JPH0450796B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a wavelength division multiplexing optical exchange for switching and connecting wavelength multiplexed optical signals, and to an optical communication network including the wavelength division multiplexing optical exchange.

(Prior Art) In recent years, demand for communication services using wideband signals such as image signals has been increasing. Since the bandwidth of wideband signals ranges from several MHz to several tens of MHz, optical fiber cables, which have advantages such as small diameter, wide band, low loss, and resistance to electromagnetic induction, are being introduced as transmission lines instead of conventional coaxial cables. Appropriate.

Furthermore, it is considered desirable to use an optical switch that exchanges and connects optical signals from each optical fiber cable as they are without converting them into electrical signals. In particular, a wavelength division multiplexing optical switch establishes communication channels between each wavelength of wavelength-multiplexed input and output optical signals. Therefore, even in communication networks,
It is sufficient to transmit wavelength-multiplexed optical signals between optical exchanges using optical fiber cables, which has the advantage that the number of optical fiber cables is extremely small compared to a case where wavelength multiplexing is not performed. As such a wavelength division multiplexing optical switch, the one shown in FIG. 6 and described in the specification of patent application No. 1983-079388 has been known. The conventional wavelength multiplexing optical switch shown in FIG.
Wavelength conversion switches 618 to 620 and wavelength conversion switches 600 to 60 whose respective outputs are connected to ~636
2 output optical waveguides 603 to 605 and input optical waveguides 606 to 6 of wavelength conversion switches 618 to 620.
Wavelength selection switch 609-6 provided between 08
It consists of 17. Optical waveguides 631-6
Wavelength multiplexed optical signals of four wavelengths λ ₁ , λ ₂ , λ ₃ , and λ ₄ are input to the optical waveguides 634 to 63.
Wavelength multiplexed optical signals of four wavelengths λ ₁ , λ ₂ , λ ₃ , and λ ₄ are also output from 6.

For example, a case will be described in which a communication channel is set between an optical signal of wavelength λ ₂ input to the optical waveguide 633 and an optical signal of wavelength λ ₄ of the optical waveguide 634.
The wavelength conversion switch 602 converts the optical signal of wavelength λ ₂ input to the optical waveguide 633 into the wavelength λ 1 under the control of a control circuit not shown here, and converts the optical signal of wavelength λ ₂ inputted to the optical waveguide 633 to
Output to 05. When the wavelength λ 1 is assigned as the selected wavelength of the wavelength selection switch 617 by a control circuit (not shown), the optical signal with the wavelength λ ₁ sent to the optical waveguide ₆₀₅ is guided to the optical waveguide 606 for wavelength conversion. It is input to switch 618.
The wavelength conversion switch 618 converts the optical signal of wavelength λ ₁ to wavelength λ ₄ under the control of a control circuit (not shown).
and output to the optical waveguide 634.

FIG. 7 shows the wavelength conversion switch 6 shown in FIG.
It is a figure which shows the specific example of 00-602 and 618-620.

According to FIG. 7, the wavelength conversion switch shown in FIG. , 702, 703, 704 and 705, and the first, second, third and fourth wavelength selection elements 701, 702, 703 and 7
first, second, third and fourth wavelength conversion elements 70 each having an input terminal connected to the other waveguide of 04 and having output wavelengths of λ ₁ , λ ₂ , λ ₃ and λ ₄ ;
6,707,708 and 709 and this first,
Second, third and fourth wavelength conversion elements 706, 7
07, 708, and 709, and an optical multiplexer 710 having a plurality of input terminals connected to the other waveguide of the wavelength selection element 705, respectively.

In FIG. 7, wavelength selection elements 701, 702,
703, 704 and 705 are control terminals 711, 712, 713, 714 and 715, respectively.
It selectively outputs an optical signal of a desired wavelength from among the optical signals having wavelengths λ ₁ , λ ₂ , λ ₃ and λ ₄ applied to the input optical waveguide 700 according to the voltage applied to the input optical waveguide 700. Proceedings of the Academic Lectures of Japan Society for Applied Physics
The LiNbO ₃ waveguide optical wavelength tunable filter described in 9P-M-9 can be used. Further, wavelength conversion elements 706, 707, 708 and 709 convert optical signals of arbitrary wavelengths applied to the input terminals into optical signals having wavelengths λ ₁ , λ ₂ , λ ₃ and λ ₄ , respectively. As this wavelength conversion element, IEEE
Journal of QE vol QE−14, No.11.Nov 1978
p810〜813“p-n-p-n Optical Detectors
It is conceivable to use a wavelength conversion element as described in ``And Light-Emitting Diodes'', but this wavelength conversion element cannot in principle convert an optical signal with a long wavelength into an optical signal with a short wavelength. As the conversion elements 706, 707, 708 and 709, for example, a harmonic optical signal having a wavelength shorter than any of λ ₁ , λ ₂ , λ ₃ and λ ₄ is converted by using a nonlinear optical crystal such as a LiNbO ₃ guiding crystal. After generating the above-mentioned “p-n-p-n optical
The wavelengths λ ₁ and λ 1 and
Means for converting into optical signals having λ ₂ , λ ₃ and λ ₄ can be considered.

In FIG. 7, for example, a control circuit (not shown) controls the second and third wavelength selection elements 702.
and 703, respectively, the optical signals having wavelengths λ ₁ and _{λ 2 applied} to _the input optical waveguide 700 are
After being converted into optical signals having wavelengths λ ₂ and λ ₃ by third wavelength conversion elements 707 and 708, respectively, the signals are outputted to an output optical waveguide 716 via an optical multiplexer 710.

FIG. 8 shows the wavelength selection switch 60 shown in FIG.
It is a figure which shows the specific example of 9-617. According to FIG. 8, the wavelength selection switch shown in FIG.
1,802,803 and 804 and this first,
Second, third and fourth wavelength selection elements 801, 8
02, 803 and 804, one input is connected to the optical waveguide 805 which is cascade-connected to the other waveguide.
and an optical multiplexer 808 whose other input is connected to the output optical waveguide 806 of the output optical waveguide 806 , and whose output is connected to the second output optical waveguide 807 .

In FIG. 8, wavelength selection elements 801, 802,
803 and 804 are control terminals 80, respectively.
9, 810, 811 and 812, the wavelength λ ₁ on the input optical waveguide 800,
Among the optical signals having wavelengths λ ₂ , λ ₃ and λ ₄ , a desired one wavelength is selectively outputted to the optical waveguide 805. For example, the wavelengths λ ₁ , λ ₂ , λ ₃ and λ ₄ on the input optical waveguide 800 are In order to selectively output optical signals having wavelengths λ ₂ and λ _{3 of the optical signals having wavelengths λ 2 and λ 3} to the second output optical waveguide 807, the wavelength selection elements 801, 802, 803 and 8
This is done by assigning the selection wavelength λ ₂ to one of the wavelengths 04 and the selection wavelength λ ₃ to the other one.

(Problems to be Solved by the Invention) In the conventional wavelength division multiplexing optical switch, the wavelength conversion elements 706 to 709 in the wavelength conversion switches 600 to 602 and 618 to 620 in FIG.
-n-p-n Optical Detectors and Light-
Emitting Diodes” are used.
However, it is difficult to make the output wavelength of such a wavelength conversion element exactly match a predetermined wavelength due to variations in material composition when manufacturing the element. For example, even if the output wavelength is planned to be 1.35μm, the output wavelength will be 1.34μm.
Otherwise, there is a high possibility that it will deviate to 1.36 μm.
Further, changes in temperature also cause variations in the output wavelength. If the output wavelength of the wavelength conversion element is not accurate,
Contamination with adjacent wavelengths occurs, making normal exchange operations impossible. In the above example, if the adjacent wavelength is set to 1.34 μm or 1.36 μm, exchange operations using these wavelengths cannot be performed due to interference. Furthermore, not only within a single wavelength division multiplexing optical switch, but also in a communication network that includes multiple wavelength division multiplexing optical switches, communication between optical switches will fail if the wavelengths of the optical signals sent out from each wavelength division multiplexing optical switch do not match. It becomes possible.

An object of the present invention is to solve the above-mentioned problems and to prevent the wavelength shift of the output optical signal due to variations in the material composition of the wavelength conversion element of the wavelength conversion switch, and the fluctuation of the wavelength of the output optical signal due to temperature changes. The purpose of the present invention is to provide a wavelength division multiplexing optical switch and a wavelength division multiplexing optical communication network.

(Means for Solving the Problem) In order to solve the above-mentioned problem, the wavelength division multiplexing optical switch provided by the present invention has a first and a second wavelength division multiplexing device having a function of converting and outputting the wavelength of a wavelength-multiplexed input signal. A wavelength multiplexing optical switch comprising a wavelength conversion switch and means for connecting the output of the first wavelength conversion switch to any of the second wavelength conversion switches, comprising: a reference light generator that outputs light of a plurality of wavelengths; Furthermore, the first and second wavelength conversion switches perform wavelength conversion by modulating the output light of the reference light generator with optical signals of different wavelengths.

Further, the wavelength division multiplexing optical communication network of the present invention includes first and second wavelength conversion switches each having a function of converting and outputting the wavelength of a wavelength multiplexed input signal, and an output of the first wavelength conversion switch. In a wavelength division multiplexing optical communication network consisting of a plurality of wavelength division multiplexing optical exchanges including means for connecting to any of the second wavelength conversion switches, further provided is a reference light generator that outputs light of the reference light generator, and distributes the output light of the reference light generator to the plurality of wavelength multiplexing optical exchangers, and the first and second wavelength conversion switches output the light of the reference light generator. It is characterized by performing wavelength conversion by modulating the output light with an optical signal of a different wavelength.

(Function) In the present invention, as described above, a reference signal generator that outputs optical signals of a plurality of wavelengths is provided, and the output signal is supplied to each wavelength converter. By modulating and converting one of the wavelengths, the output wavelength of any wavelength converter can be made accurate without using a wavelength conversion element having an accurate output wavelength.

Furthermore, in the present invention, one reference signal generator output optical signal is used to modulate and wavelength convert one of the wavelengths of the reference signal in each wavelength converter in all the wavelength division multiplexing optical exchanges in the wavelength division multiplexing optical communication network. As a result, the wavelengths of the optical signals sent out from any exchange can be made to match each other without using a wavelength conversion element having an accurate output wavelength.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a wavelength division multiplexing optical switch according to a first embodiment of the present invention, and its operation is similar to that of the conventional wavelength division multiplexing optical switch shown in FIG. In Figure 1, the same numbers as in Figure 6 refer to Figure 6.
Represents the same components as in the figure.

In FIG. 1, output DC lights from light sources 122, 123, 124, and 125 oscillating at wavelengths λ ₁ , λ ₂ , λ ₃ , and λ ₄ are fixedly multiplexed by an optical multiplexer 126, and a reference light generator 121 It is sent to the optical waveguide 127 as an output. Therefore, the output of the reference light generator 121 includes DC light having wavelengths λ ₁ to _{λ 4} . Wavelength conversion switches 100 to 102 and 118 to 12
0, the output of the reference light generator 121 is sent to the optical splitter 12.
It is fixedly branched at 8 and supplied to each.

Wavelength conversion switch 100-102, 118-1
20 uses the output of the supplied reference light generating circuit 121 to swap the wavelengths of the input wavelength multiplexed optical signal. As a result, the wavelength conversion switch 10
All of the output wavelengths 0 to 102 and 118 to 120 can be made to match the wavelengths λ ₁ to _{λ 4} of the reference light generation circuit 121, allowing normal exchange operation.

For example, an optical signal with wavelength λ ₃ enters wavelength conversion switch 100 from optical waveguide 631, is converted into wavelength λ ₄ , enters wavelength conversion switch 120 via wavelength selection switch 609, and is further converted into wavelength λ ₁ . and output.

FIG. 2 shows wavelength conversion switches 100 to 102 and 118 in the first embodiment of the present invention shown in FIG.
It is a figure showing the 1st specific example of -120. In FIG. 2, the same numbers as in the conventional wavelength conversion switch of FIG. 7 represent the same components as in FIG.

In FIG. 2, wavelength selection elements 701 to 705
As in FIG. 7, λ ₁ to λ applied to the input optical waveguide 700 correspond to voltages applied to the control terminals 711 to 715 from a control circuit not shown here.
An optical signal having a desired wavelength among the optical signals having a wavelength of λ ₄ is selectively output. Further, light obtained by branching the wavelength multiplexed output optical signal containing DC light of wavelengths λ ₁ to _{λ 4} from the reference light generator 121 in FIG. Wavelength converter 20
From this reference light, direct current light with a wavelength λ ₁ is selected by a wavelength selection element 201 and supplied to the reference light beam 6 . The wavelength converter 206 converts the wavelength of the direct current light of wavelength λ ₁ from the wavelength selection element 201 by modulating it according to the optical signal from the wavelength selection element 704 . The wavelength λ ₂ ,
Direct current light of λ ₃ and λ ₄ is supplied, and the wavelength converter 2
07, 208, and 209 select wavelength selection elements 701 to 70 for direct current lights of wavelengths λ ₂ , λ ₃ , and λ ₄ that are supplied, respectively.
The wavelength is converted by modulating the optical signal from 3. As a result, wavelength converters 206 to 20
The output wavelengths of 9 are all the reference light generator 1 in Fig. 1.
21 output wavelengths λ ₁ to λ ₄ . Wavelength converter 2
The outputs of 06 to 209 are fixedly multiplexed by an optical multiplexer 710. Therefore, in FIG. 1, since the wavelengths of the output optical signals of the wavelength conversion switches 100 to 102 are different from _λ1 to _λ4 , the wavelength selection switches 609 to 61
7, it is possible to prevent the occurrence of mixing into adjacent wavelengths. Furthermore, by temperature compensating only the light sources 122 to 125 to eliminate wavelength fluctuations due to temperature changes, it is possible to prevent fluctuations in the output wavelengths of all wavelength conversion switches due to temperature changes.

Note that in the reference light generator 121, the light sources 122 to
The outputs of 125 are not multiplexed by the optical multiplexer 126, but are directly and fixedly branched to the wavelength conversion switch 10.
Wavelength converter 20 within 0 to 102, 118 to 120
Similar effects can be obtained by supplying each of them to ports 6 to 209.

FIG. 3 shows the wavelength converters 206 to 2 in FIG.
09 is a diagram showing a specific example of No. 09. In Figure 3,
The optical waveguide 301 receives an input optical signal having a wavelength λ _i , and the optical waveguide 304 receives a DC light having a reference wavelength λ _j . Wavelength λ _i incident on optical waveguide 301
The input optical signal is once converted into an electrical signal by the photoelectric conversion element 302, then amplified by the electrical amplifier 303, and applied to the external modulator 305. The external modulator 305 amplitude-modulates the DC light of wavelength λ _j input from the optical waveguide 304 according to the output of the electric amplifier 303 and outputs it to the optical waveguide 306 .

That is, the optical signal output from the optical waveguide 306 is modulated with the same information as the input optical signal of wavelength λ _i , and the wavelength matches the wavelength λ _j of the reference DC light.
The input optical signal having the wavelength λ _i input to the optical waveguide 301 in this manner is equivalently converted into a wavelength λ _j and output from the optical waveguide 306 . The external modulator 305 may be an optical modulator using electrical/optical effects described in Applied Physics Letters, 1974, Vol. 24, page 622, or
You can use the one using the semiconductor laser listed in the Proceedings of the 1957 National Conference, lecture number 873.

FIG. 4 shows wavelength conversion switches 100 to 102 and 11 in the first embodiment of the present invention shown in FIG.
It is a figure which shows the 2nd specific example of 8-120. Fourth
In the figures, the same numbers as in FIGS. 2 and 7 represent the same components as in FIGS. 2 and 7, respectively.

In FIG. 4, a wavelength selection element 401 selects an optical signal having a wavelength λ 1 from among optical signals having wavelengths λ ₁ to _{λ 4} applied to an input optical waveguide 700 to a wavelength converter 20.
Output to 9. Similarly, wavelength selection elements 402, 40
3,404 selectively outputs optical signals of wavelengths λ ₂ , λ ₃ , and λ ₄ to wavelength converters 208 , 207 , and 206 . On the other hand, the wavelength selection elements 409 to 412 are connected to the control terminal 4
Among the reference lights having wavelengths of λ ₁ to _{λ 4} applied from the reference light generator 121 in FIG. Selected output is made to the inputs of the devices 206 to 209. The wavelength converters 206 to 209 connect the wavelength selection elements 401 to 409 so that the output wavelengths are the same as the DC light from the wavelength selection elements 409 to 412, respectively.
The wavelength of the optical signal from 404 is converted.

In FIG. 4, for example, if wavelengths λ ₂ and λ ₁ are assigned as selection wavelengths of wavelength selection elements 410 and 411, respectively, by a control circuit (not shown),
DC lights of wavelengths λ ₂ and λ ₁ are supplied to the wavelength converters 207 and 208. As a result, the wavelength selection element 40
The optical signal of wavelength λ ₂ from wavelength converter 208 is converted to wavelength λ ₁ by wavelength converter 208, and the optical signal of wavelength λ ₃ from wavelength selection element 403 is converted to wavelength λ ₂ by wavelength converter 207. After that, it is outputted to an output optical waveguide 716 via an optical multiplexer 710.

As mentioned above, the wavelength conversion switch in Fig. 4 is
It has this function of converting the wavelength of the optical signal of wavelength λ ₁ to _{λ 4} applied to the input optical waveguide 700 and outputting it to the output optical waveguide 716, and the output wavelength is converted to the reference light generator applied to the optical waveguide 200. The wavelength matches the wavelength of the reference light from 121.

FIG. 5 is a diagram showing a second embodiment of the present invention, and shows a wavelength division multiplexing communication network including a plurality of wavelength division multiplexing optical switches. In FIG. 5, a reference light generator 500 is provided with a plurality of light sources, similar to the reference light generator 121 of the first embodiment of the present invention shown in FIG. output,
Wavelength multiplexing optical exchangers 501, 502, 50 are connected by optical fiber cables 511, 512, 513, respectively.
3. Wavelength multiplexing optical switch 501-5
03 has the same configuration as the wavelength division multiplexing optical switch shown in FIG. 1, but the difference is that the reference signal generator 12
Optical fiber cable 511~ in place of the output light of 1
The wavelength conversion is performed by modulating the reference light supplied by 513 within each wavelength conversion switch. As a result, the wavelength division multiplexing optical switch 5
The wavelengths of the output optical signals 01 to 503 all match the wavelengths of the reference light output from the reference light generator 500. Furthermore, by temperature-compensating only the light source in the reference light generator 500 to eliminate wavelength fluctuations due to temperature changes, fluctuations in the output optical signal wavelengths of the wavelength multiplexing optical exchangers 501 to 503 can also be prevented. As a result, the wavelength multiplexed output optical signal from the wavelength multiplexing optical exchange 501 is transmitted to the wavelength multiplexing optical exchange 502 via the optical fiber cable 521, and the optical waveguide 6 in FIG.
When the wavelengths are inputted to the wavelength conversion switch 100 via the wavelength conversion switch 100 via the wavelength conversion switch 100, since the wavelengths are different, it is possible to prevent the wavelengths from being mixed into adjacent wavelengths within the wavelength conversion switch 100. Similarly, the wavelength multiplexed output optical signal from the wavelength multiplexing optical exchange 502 is transmitted to the optical fiber cable 502.
0 to the wavelength division multiplexing optical exchange 501, it is possible to prevent mixing into adjacent wavelengths due to different wavelengths. Furthermore, an optical fiber cable 5 is connected between the wavelength division multiplexing optical exchangers 502 and 503.
22,523, the optical fiber cable 52 connects the wavelength division multiplexing optical exchange 503,501
When connecting with 4,525, communication is still possible without interference with adjacent wavelengths.

As a result, for example, an optical signal with a wavelength λ ₃ is sent from the wavelength multiplexing optical exchange 501 through the optical fiber 524 to the wavelength multiplexing optical exchange 503 having a configuration similar to that shown in FIG. Even if it is incident, the wavelength is accurate, so normal exchange operation is possible. Further, this optical signal is wavelength-converted to wavelength λ ₄ by the wavelength conversion switch 100, and then transmitted to the wavelength conversion switch 120 via the wavelength conversion switch 609.
Even if the wavelength is further converted into wavelength λ ₁ and sent to the wavelength multiplexing optical exchange 502 via the optical waveguide 636 connected to the optical fiber 523 in FIG. 5, the wavelength is accurate, so normal switching operation is possible. is possible.

Note that the same effect can be obtained even if the outputs of the light sources in the reference light generator 500 are not multiplexed but are supplied to each wavelength division multiplexing optical exchange through different optical fiber cables for each wavelength.

(Effects of the Invention) As described above, according to the present invention, the wavelength of the output optical signal does not shift due to variations in the material composition of the wavelength conversion element of the wavelength conversion switch, and the wavelength of the output optical signal does not fluctuate due to temperature changes. A multiplex optical switch and a wavelength multiplexed optical communication network are obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a first embodiment of the present invention, and FIG.
The figure shows a first specific example of the first wavelength conversion switches 100 to 102 and 118 to 120;
The figure shows a specific example of the wavelength converters 206-209 in FIG. 2, and FIG. 4 shows the wavelength conversion switches 100-102 and 118-120 in FIG.
FIG. 5 is a diagram showing a second specific example of the present invention.
FIG. 6 is a diagram showing the configuration of a conventional wavelength multiplexing optical converter, and FIG. 7 is a diagram showing an example of the wavelength conversion switches 600-602 and 618-6 in FIG.
FIG. 8 is a diagram showing the configuration of wavelength selection switches 609 to 617 in FIG. 6. In the figure, 100-102, 118-120,
600-602, 618-620 are wavelength conversion switches, 121,500 are reference light generators, 12
2 to 125 are light sources, 126, 710, and 808 are optical multiplexers, 128 is an optical splitter, 201 to 20
4,401~404,409~419,701~
705, 801 to 804 are wavelength selection elements, 20
6 to 209 are wavelength converters, 302 is a photoelectric conversion element, 303 is an electric amplifier, 305 is an external modulator, and 501 to 503 are wavelength multiplexing optical exchangers, respectively.

Claims (1)

[Scope of Claims] 1. First and second wavelength conversion switches having the function of converting and outputting the wavelength of a wavelength-multiplexed input signal, and converting the output of the first wavelength conversion switch to any of the wavelength conversion switches. A wavelength division multiplexing optical exchange device comprising a means for connecting to the first and second wavelength conversion switches, further comprising a reference light generator that outputs light of a plurality of wavelengths, and a reference light generator that outputs light of a plurality of wavelengths; A wavelength multiplexing optical converter characterized in that wavelength conversion is performed by modulating one arbitrary wavelength of the output light of the reference light generator with an arbitrary optical signal of the optical signal. 2. First and second wavelength conversion switches having the function of converting and outputting the wavelength of a wavelength-multiplexed input signal, and connecting the output of the first wavelength conversion switch to any of the second wavelength conversion switches. A wavelength division multiplexing optical communication network comprising a plurality of wavelength division multiplexing optical exchanges having means for and distributes the output light of the reference light generator to the plurality of wavelength multiplexing optical exchangers, and generates the reference light using an arbitrary optical signal of the wavelength multiplexed optical signals inputted to the first and second wavelength conversion switches. A wavelength multiplexing optical communication network characterized by performing wavelength conversion by modulating one arbitrary wavelength of output light from a device.