JP3608571B2 - Array waveguide grating, demultiplexing device, and multiplexing device - Google Patents

Description

  The present invention relates to an arrayed waveguide grating, a demultiplexing device, and a multiplexing device including a slab waveguide, and in particular, an arrayed waveguide grating, a demultiplexing device, and a multiplexing device capable of setting light input / output characteristics to a desired one. Wave device.

  Along with the increase in capacity of data to be transmitted, further expansion of transmission capacity is desired in an optical fiber optical communication system. For this reason, for example, when using a high-density wavelength division multiplexing (Dense) wavelength division multiplexing (DWDM), the importance of an optical wavelength filter as a multiplexing / demultiplexing device for dividing or integrating each wavelength is important. Increasingly.

  There are various types of optical wavelength filters. Among them, an arrayed waveguide grating (AWG) has a narrow wavelength characteristic and a high extinction ratio, and also has characteristics as a multi-input multi-output filter device. For this reason, it is possible to separate multiplexed signals and vice versa, and there is an advantage that a wavelength multiplexing / demultiplexing device can be easily configured. The use of a slab waveguide as an arrayed waveguide grating has been proposed in the past (see, for example, Patent Document 1). In addition, a technique for performing general multiplexing or demultiplexing of light has been conventionally proposed (for example, see Patent Document 2).

  FIG. 24 shows the overall configuration of a conventional arrayed waveguide grating. The arrayed waveguide grating 11 includes one or a plurality of input waveguides 13 formed on a substrate 12, a plurality of output waveguides 14, and a channel waveguide array 15 bent in a certain direction with different curvatures. The input slab waveguide 16 that connects the input waveguide 13 and the channel waveguide array 15, and the output slab waveguide 17 that connects the channel waveguide array 15 and the output waveguide 14. The multiple signal light incident from the input waveguide 13 has its path expanded by the input slab waveguide 16. Then, the light is incident on the channel waveguide array 15 with the same phase.

  In the channel waveguide array 15, a certain optical path length difference is provided between the arrayed waveguides constituting the channel waveguide array 15, and the optical path length is set to be sequentially longer or shorter. Accordingly, the light guided through the respective arrayed waveguides is given a phase difference of a predetermined interval and reaches the output slab waveguide 17. Since there is actually chromatic dispersion, the equiphase surface is inclined depending on the wavelength. As a result, light is focused (condensed) at different positions on the interface between the output slab waveguide 17 and the output waveguide 14 depending on the wavelength. Since the output waveguide 14 is disposed at each position corresponding to the wavelength, it is possible to extract an arbitrary wavelength component from the output waveguide 14.

  Incidentally, in the conventional arrayed waveguide grating as shown in FIG. 24, when attention is paid to the output slab waveguide 17, the light transmitted from the channel waveguide array 15 into the slab waveguide is arranged on the output side. Reach multiple output waveguides. At this time, the light intensity becomes stronger toward the center of the output waveguide, and the light intensity becomes weaker toward the output waveguide in the peripheral area.

  Therefore, conventionally, proposals have been made for making the light level uniform and making the received light level uniform. For example, in order to adjust the level of each signal after light reception, an attempt is made to construct an attenuator by individually preparing a resistor for loss difference compensation in each output-side transmission line.

  It should be noted that, in an apparatus including an optical waveguide having a plurality of ports and an optical fiber array, the optical axis deviation of each optical fiber constituting the ports and the optical fiber array is set, so A proposal has also been made to set the transmission loss to a desired value (see, for example, Patent Document 3).

Japanese Patent Laid-Open No. 7-63934 (paragraph 0013, FIG. 1) Japanese Patent Laid-Open No. 7-49430 (paragraph 0026, FIG. 3) JP 2000-98177 A (paragraph 0013, FIG. 1)

  However, when such a technique is adopted, it is necessary to prepare a large number of resistors having different resistance values as the number of signal levels of received signals increases between channels. Moreover, the resistance value of the resistor varies depending on the temperature. Therefore, it is essential to use a resistor temperature adjustment circuit. For this reason, there is a problem that the conventional arrayed waveguide grating to which the resistor for compensating for the loss difference is added is not practical in terms of cost and space.

  In particular, in an arrayed waveguide grating in which monitor signals are extracted using high-order diffracted light, the monitor signal waveguide is disposed at a position away from the optical axis of light emitted from the channel waveguide array. In many cases, a large difference occurs in the light receiving level. For this reason, an apparatus structure that compensates for loss before or after light reception has been indispensable.

  It should be noted that, in the apparatus having the optical waveguide having the plurality of ports and the optical fiber array, the optical axis shift of each optical fiber constituting the ports and the optical fiber array is set, and the optical waveguide In the method of setting the transmission loss between ports to a desired value, the above-described external attenuator is unnecessary, but fine adjustment of the optical axis is necessary, and there is a problem in terms of yield and cost.

  Although the array waveguide grating has been described above, a demultiplexing device for demultiplexing light using the arrayed waveguide grating, a multiplexing device for multiplexing, and an arrayed waveguide grating or demultiplexing device or multiplexing device were used. Similarly, the optical communication system has a problem that the apparatus becomes complicated and large, and it is difficult to reduce the cost.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an arrayed waveguide grating, a demultiplexing device, and a device capable of adjusting the signal level output from each waveguide without the need for circuit components for compensating for the loss difference or high-precision component mounting work. It is to provide a multiplexing device.

In the arrayed waveguide grating of the present invention, (b) one or more input waveguides through which an optical signal can be input, (b) a channel waveguide array provided with a predetermined optical path length difference, and (c) the channel waveguide. An input slab waveguide connecting the waveguide array and the input waveguide; (d) connected to the opposite side of the channel slab waveguide where the input slab waveguide is connected; An output slab waveguide that inputs an optical signal through the waveguide array; (e) a plurality of output waveguides that can output an optical signal; and (f) provided at a connection point between the output waveguide and the output slab waveguide, The arrayed waveguide grating is provided with a loss adjusting means composed of a cladding layer inserted into the core layer of the output slab waveguide .

In the present invention, a loss adjusting means comprising a cladding layer inserted into the core layer of the output slab waveguide is provided at the connection portion between the output waveguide and the output slab waveguide, so that the circuit component for compensating for the loss difference, The signal level can be adjusted without requiring high-precision component mounting work.

  The branching device of the present invention includes the above-described arrayed waveguide grating. Therefore, in the demultiplexing device of the present invention, the level for each wavelength after demultiplexing can be set to a desired value.

  A multiplexing device of the present invention includes the arrayed waveguide grating described above, and multiplexes optical signals having a plurality of wavelengths. Therefore, in the multiplexing device of the present invention, the level for each wavelength after being multiplexed can be set to a desired value.

As described above, in the present invention, since the loss adjusting means including the cladding layer inserted into the core layer of the output slab waveguide is provided at the connection portion between the output waveguide and the output slab waveguide, the arrayed waveguide grating The input / output characteristics can be changed and the output characteristics can be flattened without disposing an attenuator or an amplifier outside the panel, and without requiring a high-precision component mounting operation. In addition, the reliability can be improved and the cost can be reduced.

  Hereinafter, the present invention will be described in detail with reference to examples.

  << First Example >>

  FIG. 1 shows an output slab waveguide of an arrayed waveguide grating in the first embodiment of the present invention. The basic configuration of the arrayed waveguide grating of this embodiment is the same as that shown in FIG. The output slab waveguide 101 is connected to a channel waveguide array 102 at the input side end portion, and light is transmitted from the output slab waveguide 101 to the inside of the output slab waveguide 101. One end of each of the waveguides 104 constituting the output waveguide 105 corresponding to the output waveguide 14 shown in FIG. 24 is connected to the output slab waveguide 101 at a position facing the connection portion of the channel waveguide array 102. Yes. Light transmitted from the channel waveguide array 102 into the output slab waveguide 101 is propagated through the output waveguide 105.

FIG. 2 is an enlarged view of a part of the output side of the output slab waveguide. The output waveguide 105 of the output slab waveguide 101 of the present embodiment includes the compensation waveguides 104 _{m to} 104 _{m + n} in which the intensity of the reaching light is compensated, and the non-compensation waveguide 104 in which the intensity of the light is not compensated. _{k to} 104 _{k + n} . The compensation waveguides 104 _{m to} 104 _{m + n} are adapted to compensate for the signal level of light, and are also used for monitoring waveguides. The uncompensated waveguides 104 _{k to} 104 _{k + n} are generally used for applications in which signal level reduction due to compensation is not desirable. Of course, all the waveguides 104 of the output waveguide 105 may constitute a compensation waveguide.

Inside the output slab waveguide 101, a core layer 111 for propagating light transmitted from the channel waveguide array 102 is disposed up to the connection portion of the output waveguide 105, and this is viewed from both the upper and lower directions (perpendicular to the paper surface). A clad layer 112 is sandwiched so as to sandwich light, and light is confined in the core layer 111. However, in the case of the output slab waveguide 101 constituting the arrayed waveguide grating of the present embodiment, the core layer 111 at a position corresponding to the compensation waveguides 104 _{m to} 104 _{m + n} is a part of the optical path 113. The clad layer 112 is disposed at the cut portion.

3 and 4 show the cut portions of the core layer in the two optical paths shown in FIG. These drawings are both obtained by cutting the output slab waveguide 101 shown in FIG. 2 along the optical path 113 _{m + n} or the optical path 113 _{m + 1} perpendicular to the paper surface. Considering a state in which a part of the core layer 111 is not cut, the optical path 113 _{m + n} reaching the compensation waveguide 104 _{m + n} shown in FIG. 3 is more compensated for the compensation waveguide 104 _m shown in FIG. The intensity of light transmitted from the channel waveguide array 102 shown in FIG. 1 is stronger than the optical path 113 _{m + 1} reaching ₊₁ . In this embodiment, such flattening of the light intensity level is adjusted by the lengths of the cutting lengths L _{m + n} and L _{m + 1} of the core layer 111.

That is, in the case of the optical path 113 _{m + n} shown in FIG. 3, the cutting length L _{m + n} is relatively short, and a considerable part of the light emitted from the core layer 111 _IN on the input side at the cutting point is The _light enters the core layer 111 _OUT on the output side and reaches the compensation waveguide 104 _{m + n} . On the other hand, in the case of the optical path 113 _{m + 1} shown in FIG. 4, the cutting length L _{m + 1} is relatively long, and the light emitted from the core layer 111 _IN on the input side at the cutting position is relatively long. Many portions do not enter the core layer 111 _OUT on the output side. For this reason, the intensity of the light reaching the compensation waveguide 104 _{m + 1} is greatly reduced.

Therefore, the intensity of light when the core layer 111 is not absent in each of the compensation waveguides 104 _{m to} 104 _{m + n} shown in FIG. 2 is obtained by measurement or theory, and these are flattened so that they are flattened. It is only necessary to partially cut the optical path 113 in the middle with a length obtained by experiment or theory. Cutting of a necessary portion of the core layer 111 can be realized by, for example, wet or dry etching.

FIG. 5 shows the relationship between the cut length of the core layer and the amount of increase in light loss due to this. It can be seen that the longer the length of the portion where the core layer 111 is cut, the more the loss of light reaching the waveguide 104 increases and reaches it after attenuation. Depending on the arrayed waveguide grating or the demultiplexing device, multiplexing device, or optical communication system using the same, there may be cases where flat signal characteristics are not always required. For example, when the output characteristics of an amplifier (not shown) arranged on the output side of the compensation waveguides 104 _{m to} 104 _{m + n} are not flat, it is necessary to design the output characteristics together with these. Therefore, in practice, the intensity of light obtained on the compensation waveguides 104 _{m to} 104 _{m + n} side is compensated according to the required output characteristics.

  << Second embodiment >>

FIG. 6 is an enlarged view of a portion around the output side of the slab waveguide portion of the arrayed waveguide grating in the second embodiment of the present invention. The basic configuration of the arrayed waveguide grating of this embodiment is the same as that shown in FIG. The output slab waveguide 131 is connected to the channel waveguide array 102 at the input side end, and light is transmitted from the input slab waveguide 101 to the inside of the input slab waveguide 101. The transmitted light is focused at the respective output port side focal positions _{Pm + n} , _{Pm + n-1} , _{Pm + n-2} ,... . Then, the light focused on the output port side focal positions P _{m + n} , P _{m + n−1} , P _{m + n− 2} ,... Is channel guided corresponding to the output waveguide 14 shown in FIG. Each of the compensating waveguides 132 _{m + n} , 132 _{m + n−1} , 132 _{m + n−2} ,... Constituting the waveguide is propagated.

The difference from the arrayed waveguide grating of the first embodiment is that the core layer (not shown) of the output slab waveguide 131 is not cut in the middle of the optical path, and that the compensation waveguides 132 _{m + n} and 132 _{m + n− 1} , 132 _{m + n-2} ,..., Part or all of the extension lines of the central axes correspond to the output waveguide side focal positions P _{m + n} , P _{m + n−1} , P _{m + n} corresponding thereto. _-2 does not agree with ......, but is in a so-called off-axis state. In the present embodiment, the state of the axis deviation is exaggerated for easy understanding.

FIGS. 7 and 8 show the light in two cases: a compensation waveguide which is arranged relatively in the periphery of the output slab waveguide and which is not compensated for power, and a compensation waveguide which is slightly compensated for output. The state of propagation of is illustrated. In the case of the compensation waveguide 132 _{m + n} shown in FIG. 7, correction for attenuating light is not performed. In this state, the positional relationship between each input port and the channel waveguide array in the normal output slab waveguide is exactly the same, and the extension line of the central axis 141 _{m + n} of the compensation waveguide 132 _{m + n} is the output waveguide side focal position P. It matches the position of _{m + n} . That is, in this case, no axis deviation occurs. In the state shown in FIG. 7, the Gaussian intensity distribution light focused at the output waveguide-side focal position P _{m + n} matches well with the compensation waveguide 132 _{m + n,} and the inside thereof. Is propagated to the output side indicated by the arrow 142.

On the other hand, in the case of the compensation waveguide 132 m + _n-1 adjacent thereto as shown in FIG. 8, the central axis 141 with respect to the corresponding output waveguide side focal position _{P m + n-1 m +} n-1 Is shifted by a slight distance d _{m + n−1} . Due to this misalignment, the Gaussian intensity distribution light focused on the output waveguide side focal position P _{m + n-1} undergoes a slight mismatch when propagating through the compensation waveguide 132 _{m + n-1.} This causes loss (attenuation). As a result, even if the intensity of the light focused on the output waveguide side focal position P _{m + n-1} is larger than that of the output waveguide side focal position P _{m + n} , the value of this axis deviation is appropriately set. Is set, the intensity of light propagating through the compensation waveguide 132 _{m + n−1} can be set equal to the intensity of light propagating through the compensation waveguide 132 _{m + n} . In this way, the compensation waveguides 132 _{m + n} , 132 _{m + n−1} , 132 _{m + n−2} ,... Can all have the same light intensity and have flat characteristics.

FIG. 9 shows the relationship between the axial shift of each output port for obtaining such a flat output characteristic and the loss obtained thereby. Similar to the first embodiment, the present embodiment need not be limited to the one that obtains flat characteristics on the output side. That is, a flat signal characteristic may not necessarily be required depending on the arrayed waveguide grating or a demultiplexing device, a multiplexing device, or an optical communication system using the same. For example, it is arranged on the final output side (not shown) after the compensation waveguides 132 _{m + n} , 132 _{m + n−1} , 132 _{m + n−2} ,. When the output characteristic of an amplifier (not shown) is not flat, it is necessary to design the output characteristic in combination with these. Therefore, in practice, the intensity of the light obtained on the compensating waveguides 132 _{m + n} , 132 _{m + n−1} , 132 _{m + n−2} ,... Is compensated according to the required output characteristics. Become.

  << Third embodiment >>

FIG. 10 is an enlarged view of the main part of the slab waveguide portion of the arrayed waveguide grating according to the third embodiment of the present invention. The basic configuration of the arrayed waveguide grating of this embodiment is the same as that shown in FIG. The output slab waveguide 161 of the third embodiment transmits the light transmitted from the channel waveguide array 102 to the respective output waveguide side focal positions P _{m + n} , P _{m + n−1} , P _{m + n−. The} phase is adjusted at the positions of ₂ ,. Corresponding to the output waveguide side focal positions P _{m + n} , P _{m + n−1} , P _{m + n− 2} ,..., Compensation waveguides 162 _{m + n} and 162 _m constituting an output waveguide (not shown _{). + n-1} , 162 _{m + n-2} ,... are arranged. Unlike the second embodiment, these compensation waveguides 162 _{m + n} , 162 _{m + n−1} , 162 _{m + n− 2} ,... There is no deviation in the positions P _{m + n} , P _{m + n-1} , P _{m + n-2} ,. Instead, in the arrayed waveguide grating of the third embodiment, the light transmitted from the light transmission point on the channel waveguide array 102 side and the output waveguide side focal positions P _{m + n} , P _{m + n− 1, P m + n-2} , the optical path 163 _m + n connecting _{......, 163 m + n-1} , 163 m + n-2, the compensation waveguide 162 respectively ...... corresponding _{m +} n, 162 _m + _The angles formed by the central axes of _n−1 , 162 _{m + n−2} ,... differ depending on the compensation amount of light intensity.

FIG. 11 illustrates the relationship between the optical path to each output port and the central axis of the compensation waveguide. Here, as in the first and second embodiments, the setting is made such that there is no loss with respect to the compensation waveguide 162 _{m + n} positioned relatively at the periphery on the input side of the output slab waveguide 161. The compensation waveguides 162 _{m + n−1} , 162 _{m + n−2} ,... Are assumed to increase in loss as they approach the center. Optical path 163 m + _n connecting the channel waveguide array output waveguide side focal position P _{m + n} in the present embodiment, the optical path 163 m + _n and the central axis 165 m + _n of the compensation waveguide 162 m + _n If the angle formed is θ _{m + n} , this is 0 degrees. That is, in this case, the light path 163 _{m + n} and the center axis 165 _{m + n} coincide with each other, and the Gaussian-shaped intensity distribution light focused at the output waveguide side focal position P _{m + n} is compensated. It matches well with the waveguide 165 _{m + n} and propagates to the output side, and the coupling efficiency is the best.

On the other hand, when the adjacent and compensation waveguide 162 m + _n compensation waveguide 162 m + _n-1, the central axis 165 m + _n-1 does not coincide with the optical path 163 m + _n-1, these are relatively It intersects at a small angle θ _{m + n-1} . Therefore, the light that focused on the output waveguide side focal position P _{m + n-1} adjacent to the output waveguide side focal position P _{m + n} is slightly when propagating through the compensation waveguide 162 m + _n-1 This causes mismatching and slightly reduces the coupling efficiency. As a result, even if the intensity of the light focused on the output waveguide side focal position P _{m + n-1} is larger than that of the output waveguide side focal position P _{m + n} , this angle θ _{m + n− If} the value of ₁ is appropriately set, the intensity of light propagating through the output waveguide, that is, the compensation waveguide 162 _{m + n−1} can be set equal to the intensity of light propagating through the compensation waveguide 162 _{m + n.} .

In the case of the compensation waveguide 162 m + _n-2 further positioned adjacent to the center side of the compensation waveguide 162 m + _n-1, the central axis 165 m + _n-2 and the optical path 163 m + _n-2 The angle θ _{m + n−2} is set larger than the angle θ _{m + n−1} by a predetermined amount. As a result, the coupling efficiency between the output waveguide side focal position P _{m + n−2} and the compensation waveguide 162 _{m + n−2} is further lowered than in the previous case. Therefore, the intensity of light propagating through the compensation waveguide 162 _{m + n-2} is also equal to the intensity of light propagating through the compensation waveguide 162 _{m + n-1} if the value of the angle θ _{m + n-2} is appropriately set. Can be set. In this way, the compensation waveguides 162 _{m + n} , 162 _{m + n−1} , 162 _{m + n−2} ,.

FIG. 12 shows the relationship between the angle θ of the central axis and the loss obtained thereby. Similar to the first and second embodiments, it is not necessary to limit the present embodiment to one that obtains flat characteristics on the output side. That is, a flat signal characteristic may not necessarily be required depending on the arrayed waveguide grating or a demultiplexing device, a multiplexing device, or an optical communication system using the same. For example, the compensation waveguides 162 _{m + n} , 162 _{m + n−1} , 162 _{m + n−2} ,... Are arranged on the final output side (not shown) (after the output waveguide 14 in FIG. 24). When the output characteristic of an amplifier (not shown) is not flat, it is necessary to design the output characteristic in combination with these. Therefore, in practice, the intensity of light obtained on the compensation waveguides 162 _{m + n} , 162 _{m + n−1} , 162 _{m + n−2} ,... Is compensated according to the required output characteristics. Become.

  << Fourth embodiment >>

FIG. 13 is an enlarged view of a part of the periphery of the output side of the slab waveguide portion of the arrayed waveguide grating in the fourth embodiment of the present invention. The basic configuration of the arrayed waveguide grating of this embodiment is the same as that shown in FIG. Similarly to the output slab waveguide 101, the output slab waveguide 191 of the fourth embodiment transmits light transmitted from a channel waveguide array (not shown) to the respective output waveguide side focal positions P _{m + a} , P _{m +. The} phases are matched at the positions of _a-1 , P _{m + a-2} ,. Then, the light focused on the output waveguide side focal positions P _{m + a} , P _{m + a−1} , P _{m + a− 2} ,... Corresponds to the corresponding compensation waveguides 192 _{m + a} , 192 _{m +. a-1} , 192 _{m + a-2} ,... are propagated.

In this embodiment, as in the case of the third embodiment, each output waveguide side focal position _{Pm + a} , _{Pm + a-1} , _{Pm + a-2} ,... Is the corresponding compensation waveguide. 192 _{m + a} , 192 _{m + a−1} , 192 _{m + a− 2} ,... Further, an optical path 193 _{m +} extending from a light transmission point (not shown) on the channel waveguide array side to each output waveguide side focal position _{Pm + a} , _{Pm + a-1} , _{Pm + a-2} ,. _a , 193 _{m + a-1} , 193 _{m + a-2} ,... are the central axes of the corresponding compensating waveguides 192 _{m + a} , 192 _{m + a-1} , 192 _{m + a-2} ,. Is consistent with Instead, in the arrayed waveguide grating of the fourth embodiment, each compensation waveguide 192 _{m + a} , 192 _{m + a-1} , 192 _{m + a-2} ,... Is connected to the output slab waveguide 191. End-side waveguide widths W _{m + a} , W _{m + a−1} , W _{m + a− 2} ,... Differ depending on the compensation amount of light intensity.

That is, in the arrayed waveguide grating of the fourth embodiment, compensation corresponding to the spot size of the light at each output waveguide side focal position P _{m + a} , P _{m + a−1} , P _{m + a− 2} ,. Waveguide widths W _{m + a} , W _{m + a-1} , W _{m + a-2} ,... Of the waveguides 192 _{m + a} , 192 _{m + a-1} , 192 _{m + a-2} ,. Is used to adjust the compensation amount of the light intensity.

FIG. 14 shows the relationship between the spot size of the focal spot and the spot size of the waveguide mode of the waveguide and the coupling loss at this ratio. As is apparent from this figure, the loss increases as the ratio of the spot size of the focal point to the spot size of the waveguide mode of the waveguide increases from 1. Since the spot size of the focal point is constant and the spot size of the waveguide mode changes when the waveguide width is changed, the compensation waveguides 192 _{m + a} , 192 _{m + a-1} , 192 _{m + a-2} ,... By setting the waveguide widths W _{m + a} , W _{m + a-1} , W _{m + a-2} ,..., The ratio of the focal spot size to the waveguide waveguide spot size is set respectively. Can be adjusted. From this, the waveguide widths W _{m + a} , W _{m + a-1} , W _{m + a-2} , of the compensating waveguides 192 _{m + a} , 192 _{m + a−1} , 192 _{m + a− 2} ,. ... Are appropriately set so that the intensity of light propagating through these compensation waveguides (output waveguides) 192 _{m + a} , 192 _{m + a-1} , 192 _{m + a-2} ,. Desired characteristics can be set.

  «Fifth embodiment»

FIG. 15 is an enlarged view of the main part of the slab waveguide portion of the arrayed waveguide grating in the fifth embodiment of the present invention. The basic configuration of the arrayed waveguide grating of this embodiment is the same as that shown in FIG. The output slab waveguide 221 of the fifth embodiment has an equiphase curve (the output waveguide-side focal positions P _{m + n} , P _{m + of the} previous embodiment) in which the output side is connected to the connection portions of the uncompensated waveguide. _n-1 , P _{m + n-2} ,... or a curve connecting the output waveguide side focal positions P _{m + a} , P _{m + a-1} , P _{m + a-2} ,. A part of the optical waveguide protrudes toward the output waveguide side as the output side, and compensation waveguides 225 _{m to} 225 _{m + n} for compensating the light intensity are connected to the protruding portion. That is, the boundary between the output slab waveguide 221 and the compensation waveguides 225 _{m to} 225 _{m + n} partially protrudes toward the output waveguide than the normal one. In this way, instead of projecting toward the output side with respect to the equiphase curve 223, the shape may be recessed into the input side of the input slab waveguide 221.

FIG. 16 is a diagram for explaining in principle the light loss due to the protruding portion on the output side of such an output slab waveguide. In this embodiment, the light that has passed through the optical path 224 _{m + n} connecting the channel waveguide array (not shown) and the output waveguide side focal position P _{m + n} is the compensation waveguide disposed at the output waveguide side focal position P _{m + n.} Matches well with 225 _{m + n} and propagates inside to the output side. In this state, the light intensity level is not corrected.

On the other hand, the light that has passed through the optical path 224 _{m + n-1} connecting the channel waveguide array and the output waveguide side focal position P _{m + n-1} has the output waveguide side focal position P _{m + n-1} at the focal position. However, the compensation waveguide 225 _{m + n−1} is disposed at a position retracted by a predetermined length (hereinafter referred to as a defocus distance) F _{m + n−1 in the} light output direction. Therefore, the light having a Gaussian waveform at the output waveguide side focal position P _{m + n-1} is propagated into the compensation waveguide 225 _{m + n-1} with a slightly enlarged distortion spot size. Mismatching causes coupling loss. As a result, by appropriately setting the defocus distance F _{m + n−1} , it occurred at the output waveguide side focal position P _{m + n−1 as} compared with the channel waveguide array side focal position P _{m + n} . A coupling loss that cancels the increase in light intensity can be generated, and the intensity level of light propagating through the compensation waveguide 225 _{m + n−1} can be adjusted to the same level as that of the compensation waveguide 225 _{m + n.} .

Compensation waveguide 225 m + _n-2 further positioned adjacent to the center side of the compensation waveguide 225 m + _n-1 is longer focal from the output waveguide side focal position P _{m + n-2} corresponding thereto It is arranged at a position retracted to the output waveguide side as the output side by the deviation distance F _{m + n−2} . As a result, the coupling efficiency between the output waveguide side focal position P _{m + n−2} and the compensation waveguide 225 _{m + n−2} is further lowered than in the previous case. Therefore, if the value of the defocus distance F _{m + n-2} is appropriately set, it can be set equal to the intensity of light propagating through the compensation waveguide 225 _{m + n-1} . In this way, the compensation waveguides 225 _{m + n} , 225 _{m + n−1} , 225 _{m + n−2} ,.

FIG. 17 shows the relationship between the defocus distance F and the loss caused thereby. As in the previous embodiments, the present embodiment need not be limited to the one that obtains flat characteristics on the output side. That is, a flat signal characteristic may not necessarily be required depending on the arrayed waveguide grating or a demultiplexing device, a multiplexing device, or an optical communication system using the same. For example, when the output characteristics of amplifiers (not shown) arranged on the output side of the compensation waveguides 225 _{m + n} , 225 _{m + n−1} , 225 _{m + n− 2} ,. Therefore, it is necessary to design the output characteristics in total. Therefore, in practice, the intensity of the light obtained on the compensating waveguides 225 _{m + n} , 225 _{m + n−1} , 225 _{m + n− 2} ,... Is compensated according to the required output characteristics. Become.

  << Possibility of modification of the first to fifth embodiments >>

  FIG. 18 shows a general input / output relationship of the slab waveguide portion of the arrayed waveguide grating. Here, the same reference numerals as those in FIG. 1 are used for the portions shown in FIG. In the previous first embodiment, light is transmitted from the channel waveguide array 102 of the output slab waveguide 101 into the output slab waveguide 101 and demultiplexed from each waveguide 104 constituting the output waveguide 105. Was output. On the contrary, by using each waveguide 104 side of the output waveguide 105 as an input and using the channel waveguide array 102 as an output side, optical signals of various wavelengths or signals are multiplexed. Can be taken out. At this time, conventionally, since the intensity of light incident from the relatively central portion of the output waveguide 105 is increased, it has been necessary to adjust the intensity level of the light at the input stage. By using the slab waveguide 101 in the input / output reverse direction, it is possible to make the signal level after the combination within an appropriate range without performing such adjustment.

  As described above, it has been described that the arrayed waveguide grating of the first embodiment can be combined as well as the demultiplexing of light. However, the arrayed waveguide gratings of the second to fifth embodiments can also be combined. The point is exactly the same. That is, these arrayed waveguide gratings can be used as optical signal multiplexers or vice versa.

  << Sixth embodiment >>

FIG. 19 shows a configuration of a demultiplexer as a sixth embodiment of the present invention. The demultiplexing device 301 includes a waveguide element 303 that inputs an optical signal 302. The waveguide element 303 may be any type of arrayed waveguide grating described in the first to fifth embodiments. However, as described in these embodiments, the input optical signal is demultiplexed and the output waveguide 304 is demultiplexed. from _{1 ~304 N} and outputs the optical signal 305 ₁ to 305 _N after these branching. Monitor amplifier circuits 306 _{1 to} 306 _N are provided at the subsequent stage of the output waveguides 304 _{1 to} 304 _N , respectively. These supervisory amplifier circuits 306 _{1 to} 306 _N are circuits that input the corresponding ones of the optical signals 305 _{1 to} 305 _N , detect their signal levels, and amplify or attenuate them so that they become a desired level. Yes, it is a kind of AGC (automatic gain control) circuit. As a result, the optical signals 305 _{1 to} 305 _N whose gains are primarily adjusted in the waveguide element 303 are finally adjusted in their gains and output as optical signals 307 _{1 to} 307 _N. It will be.

Of course, each level of the optical signals 305 _{1 to} 305 _N output by the waveguide element 303 of this embodiment can be flattened, but the output characteristics required for the demultiplexer 301 as a whole are different even if there such a characteristic makes it possible to deal with monitoring the amplifying circuit 306 ₁ ~306 _N.

  << Seventh embodiment >>

FIG. 20 shows the structure of a multiplexing apparatus as a seventh embodiment of the present invention. The multiplexer 321 includes semiconductor lasers 322 _{1 to} 322 _N that output optical signals having a plurality of wavelengths. Optical signals 323 _{1 to} 323 _N output from the semiconductor lasers 322 _{1 to} 322 _N are branched into two by branch elements 324 _{1 to} 324 _N , respectively, and one of these optical signals 325 _{1 to} 325 _N is a waveguide. The signal is input to the element 326. The waveguide element 326 combines these input optical signals 325 _{1 to} 325 _N and outputs the multiplexed optical signal 327.

On the other hand, the other optical signals 328 _{1 to} 328 _N branched by the branch elements 324 _{1 to} 324 _N are detected by the level detection circuits 329 _{1 to} 329 _N provided corresponding thereto. Level detection circuits 329 _{1 to} 329 _N can be configured by, for example, photodiodes. Based on these detection results, the level detection circuits 329 _{1 to} 329 _N control the laser output levels by the drive control circuits 331 _{1 to} 331 _N arranged corresponding to the semiconductor lasers 322 _{1 to} 322 _N , respectively. As a result, the level of the optical signal of each wavelength constituting the optical signal 327 output from the waveguide element 326 can be set to an appropriate value.

Also in the multiplexing device 321 of this embodiment, if the waveguide element 326 compensates the output characteristics so that each of the waveguide elements 326 outputs an equal level multiplexed signal, the drive control is performed. The output characteristics can be made flat without particularly using the circuits 331 _{1 to} 331 _N. However, when output characteristics different from this are required, or when high-accuracy level adjustment is required, it is possible to cope with this by using the drive control circuits 331 _{1 to} 331 _N in this way.

  << Eighth embodiment >>

FIG. 21 shows an outline of the configuration of the optical communication system in the eighth embodiment of the present invention. In this optical communication system, optical signals for N channels of wavelengths λ _{1 to} λ _N sent from an optical transmitter 401 connected to a SONET (Synchronous Optical Network) device (not shown) arranged on the transmission side are optical multiplexers ( MUX) 402, amplified by booster amplifier 403, and sent to optical transmission line 404. The optical multiplexer 402 is composed of, for example, an arrayed waveguide grating as described in the first embodiment. The multiplexed optical signal 405 is appropriately amplified by the in-line amplifier 406, then separated into the original wavelengths λ _{1 to} λ _N by the optical demultiplexer (DMUX) 408 through the preamplifier 407 and received by the optical receiver 409. However, an appropriate number of nodes (OADMs) 411 _{1 to} 411 _M are arranged on the optical transmission line 404 in the middle of them. At these nodes 411 _{1 to} 411 _M , an optical signal having a desired wavelength is input / output.

FIG. 22 shows an outline of the node configuration. Although the first node 411 ₁ is shown here, the _{second to} Mth nodes 411 _{2 to} 411 _M have the same configuration in principle. The optical transmission line 404 illustrated in FIG. 21 is input to the input-side arrayed waveguide grating (AWG) 421 of the first node 411 ₁ and is demultiplexed into optical signals for N channels having wavelengths λ ₁ to λ _N. by the wavelengths lambda ₁ to [lambda] of the two inputs and two outputs provided for each _N optical switch 422 ₁ ~422 _N, capture light signals of respective wavelengths lambda ₁ to [lambda] _N to the node-side receiving section 426 with (drop), The optical signal transmitted from the node side transmission unit 424 is inserted (Add). The outputs of the 2-input 2-output optical switches 422 _{1 to} 422 _N are input to the output-side arrayed waveguide grating 428 as they are. The output-side arrayed waveguide grating 428 is an element having a configuration opposite to that of the input-side arrayed waveguide grating 421, and multiplexes optical signals for N channels having wavelengths λ _{1 to} λ _N to form an optical signal 405 in the optical transmission line 404. It will be sent out.

In each conventional node 411 ₁ , for example, between the two-input two-output optical switches 422 _{1 to} 422 _N and the output-side arrayed waveguide grating 428 shown in FIG. 22, for each wavelength λ _{1 to} λ _N. Wavelengths λ _{1 to} λ _N after the attenuator is provided and the multiplexed optical signal 405 is multiplexed at the output side array waveguide grating 428 and the non-uniformity of the signal level when passing through the input side array waveguide grating 421 The non-uniformity of the level of the optical signal 405 for each was eliminated. In the optical communication system according to the eighth embodiment of the present invention, as described in the section of the deformability items of the first embodiment and the first to fifth embodiments, the input-side arrayed waveguide grating 421 and The output side arrayed waveguide grating 428 can perform level compensation between the waveguides. Therefore, in the present embodiment, it is possible to adopt a configuration in which an attenuator that is conventionally required is not provided in an application that does not require dynamic level correction, and in an application that requires dynamic level correction, the dynamic range characteristics of the level compensator are not affected. The demand can be relaxed.

As described above, the first node 411 ₁ shown in FIG. 22 and the second to M-th nodes 411 _{2 to} 411 _{M, the} optical multiplexer 402 and the optical demultiplexer 408 shown in FIG. Is used. Therefore, under the demand for an increase in the number N of channels of the optical signal 405, it is important to stabilize the wavelength of each laser beam extracted in multiple channels from the output slab waveguide of the arrayed waveguide grating and to monitor the output level. For this reason, as shown in FIG. 21, output monitoring control devices 431 _{1 to} 431 _M and 431 _S are attached to the nodes 411 _{1 to} 411 _M and the optical transmitter 401, respectively.

  << Possibility of modification of the eighth embodiment >>

  In the eighth embodiment described above, the arrayed waveguide grating of the first embodiment is used. However, the arrayed waveguide grating used in the second to fifth embodiments can be used instead. Thus, the same optical communication system can be realized. Of course, the demultiplexing device and the multiplexing device described in the sixth and seventh embodiments can be used in place of these arrayed waveguide gratings.

  ≪Supplementary explanation≫

  As described above, each embodiment of the present invention has been described. In the present invention, light loss is generated in the slab waveguide of the arrayed waveguide grating or the waveguide connected thereto (including the individual waveguides of the channel waveguide array). For example, the input / output characteristics of light are made desired. One method for this purpose is to use the degree of focus matching (claims 9, 10, etc.). Therefore, the concept of focus in the arrayed waveguide grating will be supplementarily described.

  FIG. 23 shows a state in which a light source and coherent light emitted from the light source propagate. When light is emitted from the point light source 501 toward the left side of the figure, the light spreads on the equiphase surface as indicated by a broken line. Since the equiphase surfaces are always equidistant from the point light source 501, they are concentrically formed.

  On the contrary, when light having an equiphase surface forming a predetermined arc is radiated from the left side to the right side in FIG. 23, the light travels in the opposite direction to that of the conventional light and is condensed at the position of the point light source 501. To do. This condensed position becomes the focal point. Although the point light source 501 does not actually exist, a light source having a width or a length can be treated as the point light source 501 if the light source can be regarded as being far away when considering light emission and light collection. .

For example, the channel waveguide array 15 shown in FIG. 24 has a structure in which light is confined three-dimensionally with the top, bottom, left and right of the core being clad. If the light emitted from such a channel waveguide exists sufficiently far away, the point light source 501 can be considered to emit or collect light. In the arrayed waveguide grating, the outlet of the channel waveguide array is arranged on the circumference. For this reason, if each array is equiphase at the exit of the channel waveguide array, it is possible to produce approximately circular equiphase light and emit light toward the center point of the circumference. So you can make a focus there.

  Even when the phase is not equal at the outlet of the channel waveguide array, if there is a phase difference for each array, the focal point is generated at a position shifted from the center of the circumference. In the demultiplexing type arrayed waveguide grating, the phase differs for each array depending on the wavelength when propagating through the channel waveguide array. Therefore, the output slab waveguide is focused at different positions depending on the wavelength.

  In the combined type arrayed waveguide grating, it is preferable to focus on the same position of the output slab waveguide regardless of the wavelength. Therefore, in such a case, it is necessary to change the input position for each wavelength so as to cancel the phase difference generated when propagating through the channel waveguide array.

It is a top view showing the whole structure of the slab waveguide of the arrayed-waveguide grating | lattice in the 1st Example of this invention. It is the principal part enlarged plan view which expanded and showed a part of the output side of a slab waveguide in the 1st Example. It is principal part sectional drawing which cut | disconnected the slab waveguide by the optical path which reaches the compensation output waveguide located in the periphery relatively comparatively in the 1st Example. It is principal part sectional drawing which cut | disconnected the slab waveguide by the optical path to the compensation output waveguide located in a comparatively center part in a 1st Example. It is a characteristic view showing the relationship between the cutting length of the core layer in the first embodiment and the amount of increase in light loss caused thereby. It is explanatory drawing which expanded and showed a part of output side periphery of the slab waveguide part of the arrayed-waveguide grating | lattice in the 2nd Example of this invention. It is explanatory drawing showing the state of propagation of the light in the compensation output waveguide which is arrange | positioned in the peripheral part of the slab waveguide in the 2nd Example and which does not perform output compensation. It is explanatory drawing showing the state of the propagation of the light in the compensation output waveguide which performed the output compensation slightly compared with the example of FIG. 7 in 2nd Example. It is a characteristic view showing the relationship between the axial shift of each output port in the 2nd Example, and the loss obtained by this. It is the principal part top view which expanded and showed the principal part of the slab waveguide part of the arrayed waveguide grating in the 3rd Example of this invention. It is explanatory drawing which showed the relationship between the optical path which reaches each output port in the 3rd Example, and the central axis of a compensation output waveguide. It is a characteristic view showing the relationship between the angle θ of the central axis and the loss obtained thereby in the third embodiment. It is the principal part top view which expanded and showed a part of output side periphery of the slab waveguide part of an arrayed-waveguide grating | lattice in the 4th Example of this invention. It is the characteristic figure which showed the relationship between the ratio of the spot size of the focus in the 4th Example, and the spot size of the waveguide mode of a waveguide, and the loss obtained by this. It is the principal part top view which expanded and showed the principal part of the slab waveguide part of the arrayed waveguide grating in the 5th Example of this invention. It is explanatory drawing which showed in principle the loss of the light by the protrusion part of the output side of a slab waveguide in a 5th Example. It is a characteristic view showing the relationship between the defocus distance F and the loss obtained thereby in the fifth embodiment. It is explanatory drawing which showed that both the demultiplexing and multiplexing of light were possible using the arrayed-waveguide grating of a 1st Example. It is a block diagram showing the structure of the branching apparatus as the 6th Example of this invention. It is a block diagram showing the structure of the multiplexer as a 7th Example of this invention. It is a system configuration | structure figure showing the outline | summary of the structure of the optical communication system in the 8th Example of this invention. It is the block diagram which showed the outline | summary of the structure of the node in the system of FIG. It is a principle figure for demonstrating the concept of the focus of this invention. It is a top view showing the whole structure of the conventional arrayed-waveguide grating | lattice.

Explanation of symbols

101, 131, 161, 191, 221 Input slab waveguide 102 Channel waveguide array 104 Waveguide 105 Output waveguide 111 Core layer 112 Clad layer 132, 162, 192, 225 Compensation waveguide 163, 193, 224 Optical path 165 Central axis 222 Uncompensated waveguide 223 Isophase curve 301 Demultiplexer 303, 326 Waveguide element 306 Supervisory amplifier 321 Multiplexer 322 Semiconductor laser 329 Level detector 331 Drive control circuit d Distance L Cutting length P _IN Input port position P _{m + n} , _{Pm + n-1} , _{Pm + n-2} , _{Pm + a} , _{Pm + a-1} , _{Pm + a-2} channel waveguide array side focal position θ angle

Claims (6)

One or more input waveguides through which optical signals can be input;
A channel waveguide array provided with a predetermined optical path length difference;
An input slab waveguide connecting the channel waveguide array and the input waveguide;
An output slab waveguide that is connected to the opposite side of the channel waveguide array to which the input slab waveguide is connected, and that inputs an optical signal from the input waveguide through the input slab waveguide and the channel waveguide array. When,
A plurality of output waveguides capable of outputting optical signals;
Loss adjusting means comprising a clad layer provided at a connection portion between the output waveguide and the output slab waveguide and inserted into a core layer of the output slab waveguide
An arrayed waveguide grating comprising: 2. The arrayed waveguide grating according to claim 1 , wherein the loss for each optical signal is adjusted by the length of the cladding layer . 3. A demultiplexer comprising the arrayed waveguide grating according to claim 1 and demultiplexing optical signals having a plurality of wavelengths. The branching device further includes:
The demultiplexing apparatus according to claim 3, further comprising monitoring amplification means for amplifying an optical signal output from the demultiplexing apparatus. A multiplexing apparatus comprising the arrayed waveguide grating according to claim 1 or 2, wherein optical signals having a plurality of wavelengths are multiplexed. The multiplexing device further includes:
6. The multiplexing device according to claim 5, further comprising optical signal output means for outputting an optical signal input to the multiplexing device.

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