JP2005203993A - Optical signal regenerating repeater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical signal regenerating repeater capable of regenerating an optical communication signal, while minimizing the occurrence of a bit errors, even in general cases wherein the mark levels and space levels form an asymmetrical distribution for inputted optical signal intensity (probability density). <P>SOLUTION: The optical signal regenerating repeater has an optical gate part 3, which obtains a regenerated optical communication signal, by transferring data to controlled light according to opening and closing of a gate, while optical communication signal pulses received as an input optical communication signal are used as control signal to open and close the gate and clock optical pulses are also supplied as continuous light as the controlled light. The optical gate part 3 has a function of compressing the intensity distribution of the input light for a binary level and the optical gate part 3 is so set that an optical identification threshold with respect to the input optical communication signal nearly agrees with the separation border line of the compression of the intensity distribution. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical repeater used in digital optical communication, and more particularly to an optical signal regenerative repeater that repeats digital signal light while identifying and reproducing the optical signal as it is, and driving conditions in such an optical signal regenerative repeater. It relates to the setting method.

  In digital optical communication, an optical communication signal (digital signal light) deteriorates due to various factors such as chromatic dispersion, nonlinear effect, and timing jitter when propagating through an optical fiber transmission line. Therefore, an optical signal regenerative repeater that relays a deteriorated optical communication signal while reproducing it to the same extent as the quality before deterioration is generally required.

  Optical signal regenerative repeaters are classified into several types according to their functions. One of such optical signal regenerative repeaters includes intensity reproduction (Reamplifying), waveform reproduction (Reshaping), and timing reproduction ( There is an optical 3R repeater that performs 3R processing of Retiming (referred to as 3R processing because each acronym is R) without converting the optical signal into an electrical signal. Here, the intensity reproduction process is a process that amplifies the weakened signal light intensity, the waveform reproduction process is a process that shapes the distorted signal waveform, and the timing reproduction process corrects the amplified and shaped optical signal. This is a process of sending at time (bit) intervals.

FIG. 1A shows a general configuration of an optical 3R repeater (see Patent Document 1 and Non-Patent Documents 1 and 2). This optical 3R repeater includes an optical branching device 1, a clock extractor / clock light source 2, and an optical gate unit 3. The optical branching device 1 branches an optical communication signal pulse having a degraded wavelength λ ₁ into two, one of the branched optical communication signal pulses is supplied to the optical gate unit 3 as control light, and the other is clock extracted. The unit / clock light source 2 is supplied. The clock extractor / clock light source 2 extracts a clock (electrical signal or optical signal) from the optical communication signal pulse supplied from the optical branching device 1 and outputs a clock light pulse having a wavelength λ ₂ in synchronization with the extracted clock. Generate. The clock light pulse generated by the clock extractor / clock light source 2 is supplied to the optical gate unit 3. The communication data is transmitted by passing the clock light pulse from the clock extractor / clock light source 2 through the optical gate unit 3 while controlling the opening and closing of the gate of the optical gate unit 3 by the deteriorated optical communication signal pulse (control light). Is transferred to the clock light pulse. In this way, identification data reproduction of the deteriorated data is performed.

  Also, as shown in FIG. 1B, a continuous light source 90 is used instead of the clock extractor / clock light source 2 of the optical 3R repeater shown in FIG. When supplied to the optical gate, it functions as an optical 2R repeater having no timing regeneration effect.

  Recently, with the rapid development of the Internet, there has been an increasing demand for an increase in optical communication capacity, and a high-speed optical gate having a transmission speed (bit rate) of 40 Gb (gigabit) / s or more is required. As a high-speed optical gate corresponding to such a bit rate of 40 Gb / s or more, there is a push / pull type optical gate using light interference. Typical examples thereof include a symmetric Mach-Zehnder optical gate (SMZ (see Patent Document 2 and Non-Patent Document 3)) shown in FIG. 2, and a polarization-separated SMZ optical gate (PD-SMZ or UNI: Ultrafast) shown in FIG. Nonlinear Interferometer (see Patent Document 3, Non-Patent Documents 1 and 4), Nonlinear Optical Loop Mirror (NOLM, SLALOM: Semiconductor Laser Amplifier in a Loop Mirror) or TOAD: Terahertz Optical Asymmetric Demultiplexer (Patent Document 1) And non-patent document 5))). A portion surrounded by a dotted line in the figure corresponds to the optical gate portion.

The symmetric Mach-Zehnder type optical gate shown in FIG. 2 includes an optical splitter 1a that splits an input optical communication signal pulse (control light) having a degraded wavelength λ ₁ into two, and a controlled light (wavelength optical pulse) having a wavelength λ _2. An optical branching device 1b for branching into two, an optical coupler 4a for combining one output of the optical branching device 1a and one output of the optical branching device 1b, and the other output of the optical branching device 1a. Connected to the optical delay circuit 10 for delaying Δt, the optical coupler 4b for combining the other output of the optical branching device 1b and the output of the optical delay circuit 10, and the outputs of the optical couplers 4a and 4b, respectively. The provided nonlinear optical phase shifters 11a and 11b, the linear optical phase shifter 5 connected to the output of the nonlinear optical phase shifter 11b, and the output of the nonlinear optical phase shifter 11a and the output of the linear optical phase shifter 5 are combined. Optical coupler 4c and optical coupler 4c A wavelength bandpass filter (BPF) 12 provided at the output, and the output light of the wavelength bandpass filter 12 is gate transmitted light of wavelength λ ₂ . The provision of the optical delay circuit 10 causes a time difference of Δt between the signal light pulses output from the optical couplers 4a and 4b, respectively, and the clock light pulse is positioned within this time difference. In FIG. 2 and the subsequent drawings, the optical pulse whose quality is deteriorated is shown by a broken pulse waveform, and the clock light pulse and the signal light pulse whose quality is not deteriorated are solid pulse waveforms. It is shown in

The polarization separation type SMZ optical gate shown in FIG. 3 includes a polarization separator 13a that separates controlled light having a wavelength λ ₂ (corresponding to a clock light pulse) and a vertical component light from the polarization separator 13a. An optical delay circuit 10a for delaying Δt with respect to (ii), and a polarization coupler 14a for combining the parallel component light (//) from the polarization separator 13a and the output light of the optical delay circuit 10a. An optical coupler 4 that combines the input optical communication signal pulse (control light) having a degraded wavelength λ ₁ and the output of the polarization coupler 14a, and a nonlinear optical phase shifter 11 provided at the output of the optical coupler 4; A polarization separator 13b that polarizes the output light of the nonlinear optical phase shifter 11, an optical delay circuit 10b that gives a delay of ΔT to the parallel component light (//) from the polarization separator 13b, and a polarization Linear optical phase shifter 5 connected to the output of the vertical component light (⊥) side of the separator 13b A polarization beam combiner 14b that combines the output of the optical delay circuit 10b and the output of the linear optical phase shifter 5, a polarizer 15 provided on the output side of the polarization beam combiner 14b, and a polarizer 15 The wavelength bandpass filter (BPF) 12 provided at the output of the wavelength bandpass filter 12 is provided, and the output light of the wavelength bandpass filter 12 is gate transmitted light of wavelength λ ₂ . By providing the optical delay circuit 10a, there is a time difference of Δt between the clock light pulses of both polarization components at the output of the optical coupler 4, and the signal light pulse is positioned within this time difference. Yes. The time difference Δt between the polarization components is eliminated by the optical delay circuit 10b. The position of the wavelength bandpass filter 12 may be immediately after the nonlinear phase shifter 11 or the polarization coupler 14b.

The nonlinear optical loop mirror type optical gate shown in FIG. 4 includes a loop-shaped optical transmission line, and an input optical communication signal pulse (control light) having a deteriorated wavelength λ ₁ is illustrated in the loop optical transmission line, for example. Optical coupler 4 for introducing clockwise into the loop transmission line, nonlinear optical phase shifter 11, optical delay circuit 10 for delaying Δt, and controlled light of wavelength λ ₂ (corresponding to clock optical pulse) And an optical coupler 16 for taking out the output light from the loop transmission line. In addition, this optical gate comprises a wavelength bandpass filter (BPF) 12 which is connected to the output port of the optical coupler 16, the output light of the wavelength bandpass filter 12 has a wavelength lambda ₂ of the gate transmission light .

  The optical gates shown in FIGS. 2 to 4 are of the interference type as described above. In these optical gates, the nonlinear optical phase shifter may be an optical fiber itself constituting an optical transmission line / loop. It doesn't matter. These optical gates are all types of optical gates that open and close the gate at high speed by using a change in the interference state at the output port by generating a nonlinear phase shift in the subsequent controlled optical pulse by the gate control optical pulse. is there.

  Ueno et al., “Y. Ueno et al., IEEE Photonics Technology Letters, No. 10, pp. 346-348, 1998 (IEEE Photonics Technology Letters” No. 10, published in 1998, Pp. 346 to 348) "(Non-Patent Document 6) proposes a DISC (Delayed Interference Signal-wavelength Converter) type wavelength converter, which is also an interference type light. This DISC wavelength converter is a type of gate that applies a phase shift to the continuous light having a wavelength different from that of the input signal light in a fractional manner on the time axis by the input signal light using a nonlinear optical phase shifter. After that, the replica of the continuous light itself is delayed for a certain time and then interfered so that the light corresponding to the delay time is cut out and output as a signal light whose wavelength has been converted. (Retimin g) It functions as an optical 2R repeater without function, and Leuthold et al., in the above-mentioned DISC type wavelength converter, uses a clock pulse light instead of continuous light, and in the case of interference. “J. Leuthold et al., IEEE Photonics Technology Letters, No. 13, pp. 2001, which was published in 2001, also functions as an optical 3R repeater by using the same amount of time as the bit period. 860-862, 2001 (IEEE Photonics Technology Letters, No. 13, pp. 860-862) (Non-Patent Document 7).

FIG. 5 shows the principle of compression and waveform shaping of the intensity (probability density) distribution of the input signal light when these interference type optical gates are used. The transfer function of a pure interferometric optical gate without gain saturation effect in an optical amplifier is represented by a trigonometric function as shown in the figure, and the slope of the function curve is close to zero (near “0” and “1”). ), The input signal light intensity (noise) distribution is compressed. That is, the intensity variation in the input light is compressed in the output light, and the intensity distribution in the input light is compressed toward the binary level in the output light. That is, when the input light is a space corresponding to “0”, even if there is some light intensity, the intensity of the output light is almost 0, and the mark corresponding to “1” is input light. Even if the light intensity varies somewhat, the light intensity in the output light is almost 1. Here, the average value of the mark level of the input signal light intensity is normalized to “1”, the nonlinear phase shift amount Δφ when the input signal light intensity is “1” is set to “π”, and the phase bias (input signal light “ In the case of 0, the initial phase when the output signal light is also “0” and the phase is “0”) φ ₀ is assumed to be “0”.

  In general, when the nonlinear phase shift amount in the nonlinear phase shifter in the interference type optical gate does not reach π, the distribution compression / waveform shaping effect is reduced. In order to exhibit an equivalent waveform reproduction (compression of signal light intensity distribution) effect on an input optical signal, an optical gate portion having a two-stage configuration is disclosed.

  In Patent Documents 5 and 6, such optical gates are connected in two stages using the above-described NORM as an optical gate, and the first probe light is modulated by the input signal light in the first optical gate to be intermediate. A configuration is disclosed in which an optical signal is output, and an output optical signal is obtained by modulating the second probe light with an intermediate optical signal in a second-stage optical gate. Here, although there is no specific description regarding optimization of the separation boundary line (≈identification threshold) in the light intensity distribution compression described later, in consideration of the phase difference Δψ in the probe light propagating in both directions through the fiber loop, Δψ = It is disclosed that the space level of the input optical signal is assigned to 0 and the mark level of the input optical signal is assigned to Δψ = π.

  In the configurations shown in Patent Documents 5 and 6, the transfer function curve in the optical gate has a light intensity level (an inflection point in the transfer function curve) that becomes a separation boundary line (≈identification threshold) of the light intensity (probability density) distribution. It is anti-symmetric with respect to the level), and vibrates at a constant period with respect to the input optical power. This is an unavoidable characteristic for interference type optical gates. In general, in this curve, when adjusting the input optical power or phase at the optical gate, this function curve has a relative expansion / contraction or shift with respect to the input optical intensity. It only happens. Therefore, for the general optical signal in which the light intensity (probability density) distribution at the mark level and the space level is asymmetric, the configurations of Patent Documents 5 and 6 cannot perform optimum identification and reproduction. In other words, by optimizing only the separation boundary line (≈identification threshold value) by the enlargement / reduction or shift described here (the optimum identification threshold value for the optical communication signal matches the separation boundary line of the light intensity distribution in the optical gate), The input light level at which the slope of the transfer function curve becomes almost zero (the level at which the light intensity distribution (noise) is compressed) deviates from the mark level or the space level, and there is no reproduction effect. Noise).

  As an alternative method for waveform shaping and signal identification / reproduction, the optical output is limited to a substantially constant value for an optical input of a certain power or higher without using an interference optical gate. There has also been proposed a method using a configuration in which only a device having an optical limiter effect and a device having an optical threshold effect that does not output light of a certain power or less are combined (see Patent Documents 7 and 8).

  For example, in Patent Document 8, an optical gate that compresses space level noise and an optical gate that compresses mark level noise are connected in two stages, and the input signal light power is changed to relatively transfer the curve. Discloses a technique for performing optimum discrimination reproduction without shifting the separation boundary line (≈identification threshold) of the intensity distribution compression and reducing the waveform reproduction / noise compression effect. That is, it is shown that by changing the input signal light intensity, the optimum discrimination threshold for the optical communication signal and the separation boundary line of the light intensity distribution in the optical gate are matched. However, there is no specific description about optimizing the separation boundary line (≈identification threshold). In the one shown in Patent Document 8, for example, an electroabsorption optical modulator or a gain clamp amplifier is used as an optical gate, and an interference optical gate is not used. Moreover, in the thing of patent document 8, when changing input signal light power and adjusting a separation boundary line, it may be necessary so that the absolute value of the input light average power may exceed 10 dBm depending on the case. In general, it is not easy to optimize the separation boundary line (≈identification threshold), for example, the amount needs to be close to 10 dB and the power of the probe light incident on the optical gate must be adjusted at the same time.

  By the way, as a clock extractor and clock light source unit applicable to the optical signal regenerative repeater as described above, there are the following.

(1) Photoelectric converter and mode-locked laser:
A clock is extracted from an electrical signal obtained by photoelectrically converting an optical communication signal pulse using a “high-Q filter” and the extracted electrical clock is applied to a mode-locked laser to generate a synchronized pulse. . The output pulse time width at this time is unique to the laser.

(2) Use only mode-locked laser (see, for example, Non-Patent Document 8):
In this case, the optical communication signal pulse is directly injected into the mode-locked laser to cause the synchronous pulse oscillation. Also at this time, the output pulse time width is unique to the laser.

(3) CW laser including a photoelectric converter and a light intensity modulator (see, for example, Non-Patent Document 9):
A clock is extracted from an electrical signal obtained by photoelectrically converting the optical communication signal pulse, and the optical intensity modulator is driven by the extracted electrical clock to generate a clock pulse from CW (continuous) light. The output pulse time width at this time depends on the time shape of the modulation. Since the time shape of the electrical clock extracted using the “High-Q filter” is almost a sine wave, it is difficult to generate a short pulse, but it is possible to generate a pulse with a time width about half that of a bit period. Is possible.
JP-A-8-163047 Japanese Patent Laid-Open No. 07-020510 Japanese Patent Laid-Open No. 08-179385 JP 2002-229081 A JP 2001-249371 A JP 2001-117125 A Japanese Patent Laid-Open No. 09-244073 JP 2003-015097 A HJ Thiele et al., Electron. Lett., 35, 230 (1999) H. Kurita et al., Proc. Of ECOC '99, PD3-6 (1999) K. Tajima, Japan J. Appl. Phys., 32, L1746 (1993) K. Tajima et al., Appl. Phys. Lett., 67, 3709 (1995) MC Farries et al., Appl. Phys. Lett., 55, 25 (1995) Y. Ueno et al., IEEE Photonics Technology Lett., 10, 346 (1998) J. Leuthold et al., IEEE Photonics Technology Lett., 13, 860 (2001) H. Kurita et al., IEICE Trans. Electron., E81-C, 129 (1998) B. Lavigne et al., Proc. Of ECOC 2001, We.F.2.6, (2002)

However, when the signal light intensity (probability density) distribution compression / waveform shaping is performed using the interference type optical gate, the compression direction of the input signal light intensity is reversed as shown in FIGS. 6B and 6C. The separation boundary line (which can be regarded as a signal identification threshold value in this optical gate) is always set to a level at which the inflection point of the trigonometric function curve representing the transfer function of the optical gate exists. That is, when Δφ = π and φ ₀ = 0, the separation boundary line is fixed at the level of 0.5, which is exactly the center. Therefore, as shown in FIG. 6A, the light intensity (noise) distribution of the mark and the space is simultaneously compressed for a general optical signal having a light intensity (probability density) distribution in which the mark level and the space level are asymmetric. When trying to do so, the signal optimum discrimination threshold (in the vicinity of “0.2” in FIG. 6A) and the separation boundary line (“0.5”) do not match, but at first glance, the waveform is reproduced, but the bit error is Conversely, the possibility of increasing increases. In the light intensity distribution shown in FIG. 6A, the probability distribution is minimal when the input light intensity I _i is 0.2, and this level can be used as a threshold for distinguishing between marks and spaces. preferable.

  The separation boundary line compresses the signal light intensity distribution using the interference type optical gate as described above, and the level of the input signal light is either the mark level (“1”) or the space level (“0”). In the case of approaching one of them, it is a level that becomes a boundary of which one of “0” and “1” approaches according to the level of the input signal light. In the case of performing a positive logic gate operation as described later, a signal having a level larger than the separation boundary is compressed toward “1”, and a signal having a level smaller than the separation boundary is compressed toward “0”. Is done. As described above, either compression to the space level or the mark level occurs depending on the magnitude relationship between the separation boundary line and the level of the input light. Therefore, the compression of the signal light intensity (probability density) distribution is performed by the input signal light. It can be considered as a form of identification of mark level or space level, and the separation boundary can be considered as an identification threshold in such identification.

  The optimum discrimination threshold of the signal is an optimum threshold for detecting the level of the input signal light and discriminating whether the input signal light is of the mark level or of the space level. If the probability density distribution has two peaks corresponding to the mark level and the space level, respectively, and shows a so-called bimodal (two-hump camel) distribution, it generally corresponds to the mark and the space, respectively. This corresponds to a level at which the distribution density is minimum between the two peaks.

  Therefore, when identifying whether the input signal light is at the mark level or the space level by compressing the intensity distribution, the separation boundary line (≈identification threshold) is almost equal to the optimum discrimination threshold of the signal (also simply referred to as the optimum threshold). It is considered that the correct state is most preferable, and the bit error is minimized in such a state.

  The difference between the optimum threshold and the separation boundary in the level is also a problem in the optical 2R repeater that does not have the timing regeneration function. FIG. 7 shows a change in the signal light intensity distribution when the reproduction process is continuously performed in a cascade using the π-shifted optical gate whose transfer function is represented in FIG. It can be seen that the tail of the mark level distribution is drawn toward the space level.

  It is an object of the present invention to process a signal optimum discrimination threshold and an optical gate even when processing a general incident optical signal in which the mark level and the space level are asymmetric in the optical signal intensity (probability density) distribution. An optical signal regenerative repeater and an optical signal regenerative repeater that can reproduce optical communication signals with the occurrence of bit errors being minimized while the separation boundaries of the light intensity distribution (≈optical gate identification thresholds) are substantially the same. It is to provide a method for setting a driving condition in.

In the interference type optical gate used conventionally, the phase bias (the initial phase when the output signal light is also “0” when the input signal light is “0” and the phase is “0”) φ ₀ and the non-linear phase shift amount Δφ corresponding to the signal light power “1” (hereinafter, the average value of the mark level of the input signal light intensity is normalized to “1”) is generally possible. . In order to change the phase bias φ ₀ , a linear phase shifter disposed inside the interference type optical gate is used. Such a linear phase shifter can be configured using, for example, a thermo-optic element, an electro-optic element, a piezoelectric element, or a wave plate. On the other hand, as a specific method of changing the nonlinear phase shift amount Δφ, the intensity and energy of signal light (control light) and clock pulse or continuous light (controlled light) incident on the nonlinear optical phase shifter inside the optical gate, It is also conceivable to adjust the injection current into the semiconductor optical amplifier (SOA) (when SOA is used as the nonlinear phase shifter inside the optical gate). The nonlinear optical phase shifter can be configured using, for example, a semiconductor optical amplifier, a highly nonlinear optical fiber, or the like.

Therefore, the drive condition setting method of the present invention modifies the transfer function of the optical gate by intentionally shifting the condition from generally set drive conditions: for example, φ ₀ = 0 or π, Δφ = π. The separation boundary line is shifted to an arbitrary level. Further, the optical signal regenerative repeater of the present invention is characterized in that it is set to drive as described above. As a result, according to the present invention, it is possible to minimize the occurrence of bit errors due to the shift between the signal optimum discrimination threshold and the separation boundary line of the light intensity distribution compression.

  However, when these separation boundary lines are shifted, the portion where the slope in the transfer function curve becomes zero is not necessarily arranged at the average level of both the mark and the space. It becomes difficult to perform noise distribution compression at the same time. That is, the distributed compression performance is lowered.

  As an auxiliary means for preventing the degradation of the distributed compression performance, a device having an optical limiter effect using gain saturation in an optical amplifier or a nonlinear phenomenon in an optical fiber immediately after or immediately after an interference optical gate, or A device having an effect of removing a weak power optical signal (light threshold effect) by a saturable absorber (SA) is disposed. As a result, it is possible to make the slope of the transfer function curve zero near the average level of marks and spaces while shifting the separation boundary line.

  Further, as another auxiliary means, there is a method in which another interference type optical gate is connected to the interference type optical gate as described above, and the negative logic gate operation is continuously performed twice (for example, Patent Documents). 4).

  The configuration for compensating for the deterioration of the noise distribution compression performance is another feature of the present invention.

[Action]
The operation of the present invention will be described below.

FIG. 8 shows the change of the optical gate transfer function when the phase bias φ ₀ is changed in the interference type optical gate. FIG. 9 shows the case where the nonlinear phase shift Δφ is changed in the interference type optical gate. The optical gate transfer function is shown. In these drawings, (a) shows the case where the optical gate is operating in positive logic, that is, the “0” level in the input signal light is transferred to the “0” level in the output signal light, and similarly “1”. The transfer function when the level is transferred to the “1” level and the logic is left as it is is shown. On the other hand, (b) shows the case where the optical gate is operating with negative logic, that is, the “0” level in the input signal light is transferred to the “1” level in the output signal light, and similarly the “1” level is changed to “1”. This corresponds to the case of transferring to 0 "level and inverting the logic. Naturally, if the negative logic gate operation is executed in two stages, the result is substantially the same as the case where the positive logic gate operation is performed.

In the present invention, by using the above variability of the separation boundary line, φ ₀ and Δφ are adjusted so that the optimum discrimination threshold and the separation boundary line of the optical gate coincide with each other, thereby optimizing the signal identification reproduction operation in the optical gate. . As an example, FIG. 10 shows a case where Δφ = 0.6π and φ0 = −0.6π (negative logic operation) are adjusted, and the optimum threshold and the separation boundary line are matched.

  Next, FIG. 11 shows a transfer function when an interference type optical gate in which Δφ = π is used in combination with a device having an optical limiter effect and an optical threshold effect. FIG. 12 shows a transfer function when an interference type optical gate satisfying Δφ <π and a device having an optical limiter effect are used in combination. FIG. 13 shows an interference type optical gate satisfying Δφ> π and an optical limiter effect. The transfer function when used together with the device is shown. In these figures, (a) and (b) correspond to the case where the optical gate performs positive logic and negative logic operations, respectively. As is clear from these figures, by using a device having an optical limiter effect and / or an optical threshold effect in combination with an interference type optical gate, the separation boundary line is shifted and the average level of marks and spaces is increased. It is possible to make the slope of the transfer function curve zero.

  FIG. 14 is a diagram for explaining the change in the signal light intensity distribution due to the reproduction process using the interference type optical gate. Assuming that the signal light having the intensity distribution at the left end in the figure is input, the upper stage is Δφ = π 2 shows the light intensity distribution after distribution compression in the optical gate of the positive logic gate operation, and the lower stage performs the regeneration processing by cascading the optical gates of the negative logic gate operation in two stages with Δφ = 0.6π. The light intensity distribution after the distribution compression in the case of performing the measurement continuously is shown (see Patent Document 4). In each stage of the optical gate, the light intensity (noise) distribution compression of only one level of “1” and “0” is performed (here, distribution compression of only the level of “0” is performed). The distribution compression of both levels (“0” and “1”) is realized by using a two-stage connection. By doing so, it is possible to compensate for the distribution compression performance that has been reduced by the shift of the separation boundary line of the intensity distribution compression in the optical gate (transformation of the transfer function). That is, even when an interference type optical gate that is not Δφ = π is used, by performing cascade connection, an effect almost equivalent to the case of using an interference type optical gate of Δφ = π can be obtained.

At this time, as shown in FIG. 15, in each of the optical gates, φ ₀ and Δφ are adjusted so that the optimum discrimination threshold and the separation boundary line of the optical gate substantially coincide with each other, and the signal reproduction operation is optimized. FIG. 15 shows a structure in which interference optical gates of negative logic gate operation are connected in two stages in cascade, and also shows the intensity distribution of input light at each optical gate and the set position of the separation boundary line. In the illustrated case, an input optical communication signal pulse having a deteriorated wavelength λ ₁ is supplied to the first-stage interference optical gate, and a clock light having a wavelength λ ₂ based on the clock extracted from the input optical communication signal pulse. Pulses are supplied from a clock extractor / clock light source. As a result, a signal pulse having a wavelength λ ₂ subjected to distributed compression is output from the first-stage interference type optical gate, which is supplied to the second-stage interference type optical gate. A clock light pulse having a wavelength λ ₁ based on the clock extracted from the output signal pulse of the first-stage interference optical gate is supplied from the clock extractor / clock light source to the second-stage interference optical gate. As a result, the second-stage interference type optical gate outputs a signal pulse of wavelength λ ₁ subjected to distributed compression. As described above, in this output signal pulse, distributed compression is performed at both the mark and space levels.

Here, in addition to the above-described two-stage configuration, in order to sufficiently compensate the distributed compression performance, gain saturation in the optical amplifier and nonlinear phenomena in the optical fiber are caused inside or after each interference optical gate. It is also possible to arrange a device having an optical limiter effect used or a device having an effect of removing a weak power optical signal (light threshold effect) by a saturable absorber (SA) or the like. In that case, the transfer function curve of each optical gate can be modified as shown in FIGS. 11 to 13 to further assist the compensation operation of the distributed compression performance by the above-mentioned two-stage optical gate configuration. However, in the optical signal regenerative repeater having the above-described two-stage configuration, if the degradation of the distribution compression effect due to the shift of the separation boundary line of the intensity distribution compression (transformation of the transfer function) is not so great, and the compensation is almost unnecessary. In particular, any combination of φ ₀ , Δφ, and optical gate can be used without having to perform negative logic gate operation twice in succession.

  As described above, according to the present invention, it is possible to execute optical 3R relay or optical 2R relay while minimizing the occurrence of bit errors. That is, according to the present invention, although the interference type optical gate is basically used, the separation boundary line (≈identification threshold) can be easily optimized without deteriorating the reproduction effect.

  In addition, there is a method (see Patent Documents 7 and 8) of performing waveform shaping / signal identification reproduction by combining only a device having an optical limiter effect and a device having an optical threshold effect without using an interference optical gate. In that case, it is difficult to change only the separation boundary (≈identification threshold) of light intensity (probability density) distribution compression by adjusting the driving conditions of the device, and the transfer function is almost determined at the time of device fabrication. End up. Further, when adjusting the relative position of the signal light intensity distribution by changing the input signal light intensity, depending on the case, it is necessary that the absolute value of the input light average power exceeds 10 dBm, or the change amount is required to be close to 10 dB. In general, it is not easy to optimize the separation boundary line (≈identification threshold) such that the power of the probe light incident on the optical gate must be adjusted at the same time. In the present invention, a device having an optical limiter effect and a device having an optical threshold effect play an auxiliary role to the last. The present invention is essentially characterized in that only the separation boundary line (≈identification threshold) of the light intensity (probability density) distribution compression can be freely and easily changed by adjusting the driving condition of the interference type optical gate. It is very different from other conventional ones. In particular, in the present invention, basically, it is possible to adjust and optimize the distribution boundary line (≈identification threshold) independently and without substantially adjusting the input signal light power and the probe light power. It is.

  In the optical signal regenerative repeater, the present invention is caused by the shift of the separation boundary between the optimum signal discrimination threshold and the light intensity distribution compression even for a general optical signal having an asymmetric light intensity distribution between the mark level and the space level. The optical 3R / 2R signal reproduction can be performed while minimizing the occurrence of bit errors.

  Next, a preferred embodiment of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 16 shows the configuration of the optical signal regenerative repeater according to the first embodiment of the present invention. In the figure, (a) shows the case where it is configured as an optical 3R repeater, and (b) shows the case where it is configured as an optical 2R repeater. Each of these optical signal regenerative repeaters has an interference type optical gate 23 for the optical gate unit 3 in the general optical 3R repeater and optical 2R repeater shown in FIGS. 1 (a) and 1 (b), respectively. It has an applied form. In this embodiment, no optical limiter device or optical threshold device is inserted after the interference type optical gate 23.

In this embodiment, in this configuration, the transfer function according to the adjustment of the nonlinear phase shift amount Δφ and the phase bias φ _{0 in} the optical gate, that is, the driving conditions (driving current, incident light power, phase adjustment voltage, etc.) of the interference optical gate 23. The shape is adjusted so that the optimum signal discrimination threshold and the separation boundary line of the optical gate 23 are matched. Further, as in the case where an optical amplifier such as a semiconductor optical amplifier (SOA) is used inside the optical gate 23, a device having an optical limiter effect or an optical threshold effect is provided inside the interference system of the interference optical gate. In the case where a device including the above is included, depending on the setting of the driving conditions as described above, the light limiter effect and the light threshold effect as shown in FIGS. It is also possible to do.

[Second Embodiment]
In the second embodiment of the present invention, as shown in FIGS. 17 to 19, in the optical 3R repeater shown in FIG. 16A, a device having an optical limiter effect on the output side of the interference type optical gate 23, that is, the subsequent stage. Or a device having a light threshold effect, or both.

  In the optical signal regenerative repeater shown in FIG. 17, a device 6 having an optical limiter effect is arranged at the latter stage of FIG. 16A, and the output from this device 6 is used as an output optical pulse signal. In this configuration, in addition to the adjustment of the driving condition of the optical gate 23, the driving condition of the optical limiter device 6 is also adjusted, and the transfer function shape is adjusted as shown in FIGS.

  In the optical signal regenerative repeater shown in FIG. 18, the device 7 having the optical threshold effect is arranged at the subsequent stage of FIG. In this configuration, in addition to the adjustment of the driving condition of the optical gate 23, the driving condition of the optical threshold device 7 is also adjusted, and the transfer function shape is adjusted as shown in FIG.

  The optical signal regenerative repeater shown in FIG. 19 includes a device 7 having an optical threshold effect and a device 6 having an optical limiter effect arranged in series at the latter stage of FIG. The output is an output optical pulse signal. However, the arrangement order of the device 7 having the optical threshold effect and the device 6 having the optical limiter effect may be reversed. In this configuration, in addition to the adjustment of the driving conditions of the optical gate 23, the driving conditions of the optical limiter device 6 and the optical threshold device 7 are also adjusted, and the transfer function shape is adjusted as shown in FIG. .

In the present embodiment, by such a configuration, the noise reduction effect and is reduced in the adjustment of Δφ and phi ₀ only, it is possible to compensate. Here, when the clock extractor / clock light source 2 is replaced with a continuous light source 90 as shown in FIG. 16B, an optical 2R repeater without a timing recovery function is obtained. Such an optical 2R repeater is also within the scope of this embodiment.

[Third Embodiment]
FIG. 20 shows an optical signal regenerative repeater according to the third embodiment of the present invention. This optical signal regenerative repeater includes an optical branching unit 1a, a clock extractor / clock light source 2a, a first optical 3R repeater comprising an interference type optical gate 23a, an optical branching unit 1b, a clock extractor / clock light source 2b, A second optical 3R repeater composed of an interference type optical gate 23b is connected in series. Here, by supplying the optical communication signal pulse having a degraded wavelength λ ₁ to the first optical 3R repeater, the above-described processing by the 3R function is continuously performed twice on the degraded optical communication signal pulse. The output optical signal pulse is obtained from the second optical 3R repeater. Note that an optical limiter device or an optical threshold device is not inserted in the subsequent stage side of the interference type optical gates 23a and 23b of each optical 3R repeater.

In this optical signal regenerative repeater, first, in the first optical 3R repeater, the input optical communication signal pulse is branched into two by the optical branching unit 1a, and one of the branched optical communication signal pulses opens and closes the gate. Is supplied to the optical gate 23a as control light for performing the above, and the other branched optical communication signal pulse is supplied to the clock extractor / clock light source 2a. The clock extractor / clock light source 2a extracts the clock of the optical communication signal pulse supplied from the optical branching device 1a, and generates a clock light pulse (wavelength λ ₂ ) synchronized with the extracted clock. This clock light pulse is supplied to the optical gate 23a as controlled light. The optical gate 23a transfers the communication data to the clock light pulse supplied from the clock extractor / clock light source 2a by controlling the opening and closing of the gate by the optical communication signal pulse supplied via the optical branching device 1a. . The clock light pulse having the wavelength λ ₂ to which the communication data is thus transferred is supplied to the second optical 3R repeater as intermediate signal light.

In the second optical 3R repeater, the intermediate signal light (wavelength λ ₂ ) supplied from the optical gate 23a is branched into two by the optical branching device 1b, and one of the branched intermediate signal lights is controlled to open and close the gate. The light is supplied as light to the optical gate 23b, and the other branched intermediate signal light is supplied to the clock extractor / clock light source 2b. The clock extractor / clock light source 2b extracts the clock of the intermediate signal light supplied from the branching device 1b, and generates a clock light pulse (wavelength λ ₃ ) synchronized with the extracted clock. The clock light pulse generated by the clock extractor / clock light source 2b is supplied to the optical gate 23b as controlled light. The optical gate 23b controls communication of the clock light pulse (wavelength λ ₃ ) supplied from the clock extractor / clock light source 2b by controlling the opening and closing of the gate by the intermediate signal light supplied from the optical branching device 1b. Transcript. The clock light pulse to which the communication data is thus transferred is output from the optical signal regenerative repeater as a regenerated optical communication signal pulse.

In this optical signal regenerative repeater in which two stages of optical 3R repeaters are connected in series, Δφ and φ ₀ adjustment in two optical gates, that is, driving conditions (driving current, incident optical power, The transfer function shape is adjusted by adjusting the phase adjustment voltage, etc., and the signal optimum discrimination threshold is matched with the separation boundary line of the intensity distribution compression in the optical gates 23a and 23b. At this time, the compression effect of the light intensity (noise) distribution is reduced, but the reduction is compensated by causing both optical gates to perform a negative logic gate operation. Further, as in the case where an optical amplifier such as a semiconductor optical amplifier (SOA) is used inside the optical gates 23a and 23b, a device having an optical limiter effect or an optical threshold value effect is provided inside the interference system of the optical gate. When devices are included, the optical limiter effect and the optical threshold effect as shown in FIGS. 11 to 13 described above can be expected by setting the driving conditions for these devices, and they should be used effectively. Is also possible.

  FIG. 21 shows another configuration example of the optical signal regenerative repeater according to the third embodiment. The optical signal regenerative repeater shown in FIG. 21 has devices 8a and 8b arranged immediately after the interference type optical gates 23a and 23b in the configuration shown in FIG. Each of the devices 8a and 8b is a device having an optical limiter effect, a device having an optical threshold effect, or a device in which both are connected in series (whichever may be arranged first). The devices 8a and 8b may be of different types. With this configuration, it is possible to further assist the compensation of the noise compression effect by the two-stage configuration of the optical gate as described above. In this case, in addition to the adjustment of the driving conditions of the optical gates 23a and 23b, the driving conditions of the devices 8a and 8b, which are devices having the optical limiter effect and / or the optical threshold effect, are also adjusted. The transfer function shape is adjusted as shown in (1).

[Fourth Embodiment]
In the optical signal regenerative repeater of the third embodiment, the clock extractor / clock light source 2b of the second optical 3R repeater is based on the intermediate signal light output from the optical gate 23a of the first optical 3R repeater. Although the clock is extracted, the clock may be extracted from the clock light pulse generated by the clock extractor / clock light source 2a (clock diversion). Here, an embodiment employing such clock diversion will be described.

  FIG. 22 is a block diagram illustrating a schematic configuration of the optical signal regenerative repeater according to the fourth embodiment. In the optical signal regenerative repeater, in the configuration shown in FIG. 21, the clock optical pulse output from the clock extractor / clock light source 2a is branched into two by the optical branching device 1b, and one of the branched clock optical pulses is divided. The light to be controlled is supplied to the optical gate 23a, and the other is supplied to the clock generator 9. The rest of the configuration is the same as that of the third embodiment described above. As the clock generator 9, for example, a clock extractor / clock light source as described above can be used. Here, devices 8a and 8b (devices having an optical limiter effect and / or devices having an optical threshold effect) are provided after the optical gates 23a and 23b, but these devices 8a and 8b are particularly provided. It doesn't have to be.

Further, in the configuration of FIG. 22, a wavelength converter can be used instead of the clock extractor / clock light source as the clock generation unit 9 of the second optical 3R repeater. When the wavelength converter is used, the clock light pulse (wavelength λ ₂ ) output from the clock extraction unit 2a is branched into two by the optical branching unit 1b, and one of the branched clock light pulses is light as controlled light. The signal is supplied to the gate 23a, and the other is supplied to the wavelength converter which is the clock generator 9. The wavelength converter converts the wavelength of the supplied clock light pulse (wavelength λ ₂ ) into λ ₃ (≠ λ ₂ ), and supplies it to the optical gate 23b as controlled light.

In this optical 3R repeater configuration, Δφ and φ ₀ in the two optical gates are adjusted, that is, the transfer function shape is adjusted by the driving conditions (driving current, incident optical power, phase adjustment voltage, etc.) of the optical gates 23a and 23b. And the signal optimum discrimination threshold is matched with the separation boundary line of the intensity distribution compression of the optical gates 23a and 23b. At this time, the noise distribution compression effect is reduced, but the reduction is compensated by causing both optical gates to operate as a negative logic gate. In addition, a device having an optical limiter effect or a device having an optical threshold effect is included in the interference system of the optical gate as in the case where an optical amplifier such as SOA is used inside the optical gates 23a and 23b. In some cases, depending on the setting of driving conditions for these devices, the optical limiter effect and the optical threshold effect as shown in FIGS. 11 to 13 can be expected, and these can be used effectively.

  In addition, devices 8a and 8b having optical limiter effect, optical threshold effect, or both connected in series at the subsequent stage of optical gates 23a and 23b (whichever may be arranged first) If it is not, it is possible to further assist the compensation of the noise compression effect by the two-stage configuration of the optical gate. In this case, in addition to the adjustment of the driving conditions of the optical gates 23a and 23b, the driving conditions of the devices 8a and 8b are also adjusted, and the transfer function shape as shown in FIGS. 11 to 13 is adjusted.

[Fifth Embodiment]
As shown in FIG. 23, a configuration in which the clock extractor / clock light source 2b in the optical signal regenerative repeater shown in FIG. In that case, continuous light of wavelength λ ₃ (≠ λ ₂ ) is supplied from the continuous light source 90 to the optical gate 23b as controlled light. Again, the devices 8a and 8b having the optical limiter effect and / or the optical threshold effect provided at the subsequent stage of the optical gates 23a and 23b may not be provided.

Also in the fifth embodiment, Δφ and φ ₀ in the two optical gates are adjusted, that is, the transfer function shape is adjusted by the driving conditions (driving current, incident light power, phase adjustment voltage, etc.) of the optical gates 23a and 23b. The signal optimum discrimination threshold is matched with the separation boundary line of the intensity distribution compression of the optical gates 23a and 23b. At this time, the noise distribution compression effect is reduced, but the reduction is compensated by causing both optical gates to operate as a negative logic gate. In addition, a device having an optical limiter effect or a device having an optical threshold effect is included in the interference system of the optical gate as in the case where an optical amplifier such as SOA is used inside the optical gates 23a and 23b. In some cases, the optical limiter effect and the optical threshold effect as shown in FIGS. 11 to 13 can be expected by setting the driving conditions for these devices, and can be used effectively.

  In addition, devices 8a and 8b having optical limiter effect, optical threshold effect, or both connected in series at the subsequent stage of optical gates 23a and 23b (whichever may be arranged first) If it is not, it is possible to further assist the compensation of the noise compression effect by the two-stage configuration of the optical gate. In this case, in addition to the adjustment of the driving conditions of the optical gates 23a and 23b, the driving conditions of the devices 8a and 8b are also adjusted, and the transfer function shape as shown in FIGS. 11 to 13 is adjusted.

  As described above, various types in which the arrangement and configuration of the clock extractor / clock light source or the form of the controlled light supplied to the optical gate are changed are considered as derivations of the optical signal regenerative repeater shown in FIG. It is done.

  Finally, in the third to fifth embodiments described above, it is possible to replace the clock extractor / clock light source with a continuous light source, but when all the clock extractor / clock light sources are replaced with continuous light sources, It is configured as an optical 2R repeater that does not have a timing regeneration function. In addition, if the degradation of the noise compression effect is not so great and there is almost no need to compensate for the noise compression effect, it is not necessary to perform the negative logic gate operation twice in succession, and an arbitrary gate operation may be performed. Needless to say.

  Next, the operation of the optical signal regenerative repeater of each embodiment described above will be described in more detail using specific examples. However, only the optical gate part is described below, and the description of the clock extraction part is omitted.

(Example 1)
24 to 27 show optical signal regenerative repeaters using symmetrical Mach-Zehnder type optical gates (SMZ) as interference type optical gates as the first embodiment of the present invention.

FIG optical signal regenerator shown in 24, an optical splitter 1a which branches an input optical communication signal pulses deterioration of the first wavelength lambda ₁ to 2, the second wavelength lambda ₂ of the optical clock pulse 2 Optical branching device 1b that branches into two, optical coupler 4a that combines one output of optical branching device 1a and one output of optical branching device 1b, and light that is connected to the other output of optical branching device 1a A delay circuit 10, an optical coupler 4b that combines the other output of the optical branching device 1b and the output of the optical delay circuit 10, and a non-linear optical phase shifter provided at the outputs of the optical couplers 4a and 4b, respectively. The first and second semiconductor optical amplifiers (SOA) 111a and 111b, the linear optical phase shifter 5 connected to the output of the first SOA 111a, the output of the second SOA 111b and the output of the linear optical phase shifter 5 The optical coupler 4c to be combined and the output of the optical coupler 4c A wave bandpass filter (BPF) 12 which is provided, equipped with an output light of a wavelength band-pass filter 12 has a wavelength lambda ₂ of the reproduced signal beam. In this optical signal regenerative repeater, a deteriorated optical signal pulse having a wavelength λ ₁ is branched into two by an optical branching unit 1 a, and a time delay Δt is given to one optical pulse by an optical delay circuit 10. Are incident on the SOAs 111a and 111b, which are nonlinear phase shifters, as SMZ control light. At the same time, a clock light pulse having a wavelength λ ₂ that is also bifurcated by the optical branching device 1b is made incident on the first and second SOAs 111a and 111b at a timing such that it is sandwiched in time by two control lights. After that, the two clock light pulses that have passed through both paths of the SMZ are caused to interfere in the optical coupler 4c, and only the controlled light having the wavelength λ ₂ is allowed to pass through the wavelength band pass filter 12. As a result, reproduced signal light having the wavelength λ ₂ is obtained. Although the clock optical pulse with the wavelength λ ₂ is not shown in FIG. 24, for example, a clock extractor that extracts the clock from the input optical communication signal pulse with the wavelength λ ₁ and generates the clock optical pulse with the wavelength λ ₂ is used. Supplied from a clock light source.

  The optical signal regenerative repeaters shown in FIGS. 25 to 27 are the same as those shown in FIG. 24, but after the wavelength bandpass filter 12, a third semiconductor optical amplifier (SOA) as an optical limiter device is provided. ) 111c is inserted (as shown in FIG. 25), saturable absorber (SA) 30 as an optical threshold device is inserted (as shown in FIG. 26), or both SOA 111c and SA30 are The difference is that it is inserted (in the case shown in FIG. 27). In the example shown in FIGS. 25 to 27, the signal light that has passed through the bandpass filter 12 then passes through the third SOA 111 c as an optical limiter device, the SA 30 as an optical threshold device, or both.

In the optical signal regenerative repeater shown in any of FIGS. 24 to 27, optical 3R identification regeneration is performed. In either case, φ ₀ is adjusted by adjusting the linear phase shifter 5, the intensity of the signal light (control light) incident on the optical gate and the clock pulse or continuous light (controlled light), and the semiconductor optical amplifier (SOA) ) Δφ is changed by adjusting the injection currents of 111a and 111b, and the optimum discrimination threshold and the separation boundary line of the intensity distribution compression of the optical gate are matched. Further, in the case shown in FIGS. 25 to 27, the driving conditions of the SOAs 111c and SA30 are also adjusted to assist the intensity distribution compression effect. As described above, in the optical signal regenerative repeater of this embodiment, it is possible to minimize the occurrence of bit errors when compressing the intensity distribution (≈signal identification).

(Example 2)
The optical signal regenerative repeater according to the second embodiment of the present invention shown in FIG. 28 uses a polarization-separated SMZ optical gate (PD-SMZ or UNI) as an optical gate. That this optical signal regenerator comprises: a polarization separator 13a for polarization splitting the optical clock pulses having a wavelength lambda _2, the optical delay circuit 10a for delaying to one polarization component light from the polarization separator 13a A polarization coupler 14a that combines the other polarization component light from the polarization separator 13a and the output light of the optical delay circuit 10a, and an input optical communication signal pulse having a degraded wavelength λ ₁ and polarization An optical coupler 4 that combines the output of the coupler 14a, a first SOA 111a that is a nonlinear optical phase shifter provided at the output of the optical coupler 4, and a polarization separator that separates the output light of the SOA 111a. 13b, a linear optical phase shifter 5 connected to the output of one polarization component light side of the polarization separator 13b, and an optical delay circuit for delaying the other polarization component light from the polarization separator 13b 10b, linear with the output of the optical delay circuit 10b Polarization synthesizer 14b that combines the output from the phase shifter 5 with polarization, a polarizer 15 provided on the output side of the polarization synthesizer 14b, and a wavelength bandpass filter (provided at the output of the polarizer 15) BPF) 12, a second SOA 111b provided at the output of the band-pass filter 12, and an SA 30 provided at the output of the second SOA 111b, and the output light of the SA 30 has a wavelength λ ₂ reproduction. It is signal light. The clock light pulse having the wavelength λ ₂ is supplied from, for example, a clock extractor / clock light source (not shown).

In this optical signal regenerative repeater, first, a clock optical pulse having the second wavelength λ ₂ is bifurcated by an optical polarization separator 13a, and relative to one polarization component pulse by a first optical delay circuit 10a. After giving a typical time delay Δt, the light is combined again by the optical polarization coupler 14a and is incident on the first SOA 111a which is a nonlinear phase shifter. At the same time, the degraded optical signal pulse having the first wavelength λ ₁ merged by the optical coupler 4 is sent to the first SOA 111a at a timing such that it is sandwiched in time by the two mutually orthogonal polarization component pulses. Make it incident. After that, the two clock light pulses having the polarization components orthogonal to each other are again branched into two by the optical polarization separator 13b, and the other polarization component pulse not delayed by the first optical delay circuit 10a. Then, after a relative time delay Δt is given by the second optical delay circuit 10b, the optical polarization coupler 14b joins and interferes, and the polarizer 15 selects only an arbitrary linearly polarized wave component. Thereafter, only the controlled light having the wavelength λ ₂ is allowed to pass through the wavelength bandpass filter 12, and further, the second SOA 111 b as an optical limiter device and the SA 30 as an optical threshold device are allowed to pass through. Here, the SOAs 111b and SA30 may not be provided, and only one of them may be provided. In the optical signal regenerative repeater of this embodiment, the optical 3R identification reproduction is performed as described above. At this time, φ ₀ is adjusted by adjusting the linear phase shifter 5, and the intensity of the signal light (control light) incident on the optical gate and the clock pulse or continuous light (controlled light) and the injection current of the SOA 111 a are adjusted. By changing Δφ, the optimum discrimination threshold and the separation boundary line of the intensity distribution compression of the optical gate are matched. Further, the intensity distribution compression effect is assisted by adjusting the driving conditions of the SOAs 111b and SA30. As described above, it is possible to minimize the occurrence of bit errors at the time of intensity distribution compression (≈signal identification). Here, the position of the wavelength bandpass filter 12 may be immediately after the first SOA 111 a or immediately before the polarizer 15. Further, the polarization separator 13a and the optical delay circuit 10a and the polarization coupler 14a, or the polarization separator 13b, the optical delay circuit 10b, and the polarization coupler 14b are each made of a birefringent crystal or fiber. It is also possible to replace them together.

(Example 3)
The optical signal regenerative repeater according to the third embodiment of the present invention shown in FIG. 29 uses a nonlinear optical loop mirror (NOLM or SLALOM) as an optical gate. That is, this optical signal regenerative repeater is provided with a loop-shaped optical transmission line (fiber loop), and an input optical communication signal pulse having a degraded wavelength λ ₁ is introduced into the loop transmission line. Optical coupler 4, first SOA 111a that is a nonlinear optical phase shifter, optical delay circuit 10, and clock light pulse of wavelength λ ₂ are introduced into the loop transmission line, and output light is taken out from the loop transmission line An optical coupler 16 is inserted. Further, this optical signal regenerative repeater includes a wavelength bandpass filter (BPF) 12 connected to the output port of the optical coupler 16, a second SOA 111b provided at the output of the bandpass filter 12, and a second SOA 111b. SA 30 provided at the output, and the output light of SA 30 is the reproduction signal light of wavelength λ ₂ . The clock light pulse having the wavelength λ ₂ is supplied from, for example, a clock extractor / clock light source (not shown).

In this optical signal regenerative repeater, the clock light pulse having the second wavelength λ ₂ is branched by the optical coupler 16 in two directions, clockwise and counterclockwise of the fiber loop. In the fiber loop, the SOA 111a, which is a nonlinear phase shifter, is arranged at a position opposite to the optical coupler 16, but the optical delay circuit 10 is inserted in only one of the two paths leading to the SOA 111a. The clock light pulse is shifted by the time delay Δt and enters the first SOA 111a. At the same time, the first SOA 111a is timed such that the deteriorated optical signal pulse having the first wavelength λ ₁ merged by the optical coupler 4 is sandwiched in time by the two clock light pulses having different rotation directions. To enter. Thereafter, the two clock light pulses having different rotation directions are recombined and interfered by the optical coupler 16, and only the controlled light having the wavelength λ ₂ is allowed to pass through the wavelength bandpass filter 12, and further, the second optical limiter device is used. The SOA 111b and SA30 as an optical threshold device are passed. Here, the SOAs 111b and SA30 may not be provided, and only one of them may be provided. In the optical signal regenerative repeater of this embodiment, the optical 3R identification reproduction is performed as described above. At this time, by adjusting the intensity of the signal light (control light) and the clock pulse or continuous light (controlled light) incident on the optical gate and the injection current of the SOA 111a, Δφ is changed, and the optimum discrimination threshold and the optical gate intensity are changed. Match separation boundaries of distribution compression. Further, the intensity distribution compression effect is assisted by adjusting the driving conditions of the SOAs 111b and SA30. As described above, it is possible to minimize the occurrence of bit errors at the time of intensity distribution compression (≈signal identification).

In general, when NOLM (SLALOM) is used as an optical gate, it is difficult to adjust φ ₀ because it passes through the same route both clockwise and counterclockwise. Further optimization (reduction of the bit error occurrence probability) becomes possible. The position of the wavelength bandpass filter 12 may be between the first SOA 111a and the optical delay circuit 10, or between the optical delay circuit 10 and the optical coupler 16.

Example 4
The optical signal regenerative repeater according to the fourth embodiment of the present invention shown in FIG. 30 uses a DISC type optical gate. That is, this optical signal regenerative repeater includes an optical coupler 4 that combines an input optical communication signal pulse having a degraded wavelength λ ₁ and a clock optical pulse 14 a having a wavelength λ ₂ , and a nonlinear function provided at the output of the optical coupler 4. A first SOA 111a that is an optical phase shifter, a polarization separator 13 that performs polarization separation of the output light of the SOA 111a, and a linear optical phase shifter that is connected to the output of one polarization component light side of the polarization separator 13 5, an optical delay circuit 10 that gives a delay to the other polarization component light from the polarization separator 13, and a polarization that combines the output of the optical delay circuit 10 and the output of the linear optical phase shifter 5. A combiner 14, a polarizer 15 provided on the output side of the polarization combiner 14, a wavelength bandpass filter (BPF) 12 provided on the output of the polarizer 15, and an output of the bandpass filter 12. A second SOA 111b; And SA30 provided at the output of the second SOA111b, has an output light of the SA30 has a wavelength lambda ₂ of the reproduced signal beam. The clock light pulse having the wavelength λ ₂ is supplied from, for example, a clock extractor / clock light source (not shown).

In this optical signal regenerative repeater, the deteriorated optical signal pulse having the first wavelength λ ₁ is joined by the optical coupler 4 at a timing such that it is temporally sandwiched between the clock light pulses having the second wavelength λ ₂ , and nonlinear The light is incident on the first SOA 111a which is a phase shifter. Thereafter, the clock light pulse is separated into two mutually orthogonal polarization component pulses by the optical polarization separator 13, and the same time delay Δt as that of the bit period is given to only one polarization component pulse by the optical delay circuit 10. The optical polarization coupler 14 joins and interferes again, and the polarizer 15 selects only an arbitrary linearly polarized wave component. Thereafter, only the controlled light having the wavelength λ ₂ is allowed to pass through the wavelength bandpass filter 12, and further, the second SOA 111 b as an optical limiter device and the SA 30 as an optical threshold device are allowed to pass through. Here, the SOAs 111b and SA30 may not be provided, and only one of them may be provided. In the optical signal regenerative repeater of this embodiment, the optical 3R identification reproduction is performed as described above. At this time, φ ₀ is adjusted by adjusting the linear phase shifter 5, and the intensity of the signal light (control light) incident on the optical gate and the clock pulse or continuous light (controlled light) and the injection current of the SOA 111 a are adjusted. By changing Δφ, the optimum discrimination threshold and the separation boundary line of the intensity distribution compression of the optical gate are matched. Further, the intensity distribution compression effect is assisted by adjusting the driving conditions of the SOAs 111b and SA30. As described above, it is possible to minimize the occurrence of bit errors at the time of intensity distribution compression (≈signal identification). Here, the position of the wavelength bandpass filter 12 may be immediately after the first SOA 111 a or immediately before the polarizer 15. Further, the polarization separator 13, the optical delay circuit 10, and the polarization coupler 14 can be replaced together by a crystal or fiber having birefringence.

(Example 5)
The optical signal regenerative repeater of the fifth embodiment of the present invention shown in FIG. 31 is obtained by connecting two stages of optical 3R repeaters using SMZ type optical gates as optical gates. As each optical 3R repeater, the same optical signal regenerative repeater as shown in the first embodiment is used.

In this optical signal regenerative repeater, an optical communication signal pulse (wavelength λ ₁ ) is transmitted through a first SMZ type optical gate and a first clock extractor / clock light source (not shown) constituting the first stage optical 3R repeater. ) Respectively. In the first clock extractor / clock light source, a clock is extracted from the supplied optical communication signal pulse (wavelength λ ₁ ), and a clock light pulse (wavelength λ ₂ ) synchronized with the extracted clock is generated. This clock light pulse (wavelength λ ₂ ) is supplied to the first SMZ type optical gate as controlled light.

In the first SMZ type optical gate, the optical communication signal pulse is supplied as control light, and at the same time, the clock light pulse from the first clock extractor / clock light source is supplied as controlled light. The supplied optical communication signal pulse is divided into first and second optical communication signal pulses in the optical branching unit 1a. The first optical communication signal pulse is supplied to the semiconductor optical amplifier (SOA) 111a, which is a nonlinear phase shifter, via the optical coupler 4a, and the second optical communication signal pulse is delayed by a delay time Δt in the optical delay circuit 10a. After receiving the delay, the signal is supplied to the semiconductor optical amplifier (SOA) 111b which is a nonlinear phase shifter via the optical coupler 4b. The clock light pulse (wavelength λ ₂ ) supplied from the first clock extractor / clock light source is divided into first and second clock light pulses in the optical splitter 1b. The first clock light pulse is supplied to the SOA 111a via the optical coupler 4a, and the second clock light pulse is supplied to the SOA 111b via the optical coupler 4b.

  The timing at which the first and second clock light pulses reach the SOAs 111a and 111b, respectively, is the same. The timing at which the first optical communication signal pulse reaches the SOA 111a is earlier than the timing at which the first clock optical pulse reaches the SOA 111a. The timing at which the second optical communication signal pulse reaches the SOA 111b is later than the timing at which the second clock optical pulse reaches the SOA 111b.

  According to such arrival timing, the first clock light pulse (or the second clock light pulse) that is the controlled light is temporally sandwiched between the first and second optical communication signal pulses that are the control light. In this state, the first SMZ type optical gate operates. Specifically, in the SOA 111a, the first optical communication signal pulse causes a nonlinear phase shift in the first clock optical pulse, and in the SOA 111b, the second clock optical pulse is before the second optical communication signal pulse. So that it passes through without undergoing a nonlinear phase shift.

The first and second clock light pulses that have passed through the SOAs 111a and 111b reach the optical coupler 4c. In the optical coupler 4c, during the positive logic gate operation, an optical pulse is output only when a phase difference occurs between the input controlled optical pulses due to interference. When there is no phase difference, the controlled light pulses cancel each other, so that no light pulse is output. Since there is a phase difference between the first clock light pulse that causes the nonlinear phase shift from the SOA 111a and the second clock light pulse that does not cause the nonlinear phase shift from the SOA 111b, during the positive logic gate operation The optical coupler 4c outputs an optical pulse (wavelength λ ₂ ) obtained by combining these clock optical pulses. The optical pulse from the optical coupler 4c passes through the wavelength bandpass filter (BPF) 12a, and further passes through the SOA 111e as the optical limiter device and the SA 30a as the optical threshold device, and then as intermediate signal light (wavelength λ ₂ ). Output from the first-stage optical 3R repeater.

The intermediate signal light output from the first-stage optical 3R repeater is transmitted to the second SMZ-type optical gate and the second clock extractor / clock light source (not shown) constituting the second-stage optical 3R repeater. Supplied respectively. In the second clock extractor / clock light source, a clock is extracted from the intermediate signal light (wavelength λ ₂ ) supplied from the first-stage optical 3R repeater, and a clock light pulse (wavelength λ) synchronized with the extracted clock. ₃ ) is generated. This clock light pulse is supplied to the second SMZ type optical gate as controlled light.

In the second SMZ type optical gate, the intermediate signal light (wavelength λ ₂ ) output from the first-stage optical 3R repeater is supplied as control light, and at the same time, output from the second clock extractor / clock light source. The clock light pulse (wavelength λ ₃ ) is supplied as controlled light. The supplied intermediate signal light is divided into first and second intermediate signal lights in the optical splitter 1c. The first intermediate signal light is supplied to the SOA 111c that is a nonlinear phase shifter via the optical coupler 4d, and the second intermediate signal light is delayed by the delay time Δt ′ in the optical delay circuit 10b, It is supplied to the SOA 111d which is a non-linear phase shifter via the coupler 4e. The clock light pulse (wavelength λ ₃ ) supplied from the second clock extractor / clock light source is divided into first and second clock light pulses in the optical branching unit 1d. The first clock light pulse is supplied to the SOA 111c via the optical coupler 4d, and the second clock light pulse is supplied to the SOA 111d via the optical coupler 4e.

  The timing at which the first and second clock light pulses arrive at the SOAs 111c and 111d, respectively, is the same. The timing at which the first intermediate signal light reaches the SOA 111c is earlier than the timing at which the first clock light pulse reaches the SOA 111c. The timing at which the second intermediate signal light reaches the SOA 111d is later than the timing at which the second clock light pulse reaches the SOA 111d.

  According to such arrival timing, the first clock light pulse (or the second clock light pulse) that is the controlled light is temporally sandwiched between the first and second intermediate signal lights that are the control light. In this state, the second SMZ type optical gate is operated. Specifically, in the SOA 111c, the first intermediate signal light causes a non-linear phase shift in the first clock light pulse, and in the SOA 111d, the second clock light pulse reaches before the second intermediate signal light. Therefore, it passes through without undergoing a nonlinear phase shift.

The first and second clock light pulses that have passed through the SOAs 111c and 111d reach the optical coupler 4f. In the optical coupler 4f, during the positive logic gate operation, an optical pulse is output only when there is a phase difference between the input controlled optical pulses due to interference. When there is no phase difference, the controlled light pulses cancel each other, so that no light pulse is output. Since there is a phase difference between the first clock light pulse that causes the nonlinear phase shift from the SOA 111c and the second clock light pulse that does not cause the nonlinear phase shift from the SOA 111d, during the positive logic gate operation The optical pulse (wavelength λ ₃ ) obtained by combining the clock optical pulses is output from the optical coupler 4f. The output optical pulse of the optical coupler 4f passes through the wavelength bandpass filter (BPF) 12b, and further passes through the SOA 111f as the optical limiter device and the SA 30b as the optical threshold device, and then the reproduced optical communication signal pulse (wavelength λ ₃ ) Is output from the optical signal regenerative repeater to the outside.

In the optical signal regenerative repeater of this embodiment, linear phase shifter 5a, a phi ₀ by adjusting 5b, also the signal light to be incident on a nonlinear phase shifter of the internal optical gate SOA111a~111d (control light) Clock By adjusting the intensity of the pulse or continuous light (controlled light) and the injection current of the SOAs 111a to 111d, Δφ is changed so that the optimum discrimination threshold and the separation boundary line of the intensity distribution compression of the optical gate coincide. Furthermore, the intensity distribution compression effect is assisted by adjusting the drive conditions of the SOAs 111e and 111f as optical limiter devices and the SAs 30a and 30b as optical threshold devices arranged at the subsequent stage of the optical gate. Both optical gates are made to perform a negative logic operation to compensate for a reduction in the noise distribution compression effect. As described above, the optical 3R / 2R relay can be performed while the bit error occurrence at the time of intensity distribution compression (≈signal identification) is minimized.

  Here, if the noise distribution compression effect can be sufficiently compensated only by arranging the optical 3R repeaters in two stages, the SOAs 111e and 111f and the SAs 30a and 30b may not be provided. Only one of them may be provided. In addition, if the reduction in noise compression effect is not so great and compensation is almost unnecessary, it is not necessary to perform the negative logic gate operation twice in succession, and any gate operation may be performed. Needless to say.

(Example 6)
The optical signal regenerative repeater of Embodiment 6 of the present invention shown in FIG. 32 is obtained by connecting two stages of optical 3R repeaters using PD-SMZ (UNI) type optical gates as optical gates. As each optical 3R repeater, the same optical signal regenerative repeater as shown in the second embodiment is used.

In this optical signal regenerative repeater, the optical communication signal pulse (wavelength λ ₁ ) is also used as the first PD-SMZ (UNI) type optical gate and the first clock extractor constituting the first stage optical 3R repeater. Each is supplied to a clock light source (not shown). In the first clock extractor / clock light source, a clock is extracted from the supplied optical communication signal pulse (wavelength λ ₁ ), and a clock light pulse (wavelength λ ₂ ) synchronized with the extracted clock is generated. The clock light pulse (wavelength λ ₂ ) is supplied to the first PD-SMZ (UNI) type optical gate as controlled light.

  In the first PD-SMZ (UNI) type optical gate, the first and second clock light pulses supplied from the first clock extractor / clock light source have first and second polarization components orthogonal to each other in the optical polarization separator 13a. Separated into second polarization component pulses. The second polarization component pulse is given a relative time delay Δt by the optical delay circuit 10a, and then combined with the first polarization component pulse by the optical polarization coupler 14a. The first and second polarization component pulses thus combined are sequentially supplied to the SOA 111a which is a nonlinear phase shifter via the optical coupler 4a. At the same time, an optical communication signal pulse is also supplied to the SOA 111a via the optical coupler 4a.

  The timing at which the optical communication signal pulse reaches the SOA 111a is later than the timing at which the first polarization component pulse reaches the SOA 111a, and is earlier than the timing at which the second polarization component pulse reaches the SOA 111a. According to this arrival timing, the first PD-SMZ (UNI) with the optical communication signal pulse as the control light sandwiched in time by the first and second polarization component pulses as the controlled light. The mold optical gate will operate.

In the SOA 111a, since the first polarization component pulse arrives before the optical communication signal pulse, it passes through without undergoing a nonlinear phase shift, and the second polarization component pulse arrives after the optical communication signal pulse. Therefore, it undergoes a nonlinear phase shift due to the optical communication signal pulse. The first and second polarization component pulses that have passed through the SOA 111a are separated again by the optical polarization separator 13b. The re-separated first polarization component pulse is given a relative time delay Δt by the optical delay circuit 10b, and then combined with the second polarization component pulse by the optical polarization coupler 14b. The first and second polarization component pulses thus combined interfere and multiplex, and then an arbitrary linear polarization component is selected in the polarizer 15a. The pulse of the selected linearly polarized wave component passes through the wavelength bandpass filter (BPF) 12a, and further passes through the SOA 111c as an optical limiter device and the SA 30a as an optical threshold device, and then as intermediate signal light (wavelength λ ₂ ). Output from the first-stage optical 3R repeater.

The intermediate signal light output from the first-stage optical 3R repeater is a second PD-SMZ (UNI) type optical gate and second clock extractor / clock light source that constitute the second-stage optical 3R repeater. (Not shown). In the second clock extractor / clock light source, a clock is extracted from the intermediate signal light (wavelength λ ₂ ) supplied from the first-stage optical 3R repeater, and a clock light pulse (wavelength λ) synchronized with the extracted clock. ₃ ) is generated. This clock light pulse is supplied to the second PD-SMZ (UNI) type optical gate as controlled light.

In the second PD-SMZ (UNI) type optical gate, the clock light pulse (wavelength λ ₃ ) supplied from the second clock extractor / clock light source has a polarization component mutually separated in the optical polarization separator 13c. It is separated into orthogonal first and second polarization component pulses. The second polarization component pulse is given a relative time delay Δt ′ by the optical delay circuit 10c, and then combined with the first polarization component pulse by the optical polarization coupler 14c. The first and second polarization component pulses thus combined are sequentially supplied to the SOA 111b which is a nonlinear phase shifter via the optical coupler 4b. At the same time, the intermediate signal light (wavelength λ ₂ ) supplied as control light from the first-stage optical 3R repeater is also supplied to the SOA 111b via the optical coupler 4b.

  The timing at which the intermediate signal light reaches the SOA 111b is later than the timing at which the first polarization component pulse reaches the SOA 111b, and is earlier than the timing at which the second polarization component pulse reaches the SOA 111b. According to this arrival timing, in the state where the intermediate signal light (control light) is sandwiched in time by the first and second polarization component pulses (controlled light), the second PD-SMZ (UNI) type The optical gate will operate.

In the SOA 111b, since the first polarization component pulse arrives before the intermediate signal light, it passes without undergoing a nonlinear phase shift, and the second polarization component pulse arrives after the intermediate signal light. It undergoes nonlinear phase shift due to the intermediate signal light. The first and second polarization component pulses that have passed through the SOA 111b are separated again by the optical polarization separator 13d. The re-separated first polarization component pulse is given a relative time delay Δt ′ by the optical delay circuit 10d, and then combined with the second polarization component pulse by the optical polarization coupler 14d. The first and second polarization component pulses thus combined interfere and multiplex, and an arbitrary linear polarization component is selected in the polarizer 15b. The pulse of the selected linearly polarized wave component passes through the wavelength bandpass filter (BPF) 12b, and further passes through the SOA 111d as the optical limiter device and the SA 30b as the optical threshold device, and then the reproduced optical communication signal pulse (wavelength λ ₃ ) Is output to the outside of the optical signal regenerative repeater.

In the optical signal regenerative repeater of the present embodiment, the signal light (control light) and the clock that make φ ₀ incident on the SOAs 111a and 111b, which are nonlinear phase shifters inside the optical gate, are adjusted by adjusting the linear phase shifters 5a and 5b. By adjusting the intensity of the pulse or continuous light (controlled light) and the injection current of the SOAs 111a and 111b, Δφ is changed so that the optimum discrimination threshold and the separation boundary line of the intensity distribution compression of the optical gate coincide. Further, the intensity distribution compression effect is assisted by adjusting the driving conditions of the SOAs 111c and 111d and the SAs 30a and 30b as the optical limiter devices after the optical gate. Both optical gates perform negative logic gate operation to compensate for the reduction in noise distribution compression effect. As described above, the optical 3R / 2R relay can be performed while the bit error occurrence at the time of intensity distribution compression (≈signal identification) is minimized.

  Here, if the noise distribution compression effect can be sufficiently compensated only by arranging the optical 3R repeaters in two stages, the SOAs 111c and 111d and the SAs 30a and 30b may not be provided. Only one of them may be provided. In addition, if the reduction in noise compression effect is not so great and compensation is almost unnecessary, it is not necessary to perform the negative logic gate operation twice in succession, and any gate operation may be performed. Needless to say.

  In the first PD-SMZ (UNI) type optical gate, the position of the wavelength bandpass filter 12a may be immediately after the SOA 111a or immediately before the polarizer 15a. Further, a transmission path unit including the polarization separator 13a, the optical delay circuit 10a, and the polarization coupler 14a, or a transmission path unit including the polarization separator 13b, the optical delay circuit 10b, and the polarization coupler 14b is a complex. It is also possible to replace them with a crystal or fiber having refractive properties.

  In the second PD-SMZ (UNI) type optical gate, the position of the wavelength bandpass filter 12b may be immediately after the SOA 111b or immediately before the polarizer 15b. Further, the transmission path unit including the polarization separator 13c, the optical delay circuit 10c, and the polarization coupler 14c, or the transmission path unit including the polarization separator 13d, the optical delay circuit 10d, and the polarization coupler 14d is a complex. It is also possible to replace them with a crystal or fiber having refractive properties.

(Example 7)
The optical signal regenerative repeater of Embodiment 7 of the present invention shown in FIG. 33 is obtained by connecting two stages of optical 3R repeaters using a NOLM (SLALOM) type optical gate as an optical gate. As each optical 3R repeater, the same optical signal regenerative repeater as shown in the third embodiment is used.

In this optical signal regenerative repeater, an optical communication signal pulse (wavelength λ ₁ ) is transmitted from a first NOLM (SLALOM) type optical gate and a first clock extractor / clock light source (wavelength light source) constituting the first stage optical 3R repeater. (Not shown). In the first clock extractor / clock light source, a clock is extracted from the supplied optical communication signal pulse (wavelength λ ₁ ), and a clock light pulse (wavelength λ ₂ ) synchronized with the extracted clock is generated. This clock light pulse (wavelength λ ₂ ) is supplied to the first NOLM (SLALOM) type optical gate as controlled light through the optical coupler 16a.

  The first NOLM (SLALOM) type optical gate has a loop structure, and includes a SOA 111a that is a nonlinear optical phase shifter at a position of the fiber loop facing the optical coupler 16a. An optical coupler 4a and an optical delay circuit 10a are provided on the transmission line connecting the optical coupler 16a and the SOA 111a in the fiber loop.

A clock light pulse (wavelength λ ₂ ) from the first clock extractor / clock light source is introduced into the fiber loop from the optical coupler 16a, and at the same time, an optical communication signal pulse (λ ₁ ) as control light is coupled to the optical coupler. 4a is introduced into the fiber loop. The clock light pulse introduced into the fiber loop from the first clock extractor / clock light source via the optical coupler 16a propagates counterclockwise with the first clock light pulse propagating clockwise in the fiber loop. And the second clock light pulse.

  The first clock light pulse reaches the SOA 111a as it is, and the second clock light pulse reaches the SOA 111a after being given a time delay Δt by the optical delay circuit 10a. The optical communication signal pulse introduced from the optical coupler 4a into the fiber loop propagates clockwise in the fiber loop and reaches the SOA 111a. Each optical pulse reaches the SOA 111a in the order of the first clock light pulse, the optical communication signal pulse, and the second clock light pulse. According to this arrival timing, the first NOLM (SLALOM) type optical gate in a state where the optical communication signal pulse (control light) is sandwiched in time by the first and second clock light pulses (controlled light). Will work. In the SOA 111a, since the first clock light pulse arrives before the optical communication signal pulse, it passes without undergoing a nonlinear phase shift, and the second clock light pulse arrives after the optical communication signal pulse. It undergoes a nonlinear phase shift due to the optical communication signal pulse.

The second clock light pulse that has passed through the SOA 111a reaches the optical coupler 16a as it is. On the other hand, the first clock light pulse that has passed through the SOA 111a reaches the optical coupler 16a after being delayed by the delay time Δt in the optical delay circuit 10a. Therefore, the arrival timings of the first and second clock light pulses to the optical coupler 16a are the same, and the first and second clock light pulses interfere with each other. Since this interference causes a phase difference between the first and second clock light pulses, in general, an optical pulse (wavelength λ ₂ ) obtained by combining these clock light pulses is transmitted from the optical coupler 16a to the fiber loop. It is taken out. The optical pulse thus extracted passes through the wavelength bandpass filter (BPF) 12a, and further passes through the SOA 111c as the optical limiter device and the SA 30a as the optical threshold device, and then the first stage as intermediate signal light (wavelength λ ₂ ). Output from the optical 3R repeater.

The intermediate signal light output from the first-stage optical 3R repeater is supplied with a second NOLM (SLALOM) type optical gate and a second clock extractor / clock light source (non-light source) that constitute the second-stage optical 3R repeater. Respectively). In the second clock extractor / clock light source, a clock is extracted from the intermediate signal light (wavelength λ ₂ ) supplied from the first-stage optical 3R repeater, and a clock light pulse (wavelength λ) synchronized with the extracted clock. ₃ ) is generated. The clock light pulse having the wavelength λ ₃ is supplied to the second NOLM (SLALOM) type optical gate as controlled light.

  The second NOLM (SLALOM) type optical gate also has a loop structure, and includes a SOA 111b as a nonlinear optical phase shifter at a position of the fiber loop facing the optical coupler 16b. An optical coupler 4b is provided on one transmission line connecting the optical coupler 16b and the SOA 111b of the fiber loop, and an optical delay circuit 10b is provided on the other transmission line.

A clock light pulse (wavelength λ ₃ ) from the second clock extractor / clock light source is introduced into the fiber loop from the optical coupler 16b, and at the same time, intermediate signal light (wavelength λ ₂ ) as control light is coupled to the optical coupler. 4b is introduced into the fiber loop. The clock light pulse introduced into the fiber loop from the second clock extraction unit via the optical coupler 16b is propagated in the counterclockwise direction with the first clock light pulse propagating in the clockwise direction in the fiber loop. Are divided into clock light pulses.

  The first clock light pulse reaches the SOA 111b as it is, and the second clock light pulse reaches the SOA 111b after being given a time delay Δt ′ by the optical delay circuit 10b. The intermediate signal light introduced from the optical coupler 4b into the fiber loop propagates through the fiber loop in the clockwise direction and reaches the SOA 111b. The first clock light pulse, the intermediate signal light, and the second clock light pulse arrive at the SOA 111b in this order. According to this arrival timing, in a state where the intermediate signal light (control light) is sandwiched in time by the first and second clock light pulses (controlled light), the second NOLM (SLALOM) type optical gate is Will work. In the SOA 111b, since the first clock light pulse arrives before the intermediate signal light, it passes through without being subjected to the nonlinear phase shift, and the second clock light pulse arrives after the intermediate signal light. It undergoes nonlinear phase shift due to signal light.

The second clock light pulse that has passed through the SOA 111b reaches the optical coupler 16b as it is. On the other hand, the first clock light pulse that has passed through the SOA 111b is delayed by the delay time Δt ′ in the optical delay circuit 10b, and then reaches the optical coupler 16b. Therefore, the arrival timings of the first and second clock light pulses to the optical coupler 16b are the same, and the first and second clock light pulses interfere with each other. Since this interference causes a phase difference between the first and second clock light pulses, generally, an optical pulse (wavelength λ ₃ ) obtained by combining these clock light pulses is transmitted from the optical coupler 16b to the fiber loop. It is taken out. The optical pulse thus extracted passes through the wavelength bandpass filter (BPF) 12b, and further passes through the SOA 111d as the optical limiter device and the SA 30b as the optical threshold device, and then the second stage as a reproduction signal pulse (wavelength λ ₃ ). Output from the optical 3R repeater.

  In the first NOLM (SLALOM) type optical gate, the position of the wavelength bandpass filter 12a may be between the SOA 111a and the optical delay circuit 10a, or between the optical delay circuit 10a and the optical coupler 16a. Similarly, in the second NOLM (SLALOM) type optical gate, the position of the wavelength bandpass filter 12b may be between the SOA 111b and the optical delay circuit 10b, or between the optical delay circuit 10b and the optical coupler 16b.

In the optical signal regenerative repeater of the present embodiment, the intensity of signal light (control light) and clock pulses or continuous light (controlled light) incident on the SOAs 111a and 111b, which are nonlinear phase shifters inside the optical gate, and the SOAs 111a and 111b, By adjusting the injection current of 111b, Δφ is changed, and the optimum discrimination threshold and the separation boundary line of the intensity distribution compression of the optical gate are made to coincide. Further, the intensity distribution compression effect is assisted by adjusting the driving conditions of the SOAs 111c and 111d and the SAs 30a and 30b as the optical limiter devices after the optical gate. In general, when a NOLM (SLALOM) type optical gate is used, it is difficult to adjust φ ₀ because it passes through the same route both clockwise and counterclockwise. However, if this can be done, both optical gates A negative logic gate operation is performed to compensate for a decrease in the noise distribution compression effect, and the optimum discrimination threshold and the optical gate separation boundary line are matched. As described above, it is possible to perform the light 3R / 2R while minimizing the occurrence of bit errors during the intensity distribution compression (≈signal identification).

  Here, if the noise distribution compression effect can be sufficiently compensated only by arranging the optical 3R repeaters in two stages, the SOAs 111c and 111d and the SAs 30a and 30b may not be provided. Only one of them may be provided. In addition, if the reduction in noise compression effect is not so great and compensation is almost unnecessary, it is not necessary to perform the negative logic gate operation twice in succession, and any gate operation may be performed. Needless to say.

(Example 8)
The optical signal regenerative repeater according to the eighth embodiment of the present invention shown in FIG. 34 is obtained by connecting two stages of optical 3R repeaters using DISC type optical gates as optical gates. As each optical 3R repeater, the same optical signal regenerative repeater as shown in the fourth embodiment is used.

In this optical signal regenerative repeater, an optical communication signal pulse (wavelength λ ₁ ) is sent from a first DISC type optical gate and a first clock extractor / clock light source (not shown) constituting the first stage optical 3R repeater. Are supplied respectively. In the first clock extractor / clock light source, a clock is extracted from the supplied optical communication signal pulse (wavelength λ ₁ ), and a clock light pulse (wavelength λ ₂ ) synchronized with the extracted clock is generated. This clock light pulse is supplied to the first DISC type optical gate as controlled light.

In the first DISC type optical gate, the optical communication signal pulse (wavelength λ ₁ ) is supplied as control light, and the supplied optical communication signal pulse is a nonlinear phase shifter via the optical coupler 4a. At the same time as being supplied to the semiconductor optical amplifier (SOA) 111a, the clock light pulse (wavelength λ ₂ ) supplied from the first clock extractor / clock light source is supplied to the SOA 111a via the optical coupler 4a.

  Here, the optical communication signal pulse is inserted between the successive first and second clock light pulses in the clock light pulse. The timing at which the optical communication signal pulse reaches the SOA 111a is later than the timing at which the first clock light pulse reaches the SOA 111a, and is earlier than the timing at which the second clock light pulse reaches the SOA 111a. According to such arrival timing, the first DISC type optical gate is in a state in which the optical communication signal pulse as the control light is sandwiched in time by the first and second clock light pulses as the controlled light. Will work.

In the SOA 111a, since the first clock light pulse arrives before the optical communication signal pulse, it passes without undergoing a nonlinear phase shift, and the second clock light pulse arrives after the optical communication signal pulse. It undergoes a nonlinear phase shift due to the optical communication signal pulse. The first and second clock light pulses that have passed through the SOA 111a are separated into first and second polarization component pulses whose polarization components are orthogonal to each other in the optical polarization separator 13a. The first polarization component pulse is given a relative time delay Δt (corresponding to a bit period) by the optical delay circuit 10a, and then combined with the second polarization component pulse in the optical polarization coupler 14a. The The first and second polarization component pulses combined in this way interfere and multiplex, and an arbitrary linear polarization component is selected in the polarizer 15a. The pulse of the selected linearly polarized wave component passes through the wavelength bandpass filter (BPF) 12a, and further passes through the SOA 111c as an optical limiter device and the SA 30a as an optical threshold device, and then as intermediate signal light (wavelength λ ₂ ). Output from the first-stage optical 3R repeater.

The intermediate signal light output from the first-stage optical 3R repeater is sent to a second DISC type optical gate and a second clock extractor / clock light source (not shown) constituting the second-stage optical 3R repeater. Supplied respectively. In the second clock extractor / clock light source, a clock is extracted from the intermediate signal light (wavelength λ ₂ ) supplied from the first-stage optical 3R repeater, and a clock light pulse (wavelength λ) synchronized with the extracted clock. ₃ ) is generated. This clock light pulse is supplied to the second DISC type optical gate as controlled light.

In the second DISC type optical gate, the intermediate signal light (wavelength λ ₂ ) output from the first-stage optical 3R repeater is supplied as control light, and the supplied intermediate signal light is used as the optical coupler 4b. The clock light pulse (wavelength λ ₃ ) supplied as the controlled light from the second clock extractor / clock light source is optically coupled to the semiconductor optical amplifier (SOA) 111b which is a nonlinear phase shifter via It is supplied to the SOA 111b through the vessel 4b. The intermediate signal light is inserted between the first and second clock light pulses that are continuous with the clock light pulse. The timing at which the intermediate signal light reaches the SOA 111b is later than the timing at which the first clock light pulse reaches the SOA 111b, and is earlier than the timing at which the second clock light pulse reaches the SOA 111b. According to this arrival timing, the second DISC type optical gate operates in a state where the intermediate signal light that is the control light is temporally sandwiched between the first and second clock light pulses that are the controlled light. become.

In the SOA 111b, since the first clock light pulse arrives before the intermediate signal light, it passes through without being subjected to the nonlinear phase shift, and the second clock light pulse arrives after the intermediate signal light. It undergoes nonlinear phase shift due to signal light. The first and second clock light pulses that have passed through the SOA 111b are separated into first and second polarization component pulses whose polarization components are orthogonal to each other in the optical polarization separator 13b. The first polarization component pulse is given a relative time delay Δt (corresponding to a bit period) in the optical delay circuit 10b, and then combined with the second polarization component pulse in the optical polarization coupler 14b. The The first and second polarization component pulses thus combined interfere and multiplex, and an arbitrary linear polarization component is selected in the polarizer 15b. The pulse of the selected linearly polarized wave component passes through the wavelength bandpass filter (BPF) 12b, and further passes through the SOA 111d as the optical limiter device and the SA 30b as the optical threshold device, and then the reproduced optical communication signal pulse (wavelength λ ₃ ) Is output to the outside of the optical signal regenerative repeater.

  In this embodiment, the position of the wavelength bandpass filter 12a in the first DISC type optical gate may be immediately after the SOA 111a or immediately before the polarizer 15a. Further, the polarization separator 13a, the optical delay circuit 10a, and the polarization coupler 14a may be collectively formed by a birefringent crystal or fiber. Similarly, the position of the wavelength bandpass filter 12b in the second DISC type optical gate may be immediately after the SOA 111b or immediately before the polarizer 15b. Further, the polarization separator 13b, the optical delay circuit 10b, and the polarization coupler 14b may be formed together by using a crystal or fiber having birefringence.

In the optical signal regenerative repeater of the present embodiment, the signal light (control light) and the clock that make φ ₀ incident on the SOAs 111a and 111b, which are nonlinear phase shifters inside the optical gate, are adjusted by adjusting the linear phase shifters 5a and 5b. By adjusting the intensity of the pulse or continuous light (controlled light) and the injection current of the SOAs 111a and 111b, Δφ is changed so that the optimum discrimination threshold and the separation boundary line of the intensity distribution compression of the optical gate coincide. Further, the intensity distribution compression effect is assisted by adjusting the driving conditions of the SOAs 111c and 111d and the SAs 30a and 30b as the optical limiter devices after the optical gate. Note that both optical gates perform a negative logic gate operation to compensate for a reduction in the noise distribution compression effect. As described above, it is possible to perform the light 3R / 2R while minimizing the occurrence of bit errors during the intensity distribution compression (≈signal identification).

  Here, if the noise distribution compression effect can be sufficiently compensated only by arranging the optical 3R repeaters in two stages, the SOAs 111c and 111d and the SAs 30a and 30b may not be provided. Only one of them may be provided. In addition, if the reduction in noise compression effect is not so great and compensation is almost unnecessary, it is not necessary to perform the negative logic gate operation twice in succession, and any gate operation may be performed. Needless to say.

Example 9
The optical signal regenerative repeater of the ninth embodiment of the present invention shown in FIG. 35 is the same as the optical signal regenerative repeater of the fifth embodiment shown in FIG. 31 except that the second-stage optical 3R repeater is replaced with a DISC type optical gate. In the second stage optical 3R repeater, continuous light of wavelength λ ₃ is supplied instead of the clock light pulse.

In this optical signal regenerative repeating period, the operation of the first-stage optical 3R repeater is the same as that shown in FIG. The intermediate signal light (wavelength λ ₂ ) output from the first-stage optical 3R repeater is supplied to the DISC type optical gate as control light. At the same time, continuous light (wavelength λ ₃ ) is supplied to the DISC type optical gate as controlled light.

In the second-stage optical 3R repeater, that is, the DISC type optical gate, the intermediate signal light output from the first-stage optical 3R repeater is a nonlinear optical phase shifter (SOA) 111c via the optical coupler 4d. At the same time, continuous light supplied as controlled light is supplied to the SOA 111c via the optical coupler 4d. The intermediate signal light (wavelength λ ₂ ) is inserted at an arbitrary timing with respect to the continuous light (wavelength λ ₃ ). In the SOA 111c, the first part of the continuous light that reaches before the intermediate signal light passes through without being subjected to the nonlinear phase shift, and the second part that reaches after the intermediate signal light is caused by the intermediate signal light. Subject to nonlinear phase shift. The continuous light that has passed through the SOA 111c is separated by the optical polarization separator 13 into first and second polarization component pulses whose polarization components are orthogonal to each other. The first polarization component pulse is given a relative time delay Δt by the optical delay circuit 10 b and then combined with the second polarization component pulse by the optical polarization coupler 14. The first and second polarization component pulses combined in this way interfere and combine, and an arbitrary linear polarization component is selected in the polarizer 15. The pulse of the selected linearly polarized wave component (the pulse time width is substantially determined by the time delay Δt given by the optical delay circuit 10b) passes through the wavelength bandpass filter (BPF) 12b, and further, the SOA 111e as an optical limiter device. Then, after passing through the SA 30 b as an optical threshold device, it is outputted as a regenerated optical communication signal pulse (wavelength λ ₃ ) to the outside of this optical signal regenerative repeater.

  In this embodiment, the position of the wavelength bandpass filter 12b in the DISC type optical gate may be immediately after the SOA 111c or immediately before the polarizer 15. Further, the polarization separator 13, the optical delay circuit 10b, and the polarization coupler 14 may be configured as a single unit by a crystal or fiber having birefringence.

In the optical signal regenerative repeater of this embodiment, linear phase shifter 5a, a phi ₀ by adjusting 5b, also the signal light to be incident on a nonlinear phase shifter of the internal optical gate SOA111a~111c (control light) Clock By adjusting the intensity of the pulse or continuous light (controlled light) and the injection current of the SOAs 111a to 111c, Δφ is changed, and the optimum discrimination threshold and the separation boundary of the intensity distribution compression of the optical gate are made to coincide. Further, the intensity distribution compression effect is assisted by adjusting the driving conditions of the SOAs 111d and 111e and the SAs 30a and 30b as the optical limiter devices after the optical gate. It should be noted that both optical gates perform negative logic gate operation to compensate for a reduction in noise distribution compression effect. As described above, it is possible to perform the light 3R / 2R while minimizing the occurrence of bit errors during the intensity distribution compression (≈signal identification).

  Here, if the noise distribution compression effect can be sufficiently compensated only by arranging the optical 3R repeaters in two stages, the SOAs 111d and 111e and the SAs 30a and 30b may not be provided. Only one of them may be provided. In addition, if the reduction in noise compression effect is not so great and compensation is almost unnecessary, it is not necessary to perform the negative logic gate operation twice in succession, and any gate operation may be performed. Needless to say.

  Although the embodiments of the present invention have been described above, in the present invention, any combination of interference type optical gates is possible in addition to the combinations of optical gates of the above-described embodiments. In all of the above embodiments, the clock extraction unit / clock pulse light source can be replaced with a continuous light source, and the clock light can be made continuous light. However, when all the clock light is replaced with continuous light, it is configured as an optical 2R repeater without a timing recovery function.

  In addition, this invention is not limited to the structure of said each Example, In the range which does not deviate from the meaning of this invention, it can change suitably.

(A) is a block diagram which shows the basic composition of the conventional optical 3R repeater, (b) is a block diagram which shows the basic composition of the conventional optical 2R repeater. It is a block diagram which shows the structure of a symmetrical Mach-Zehnder type optical gate. It is a block diagram which shows the structure of a polarization split type symmetrical Mach-Zehnder type optical gate. It is a block diagram which shows the structure of a nonlinear optical loop mirror type | mold optical gate. It is a figure explaining compression of signal light intensity (probability density) distribution in an interference type optical gate. In the interference type optical gate, it is a diagram showing a case where the signal optimum discrimination threshold and the separation boundary line of the optical gate intensity distribution compression do not match, (a) is a diagram showing the input signal light intensity distribution, ( (b), (c) is a figure which shows the transfer function curve of an optical gate. It is a figure which shows the change of light intensity distribution when performing a reproduction | regeneration process continuously, when the optimal signal discrimination threshold and the separation boundary line of intensity distribution compression do not correspond in the interference type optical gate. FIG. 9 is a diagram showing a change in transfer function curve when the phase bias φ ₀ is changed in the case where the nonlinear phase shift amount Δφ corresponding to the input light intensity “1” is π in the interference type optical gate. (A) is a figure which shows the change of the transfer function curve when carrying out the positive logic gate operation | movement, (b) is a figure which shows the change of the transfer function curve when carrying out the negative logic gate operation. . In the interference type optical gate, it is a diagram showing the change of the transfer function curve when the corresponding nonlinear phase shift amount Δφ is changed when the input light intensity is “1” while the phase bias φ ₀ is fixed, (A) is a figure which shows the change of the transfer function curve when carrying out the positive logic gate operation | movement, (b) is a figure which shows the change of the transfer function curve when carrying out the negative logic gate operation. (A), (b) respectively shows the input signal light intensity distribution and the transfer function curve of the optical gate when the signal optimum discrimination threshold value and the separation boundary line of the intensity distribution compression match in the interference type optical gate. FIG. It is a figure which shows the transfer function curve at the time of using together the device which has an interference type optical gate ((DELTA) (phi) = (pi)), an optical limiter effect, and an optical threshold value effect, Comprising: (a) is when carrying out positive logic gate operation | movement (B) is a figure which shows a transfer function curve in the case of carrying out a negative logic gate operation | movement. It is a figure which shows the transfer function curve at the time of using together the device which has an interference type optical gate ((DELTA) (phi) <(pi)), and an optical limiter effect, Comprising: (a) is a transfer function curve at the time of carrying out positive logic gate operation | movement. FIG. 7B is a diagram illustrating a transfer function curve when a negative logic gate operation is performed. It is a figure which shows the transfer function curve at the time of using together the device which has an interference type optical gate ((DELTA) (phi)> (pi)), and an optical limiter effect, Comprising: (a) is a transfer function curve at the time of carrying out positive logic gate operation | movement. FIG. 7B is a diagram illustrating a transfer function curve when a negative logic gate operation is performed. It is a figure which shows the change of signal light intensity distribution by the reproduction | regeneration processing using an interference type optical gate. The figure which shows the change of signal light intensity distribution and the optimal setting position of the separation boundary line in each optical gate when the optical 3R repeater is connected in two stages in cascade and the regeneration process by the negative logic gate operation is performed twice. It is. (A), (b) is a figure which shows the structure of the optical signal regenerative repeater of the 1st Embodiment of this invention. It is a block diagram which shows the structure of the optical signal regenerative repeater of the 2nd Embodiment of this invention by providing the optical limiter device in the output side of an interference type gate. It is a block diagram which shows the structure of the optical signal regenerative repeater of 2nd Embodiment by providing the optical threshold value device in the output side of an interference type gate. It is a block diagram which shows the structure of the optical signal regenerative repeater of 2nd Embodiment by providing the optical threshold value device and the optical limiter device in the output side of an interference type gate. It is a block diagram which shows the structure of the optical signal regenerative repeater of 3rd Embodiment. It is a block diagram which shows another structural example of the optical signal regenerative repeater of 3rd Embodiment. It is a block diagram which shows the structure of the optical signal regenerative repeater of 4th Embodiment. It is a block diagram which shows the structure of the optical signal regenerative repeater of 5th Embodiment. It is a block diagram which shows the 1st structural example of the optical signal regenerative repeater of Example 1. FIG. It is a block diagram which shows the 2nd structural example of the optical signal regenerative repeater of Example 1. FIG. FIG. 6 is a block diagram illustrating a third configuration example of the optical signal regenerative repeater according to the first embodiment. FIG. 6 is a block diagram illustrating a fourth configuration example of the optical signal regenerative repeater according to the first embodiment. It is a block diagram which shows the structure of the optical signal regenerative repeater of Example 2. It is a block diagram which shows the structure of the optical signal regenerative repeater of Example 3. It is a block diagram which shows the structure of the optical signal regenerative repeater of Example 4. It is a block diagram which shows the structure of the optical signal regenerative repeater of Example 5. It is a block diagram which shows the structure of the optical signal regenerative repeater of Example 6. It is a block diagram which shows the structure of the optical signal regenerative repeater of Example 7. It is a block diagram which shows the structure of the optical signal regenerative repeater of Example 8. It is a block diagram which shows the structure of the optical signal regenerative repeater of Example 9.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a-1d Optical branching device 2, 2a, 2b Clock extractor and clock light source 3 Optical gate part 4, 4a-4f Optical coupler 5, 5a, 5b Linear optical phase shifter 6 Optical limiter device 7 Optical threshold device 8, 8a, 8b device (optical limiter device and / or optical threshold device)
9 Clock generator (clock extractor and clock light source or wavelength converter)
10, 10a to 10d Optical delay circuit 11, 11a, 11b Nonlinear optical phase shifter 12, 12a, 12b Wavelength bandpass filter 13, 13a to 13d Polarization separator 14, 14a to 14d Polarization coupler 15, 15a, 15b Polarization Child 16, 16a, 16b Optical coupler 23, 23a, 23b Interference type optical gate 30, 30a, 30b Saturable absorber (SA)
90 Continuous light sources 111a to 111f Semiconductor optical amplifier (SOA)

Claims (13)

An optical signal regenerative repeater that receives an optical communication signal pulse as an input optical communication signal with degraded quality, regenerates the optical communication signal pulse, and outputs a regenerated optical communication signal,
The gate is opened and closed using the optical communication signal pulse as control light, and a clock light pulse or continuous light is supplied as controlled light, and data is transferred to the controlled light in response to opening and closing of the gate. Having an optical gate unit for obtaining a reproduction optical communication signal;
The optical gate unit has a function of compressing the intensity distribution of input light with respect to a binary level, and in the optical gate unit, an optimum discrimination threshold for the input optical communication signal and a separation boundary between compression of the intensity distribution An optical signal regenerative repeater, which is set so that the line almost coincides.   2. The optical signal regenerative repeater according to claim 1, wherein a driving condition of the optical gate is adjustable, and the separation boundary line is made to coincide with the optimum discrimination threshold by adjusting the driving condition.   The optical signal regenerative repeater according to claim 1, wherein the optical gate unit is configured by an interference optical gate. The interference optical gate includes at least a linear phase shifter and a nonlinear phase shifter, and the phase bias φ ₀ can be adjusted by the linear phase shifter and the nonlinear phase shift amount Δφ can be adjusted by the nonlinear phase shifter, The optical signal regenerative repeater according to claim 3, wherein the separation boundary line can be adjusted by adjusting the phase bias and the nonlinear phase shift amount.   The optical signal regenerative repeater according to claim 3, wherein a device having an optical limiter effect and / or an optical threshold effect is arranged inside the optical gate unit or connected to an output of the optical gate unit. An optical signal regenerative repeater that receives an optical communication signal pulse as an input optical communication signal with degraded quality, regenerates the optical communication signal pulse, and outputs a regenerated optical communication signal,
The gate is opened and closed using the optical communication signal pulse as control light, and a clock light pulse or continuous light is supplied as the first controlled light, and data is transferred to the first controlled light according to the opening and closing of the gate. A first optical gate unit for obtaining intermediate signal light by transferring;
The gate is opened and closed using the intermediate signal light as control light, and a clock light pulse or continuous light is supplied as second controlled light, and data is transferred to the second controlled light in response to the opening and closing of the gate. A second optical gate unit for obtaining the reproduction optical communication signal by:
Have
Each of the optical gate units has a function of compressing the intensity distribution of the input light with respect to a binary level, and in each of the optical gate units, an optimum discrimination threshold for the input optical communication signal and compression of the intensity distribution are provided. An optical signal regenerative repeater that is set so as to substantially coincide with the separation boundary line.   The optical signal regenerative repeater according to claim 6, wherein each of the optical gate units is configured by an interference optical gate. The interference optical gate includes at least a linear phase shifter and a nonlinear phase shifter, and the phase bias φ ₀ can be adjusted by the linear phase shifter and the nonlinear phase shift amount Δφ can be adjusted by the nonlinear phase shifter, The optical signal regenerative repeater according to claim 7, wherein the separation boundary line can be adjusted by adjusting the phase bias and the nonlinear phase shift amount.   8. The optical signal regenerative repeater according to claim 7, wherein each of the first optical gate unit and the second optical gate unit operates as a negative logic gate.   The optical signal according to claim 7, wherein a device having an optical limiter effect and / or an optical threshold effect is arranged inside the at least one optical gate unit or connected to an output of at least one optical gate unit. Regenerative repeater.   The optical signal regenerative repeater according to claim 10, wherein each of the first optical gate unit and the second optical gate unit operates as a negative logic gate. A method for setting a driving condition of an optical signal regenerative repeater that receives an optical communication signal pulse as an input optical communication signal with degraded quality, regenerates the optical communication signal pulse, and outputs a regenerated optical communication signal,
The optical signal regenerative repeater is opened and closed with the optical communication signal pulse as control light, and a clock light pulse or continuous light is supplied as controlled light, and the controlled light according to the opening and closing of the gate. An optical gate unit for obtaining the reproduction optical communication signal by transferring data to
The optical gate unit has a function of compressing the intensity distribution of input light to a binary level, and the optical gate unit compresses the intensity distribution with respect to an optimum discrimination threshold for the input optical communication signal. A setting method in which the separation boundary lines are set to almost coincide. The optical gate is an interference optical gate including at least a linear phase shifter and a nonlinear phase shifter, the phase bias φ ₀ is adjusted by the linear phase shifter, and the nonlinear phase shift amount Δφ is adjusted by the nonlinear phase shifter. 13. The setting method according to claim 12, wherein the adjustment is set so that a separation boundary line of the compression of the intensity distribution substantially matches an optimum discrimination threshold for the input optical communication signal.

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