JPH09232655A - Light pulse generating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a light pulse generating device which is capable of outputting light pulses which are the same in repetition frequency and variable and narrow in pulse width. SOLUTION: An electric pulse A1 out of electric pulses A1 and A2 of the same phase generated by a pulse generator is turned to an electric pulse A delayed in phase by a prescribed time through a line, and the electric pulse A2 is turned to an electric pulse B passing through a variable delay device, and a phase difference Δt occurs between the electric pulses A and B. The pulses A and B are used as drive signals for a first and a second light modulators 3 and 4, and a light input is turned into a light signal which is of pulse width tw and delayed by T+Δt through the first light modulator, and the light signal is modulated by the second light modulator 4 into a light signal of pulse width tw-Δt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pulse generator, and more particularly to an optical pulse generator capable of varying only the pulse width without changing the repetition frequency of the optical pulse in the generation of an ultrafast optical pulse. Is.

[0002]

2. Description of the Related Art Conventionally, a ring laser oscillator (hereinafter, simply referred to as a ring laser) used in ultrahigh-speed pulse generation has a structure shown in FIG.

In FIG. 4, reference numeral 1 is a pulse generator, and 3 is an optical modulator, which modulates light by an electric pulse signal from the pulse generator 1. Reference numeral 5 is an optical amplifier for receiving and amplifying the output of the optical modulator 3, 6 is an optical bandpass filter of variable wavelength for receiving the output of the optical amplifier 5 and cutting wavelengths other than the output wavelength, and 7 is the optical An optical coupler which receives the output of the bandpass filter 6 and branches it into an optical pulse signal output and a ring output and outputs it from the output terminals C and D. Reference numeral 8 is a variable light for adjusting the length of the entire ring so that mode synchronization is applied. It is a delay device.

The operation of the conventional ring laser shown in FIG. 4 will be described with reference to FIG.

The oscillation threshold in FIG. 5 is determined by the structure of the ring laser. When the peak value is set to 1 and normalized, it becomes about 0.9. The pulse width of the ring laser is determined by the width a in FIG. Therefore, in order to obtain a narrow pulse width, a high frequency wave having a high repetition frequency may be input to the optical modulator 3.

However, the frequency band of the optical modulator 3 is currently limited to about 70 GHz. When a 70 GHz sine wave is input, the pulse width is calculated by the equation (1).

[0007]

[Equation 1] Therefore, the pulse output has a full width at half maximum of 2.5 ps from the equation (1). In the current ring laser, this is the limit of the output pulse width.

As described above, in the conventional ring laser, the pulse width of the optical output depends on the frequency of the drive signal, and the frequency of the drive signal is increased in order to obtain an output with a short pulse width. The pulse repetition frequency, which is determined by the signal frequency, has changed. When the frequency is increased, the optical modulator 3 may not operate, and the pulse width of the optical pulse output of the ring laser is limited by the upper limit of the frequency of the drive signal.

[0009]

As described above, in the conventional ring laser, the pulse repetition frequency is changed when the pulse width is narrowed. Also, when performing signal observation by synchronizing the optical pulse generator with an external signal, the repetition frequency is determined by the external signal, so the pulse width changes and signal observation is performed with the best performance (shortest output pulse width). I will not be able to. Furthermore, it is difficult to obtain a thin optical pulse output at a slow repetition frequency.

The present invention focuses on the fact that the pulse width of the drive signal in the conventional ring laser can be equivalently shortened by changing the phase of the drive signal using two optical modulators, and the same repetition is repeated. An object of the present invention is to provide an optical pulse generator capable of varying the pulse width of the optical pulse output depending on the frequency.

[0011]

An optical pulse generator according to the present invention has an optical input terminal and an output terminal, receives an electric pulse signal (B) from the variable delay device, and is inputted from the optical input terminal. The optical pulse signal (A1) has a first optical modulator (3) that intensity-modulates the emitted light according to the electric pulse signal of the variable delay device and outputs it to the output terminal of the light, and an input terminal and an output terminal of the light. ) Receives the electric pulse signal (A) fixedly delayed by the line, intensity-modulates the light input from the light input terminal according to the electric pulse signal (A), and outputs the second light to the light output terminal. Modulator (4) and this second
An optical amplifier (5) for amplifying the output of the optical modulator, an optical bandpass filter (6) for transmitting only a desired wavelength of the output of the optical amplifier and cutting other wavelengths, an optical input terminal and 2 An optical coupler (7) having two optical output terminals (C) and (D) and a variable optical delay device (8) for mode-locking are provided, and these are connected in a ring shape.

[0012]

In the present invention, the output pulse width changes without changing the operating frequency of the optical modulator by changing the phase difference between the electric pulse signals for modulation input to the two optical modulators.

[0013]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

In FIG. 1, 1 is a pulse generator that repeatedly generates two synchronized electric pulse signals A1 and A2, and 2 is a pulse generator that changes the electric line length to generate an electric pulse signal A2.
A variable delay device 3 that produces a variable delay in the electric pulse signal B is a first optical modulator that constitutes a ring laser. The electric pulse signal B of the variable delay device 2 is a high frequency component and a DC bias component (Fig. (Not shown) to modulate the light intensity of the light input and output it. Reference numeral 4 denotes a second optical modulator that constitutes a ring laser. The electric pulse signal A1 is a high frequency component of the electric pulse signal A which is fixed and delayed by a line, and is combined with a DC bias component (not shown) to generate a light beam. It modulates the light intensity of the input and outputs it. An optical amplifier 5 constitutes a ring laser, and an erbium-doped fiber amplifier or the like is used. Reference numeral 6 is an optical bandpass filter that constitutes a ring laser, and the oscillation wavelength of the ring laser is the transmission intermediate wavelength. An optical coupler 7 constitutes a ring laser, which branches an optical output signal from the ring laser. Reference numeral 8 is a variable optical delay device for adjusting the ring length so that the ring laser operates stably.

Next, the operation of the embodiment shown in FIG. 1 will be described with reference to FIGS.

FIG. 2 is a diagram showing the operating principle of the present invention.
As shown in FIG. 2A, the second optical modulator 4 has a pulse width tw.
When the electric pulse signal A for driving is input, an optical output corresponding to the electric pulse signal A is output from the second optical modulator 4. As shown in FIG. 2B, when the electric pulse signal B whose phase is delayed by Δt from the electric pulse signal A is input to the first optical modulator 3, the first optical modulator 3 outputs an optical output. The phase of the optical output is an optical output whose phase is delayed by Δt from the optical output from the second optical modulator 4. Therefore, as shown in FIG.
Considering the optical modulator equivalent block 10 in which (b) is combined, it is equivalent to inputting an electric pulse signal for driving, which has a width tw-Δt in which the driving signals A and B are overlapped with each other. The signal is obtained. The larger Δt is, the narrower the pulse width becomes.

FIG. 3 is a block diagram showing the main part of the configuration of the embodiment of FIG. 1 using the above principle. In this figure, the delay time T is a fixed delay that occurs in a cable or the like.
Therefore, the delay time T naturally occurs also on the variable delay device 2 side. In short, the variable delay device 2 is used to provide a phase difference between the driving electric pulse signals A and B input to the first and second optical modulators 3 and 4. In the first optical modulator 3, the optical input is modulated in the first optical modulator 3 by the electric pulse signal B to which the delay time of T + Δt is given by the variable delay device 2 (Δt is variable), and the pulse width tw Then, the optical input is modulated into an optical pulse delayed by t = T + Δt with respect to the reference time t = 0. The optical signal modulated by the first optical modulator 3 is again modulated by the second optical modulator 4 in the next stage, and as described in the principle diagram of FIG. 2, the optical signal having the pulse width tw-Δt. Is obtained. The optical signal thus obtained is output from the output terminal C of the optical coupler 7. The optical signal obtained from the output terminal D of FIG. 1 is used again as an optical input in the ring laser.

The minimum value of the actual pulse width is determined by the first modulation bandwidth and an electric pulse signal B of the second optical modulator 3 and 4, the rise of the A time t _r and fall time t _f.
Therefore, of the electrical pulse signal by using the doubler such as t _r, t _f
A short pulse is not always generated compared to when the pulse width is shortened, but since the pulse width can be swept,
There is a possibility that it can be applied to a new measurement method by using the pulse width changing part.

As described above, by shifting the electric pulse signal having the pulse width tw by Δt seconds and applying it to the first optical modulator 3, the optical output passing through the two optical modulators 3 and 4 has a width of tw-Δt. Therefore, by changing Δt, optical modulation with an arbitrary pulse width between 0 and tw can be performed. As a result, the optical pulse output also changes according to equation (1).

[0020]

As described above, the present invention has the optical input terminal and the output terminal, receives the electric pulse signal (B) of the variable delay device, and receives the light input from the optical input terminal by the variable delay. Has a first optical modulator (3) that intensity-modulates according to an electric pulse signal of the device and outputs it to an output terminal of light, and an input terminal and an output terminal of the light, and the electric pulse signal (A1) is fixedly delayed by a line. A second optical modulator (4) for receiving the generated electric pulse signal (A), intensity-modulating the light input from the light input terminal according to the electric pulse signal (A), and outputting the intensity-modulated light to the light output terminal. An optical amplifier (5) for amplifying the output of the second optical modulator, an optical bandpass filter (6) for transmitting only a desired wavelength of the output of the optical amplifier and cutting other outputs, Also has an input terminal and two optical output terminals (C) and (D) Since the optical coupler (7) and the variable optical delay device (8) for mode-locking are provided and connected in a ring shape, two electric signal pulses for driving the first and second optical modulators are provided. It is possible to change the pulse width without changing the repetition frequency by changing the phase difference between them, and when used as a pulse light source using sampling light used for optical signal observation, even when observing a signal with a long period, it is short Sampling pulse light can be generated, and the waveform of light can be observed accurately.

Further, by using it as a pulse light source for sweeping the pulse width, a waveform observing device capable of increasing the time resolution to the limit of the stability of the sampling pulse width like a sampling pulse width sweeping optical sampling device is realized. it can.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram for explaining the operating principle of the present invention.

FIG. 3 is a diagram for explaining the operation of the main part of the embodiment of FIG.

FIG. 4 is a block diagram showing a configuration example of a conventional ring laser.

FIG. 5 is a waveform diagram for explaining the operation of the conventional ring laser.

[Explanation of symbols]

 1 pulse generator 2 variable delay device 3 first optical modulator 4 second optical modulator 5 optical amplifier 6 optical bandpass filter 7 optical coupler 8 variable optical delay device A electrical pulse signal A1 electrical pulse signal A2 electrical pulse signal B electric pulse signal

Claims (1)

[Claims] 1. A pulse generator (1) for outputting two synchronized electric pulse signals (A1), (A2), and an electric pulse signal (A2) from the pulse generator for generating a variable delay. A variable delay device (2) for obtaining an electric pulse signal (B), an optical input terminal and an output terminal for receiving the electric pulse signal (B) of the variable delay device, and a light input from the optical input terminal. Has a first optical modulator (3) for intensity-modulating according to the electric pulse signal of the variable delay device and outputting it to an output terminal of light, and an input terminal and an output terminal of the optical pulse, and the electric pulse signal (A1) is A second optical modulator for receiving the electric pulse signal (A) fixedly delayed by the line, intensity-modulating the light input from the light input terminal according to the electric pulse signal (A), and outputting the light to the light output terminal. (4) and the output of this second optical modulator Amplified optical amplifier (5)
An optical bandpass filter (6) that transmits only a desired wavelength of the output of the optical amplifier and cuts other wavelengths, and an optical input terminal and two optical output terminals (C) and (D) A coupler (7) and a variable optical delay device (8) for mode-locking are provided, and the first and second optical modulators, optical amplifiers, optical bandpass filters, and optical output terminals (D) are provided. An optical pulse generator characterized in that an optical coupler to be used and a variable optical delay device are connected in a ring shape, and an optical pulse output is obtained from one optical output terminal (C) of the optical coupler.