JPH0445428A - Optical wavelength converter - Google Patents

Abstract

PURPOSE:To allow the sepn. of an input signal and conversion output with an optical directional coupler and to obtain the simple device by adopting the constitution to allow the incidence of wavelength multiplex signals and 1st probe light from one side of the input and output parts of an optical amplifier and 2nd probe light from the opposite side. CONSTITUTION:The wavelength multiplex signals 3 (designated as S1 to S4) are multiplexed with the 1st probe light 1 by the optical directional coupler 5 and are made incident on the optical amplifier 4. The 2nd probe light 2 is made incident on the optical amplifier 4 from the side reverse therefrom. The frequency (wavelength) of the 1st probe light 1 is set in proximity to the frequency (wavelength) of the channel S1 to be converted. The mixing of the four light waves in the optical amplifier is generated only between the signals of the proximate frequencies and, therefore, the channel where the mixing of the 4 light waves with the 1st probe light 1 is only in the channel of S1 and the other channels do not interfere. Then, the taking out of the f2+ or -DELTAf alone is allowed by making the 2nd probe light 2 incident in the direction reverse from the 1st probe light 1. The sepn. of the signal to be converted and the conversion signal is executed by the simple directional coupler. The need for optical filters is eliminated and the device constitution is simplified.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention extracts an optical signal of a specific wavelength from a wavelength-multiplexed optical signal, and transfers the extracted optical signal to a different wavelength. ) Concerning a conversion device.

[Conventional technology]

In addition to a wavelength-multiplexed optical signal, two types of probe lights are input into an optical amplifier from the same direction, and the wavelengths are converted using the four-wave mixing phenomenon that occurs between them. In other words, the wavelength of the first probe light is A system that selectively causes a four-wave mixing phenomenon by setting it near the signal light of a predetermined channel and converts only the signal component to the wavelength of the remaining second probe light is proposed by G. Grosskot et al. : Frequency Conversion Using Semiconductor Laser Amplifiers for Coherent Optical Frequency Division Switches: IOC, 1989, 19C,
4-4, pp. 136-137 (G.

Grosskoph et al.: Freque
ncy Conversio+with Sem1c
onductor La5er Amplifier
rs for Coherent 0ptical
Frequency-DivisionS t++i
tching: I○○C, 1989, 19C4-
4°pρ, 136-137).

[Problem to be solved by the invention]

However, the above conventional method has various problems as described below.

First, in the conventional method described above, when the second probe light is set in a wavelength range close to the optical signal, four-wave mixing occurs between the second probe light and the optical signal, which causes crosstalk between the optical signals. Put it away. Therefore, the wavelength of the second probe light (conversion destination wavelength) must be set in a different region from that of the wavelength multiplexed signal.

Therefore, in order to exchange signals between wavelength multiplexed signals, first convert the wavelength to a wavelength range outside the wavelength range where the -degree signal exists, remove unnecessary signals with a predetermined optical filter, and then perform wavelength conversion again. It is necessary to perform an operation to return to the original wavelength range.

Therefore, the device configuration becomes complicated.

Further, even when a single wavelength conversion is performed, the above-mentioned conventional technology requires a narrow band optical filter in addition to an optical amplifier to configure the device. However, it is not easy to realize a narrow band optical filter. Currently, the only optical filters that can be used are waveguide type optical filters or L
An active filter using D (laser diodes), etc. can be considered.

In either case, it is necessary to precisely control the temperature of the element in order to stabilize the selected wavelength, so they lack practicality.

Furthermore, in the above-mentioned prior art, the selection of the signal to be converted and the setting of the conversion destination wavelength are performed by switching the wavelength of the incident probe light.

However, switching the wavelength of a tunable wavelength light source requires accurately changing parameters such as injection current and element temperature, which usually requires a time of about milliseconds, and the wavelength switching speed is slow.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical wavelength conversion device that can solve the above-mentioned problems of the prior art and has a simple device configuration.

[Means to solve the problem]

In order to achieve the above object, the present invention employs the following configuration.

First, the wavelength-multiplexed optical signal and the first probe light are input to the input/output section on one side of an optical waveguide made of a nonlinear optical medium that functions as an optical amplifier, and the input/output section on the opposite side is input. In addition, a second probe light having a different wavelength from the first probe light is made incident.

Second, at the input/output section on one side of the optical amplifier, a wavelength multiplexed optical signal with a predetermined polarization plane, a first probe light having the same polarization plane, and a first probe light having a different wavelength and A second probe light whose polarization plane is perpendicular to each other is input, and a device for separating the emitted light according to the polarization plane is connected to the input/output section on the opposite side.

Third, a wavelength-multiplexed optical signal having a predetermined polarization plane and a first probe light having the same polarization plane are input to the input/output section on one side of the optical amplifier, and the input/output section on the opposite side is inputted. To,
A configuration is adopted in which a second probe light having a polarization plane orthogonal to the polarization plane of the first probe light and having a wavelength different from that of the first probe light is incident.

Fourth, a device for multiplexing the wavelength multiplexed signal having the same polarization plane and the first probe light, and a means for separating the lights according to the polarization plane are connected in cascade to the input/output section on one side of the optical amplifier. The configuration is such that a second probe light whose wavelength is different from that of the first probe light and whose polarization plane is perpendicular to that of the first probe light is made to enter the input/output section on the opposite side.

Fifth, the configuration is such that one or both of the first probe light and the second probe light in the above configuration is obtained by switching a plurality of fixed wavelength light sources that emit light at different wavelengths using an optical switch.

Sixth, two or more light wave conversion devices, for example n
The wavelength-multiplexed optical signal is branched into n outputs to supply the wavelength-multiplexed optical signal to each device when the devices are arranged in parallel. The configuration is such that it is separated according to frequency.

Furthermore, the 8th. Ninth, as the nonlinear optical medium, a semiconductor into which carriers are injected and a dielectric material containing a rare earth element excited by pump light are used.

[Effect]

The wavelength-converted signal propagates in the same direction as the second probe light. Therefore, if the second probe light is incident on the optical amplifier in the opposite direction to the wavelength-multiplexed optical signal and the first probe light, the wavelength converted output will be in the opposite direction to the first probe light and the wavelength-multiplexed optical signal. Therefore, it is possible to separate the input signal component and the output signal component (wavelength conversion output) using a directional coupler. This eliminates the need for a precise optical filter and significantly simplifies the device configuration.

Furthermore, by making the polarization planes of the wavelength-multiplexed optical signal and the first probe light the same and setting the second probe light to have a different polarization plane, the polarization plane between the wavelength-multiplexed optical signal and the second probe light can be changed. Since the four-wave mixing is suppressed, crosstalk between signals will not occur even if the wavelength of the second probe light and the input signal are selected to be in the same wavelength range. This makes it possible to exchange signals between wavelength-multiplexed optical signals with a single wavelength conversion, thereby simplifying the configuration of the device.

In addition, instead of switching the conversion wavelength using a variable wavelength light source, if you use an optical switch to switch between multiple fixed wavelength light sources that emit light at different wavelengths, the time required to switch the wavelength will be the same as the switching time of the optical switch. It becomes only. Optical switches that operate at a frequency of several hundred MHz to several GHz have already been reported, and by adopting this configuration, the time required for wavelength switching is significantly shortened.

〔Example〕

FIG. 1 is an optical system diagram showing a first embodiment of the present invention and a diagram explaining the input/output relationship using a frequency spectrum. The wavelength multiplexed optical signal 3 (denoted as S□ to S4) is the first
The probe light 1 is multiplexed by the optical directional coupler 5 and input to the optical amplifier 4.

The second probe light 2 enters the optical amplifier 4 from the opposite side. The frequency (wavelength) of the first probe light 1 is set close to the frequency (wavelength) of the channel S1 to be converted. Since the four-wave mixing phenomenon in the optical amplifier occurs only between signals with close frequencies, only the channel S produces four-wave mixing with the first probe light 1, and other channels do not interfere. Now, number 1. If the frequencies of the second probe lights 1 and 2 are f and f2, and the frequency difference between Sl and the first probe light 1 is Δf, then 4
The frequency of the signal generated by light wave mixing is f□+Δf,fl
−2Δf, f, ±Δf. Among these signals, f
1+Δf and fl−2Δf are waves that propagate in the same direction as the first probe light 1, but f2±Δf appears as waves that propagate in the same direction as the second probe light 2. Therefore, by making the second probe light 2 incident in the opposite direction to the first probe light 1, it becomes possible to independently extract the signal j2±Δf. This resulted in 81 signals!
, -f1 corresponds to frequency conversion (wavelength conversion). Moreover, since the signal to be converted and the converted signal can be separated by a simple directional coupler, and complicated parts such as optical filters are not required, the device configuration is simplified. The diagram at the bottom of Figure 1 shows the above frequency conversion on a spectrum, and shows the relationship between the wavelength multiplexed optical signals 81 to S4, the 1st and 2nd probe lights 1 and 2, and the frequency conversion output. ing. 81 is selected from the multiplexed optical signal by the first probe light 1 placed near the optical signal S1 to be converted, and the information is converted into the frequency range of the second probe light 2. There is.

FIG. 2 shows another embodiment of the present invention, the characteristics of which are that the polarization planes of the first probe light 1 and the multiplexed optical signal 3 are matched, and the second probe light 2 is orthogonal to the polarization plane of the first probe light 1 and the multiplexed optical signal 3. The reason is that it is a polarized plane of light. By doing this, interference between the second probe light 2 and the multiplexed optical signal 3 is eliminated. Therefore, it becomes possible to arbitrarily set the wavelength (frequency) of the second probe light 2. On the other hand, in the case of a configuration in which the plane of polarization is not orthogonal between the multiplexed optical signal and the second probe light, it is necessary to set the wavelength of the second probe light away from the wavelength range of the multiplexed optical signal. Since this embodiment does not have this restriction, it is possible to exchange signals between multiplexed optical signals in a single conversion, and the device configuration is significantly simplified. (a=1) The configuration in the figure is the first and second
The probe lights of 2 are incident from the same direction, and the signal to be converted (multiplexed optical signal) and the converted output are separated by a polarizer 6. Figure (a-2) shows the frequency spectrum in that case. This is what is shown. In addition, the TE wave in the figure, T
The M wave is an example of light whose polarization planes are orthogonal to each other, and when a transverse electric field (TE) wave is used as the first probe light, the second
As a probe light, a transverse magnetic field (
TM) wave is used. Also, (b
) In the configuration shown in the figure, the first probe light 1 and the second probe light 2 are incident from opposite directions, and the converted signal (multiplexed optical signal) and the converted output are separated as in the case of the embodiment shown in FIG. In this example, the optical directional coupler 5 is used. The structure of figure (c) is the same as the structure of figure 1. Second probe light 1
, 2 are incident from opposite directions, but the feature is that the conversion outputs are separated by a polarization splitter [7].

FIG. 3 shows yet another embodiment of the present invention, the feature of which is that the wavelength of the probe signal is switched by connecting the outputs of a plurality of fixed wavelength light sources with different wavelengths using an optical switch 8. The point is that As a result, the time required for wavelength switching is reduced to only the switching time of the optical switch, which can be significantly shortened compared to the switching time when a variable wavelength light source is used. Furthermore, since the light source may have a fixed wavelength, the stability of wavelength setting is also improved. In figure (a),
A first probe light obtained by selecting one wave of frequencies f□ to J4 by the optical space switch 8.

The second probe light is made incident on the optical amplifier from the same direction, and the optical filter 9 separates the signal to be converted (multiplexed optical signal) and the converted output. Incidentally, as in the case of the embodiment in FIG. 2, if the plane of polarization of each optical signal is appropriately set, separation can also be performed using a polarizer. (b) The figure shows the first
This is an example in which the second probe light and the second probe light are incident on the optical amplifier 4 from opposite directions.

(c) The figure shows a signal that is wavelength-multiplexed with n-wave channels.
This is an example of the configuration of a device that performs mutual wavelength conversion at once. In this configuration example, the wavelength multiplexed optical signal 3 is divided into n outputs by the optical branching section 10, and wavelength conversion is performed on each output. The wavelength of the probe signal is determined corresponding to each channel. Therefore, nX as shown in (C)
Even in the case of the n configuration, n fixed wavelength light sources are sufficient, as in the case of wavelength conversion of only one channel as shown in FIGS. Therefore, a device configuration using a combination of a fixed wavelength light source and an optical switch has no difference in terms of the number of parts compared to a configuration using a variable wavelength light source. Optical branch part 1
In addition to a normal star coupler, it is also possible to use an optical demultiplexer that splits light into frequencies. A feature of using an optical demultiplexer is that there is no attenuation of signal strength due to branching.

The optical amplifier 4 in the embodiments of FIGS. 1 to 3 described above is an optical waveguide made of a nonlinear optical medium. In this case, the nonlinear optical medium may be a semiconductor into which carriers are injected, a dielectric containing a rare earth element excited by pump light, or the like. In addition to the effect of simplifying the device configuration described above, using a leading waveguide formed of the former type of semiconductor has the advantage of making the device extremely compact; If an optical waveguide is used, in addition to the above-mentioned advantages, there is an advantage that the amplification characteristics can be further improved. [Effects of the Invention] According to the present invention, there are the following effects.

(1) According to the configuration of the first invention, in which the wavelength multiplexed signal and the first probe light are inputted from one side of the input/output section of the optical amplifier, and the second probe light is inputted from the opposite side, the input signal and the input signal are converted. It is now possible to separate the output using an optical directional coupler,
Precise optical filters required in conventional configurations are no longer required,
An optical wavelength (frequency) conversion device can be realized with a simple device configuration.

(2) Second. Third. The wavelength multiplexed signal of the fourth invention and the first invention
According to the configuration in which the planes of polarization of the probe light are made to match and the plane of polarization of the second probe light is made to be orthogonal thereto, crosstalk due to interference between the wavelength multiplexed signal and the second probe light is suppressed,
It is no longer necessary to set the wavelength of the second probe light apart from the wavelength range of the wavelength multiplexed signal, and as a result, signals can be exchanged between wavelength multiplexed signals by one wavelength conversion.

(3) Switching the wavelength of the probe signal according to the fifth invention,
By using an optical switch to use a fixed wavelength light source that oscillates at multiple different wavelengths, the time required to switch wavelengths can be significantly shortened compared to when using a variable wavelength light source, and the stability of wavelength settings can be improved. can be improved.

(4) According to the configuration of the sixth invention, in which a signal wavelength-multiplexed with n channels is branched and supplied to the n optical wavelength conversion devices, and the wavelength is converted at - degrees, the n optical wavelength conversion devices A light source will be sufficient.

Therefore, the device configuration using the combination of the fixed wavelength light source and the optical switch of the present invention has the advantage of shortening the time required for wavelength switching as described above, and there is no difference in the number of parts compared to the configuration using the variable wavelength light source. There is an advantage.

(5) According to the configuration in which an optical demultiplexer that separates light by frequency is used for optical branching according to the seventh aspect of the invention, there is an advantage that light can be branched without attenuation of signal strength.

(6) According to the configuration of the eighth invention, in which an optical waveguide made of a semiconductor into which carriers are injected is used in an optical amplifier, the entire device can be made extremely compact.

(7) According to the ninth aspect of the invention, in which the optical amplifier uses a leading waveguide made of a rare-earth element-containing dielectric excited by pump light, the amplification characteristics can be improved by approximately two orders of magnitude compared to the semiconductor configuration described above. It can be improved to some extent.

[Brief explanation of drawings]

FIG. 1 is an optical path diagram and a frequency spectrum diagram of one embodiment of the present invention, and FIG. 21 is a diagram of another embodiment of the present invention. (a-1) is the first. Optical path diagram of an example in which the second probe light is incident from the same direction, (a-2) is its frequency spectrum diagram, (b) is an optical path diagram of an example in which the second probe light is incident from the opposite direction and the output is separated by a directional coupler Route map. (c) is an optical path diagram of an example in which the probe light is incident in the opposite direction and the output is taken out by a polarization separation device, and FIG. 3 is an optical path diagram of still another embodiment of the present invention, which is (a). (b) is a configuration that converts the wavelength of one channel signal.
(c) is a diagram illustrating a configuration for converting n-channel signals at once. Explanation of symbols> 1... First probe light 2... Second probe light 3... Wavelength multiplexed optical signal 4... Optical amplifier 5...
Optical directional coupler 6...Polarizer 7...Polarization separation device! 8... Optical switch 9... Optical filter 10
... Optical Branching Department Patent Attorney Junnosuke Nakamura Diagram (a (backward direction)゛input) (b) (backward slope 0-)゛input) iI output TMjJ 屹 (C) ( Hasukata city profile entry (1st edition) Fig. 2 Fig.

Claims (1)

[Claims] 1. In an optical wavelength conversion device that extracts an optical signal of a specific wavelength from a wavelength-multiplexed optical signal and transfers the optical signal to a different wavelength, an input on one side of an optical waveguide made of a nonlinear optical medium is used. An optical directional coupler for multiplexing the wavelength multiplexed optical signal and the first probe light is connected to the output section, and a second probe light having a wavelength different from the first probe light is connected to the input/output section on the opposite side. An optical wavelength conversion device characterized in that a means for inputting probe light is connected thereto. 2. In an optical wavelength conversion device that extracts an optical signal of a specific wavelength from a wavelength-multiplexed optical signal and transfers the optical signal to a different wavelength, a predetermined a wavelength multiplexed optical signal having a plane of polarization;
A device for multiplexing a first probe light having the same polarization plane and a second probe light having a different wavelength and orthogonal polarization plane to the first probe light is connected, and an input device on the opposite side is connected. An optical wavelength conversion device characterized in that an output section is connected to a device that separates or selects light according to its polarization plane. 3. The wavelength multiplexed optical signal according to claim 1 and the first probe light are lights having the same polarization plane, and the second probe light is light having a polarization plane orthogonal thereto. Optical wavelength conversion device. 4. In an optical wavelength conversion device that extracts an optical signal of a specific wavelength from a wavelength-multiplexed optical signal and transfers that optical signal to a different wavelength, the same A device for combining a wavelength multiplexed optical signal set to have a polarization plane and a first probe light, and a means for separating the light according to the polarization plane are connected in cascade, and An optical wavelength conversion device, characterized in that a means for inputting a second probe light having a wavelength different from that of the first probe light and a plane of polarization perpendicular to the first probe light is connected thereto. 5. The means for forming at least one of the first probe light and the second probe light according to claims 1 to 4 receives light from a plurality of light sources emitting light at different wavelengths and switches the optical path. 1. An optical wavelength conversion device comprising a switch that outputs light of a predetermined wavelength. 6. At least two optical wavelength conversion devices according to claims 1 to 5 are used, and the supply of wavelength-multiplexed optical signals to these optical wavelength conversion devices is performed via means for branching the wavelength-multiplexed optical signals. Features of optical wavelength conversion device. 7. The means for branching the wavelength multiplexed optical signal according to claim 6,
An optical wavelength conversion device characterized by having a function of separating light according to frequency. 8. An optical wavelength conversion device, wherein the nonlinear optical medium according to claim 1 is made of a semiconductor into which carriers are injected. 9. An optical wavelength conversion device, wherein the nonlinear optical medium according to any one of claims 1 to 7 is made of a dielectric material containing a rare earth element excited by pump light.