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Optical signal amplifying triode and optical signal transfer method, optical signal relay device, and optical signal storage device using the same

Foreign code F110005722
File No. Y0345WO
Posted date Sep 12, 2011
Country United States of America
Application number 53242203
Gazette No. 20060008203
Gazette No. 7274841
Date of filing Sep 19, 2003
Gazette Date Jan 12, 2006
Gazette Date Sep 25, 2007
International application number JP2003011961
International publication number WO2004038492
Date of international filing Sep 19, 2003
Date of international publication May 6, 2004
Priority data
  • P2002-308946 (Oct 23, 2002) JP
  • P2003-059382 (Mar 6, 2003) JP
  • P2003-287576 (Aug 6, 2003) JP
Title Optical signal amplifying triode and optical signal transfer method, optical signal relay device, and optical signal storage device using the same
Abstract When in an optical signal amplifying triode 10 , light of a second wavelength lambda2, selected from among light from a first optical amplifier 26 , into which a first input light L1 of a first wavelength lambda1 and a second input light L2 of second wavelength lambda2 have been input, and a third input light (control light) L3of a third wavelength lambda3 are input into a second optical amplifier 34 , an output light L4 of the third wavelength lambda3, selected from among the light output from the second optical amplifier 34 , is light that is modulated in response to the intensity variation of one or both of the first input light L1 of the first wavelength lambda1 and the third input light L3 of the third wavelength lambda3 and is an amplified signal, with which the signal gain with respect to the third input light (control light) L3 of the third wavelength lambda3 is of a magnitude of 2 or more. An optical signal amplifying triode 10 , which can directly perform an optical signal amplification process using control input light, can thus be provided.
Outline of related art and contending technology BACKGROUND ART
Wide deployment of moving image communication, video distribution, and other new broadband services, using optical fiber communication that enables broadband and high-speed transmission, is anticipated. However, a functional (signal amplification) element, which, for example, corresponds to a triode transistor in electronics, that is, an optical functional element that performs signal amplification of optical signals by direct control by other optical signals has not been realized as of yet.
Thus presently, optical signals that have been transmitted at high speed are converted once into electrical signals, which are then subject to information processing in an electronic circuit, and the processed signals are converted back into and transmitted as optical signals. A limit is thus placed in the speed of signal processing due to the inability to directly control light by light. It is said that if signal processing can be performed on optical signals as they are, parallel processing will be enabled and further shortening of the processing time can be anticipated.
In this regard, the devices described in Document 1 or Document 2 are simply devices that switch light, in other words, gate switching devices that make use of wavelength conversion by Mach-Zehnder optical interferometry, and these devices had problems of being weak against temperature change and vibration and being strict in terms of setting conditions. Such conventional arts do not disclose anything in regard to arranging an optical signal amplifying triode, which, like a transistor in an electronic circuit, is equipped with a function of using input light as control light to obtain signal-amplified output light.
In the field of optical communication enabling broadband, high-speed, and high-capacity signal transmission, it is anticipated that communication, transfer, and distribution of optical signals be performed without degradation of the properties of high speed and high capacity. For an optical network based on wavelength division multiplexing (WDM), which is predicted to be constructed in the relatively near future, an optical signal transfer (optical signal relaying) art, of transferring wavelength division multiplexed optical signals, which are a plurality of types of laser light differing in wavelength and which have been transmitted from one optical transmission path, to desired optical transmission paths according to wavelength, will be important. In optical signal transfer for transferring an optical signal train (for example, a packet signal) that has been propagated via an optical fiber or other predetermined transmission path (for example, a wavelength bus) to other transmission paths indicated by labels, tags, or other routing information attached to the optical signal train, that is for example, in routing within an optical network or among optical networks, the high-capacity and high-speed characteristics of optical signal transmission must not be degraded and routers, that is, optical signal relay (transfer) devices are required to perform transfer processes at high-speed, be high in reliability, and be compact.
An optical path cross-connection device, such as that described in Document 3, has been proposed for this purpose. This device is equipped with a wavelength splitter, which splits a wavelength bus for wavelength multiplex transmission link into N wavelength group buses of G wavelengths each, and a routing processor, which executes a routing process on each of the wavelength groups split by the wavelength splitter, and is thus arranged to perform the routing process according to wavelength group. The routing processor of this optical path cross-connection device comprises a wavelength converter, which performs wavelength conversion according to each wavelength group, and an optical matrix switch, which distributes the wavelength-converted light and is controlled by a controller. This optical matrix switch is arranged with a mechanically-operated reflecting mirror switch that is positioned at the intersection of matrix-like optical paths and is alternatively operated by the controller to make one wavelength group, among the plurality of wavelength groups, be reflected by the reflecting mirror switch and thereby be output to a desired transmission path (paragraph 0042, FIG. 10(1)), or has an optical switch, which is alternatively operated by the controller, and mesh wiring and is arranged to make one wavelength group, among the plurality of wavelength groups, be transmitted by the optical switch and thereby be output to one transmission path inside the mesh wiring (paragraph 0043, FIG. 10(2)).
However, with the above-described conventional optical path cross-connection device, since the routing process is performed by the reflecting mirror switch or the optical switch, the operation of which is controlled by the controller, the switching operation of the reflecting mirror switch or the optical switch is performed in accordance with a command signal, which indicates the routing destination (destination) and is an output that is electronically processed at the controller. A portion of the optical signal thus had to be converted to an electrical signal, the destination information contained in the electrical signal, that is, a transfer-related signal included in a label or tag of a packet had to be extracted, and the optical signal had to transferred upon electrically controlling the operation of the reflecting mirror switch or the optical switch in accordance with the transfer-related signal. Thus, an adequate response speed could not be obtained. Also besides the above-described routing processor, since a wavelength converter, for performing wavelength conversion in accordance with the wavelength of the transmission path (wavelength bus) of the transfer destination, is equipped, and such a wavelength converter is disposed in addition to the routing processor, the device became large and in some cases, especially when a mechanically operated reflecting mirror switch is used, reliability could not be obtained.
Furthermore, in the field of optical communication enabling broadband, high-speed, and high-capacity signal transmission, it is anticipated that the identification, multiplexing and splitting, switching, and routing (transfer, distribution) of optical signals (optical data, such as packet signals) be performed without degrading the characteristics of broadband, high speed, and high capacity. In this field of optics, optical signal storage devices, which enable temporary storage and take-out at desired timings of optical signals, are generally demanded for optical signal processing systems that process optical signals and are represented, for example, by photonic router systems. This is because, just as memories are essential in signal processing in the field of electronics, optical signal storage devices, referred to as optical memories or optical buffers, are essential in the field of optical signal processing.
In this regard, optical memory devices, such as that described in Patent Document 1, have been proposed. With this device, a plurality of optical waveguide means 105 to 108, respectively arranged from optical fibers of different length in order to provide a plurality of types of delay times, are prepared, and arrangements to pass an optical signal through any of optical waveguide means 105 to 108 and enable storage of the optical signal by just the delay time corresponding to the propagation time in the corresponding optical waveguide means among optical waveguide means 105 to 108.
However, with this conventional optical memory device, the storage time of an optical signal is only determined in advance by the delay time corresponding to the propagation time in the optical waveguide means among optical waveguide means 105 to 108 through which the optical signal is made to propagate and the optical signal thus cannot be taken out at a desired timing. The degree of freedom of optical signal processing was thus limited and lowering of signal processing efficiency could not be avoided.
[Document 1] K. E. Stubkjaer, “Semiconductor optical amplifier-based all-optical gates for high-speed optical processing,” IEEE J. Quantum Electron., vol. 6, no. 6, pp. 1428-1435, November/December 2000.
[Document 2] T. Durhuus, C. Joergensen, B. Mikkelsen, R. J. S. Pedersen, and A. E. Stubkjaer, “All optical wavelength conversion by SOAs in a Mach-Zehnder configuration,” IEEE Photon. Technol. Lett., vol. 6, pp. 53-55, January 1994.
[Document 3] Japanese Published Unexamined Patent Application No. 2002-262319
[Document 4] Japanese Published Unexamined Patent Application No. Hei 8-204718
This invention has been made with the above circumstances as a background, and a first object thereof is to provide an optical signal amplifying triode that can perform an amplification process directly on optical signals by using control light. A second object is to provide an optical signal transfer method and an optical signal relay device, with which the routing of optical signals can be processed at high speed or by a compact device. A third object is to provide an optical signal storage device that enables storage of optical signals and taking out of the optical signals at an arbitrary time.
Upon carrying out various examinations with the above circumstances as the background, the present inventor found that in an optical amplifier, such as a semiconductor optical amplifier, a rare-earth-element-doped fiber amp, etc., spontaneously emitted light of peripheral wavelengths of an input light of a predetermined wavelength λ1 vary in intensity in response to intensity variations of the input light and this intensity variation varies inversely with respect to that of the signal intensity variation of the input light, and found a laser-induced signal enhancement effect, that is, a phenomenon wherein when laser light of another wavelength λ2 within the wavelength range of the spontaneously emitted light, that is, within the peripheral wavelength range of the input light is made incident upon being multiplexed with the input light, the overall intensity increases suddenly, with the signal (amplitude) variation of the spontaneously emitted light being maintained. The present inventor grasped this phenomenon as a wavelength conversion function from wavelength λ1 to λ2 and conceived an optical triode based on a tandem wavelength converter (All-Optical Triode Based on Tandem Wavelength Converter), with which this wavelength conversion is connected in two stages, and thus came to conceive an optical signal amplifying triode. A first aspect of this invention was made based on this knowledge.
The present inventor also noted that the optical amplifier of the above-mentioned optical signal amplifying triode not only has the function of wavelength conversion from wavelength λ1 to λ2 but is also a functional element equipped with the wavelength conversion function and a switching function and found that, by multiplexing optical signals with routing information by amplitude modulation, the functional element can be used favorably as a routing device, that is, a transfer device for wavelength multiplexed signals. A second and a third aspect of this invention was made based on this knowledge.
The present inventor also found that by making an optical amplifier of an optical signal amplifying triode, which exhibits the above-described phenomenon, perform the function of wavelength conversion from wavelength λ1 to λ2 and at the same time combining this optical amplifier with a wavelength splitter that performs distribution to different output transmission paths in accordance with the input wavelengths and interposing this combination in a ring transmission path in which optical signals circulate, the optical signals that are stored by being made to circulate can be taken out at an arbitrary timing. A fourth aspect of this invention was made based on this knowledge.
Scope of claims [claim1]
1. An optical signal storage device, storing an optical signal input from an input optical transmission path and enabling taking out of the optical signal at an arbitrary time, comprising:
a control light generator, generating control light for converting the optical signal input from the input optical transmission path to wavelengths, which correspond to the transmission destinations contained in the input signal and are the same as or different from that of the optical signal;
a main optical signal amplifying triode unit, receiving the optical signal that has been input and the control light and converting the optical signal that has been input to optical signals of the wavelengths of the control light;
an optical distributor, distributing the optical signals, output from the main optical signal amplifying triode unit, in accordance with the wavelengths of the optical signals;
an optical buffer memory element, temporarily storing an optical signal of a storage wavelength that has been distributed by the optical distributor;
an optical feedback transmission path, feeding back the optical signal output from the optical buffer memory element to the input optical transmission path to re-input the optical signal into the main optical signal amplifying triode unit; and
an optical signal storage control means, making the control light generator output control light for conversion of the optical signal, which is repeatedly circulated through the main optical signal amplifying triode unit, optical distributor, optical buffer memory element, and the optical feedback transmission path, to an output wavelength at the main optical signal amplifying triode unit.

[claim2]
2. The optical signal storage device according to claim 1, further comprising an optical signal gain control means, controlling the optical signal, fed back by the optical feedback transmission path, or the control light supplied to the main optical signal amplifying triode unit in order to restrain the increase and decrease of the gain of the optical signal that is circulated.

[claim3]
3. The optical signal storage device according to claim 2, wherein the main optical signal amplifying triode unit comprises: a first semiconductor optical amplifier, which performs conversion to a wavelength of a bias light and inversion of the optical signal; and a second semiconductor optical amplifier, which performs conversion to the wavelength of the control light and inversion of the optical signal that has been inverted by the first semiconductor optical amplifier; and
the optical signal gain control means controls the optical signal, fed back to the optical feedback transmission path, based on the increase or decrease of the gain of the bias light contained in the output light from the second semiconductor optical amplifier.

[claim4]
4. The optical signal storage device according to claim 2, wherein the optical signal gain control means comprises: a first gain control optical amplifier, receiving the bias light and a gain control light, which is a continuous light of a wavelength that differs from that of the bias light, and outputs a gain control light, which decreases in gain in accompaniment with an increase of the gain of the bias light; and a second gain control optical amplifier, receiving the output light from the first gain control optical amplifier and the optical signal, which is fed back by the optical feedback transmission path, and outputs an optical signal, which increases in gain in accompaniment with a decrease of the gain of the gain control light.

[claim5]
5. The optical signal storage device according to claim 4, wherein either or each of the first gain control optical amplifier and second gain control optical amplifier is arranged from an optical fiber amplifier or an optical waveguide amplifier into which a rare earth element is doped.

[claim6]
6. The optical signal storage device according to claim 2, wherein the optical signal gain control means comprises: an optical operational controller, which controls the gain of the control light supplied to the main optical signal amplifying triode unit based on the increase/decrease of the gain of the optical signal fed back by the optical feedback transmission path in order to maintain fixed the gain of the optical signal that is circulated.

[claim7]
7. The optical signal storage device according to claim 1, further comprising:
an electronic controller, controlling the control light generator;
a photoelectric signal converter, converting the optical signal branched by the optic splitter into an electrical signal and supplying the electrical signal to the electronic controller; and
an optical delay element, disposed at the downstream side of the optical splitter and delaying the optical signal that is to be input into the main optical signal amplifying triode unit upon passage through optical splitter; and
wherein the electronic controller makes the control light, for conversion of the optical signal to the output wavelength, be generated from the control light generator in response to an output timing indicated by stored signal output information that is supplied from the exterior or is contained in the optical signal.

[claim8]
8. The optical signal storage device according to claim 1, further comprising an all-optical operational controller, which makes the control light, for conversion of the optical signal to the output wavelength, be generated from the control light generator in response to an output timing indicated by stored signal output information that is supplied from the exterior or is contained in the optical signal.
  • Inventor, and Inventor/Applicant
  • MAEDA YOSHINOBU
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
IPC(International Patent Classification)
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