JP2004048700A - Optical multiplex communication method, optical multiplex communication system, optical signal multiplexing device, and optical multiplex signal demultiplexing device - Google Patents

Abstract

An optical multiplex communication method, an optical multiplex communication system, an optical signal multiplexing device, and an optical multiplexing signal demultiplexing device that realize ultra-high-speed transmission using an optical multiplexing signal having a pulse width that can be easily transmitted at low cost. I do.
An optical signal multiplexing device encodes and generates a plurality of optical pulse trains each having a specific amplitude for each communication channel as an optical signal, and multiplexes the plurality of optical pulse trains on a time axis to perform optical multiplexing. The optical multiplexing signal separation device, which generates and transmits a signal and receives the optical multiplexing signal transmitted through the optical transmission line, inputs the optical multiplexing signal to the optical frequency conversion unit, The optical pulse train is converted into a plurality of different optical pulse trains, and the plurality of optical pulse trains are separated for each communication channel.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical signal multiplex communication method, an optical multiplex communication system, an optical signal multiplexing apparatus, and an optical multiplex signal demultiplexing apparatus in a high-speed optical transmission system, a wavelength multiplex transmission system, an optical signal processing system, and the like.
[0002]
[Prior art]
With the rapid increase in traffic in data communication, ultra-high-speed optical transmission systems aiming at increasing the capacity of optical communication systems are being studied. Specifically, attempts have been made to replace the demultiplexing circuit constituted by an electronic circuit with an all-optical type optical signal processing circuit to eliminate the electronic circuit limitation of transmission speed.
[0003]
The basic concept of such conventional technology is that the optical modulator and photodetector that can process electronic circuits are processed at low speed electrically, and the parts that can process all light are realized by optical time division multiplexing. And processing as an ultra-high-speed signal exceeding the operating speed of the electronic circuit. Ultra-high-speed transmission experiments at 400 Gbit / s, 640 Gbit / s, 1.28 Tbit / s, etc. have been reported to date in accordance with this concept.
[0004]
FIG. 10 is an explanatory diagram schematically showing a conventional ultra-high-speed optical communication system using optical time division multiplexing. As shown in the figure, the optical pulse train of F0 列 Hz before multiplexing generated from the light source 51 is time-divisionally N-separated by an optical signal multiplexer (optical MUX: Multiplexer) 53, and is divided into optical signals. The optical multiplexed signal is electrically modulated by the modulator 52, multiplexed again by N, transmitted as an optical multiplexed signal of N × F0 bit / s through an optical transmission line, and an optical multiplexed signal demultiplexer (optical DEMUX) for receiving the optical multiplexed signal. : Demultiplexer) 54 separates the optical signals into F0 @ bit / s optical signals of N communication channels (N channels). The separated optical signal of F0 @ bit / s is converted into an electric signal by a photodetector 55 provided in each communication channel, and is electrically processed.
[0005]
FIG. 11 is an explanatory diagram illustrating a configuration example of a conventional optical signal multiplexing device 53. The optical signal multiplexing device 53 shown in the figure is composed of a delay line 56 capable of realizing an ultra-high-speed signal pulse train of N × F0 bit / s by performing N multiplexing in time and N optical branching couplers 57. At this time, the branching ratio of the optical branching coupler 57 is fixed so that each of the multiplexed optical signal pulse trains has the same amplitude. FIG. 12 schematically shows the concept of the conventional optical signal multiplexing described above.
[0006]
A typical optical signal multiplexing device proposed so far is a device in which delay lines having a constant time delay difference are combined in multiple stages and multiplexed, and an optical multiplexing signal demultiplexing device is a non-linear optical multiplexer of a Sagnac interferometer. This is a combination of a loop mirror (NOLM: Nonlinear Optical Loop Mirror) and an optical Kerr effect.
[0007]
FIG. 13 is an explanatory diagram schematically illustrating a configuration example of the optical multiplexed signal separation device 54. As shown in the figure, a control pulse of F0 bit / s is indispensable to separate a signal component of F0 bit / s from an ultra-high-speed signal pulse of N × F0 bit / s. At this time, in order to utilize the interference effect generated between the optical signal and the control pulse wave, the control pulse wave is synchronized in time with the temporally multiplexed incident optical signal, and at the same time the polarization direction matches. It is required that the optical signal has a sufficiently high light intensity as compared with the optical signal.
[0008]
[Problems to be solved by the invention]
Among the above-mentioned prior arts, the optical signal multiplexing apparatus requires the pulse width of the optical signal to be multiplexed because the time interval T0 between the optical signals becomes short if the number of multiplexing is increased to increase the capacity. T must be narrowed, and it is necessary to use an ultra-short optical pulse, which is difficult to transmit, for the signal light, and there is a problem that adaptation to the system is difficult.
[0009]
On the other hand, on the optical multiplex signal separation device side, there is a problem that a high-output short pulse light source must be prepared for a control pulse, and it is very difficult to synchronize the timing of an optical signal and a control pulse with time. The optical phase synchronization control using the optical phase synchronization controller (optical PLL: Phase @ Lock @ Loop) 58 was required. In addition, it is often difficult to match the polarization directions, and for that purpose, it is necessary to configure the entire system with a medium capable of maintaining the polarization direction, and there is a problem that a system having the above configuration is very expensive. Was.
[0010]
FIG. 14 is an explanatory diagram illustrating a configuration example of a conventional optical time division multiplexer 102. In the optical time-division multiplexer 102 shown in the figure, an incident optical pulse train having a clock frequency of F0 Hz is N-branched by a light intensity branching unit 106, and each of the branched light pulse trains has a delay time difference of a constant multiple. After being encoded by the optical intensity modulator 107 having a delay line, it is multiplexed again by the optical multiplexer 108, and an optical time division multiplexed signal of N × F0 信号 bit / s is transmitted.
[0011]
In the optical time division demultiplexer 103, as shown in FIG. 15, a control pulse train having a repetition frequency of F0 Hz is synchronized with a signal light of N × F0 bit / s using an optical phase synchronization controller 109, and a nonlinear mutual The optical time division multiplexed signal is separated into an optical signal of F0 bit / s by an operation (optical Kerr effect).
[0012]
As shown in FIG. 16, in the optical time division multiplexer 102, an N × F0 bit / s ultra-high-speed signal that is temporally N-multiplexed is generated. At this time, the signal (pulse) interval, which was 1 / F0 seconds before multiplexing, is multiplied by 1 / N by multiplexing, and the signal interval is reduced to (1 / N) × (1 / F0 seconds). Therefore, it is very difficult to synchronize with the control pulse having the repetition frequency F0 Hz in the optical time division demultiplexer 103 in inverse proportion to the multiplicity. Further, the timing of a signal propagated through a conventional transmission path is shifted due to environmental changes such as temperature, so that synchronization with a control pulse is more difficult. In addition, in order for the signal light and the control light to interact with each other with high efficiency, the polarization directions need to match, and the entire transmission system must be formed of a medium capable of maintaining the polarization direction. That was costly.
[0013]
The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical multiplex communication method and an optical multiplex communication that realize ultra-high-speed transmission using an optical multiplex signal having a pulse width that can be easily transmitted at low cost. A system, an optical signal multiplexing device, and an optical multiplexing signal demultiplexing device are provided.
[0014]
Another object of the present invention is to provide an ultra-high-speed optical multiplexed signal demultiplexer that operates asynchronously and does not require a control pulse.
[0015]
[Means for Solving the Problems]
According to the present invention, there is provided an optical multiplex communication method for performing communication of an optical multiplex signal obtained by multiplexing a plurality of optical signals having the same carrier frequency via an optical transmission line. Using an optical frequency conversion unit having an optical nonlinear medium having a varying refractive index, frequency-converting an optical multiplexed signal having a different amplitude for each communication channel into a plurality of optical pulse trains having different carrier wave frequencies for each communication channel. (B) separating the plurality of frequency-converted optical pulse trains into optical pulse trains for each communication channel by using an optical frequency selection unit that selects and separates an optical signal according to a frequency. An optical multiplex communication method is provided.
[0016]
Also, the present invention provides (c) an optical signal multiplexing device that generates a plurality of optical pulse trains having different amplitudes for each communication channel; and (d) an optical signal multiplexing device that generates the plurality of optical pulse trains. Multiplexing on a time axis to generate an optical multiplexed signal, and transmitting the optical multiplexed signal, wherein the steps (a) and (b) are performed by an optical multiplexed signal demultiplexing device, and A) is characterized in that frequency conversion of an optical multiplex signal having a different amplitude for each communication channel received from the optical signal multiplexer is performed.
[0017]
Further, the present invention is characterized in that the step (c) generates an optical pulse train having at least one of a phase and a polarization direction different for each communication channel.
[0018]
Also, the present invention provides (c) an optical signal multiplexing device that generates a plurality of optical pulse trains having different amplitudes for each communication channel; and (d) an optical signal multiplexing device that generates the plurality of optical pulse trains. Multiplexing on the time axis to generate an optical time-division multiplexed signal; and (e) repeating the above steps (c) and (d) in the optical signal multiplexing apparatus, and Obtaining a division multiplexed signal, multiplexing the plurality of sets of optical time division multiplexed signals on a frequency axis to generate an optical multiplexed signal, and transmitting the optical multiplexed signal; (B) is performed by an optical multiplexing signal demultiplexing device, and the step (a) is characterized in that frequency conversion of an optical multiplexing signal having a different amplitude for each communication channel received from the optical signal multiplexing device is performed.
[0019]
Further, the present invention is characterized in that the step of generating the optical pulse train includes a procedure of generating an optical pulse train in which at least one of the phase and the polarization direction differs for each communication channel.
[0020]
Further, in the invention, it is preferable that the optical frequency conversion unit includes means for compressing a pulse width of the optical multiplex signal.
[0021]
Also, the present invention provides (c) an optical signal multiplexing device for generating a plurality of optical pulse trains having the same amplitude for all communication channels; and (d) an optical signal multiplexing device for generating the plurality of optical pulse trains. Generating an optical multiplexed signal by multiplexing the pulse train on the time axis, and transmitting the optical multiplexed signal; and (e) communicating with the optical multiplexed signal separating device from the optical multiplexed signal received from the optical signal multiplexing device. Generating the optical multiplexed signal having a different amplitude for each channel, wherein the steps (a) and (b) are performed by an optical multiplexed signal demultiplexer, and the step (a) includes the step (a). The frequency conversion of an optical multiplex signal having a different amplitude for each communication channel generated in e) is performed.
[0022]
Also, the present invention provides (c) an optical signal multiplexing device for generating a plurality of optical pulse trains having the same amplitude for all communication channels; and (d) an optical signal multiplexing device for generating the plurality of optical pulse trains. Multiplexing the pulse train on the time axis to generate an optical multiplex signal, and transmitting the optical multiplex signal;
(E) a terminal device provided on an optical transmission line between an optical signal multiplexing device and an optical multiplexing signal demultiplexing device, wherein the terminal device has a different amplitude for each communication channel from an optical multiplexed signal received from the optical signal multiplexing device. Generating an optical multiplexed signal, wherein the steps (a) and (b) are performed by a terminal device, and the step (a) differs for each communication channel generated in the step (e). The frequency conversion of an optical multiplexed signal having an amplitude is performed.
[0023]
Further, according to the supplementary invention, there is provided an optical multiplex communication system for performing communication of an optical multiplexed signal obtained by multiplexing a plurality of optical signals having the same carrier frequency, wherein a plurality of optical pulse trains are generated, and the plurality of optical pulse trains are time-divided. An optical signal multiplexing device for multiplexing on the axis to generate an optical multiplexed signal and transmitting the optical multiplexed signal, an optical transmission line for transmitting the optical multiplexed signal, and an optical transmission line transmitted through the optical transmission line. The optical multiplexed signal is received, and an optical multiplexed signal having a different amplitude for each communication channel is provided by using an optical frequency conversion unit including an optical nonlinear medium whose refractive index changes according to the light intensity of the received incident light. An optical multiplexing signal demultiplexer for converting a plurality of optical pulse trains having different carrier frequencies for each communication channel and separating the plurality of optical pulse trains for each communication channel, or optical transmission between the optical signal multiplexing device and the optical multiplexing signal demultiplexing device. To provide an optical multiplex communication system characterized by comprising a terminal device provided above.
[0024]
Also, in the present invention, the optical signal multiplexing device generates a plurality of optical pulse trains having different amplitudes for each communication channel, and multiplexes the plurality of optical pulse trains on a time axis to generate an optical multiplexed signal, Transmitting the optical multiplexed signal, wherein the frequency conversion and separation are performed in an optical multiplexed signal demultiplexer, and the frequency conversion is performed by frequency conversion of an optical multiplexed signal having a different amplitude for each communication channel received from the optical signal multiplexed device. Is performed.
[0025]
Also, in the present invention, the optical signal multiplexing device repeatedly generates a plurality of optical pulse trains having different amplitudes for each communication channel, and multiplexes the plurality of optical pulse trains on a time axis to generate an optical time-division multiplexed signal. Repeatedly generating, obtaining a plurality of sets of optical time division multiplexed signals having different carrier wave frequencies from each other, multiplexing the plurality of sets of optical time division multiplexed signals on the frequency axis to generate an optical multiplexed signal, Transmitting, the frequency conversion and demultiplexing are performed by an optical multiplexing signal demultiplexing device, and the frequency conversion is performed by performing frequency conversion of an optical multiplexed signal having a different amplitude for each communication channel received from the optical signal multiplexing device. And
[0026]
Further, according to the present invention, the optical signal multiplexing apparatus generates a plurality of optical pulse trains having the same amplitude in all communication channels, and multiplexes the plurality of optical pulse trains on a time axis to generate an optical multiplexed signal. Transmitting the optical multiplexed signal, the optical multiplexed signal demultiplexer generates the optical multiplexed signal having a different amplitude for each communication channel from the optical multiplexed signal received from the optical signal multiplexer, and performs the frequency conversion. The demultiplexing is performed by an optical multiplexed signal demultiplexer, and the frequency conversion is performed by performing frequency conversion of an optical multiplexed signal having a different amplitude for each communication channel generated by the optical multiplexed signal demultiplexer.
[0027]
Further, according to the present invention, the optical signal multiplexing apparatus generates a plurality of optical pulse trains having the same amplitude in all communication channels, and multiplexes the plurality of optical pulse trains on a time axis to generate an optical multiplexed signal. Transmitting the optical multiplexed signal, and the terminal device provided on the optical transmission path between the optical signal multiplexing device and the optical multiplexed signal demultiplexing device performs communication based on the optical multiplexed signal received from the optical signal multiplexing device. The optical multiplexed signal having a different amplitude for each channel is generated, the frequency conversion and separation are performed in a terminal device, and the frequency conversion is performed for an optical multiplexed signal having a different amplitude for each communication channel generated in the terminal device. The frequency conversion is performed.
[0028]
Further, according to the present invention, there is provided an optical signal multiplexing apparatus that multiplexes a plurality of optical signals having the same carrier frequency to generate an optical multiplexed signal, and generates a plurality of optical pulse trains having different amplitudes for each communication channel. An optical signal multiplexing apparatus comprising: a pulse train generating unit; and a multiplexing unit that multiplexes the plurality of optical pulse trains on a time axis to generate an optical multiplexed signal.
[0029]
Further, the present invention is characterized by further comprising a modulating means for performing different coding on each optical pulse train for each communication channel.
[0030]
Further, the invention is characterized in that the multiplexing means has a function of multiplexing a plurality of sets of optical multiplexed signals having different carrier frequencies on a frequency axis.
[0031]
Further, according to the present invention, the pulse train generating means includes at least one of a phase control means for giving a different phase to the optical pulse train for each communication channel, and a polarization control means for giving a different polarization direction to the optical pulse train for each communication channel. It is further characterized by having.
[0032]
Further, the invention is characterized in that the pulse train generating means includes a pulse light source for generating an optical pulse, and an optical signal splitting means for splitting the optical pulse at a predetermined splitting ratio.
[0033]
Further, the present invention is characterized in that the pulse train generating means includes a light source that generates continuous light having a constant amplitude over time, and a sideband generator including an optical resonator having a modulator inside. And
[0034]
Further, according to the present invention, there is provided an optical multiplexing signal separating apparatus for separating an optical multiplexed signal obtained by multiplexing a plurality of optical signals having the same carrier frequency into a plurality of optical signals, wherein the optical multiplexing signal is refracted according to the light intensity of the incident light. An optical non-linear medium having a changing rate, an optical frequency converting means for frequency-converting the received optical multiplexed signal into a plurality of optical pulse trains having different carrier frequencies for each communication channel, and the plurality of optical frequency converting means converted by the optical frequency converting means. An optical frequency selecting unit for selecting an optical pulse train according to a frequency and separating the optical pulse train for each communication channel.
[0035]
Further, the present invention is characterized in that the optical frequency converting means includes an amplifying means for amplifying an amplitude level of an incident optical multiplex signal and for inputting the amplified optical multiplex signal to the optical nonlinear medium.
[0036]
Further, the present invention is characterized in that the optical frequency conversion means includes a compression means for compressing a pulse width of the optical pulse train.
[0037]
Also, in the present invention, the optical nonlinear medium has a zero-dispersion wavelength at which the propagation velocity is maximum at a wavelength shorter than the central wavelength of the optical pulse, and +1 ps / nm / km at the central wavelength of the optical pulse. It is an optical fiber having the above chromatic dispersion.
[0038]
Further, the present invention is characterized by further comprising an optical amplitude control means for controlling the optical intensity of the incident optical signal to obtain an optical multiplex signal having a different amplitude for each communication channel.
[0039]
Also, the present invention is provided between the optical amplitude control means and the optical frequency conversion means, the optical multiplex signal obtained by the optical amplitude control means, while maintaining the ratio of the light intensity of the optical multiplex signal It is characterized by further comprising an optical amplification means for amplifying.
[0040]
Further, the present invention is characterized by further comprising an optical signal compression means provided between the optical amplitude control means and the optical frequency conversion means or inside the optical frequency conversion means for compressing a pulse width of an optical multiplex signal. And
[0041]
Further, the invention is characterized in that the light amplitude control means is constituted by a light intensity modulator.
[0042]
BEST MODE FOR CARRYING OUT THE INVENTION
First, a first embodiment of the present invention will be described in detail with reference to FIGS.
[0043]
FIG. 1 is a block diagram illustrating an optical multiplex communication system according to the first embodiment of the present invention. The optical multiplex communication system 100 shown in FIG. 1 includes an optical signal multiplexing device 1 as a transmitting device, an optical transmission line 2 such as an optical fiber, and an optical multiplexing signal demultiplexing device 3 as a receiving device.
[0044]
The optical signal multiplexing apparatus 1 includes a pulse train generating unit 11 and a multiplexing unit 12 that generates an optical pulse train having a unique amplitude for each channel, and time-division multiplexes and transmits the generated optical pulse train on a time axis. At least.
[0045]
The optical multiplexed signal demultiplexing device 3 has at least an optical frequency conversion unit 31 partially composed of an optical non-linear medium such as an optical fiber, and an optical frequency selection unit 32 composed of an optical filter or the like.
[0046]
Hereinafter, the detailed configuration and operation of each device will be described.
[0047]
<Optical signal multiplexing device 1>
FIG. 2 is a block diagram illustrating a configuration example of the optical signal multiplexing apparatus 1. In the optical signal multiplexing apparatus 1 shown in the figure, an optical signal is output from one pulse light source 111 in a pulse train generating unit 11, and this optical signal is branched into N (N is an integer of 2 or more) by a branching unit 112. An N-channel optical pulse train is generated. After a given delay time and amplitude are given to each of the branched signals by the delay / amplitude control unit 113 for each communication channel, the signals are encoded as optical signals by modulators 114 provided for each communication channel.
[0048]
After that, the multiplexing unit 12 combines all communication channels to generate an optical multiplexed signal.
[0049]
FIG. 3 is a block diagram showing another configuration example of the optical signal multiplexing device 1. The optical signal multiplexing apparatus 1 shown in the figure shows a case in which N optical pulse trains are generated by using a variable branching ratio coupler 112 in N-1 stages.
[0050]
The amplitude of the optical pulse train is determined by the branch ratio of the variable branch ratio coupler 112. For example, if the branch ratios of the respective branch ratio variable couplers 112-1,..., 112- (N-1) are all set to 1: 1, the pulse of the pulse branched by the first branch ratio variable coupler 112-1 is changed. Assuming that the intensity is 1, the intensity of the pulse branched by the next branching ratio variable coupler 112-2 is 、, the intensity of the next branched pulse is ４, and so on every time it is branched. The strength decreases by / 2.
[0051]
As the branching ratio variable coupler 112, for example, a Mach-Zehnder interferometer that is manufactured on a glass substrate (PLC: Planar Lightwave Circuit) and has a coupling ratio changed by a thermo-optic effect (thermooptic (TO: ThermoOptic) effect) is used. Can be. In this case, the refractive index of the glass changes due to heat, so that the coupling ratio changes. According to actual measurements, the delay line at this time multiplexes incident light pulses with a delay time difference of about 0.78 ps, and is used for an ultra-high-speed signal of 1.28 Tbit / s.
[0052]
It is needless to say that the branching ratio variable coupler 112 is not limited to this, and its configuration is arbitrary as long as the coupling ratio can be controlled. For example, using a conventional optical signal multiplexing apparatus, it is possible to adopt a configuration in which multiplexing is performed without matching optical phases and polarization directions so that interference does not occur between optical signals when multiplexing. is there.
[0053]
Each of the branched signals is controlled in delay time and amplitude by a delay / amplitude control unit 113 provided in each communication channel, and further encoded by each modulator 114 as an optical signal. The optical pulse trains are combined to generate and transmit an optical multiplex signal.
[0054]
FIG. 3 shows a case where the multiplexing unit 12 combines two pulse trains by using a two-branch coupler 121. As the two-branch coupler 121, the same one as the branch ratio variable coupler 112 described above can be used. Further, it is not always necessary to use a plurality of two-branch couplers 121 as the multiplexing unit 12. More preferably, the multiplexing unit 12 may be configured by using a device that can multiplex N-channel signals at a time.
[0055]
It is needless to say that the multiplexing unit 12 shown in FIG. 3 is also applicable to the optical signal multiplexing apparatus 1 having the configuration shown in FIG. 1 described above and FIG. 4 described later.
[0056]
FIG. 4 is a block diagram illustrating a third configuration example of the optical signal multiplexing device 1 according to the present embodiment. In the figure, continuous light generated from a laser light source 115 that generates continuous light having a constant amplitude over time is incident on a sideband generator 116 including an optical resonator having a modulator 116a therein. Then, an optical pulse train is generated by passing through the optical filter 117. In each communication channel, the amplitude and time interval of the optical pulse train are controlled by the amplitude / time interval control unit 118, respectively, and then multiplexed by the multiplexing unit 12, and then transmitted.
[0057]
FIGS. 5 and 6 are explanatory diagrams showing an example of multiplexing of optical signals performed by the optical signal multiplexing apparatus 1 having the above configuration. Here, the case where the number of communication channels is four will be described as an example, but it goes without saying that the same applies to the case of other numbers of communication channels.
[0058]
The four optical pulse trains shown in FIGS. 5 (a) to 5 (d) are generated by the pulse train generating unit 11, and have the same period, that is, the same carrier frequency, although their amplitudes are different from each other. I have.
[0059]
FIG. 6 is an explanatory diagram showing an optical multiplexed signal obtained by multiplexing the four optical pulse trains described above on the time axis. In this figure, CH1 is the optical signal of channel 1 shown in FIG. 5A, and hereinafter, CH2, CH3, and CH4 are also shown in FIGS. 5B, 5C, and 5D, respectively. ).
[0060]
As described above, the optical multiplexed signal is composed of a plurality of optical pulse trains all having the same carrier frequency, and the optical signal multiplexing apparatus 1 uses the branching ratio variable coupler 112 and the delay / amplitude control unit 113 to control each communication channel. Control is performed so that the pulse intensities are different.
[0061]
In each configuration example of the optical signal multiplexing apparatus 1 described above, when performing multiplexing in the multiplexing unit 12, in addition to the time division multiplexing on the time axis shown in FIG. It is also possible to generate a multiplexed (second optical multiplexed signal) a plurality of multiplexed optical multiplexed signals (first optical multiplexed signals) having different carrier frequencies from each other on the frequency axis.
[0062]
When the time interval between pulses is shorter than the time width (pulse width) of an optical pulse to be time-division multiplexed, that is, when the pulses overlap each other on the time axis, In order to prevent the optical intensity from changing due to interference of the optical signals, the optical pulse train is controlled so as to have a different phase or at least one of the polarization directions for each communication channel. For this control, the optical signal multiplexing apparatus 1 is provided with at least one of a phase control means for controlling a phase and a polarization control means for controlling a polarization direction.
[0063]
According to the optical signal multiplexing apparatus according to the present embodiment described above, a plurality of optical pulse trains having the same carrier frequency are multiplexed while being controlled such that their intensities are different for each communication channel. , And communication of an optical multiplexed signal having a large capacity can be easily realized.
[0064]
<Optical multiplex signal separation device 3>
FIG. 7 is a block diagram illustrating a configuration of the optical multiplexed signal demultiplexing device 3 according to the present embodiment. The optical multiplex signal separation device 3 shown in FIG. 1 can separate an optical signal by a frequency (wavelength) from an optical frequency conversion unit 31 having an optical nonlinear medium whose center wavelength changes according to the light intensity of incident light as described above. It has at least an optical frequency selection unit 32.
[0065]
The optical frequency conversion unit 31 includes an amplification unit 311 that amplifies the amplitude level of an incident optical signal and a compression unit 312 that compresses the time width (pulse width) of the optical signal. As an example of the compression unit 312, an optical nonlinear medium including a dispersion shift fiber or the like is used.
[0066]
When the optical multiplex signal is input to the optical frequency conversion unit 31 via the optical transmission line 2, the frequency of each pulse shifts according to the intensity.
[0067]
More specifically, a soliton self-frequency shift utilizing the optical Kerr effect (a frequency shift that occurs in a Raman soliton, which is an optical pulse subjected to stimulated Raman scattering, according to the light intensity) occurs. This phenomenon is very fast operation (1 ps (picosecond) = 10^-12s or less), and the short-wavelength component inherent in the light pulse functions as a pump that induces the Raman gain obtained by stimulated Raman scattering, and occurs by continuously converting the soliton energy into a long-wavelength component. . The frequency shift amount is the fourth power of the pulse width T of the incident pulse, that is, T⁴Is inversely proportional to Specifically, the frequency shift amount dλ (THz / km) and the pulse width T are given by the following relational expression.
dλ = 0.0436 / T⁴(1)
[0068]
FIG. 8 is an explanatory diagram showing the results of an experiment in which a frequency shift was induced by the intensity of an incident optical signal using an optical pulse train having a carrier frequency of 10 GHz and a pulse width of about 1 ps. In this experiment, a dispersion-shifted fiber having a length of about 20 km was used as an optical nonlinear medium. From FIG. 8, it can be seen that by changing the intensity of the incident light signal, a wavelength shift of several nm to several tens of nm, and even several hundred nm depending on the conditions, is possible.
[0069]
Note that the optical nonlinear medium used in the present embodiment is not limited to the dispersion-shifted fiber used in the above experiment. Even when an optical fiber is used, its type and length need to be optimized each time depending on the conditions of the incident light, and at the same time, the zero dispersion of the optical fiber is required to generate a soliton wave (pulse wave) in the optical fiber. The wavelength (the wavelength at which the propagation speed is maximized) must be shorter than the center wavelength of the incident light. In addition, in order to generate the soliton self-frequency shift efficiently, it is required that the chromatic dispersion of the optical fiber be +1 ps / nm / km or more at the central wavelength of the incident light. This requirement is imposed because, when the chromatic dispersion is small, four-wave mixing, which has a lower threshold than the soliton self-frequency shift, is induced, making it difficult to generate a soliton self-frequency shift that easily separates optical multiplexed signals. Because it becomes.
[0070]
FIG. 9 is a block diagram illustrating a configuration of the optical frequency selection unit 32. The optical frequency selection unit 32 shown in FIG. 3 is an AWG (Arrayed Waveguide Grating) fabricated on a glass substrate PLC, and an optical multiplexed signal incident from an input waveguide 321 is spatially spread by a slab waveguide 322. After that, the light passes through the array waveguide 323. After that, they are spatially bundled by the slab waveguide 324, and are separated and output from the N output waveguides 325 to each communication channel according to the wavelength.
[0071]
The optical frequency selection unit 32 is not limited to the above-described AWG, but may be a multilayer filter as long as it is an optical filter having frequency selectivity, and the filter structure is not particularly limited.
[0072]
Since the optical multiplex signal is composed of a plurality of optical pulse trains having different intensities for each communication channel, the optical multiplex signal output from the optical frequency conversion unit 31 has a different frequency for each communication channel due to the soliton self-frequency shift described above. The optical signal is converted to an optical signal and output in a state of being frequency-multiplexed. By inputting this optical signal to the optical frequency selection unit 32 that separates light for each frequency, it becomes possible to separate the received optical multiplexed signal for each communication channel.
[0073]
The separated optical pulse train is converted into an electric signal by a photodetector provided in each communication channel and then processed electrically, as in FIG.
[0074]
The optical multiplexing signal demultiplexing apparatus 3 described above is an asynchronous type configuration that does not require an external control signal for time division demultiplexing. It is possible to separate. This makes it possible to realize a high-performance system that cannot be realized by conventional techniques such as optical routing and optical signal processing.
[0075]
Further, the optical multiplexed signal demultiplexing apparatus according to the present embodiment operates using soliton waves (optical pulse waves) that operate particularly stably among optical nonlinear phenomena, so that an extremely stable optical signal can be obtained.
[0076]
As a result, it is possible to provide an optical multiplexed signal demultiplexing device that is extremely practical and has a wide application range.
[0077]
According to the first embodiment of the present invention described above, while suppressing interference between signals in the optical signal multiplexing device, an asynchronous optical multiplexing signal demultiplexing device is used to generate an optical signal wider than the time interval T between signals. It is possible to provide multiplexing with a time width (pulse width) T0}, and to provide an ultra-high-speed signal with a pulse width that is easy to transmit and a communication method of the signal.
[0078]
Further, since the present embodiment uses an optical pulse having a single carrier frequency, the communication capacity can be further increased by using it in combination with an existing wavelength multiplexing method.
[0079]
Next, a second embodiment of the present invention will be described in detail with reference to FIGS.
[0080]
In the first embodiment, an amplitude (light intensity) difference between different communication channels is generated on the optical signal multiplexing apparatus side, whereas in the second embodiment, the amplitude (light intensity) between different communication channels is generated. Intensity) difference is generated on the side of the optical multiplex signal demultiplexer.
[0081]
FIG. 17 shows a configuration of an optical multiplexed signal demultiplexing apparatus according to the second embodiment. The optical multiplexed signal demultiplexing apparatus of the second embodiment has an asynchronous configuration that does not require a control pulse signal synchronized with signal light for time division multiplexing and demultiplexing of a signal. Therefore, as shown in FIG. 17, the configuration is simple, an optical amplitude control unit 211 that controls the light intensity of the incident signal light, and an optical frequency conversion unit 212 that converts the wavelength according to the light intensity of the signal light. , An optical frequency selector 213 having wavelength selectivity.
[0082]
In the optical frequency conversion unit 212, a soliton self-frequency shift using the optical Kerr effect or a frequency shift according to the light intensity occurs due to stimulated Raman scattering in a pulse of Raman soliton. Since this phenomenon is a very fast operation, the frequency shift is picosecond (10^-12s) Happens below. The frequency shift occurs when the short wavelength component included in the pulse functions as a pump for inducing Raman gain, and continuously converts soliton energy to a long wavelength component.
[0083]
As a specific example, the light amplitude control unit 211 includes a light intensity modulator. At this time, when the sawtooth modulation signal shown in FIG. 18A or 18B is input to the light intensity modulator and the input signal light shown in FIG. The light signal is given a light intensity difference as shown in FIG. 19B or 19C, and the light intensity can be controlled. Note that the sawtooth modulated signal shown in FIGS. 18A and 18B has a repetition frequency F0 # that matches the frequency F0 # of the signal to be separated.
[0084]
FIG. 20 shows the result of an experiment in which the conversion wavelength was controlled by the light intensity. In this experiment, a 10 Gbit / s pseudo-random signal having a center wavelength of 1550 nm was used as signal light. FIG. 20 shows that the conversion wavelength can be controlled to 30 nm or more by changing the light intensity of the incident light.
[0085]
As a specific example, as shown in FIG. 21A, when the repetition frequency of the signal light before multiplexing is 10 GHz (center wavelength 1550 nm), and the signal light is optically time-division multiplexed by 10 times to 100 Gbit / s, Assuming that the repetition frequency of the sawtooth modulation signal input to the light intensity modulator is 10 GHz, as shown in FIG. 21B, the signal of 10 Gbit / s having a different wavelength by the optical multiplexed signal demultiplexer of the present embodiment is used. Waves (about 2 nm apart) can be separated.
[0086]
The frequency used in this example is not limited to this, and any frequency can be used. Also, the drive voltage waveform of the sawtooth modulation signal input to the light intensity modulator used in this example is not limited to this, but any waveform as long as the light intensity of each transmitted optical signal can be controlled. May be used.
[0087]
Further, since the drive voltage waveform of the sawtooth modulation signal input to the light intensity modulator takes the same voltage value V ′ twice within a one-cycle waveform as shown in FIG. When the signal bits A and B having the same amplitude of the optical signal transmitted through the optical intensity modulator are generated as shown in b), the optical frequency converter 212 converts the channels A and B into the same wavelength. Therefore, signal separation becomes difficult. In such a case, as shown in FIGS. 23 (a), (b) and (c), at the time of optical time division multiplexing, by periodically inserting a bit T 'which is blank in time, , Signal separation becomes possible.
[0088]
As another method, as shown in FIG. 24, the multiplexed signal input to the optical amplitude control unit 211 is branched into two, and the optical signal is transmitted through the optical intensity modulator by using two sets of an optical intensity modulator and an optical switch. It is possible to prevent the amplitudes of the optical signals from being equal. Specifically, the multiplexed signal is split into two, and is input to each light intensity modulator with a delay time difference. At this time, the delay time difference is set to a half (F0 / 2) of one cycle of the repetition frequency F0 Hz of the drive voltage waveform for driving the light intensity modulator.
[0089]
The two light intensity modulators operate at different drive voltages and have transmission characteristics as shown in FIGS. 25 (a) and 25 (b). At this time, the multiplex signal passing through the light intensity modulator is incident with a shift of a half cycle by the delay line. Further, the C-bit light intensity having the smallest light intensity in the optical signal of FIG. 25B transmitted through the light intensity modulator having a high transmittance is transmitted through the light intensity modulator having a low transmittance in FIG. 25A. The transmittance (driving voltage) is adjusted so that the light intensity of the optical signal is higher than the light intensity of the maximum D bit.
[0090]
The optical signal whose light intensity is transmitted through the light intensity modulator and is incident on each of the optical switches, where the light signal is controlled as shown in FIGS. 26 (a) and 26 (b). An optical signal for a half cycle is transmitted, and the other optical signals are cut off. Thereafter, the transmitted optical signals are multiplexed with their timing adjusted by the delay line 216 shown in FIG. 24, and optical signals having the same optical amplitude can be eliminated within the separation period shown in FIG. Thus, the signal is converted into a wavelength corresponding to the light intensity in the optical frequency conversion unit 212, so that the signal can be separated into low-speed signals.
[0091]
As shown in FIG. 28A, the optical multiplexed signal demultiplexing apparatus according to the second embodiment has an optical amplifier 217 capable of amplifying only the entire signal level without changing the light intensity ratio of each optical signal. 28 is inserted after the optical amplitude control unit 211, or as shown in FIG. 28B, an optical signal compression unit 218 for compressing the time width (pulse width) of the optical signal is provided before or inside the optical frequency conversion unit. Can be adopted.
[0092]
As described above, according to the second embodiment, the optical multiplexed signal demultiplexing apparatus can realize asynchronous ultra-high-speed signal demultiplexing that cannot be realized by the conventional technology. Further, the optical multiplexed signal demultiplexing device of the present embodiment can demultiplex multiple communication channels at once. This makes it possible to realize a high-performance system that cannot be realized by conventional techniques such as optical routing and optical signal processing.
[0093]
Further, since the optical multiplexed signal demultiplexing device of the present embodiment operates using soliton waves that operate particularly stably among optical nonlinear phenomena, an extremely stable optical signal can be obtained.
[0094]
As a result, it is possible to provide an optical multiplexed signal demultiplexing device that is extremely practical and has a wide application range.
[0095]
Next, a third embodiment of the present invention will be described in detail with reference to FIGS.
[0096]
In the first and second embodiments, an amplitude (light intensity) difference between different communication channels is generated on the optical signal multiplexing device side or the optical multiplexing signal demultiplexing device side. In the above, an amplitude (light intensity) difference between different communication channels is generated in a terminal located between an optical signal multiplexing device and an optical multiplexing signal demultiplexing device.
[0097]
FIG. 29 shows a configuration example of the optical multiplex communication system of the third embodiment. In this configuration, in the transmission / reception terminal 250 for distributing only necessary signals from the backbone network serving as the backbone to the metro network and the access network, only necessary signals (wavelength channels) are selectively selected from the optical multiplexed / demultiplexed signals. And an optical signal add / drop function capable of multiplexing and transmitting a new signal again if necessary. Here, the signal distributed to the metro system and the access system may be an electric signal converted in the receiver, or an unconverted optical signal as it is.
[0098]
In this configuration, in the signal separator 251, signal separation is performed by wavelength conversion in which the wavelength converted by the light intensity of the signal can be controlled, the wavelength signal is separated by the wavelength separator 253, and each wavelength signal is converted into each optical switch 254. Is incident on. In the optical switch 254, only a desired signal enters the receiver 256 by a switching operation. At this time, the optical switch 254 does not switch the optical path for the wavelength signals that do not need to be received, and these wavelength signals enter the signal multiplexer 252 via the optical multiplexer 255. Since the signal multiplexer 252 holds the timing of each wavelength-separated signal, the wavelength signals do not overlap on the time axis.
[0099]
When there is a signal that needs to be transmitted from the transmission / reception terminal 250, the timing is extracted from the received signal by the timing extraction unit 258, and an appropriate delay time is given so as not to overlap other signals on the time axis. The signal enters the signal multiplexer 252 via the optical multiplexer 255. At this time, if there is no signal received at the transmission / reception terminal 250, there is no empty bit into which a new signal can be inserted so that the signals do not overlap on the time axis, so that a new signal cannot be transmitted. Therefore, a function is provided that can delay the timing of signal transmission until the signal is received by the transmission / reception terminal 250.
[0100]
FIG. 30 shows a configuration example of the signal multiplexer 252 in FIG. The signal multiplexer 252 of FIG. 30 includes a light source 260 having a center wavelength λ0 ° and a clock frequency F0 ° Hz, and a 1 × N time multiplexing circuit 261. This time multiplexing circuit 261 is composed of one light intensity splitter 262, N sets of light intensity modulators 263 and light intensity multiplexers 264, and (N-1) sets of delay lines of an appropriate length. You. The light intensity modulator 263 in the time multiplexing circuit 261 converts the optical signal separated by the signal separator 251 in the transmission / reception terminal 250 into an electric signal by the photoelectric converter 265 and inputs the electric signal as a driver of the light intensity modulator 263. Thus, the pulse train from the light source 260 can be encoded. This makes it possible to generate and transmit a new optical multiplex signal having the same wavelength and the same clock frequency as the optical multiplex signal input to the transmission / reception terminal 250.
[0101]
According to the third embodiment, the same effects as those of the first and second embodiments can be obtained.
[0102]
【The invention's effect】
According to the present invention described above, an optical multiplex communication method, an optical multiplex communication system, an optical signal multiplexing device, and an optical multiplex communication method that realize ultra-high-speed transmission using an optical multiplex signal having a pulse width that can be easily transmitted at low cost A multiplex signal separation device can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration example of an optical multiplex communication system using optical time division multiplex according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing a first configuration example of the optical signal multiplexing device according to the first embodiment of the present invention.
FIG. 3 is a block diagram showing a second configuration example of the optical signal multiplexing device according to the first embodiment of the present invention.
FIG. 4 is a block diagram showing a third configuration example of the optical signal multiplexing device according to the first embodiment of the present invention.
FIG. 5 is a graph showing a waveform example of four channels of an optical pulse train to be multiplexed in the first embodiment of the present invention.
FIG. 6 is a graph showing an example of an optical multiplexed signal obtained by multiplexing the optical pulse train of FIG. 5 in the first embodiment of the present invention.
FIG. 7 is a block diagram showing a configuration example of an optical multiplexed signal separation device according to the first embodiment of the present invention.
FIG. 8 is a graph showing a measurement result of a wavelength shift according to an incident light intensity in the optical multiplexed signal demultiplexing device according to the first embodiment of the present invention.
FIG. 9 is a diagram illustrating a configuration example of an optical frequency selection unit in the optical multiplexed signal demultiplexing apparatus according to the first embodiment of the present invention.
FIG. 10 is a block diagram showing a configuration of a conventional ultra-high-speed optical communication system.
FIG. 11 is a diagram showing a configuration example of a conventional optical signal multiplexing device.
FIG. 12 is an explanatory diagram schematically showing the concept of conventional optical signal multiplexing.
FIG. 13 is an explanatory view schematically showing the concept of conventional optical multiplex signal separation.
FIG. 14 is a diagram showing a configuration example of a conventional optical time division multiplexer.
FIG. 15 is an explanatory diagram schematically showing the concept of signal separation of a conventional optical multiplex signal.
FIG. 16 is a conceptual diagram of a conventional optical multiplexed signal waveform.
FIG. 17 is a block diagram showing a configuration example of an optical multiplexed signal demultiplexing device according to a second embodiment of the present invention.
FIG. 18 is a graph showing a waveform example of a drive voltage of an optical intensity modulator used as an optical amplitude controller in an optical multiplexed signal demultiplexing apparatus according to a second embodiment of the present invention.
FIG. 19 is a graph showing a waveform example of an input / output signal of an optical intensity modulator used as an optical amplitude controller in an optical multiplexed signal demultiplexing apparatus according to a second embodiment of the present invention.
FIG. 20 is a graph showing a measurement result of a wavelength shift according to an incident light intensity in an optical frequency converter in an optical multiplexed signal demultiplexing apparatus according to a second embodiment of the present invention.
FIG. 21 is a graph showing signal waveform examples before and after signal separation in an optical multiplexed signal demultiplexing apparatus according to a second embodiment of the present invention.
FIG. 22 is a graph showing a drive voltage of a light amplitude control unit and a waveform example of an output signal in an optical multiplexed signal separation device according to a second embodiment of the present invention.
FIG. 23 is a graph showing waveform examples of other input signals, drive voltages, and output signals of the optical amplitude control unit in the optical multiplexed signal demultiplexing apparatus according to the second embodiment of the present invention.
FIG. 24 is a block diagram illustrating a configuration example of an optical amplitude control unit in the optical multiplexed signal demultiplexing apparatus according to the second embodiment of the present invention.
FIG. 25 is a graph showing a waveform example of an output signal of a light intensity modulator in the light amplitude control unit of FIG. 24;
FIG. 26 is a graph showing a waveform example of an output signal of an optical switch in the optical amplitude control unit of FIG. 24;
FIG. 27 is a graph showing a waveform example of an output signal of the optical amplitude control unit in FIG. 24;
FIG. 28 is a block diagram showing a modified configuration example of the optical multiplexed signal demultiplexing device according to the second embodiment of the present invention.
FIG. 29 is a block diagram showing a configuration example of a transmission / reception terminal used in the optical multiplex communication system according to the third embodiment of the present invention.
30 is a block diagram showing a configuration example of a signal multiplexer in the transmission / reception terminal of FIG. 29.
[Explanation of symbols]
1. Optical signal multiplexer (optical MUX)
2 Optical transmission line
3 Optical multiplexed signal demultiplexer (optical DEMUX)
11 pulse train generator (pulse train generator)
12 Multiplexer (multiplexer)
31. Optical frequency converter (optical frequency converter)
32 ° optical frequency selection unit (optical frequency selection means)
51 ° light source
52 ° optical modulator
53 Optical Signal Multiplexer (Optical MUX)
54 optical multiplex signal separation device (optical DEMUX)
55 ° photodetector
56 ° delay line
57 fixed branch ratio type branch coupler
58 ° optical phase lock controller (optical PLL)
100 ° optical multiplex communication system
102 optical signal multiplexer (optical MUX)
103 Optical multiplexed signal demultiplexer (optical DEMUX)
105 ° control pulse light source
106 light intensity splitter
107 ° light intensity modulator
108 ° optical multiplexer
109 Optical phase synchronization controller (optical PLL)
111 ° pulse light source
112 ° branching unit (example of optical signal branching unit)
112-1, 112-2,..., 112- (N-1) variable ratio coupler (example of optical signal branching means)
113 ° delay / amplitude control unit
114, 116a modulator (modulation means)
115 ° laser source 116 ° sideband generator
117 ° optical filter
118 ° amplitude / time interval controller
121 2 branch coupler
210 ° optical multiplex signal demultiplexer (optical DEMUX)
211 ° light amplitude controller
212 optical frequency converter
213 Optical frequency selector
214 light intensity modulator
215 ° optical switch
216 ° delay line
217 ° Optical Amplifier
218 ° optical signal compression unit
250 transmitting / receiving terminal
251 signal separator
252 signal multiplexer
253 wavelength separator
254 optical switch
255 ° optical multiplexer
256 receiver
257 transmitter
258 ° timing extractor
260 ° light source
261 time multiplexing circuit
262 light intensity splitter
263 light intensity modulator
264 ° light intensity multiplexer
265 ° photoelectric converter
311 amplifying unit (amplifying means)
312 compression unit (compression means)
321 input waveguide
322,324 ° slab waveguide
323 array waveguide
325 ° output waveguide

Claims (27)

An optical multiplex communication method for performing communication of an optical multiplex signal obtained by multiplexing a plurality of optical signals having the same carrier frequency via an optical transmission path,
(A) Using an optical frequency conversion unit including an optical nonlinear medium whose refractive index changes according to the light intensity of incident light, an optical multiplexed signal having a different amplitude for each communication channel is converted into a carrier frequency of each communication channel. Frequency converting to a plurality of different optical pulse trains;
(B) separating the plurality of frequency-converted optical pulse trains into optical pulse trains for each communication channel using an optical frequency selection unit that selects and separates an optical signal according to a frequency. Optical multiplex communication method. (C) generating a plurality of optical pulse trains having different amplitudes for each communication channel in the optical signal multiplexing device;
(D) generating an optical multiplexed signal by multiplexing the plurality of optical pulse trains on a time axis with an optical signal multiplexing device, and transmitting the optical multiplexed signal;
The steps (a) and (b) are performed by an optical multiplexing signal demultiplexing apparatus, and the step (a) performs frequency conversion of an optical multiplexing signal having a different amplitude for each communication channel received from the optical signal multiplexing apparatus. The optical multiplex communication method according to claim 1, wherein: 3. The optical multiplex communication method according to claim 2, wherein said step (c) generates an optical pulse train having at least one of a phase and a polarization direction different for each communication channel. (C) generating a plurality of optical pulse trains having different amplitudes for each communication channel in the optical signal multiplexing device;
(D) generating an optical time-division multiplexed signal by multiplexing the plurality of optical pulse trains on a time axis in an optical signal multiplexing device;
(E) The optical signal multiplexing apparatus repeats the above steps (c) and (d) to obtain a plurality of sets of optical time division multiplexed signals having different carrier frequencies from each other. Generating an optical multiplexed signal by multiplexing the above, and transmitting the optical multiplexed signal,
The steps (a) and (b) are performed by an optical multiplexing signal demultiplexing apparatus, and the step (a) performs frequency conversion of an optical multiplexing signal having a different amplitude for each communication channel received from the optical signal multiplexing apparatus. The optical multiplex communication method according to claim 1, wherein: 5. The optical multiplex communication method according to claim 4, wherein the step of generating the optical pulse train includes a step of generating an optical pulse train having at least one of a phase and a polarization direction different for each communication channel. 2. The optical multiplex communication method according to claim 1, wherein said optical frequency converter includes means for compressing a pulse width of said optical multiplex signal. (C) generating, in the optical signal multiplexing apparatus, a plurality of optical pulse trains having the same amplitude for all communication channels;
(D) using an optical signal multiplexing device to multiplex the plurality of optical pulse trains on a time axis to generate an optical multiplexed signal, and transmitting the optical multiplexed signal;
(E) generating an optical multiplexed signal having a different amplitude for each communication channel from the optical multiplexed signal received from the optical signal multiplexing device by the optical multiplexed signal demultiplexer;
The steps (a) and (b) are performed by an optical multiplex signal demultiplexing device, and the step (a) performs frequency conversion of the optical multiplex signal having a different amplitude for each communication channel generated in the step (e). The optical multiplex communication method according to claim 1, wherein the method is performed. (C) generating, in the optical signal multiplexing apparatus, a plurality of optical pulse trains having the same amplitude for all communication channels;
(D) using an optical signal multiplexing device to multiplex the plurality of optical pulse trains on a time axis to generate an optical multiplexed signal, and transmitting the optical multiplexed signal;
(E) a terminal device provided on an optical transmission line between an optical signal multiplexing device and an optical multiplexing signal demultiplexing device, wherein the terminal device has a different amplitude for each communication channel from an optical multiplexed signal received from the optical signal multiplexing device. Generating an optical multiplex signal.
The steps (a) and (b) are performed in a terminal device, and the step (a) performs frequency conversion of an optical multiplexed signal having a different amplitude for each communication channel generated in the step (e). The optical multiplex communication method according to claim 1, wherein: An optical multiplex communication system for communicating an optical multiplex signal obtained by multiplexing a plurality of optical signals having the same carrier frequency,
An optical signal multiplexer that generates a plurality of optical pulse trains, multiplexes the plurality of optical pulse trains on a time axis to generate an optical multiplexed signal, and transmits the optical multiplexed signal;
An optical transmission line for transmitting the optical multiplexed signal,
The communication channel is received by using an optical frequency conversion unit including an optical nonlinear medium that receives the optical multiplex signal transmitted through the optical transmission path and changes the refractive index according to the light intensity of the received incident light. Multiplexed signal separating device or optical signal multiplexing device that converts an optical multiplexed signal having a different amplitude for each communication channel into a plurality of optical pulse trains having different carrier wave frequencies for each communication channel, and separates the plurality of optical pulse trains for each communication channel An optical multiplex communication system comprising: a terminal device provided on an optical transmission line between the optical multiplex signal separation device and the optical multiplex signal separation device. The optical signal multiplexing apparatus generates a plurality of optical pulse trains having different amplitudes for each communication channel, multiplexes the plurality of optical pulse trains on a time axis to generate an optical multiplex signal, and transmits the optical multiplex signal. And
The frequency conversion and demultiplexing are performed by an optical multiplex signal demultiplexing device, and the frequency conversion is performed by performing frequency conversion of an optical multiplexed signal having a different amplitude for each communication channel received from the optical signal multiplexing device. Item 10. An optical multiplex communication system according to Item 9. The optical signal multiplexing device repeatedly generates a plurality of optical pulse trains having different amplitudes for each communication channel, multiplexes the plurality of optical pulse trains on a time axis to repeatedly generate an optical time division multiplexed signal, and Obtain a plurality of sets of optical time division multiplexed signals having different carrier frequencies, generate an optical multiplexed signal by multiplexing the plurality of sets of optical time division multiplexed signals on the frequency axis, and transmit the optical multiplexed signal,
The frequency conversion and demultiplexing are performed by an optical multiplex signal demultiplexing device, and the frequency conversion is performed by performing frequency conversion of an optical multiplexed signal having a different amplitude for each communication channel received from the optical signal multiplexing device. Item 10. An optical multiplex communication system according to Item 9. The optical signal multiplexing apparatus generates a plurality of optical pulse trains having the same amplitude for all communication channels, multiplexes the plurality of optical pulse trains on a time axis to generate an optical multiplexed signal, and generates the optical multiplexed signal. And send
The optical multiplexing signal demultiplexing device generates the optical multiplexing signal having a different amplitude for each communication channel from the optical multiplexing signal received from the optical signal multiplexing device,
The frequency conversion and separation are performed by an optical multiplex signal separation device, and the frequency conversion is performed by performing frequency conversion of an optical multiplex signal having a different amplitude for each communication channel generated by the optical multiplex signal separation device. The optical multiplex communication system according to claim 9. The optical signal multiplexing apparatus generates a plurality of optical pulse trains having the same amplitude for all communication channels, multiplexes the plurality of optical pulse trains on a time axis to generate an optical multiplexed signal, and generates the optical multiplexed signal. And send
The terminal device provided on the optical transmission line between the optical signal multiplexing device and the optical multiplexing signal demultiplexing device is configured to convert the optical multiplexed signal received from the optical signal multiplexing device into an optical multiplex having a different amplitude for each communication channel. Generate a signal,
10. The optical device according to claim 9, wherein the frequency conversion and the separation are performed in a terminal device, and the frequency conversion performs frequency conversion of an optical multiplexed signal having a different amplitude for each communication channel generated in the terminal device. Multiplex communication system. An optical signal multiplexer for multiplexing a plurality of optical signals having the same carrier frequency to generate an optical multiplexed signal,
Pulse train generating means for generating a plurality of optical pulse trains having different amplitudes for each communication channel,
Multiplexing means for multiplexing the plurality of optical pulse trains on a time axis to generate an optical multiplexed signal. 15. The optical signal multiplexing apparatus according to claim 14, further comprising a modulation unit that performs different encoding for each optical pulse train for each communication channel. 15. The optical signal multiplexing apparatus according to claim 14, wherein said multiplexing unit has a function of multiplexing a plurality of sets of optical multiplexed signals having different carrier frequencies on a frequency axis. The pulse train generating means further comprises at least one of a phase control means for giving a different phase to the optical pulse train for each communication channel, and a polarization control means for giving a different polarization direction to the optical pulse train for each communication channel. The optical signal multiplexing device according to claim 14, wherein The pulse train generating means,
A pulse light source for generating a light pulse;
15. The optical signal multiplexing apparatus according to claim 14, further comprising: an optical signal branching unit that branches the optical pulse at a predetermined branching ratio. The pulse train generating means,
A light source that generates continuous light with a constant amplitude over time,
The optical signal multiplexing apparatus according to claim 14, further comprising a sideband generator including an optical resonator having a modulator therein. An optical multiplexed signal demultiplexing apparatus that separates an optical multiplexed signal in which a plurality of optical signals having the same carrier frequency are multiplexed into a plurality of optical signals,
An optical non-linear medium whose refractive index changes according to the light intensity of the incident light, an optical frequency conversion means for frequency-converting the received optical multiplexed signal into a plurality of optical pulse trains having different carrier frequencies for each communication channel,
An optical multiplexing signal separating device, comprising: an optical frequency selecting unit that selects the plurality of optical pulse trains converted by the optical frequency converting unit in accordance with a frequency and separates them for each communication channel. 21. The optical multiplexing apparatus according to claim 20, wherein said optical frequency converting means comprises an amplifying means for amplifying an amplitude level of an incident optical multiplex signal, and inputting the amplified optical multiplex signal to said optical nonlinear medium. Signal separation device. 21. The optical multiplexed signal demultiplexing apparatus according to claim 20, wherein said optical frequency conversion means includes compression means for compressing a pulse width of said optical pulse train. The optical nonlinear medium has a zero-dispersion wavelength at which the propagation velocity is maximized at a wavelength shorter than the center wavelength of the optical pulse, and has a chromatic dispersion of +1 ps / nm / km or more at the center wavelength of the optical pulse. 21. The optical multiplex signal separation device according to claim 20, wherein the device is an optical fiber. 21. The optical multiplex signal demultiplexing apparatus according to claim 20, further comprising an optical amplitude control means for controlling an optical intensity of an incident optical signal to obtain an optical multiplex signal having a different amplitude for each communication channel. An optical amplifying unit provided between the optical amplitude control unit and the optical frequency conversion unit and amplifying the optical multiplexed signal obtained by the optical amplitude control unit while maintaining the light intensity ratio of the optical multiplexed signal; 25. The optical multiplexed signal demultiplexing device according to claim 24, further comprising: 25. An optical signal compressing means provided between the optical amplitude control means and the optical frequency converting means or inside the optical frequency converting means for compressing a pulse width of an optical multiplex signal. Optical multiplex signal demultiplexer. 25. The optical multiplex signal demultiplexing apparatus according to claim 24, wherein said optical amplitude control means is constituted by an optical intensity modulator.

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