JP4051324B2 - Optical signal processing apparatus and optical signal processing method - Google Patents

Description

  The present invention relates to an optical signal processing device and an optical signal processing method, and more specifically, an optical signal processing device having a function of exchanging an optical label attached to an optical packet signal having a high bit rate, and an implementation thereof. The present invention relates to an optical signal processing method.

  In order to realize a flexible optical packet communication network based on a label switching technology such as MPLS (Multi Protocol Label Switching), an optical label switching technology at a node in the network is indispensable. Here, the optical label switching technology recognizes and decodes an optical label attached to an optical packet signal input to a node, and assigns a new optical label to the optical signal before forwarding the optical packet signal to the next node. This is a technology for changing labels.

  As such an optical label exchange method, for example, a subcarrier method is adopted as an optical label coding method, and an optical label pasting by subcarrier modulation and an optical label erasing by frequency filtering are sequentially executed. (See, for example, Non-Patent Document 1).

JP 2002-148574 A JP 2002-135208 A J. Cao et. Al., “Error-Free Multi-Hop Cascade Operation of Optical Label Switching Routers with All-Optical Label Swapping” Proceedings of OFC2003, FS1 (March 28, 2003).

  However, in the subcarrier method that is an optical label coding method, the frequency band that can be allocated to the signal sequence (payload) that transmits the main information of the optical packet is separated from the frequency band used by the subcarrier. There is a problem that it is difficult to increase the payload bit rate because it is limited to a low frequency band.

  The present invention has been made in view of such a problem, and an object thereof is to enable replacement of an optical label attached to an optical packet signal having a high bit rate payload exceeding 40 Gbit / s. An optical signal processing apparatus and an optical signal processing method for realizing the same are provided.

In order to achieve the above object, according to the present invention, an invention according to claim 1 includes an optical demultiplexing unit for bifurcating an input serial optical signal string, and the two-branched serial optical signal string. One optical pulse generating means for generating a single optical pulse whose timing is synchronized with the serial optical signal sequence, and the other of the two branched serial optical signal sequences are input, and the single optical pulse is input Optical-optical serial-parallel conversion means for developing the serial optical signal train in parallel using a single optical pulse output from the generating means, and optical signals expanded in parallel by the optical-optical serial-parallel conversion means Photoelectric conversion means for converting the parallel electrical signal, an electronic circuit that processes the parallel electrical signal and outputs a parallel electrical signal associated with a new serial optical signal sequence, and the single Using a single light pulse outputted from the pulse generating means, the parallel electric signal associated with the new serial optical signal train, a constant delay value determined for the input serial optical signal train An optical signal processing apparatus comprising: an electro-optical parallel / serial conversion means for reconstructing and outputting a new serial optical signal sequence.

  According to a second aspect of the present invention, in the optical signal processing device according to the first aspect, the single optical pulse generator detects a leading pulse of the input optical signal train and holds a predetermined voltage value. A sample-and-hold circuit for generating an electric signal; an electric pulse generating means for detecting a rising edge of the stepped electric signal to generate a single electric pulse signal; and the input light based on a modulation signal of the electric pulse signal And a semiconductor laser diode that generates a single optical pulse synchronized in timing with the leading pulse of the signal train.

  According to a third aspect of the present invention, in the optical signal processing device according to the first aspect, the single optical pulse generating means receives one of the two branched input optical signal sequences, and the input optical signal sequence A sample-and-hold circuit for detecting a leading pulse and generating a stepped electric signal holding a predetermined voltage value, and an electric pulse generating means for detecting a rising edge of the stepped electric signal and generating a single electric pulse signal And the other of the two-branched input optical signal train and the electric pulse signal are input, and based on the electric pulse signal, the first pulse of the other input optical signal train is extracted and output. And means.

According to a fourth aspect of the present invention, in the optical signal processing device according to the first aspect, the single optical pulse generating means includes a first single pulse generating means and a second single pulse generating means. Each of the first single pulse generating means and the second single pulse generating means has a different configuration from any of the single pulse generating means according to claim 2 or claim 3, The first single pulse generating means supplies a single optical pulse to the optical-optical serial / parallel converting means, while the second single pulse generating means is the electro-optical serial / parallel converting means. A single light pulse is supplied to the first.

According to a fifth aspect of the present invention, in the optical signal processing device according to the first aspect, a delay value having a constant value is provided between the optical demultiplexing unit and the optical-optical serial / parallel conversion unit. A single optical delay device, and a second optical delay device having a fixed delay value between the single optical pulse generator and the electro-optical parallel / serial converter. The delay time between the inputted serial optical signal train and the outputted single optical pulse in one optical pulse generating means is characterized by being constant.
The invention described in claim 6, in the optical signal processing apparatus according to any one of claims 1 to 5, the correspondence between the parallel electric signal and the new serial optical signal train, rewritable verification externally It is made by a table.

According to a seventh aspect of the present invention, in the optical signal processing device according to any one of the first to sixth aspects, the serial optical signal sequence includes an optical label as a component, and the optical signal processing device includes the optical label of the optical label. It is characterized by exchanging.

The invention according to claim 8 is an optical signal processing system for processing a finite-length serial optical signal sequence composed of a plurality of fractions, an optical demultiplexing means for bifurcating the input optical signal sequence, One of the branched optical signal trains is input, an electric pulse generating means for generating a rectangular wave electric signal synchronized in timing with the optical signal train, and the other of the two branched optical signal trains is input, and the electric pulse based on a control signal from the generating means, and an optical switch for outputting the separating the optical signal train into two fractions, one of claims 1 to 7 one of the two fractions of the optical signal train is input An optical signal processing device according to claim 1, and a multiplexing means for combining and outputting the other fraction of the optical signal sequence output from the optical switch and the optical signal sequence output from the optical signal processing device. The For example, characterized in that is.

The invention according to claim 9 is an optical signal processing method, comprising: a first step of bifurcating an input serial optical signal string; and one of the two branched serial optical signal strings is converted into a single optical pulse. Based on the second step of generating a single optical pulse that is input to the generation means and synchronized in timing with the serial optical signal train, and based on the single optical pulse output from the single optical pulse generation means, the 2 A third step of developing the other of the branched serial optical signal trains in parallel, a fourth step of converting the parallel-developed optical signal trains into parallel electrical signals, and processing the parallel electrical signals to generate new A fifth step of outputting a parallel electric signal associated with the serial optical signal sequence, and the new serial optical signal based on the single optical pulse output from the single optical pulse generating means. Parallel electrical signals correlated to the, and a sixth step of outputting the reconstructed new serial optical signal train having a constant delay value determined for the input serial optical signal train It is characterized by.

According to a tenth aspect of the present invention, in the optical signal processing method according to the ninth aspect of the invention, the single optical pulse generating means includes a first single pulse generating means and a second single pulse generating means. Each of the first single pulse generating means and the second single pulse generating means has a different configuration from any of the single pulse generating means according to claim 2 or claim 3, parallel development of serial optical signal train is performed based on a single light pulse supplied from one of said first single pulse generating means and said second single pulse generating means in the third step, The reconstruction of the serial optical signal train in the sixth step is executed based on a single optical pulse supplied from the other of the first single pulse generating means and the second single pulse generating means. That features To.

  The payload bit rate in the subcarrier method is limited to the modulation band of label coding, but according to the optical signal processing method of the present invention, such limitation can be eliminated.

  According to the present invention, replacement of an optical label exceeding 40 Gbit / s attached to an optical packet signal having a payload exceeding 40 Gbit / s, which has been difficult to realize by the subcarrier system which is a conventional optical label coding system. An optical signal processing device and an optical signal processing method that enable the above can be provided.

  In addition, according to the present invention, it is possible to perform efficient optical label exchange, which is transparent (no photoelectric conversion or signal processing) for the payload, but performs photoelectric conversion and signal processing only for the optical label. Apparatus and method can be provided.

  In addition, according to the present invention, the properties (wavelength, intensity, pulse width, polarization) of the optical pulse constituting the output optical label signal sequence are the same while retaining the properties of the optical pulse constituting the input optical label signal sequence. Can be.

  In addition, according to the present invention, even if the properties (wavelength, intensity, pulse width, polarization) of the optical pulse constituting the input optical label signal sequence are uncertain, the light constituting the output optical label signal sequence It is also possible to newly define the nature of the pulse.

  Furthermore, according to the present invention, it is possible to provide an apparatus and a method that enable flexible optical label exchange using a collation table that can be rewritten as needed.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram for explaining a basic configuration example of a system (apparatus) using an optical signal processing apparatus of the present invention. In this figure, an optical signal to be processed by an optical signal processing system is a payload and this payload. A case where the optical signal sequence is a finite-length serial optical signal sequence (optical packet) composed of an optical label attached to is described. In the present specification, the description will be made assuming that the component of the input optical signal sequence is an optical label. However, the input optical signal sequence may be a serial optical signal sequence, and the optical label is necessarily used as the component. There is no need.

  In the figure, reference numeral 10 denotes an input optical signal (input optical packet) input to the optical signal processing apparatus, and is composed of an optical label 10a and a payload 10b. Reference numeral 11 denotes an optical demultiplexer that divides the input optical packet 10 into two branches, and 12 denotes an electric pulse generation that generates one of the two branched optical packets as an input and generates a rectangular wave electric signal synchronized in timing with the input optical packet. It is a vessel. The electric pulse generator 12 generates a single electric pulse that is synchronized in timing with the leading pulse of the input optical packet.

  13 is provided with two output ports for separating the payload 10b and the optical label 10a of the input optical packet 10 from each other and inputting the other one of the optical packets branched in two by the optical demultiplexer 11, and outputting each of them. The switch distributes the payload 10b and the optical label 10a to each output port in time according to the value of the control voltage that changes with time, and outputs them. In the optical signal processing system having the configuration shown in FIG. 1, the output from the electric pulse generator 12 is used as a control voltage for this purpose.

  Reference numeral 14 denotes an optical label exchange device that inputs the optical label 10 a separated by the 1 × 2 switch 13 and outputs a new optical label 10 a ′. Reference numeral 15 denotes a new optical label 10 a ′ output from the optical label exchange device 14. And the payload 10b output from the 1 × 2 switch 13 are combined and output as an output optical signal (output optical packet) 10 ′.

  FIG. 2 is a diagram for explaining a first configuration example of the optical label exchange apparatus provided in the optical signal processing system of the present invention. The optical label switching device 14 receives an optical demultiplexer 21a that bifurcates an optical label 10a that is an input optical signal sequence, and inputs one optical signal sequence of the bifurcated optical label 10a as a timing to an input optical signal sequence. A single optical pulse generator 22 that generates a single synchronized optical pulse, an optical demultiplexer 21b that splits the single optical pulse output from the single optical pulse generator 22, and a light that has been split into two An optical-optical serial-to-parallel converter 23 that spatially develops the other input optical signal sequence of the label 10a in parallel using a single optical pulse output from the single optical pulse generator 22; Photoelectric converter 24 for converting the parallel optical signal expanded in parallel by the serial-to-parallel converter 23 into a parallel electrical signal, and processing the parallel electrical signal converted by the photoelectric converter 24 to produce a new optical label 10a ′ Vs. The parallel electrical signal output from the electronic circuit 25 is re-converted into a new serial optical signal sequence using the electronic circuit 25 that outputs the parallel electrical signal and the single optical pulse output from the single optical pulse generator 22. And an electro-optical parallel-serial converter 26 that is constructed and outputs a new optical signal sequence.

  The optical label switching device 14 has an input terminal and an output terminal (not shown). When an n-bit serial optical signal sequence (optical label 10a) is input, the input optical label 10a is optical. The signal is branched into two by a demultiplexer 21, one being led to a single optical pulse generator 22 and the other being led to an optical-optical serial / parallel converter 23.

  The single optical pulse generator 22 outputs a single optical pulse synchronized in timing with the leading pulse of the optical label 10a, and this optical pulse is branched into two by an optical demultiplexer 21b, one of which is an optical-optical serial The control light pulse for the parallel converter 23 is used, while the other is the single light pulse input for the electro-optical parallel / serial converter 26. At this time, by adjusting the input timing of the optical label 10a to the optical-optical serial / parallel converter 23 using the fixed optical delay device 27, the time window in the optical-optical serial / parallel conversion is adjusted. The timing is matched with the input timing of the control light pulse. By adjusting the timing of this time window, optical-optical serial / parallel conversion of the optical label 10a is executed correctly.

  The optical label 10 a developed in parallel by the optical-optical serial / parallel converter 23 is converted into a parallel electric signal by the photoelectric converter 24 and input to the electronic circuit 25. The electronic circuit 25 recognizes the pattern of the optical label 10a and generates a new n-bit optical label pattern based on the recognition result in the form of a parallel electric signal.

  An n-channel parallel electric signal output from the electronic circuit 25 is input to the electro-optical parallel / serial converter 26, and in synchronization with a single optical pulse supplied from the single optical pulse generator 22, An n-bit serial optical label signal (new optical label 10a ') is reconstructed. At this time, the optical delay unit 28 delays the input timing of the single optical pulse supplied to the electro-optical parallel / serial converter 26 until the timing of the parallel electrical signal input from the electronic circuit 25 is determined. Thus, the electro-optical parallel / serial conversion of the new optical label 10a ′ is correctly executed. This delay value is set approximately equal to the sum of the optical-optical serial / parallel conversion in the optical-optical serial / parallel converter 23, the photoelectric conversion in the photoelectric converter 24, and the signal processing time in the electronic circuit 25. Is done. In addition, when the processing algorithm in the electronic circuit 25 is the same, it can be set as the fixed fixed value.

  FIG. 3 is a diagram for explaining a configuration example of the single optical pulse generator 22 (see Patent Document 1). The single optical pulse generator 22 generates a stepped electric signal generated by the sample and hold circuit 31. Based on this, an electric pulse is generated by the rising edge detection type electric pulse generation circuit 32, and the semiconductor laser diode 33 is driven by this pulse-like modulation signal to obtain a single optical pulse output. By using the single optical pulse generator configured as described above, it is possible to generate a single optical pulse that is synchronized in timing with the leading pulse of the input optical signal string, in other words, the leading pulse of the input optical signal string. It becomes possible to make the time delay which arises between input timing and the output timing of a single optical pulse into the fixed fixed value. In this case, the characteristic (wavelength, intensity, pulse width, polarization) of the output optical pulse is a definite value newly defined irrespective of the input signal.

  As described above, the single optical pulse generator 22 which is an optical signal input unit of the optical label switching apparatus having the configuration shown in FIG. 2 is inherent as a delay time generated between the input optical signal and the output optical signal. Also, as will be described later, an electro-optical parallel / serial converter 26 which is an optical signal output unit of the optical label switching apparatus is also generated between the input optical signal and the output optical signal. It has a specific fixed value as a delay time. Further, the electro-optical parallel / serial converter 26 receives the output optical signal of the single optical pulse generator 22, and the single optical pulse generator 22 and the electro-optical parallel / serial converter 26. The optical delay device 28 inserted between the two is a fixed delay device having a fixed fixed delay time. Accordingly, the optical label switching device 14 having the configuration shown in FIG. 2 has a fixed delay value between the signal input timing at the input terminal and the signal output timing at the output terminal. Is.

  Further, the single optical pulse generator 22 included in the optical label switching device 14 is configured to use an independent light source that generates a new optical pulse different from the input optical pulse, thereby forming an input optical label signal sequence. Even if the properties (wavelength, intensity, pulse width, polarization) of the optical pulse to be generated are uncertain, the properties of the optical pulse constituting the output optical label signal sequence have a newly defined definite value. Can be.

  Instead of the single pulse generator shown in FIG. 3, the configuration shown in FIG. 4 may be used (see Patent Document 2). The single optical pulse generator 22 having the configuration shown in this figure inputs one of the two branched input signals to the sample and hold circuit 31 and detects the rising edge based on the generated stepped electric signal to thereby generate an electric signal. In this configuration, an electric pulse is generated by the pulse generation circuit 32, and only the head pulse is transmitted from the other input signal branched in two by the intensity optical modulator 34 driven by this electric pulse, and a single optical pulse output is obtained.

  When the single optical pulse generator 22 is configured in this way, a single optical pulse that is synchronized in timing with the leading pulse of the input optical signal train is generated, that is, the input timing of the leading pulse of the input optical signal train is The time delay that occurs during the output timing of one light pulse can be a fixed constant value. In this case, the characteristics (wavelength, intensity, pulse width, polarization) of the output optical pulse are characterized in that the characteristics of the leading pulse of the input optical signal sequence are maintained as they are and the two characteristics are the same. It should be noted that a fixed loss is incurred with respect to strength.

  In the optical label switching apparatus including the single optical pulse generator having the configuration shown in FIG. 4, the input terminal thereof is similar to the optical label switching apparatus having the single optical pulse generator having the configuration illustrated in FIG. 3. In this case, a certain fixed delay value is obtained between the signal input timing at and the signal output timing at the output terminal.

  On the other hand, the optical label switching apparatus including the single optical pulse generator configured as shown in FIG. 4 is different from the optical label switching apparatus including the single optical pulse generator configured as shown in FIG. The single optical pulse generator shown in Fig. 1 transmits and extracts the first pulse of the optical label before conversion, so that the properties (wavelength, intensity, pulse width) of the optical pulse constituting the output optical label signal sequence , Polarization) is characterized in that the properties of the optical pulses constituting the input optical label signal sequence are the same (characterized by incurring a certain fixed loss with respect to intensity). .

  FIG. 5 is a diagram for explaining a second configuration example of the optical label exchange apparatus provided in the optical signal processing apparatus of the present invention. In the optical label switching device 14, in the optical label conversion device having the configuration shown in FIG. 2, the single optical pulse generator is composed of first and second single pulse generators.

That is, in this optical label conversion device, one optical signal sequence of the optical label 10a branched into two by the optical demultiplexer 21 is branched into two by the optical demultiplexer 29, and one optical label signal sequence is converted into the first single signal sequence. One optical pulse generator 22a is input, and the other optical label signal train is input to the second single optical pulse generator 22b. Here, the first single optical pulse generator 22a is set to one configuration of the configuration shown in FIG. 3 or FIG. 4, a second single optical pulse generator 22b is 3 or 4 The other configuration different from the first single optical pulse generator 22a is shown. The first single optical pulse generator 22a supplies a control optical pulse to the optical-optical serial / parallel converter 23, and the second single optical pulse generator 22b is an electro-optical parallel / parallel converter. A single light pulse is supplied to the serial converter 28.

  Also in the optical label switching apparatus having the configuration shown in FIG. 5, between the signal input timing at the input terminal and the signal output timing at the output terminal based on the same principle as the optical label switching apparatus having the configuration shown in FIG. Is characterized by having a fixed fixed delay value.

  Further, the optical label switching apparatus having the configuration shown in FIG. 5 supplies two single optical pulses to the optical-optical serial / parallel converter 23 and the electro-optical parallel / serial converter 26 independently. Since the single optical pulse generator (22a, 22b) is provided, the properties of the two single optical pulses supplied to these parallel / serial converters (23, 26) can be made different from each other. It becomes. This feature provides a control light having an optimum property according to the type of optical-optical serial / parallel converter used, and an output optical signal having a property suitable for an optical communication system to be applied. Making it possible to achieve both

  For example, when an optical label conversion apparatus is configured using an optical-optical serial / parallel converter as shown in FIG. 6 to be described later, the polarization state of the control light pulse to be supplied is determined as a linear polarization having a fixed direction. A wave is desirable. In this case, the first single light pulse generator 22a for generating the control light pulse may be configured as shown in FIG. On the other hand, when it is desired to keep the wavelength and pulse width of the newly generated optical label the same as that of the optical label before conversion, the first step of supplying the optical pulse to the electro-optical parallel / serial converter 26 is performed. The two single optical pulse generators 22b may be configured as shown in FIG.

  6 and 7 are diagrams for explaining a configuration example of the optical-optical serial / parallel converter (FIG. 6) and the electro-optical parallel / serial converter (FIG. 7) included in the optical label conversion apparatus of the present invention. (See Patent Document 1).

  The optical-optical serial / parallel converter shown in FIG. 6 is demultiplexed by the 1-to-n optical demultiplexer 61 that demultiplexes the input n-bit serial optical signal train into n and the optical demultiplexer 61. N optical delay devices 62 corresponding to each light, a polarizing beam splitter (PBS) 63, a quarter wavelength plate (λ / 4 plate) 64, a condenser lens 65, and a reflection type surface light. The optical switch 66;

The input optical signal is an n-bit serial optical pulse signal train, and this input signal is demultiplexed into n by the optical demultiplexer 61, and each optical delay device is arranged so that each optical wave is shifted in time by 1 bit. Delayed by (62 ₁ , 62 ₂ ,... 62 _n ). In this case, there exists a time window 67 in which n-bit optical pulses of the original serial optical signal are included one by one in the n parallel optical signals. A single optical pulse whose timing coincides with the time window 67 is input as control light to the PBS 63 together with the parallel optical signal. The parallel optical signal and the control light are set to linearly polarized light in advance so as to pass through the PBS 63, pass through the PBS 63, and irradiate one point of the surface light-optical switch 66 by the condenser lens 65. The control light is converted into circularly polarized light by the λ / 4 plate 64 disposed between the PBS 63 and the condensing lens 65 and is applied to the surface light-optical switch 66.

  The planar light-optical switch 66 is a switch that utilizes a saturable absorption phenomenon in a semiconductor multiple quantum well structure. Since the circularly polarized control light selectively excites only carriers (electron-hole pairs) having either “upward” or “downward” spins, each signal light is “clockwise” or The reflection coefficient of only one of the “counterclockwise” circularly polarized components increases. As a result, the signal light reflected from the optical switch 66 is in an elliptically polarized state. Here, since the multi-quantum well structure increases the lifetime of excited carriers to 1 to 10 ps or less by low-temperature growth and Be doping, the control light can be used for an optical signal with an ultrahigh bit rate of 40 Gbit / s or more. Only the signal light existing in the same time window 67 is converted into elliptically polarized light.

  Most of the signal light outside the time window 67 is absorbed in the optical switch 66 in the first place, but the signal light that is reflected without being absorbed and enters the PBS 63 remains in its original linear polarization state. Therefore, it passes through the PBS 63 and returns to the left path in the figure. On the other hand, since the signal light of n pits in the time window 67 is converted into elliptically polarized light and reflected, it includes a linearly polarized component orthogonal to the original linearly polarized light, and the orthogonal component is reflected by the PBS 63 and is reflected in the n channel. A parallel optical signal is spatially expanded in parallel and output. Since this parallel output signal does not include any signal outside the time window 67, an extremely high extinction ratio can be obtained.

  In this way, an optical-optical serial / parallel converter for converting an n-bit serial optical signal into an n-channel parallel electrical signal can be configured. Note that it is possible to make the input signal polarization independent by using two optical-optical switches.

  The electro-optical parallel / serial converter shown in FIG. 7 has a 1-to-n optical demultiplexer 71 that demultiplexes an input optical signal into n, and n that are individually driven by n-channel parallel input electrical signals. Optical modulator 72, an optical delay 73 provided corresponding to each of the optical modulators, and an n-to-1 optical multiplexer 74 that multiplexes n parallel optical signals into one. Yes.

A single optical pulse, which is an input optical signal, is demultiplexed into n by the demultiplexer 71, and n parallel optical pulses are generated. Each of these n optical pulses is intensity | strength using an optical modulator (72 ₁ , 72 ₂ , 72 ₃ ,... 72 _n ) by one channel signal among n-channel parallel input electrical signals. Modulated. The intensity-modulated n pulse signals are combined after being delayed by optical delay devices (73 ₁ , 73 ₂ , 73 ₃ ,... 73 _n ) so that each of them is shifted in time by 1 bit. Combined by a device 74.

  In this way, an electro-optical parallel / serial converter that converts an n-channel parallel electric signal into an n-bit serial optical signal is configured. Here, the time delay generated between the input timing of the single optical pulse and the output timing of the n-bit serial optical signal becomes a fixed constant value determined by the length of the optical modulator 72 and the connecting fiber used. It is a feature.

  The optical-optical serial / parallel converter and the electro-optical parallel / serial converter included in the optical signal processing apparatus of the present invention are not limited to the configurations shown in FIGS. .

  In addition, in the above description, all of the properties (wavelength, intensity, pulse width, polarization) of the optical pulses that make up the output optical label signal sequence are collectively defined regardless of the properties of the input optical pulse. In this example, the output from the electro-optical parallel / serial converter is converted by a wavelength converter using an SOA (Semiconductor Optical Amplifier) or the like. Then, by adopting a configuration that leads to the output terminal after that, it is possible to easily provide a method for newly defining only a part of the properties of the optical pulse constituting the output optical label signal sequence (in this case, only the wavelength).

  Hereinafter, an embodiment of the optical signal processing apparatus of the present invention having the configuration shown in FIG. 1 will be described. In this embodiment, the optical label exchanging apparatus having the configuration shown in FIG. 2 is adopted. The optical label exchanging apparatus employs a single optical pulse generator having the configuration shown in FIG. The serial / parallel converter and the electro-optical parallel / serial converter have the configurations shown in FIGS. 6 and 7, respectively.

FIG. 8 is a diagram for explaining a sample-and-hold circuit used in a single optical pulse generator (see Patent Document 1). This sample-and-hold circuit performs an optical-current conversion on an input optical signal 81. PD (Metal-Semiconductor-Metal Photodetector ) 82, a constant voltage source _V pd 83 and _V rs 84, consisting of the hold capacitor 85, reset FET 86, and the output buffer 87. In this circuit, the potential of the hold capacitor 85 (the potential of the upper electrode) is reset to V _rs by inputting an electrical reset signal to the reset FET 86 in advance. When the leading pulse of the input optical signal 81 is input to the MSM-PD 82 in this reset state, the potential of the hold capacitor 85 is charged from V _rs to V _pd by the generated photocurrent. Since the charged charge of the hold capacitor 85 is held, the potential of the hold capacitor 85 is kept fixed at V _pd without being affected by the second and subsequent input light pulses. Then, the potential of the hold capacitor 85 is output to the outside through the output buffer 87 as an electric signal. By this series of operations, the sample and hold circuit outputs a stepped electric signal having a rising timing synchronized with the leading pulse of the input optical signal sequence.

  The sample and hold circuit of this example was fabricated as a monolithic integrated circuit on an InP substrate, which was composed of an MSM-PD82, a hold capacitor 85, and an FET 86 having InGaAs as a light absorption layer having sensitivity in the 1.55 micron band. The FET 86 is used to configure a reset switch and an output buffer 87 for extracting the capacitor voltage to the outside, and by making it monolithically integrated, the parasitic capacitance associated with the MSM-PD 82 and the output buffer 87 is made almost zero. I was able to. Due to this reduction in capacitance, a high sensitivity value of 0.5 picojoule per pulse could be obtained as the sensitivity of the sample and hold circuit. Further, if the energy of the first pulse is 0.5 picojoules or more, a desired step signal can be generated regardless of the second and subsequent input light pulses.

  The electric pulse generation circuit 32 is composed of an IC made of GaAs capable of signal processing of 10 Gbit / s. As a result, a rectangular electric pulse having both rise time and fall time of 40 ps or less could be generated.

  The semiconductor laser diode 33 is a DFB (Distributed Feedback) laser. As a result, it was possible to generate a single optical pulse having a pulse width of 10 picoseconds which was synchronized in timing with an accuracy of ± 2 picoseconds with respect to the leading pulse of the input optical signal sequence.

The time step width (τ) of the optical delay device constituting the optical-optical serial / parallel converter 23 was set to 25 picoseconds. The response speed of the reflective surface light-optical switch 66 was set as follows. The growth temperature of the saturable absorber InGaAs / InAlAs multiple quantum well structure was set to a low temperature of 200 ° C., and Be was added as a dopant at 2 × 10 ¹⁷ cm ⁻³ . As a result, the lifetime of the excited carrier is as short as 10 picoseconds or less, and parallel conversion of a 40 Gbit / s RZ (Return to Zero) serial optical signal is possible.

  The optical modulator 72 constituting the electro-optical parallel / serial converter 26 has a waveguide type intensity using QCSE (Quantum-confined Stark Effect) using an InP-based semiconductor multiple quantum well structure as an absorption layer. A modulator was used. With this modulator, an extinction ratio of 20 dB or more can be obtained with a drive voltage amplitude of 3.3V. Therefore, direct drive by the output voltage from the silicon CMOS circuit operating with a power supply voltage of 3.3V is possible. In addition, by setting the time interval (τ) of the optical delay device 73 to 25 picoseconds, it is possible to output a 40 Gbit / s RZ serial optical signal.

  Hereinafter, the result of an optical label exchange experiment performed using the optical signal processing apparatus having the above-described configuration will be described.

  The format of the input optical packet is an RZ format with a bit rate of 40 Gbit / s, and the payload is composed of a 16-bit label, a 1-bit zero (guard time), and an arbitrary number of bits in order from the beginning of the packet. The bit rate is 40 Gbit / s for both the label and the payload, and the optical pulse constituting the optical packet has a wavelength of 1.55 μm and a pulse width of 10 picoseconds.

  The input optical packet is branched into two and led to the 1 × 2 switch 13 and the electric pulse generator 12. The electric pulse generator 12 has a configuration in which the semiconductor laser diode is omitted from the single optical pulse generator shown in FIG. 3, and generates a single electric pulse synchronized in timing with the leading pulse of the input optical packet. Here, the generated electric pulse width is set to 600 picoseconds, which is slightly longer than the duration of the 16-bit label.

  The 1 × 2 switch 13 is a switch having a bandwidth of 20 Gbit / s made of LN (Lithium Niobate). This 1 × 2 switch 13 distributes one optical packet branched in two to two output ports in time according to a control voltage value that changes with time, and outputs it. The output from the electric pulse generator 12 is used as the control voltage for this purpose, and the timing is adjusted using a fixed optical delay device so that the falling timing of the control voltage pulse coincides with the guard time in the optical packet. .

  By such setting and timing adjustment of the electric pulse width, the 1 × 2 switch 12 separates the optical label 10a and the payload 10b of the input optical packet and outputs each from the two output ports.

  Here, a conceptual diagram for explaining the configuration and function of the electronic circuit used in the optical label switching device 14 is shown in FIG. As an electronic circuit, a silicon CMOS circuit that operates with a power supply voltage of 3.3 V, which has 16 parallel input terminals and 16 parallel output terminals, is used. In the circuit, a collation table that associates the old label pattern before conversion and the new label pattern after conversion is stored, and this collation table can be rewritten from the outside. The process executed by this circuit is to collate the input signal with a collation table and generate an output signal associated with the input signal. For example, if the input old label pattern is B, B ′ Is generated as a new label pattern. As a matter of course, both B and B ′ are 16-bit patterns.

  The optical label switching device 14 receives the old optical label 10a separated / extracted by the 1 × 2 switch 13, and executes a process according to the above collation table in the CMOS circuit to generate a new optical label 10a ′. To do. The new optical label 10a ′ and the payload 10b extracted by the 1 × 2 switch 13 are combined by the optical multiplexer 15 to construct an output optical packet 10 ′.

  As described above, the optical label switching apparatus has a fixed fixed delay value between the signal input timing at the input terminal and the signal output timing at the output terminal. The time delay that occurs between the output timing of the extracted payload 10b output from the × 2 switch 13 and the generation timing of the new optical label 10a ′ is also a fixed value that is determined. With this feature, it is possible to adjust the timing of combining the extracted payload and the new optical label by a fixed optical delay device, and to make the format of the output optical packet 10 ′ the same as that of the input packet. That is, the RZ format has a bit rate of 40 Gbit / s, and the 16-bit new label, 1-bit zero (guard time), and payload can be configured in order from the beginning of the packet. In this way, optical label exchange of 40 Gbit / s optical packets, which is controlled by a rewritable collation table, can be executed.

  In this embodiment, a switch made of LN is used as the 1 × 2 switch. However, the configuration uses one one-to-two optical demultiplexer and two complementary driven SOAs. Thus, other switch configurations can be used.

  In the above embodiment, the payload bit rate is 40 Gbit / s. However, the payload bit rate may be arbitrary.

  In the above embodiment, the number of bits of the optical label is 16 and the bit rate is 40 Gbit / s. However, as long as it is a predetermined constant value and within the operable range of the optical label switching apparatus, Any number of bits and any bit rate may be used. However, when changing the number of bits and the bit rate of the optical label, it is natural that the configuration of the optical label switching apparatus needs to be changed in accordance with the number of bits and the bit rate.

  Furthermore, in the above embodiment, the guard time between the optical label and the payload is 1 bit length, but it may be as short as possible within the allowable range of the band of the 1 × 2 switch.

  For example, by using a 1 × 2 switch having a bandwidth of 40 Gbit / s, the optical packet format is configured as a 32-bit label of 40 Gbit / s (n = 32), no guard time, and a payload of 160 Gbit / s. Or, it is possible to adopt a structure of a 64-bit label (n = 64) of 80 Gbit / s, a guard time of 1 bit, and a payload of 320 Gbit / s.

  The present invention makes it possible to provide an optical signal processing apparatus having a function of exchanging an optical label given to an optical packet signal having a high bit rate, and an optical signal processing method for realizing the optical signal processing apparatus.

It is a figure for demonstrating the example of a basic composition of the optical signal processing system of this invention. It is a figure for demonstrating the 1st structural example of the optical label switching apparatus with which the optical signal processing apparatus of this invention is provided. It is a figure for demonstrating the 1st structural example of a single optical pulse generator. It is a figure for demonstrating the 2nd structural example of a single optical pulse generator. It is a figure for demonstrating the 2nd structural example of the optical label switching apparatus with which the optical signal processing apparatus of this invention is provided. It is a figure for demonstrating the structural example of the optical-optical type serial parallel converter with which the optical label converter of this invention is provided. It is a figure for demonstrating the structural example of the electro-optical type parallel serial converter with which the optical label converter of this invention is provided. It is a figure for demonstrating the sample hold circuit used for the single optical pulse generator. It is a conceptual diagram for demonstrating the structure and function of an electronic circuit used for the optical label switch apparatus.

Explanation of symbols

10 Input optical signal (input optical packet)
10 'output optical signal (output optical packet)
10a, 10a ′ Optical label 10b Payload 11 Optical demultiplexer 12 Electric pulse generator 13 1 × 2 switch 14 Optical label switching device 15 Optical multiplexer 21 Optical demultiplexer 22 Single optical pulse generator 23 Optical-optical serial Parallel converter 24 Photoelectric converter 25 Electronic circuit 26 Electric-optical parallel / serial converter 27, 28 Optical delay device 29 Optical demultiplexer 31 Sample hold circuit 32 Electric pulse generation circuit 33 Semiconductor laser diode 34 Intensity optical modulator 61 1-to-n optical demultiplexer 62 Optical delay device 63 Polarizing beam splitter (PBS)
64 1/4 wavelength plate (λ / 4 plate)
65 condensing lens 66 surface type optical-optical switch 67 time window 71 1-to-n optical demultiplexer 72 optical modulator 73 optical delay unit 74 n-to-1 optical multiplexer 81 input optical signal 82 MSM-PD
83 Constant voltage source V _pd
84 Constant voltage source V _rs
85 Hold capacitor 86 Reset FET
87 Output buffer

Claims (10)

Optical demultiplexing means for branching the input serial optical signal train into two branches;
Single optical pulse generating means for inputting one of the two branched serial optical signal trains and generating a single optical pulse synchronized in timing with the serial optical signal train;
Optical-optical serial / parallel conversion in which the other of the two-branched serial optical signal train is input and the serial optical signal train is developed in parallel using a single optical pulse output from the single optical pulse generator Means,
Photoelectric conversion means for converting the optical signal developed in parallel by the optical-optical serial / parallel conversion means into parallel electric signals;
An electronic circuit that processes the parallel electrical signal and outputs a parallel electrical signal associated with the new serial optical signal sequence;
Using a single optical pulse output from the single optical pulse generating means, a parallel electrical signal associated with the new serial optical signal sequence is fixed with respect to the input serial optical signal sequence. An optical signal processing apparatus comprising: an electro-optical parallel / serial conversion means for reconstructing and outputting a new serial optical signal sequence having a delay value of: The single light pulse generating means includes
A sample-and-hold circuit that detects a leading pulse of an input optical signal sequence and generates a stepped electrical signal that holds a predetermined voltage value;
An electric pulse generating means for detecting a rising edge of the stepped electric signal and generating a single electric pulse signal;
A semiconductor laser diode that generates a single optical pulse that is synchronized in timing to the leading pulse of the input optical signal sequence based on the modulation signal of the electrical pulse signal;
The optical signal processing apparatus according to claim 1, comprising: The single light pulse generating means includes
A sample-and-hold circuit that receives one of the two branched input optical signal trains, detects a leading pulse of the input optical signal train, and generates a stepped electrical signal holding a predetermined voltage value;
An electric pulse generating means for detecting a rising edge of the stepped electric signal and generating a single electric pulse signal;
Intensity light modulation means for inputting the other of the two branched optical signal sequences and the electric pulse signal, and extracting and outputting the leading pulse of the other input optical signal sequence based on the electric pulse signal; The optical signal processing apparatus according to claim 1, comprising: The optical signal processing device according to claim 1,
The single optical pulse generating means is composed of a first single pulse generating means and a second single pulse generating means,
Each of said first single pulse generating means and said second single pulse generating means has a different configuration of either a single pulse generator according to claim 2 or claim 3,
The first single pulse generating means supplies a single optical pulse to the optical-optical serial / parallel converting means, while the second single pulse generating means is the electro-optical serial / parallel converting means. A single optical pulse is supplied to the optical signal processing apparatus. A first optical delay device having a fixed delay value between the optical demultiplexing means and the optical-optical serial-parallel conversion means;
A second optical delay device having a constant delay value between the single optical pulse generating means and the electro-optical parallel / serial conversion means;
2. The optical signal processing according to claim 1, wherein a delay time between the input serial optical signal train and the output single optical pulse in the single optical pulse generation unit is constant. Equipment . 6. The optical signal processing according to claim 1, wherein the parallel electric signal and the new serial optical signal string are associated with each other by a collation table rewritable from the outside. Equipment . 7. The optical signal processing apparatus according to claim 1, wherein the serial optical signal sequence includes an optical label as a constituent element, and the optical signal processing apparatus exchanges the optical label. . An optical signal processing system for processing a finite-length serial optical signal sequence composed of a plurality of fractions,
Optical demultiplexing means for bifurcating the input optical signal train;
One of the two branched optical signal trains is inputted, and an electric pulse generating means for generating a rectangular wave electrical signal synchronized in timing with the optical signal train,
An optical switch that receives the other of the two branched optical signal trains and separates the optical signal train into two fractions based on a control signal from the electric pulse generator;
The optical signal processing device according to any one of claims 1 to 7, wherein one of two fractions of the optical signal train is input;
Multiplexing means for combining and outputting the other fraction of the optical signal sequence output from the optical switch and the optical signal sequence output from the optical signal processing device;
An optical signal processing system comprising: A first step of branching the input serial optical signal string into two branches;
A second step of inputting one of the two branched serial optical signal trains to a single optical pulse generator and generating a single optical pulse timing-synchronized with the serial optical signal train;
A third step of developing in parallel the other of the two-branched serial optical signal sequence based on the single optical pulse output from the single optical pulse generating means;
A fourth step of converting the parallel-developed optical signal sequence into a parallel electric signal;
A fifth step of processing the parallel electrical signal and outputting a parallel electrical signal associated with the new serial optical signal sequence;
Based on the single optical pulse output from the single optical pulse generating means, the parallel electrical signal associated with the new serial optical signal sequence is fixed with respect to the input serial optical signal sequence. A sixth step of reconstructing and outputting a new serial optical signal sequence having a delay value of
An optical signal processing method comprising: The optical signal processing method according to claim 9, wherein
The single optical pulse generating means is composed of a first single pulse generating means and a second single pulse generating means,
Each of the first single pulse generating means and the second single pulse generating means has a different configuration from any of the single pulse generating means according to claim 2 or claim 3,
The parallel development of the serial optical signal train in the third step is executed based on a single optical pulse supplied from one of the first single pulse generating means and the second single pulse generating means,
The reconstruction of the serial optical signal train in the sixth step is executed based on a single optical pulse supplied from the other of the first single pulse generating means and the second single pulse generating means.
An optical signal processing method .

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