Wavelength detection device

Abstract

The wavelength detection device is provided, for example, with: a plurality of waveguides for guiding light; a multiplexing unit that multiplexes a plurality of light beams that are guided by the waveguides and have different wavelengths; a filter unit to which the light outputted from the multiplexer is inputted, the filter unit having a characteristic in which the transmittance of the light varies depending on the wavelength; and a detection unit that detects the intensity of the light output from the filter unit, and the plurality of waveguides, the multiplexing unit, and the filter unit are configured in a planar lightwave circuit. The wavelength detection device may also be provided with a switch unit that is provided corresponding to each of the plurality of light beams and that switches between a state in which the light is transmitted and a state in which the transmission is suppressed. In addition, the multiplexing unit may include a wavelength division multiplexing coupler.

Description

Technical Field

[0001] The present invention relates to a wavelength detection device. Background Art

[0002] Conventionally, a wavelength detection device (wavelength monitoring unit) for detecting the wavelength of light output from a laser device has been known.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: International Publication No. 2020 / 166615 Summary of the Invention

[0006] -Problems to be Solved by the Invention-

[0007] In Patent Document 1, the wavelength of light output from one light source is detected by one wavelength detection device.

[0008] For example, in an optical device having a plurality of light sources with different output light wavelengths, it is beneficial if the wavelength detection device can be shared.

[0009] Therefore, one of the problems of the present invention is to obtain, for example, a new and improved wavelength detection device that can be shared for a plurality of lights with different wavelengths.

[0010] -Means for Solving the Problems-

[0011] The wavelength detection device of the present invention includes, for example: a plurality of waveguides for guiding light; a multiplexing unit for multiplexing a plurality of lights with different wavelengths respectively guided by the waveguides; a filtering unit that is input with the light output from the multiplexing unit and has a characteristic that the light transmittance varies according to the wavelength; and a detection unit that detects the intensity of the light output from the filtering unit, and the plurality of waveguides, the multiplexing unit, and the filtering unit are formed in a planar lightwave circuit.

[0012] The wavelength detection device may also include a switching unit that is provided corresponding to each of the plurality of lights and switches between a state where the light passes through and a state where the light transmission is suppressed.

[0013] In the wavelength detection device, the multiplexing unit may include a wavelength division multiplexing coupler.

[0014] In the wavelength detection device, alternatively, the plurality of lights may include: a first light having a center wavelength of a first wavelength; a second light having a center wavelength of a second wavelength longer than the first wavelength; a third light having a center wavelength of a third wavelength longer than the second wavelength; and a fourth light having a center wavelength of a fourth wavelength longer than the third wavelength. The multiplexing unit has the following wavelength division multiplexing coupler as the wavelength division multiplexing coupler: a first wavelength division multiplexing coupler having a port into which the first light is input and the transmittance of the input light peaks at the first wavelength, and a port into which the third light is input and the transmittance of the input light peaks at the third wavelength; a second wavelength division multiplexing coupler having a port into which the second light is input and the transmittance of the input light peaks at the second wavelength, and a port into which the fourth light is input and the transmittance of the input light peaks at the fourth wavelength; and a third wavelength division multiplexing coupler having a port into which the output light from the first wavelength division multiplexing coupler is input and the transmittance of the input light peaks at the first wavelength and the third wavelength; and a port into which the output light from the second wavelength division multiplexing coupler is input and the transmittance of the input light peaks at the second wavelength and the fourth wavelength.

[0015] In the wavelength detection device, the filtering unit may also have a plurality of filters with different wavelength-dependent transmittance characteristics.

[0016] In the wavelength detection device, alternatively, the waveguide has an extending portion extending linearly, and the multiplexing unit and the filtering unit are located at positions deviated from the extension line of the extending portion.

[0017] In the wavelength detection device, alternatively, the waveguide has an extending portion extending linearly, and the multiplexing unit and the filtering unit are located at positions deviated from the traveling path of the virtual reflected light on the side surface of the planar optical waveguide circuit of the virtual stray light that leaks from the extending portion and travels along the extension line of the extending portion.

[0018] In the wavelength detection device, alternatively, a space is provided at a portion of the planar optical waveguide circuit deviated from the waveguide.

[0019] The wavelength detection device may also include: an absorption portion covering the side surface of the planar optical waveguide circuit to absorb light.

[0020] The wavelength detection device may also include: a mode filter that restricts the propagation mode of the light guided in the waveguide.

[0021] -Advantages of the Invention-

[0022] According to the present invention, for example, a new and improved wavelength detection device that can be shared by a plurality of lights with different wavelengths can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is an exemplary and schematic top view of the wavelength detection device of the first embodiment.

[0024] Figure 2 It is an exemplary schematic structural diagram of the multiplexing unit included in the wavelength detection device of the first embodiment.

[0025] Figure 3 It is an exemplary graph showing the relationship between the wavelength and the transmittance of the multiplexing unit included in the wavelength detection device of the first embodiment.

[0026] Figure 4 It is an exemplary and schematic top view of the wavelength detection device of the second embodiment.

[0027] Figure 5 It is an exemplary and schematic top view of the wavelength detection device of the third embodiment.

[0028] Figure 6 It is an exemplary and schematic top view of the wavelength detection device of the fourth embodiment.

[0029] Figure 7 It is an exemplary and schematic side view of a part of the wavelength detection device of the fourth embodiment.

[0030] Figure 8 It is an exemplary and schematic top view of the wavelength detection device of the fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, a plurality of exemplary embodiments of the present invention will be disclosed. The structures of the embodiments shown below, the actions and results (effects) brought about by the structures are examples. The present invention can also be implemented by structures other than the structures disclosed in the following embodiments. In addition, according to the present invention, at least one of various effects (including derived effects) obtained by the structure can be obtained.

[0032] The plurality of embodiments shown below have the same structure. Therefore, based on the structure of each embodiment, the same actions and effects based on the same structure can be obtained. In addition, hereinafter, the same reference numerals may be given to these same structures, and repeated descriptions may be omitted.

[0033] In the specification, ordinal numbers are given for the convenience of distinguishing lights, wavelengths, structures, etc., and do not represent priority order, sequence, nor limit the number.

[0034] In the respective figures, the X direction is indicated by an arrow X, the Y direction is indicated by an arrow Y, and the Z direction is indicated by an arrow Z. The X direction, the Y direction, and the Z direction intersect each other and are orthogonal to each other. The Z direction may also be referred to as the stacking direction or the height direction.

[0035] In addition, the respective figures are schematic diagrams for illustrative purposes, and the scales and ratios in the respective figures and the actual objects are not necessarily the same.

[0036] [First Embodiment]

[0037] [Overall Structure]

[0038] Figure 1 FIG. is a plan view schematically showing the structure of a wavelength detection device 100A (100) according to the first embodiment. The wavelength detection device 100 detects the wavelengths of the light output from each of laser devices 10-1 to 10-4 serving as light sources.

[0039] The laser devices 10-1 to 10-4 respectively output light having different wavelengths. The laser devices 10-1 to 10-4 include, for example, semiconductor laser elements that output light according to a supplied current.

[0040] In the present embodiment, the laser device 10-1 outputs light having a center wavelength of λ1. The laser device 10-2 outputs light having a center wavelength of λ2 that is longer than λ1. The laser device 10-3 outputs light having a center wavelength of λ3 that is longer than λ2. In addition, the laser device 10-4 outputs light having a center wavelength of λ4 that is longer than λ3.

[0041] The wavelength detection device 100 includes a planar lightwave circuit 101 (PLC: planar lightwave circuit), a plurality of switches 150A (150), and a detection unit 140.

[0042] The switches 150 are respectively provided corresponding to the laser devices 10-1 to 10-4. The switches 150 can respectively switch between a state in which light passes through and a state in which the passage of light is suppressed. The switch 150A can be configured as, for example, a gate switch of the laser devices 10-1 to 10-4. The switch 150 is an example of a switch unit.

[0043] In the planar lightwave circuit 101, a plurality of waveguide paths 102, a multiplexing unit 110, a branching unit 120, and a filtering unit 130 are formed. The planar lightwave circuit 101 has a substrate and a stacked portion stacked on the substrate. In addition, the planar lightwave circuit 101 is made of, for example, a quartz-based glass material or a silicon-based material.

[0044] The light output from the laser devices 10-1 to 10-4 is respectively input to different waveguide paths 102 via the switches 150. In the present embodiment, as an example, the light output from the four laser devices 10-1 to 10-4 is input to the four waveguide paths 102.

[0045] The optical waveguide path 102 is composed of a core portion and a cladding layer surrounding the core portion, and light is guided through the core portion in the optical waveguide path. In Figure 1 it, the core portion of the optical waveguide path 102 is depicted as a line.

[0046] The multiplexing section 110 multiplexes lights that are input from the laser devices 10-1 to 10-4 and transmitted through the optical waveguide paths 102, that is, a plurality of lights having different wavelengths. In the present embodiment, the multiplexing section 110 can multiplex four lights having different wavelengths guided by four optical waveguide paths 102. The detailed structure of the multiplexing section 110 will be described later.

[0047] The branching section 120 branches the light output from the multiplexing section 110 to a plurality of optical waveguide paths 102. In the present embodiment, the branching section 120 includes splitters 121 and 122, and these splitters 121 and 122 are each configured as a 1×2 splitter. The branching section 120 branches the light output from the multiplexing section 110 to three optical waveguide paths 102.

[0048] The light that has passed through two of the three optical waveguide paths 102 is output from the planar lightwave circuit 101 via the filtering section 130, and the light that has passed through the remaining one optical waveguide path 102 (102-0) is output from the planar lightwave circuit 101 without passing through the filtering section 130.

[0049] The filtering section 130 includes filters 131 and 132. The filters 131 and 132 have the characteristic that the light transmittance varies according to the wavelength, that is, the transmittance is maximum at a periodic or a specific wavelength (peak wavelength), and the transmittance decreases as the wavelength moves away from the peak wavelength.

[0050] In addition, the characteristics of the filters 131 and 132, that is, the characteristics of the transmittance with respect to the wavelength, are different from each other. As an example, the filters 131 and 132 can be configured such that the wavelength at which the change rate of the transmittance of one filter with respect to the wavelength is maximum is substantially the same as the peak wavelength of the other filter. The filters 131 and 132 can be configured as, for example, ring resonators or Mach-Zehnder interferometers.

[0051] The light passing through the filter 131 is output from the planar lightwave circuit 101 through the optical waveguide path 102 (102-1), and the light passing through the filter 132 is output from the planar lightwave circuit 101 through the optical waveguide path 102 (102-2).

[0052] The detection sections 140-0 to 140-2 respectively detect the intensities of the lights passing through the optical waveguide paths 102-0 to 102-2. The detection sections 140-0 to 140-2 can be configured as, for example, photodiodes.

[0053] In the case of the structure of the detection units 140-0 to 140-2, a control unit (not shown) can detect the wavelength of light based on the ratio of the intensity of the light detected by the detection unit 140-1 to the intensity of the light detected by the detection unit 140-0 (intensity ratio), and the ratio of the intensity of the light detected by the detection unit 140-2 to the intensity of the light detected by the detection unit 140-0 (intensity ratio).

[0054] In addition, the structures of the branching unit 120, the filtering unit 130, and the detection unit 140 are not limited to Figure 1 the structure shown, and various modifications can be made. For example, the number of filtering units 130 can be 1, and the number of detection units 140 can be 1 or 2.

[0055] [Structure of the multiplexing unit]

[0056] Figure 2 is a schematic structural diagram illustrating the multiplexing unit 110. As Figure 2 shown, in the present embodiment, the multiplexing unit 110 is configured to include three wavelength division multiplexing couplers 111, 112, and 113.

[0057] Light L11 from the laser device 10-1 is input to the port 111a of the wavelength division multiplexing coupler 111, and light L13 from the laser device 10-3 is input to the port 111b. The wavelength division multiplexing coupler 111 can multiplex the light L11 and the light L13. The light L11 is an example of the first light, and the light L13 is an example of the third light.

[0058] Light L12 from the laser device 10-2 is input to the port 112a of the wavelength division multiplexing coupler 112, and light L14 from the laser device 10-4 is input to the port 112b. The wavelength division multiplexing coupler 112 can multiplex the light L12 and the light L14. The light L12 is an example of the second light, and the light L14 is an example of the fourth light.

[0059] Light L21 output from the wavelength division multiplexing coupler 111 is input to the port 113a of the wavelength division multiplexing coupler 113, and light L22 output from the wavelength division multiplexing coupler 112 is input to the port 113b. The wavelength division multiplexing coupler 113 can multiplex the light L21 and the light L22.

[0060] Figure 3 is a graph showing the wavelength and transmittance characteristics of the three wavelength division multiplexing couplers 111, 112, and 113. The lower part of the graph shows the characteristics of the wavelength division multiplexing couplers 111 and 112, and the upper part of the graph shows the characteristics of the wavelength division multiplexing coupler 113.

[0061] In Figure 3In the lower part of the graph, the wavelength-transmittance characteristics of the wavelength division multiplexing coupler 111 are represented by a thick solid line and a thick dashed line. The thick solid line represents the wavelength-transmittance characteristics for the light input to port 111a, and the thick dashed line represents the wavelength-transmittance characteristics for the light input to port 111b. As shown by these thick solid line and thick dashed line, the wavelength division multiplexing coupler 111 is configured such that the transmittance varies sinusoidally with respect to the wavelength. The wavelength division multiplexing coupler 111 is configured such that, for the light input to port 111a, the transmittance is maximum (peak) at wavelength λ1 and minimum (trough) at wavelength λ3. In addition, the wavelength division multiplexing coupler 111 is configured such that, for the light input to port 111b, the transmittance is minimum (trough) at wavelength λ1 and maximum (peak) at wavelength λ3. In such a structure, by inputting light L11 having a center wavelength of wavelength λ1 to port 111a and inputting light L13 having a center wavelength of wavelength λ3 to port 111b, a waveguide path with low loss for both lights L11 and L13 can be formed in the wavelength division multiplexing coupler 111.

[0062] In Figure 3 In the lower part of the graph, the wavelength-transmittance characteristics of the wavelength division multiplexing coupler 112 are represented by a thin solid line and a thin dashed line. The thin solid line represents the wavelength-transmittance characteristics for the light input to port 112a, and the thin dashed line represents the wavelength-transmittance characteristics for the light input to port 112b. As shown by these thin solid line and thin dashed line, the wavelength division multiplexing coupler 112 is configured such that the transmittance varies sinusoidally with respect to the wavelength. The wavelength division multiplexing coupler 112 is configured such that, for the light input to port 112a, the transmittance is maximum (peak) at wavelength λ2 and minimum (trough) at wavelength λ4. In addition, the wavelength division multiplexing coupler 112 is configured such that, for the light input to port 112b, the transmittance is minimum (trough) at wavelength λ2 and maximum (peak) at wavelength λ4. In such a structure, by inputting light L12 having a center wavelength of wavelength λ2 to port 112a and inputting light L14 having a center wavelength of wavelength λ4 to port 112b, a waveguide path with low loss for both lights L12 and L14 can be formed in the wavelength division multiplexing coupler 112.

[0063] In addition, in Figure 3In the upper part of the graph, the wavelength-transmittance characteristics of the wavelength division multiplexing coupler 113 are represented by solid and dashed lines. The solid line represents the wavelength-transmittance characteristics for the light input to port 113a, and the dashed line represents the wavelength-transmittance characteristics for the light input to port 113b. As shown by these solid and dashed lines, the wavelength division multiplexing coupler 113 is configured such that the transmittance varies sinusoidally and periodically with respect to the wavelength. The wavelength division multiplexing coupler 113 is configured such that, for the light input to port 113a, the transmittance is maximum (peak) at wavelengths λ1 and λ3, and minimum (trough) at wavelengths λ2 and λ4. Further, the wavelength division multiplexing coupler 113 is configured such that, for the light input to port 113b, the transmittance is maximum (peak) at wavelengths λ2 and λ4, and minimum (trough) at wavelengths λ1 and λ3. In such a configuration, by inputting light L21, which is output from the wavelength division multiplexing coupler 111 and includes light L11 with a center wavelength of λ1 and light L13 with a center wavelength of λ3, to port 113a, and inputting light L22, which is output from the wavelength division multiplexing coupler 112 and includes light L12 with a center wavelength of λ2 and light L14 with a center wavelength of λ4, to port 113b, a waveguide path with low loss for both lights L21 and L22, i.e., lights L11, L12, L13, and L14, can be formed in the wavelength division multiplexing coupler 113.

[0064] As described above, in the present embodiment, since the wavelength detection device 100 includes the multiplexing unit 110 that multiplexes a plurality of lights L11 to L14 having different wavelengths, the structures of the branching unit 120, the filter unit 130, and the detection unit 140 can be shared among the plurality of lights L11 to L14. Therefore, according to the present embodiment, for example, compared with a configuration in which the branching unit 120, the filter unit 130, and the detection unit 140 are provided respectively for a plurality of lights having different wavelengths, the following effects can be obtained: the wavelength detection device 100 can be made smaller, and the labor and cost required for manufacturing the wavelength detection device 100 can be suppressed.

[0065] [Second Embodiment]

[0066] Figure 4 is a top view showing a schematic configuration of the wavelength detection device 100B (100) according to the second embodiment. The wavelength detection device 100B of the present embodiment includes a switch 150B (150) within the planar lightwave circuit 101 instead of the switch 150A outside the planar lightwave circuit 101 included in the wavelength detection device 100A of the first embodiment. The switch 150B can be configured as, for example, a variable optical attenuator (VOA).

[0067] Except that the switch 150 is different, the wavelength detection device 100B of the present embodiment has the same structure as the wavelength detection device 100A of the first embodiment. According to the present embodiment, the same effects as those of the first embodiment can also be obtained.

[0068] [Third Embodiment]

[0069] Figure 5 It is a top view showing the schematic structure of the wavelength detection device 100C (100) of the third embodiment. The wavelength detection device 100C of the present embodiment has the same structure as the wavelength detection device 100A of the first embodiment. Therefore, according to the present embodiment, the same effects as those of the first embodiment can also be obtained.

[0070] However, the path of the waveguide 102 of the wavelength detection device 100C of the present embodiment is different from that of the first and second embodiments.

[0071] Specifically, first, the light input from the laser devices 10-1 to 10-4 is respectively guided in the section 102e that extends linearly in the X direction along the waveguide 102, and the multiplexer 110, the demultiplexer 120, and the filter section 130 are located at positions deviated from the extension line of this section 102e ( Figure 5 the arrow of the double-dot dash line facing the X direction in). The section 102e is an example of an extension section.

[0072] Furthermore, it is located at a position deviated from the traveling path of the virtual reflected light on the side surface 101b1 (101b) of the planar lightwave circuit 101 of the virtual stray light that leaks from the section 102e and travels along the extension line of this section 102e ( Figure 5 the arrow of the double-dot dash line in the opposite direction of the X direction to which it faces in).

[0073] According to the present embodiment having such a structure, it is possible to suppress the stray light leaking from the section 102e and the reflected light of this stray light on the side surface 101b1 from being coupled to the multiplexer 110, the demultiplexer 120, and the filter section 130, which may interfere with the intensity detection of the detection section 140 and further with the wavelength detection of the wavelength detection device 100.

[0074] [Fourth Embodiment]

[0075] Figure 6 It is a top view showing the schematic structure of the wavelength detection device 100D (100) of the fourth embodiment. The wavelength detection device 100D of the present embodiment has the same structure as the wavelength detection device 100A of the first embodiment. Therefore, according to the present embodiment, the same effects as those of the first embodiment can also be obtained.

[0076] However, in the wavelength detection device 100D of the present embodiment, a space 101c is provided at a position of the planar optical waveguide circuit 101 that deviates from the waveguide path 102. The space 101c is formed, for example, by an opening that opens on the top surface 101a at the end in the Z direction of the planar optical waveguide circuit 101. The space 101c may also be referred to as a groove or a recess.

[0077] The space 101c can be provided at various positions that deviate from the waveguide path 102. The space 101c can suppress the propagation of stray light in the planar optical waveguide circuit 101.

[0078] The space 101c1 in the space 101c is located between the multiplexing section 110, the branching section 120, the filtering section 130, and the interval 102e of the waveguide path 102 that guides the light output from the laser devices 10-1 to 10-4 and input to the planar optical waveguide circuit 101 via the switch 150. According to such a structure, the stray light leaking from the interval 102e can be blocked by the space 101c1, so that the coupling of the stray light with the multiplexing section 110, the branching section 120, and the filtering section 130 can be suppressed, thereby preventing the detection of the intensity of the detection section 140 and further the detection of the wavelength of the wavelength detection device 100 from being hindered.

[0079] In addition, the space 101c2 in the space 101c is provided between the waveguide paths 102 near the side surface 101b2 of the output light of the planar optical waveguide circuit 101. According to such a structure, when the return light from the outside to the side surface 101b2, for example, the reflected light from the detection section 140 with respect to the output light enters the planar optical waveguide circuit 101, the propagation of this light in the planar optical waveguide circuit 101 can be suppressed.

[0080] Furthermore, in the present embodiment, an absorption layer 160 that absorbs light is provided on the side surface 101b, which is an end surface in the direction (X direction, Y direction) intersecting the Z direction, of the planar optical waveguide circuit 101 so as to cover the side surface 101b. The absorption layer 160 is, for example, a black coating film. According to the absorption layer 160, the stray light propagating in the planar optical waveguide circuit 101 can be suppressed from being reflected by the side surface 101b, and the light can be suppressed from entering the planar optical waveguide circuit 101 from the outside via the side surface 101b. The absorption layer 160 is an example of an absorption section.

[0081] Figure 7 It is a side view of the output end vicinity of the waveguide path 102 of the planar optical waveguide circuit 101 of the present embodiment. As Figure 7 shown, the planar optical waveguide circuit 101 includes a substrate 101d and a stacked portion 101e formed on the substrate 101d. The core portion 102a and the cladding 102b are formed in the stacked portion 101e. And as Figure 7As shown, the absorption layer 160 is arranged to cover, on the side surface 101b2, the portion of the output end of the waveguide path 102 other than the core portion 102a and a part of the cladding 102b. With such a structure, it is possible to prevent the absorption layer 160 from obstructing the transmission of the original light in the waveguide path 102.

[0082] [Fifth Embodiment]

[0083] Figure 8 is a top view showing the schematic structure of the wavelength detection device 100E (100) according to the fifth embodiment. The wavelength detection device 100E of the present embodiment has the same structure as the wavelength detection device 100A of the first embodiment. Therefore, according to the present embodiment, the same effects as those of the first embodiment can also be obtained.

[0084] However, in the wavelength detection device 100E of the present embodiment, a mode filter 170 for restricting the propagation mode of the light guided in the waveguide path 102 is provided in the planar optical waveguide circuit 101. By the mode filter 170, the propagation of light in the higher-order mode can be suppressed, and thus the leakage of light from the waveguide path 102 to generate stray light can be suppressed. Therefore, according to such a structure, it is possible to suppress the coupling of the stray light with the multiplexing section 110, the branching section 120, and the filtering section 130 and to prevent the detection of the intensity of the detection section 140 and, further, the detection of the wavelength of the wavelength detection device 100 from being hindered.

[0085] The embodiments of the present invention have been illustrated above, but the above embodiments are examples and do not intend to limit the scope of the invention. The above embodiments can be implemented in various other ways, and various omissions, substitutions, combinations, and changes can be made without departing from the gist of the invention. In addition, various specifications (structures, types, directions, forms, sizes, lengths, widths, thicknesses, heights, numbers, arrangements, positions, materials, etc.) of each structure, shape, etc. can be appropriately changed and implemented.

[0086] Industrial Applicability

[0087] The present invention can be applied to a wavelength detection device.

[0088] -Description of Reference Numerals-

[0089] 10-1 to 10-4... Laser devices

[0090] 100, 100A to 100E... Wavelength detection devices

[0091] 101... Planar optical waveguide circuit

[0092] 101a... Top surface

[0093] 101b, 101b1, 101b2... Side surfaces

[0094] 101c, 101c1, 101c2... space

[0095] 101d... substrate

[0096] 101e... stacked portion

[0097] 102, 102-0 to 102-2... optical waveguide

[0098] 102a... core

[0099] 102b... cladding

[0100] 102e... section (extension part)

[0101] 110... multiplexing section

[0102] 111... wavelength division multiplexing coupler (first wavelength division multiplexing coupler)

[0103] 112... wavelength division multiplexing coupler (second wavelength division multiplexing coupler)

[0104] 113... wavelength division multiplexing coupler (third wavelength division multiplexing coupler)

[0105] 111a, 111b, 112a, 112b, 113a, 113b... ports

[0106] 120... branching section

[0107] 121, 122... optical splitter

[0108] 130... filtering section

[0109] 131, 132... filters

[0110] 140, 140-0 to 140-2... detection section

[0111] 150, 150A, 150B... switch (switching section)

[0112] 160... absorption layer (absorption section)

[0113] 170... mode filter

[0114] L11... light (first light)

[0115] L12... light (second light)

[0116] L13... light (third light)

[0117] L14... light (fourth light)

[0118] L21, L22... light

[0119] X... direction

[0120] Y… direction

[0121] Z… direction

[0122] λ1 to λ4... wavelengths

Claims

1. A wavelength detection device, characterized in that, it comprises: a plurality of optical waveguides for guiding light; a multiplexing section for multiplexing a plurality of lights with different wavelengths respectively guided by the optical waveguides; a filtering section which is input with the light output from the multiplexing section and has a characteristic that the light transmittance varies according to the wavelength; and a detection section for detecting the intensity of the light output from the filtering section, wherein the plurality of optical waveguides, the multiplexing section and the filtering section are formed in a planar optical waveguide circuit.

2. The wavelength detection device according to claim 1, wherein, the wavelength detection device comprises: a switching section provided corresponding to the plurality of lights respectively, for switching between a state allowing the light to pass through and a state suppressing the passage.

3. The wavelength detection device according to claim 1, wherein, the multiplexing section includes a wavelength division multiplexing coupler.

4. The wavelength detection device according to claim 3, wherein, the plurality of lights include: a first light with a center wavelength of a first wavelength; a second light with a center wavelength of a second wavelength longer than the first wavelength; a third light with a center wavelength of a third wavelength longer than the second wavelength; and a fourth light with a center wavelength of a fourth wavelength longer than the third wavelength, and the multiplexing section has the following wavelength division multiplexing coupler as the wavelength division multiplexing coupler: a first wavelength division multiplexing coupler having a port for inputting the first light and a port for inputting the third light, and the transmittance of the input light peaks at the first wavelength and the third wavelength respectively; a second wavelength division multiplexing coupler having a port for inputting the second light and a port for inputting the fourth light, and the transmittance of the input light peaks at the second wavelength and the fourth wavelength respectively; and a third wavelength division multiplexing coupler having a port for inputting the output light from the first wavelength division multiplexing coupler and a port for inputting the output light from the second wavelength division multiplexing coupler, and the transmittance of the input light peaks at the first wavelength, the third wavelength, the second wavelength and the fourth wavelength respectively.

5. The wavelength detection device according to claim 1, wherein, the filtering section has a plurality of filters with different characteristics of transmittance with respect to the wavelength.

6. The wavelength detection device according to claim 1, wherein, the optical waveguide has an extending portion extending linearly, and the multiplexing section and the filtering section are located at positions deviated from the extension line of the extending portion.

7. The wavelength detection device according to claim 1, wherein, the optical waveguide has an extending portion extending linearly, and the multiplexing section and the filtering section are located at positions deviated from the traveling path of the virtual reflected light on the side surface of the planar optical waveguide circuit of the virtual stray light leaking from the extending portion and traveling along the extension line of the extending portion.

8. The wavelength detection device according to claim 1, wherein, a space is provided at a portion of the planar optical waveguide circuit deviated from the optical waveguide.

9. The wavelength detection device according to claim 1, wherein, The wavelength detection device includes an absorption portion that covers a side surface of the planar optical waveguide and absorbs light.

10. The wavelength detection device according to claim 1, wherein the wavelength detection device includes a mode filter that restricts a propagation mode of light guided in the waveguide.

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