JPH07270641A - Array waveguide diffraction grating type optical multiplexer/demultiplexer with loop back optical path - Google Patents

Abstract

PURPOSE:To obtain an array waveguide diffraction grating type multiplexer/ demultiplexer having loop back paths with which difference in the loss according to wavelengths can be decreased, and thereby, the margin in a practical optical transmission circuit system can be decreased. CONSTITUTION:This device is equipped with an array waveguide diffraction grating type multiplexer/demultiplexer 11 having plural numbers of input waveguides 14 and output waveguides 18, optical path for input 4 connected to at least one input waveguide I4, optical path for output 5 connected to at least one output waveguide J6 in the asymmetric position to the input waveguide I4, plural numbers of loop back circuits 12 connecting plural numbers of input waveguides I1-I11 and output waveguides J1-J11 corresponding to the input waveguides Ii in the asymmetric position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is preferably used in an optical wavelength division multiplexing transmission system or the like, and one or more signal lights among a plurality of wavelength-multiplexed signal lights are provided with wavelengths for branching / addition. The present invention relates to an arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path that performs unique signal processing.

[0002]

2. Description of the Related Art Conventionally, an optical add / drop multiplexer (ADM) as shown in FIG. 4 has been known as a key device used for adding / dropping wavelength-division multiplexed signal light. The optical add / drop circuit is composed of a demultiplexer 1, a multiplexer 2, and N optical fibers 3a, 3b, ..., 3n. The demultiplexer 1 has an optical fiber transmission line ( An input optical path 4 is connected to the multiplexer 2, and an optical fiber transmission path (output optical path) 5 is connected to the multiplexer 2. Here, it is assumed that N-wave multiplexed signal lights having wavelengths of λ1, λ2, ..., λN respectively propagate through the optical fiber transmission line 4. In this optical add / drop circuit, the input multiplexed signal light is separated into N signal lights having different wavelengths by the demultiplexer 1, and the necessary signal light λi (1 ≦ i ≦ N) is extracted to the outside by the optical fiber 3i. . The remaining signal lights λ1, λ2, ..., λi−
1, λi + 1, ..., λN are optical fibers 3a, 3b,
, 3i-1, 3i + 1, ..., 3n, and these signal lights .lamda.1, .lamda.2, ..., .lamda.i-1, .lamda.
, λN and the signal light of wavelength λi inserted from the outside are multiplexed and output as multiplexed signal light of wavelengths λ1, λ2, ..., λN.

On the other hand, Y. Tachikawa et al., As an optical add / drop circuit based on the same principle as the optical add / drop circuit, is a loopback optical path including a loopback optical path in a single array waveguide diffraction grating type optical multiplexer / demultiplexer as shown in FIG. We have proposed an arrayed waveguide grating type optical multiplexer / demultiplexer with reference (Reference; Y. Tachikawa et al., Electronics Letters, vol.2).
9, No. 24, 25th November 1993, pp. 2133-2134). This arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path includes an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11, an optical fiber transmission path (input optical path) 4, and an optical fiber transmission path (output optical path). ) 5 and N-1 optical fibers Ki (i = 1,
2, ..., 5, 7, ..., 11) and a loopback optical path 12. The arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 includes N input waveguides 14, concave slab waveguides 15 and 16, an arrayed waveguide diffraction grating 17, and N output waveguides on a substrate 13. 18 is provided.

Generally, the number N of the input waveguides 14 and the output waveguides 18 of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 is arbitrary, but here N = 11 for simplicity. Therefore, in this arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path, the input waveguide 14 is composed of the waveguides I1 to I11, and the output waveguide 18 is composed of the waveguides J1 to J11. The fiber transmission line 4 is the waveguide I6.
In addition, the optical fiber transmission line 5 is connected to the waveguide J6, and the waveguide Ji (i = 1, 2, ..., 5, 5) is provided between the waveguides J1 to J11 and the waveguides I1 to I11.
, ..., 11) to input the signal light output from the optical fiber Ki to the waveguide Ii corresponding to the waveguide Ji.
(I = 1, 2, ..., 5, 7, ..., 11) are connected. The optical fiber K7 has a function as a add / drop circuit that drops / adds the signal light λ7 to the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path.

In the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path, wavelengths λ1, λ2, ..., λ
The WDM signal light consisting of 11 waves of 11 propagates through the optical fiber transmission line 4 and then enters the slab waveguide 15 via the waveguide I6 at the center of the input waveguide 14. In the slab waveguide 15, the wavelength-multiplexed signal light spreads by diffraction and is input to a plurality of waveguides forming the arrayed waveguide diffraction grating 17. This signal light is transmitted to the arrayed waveguide diffraction grating 17
Is propagated through the slab waveguide 16 and then condensed by the slab waveguide 16,
Due to the phase difference generated while propagating in the arrayed waveguide diffraction grating 17, the converged position of the converged light differs depending on the wavelength. Here, if the conditions are set appropriately, for example, the wavelength λ
1 is from the waveguide J1, wavelength λ2 is from the waveguide J2, ...
The wavelength λ11 is the wavelength λ11 from the waveguide J11.
i (i = 1, 2, ..., 11) is taken out from the waveguide Ji corresponding to each wavelength.

Here, for example, if the signal light having the wavelength λ7 is to be branched, the signal light having the wavelength λ7 is directly extracted to the outside by the optical fiber K7. On the other hand, the remaining signal lights respectively correspond to the corresponding optical fibers K1 and K.
2, ..., K11, and is returned from the input waveguide 14 to the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 together with the signal light of wavelength λ7 inserted from the outside by the optical fiber K7. The signal light returned to the input waveguide 14 is combined in the output waveguide 18 by the same operation as described above.

The important point here is the i-th optical fiber K.
i is a point connected to the i-th input waveguide Ii. In general, since the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 is set to be symmetrical with respect to the input / output, conversely, the wavelength multiplexed signal light is input only to the waveguide J6 of the output waveguides 18. Considering the case, the wavelength λ1 is equal to the input waveguide 1
From the waveguide I1 out of 4, the wavelength λ2 is from the waveguide I2,
The wavelength λ11 (i = 1, 2, ..., 11) is extracted from the waveguide Ii. Therefore, conversely, the signal light of the wavelength λi input from the waveguide Ii is output from the waveguide J6. In this way, the optical fiber Ki (i = 1, 2, ..., 1
1) Wavelength λi propagating in the waveguide and input again to the waveguide Ii
Signal light from the waveguide J6 to the optical fiber transmission line 5
Will be output to.

In the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path, only the signal light of wavelength λ6 among the wavelength multiplexed signal lights of wavelengths λ1, λ2, ..., λ11 is allowed to pass through the loopback optical path 12. No, waveguide I6, slab waveguide 1
5, the arrayed waveguide diffraction grating 17, the slab waveguide 16, and the waveguide J6, respectively, and output to the optical fiber transmission line 5. Therefore, only the signal light of wavelength λ6 cannot be dropped / added by using this optical multiplexer / demultiplexer.

[0009]

By the way, in the above-mentioned arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path, the signal light is input from the optical fiber transmission path 4 and output to the optical fiber transmission path 2. However, there has been a problem that the amount of loss received up to this point varies greatly depending on the wavelength of the signal light.

Here, this problem will be described in detail. For example, consider a case where the wavelength-multiplexed signal light is input from the optical fiber transmission line 4 to the waveguide I6 at the center of the input waveguide 14. This signal light passes through the slab waveguide 15 and then propagates through a plurality of waveguides forming the arrayed waveguide diffraction grating 17, so that the slab waveguide 16 positions the signal light at different positions depending on the wavelength. Converge. That is, the signal light is focused on the waveguide Ji corresponding to the wavelength λi.

This condensing is converged as a result of superposition of the respective lights which are emitted from the individual waveguides constituting the arrayed waveguide diffraction grating 17 and are spatially spread, and therefore, the individual waveguides are converged. The spatial distribution of the light intensity of the emitted light from is generally approximated by a Gaussian distribution. Therefore, the light intensity when the signal light propagating through the plurality of waveguides forming the arrayed waveguide diffraction grating 17 is condensed by the slab waveguide 16 is the convergence position (the waveguide Ji corresponding to the wavelength λi. ) According to the Gaussian distribution. That is, if the convergence position is x and the light intensity of the signal light that converges at this convergence position x is P (x), P (x) is approximated by the following equation. P (x) = exp [−2 (x / w) ² ] ... (1) Here, x is the interval of the waveguide Ji of the output waveguide 18, and
Further, P (x) is the light intensity at x = 0 (the central waveguide J6) and is normalized. Further, w is the spot size of the Gaussian distribution normalized by the interval of the waveguide Ji of the output waveguide 18.

In reality, 0 extracted from the waveguide Ji
Since high-order diffracted light such as ± first-order diffracted light and ± second-order diffracted light are simultaneously generated in addition to the second-order diffracted light, these m-th-order diffracted lights (m = ± 1, ± 2, ...) It converges to a different position x ± mN and becomes a loss. Therefore, for example, the actual P (x) when the ± 1st order diffracted light is taken into consideration is given by the following equation.

[Equation 1] The Gaussian distribution of the above equation (2) is sufficiently well approximated by the Gaussian distribution P (x) = exp [−2 (x / w ′) ² ] (3) obtained by appropriately changing w in the equation (1). You can

FIG. 6 is a diagram showing the above equations (1) to (3), in which the curve (a) is the equation (1), the curve (b) is the equation (2) and the curve ( c) represents the equation (3), respectively. However, here, N = 11 and w ′ = 1.2w. Since FIG. 6 is normalized by the light intensity of x = 0, the loss when x ≠ 0 is relatively smaller in the curves (b) and (c) than in the curve (a).

For example, in the above-described arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path, the center of the 11 waveguides Ji (i = 1, 2, ..., 11) of the output waveguide 18 is provided. The waveguide J6 is located at x = 0, and the waveguide J5,
It can be considered that J7 is located at x = ± 1, waveguides J4 and J8 are located at x = ± 2, ..., And waveguides J1 and J11 are located at x = ± 5.
Here, of the wavelength-multiplexed signal light input from the central waveguide I6, for example, the loss D of the signal light of the respective wavelengths λ5 and λ7 output to the waveguides J5 and J7 is x = By setting it to 1, D = −10 · log (P (1)) [dB]. On the other hand, the loss of the signal lights of the wavelengths λ4 and λ8 output to the waveguides J4 and J8 is x in the formula (1).
By setting = 2, D = -10 · log (P (2)) [dB].

By the way, P (2) is calculated by the equation (3).

[Equation 2] Therefore, the loss incurred by the signal lights of wavelengths λ4 and λ8 is (2 ³ ) D [dB]. Hereinafter, similarly, the wavelength λi output to the waveguide Ji (i = 1, 2, ..., 11)
The loss incurred by the signal light is approximated to ((i-6) ² ) D [dB].

Further, of the respective wavelengths λi (i = 1, 2, ..., 11) re-input to the corresponding waveguides Ii (i = 1, 2, ..., 11) via the loopback optical path 12. Signal light is slab waveguide 15, arrayed waveguide diffraction grating 1
7. In the case of focusing on the central waveguide J6 via the slab waveguide 16 as well, the array waveguide diffraction grating type optical multiplexer / demultiplexer 11 is symmetric with respect to the input and output, so that the same loss characteristics are obtained. Indicates. For example, the input waveguide Ii (i = 1,
The signal light of wavelength λi input from 2, ..., 11) suffers a loss of ((i-6) ² ) D [dB]. Therefore, in the above-described arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path, the signal light is transmitted through the optical fiber transmission line 4
While the signal light of wavelengths λ5 and λ7 is the smallest (1 ² ± 1 ² ) D = 2D [dB], the magnitude of the loss received from the input to the optical fiber transmission line 5 after being input from , The wavelengths λ1 and λ11 are the largest (5 ²
+5 ² ) D = 50 D [dB], and there is a problem that a maximum loss difference of 48 D [dB] occurs depending on the wavelength.

In the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11, the loss in the case of outputting from the central waveguide I6 to the end waveguide J1 (or the waveguide J11) is output to the central waveguide J6. It is about 2 to 3 dB larger than that of the case. Therefore, for example, the loss at the end ((5 ² ) D [d
B]) is 2 dB, a loss difference of about 4 dB will occur depending on the wavelength. In fact, Y. Tach
Also in the report of Ikawa et al., the loss difference according to the wavelength when N = 16 is 4 dB at maximum.

As described above, when the loss difference depending on the wavelength becomes large, when constructing an optical communication system using the wavelength division multiplexing system, a sufficiently low code error is obtained even when the light of the wavelength having the largest loss is used. To communicate at a rate,
A new problem arises that the design must be performed with a large margin. In particular, in an actual optical transmission system, a plurality of optical add / drop multiplexers are often connected in cascade to be used, and there is a drawback that a loss difference is accumulated.

The present invention has been made in view of the above circumstances, and it is possible to reduce the loss difference depending on the wavelength, and therefore a loopback that can reduce the margin in an actual optical transmission line system. An object is to provide an arrayed waveguide diffraction grating type multiplexer / demultiplexer with an optical path.

[0020]

In order to solve the above problems, the present invention employs an arrayed waveguide diffraction grating type multiplexer / demultiplexer with a loopback optical path as follows. That is, the arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path according to claim 1 is at least an arrayed waveguide diffraction grating optical multiplexer / demultiplexer having a plurality of input waveguides and a plurality of output waveguides. An input optical path connected to one of the input waveguides, an output optical path connected to at least one of the output waveguides at an asymmetric position with respect to the input waveguide, a plurality of the input waveguides, It is characterized by comprising a plurality of loopback optical paths that are asymmetric with respect to the input waveguide and that respectively connect the plurality of output waveguides corresponding to the input waveguide.

According to a second aspect of the present invention, there is provided an arrayed waveguide diffraction grating type multiplexer / demultiplexer with a loopback optical path including a plurality of input waveguides Ii (i = 1, 2, ..., N; N is a natural number) and a plurality of input waveguides Ii. An arrayed waveguide diffraction grating type optical multiplexer / demultiplexer having an output waveguide Jj (j = 1, 2, ..., N), and the input waveguide Ip (1
≦ p ≦ N; p is a natural number and the input optical path is connected to the output waveguide Jr (1 ≦ r ≦ N; r is a natural number and r ≠.
output optical path connected to p) and the input waveguide Ip '.
(1 ≦ p ′ ≦ N; p ′ is a natural number and p ′ ≠ p), and the input branch optical path and the output waveguide Jr ′ (1 ≦
r ′ ≦ N; r ′ is a natural number and r ′ ≠ p ′), and an output branch optical path and a plurality of output waveguides Js (1 ≦ s).
≦ N; s is a natural number and s ≠ r, s ≠ r ′) and the plurality of input waveguides It (t = Mod [(s−1) + (p−r))
+ N, N] +1, where Mod [a, b] is provided with a plurality of loopback optical paths respectively connected to (a remainder when a is divided by b).

According to a third aspect of the present invention, there is provided an arrayed waveguide diffraction grating type multiplexer / demultiplexer with a loopback optical path, wherein the natural number p is equal to the natural number p. And r are | {| p-r |-(N
/ 2)} | ≦ 1.

An array waveguide diffraction grating type multiplexer / demultiplexer with a loopback optical path according to a fourth aspect is the array waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path according to the third aspect. Is characterized by satisfying either | p- (N / 4) | <2 or | p- (3N / 4) | <2.

[0024]

In the arrayed waveguide diffraction grating type multiplexer / demultiplexer with loopback optical path according to claim 1 of the present invention, at least one input waveguide at an asymmetric position of the arrayed waveguide diffraction grating type multiplexer / demultiplexer and An input optical path and an output optical path are respectively connected to the output waveguides, and the plurality of input waveguides and the plurality of output waveguides that are asymmetrical to the respective input waveguides and correspond to the input waveguides are provided. Each is connected by a loopback optical path, and the periodic multiplexing / demultiplexing characteristics of the arrayed waveguide grating type optical multiplexer / demultiplexer are used. As a result, the signal light of each wavelength passes through the arrayed-waveguide diffraction grating-type optical multiplexer / demultiplexer when it first passes through the arrayed-waveguide diffraction grating-type optical multiplexer / demultiplexer. It is output after receiving a different loss. Therefore, it is possible to configure an arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path, in which variations in the loss for each wavelength are reduced and the loss difference depending on the wavelength is small.

Further, in the arrayed waveguide diffraction grating type multiplexer / demultiplexer with a loopback optical path according to a second aspect, the input waveguide Ip (1≤p≤N; p of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer).
Is an input optical path, and the output waveguide Jr (1 ≦ r ≦
N; r is a natural number and r ≠ p, and the output optical paths are connected to each other, and the input waveguide Ip ′ (1 ≦ p ′ ≦ N; p ′)
Is a natural number and p ′ ≠ p), and the output waveguide Jr ′ (1 ≦ r ′ ≦ N; r ′ is a natural number and r ′ ≠).
The output branch optical paths are connected to p '). And
Output waveguide Js (1 ≦ s ≦ N; s is a natural number and s ≠ r,
s ≠ r ′) and the input waveguide It (t = Mod [(s−1)
+ (P−r) + N, N] +1, where Mod [a, b]
Is connected with a loopback optical path when a is divided by b), and the periodic multiplexing / demultiplexing characteristic of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer is used.

Thus, the signal light of each wavelength passes through the arrayed-waveguide diffraction grating-type optical multiplexer / demultiplexer when passing through the arrayed-waveguide diffraction grating-type optical multiplexer / demultiplexer for the first time. It is output with different losses depending on the time. Therefore, it is possible to configure an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path in which the loss for each wavelength is averaged and the loss difference due to the wavelength is small. Also,
An input branch optical path is connected to the input waveguide Ip ′ and an output waveguide J
By providing the branching optical path for output at r ′, the branched signal light is averaged with different losses when passing through the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer, and therefore the loss difference due to wavelength is It becomes possible to split a small signal light and take it out.

Further, in the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path according to a third aspect, the natural number p
And r satisfy | {| p−r | − (N / 2)} | ≦ 1, the output waveguide Js and the input waveguide It connected by the loop-back optical path are such that | s−t | is N. The combination will be a value near / 2. Therefore, the signal light of the wavelength that has received the largest loss by the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer during the first passage passes through the loopback optical path and passes through the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer again. You will suffer the smallest loss when you do. On the contrary, the signal light of the wavelength that received the smallest loss when passing through the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer for the first time is the most signalized light when passing through the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer again. You will lose a lot of money. In this way, each time the light passes through the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer, it is output with a different loss, and therefore the loss for each wavelength is averaged,
It becomes possible to construct an arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path in which the loss difference due to wavelength is extremely small.

Further, in the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path according to a fourth aspect, the natural number p
Is | p- (N / 4) | <2 or | p- (3N / 4) |
By satisfying any one of <2, by selecting the input waveguide Ip used for external input so that p becomes a value near N / 4 or 3N / 4, the output waveguide Jr used for external output also r is selected to be 3N / 4 or a value near N / 4, and the input waveguide Ip and the output waveguide J are
Let r be a waveguide that is as close to the center as possible. Therefore, the loss difference depending on the wavelength becomes extremely small, and it becomes possible to configure an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path having a small absolute value of loss.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Each embodiment of an arrayed waveguide diffraction grating type multiplexer / demultiplexer with a loopback optical path according to the present invention will be described in detail below with reference to the drawings. (Embodiment 1) FIG. 1 is a configuration diagram showing an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path according to Embodiment 1 of the present invention. In this arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path, the optical fibers K1 to K11 constituting the optical fiber transmission lines 4, 5, the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11, and the loopback optical path 21. The respective constituent elements are completely the same as those of the conventional arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path.

In this arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path, the optical fiber transmission line 4 is connected to the waveguide I4 of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11,
The optical fiber transmission line 5 is connected to the waveguide J6 which is asymmetrical to the waveguide I4, and each waveguide Jj (j
, 1, 2, 3, ..., 5, 7, ..., 11) and each waveguide Ii (i = 1, 2, 3, 5, ..., 11) of the input waveguide 14 respectively. An optical fiber Kj is provided for inputting the signal light output from Jj to the waveguide Ii corresponding to this waveguide Jj. The combination (j, i) of j and i in this case is (1, 10), (2, 11), (3,
1), (4, 2), etc. The optical fiber K4 is drawn to the outside, and the side connected to the waveguide I2 is the input branch optical path and the side connected to the waveguide J4 is the output branch optical path.

In this arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path, 11 wavelength-multiplexed signal lights of wavelengths λ1, λ2, ..., λ11 propagate through the optical fiber transmission line 4 and then are arrayed. The light is input from the waveguide I4 of the waveguide diffraction grating type optical multiplexer / demultiplexer 11 to the slab waveguide 15. In the slab waveguide 15, this wavelength-multiplexed signal light spreads due to diffraction,
The light is input to a plurality of waveguides forming the arrayed waveguide diffraction grating 17. The signal light is transmitted to the arrayed waveguide diffraction grating 17
After being propagated through the slab waveguide 16, the light is condensed by the slab waveguide 16. However, the convergence position of the converged light differs depending on the wavelength due to the phase difference generated while propagating in the arrayed waveguide diffraction grating 17.

Here, if the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 is designed to obtain desired characteristics,
11 in each of the waveguides I1 to I11 of the input waveguide 14
When the wavelength-multiplexed signal light of the wave is input, it is demultiplexed into different waveguides Ii for each wavelength λi, and the other waveguides Ik (k =
1, 2, ..., I-1, i + 1, ..., 11), and can be configured to be combined with the signal light. That is,
According to the wavelength multiplexing / demultiplexing characteristics as shown in Table 1 below, the signal light can be configured to be multiplexed / demultiplexed.

[Table 1] Here, Table 1 shows the wavelengths output from the waveguide Ii to the waveguide Jj. (For the wavelength multiplexing / demultiplexing characteristics, see, for example, S. Alexander et al., IEEE Journal of L
ightwave Technology, vol.11, No.5 / 6, May / June 1993, p
p.714-735).

Therefore, in this arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path, the signal light of wavelength λ1 among the wavelength-multiplexed signal light input from the optical fiber transmission path 4 to the waveguide I4 is used. The signal light of wavelength λ2 from the waveguide J9 is from the waveguide J10, and the signal light of wavelength λ3 is from the waveguide J9.
11, the signal light of the wavelength λ4 is extracted from the waveguide J1, the signal light of the wavelength λ11 is extracted from the waveguide J8. That is, the signal light of wavelength λk is extracted from the j-th waveguide Jj of the output waveguide 18. However, k is represented by k = Mod [(j-1) + (p-1), N] +1, and p is 4 and N is 11.

Here, the wavelength to be branched, for example, λ7
Of the signal light is taken out as it is, while the remaining signal lights λi (i = 1, 2, ..., 6, 8, ..., 11) respectively correspond to the corresponding optical fibers K1, K2, ..., K6, K.
, ..., K11) and is returned to the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 again together with the signal light of wavelength λ7 inserted from the outside. That is, in the j-th optical fiber Kj, the wavelength λk (k = Mod [j + 2,11] +
This means that the signal light of 1) is propagating.

The signal light returned to the input waveguide 14 is combined with the output waveguide 18 as in the first time. What is important here is that the sth optical fiber Ks is Mod [(s-1)
+ (P-r) + N, N] + 1st (tth) waveguide I
is connected to t. Here, p, r, N
Are 4, 6 and 11, respectively, the waveguide It connected to the optical fiber Ks is t = Mod [s + 8, 11].
It is +1. That is, the optical fiber K1 is the waveguide I10.
The optical fiber K2 is connected to the waveguide I11, and the optical fiber K3 is connected to the waveguide I11.
, Are connected to the waveguide I1, and the optical fiber K11 is connected to the waveguide I9. Therefore, the signal light of wavelength λm is re-input to the i-th waveguide Ii. However,
m = Mod [(i-1) + (r-1), N] +1, where r and N are 6 and 11, respectively.

The signal light having the wavelength λm input to the waveguide Ii (i = 1, 2, ..., 11) is guided to the waveguide J6 without depending on i due to the multiplexing / demultiplexing characteristics shown in Table 1. Is output. That is, the signal lights of all wavelengths λ1, λ2, ..., λ11 are sent out from the waveguide J6 to the optical fiber transmission line 5.
However, the wavelength λq (q = Mod
[(R-1) + (p-1), N] +1, where p,
Since r and N are 4, 6 and 11, respectively, q = 9), only the signal light does not pass through the loopback optical path 12,
The light is output to the optical fiber transmission line 5 via the waveguide I4, the slab waveguide 15, the arrayed waveguide diffraction grating 17, the slab waveguide 16, and the waveguide J6. Therefore, it is not possible to add / drop only the signal light of wavelength λ9.

From the above, the respective waveguides of the input waveguide 14 and the output waveguide 18 through which the signal light of each wavelength passes in this arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path are summarized as shown in Table 2. be able to.

[Table 2]

Here, the reason why the loss of the signal light of each wavelength is averaged will be described. When the wavelength-multiplexed signal light passes through the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 for the first time, the largest loss is output to the waveguides J1 and J11 located fifth from the central waveguide J6. Wavelength λ
These are signal lights of 4, λ3, and each of them suffers a loss of 5 ² D [dB] according to the above-mentioned Gaussian distribution. When the signal lights having the wavelengths λ4 and λ3 pass through the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 for the second time, the respective signal lights are input from the waveguides I10 and I9, respectively. here,
Since the waveguides I10 and I9 are respectively located at the 4th and 3rd positions as viewed from the center waveguide I6, the signal lights of the wavelengths λ4 and λ3 are arrayed for the second time by using the above approximate expression based on the Gaussian distribution. The losses when passing through the waveguide diffraction grating type optical multiplexer / demultiplexer 11 are only 4 ² D and 3 ² D [dB], respectively.

In this arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path, unlike the conventional arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path, the optical fiber transmission line 4 which is an external optical path is used. Since the connected input waveguide is the second waveguide I4 from the center, a loss of 2 ² D [dB] is added to the signal light of any wavelength. Therefore, the magnitudes of the losses received by the signal lights of wavelengths λ4 and λ3 are (5 ² +4 ² ) +2 ² = 45D,
(5 ² +3 ² ) +2 ² = 38 D [dB]. Table 2 shows the magnitude of the loss received by the signal light of each wavelength obtained in the same manner.
Shown in.

Therefore, in this arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path, among the signal lights of wavelengths λ1, ..., λ8, λ9, ... The loss difference between λ4 (or λ5) and the wavelength λ10 with the smallest loss is (45
-6) D = 39D. This is because the loss difference of the conventional arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path is 4
It is possible to reduce the loss difference as much as 19% as compared with the case of 8D [dB]. That is, for example, in the conventional case, a maximum loss difference of 4 dB occurs depending on the wavelength.
A loss difference of 25 dB will suffice.

As described above, according to the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path of the first embodiment, the waveguide I of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 is used.
4, the optical fiber transmission line 4 is connected to the waveguide J6, the optical fiber transmission line 5 is connected to the waveguide J6, and the output waveguide Js and the input waveguide It (t ≠ s) are connected by the loopback optical path.
When the signal light of each wavelength passes through the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 for the first time, and when it passes through the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 again via the loopback optical path 12. It is possible to construct an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loop-back optical path that can output the light after receiving different losses at each wavelength, average the losses at each wavelength, and suppress the loss difference depending on the wavelength. it can.

Since the side of the optical fiber K4 connected to the waveguide I2 is the input branch optical path and the side connected to the waveguide J4 is the output branch optical path, the loss of the branched signal light is averaged. Therefore, it is possible to split the signal light having a small loss difference depending on the wavelength and take it out to the outside.

Although the loss difference due to the position of the input / output waveguide is approximated by the Gaussian distribution in the first embodiment, the distribution used as the approximation formula is as the position of the waveguide moves away from the center. Any distribution function with which the loss fluctuates may be used, and similar effects can be obtained even if approximation is performed using the distribution function. This is because when the array waveguide diffraction grating type optical multiplexer / demultiplexer is configured to pass through the input / output waveguides with different losses when passing through the arrayed waveguide grating type optical multiplexer / demultiplexer twice as in the first embodiment, the conventional array guide with loopback optical path is used. This is because it is clear that the loss difference is improved as compared with the waveguide diffraction grating type optical multiplexer / demultiplexer.

(Embodiment 2) FIG. 2 is a configuration diagram showing an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path according to Embodiment 2 of the present invention. The difference between the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path and the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path of the first embodiment is that the optical fiber transmission line 4 is Fiber transmission line 5
For the connected waveguide J6 of | {| p−r | − (N / 2)} | ≦ 1 (here, N = 1
It is connected to the waveguide I1 satisfying 1), and the connection of the optical fibers K1 to K11 of the loopback optical path 12 is changed accordingly. Since the components other than the above are the same as those in the first embodiment, the same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In this arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path, the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 has the wavelength multiplexing / demultiplexing characteristics shown in Table 1 above. Of the wavelength multiplexed signal light input from the optical fiber transmission line 4 to the waveguide I1, the signal light of the wavelength λ1 is guided from the waveguide J1, the signal light of the wavelength λ2 is guided from the waveguide J2, ..., The signal light of the wavelength λ11 is guided. Each is taken out from the waveguide J11. That is, the signal light of the wavelength λk is extracted from the j-th waveguide Jj, and k is represented by k = Mod [(j-1) + (p-1), N] +1, and p and N are Since they are 1 and 11, respectively, k
= J. That is, the signal light of wavelength λj is extracted from the j-th output waveguide Ji.

Here, the wavelength to be branched, for example, λ7
Signal light is taken out as it is. On the other hand, the remaining signal lights λ1, ..., λ6, λ8, ..., λ11 respectively correspond to the corresponding optical fibers K1, ..., K6, K8 ,.
The signal propagates through the inside and is inputted again to the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 together with the signal light of wavelength λ7 to be inserted from the outside. That is, the signal light of wavelength λj is propagating in the j-th optical fiber Kj.

The signal light returned to the input waveguide 14 is combined with the output waveguide 18 as in the first time. Where s
The th optical fiber Ks is Mod [(s-1) + (p-
r) + N, N] + 1th input waveguide,
Since p, r, and N are 1, 6 and 11, respectively, after all, j
The th optical fiber Kj is Mod [j + 5,11] +1.
Will be connected to the second input waveguide. That is,
The optical fiber K1 is connected to the waveguide I7, the optical fiber K2 is connected to the waveguide I8, ..., The optical fiber K11 is connected to the waveguide I6. Therefore, the signal light of the wavelength λm (m = Mod [i + 4,11] +1) is input to the i-th waveguide Ii. Therefore, similarly to the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path of the first embodiment, the signal lights of all wavelengths λ1, λ2, ..., λ11 are transmitted from the waveguide J6 to the optical fiber transmission line 5. Sent out.

However, of the wavelength multiplexed signal light, the wavelength λq
(Q = Mod [(r-1) + (p-1), N] +1,
Here, since p, r, and N are 1, 6 and 11, respectively, q = 6).
It does not pass through 2 and is output to the optical fiber transmission line 5 via the waveguide I1, the slab waveguide 15, the arrayed waveguide diffraction grating 17, the slab waveguide 16, and the waveguide J6.
Therefore, it is not possible to add / drop only the signal light of wavelength λ6.

From the above, the respective waveguides of the input waveguide 14 and the output waveguide 18 through which the signal light of each wavelength passes in this arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path are summarized as shown in Table 3. be able to.

[Table 3]

Here, the reason why the loss of the signal light of each wavelength is averaged will be described. When the array waveguide diffraction grating type optical multiplexer / demultiplexer 11 passes through the first time, the largest loss is the wavelength λ1, which is output to the waveguides J1 and J11 located fifth from the central waveguide J6. The signal light has a wavelength of λ11, and each has a Gaussian distribution of 5
² D [dB] will be lost. Wavelength λ1, λ
The signal light 11 is an array waveguide diffraction grating type optical multiplexer / demultiplexer 11
When passing through the second time, each signal light is guided by the waveguide I.
7 and I6 are input. Here, the waveguides I7 and I6
Are respectively located at the 1st and 0th positions as viewed from the center waveguide I6. Therefore, if the approximate expression based on the above-mentioned Gaussian distribution is used, each signal light of wavelengths λ1 and λ11 will be the second array waveguide diffraction grating type. The losses when passing through the optical multiplexer / demultiplexer 11 are 1 ² D and 0 ² D [dB], respectively.

In this arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path, unlike the conventional arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path, the input waveguide from the outside is 5 from the center. Since it is the second waveguide I1, a loss of 5 ² D [dB] is added to the signal light of any wavelength. Therefore, the magnitudes of the losses received by the signal lights of wavelengths λ1 and λ11 are (5 ² +1 ² ) respectively.
+5 ² = 51D, (5 ² +0 ² ) +5 ² = 50D [dB]. Table 3 shows the magnitude of the loss that the signal light of each wavelength obtained in the same manner receives.

Therefore, in this arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path, the wavelength with the largest loss among the signal lights of the wavelengths λ1, ..., λ5, λ7, ..., λ11 that can be added / dropped. The loss difference between λ1 (or λ5) and the wavelength λ8 (or λ9) with the smallest loss is
(51-38) D = 13D. This can reduce the loss difference by 73% as compared with the loss difference of the conventional arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path being 48 D [dB]. That is, for example, a loss difference of 4 dB at maximum depending on the wavelength in the related art can be reduced to a loss difference of 1.08 dB.

As a reference, the waveguide Ip for external input is used.
Is fixed to the waveguide I1 (p = 1) and the waveguide Jr for external output is changed, the result of obtaining the loss difference by the approximate expression using the Gaussian distribution is shown in Table 4.

[Table 4] According to Table 4, | {| p-r |-(N / 2)} | ≦
It can be seen that the loss difference is smallest when r = 6 and 7 that satisfy 1.

As described above, according to this arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path, p and r are represented by | {| p-r |-(N / 2)} | ≦ 1. Since it has been satisfied, the signal light that has received the largest loss when passing through the arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer 11 for the first time receives the smallest loss when passing through the second time. It is possible to average the loss for each wavelength and suppress it to the minimum, and to configure an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path in which the loss difference due to the wavelength is extremely small.

In the second embodiment, the loss difference due to the position of the input / output waveguide is approximated by the Gaussian distribution, but the distribution used as the approximation formula is such that the loss distribution is near the center of the waveguide. The distribution should be small so that the loss monotonically increases as the position of the waveguide moves away from the center. Even if the distribution function is used for approximation, the same effect can be obtained. This is because, as in the second embodiment, the signal light that is subject to the maximum loss when passing through the arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer once is subjected to the minimum loss when passing the second time. This is because it is clear that the variation in the loss difference is remarkably reduced.

(Embodiment 3) FIG. 3 is a configuration diagram showing an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path according to Embodiment 3 of the present invention. The difference between this arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path and the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path of the second embodiment is that the optical fiber transmission line 4 is | p. -(N / 4) | <2 (N = 11 in this case) is connected to the waveguide I3, and the optical fiber transmission line 5 is | {| p-r |-(N / 2)} | ≦ 1 (here, N = 1
It is a point connected to the waveguide J8 satisfying 1). Along with this, the optical fibers K1 to K11 of the loopback optical path 12
Some of the connections have been changed. Since the components other than the above are the same as those in the second embodiment, the same components as those in the second embodiment are designated by the same reference numerals, and the description thereof will be omitted.

In this arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path, the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 has the wavelength multiplexing / demultiplexing characteristics shown in Table 1 above. Signal light of wavelength λk is extracted from the j-th waveguide Jj, and k is represented by k = Mod [(j-1) + (p-1), N] +1, and p and N are 3 respectively. , 11 Therefore, from the j-th waveguide Jj, the wavelength λm (m = Mod
The signal light of [j + 1,11] +1) is extracted.

Here, the wavelength to be branched, for example, λ7
Signal light is taken out as it is. On the other hand, the remaining signal lights λ1, ..., λ6, λ8, ..., λ11 respectively correspond to the corresponding optical fibers K1, ..., K6, K8 ,.
The signal propagates through the inside and is inputted again to the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 together with the signal light of wavelength λ7 to be inserted from the outside.

The signal light returned to the input waveguide 14 is combined with the output waveguide 18 as in the first time. Where s
The th optical fiber Ks is Mod [(s-1) + (p-
r) + N, N] + 1th input waveguide,
Since p, r, and N are 3, 8 and 11, respectively, j
The th optical fiber Kj is Mod [j + 5,11] +1.
Will be connected to the second input waveguide. That is,
The optical fiber K1 is connected to the waveguide I7, the optical fiber K2 is connected to the waveguide I8, ..., The optical fiber K11 is connected to the waveguide I6. Therefore, the signal light of wavelength λm (m = Mod [i + 6,11] +1) is input to the i-th waveguide Ii. Therefore, as in the case of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path of the first embodiment,
Signal lights of all wavelengths of 1, λ2, ..., λ11 are sent out from the waveguide J6 to the optical fiber transmission line 5.

However, of the wavelength multiplexed signal light, the wavelength λq
(Q = Mod [(r-1) + (p-1), N] +1,
In this case, p, r, and N are 3, 8 and 11, respectively, so that q = 10) does not pass through the loopback optical path 12, but the waveguide I3, the slab waveguide 15, and the array waveguide. Waveguide diffraction grating 17, slab waveguide 16, waveguide J8
It is output to the optical fiber transmission line 5 via each. Therefore, it is not possible to add / drop only the signal light of wavelength λ10.

From the above, the respective waveguides of the input waveguide 14 and the output waveguide 18 through which the signal light of each wavelength passes in this arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path are summarized in Table 5. be able to.

[Table 5]

Here, the dispersion of the loss of the signal light of each wavelength is averaged so as to be the same as that of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path of the second embodiment. . That is, the signal light of the wavelength λ2 having the largest loss when passing through the arrayed waveguide grating type optical multiplexer / demultiplexer 11 for the first time is input to the waveguide I6 having the smallest loss when passing through the second time. It On the other hand, the signal light of the wavelength λ8 having the smallest loss at the first time is input to the waveguide J6 having the largest loss at the second time. Therefore, as in the second embodiment, assuming that the loss distribution for each waveguide follows a Gaussian distribution, the loss difference is significantly improved to 13 D [dB].

In the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path of this embodiment, unlike the case of the second embodiment, the input waveguide from the outside is the third waveguide I3 from the center and the outside. Since the output waveguide to is the second waveguide J8 from the center, for signal light of any wavelength,
The added loss is (p-6) ² + (r-6) ² = 13D
Stay at [dB]. This is 48 compared to the case of the second embodiment in which the magnitude of the added loss is 25 D [dB].
% Also indicates that the loss is reduced.

For reference, | p−r | is defined as the waveguide Ip for external input and the waveguide Ir for external output.
| {| P−r | − (N / 2)} | ≦ 1 fixed to 5 or 6 and p is changed, and the result of calculating the loss to be added by the approximate expression using the Gaussian distribution Are shown in Tables 6 and 7.

[Table 6]

[Table 7] According to these tables 6 and 7, the values of p satisfying | p- (N / 4) | <2 or | p- (3N / 4) | <2 are 3, 4,
It can be seen that the loss decreases in either case of 8 or 9.

As described above, according to the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path, p is |
p- (N / 4) | <2 or | p- (3N / 4) | <2
Since either of the above is satisfied, the waveguide Ip used for the external input is selected so that p becomes a value near N / 4 or 3N / 4, and the waveguide Jr used for the external output has r of 3 as well.
By selecting N / 4 or a value near N / 4, both the waveguide Ip and the waveguide Jr can be made as close to the central waveguide as possible, and the absolute value of loss is small. An arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path can be constructed.

In the first to third embodiments described above,
The case where p, r, and N each take a specific value has been described, but N is preferably a natural number of 3 or more.
Need only be natural numbers that satisfy 1 ≦ p and r ≦ N, and satisfy the above-described conditional expressions. Also in this case, the same operation as in the first to third embodiments described above
It is possible to exert an effect.

Further, although the input / output optical paths or the loopback optical paths are connected to all the input / output waveguides, if there is an unused wavelength, the corresponding loopback optical path may be omitted. Further, although only the signal light of the single wavelength λ7 is added / dropped, it is needless to say that signals of wavelengths other than the above may be added, and signal lights of a plurality of wavelengths may be added / dropped.

Although the loopback optical path 12 is composed of the optical fibers K1 to K11, the optical fibers K1 to K11 may be composed of waveguides. In this case, it may be integrated with the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 11 on the substrate 13. If necessary, signal processing means such as an optical fiber delay line or an optical amplifier may be arranged in the loopback optical path 12. As a result, the signal processing required for the signal light of each wavelength can be performed for each wavelength separately and with a small loss difference.

[0069]

As described above in detail, according to the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path according to claim 1 of the present invention, at least one of the input waveguides is provided.
Input optical path connected to one, an output optical path connected to at least one of the output waveguides that does not correspond to the input waveguide, a plurality of the input waveguides, and a plurality of input waveguides that do not correspond to the input waveguides. Since a plurality of loopback optical paths respectively connected to the output waveguides of (1) are provided, when the signal light of each wavelength passes through the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer for the first time, When passing through the arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer again, it is output with a different loss. Therefore, it is possible to reduce the variation of the loss for each wavelength and the loss difference due to the wavelength is small. An arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path can be constructed.

According to the arrayed waveguide diffraction grating type multiplexer / demultiplexer with a loopback optical path of the present invention, for input connected to the input waveguide Ip (1≤p≤N; p is a natural number). An optical path, an output optical path connected to the output waveguide Jr (1 ≦ r ≦ N; r is a natural number and r ≠ p), and the input waveguide Ip ′ (1 ≦ p ′ ≦ N; p ′ is a natural number. And p '≠
p), the input branch optical path, and the output waveguide J
r '(1≤r'≤N;r'is a natural number and r' ≠ p '), and an output branch optical path, and a plurality of the output waveguides J
s (1 ≦ s ≦ N; s is a natural number and s ≠ r, s ≠ r ′) and a plurality of the input waveguides It (t = Mod [(s−1) +
(P−r) + N, N] +1, where Mod [a, b] is a remainder when a is divided by b) and a plurality of loopback optical paths respectively connected to each other. Is 1
It is output with different loss when passing through the arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer and when passing through the loop-back optical path and again through the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer. The loss for each wavelength can be averaged, and an arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path can be configured with a small loss difference depending on the wavelength. Further, since the input waveguide Ip 'is provided with the input branch optical path and the output waveguide Jr' is provided with the output branch optical path, when the branched signal light passes through the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer. Averaged over different losses and therefore
It is possible to split the signal light having a small loss difference depending on the wavelength and take it out to the outside.

According to the arrayed-waveguide diffraction grating type multiplexer / demultiplexer with loopback optical path described in claim 3, the natural numbers p and r are | {| p-r |-(N / 2)} | ≤ Since 1 is satisfied, the signal light passing through is output with a different loss each time it passes through the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer, and therefore the loss for each wavelength can be averaged. It is possible to configure an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path in which the loss difference due to the wavelength is extremely small.

According to the arrayed waveguide diffraction grating type multiplexer / demultiplexer with a loopback optical path of claim 4, the natural number p is | p- (N / 4) | <2 or | p- (3N / 4)
Since it is decided that either of | <2 is satisfied, the input waveguide Ip used for the external input is p = N / 4 or 3N / 4.
The input waveguide Ip and the output waveguide Jr are selected by selecting the values close to each other, and also selecting the output waveguide Jr used for the external output so that r is 3N / 4 or a value near N / 4. It is possible to make the waveguide as close to the center as possible,
Therefore, it is possible to remarkably reduce the loss difference depending on the wavelength, and to configure an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path having a small absolute value of loss.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path according to a third embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing a conventional optical add / drop circuit.

FIG. 5 is a configuration diagram showing a conventional arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path.

FIG. 6 is a diagram showing a relationship between a waveguide position and an optical loss in a conventional arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path.

[Explanation of symbols] 4 optical fiber transmission line (input optical path) 5 optical fiber transmission line (output optical path) 11 arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 12 loopback optical path 13 substrate 14 input waveguide 15, 16 slab Waveguide 17 Array waveguide Diffraction grating 18 Output waveguide I1 to I11 Waveguide J1 to J11 Waveguide K1 to K11 Optical fiber

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location H04B 9/00 U (72) Inventor Hiroshi Toba 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (4)

[Claims] 1. An arrayed waveguide diffraction grating type optical multiplexer / demultiplexer having a plurality of input waveguides and a plurality of output waveguides, an input optical path connected to at least one of the input waveguides, and the input waveguide. An output optical path connected to at least one of the output waveguides in an asymmetrical position with respect to the waveguide; a plurality of the input waveguides; and a plurality of asymmetrical positions with the respective input waveguides and corresponding to the input waveguides. 2. An array waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path, comprising: a plurality of loopback optical paths that are respectively connected to the output waveguides. 2. A plurality of input waveguides Ii (i = 1, 2,
..., N; N is a natural number, and a plurality of output waveguides Jj (j =
, 1, 2, ..., N), an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer, an input optical path connected to the input waveguide Ip (1 ≦ p ≦ N; p is a natural number), and the output Waveguide Jr (1 ≦ r ≦ N; r is a natural number and r ≠
p), an output optical path connected to p), an input branch optical path connected to the input waveguide Ip ′ (1 ≦ p ′ ≦ N; p ′ is a natural number and p ′ ≠ p), and the output waveguide Jr. ′ (1 ≦ r ′ ≦ N; r ′ is a natural number and r ′ ≠ p ′), and a plurality of output waveguides Js (1 ≦ s ≦ N; s is a natural number and s ≠). r, s ≠ r ′) and a plurality of the input waveguides It (t
= Mod [(s−1) + (p−r) + N, N] +1, where Mod [a, b] is the remainder when a is divided by b) and a plurality of loopback optical paths connected to each other. An arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path, which is characterized by being provided. 3. The arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path according to claim 2, wherein the natural numbers p and r are | {| p−r | − (N / 2)}.
An arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path, which satisfies | ≦ 1. 4. The array waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path according to claim 3, wherein the natural number p is | p− (N / 4) | <2 or | p−.
An arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer with a loopback optical path, which satisfies any of (3N / 4) | <2.