JP2003066253A - Wavelength branching filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To branch a wavelength multiplex signal into a plurality of signal groups and also to facilitate the arrangement or a connecting operation of an optical fiber which is connected in a wavelength branching filter. SOLUTION: The wavelength branching filter is constituted by using an optical waveguide type wavelength filter having a ring resonator. The wavelength multiplex signal is branched into a plurality of signal groups by a configuration where a plurality of optical waveguide type wavelength filters are arranged along an input side optical waveguide and the output of each wavelength filter is taken-out from an output side optical waveguide. The output ends of the output side optical waveguides are arranged on the same end surface so that the optical fiber is easily arranged and connected. The wavelength branching filter 1 is provided with the input side optical waveguide 2, a plurality of output side optical waveguides 3 and a plurality of optical waveguide type wavelength filters 4 having the ring resonator 5. The wavelength filters 4 are arranged to be adjacent to the optical waveguide along the optical route direction of the input side optical waveguide 2 and, then, the output side optical waveguides 3 are adjacently arranged at each arranged optical waveguide type wavelength filter 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide type wavelength demultiplexer using a ring resonator.

[0002]

2. Description of the Related Art Dense Wavelength Div
ision multiplexing (DWDM) In optical communication, it is required for optical multiplexers / demultiplexers for multiplexing and demultiplexing multiple optical signals to expand the number of wavelengths of channels and narrow the intervals between channels. . FIG. 20 is a diagram for explaining conventional branching. Conventionally, as an optical multiplexer / demultiplexer that splits a wavelength multiplexed optical signal, an arrayed waveguide
Grating: AWG) and multilayer filters are known.

In FIG. 20 (a), an optical signal containing a plurality of wavelengths (for example, λ1 to λ10) is demultiplexed by an optical multiplexer / demultiplexer 101 into channels of each wavelength. In order to expand the amount of information in optical communication, it is necessary to increase the number of wavelength channels, and it is necessary to further reduce the channel spacing and center wavelength spacing of optical multiplex signals. For this purpose, a higher-performance multiplexer / demultiplexer is required, but a configuration that combines a wavelength demultiplexer and a multiplexer / demultiplexer instead of the configuration of only the multiplexer / demultiplexer is advantageous in terms of cost and productivity. It is said that.

The wavelength demultiplexer 102 demultiplexes the input wavelength-multiplexed optical signal into two sets of signal sequences having a double wavelength interval,
Conversely, two sets of wavelength-multiplexed optical signals are combined into one signal series having a half wavelength interval, which is also called an interleaver. In FIG. 20B, an optical signal including a plurality of wavelengths (for example, λ1 to λ20) has two sets of signal sequences (for example, wavelengths λ1 and λ3 to λ1) that are processed by the wavelength demultiplexer 102.
9 odd-numbered channels and wavelengths λ2, λ4 to λ20 even-numbered channels). Each demultiplexed signal sequence is
The wavelengths are demultiplexed into respective wavelengths by the two sets of optical multiplexers / demultiplexers 101a and 101b in the latter stage. As a result, the optical multiplexer / demultiplexer can obtain the effect of the same characteristic as a whole with the filter characteristic having a double wavelength interval as compared with the case where the wavelength demultiplexer is not used.

FIG. 21 is a diagram for explaining demultiplexing by a wavelength demultiplexer and an optical multiplexer / demultiplexer. In the wavelength-division-multiplexed optical signal shown in FIG. 21A, the solid line indicates the even-numbered channel signal series, and the broken line indicates the odd-numbered channel signal series. The wavelength demultiplexer is an even channel wavelength signal (see FIG. 21).
(B)) and wavelength signals of odd channels (Fig. 21 (c))
Of the two signal sequences. This widens the wavelength interval between the signals to facilitate demultiplexing by the optical multiplexer / demultiplexer. FIGS. 21D, 21E, and 21F are examples of demultiplexing by the optical multiplexer / demultiplexer, in which wavelength signals of even channels are demultiplexed to obtain separated wavelength signals.

As the wavelength demultiplexer, a fiber type, a multilayer film type, a birefringence type, a waveguide type and the like are known. Among them, a configuration using a ring resonator as a waveguide type wavelength demultiplexer has been proposed. The wavelength demultiplexer using this ring resonator has a ring resonator between the input side optical waveguide and the output side optical waveguide, and only the optical signal of the wavelength that matches the resonance wavelength of the ring resonator. Is taken out to the output side optical waveguide through the ring resonator, emitted from the DROP port of the output side optical waveguide, and optical signals of other wavelengths are directly emitted from the through port of the input side optical waveguide.

[0007]

In order to expand the amount of information in optical communication, it is necessary to increase the number of wavelength channels, and it is necessary to narrow the channel spacing and center wavelength spacing of optical multiplex signals. For this purpose, a higher-performance multiplexer / demultiplexer is required, but a configuration that combines a wavelength demultiplexer and a multiplexer / demultiplexer instead of the configuration of only the multiplexer / demultiplexer is advantageous in terms of cost and productivity. It is said that.

A conventionally known wavelength demultiplexer has two output terminals.
Since two 2-port outputs are used, it is necessary to cascade the wavelength demultiplexers in multiple stages in order to perform higher density optical communication. For example, in FIG. 20, when the number of wavelengths of the channel is increased (in FIG. 20C, ch1 to ch40 (λ1 to
λ40)) includes three sets of wavelength demultiplexers 102a to 102c.
Is used to make a two-stage cascade connection, and the first-stage wavelength demultiplexer 10
After being divided into two sets of signal sequences by 2a, it is further divided into two sets of signal sequences by the second-stage wavelength demultiplexers 102b and 120c, respectively, and a total of four sets of each signal sequence (in FIG.
1, ch5, ..., ch37, ch3, ch7, ..., ch
39, ..., Ch4, ..., Ch40), and each signal series is demultiplexed by the optical multiplexer / demultiplexers 101a to 101d.

However, in the structure using such a two-port wavelength demultiplexer, a plurality of wavelength demultiplexers are required, and therefore a large number of wavelength demultiplexers are required as the number of wavelength channels increases. At the same time, since a large number of wavelength demultiplexers are arranged, the device area required for multiplexing and demultiplexing increases, which causes problems in cost and compactness.

Further, the conventional wavelength demultiplexer has problems in the arrangement of the optical fibers to be connected and the operability of the connection. For example, in a wavelength demultiplexer using a ring resonator, since the DROP port and the through port, which are output ends, are arranged on different end faces, the arrangement of optical fibers connecting these ports and the optical multiplexer / demultiplexer is arranged. The configuration becomes complicated, and in the connection between the optical fiber and the port, it is necessary to change the end face of the optical fiber for each port and perform the connection operation, which makes the operation complicated.

Therefore, an object of the present invention is to solve the above-mentioned conventional problems and to provide a wavelength demultiplexer for demultiplexing a wavelength division multiplexed signal into a plurality of signal sequences. It is another object of the present invention to provide a wavelength demultiplexer that simplifies the arrangement and connection operation of optical fibers to be connected.

[0012]

According to the present invention, a wavelength demultiplexer is constructed using an optical waveguide type wavelength filter having a ring resonator, and a plurality of optical waveguide type wavelengths are arranged along an input side optical waveguide. By arranging a filter and demultiplexing the output of each optical waveguide type wavelength filter from the output side optical waveguide into multiple signal series, and by arranging the output end of the output side optical waveguide on the same end face, Simplify fiber placement and connection.

The wavelength demultiplexer of the present invention comprises an input side optical waveguide, a plurality of output side optical waveguides, and a plurality of optical waveguide type wavelength filters provided with ring resonators, and inputs a plurality of optical waveguide type wavelength filters. The optical waveguide is arranged adjacent to the optical waveguide along the optical path direction of the side optical waveguide, and the output optical waveguide is arranged adjacent to each of the arranged optical waveguide wavelength filters. With this configuration, a plurality of signal sequences can be demultiplexed to the output side optical waveguide from the wavelength division multiplexed signal input to the input side optical waveguide.

The wavelength demultiplexer of the present invention can output a plurality of signal sequences demultiplexed to the output side optical waveguide from the output end arranged on the same end face. The output ends arranged on the same end face may be arranged on the end face on the same side as the input end of the input side optical waveguide, or may be arranged on the end face opposite to the input end of the input side optical waveguide. With this configuration, the arrangement of the optical fibers connected to the output end and the optical fiber connection can be simplified.

Further, from the through port of the input side optical waveguide, the remaining signal series removed by each optical waveguide wavelength filter can be taken out. By using this through port as the output end and arranging it on the end face on the same side as the output end of the output side optical waveguide, all the wavelength-multiplexed signals input to the input side optical waveguide are demultiplexed into each signal series, and the same end face Can be taken from. In the arrangement configuration of the optical waveguide type wavelength filter, it may be arranged in order on one side of the input side optical waveguide or alternately on both sides.

Each optical waveguide type wavelength filter used in the wavelength demultiplexer of the present invention can be composed of a plurality of ring resonators, and the plurality of ring resonators are arranged in parallel along the input side optical waveguide and the output side optical waveguide. Connect or connect in series. By connecting multiple ring resonators in parallel and adjusting the spacing between each ring resonator, the filter characteristics of each optical waveguide type wavelength filter are adjusted, the pass band is flattened, and the pass band and the stop wavelength band are adjusted. The boundary of can be made steep.
Also, by connecting multiple ring resonators with the same ring diameter in series, the transmission band is flattened, the stop amount in the stop wavelength region is increased, and the transition region from the transmission band to the stop wavelength region is made steep. can do.

Further, the transmission wavelength band width of each optical waveguide type wavelength filter used in the wavelength demultiplexer of the present invention and the wavelength interval between each optical waveguide type wavelength filter can be set arbitrarily. By setting this transmission wavelength bandwidth to be one of the demultiplexing numbers of the intervals of the resonance wavelength of each optical waveguide type wavelength filter, each signal series demultiplexed by the wavelength demultiplexer is set to have substantially equal wavelength intervals. can do. The center wavelength of each optical waveguide type wavelength filter and the interval between the resonance wavelengths can be determined based on the ring diameter of the ring resonator.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram for explaining the outline of the wavelength demultiplexer of the present invention. In FIG. 1, the wavelength demultiplexer 1 includes an input end IN and an output end OUT4 of an optical waveguide having a curved portion at one end (left side in the drawing).
And the input side optical waveguide 2 to be arranged in the
Optical waveguide type filters 4 (4
a, 4b, 4c) and the output side optical waveguide 3 (3a, 3b, 3c) adjacent to each optical waveguide type filter 4. Output ends OUT1, O of the output side optical waveguides 3a, 3b, 3c
UT2, OUT3, and the output end (through port) of the input side optical waveguide type 2 are arranged at one end (left side in the drawing).

The wavelength demultiplexer 1 demultiplexes the wavelength-multiplexed signal input to the input end IN into each optical waveguide type filter 4 with each wavelength characteristic, and outputs each output end OUT1, OUT2, OUT3.
Output from OUT4. Output terminals OUT1, OUT2, O
Since the UT3 and OUT4 are integrated on one end face of the wavelength demultiplexer 1, the optical fibers can be connected at the same end face. Further, the input end IN can also be arranged on the same end face as the output end, whereby all the optical fibers can be arranged on the same end face side.

FIG. 2 is a schematic signal diagram for explaining a demultiplexing state by the 4-port wavelength demultiplexer having the four output terminals shown in FIG. Here, an example is shown in which the input wavelength division multiplexed signal is demultiplexed into four signal series. Figure 2 (a)
Shows an example of the wavelength division multiplexed signal input to the input terminal IN,
λ1, λ2, ..., λn, λn + 1, λn + 2, λn + 3
Each wavelength component of Further, FIG. 2B shows an example of the filter characteristics of the wavelength demultiplexer, and shows the resonance wavelength interval (FS).
R) comprises four filter parts with a periodic transmission wavelength range. The wavelength demultiplexer is used for wavelength division multiplexed signals λ1, λ2,
, .Lamda.n, .lamda.n + 1, .lamda.n + 2, .lamda.n + 3 are demultiplexed by the filter characteristic of FIG.
1, OUT2, OUT3 and OUT4 are respectively shown in FIG.
As shown in (c), FIG. 2 (d), FIG. 2 (e), and FIG. 2 (f), wavelength components are output for each resonance wavelength interval (FSR).

By combining the wavelength demultiplexer of the present invention and the optical demultiplexer, λ1, λ2 of the wavelength division multiplexed signal
, .Lamda.n, .lamda.n + 1, .lamda.n + 2, .lamda.n + 3, ... Can be separated. FIG. 3 is a schematic diagram for explaining a configuration in which the wavelength demultiplexer of the present invention and the optical demultiplexer are combined. In the configuration shown in the figure, four optical multiplexers / demultiplexers 11 are provided for one wavelength demultiplexer 1 via an optical fiber.
a, 11b, 11c, 11d are connected to each optical multiplexer / demultiplexer 1
Input four signal sequences demultiplexed into 1a to 11d. For example, wavelength multiplexed signals ch1 to ch4 for 40 channels
When demultiplexing 0 (λ1 to λ40), the wavelength demultiplexer 1
Four signal sequences (ch1, ch5, ..., ch3
7, ch2, ch6, ..., ch38, ch3, ch7,
, Ch39, ch4, ch8, ..., ch40), and each signal sequence is divided into four optical multiplexers / demultiplexers 11a, 11b, 1
The signals are demultiplexed into each channel by 1c and 11d.

According to the wavelength demultiplexer of the present invention, one wavelength demultiplexer can be divided into a large number of signal series (for example, four signal series in a wavelength demultiplexer having 4 ports). Compared to using a port wavelength demultiplexer, the number of wavelength demultiplexers can be reduced, and an inexpensive optical demultiplexer can be used without using a high-performance optical demultiplexer. You can

A more detailed configuration example of the wavelength demultiplexer of the present invention will be described below with reference to FIGS. 4 to 19. FIG. 4 is a schematic diagram for explaining a first configuration example of the wavelength demultiplexer of the present invention. The wavelength demultiplexer 1a has an input side optical waveguide 2 and an output side optical waveguide 3 (3a, 3a) as in the configuration example shown in FIG.
b, 3c) and the optical waveguide type filter 4 (4a, 4b, 4)
c) and the optical waveguide type filters 4a, 4b and 4c are arranged along the input side optical waveguide 2. Here, each optical waveguide type filter 4a, 4b, 4c is configured by connecting a plurality of ring resonators 5 in parallel along the input side optical waveguide 2 and the output side optical waveguide 3. Output terminals OUT1, OUT
2, OUT3 are optical waveguide filters 4a, 4b, 4c
The end portions of the output side optical waveguides 3a, 3b, 3c connected to the above are arranged on the same end face side. In addition, the through port of the input side optical waveguide 2 is set as the output end OUT4 and arranged on the same end face side.

The plurality of ring resonators 5 constituting each optical waveguide type filter 4a, 4b, 4c can adjust the center wavelength and the resonance wavelength of each stage by adjusting the diameter of the ring. In a ring resonator, a resonance wavelength interval (FSR) that represents a periodic spectral response is determined by an effective refractive index of an optical waveguide forming the ring and the total length of the ring, and can be expressed by FSR = λ ₀ ² / 2ΔL.
λ ₀ is the resonance wavelength at a certain resonance order near the wavelength of interest, and ΔL is the optical length of the ring. The optical length ΔL of the ring is represented by the physical length of the ring (2πR) × effective refractive index, where R is the radius of the ring.

FIG. 5 is a schematic view showing one structural example of a ring resonator applied to the first structural example. In the configuration example shown in FIG. 5, four ring resonators 5a, 5b, 5c and 5d are connected in parallel along the input side optical waveguide A and the output side optical waveguide B,
The distance between the ring resonator 5a and the ring resonator 5b and the distance between the ring resonator 5c and the ring resonator 5d are 2πR,
The interval between the ring resonator 5b and the ring resonator 5c is πR. With this configuration, the filter characteristic of the optical waveguide type filter 4 can be made a box type characteristic with a flat transmission band. FIG. 6 shows an example of filter characteristics of the optical waveguide type filter provided in the wavelength demultiplexer of the present invention.

The filter characteristics of the configuration in which a plurality of ring resonators are connected in parallel will be described below with reference to FIGS. FIG. 7 shows a model in which i ring resonators having the same radius are connected in parallel. Here, R is a ring radius, Li is an interval between the rings between the i-th ring resonator and the (i + 1) th ring resonator, A and B are bus lines,
A ₀ , A ₁ , B ₀ and B ₁ are input / output.

The filter characteristic of the single ring resonator is Lorentz type and the flatness of the transmission region is poor. On the other hand, by connecting the ring resonators in parallel in multiple stages and adjusting the arrangement between the ring resonators, the transmission region can be flattened. In the model of FIG. 7, the relationship between input and output amplitudes can be expressed by the following matrix using a transfer matrix.

[0028]

[Equation 1]

Here, Ti represents the transfer matrix of the i-th ring resonator, and Λi represents the transfer matrix between the i-th and the (i + 1) -th. The model also assumes that the ring and bus lines have equal propagation constants and no strength loss.

The parameters that determine the filter characteristics of one ring resonator are the ring radius and the coupling degree κl between the ring and the bus line. The resonance wavelength interval (FSR) is adjusted by the ring radius, and the coupling degree κl is adjusted. The width of each spectrum can be adjusted. On the other hand, in the configuration in which a plurality of ring resonators are connected in parallel, the distance between the ring resonators is added as a parameter that determines the filter characteristic.

FIG. 8 shows a comparison between the filter characteristic of a single ring resonator and the filter characteristic of a parallel connection of two ring resonators. Comparing the flatness of both transmission regions, the flatness is poor in a single ring resonator, but the flatness is improved by connecting two ring resonators in parallel.

FIG. 9 shows the dependence of the ring spacing on the parallel connection of two ring resonators. When two ring resonators are connected in parallel, the output resulting from the contribution of the first ring resonator from the input and the output resulting from the contribution of the second ring resonator appear as the overall output. For example, when the ring interval is πR (the filter characteristic shown by the solid line in FIG. 9), it becomes a box shape near the peak, and the transmittance decreases in the middle of the resonance wavelength. Further, when the ring interval is 2πR (the filter characteristic shown by the broken line in FIG. 9), it becomes more box-shaped near the peak and shows the characteristic that the transmittance increases in the middle of the resonance wavelength. The filter characteristic shown in FIG. 6 can be obtained by combining the cases where the ring spacing is πR and 2πR.

In order to obtain a filter characteristic for demultiplexing into a large number of signal series, the filter characteristics of each stage are such that the center wavelength is shifted corresponding to each signal series with respect to the resonance wavelength interval (FSR) and the band is divided into bands. It is necessary to narrow the width. For example, 4
When configuring a port wavelength demultiplexer, the ring radius R
Is adjusted to shift the center wavelength of each stage by 1/4 of the resonance wavelength interval (FSR), and the bandwidth is set to about 1/4 of the resonance wavelength interval (FSR). Further, in order to provide the output region of each signal series with flatness, the ring interval and coupling degree κl connected in parallel are adjusted.

FIG. 10 shows that in the wavelength band of 1.55 μm,
A filter characteristic in which three optical waveguide type filters having a resonance wavelength interval (FSR) of 1.6 nm (corresponding frequency interval is 200 GHz) are vertically connected in three stages, and each stage filter demultiplexes into four signal series at 50 GHz intervals. It is an example of configuring. Here, the ring radius R is R≈150 μm, ΔR = 40 n
m and the degree of coupling κl = π / 7. The bandwidth of each output terminal is shown in the table below.

[0035]

[Table 1]

The Spape Factor is a numerical value that quantitatively represents the flatness of the transmission region, and is represented by SpapeFactor = (-1 dB bandwidth / -10 dB bandwidth). The Spape Factor has a theoretical value of 0.17 for the Lorentz filter characteristic with a single ring resonator, and 1.0 for the ideal box-shaped filter characteristic.

FIG. 11 shows that in the wavelength band of 1.55 μm,
Three optical waveguide filters with a resonance wavelength interval (FSR) of 0.8 nm (corresponding frequency interval of 100 GHz)
This is an example in which filters are connected in a cascade connection and each filter has a filter characteristic of demultiplexing into four signal sequences at 25 GHz intervals.

The wavelength demultiplexer of the present invention can be applied with various modes in the arrangement of the optical waveguide type filter.
Hereinafter, an arrangement example of the optical waveguide type filter will be described with reference to FIGS. FIG. 12 shows the second wavelength demultiplexer of the present invention.
3 is a schematic diagram for explaining a configuration example of FIG. The second configuration example is the same as the first configuration example except that the wavelength demultiplexer 1b does not use the through port of the input side optical waveguide 2 as an output end, and the optical waveguide type filters 4a, 4b and 4c are followed by the optical waveguide type filter 4d.
Is added to the input side optical waveguide 2, and the output of this optical waveguide type filter 4d is passed through the output side optical waveguide 3d to the output end OUT.
Output from 4. The output terminals OUT1 to OUT4 are arranged on the same end face as in the first configuration example.

FIG. 13 is a schematic diagram for explaining a third configuration example of the wavelength demultiplexer of the present invention. In the first configuration example, the optical waveguide type filters 4a, 4b, 4c are arranged only on one side of the curved input side optical waveguide 2. In contrast to this configuration, the wavelength demultiplexer 1c of the third configuration example has a configuration in which optical waveguide type filters are arranged on both sides of the curved portion of the input side optical waveguide 2, and the optical waveguide type filter is disposed on one side in the figure. In this configuration, the waveguide filters 4a and 4b are arranged, and the optical waveguide filter 4c is arranged on the other side with the curved portion 2a interposed therebetween. Similar to the first configuration example, output side optical waveguides 3a, 3b, 3c are arranged adjacent to each of the optical waveguide type filters 4a, 4b, 4c, and the output ends OUT1 to OUT4 are the first configuration example. Place on the same end face as in.

FIG. 14 is a schematic diagram for explaining a fourth configuration example of the wavelength demultiplexer of the present invention. In the wavelength demultiplexer 1d of the fourth configuration example, the optical waveguide type filters 4a, 4b, ... 4n are sequentially arranged on one side of the linearly arranged input side optical waveguide 2, and the output side optical waveguides 3a, 3b are arranged. , 3n are arranged adjacent to each other, and the output ends OUT1 to OUTn are arranged on the same end face.

FIG. 15 is a schematic diagram for explaining a fifth configuration example of the wavelength demultiplexer of the present invention. In the wavelength demultiplexer 1e of the fifth configuration example, the optical waveguide type filters 4a, 4b, 4c and the optical waveguide type filters 4d, 4e, 4f are sequentially arranged on one side of each of the curved input side optical waveguides 2. Then
The output side optical waveguides 3a, 3b, 3c and the output side optical waveguides 3d, 3e, 3f are arranged adjacent to each other, and the output end OUT1 is provided.
~ OUT6 are arranged on the same end face. Further, the through port of the input side optical waveguide 2 is arranged on the same end face as the output end OUT7.

FIG. 16 is a schematic diagram for explaining a sixth configuration example of the wavelength demultiplexer of the present invention. The wavelength demultiplexer 1f of the sixth configuration example has optical waveguide type filters 4a, 4b, 4c and optical waveguide type filters 4d, 4e, 4f alternately on both sides of each curved input side optical waveguide 2. The output side optical waveguides 3a, 3b, 3c and the output side optical waveguides 3d, 3e, 3f are disposed adjacent to each other, and the output end OU
T1 to OUT6 are arranged on the same end face. Further, the through port of the input side optical waveguide 2 is arranged on the same end face as the output end OUT7.

FIG. 17 is a schematic diagram for explaining the seventh configuration example of the wavelength demultiplexer of the present invention. The wavelength demultiplexer 1g of the seventh configuration example uses a ring resonator having a different configuration from the first configuration example. The structure of this ring resonator is such that the input side optical waveguide 2 and the output side optical waveguide 3 (3a, 3
b, 3c) and the optical waveguide type filter 4 (4a, 4b, 4)
c) and each optical waveguide type filter 4a, 4b, 4c
Is configured by connecting a plurality of ring resonators in series. That is, one of the ends of the plurality of ring resonators (the first ring resonator) is coupled to the input side optical waveguide 2 and the second ring resonator, and the other ring resonator is connected to the output side optical waveguide 3. The ring resonator in the middle is coupled only to adjacent ring resonators and is not coupled to the input side optical waveguide 2 and the output side optical waveguide 3. When the optical waveguide type filter is composed of only two ring resonators, one ring resonator is coupled to the input side optical waveguide and the other ring resonator and coupled to the output side optical waveguide. The other ring resonator is coupled to the output side optical waveguide and the one ring resonator and is not coupled to the input side optical waveguide.

In the case where the ring radii of all the ring resonators are the same in the series connection of the ring resonators,
As shown in FIG. 18, the transmission band is flattened, the amount of stoppage in the stopband is increased, crosstalk is reduced, and the transition region from the stopband to the stopband sharply changes. It is possible to realize a filter characteristic close to. Further, the transmission bandwidth can be designed to be any width by adjusting the coupling coefficient between the ring resonators or between the ring resonator and the input side optical waveguide or the output side optical waveguide.

Further, the wavelength demultiplexer of the present invention can be applied with another mode in the arrangement of the output ends. In each of the above-described configuration examples, the output end is arranged on the same side as the input end, but the output end may be arranged on the opposite side to the input end. In FIG. 19, the wavelength demultiplexer 1h of the configuration example is
Is provided with optical waveguide type filters 4a, 4b, 4c adjacent to one side of the linearly arranged input side optical waveguide 2, and the optical waveguide type filters 4a, 4b, 4c are provided with output side optical waveguides 3 respectively.
a, 3b, 3c are provided adjacent to each other, and the output side optical waveguide 3a,
Inside the ends of 3b and 3c, the opposite side to the input end IN is output end O
UT1 to OUT3. In addition, the through port of the input side optical waveguide 2 is defined as the output end OUT4, and the output ends OUT1 to O
Place on the same side as UT3.

Thus, the output end can be provided on the same end face, and the input end can be provided on the side opposite to the output end. According to this configuration, the output ends can be integrated into the same end face, and the input end and the output end can be arranged separately.

[0047]

As described above, according to the wavelength demultiplexer of the present invention, the wavelength division multiplexed signal can be demultiplexed into a plurality of signal series. Further, in the wavelength demultiplexer, the arrangement and connecting operation of the optical fibers to be connected can be simplified.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining an outline of a wavelength demultiplexer of the present invention.

FIG. 2 is a schematic signal diagram for explaining a demultiplexing state by the 4-port wavelength demultiplexer of the present invention.

FIG. 3 is a schematic diagram for explaining a configuration in which a wavelength demultiplexer and an optical multiplexer / demultiplexer according to the present invention are combined.

FIG. 4 is a schematic diagram for explaining a first configuration example of the wavelength demultiplexer of the present invention.

FIG. 5 is a schematic diagram showing a configuration example of a ring resonator applied to the first configuration example.

FIG. 6 is an example of filter characteristics of an optical waveguide filter provided in the wavelength demultiplexer of the present invention.

FIG. 7 is a schematic diagram for explaining a model in which i ring resonators are connected in parallel.

FIG. 8 is a filter characteristic diagram comparing a filter characteristic of a single ring resonator and a filter characteristic of two ring resonators connected in parallel.

FIG. 9 is a filter characteristic diagram showing the dependency of ring spacing in parallel connection of two ring resonators.

FIG. 10 is a filter characteristic diagram in which optical waveguide type filters of 200 GHz are vertically connected in three stages.

FIG. 11 is a filter characteristic diagram in which 100 GHz optical waveguide filters are vertically connected in three stages.

FIG. 12 is a schematic diagram for explaining a second configuration example of the wavelength demultiplexer of the present invention.

FIG. 13 is a schematic diagram for explaining a third configuration example of the wavelength demultiplexer of the present invention.

FIG. 14 is a schematic diagram for explaining a fourth configuration example of the wavelength demultiplexer of the present invention.

FIG. 15 is a schematic diagram for explaining a fifth configuration example of the wavelength demultiplexer of the present invention.

FIG. 16 is a schematic diagram for explaining a sixth configuration example of the wavelength demultiplexer of the present invention.

FIG. 17 is a schematic diagram for explaining a seventh configuration example of the wavelength demultiplexer of the present invention.

FIG. 18 is a diagram for explaining filter characteristics according to a seventh configuration example of the wavelength demultiplexer of the present invention.

FIG. 19 is a schematic diagram for explaining another configuration example of the wavelength demultiplexer of the present invention.

FIG. 20 is a diagram for explaining conventional branching.

FIG. 21 is a diagram for explaining demultiplexing by a wavelength demultiplexer and an optical multiplexer / demultiplexer.

[Explanation of symbols]

1, 1a to 1h ... Wavelength demultiplexer 2 ... Input side optical waveguide 3, 3a to 3d ... Output side optical waveguide 4, 4a-4d ... Optical waveguide type filter 5, 5a to 5d ... Ring resonator 11a to 11d, 101a to 101d ... Optical multiplexer / demultiplexer.

Claims (7)

[Claims] 1. An optical waveguide type wavelength filter comprising an input side optical waveguide, a ring resonator arranged along the optical path direction of the input side optical waveguide and adjacent to the optical waveguide, and each of the optical waveguides. An output side optical waveguide arranged adjacent to each of the waveguide type filters is provided, and all output ends of the plurality of output side optical waveguides are arranged on an end face on the same side as the input end of the input side optical waveguide. , Wavelength demultiplexer. 2. An optical waveguide type wavelength filter comprising an input side optical waveguide, a ring resonator arranged along the optical path direction of the input side optical waveguide and adjacent to the optical waveguide, and each of the optical waveguides. An output side optical waveguide arranged adjacent to each of the waveguide type filters, wherein all output ends of the plurality of output side optical waveguides are arranged on an end face opposite to the input end of the input side optical waveguide. Yes, a wavelength demultiplexer. 3. The through port of the input side optical waveguide is arranged on an end face on the same side as the output end of the output side optical waveguide, and the through port is used as an output end. The described wavelength demultiplexer. 4. Each of the optical waveguide type wavelength filters comprises a plurality of ring resonators connected in parallel or in series along the input side optical waveguide and the output side optical waveguide, or a combination of parallel connection and series connection. The wavelength demultiplexer according to any one of claims 1 to 3, characterized in that: 5. The wavelength component according to claim 1, wherein a transmission wavelength bandwidth of each of the optical waveguide type wavelength filters is one of a number of demultiplexed wavelengths of a resonance wavelength. Wave instrument. 6. The optical waveguide type wavelength filter according to claim 1, wherein an interval between the center wavelength and the resonance wavelength is determined based on the ring diameter of the ring resonator. Wavelength demultiplexer. 7. The optical waveguide type wavelength filter is arranged on one side of the input side optical waveguide in order, or alternately arranged on both sides of the input side optical waveguide.
The described wavelength demultiplexer.