JPH02143728A - Optical pulse pattern generator - Google Patents

Abstract

PURPOSE:To stably obtain an optical pulse pattern in an ultrahigh frequency amounting to several tens of GHz by collecting optical short pulses from plural optical pulse generators into one output while deviating the phase. CONSTITUTION:Signals with deviated phases are outputted from plural synthesizer oscillators 2(1)-2(n) and optical short pulses are outputted from optical pulse generators 3(1)-3(n) based on the signal. Since the phases of the optical short pulses are deviated, an optical mixer 4 collects them into one output, then an optical pulse pattern in an ultrahigh frequency whose phase deviation corresponds to one period is generated repetitively. Thus, the optical pulse train in ultrahigh speed reaching the GHz - THz is stably generated.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an optical pulse pattern generator that is an experimental signal source for optical digital communication systems, and in particular to an optical pulse pattern generator for large-capacity communication systems. This invention relates to a high-speed optical pulse pattern generator.

[Conventional technology]

Conventional optical pulse pattern generators include those that apply a high-speed signal to a laser diode (LD) to generate a high-speed optical pulse pattern, and those that use a mode-locked pulse laser to generate ultrashort pulses of light over multiple optical paths. There was one that generated an ultra-high-speed optical pulse train by branching into two and changing the optical path length of each.

[Problem to be solved by the invention]

However, the former device only applies a high-speed signal to one laser diode, and considering the ability of the driving amplifier to realize this, the frequency of the output optical pulse is limited to about 5 GHz at most. Ta. On the other hand, the speed of optical communication systems has progressed considerably in recent years, and experiments have already shown that 10
Products that exceed GHz have been announced. Therefore, experiments and evaluations of such ultrahigh-speed optical communication systems cannot be performed using conventional optical pulse pattern generators using laser diodes.

Furthermore, since the latter device uses a mode-locked pulse laser, it can generate ultra-high-speed optical pulse trains ranging from GHz to THz, but mode-locked pulse lasers are expensive and difficult to handle. Due to problems such as being small, large, and unstable, it is only used by a small number of researchers.

An object of the present invention is to solve these problems.

[Means to solve the problem]

In order to solve the above problems, the optical pulse pattern generation device of the present invention includes a reference signal generation means for generating a reference signal;
A plurality of synthesizer oscillators that output a signal that is phase-synchronized with a reference signal while controlling the phase based on an external signal, and a plurality of synthesizer oscillators that are provided for each synthesizer oscillator and output short optical pulses based on the output signal of the corresponding synthesizer oscillator. The optical pulse generator is equipped with an optical pulse generator, and an optical mixer that combines the optical short pulses output from each optical pulse generator into one output.

[Effect]

Each of the plurality of synthesizer oscillators outputs signals that are out of phase with each other, and based on these signals, the optical pulse generator outputs short optical pulses.

Since the phases of these short optical pulses are shifted from each other, when they are combined into one output by an optical mixer, an ultra-high frequency optical pulse pattern whose phase shift corresponds to one cycle is repeatedly generated.

〔Example〕

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the present invention. The reference signal generator 1 is a means for generating a 5 MHz reference signal. Synthesizer oscillator 2(1)~2
(n) is means for taking in the basic signal from the reference signal generator 1 and outputting a 100 MHz signal using this reference signal, and is externally connected to terminals 4(1) to 4(n). The phase of the output signal can be controlled by the applied voltage.

The optical Hals generators 3(1) to 3(n) are means for outputting optical pulses in response to electrical signals from the synthesizer oscillators 2(1) to 2(n), and are connected to terminals 5(1) to 5(n). The output optical pulse signal can be turned on and off by the direct current applied to n). The multi-channel optical mixer 4 is a means for combining the optical pulse signals input to the terminals 6(1) to 6(n) into one optical pulse output, and the output from this is the final output of this embodiment. .

FIG. 2 is a block diagram showing the internal configuration of the synthesizer oscillator 2(1). The phase comparator 10 compares a 5 MHz reference signal from the reference signal generator 1 with a 5 MHz signal from a frequency divider 13, which will be described later, and outputs a voltage according to the phase shift between the two signals. . That is, if the phase of the signal from the frequency divider 13 matches the phase of the reference signal, a predetermined reference voltage is output, and the phase of the signal from the frequency divider 13 leads the phase of the reference signal. If it is, the voltage will be lower than the reference voltage depending on the degree of advance; conversely, if it is delayed, it will be higher than the reference voltage depending on the degree of delay.

The adder 11 is a means for adding two input voltages, and adds the output voltage of the phase comparator 10 and the output voltage of an externally provided phase control signal generator 15. The voltage controlled oscillator (VCO) 12 is an oscillator whose oscillation frequency can be controlled by an input voltage, and its basic oscillation frequency is 25 MHz.

This VCO 12 performs 25 MHz oscillation when the reference voltage of the phase comparator 10 is applied. The frequency divider 13 has a frequency division ratio of 1/5, and divides the signal frequency from the VCO 12 into 1/5 and outputs the divided signal frequency.

The above phase comparator 10, adder 11, VCO 12, and frequency divider 13 provide a phase-controllable phase synchronization circuit (P
LL, phase-locked loop) is formed. That is, the output of this PLL is, in principle, phase synchronized with the reference signal given from the reference signal generator 1, and its phase is shifted according to the voltage value given from the phase control signal generator 15. However, in this PLL, the input reference signal is 5 MHz, while the output signal is 25 MHz, so five cycles of the output signal correspond to one cycle of the reference signal. The frequency multiplier 14 is a means for multiplying the frequency of an input signal by four times, and receives a 25 MHz signal and outputs a 100 MHz frequency signal. From the above, this synthesizer oscillator 2 (1) uses the phase of the 5 MHz reference signal from the reference signal generator 1 as a reference, and the terminal 4 (
1 whose phase is appropriately controlled according to the voltage applied to 1)
A frequency signal of 00 MHz can be output.

Note that the configurations and operations of the synthesizer oscillators 2(2) to 2(n) are also the same as those of the synthesizer oscillator 2(1) described above, so a description thereof will be omitted.

FIG. 3 is a block diagram showing the internal configuration of the optical pulse generator 3(1). The amplifier 20 is a synthesizer oscillator 2
(1) is a means for inputting the signal and amplifying the input signal to sufficient power to drive the laser diode 23. The comb generator 21 is a means for changing the duty of the input signal to shorten the pulse, and converts a 100 MHz sine wave from the synthesizer oscillator 2 (1) into a pulse train having the same frequency of 100 MHz and a pulse width of 150 ps. The bias tee 22 is a means for superimposing the control direct current from the bias current control section 24 and the high frequency current from the comradiator 21 with good matching, and drives the laser diode 23 with its output. When the bias current from the bias current control section 24 is in the forward direction of the laser diode 23, the laser diode 23 outputs a short optical pulse based on the signal output by the comb generator 21, and when it is in the reverse direction, the laser diode 23 outputs a short optical pulse based on the signal output from the comb generator 21. Regardless of the output signal of the comb generator 21, the laser diode 23 is turned off. As mentioned above, the laser diode 23 has 1
A drive signal with a pulse width of 50 ps will be given, but if adjustments are made so that only the first pulse of relaxation oscillation of the laser diode 23 is generated during this 150 ps, the pulse width will be around 40 ps. A single pulse can be generated. Note that the bias current control section 2
Whether the bias current outputted by 4 is in the forward direction or in the reverse direction is controlled by a control signal externally applied to the terminal 25. Since the optical pulse generator 3 (1) is configured as described above, the synthesizer oscillator 2
A short optical pulse can be output based on the electrical signal from (1), and its operation can be controlled on and off by an external control signal. In this example, the bias tee 22 is used for on/off control, but
The operation of the amplifier 20 can also be controlled to turn it on and off. The above is a description of the optical pulse generator 3(1), but the configuration and operation of the optical pulse generators 3(2) to 3(n) are also the same as the optical pulse generator 3(1), so The explanation will be omitted.

Next, the overall operation will be explained using the waveform diagram shown in FIG. Here, for the sake of simplicity, it will be explained as n-3.

By applying phase control signals with different voltage values to the external input terminals 4(1) to 4(3) of the synthesizer oscillators 2(1) to 2(3), 100MHz signals with mutually different phases can be generated. Synthesizer oscillator 2 (1)
~2(3) are output respectively. The resolution of the phase difference at this time is 500 ns of one period (200 ns) of the reference signal.
1/0, that is, about 40 ps can be obtained. Here, for example, the phase control signal for each of synthesizer oscillators 2(1) to 2(3) is adjusted to increase the phase of the output signal by 1.
Assume that the distance is shifted by 00 ps. Synthesizer oscillator 2 (
The output signal of 1) is input to the optical pulse generator 3 (1),
A short optical pulse with a pulse width of 40 ps as shown in FIG. 4(A) is output. Similarly, the output signals of synthesizer oscillators 2 (2) and 2 (3) are respectively output from optical pulse generator 3 (
2) and 3(3), and the same figure (B) and (C
), short optical pulses (with a pulse width of 40 ps) delayed by 100 ps and 200 ps with respect to the output of the optical pulse generator 33 (1) are output. These optical short pulses are combined into one output by the multi-channel optical mixer 4, and the pulse interval is 100p as shown in the same figure (D).
s or a pulse train (3 pulses) with a frequency of 10 GHz
is output. Here, synthesizer oscillator 2
Although the phase difference between the output signals of (1) to 2(n) is expressed as Loops, if it is set to 5 ps, for example, the frequency can be set to 20 GHz.

Furthermore, by increasing the value of n, the number of pulses in the pulse train can be increased.

〔Effect of the invention〕

As explained above, according to the optical pulse pattern generator of the present invention, by shifting the phases of optical short pulses from a plurality of optical pulse generators and combining them into a single output, ultra-high frequency waves of several tens of GHz can be generated. A light pulse pattern can be stably obtained. Furthermore, the device according to the present invention can be constructed at a lower cost than conventional devices. Therefore, by using the present invention for evaluation and testing of various optical transmission and light receiving devices for optical communications, it will be extremely useful for future research on ultrahigh-speed optical communications.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing the internal configuration of the synthesizer oscillator 2 (1), and FIG. 3 is the internal structure of the optical pulse generator 3 (1). A block diagram showing the configuration and FIG. 4 are waveform diagrams showing the operation of the embodiment. DESCRIPTION OF SYMBOLS 1... Reference signal generator, 2(1)-2(n)... Synthesizer oscillator, 3(1)-2(n)... Optical pulse generator, 4... Multi-channel optical mixer . Patent applicant Hamamatsu Photonics Co., Ltd. Representative Patent Attorney
Yoshikima Shio for Hase
1) Tatsuya diagram

Claims (1)

[Scope of Claims] A reference signal generating means for generating a reference signal; a plurality of synthesizer oscillators for outputting a signal whose phase is synchronized with the reference signal by controlling the phase based on an external signal; and a plurality of synthesizer oscillators provided for each synthesizer oscillator. , a plurality of optical pulse generators that output short optical pulses based on output signals of corresponding synthesizer oscillators, and an optical mixer that combines the optical short pulses output from each optical pulse generator into one output. Pulse pattern generator.