JP2005134668A - Optical power monitoring apparatus and optical transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical power monitoring apparatus which exhibits suppressed cross talk and the cost of which can be reduced, and to provide an optical transmission system including the optical power monitoring apparatus. <P>SOLUTION: An optical power monitoring apparatus 42 is provided with: a 1st optical waveguide 90a for transmitting signal light of wavelengths in a range of 1520 to 1610 nm; an optical filter 100a which is arranged in the optical path of the signal light outputted from an output end 93 of the 1st optical waveguide, reflects part of the signal light and transmits the other part; a 2nd optical waveguide 110a for transmitting the transmission signal light which is part of the signal light having passed through the optical filter and having been inputted from an input end; and a photodetector 120a for detecting the power of the component of the signal light reflected by the optical filter. In the optical power monitoring apparatus, the proportion of the reflected signal light intersecting the 1st optical waveguide in the energy of the reflected signal light is 20% or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical power monitoring device and an optical transmission system including the optical power monitoring device.

  In an optical transmission system, the power of signal light is monitored in order to keep the power of transmitted signal light constant. The power of the signal light is monitored as follows, for example. That is, a part of the signal light transmitted through the transmission path is extracted, and the power of the extracted signal light is monitored. As a technique for extracting part of the signal light, for example, Patent Document 1 discloses a technique using an optical filter.

  The optical filter built-in optical communication component described in Patent Document 1 includes an optical fiber having a groove formed so as to intersect the optical axis, an optical filter inserted into the groove, and signal light reflected by the optical filter. And a light receiving element. In the optical communication component with a built-in optical filter, part of the signal light propagating through the optical fiber is reflected by the optical filter, and the reflected signal light is received by the light receiving element.

  As a technique for extracting a part of signal light using an optical filter, a technique disclosed in Patent Document 2 is also known.

That is, an optical filter element in which filters having different wavelength characteristics are arranged at equal intervals on a glass plate is formed. Then, the optical filter element is moved with respect to the output end of the first optical fiber (incident optical fiber), and the signal light from the first optical fiber is incident on each filter. At this time, the reflected signal light from the filter is incident on the second optical fiber (reflection optical fiber), and the transmitted signal light transmitted through the filter is incident on the third optical fiber (outgoing optical fiber).
Japanese Patent Laid-Open No. 10-300936 Japanese Patent Laid-Open No. 2003-121683

  When an optical filter is inserted into the groove of the optical fiber and reflected as described in Patent Document 1, the reflected signal light crosses the optical fiber (in other words, the reflected signal light is incident on the optical axis of the optical fiber. On the other hand, it passes through the optical fiber obliquely and reaches the light receiving element. When the reflected signal light intersects the optical fiber, the reflected signal light diffuses due to the surface roughness of the groove wall surface. For this reason, when a plurality of sets of optical fibers and light receiving elements in which optical filters are inserted in the grooves are arranged in parallel, the reflected signal light of one set of two adjacent sets is incident on the other set of light receiving elements. Talk occurs. When this crosstalk occurs, the power of the signal light cannot be accurately monitored.

  In the technique disclosed in Patent Document 2, the first and third optical fibers are separated to such an extent that the optical filter element can move. A collimating lens is provided in that the spread of the signal light due to the separation between the first and third optical fibers is suppressed, and the loss when the transmitted signal light is incident on the third optical fiber is reduced. Is used. When the collimating lens is used in this way, there is a problem that the cost increases.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical power monitoring device capable of suppressing crosstalk and reducing the cost, and an optical transmission system including the optical power monitoring device. It is.

  In order to solve the above-described problems, an optical power monitoring device according to the present invention includes a first optical waveguide that transmits signal light of any wavelength in the wavelength range of 1520 to 1610 nm, and an output end of the first optical waveguide. An optical filter that is arranged on the optical path of the output signal light, reflects a part of the signal light and transmits the other, and transmits the transmitted signal light that passes through the optical filter and is input from the input end. A reflected signal light that intersects the first optical waveguide out of the energy of the reflected signal light, and a light receiving element that detects the power of the reflected signal light reflected by the optical filter of the signal light. The energy ratio is 20% or less.

  In the above configuration, a part of the signal light transmitted through the first optical waveguide is reflected by the optical filter and the other is transmitted. The reflected signal light reflected by the optical filter in the signal light is received by the light receiving element, and its power is detected. The transmitted signal light that has passed through the optical filter out of the signal light is transmitted by the second optical waveguide. Thereby, the power of the signal light can be monitored by monitoring the power of the reflected signal light with the light receiving element while transmitting the signal light from the first optical waveguide to the second optical waveguide.

  The ratio of the reflected signal light energy that intersects the first optical waveguide (in other words, passes through the first optical waveguide obliquely with respect to the optical axis of the first optical waveguide) in the reflected signal light energy is: 20% or less. Therefore, compared with the case where all of the reflected signal light is received by the light receiving element crossing the first optical waveguide, the reflected signal light is suppressed from being diffused by the surface roughness of the output end.

  Therefore, when a plurality of sets of the first optical waveguide, the optical filter, the second optical waveguide, and the light receiving element are arranged in parallel, crosstalk between the respective sets is reduced.

  Further, in the above configuration, no lens is used when the signal light from the first optical waveguide is incident on the optical filter and when the transmitted signal light is incident on the second optical waveguide. Therefore, the cost can be reduced as compared with the case of using a lens.

  In the optical power monitoring device according to the present invention, the ratio of the reflected signal light energy that intersects the first optical waveguide out of the reflected signal light energy is preferably 5% or less. In this case, since the ratio of the reflected signal light that intersects the first optical waveguide is smaller, the diffusion of the reflected signal light is further suppressed.

  Furthermore, in the optical power monitor device according to the present invention, it is desirable that the reflected signal light does not intersect the first optical waveguide. In this case, the reflected signal light is received by the light receiving element without intersecting the first optical waveguide. For this reason, the reflected signal light is not diffused by the surface roughness of the output end.

  Furthermore, in the optical power monitoring device according to the present invention, the optical path of the signal light between the first optical waveguide and the optical filter, and the optical path of the transmitted signal light between the optical filter and the second optical waveguide. Further, it is preferable that a medium is provided.

  In such a configuration, the refractive index change at the interface between the output end of the first optical waveguide and the medium is smaller than that at the interface with air. Therefore, diffusion of the signal light and the reflected signal light is suppressed by the surface roughness of the output end. If the medium is a solid or is made of a curable material, the optical filter can be fixed by the medium.

  In the optical power monitoring device according to the present invention, the optical path of the signal light between the first optical waveguide and the optical filter, the optical path of the reflected signal light between the optical filter and the light receiving element, and the optical filter It is preferable that a medium is provided in the optical path of the transmitted signal light between the second optical waveguide.

  In this case, a medium is provided in the optical path of the signal light, the transmitted signal light, and the reflected signal light. The reflected signal light propagates through the medium until it reaches the light receiving element. Therefore, scattering due to a change in refractive index is unlikely to occur and diffusion of reflected signal light is suppressed. If the medium is a solid or is made of a curable material, the optical filter can be fixed by the medium.

  Furthermore, in the optical power monitoring apparatus according to the present invention, it is preferable that a plurality of sets of the first optical waveguide, the optical filter, the second optical waveguide, and the light receiving element are provided in parallel.

  In the set of the first optical waveguide, the optical filter, the second optical waveguide, and the light receiving element, diffusion of reflected signal light from the optical filter is suppressed. Therefore, in the optical power monitoring device in which a plurality of sets are arranged in parallel, the ratio of the reflected signal light of one set of the two adjacent sets to the light receiving element of the other set is small. Therefore, it is possible to shorten the interval between two adjacent sets, and the optical power monitor device can be made compact.

  Furthermore, in the optical power monitoring device according to the present invention, it is desirable that the core diameters at the output end of the first optical waveguide and the input end of the second optical waveguide are enlarged.

  In this case, since the core diameter at the output end of the first optical waveguide is enlarged, the spread of the signal light output from the first optical waveguide is suppressed. For this reason, the spread of the reflected signal light is also reduced. Further, the spread of the transmitted signal light transmitted through the optical filter is suppressed, and the core diameter at the input end of the second optical waveguide is enlarged, so that the transmitted signal light is incident on the second optical waveguide. Loss can be reduced.

  The optical transmission system according to the present invention is an optical transmission system having an optical transmission path for transmitting signal light of any wavelength in the wavelength range of 1520 to 1610 nm, and the optical power monitor according to the present invention is included in the optical transmission path. A device is provided.

  A part of the signal light transmitted through the optical transmission path is reflected by the optical filter of the optical power monitor device provided in the optical transmission path, and the power of the reflected signal light is detected by the light receiving element. Thereby, it is possible to monitor the power of the signal light.

  In the optical power monitor device, the ratio of the reflected signal light energy that intersects the first optical waveguide out of the reflected signal light energy is 20% or less. For this reason, the reflected signal light is prevented from diffusing due to the surface roughness of the output end of the first optical waveguide. Therefore, even when a plurality of sets of the first optical waveguide, the optical filter, the second optical waveguide, and the light receiving element are arranged in parallel, crosstalk between the sets is reduced. Therefore, it is possible to more accurately monitor the power of the signal light transmitted through one first optical waveguide.

  According to the present invention, crosstalk can be suppressed and the cost can be reduced.

  In the following, preferred embodiments of the present invention will be described with reference to the drawings. In the following description, the same reference numerals are used for the same elements, and duplicate descriptions are omitted.

  FIG. 1 is a schematic diagram showing the configuration of the optical transmission system of the present embodiment.

  The optical transmission system 1 includes an optical transmitter 10, an optical amplifier 20, an optical ADM (Add-Drop Multiplexer) 30, an optical power monitor unit 40, an optical amplifier 50, and an optical receiver 60. ing. Optical fibers 70, 71, 72 are laid between the optical transmitter 10 and the optical amplifier 20, between the optical amplifier 20 and the optical ADM 30, and between the optical ADM 30 and the optical power monitor unit 40. . Optical fibers 73 and 74 are laid between the optical power monitor unit 40 and the optical amplifier 50 and between the optical amplifier 50 and the optical receiver 60.

The optical transmitter 10 includes eight light sources 11 a to 11 h and a multiplexer 12. The light sources 11a to 11h are, for example, semiconductor lasers. Each of the light sources 11a to 11h outputs signal light having different wavelengths λ _{1 to} λ _{8 in} the wavelength range 1520 to 1610 nm. The multiplexer 12 multiplexes the signal lights having the wavelengths λ _{1 to} λ ₈ output from the light sources 11 a to 11 h and outputs the multiplexed signal light to the optical fiber 70.

The optical amplifier 20 is, for example, an erbium-doped fiber amplifier. The optical amplifier 20 amplifies the signal light having multiple wavelengths λ _{1 to} λ ₈ transmitted through the optical fiber 70 and outputs the amplified signal light to the optical fiber 71.

Further, the optical ADM 30 drops the signal light having the wavelength λ ₁ among the multiple wavelengths λ _{1 to} λ ₈ transmitted through the optical fiber 71 into the optical fiber 75. Then, the signal light of multiple wavelengths lambda ₂ to [lambda] ₈ where the signal light of the wavelength lambda ₁ is branched, insert a signal light of the wavelength lambda ₁ from the optical fiber 76 (the add) to multiple wavelengths lambda ₁ to [lambda] ₈ The signal light is output to the optical fiber 72.

The optical power monitor unit 40 includes a duplexer 41, optical power monitor devices 42 and 44, a multiplexer 43, optical amplifiers 45a to 45h, and variable attenuators 46a to 46h. The demultiplexer 41 divides the signal light having multiple wavelengths λ _{1 to} λ ₈ transmitted by the optical fiber 72 into signal light having wavelengths λ _{1 to} λ ₈ and inputs the signal light to the optical power monitor device 44. The optical power monitoring device 44 monitors the power of the signal light of each wavelength λ _{1 to} λ ₈ and outputs it to the optical amplifiers 45a to 45h.

The optical amplifiers 45a to 45h are, for example, erbium-doped fiber amplifiers. Each of the optical amplifiers 45 a to 45 h amplifies the signal light of each wavelength λ _{1 to} λ ₈ and outputs the amplified signal light to the optical power monitor device 42. The optical power monitoring device 42 monitors the power of the signal light amplified by the optical amplifiers 45a to 45h and outputs it to the variable attenuators 46a to 46h.

Each of the variable attenuators 46 a to 46 h attenuates the power of the incident signal light in accordance with the power of the signal light having the wavelengths λ _{1 to} λ ₈ monitored by the optical power monitor device 42, and supplies it to the multiplexer 43. Output. At this time, the variable attenuators 46 a to 46 h align the powers of the signal lights and output them to the multiplexer 43. The multiplexer 43 multiplexes the signal light of each wavelength λ _{1 to} λ ₈ adjusted so that the power becomes constant by the variable attenuators 46a to 46h, and the signal light of multiple wavelengths λ _{1 to} λ ₈ is optical fiber. To 73. The optical amplifier 50 amplifies the signal light from the optical fiber 73 and outputs it to the optical fiber 74.

The optical receiver 60 is divided by a demultiplexer 61 and a demultiplexer 61 that divide the signal light having multiple wavelengths λ _{1 to} λ ₈ transmitted through the optical fiber 74 into signal light having wavelengths λ _{1 to} λ _8. In addition, _eight light receiving elements 62a to 62h that receive the signal light having the respective wavelengths λ _{1 to} λ 8 are provided. The light receiving elements 62a to 62h are, for example, photodiodes.

In the optical transmission system 1, the signal lights having the multiple wavelengths λ _{1 to} λ ₈ output from the optical transmitter 10 are amplified and transmitted by the optical amplifier 20 and then input to the optical ADM 30. In the optical ADM 30, the signal light having the wavelength λ ₁ is branched to the optical fiber 75 from the signal light having the multiple wavelengths λ _{1 to} λ ₈ from the optical transmitter 10, and the new wavelength λ ₁ transmitted through the optical fiber 76. Signal light is inserted.

The signal lights having multiple wavelengths λ _{1 to} λ ₈ output from the optical ADM 30 are input to the optical power monitor unit 40. In the optical power monitor unit 40, the signal light of multiple wavelengths lambda ₁ to [lambda] ₈ is a demultiplexer 41 is divided into signal lights of respective wavelengths lambda ₁ to [lambda] _8, a power of each signal light is an optical power monitoring device 44 Monitored. The signal lights having the wavelengths λ _{1 to} λ ₈ that have passed through the optical power monitor device 44 are amplified by the optical amplifiers 45a to 45h.

Each signal light amplified by the optical amplifiers 45 a to 45 h is input to the optical power monitor device 42. The optical power monitoring device 42 monitors the power of the signal light having the wavelengths λ _{1 to} λ ₈ . Then, the signal light of each wavelength lambda ₁ to [lambda] ₈ output from the optical power monitor unit 42 is input to the variable attenuator 46A.

The variable attenuators 46a to 46h align the power of the signal light having the wavelengths λ _{1 to} λ ₈ . The signal lights of the wavelengths λ _{1 to} λ ₈ output from the variable attenuators 46 a to 46 h and having the same power are input to the multiplexer 43 and multiplexed. The signal light having the multiple wavelengths λ _{1 to} λ ₈ output from the multiplexer 43 of the optical power monitor unit 40 is amplified by the optical amplifier 50 and transmitted, and then received by the optical receiver 60.

  As described above, the optical transmission system 1 is a system that transmits signal light of any wavelength in the wavelength range of 1520 nm to 1610 nm from the optical transmitter 10 to the optical receiver 60. The optical power monitor unit 40 is provided on an optical transmission line composed of the optical fibers 70 to 74, the optical amplifiers 20 and 50, and the optical ADM 30.

  Next, the optical power monitoring devices 42 and 44 of the present embodiment used in the optical power monitoring unit 40 will be described. The optical power monitoring devices 42 and 44 have the same configuration although the installation positions in the optical power monitoring unit 40 are different. Therefore, the optical power monitoring device 42 will be described below.

  FIG. 2 is a perspective view of the optical power monitor device 42.

  The optical power monitoring device 42 includes a substrate 80, eight input side optical fibers (first optical waveguides) 90a to 90h, an optical filter unit 100, and eight output side optical fibers (second optical waveguides). 110a to 110h and the light receiving element array 120.

  The substrate 80 is made of, for example, quartz glass and has a substantially rectangular shape.

Each input side optical fiber 90a-90h transmits the signal light of any wavelength of each wavelength (lambda) _1- (lambda) ₈ . The input side optical fibers 90a to 90h are arranged in parallel, one end is connected to the optical amplifiers 45a to 45h (see FIG. 1), and the end (output end) side opposite to the optical amplifiers 45a to 45h is on the substrate 80. It is installed. The input side optical fibers 90 a to 90 h may be mounted in, for example, a V groove provided on the substrate 80. The distance t between the optical axes of adjacent input side optical fibers (for example, the input side optical fibers 90g and 90h) is, for example, about 250 μm.

  The optical filter unit 100 includes eight optical filters 100a to 100h. The optical filters 100a to 100h are disposed on the substrate 80 on the optical path of the signal light output from the input side optical fibers 90a to 90h. The optical filter unit 100 may be a single plate-like body in which eight optical filters 100a to 100h are arranged in the arrangement direction of the input side optical fibers 90a to 90h.

  Each of the optical filters 100a to 100h has a reflection characteristic of reflecting a part of signal light in the wavelength range of 1520 nm to 1610 nm and transmitting the other. The optical filters 100a to 100h are, for example, dielectric multilayer filters. The optical filters 100a to 100h desirably have similar reflection characteristics in the wavelength range of 1520 nm to 1610 nm.

Each of the output side optical fibers 110a to 110h transmits signal light having any one of the wavelengths λ _{1 to} λ ₈ . The output side optical fibers 110a to 110h are arranged in parallel so as to correspond to the input side optical fibers 90a to 90h.

  One ends of the output side optical fibers 110a to 110h are connected to the variable attenuators 46a to 46h (see FIG. 1), and the end (input end) side opposite to the variable attenuators 46a to 46h is mounted on the substrate 80. Yes. On the substrate 80, the output side optical fibers 110 a to 110 h are disposed on the side opposite to the input side optical fibers 90 a to 90 h when viewed from the optical filter unit 100. The output side optical fibers 110a to 110h may be mounted in, for example, a V groove provided on the substrate 80.

  The input side optical fibers 90a to 90h, the output side optical fibers 110a to 110h, and the optical filters 100a to 100h are fixed to the substrate 80 by a resin (medium) 130. As a material of the resin 130, for example, an acrylic resin having translucency in a wavelength range of 1520 nm to 1610 nm is preferable.

  The light receiving element array 120 is disposed on the substrate 80. The resin 130 has a function of fixing the light receiving element array 120 as well as a function of fixing the input side optical fibers 90a to 90h, the output side optical fibers 110a to 110h, and the optical filters 100a to 100h. The light receiving element array 120 includes eight light receiving elements 120a to 120h.

  The light receiving elements 120a to 120h are, for example, photodiodes. In the light receiving element array 120, the eight light receiving elements 120a to 120h are arranged so that one light receiving element corresponds to one set (one channel) of the input side optical fiber, the optical filter, and the output side optical fiber. Yes. Each of the light receiving elements 120a to 120h has a light receiving surface on the substrate 80 side or the side facing the optical filters 100a to 100h, and the surface opposite to the substrate 80 has eight electrodes 140a to 140a formed on the resin 130. It is electrically connected to 140h via a lead wire or the like.

  As described above, the optical power monitoring device 42 includes the optical filters 100a to 100h, the output side optical fibers 110a to 110h, and the light receiving elements 120a to 120h corresponding to the input side optical fibers 90a to 90h. ing. In other words, the optical power monitoring device 42 is configured by arranging eight sets of an input side optical fiber, an optical filter, an output side optical fiber, and a light receiving element in parallel.

  Next, among the above eight sets, for example, the configuration of the optical power monitoring device 42 will be described in more detail using a set of the input side optical fiber 90a, the optical filter 100a, the output side optical fiber 110a, and the light receiving element 120a as an example.

  FIG. 3 is a schematic diagram of a cross-sectional configuration along the line III-III.

  The input side optical fiber 90 a includes a core region 91 and a cladding region 92 that surrounds the core region 91. The core diameter of the core region 91 at the output end 93 of the input side optical fiber 90a is preferably enlarged. By increasing the core diameter, the NA is reduced, and the spread of the signal light output from the output end 93 is suppressed. Therefore, there is little need to use a lens to suppress the spread of signal light. The core diameter is expanded by, for example, thermal diffusion or ultraviolet irradiation.

  The output side optical fiber 110a has a core region 111 and a clad region 112 like the input side optical fiber 90a. The core diameter of the core region 111 at the input end 113 of the output side optical fiber 110a is preferably enlarged in the same manner as the output end 93 of the input side optical fiber 90a. Loss when the transmitted signal light that has passed through the optical filter 100a enters the output-side optical fiber 110a is reduced. The core diameter of the input end 113 of the output side optical fiber 110a is more preferably substantially equal to the core diameter of the input side optical fiber 90a. This is because the loss when the transmitted signal light is input to the output side optical fiber 110a is further reduced.

  The input side optical fiber 90a and the output side optical fiber 110a are disposed on the substrate 80 with the optical filter 100a interposed therebetween. In other words, the optical filter 100a is disposed between the pair of input side optical fibers 90a and the output side optical fiber 110a. The output end 93 of the input side optical fiber 90a and the input end 113 of the output side optical fiber 110a are separated by a predetermined distance (for example, several tens of μm).

  The input-side optical fiber 90a and the output-side optical fiber 110a may be arranged such that two different optical fibers are opposed to each other, but it is preferable that they are formed as follows. That is, an optical fiber is disposed on the substrate 80. And an optical fiber is cut | disconnected with a dicing saw etc., and it is set as a pair of input side optical fiber 90a and the output side optical fiber 110a. When the optical fiber is cut, the optical filter 100a is cut between the input side optical fiber 90a and the output side optical fiber 110a. In this case, it is not necessary to match the optical axes of the input-side optical fiber 90a and the output-side optical fiber 110a as compared to the case where two different optical fibers are arranged facing each other.

  The substrate 80 between the output end 93 of the input side optical fiber 90a and the input end 113 of the output side optical fiber 110a is provided with a groove 81 for placing the optical filter 100a. The groove 81 extends, for example, in the arrangement direction of the input side optical fibers 90a to 90h, that is, in the direction perpendicular to the paper surface.

  The optical filter 100a is disposed on the groove 81 between the input side optical fiber 90a and the output side optical fiber 110a. The optical filter 100a is located on the optical path of the signal light output from the output end 93 of the input side optical fiber 90a. The optical filter 100a is inclined with respect to the optical axis of the input side optical fiber 90a. The inclination angle α / 2 formed by the normal line of the optical filter 100a and the optical axis of the input side optical fiber 90a is, for example, 22.5 degrees. However, this is a case where the distance between the incident side optical fiber 90a and the optical filter 100a is 100 μm.

  Here, the inclination angle α / 2 is the energy of the reflected signal light incident on the input side optical fiber 90a so as to pass through the input side optical fiber 90a obliquely out of the energy of the reflected signal light on the surface of the optical filter 100a. The angle is 20% or less. In other words, the inclination angle α / 2 is the energy of the reflected signal light distributed on the plane orthogonal to the principal ray of the reflected signal light at the position where the input side optical fiber 90a and the reflected signal light intersect. The angle at which the ratio of the energy overlapping the input side optical fiber 90a is 20% or less.

  The input side optical fiber 90 a and the output side optical fiber 110 a are covered with a resin 130 and fixed to the substrate 80. A resin 130 is also provided between the output end 93 of the input side optical fiber 90 a and the input end 113 of the output side optical fiber 110 a, and the optical filter 100 a is fixed by the resin 130.

  The light receiving element array 120 is disposed above the input side optical fiber 90a and on the resin 130 so that the reflected signal light from the optical filter 100a is incident on the light receiving element 120a.

With the above configuration, the signal light output from the output end 93 of the input side optical fiber 90a propagates through the resin 130 and reaches the optical filter 100a. The signal light transmitted by the input-side optical fiber 90a is signal light having any one of the wavelengths λ _{1 to} λ ₈ (for example, wavelength λ ₁ ) divided by the duplexer 41. A part of the signal light is reflected by the optical filter 100a.

  The reflected signal light reflected by the optical filter 100a propagates through the resin 130 and is received by the light receiving element 120a. Thereby, the power of the reflected signal light is detected by the light receiving element 120a. The power of the reflected signal light detected by the light receiving element 120a is extracted to the outside through the electrode 140a (see FIG. 2). Here, since the reflectance of the optical filter 100a is known, the power of the signal light is calculated from the power of the reflected signal light.

  In addition, the transmitted signal light transmitted through the optical filter 100a out of the signal light output from the output end 93 propagates through the resin 130 and is input from the input end 113 to the output side optical fiber 110a.

The transmitted signal light input to the output side optical fiber 110a is input to the variable attenuator 46a. Then, the power of the signal light is adjusted so that the power of the signal light having the wavelengths λ _{1 to} λ ₈ is constant. Then, it is combined with the transmitted signal light from the other output-side optical fibers 110b to 110h by the multiplexer 43 and is output to the optical fiber 73 shown in FIG. 1 as signal light having multiple wavelengths λ _{1 to} λ ₈ .

  As described above, the optical filter 100a is inclined such that the inclination angle between the normal line of the optical filter 100a and the optical axis of the input side optical fiber 90a is α / 2. In this case, the energy of the reflected signal light on the surface of the optical filter 100a is incident again on the input side optical fiber 90a so as to pass through a part of the input side optical fiber 90a (in other words, the input side optical fiber 90a. The ratio of the energy of the reflected signal light (which intersects) is 20% or less. Therefore, the reflected signal light is suppressed from being scattered and diffused by the surface roughness of the output end 93 as compared with the case where all the reflected signal light intersects the input side optical fiber 90a and then enters the light receiving element 120a. Yes.

  In addition, it is preferable that the ratio of the energy of the reflected signal light that intersects the input-side optical fiber 90a in the reflected signal light energy is 5% or less. This is because the diffusion of reflected signal light caused by the surface roughness of the output end 93 is further suppressed. It is further preferable that the reflected signal light does not intersect the input side optical fiber 90a. This is because the reflected signal light is not diffused by the surface roughness of the output end 93.

  Further, the optical path of the signal light between the input side optical fiber 90a and the optical filter 100a, the optical path of the reflected signal light between the optical filter 100a and the light receiving element 120a, and between the optical filter 100a and the output side optical fiber 110a. A resin 130 is provided in the optical path of the transmitted signal light.

  The refractive index of the resin 130 is closer to the refractive index of the core region 91 of the input side optical fiber 90a than the refractive index of air. Therefore, it is possible to suppress the reflected signal light from being scattered by the surface roughness of the output end 93 as compared with the case where the resin 130 is not provided.

  The set of the input side optical fiber 90a, the light receiving element 120a, the output side optical fiber 110a, and the optical filter 100a provided on the substrate 80 shown in FIG. 3 has been described above. However, the other groups have the same configuration, and the reflected signal light from the optical filter is suppressed from being diffused by the surface roughness of the output end of the input side optical fiber.

  Therefore, as in the optical power monitor device 42 shown in FIG. 2, even if the sets of the input side optical fiber, the optical filter, the output side optical fiber, and the light receiving element are arranged in parallel at equal intervals, Crosstalk in which one set of reflected signal light enters the other set of light receiving elements is less likely to occur.

Therefore, the power of the signal light having the wavelengths λ _{1 to} λ ₈ in the optical transmission system 1 of FIG. 1 can be measured more accurately. Since crosstalk is unlikely to occur, the interval between adjacent sets can be shortened, and the optical power monitoring device 42 can be made compact.

  Further, in the optical power monitor device 42, the optical filter unit 100 is not moved, so that the distance between the output ends of the input side optical fibers 90a to 90h and the input ends of the output side optical fibers 110a to 110h may be several tens of μm. Therefore, it is not necessary to use a lens in order to reduce the loss when the transmitted signal light enters the input end 113 of the output side optical fibers 110a to 110h. Therefore, it is possible to reduce the cost of the optical power monitor device 42 as compared with the case where a lens is used.

  In addition, if the core diameters of the core regions 91 and 111 at the output end 93 of the input side optical fibers 90a to 90h and the input end 113 of the output side optical fibers 110a to 110h are enlarged, the transmitted signal light is transmitted to the input end 113. This is preferable because the loss upon incidence is further reduced.

  Further, when the core diameter is increased, the output end 93 of the input side optical fibers 90a to 90h and the input end 113 of the output side optical fibers 110a to 110h can be further separated. In this case, the optical filters 100a to 100h (in other words, the optical filter unit 100) are tilted with respect to the optical axes of the input side optical fibers 90a to 90h. Therefore, it is possible to reduce the portion of the reflected signal light from each of the optical filters 100a to 100h that intersects with the input side optical fibers 90a to 90h.

In the optical transmission system 1, the light output from the optical power monitor device 42 is input to the multiplexer 43 through the variable attenuators 46 a to 46 h. The variable attenuators 46 a to 46 h adjust the power of the signal light of the wavelengths λ _{1 to} λ ₈ according to the monitoring result of the optical power monitoring device 42, and input the signal light to the multiplexer 43 with the power of the signal light constant. doing. As described above, in the optical power monitor device 42, the signal lights having the wavelengths λ _{1 to} λ ₈ can be measured more accurately. Therefore, in the optical transmission system 1, it is possible to transmit the signal light in which the powers of the signal lights having the wavelengths λ _{1 to} λ ₈ are more uniform.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. For example, the optical transmission system may have an optical transmission path for transmitting signal light having a wavelength range of 1520 nm to 1610 nm, and the optical power monitoring device 42 may be provided in the optical transmission path.

  Further, the optical power monitoring device 42 has a configuration in which eight sets of an input side optical fiber, an optical filter, an output side optical fiber, and a light receiving element are arranged in parallel, but is not limited to eight sets. A plurality of sets may be provided according to the number of signal lights to be measured, or one set may be used.

  Furthermore, the optical path of the signal light between the input side optical fiber and the optical filter, the optical path of the reflected signal light between the optical filter and the light receiving element, and the optical path of the transmitted signal light between the optical filter and the output side optical fiber Although the resin 130 is provided in, the resin may not be provided.

  In the case where no resin is provided, for example, it is preferable to provide a medium having translucency for light in the wavelength range of 1520 nm to 1610 nm in each optical path, but it may be a space.

  Furthermore, the medium may be provided only in the optical path of the signal light between the input side optical fiber and the optical filter and in the optical path of the transmitted signal light between the optical filter and the output side optical fiber.

  Furthermore, although the first optical waveguide and the second optical waveguide are optical fibers, they may be planar optical waveguides formed on a substrate. In this case, for example, a groove may be provided so as to intersect the optical axis of the planar optical waveguide, and one of the grooves may be a first optical waveguide and the other may be a second optical waveguide. The first optical waveguide and the second optical waveguide only have to be able to transmit light having a wavelength range of 1520 nm to 1610 nm.

It is a schematic diagram which shows the structure of one Embodiment of the optical transmission system which concerns on this invention. It is a perspective view of the optical power monitor apparatus of FIG. It is a schematic diagram which shows the cross-sectional structure along the III-III line of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Optical transmission system, 40 ... Optical power monitor part, 42, 45 ... Optical power monitor apparatus, 80 ... Board | substrate, 81 ... Groove, 90a-90h ... Input side optical fiber (1st optical waveguide), 91 ... Core area | region , 92 ... cladding region, 93 ... output end, 100 ... optical filter part, 100a to 100h ... optical filter, 110a-110h ... output side optical fiber (second optical waveguide), 111 ... core region, 112 ... cladding region, 113 ... Input end, 120 ... Light receiving element array, 120a to 120h ... Light receiving element, 130 ... Resin (medium).

Claims (8)

A first optical waveguide that transmits signal light of any wavelength in the wavelength range of 1520 to 1610 nm;
An optical filter that is disposed on the optical path of the signal light output from the output end of the first optical waveguide and reflects a part of the signal light and transmits the other;
A second optical waveguide that transmits the transmitted signal light transmitted from the input end through the optical filter of the signal light;
A light receiving element for detecting the power of the reflected signal light reflected by the optical filter out of the signal light,
The ratio of the reflected signal light energy that intersects the first optical waveguide out of the reflected signal light energy is 20% or less.   2. The optical power monitor device according to claim 1, wherein the ratio of the reflected signal light energy that intersects the first optical waveguide out of the reflected signal light energy is 5% or less. 3.   The optical power monitor apparatus according to claim 1, wherein the reflected signal light does not intersect the first optical waveguide.   A medium is provided in the optical path of the signal light between the first optical waveguide and the optical filter and in the optical path of the transmitted signal light between the optical filter and the second optical waveguide. The optical power monitor apparatus according to claim 1.   The optical path of the signal light between the first optical waveguide and the optical filter, the optical path of the reflected signal light between the optical filter and the light receiving element, and the optical filter and the second optical waveguide 2. The optical power monitor device according to claim 1, wherein a medium is provided in an optical path of the transmitted signal light between the first and second optical signals.   The optical power monitoring apparatus according to claim 1, wherein a plurality of sets of the first optical waveguide, the optical filter, the second optical waveguide, and the light receiving element are provided in parallel.   The optical power monitoring apparatus according to claim 1, wherein core diameters at the output end of the first optical waveguide and the input end of the second optical waveguide are enlarged. An optical transmission system having an optical transmission path for transmitting signal light of any wavelength in the wavelength range of 1520 to 1610 nm,
An optical transmission system, wherein the optical power monitoring device according to claim 1 is provided in the optical transmission path.

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