JP3238061B2 - Optical pulse modulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pulse modulator in an optical transmission system for transmitting an optical pulse train by modulating the data.

[0002]

2. Description of the Related Art With the development of the information-oriented society, the information transmission rate of a trunk system is increasing, and 10 Gbps is about to be put to practical use soon. Further, when the transmission rate is higher than 10 Gbps, it becomes difficult to perform electrical signal processing at the same rate. Therefore, multiplexing and demultiplexing are performed in the state of an optical signal, and portions requiring electrical signal processing can be processed. Attempts have been made to stay at the bit rate. Optical signal multiplexing includes optical time division multiplexing and wavelength multiplexing. Here, optical time division multiplexing will be described.

In the optical time division multiplexing, as shown in FIG. 9, data modulation is independently performed on a plurality of optical pulse trains having a low bit rate B (bps), and the modulated optical pulse trains are shown on the right side of FIG. As described above, the phase is shifted little by little and the signals are combined, so that the total bit rate B × n (bp
s).

Here, when data modulation is performed on a low bit rate optical pulse train, as shown in FIG. 10A, the phase of a data signal (modulation signal) input to the data modulator and the light signal incident on the data modulator are modulated. It is necessary that the phases of the optical pulse trains are matched. If the phase relationship is deviated, transmission characteristics deteriorate. That is , if the data signal is NRZ (non-return-to
In the case of the ( -zero) pattern, when the phase relation is shifted , FIG.
0 (b), “1” → “0”, “0” →
When the data transition of “1” occurs, the amplitude of the optical pulse that should be “1” is reduced, and the amplitude of the optical pulse that is “0” and the pulse amplitude should be almost zero increases. eye-opening you deterioration.

[0005] In addition, even though an optical pulse train has a low bit rate, its rate is in the 10 Gbps class, and the length of one bit is only about 2 cm in an optical fiber having a refractive index of 1.5. In addition, when the signal becomes 10 Gbps, the modulated signal becomes less than that shown in FIG.
The waveform does not have a rectangular shape as shown in FIG. Therefore, unless the incident light pulse is located close to the center of the bit of the data signal in the data modulator, the transmission characteristics deteriorate.

As described above, even when the phase of an optical pulse train and a data signal are adjusted when the system is introduced, the optimum phase state is obtained if the length of the optical fiber or the cable for transmitting the data signal to the modulator changes with temperature. There is a possibility that it will deviate from.

[0007]

As described above, in the conventional optical pulse modulation apparatus that performs data modulation on an optical pulse train and outputs the data, when the transmission rate becomes 10 Gbps class,
There is a problem that the relative phase between the data signal and the optical pulse is shifted due to a change in temperature or the like, and the transmission characteristics are deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide an optical pulse modulation device capable of preventing the deterioration of transmission characteristics by keeping the relative phase between a data signal and an optical pulse at an optimum level. Aim.

[0009]

In order to solve the above-mentioned problems, an optical pulse modulation apparatus according to the present invention comprises a data modulation means for modulating an incident light pulse train by a data signal synchronized with a clock signal, and a data modulation means. Optical modulating means for branching and inputting an optical pulse train before or after modulation by a modulator, and modulating the branched and input optical pulse train with a clock signal to output a modulated optical current; a data signal and an incident light based on the modulated optical current Phase control means for controlling at least one phase of the pulse train so that the relative phases of the data signal and the incident light pulse train are optimized. Here, as the light modulating means, for example, an electro-absorption modulator whose light transmittance is changed by an electric field is preferably used.

An optical pulse modulator according to the present invention comprises: a data modulating means for modulating an incident optical pulse train with a data signal synchronized with a clock signal; and an optical pulse train before or after modulation by the data modulating means is branched and inputted; An optical modulation unit that modulates the branched optical pulse train with a clock signal and outputs a modulated optical signal; a photoelectric conversion unit that detects a modulated optical signal output from the optical modulation unit and outputs a modulated optical current; Phase control means for controlling the phase of at least one of the data signal and the incident light pulse train based on the modulated photocurrent so that the relative phases of the data signal and the incident light pulse train are optimized.

The data signal is an NRZ pattern signal, and the phase control means controls the phase of at least one of the data signal and the incident light pulse train so that the modulated photocurrent becomes minimum or maximum.

When the optical pulse train before or after data modulation is branched and input to the optical modulation means and modulated with a clock signal synchronized with the data signal, when the data signal has an NRZ pattern, the clock signal is If the light modulating means is an electroabsorption modulator, the photocurrent due to the light absorbed by the light modulator changes according to the relative phase of the light pulse train.
Also, when a normal optical modulator is used as the optical modulator, the optical power transmitted through the optical modulator changes according to the relative phase of the clock signal and the optical pulse train, and is output from this optical modulator. The photocurrent from the photoelectric conversion means for detecting the optical signal changes. That is, regardless of whether the electro-absorption modulator or the ordinary optical modulator is used as the optical modulator, a modulated photocurrent corresponding to the relative phase between the clock signal and the optical pulse train is finally generated.

Here, if the optical pulse modulation device is configured to be compact as a whole and the internal phase fluctuation can be almost ignored, or if it is generated so that it will be canceled naturally, the modulated light The relative phase between the clock signal detected as the current and the optical pulse train corresponds to the relative phase between the data signal input to the data modulator and the incident optical pulse train. Therefore, by controlling the phase of the data signal input to the data modulation means or the phase of the incident optical pulse train or both based on the relative phase of the clock signal and the optical pulse train based on the modulated photocurrent, the data signal and the incident light pulse train are controlled. The relative phase of the optical pulse train can be optimized.

Further, when the data signal supplied to the data modulating means is an NRZ pattern, initial setting is performed so that the relative phase between the data signal and the incident light pulse becomes optimal when the modulated photocurrent is minimum or maximum. By doing so, the relative phase between the data signal and the incident light pulse train can be more easily optimized without being affected by an increase or decrease in the power of the incident pulse train or a change in the mark ratio.

Another optical pulse modulation device according to the present invention provides an RZ (return-to-to-
(-zero) Data modulation means for modulating by a data signal of a pattern, photoelectric conversion means for detecting the optical power of the optical pulse train after modulation by the data modulation means, and the optical power detected by this photoelectric conversion means is maximized. Phase control means for controlling the phase of at least one of the data signal and the incident light pulse train.

As described above, when data modulation is performed on the incident light pulse train by the data signal of the RZ pattern, the optical power of the output light pulse train after the modulation changes by directly reflecting the relative phase shift between the data signal and the incident light pulse train. Therefore, this output light pulse train is photoelectrically converted to detect the optical power of the output light train, and the data signal and / or the incident light pulse train are controlled by controlling the phases of the data signal and / or the incident light pulse train so as to maximize the power. The relative phase of the pulse train can be optimized.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is a block diagram of an optical pulse modulation device according to a first embodiment. The optical pulse modulator includes a data modulator 1 for performing data modulation on an incident optical pulse train, an optical coupler 2 for branching an output optical pulse train from the data modulator 1 into two, and an optical pulse train branched and input from the optical coupler 2. Electro-absorption optical modulator 3 that modulates the signal with a clock signal, and a controller 4 that generates a control signal based on a modulated photocurrent output from the electro-absorption optical modulator 3
A variable phase shifter 5 whose phase shift amount (phase shift amount) is controlled by a control signal from the controller 4, a semi-fixed phase shifter 6, and data supplied to the data modulator 1 based on a clock signal. And a data retiming circuit 7 for retiming the signal.

Next, the detailed configuration of this embodiment will be described together with the operation. An optical pulse train 11 having a repetition rate synchronized with a data signal 14 input as a modulation signal enters the data modulator 1, and is modulated by the data signal 14. Specifically, the data modulator 1 includes an incident light pulse train 11
Out of the data signal 14, for example, only the light pulse incident during the period of “1” is emitted as the light pulse train 12. This operation is called data modulation. Here, the data signal 14 as a modulation signal input to the data modulator 1 has an NRZ pattern. When data modulation is performed on the incident light pulse train 11 by the data signal 14 having the NRZ pattern, as a result, RZ
An emitted light pulse train 12 of the pattern is obtained.

An output light pulse train 12 from the data modulator 1 is branched into two by an optical coupler 2, one of which is taken out as an output of an optical pulse modulator, and the other is incident on an electro-absorption modulator 3 which is an optical modulator. Is done. The electro-absorption modulator 3 is an optical modulator whose light transmittance (light absorption) changes due to an electric field, and an optical coupler using a clock signal 18 obtained by phase-shifting a clock signal 17 input from the outside by the variable phase shifter 5. The optical pulse train branched from 2 is modulated to output a modulated photocurrent 15. In this case, corresponding to the relative phase between the clock signal 18 and the optical pulse train 12, the photocurrent due to the light absorbed by the electroabsorption modulator 3 , that is, the modulated photocurrent 1
5 changes. That is, the relative phase between the clock signal 18 and the optical pulse train 12 can be detected as the magnitude of the modulated photocurrent 15 by the electroabsorption modulator 3.

The modulated photocurrent 15 from the electroabsorption modulator 3
Is input to the controller 4 to generate a control signal 16 for controlling the amount of phase shift of the variable phase shifter 5. The variable phase shifter 5 receives a clock signal 17 from the outside and outputs a control signal 1
6 to output the clock signal 18 that has been phase-shifted. The phase-shifted clock signal 18 is supplied to the electroabsorption modulator 3 as a modulation signal as described above, and is also supplied to the data retiming circuit 7 via the semi-fixed phase shifter 6.

Here, the optical pulse modulator shown in FIG. 1 is configured to be compact as a whole, and the phase fluctuation in the system is made almost negligible, or is canceled naturally even if it occurs. . This applies to the second to fifth embodiments described below. In this way, the relative phase between the clock signal 18 and the optical pulse train 12 detected by the electroabsorption modulator 3 as a change in the modulated optical current 15 is determined by the data signal 14 input to the data modulator 1 and the incident optical pulse train 11 And the relative phase of

Therefore, the controller 4 controls the electroabsorption modulator 3
Signal 1 indicated by modulated photocurrent 15 from
8 and the relative phase of the optical pulse train 12, the presence or absence and the magnitude of the relative phase shift between the data signal 14 and the incident optical pulse train 11, that is, the incident light pulse train 1
It can be determined whether data modulation is performed with the correct phase for 1 and, if the phase is shifted, how much the data is shifted.

Therefore, the controller 4 controls the modulation photocurrent 15
, A control signal 16 indicating the relative phase between the clock signal 18 and the optical pulse train 12 by, for example, a voltage value, and controlling the phase of the clock signal 18 by changing the amount of phase shift of the variable phase shifter 17 with the control signal 16 Then, the relative phase between the data signal 14 and the incident light pulse train 11 can be optimized.

The above operation will be described more specifically.
It is as follows. FIG. 2 shows a temporal change in the light transmittance of the electro-absorption modulator 3 when the electro-absorption modulator 3 is driven using the clock signal 18 as a modulation signal. Now, when the output light pulse train 12 from the data modulator 2 passes through the electro-absorption modulator 3 at the timing shown in FIG. 2A, the optical power absorbed by the electro-absorption modulator 3 is minimum, and The modulated photocurrent 15 is minimal, and
When transmitted at the timing indicated by, the modulated photocurrent 1
5 is the maximum.

[0025] Here, in the case of transmission at a timing when output optical pulse train 12 from the data modulator 1 is shown an electric field absorption type optical modulator 3 in the a or b 2, the incident light pulse 1
The phase shift amount of the semi-fixed phase shifter 6 is adjusted in advance, for example, at the time of various adjustments at the time of introducing the system, so that 1 transmits through the data modulator 1 at an optimum timing. In this way, when the modulated light current 15 outputted from the electro-absorption type modulator 3 is shifted from the minimum (or maximum), variable phase shifter to return to the minimum modulation photocurrent 15 again (or maximum) 5 is controlled by the control signal 16 from the controller 4, the data signal 14 supplied from the data retiming circuit 7 to the data modulator 1 and the relative phase of the incident light pulse 11 are again optimized. You can go back.

The controller 4 determines whether or not the modulated photocurrent 15 is kept at the minimum state.
That is, if the modulated photocurrent 15 is hardly detected, it can be easily performed by deviating therefrom. In this way, when it is determined that the modulated optical current 15 has deviated from the optimum, the controller 4 changes the phase shift amount of the variable phase shifter 5 by a control signal 16 back and forth by a small amount, and It is only necessary to detect the decreasing direction, change the phase shift direction so that the modulated photocurrent 15 changes in that direction, and stop the phase shift when the modulated photocurrent 15 is hardly detected.

Even when the minimum of the modulated light current 15 is not 0, or when the modulated light current 15 is locked at the maximum, the same control may be performed when it is determined that the modulated light current 15 has shifted. However, the phase shift amount of the variable phase shifter 5 may always be changed to a very small amount so as to be kept at the minimum or maximum by the hill-climbing method. Alternatively, a control signal consisting of a low-frequency signal (on the order of kHz) having a small amplitude is supplied to the variable phase shifter 5 so that the phase of the clock signal 18 is always changed, and the modulated photocurrent 15 is synchronously detected with the low-frequency signal. For example, an analog feedback loop can be formed, and the phase can be automatically fixed to the optimum phase.

Although the semi-fixed phase shifter 6 is inserted between the output side of the variable phase shifter 5 and the clock signal input terminal of the data retiming circuit 7 in FIG.
A semi-fixed phase shifter may be inserted at a position immediately before the modulation signal input terminal. In this case, the clock signal output from the variable phase shifter 5 is directly input to the data retiming circuit 7. If there is no problem in the operation band, the insertion position of the semi-fixed phase shifter may be immediately before the data signal input terminal of the data modulator 1. At this time, the semi-fixed phase shifter may be configured as a device, or a cable having an optimal phase shift amount may be selectively used from a plurality of types of cables having different lengths. Further, an optical delay unit for handling an optical signal may be used as a semi-fixed phase shifter, and may be inserted on the input side of the optical pulse train of the electroabsorption modulator 3.

On the other hand, in FIG. 1, the variable phase shifter 5 is inserted in the path of the clock signal which is an electric signal. However, an optical delay device for handling an optical signal is used as the variable phase shifter, and this is used as the data modulator 1. May be inserted at the input side of the optical pulse train. FIG.
And the optical delay unit inserted on the optical pulse train input side of the data modulator 1 may be used in combination. Further, by supplying a clock signal, which is a clock signal, which is an electric signal, to a phase shifter 5 by a variable phase shifter 5, to an optical pulse generation source for generating an optical pulse train incident on the data modulator 1, The phase of the pulse train may be shifted. In short, the variable phase shifter only needs to be able to control the phase of at least one of the data signal and the incident light pulse train so that the relative phase between the data signal input to the data modulator 1 and the incident light pulse train is optimized.

Such a change in the insertion position of the semi-fixed phase shifter or the variable phase shifter is similarly possible in the following embodiments. (Second Embodiment) FIG. 3 is a block diagram of an optical pulse modulator according to a second embodiment, in which two variable phase shifters 5 are used.
-1 and 5-2 are different from the first embodiment.

In the method of always shifting the phase of the clock signal 18 as described in the first embodiment , the phase of the data signal 14 input to the data modulator 1 is also always slightly changed. Then, it is subjected to phase modulation. If the amplitude of the phase modulation of the data signal 14 is sufficiently small, there is no problem in many cases. However, if this is a problem, the configuration of the second embodiment is effective.

That is, in the present embodiment, the variable phase shifter 5-1 for changing the phase of the clock signal supplied to the electroabsorption modulator 3 and the variable phase shifter for changing the phase of the data signal input to the data modulator 1 are provided. The phase shifters 5-2 are separately provided, and only the variable phase shifter 5-1 for changing the phase shift amount by a small amount is provided. However, the feedback signal detected by shifting the phase back and forth by a small amount, that is, the control signal generated by the controller 4 is supplied to both the variable phase shifters 5-1 and 5-2. In this way, it is possible to avoid the phenomenon that the phase of the data signal always fluctuates around a very small amount.

(Third Embodiment) FIG. 4 is a block diagram of an optical pulse modulation device according to a third embodiment, in which a variable phase shifter 5-2 for shifting the phase of a data signal is used for the data signal. The difference from the second embodiment shown in FIG. That is, the variable phase shifter 5-2 does not change the phase of the clock signal supplied to the retiming circuit 7 for the data signal as in the second embodiment, but changes the phase of the data signal input to the data modulator 1. Change the phase directly.
Such a configuration is possible if there is no problem in the operation band of the variable phase shifter 5-2.

In the configurations of the first and second embodiments shown in FIGS. 1 and 3, if the relative phase shift between the data signal and the incident light pulse train is increased to nearly half a bit, an error occurs during data retiming. Although this may occur, the configuration of the present embodiment does not change the phase of data retiming, and therefore can cope with such a large phase shift close to half a bit.

(Fourth Embodiment) FIG. 5 is a block diagram of an optical pulse modulator according to a fourth embodiment. An optical coupler 2 is arranged on the input side of a data modulator 1, and this optical coupler 2 Thus, an optical pulse branched from an optical pulse incident on the data modulator 1 is input to the electro-absorption modulator 3.

In the first to third embodiments, the outgoing light pulse train from the data modulator 1 is branched by the optical coupler 2, and the electroabsorption modulator for detecting the relative phase between the data signal and the incoming light pulse train. Entered in 3. As the data modulator 1, a lithium niobate modulator is usually used. Since the bias point fluctuates over time, an output light pulse train from the data modulator 1 is branched to stabilize the bias point. It is common to input to a point detection system. Therefore, if a part of the optical power of the optical pulse train branched for stabilizing the bias point as in the first to third embodiments is further branched and incident on the electroabsorption modulator 3, the main optical transmission line There is less branching of the optical power from the light source.

However, when there is a possibility that the control of the relative phase between the data signal and the incident light pulse train may conflict with the control for stabilizing the bias point, the data modulator 1 is used as in this embodiment. Optical pulse train to the optical coupler 2
And incident on the electro-absorption modulator 3,
A configuration that controls the relative phase between the data signal and the incident light pulse train is effective.

FIG. 5 shows an example in which the position of the optical coupler 2 is changed with respect to the structure of FIG. 1, but the position of the optical coupler 2 is changed with respect to the structure of FIG. 3 or FIG. It is also possible to adopt a configuration in which:

(Fifth Embodiment) FIG. 6 is a block diagram of an optical pulse modulation device according to a fifth embodiment. Instead of the electroabsorption modulator 3 in the configuration of FIG. The detector 21 and the photodetector 22 are used. That is, the optical modulator 21 generates a modulated optical signal 23 modulated by the clock signal. This modulated optical signal 23 is converted into a photocurrent by the photodetector 22 and becomes a modulated optical current 24. This light modulation current 24 is the same as the modulation light current output from the electroabsorption modulator 3 in FIG. Therefore, basically the same effects as in the first embodiment can be obtained by the configuration of the present embodiment.

It should be noted that the second to fourth embodiments shown in FIGS.
Needless to say, the electroabsorption modulator 3 in FIG. 5 can be replaced with a configuration in which a normal optical modulator and a photodetector are combined.

(Sixth Embodiment) FIG. 7 is a block diagram of an optical pulse modulation device according to a sixth embodiment. An NRZ-RZ conversion circuit 8 converts an NRZ pattern data signal 13 input from the outside. After converting into the data signal 18 of the RZ pattern, the data modulator 1
A configuration for inputting a modulated signal to. In this case, the data signal input to the data modulator 1 as a modulation signal is NR
A simpler configuration can be achieved as compared with the first to fifth embodiments that are the Z pattern.

As in the present embodiment, the data modulator 1
The data signal 18 of the Z pattern is input as a modulation signal
And the optical power of the light pulse train emitted from the data modulator 1
Is the data signal supplied to the data modulator 1 and the incident light
This reflects the relative phase shift of the Luth train. That is, the data
The relative phase of the signal 18 and the optical pulse train8As in (a)
If it is correct, the light transmitted through the data modulator 1
Power is at its maximum. On the other hand, the relative phase8
If it is shifted as in (b), it passes through the data modulator 1.
Of the RZ pattern in which a part of the optical pulse
Data 18 is deleted by the waveform of the data signal 18.
The optical power transmitted through the modulator 1 is reduced.

Therefore, as shown in FIG.
An optical pulse train emitted from the optical modulator 2 is branched by the optical coupler 2 and is incident on the photodetector 9 so that the data modulator 1
Is detected, and the amount of phase shift of the variable phase shifter 5 inserted in the path of the clock signal to the NRZ-RZ conversion circuit 8 is controlled so that the power becomes maximum. Is controlled, the relative phase between the data signal 18 input to the data modulator 1 and the incident optical pulse train can be optimized.

Here, when the light pulse incident on the data modulator 1 is very thin and the data signal 18 has a waveform close to a rectangular wave, the position of the light pulse is slightly shifted from the center of the data signal 18. In this case, the optical power transmitted through the data modulator 1 may not change. However, when the relative phase between the data signal 18 and the incident light pulse train is slightly shifted in this way, the optical power transmitted through the data modulator 1 remains maximum and is not different from the case where the data signal 18 is at the center of the data signal 18. Since the eye opening of the modulated output light pulse train from the data modulator 1 is the same as that in the case where the light pulse is located at the center of the data signal 18, the transmission characteristics do not deteriorate. Small deviations are not a problem.

In FIG. 7, the variable phase shifter 5 is inserted in the path of the clock signal. However, between the NRZ-RZ conversion circuit 8 and the data modulator 1 or the incident light pulse of the data modulator 1 is input. It may be inserted on the side.

According to the present embodiment, it is unnecessary to particularly make the detection system , phase system, and control system of the relative phase of the data signal and the incident light pulse train compact and to reduce the internal phase fluctuation. Further, even when noise other than the light pulse is mixed in the incident light pulse train, there is an advantage that most of the noise can be removed.

[0047]

As described above, according to the optical pulse modulator according to the present invention, the optical pulse train branched near the data modulator is transmitted to the optical modulator driven by the clock signal synchronized with the data signal. The modulated optical current directly obtained from the optical modulator or the optical signal output from the optical modulator is photoelectrically converted, and the modulated optical current obtained from the modulated optical current is input to the data modulator. By detecting the phase and controlling the phase of at least one of the data signal and the incident light pulse train based on the detected phase, the relative phase between the data signal and the incident light pulse train can be optimized.

According to another optical pulse modulation apparatus of the present invention, a modulation signal for performing data modulation on an optical pulse train in a data modulator is an RZ pattern data signal, and an output light pulse train from the data modulator is converted into an RZ pattern data signal. By controlling the phase of at least one of the data signal and the incident light pulse train so that the optical power is maximized, the relative phase between the data signal and the incident light pulse train can be optimized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical pulse modulation device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a time change of a light transmittance of an electro-absorption modulator for explaining the first embodiment;

FIG. 3 is a configuration diagram of an optical pulse modulation device according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of an optical pulse modulation device according to a third embodiment of the present invention.

FIG. 5 is a configuration diagram of an optical pulse modulation device according to a fourth embodiment of the present invention.

FIG. 6 is a configuration diagram of an optical pulse modulation device according to a fifth embodiment of the present invention.

FIG. 7 is a configuration diagram of an optical pulse modulation device according to a sixth embodiment of the present invention.

FIG. 8 is a diagram for explaining a phase relationship between an RZ pattern data signal and an optical pulse according to a sixth embodiment.

FIG. 9 is a diagram for explaining optical time division multiplexing;

FIG. 10 is a diagram for explaining a phase relationship between a data signal and an optical pulse;

FIG. 11 is a diagram for explaining a data signal waveform;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Data modulator 2 ... Optical coupler 3 ... Electroabsorption modulator 4 ... Controller 5 ... Variable phase shifter 6 ... Semi-fixed phase shifter 7 ... Data retiming circuit 8 ... Photodetector 9 ... NRZ-RZ conversion circuit 11 ... incident light pulse train 12 ... outgoing light pulse train 13 ... data signal 14 ... data signal 15 ... modulation light current 16 ... control signal 17 ... clock signal 18 ... clock signal 21 ... light modulator 22 ... photodetector 23 ... modulation light signal 24 ... modulation Photocurrent

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-304432 (JP, A) JP-A-5-284117 (JP, A) JP-A-61-244139 (JP, A) JP-A-9-9 83447 (JP, A) JP-A-7-162394 (JP, A) JP-A-5-110518 (JP, A) JP-A-3-1711036 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 10/00-10/28 H04J 14/00-14/08 G02F 1/00-1/01

Claims (6)

(57) [Claims] 1. A data modulating means for modulating an incident optical pulse train by a data signal synchronized with a clock signal, an optical pulse train before or after modulation by said data modulating means is branched and inputted, and said branched and inputted optical pulse train is converted into said optical pulse train. An optical modulating means for modulating with a clock signal to output a modulated optical current; and a phase of at least one of the data signal and the incident optical pulse train based on the modulated optical current is optimized relative to the data signal and the incident optical pulse train. An optical pulse modulation device comprising: 2. An optical pulse modulation device according to claim 1, wherein said optical modulation means is an electro-absorption modulator whose light transmittance is changed by an electric field. 3. A data modulating means for modulating an incident light pulse train by a data signal synchronized with a clock signal, and an optical pulse train before or after modulation by the data modulating means is branched and inputted, and the branched and inputted optical pulse train is converted into the light pulse train. An optical modulator that modulates with a clock signal and outputs a modulated optical signal; a photoelectric converter that detects the modulated optical signal and outputs a modulated optical current; the data signal and the incident optical pulse train based on the modulated optical current A phase control means for controlling at least one of the phases so that the relative phases of the data signal and the incident light pulse train are optimized. 4. The data signal is an NRZ pattern signal, and the phase control means controls the phase of at least one of the data signal and the incident light pulse train so that the modulated photocurrent becomes minimum or maximum. The optical pulse modulation device according to claim 2, wherein: 5. The data signal is an NRZ pattern signal.
And when the modulated photocurrent is at a minimum or maximum
The relative phase of the data signal and the incident light pulse train is
It has a means to perform initial setting so that it is suitable
The light pulse according to any one of claims 1 to 3,
Modulation device. 6. A data modulation means for modulating an incident light pulse train with a data signal of an RZ pattern synchronized with a clock signal, a photoelectric conversion means for detecting a light power of a light pulse train modulated by the data modulation means, and An optical pulse modulation device comprising: a phase control unit that controls at least one phase of the data signal and the incident optical pulse train so that the optical power detected by the conversion unit is maximized.