JPH116928A - Arrayed waveguide grating type wavelength multiplexer /demultiplexer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate light of unwanted wavelengths and to improve crosstalk by inserting a dielectric multilayer film filter having a band-pass operation at a post stage. SOLUTION: A plurality of input waveguides 1, output waveguides 2, two slab waveguides 3, 4, and arrayed waveguides 5 with mutually different wave path lengths are formed on an Si substrate 10. When incident light is inputted to one of the input waveguides 1, it is sequentially propagated to the slab waveguide 3, arrayed waveguide 5, and slab waveguide 4, and outputted from one of output waveguides 2. At a post stage, namely, at a plurality of the output waveguides 2, dielectric multilayer film filters 6 having band-pass operation are arranged. The dielectric multilayer film filters 6 are not individually arranged on six-teen output waveguides 2 but extended over multiple output waveguides 2. The arrangement of the dielectric multilayer film filters 6 is achieved by forming grooves 1 on the substrate 10 to intersect the multiple output waveguides 2, inserting the dielectric multilayer film 6 in the grooves 7, and fixing them with an adhesive 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an arrayed waveguide grating type wavelength multiplexer / demultiplexer. For example, the present invention relates to a waveguide type optical element used in fields such as optical communication and optical information processing. Specifically, an arrayed waveguide grating type wavelength multiplexer / demultiplexer (AWG:
The present invention relates to a waveguide type optical device characterized in that the crosstalk is reduced by using band-pass characteristics of a dielectric multilayer filter in an arrayed-waveguide grating.

[0002]

2. Description of the Related Art In recent years, a planar lightwave circuit (PLC: Planner Lightwave Circit) constituted by a silica-based optical waveguide formed on a silicon substrate has been actively studied. The most important circuit among them is an arrayed waveguide grating type wavelength multiplexer / demultiplexer.

The arrayed waveguide grating type wavelength multiplexing / demultiplexing device has a structure in which the optical path lengths arranged in parallel are different from each other by n × ΔL.
A wavelength multiplexing / demultiplexing function of light is realized by interference of a plurality of lights propagated through about 100 arm waveguides. Here, n is the effective refractive index of the waveguide, and ΔL is a value of about 10 to 100 μm. The feature of this circuit is that light of a plurality of wavelengths is realized by one-stage multi-beam interference.

As a result, the following two features occur. One is that the circuit insertion loss does not depend on the number of wavelength channels. The other is that the distance between the channel wavelengths to be demultiplexed is determined by the accuracy of the photomask, and can be manufactured with an accuracy of 0.1 nm or less.

[0005] Due to these features, it is reported that in the future, in an optical communication system using multi-wavelength light, an arrayed waveguide grating type wavelength multiplexer / demultiplexer is expected to be a very important optical circuit. (H. Takahashi et al., "Arrayed-W
aveguide Grating for Wavelength Division Multi / Dem
ultiplexer with Nanometre Resolution, "Electron.Le
tt., vol.26, no.2, pp.87-88, 1990.)

FIG. 6 shows the circuit configuration, and FIG. 7 shows the transmission wavelength characteristic from the central input port to the central output port. FIG.
As shown in FIG. 2, on the Si substrate 10, a plurality of input waveguides 1, output waveguides 2, two slab waveguides 3, 4 made of silica-based optical waveguides, and array waveguides having optical path lengths n × ΔL different from each other. When the waveguide 5 is formed and incident light enters one of the input waveguides 1, the light propagates through the slab waveguide 3, the array waveguide 5, and the slab waveguide 4 in order, and is emitted from the output waveguide 2. become.

Here, when a plurality of lights interfere with each other during propagation in the array waveguide 5, a wavelength multiplexing / demultiplexing function of the lights is realized. For example, as shown in FIG. 7, it can be seen that only a specific wavelength is transmitted from the central input port to the central output port, and light of other wavelengths is blocked. At present, the crosstalk expressed by the ratio between the transmittance at the stop wavelength and the transmittance at the transmission wavelength is about 30 dB.

[0008] Reducing this crosstalk is a very important issue as a wavelength multiplexing / demultiplexing function. The reason that the crosstalk is limited to about −30 dB is due to a manufacturing error of the waveguide, and it is not easy to significantly improve the crosstalk in the current process technology.

On the other hand, an optical component using a dielectric multilayer filter has been reported as an optical component having the same wavelength multiplexing / demultiplexing function as an arrayed waveguide grating type wavelength multiplexing / demultiplexing device (MAScobey).
et al. "Passive DWDM components using MicroPlasma
optical interference filters, "OFC'96 Technical Di
gest ThKl pp.242-243.)

In general, a wavelength multiplexer / demultiplexer using a dielectric multilayer filter requires the same number of dielectric multilayer filters as the number of wavelengths to be demultiplexed, and it is necessary to align each input / output fiber. is there. For this reason, there is a problem that the cost of the parts increases. Further, it is necessary to adjust the transmission center wavelengths of the plurality of dielectric multilayer filters to be used with an accuracy of 0.1 nm or less, which limits the yield of parts.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to improve the crosstalk of an arrayed waveguide grating type wavelength multiplexer / demultiplexer.

[0012]

As a means for improving the crosstalk of the arrayed waveguide grating type wavelength multiplexing / demultiplexing device, a dielectric multilayer filter having a bandpass function is used. Specifically, after multi-wavelength light is demultiplexed at once by an arrayed waveguide grating type wavelength multiplexer / demultiplexer, a dielectric multilayer filter is inserted into a plurality of output waveguides to emit light of an unnecessary wavelength. The removal improves the crosstalk of the arrayed waveguide grating wavelength multiplexer / demultiplexer.

The combination of the arrayed waveguide grating type wavelength multiplexer / demultiplexer and the dielectric multilayer filter has the following features. That is, as shown in the prior art, the arrayed waveguide grating type wavelength multiplexer / demultiplexer has a substantially constant loss irrespective of the number of channel wavelengths to be demultiplexed, and the wavelength of each of the demultiplexed channel wavelengths. The interval can be set with high precision. By inserting a dielectric multilayer filter having a bandpass function at the subsequent stage of the arrayed waveguide grating type wavelength multiplexer / demultiplexer, extremely low crosstalk which could not be realized by the arrayed waveguide grating type wavelength multiplexer / demultiplexer alone To achieve.

Here, since the dielectric multilayer filter is used only for removing the crosstalk light of the arrayed waveguide grating type wavelength multiplexer / demultiplexer, only a relatively loose specification is required for the center wavelength. It is possible to use an inexpensive filter with a high yield.

[0015]

1 (a) and 1 (b) show an arrayed waveguide grating type wavelength multiplexer / demultiplexer using a dielectric multilayer filter according to the present invention. The basic function of this circuit is that the arrayed waveguide grating type wavelength multiplexer / demultiplexer has multiple wavelengths (10 in this embodiment).
The crosstalk is improved by splitting the light having a wavelength of 0 GHz (16 wavelengths between channels) and using a dielectric multilayer filter 6 inserted into the output waveguide 2.

That is, as shown in FIG. 1A, a plurality of input waveguides 1, output waveguides 2, two slab waveguides 3, 4 and a plurality of slab waveguides 3 made of a silica-based optical waveguide are provided on a Si substrate 10. Array waveguides 5 having optical path lengths different by n × ΔL are formed, and when incident light enters one of the input waveguides 1, the light propagates through the slab waveguide 3, the array waveguide 5, and the slab waveguide 4 in order. Thus, the light is emitted from the output waveguide 2.

A dielectric multilayer filter 6 having a band-pass function is disposed downstream of the arrayed waveguide grating type wavelength multiplexer / demultiplexer having such a configuration, that is, in a plurality of output waveguides 2. The dielectric multilayer filter 6 is not arranged individually on the 16 output waveguides, but over a plurality of output waveguides 2 (in the present embodiment, over 8 output waveguides).

The arrangement of the dielectric multilayer filter 6 is, for example, such that the substrate 1 is crossed with a plurality of output waveguides 2.
A groove 7 is formed in the groove 7, and the dielectric multilayer film 6 is inserted into the groove 7 and fixed with an adhesive 8. FIG.
FIG. 1B is an enlarged cross-sectional view taken along line aa ′ in FIG. The thickness of the dielectric multilayer filter 6 is about 50 μm,
Was 55 μm, and the depth of the groove 7 was 300 μm.

Each output waveguide 2 has a different angle at which it crosses the dielectric multilayer filter 6, and the difference in the crossing angle causes the wavelength transmitted through the dielectric multilayer filter 6 to be:
It is designed to match each output channel wavelength demultiplexed by the arrayed waveguide grating type wavelength multiplexer / demultiplexer. That is, as shown in FIG. 3, the transmission wavelength characteristic when the dielectric multilayer filter 6 is inserted into the linear waveguide has a peak at a specific wavelength, but the incident angle of the linear waveguide with respect to the dielectric multilayer filter 6 varies. Then, the transmission wavelength changes as shown in FIG.

Therefore, utilizing the dependence of the transmission wavelength on the incident angle as shown in FIG. 4, the wavelength transmitted through the dielectric multilayer filter 6 is demultiplexed by the arrayed waveguide grating type wavelength multiplexer / demultiplexer. It can be designed to match each output channel wavelength. Note that, as the incident angle increases, the change in the transmission wavelength due to the polarization increases, so that the incident angle is preferably 10 ° or less.

The array waveguide grating type wavelength multiplexer / demultiplexer using the dielectric multilayer film of the present embodiment having the above-described configuration has the following effects. First, as a premise, the arrayed waveguide grating type wavelength multiplexer / demultiplexer has a substantially constant loss regardless of the number of channel wavelengths to be demultiplexed, and the interval between the wavelengths of each demultiplexed channel is accurately determined. Can be set.

Further, by inserting a dielectric multilayer filter 6 having a band-pass function at the subsequent stage of the arrayed waveguide grating type wavelength multiplexer / demultiplexer, unnecessary wavelength light is removed. Extremely low crosstalk, which could not be realized by the wavelength multiplexer / demultiplexer alone, can be realized. For example, as shown in FIG. 5, the transmission wavelength characteristic of the arrayed-waveguide-grating type wavelength multiplexer / demultiplexer using the dielectric multilayer filter in the present embodiment is 1 compared with the conventional example shown in FIG.
Although an excess loss of about dB occurs, a significant improvement in crosstalk of 10 dB or more is recognized.

Here, since the dielectric multilayer filter 6 is used only for removing the crosstalk light of the arrayed waveguide grating type wavelength multiplexer / demultiplexer, only a relatively loose specification is required for the center wavelength. Therefore, it is possible to use an inexpensive filter with a high yield.

In the embodiment described above, the 16 output waveguides 2 are grouped into eight output waveguides and the dielectric multilayer filter 6 is inserted. However, if necessary, four output waveguides 2 are inserted. Alternatively, the dielectric multilayer filter 6 may be separately inserted into each of the two output waveguides or the 16 output waveguides 2. In this case, the transmission center wavelength of the dielectric multilayer film to be inserted, the intersection angle with the waveguide, and the like may be appropriately set in accordance with these configurations.

As shown in FIG. 2, the output waveguide 2
A parabola-shaped portion 9 is provided at a portion crossing the dielectric multilayer filter 6. The parabola-shaped portion 9 reduces the radiation loss of light due to the filter groove 7, and
This is a means for making the light incident on the beam closer to a parallel beam.

[0026]

As described above in detail with reference to the embodiments, the arrayed waveguide grating type wavelength multiplexer / demultiplexer using the dielectric multilayer filter of the present invention is an arrayed waveguide grating type wavelength multiplexer / demultiplexer. By inserting a dielectric multilayer filter with a band-pass function at the subsequent stage of the duplexer, unnecessary wavelength light is removed, and crosstalk is significantly greater than that of the conventional arrayed waveguide grating wavelength multiplexer / demultiplexer. Is improved.

[Brief description of the drawings]

FIG. 1A is a circuit configuration diagram of an arrayed waveguide grating type wavelength multiplexer / demultiplexer using a dielectric multilayer filter according to the present invention;
FIG. 1B is an enlarged cross-sectional view taken along the line aa ′ in FIG.

FIG. 2 is an enlarged top view of a portion where a dielectric multilayer filter is inserted.

FIG. 3 is a graph showing transmission wavelength characteristics of a dielectric multilayer filter inserted into a straight waveguide.

FIG. 4 is a graph showing a relationship between an incident angle of a waveguide crossing a dielectric multilayer filter and a center wavelength of a transmission spectrum.

FIG. 5 is a graph showing transmission wavelength characteristics of an arrayed waveguide grating type wavelength multiplexer / demultiplexer using the dielectric multilayer filter of FIG. 1;

FIG. 6 is a circuit configuration diagram of an arrayed waveguide grating type wavelength multiplexer / demultiplexer.

FIG. 7 is a graph showing a transmission wavelength characteristic from a center input port to a center output port of the arrayed waveguide grating type wavelength multiplexer / demultiplexer shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input waveguide 2 Output waveguide 3, 4 Slab waveguide 5 Array waveguide 6 Dielectric multilayer film filter 7 Groove 8 Adhesive 9 Parabolic shape part

Claims (3)

[Claims] 1. An arrayed-waveguide grating wavelength multiplexer / demultiplexer having a plurality of output waveguides formed on a planar substrate and guiding demultiplexed output light, a groove is formed in the plurality of output waveguides. An arrayed waveguide grating type wavelength multiplexer / demultiplexer, wherein a dielectric multilayer filter is inserted into the groove. 2. An angle at which the plurality of output waveguides intersect the groove is not constant.
An arrayed waveguide grating type wavelength multiplexer / demultiplexer as described in the above. 3. The arrayed waveguide grating type wavelength according to claim 1, wherein the waveguide has a parabolic shape at an intersection of the plurality of output waveguides and the groove. Multiplexer / demultiplexer.