此，凡是未脱离本发明技术方案的内容，依据本发明的技术实质对以上实施例所做的任何简单修改、等同变化及修饰，均仍属于本发明技术方案保护的范围内。

Claims (10)

  1. 一种反射式光衰减器，包括：输入光纤、透镜、反射镜和输出光纤，其特征在于，所述反射式光衰减器还包括：
    位于所述透镜与所述反射镜之间的光阑，所述光阑用于部分遮挡光波，使所述光波中较长波长的光波被遮挡的能量多于较短波长的光波，以达到减小所述反射式光衰减器WDL的目的。
  2. 根据权利要求1所述的反射式光衰减器，其特征在于，所述光阑遮挡所述光波的边为一条直边。
  3. 根据权利要求2所述的反射式光衰减器，其特征在于，所述光波所呈的光斑的中心与所述光阑遮挡所述光波的边的垂直距离为4μm～8μm，包括端点值。
  4. 根据权利要求3所述的反射式光衰减器，其特征在于，所述光波所呈的光斑的中心与所述光阑遮挡所述光波的边的垂直距离为6μm。
  5. 根据权利要求1所述的反射式光衰减器，其特征在于，所述光波从所述输入光纤至所述输出光纤的光路上仅经过所述光阑一次。
  6. 根据权利要求5所述的反射式光衰减器，其特征在于，所述光阑位于所述光波被所述反射镜反射前的光路上。
  7. 根据权利要求5所述的反射式光衰减器，其特征在于，所述光阑位于所述光波被所述反射镜反射后的光路上。
  8. 根据权利要求1所述的反射式光衰减器，其特征在于，所述输入光纤的中轴线、所述输出光线的中轴线和所述透镜的光轴三者相互平行。
  9. 根据权利要求8所述的反射式光衰减器，其特征在于，所述输入光纤的中轴线与所述透镜的光轴的距离等于所述输出光纤的中轴线与所述透镜的光轴的距离。
  10. 一种对光波的功率进行衰减的方法，其特征在于，包括：
    将权利要求1～9任一项所述反射式光衰减器的光阑调整至预设位置；
    利用所述反射式光衰减器对光波的功率进行衰减，使位于所述预设位置的光阑部分遮挡所述光波，以减小所述反射式光衰减器的波长相关损耗。
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