JP3147323B2 - Light dispersion equalization circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical dispersion equalizing circuit for shaping the waveform of an optical signal which is distorted by propagating through an optical fiber having dispersion.

[0002]

2. Description of the Related Art At present, an optical fiber (quartz fiber) generally used has a zero dispersion at a wavelength of 1.3 μm, and a wavelength of 1.3 μm.
It has the characteristic that the loss is minimized at 1.55 μm. When an optical signal having a wavelength of 1.55 μm is incident on the optical fiber, the propagation delay time τ decreases as the optical signal frequency (modulation frequency) f increases because the dispersion of the optical fiber does not become zero (the propagation speed increases). . That is, the optical signal propagating through this optical fiber has a difference in propagation time due to a slight difference in frequency (wavelength difference) in the optical signal pulse, so that the optical signal pulse is distorted. When this distortion increases, the transmission capacity or transmission distance of the optical fiber is limited.

[0003] Therefore, an optical dispersion equalization circuit that shapes the waveform of an optical signal that has been distorted by propagating through an optical fiber having dispersion is used. As a conventional light dispersion equalizing circuit, a microwave strip line which converts an optical signal into an electric signal and uses the same is known. Its structure is as shown in FIG.
Dielectric 91 and metal conductors 92 and 93 bonded to both surfaces thereof
It is. Here, the length of the strip line is L.
The propagation delay time τ is, as shown in FIG.
(Propagation speed decreases). Further, the ratio increases according to the length L of the strip line.

As described above, the propagation delay characteristics are reversed between the microwave stripline and the optical fiber. Therefore, the optical signal propagated through the optical fiber having dispersion is converted into an electric signal and then passed through a microwave strip line having a length L corresponding to the dispersion and the optical fiber length, thereby canceling out the influence of dispersion in the optical fiber. can do.

[0005]

However, in an optical transmission system having a conventional optical dispersion equalizing circuit, it is necessary to temporarily convert an optical signal into an electric signal for waveform shaping. could not. Further, the signal frequency f
However, it is difficult to increase both the transmission capacity and the transmission distance of the optical fiber even if the waveform of the optical signal is shaped because the conductor loss of the strip line increases as the transmission line becomes higher.

According to the present invention, an optical signal that has been distorted by propagating through an optical fiber having dispersion can be shaped as an optical signal without converting it into an electric signal, and has a large capacity.
An object of the present invention is to provide an optical dispersion equalization circuit suitable for long-distance optical communication.

[0007]

According to a first aspect of the present invention, there is provided an optical dispersion equalizing circuit comprising at least one input waveguide, a first slab waveguide, and a plurality of waveguides which are sequentially elongated by a predetermined waveguide length difference. A first array waveguide consisting of waveguides, a second slab waveguide, a first array waveguide diffraction grating having a structure in which a plurality of output waveguides are sequentially connected, and a second array waveguide diffraction having a similar structure The output waveguide of the first arrayed waveguide diffraction grating and the output waveguide of the second arrayed waveguide diffraction grating, the output waveguide being composed of a grating and a plurality of waveguides that are sequentially elongated by a waveguide length difference giving a predetermined delay time. And a second slab waveguide of the first arrayed waveguide grating.
And second slab waveguide and second array waveguide diffraction
The first slab waveguide and the second slab waveguide of the grating are
An optical signal is input to the input waveguide of the first arrayed waveguide grating, and an optical signal is output from the input waveguide of the second arrayed waveguide grating.

According to a second aspect of the present invention, there is provided a light dispersion equalizing circuit comprising a similar arrayed waveguide diffraction grating and a plurality of waveguides which are sequentially elongated by a waveguide length difference giving a predetermined delay time. A second waveguide array connected to the output waveguide of the arrayed waveguide grating, a high-reflectance termination that folds light emitted from the other end of the second waveguide array, and an input waveguide of the arrayed waveguide grating. An optical circulator is provided for splitting an optical signal input to the waveguide and an optical signal output from the input waveguide.

A light dispersion equalizing circuit according to a third aspect of the present invention comprises a first input waveguide, a first slab waveguide, and a first waveguide comprising a plurality of waveguides which are sequentially elongated by a predetermined waveguide length difference. An arrayed waveguide diffraction grating having a structure in which a waveguide array, a second slab waveguide, and a plurality of output waveguides are sequentially connected; A second waveguide array comprising two waveguides, one end of which is connected to the output waveguide of the arrayed waveguide diffraction grating and the other end is connected to two adjacent waveguides,
An optical signal is input to a predetermined input waveguide of the arrayed waveguide grating, and an optical signal is output from an input waveguide adjacent to the input waveguide.

According to a fourth aspect of the present invention, there is provided an optical dispersion equalizing circuit comprising a first optical waveguide circuit having a similar arrayed waveguide diffraction grating and a similar second waveguide array and a second optical waveguide circuit having a similar configuration. An optical waveguide circuit is provided, and when the respective waveguides of the second waveguide array of the first optical waveguide circuit and the second waveguide array of the second optical waveguide circuit are grouped in order from the top, The waveguide is configured to be elongated by one or two units by a waveguide length difference giving a predetermined delay time, and both sides of the predetermined input waveguide for inputting an optical signal among the input waveguides of the first optical waveguide circuit. The two waveguides and two waveguides on both sides of a predetermined input waveguide that outputs an optical signal among the input waveguides of the second optical waveguide circuit are interconnected.

According to a fifth aspect of the present invention, there is provided an optical dispersion equalizing circuit including a similar arrayed waveguide diffraction grating and a similar second waveguide array, and a plurality of waveguides of the second waveguide array. When the optical waveguides are divided into two halves, and each group is sequentially arranged from the top, each waveguide is lengthened by one or two groups by a waveguide length difference giving a predetermined delay time. Two predetermined waveguides for inputting and outputting signals are connected to two waveguides arranged on both sides.

According to a sixth aspect of the present invention, there is provided an optical dispersion equalizing circuit according to any one of the third to fifth aspects, wherein the second waveguide array comprises two adjacent waveguides. The waveguides are connected to each other using a directional coupler having a coupling ratio of 50% and a high-reflectance termination.

[0013] Light dispersion equalization circuit according to claim 7, wherein
In the optical dispersion equalizing circuit according to any one of claims 2 to 6, a plurality of slab waveguides are shared by one slab waveguide.

[0014]

In the first arrayed waveguide diffraction grating, the optical signal input from the input waveguide is split into light of each frequency, and is guided from a plurality of output waveguides to the second waveguide array. In the second waveguide array, light of each frequency is given a corresponding delay time, and is guided to the second arrayed waveguide diffraction grating. In the second arrayed waveguide diffraction grating, light of each frequency input from a plurality of output waveguides is multiplexed into one output waveguide, restored to an original optical signal, and output.

Here, the demultiplexing (combining) characteristics of the first and second arrayed waveguide diffraction gratings and the waveguide length difference of the second waveguide array are set so as to give a predetermined delay time. As a result, an arbitrary propagation delay characteristic can be realized.
Thus, the waveform of the optical signal can be shaped without converting the optical signal into an electric signal, and an optical dispersion equalizing circuit that cancels the dispersion of the optical fiber can be realized.

In the light dispersion equalizing circuit according to the second to fifth aspects, the second waveguide array has a folded configuration, and the first array waveguide diffraction grating and the second array The configuration is such that the waveguide diffraction grating is shared.

Therefore, in the optical dispersion equalizing circuit according to the second aspect, since the input and output waveguides of the optical signal are the same, the input and output optical signals are separated using the optical circulator. In the optical dispersion equalizing circuit according to the third aspect, an optical signal whose waveform has been shaped can be output to the waveguides on both sides of the optical signal input waveguide. However, the power of the output optical signal is divided into two by the two waveguides.

In the optical dispersion equalizing circuit according to claim 4, 2
By using two optical waveguide circuits, the output optical signal divided into two can be multiplexed into one optical signal again. At this time, two second waveguide arrays that provide a predetermined delay time to light of each frequency are provided. By setting each of the waveguides of the two second waveguide arrays in order from the top and setting the delay time, a predetermined propagation delay characteristic can be realized by only one of them, or a predetermined combination of both can be realized. Can be realized.

In the optical dispersion equalizing circuit according to claim 5, 2
In this configuration, the first slab waveguides and the second slab waveguides of one optical waveguide circuit are each realized by one slab waveguide.

[0020]

FIG. 1 shows a basic configuration of an optical dispersion equalizing circuit according to the present invention . In the figure, a light dispersion equalization circuit according to the present embodiment includes a waveguide array 13 including a plurality of input waveguides 11, slab waveguides 12, and n waveguides having a waveguide length difference ΔL formed on a substrate 10. , Slab waveguide 14, waveguide length difference δL
A waveguide array 15 composed of N waveguides having a slab waveguide 16, a waveguide array 17 composed of n waveguides having a waveguide length difference ΔL, a slab waveguide 18, and a plurality of output waveguides 19 are provided. The configuration is such that they are sequentially connected. Here, the portion from the input waveguide 11 to the waveguide array 15 corresponds to the first arrayed waveguide grating, and the portion from the waveguide array 15 to the output waveguide 19 corresponds to the second arrayed waveguide grating. Waveguide array 15 corresponds to the second waveguide array. Note that the first arrayed waveguide grating and the second arrayed waveguide grating are arranged symmetrically via the waveguide array 15, and the input waveguide in the second arrayed waveguide grating is referred to here. The output waveguide 19 is used.

The light dispersion equalization circuit of the present embodiment uses, for example, when a silicon substrate is used as the substrate 10, each waveguide (core size 6.5 × 6.5 μm) by a combination of a flame deposition method and a reactive ion etching method. , A relative refractive index difference of 0.75%).

Hereinafter, the operation principle of the optical dispersion equalizing circuit of the present invention will be described based on the configuration of the present embodiment. The optical signal incident from the input waveguide 11 of ♯i spreads by diffraction in the slab waveguide 12 and is guided to the waveguide array 13 arranged perpendicular to the diffraction plane. The waveguide array 13
Since each waveguide is sequentially elongated by the waveguide length difference ΔL,
Light that propagates through each waveguide and reaches the slab waveguide 14 has a phase difference corresponding to the waveguide length difference ΔL. Since this phase difference varies depending on the optical frequency, when the light is focused on the input end of the waveguide array 15 by the lens effect of the slab waveguide 14, it is focused on a different position for each optical frequency.
That is, in the first arrayed waveguide diffraction grating having the above configuration, the optical signal input from the input waveguide 11 is split into light of each frequency, and the light is guided to each waveguide of the waveguide array 15. Acts as a vessel.

The optical frequency dependency of the focusing position shift at the input end of the waveguide array 15 is as follows: the focusing position is x, the light frequency is ν, the light wavelength is λ, the lens focal length of the slab waveguide is f,
The diffraction order is m, the effective refractive index of the slab waveguide is n _S , the effective refractive index of the waveguide is n _C , the waveguide pitch of the waveguide array 13 at the connection point of the slab waveguide is d, and the input waveguide in the middle is Assuming that the center wavelength at which the optical signal input from 11 is split into the center of the waveguide array 15 is λ ₀ , and the speed of light in vacuum is c,

[0024]

(Equation 1)

Can be expressed as follows. Light is branched into each predetermined optical frequency interval .DELTA..nu, as shown in FIG, [nu ₁ in ascending order of the optical _{frequency, ν 2, ν 3, ...} , propagated through the waveguide array 15 side by side as [nu _N I do.

Since each waveguide in the waveguide array 15 is sequentially elongated by the waveguide length difference δL, light having a higher frequency propagates through a longer waveguide to give a larger delay. That is, the waveguide array 15 composed of N waveguides
In, the optical frequency range W that gives a delay and the maximum delay time τ are:

[0027]

(Equation 2)

Given by In this manner, the light divided for each optical frequency and given a predetermined delay time is input to the second arrayed waveguide diffraction grating including the slab waveguide 16, the waveguide array 17, and the slab waveguide 18. Is done. The second arrayed waveguide grating operates as an optical multiplexer, contrary to the first arrayed waveguide grating, and the light of each frequency is focused on the output waveguide 19 of ♯i.

As described above, in the light dispersion equalizing circuit of the present invention, the light of each frequency demultiplexed by the first arrayed waveguide diffraction grating has higher light intensity in the waveguide array 15. Large delays can be given. That is,
Propagation delay characteristics opposite to the case where an optical signal of 1.55 μm is propagated through a 1.3 μm zero-dispersion optical fiber can be realized. Accordingly, the waveform of the optical signal can be shaped without converting the optical signal into an electric signal, and the dispersion of the optical fiber can be canceled.

In the light dispersion equalizing circuit of the present embodiment, f = 16 m
m, d = 10 μm, m = 2222, ΔL = 2.38 mm, n = 144
, The waveguide pitch Δx of the waveguide array 15 at the connection point of the slab waveguides 14 and 16 is 20 μm, Δν = 1 GHz,
δL = 1.49 mm and N = 64. At this design value,
The optical frequency range W that gives the delay is 63 GHz, and the maximum delay τ is
469 psec, resulting in a delay time of 930 psec / nm (=
469 psec / 63 GHz). This is 60km 1.
This shows that waveform distortion due to dispersion (15 to 16 psec / km / nm) when an optical signal of 1.55 μm is propagated through a 3 μm zero-dispersion optical fiber can be offset.

Since this embodiment is an optical dispersion equalizing circuit when an optical signal of 1.55 μm is propagated through a 1.3 μm zero-dispersion optical fiber, the longer the light in the waveguide array 15 is, the larger the delay is. Is to give. On the other hand, for example, in order to configure an optical dispersion equalization circuit when a 1.3 μm optical signal is propagated through a 1.55 μm zero-dispersion optical fiber, it is necessary to reverse the arrangement of the waveguides in the waveguide array 15 to reduce the frequency of the low frequency light. What is necessary is just to give a large delay. in this way,
An arbitrary propagation delay characteristic can be realized only by appropriately setting the pattern of the waveguide array 15, so that it can be used not only as an optical dispersion equalization circuit but also as a pseudo line having an arbitrary wavelength dispersion.

As shown in FIG. 1, by providing a plurality of input waveguides 11 and a plurality of output waveguides 19, an optical dispersion equalization circuit for simultaneously shaping a multi-channel optical signal with one circuit. Can be realized.

FIG. 2 shows the configuration of a first embodiment of the optical dispersion equalization circuit according to the second aspect. In the figure, a light dispersion equalization circuit according to the present embodiment includes a plurality of input waveguides 21, a slab waveguide 22, a waveguide array 23 having a waveguide length difference ΔL, a slab waveguide 24, Wavelength difference δL / 2
Are sequentially connected, and a high-reflectance termination 26 is arranged at the other end of the waveguide array 25.
Further, an input optical fiber 27 and an output optical fiber 28
The optical circulator 29 and the input waveguide 21 are connected by a connection optical fiber 30. Here, the high reflectance termination 26 can be formed, for example, by depositing gold on the end face of the optically polished waveguide.

The operating principle of this embodiment is basically the same as that of the embodiment shown in FIG. An optical signal that has entered the optical circulator 29 from the input optical fiber 27 is input to the input waveguide 21 via the connection optical fiber 30. As described above, the array waveguide diffraction grating including the slab waveguide 22, the waveguide array 23, and the slab waveguide 24 separates the optical signal input from the input waveguide 21 into light of each frequency,
It operates as an optical demultiplexer for guiding each waveguide of the waveguide array 25.

In the waveguide array 25, as shown in FIG. 2 (2), each waveguide is sequentially elongated by a waveguide length difference δL / 2, and a high reflectivity termination 26 is provided at the end of the waveguide. ing. Therefore, the light demultiplexed into each frequency is equivalent to the light traveling back and forth in the waveguide array 25 and having propagated through the waveguide array having the waveguide length difference δL. That is, the waveguide array 25 and the high-reflectance termination 26 have the same function as the waveguide array 15 shown in FIG. 1, and the higher the frequency of the light, the greater the delay.

Light of each frequency given a predetermined delay time while reciprocating in the waveguide array 25 is input to the slab waveguide 24 again. The arrayed waveguide diffraction grating composed of the slab waveguide 24, the waveguide array 23, and the slab waveguide 22 operates as an optical multiplexer for the backward light, and the light of each frequency is transmitted to the same input waveguide 21 at the time of input. Collect light.
Thereafter, the optical signal passes through the connection optical fiber 30 and is output from the output optical fiber 28 via the optical circulator 29.

As described above, also in the configuration of the present embodiment, it is possible to give a delay time for realizing a predetermined propagation delay characteristic to the light of each demultiplexed frequency, and operate the optical dispersion equalization circuit. Can be. This embodiment is characterized in that one array waveguide diffraction grating is used in both directions, and the functions of the optical demultiplexer and the optical multiplexer are realized by the same circuit. In the configuration of the present embodiment, since the input and output waveguides for optical signals are the same, it is necessary to use the optical circulator 29 to separate the input and output optical signals.

FIG. 3 shows the configuration of a first embodiment of the optical dispersion equalizing circuit according to claim 3 (corresponding to claim 6). In the figure, the light dispersion equalization circuit of the present embodiment includes a plurality of input waveguides 21 formed on a substrate 20, a slab waveguide 22, a waveguide array 23 having a waveguide length difference ΔL, a slab waveguide 24,
In this configuration, waveguide arrays 25 having a waveguide length difference δL / 2 are sequentially connected, and the other end of the waveguide array 25 is connected to a directional coupler 31 having a coupling rate of 50% and a high-reflectance termination 26.

The components having the same functions as those of the embodiment shown in FIG. 2 are denoted by the same reference numerals. This embodiment is characterized in that two adjacent waveguides of the waveguide array 25 are connected to each other using a directional coupler 31 having a coupling ratio of 50% and a high-reflectance termination 26. In this configuration, since the input and output waveguides of the optical signal are different, the optical circulator which is indispensable in the embodiment shown in FIG. 2 is not required.

Hereinafter, the operation principle of this embodiment will be described. As described above, the arrayed waveguide diffraction grating including the slab waveguide 22, the waveguide array 23, and the slab waveguide 24 separates the optical signal input from the input waveguide 21 of ♯i into light of each frequency. , And operates as an optical demultiplexer for guiding each waveguide of the waveguide array 25.

In the waveguide array 25, each waveguide is sequentially elongated by a waveguide length difference δL / 2. At the end of the waveguide, a directional coupler 31 having a coupling ratio of 50% for connecting two adjacent waveguides and a high reflectance termination 26 are provided. Therefore, the light split into each frequency has a coupling ratio of 50
After passing through the% directional coupler 31 and reflected at the high-reflectance termination 26, it passes through the directional coupler 31 having a coupling ratio of 50% again, so that it is 100% coupled to the adjacent waveguide. That is, the waveguide array 25, the directional coupler 31, and the high-reflectance termination 26 are equivalently configured as shown in FIG. As a result, the light split into two adjacent waveguides propagates in the same two waveguides at equal distances in opposite directions. In addition, assuming that two adjacent waveguides are one set,
The difference between the waveguide lengths of each set is 2δL.

Further, the waveguide array 25 from the slab waveguide 24, the optical frequencies _{ν 1, ν 2, ν 3} , ν 4, ..., ν N-1, the light is branched in the order of [nu _N is reflected when returned to the slab waveguide 24 and _{is, ν 2, ν 1, ν} 4, ν 3, ..., ν N, as [nu _N-1, the state in which the order of the optical frequency is replaced every other one Has become.

The lights of different frequencies (optical pairs) propagate through the same waveguide length during the reflection and return as described above, and a 2δL waveguide length difference occurs between the optical pairs. Therefore, an optical pair having a higher frequency propagates through a longer waveguide. That is, light having a higher frequency in units of two frequencies can provide a larger delay.

The light of each frequency given a predetermined delay time is incident on the slab waveguide 24 again. However, the incident position is different from the exit position, one repeated up light as described above _{(ν 2, ν 4, ...} , ν N) and one repeat down light _{(ν 1, ν 3, ...} , ν N _-1 ). Therefore, the arrayed waveguide diffraction grating including the slab waveguide 24, the waveguide array 23, and the slab waveguide 22 operates as an optical multiplexer for the light on the return path. The light is not focused on the input waveguide 21 of i. One light (ν ₂ , ν ₄ ,..., Ν _N ) is ♯i
-1 is focused on the input waveguide 21 and the other light (ν ₁ ,
ν ₃ ,..., ν _N-1 ) are condensed on the input waveguide 21 of ♯i + 1 and output respectively.

As described above, in the present embodiment, the input waveguides (♯i−1, Δi +) on both sides of the input waveguide (♯i) for the optical signal.
From 1), it is possible to output an optical signal whose waveform is shaped by the same delay characteristic. However, each output optical signal is
Since the light having different frequencies is multiplexed, the optical power is divided into two. However, since the difference in the waveguide length through which the light of each frequency propagates is set to 2δL, FIG. , An optical dispersion equalization circuit equivalent to the embodiment shown in FIG. If the optical frequency interval for demultiplexing is halved and the waveguide length difference δL / 4 of the waveguide array 25 (the waveguide length difference δL through which light of each frequency propagates), every other optical frequency is used. The problem that has become rough can be solved.

In the configuration of the present embodiment shown in FIG. 3, when two adjacent waveguides of the waveguide array 25 are set as one set, if the difference in the waveguide length of each set becomes 2δL, it is not necessarily required. Each waveguide does not have to be sequentially elongated by the waveguide length difference δL / 2. For example, as shown equivalently in FIG. 3 (3), the same applies to the case where the length of one set of waveguides is made equal and the length is sequentially increased by a waveguide length difference δL in units of two.

FIG. 4 shows a second embodiment of the optical dispersion equalizing circuit according to the third aspect. In the configuration of the first embodiment shown in FIG. 3, optical coupling between adjacent waveguides is realized by the directional coupler 31 having a coupling ratio of 50% and the high-reflectance termination 26. It is characterized in that a waveguide 32 is used. Other configurations and functions are the same as those of the first embodiment. In the configuration of the present embodiment, each waveguide of the waveguide array 25 is also sequentially lengthened by the waveguide length difference δL / 2, or is sequentially lengthened by two waveguide length differences δL. It is the same even if it does.

FIG. 5 shows the configuration of a first embodiment (corresponding to claim 6) of an optical dispersion equalization circuit according to claim 4. In the configuration of the embodiment shown in FIGS. 3 and 4, although the waveguide for inputting and outputting the optical signal can be separated, the optical signal subjected to the waveform shaping is separated into two waveguides and output, and the optical power is reduced. Two minutes. Therefore, the optical signal divided into two is again changed to 1
The problem can be solved by combining the two optical signals. The embodiment shown in FIG. 5 realizes this.

In the figure, an input waveguide 21, a slab waveguide 22, a waveguide array 23 having a waveguide length difference ΔL, a slab waveguide 24, a waveguide array 25 having a waveguide length difference δL / 2, a coupling ratio 50 The% directional coupler 31 and high reflectivity termination 26 are exactly the same as those shown in FIG.
That is, from the input waveguides (# i-1, # i + 1) on both sides of the optical signal input waveguide (#i), optical signals whose waveforms are shaped by the same delay characteristics are output.

In this embodiment, an input waveguide 41, a slab waveguide 42, a waveguide array 43 having a waveguide length difference ΔL, a slab waveguide 44, and a waveguide array 4 having the same configuration.
5. A directional coupler 46 having a coupling ratio of 50% and a high-reflectance termination 47 are provided.
i−1, i + 1) are connected to each other. However, the waveguide length of each waveguide in the waveguide array 45 is equal. The optical signal is output from the input waveguide 41 of ２１i when input to the input waveguide 21 of ♯i.

Hereinafter, the operation after the waveform-shaped optical signal is output from the slab waveguide 22 to the input waveguides 21 of ♯i−1 and ♯i + 1 will be described. Each optical signal is input to the slab waveguide 42 from the input waveguide 41 having the same number via the connection waveguide 48. The array waveguide diffraction grating including the slab waveguide 42, the waveguide array 43, and the slab waveguide 44 similarly divides each optical signal into light of each frequency and guides the light to each waveguide of the waveguide array 45. Operates as a duplexer. At this time, the order of the optical frequencies is such that the order of the optical frequencies is switched every other, such as ν ₂ , ν ₁ , ν ₄ , ν ₃ ,..., Ν _N , ν _N−1 . Also, when you return to the slab waveguide 44 is reflected by the high reflectance end 47 and the coupling ratio of 50% of the directional coupler _{46, ν 1, ν 2, ν} 3, ν 4, ..., ν N-1 , Ν _N are replaced again in the first order. At this time, since the waveguide lengths of the respective waveguides of the waveguide array 45 are equal, the delay time difference of the light of each frequency does not change.

The light whose optical frequency has returned to the state at the time of the first demultiplexing by the slab waveguide 22, the waveguide array 23, and the slab waveguide 24 is converted into a slab waveguide 44 operating as an optical multiplexer, and a waveguide. Array 43 and slab waveguide 4
2, the light is focused on the input waveguide 41 of ♯i.

As described above, in this embodiment, the optical signal split into two waveguides can be multiplexed into one waveguide again, so that the optical power is reduced by half or the optical frequency is reduced by one.
It is possible to solve the problem of roughening every other. In addition,
Instead of the directional couplers 31 and 46 having a coupling ratio of 50% for performing optical coupling between adjacent waveguides and the high-reflectance terminations 26 and 47,
The same applies to the case where a bent waveguide 32 as shown in FIG. 4 is used.

In this embodiment, as shown in FIG. 6A, a predetermined delay time is given to the light of each frequency by the difference in the waveguide length of the waveguide array 25. However, since an optical pair (for example, light having frequencies ν ₁ and ν ₂ ) passes through the waveguide array 25 and the waveguide array 45, a predetermined delay time may be given to both of them. For example, as shown in FIG. 6 (2), the same propagation delay characteristic can be realized even if both of the waveguide arrays 25 and 45 are formed of waveguides having a waveguide length difference δL / 4. Further, as shown in FIG. 6 (3), both of the waveguide arrays 25 and 45 are arranged in units of two and the waveguide length difference .delta.
A similar propagation delay characteristic can be realized by using an L / 2 waveguide. As described above, the same applies to a configuration in which the waveguides of the waveguide array 25 and the waveguide array 45 are treated as a set in order from the top, and are extended in units of one set or two sets corresponding to a predetermined propagation delay characteristic. is there.

FIG. 7 shows the configuration of a first embodiment (corresponding to claim 6) of an optical dispersion equalization circuit according to claim 5. In this embodiment, the slab waveguide 22 and the slab waveguide 42 shown in FIG.
The slab waveguide 24 and the slab waveguide 44 are realized by one slab waveguide 51 and 52, respectively.
Regarding other configurations, the same reference numerals are given to components corresponding to each unit shown in FIG. The waveguide arrays 25 and 45
6 (2) was adopted, and both were set to the waveguide length difference δL / 4.

The principle of operation of this embodiment is basically the same as that of the embodiment shown in FIG. However,
The light demultiplexed from the optical signal input to the predetermined input waveguide 21 is input from the slab waveguide 52 to the waveguide array 25 and is demultiplexed from the optical signal input again via the connection waveguide 48. The reflected light is transmitted from the slab waveguide 52 to the waveguide array 45.
So that an optical signal whose waveform has been further shaped is output from the slab waveguide 51 to a predetermined input waveguide 41,
The slab waveguide 51, the waveguide array 23 (43), the slab waveguide 52, and the respective waveguide arrays 25 and 45 are appropriately designed.

FIG. 8 shows an embodiment of the optical dispersion equalizing circuit according to the first aspect. In this embodiment, the slab waveguides 12, 14, 16, and 18 shown in FIG.
This is the configuration realized in. For other configurations, see FIG.
The same reference numerals are given to parts corresponding to the respective parts shown in FIG. That is, the slab waveguide 61 functions as the slab waveguide 12 between the input waveguide 11 and the waveguide array 13, and functions as the slab waveguide 14 between the waveguide array 13 and the waveguide array 15, The slab waveguide 16 functions as the slab waveguide 16 between the waveguide array 15 and the waveguide array 17 and the slab waveguide 1 between the waveguide array 17 and the output waveguide 19.
This is a configuration that functions as 8. The operation principle is the same as that of the embodiment shown in FIG.

FIG. 9 shows a second embodiment (corresponding to claim 7) of an optical dispersion equalizing circuit according to claim 2. This embodiment has a configuration in which the slab waveguides 22 and 24 shown in FIG. In other configurations, the same reference numerals are given to components corresponding to the respective components shown in FIG. That is, the slab waveguide 62 functions as the slab waveguide 22 between the input waveguide 21 and the waveguide array 23, and functions as the slab waveguide 24 between the waveguide array 23 and the waveguide array 25. It is. The operation principle is the same as that of the embodiment shown in FIG.

FIG. 10 shows a third embodiment (corresponding to claims 6 and 7) of an optical dispersion equalization circuit according to claim 3. This embodiment has a configuration in which the slab waveguides 22 and 24 shown in FIG. In other configurations, the same reference numerals are given to components corresponding to each unit shown in FIG. That is, the slab waveguide 62 is the input waveguide 2
1 and the waveguide array 23 function as a slab waveguide 22, and between the waveguide array 23 and the waveguide array 25 function as a slab waveguide 24. The operation principle is the same as that of the embodiment shown in FIG.

FIG. 11 shows the configuration of a fourth embodiment (corresponding to claim 7) of the optical dispersion equalization circuit according to claim 3. This embodiment has a configuration in which the slab waveguides 22 and 24 shown in FIG. In other configurations, the same reference numerals are given to components corresponding to the respective components shown in FIG. The principle of operation is the same as that of the embodiment shown in FIGS.

FIG. 12 shows the configuration of a second embodiment of the optical dispersion equalizing circuit according to claim 4 (corresponding to claims 6 and 7). In this embodiment, the slab waveguides 22, 24, 42, 4 shown in FIG.
4 is realized by one slab waveguide 63. Regarding other components, the same reference numerals are given to components corresponding to the respective components shown in FIG. That is, the slab waveguide 63 is
Input waveguide 21 (connection waveguide 48) and waveguide array 2
3 functions as a slab waveguide 22, and between the waveguide array 23 and the waveguide array 25, the slab waveguide 2
4, the input waveguide 41 (connection waveguide 48)
The waveguide array 43 functions as a slab waveguide 42 between the waveguide array 43 and the waveguide array 43, and functions as a slab waveguide 44 between the waveguide array 43 and the waveguide array 45. The operation principle is the same as that of the embodiment shown in FIG.

FIG. 13 shows a second embodiment (corresponding to claims 6 and 7) of an optical dispersion equalization circuit according to claim 5. This embodiment has a configuration in which the slab waveguides 51 and 52 shown in FIG. In other configurations, the same reference numerals are given to components corresponding to the respective components shown in FIG. That is, the slab waveguide 64 is the input waveguide 2
The configuration functions as a slab waveguide 51 between the waveguide arrays 23 and 43 and the waveguide array 23 (43), and functions as a slab waveguide 52 between the waveguide array 23 (43) and the waveguide arrays 25 and 45. is there. The operation principle is the same as that of the embodiment shown in FIGS.

In the embodiments shown in FIGS. 12 and 13, instead of the directional couplers 31 and 46 having a coupling ratio of 50% and the high-reflectance terminations 26 and 47, a bent waveguide as shown in FIG. 32 can be used. In addition, the waveguide array 2
The patterns of 5, 45 can also be freely selected as long as a predetermined propagation delay characteristic can be obtained.

[0064]

As described above, according to the present invention, the design value of the arrayed waveguide diffraction grating functioning as an optical multiplexer / demultiplexer and the waveguide length difference δL of the waveguide array coupling therebetween are appropriately selected. , Arbitrary propagation delay characteristics can be realized. Therefore, the optical signal distortion due to the dispersion of the optical fiber can be canceled without converting the optical signal into an electric signal.

In addition, the loss due to the arrayed waveguide diffraction grating is small in principle, and the wavelength multiplexing / demultiplexing characteristics can be realized with high precision on the order of the optical frequency. It is possible to configure a simple light dispersion equalization circuit.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of an optical dispersion equalization circuit according to the present invention .

FIG. 2 is a diagram showing the configuration of a first embodiment of the optical dispersion equalization circuit according to claim 2;

FIG. 3 is a diagram showing the configuration of a first embodiment (corresponding to claim 6) of the optical dispersion equalization circuit according to claim 3;

FIG. 4 is a diagram showing a configuration of a second embodiment of the optical dispersion equalization circuit according to claim 3.

FIG. 5 is a diagram showing the configuration of a first embodiment (corresponding to claim 6) of the optical dispersion equalization circuit according to claim 4;

6 is a diagram showing a relationship between the waveguide array 25 and the waveguide array 45 in FIG.

FIG. 7 is a diagram showing the configuration of a first embodiment (corresponding to claim 6) of the optical dispersion equalization circuit according to claim 5;

Figure 8 is a real light dispersion equalization circuit of claim 1
The figure which shows an Example structure .

FIG. 9 is a diagram showing a configuration (corresponding to claim 7) of a second embodiment of the optical dispersion equalization circuit according to claim 2;

FIG. 10 is a diagram showing a configuration (corresponding to claims 6 and 7) of a third embodiment of the optical dispersion equalization circuit according to claim 3;

FIG. 11 is a diagram showing a configuration (corresponding to claim 7) of a fourth embodiment of the optical dispersion equalization circuit according to claim 3;

FIG. 12 is a diagram showing a configuration (corresponding to claims 6 and 7) of a second embodiment of the optical dispersion equalization circuit according to claim 4;

FIG. 13 is a diagram showing a configuration (corresponding to claims 6 and 7) of a second embodiment of the optical dispersion equalization circuit according to claim 5;

FIG. 14 is a diagram showing a conventional light dispersion equalization circuit using a microwave strip line.

FIG. 15 is a graph showing transmission delay characteristics of a microwave strip line.

[Explanation of symbols]

10, 20 Substrate 11, 21, 41 Input waveguide 12, 14, 16, 18, 22, 24, 42, 44 Slab waveguide 13, 15, 17, 23, 25, 43, 45 Waveguide array 19 Output waveguide 26, 47 High reflectance termination 27 Input optical fiber 28 Output optical fiber 29 Optical circulator 30 Connection optical fiber 31, 46 Directional coupler 48 Connection waveguide 61, 62, 63, 64 Slab waveguide

Continuation of front page (56) References JP-A-62-150304 (JP, A) JP-A-63-44603 (JP, A) JP-A-2-244105 (JP, A) (58) Fields investigated (Int) .Cl. ⁷ , DB name) G02B 6/00 G02B 6/12-6/14 G02B 6/28-6/293

Claims (7)

(57) [Claims] 1. A first waveguide array comprising at least one input waveguide, a first slab waveguide, a plurality of waveguides sequentially elongated by a predetermined waveguide length difference, and a second slab waveguide. A first arrayed waveguide diffraction grating having a structure in which a plurality of output waveguides are sequentially connected and a second arrayed waveguide diffraction grating having a similar structure, which are sequentially increased by a waveguide length difference giving a predetermined delay time. made of a plurality of waveguides, and a second waveguide array to connect the output waveguides of the output waveguide and the second arrayed waveguide grating of the first array waveguide grating, the second 1st slab waveguide of 1 array waveguide diffraction grating
And a second slab waveguide, and the second array waveguide
First slab waveguide and second slab waveguide of diffraction grating
A path is shared by one slab waveguide, an optical signal is input to an input waveguide of the first arrayed waveguide grating, and an optical signal is input from the input waveguide of the second arrayed waveguide grating. A light dispersion equalization circuit characterized by outputting. 2. A first waveguide array comprising at least one input waveguide, a first slab waveguide, a plurality of waveguides which are sequentially elongated by a predetermined waveguide length difference, and a second slab waveguide. An arrayed waveguide diffraction grating having a structure in which a plurality of output waveguides are sequentially connected, and a plurality of waveguides sequentially elongated by a waveguide length difference giving a predetermined delay time. A second waveguide array connected to the output waveguide of the grating; a high-reflectance termination that folds light emitted from the other end of the second waveguide array; and an input waveguide of the arrayed waveguide grating. An optical dispersion equalizing circuit comprising: an optical circulator for splitting an input optical signal and an optical signal output from an input waveguide. 3. A first waveguide array comprising a plurality of input waveguides, a first slab waveguide, a plurality of waveguides sequentially elongated by a predetermined waveguide length difference, a second slab waveguide, An arrayed waveguide diffraction grating having a structure in which a plurality of output waveguides are sequentially connected, and a plurality of waveguides that are sequentially or two-units longer by a waveguide length difference giving a predetermined delay time, and one end of which is A second waveguide array connected to the output waveguide of the arrayed waveguide grating and connecting two adjacent waveguides at the other end, and a predetermined input waveguide of the arrayed waveguide grating. An optical dispersion equalization circuit, which receives an optical signal and outputs an optical signal from an input waveguide adjacent to the input waveguide. 4. A first waveguide array comprising a plurality of input waveguides, a first slab waveguide, a plurality of waveguides sequentially elongated by a predetermined waveguide length difference, a second slab waveguide, An arrayed waveguide diffraction grating having a structure in which a plurality of output waveguides are sequentially connected; and a plurality of waveguides, one end of which is connected to the output waveguide of the arrayed waveguide diffraction grating, and two adjacent ones at the other end. A second optical waveguide circuit having a second optical waveguide circuit and a second optical waveguide circuit having a similar configuration, and a second optical waveguide circuit of the first optical waveguide circuit. And the second
When the respective waveguides of the second waveguide array of the optical waveguide circuit of the above are grouped in order from the top, each waveguide is lengthened by one or two units by a waveguide length difference giving a predetermined delay time. And two waveguides on both sides of a predetermined input waveguide for inputting an optical signal among the input waveguides of the first optical waveguide circuit, and an optical waveguide among the input waveguides of the second optical waveguide circuit. An optical dispersion equalizing circuit, wherein two waveguides on both sides of a predetermined input waveguide for outputting a signal are connected to each other. 5. A first waveguide array comprising a plurality of input waveguides, a first slab waveguide, a plurality of waveguides which are sequentially elongated by a predetermined waveguide length difference, a second slab waveguide, An arrayed waveguide grating having a structure in which a plurality of output waveguides are sequentially connected; and a plurality of waveguides, one end of which is connected to the output waveguide of the arrayed waveguide grating and the other end adjacent to the other end.
A second waveguide array in which two waveguides are connected to each other, wherein a half of the plurality of waveguides of the second
When each of the input waveguides is grouped in order from the top, each waveguide is lengthened by one or two groups by a waveguide length difference giving a predetermined delay time, and an optical signal of the input waveguide is An optical dispersion equalizing circuit, wherein two predetermined waveguides for inputting and outputting are connected to two waveguides arranged on both sides, respectively. 6. The optical dispersion equalization circuit according to claim 3, wherein the second waveguide array is a directional coupling having a coupling ratio of 50% between two adjacent waveguides. A light dispersion equalization circuit, wherein the light dispersion equalization circuit has a configuration in which the light distribution equalization is performed by using a high reflectance terminal. 7. The optical dispersion equalizing circuit according to claim 2, wherein a plurality of slab waveguides are shared by one slab waveguide. Equalization circuit.