JPH07245582A - Optical pulse generator - Google Patents

Abstract

PURPOSE:To generate an optical signal with a pulse pattern whose frequency exceeds an upper limit frequency of the operating of an electronic circuit by delaying one of optical signals outputted from two pulse pattern generators and subjecting the delayed signal to waveform synthesis with the other optical signal. CONSTITUTION:Optical pulse pattern generators 11, 12 outputting optical pulses at a random time interval have a pseudo random pulse generating means comprising an electronic circuit and an electric signal (pseudo random pattern) generated by the pseudo random pulse generating means is converted into an optical signal by a proper modulation means and outputted. Then an optical delay device 22 delays the optical signal outputted from the optical pulse pattern generator 12 by 1/2 period, that is, T/2 (T is a basic clock period). Furthermore, an optical waveform synthesizer 3 multiplexes an optical signal outputted from the optical pulse pattern generator 11 and the optical signal outputted from the optical delay device 22 and the optical signal having a frequency twice the frequency of the optical pulse pattern generators 11, 12 is outputted.

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 used for evaluation of transmission characteristics in the field of ultrahigh-speed optical communication and various measurements of receivers.

[0002]

2. Description of the Related Art Generally, as a method for evaluating transmission characteristics in an optical communication system and measuring a receiving device,
A method is known in which an optical pulse is incident on an object to be measured and an output signal generated as a result is measured. An optical pulse generator that generates such an optical pulse generates an electric pulse by a pulse generating means, converts the electric pulse into an optical pulse pattern, and outputs the optical pulse pattern.

Examples of the pulse generating means include a "random pulse pattern generating circuit" disclosed in Japanese Patent Laid-Open No. 01-073813 and a "pulse generator" disclosed in Japanese Patent Laid-Open No. 01-278115. These constitute a pseudo random pattern generation means by an electronic circuit, and terminate at a nominal resistance of 50Ω by a buffer amplifier, an open collector, an open drain, etc. at an output stage to output an electric signal. In an optical pulse generator using such a pulse generating means, in order to generate an optical pulse pattern, a signal corresponding to the above electric signal is used to directly modulate a semiconductor laser by an electro-optical conversion or an optical driving method. It is necessary to perform modulation using a modulator at ultra-high speed.

[0004]

By the way, in the next-generation ultrahigh-speed optical communication system, it is expected that transmission at a speed of 100 Gb / s or more will be possible in the future. Then, it cannot be used as an optical pulse generating means for evaluating transmission characteristics. that is,
The operation limit frequencies (theoretical predicted values) of semiconductor electronic elements, which are constituent elements of electronic circuits constituting the optical pulse generator, or functional devices such as flip-flops are about 100 Gb / s and about 20 Gb / s, respectively. ,
It is considered impossible to construct various logic electronic circuits that operate at higher speeds. This is not possible even when a wideband optical modulator that can operate up to a higher frequency than the response of the electronic circuit is used because it is regulated by the electronic circuit.

[0005]

The invention according to claim 1 is
Two pulse pattern generators having pulse generating means for outputting an electric pulse signal generated at a constant repetition frequency, converting the output of the pulse generating means into an optical signal and outputting the optical signal, and the two pulse patterns An optical delay device that delays and outputs one of the optical signals output from the generator, the other of the optical signals output from the two pulse pattern generators, and an output from the optical delay device. And an optical multiplexer that multiplexes and outputs the generated optical signal.

According to a second aspect of the present invention, there is provided a pulse generating means for outputting an electric pulse signal generated at a constant repetition frequency, and a plurality of pulse patterns for converting the output of the pulse generating means into an optical signal for output. A generator, an optical delay device that delays the optical signals output from the plurality of pulse pattern generators so that the respective generation timings are shifted, and outputs the combined optical signal output from the optical delay device. It is characterized by comprising an optical multiplexer for wave output.

According to a third aspect of the present invention, a plurality of pulse generating means for outputting an electric pulse signal generated at a constant repetition frequency and respective outputs of the plurality of pulse generating means are shifted in their respective generation timings. A delay device that delays and outputs, an electro-optical converter that converts each output of the delay device into an optical signal, and an optical multiplexer that multiplexes and outputs each optical signal output from the electro-optical converter It is characterized by having.

The invention according to claim 4 is the invention according to claim 1 or 2.
The invention described above is characterized in that the optical multiplexer is constituted by forming an optical waveguide on a substrate.

[0009]

According to the invention described in claim 1, one of the optical signals output from the two pulse pattern generators is delayed by the optical delay device, and is multiplexed with the other of the optical signals in the optical multiplexer. It As a result, the repetition frequency of the optical signal output from the optical multiplexer is higher than the repetition frequency of each pulse pattern generator. According to the second aspect of the present invention, the optical signals output from the plurality of pulse pattern generators are delayed by the optical delay device so that their respective generation timings are deviated, and then combined in the optical multiplexer. As a result, the repetition frequency of the optical signal output from the optical multiplexer increases according to the amount of delay given by the optical delay device and the number of pulse pattern generators. Further, according to the invention of claim 3, the respective outputs of the plurality of pulse generating means are delayed by the delay device so that the respective generation timings thereof are deviated, and after being converted into an optical signal in the electro-optical converter, It is multiplexed by an optical multiplexer. Further, according to the invention described in claim 4, the optical delay device can be constituted by the optical waveguide on the substrate.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. §1. First Embodiment FIG. 1 is a block diagram showing a configuration of an optical pulse generator according to a first embodiment of the present invention, and FIG. 2 is a diagram showing a time axis waveform of each output in the optical pulse generator. Figure 1
, 11 and 12 are optical pulse pattern generators which output optical pulses at random time intervals, and which have pseudo random pulse generating means constituted by an electronic circuit, and which generate electric pulses by the pseudo random pulse generating means. A signal (pseudo random pattern) is converted into an optical signal by an appropriate modulating means and then output. Also, these optical pulse pattern generators 11 and 1
2 are synchronized with each other at a repetition frequency of 10 GHz. The optical pulse pattern generators 11 and 12
Is similar to the optical pulse pattern generating means according to the conventional technique, and the functions such as setting the basic clock period (T) and the mark ratio (M) are based on the conventional method.

An optical delay unit 22 delays the optical signal output from the optical pulse pattern generator 12 by 1/2 cycle, that is, T / 2. Here, the time td of T / 2 is 5
It is set to 0 psec. An optical multiplexer 3 multiplexes the optical signal output from the optical pulse pattern generator 11 and the optical signal output from the optical delay device 22.

In such a configuration, the optical pulse pattern generator 11 outputs an optical signal having the pulse pattern shown in FIG. 2 (a), for example. The optical pulse pattern generator 12 also outputs an optical signal, and this optical signal is transmitted to the optical delay device 2
At 2, the signal is delayed by the time td and is output as an optical signal having a pulse pattern shown in FIG. 2B, for example. These optical signals are multiplexed in the optical multiplexer 3. As a result,
As shown in FIG. 2C, the optical multiplexer 3 outputs an optical signal having a repetition frequency of 20 GHz which is twice the repetition frequency of the optical pulse pattern generators 11 and 12.

In the case of the present embodiment, if the pulse widths of the optical signal from the optical pulse pattern generator 11 and the optical signal from the optical delay device 22 are wide, the two signals may be combined and the waveforms may overlap. There is. Therefore, the pulse widths of both signals are shaped as necessary so that such a problem does not occur.

As described above, according to this embodiment, the operating upper limit frequency of the electronic device and the electronic circuit is about 20 GHz.
It is possible to generate a light pulse pattern that exceeds

§2. Second Embodiment FIG. 3 is a block diagram showing a configuration of an optical pulse generator according to a second embodiment of the present invention, and FIG. 4 is a diagram showing a time axis waveform of each output in the optical pulse generator. Figure 3
In, the optical signal output from the optical pulse pattern generator 12 is delayed by the optical delay device 22 by T / 3. An optical pulse pattern generator 13 is newly provided, and the optical signal output from the optical pulse pattern generator 13 is delayed by 2T / 3 by the optical delay unit 23.

That is, assuming that the optical pulse pattern generator 11 outputs an optical signal having a pulse pattern as shown in FIG. 4A, the optical delay device 22 outputs the optical signal shown in FIG.
An optical signal having a pulse pattern delayed by T / 3 is output as shown in FIG. 4, and an optical signal having a pulse pattern delayed by 2T / 3 is output from the optical delay unit 23 as shown in FIG. 4C. . These are input to the optical multiplexer 3 and are respectively multiplexed, so that the optical multiplexer 3 outputs an optical signal having an optical pulse pattern as shown in FIG. 4D. As a result, the optical multiplexer 3 outputs an optical signal in a pulse pattern with a clock cycle of T / 3.

As described above, according to the optical pulse generator of the second embodiment, it is possible to obtain an optical signal whose clock rate is increased to three times the basic clock period. Also,
The clock rate can be further increased by combining four or more optical pulse pattern generators and adjusting the delay time of the optical delay device accordingly.

As described above, in the first and second embodiments, the output of the pulse generating means is converted into an optical signal by the optical pulse pattern generator constructed in the prior art, and the optical signal is output. I'm trying to delay it. However, the electric signal output from the pulse generating means may be delayed as it is and converted into light by an electro-optical converter such as a semiconductor laser before being combined.

In any case, since the basic clock cycle proposed here is about 100 psec (10 GHz), the delay device is a coaxial code or an optical fiber code (each having a delay time of about 5 nsec / m per unit length).
Can be obtained). Alternatively, a method of allowing parallel light to pass through the space is also possible, in which case about 3 nsec / m can be obtained.

As the optical multiplexer, an optical coupler, an optical coupler, an optical mixer, an optical star coupler or the like can be used. The upper limit of the operation of the optical multiplexer is estimated from the operating speed limit of normal photons, and a frequency of 1 T (tera) Hz or higher can be expected.

FIG. 5 shows an example in which the optical pulse generator according to the first embodiment is manufactured as an optical waveguide structure using a substrate such as LiNbO3 or quartz. According to this configuration, since the optical delay device 22 having an optical waveguide length of about 1 cm can be built at the same time as other optical circuit parts in order to give a time delay amount of about 50 psec, cost reduction and manufacturing processing can be performed. Shortening and stabilizing the process can be realized.

[0022]

As described above, according to the present invention, since the optical multiplexer can operate up to the operation upper limit frequency, an optical signal having a pulse pattern exceeding the operation upper limit frequency of the electronic element and the electronic circuit is generated. Can be made. Therefore, it becomes possible to realize an optical pulse generating means for evaluating transmission characteristics in the ultrahigh-speed optical communication system.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an optical pulse generator according to a first embodiment of the present invention.

FIG. 2 is a waveform chart of each output in the embodiment.

FIG. 3 is a block diagram showing a configuration of an optical pulse generator according to a second embodiment of the present invention.

FIG. 4 is a waveform diagram of each output in the example.

FIG. 5 is a perspective view showing an optical multiplexer 3 according to the first embodiment manufactured on a substrate with an optical waveguide structure.

[Explanation of symbols]

 3 Optical multiplexer 11, 12, 13 Optical pulse pattern generator 22 Optical delay device 23 Optical delay device

Claims (4)

[Claims] 1. A two pulse pattern generator having pulse generating means for outputting an electric pulse signal generated at a constant repetition frequency, and converting the output of said pulse generating means into an optical signal for output. An optical delay device that delays and outputs one of the optical signals output from the two pulse pattern generators; the other of the optical signals output from the two pulse pattern generators; An optical pulse generator comprising: an optical multiplexer that multiplexes and outputs an optical signal output from an optical delay device. 2. A plurality of pulse pattern generators having pulse generating means for outputting an electric pulse signal generated at a constant repetition frequency, converting the output of the pulse generating means into an optical signal for output, Of the optical signal output from the pulse pattern generator, and an optical delay unit that delays and outputs the optical signals so that the respective generation timings are shifted, and an optical combiner that multiplexes and outputs the optical signals output from the optical delay unit. An optical pulse generation device comprising: a wave device. 3. A plurality of pulse generating means for outputting an electric pulse signal generated at a constant repetition frequency, and a delay for delaying and outputting each output of the plurality of pulse generating means so that their respective generation timings are deviated. And an electro-optical converter that converts each output of the delay device into an optical signal, and an optical multiplexer that multiplexes and outputs each optical signal output from the electro-optical converter. Optical pulse generator. 4. The optical multiplexer is formed by forming an optical waveguide on a substrate.
Alternatively, the optical pulse generator described in 2.