JP2000292645A - Wavelength multiplexing filter - Google Patents

Abstract

(57) [Problem] To provide a wavelength-division multiplexing filter that is low in cost, small in size, and requires less fiber routing. SOLUTION: This is a circuit in which a first module 11 forming a first filter is combined with a directional coupler 141 formed of a silica-based glass waveguide and a Bragg grating 142, each of which is a first module. A circuit having wavelength selection characteristics corresponding to a plurality of output ports of the first module 11 is connected by the number of output ports of the first module 11, and the second module 14 constituting the second filter is formed of an 8-core tape. By connecting via the fiber 15a, circuit integration and connection between circuits are simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength multiplexing filter comprising an optical circuit formed on a flat substrate such as a Si substrate, and more particularly to an optical circuit structure capable of improving wavelength separation (crosstalk) characteristics. And a wavelength multiplexing (WDM) filter.

[0002]

2. Description of the Related Art Due to the explosive spread of the Internet and e-mail, the capacity of communication lines has been rapidly increased mainly in the United States. The key technology for increasing the capacity is a high-density wavelength division multiplexing (DWDM) system, which simultaneously propagates a plurality of signal lights having different wavelengths on one optical fiber to dramatically increase the communication capacity. . Up to now, in the DWDM system, the number of multiplexed wavelengths has been expanded from 8 channels to 16 channels, and the transmission capacity of communication has been expanded in accordance with the development of the multimedia industry such as the Internet.

[0003] In a DWDM system, 100 GH is usually used.
8 or 16 wavelengths at z or 200 GHz intervals
Wave splitting. Therefore, a high-performance wavelength filter is one of the key devices. A wavelength filter is required to have high-precision wavelength matching, low loss, and high-performance crosstalk characteristics.

[0004] Up to eight waves, an interference film filter type multiplexing / demultiplexing device mainly composed of micro optics has been used. However, as the number of channels increases, the cost of the interference film filter type increases, and the planar waveguide (PLC) type has been applied. This tendency is considered to become more significant as the number of wavelengths increases.

[0005] The most common device of the PLC type is a filter formed of a silica glass waveguide. In a silica-based glass waveguide, a device utilizing the interference effect can be precisely manufactured, and a high-performance filter can be formed. In particular, in a silica glass waveguide, a plurality of input waveguides, a plurality of output waveguides,
Array waveguide diffraction grating mainly composed of a pair of slab waveguides and a waveguide array composed of a number of waveguides having different lengths
(AWG) has been used as a wavelength multiplexing filter.

FIG. 1 shows a wavelength multiplexing filter using AWG.
(Wavelength multiplexer / demultiplexer), in which 1 is S
i-substrate, 2 is an input waveguide, 3 is an output waveguide, 4a, 4b
Is a slab waveguide, and 5 is a waveguide array. FIG. 2 shows a typical spectrum of this filter, where AWG
Since the output waveguide is determined depending on the wavelength, the wavelength can be multiplexed / demultiplexed. An AWG composed of a silica-based glass waveguide achieves low loss, high wavelength accuracy, and high crosstalk, and is used in a DWDM system.

However, as the number of wavelengths of wavelength division multiplexing increases, it is necessary to improve the performance of filters. In particular, in order to separate a large number of wavelengths, it has been strongly required to improve crosstalk characteristics. . For example, in an AWG of 32 ch channel composed of a silica glass waveguide, 3
Crosstalk of 0 dB or more is required. As described above, since the characteristics of the PLC-type AWG are exhibited when the number of channels increases, the improvement of the crosstalk is important for the AWG.

Further, in DWDM, the separation wavelength interval is 25G.
When the frequency is as narrow as less than Hz, the AWG circuit is susceptible to the phase error of the waveguide, and the crosstalk deteriorates. Usually, the number of channels increases as the wavelength interval decreases,
The influence of this crosstalk deterioration becomes significant. for that reason,
Improvement of the crosstalk characteristic is essential for using an AWG having a narrow wavelength interval and a large number of channels in a WDM system.

Conventionally, in order to improve the crosstalk characteristics, a method of using two filters has been adopted. A
In the configuration using the WG in the first stage, a method of improving crosstalk by attaching an external filter to each output port of the AWG has been adopted.

FIG. 3 shows a schematic configuration of a conventional wavelength multiplexing filter in which crosstalk is improved by using an external filter. In FIG.
Is an external filter, and 8a, 8b and 8c are optical fibers. As the external filter 7, an interference film filter is used, and the structure thereof is such that the interference film filter is sandwiched by an optical fiber having a selfoc lens attached to the tip. A parallel beam is emitted from the fiber with the SELFOC. The interference film filter has characteristics of low loss and good crosstalk, and is effective in terms of optical characteristics as an external filter.

[0011]

As described above, in a conventional DWDM filter, an external filter is generally used to improve crosstalk. However, this method increases cost and size. There was a disadvantage. In addition, there is a problem that fiber routing becomes difficult.

An object of the present invention is to provide a wavelength division multiplexing filter which is low in cost, small in size, and requires little fiber routing.

[0013]

According to the present invention, in order to achieve the above object, a planar optical circuit composed of a planar optical waveguide is used as an external filter, and the operating wavelength is set to the first stage such as AWG. It is characterized in that a plurality of planar optical circuits designed to match the wavelengths corresponding to a plurality of output ports in a filter are formed (arrayed) on a single substrate or on a plurality of substrates. is there.

Thus, there is an advantage of an integration effect that a large number of circuits can be integrally formed on a flat substrate. Also, 1
Since it is possible to integrate with the filter of the stage,
It is possible to reduce the size of the entire device. Further, since the optical fiber needs to be routed little, handling at the time of manufacturing or the like becomes simple.

By the above-mentioned integration effect and reduction of the manufacturing time,
Significant cost reduction can be expected.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1 (AWG + 1-stage grating, separation type)] Embodiment 1 shows an example in which a crosstalk is improved by combining a 32-channel AWG and a grating. The device was composed of a silica glass waveguide. FIG. 4 shows a schematic configuration thereof.

In FIG. 4, reference numeral 11 denotes a first module containing a 1 × 32 AWG chip in a case;
Core fibers, 13a and 13b are connectors, 14 is a second module, 15a and 15b are 8-core tape fibers (actually, there are four 8-core tape fibers, respectively),
Reference numeral 16 denotes a tape fiber branch, and 17 denotes an isolator. The two modules 11 and 14 use a Peltier element to stabilize the temperature of the PLC chip in order to stabilize the operating wavelength.

The second module 14 constitutes a second filter. As shown in an enlarged view in FIG. 2, a directional coupler (DC) 141 formed of a silica glass waveguide and a directional coupler 141
The number of the output ports of the first module (first filter) 11, that is, 32 chips are connected to each other in units of a circuit in which a combination with a rag grating (BG) 142 is used. ing.

In the second module 14, the DC coupling rate is designed to be 50%.
A desired wavelength is selectively reflected by adjusting the agg wavelength and the bandwidth. Then, a large number of wavelengths (λ1, λ2,...)
When (λn) is incident, only the wavelength that matches the Bragg wavelength in the BG, for example, λi, is reflected and returns to the other DC port. In module 14, 3
The operating wavelength of each BG produced by connecting two BGs is shifted corresponding to each channel of the module 11.

In a DC + BG device, if the DC coupling ratio deviates from 50%, the light reflected by the BG returns to the input port, so that a measure against reflection is necessary.
Therefore, in the device prototyped in the present embodiment, the isolator 17 is incorporated in the input-side single-core fiber 12.

The quartz glass waveguide constituting the optical device shown in FIG. 4 is formed by forming a glass film by flame deposition (FHD), forming a core by photolithography and reactive etching, and embedding the core again by FHD. did. 1m board
The thickness was m.

The manufacturing conditions and parameters of each device are as follows.

-AWG-Core: 6 × 6 μm, Δ △ 0.75% —Wavelength interval: 100 GHz —Channels: 32 —Chip size: 30 × 25 mm —Bragg grating—Core: 8 × 8 μm, Δ △ 0.3 %-UV laser: excimer ArF-Preparation method: phase mask method-Irradiation intensity: １００100 J / cm ² -Irradiation time: 10 minutes-Grating length: 10 mm-Chip size: 10 × 25 mm As described above, DC + BG 10 × in device size
The size of the module to which the optical fiber was connected was 25 mm, which was as small as 30 × 60 × 25 mm. 3
For two DC + BG devices, the Bragg of each BG
The wavelength was adjusted by irradiating a UV laser without passing through a phase mask so as to match the wavelength of each output port of the AWG.

In the present embodiment, as shown in FIG.
G chip and DC + BG chip, 8 core tape fiber 4
Connected through a book.

The spectrum of each manufactured device was measured using an optical spectrum analyzer and a broadband wavelength light source. 5 to 7 show the measured spectra.

FIG. 5 shows 32 channels of the produced AWG. In this 32 channel AWG,
The operating wavelength was tuned to the ITU grid by adjusting the temperature of the Peltier device.

FIG. 6 shows one of the 32 channels, here No. 24 shows a DC + BG spectrum (black circles in the figure) corresponding to channel No. 24 of AWG. 24 spectra (open circles in the figure) are also shown. From both spectra, it can be seen that the wavelengths match. This is because the wavelength of BG can be accurately controlled by uniform UV irradiation.

FIG. 7 shows a channel No. in the entire device of the present embodiment manufactured by connecting both. It shows 24 spectra (open triangles in the figure), in which the two spectra are superimposed. In addition, channel No. The AWG spectrum (open circles in the figure) and the DC + BG spectrum (black circles in the figure) corresponding to 24 are also shown.

FIG. 7 shows that the crosstalk is 50 dB or more, and the crosstalk is remarkably improved as compared with the conventional AWG.

The reflected light returning to the input side was 50 dB or less due to the isolator incorporated in the fiber on the input side as a measure against reflection.

As described above, the effectiveness of the present invention has been confirmed.

The DC + BG used in the present embodiment has the following advantages.

1) In DC + BG, reflection on the input port usually poses a problem. This is because the amount of reflection depends on the DC coupling rate. If the coupling ratio is shifted by 1% to 49%, the reflectance becomes 20 dB. Therefore, the multiple formed D
In order to use a C + BG device, it is necessary to reduce the reflection. However, in the present invention, the problem of reflection can be solved by using only one isolator on the input side of the AWG.

2) When DC + BG is used as a single filter, it is necessary to precisely adjust the wavelength and the bandwidth, and the manufacturing conditions become strict. But AWG
When used as a second filter in combination with
The bandwidth can be set large to ease the wavelength alignment accuracy. When the bandwidth is widened, the effect of reducing the crosstalk with the adjacent channel is small, but the other channels have a sufficient effect of reducing the crosstalk. When the number of channels is large, the contribution of the crosstalk reduction effect is large. Therefore, the manufacturing accuracy can be relaxed, and multiple DC + BGs can be efficiently manufactured.

[Embodiment 2 (AWG + two-stage grating, integrated type)] In Embodiment 2, 16 channels A
An example is shown in which an optical device in which WG and DC + BG are combined in two stages is manufactured to realize a PLC type DWDM filter with improved crosstalk. FIG. 8 schematically shows the configuration.

In FIG. 8, 21 is 1 × 16 AWG and 2
Module in which a chip in which DC + BG integrated in each stage is integrated is put in a case, 22 is an input-side single-core fiber, 23a and 23b
Is a connector, 24 is an 8-core tape fiber (actually, 8
There are two core tape fibers. ) And 25 are a tape fiber branch part, and 26 is an isolator. Module 21
, A PLC chip to which an optical fiber is connected is packaged. Also in this embodiment, as in the first embodiment, an isolator is incorporated in the input single-core fiber 22 as a measure against reflection.

FIG. 9 shows a detailed configuration of the PLC chip. In FIG. 9, 31 is a plurality, here 16 input waveguides, 32 is the same 16 output waveguides, 33a and 33b.
Is a pair of slab waveguides, 34 is a waveguide array composed of many waveguides having different lengths, and 35 is a grating portion.

The grating section 35 constitutes a second filter. As shown in FIG.
1 and a BG 352 and a circuit combining a DC 353 and a BG 354 are connected in two stages, which constitute an input waveguide 31, an output waveguide 32, slab waveguides 33a and 33b, and a waveguide array. 34, the number of output waveguides of 1 × 16 AWG (first filter),
That is, 16 pieces are connected and integrated into one chip together with the AWG (input and output fibers are connected to the integrated PLC chip and put into a case to be modularized).

As described above, by providing the DC + BG structure in two stages, the crosstalk can be improved compared to the one-stage type. Further, since the output direction is opposite to the input side, there is an advantage that it is suitable for integration. It is to be noted that the operation wavelengths of the BG in the 16 grating sections 35 are shifted correspondingly to the respective output waveguides of the AWG, as in the case of the first embodiment.

The quartz glass waveguide constituting the optical device of FIG. 9 was manufactured in the same manner as in the first embodiment. The substrate was 1 mm thick Si. The core of the quartz glass waveguide is
6 × 6 μm, △ to 0.75%, chip size is 60 × 5
It was 0 mm.

The manufacturing conditions and parameters of each device are as follows.

[0043] -AWG - Wavelength Interval: 100 GHz - Number of channels: 16 -Bragg Grating -UV laser: excimer ArF - preparation method: Phase mask method - irradiation intensity: ~100J / cm ² - irradiation time: 10 minutes - grating length: The spectrum of each device produced was measured with an optical spectrum analyzer and a broadband wavelength light source. 6 crosstalk
0 dB or more, indicating that the crosstalk was further improved as compared with the conventional AWG.

As described above, the effectiveness of the present invention was confirmed.

[Third Embodiment (AWG + Two-Step Chirped Grating, Integrated Type)] In the third embodiment, an optical device in which a 16-channel AWG and a chirped grating (CG) are combined in two steps is manufactured to reduce crosstalk. An example in which an improved planar waveguide type DWDM filter is realized will be described. FIG. 10 shows a detailed configuration of a PLC chip in a planar waveguide type DWDM filter (the overall configuration of the device is the same as that of the second embodiment shown in FIG. 8 except that the module 21 is replaced with the chip of this example). is there.).

In FIG. 10, reference numeral 41 denotes a plurality, here 1
6 input waveguides, 42 are also 16 output waveguides,
43a and 43b are a pair of slab waveguides, 44 is a waveguide array composed of a number of waveguides having different lengths, and 45 is a grating section.

The grating section 45 constitutes a second filter. As shown in the enlarged view of FIG. 2, a two-stage chirped grating (CG) 451, 452 includes an input waveguide 41 and an output waveguide 42. , Slab waveguide 43a,
1 × 16 AWG consisting of 43b and waveguide array 44
(The first filter) are connected to the respective output waveguides 42, and are integrated together with the AWG on one chip (input / output fiber is connected to the integrated PLC chip and put in a case). Is modularized.)

The two-stage chirped grating (C)
G) The reflection wavelength ranges of 451 and 452 are different from each other, and these boundary areas are set so as to be the wavelength of the corresponding channel. In addition, 16 grating sections 4
5, the operating wavelength of CG 451 and CG 452 is AWG
Are shifted corresponding to the respective output waveguides in the same manner as in the first embodiment.

As shown in FIG. 10, the PL of this embodiment is
In the C chip, two CGs with different reflection wavelength ranges are AWG
, The crosstalk can be improved. Further, since a wide reflection band can be formed in the CG, wavelengths other than the signal light can be stopped at each port. Further, since the signal light intensity reflected by the CG is weak, there is no problem of reflection at the input port.

The quartz glass waveguide constituting the optical device shown in FIG. 10 was manufactured in the same manner as in the first embodiment. The substrate was 1 mm thick Si. The core of the quartz glass waveguide is 4 × 5 μm, △ to 1.5%, and the chip size is 40 ×
It was 50 mm.

The manufacturing conditions and parameters of each device are as follows.

-AWG-Wavelength interval: 50 GHz-Number of channels: 16-Grating-Fabricated by etching process-Pitch: about 1.6 µm-Single grating length: 15 mm The spectrum of each fabricated device is measured with an optical spectrum analyzer and a broadband wavelength. Measured with a light source. FIG. 11 shows the measured spectrum. In the figure, a white circle indicates a spectrum of the CG 451 corresponding to one of 16 channels, a black circle indicates a spectrum of the CG 452 corresponding to the same channel, and a white triangle indicates a spectrum of the same channel in the entire device of the present embodiment.

FIG. 11 shows that the crosstalk was 60 dB or more, and the crosstalk was further improved as compared with the conventional AWG.

From the above, the effectiveness of the present invention was confirmed.

[Fourth Embodiment (AWG + AWG, Separation Type)] In the fourth embodiment, an example is described in which an optical device in which AWGs are combined in two stages is manufactured to realize a planar waveguide type DWDM filter with improved crosstalk. Show. FIG. 12 shows a schematic configuration thereof.

In FIG. 12, reference numeral 51 denotes a first module containing a 1 × 32 AWG chip in a case; 52, an input-side single-core fiber; 53a, 53b, 53c, connectors 5;
4a54b is the second module, 55a, 55b, 55
c and 55d are 8-core tape fibers (actually, there are two 8-core tape fibers, respectively), and 56a and 56b are tape fiber branch portions.

The second modules 54a and 54b constitute a second filter. Each of the AWGs has an AWG equal to 1 / the number of output ports of the first module (first filter) 51.
Two minutes, that is, a chip made by connecting 16 chips is put in a case. FIG. 13 shows a detailed configuration of one of them.

In FIG. 13, reference numeral 61 denotes an input waveguide;
Is an output waveguide, 63a and 63b are a pair of slab waveguides,
Reference numeral 64 denotes a waveguide array composed of a number of waveguides having different lengths, each provided for 16 channels.

Here, the size is reduced by using one input waveguide and one output waveguide, thereby making it possible to integrate the arrayed AWGs on a single substrate. And good wavelength uniformity can be obtained. Also, the total of the second modules 54a and 54b is 3
As in the first embodiment, the operating wavelengths of the two AWGs are shifted corresponding to the respective output waveguides of the first-stage AWG.

In this embodiment, the module 51
And the two modules 54a and 54b
It was connected via two core tape fibers.

Also in this embodiment, the module 51
, 54a and 54b use a Peltier element to stabilize the temperature of the PLC chip in order to stabilize the operating wavelength.

Also in this embodiment, the optical device is formed of a silica glass waveguide, and the manufacturing method is the same as that of the first embodiment.

The manufacturing conditions and parameters of each device are as follows.

First-stage AWG-Core: 6 × 6 μm, Δ △ 0.75%-Wavelength interval: 100 GHz-Number of channels: 32-Chip size: 30 × 25 mm Second-stage AWG-Core: 6 × 6 μm Δ to 0.75%-Wavelength interval: 200 GHz-Number of channels: 16-Chip size: 50 x 25 mm In the second-stage AWG, the center wavelength of each AWG deviates slightly from the set value by 1 due to manufacturing error. There is. However, the deviation can be adjusted individually by irradiating a UV laser.

FIG. 14 shows the spectrum of each of the fabricated devices measured with an optical spectrum analyzer and a broadband wavelength light source.
〜16 shows the measured spectrum.

FIG. 14 shows the first AWG on the long wavelength side of the AWG.
FIG. 15 shows the spectra of six channels, and FIG. 15 shows the spectra of the second-stage long wavelength AWG.

FIG. 16 shows a spectrum for one channel (open circles in the figure) of the entire device of the present embodiment fabricated by connecting both, and the two spectra are superposed. The spectrum of the first-stage AWG for eight channels (solid line in the figure) and the spectrum of the second-stage AWG for one channel (black circle in the figure) are also shown.

FIG. 16 shows that the crosstalk has been significantly improved as compared with the conventional AWG.

The wavelength characteristics were determined from each of the measured spectra. The characteristics in each case are summarized in the following table.

[0070]

[Table 1]

From Table 1, it can be seen that the insertion loss increases by about 2 to 3 dB, but the effect on the bandwidth of the first-stage AWG can be reduced by setting the bandwidth of the second-stage AWG sufficiently wide. it can. Also, both near and far end crosstalk are significantly improved.

Further, in the present embodiment, the first stage 1 × 3
The 2AWG and the second-stage arrayed AWGs were connected via an optical fiber, but two second-stage arrayed AWG chips were integrated into one chip, and the first-stage AWG and the PLC chips were connected to each other. It is also possible. A UV-curable adhesive is used for the connection. It is also possible to integrate all the PLC chips into one chip.

As described above, the effectiveness of the present invention was confirmed.

Further, in the second-stage arrayed AWG, a heater can be formed using a metal thin film (such as Cr) for the clad layer on the waveguide array 64 of each AWG, and the heater can be used to form the waveguide. By adjusting the temperature of the array, it is possible to precisely control the operating wavelength of individual AWGs.

[Fifth Embodiment (AWG + AWG, Another Example of Separation Type)] In the fifth embodiment, the AWG is the same as in the fourth embodiment.
Is combined in two stages, the second AW
This is an example of realizing a planar waveguide type DWDM filter in which crosstalk is improved while realizing miniaturization of a circuit by arranging G in a vertical and horizontal direction on a substrate. FIG. 17 shows a schematic configuration thereof. Here, the vertical direction refers to the light waveguide direction, and the horizontal direction refers to the direction perpendicular to the substrate surface.

In FIG. 17, reference numeral 71 denotes a first module containing a 1 × 32 AWG chip in a case; 72, an input-side single-core fiber; 73, connectors a, 73b, and 73c;
74 is the second module, and 75a and 75b are 8-core tape fibers (actually, 8-core tape fibers
There is a book. ) And 76 are tape fiber branch portions.

The first module 71 uses the same module as the first module 51 used in the fourth embodiment.

The second module 74 constitutes a second filter, and includes a first module (a first filter).
The detailed configuration of a chip manufactured by connecting 71 output ports, that is, 32 AWGs on a single substrate is shown in the case.

In FIG. 18, 81 is an input waveguide, 82
Is an output waveguide, and 83a and 83b are waveguide arrays composed of a pair of a large number of waveguides. Similarly to the case where 32 channels are provided, the operating wavelength of a total of 32 AWGs is equal to that of the first-stage AWG. The output waveguides are shifted correspondingly.

The 32 AWGs have 16 rows in the vertical direction,
By arranging (arraying) two rows in a row in the horizontal direction,
It is arranged on a single substrate. In this arrangement method, the number of columns in the vertical direction and the horizontal direction is not limited to the embodiment of FIG. 18; any M columns in the vertical direction and any N columns (M, N Is a natural number) and M × N AWs
G can be arrayed. According to this arrangement method, the degree of freedom in designing the second-stage arrayed AWGs is increased, and by selecting the optimal number of columns (M, N) according to the design of the individual AWGs to be arrayed, the high-density array is realized. Array. Therefore, according to this arrangement method, it is possible to reduce the size of the second-stage chip or to integrate a larger number of AWGs on a single substrate, and to obtain good wavelength uniformity among the AWGs.

In this embodiment, the module 71
And the module 74 were connected via four 8-core tape fibers. Also in the present embodiment, the module 71
In and 74, the temperature of the PLC chip is stabilized using a Peltier element in order to stabilize the operating wavelength. Also in the present embodiment, the optical device is formed of a silica glass waveguide, and the manufacturing method is the same as that of the first embodiment.

The manufacturing conditions of the AWG arrayed in the second stage,
The parameters are as follows.

Core: 6 × 6 μm, △ to 0.75% Wavelength interval: 200 GHz Number of channels: 32 Chip size: 33.5 × 27.0 mm The second stage of the AWG is the above array Since the AWGs can be arranged with high density by the method, a very small chip size is realized while 32 AWGs are arrayed on a single substrate.

In the second stage AWG array,
The center wavelength of each AWG may deviate slightly from the set value due to fabrication errors. However, the deviation can be adjusted individually by irradiating a UV laser.

The spectrum of the manufactured device was measured with an optical spectrum analyzer and a broadband wavelength light source. The first-stage AWG is the same as the first-stage AWG in the fourth embodiment, and its 16-channel spectrum on the longer wavelength side is as shown in FIG.

FIG. 19 shows spectra of all 32 channels of the AWG arrayed in the second stage. According to the above arrangement method, 32 AWGs are densely arranged on a single substrate.
The same spectrum characteristics as those of the AWG at the stage are obtained.

FIG. 20 shows one example of the entire device of the present embodiment manufactured by connecting the first and second modules.
It shows the spectrum (open circles in the figure) for the channels. Note that the spectrum for one channel of the first stage AWG (solid line in the figure) and the first stage of the arrayed AWG
The spectra for the channels (black circles in the figure) are also shown.

From FIG. 20, it can be seen that also in the present embodiment, similar to the fourth embodiment, the crosstalk is remarkably improved as compared with the conventional AWG.

In the present embodiment, the 1 × 3
The 2AWG and the second-stage arrayed AWG are connected via an optical fiber, but it is also possible to connect PLC chips of the first-stage AWG chip and the second-stage arrayed AWG chip. . A UV-curable adhesive is used for the connection. Further, all the PLC chips can be integrated into one chip.

[0090]

As described above, according to the present invention, an external filter is constituted by a planar optical waveguide (PLC) type, and an AW
It is characterized in that it is manufactured on one or a plurality of substrates, the number of which corresponds to the number of outputs of the first-stage filter such as G. This has the following advantages.

1) Since a large number of circuits are integrally formed on a flat substrate, cost and size can be reduced by the integration effect.

2) When the first-stage filter is of the PLC type, all the PLC chips can be integrated on a single substrate, so that the size of the entire device can be further reduced.

3) By increasing the bandwidth of the external filter, manufacturing errors related to wavelength accuracy and the like can be tolerated. Even if the bandwidth is widened, there is a sufficient crosstalk reduction effect when the number of channels is large, and the greater the number of channels, the greater the contribution of the crosstalk reduction effect. Therefore, by reducing the manufacturing accuracy, multiple external filter circuits can be efficiently manufactured.

4) Tape fibers can be used by integration, and fiber routing can be reduced. In addition, if all the circuits are integrated on a unit substrate, an intermediate connection optical fiber becomes unnecessary. Thereby, the manufacturing time can be reduced.

5) Due to the integration, it is only necessary to control the wavelength of a single or a small number of substrates according to the temperature, so that the wavelength control of the external filter is simplified and uniform wavelength control is possible.

As already described in the above embodiment, the substrate on which the second-stage external filter is formed may be a single substrate or two or three substrates. In the embodiment, the AWG is mainly described as the first-stage filter, but a filter other than the AWG may be used. Furthermore, although a quartz glass waveguide has been described, similar effects can be exerted by using other waveguides such as semiconductors and polymers, and the present invention is not limited to the materials constituting the waveguide.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of a wavelength multiplexing filter using AWG.

FIG. 2 is a diagram showing a typical spectrum of a wavelength multiplexing filter based on AWG.

FIG. 3 is a conceptual configuration diagram of a conventional wavelength multiplexing filter in which crosstalk is improved by using an external filter.

FIG. 4 is a configuration diagram showing Embodiment 1 of the wavelength division multiplexing filter of the present invention.

FIG. 5 is a diagram showing a spectrum in a 32-channel AWG according to the first embodiment.

FIG. 6 shows one channel (No. 2) in the first embodiment.
It is a figure which shows the spectrum in DC + BG of 4).

FIG. 7 shows one channel (N
o. It is a figure which shows the spectrum of 24).

FIG. 8 is a configuration diagram illustrating a wavelength division multiplexing filter according to a second embodiment of the present invention.

FIG. 9 is a detailed configuration diagram of a PLC chip according to a second embodiment of the present invention.

FIG. 10 shows a wavelength division multiplexing filter according to a third embodiment of the present invention.
FIG. 3 is a detailed configuration diagram of a PLC chip showing the above.

FIG. 11 shows a grating and A according to the third embodiment.
It is a figure showing a spectrum of WG.

FIG. 12 is a wavelength multiplexing filter according to a fourth embodiment of the present invention.
FIG.

FIG. 13 shows a second-stage AW according to the fourth embodiment of the present invention.
It is a detailed block diagram of G.

FIG. 14 is a diagram illustrating a 1st stage AWG in the fourth embodiment.
It is a figure showing a spectrum for six channels.

FIG. 15 is a diagram showing 1 in the second-stage AWG in the fourth embodiment.
It is a figure showing a spectrum for six channels.

FIG. 16 is a diagram showing a spectrum of one channel in the fourth embodiment.

FIG. 17 is a wavelength multiplexing filter according to a fifth embodiment of the present invention.
FIG.

FIG. 18 is a detailed configuration diagram of a second-stage arrayed AWG according to the fifth embodiment of the present invention.

FIG. 19 is a diagram illustrating a second-stage arrayed AW according to the fifth embodiment.
It is a figure showing the spectrum for 32 channels in G.

FIG. 20 is a diagram showing a spectrum of one channel in the embodiment.

[Explanation of symbols]

11, 14, 21, 51, 54a, 54b, 71, 74
Modules 12, 22, 52, 72 Input-side single-core fibers 13a, 13b, 23a, 23b, 53a, 53b, 5
3c, 73a, 73b Connector 15a, 15b, 24, 55a, 55b, 55c, 55
d, 75a, 75b 8-core tape fiber 16, 25, 56a, 56b, 76 Tape fiber branch 17, 26 Isolator 31, 41, 61, 81 Input waveguide 32, 42, 62, 82 Output waveguide 32a, 33b, 43a, 43b, 63a, 63b, 8
3a, 83b Slab waveguide 34, 44, 64, 84 Waveguide array 35, 45 Grating section

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Jun Abe 2-3-1 Otemachi, Chiyoda-ku, Tokyo Inside Nippon Telegraph and Telephone Corporation (72) Takuya Tanaka 2-3-3, Otemachi, Chiyoda-ku, Tokyo 1 Nippon Telegraph and Telephone Corporation (72) Inventor Kamei Shin 3-1-1 Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Akimasa Kaneko 2-chome, Otemachi, Chiyoda-ku, Tokyo No.3-1 in Nippon Telegraph and Telephone Corporation

Claims (8)

[Claims] 1. A first filter for demultiplexing a plurality of signal lights having different wavelengths and outputting the demultiplexed signal lights to a plurality of output ports corresponding to each wavelength, and an optical waveguide comprising a core and a clad formed on a plane substrate. A plurality of planar optical circuits, each planar optical circuit having a second filter having a wavelength selection characteristic corresponding to each of a plurality of output ports of the first filter, and at least the second filter A wavelength division multiplexing filter, wherein a plurality of planar optical circuits are formed on a single substrate or on a plurality of substrates, and are arranged so as to be combined with each output port of a first filter. 2. The planar optical circuit of the second filter,
2. The wavelength multiplexing filter according to claim 1, wherein a planar optical circuit including a directional coupler and a Bragg grating is used. 3. A plurality of input waveguides, a plurality of output waveguides, and a pair of slab waveguides, each of which is constituted by an optical waveguide formed of a core and a clad formed on a plane substrate, as a first filter. And a planar optical circuit including at least two gratings as the planar optical circuit of the second filter, using an AWG mainly composed of a waveguide array composed of a number of waveguides having different lengths. A plurality of planar optical circuits constituting the filter of
Wherein the plurality of output waveguides of the AWG constituting the first filter are arranged in a multiple form on the same single substrate as the AWG constituting the first filter. Item 2. The wavelength division multiplexing filter according to Item 1. 4. The planar optical circuit of the second filter,
A plurality of input waveguides, a plurality of output waveguides, a pair of slab waveguides, and a number of waveguides having different lengths, each of which includes an optical waveguide formed of a core and a clad formed on a planar substrate. 2. The wavelength multiplexing apparatus according to claim 1, wherein an AWG mainly including a waveguide array is used, and a plurality of AWGs constituting the second filter are formed on a single substrate or on a plurality of substrates. filter. 5. A plurality of input waveguides, a plurality of output waveguides, and a pair of slab waveguides, each of which is constituted by an optical waveguide composed of a core and a clad formed on a plane substrate, as a first filter. An AWG mainly including a waveguide array composed of a number of waveguides having different lengths is used, and an optical waveguide composed of a core and a clad formed on a planar substrate is used as a planar optical circuit of a second filter. Using an AWG mainly composed of a plurality of input waveguides, a plurality of output waveguides, a pair of slab waveguides, and a waveguide array composed of a number of waveguides having different lengths, A plurality of AWGs forming the filter are formed in a multiple on the same single substrate as the AWGs forming the first filter, and each of the plurality of output waveguides of the AWG forming the first filter is formed. Combination Wavelength multiplexing filter according to claim 1, wherein the arrangement was such that. 6. A plurality of AWGs constituting a second filter
6. The wavelength division multiplexing filter according to claim 4, wherein a thin film metal heater is deposited on the cladding layer above the waveguide array. 7. A plurality of AWGs constituting a second filter
6. The wavelength division multiplexing filter according to claim 4, wherein a plurality of are arranged in a longitudinal direction and a lateral direction on the substrate. 8. A plurality of AWGs constituting a second filter
Are arranged in multiples in the vertical and horizontal directions on the substrate, and the entire arrangement of the plurality of AWGs is symmetrical on the input side and the output side, and the optical path lengths of the AWGs are equal. The wavelength division multiplexing filter according to claim 4 or 5, wherein