JP3053294B2 - Optical multiplexer / demultiplexer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arrayed waveguide grating type optical multiplexer / demultiplexer used for wavelength division multiplexing communication.

[0002]

2. Description of the Related Art In recent years, in optical communication, research and development on optical frequency multiplexing communication have been actively conducted as a method of dramatically increasing the transmission capacity. In order to increase the transmission capacity, a device capable of multiplexing / demultiplexing light having a small wavelength interval is required. An example of a device capable of multiplexing / demultiplexing light having a small wavelength interval (having good resolution) and having high diffraction efficiency. A method using an array waveguide diffraction grating is known.

[0003] "Arrayed-waveguide grating for wav"
elength division multi / demultiplexer with nano
meter resolution ”; Electronics Letters, vol.2
6, pp. 87-88, 1990 and JP-A-2-244105 disclose the prior art.

Here, an example in which a conventional array waveguide diffraction grating type optical multiplexer / demultiplexer is used as an optical frequency multiplexer / demultiplexer will be described. FIG. 9 is a diagram showing a configuration of an arrayed waveguide grating optical multiplexer / demultiplexer. FIG. 10 is an enlarged sectional view taken along line DD 'in FIG. An input waveguide 2 on a silicon substrate 1
Is connected to an optical fiber on the transmission side, and frequency-multiplexed light is incident on the optical fiber. The light spread by the diffraction effect in the input side slab waveguide 3 enters a plurality of channel waveguides forming the array waveguide diffraction grating 4, propagates to the output side slab waveguide 5, and is collected in the output waveguide 6. Be lighted. In this case, since the lengths of the individual channel waveguides constituting the array waveguide diffraction grating 4 are different, the phase of the individual light after the propagation of the channel waveguide is shifted, and the wavefront of the focused light is changed according to the shift amount. Lean. The light condensing position is determined by the tilt angle. However, since the phase shift amount of light depends on the optical frequency and the optical frequency is different, the light condensing position is determined for each optical frequency, and the output waveguide 6 is placed at that position. With this arrangement, signal light can be extracted for each optical frequency.

A feature of the arrayed waveguide grating 4 is that its optical frequency resolution is proportional to the difference (ΔL) between the lengths of the channel waveguides constituting the arrayed waveguide grating.
That is, by designing ΔL to be large, the above-mentioned phase shift amount becomes large, and it becomes possible to multiplex / demultiplex multiplexed light having a narrow optical frequency interval, which cannot be realized by the conventional diffraction grating.
FIG. 11 shows the result of measuring the characteristics in the output waveguide 6 by performing demultiplexing around the optical wavelength of 1.55 μm and measuring the characteristics of the output waveguide 6. It is shifted by _z . In other words, transmission wavelength of the output waveguide 6 is different by 10GH _z, and good branching characteristics. In an arrayed waveguide grating optical multiplexer / demultiplexer,
Since all functions such as input / output system, light condensing system, and diffraction grating can be manufactured on the substrate 1 collectively by using the optical waveguide, mass productivity and stable characteristics can be achieved compared to the bulk type in which lenses and diffraction gratings are assembled. It is advantageous in terms of properties, low price, and the like.

However, the above-mentioned conventional array waveguide diffraction grating type optical multiplexer / demultiplexer has only a completely passive optical wavelength multiplexer / demultiplexer function by a diffraction grating. However, if an optical frequency selection function and a transmission wavelength width variable function can be added to the multiplexing / demultiplexing function, the applicable range can be further expanded.

An object of the present invention is to provide an optical multiplexer / demultiplexer which realizes an optical frequency selection function and a transmission wavelength width variable function in order to expand the above-mentioned application range.

[0008]

According to a first aspect of the present invention, there is provided an input waveguide and a first slider.
Waveguide, a plurality of channel waveguides of different lengths, a second
Slab waveguide and output waveguide are connected in order on the substrate
As well as multiple channels
An optical multiplexer / demultiplexer with an optical phase controller inserted in the waveguide
The waveguide is a quartz glass formed on a silicon substrate.
Optical phase controller is a thin film heater
The optical phase shifter has a length corresponding to the length of the channel waveguide.
It is characterized by different sizes. Issue of [Claim 2]
Ming, input waveguide, first slab waveguide, different length
A plurality of channel waveguides, a second slab waveguide, and
When the force waveguide is created by being connected on the substrate in order
In both cases, an optical phase controller is inserted into the multiple channel waveguides.
In the optical multiplexer / demultiplexer, the input waveguide, the first
Slab waveguide, multiple channel waveguides of different lengths
The waveguide, the second slab waveguide, and the output waveguide are silicon-based.
A quartz glass waveguide formed on a plate, wherein the optical phase
The controller is a waveguide and electrodes formed on a LiNbO ₃ substrate.
The length of the electrode corresponding to the length of the channel waveguide
It is characterized by different sizes.

[0009]

By inserting an optical phase controller into a plurality of channel waveguides corresponding to their lengths, the waveguides have a function of equivalently increasing or decreasing the length ΔL of the waveguides, and transmitting light. It becomes an optical frequency selection switch for switching the frequency, and it can temporally select and extract a signal weighed at a plurality of optical frequencies, and operates as a tuner in the optical frequency domain. Further, by inserting an optical phase controller into a plurality of channel waveguides, the width of the transmission wavelength (transmission band width) can be controlled, and the widening of the width enables optimal control as a filter.

[0010]

FIG. 1 to FIG. 8 show an embodiment of the present invention.
This will be described with reference to FIG. [Embodiment 1] FIG. 1 is a plan view of an optical waveguide selectable array waveguide grating type optical multiplexer / demultiplexer according to a first embodiment.
On a substrate 1, an input waveguide 2 (for example, eleven), a first slab waveguide 3, and a plurality of channel waveguides 4 (for example, 41).
Book), a second slab waveguide 5, and an output waveguide 6 (for example, 11). Here, a plurality of channel waveguides 4 having the same curvature and different lengths are formed, and are formed so that the length ΔL of the waveguide is increased so that the resolution can be increased even at a narrow frequency interval. Further, the channel waveguide 4 is loaded with a thermo-optic phase shifter 7 which is a phase controller formed for each waveguide corresponding to the length of the waveguide. The thermo-optic phase shifter 7 is a thin-film heater, and shifts the optical frequency by changing the temperature to change the refractive index. The reason why the thermo-optic phase shifter 7 is made to correspond to the length of the channel waveguide 4 is that the frequency shift in each channel waveguide is similarly performed in all the waveguides.

In manufacturing the optical multiplexer / demultiplexer, as shown in FIG. 2, an under clad film of quartz glass is first deposited on a silicon substrate 1 by a flame deposition method to a thickness of 30 μm.
Next, 7 μm of quartz glass to which Ge was added was deposited as a core film. The refractive index of the core film was 0.75% higher than that of the under clad and over clad quartz glass. Next, unnecessary portions of the core film were cut off by photolithography and reactive ion etching to produce the waveguide shapes shown in FIGS. Further, a buried type three-dimensional optical waveguide 4 was manufactured by depositing an over-cladding film of quartz glass by a flame deposition method. The waveguide core size was 7 μm × 7 μm. Finally, the thermo-optic phase shifter 7 was manufactured by photolithography and metal vapor deposition.

In designing an optical waveguide circuit, an array
The pitch of the waveguide grating (the channel that constitutes the array waveguide)
(Spacing of the slab waveguides 3 and 5 of the tunnel waveguide 4)
d is 20 μm, and the radius of curvature f of the slab waveguide is 5762 μm.
m, next to the channel waveguide that constitutes the array waveguide
Was set to 1656 μm. this
When the linear dispersion of the output waveguide 6 at the end of the slab waveguide 5 is obtained.
Is 10 GH in the optical wavelength 1.55 μm band._Z25 per hit
μm interval, so wavelength multiplexing interval 10GH _ZGot
The distance between the input portions of the output waveguide 6 is 25 μm.
And Each channel waveguide of the thermo-optic phase shifter 7
Length is ΔL = 2 mm compared to the length overlapping the adjacent waveguide.
Only different. Optical frequency selectable in this embodiment
In an arrayed waveguide grating optical multiplexer / demultiplexer, a thermo-optic phase shifter is used.
By driving the lid 7, the channel of the array waveguide is
The optical path length difference ΔL between the optical waveguides can be changed.
The focus position of light of a certain frequency can be moved,
The optical frequency could be switched. The actual at this time
Between the waveguide temperature of the thermo-optic phase shifter and the optical frequency shift
The relationship is 1.7GH_Z/ ° C. Also channel off
The time required for the replacement was 100 msec. This light frequency
Selectable number of optical multiplexer / demultiplexers can output signals of any optical frequency
Very effective in that it can be taken out from the output port of
Work as a simple part.

[Embodiment 2] FIG. 3 is a plan view of an array waveguide diffraction grating type optical multiplexer / demultiplexer having a variable pass band width according to a second embodiment of the present invention, and FIG. 4 is an enlarged sectional view taken along the line BB '. Is shown.
Its configuration is almost the same as that of the optical multiplexer / demultiplexer of the first embodiment, except that the thermo-optic phase shifter 8 is mounted on every other channel waveguide 4 of the array diffraction grating. The filter characteristics of the optical multiplexer / demultiplexer when the thermo-optic phase shifter 8 is not driven are shown by black circles in FIG. On the other hand, the filter characteristics of the optical multiplexer / demultiplexer when the thermo-optic phase shifter 8 is driven to increase the waveguide temperature in a certain portion of the thermo-optic phase shifter by 3 ° C. with respect to the non-wavelength portion is shown by a white circle in FIG. Indicated by As described above, by driving with the thermo-optic phase shifter 8 provided every other channel waveguide 4, in the first embodiment, the frequency selection is performed with the thermo-optic phase shifter provided in all the channel waveguides 4. On the other hand, the length Δ
As a result of changing L equivalently, the light-collecting frequency band can be changed. As a result, when used as an optical frequency multiplexer / demultiplexer, it is preferable that the transmission bandwidth is optimally given by the signal capacity carried on the used signal light. The array waveguide diffraction grating type optical multiplexer / demultiplexer having a variable transmission bandwidth of this embodiment is very effective in that the optimum transmission bandwidth can be changed depending on the signal light used.

Although the phase controller in the second embodiment has a structure provided for every other channel waveguide, the transmission wavelength width can be changed by changing the length ΔL every other line. A phase controller may be provided such as every other or every third. In addition, a plurality of channel waveguides 4
Even if the number of phase controllers is provided in all of the above, the position to be provided is changed, the phase controller is provided without being proportional to the length of the channel waveguide, and the temperature is changed for each book. Also in this case, the transmission wavelength width can be changed and the filter can function as a filter.

[Embodiment 3] The first embodiment and the second embodiment are as follows.
Although the example in which the thermo-optical phase shifters 7 and 8 are provided as the phase controller has been described, the present embodiment includes the electro-optical phase shifter. That is, the refractive index is changed by the electro-optic effect and the length Δ
The configuration for changing L is shown. FIG. 6 is a plan view of an arrayed waveguide grating type optical multiplexer / demultiplexer capable of selecting an optical frequency according to a third embodiment. FIG. 7 is an enlarged sectional view taken along the line CC 'in FIG. FIG. 8 is an enlarged plan view for explaining the wiring of the electro-optical phase shifter electrode 11 in FIG.
The operating principle of this optical multiplexer / demultiplexer is exactly the same as that of the optical multiplexer / demultiplexer of the first embodiment. However, in the optical multiplexer / demultiplexer of the present embodiment, the electro-optic effect of LiNbO ₃ crystal is used as an optical phase shifter inserted into the array waveguide. In that it is a waveguide type phase shifter 11 utilizing the In portions other than the optical phase shifter, a glass waveguide having a small light loss due to bending is used.

In manufacturing the LiNbO ₃ optical waveguide and the electrode 11 for the electro-optical phase shifter, a Ti thin film was adhered to the surface of the LiNbO ₃ substrate 9 by sputtering, and a waveguide pattern was formed by lithography and dry etching. Then 1
By thermally diffusing Ti at 050 degrees, a Ti-diffused three-dimensional optical waveguide 10 was formed on the LiNbO ₃ surface layer. Then S
The iO ₂ buffer layer 12 was formed by a sputtering method, and an electrode was formed by Au by a vapor deposition method. The configuration of the optical multiplexer / demultiplexer includes a waveguide bending portion such as an input / output unit and a slab development unit,
A glass waveguide with small light loss is used, and a linear Ti-diffused LiNbO ₃ waveguide 1 is used only in a portion where phase modulation is necessary.
0 was used. Since the optical multiplexer / demultiplexer of the present embodiment utilizes the phase modulation using the electro-optic effect, the selection of the transmitted light frequency can be made within 1 μsec or less, which is much faster than the first embodiment utilizing the thermo-optic effect. did it. Further, since the phase is controlled by the electro-optic effect, it is a very advantageous method in that heat is not generated essentially.

[0017]

As described above, the arrayed waveguide grating type optical multiplexer / demultiplexer according to the present invention can be applied to an optical multiplexer / demultiplexer which has only a completely passive function in the past. A variable bandwidth function can be provided. This is effective in that the applicable range of the arrayed waveguide grating type optical multiplexer / demultiplexer is widened.

[Brief description of the drawings]

FIG. 1 is a plan view of an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer capable of selecting an optical frequency according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view taken along line AA ′ in FIG.

FIG. 3 is a plan view of an arrayed waveguide grating optical multiplexer / demultiplexer having a variable transmission bandwidth according to a second embodiment of the present invention.

FIG. 4 is an enlarged sectional view taken along the line BB ′ in FIG. 3;

FIG. 5 is a transmission characteristic diagram from one output port of an arrayed waveguide grating optical multiplexer / demultiplexer having a variable transmission bandwidth according to a second embodiment of the present invention.

FIG. 6 is a plan view of an arrayed waveguide grating optical multiplexer / demultiplexer capable of selecting an optical frequency according to a third embodiment of the present invention.

FIG. 7 is an enlarged sectional view taken along line CC ′ in FIG. 6;

FIG. 8 is an enlarged plan view for explaining wiring of electrodes for an electro-optical phase shifter in FIG. 6;

FIG. 9 is a plan view of an array waveguide diffraction grating type optical multiplexer / demultiplexer according to the related art.

FIG. 10 is an enlarged sectional view taken along line DD ′ in FIG. 9;

FIG. 11 is a transmission optical frequency characteristic diagram of a conventional arrayed waveguide grating optical multiplexer / demultiplexer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Input waveguide 3 Input side slab waveguide 4 Array waveguide diffraction grating 5 Output side slab waveguide 6 Output waveguide 7,8 Thermo-optic phase shifter 9 LiNbO ₃ substrate 10 Ti diffusion LiNbO ₃ optical waveguide 11 Electro-optics Electrode for phase shifter 12 SiO ₂ buffer layer 13 -electrode for electro-optical phase shifter 14 + electrode for electro-optical phase shifter

──────────────────────────────────────────────────続 き Continuing on the front page (72) Oota Suzuki, Inventor 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Toshimi Kominato 1-16-1 Uchisaiwaicho, Chiyoda-ku, Tokyo No. Nippon Telegraph and Telephone Corporation (72) Inventor Hiroshi Takahashi 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Yasuhiro Hita 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Japan (56) References JP-A-4-326308 (JP, A) US Patent 5002350 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/29- 1/313 G02F 1/00-1/035 G02B 6/12 G02B 6/28

Claims (2)

(57) [Claims] An input waveguide, a first slab waveguide, a plurality of channel waveguides having different lengths, a second slab waveguide,
And output waveguides is <br/> been created are connected in this order in substrate Rutotomoni, optical phase control to the plurality of channel waveguides
In the optical multiplexer / demultiplexer in which a waveguide is inserted, the waveguide is a quartz glass waveguide formed on a silicon substrate.
The optical phase controller is a thermo-optic consisting of a thin film heater.
Use the phase shifter to adjust the length according to the length of the channel waveguide.
An optical multiplexer / demultiplexer characterized by being different. 2. An input waveguide, a first slab waveguide, a length of
A plurality of different channel waveguides, a second slab waveguide,
And the output waveguides are connected and created on the substrate in order
And optical phase control to the plurality of channel waveguides.
In the optical multiplexer / demultiplexer in which the optical waveguide is inserted, the input waveguide, the first slab waveguide,
A number of channel waveguides, a second slab waveguide, and an output
The waveguide is a quartz glass waveguide formed on a silicon substrate
Wherein the optical phase controller is formed on a LiNbO ₃ substrate.
Length of channel waveguide consisting of waveguide and electrode
The feature is that the length of the electrode is changed according to
Optical multiplexer / demultiplexer.