JP2007258604A - Optical fiber modulating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber modulating device, capable of performing modulation with high modulation frequencies, without having to impress loading circuits or light sources that are used for pulse driving. <P>SOLUTION: The optical fiber modulating device includes a pulse drive control section 5 which controls a frequency, generation timing and the duty ratio of each of first modulation timing and second modulation timing, by generating a first pulse control signal controlling the first modulation timing and a second pulse control signal controlling the second modulation timing, a first pulse drive section 18 and a second pulse drive section 19, which generate first and second pulsating signals turing on/off, according to the first and second pulse control signals; a first fiber amplifier exciting light source 11 and a second fiber exciting light source 14, which generate pulsating laser light beams according to the first and second drive signals, and a fiber amplifier 16, which imparts energies modulated and excited with the first laser light and second laser light to external seed light to amplify it and outputs the resulting light as a third laser light. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical fiber modulation device that amplifies and modulates input seed light, and more particularly to a technique for improving a modulation frequency.

  Conventionally, an optical fiber amplifier that amplifies an input optical signal is known (see, for example, Patent Document 1). FIG. 9 is a block diagram showing the configuration of an optical fiber modulation device obtained by combining this type of conventional optical fiber amplifier with an optical modulation device.

  This optical fiber modulation device includes a first DC drive unit 10, a first fiber amplifier excitation light source 11, a first optical multiplexer 12, a second DC drive unit 13, a second fiber amplifier excitation light source 14, and a second optical multiplexing. It comprises a device 15, a fiber amplifier 16 and a modulation device 17.

  The first DC drive unit 10 generates a drive signal composed of a DC current and supplies it to the first fiber amplifier excitation light source 11. The first fiber amplifier excitation light source 11 is composed of a semiconductor laser oscillator, and is driven by a drive signal supplied from the first DC drive unit 10 to generate laser light of a certain size. The laser light generated by the first fiber amplifier excitation light source 11 is sent to the first optical multiplexer 12. The first optical multiplexer 12 transmits light of a specific wavelength of an optical signal input from the outside and sends it to one end of the fiber amplifier 16, and transmits the laser light from the first fiber amplifier excitation light source 11 to the fiber amplifier 16. Send it to one end.

  Similar to the first DC drive unit 10, the second DC drive unit 13 generates a drive signal composed of a DC current and supplies it to the second fiber amplifier excitation light source 14. Similar to the first fiber amplifier excitation light source 11, the second fiber amplifier excitation light source 14 is composed of a semiconductor laser oscillator, and is fixed by being driven by a drive signal supplied from the second DC drive unit 13. A laser beam of the size of is generated. The laser beam generated by the second fiber amplifier excitation light source 14 is sent to the second optical multiplexer 15. The second optical multiplexer 15 sends the laser light from the second fiber amplifier excitation light source 14 to the other end of the fiber amplifier 16.

  The fiber amplifier 16 is composed of an optical fiber, and a laser beam sent from the first fiber amplifier excitation light source 11 via the first optical multiplexer 12 and a second optical multiplexing from the second fiber amplifier excitation light source 14. The energy given by the laser beam sent via the device 15 is accumulated, and the accumulated energy is given to the seed light inputted from the outside via the first optical multiplexer 12. As a result, the optical signal is amplified and an optical signal having a predetermined energy level is output. The optical signal output from the fiber amplifier 16 is sent to the modulation device 17 via the second optical multiplexer 15.

  The modulation device 17 includes a modulation element that is an optical system component. The modulation device 17 controls transmission / blocking of an optical signal by applying an electric field from the outside (not shown), and modulates the input optical signal. The optical signal modulated by the modulation device 17 is output as a pulsed optical signal.

  By the way, the conventional optical fiber modulation device configured as described above must be provided with an optical system component called the modulation device 17 therein, so that the size of the device is increased and the modulation device 17 is driven. Since electric power is required, there is a disadvantage that power consumption increases.

  Therefore, an improved optical fiber modulation device as shown in FIG. 10 is considered as a solution to such a drawback. This improved optical fiber modulator drives the first fiber amplifier excitation light source 11 and the second fiber amplifier excitation light source 14 in accordance with the modulation timing, and creates the excitation state of the fiber amplifier 16 as a pulse to generate an optical signal. Is configured to amplify and modulate.

  Specifically, the improved optical fiber modulator replaces the first DC driving unit 10 and the second DC driving unit 13 shown in FIG. 9 with a first pulse driving unit 18 and a second pulse driving unit 19, respectively. Configured. As a result, a drive signal composed of a pulse current corresponding to the modulation timing is supplied from the first pulse driver 18 and the second pulse driver 19 to the first fiber amplifier excitation light source 11 and the second fiber amplifier excitation light source 14, respectively. , A pulsed laser beam is generated. Therefore, the fiber amplifier 16 outputs an optical signal in which the seed light is amplified and modulated.

  However, in the conventional improved optical fiber modulation device described above, since the time from the ground state to the pumping state of the fiber amplifier 16 is long, an upper limit occurs in the modulation frequency of the output optical signal, and the modulation frequency is increased. There was a problem that I could not. In order to solve this problem, an optical fiber modulation device capable of modulating at a high modulation frequency as shown in FIG. 11 has been considered (see Patent Document 2).

    The optical fiber modulator includes a first bias pulse driving unit 20, a first fiber amplifier excitation light source 11, a first optical multiplexer 12, a second bias pulse driving unit 21, a second fiber amplifier excitation light source 14, and a second optical amplifier. An optical multiplexer 15 and a fiber amplifier 16 are included. Specifically, the improved optical fiber modulation device includes a first pulse driving unit 18 and a second pulse driving unit 19 shown in FIG. 10 replaced by a first bias pulse driving unit 20 and a second bias pulse driving unit 21. Each is replaced.

  As shown in FIG. 12B, the first bias pulse driver 20 is turned on / off according to the modulation timing and generates a drive signal composed of a biased pulsed current signal. In the first bias pulse driving unit 20, a direct current (bias current) and a pulse current are superimposed and output as a drive signal. The drive signal generated by the first bias pulse driver 20 is supplied to the first fiber amplifier excitation light source 11. The laser light generated by the first fiber amplifier excitation light source 11 is sent to the first optical multiplexer 12. The first optical multiplexer 12 transmits light having a specific wavelength of an optical signal input from the outside as shown in FIG. 12A to the fiber amplifier 16 and from the first fiber amplifier excitation light source 11. Is sent to one end of the fiber amplifier 16. The same applies to the second bias pulse driving unit 21 side.

  With this configuration, when a drive signal composed of a biased current signal is output from the first bias pulse drive unit 20 or the second bias pulse drive unit 21, the fiber amplifier 16 is driven to the ground state by the drive signal. From a state maintained at a higher energy state to an excited state. Accordingly, the fiber amplifier 16 is excited by a biased pulsed laser beam, and energy having the excitation is applied to an optical signal input from the outside to be amplified, and light having a bias as shown in FIG. Since it is configured to output a signal, the pulsed laser light output from the fiber amplifier excitation light source repeats on / off between the energy state higher than the ground state and the excited state, and the ground state Since the time from the higher energy state to the excited state is shorter than the time in the conventional optical fiber modulator, the upper limit of the modulation frequency of the output optical signal can be extended.

In addition, since the fiber amplifier excitation light source is turned on / off between an energy state higher than the ground state and the excited state, it is compared with a conventional optical fiber modulator that is turned on / off between the ground state and the excited state. The load of the fiber amplifier excitation light source is reduced. As a result, the life of the fiber amplifier excitation light source can be extended.
JP-A-7-193306 JP 2005-259822 A

  However, even in the conventional optical fiber modulation device described above, an upper limit is generated in the modulation frequency of the output optical signal depending on the time until the fiber amplifier 16 is excited, and it is difficult to increase the modulation frequency. In addition, the upper limit of the modulation frequency is determined by the performance of the bias pulse driving unit and the excitation light source, and using a high modulation frequency places a heavy burden on the circuit and the light source, so there is a problem that the lifetime becomes very short. .

  Accordingly, an object of the present invention is to provide an optical fiber modulation device that can perform modulation at a high modulation frequency without imposing a burden on a circuit or a light source used for pulse driving.

  In order to solve the above-described problems, an optical fiber modulation device according to the present invention includes a first pulse control signal for controlling the first modulation timing and a second pulse control for controlling the second modulation timing. A pulse drive control unit that controls the frequency, timing, and duty ratio of the first modulation timing and the second modulation timing by generating a signal, and a pulse-shaped first that is turned on / off according to the first pulse control signal A first pulse driving unit that generates a driving signal; a second pulse driving unit that generates a pulse-shaped second driving signal that is turned on / off in accordance with the second pulse control signal; and in response to the first driving signal. A first fiber amplifier excitation light source for generating a pulsed first laser beam and a second fiber amplifier excitation for generating a pulsed second laser beam in response to the second drive signal And a fiber amplifier that amplifies the energy modulated and excited by the first laser light and the second laser light by applying the seed light from the outside to the seed light, and outputs the seed light as a third laser light. .

  According to a second aspect of the present invention, in the first aspect of the present invention, one of the first modulation timing and the second modulation timing is fixed, and the other modulation timing is made variable, whereby the duty of the third laser light is changed. The ratio is variable.

  According to a third aspect of the present invention, in the first aspect, the first modulation timing is different from the second modulation timing.

  According to a fourth aspect of the present invention, in the third aspect, the third laser light has a frequency twice that of the first laser light or the second laser light.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the bias is removed by slicing the third laser light output from the fiber amplifier at a predetermined threshold value. It further comprises laser beam shaping means for outputting three laser beams.

  A sixth aspect of the present invention is characterized in that, in the fifth aspect, the laser beam shaping means comprises an optical parametric oscillator.

  According to the optical fiber modulation device of the first invention, the two pulsed laser lights generated by driving the two fiber amplifier excitation light sources excite the fiber amplifier and transfer the energy from the excitation to the outside. Is applied to the seed light input from, and is amplified to output laser light. At this time, since the pulse drive control unit controls the timing and the duty ratio of the two pulsed laser beams, the modulation frequency and the duty ratio of the laser beams output from the fiber amplifier can be controlled. In addition, the energy accumulated in the fiber amplifier is in an excited state at the timing when two pulsed laser beams output from the fiber amplifier excitation light source are simultaneously output. Therefore, when transitioning from the state in which one pulsed laser beam is output to the state in which both pulsed laser beams are output, the energy accumulated in the fiber amplifier is higher than the ground state. From the state to the pumping state, the time to the pumping state is shorter than that of the conventional optical fiber modulator, and the upper limit of the modulation frequency of the output optical signal can be extended.

  Further, by shifting the timing of the two pulsed laser beams output from the fiber amplifier excitation light source, the modulation frequency applied to the seed beam can be set to twice the original pulse frequency. Therefore, the upper limit of the modulation frequency can be doubled. In this case, the frequency applied to the two pulsed laser beams output from the fiber amplifier excitation light source is only half of the desired modulation frequency. The life can be extended without imposing a burden on the light source.

  According to the optical fiber modulation device of the second invention, one of the timings of the two pulsed laser beams output from the fiber amplifier excitation light source is fixed and one of the timings is made variable. The duty ratio of the output third laser beam can be changed.

  According to the optical fiber modulation device of the third invention, the duty ratio of the third laser light output from the fiber amplifier by shifting the timings of the two pulsed laser lights output from the fiber amplifier excitation light source. Can be changed.

  According to the optical fiber modulation device of the fourth invention, by shifting the timings of the two pulsed laser beams output from the fiber amplifier excitation light source so that they overlap each other at the beginning and end of the output, 2 times the modulation frequency.

  According to the optical fiber modulation device of the fifth aspect of the invention, the laser light output from the fiber amplifier by the laser light shaping means is sliced at a predetermined threshold value so as to output the laser light from which the bias is removed. Therefore, the laser beam changes between the zero level and the original high level, and the degree of modulation can be increased.

  Further, according to the optical fiber modulation device of the sixth invention, since the laser light shaping means is composed of an optical parametric oscillator, it is possible to use conventionally used optical system parts, Can be configured at low cost.

  Embodiments of an optical fiber modulation device of the present invention will be described below in detail with reference to the drawings. In the following description, the same reference numerals as those used in the background art section are used for the portions corresponding to the constituent parts described in the background art section.

  FIG. 1 is a block diagram showing a configuration of an optical fiber modulation device according to Embodiment 1 of the present invention. This optical fiber modulator includes a pulse drive control unit 5, a first pulse drive unit 18, a first fiber amplifier excitation light source 11, a first optical multiplexer 12, a second pulse drive unit 19, and a second fiber amplifier excitation light source. 14, a second optical multiplexer 15 and a fiber amplifier 16.

  In this specification, the first pulse driver 18 and the second pulse driver 19 are referred to as “bias pulse driver”, the first fiber amplifier excitation light source 11 and the second fiber amplifier excitation light source 14 are referred to as “fiber amplifiers”. Collectively referred to as “excitation light source”.

  The pulse drive control unit 5 generates a first pulse control signal and a second pulse control signal and sends them to the first pulse drive unit 18 and the second pulse drive unit 19, respectively. The first pulse control signal and the second pulse control signal are for controlling the first modulation timing and the second modulation timing, respectively. Specifically, the pulse drive control unit 5 controls each timing, duty ratio, and frequency of the first modulation timing and the second modulation timing. The first pulse driver 18 is turned on / off at the first modulation timing in accordance with the input first pulse control signal, and generates a first drive signal composed of a pulsed current signal. The first drive signal generated by the first pulse driver 18 is supplied to the first fiber amplifier excitation light source 11.

  The first fiber amplifier excitation light source 11 is composed of a semiconductor laser oscillator, and is driven by a drive signal supplied from the first pulse driver 18 to generate a pulsed first laser beam. The first laser light generated by the first fiber amplifier excitation light source 11 is sent to the first optical multiplexer 12. The first optical multiplexer 12 transmits light having a specific wavelength of seed light input from the outside to the fiber amplifier 16 and transmits the first laser light from the first fiber amplifier excitation light source 11 to the fiber amplifier 16. Send to one end.

  Similarly to the first pulse drive unit 18, the second pulse drive unit 19 turns on / off at the second modulation timing in accordance with the input second pulse control signal, and performs the second drive composed of a pulsed current signal. Generate a signal. The second drive signal generated by the second pulse driver 19 is supplied to the second fiber amplifier excitation light source 14.

  Similar to the first fiber amplifier excitation light source 11, the second fiber amplifier excitation light source 14 is composed of a semiconductor laser oscillator, and is driven by the second drive signal supplied from the second pulse driver 19. To generate a pulsed second laser beam. The second laser light generated by the second fiber amplifier excitation light source 14 is sent to the second optical multiplexer 15. The second optical multiplexer 15 sends the second laser light from the second fiber amplifier excitation light source 14 to the other end of the fiber amplifier 16.

  The fiber amplifier 16 includes a pulsed first laser beam sent from the first fiber amplifier excitation light source 11 via the first optical multiplexer 12 and a second optical multiplexer 15 from the second fiber amplifier excitation light source 14. The energy imparted by the pulsed second laser light transmitted via the first optical multiplexer 12 is accumulated, and the accumulated energy is imparted to the seed light input via the first optical multiplexer 12 from the outside. As a result, the fiber amplifier 16 amplifies the seed light and outputs the third laser light modulated according to the first modulation timing and the second modulation timing controlled by the pulse drive control unit 5. The output of the fiber amplifier 16 is output to the outside as a modulation output via the second optical multiplexer 15.

The operation of the thus configured optical fiber modulation device according to Embodiment 1 of the present invention will be described. FIG. 2 shows the first fiber amplifier excitation light source from the first pulse driving unit 18 and the second pulse driving unit 19 when the first modulation timing and the second modulation timing are exactly the same in the optical fiber modulation device of the present invention. 11 is a diagram showing the relationship between the current supplied to each of 11 and the second fiber amplifier excitation light source 14 and the third laser light output from the fiber amplifier 16. This shows the same operation as that of the prior art in the configuration shown in FIG. When the first drive signal and the second drive signal, which are current signals, are simultaneously output from the first pulse drive unit 18 and the second pulse drive unit 19 under the control of the pulse drive control unit 5, the fiber amplifier 16 is excited. The excited state is reached from the ungrounded state over time Δt ₁ .

On the other hand, FIG. 3 shows a case where the first modulation timing is fixed and the second modulation timing is shifted. When the first drive signal and the second drive signal composed of current signals are output at different timings from the first pulse drive unit 18 and the second pulse drive unit 19 under the control of the pulse drive control unit 5, both drive signals are output. The fiber amplifier 16 reaches the excited state over time Δt ₂ from the state where the fiber amplifier 16 is maintained in the energy state higher than the ground state by the drive signal at the timing when the two overlap. Also, as shown in FIG. 3, when pulse drive control is performed at a timing at which one of the drive signals is always output, the fiber amplifier 16 is applied with a certain bias when only one of the drive signals is output. It will be in the state.

Here, assuming that the rising characteristics of energy storage of the fiber amplifier 16 are constant, the relationship of time Δt ₂ <time Δt ₁ is established. Therefore, in the optical fiber modulation device according to the first embodiment of the present invention, in order to obtain the same excitation time as the excitation time that is the time when the fiber amplifier 16 of the conventional optical fiber modulation device is in the excitation state, the drive signal The pulse width can be reduced. This means that the modulation frequency can be increased as compared with the conventional optical fiber modulator.

  Further, when FIG. 2 and FIG. 3 are compared, the modulation frequency of the fiber amplifier output is the same, but the duty ratio is different. In this way, by adjusting the time at which the first modulation timing and the second modulation timing overlap, the duty ratio of the modulation applied to the fiber amplifier output can be controlled.

  FIG. 4 shows a case where the time over which the first modulation timing and the second modulation timing overlap is further shortened than in the case of FIG. In addition, all the duty ratios are changed to be small. In this case, since the overlapping time is shortened, the duty ratio of the fiber amplifier output becomes smaller than that in the case of FIG. In the case of FIG. 4, there is a time during which neither the first drive signal nor the second drive signal is output. At that time, the fiber amplifier output falls from the biased state to the ground state. The OPO output will be described in the second embodiment.

  FIG. 5 shows a case in which pulse drive control is performed at a timing such that the output of the other drive signal spans when the output of one drive signal ends and occurs. At this time, the modulation frequency applied to the fiber amplifier output is twice the frequency of the first modulation timing or the second modulation timing. This will be explained more specifically. In the period T1 shown in FIG. 5, the first drive signal and the second drive signal are simultaneously output. Therefore, the output of the fiber amplifier is excited with a certain time from the first part of T1, and then enters an excited state. In the period T2, only the second drive signal is output. Therefore, the fiber amplifier output is attenuated with a certain time, and thereafter the biased state is maintained. In the period T3, the first drive signal and the second drive signal are simultaneously output again. Therefore, the fiber amplifier output is excited again for a certain time, and then enters an excited state. In the periods T1, T2, and T3, the second drive signal is continuously output from before the end of the output of the first drive signal until after it is generated again. As a result, the fiber amplifier output has a frequency twice that of the first modulation timing and the second modulation timing. The OPO output will be described in the second embodiment.

  As described above, according to the optical fiber modulation device according to the first embodiment of the present invention, the two pulsed laser beams generated by driving the two fiber amplifier excitation light sources in a pulsed manner are the fiber amplifiers. Excitation is performed, and energy by excitation is applied to seed light input from the outside to be amplified, and laser light is output. At this time, the pulse drive control unit controls the frequency, generation timing, and duty ratio of the two pulsed laser beams.

  As a result, the modulation frequency and duty ratio of the laser light output from the fiber amplifier can be controlled. In addition, the energy accumulated in the fiber amplifier is in an excited state at the timing when two pulsed laser beams output from the fiber amplifier excitation light source are simultaneously output.

  Therefore, when transitioning from the state in which one pulsed laser beam is output to the state in which both pulsed laser beams are output, the energy accumulated in the fiber amplifier is higher than the ground state. From the state to the pumped state, the time to the pumped state is shorter than that of the conventional optical fiber modulator, and the upper limit of the modulation frequency of the output laser light can be extended.

  Also, the duty ratio of the third laser light output from the fiber amplifier is changed by fixing one of the timings of the two pulsed laser lights output from the fiber amplifier excitation light source and making one variable. be able to.

  Furthermore, by shifting the generation timing of the two pulsed laser beams output from the fiber amplifier excitation light source so that they overlap each other at the beginning and end of the output, it is possible to apply a modulation frequency twice that of the prior art. . Therefore, the upper limit of the modulation frequency can be doubled. In this case, the frequency applied to the two pulsed laser beams output from the fiber amplifier excitation light source is only half of the desired modulation frequency. The life can be extended without imposing a burden on the light source.

  Next, a second embodiment of the present invention will be described. The optical fiber modulation device according to the second embodiment of the present invention is characterized in that the degree of modulation is increased by further slicing the laser light output from the optical fiber modulation device according to the first embodiment with a predetermined threshold. It is what.

  FIG. 6 is a block diagram showing a configuration of an optical fiber modulation device according to Embodiment 2 of the present invention. This optical fiber modulator is configured by adding an optical parametric oscillator (OPO) 30 to the optical fiber modulator according to the first embodiment.

  The optical parametric oscillator 30 corresponds to the laser beam shaping means of the present invention, and converts the wavelength of the input laser beam into another wavelength when the energy level of the input laser beam is not less than a predetermined threshold. Output. On the other hand, when the energy level of the input laser beam is smaller than a predetermined threshold value, the wavelength of the input laser beam is not converted and zero is output.

  In the optical fiber modulation device according to the second embodiment configured as described above, the operation until the laser light is output from the fiber amplifier 16 via the second optical combiner 15 is the same as the optical fiber modulation according to the first embodiment described above. It is the same as the operation of the device. The laser beam output from the fiber amplifier 16 via the second optical combiner 15 is modulated in accordance with the drive signal from the first pulse driver 18 or the second pulse driver 19 as shown in FIG. And a biased signal that is supplied to the optical parametric oscillator 30.

  The optical parametric oscillator 30 slices the laser beam shown in FIG. 7B with a predetermined threshold and outputs the laser beam as shown in FIG. 7C to the outside as a modulation output. The operation of the optical parametric oscillator 30 will be described in more detail with reference to FIG.

FIG. 8A shows an enlarged view of the laser light (same as that shown in FIG. 7B) output from the fiber amplifier 16, and this laser light is input to the optical parametric oscillator 30. . If the high energy part of the laser beam is V _H and the low part is V _L , the degree of modulation can be expressed as “(V _H −V _L ) / V _H ”. As the optical parametric oscillator 30, one having a threshold for slicing between V _H and V _L is selected. When the threshold value is between V _H and V _L , the modulation degree is about “0.5”. When the optical parametric oscillator 30 receives laser light as shown in FIG. As shown in FIG. 8B, the portion smaller than the threshold value outputs zero, and the portion higher than the threshold value is wavelength-converted and output while maintaining the energy level of the input laser beam. The modulation degree in this case can be represented by “(V _H −0) / V _H ”. Therefore, the modulation degree is “1”.

  As described above, according to the optical fiber modulation device according to the second embodiment of the present invention, the laser beam output from the fiber amplifier 16 is sliced by the optical parametric oscillator 30 with the predetermined threshold, so that the bias component is removed. Since the laser beam is configured to be output, the laser beam changes between the zero energy level and the original high energy level, and the degree of modulation can be increased.

  Further, since the laser beam shaping means is constituted by an optical parametric oscillator, it is possible to use conventionally used optical system parts and to construct an optical fiber modulation device at low cost.

  The OPO output graphs of FIGS. 4 and 5 of the first embodiment are also the same. A fiber amplifier output smaller than the threshold is output as zero, and a fiber amplifier output with an abnormal threshold is output while maintaining the energy level.

  In the first and second embodiments described above, the outputs of the first fiber amplifier excitation light source 11 and the second fiber amplifier excitation light source 14 are supplied to the fiber amplifier 16 to store the energy accumulated in the fiber amplifier 16. Although it is configured to increase the amplification factor of the seed light by this, it is configured to include only one of the first fiber amplifier excitation light source 11 and the second fiber amplifier excitation antigen 14. You can also. Also in this case, the same operations and effects as those of the first and second embodiments described above can be achieved.

  The present invention can be applied to a device that amplifies and modulates input seed light and outputs it as laser light, for example, a light wave interference device, a laser oscillator, or the like.

It is a block diagram which shows the structure of the optical fiber modulation apparatus which concerns on Example 1 of this invention. It is a wave form diagram which shows the operation | movement waveform of each part of the optical fiber modulation apparatus shown in FIG. It is a wave form diagram which shows the operation | movement waveform of each part of the optical fiber modulation apparatus shown in FIG. It is a wave form diagram which shows the operation | movement waveform of each part of the optical fiber modulation apparatus shown in FIG. It is a wave form diagram which shows the operation | movement waveform of each part of the optical fiber modulation apparatus shown in FIG. It is a block diagram which shows the structure of the optical fiber modulation apparatus which concerns on Example 2 of this invention. It is a wave form diagram which shows the operation | movement waveform of each part of the optical fiber modulation apparatus shown in FIG. It is a wave form diagram for explaining operation of an optical fiber modulation device concerning Example 2 of the present invention in detail. It is a block diagram which shows the structure of the conventional optical fiber modulation apparatus. It is a block diagram which shows the structure of the conventional improved optical fiber modulation apparatus. It is a block diagram which shows the structure of the conventional further improved optical fiber modulation apparatus. It is a wave form diagram for demonstrating operation | movement of the optical fiber modulation apparatus shown in FIG.

Explanation of symbols

5 Pulse Drive Control Unit 10 First DC Driver 11 First Fiber Amplifier Excitation Light Source 12 First Optical Multiplexer 13 Second DC Driver 14 Second Fiber Amplifier Excitation Light Source 15 Second Optical Multiplexer 16 Fiber Amplifier 17 Modulation Device 18 First pulse driver 19 Second pulse driver 20 First bias pulse driver 21 Second bias pulse driver 30 Optical parametric oscillator

Claims (6)

By generating a first pulse control signal that controls the first modulation timing and a second pulse control signal that controls the second modulation timing, the frequency, generation timing, and duty ratio of the first modulation timing and the second modulation timing are controlled. A pulse drive control unit,
A first pulse driver that generates a pulsed first drive signal that is turned on / off in response to the first pulse control signal;
A second pulse driving unit that generates a pulsed second driving signal that is turned on / off in response to the second pulse control signal;
A first fiber amplifier excitation light source for generating a pulsed first laser light in response to the first drive signal;
A second fiber amplifier excitation light source that generates a pulsed second laser light in response to the second drive signal;
A fiber amplifier for applying and amplifying energy modulated and excited by the first laser light and the second laser light to the seed light from the outside, and outputting it as a third laser light;
An optical fiber modulation device comprising:   2. The duty ratio of the third laser beam is made variable by fixing one timing of the first modulation timing and the second modulation timing and making the other modulation timing variable. The optical fiber modulation device described.   The optical fiber modulation device according to claim 1, wherein the first modulation timing is different from the second modulation timing.   4. The optical fiber modulator according to claim 3, wherein the third laser beam has a frequency twice that of the first laser beam or the second laser beam.   The laser beam shaping means which outputs the said 3rd laser beam from which the bias was removed by slicing the said 3rd laser beam output from the said fiber amplifier with a predetermined threshold value, The further characterized by the above-mentioned. The optical fiber modulation device according to claim 4. 6. The optical fiber modulation device according to claim 5, wherein the laser beam shaping means comprises an optical parametric oscillator.

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