JP2008176145A - Planar light wave circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planar light wave circuit in which a high reflective attenuation can be obtained in an incident port, and deterioration in characteristics of a signal light can be avoided without necessity of large circuit size. <P>SOLUTION: In a planar light wave circuit 1, optical waveguides including two output waveguides including an output waveguide 4 that is connected to an exit port 3 and an idle waveguide 5 that is unconnected to a waveguide end face 2a on the emitting port side are formed on a silicon substrate 2. This planar light wave circuit 1 includes a groove 10 that intersects the idle waveguide 5 at an angle θ less than 90 degrees (θ<90°), wherein the idle waveguide 5 is terminated at the intersection 11 with the groove 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a planar lightwave circuit in which an optical waveguide is formed on a substrate.

  FIG. 11 shows a conventional planar lightwave circuit configured as a PLC type variable optical attenuator. This planar lightwave circuit includes an incident port 100, an input waveguide 101 connected to the incident port 100, an input waveguide 102 not connected to the incident port 100, input waveguides 101 and 102, and output waveguides 103 and 104. 2 × 2 Mach-Zehnder interferometer circuit 105 and an output port 106 connected to each other. The output waveguide 103 is connected to the output port 106, but the output waveguide 104 is not connected to the output port 106. In the following description, an output waveguide whose end is not connected to the waveguide end surface 107a on the output port side of the substrate 107 having the output port 106, such as the output waveguide 104, is referred to as an “idle waveguide”. .

FIG. 13 shows a conventional planar lightwave circuit configured as a PLC type variable optical attenuator array. The planar lightwave circuit includes a plurality of incident ports 100 _{1 to} 100 _n , a plurality of input waveguides 101 _{1 to} 101 _n connected to the respective incident ports, and a plurality of input waveguides 102 ₁ to 102 _n not connected to the respective incident ports. 102 _n and 2 × 2 Mach-Zehnder interferometer circuits 105 ₁ ... Connected between the output waveguides 103 _{1 to} 103 _n , 104 ₁ ... And output ports 106 _{1 to} 106 _n. . The output waveguides 104 ₁ ... Are idle waveguides.

Japanese Patent Application Laid-Open No. 11-142667 proposes a technique for processing near the output port to prevent interference.
JP 11-142667 A

  By the way, in the conventional PLC type variable optical attenuator that does not process the idle waveguide 104 shown in FIG. 11, light propagating through the idle waveguide 104 is radiated to the clad layer of the substrate 107 and becomes stray light, and the stray light becomes a signal. There is a problem that the coherent interference with light causes the characteristics of signal light to deteriorate. In this case, the signal light from the emission port 106 exhibits wavelength characteristics as shown in FIG. 12, for example, although it is designed not to have wavelength dependency. That is, the signal light from the emission port 106 is deteriorated in characteristics due to the influence of interference.

Further, in the conventional planar lightwave circuit shown in FIG. 13, since the idle waveguides 104 ₁ ... Exist on the extension of the exit port group composed of the exit ports 106 _{1 to} 106 _n, they are particularly susceptible to stray light. Patent Document 1 proposes a technique for performing processing near the emission port to prevent interference. However, with this configuration, there is a problem in that a bypass portion of the waveguide is required, resulting in an increase in circuit size.

  The present invention has been made in view of such conventional problems, and its purpose is to obtain a high return loss at the incident port, avoiding deterioration of signal light characteristics without causing an increase in circuit size. An object of the present invention is to provide a planar lightwave circuit that can be used.

  In order to solve the above-described problem, the planar lightwave circuit according to the first aspect of the present invention includes at least two output waveguides, ie, an output waveguide connected to the output port and an idle waveguide not connected to the waveguide end face on the output port side. In a planar lightwave circuit in which an optical waveguide including an output waveguide is formed on a substrate, the optical waveguide includes a groove that intersects the idle waveguide at an angle of less than 90 degrees, and the idle waveguide is terminated at an intersection with the groove. It is a summary.

  According to this aspect, of the two output waveguides, the idle waveguide that is not connected to the waveguide end face on the output port side of the substrate is terminated at the intersection with the groove intersecting at an angle of less than 90 degrees. The light propagating through the waveguide does not reach the exit port to which the output waveguide is connected. As a result, coherent interference between the signal light at the exit port and the light propagated through the idle waveguide does not occur, and the characteristic deterioration of the signal light can be avoided.

  Further, since the idle waveguide and the groove intersect at an angle of less than 90 degrees, generation of reflected return light at the intersection can be suppressed, and a high return loss can be obtained at the incident port. Further, since the groove can be formed in a small area of several hundred μm square, it is possible to avoid the deterioration of the signal light characteristics without increasing the circuit size. Thereby, it is possible to avoid the deterioration of the characteristics of the signal light even in the planar lightwave circuit in which the optical waveguides are close to each other as arranged in an array.

  The shape of the groove is, for example, a parallelogram, a non-parallelogram or the like, and the shape is not limited. The “planar lightwave circuit” here refers to a PLC (Planer Lightwave Circuit) in which an optical waveguide is formed on a substrate such as a silicon substrate by combining optical fiber manufacturing technology and semiconductor microfabrication technology.

  In a planar lightwave circuit according to another aspect of the present invention, the idle waveguide at the intersection is a curved waveguide so that the intersection angle between the idle waveguide and the groove is small and the cross-sectional area of the intersection is large. The summary is as follows. According to this aspect, since the idle waveguide at the intersection is a curved waveguide, the generation of reflected return light at the intersection can be further suppressed, and a higher return loss can be obtained at the incident port.

  The gist of the planar lightwave circuit according to another aspect of the present invention is that the idle waveguide has a curved waveguide for propagating light emission immediately before the intersection with the groove. According to this aspect, a part of the light propagating through the idle waveguide is radiated and attenuated by the curved waveguide for propagating light emission and reaches the intersection with the groove, so that the reflected return light is generated at the intersection. Can be further suppressed, and a higher return loss can be obtained at the incident port.

  The gist of a planar lightwave circuit according to another aspect of the present invention is that a material that absorbs propagating light is injected into the groove. According to this aspect, since the light that has propagated through the idle waveguide and reached the intersection is absorbed and attenuated by the material that absorbs the propagation light injected into the groove, the generation of reflected return light at the intersection is further reduced. Therefore, a higher return loss can be obtained at the incident port. The material that absorbs the propagation light is, for example, resin.

  In the planar lightwave circuit according to another aspect of the present invention, the optical waveguide includes two incident ports, two input waveguides respectively connected to the two incident ports, the two input waveguides, and the 2 A 2 × 2 Mach-Zehnder interferometer circuit connected between two output waveguides, and one waveguide branched from the Mach-Zehnder interferometer circuit is an output waveguide connected to the output port; The other waveguide is the idle waveguide, and is summarized as a PLC type optical branching coupler. According to this aspect, in the planar lightwave circuit configured as a PLC type optical branching coupler, it is possible to avoid the deterioration of the characteristics of the signal light without increasing the circuit size.

  The planar lightwave circuit according to another aspect of the present invention is connected to an incident port group composed of a plurality of incident ports each including two incident ports, and to each of the two incident ports in each of the incident port groups. An input waveguide group consisting of a plurality of sets of input waveguides, each having two sets of input waveguides, and an output waveguide group consisting of a plurality of sets of output waveguides, each consisting of the two output waveguides A Mach-Zehnder interferometer circuit group composed of a plurality of 2 × 2 Mach-Zehnder interferometer circuits connected between the input waveguide group and the output waveguide group, respectively, and an output guide of each set of the output waveguide groups. And an output port group composed of a plurality of output ports connected to one output waveguide of the waveguide, respectively, and is configured as a PLC type optical branching coupler array.

  In a planar lightwave circuit configured as a PLC-type optical branching coupler array, there is an idle waveguide of each set of the exit port group on the extension of the exit port group, so that light propagating through each idle waveguide is clad on the substrate. There is a problem in that stray light is emitted to the layer, and the stray light causes coherent interference with the signal light to deteriorate the characteristics of the signal light. On the other hand, according to this aspect, since each idle waveguide and the groove intersect at an angle of less than 90 degrees, an increase in circuit size in a planar lightwave circuit configured as a PLC type optical branching coupler array Therefore, it is possible to avoid the deterioration of signal light characteristics.

  In the planar lightwave circuit according to another aspect of the present invention, the optical waveguide has two input waveguides: one incident port, an input waveguide connected to the incident port, and an input waveguide not connected to the incident port. And a 2 × 2 Mach-Zehnder interferometer circuit connected between the two input waveguides and the two output waveguides, and a phase in at least one of the two waveguides of the Mach-Zehnder interferometer circuit The gist is that an adjuster is provided and configured as a PLC type variable optical attenuator. According to this aspect, in the planar lightwave circuit configured as a PLC type variable optical attenuator, it is possible to avoid the deterioration of the characteristics of the signal light without increasing the circuit size.

  In the planar lightwave circuit according to another aspect of the present invention, the optical waveguide includes one incident port, an input waveguide connected to the incident port, the input waveguide, and the two output waveguides. A 1 × 2 Mach-Zehnder interferometer circuit connected in between, and a phase adjuster is provided in at least one of the two waveguides of the Mach-Zehnder interferometer circuit, and is configured as a PLC type variable optical attenuator. It is a summary. According to this aspect, in the planar lightwave circuit configured as a PLC type variable optical attenuator, it is possible to avoid the deterioration of the characteristics of the signal light without increasing the circuit size.

  A planar lightwave circuit according to another aspect of the present invention includes an incident port group including a plurality of incident ports, an input waveguide connected to each incident port of the incident port group, and an input waveguide not connected to the incident port. An input waveguide group consisting of a plurality of sets of input waveguides, each having two sets of input waveguides, and an output waveguide group consisting of a plurality of sets of output waveguides, each consisting of the two output waveguides, A Mach-Zehnder interferometer circuit group composed of a plurality of 2 × 2 Mach-Zehnder interferometer circuits connected between the input waveguide group and the output waveguide group, respectively, and an output waveguide of each set of the output waveguide groups An output port group composed of a plurality of output ports respectively connected to one of the output waveguides, and a phase adjuster in each of at least one of the two waveguides of the plurality of Mach-Zehnder interferometer circuits Vignetting is, the gist that it is configured as a PLC-type variable optical attenuator array. According to this aspect, in the planar lightwave circuit configured as a PLC-type variable optical attenuator array, it is possible to avoid deterioration of signal light characteristics without increasing the circuit size.

  A planar lightwave circuit according to another aspect of the present invention includes an incident port group including a plurality of incident ports, an input waveguide group including input waveguides connected to the respective incident ports of the incident port group, and the 2 An output waveguide group composed of a plurality of sets of output waveguides each having one output waveguide, and a plurality of 1 × 2 Mach-Zehnder interferences respectively connected between the input waveguide group and the output waveguide group A Mach-Zehnder interferometer circuit group consisting of meter circuits, and an output port group consisting of a plurality of output ports respectively connected to one output waveguide of each set of output waveguides of the output waveguide group. The gist is that a phase adjuster is provided in at least one of the two waveguides of the Mach-Zehnder interferometer circuit, and is configured as a PLC type variable optical attenuator array. According to this aspect, in the planar lightwave circuit configured as a PLC-type variable optical attenuator array, it is possible to avoid deterioration of signal light characteristics without increasing the circuit size.

  In the planar lightwave circuit according to another aspect of the present invention, the Mach-Zehnder interferometer circuit group includes two 2 × 2 Mach-Zehnder interferometer circuits vertically connected in two stages, and the Mach-Zehnder interferometer circuit group. The idle waveguide branched from the preceding Mach-Zehnder interferometer circuit of the two Mach-Zehnder interferometer circuits and the idle waveguide branched from the subsequent 2 × 2 Mach-Zehnder interferometer circuit It is terminated at the intersection with the same groove, and is summarized as a PLC type two-stage variable optical attenuator array. According to this aspect, in a planar lightwave circuit configured as a PLC type two-stage optical branching coupler array, it is possible to avoid deterioration of signal light characteristics without causing an increase in circuit size.

  In the planar lightwave circuit according to another aspect of the present invention, the optical waveguide includes two incident ports, two input waveguides respectively connected to the two incident ports, the two input waveguides, and the 2 A 2 × 2 Mach-Zehnder interferometer circuit connected between two output waveguides, and one waveguide branched from the Mach-Zehnder interferometer circuit is an output waveguide connected to the output port; The other waveguide is the idle waveguide, and is summarized as a PLC type 2 × 1 optical switch. According to this aspect, in the planar lightwave circuit configured as a PLC type 2 × 1 optical switch, it is possible to avoid deterioration of the characteristics of signal light without increasing the circuit size.

  The planar lightwave circuit according to another aspect of the present invention is connected to an incident port group composed of a plurality of incident ports each including two incident ports, and to each of the two incident ports in each of the incident port groups. An input waveguide group consisting of a plurality of sets of input waveguides, each having two sets of input waveguides, and an output waveguide group consisting of a plurality of sets of output waveguides, each consisting of the two output waveguides A Mach-Zehnder interferometer circuit group composed of a plurality of 2 × 2 Mach-Zehnder interferometer circuits connected between the input waveguide group and the output waveguide group, respectively, and an output guide of each set of the output waveguide groups. And an output port group including a plurality of output ports connected to one output waveguide of the waveguide, respectively, and is configured as a PLC type optical switch array. According to this aspect, in the planar lightwave circuit configured as the PLC type optical switch array, it is possible to avoid the deterioration of the characteristics of the signal light without increasing the circuit size.

  According to the present invention, since the idle waveguide that is not connected to the waveguide end face on the exit port side of the substrate is terminated at the intersection with the groove that intersects at an angle of less than 90 degrees, the light propagated through the idle waveguide 5 is It does not reach the exit port to which the output waveguide is connected. As a result, coherent interference between the signal light at the exit port and the light propagated through the idle waveguide does not occur, and the characteristic deterioration of the signal light can be avoided. Further, since the idle waveguide and the groove intersect at an angle of less than 90 degrees, generation of reflected return light at the intersection can be suppressed, and a high return loss can be obtained at the incident port. Further, since the groove can be formed in a small area of several hundred μm square, it is possible to avoid the deterioration of the signal light characteristics without increasing the circuit size.

  In this way, the light propagating through the idle waveguide is radiated to the clad to become stray light, and the stray light causes coherent interference with the signal light, thereby degrading the characteristics of the signal light, without increasing the circuit size. Can be solved.

  Embodiments of a planar lightwave circuit embodying the present invention will be described with reference to the drawings. In the description of each embodiment, similar parts are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
A planar lightwave circuit according to a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a schematic configuration of a planar lightwave circuit according to the first embodiment. FIG. 2 is an explanatory diagram showing the main part of the planar lightwave circuit, and FIG. 3 is a graph showing the wavelength characteristics of the signal light from the emission port.

  In the planar lightwave circuit 1 shown in FIG. 1, an optical waveguide including two output waveguides, that is, an output waveguide 4 connected to the output port 3 and an idle waveguide 5 not connected to the waveguide end surface 2a on the output port side is a silicon substrate. (Substrate) 2 is formed. As shown in FIGS. 1 and 2, the planar lightwave circuit 1 includes a groove 10 that intersects with an idle waveguide 5 at an angle θ of less than 90 degrees (θ <90 °), and the idle waveguide 5 is a groove. It is in the point terminated at the intersection 11 with 10. The shape (planar shape) of the groove 10 is a parallelogram.

  Specifically, the planar lightwave circuit 1 is configured as a PLC type optical branching coupler. In the planar lightwave circuit 1, the optical waveguide formed on the silicon substrate 2 includes two incident ports 6 and 7 and two input waveguides 8 and 9 connected to the two incident ports 6 and 7, respectively. A 2 × 2 Mach-Zehnder interferometer circuit 20 connected between the two input waveguides 8 and 9 and the two output waveguides 4 and 5 is provided.

The Mach-Zehnder interferometer circuit 20 includes two directional couplers 15 and 16 and two waveguides 17 and 18 connected between the two directional couplers 15 and 16. One waveguide branched from the Mach-Zehnder interferometer circuit 20 is the output waveguide 4, and the other waveguide is the idle waveguide 5.
Each optical waveguide formed in a planar lightwave circuit (PLC) 1 having such a configuration is a quartz glass optical waveguide formed on a silicon substrate 2 by combining optical fiber manufacturing technology and semiconductor microfabrication technology. It is. Each optical waveguide may be another one such as a Si waveguide.

For example, the planar lightwave circuit is manufactured by the following method. Glass particles that form the lower clad layer and core layer are deposited on the silicon substrate 2 by flame direct deposition (FHD), which is an application of optical fiber manufacturing technology.
The glass film is melted and transparentized by heating. Thereafter, a desired waveguide pattern is formed by photolithography and reactive ion etching (RIE), which are semiconductor integrated circuit manufacturing techniques, and an upper cladding is formed again by the FHD method.

  According to 1st Embodiment which has the above structure, there exist the following effects.

  Of the two output waveguides 4 and 5, the idle waveguide 5 that is not connected to the waveguide end face 2a on the output port side of the substrate 2 is terminated at the intersection 11 with the groove 10 that intersects at an angle of less than 90 degrees. The light propagated through the idle waveguide 5 does not reach the exit port 3 to which the output waveguide 4 is connected. Thereby, coherent interference between the signal light at the exit port 3 and the light propagated through the idle waveguide 5 does not occur, and the characteristic deterioration of the signal light can be avoided.

  O Since the idle waveguide 5 and the groove 10 intersect at an angle of less than 90 degrees, generation of reflected return light at the intersection 11 can be suppressed, and a high return loss can be obtained at the incident port.

  O Since the groove 10 can be formed in a small area of several hundred μm square, it is possible to avoid deterioration of signal light characteristics without increasing the circuit size.

  As described above, according to the present embodiment, the signal light from the emission port 3 does not have wavelength characteristics due to interference as shown in FIG. In order to compare with this characteristic, FIG. 12 shows the characteristic in the case of manufacturing in the above conventional example in which no termination treatment is provided. Comparing both FIG. 12 and FIG. 13, it can be seen that according to the present embodiment, the wavelength characteristics due to interference are clearly improved. The return loss at the incident ports 6 and 7 was 40 dB or more. That is, according to the present embodiment, the above-described characteristic deterioration of the signal light can be avoided and the generation of reflected return light can be suppressed.

  In the planar lightwave circuit 1 configured as a PLC type optical branching coupler, it is possible to avoid the deterioration of the characteristics of the signal light without increasing the circuit size.

(Second Embodiment)
FIG. 4 shows a main part of the planar lightwave circuit according to the second embodiment.

  The planar lightwave circuit 1 shown in FIG. 4 is characterized in that, in the planar lightwave circuit 1 according to the first embodiment configured as a PLC type optical branching coupler, the crossing angle (the angle θ described above) between the idle waveguide 5 and the groove 10. ) And the cross-sectional area of the intersecting portion 11 is increased, and the idle waveguide 5 in the intersecting portion 11 is a curved waveguide 5a. Other configurations are the same as those in the first embodiment.

  In the present embodiment, the intersection angle between the line extending from the straight waveguide of the idle waveguide 5 and the end face of the groove 10 is 15 °, and the bending angle by the curved waveguide 5a is, for example, 3 ° (not limited to 3 °). ) And the shape of the groove 10 was a parallelogram. Note that the bending angle of the curved waveguide 5a is not limited to 3 °.

  According to 2nd Embodiment which has the above structure, in addition to the effect which the said 1st Embodiment show | plays, there exist the following effects.

  O By making the idle waveguide 5 at the intersecting portion 11 the curved waveguide 5a, the generation of reflected return light at the intersecting portion 11 can be further suppressed, and a higher return loss can be obtained at the incident ports 6 and 7.

(Third embodiment)
FIG. 5 shows a main part of the planar lightwave circuit according to the third embodiment.

  The planar lightwave circuit 1 shown in FIG. 5 is characterized in that, in the planar lightwave circuit 1 according to the first embodiment configured as a PLC-type optical branching coupler, a curve guide for propagating light radiation is provided immediately before the intersection 11 with the groove 10. This is in the point having the waveguide 5b. Other configurations are the same as those in the first embodiment.

    According to 3rd Embodiment which has the above structure, in addition to the effect which the said 1st Embodiment show | plays, there exist the following effects.

  A part of the light propagating through the idle waveguide 5 is radiated and attenuated by the propagating light radiation curved waveguide 5b and reaches the intersection 11 with the groove 10, so that reflected return light is generated at the intersection 11. Can be further suppressed, and a higher return loss can be obtained at the incident port.

(Fourth embodiment)
FIG. 6 shows a main part of a planar lightwave circuit according to the fourth embodiment.

  The planar lightwave circuit 1 shown in FIG. 6 is characterized in that a material 12 that absorbs propagating light is injected into the groove 10 in the planar lightwave circuit 1 according to the first embodiment configured as a PLC type optical branching coupler. There is in point. Other configurations are the same as those in the first embodiment. The material 12 that absorbs propagating light is, for example, resin.

  According to 4th Embodiment which has the above structure, in addition to the effect which the said 1st Embodiment show | plays, there exist the following effects.

  According to this aspect, the light that has propagated through the idle waveguide 5 and reached the intersection 11 is absorbed and attenuated by the material 12 that absorbs the propagation light injected into the groove 10, so that reflection at the intersection 11 is performed. The generation of return light can be further suppressed, and a higher return loss can be obtained at the incident ports 6 and 7.

(Fifth embodiment)
FIG. 7 shows a schematic configuration of a planar lightwave circuit according to the fifth embodiment of the present invention.

  The planar lightwave circuit 1 shown in FIG. 7 includes an end face on the intersection 11 side with the idle waveguide 5 in place of the parallelogram groove 10 in the first embodiment configured as a PLC type optical branching coupler. A groove 10A having a quadrangular shape with opposite end faces being non-parallel is used. Other configurations are the same as those in the first embodiment. Here, the crossing angle (angle θ) between the idle waveguide 5 and the end face of the groove 10 is 15 °. However, the angle θ is not limited to 15 ° and may be less than 90 degrees.

  According to 5th Embodiment which has the above structure, in addition to the effect which the said 1st Embodiment show | plays, there exist the following effects.

  ○ Since the shape of the groove 10A is a quadrangular shape in which the end surface facing the crossing portion 11 side with the idle waveguide 5 is non-parallel, reflection return due to reflection inside the groove 10A is less likely to occur, The generation of reflected return light at the section 11 can be further suppressed, and higher reflection attenuation can be obtained at the incident ports 6 and 7. The return loss at the incident ports 6 and 7 was 40 dB or more. That is, according to the present embodiment, the above-described characteristic deterioration of the signal light can be avoided and the generation of reflected return light can be suppressed.

(Sixth embodiment)
FIG. 8 shows a schematic configuration of a planar lightwave circuit according to the sixth embodiment of the present invention.

  The planar lightwave circuit 1 shown in FIG. 8 is configured as a PLC type variable optical attenuator. In the planar lightwave circuit 1, the optical waveguide includes one incident port 7, two input waveguides 9, an input waveguide 9 connected to the incident port 7 and an input waveguide 8 </ b> A not connected to the incident port 7, A 2 × 2 Mach-Zehnder interferometer circuit 20 connected between the input waveguides 8A and 9 and the two output waveguides 4 and 5 is provided. A phase adjuster 30 is provided on one of the two waveguides 17 and 18 (waveguide 17) of the Mach-Zehnder interferometer circuit 20.

  According to 6th Embodiment which has the above structure, in addition to the effect which the said 1st Embodiment show | plays, there exist the following effects.

  In the planar lightwave circuit 1 configured as a PLC-type variable optical attenuator, it is possible to avoid deterioration of signal light characteristics without increasing the circuit size.

(Seventh embodiment)
FIG. 9A shows a schematic configuration of the planar lightwave circuit according to the seventh embodiment, and FIG. 9B shows a main part of the planar lightwave circuit.

The planar lightwave circuit 1 shown in FIG. 9A is configured as a PLC variable optical attenuator array. The planar lightwave circuit 1 includes an incident port group 40 including a plurality of incident ports 7 _{1 to} 7 _n , input waveguides 9 _{1 to} 9 _n connected to the incident ports of the incident port group 40, and the incident ports. And an input waveguide group composed of a plurality of sets of input waveguides, each including two input waveguides 8A _{1 to} 8A _n that are not input.

Further, the planar lightwave circuit 1 includes an output waveguide group including a plurality of output waveguides each including two output waveguides 4 ₁ to 4 _n and 5 _{1 to} 5 _n , an input waveguide group, and an output waveguide. The Mach-Zehnder interferometer circuit group composed of a plurality of 2 × 2 Mach-Zehnder interferometer circuits 20 _{1 to} 20 _n respectively connected to the waveguide group, and the output waveguide of each set of output waveguides of the output waveguide group An emission port group 41 including a plurality of emission ports 3 _{1 to} 3 _n connected to the waveguides 4 ₁ to 4 _n , respectively. A phase adjuster 30 is provided in one of each of the two waveguides 17 and 18 of the plurality of Mach-Zehnder interferometer circuits.

Further, in this planar lightwave circuit 1, similarly to the third embodiment shown in FIG. 5, each of the idle waveguides 5 _{1 to} 5 _n has a propagating light emission curved waveguide 5 b immediately before the intersection 11 with the groove 10. (See FIG. 9B).

  According to 7th Embodiment which has the above structure, in addition to the effect which the said 1st Embodiment show | plays, there exist the following effects.

  In the planar lightwave circuit 1 configured as a PLC-type variable optical attenuator array, it is possible to avoid deterioration of signal light characteristics without causing an increase in circuit size.

(Eighth embodiment)
FIG. 10A shows a schematic configuration of the planar lightwave circuit according to the eighth embodiment, and FIG. 10B shows a main part of the planar lightwave circuit.

The planar lightwave circuit 1 shown in FIG. 10A is configured as a PLC type two-stage variable optical attenuator array. The planar lightwave circuit 1 includes two 2 × 2 Mach-Zehnder interferometer circuits 21 _{1 to} 21, in which Mach-Zehnder interferometer circuit groups are vertically connected in two stages in the seventh embodiment shown in FIG. 9A. _n and 22 _{1 to} 22 _n are provided.

Preceding Mach-Zehnder interferometer circuit 21 ₁ to 21 and an idle waveguide 51 ₁ to 51 _n which is branched from _n, the subsequent 2 × 2 Mach out of the two Mach-Zehnder interferometer circuit Mach-Zehnder interferometer circuit group They are respectively terminated at the intersection of the same groove 10 and the Zehnder interferometer circuit ₂₂ 1-22 idle waveguide ₅₂ 1 which is branched from _n to 52 _n.

Further, in the planar lightwave circuit 1, and idle waveguide ₅₁ 1 to 51 _n, the idle waveguide ₅₂ 1 to 52 _n, as in the second embodiment shown in FIG. 4, the idle guide at the intersection 11 The waveguide was a curved waveguide 5a (see FIG. 10B).

Further, each of the idle waveguides 51 _{1 to} 51 _n and each of the idle waveguides 52 _{1 to} 52 _n is provided with a curved waveguide 5 b for propagating light emission just before the intersection 11 with the groove 10. The bend radius of each propagation light radiation curved waveguide 5B is a value calculated in advance by the beam propagation method so that an optical loss of about 5 dB occurs. The crossing angle (the angle θ9 is set to 15 °, for example, 15 °, and the curved waveguide 5a is formed by extending the straight waveguides of the idle waveguides 51 _{1 to} 51 _n and the straight waveguides of the idle waveguides 52 _{1 to} 52 _n. The bending angle was, for example, 3 °, and the shape of the groove 10 was a parallelogram.

  According to 6th Embodiment which has the above structure, in addition to the effect which the said 1st Embodiment show | plays, there exist the following effects.

The signal light from each of the exit ports 3 _{1 to} 3 _n had almost no wavelength characteristics due to interference. In addition, the return loss of each of the incident ports 7 _{1 to} 7 _n was 50 dB or more, and a higher return loss was obtained. That is, according to the present embodiment, the above-described characteristic deterioration of the signal light can be avoided, and generation of reflected return light can be suppressed.

  In a planar lightwave circuit configured as a PLC type two-stage variable optical attenuator array, it is possible to avoid deterioration of signal light characteristics without increasing the circuit size.

  In addition, this invention can also be changed and embodied as follows.

  In the planar lightwave circuit 1 according to the fifth embodiment shown in FIG. 7 configured as a PLC type optical branching coupler, the configuration shown in FIG. 4, that is, the crossing angle (angle θ) between the idle waveguide 5 and the groove 10. The present invention can also be applied to a configuration in which the idle waveguide 5 at the intersection 11 is a curved waveguide 5a so that the cross-sectional area of the intersection 11 is increased and the cross-sectional area of the intersection 11 is increased.

  In the fifth embodiment shown in FIG. 7, the present invention is also applied to the configuration shown in FIG. 5, that is, the configuration in which the curved waveguide 5 b for propagating light radiation is provided in the idle waveguide 5 immediately before the intersection 11 with the groove 10. Applicable.

  In the fifth embodiment shown in FIG. 7, the present invention can be applied to the configuration shown in FIG. 6, that is, the configuration in which the material 12 that absorbs propagating light is injected into the groove 10.

  In the planar lightwave circuit 1 according to the sixth embodiment configured as a PLC type variable optical attenuator and shown in FIG. 8, the present invention is also applied to a configuration in which the idle waveguide 5 at the intersection 11 is a curved waveguide 5a (see FIG. 4). The invention is applicable.

  In the sixth embodiment shown in FIG. 8, the present invention can be applied to a configuration (see FIG. 5) in which the propagation waveguide for radiating light radiation 5b is provided in the idle waveguide 5 just before the intersection 11 with the groove 10. is there.

  -In 6th Embodiment shown in FIG. 8, this invention is applicable also to the structure (refer FIG. 6) which injected the material 12 which absorbs propagation light into the groove | channel 10. FIG.

  In the planar lightwave circuit according to the seventh embodiment shown in FIGS. 9A and 9B configured as a PLC type variable optical attenuator array, the configuration without the propagation light emitting curved waveguide 5b or the groove 10 The present invention is also applicable to a configuration in which the material 12 for absorbing propagating light is not injected.

In the planar lightwave circuit 1 according to the eighth embodiment shown in FIGS. 10A and 10B configured as a PLC type two-stage variable optical attenuator array, each idle waveguide 51 _{1 to} 51 _n , and each idle The present invention can also be applied to a configuration in which the waveguides 52 _{1 to} 52 _{n do not} have the curved waveguide 5a or a configuration in which the propagation light emission curved waveguide 5b does not exist.

  In the planar lightwave circuit 1 according to the sixth embodiment shown in FIG. 8, the phase adjuster 30 is provided in one of the two waveguides 17 and 18 (waveguide 17) of the Mach-Zehnder interferometer circuit 20. The present invention can also be applied to a configuration in which the adjuster 30 is provided in both or the other of the two waveguides 17 and 18 (waveguide 18). The same can be said for the seventh embodiment shown in FIGS. 9A and 9B and the eighth embodiment shown in FIGS. 10A and 10B.

  The present invention is also applicable to a planar lightwave circuit configured as a PLC type 2 × 1 optical switch having the following configuration. In this planar lightwave circuit, the optical waveguide is connected between two incident ports, two input waveguides respectively connected to the two incident ports, and two input waveguides and two output waveguides. 2 × 2 Mach-Zehnder interferometer circuit. One waveguide branched from the Mach-Zehnder interferometer circuit 20 is an output waveguide connected to the output port, and the other waveguide is the idle waveguide 5. According to this, in the planar lightwave circuit configured as a PLC type 2 × 1 optical switch, it is possible to avoid deterioration of signal light characteristics without causing an increase in circuit size.

  The present invention is also applicable to a planar lightwave circuit configured as a PLC type optical switch array having the following configuration. This planar lightwave circuit includes an incident port group composed of a plurality of sets of incident ports each including two incident ports, and two input waveguides connected to two incident ports of each set of incident port groups. An input waveguide group including a plurality of sets of input waveguides, and an output waveguide group including a plurality of sets of output waveguides including two output waveguides as one set. Further, the planar lightwave circuit includes a Mach-Zehnder interferometer circuit group composed of a plurality of 2 × 2 Mach-Zehnder interferometer circuits connected between the input waveguide group and the output waveguide group, and each of the output waveguide groups. An output port group including a plurality of output ports respectively connected to one output waveguide of the set of output waveguides. According to this, in a planar lightwave circuit configured as a PLC-type optical switch array, it is possible to avoid deterioration of signal light characteristics without causing an increase in circuit size.

The schematic block diagram which shows the planar lightwave circuit which concerns on 1st Embodiment. Explanatory drawing which shows the principal part of the same planar lightwave circuit. The graph which shows the wavelength characteristic of the signal light from the output port of the same plane lightwave circuit. Explanatory drawing which shows the principal part of the planar lightwave circuit which concerns on 2nd Embodiment. Explanatory drawing which shows the principal part of the planar lightwave circuit which concerns on 3rd Embodiment. Explanatory drawing which shows the principal part of the planar lightwave circuit which concerns on 4th Embodiment. The schematic block diagram which shows the planar lightwave circuit which concerns on 5th Embodiment. The schematic block diagram which shows the planar lightwave circuit which concerns on 6th Embodiment. (A) is a schematic block diagram which shows the planar lightwave circuit which concerns on 7th Embodiment, (B) is explanatory drawing which shows the principal part of the planar lightwave circuit. (A) is a schematic block diagram which shows the planar lightwave circuit which concerns on 8th Embodiment, (B) is explanatory drawing which shows the principal part of the planar lightwave circuit. The schematic block diagram which shows a prior art example. The graph which shows the wavelength characteristic of the signal light from the output port of the same plane lightwave circuit. The schematic block diagram which shows another prior art example.

Explanation of symbols

1 ... planar lightwave circuit, 2 ... silicon substrate, 2a ... waveguide end face, _3,3 1 to 3 n _... output port,
4, 4 ₁ to 4 _n ... output waveguide, 5, 5 _{1 to} 5 _n ... idle waveguide, 5a ... curved waveguide,
5b ... Curved waveguide for propagating light radiation, 6, 7 ... Incident port, 7 _{1 to} 7 _n ... Incident port,
8, 8A, 9... Input waveguide, 8A _{1 to} 8A _n ... Input waveguide, 9 _{1 to} 9 _n .
10, 10A ... groove, 11 ... intersection, 12 ... material that absorbs propagating light,
15, 16 ... Directional couplers, 17, 18 ... Waveguides,
20, 20 _{1 to} 20 _n , 22 _{1 to} 22 _n ... 2 × 2 Mach-Zehnder interferometer circuit,
30 ... Phase adjuster, 40 ... Incoming port group, 41 ... Outgoing port group,
51 _{1 to} 51 _n , 52 _{1 to} 52 _n ... idle waveguides.

Claims (13)

In a planar lightwave circuit in which an optical waveguide including at least two output waveguides, that is, an output waveguide connected to an output port and an idle waveguide not connected to a waveguide end surface on the output port side, is formed on a substrate.
A groove that intersects the idle waveguide at an angle of less than 90 degrees;
A planar lightwave circuit, wherein the idle waveguide is terminated at an intersection with the groove.   The idle waveguide at the intersection is a curved waveguide so that a crossing angle between the idle waveguide and the groove is small and a cross-sectional area of the intersection is large. Planar lightwave circuit.   3. The planar lightwave circuit according to claim 1, wherein the idle waveguide has a curved waveguide for propagating light radiation immediately before an intersection with the groove. 4.   4. The planar lightwave circuit according to claim 1, wherein a material that absorbs propagating light is injected into the groove.   The optical waveguide has two incident ports, two input waveguides respectively connected to the two incident ports, and 2 × connected between the two input waveguides and the two output waveguides. Two Mach-Zehnder interferometer circuits, one waveguide branched from the Mach-Zehnder interferometer circuit is an output waveguide connected to the output port, the other waveguide is the idle waveguide, 5. The planar lightwave circuit according to claim 1, wherein the planar lightwave circuit is configured as a PLC type optical branching coupler.   An incident port group composed of a plurality of sets of incident ports each having two incident ports as a set, and a plurality of sets each including two input waveguides connected to the two incident ports of each set of the incident port groups. An input waveguide group composed of a pair of input waveguides, an output waveguide group composed of a plurality of output waveguides, each of which consists of the two output waveguides, and the input waveguide group and the output waveguide group A plurality of Mach-Zehnder interferometer circuit groups each consisting of a plurality of 2 × 2 Mach-Zehnder interferometer circuits, and a plurality of output waveguides connected to one output waveguide of each set of the output waveguide groups. The planar lightwave circuit according to any one of claims 1 to 4, wherein the planar lightwave circuit is configured as a PLC type optical branching coupler array. The optical waveguide includes one incident port, two input waveguides, an input waveguide connected to the incident port and an input waveguide not connected to the incident port, the two input waveguides, and the two outputs. A 2 × 2 Mach-Zehnder interferometer circuit connected between the waveguide and
The phase adjuster is provided in at least one of the two waveguides of the Mach-Zehnder interferometer circuit, and is configured as a PLC type variable optical attenuator. A planar lightwave circuit according to claim 1. The optical waveguide includes one incident port, an input waveguide connected to the incident port, and a 1 × 2 Mach-Zehnder interferometer circuit connected between the input waveguide and the two output waveguides. And
The phase adjuster is provided in at least one of the two waveguides of the Mach-Zehnder interferometer circuit, and is configured as a PLC type variable optical attenuator. A planar lightwave circuit according to claim 1.   A plurality of sets each including an input port group composed of a plurality of incident ports, an input waveguide connected to each incident port of the incident port group, and an input waveguide not connected to the incident port. An input waveguide group consisting of two input waveguides, an output waveguide group consisting of a plurality of output waveguides each including the two output waveguides, and the input waveguide group and the output waveguide group. A Mach-Zehnder interferometer circuit group composed of a plurality of 2 × 2 Mach-Zehnder interferometer circuits each connected in between, and a plurality of output waveguides respectively connected to one output waveguide of each set of output waveguides of the output waveguide group And a phase adjuster is provided in at least one of the two waveguides of the plurality of Mach-Zehnder interferometer circuits, and a PLC type variable optical attenuator array is provided. Planar lightwave circuit according to any one of claims 1 to 4, characterized in that it is constructed as a.   An input port group composed of a plurality of incident ports, an input waveguide group composed of input waveguides connected to the respective incident ports of the incident port group, and a plurality of sets of outputs each including the two output waveguides An output waveguide group composed of waveguides, a Mach-Zehnder interferometer circuit group composed of a plurality of 1 × 2 Mach-Zehnder interferometer circuits connected between the input waveguide group and the output waveguide group, and the output An output port group comprising a plurality of output ports respectively connected to one output waveguide of each set of output waveguides of the waveguide group, and at least two waveguides of the plurality of Mach-Zehnder interferometer circuits 5. The planar lightwave circuit according to claim 1, wherein each of the phase adjusters is provided on one side, and is configured as a PLC-type variable optical attenuator array. . Each of the Mach-Zehnder interferometer circuit groups includes two 2 × 2 Mach-Zehnder interferometer circuits that are vertically connected in two stages,
Of the two Mach-Zehnder interferometer circuits of the Mach-Zehnder interferometer circuit group, the idle waveguide branched from the preceding Mach-Zehnder interferometer circuit, and branched from the subsequent 2 × 2 Mach-Zehnder interferometer circuit 10. The planar lightwave circuit according to claim 9, wherein the idle waveguide is terminated at the intersection with the groove, and is configured as a PLC type two-stage variable optical attenuator array.   The optical waveguide has two incident ports, two input waveguides respectively connected to the two incident ports, and 2 × connected between the two input waveguides and the two output waveguides. Two Mach-Zehnder interferometer circuits, one waveguide branched from the Mach-Zehnder interferometer circuit is an output waveguide connected to the output port, the other waveguide is the idle waveguide, 5. The planar lightwave circuit according to claim 1, wherein the planar lightwave circuit is configured as a PLC type 2 × 1 optical switch.   An incident port group composed of a plurality of sets of incident ports each having two incident ports as a set, and a plurality of sets each including two input waveguides connected to the two incident ports of each set of the incident port groups. An input waveguide group composed of a pair of input waveguides, an output waveguide group composed of a plurality of output waveguides, each of which consists of the two output waveguides, and the input waveguide group and the output waveguide group A plurality of Mach-Zehnder interferometer circuit groups each consisting of a plurality of 2 × 2 Mach-Zehnder interferometer circuits, and a plurality of output waveguides connected to one output waveguide of each set of the output waveguide groups. A planar lightwave circuit according to any one of claims 1 to 4, wherein the planar lightwave circuit is configured as a PLC type optical switch array.

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