JP3444544B2 - Optical matrix switch - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical matrix switch used for optical signal exchange processing. In particular, the present invention relates to an optical matrix switch used for exchanging optical signals of different wavelengths transmitted by a wavelength division multiplexing communication system. 2. Description of the Related Art FIG. 4 shows a configuration example of a conventional optical matrix switch. Here, the literature (Okuno, Sugita,
Matsunaga, Kawachi, "Wavelength characteristics of quartz-based thermo-optic 8x8 matrix switch", IEICE Autumn Meeting 1991, C-17
What is described in 1) is simplified and shown in a 4 × 4 configuration. [0003] In the figure, four input ports 31 _{1 to} 3 ₁
1 ₄ and, the four output ports 321 _to 323 _4, 2 16
Via input 2 output optical switch 40 _{11-40 44} are coupled to a matrix. Note that optical signals of the same wavelength are input to each input port. FIG. 5 shows a configuration example of a two-input two-output optical switch 40. In the figure, a two-input two-output optical switch 40
Has a two-input, two-output Maha-Zehnder interferometer type switch configuration. That is, the 3 dB coupler 4 connected to the input waveguides 41 _{1 and} 41 ₂ and the output waveguides 42 _{1 and} 42 ₂
3 _1, and 43 _2, a configuration of arranging the thermo-optic phase shifter 44 to set the phase difference between them of two links. By setting a predetermined phase difference with the thermo-optic phase shifter 44, the two optical signals input from the input waveguides 41 _{1 and} 41 ₂ are output to the output waveguides 42 ₂ and 42 ₁ by exchanging the spatial positions. (Cross state) or the output waveguide 42 _{1 as it is}
It can be output in 42 ₂ (bar state). That is, the two-input two-output optical switch 40 can be operated as a space switch. [0005] The optical matrix switch shown in FIG. 4 is obtained by combining the two-input two-output optical switches 40 in a matrix. That is, the output waveguides 4 of the two-input two-output optical switches adjacent to the left and right (for example, 40 ₁₁ and 40 ₁₂ ).
2 _1, and coupling the input waveguide 41 _2, coupling the output waveguide 42 ₂ and the input waveguide 41 ₁ of 2 input 2 output optical switch vertically adjacent (eg 40 _11, 40 _21). Further, each input waveguide 41 ₂ of the left end of the 2-input 2 output optical switch 40 _{11-40 41} and the input port 31 ₁ to 31 _4, each of the output waveguides of the 2-input 2 output optical switch 40 _{41-40 44} at the lower end 42
₁ and the output port 321 _to 323 _4. This allows the optical matrix switch shown in FIG. 4 to function as a 4-input 4-output space switch. In order to exchange optical signals of different wavelengths transmitted by the wavelength division multiplexing communication system, two-input two-output light for switching optical signals of the same wavelength is required. The switch 40 cannot be used as a basic element as it is. In order to switch optical signals of different wavelengths, two signals between the 3 dB couplers 43 _{1 and} 43 ₂ are used.
A predetermined path length difference is set for each link, and its wavelength multiplexing / demultiplexing function is used. However, since such an optical switch also functions as a space switch, it is impossible to distribute optical signals of different wavelengths input to each input waveguide to the same output waveguide. That is, in the optical matrix switch having the configuration shown in FIG. 4, optical signals having different wavelengths input to each input port cannot be distributed to each output port in any combination. In order to realize this, an optical matrix switch having M inputs (M × N) outputs is formed, and output waveguides of (M × N) optical matrix switches are merged for every M lines to form an output port. It is necessary to use a 2-input 2-output optical switch (M ×
M × N) pieces had to be prepared. In the two-input two-output optical switch, crosstalk occurs between optical signals output to the two output waveguides in either the cross state or the bar state. In an optical matrix switch in which the two-input two-output optical switches are coupled in a matrix, crosstalk is accumulated, and the difference (SN ratio) between the intensity of the optical signal and the crosstalk light is reduced according to the magnitude thereof, making it difficult to determine the signal. become. Generally, the signal-to-crosstalk ratio SXR of a matrix switch having N switch stages is given by SXR = X− ₁₀ log ₁₀ (N−1) [dB] where X is the average crosstalk per optical switch. (H.Okayama, A.Matoba, R.Shibuya, T.Is
hida, "Optical SwitchMatrix with Simplified N × NT
ree Structure ", IEEE Journal of LightwaveTechnolo
gy vol. 7, No. 7, pp. 1023-1028, 1989). Therefore, 8 ×
In the case of an 8-matrix switch, the number of switch stages is 15, which causes a deterioration of about 11 dB. In the case of a 16 × 16 matrix switch, since the number of switch stages is 31, a deterioration of about 15 dB is caused. According to the above-mentioned document, the crosstalk value is -20 dB on average per one 2-input / 2-output optical switch.
Therefore, the SN ratio becomes about 9 dB in the 8 × 8 matrix switch, and the SN ratio in the 16 × 16 matrix switch.
The ratio becomes about 5 dB. As described above, when the size of the optical matrix switch is increased, it has been difficult to process a high-speed optical signal. According to the present invention, optical signals having different wavelengths input to each input port can be distributed to each output port in an arbitrary combination by using as few optical switches as possible, and optical signals having small crosstalk accumulation can be distributed. An object is to provide a matrix switch. An optical matrix switch according to the present invention has first and second input lines to which an optical signal is input, and one-input two-output light connected to the first input line. A switch, a first output line connected to one output of the one-input, two-output optical switch, and light for combining the optical signal of the other output of the one-input, two-output optical switch and the optical signal of the second input line. The filter and the second output line connected to the output of the optical filter are one unit of a two-input, two-output unit switch, and the two-input, two-output unit switches are arranged in M rows and N columns. , The first output line and the first input line of the two-input two-output unit switch, and the second output line and the second input line of the two-input two-output unit switch in each row are connected to each other.
The first input lines of the two 2-input 2-output unit switches are connected to the M input ports, respectively, and the N 2-input 2 switches in the M-th row are connected.
N output ports are connected to the second output line of the output unit switch to form an M-input N-output switch configuration. The optical matrix switch of the present invention has a configuration in which a two-input, two-output unit switch is arranged at the intersection of an M × N matrix. An optical signal input from one of the M input ports is selected by one of N 2-input 2-output unit switches corresponding to each output port cascaded in the row direction, and passed through the optical filter. 2 inputs 2 of the next row from the 2nd output line
It is sent to the output unit switch. In the two-input two-output unit switch in the next row, the optical signal input from the second input line is transmitted to the two-input two-output unit switch in the next row via the optical filter and the second output line. Similarly, the optical signal is transmitted to the output port through the two-input two-output unit switches arranged in the column direction. With such a configuration, optical signals having different wavelengths input to each input port can be distributed to each output port in an arbitrary combination. For example,
It is also possible to wavelength multiplex optical signals input from different input ports i and j to the same output port k and transmit them. At this time, wavelength multiplexing of both optical signals is performed by an optical filter of a 2-input / 2-output unit switch of j rows and k columns. In a two-input two-output optical switch, crosstalk appears mutually, but in a one-input two-output optical switch, only one optical signal is input, so crosstalk accompanying switching also appears on the non-switching side. Only. Moreover, the crosstalk generated from the 1-input 2-output optical switch of each 2-input 2-output unit switch to the output port side does not depend on the number of 2-input 2-output unit switches arranged in the row direction. Therefore, the crosstalk appearing at each output port is at most only the sum of the crosstalk in the two-input, two-output unit switches arranged in the column direction, and the accumulation of crosstalk can be effectively and significantly reduced. FIG. 1 shows the configuration of a first embodiment of the present invention.
Here, the number of input ports M is 4 and the number of output ports N
Is shown as 3, but the number of input ports and the number of output ports can both be arbitrarily set. In the figure, four input ports 31 _{1 to} 3 ₁
1 ₄ and three output ports 321 _to 323 in the _third intersection, two inputs and two outputs unit switches 10 _11-1, which is a feature of the present invention
0 ₄₃ is arranged. Each 2-input / 2-output unit switch 10
An input line, a one-input two-output optical switch 11 connected to the input line, and an output a of the one-input two-output optical switch 11
And an output line connected to the optical switch 11
And an output line connected to the output of the optical filter 12. The optical filter 12 combines the optical signal of the output b and the optical signal of the input line. A two-input, two-output unit switch 10 _{11 in} the first row
10 each input port 31 of each input line of _{41 1-3}
And 1 _4, to connect the respective input lines of the second column of two inputs and two outputs unit switches 10 ₁₂ to 10 ₄₂ to each output line. Hereinafter, cascade connection is performed in the same manner for each column. Further, to the output line of the first row of the two inputs and two outputs unit switches ₁₀₁₁ to _13, connects each input line of the second row of the two inputs and two outputs unit switches 10 ₂₁ to 10 _23. Hereinafter similarly cascaded line by line, to a respective output line of the fourth row of the two inputs and two outputs unit switches 10 ₄₁ to 10 ₄₃ and the output port _{321 to} 323. 1-input 2-output optical switch 11 of this embodiment
Uses a Maha-Zehnder interferometer type switch having a wavelength demultiplexing function with one input and two outputs. Alternatively, if it can operate in the wavelength band to be used, an optical switch using a semiconductor, a waveguide type switch, a gate switch using an element such as a liquid crystal or an acousto-optic element capable of controlling passage or blocking of light can be used. Can be used. The optical filter 12 uses an element that transmits or reflects according to the wavelength of an optical signal. For example, an acousto-optic filter using an acousto-optic element, a Mach-Zehnder filter using a Mach-Zehnder interferometer, a dielectric multilayer filter, or the like can be used. Its function is to reflect the optical signal of the output b of the one-input two-output optical switch 11 to the output port side and to transmit the optical signal of the input line to the output port side, thereby wavelength-multiplexing the optical signal going to the same output port. I do. In addition, in wavelength multiplexing using the optical filter 12, there is in principle no merger loss. In the configuration of this embodiment, each input port 31 ₁
It is in principle for inputting an optical signal having a wavelength different to 31 _4. Note that optical signals of the same wavelength may be input from different input ports as long as they are not output to the same output port. The following is a specific example based on the principle. The input ports 31 ₁ , 31 ₂ , 31 ₃ , 31
The wavelength of the optical signal input to ₄ is λ according to the arrangement on the wavelength axis.
₁ , λ ₂ , λ ₃ , and λ ₄ . At this time, the optical filter 12 mounted on the two-input two-output unit switch 10 of each row
Use those having characteristics shown in FIGS. 2 (1) to 2 (4). That is, as shown in FIG. 2A, the optical filters 12 of the two-input, two-output unit switches 10 ₁₁ to 10 ₁₃ in the first row are set to have a characteristic of reflecting an optical signal having a wavelength λ ₁ . Thereby, the output b of the 1-input 2-output optical switch 11
It can be sent to the retrieved wavelength lambda ₁ of the output lines of the optical signal output port side. The 2 input 2 output unit switch 10 _{21 in} the second row
The optical filter 12 of 10 _23, as shown in FIG. 2 (2),
Transmits the optical signal of the wavelength lambda _1, is set to the characteristic of reflecting the optical signal of the wavelength lambda _2. This allows the optical signal of wavelength λ ₁ input from the input line to pass through the output line,
The optical signal of the wavelength λ ₂ taken out from the output b of the one-input two-output optical switch 11 can be sent to the output line on the output port side. At this time, the optical signals of the wavelengths λ ₁ and λ ₂ are wavelength-multiplexed. A two-input, two-output unit switch 10 _{31 in} the third row
10 ₃₃ optical filter 12, as shown in FIG. 2 (3),
The characteristic is set so that an optical signal having a wavelength of λ ₂ or less is transmitted and an optical signal having a wavelength of λ ₃ is reflected. As a result, the optical signals of wavelengths λ ₁ and λ ₂ input from the input line can be transmitted to the output line, and the optical signal of wavelength λ ₃ extracted to the output b of the one-input / two-output optical switch 11 is transmitted to the output port side. Output line. At this time, the optical signals of the wavelengths λ ₁ , λ ₂ and λ ₃ are wavelength-multiplexed. The second-input / two-output unit switch 10 _{41 in} the fourth row
10 ₄₃ optical filter 12, as shown in FIG. 2 (4),
Transmitted through the wavelength lambda ₃ following optical signals, set the property of reflecting the optical signal of the wavelength lambda _4. As a result, optical signals of wavelengths λ ₁ , λ ₂ , λ ₃ inputted from the input line can be transmitted to the output line, and the output b of the 1-input 2-output optical switch 11 can be transmitted.
The optical signal of the wavelength λ ₄ extracted at the above can be sent to the output line on the output port side. At this time, the wavelengths λ ₁ , λ ₂ , λ ₃ ,
optical signal of lambda ₄ are wavelength-multiplexed. Here, a specific switching example will be described. Input from the input port 31 ₁ light signals (lambda
Description will be given of a case where outputs ₁₎ to the output port 32 _2. Of the three 2-input 2-output unit switches 10 ₁₁ to 10 ₁₃ arranged in the row direction with respect to the input port 31 ₁ , the 2-input 2-output unit switch 10 corresponding to the output port 32 _{2
The 12} 1-input 2-output optical switches 11 are set to the output b side,
Others are set on the output a side where the optical signal goes straight. As a result, the optical signal input from the input port 31 ₁ is converted into two-input two-output unit switches 10 ₁₁ , 10 ₁₂ , 10 ₂₂ , 10 ₃₂ ,
Output 10 ₄₂ through the output port 32 _2. In addition,
The route is one way. The two-input / two-output unit switch 10 ₁₁ outputs the input optical signal to the output a of the one-input / two-output optical switch 11.
From the two-input two-output unit switch 10 via the output line.
Send to ₁₂ . The two-input two-output unit switch 10 ₁₂ converts the optical signal input from the input line into a one-input two-output optical switch 1
Output from the first output b, and sends reflected by the optical filter 12 through the output line 2 input 2 to the output unit switches 10 _22.
In 2 Input 2 Output unit switches 10 _22, and sends the optical signal input from the input line passes through an optical filter 12, via the output line 2 input 2 to the output unit switches 10 _32. At this time, the two-input two-output unit switch 10
In _22, if the optical signal traveling from the input port 31 ₂ to the output port 32 _3, the optical signal of the input line optical signal output a 1-input 2-output optical switch 11 and intersect both the straightness of light The signals are transmitted without interfering with each other.
Also, if there is an optical signal going from the input port 31 ₂ to the output port 32 ₂ , the output b of the 1-input 2-output optical switch 11
The optical signal (λ ₂ ) and the optical signal (λ ₁ ) of the input line are input to the optical filter 12, the former is reflected and the latter is transmitted and wavelength-multiplexed, and then to the next-stage two-input two-output unit switch 10 ₃₂ . Sent. As described above, the optical filter 12 has a function of wavelength-multiplexing optical signals going to the same output port. Similarly, the optical signal is supplied to the two-input two-output unit switches 10 ₃₂ and 10 ₃₂ .
₄₂ is transmitted through the respective optical filters 12 are output to the output port 32 _2. As described above, in order to facilitate the description of the optical filter 12, the case where the wavelength of the optical signal input to each input port is fixed is shown. However, an optical signal input to the input port 31 ₁ to 31 ₄ can be any wavelength as long as different wavelengths. In that case, an optical filter having a characteristic of reflecting only an optical signal of a specific wavelength is used as the optical filter 12. An example is shown in FIG. When an optical signal having a wavelength λ ₄ is input to the input port 31 ₁ , as shown in FIG. 3A, the optical filter 12 of the two-input two-output unit switch at the position corresponding to the output port is used. , reflects the optical signal of the wavelength lambda _4, sets a property of transmitting light signals of other wavelengths. Thus, the wavelength λ extracted to the output b of the one-input two-output optical switch 11
₄ optical signals can be sent to the output line. [0031] When inputting the optical signal of the wavelength lambda ₂ to the input port 31 _2, as shown in FIG. 3 (2), likewise the wavelength lambda
_The characteristic of reflecting the optical signal of No. ₂ and transmitting optical signals of other wavelengths is set in the optical filter 12. Thus, the wavelength λ
With the _fourth optical signal can pass from the input line to the output line, it sends the wavelength lambda ₂ of the optical signal obtained from an output b of one input and two output optical switch 11 to the output line. When the optical signals of the wavelengths λ ₄ and λ ₂ input from the input ports 31 ₁ and 31 ₂ are directed to the same output port, the two optical signals are wavelength-multiplexed and transmitted to the output line. When an optical signal having a wavelength of λ ₃ is input to the input port 31 ₃ , similarly, as shown in FIG.
_The characteristic of reflecting the optical signal of No. ₃ and transmitting optical signals of other wavelengths is set in the optical filter 12. Thus, the wavelength λ
₂ and λ ₄ can be transmitted from the input line to the output line, and the optical signal having the wavelength λ ₃ extracted to the output b of the one-input two-output optical switch 11 can be transmitted to the output line. When optical signals of wavelengths λ ₄ , λ ₂ , and λ ₃ input from the input ports 31 ₁ , 31 ₂ , and 31 _{3 go} to the same output port, each optical signal is wavelength-multiplexed and transmitted to an output line. . [0033] When inputting the optical signal of the wavelength lambda ₁ to the input port 31 _4, as shown in FIG. 3 (4), likewise the wavelength lambda
_The characteristic that reflects _one optical signal and transmits optical signals of other wavelengths is set in the optical filter 12. Thus, the wavelength λ
The optical signal of _{2 to} λ ₄ can be transmitted from the input line to the output line, and the optical signal of the wavelength λ ₁ extracted to the output b of the one-input two-output optical switch 11 can be transmitted to the output line. Incidentally, when the input port 31 _1, 31 _2, 31 _3, 31 ₄ wavelength lambda ₄ input from, lambda _2, lambda _3, lambda ₁ of the optical signal is directed to the same output port, the optical signal is wavelength-multiplexed Sent to the output line. As described above, even if the wavelength of the optical signal to be input to each input port is arbitrarily selected, the optical filter 1 of the two-input two-output unit switch where the input port and the output port cross each other is selected.
By setting the corresponding reflection wavelength and the transmission wavelength on both sides for wavelength 2, wavelength multiplexing processing of optical signals going to the same output port can be realized. By the way, the two-input two-output unit switch 10
In this case, crosstalk occurs only in the one-input / two-output optical switch 11 and appears only on the non-switching side. Further, crosstalk generated on the output b side of the one-input two-output optical switch 11 of each two-input two-output unit switch 10 is added by the optical filter 12, extracted to the output port, and arranged in the row direction. It does not depend on the number of unit switches. Therefore, the maximum value of the crosstalk appearing at each output port is the sum of the crosstalk in the 2-input 2-output unit switches arranged in the column direction. Assuming that the crosstalk level of the one-input two-output optical switch is -20 dB as in the conventional example, the 8 × 8 matrix switch deteriorates by at most 9 dB (SN ratio: 11 dB). Thus, in the optical matrix switch of the present invention, crosstalk can be significantly reduced. FIG. 4 shows the configuration of the second embodiment of the present invention. In this embodiment, the wavelength multiplexed wavelengths λ _{1 to} λ ₄
This is an example of a configuration for distributing the optical signal of FIG. Both the number of wavelength multiplexing and the number of output ports can correspond to an arbitrary number. In the figure, the wavelength multiplexed signal input port 13
Is input with wavelength-multiplexed optical signals of wavelengths λ _{1 to} λ ₄ . This wavelength-division multiplexed optical signal is demultiplexed for each wavelength by the optical signal demultiplexer 14 and input to _four input ports 31 _{1 to} 314 of the optical matrix switch. 4 input ports 3
1 _{1-31 4,} three output ports _{321 to} 323, 1 binding relationship between the input 2 output unit switches ₁₀₁₁ to ₄₃ is the same as the first embodiment. However, in the two-input / two-output unit switches 10 ₁₁ to 10 ₁₃ in the first row, there is no other optical signal which is wavelength-multiplexed and goes to the same output port.
2, the output b of the 2-input 2-output unit switch 11 is directly connected to the output line. In the configuration of this embodiment, each input port 31 ₁
Because to 31 ₄ to an optical signal of wavelength lambda ₁ to [lambda] ₄ is inputted in this order, is mounted on two inputs and two outputs unit switches 10 to the optical filter 12 each row having the characteristics shown in FIG. The function as an optical matrix switch is the same as that of the first embodiment, and the wavelength-multiplexed optical signals of wavelengths λ _{1 to} λ ₄ can be distributed to each output port in any combination. That is, each optical signal can be wavelength-multiplexed and transmitted to the same output port in any combination. As described above, the M-input / N-output optical matrix switch according to the present invention includes the optical signals of different wavelengths input from the respective input ports, including the wavelength multiplexing at the respective output ports. Can be sorted in any combination. In addition, since M × N 1-input 2-output optical switches can be arranged in a matrix, the size and power consumption can be reduced. Further, by using the one-input two-output optical switch, it is possible to realize an optical matrix switch in which the accumulation of crosstalk is small. Therefore, the SN ratio of the optical signal is improved, and it is possible to cope with a high-speed optical signal. Further, the scale of the optical matrix switch can be easily increased. In particular, since the accumulation of crosstalk does not depend on the number of 2-input / 2-output unit switches arranged in the row direction, it is effective when configuring an optical matrix switch having a large size in the row direction.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention. FIG. 2 is a diagram illustrating a relationship between a wavelength of an input port and characteristics of an optical filter 12; FIG. 3 is a diagram illustrating a relationship between a wavelength of an input port and characteristics of an optical filter 12; FIG. 4 is a block diagram showing a configuration of a second embodiment of the present invention. FIG. 5 is a block diagram showing a configuration example of a conventional optical matrix switch. FIG. 6 is a diagram showing a configuration example of a two-input two-output optical switch 40; DESCRIPTION OF SYMBOLS 10 2 input 2 output unit switch 11 1 input 2 output optical switch 12 optical filter 13 wavelength multiplexed signal input port 14 optical signal splitter 31 input port 32 output port 40 2 input 2 output optical switch 41 input guide Waveguide 42 Output waveguide 43 3 dB coupler 44 Thermo-optic phase shifter

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04Q 3/52

Claims (1)

(57) Claims 1. A light having a plurality of M input ports and a plurality of N output ports, and outputting an optical signal input from an arbitrary input port to an arbitrary output port. In the matrix switch, first and second input lines to which an optical signal is input, a one-input two-output optical switch connected to the first input line, and one output of the one-input two-output optical switch are connected. A first output line, an optical filter for joining the optical signal of the other output of the one-input two-output optical switch and the optical signal of the second input line, and a second output line connected to the output of the optical filter Are one unit of a two-input, two-output unit switch, and the two-input, two-output unit switches are arranged in M rows and N columns.
And the first input line, and the second output line and the second input line of the two-input two-output unit switch in each row, and the second one of the M two-input two-output unit switches in the first column. 1 input line and the M input ports, respectively, and
N is connected to the second output lines of the two-input two-output unit switches.
An optical matrix switch, wherein a plurality of output ports are connected to form a switch configuration of M inputs and N outputs.