JP2010117626A - Arrayed waveguide type diffraction grating and optical multiplexer having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress loss and to eliminate the wavelength dependency of an input port. <P>SOLUTION: The shape of an input side 27 and the shape of an output side 28 are asymmetry satisfying at least one of relations (1), (2), (3) and (4). (1): fin>fout, (2): Δxin<Δout, (3): din<dout, (4): Δxin<ΔWout, wherein fin: focal length of an input side slab waveguide, fout: focal length of output side slab waveguide, Δxin: input port distance, Δxout: output port distance, din: distance between array waveguides connected to the input side slab waveguide, dout: distance between array waveguides connected to the output side slab waveguide, and ΔWout: core opening width of an output waveguide. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an arrayed waveguide grating and an optical multiplexing device including the same.

  In wavelength division multiplexing (WDM) optical communication, it is necessary to multiplex optical signals of various wavelengths supplied from a number of wavelength variable light sources and wavelength division multiplexing networks. Devices used for multiplexing optical signals when the wavelength input to the input port is switched include a 3 dB coupler, a star coupler, and a polarization beam combiner. However, the loss at the time of multiplexing is large in the 3 dB coupler and the star coupler, and it is necessary to separately provide an amplifier to compensate for the loss. In addition, in the polarization beam combiner, although it is possible to multiplex with a low loss compared to a 3 dB coupler or a star coupler, it is a combination of longitudinal linearly polarized waves and transversely linearly polarized waves. The number of inputs is limited to a maximum of 2 ports, and an optical signal whose polarization state fluctuates, such as an optical signal transmitted through a normal single mode fiber, cannot be multiplexed.

  As a multiplexing method when a fixed wavelength is assigned to each input port, multiplexing is performed with low loss using an arrayed waveguide grating (AWG) having multiple inputs and one output. It is considered. The concept of AWG is shown in FIGS. The AWG 101 includes an input-side slab waveguide 102, an output-side slab waveguide 103, and an arrayed waveguide 104, and the input-side slab waveguide 102 and the output-side slab waveguide 103 have the same shape. That is, the focal length f of each of the waveguides 102 and 103 and the interval d of the arrayed waveguides 104 connected to the input-side slab waveguide 102 or the output-side slab waveguide 103 are the same. As shown in FIG. 18, a plurality of output ports may be provided in the output side slab waveguide 103 of the AWD to be used as a multi-input / multiple-output optical multiplexer / demultiplexer. The interval Δxin between the input ports of the waveguide 102 and the interval Δxout between the output ports of the output side slab waveguide 103 are the same.

  The wavelength of the input optical signal is assigned to each input port of the input-side slab waveguide 102. By inputting an optical signal having a wavelength that matches the assigned wavelength to the input port, the optical signal is multiplexed and single-ended. It is possible to output from one output port and to multiplex optical signals of multiple wavelengths. For example, in the AWG 101 of FIG. 16, the wavelength assigned to the first input port 102a is λ1, the wavelength assigned to the second input port 102b is λ2, the wavelength assigned to the third input port 102c is λ3, and the fourth input port. Assuming that the wavelength assigned to 102d is λ4, the optical signal of wavelength λ1 inputted to the first input port 102a is outputted from the output port 103a, but inputted to the input ports 102b to 102d different from the assigned wavelength. Optical signals having wavelengths λ4, λ2, and λ3 are not output from the output port 103a.

  An example of using AWG as an optical multiplexer / demultiplexer is disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-164758.

JP 2005-164758 A

  However, although the above-described AWG 101 has the advantage of being able to multiplex with low loss, in order to multiplex input optical signals and output them from a single output port 103a, each input port 102a to 102d It is necessary to input an optical signal having an assigned wavelength. That is, the input port has wavelength dependency. Therefore, for use as a multiplexer for WDM optical communication, for example, as shown in FIG. 19, the splitter 105 that distributes the input signal according to wavelength in the previous stage, and the input light that is assigned by wavelength by switching the input light. The active optical switch 106 that outputs to the input ports 102a to 102d is necessary, and the apparatus required for multiplexing increases in size and the manufacturing cost increases.

  It is an object of the present invention to provide an optical multiplexing device having no wavelength dependency at an input port while maintaining the advantage of being able to perform multiplexing with low loss. Another object of the present invention is to provide an arrayed waveguide type diffraction grating suitable for use in the optical multiplexer. It is another object of the present invention to provide an arrayed waveguide type diffraction grating having no wavelength dependency at the input port.

In order to achieve this object, the invention according to claim 1 is characterized in that the shape on the input side and the shape on the output side are asymmetric satisfying at least one of formulas 5, 6, 7, and 8, and An output port is provided for outputting an optical signal input from any input port among a plurality of input ports provided on the input side, whose wavelength matches the assigned wavelength.
<Equation 5>
fin> fout
<Equation 6>
Δxin <Δxout
<Equation 7>
din <dout
<Equation 8>
Δxin <ΔWout
Here, fin: focal length of the input side slab waveguide, fout: focal length of the output side slab waveguide, Δxin: spacing of the input port, Δxout: spacing of the output port, din: connected to the input side slab waveguide The distance between the arrayed waveguides, dout: the distance between the arrayed waveguides connected to the output-side slab waveguide, and ΔWout: the core opening width of the output waveguide.

  The input side means the input side slab waveguide, the portion near the input side slab waveguide of the arrayed waveguide, and the portion near the input side slab waveguide of the input waveguide. The output side means an output side slab waveguide, a portion near the output side slab waveguide of the arrayed waveguide, and a portion near the output side slab waveguide of the output waveguide.

Therefore, the relationship between the wavelength interval Δλin between the input ports adjacent to each other on the input side slab waveguide and the wavelength interval Δλout between the output ports adjacent to the output side slab waveguide satisfies Equation 9 or is adjacent to the input side slab waveguide. The relationship between the wavelength interval Δλin of the input port and the transmission bandwidth ΔB of the output port of the output-side slab waveguide satisfies Expression 10, and the optical signal is output from the output port of the assigned wavelength regardless of which input port is input. Is output.
<Equation 9>
NΔλin ≦ Δλout
<Equation 10>
NΔλin ≦ ΔB
Here, Δλin is expressed by Equation 11, Δλout is expressed by Equation 12, and ΔB is expressed by Equation 13. N is an integer of 2 or more.
<Equation 11>
Δλin = (Δxin / fin) · (din · ns / m) · (ng / ns) ^-1
<Equation 12>
Δλout = (Δxout / fout) · (dout · ns / m) · (ng / ns) ^-1
<Equation 13>
ΔB = (ΔWout / fout) · (dout · ns / m) · (ng / ns) ^-1
Here, Δxin: input port interval, fin: focal length of input side slab waveguide, din: interval of arrayed waveguide connected to input side slab waveguide, ns: effective refractive index of slab waveguide, m: Diffraction order, ng: group refractive index, Δxout: output port spacing, fout: focal length of output slab waveguide, dout: spacing of arrayed waveguides connected to output slab waveguide, ΔWout: output waveguide Core opening width.

  That is, when considering an optical signal of a certain wavelength, when viewed from the output port to which that wavelength is assigned, even if the input port is changed, the optical signal of that wavelength is input from the same input port. looks like. Therefore, the wavelength band of the optical signal output from each output port is the same regardless of which input port is used.

  For example, as shown in FIG. 3, a case where four input ports 3 and four output ports 5 are provided will be described as an example. In addition, in order to distinguish each input port 3, it is called input ports 3a, 3b, 3c, 3d, and in order to distinguish each output port 5, it is called output ports 5A, 5B, 5C, 5D. In addition, four types of wavelengths of λ1, λ2, λ3, and λ4 are used as wavelengths of optical signals. Further, the assigned wavelength of each output port 5 is assumed to be output port 5A: λ1, output port 5B: λ2, output port 5C: λ3, and output port 5D: λ4. An optical signal having the wavelength λ1 input to the input port 3a is referred to as λ1a, an optical signal having the wavelength λ2 input to the input port 3a is referred to as λ2a, and an optical signal having the wavelength λ1 input to the input port 3b is referred to as λ1b. Other optical signals are described in the same manner.

  For example, the optical signal λ1a of wavelength λ1 input to the input port 3a is output from the output port 5A, and the optical signal λ2a of wavelength λ2 input to the input port 3a is output from the output port 5B and input to the input port 3a. The optical signal λ3a having the wavelength λ3 is output from the output port 5C, and the optical signal λ4a having the wavelength λ4 input to the input port 3a is output from the output port 5D. The optical signal λ1b of wavelength λ1 input to the input port 3b is output from the output port 5A, and the optical signal λ2b of wavelength λ2 input to the input port 3b is output from the output port 5B and input to the input port 3b. The optical signal λ3b having the wavelength λ3 is output from the output port 5C, and the optical signal λ4b having the wavelength λ4 input to the input port 3b is output from the output port 5D. That is, the optical signal of wavelength λ1 is output from the output port 5A regardless of which input port 3a,..., 3d is input, and the optical signal of wavelength λ2 is input from any input port 3a,. Are output from the output port 5B, the optical signal having the wavelength λ3 is output from the output port 5C regardless of which input port 3a,..., 3d is input, and the optical signal having the wavelength λ4 is output from any input port 3a,. , 3d, it is output from the output port 5D.

  As a method of satisfying Equation 9 or Equation 10, it is possible to use fin> fout (Equation 5), Δxin <Δxout (Equation 6), or din <dout ( Formula 7) may be used, or Δxin <ΔWout (Formula 8) may be used. These may be adopted one by one, but two, three, or four of them may be combined.

  According to a second aspect of the present invention, there is provided an optical multiplexer comprising: an optical demultiplexer comprising the arrayed waveguide type diffraction grating according to the first aspect; and an optical multiplexer, wherein the output demultiplexer includes a plurality of output side slab waveguides. The optical multiplexer combines the optical signals output from the plurality of output ports and outputs from the single output port.

  Therefore, the optical signal input to the preceding optical demultiplexer is output from the output port whose wavelength matches the assigned wavelength, regardless of which input signal is input to the optical demultiplexer. Input, combined, and output from a single output port. At this time, the light output from each output port of the front-end optical demultiplexer is set by matching the assigned wavelength of the input port of the rear-stage optical multiplexer to the assigned wavelength of the output port of the front-end optical demultiplexer. The signal can be multiplexed by a subsequent optical multiplexer.

  Furthermore, the optical multiplexing device according to claim 3 is provided with a plurality of optical demultiplexers in parallel, and the optical multiplexer combines the optical signals output from the plurality of optical demultiplexers to output from a single output port. The output unit is provided in the front stage of each optical demultiplexer, and includes distribution means for making an input optical signal of an adjacent wavelength enter a different optical demultiplexer.

  When the number N of input ports increases, the band of N × Δλin approaches the wavelength interval Δλout between the adjacent output ports of the output side slab waveguide, and the end of the transmission band is used for the wavelength of the input light. Loss increases. By providing the sorting means in the preceding stage of the plurality of optical demultiplexers provided in parallel, it is possible to suppress the increase in loss by increasing Δλout and widening the transmission bandwidth ΔB.

  If the wavelength of the optical signal is, for example, λ1, λ2, λ3, λ4 and the number of optical demultiplexers is 2, for example, the optical signals of wavelengths λ1, λ3 are distributed to the first optical demultiplexer by the distributing means. The optical signals of wavelengths λ2 and λ4 are distributed to the second optical demultiplexer by the distributing means. Therefore, compared with the case where the number of optical demultiplexers is 1, the wavelength interval Δλout for each optical demultiplexer is widened.

  In the arrayed waveguide grating according to claim 1, the wavelength band of the optical signal output from each output port can be made the same regardless of which input port is used. Can be output from the output port of the corresponding wavelength band (assigned wavelength). Therefore, it is possible to provide an optical demultiplexer suitable for use in an optical multiplexer described later, and to provide an optical demultiplexer suitable for use in, for example, PON.

  Further, in the optical multiplexing device according to claim 2, since the optical signals of different wavelengths input to the plurality of input ports can be multiplexed without depending on the input port, and output from the single output port, Light of various wavelengths can be multiplexed without using an active optical switch or the like. Therefore, for example, an optical multiplexer suitable for use in WDM optical communication or the like can be provided at low cost. In addition, a small optical multiplexing device can be provided. Furthermore, there is no need to use a 3 dB coupler, a star coupler, etc., and the optical demultiplexer, which is an arrayed waveguide demultiplexer, operates to output a wavelength channel determined from its output port. Can do waves. Especially when the number of input ports is large, the low loss becomes more remarkable.

  Further, in the optical multiplexing device according to claim 3, since a plurality of optical demultiplexers are provided and the input optical signals of adjacent wavelengths are made incident on different optical demultiplexers using the distributing means, the channel spacing Can be widened, the transmission bandwidth can be widened, characteristics can be stabilized, and the number of input wavelengths can be increased.

  Hereinafter, the configuration of the present invention will be described in detail based on the best mode shown in the drawings.

First, the arrayed waveguide type diffraction grating of the present invention will be described. 1 to 3 show an example of an embodiment of an arrayed waveguide type diffraction grating of the present invention. The arrayed waveguide type diffraction grating 1 of the present embodiment is used as an optical demultiplexer (hereinafter referred to as an optical demultiplexer 1). The optical demultiplexer 1 is asymmetric in which the shape of the input side 27 and the shape of the output side 28 satisfy at least one of the formulas 14, 15, 16, and 17, and the output side 28 includes the input side An output port 5 is provided for outputting an optical signal input from any one of the plurality of input ports 3 provided at 27, the wavelength of which coincides with the assigned wavelength.
<Expression 14>
fin> fout
<Expression 15>
Δxin <Δxout
<Equation 16>
din <dout
<Equation 17>
Δxin <ΔWout
Here, fin: focal length of the input side slab waveguide 2, fout: focal length of the output side slab waveguide 4, Δxin: interval of the input port 3, Δxout: interval of the output port 5, din: input side slab waveguide 2 is the interval between the arrayed waveguides 6 connected to 2, dout is the interval between the arrayed waveguides connected to the output-side slab waveguide 4, and ΔWout is the core opening width of the output waveguide 20 (see FIG. 20).

  The input side 27 refers to the input side slab waveguide 2, the portion near the input side slab waveguide 2 of the arrayed waveguide 6, and the portion near the input side slab waveguide 2 of the input waveguide 29. The output side 28 refers to the output side slab waveguide 4, the portion near the output side slab waveguide 4 of the arrayed waveguide 6, and the portion near the output side slab waveguide 4 of the output waveguide 20.

By making it asymmetric in this way, the wavelength interval Δλin between the adjacent input ports 3 of the input-side slab waveguide 2 expressed by Equation 18 and the adjacent output port 5 of the output-side slab waveguide 4 expressed by Equation 19 are used. The relationship between the wavelength interval Δλout and the output port of the output side slab waveguide 4 expressed by the equation 21 and the wavelength interval Δλin of the input port 3 adjacent to the input side slab waveguide 2 expressed by the equation 18 5 satisfies the relationship of Equation 22 with the transmission bandwidth ΔB of 5.
<Equation 18>
Δλin = (Δxin / fin) · (din · ns / m) · (ng / ns) ^-1
<Equation 19>
Δλout = (Δxout / fout) · (dout · ns / m) · (ng / ns) ^-1
<Expression 20>
NΔλin ≦ Δλout
<Expression 21>
ΔB = (ΔWout / fout) · (dout · ns / m) · (ng / ns) ^-1
<Equation 22>
NΔλin ≦ ΔB
Here, Δxin: the distance between the input ports 3, fin: the focal length of the input side slab waveguide 2, din: the distance between the arrayed waveguides 6 connected to the input side slab waveguide 2, ns: the slab waveguides 2, 4. Effective refractive index, m: diffraction order, ng: group refractive index, Δxout: spacing of output port 5, fout: focal length of output side slab waveguide 4, dout: array conductor connected to output side slab waveguide 4 An interval between the waveguides 6, N: an integer of 2 or more in terms of the number of input ports, and ΔWout: a core opening width of the output waveguide 20.

  This optical demultiplexer 1 is an arrayed waveguide type diffraction grating (AWG) which is a planar optical circuit (PLC), and the input side slab waveguide 2 and the output side slab waveguide 4 have different shapes (from the input side 27). The output side 28 is asymmetric). In the present embodiment, the relationship of fin in Formula 18 and fout in Formula 19 is set to satisfy fin> fout so that the relationship of Formula 20 is satisfied. That is, as shown in FIG. 18, in a commercially available AWG for wavelength multiplexing / demultiplexing or an AWG having wavelength circulation, the shapes of the input side slab waveguide 102 and the output side slab waveguide 103 are the same (input side 107). And the output side 108 are symmetrical). On the other hand, in the optical demultiplexer 1 of the present invention, the shapes of the input-side slab waveguide 2 and the output-side slab waveguide 4 are asymmetric, and the shape of the slab waveguides 2 and 4 is made by setting fin> fout. It is asymmetric. For example, if the size is approximately the same as a commercially available AWG, it is preferable to satisfy fin> fout by increasing the focal length fin of the input-side slab waveguide 2 with respect to the dimensions of the AWG. In a commercially available AWG, the focal lengths fin and fout of the slab waveguides 2 and 4 are already small, and the input-side slab is smaller than the focal length fout of the output-side slab waveguide 4. This is because it is easier to manufacture if the focal length fin of the waveguide 2 is increased. However, the focal length fout of the output side slab waveguide 4 may be reduced to satisfy fin> fout, or the focal length fin of the input side slab waveguide 2 may be increased and the output side slab waveguide 4 may be set. The focal length fout may be reduced to satisfy fin> fout. By satisfying fin> fout, the relationship between the wavelength interval Δλin and the wavelength interval Δλout satisfies the relationship of Equation 20, and the wavelength interval Δλin of the optical signal input to each arrayed waveguide 6 in the input side slab waveguide 2 is reduced. As seen from the output port 5, the input port 3 can be seen as one.

  For example, four input ports 3 are provided in the input side slab waveguide 2. However, the number of input ports 3 is not limited to four. The output side slab waveguide 4 is provided with the same number of output ports 5 as the types of wavelengths of the optical signals used. The output port 5 is assigned a wavelength of the optical signal to be used, which is different from the other output ports 5. The optical signal is output from the output port 5 of the assigned wavelength regardless of which input port 3 is input. In the present embodiment, there are four types of wavelengths λ1, λ2, λ3, and λ4 used as optical signals, and four output ports 5 are provided. However, the number of wavelengths of the optical signal and the number of output ports 5 are not limited to four. Here, in order to facilitate explanation and understanding, the number of input ports, the number of output ports, and the number of wavelengths of optical signals are set to 4, but actually, for example, 16, 32, 64, etc. For example, 256, 400, etc. are possible, and other numbers may be used. Hereinafter, for the sake of explanation, the four input ports 3 are distinguished from each other by appropriately describing the input ports 3a, 3b, 3c, 3d and the four output ports 5 as output ports 5A, 5B, 5C, 5D. In FIG. 2, the input ports 3a, 3b, 3c, 3d are simply described as input ports a, b, c, d, and the output ports 5A, 5B, 5C, 5D are simply output ports A, B, C, D is distinguished by being described (the same applies to FIGS. 11, 13, 15, 21, and 23).

  Wavelength λ1 is assigned to output port 5A, wavelength λ2 is assigned to output port 5B, wavelength λ3 is assigned to output port 5C, and wavelength λ4 is assigned to output port 5D. That is, the optical demultiplexer 1 is formed so that these wavelengths are assigned to the output ports without depending on the input ports.

  FIG. 2 shows the relationship between each output port 5 and the wavelength of the output optical signal. For reference, the relationship when fin = fout is indicated by a virtual line. Optical signal λ1a of wavelength λ1 input to input port 3a, optical signal λ1b of wavelength λ1 input to input port 3b, optical signal λ1c of wavelength λ1 input to input port 3c, wavelength input to input port 3d The optical signal λ1d of λ1 is output from the output port 5A. That is, in the AWG that is generally sold with wavelength circulatory properties, as shown in FIG. 16, the optical signal of wavelength λ1 is output from the output port only when it is input to the input port 102a having the same assigned wavelength. In the optical demultiplexer 1 according to the present invention, the light is output from the output port 5A to which the wavelength λ1 is assigned irrespective of the input port 3, that is, regardless of which input port 3a to 3d is input.

  Similarly, an optical signal λ2a of wavelength λ2 input to the input port 3a, an optical signal λ2b of wavelength λ2 input to the input port 3b, an optical signal λ2c of wavelength λ2 input to the input port 3c, and input to the input port 3d The optical signal λ2d having the wavelength λ2 is output from the output port 5B having the wavelength λ2 assigned. Similarly, the optical signals λ3a to λ3d of wavelength λ3 input to the input ports 3a to 3d are output from the output port 5C to which the wavelength λ3 is assigned, and the optical signals of wavelength λ4 input to the input ports 3a to 3d. λ4a to λ4d are output from the output port 5D to which the wavelength λ4 is assigned.

  That is, as shown in FIG. 3, regardless of which input port 3a,..., 3d is used, the optical signal of each wavelength is output from the output ports 5A,. Thus, in the optical demultiplexer 1 of the present invention, the wavelength band of the optical signal output from each output port 5 can be made the same regardless of which input port 3 is used. Even if optical signals of various wavelength bands are input, they can be output from the output port 5 of the corresponding wavelength band (assigned wavelength). Therefore, the optical demultiplexer 1 suitable for use in the optical multiplexing device 7 described later can be provided.

  Next, the optical multiplexing device 7 of the present invention will be described. FIG. 4 shows an example of an embodiment of the optical multiplexing device 7 of the present invention. The optical multiplexer 7 includes the above-described optical demultiplexer 1 and an optical multiplexer 8 that multiplexes the optical signals output from the output port 5 of the optical demultiplexer 1 and outputs them from a single output port 11. Is.

  The optical multiplexer 8 of this embodiment is an arrayed waveguide type multiplexer (arrayed waveguide diffraction grating: AWG). For example, as shown in FIG. 5, the input-side slab waveguide 9 is the optical demultiplexer 1. The same number of input ports 10 as the output ports 5 are provided, and each input port 10 is assigned the same wavelength as the output port 5 of the corresponding optical demultiplexer 1. That is, the optical multiplexer 8 includes an input side slab waveguide 9 having the same number of input ports 10 as the output ports 5 of the optical demultiplexer 1, an output side slab waveguide 12 having a single output port 11, and an input An arrayed waveguide 13 that connects the side slab waveguide 9 and the output side slab waveguide 12 is provided. In this optical multiplexer 8, the shapes of the input-side slab waveguide 9 and the output-side slab waveguide 12 are symmetrical, that is, the focal lengths fin and fout and the array waveguide intervals din and dout are the same, and are generally sold. It is possible to use an AWG for wavelength multiplexing.

  The output port 5 of the optical demultiplexer 1 and the input port 10 of the optical multiplexer 8 are connected to each other by the connecting waveguide 14 to which the same wavelength is assigned. In the present embodiment, since the optical demultiplexer 1 is provided with the four output ports 5, the four input ports 10 of the optical multiplexer 8 are also provided. Hereinafter, for the sake of explanation, the four input ports 10 of the optical multiplexer 8 are distinguished as input ports 10a, 10b, 10c, and 10d. The wavelength λ1 is assigned to the input port 10a, the wavelength λ2 is assigned to the input port 10b, the wavelength λ3 is assigned to the input port 10c, and the wavelength λ4 is assigned to the input port 10d.

  In the optical multiplexer 8, as shown in FIG. 6, when optical signals of wavelengths λ1,..., Λ4 matching the assigned wavelength are input to the input ports 10a,. Output from the output port 11. On the other hand, as shown in FIG. 16, when an optical signal having a wavelength different from the assigned wavelength is input to the input port 10, it cannot be properly multiplexed, and the input ports 10b, 10c, The optical signals λ4, λ2, and λ3 input to 10d are not output.

  In the optical multiplexer 7, the optical demultiplexer 1 is provided in front of the optical multiplexer 8, so that the optical signals of the wavelengths λ 1,..., Λ 4 assigned to the input ports 10 a,. Is entered. Therefore, all of the optical signals input to the optical multiplexer 8 are combined and output from the output port 11 of the optical multiplexer 8. That is, as shown in FIG. 4, all of the optical signals input to the optical multiplexer 7 are combined and output from the output port 11. In this way, even if the active optical switch 106 as shown in FIG. 19 is not provided, the optical signals input to the input ports 3a,..., 3d are combined and output from the single output port 11. Can do.

  In addition, since the front-stage optical demultiplexer 1 and the rear-stage optical multiplexer 8 are both arrayed waveguide type diffraction gratings and are planar optical circuits (PLCs), they can be created on the same planar optical circuit. The connection between the optical demultiplexer 1 at the front stage and the optical multiplexer 8 at the rear stage can be made compatible, and the loss for connection can be kept low.

  FIG. 7 shows a concept of transmitting optical signals of different wavelengths through one optical fiber 15 in wavelength division multiplexing (WDM). Reference numeral 18 in FIG. 7 denotes a duplexer that demultiplexes an optical signal transmitted through the optical fiber 15 according to its wavelength. When realizing this communication method, by using the optical multiplexer 7 of the present invention as a multiplexer, for example, as shown in FIG. 8, the wavelength variable light source 16 can be connected, or for example, as shown in FIG. It becomes possible to connect the WDM network 17. When the number of input ports is large, the optical multiplexer 7 has a lower loss than a 3 dB coupler or a star coupler, and can realize an efficient WDM.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention.

  For example, in the above description, by setting fin> fout, that is, by making the focal length asymmetrical, the shape of the input side 27 and the shape of the output side 28 are asymmetrical, whereby NΔλin ≦ Δλout or NΔλin ≦ ΔB. Although the relationship is satisfied, it is not necessarily limited to this method, and other methods may be used. For example, as shown in FIGS. 10 and 11, by setting Δxin <Δxout, that is, by making the interval Δxin of the input port 3 and the interval Δxout of the output port 5 asymmetric, the shape of the input side 27 and the output side 28 The shape may be asymmetrical so that the relationship of NΔλin ≦ Δλout may be satisfied, or, for example, as shown in FIGS. 12 and 13, din <dout, that is, connected to the input-side slab waveguide 2 By making the interval din of the arrayed waveguide 6 and the interval dout of the arrayed waveguide 6 connected to the output side slab waveguide 4 asymmetric, the shape of the input side 27 and the shape of the output side 28 are made asymmetrical. The relationship of NΔλin ≦ Δλout or NΔλin ≦ ΔB may be satisfied. Furthermore, for example, as shown in FIGS. 20 and 21, by making Δxin <ΔWout, the shape of the input side 27 and the shape of the output side 28 are made asymmetric, thereby satisfying the relationship of NΔλin ≦ ΔB. good. When the port intervals Δxin and Δxout in FIGS. 10 and 11 are asymmetric, the port interval Δxout of the output port 5 is increased, and the output ports 5A,..., 5D due to the difference between the input ports 3a,. It is preferable that the change in the focus position falls within the size range of the output ports 5A,..., 5D. In the embodiment of FIG. 10, the output port 5 is gradually reduced in diameter and connected to, for example, the connection waveguide 14. That is, the focus position at the output ports 5A,..., 5D is shifted by switching the input ports 3a,..., 3d, but the change is within the widened taper of the output port 5. In addition, what is shown with a virtual line in FIG. 11 is a case where the taper part which diameter-reduces the output port 5 gradually is not formed. The bandwidth is different from that of the tapered portion. Further, in FIG. 13, what is indicated by a virtual line is a case where din = dout. The center wavelength and bandwidth are different from the case of din <dout. Further, the above-described method of making the focal lengths fin and fout asymmetric (fin> fout), the method of setting the port intervals Δxin and Δxout asymmetric (Δxin <Δxout), and the connection intervals din and dout of the arrayed waveguide 6 are asymmetric (din) <Dout), and the method of setting the input port 3 interval Δxin <the core opening width ΔWout of the output waveguide 20, any two or three may be combined, or all four may be combined Also good.

  Moreover, in the above-mentioned optical multiplexing device 7, an arrayed waveguide type multiplexer is used as the optical multiplexer 8. However, as long as it can multiplex a plurality of inputs and obtain one output, An optical multiplexer other than the arrayed waveguide multiplexer, for example, a multilayer filter connected in multiple stages, a concave diffraction grating, a transmission diffraction grating, a reflection diffraction grating, or the like may be used. An arrayed waveguide multiplexer or other optical multiplexer may be used in a multistage manner.

  For example, as shown in FIGS. 14 and 15, a plurality of optical demultiplexers 1 are provided in parallel, and input optical signals having adjacent wavelengths are input to different optical demultiplexers 1 before each optical demultiplexer 1. The optical multiplexer 8 may be provided with a distribution unit 19 that makes the light incident, and the optical signals output from the plurality of optical demultiplexers 1 may be combined and output from a single output port 11. In this embodiment, two optical demultiplexers 1 are provided. However, the number of optical demultiplexers 1 is not limited to two, and may be three or more, depending on the number of types of wavelengths of optical signals used, the number of required output ports 5, and the like. An appropriate number is provided.

  The distribution means 19 is an interleaver, for example. However, the distribution means 19 is not limited to an interleaver, and an optical filter that periodically changes the level of transmitted (reflected) light, such as an etalon, can be used. In short, input optical signals are adjacent to each other. There is no particular limitation as long as it allows light having a wavelength to enter different optical demultiplexers 1. Here, the adjacent wavelengths refer to adjacent wavelengths when the wavelengths used as optical signals are arranged in the order of their sizes, for example, there are four types of wavelengths used, λ1, λ2, λ3, and λ4. If the wavelength increases in this order, λ1, λ2, λ2, λ3, λ3, and λ4 are adjacent wavelengths. In the present embodiment, since two optical demultiplexers 1 are provided, the distribution means 19 distributes optical signals to the two optical demultiplexers 1, for example, one input port and two output ports (1 Use an interleaver with 2 inputs). An optical signal is input to the input port of the distribution means 19. One of the two output ports is connected to the first optical demultiplexer 1 and the other is connected to the second optical demultiplexer 1. The number of distribution means 19 is the same as the number of input ports 3 of each optical demultiplexer 1. Since the optical demultiplexer 1 of this embodiment has four input ports 3, it has four distribution means 19.

  In addition, when many optical demultiplexers 1 are provided, the distribution means 19 may be multistage. For example, 1-input 2-output distribution means 19 can be assigned to 2 ports by assigning it to 2 ports, and 3 inputs to assign input from 1 port to 8 ports. Therefore, when four optical demultiplexers 1 are provided, the 1-input 2-output distribution means 19 may be a two-stage type, and when eight optical demultiplexers 1 are provided, one input-two outputs. The distribution means 19 may be a three-stage type, and the number of distribution means 19 may be appropriately set according to the number of optical demultiplexers 1 and the number of output ports in one stage.

  The optical signal input to the distribution unit 19 is distributed to the first optical demultiplexer 1 or the second optical demultiplexer 1 according to the frequency, and is output from the output port 5 having the same assigned wavelength. The signals are combined by a unit 8 and output from a single output port 5. In particular, when the number N of input ports 3 increases, the band of NΔλin approaches the transmission bandwidth, and the end of the transmission band is also used, increasing the loss. By providing the distribution means 19 and allowing optical signals of adjacent wavelengths to enter different optical demultiplexers 1, the channel spacing can be increased and the transmission bandwidth can be increased. Therefore, it is possible to suppress loss and stabilize characteristics, and to increase the number of wavelengths of the input optical signal. For example, the input optical signal is branched into two by the distribution means 19, and the branched output is divided into each optical demultiplexer 1 to widen the channel interval Δλout and the transmission bandwidth, and each optical demultiplexer 1 specifies a specific wavelength for each wavelength. By outputting from the output port 5, the characteristics can be improved without reducing the total number of wavelength channels.

  In the above description, the arrayed waveguide grating 1 of the present invention is an optical demultiplexer, but may be an optical multiplexer. In the case of an optical multiplexer, the output port 5 to which the wavelength of the optical signal to be used is assigned is used as the actual output port. That is, an output port other than the output port 5 to which the wavelength of the optical signal to be used is assigned may or may not exist. For example, when the output side slab waveguide 4 is provided with four output ports 5A, 5B, 5C, and 5D, and the wavelengths λ1, λ2, λ3, and λ4 are assigned to them, the wavelength of the optical signal to be used is λ1. , The output port 5A is an output port that is actually used. In this case, the output ports 5B, 5C, and 5D to which the wavelengths λ2, λ3, and λ4 are assigned may or may not be present. That is, the output ports 5B, 5C, and 5D may be provided at the focal positions of the optical signals having the wavelengths λ2, λ3, and λ4, or may not be provided. It is sufficient if the actual number of output ports 5 is the same as the number of wavelengths of the optical signal used. Here, the case where the wavelength of the optical signal to be used is one is taken as an example, but the same applies to the case where two or more wavelengths are used.

  The optical multiplexer 1 when the number of output ports 5 is one is shown in FIGS. When there is one output port 5, Δλin in Expression 18 and ΔB in Expression 21 satisfy the relationship of Expression 22 by satisfying at least one of Expression 14, Expression 16, and Expression 17 described above. To.

  FIG. 24 shows an example in which the arrayed waveguide grating 1 is used as an optical multiplexer (hereinafter referred to as an optical multiplexer 1). A plurality of communication devices 21 having the same wavelength and different transmission timings are used as light sources. In the present embodiment, the communication device 21 outputs a signal having a wavelength λ1, for example. The optical signal from the communication device 21 is input to each input port 3 of the input-side slab waveguide 2 of the optical multiplexer 1. An output port 5 is formed at the focal position of the light of wavelength λ1 in the output-side slab waveguide 4 of the optical multiplexer 1. Even in this case, the optical signal having the assigned wavelength λ1 can be output from the single output port 5 without depending on the input port 3.

  The optical demultiplexer 1 of the present invention can be applied to, for example, a PON (Passive Optical Network). PON is a system in which a star coupler is provided in the middle of an optical fiber extending from a central office to a subscriber's house and is drawn into a plurality of subscriber houses. In the communication of the PON upstream line (from the subscriber's home to the central office), the ONU (optical network unit: optical line terminator on the subscriber's home side) transmits the optical signal to the OLT (optical line terminal: central office side). ) Each ONU transmits an optical signal at a different timing so that the optical signals do not collide. When passing through a star coupler with N branches, the intensity of the optical signal becomes 1 / N or less, and the loss increases when the number of branches is large.

  The optical multiplexer 1 of the present invention is used in place of this star coupler. FIG. 25 shows an example applied to PON. An optical fiber 25 extending from each ONU 23 is connected to each input port 3 of the optical multiplexer 1. For example, a personal computer 24 is connected to each ONU 23. Each ONU 23 outputs an optical signal having a wavelength λ1, for example. Further, an optical fiber 26 directed to the OLT 22 is connected to the single output port 5 of the optical multiplexer 1. The output port 5 is assigned a wavelength λ1.

  The optical signals of wavelength λ1 output from the respective ONUs 23 at different timings are multiplexed by the optical multiplexer 1 and supplied to the OLT 22. By using the optical multiplexer 1 for multiplexing optical signals, it is possible to reduce loss compared to the case where a star coupler is used. Therefore, it is possible to use a small laser output as each ONU 23 and to reduce power consumption.

It is a top view which shows 1st Embodiment at the time of using the arrayed waveguide type diffraction grating of this invention as an optical demultiplexer. It is a figure which shows the output spectrum image of the same optical demultiplexer. It is a conceptual diagram which shows the relationship between the wavelength of the input light of the same optical demultiplexer, and output light. It is a conceptual diagram which shows 1st Embodiment of the optical multiplexing apparatus of this invention. It is a top view which shows an example of the optical multiplexer used with the optical multiplexing apparatus. It is a conceptual diagram which shows the relationship between the wavelength of the input light and output light of the optical multiplexer. It is the conceptual diagram which applied the optical multiplexing apparatus of this invention to WDM optical communication. It is a conceptual diagram at the time of connecting a wavelength variable light source as a light source of the optical multiplexing apparatus of this invention. It is a conceptual diagram at the time of connecting a WDM network as a light source of the optical multiplexing apparatus of this invention. It is a top view which shows 2nd Embodiment at the time of using the arrayed waveguide type diffraction grating of this invention as an optical demultiplexer. It is a figure which shows the output spectrum image of the optical demultiplexer of FIG. It is a top view which shows 3rd Embodiment at the time of using the arrayed waveguide type diffraction grating of this invention as an optical demultiplexer. It is a figure which shows the output spectrum image of the optical demultiplexer of FIG. It is a conceptual diagram which shows 2nd Embodiment of the optical multiplexing apparatus of this invention. It is a figure which shows the output spectrum image of the optical demultiplexer used with the optical multiplexing apparatus of FIG. It is a conceptual diagram which shows the relationship between the wavelength of the input light and output light of the conventional optical multiplexer. It is a top view of the conventional optical multiplexer (multiple input and 1 output). It is a top view of the conventional optical multiplexer (multiple input and multiple output). It is the conceptual diagram which applied the optical multiplexer of FIG. 17 to WDM optical communication. The 4th Embodiment at the time of using the arrayed waveguide type diffraction grating of this invention as an optical demultiplexer is shown, (a) is a conceptual diagram of an input side slab waveguide, (b) is an output side slab waveguide. It is a conceptual diagram. It is a figure which shows the output spectrum image of the optical demultiplexer of FIG. The embodiment at the time of using the arrayed waveguide type diffraction grating of the present invention as an optical multiplexer is shown, (a) is a conceptual diagram of an input side slab waveguide, (b) is a conceptual diagram of an output side slab waveguide. . It is a figure which shows the output spectrum image of the optical multiplexer of FIG. It is a conceptual diagram at the time of connecting the some transmitter which shifted transmission timing with the same wavelength as a light source. It is a conceptual diagram at the time of applying to the PON the arrayed waveguide type diffraction grating of this invention as an optical multiplexer.

Explanation of symbols

1 Arrayed waveguide grating (optical demultiplexer, optical multiplexer)
2 Input side slab waveguide 3 Input port 4 Output side slab waveguide 5 Output port 6 Array waveguide 7 Optical multiplexer 8 Optical multiplexer 11 Output port 19 Sorting means 27 Input side 28 Output side

Claims (3)

The shape on the input side and the shape on the output side are asymmetrical satisfying at least one of Formulas 1, 2, 3, and 4, and the output side includes a plurality of input ports provided on the input side. An arrayed waveguide grating characterized in that an output port is provided for outputting an optical signal input from any input port whose wavelength matches the assigned wavelength.
<Equation 1>
fin> fout
<Equation 2>
Δxin <Δxout
<Equation 3>
din <dout
<Equation 4>
Δxin <ΔWout
Here, fin: focal length of the input side slab waveguide, fout: focal length of the output side slab waveguide, Δxin: spacing of the input port, Δxout: spacing of the output port, din: connected to the input side slab waveguide The distance between the arrayed waveguides, dout: the distance between the arrayed waveguides connected to the output-side slab waveguide, and ΔWout: the core opening width of the output waveguide.   An optical demultiplexer comprising the arrayed waveguide grating according to claim 1 and an optical multiplexer, and an output slab waveguide of the optical demultiplexer has a plurality of the output ports, The optical multiplexer combines the optical signals output from the plurality of output ports and outputs the optical signals from a single output port.   A plurality of the optical demultiplexers are provided in parallel, and the optical multiplexer multiplexes the optical signals output from the plurality of optical demultiplexers and outputs them from a single output port. 3. The optical multiplexing apparatus according to claim 2, further comprising a distribution unit that is provided in a front stage of the demultiplexer and that makes an input optical signal having an adjacent wavelength incident on the different optical demultiplexer.

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