Optical sampling pulse generation apparatus and optical sampling pulse generation method

Abstract

An optical sampling pulse generation device (10) comprises: a light source (20) that repeatedly emits a broadband optical pulse (30) at a first frequency; a disperser (22) that outputs time-varying spectrum light beams (32a to 32d) optical time-stretched by wavelength dispersing the broadband optical pulse (30) while temporally superimposing n (n≥2) time-varying spectrum light beams (32a to 32d); a modulator (26) that outputs optical pulses (36a to 36e) having n wavelength components by intensity-modulating lines of the time-varying spectral light beams (32a to 32d) by a sampling pulse (34) repeatedly outputted at a frequency that is m (≥1) times the first frequency from a signal generator (24); and a dispersion compensator (28) that generates an optical sampling pulse train (38) in which the first frequency is multiplied by n×m by performing dispersion compensation (optical time compression) on the optical pulses (36a to 36e).

Description

Technical Field

[0001] The present disclosure relates to an optical sampling pulse generation device and an optical sampling pulse generation method, and particularly relates to a technique for generating an interleaved optical sampling pulse train by wavelength multiplexing using a low-frequency - high-frequency conversion technique.

Background Art

[0002] For obtaining and waveform measuring terahertz-level signals that cannot be measured by a broadband oscilloscope, higher speed analog / digital conversion is required. Conventionally, as a technique for higher speed analog / digital conversion, a technique using an optical sampling pulse train has been proposed (see Non-Patent Documents 1 and 2, etc.).

[0003] According to the techniques of Non-Patent Documents 1 and 2, the utilization of an optical pulse train having low time jitter characteristics from an optical pulse light source is central, and an interleaving function is imparted using wavelength multiplexing technology. For shaping an optical pulse waveform suitable for sampling (e.g., a Nyquist pulse) and wavelength multiplexing for the interleaving function, spectral filtering of optical pulses by wavelength selective switches (Wavelength Selective Switches; WSS) is mainly used. That is, by using wavelength selective switches, an interleaved optical sampling pulse train by wavelength multiplexing is generated.

[0004] Note that an interleaved optical sampling pulse train by wavelength multiplexing is a repetition of an arrangement of optical pulses in which the central wavelength of each optical pulse increases or decreases with time.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

[0006] However, a challenge with the technologies described in Non-Patent Documents 1 and 2 is that the waveform accuracy of the sampled light and the variability of wavelength multiplicity are limited by the performance of the wavelength selective switch. Furthermore, the current use of extremely expensive wavelength selective switches (e.g., costing several million yen) is also a problem.

[0007] Therefore, the object of this disclosure is to provide an optical sampling pulse generation apparatus and an optical sampling pulse generation method that can generate high-frequency, high-precision optical sampling pulse trains interleaved by wavelength division multiplexing without using expensive wavelength selective switches. [Means for solving the problem]

[0008] To achieve the above objective, an optical sampling pulse generation apparatus according to one embodiment of the present disclosure comprises: a light source that repeatedly emits broadband optical pulses at a first frequency; a disperser that outputs a sequence of time-varying spectral light in which n (n≧2) time-varying spectral light overlaps in time by wavelength-dispersing the broadband optical pulses emitted from the light source to generate time-varying spectral light (chirped light) in which the wavelength increases or decreases over time for a period longer than the period corresponding to the first frequency; a signal generator that repeatedly outputs sampling pulses at a second frequency which is m (≧1) times the first frequency; a modulator that outputs an optical pulse having n wavelength components included in the n time-varying spectral light at the time the sampling pulse was input, by intensity-modulating the sequence of time-varying spectral light output from the disperser with a sampling pulse output from the signal generator; and a dispersion compensator that generates an optical sampling pulse sequence in which the sequence of optical pulses having each of the n × m wavelength components is repeated at the first frequency by dispersion compensation on the optical pulse output from the modulator.

[0009] To achieve the above objective, a method for generating optical sampling pulses according to one embodiment of the present disclosure includes: a dispersion step of generating a sequence of time-varying spectral light in which n (n≧2) time-varying spectral light overlaps in time by wavelength dispersion of broadband optical pulses repeatedly emitted from a light source at a first frequency, thereby generating time-varying spectral light (chirped light) in which the wavelength increases or decreases over time for a period longer than the period corresponding to the first frequency; a modulation step of outputting an optical pulse for each sampling pulse having n wavelength components included in the n time-varying spectral light at the time the sampling pulse was input by intensity modulation of the sequence of time-varying spectral light output in the dispersion step with a sampling pulse repeatedly output from a signal generator at a second frequency which is m (≧1) times the first frequency; and a dispersion compensation step of generating an optical sampling pulse sequence in which the sequence of optical pulses having each of the n × m wavelength components is repeated at the first frequency by dispersion compensation of the optical pulses output in the modulation step. [Effects of the Invention]

[0010] This disclosure provides an optical sampling pulse generation apparatus and an optical sampling pulse generation method that can generate high-frequency, high-precision optical sampling pulse trains interleaved by wavelength division multiplexing without using expensive wavelength selective switches. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a block diagram illustrating a conventional optical sampling pulse generation method. [Figure 2] Figure 2 is a block diagram showing the configuration of an optical sampling pulse generation device according to an embodiment. [Figure 3] Figure 3 is a diagram illustrating the operation of the optical sampling pulse generation device shown in Figure 2. [Figure 4] Figure 4 is a block diagram showing the configuration of the optical sampling pulse generation device in an experimental example. [Figure 5A] Figure 5A shows the measurement results obtained using the optical sampling pulse generator in the experimental example shown in Figure 4. [Figure 5B] Figure 5B shows the measurement results before and after the array waveguide grating (AWG) from the optical sampling pulse generation device related to the experimental example shown in Figure 4. [Figure 6] Figure 6 is a flowchart showing the procedure for the optical sampling pulse generation method according to the embodiment. [Figure 7] Figure 7 illustrates a method for generating optical sampling pulses according to a first modified example of the embodiment. [Figure 8] Figure 8 illustrates a method for generating optical sampling pulses according to a second modified example of the embodiment. [Modes for carrying out the invention]

[0012] Before describing embodiments of this disclosure, the prior art relating to Non-Patent Documents 1 and 2 will be described.

[0013] Figure 1 is a block diagram illustrating a conventional optical sampling pulse generation method. In the conventional optical sampling pulse generation method, an interleaved optical sampling pulse train is generated by wavelength division multiplexing using a wavelength selection switch. More specifically, in the conventional optical sampling pulse generation method, a repeating broadband optical pulse with period T emitted from a mode-locked laser (MLL) light source is separated into wavelength-specific paths (waveguides) by a wavelength demultiplexer (DEMUX). After the separated optical pulses pass through each path at different speeds for each wavelength, they are multiplexed into a single path by a wavelength multiplexer (MUX) and output, thereby generating an interleaved optical sampling pulse train arranged at time intervals of T / N by wavelength division multiplexing. The density of each optical pulse in the diagram in Figure 1 (i.e., dot density) corresponds to the wavelength.

[0014] However, in the conventional method for generating an optical sampling pulse train using such a wavelength selection switch, there are many limitations regarding the waveform accuracy of the sampling light and the variability of wavelength multiplexing, lacking flexibility. There is also a problem that the wavelength selection switch is expensive.

[0015] Therefore, the present disclosure provides an optical sampling pulse generation device and an optical sampling pulse generation method that can generate a high-frequency and high-precision optical sampling pulse train interleaved by wavelength multiplexing without using an expensive wavelength selection switch.

[0016] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that each of the embodiments described below shows a specific example of the present disclosure. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components, steps, order of steps, etc. shown in the following embodiments are examples and are not intended to limit the present disclosure. Also, each drawing is not necessarily drawn precisely. In each drawing, substantially the same configuration is denoted by the same reference numeral, and overlapping descriptions are omitted or simplified. Also, the "connection" of each component means an optical or electrical connection, and includes not only the case where two components are directly connected, but also the case where two components are indirectly connected with other components inserted between them.

[0017] FIG. 2 is a block diagram showing the configuration of an optical sampling pulse generation device 10 according to an embodiment. The optical sampling pulse generation device 10 is a device that can generate a high-frequency and high-precision optical sampling pulse train 38 interleaved by wavelength multiplexing without using an expensive wavelength selection switch, and includes a light source 20, a disperser 22, a signal generator 24, a modulator 26, and a dispersion compensator 28. The light source 20, the disperser 22, the modulator 26, and the dispersion compensator 28 are connected by an optical fiber 12, and the signal generator 24 and the modulator 26 are connected by a wire cable 14.

[0018] The light source 20 is a light source that repeatedly emits broadband optical pulses 30 at a first frequency, and is, for example, a mode-locked fiber laser (MLFL) or the like.

[0019] The disperser 22 is a dispersion device that generates time-varying spectral lights 32a to 32c (i.e., chirped lights) whose wavelengths increase or decrease with time over a time longer than the period corresponding to the first frequency by wavelength-dispersing (i.e., D1 conversion) the broadband optical pulse 30 emitted from the light source 20, and outputs a series of time-varying spectral lights 32a to 32c in which n (n ≥ 2) time-varying spectral lights overlap temporally. The disperser 22 is, for example, a chirped fiber Bragg grating (CFBG), an arrayed waveguide grating (AWG), or the like.

[0020] The signal generator 24 is a device that repeatedly outputs a sampling pulse 34 at a second frequency that is m (≥ 1) times the first frequency, and is, for example, an arbitrary waveform generator (AWG) or the like. Note that the second frequency may be the same as the first frequency, which is the repetition frequency of the broadband optical pulse 30 (i.e., m = 1), or may be a higher frequency (i.e., m > 1). Also, the sampling pulse 34 is, for example, a Nyquist pulse having a sinc function waveform. By using a Nyquist pulse, there is an advantage that the sampling pulse 34 can be temporally approximated (i.e., made higher frequency). However, the waveform of the sampling pulse 34 is not limited to the sinc function, and may be a Gaussian function, a triangular wave, or the like.

[0021] The modulator 26 modulates (i.e., samples) the sequence of time-varying spectral light 32a to 32c output from the disperser 22 with a sampling pulse 34 output from the signal generator 24, thereby outputting an optical pulse for each sampling pulse 34 that contains n wavelength components included in the n time-varying spectral light 32a to 32c at the time the sampling pulse 34 was input. The modulator 26 is, for example, an electro-optical modulator (EOM) such as a Mach-Zehnder modulator (MZM), an EA (Electro-Absorption) modulator, or an ER (Electro-Refractive) modulator.

[0022] The dispersion compensator 28 is an inverse dispersion device that generates an optical sampling pulse train 38 in which a sequence of optical pulses, each having n × m wavelength components, is repeated at a first frequency (i.e., the first frequency has been multiplied by n × m) by performing dispersion compensation (i.e., optical time compression; -D2 conversion) on the optical pulse output from the modulator 26, and outputs this train to an optical measurement system such as an analog / digital converter. The dispersion compensator 28 is, for example, a dispersion compensation fiber (DCF) or a chirp fiber Bragg grating (CFBG).

[0023] Figure 3 illustrates the operation of the optical sampling pulse generator 10 shown in Figure 2. More specifically, Figure 3(a) shows a sequence of broadband optical pulses 30 repeatedly emitted from the light source 20 at a first frequency (here, 100 MHz). Figure 3(b) shows a sequence of time-varying spectral light 32a to 32d, repeatedly output from the disperser 22, in which n (here, 2) time-varying spectral light overlaps in time. Figure 3(c) shows a sequence of sampling pulses 34 repeatedly output from the signal generator 24 at a second frequency (here, 100 MHz, i.e., m=1). Figure 3(d) shows a sequence of optical pulses 36a to 36e, each having n wavelength components (here, 1 initially, and 2 thereafter), output from the modulator 26. Figure 3(e) shows a sequence of wavelength-division multiplexed interleaved optical sampling pulses 38 repeatedly output from the dispersion compensator 28 at a higher frequency (here, 200 MHz).

[0024] As shown in Figure 3(b), a series of broadband optical pulses 30 repeatedly emitted from the light source 20 at a first frequency (here, 100 MHz) (Figure 3(a)) is optically stretched by the disperser 22, generating a series of time-varying spectral light 32a to 32d in which n (here, 2) time-varying spectral light overlaps over time, resulting in time-varying spectral light where the wavelength increases or decreases over time (here, increases) for a longer period (i.e., 10 ns) than the period corresponding to the first frequency (here, 100 MHz).

[0025] Furthermore, as shown in Figure 3(d), the sequence of time-varying spectral light 32a to 32d output from the disperser 22 (Figure 3(b)) is sampled (i.e., intensity-modulated) by the modulator 26 (Figure 3(c)), extracting only n wavelength components (here, one initially, and two thereafter), thereby generating a sequence of optical pulses 36a to 36e with n wavelength components.

[0026] Furthermore, as shown in Figure 3(e), the sequence of optical pulses 36a to 36e output from the modulator 26 (Figure 3(d)) undergoes optical time compression by the dispersion compensator 28, which converts it back from time-varying spectral light (Figure 3(b)) to broadband optical pulses 30 (Figure 3(a)). This converts the sequence into an optical pulse train in which optical pulses containing each of the n wavelength components (here, one initially, and two thereafter) contained in each optical pulse are arranged at equal time intervals (here, 5ns intervals) (i.e., an optical pulse train in which n(2) × m(1) optical pulse trains are repeated at the first frequency (100MHz)). As a result, an interleaved high-frequency (here, 200MHz) optical sampling pulse train 38 is generated by wavelength division multiplexing.

[0027] Thus, the optical sampling pulse generation device 10 according to this embodiment can generate high-frequency, high-precision optical sampling pulse trains with interleaved frequency by wavelength division multiplexing, using a simple low-frequency-to-high-frequency conversion technique (i.e., a technique for multiplying the first frequency by n × m), rather than using an expensive and restrictive wavelength selection switch as in the conventional technology.

[0028] Figure 4 is a block diagram showing the configuration of the optical sampling pulse generator 10a in an experimental example. The optical sampling pulse generator 10a has a configuration in which a measuring instrument for observing its output is connected to the optical sampling pulse generator 10 according to the embodiment shown in Figure 2. Specifically, it consists of a mode-locked fiber laser (MLFL) 40, a wavelength-selective switch (WSS) 41, a chirp fiber Bragg grating (CFBG) 42, a polarization controller 43, an arbitrary waveform generator (AWG) 44, a Mach tender modulator (MZM) 46, an amplifier 47, a highly dispersion-compensated fiber (DCF) 48, an optical distributor 49, an optical spectrum analyzer (OSA) 50, an array waveguide diffraction grating (AWG) 51, and an oscilloscope (OSC) 52.

[0029] The mode-locked fiber laser (MLFL) 40 and wavelength-selective switch (WSS) 41 are used to shape the broadband optical pulse emitted from the mode-locked fiber laser (MLFL) 40 at a repetition frequency of 30.025 MHz (i.e., the first frequency) into a Gaussian waveform using the wavelength-selective switch (WSS) 41, and correspond to the light source 20 in Figure 2. The chirp fiber Bragg grating (CFBG) 42 corresponds to the disperser 22 in Figure 2, and optically extends the input broadband optical pulse at a rate of +1981 ps / nm, resulting in the generation of time-varying spectral light that is time-extended to approximately 66 ns (= (1000 / 30.025) × 1.981) (i.e., it outputs n (2) time-varying spectral light superimposed).

[0030] The polarization controller 43 controls the polarization state of the input time-varying spectral light so that it can be appropriately intensity-modulated by the next-stage Mach Tender Modulator (MZM) 46. The arbitrary waveform generator (AWG) 44 corresponds to the signal generator 24 in Figure 2 and generates sampling pulses with a sinc function waveform at a repetition frequency of 30.025 MHz (i.e., the second frequency is m(1) times the first frequency). The Mach Tender Modulator (MZM) 46 corresponds to the modulator 26 in Figure 2. The amplifier 47 amplifies the input optical pulse.

[0031] The highly dispersed compensated fiber (DCF) 48 corresponds to the dispersion compensator 28 in Figure 2, compressing the optical time at a rate of 1020 ps / nm, and as a result generating an optical sampling pulse train of 60.05 MHz, which corresponds to an n × m (2) multiplication of the broadband optical pulse repetition frequency of 30.025 MHz (first frequency). The optical distributor 49 distributes the input optical sampling pulse train at a power ratio of 99:1 and outputs it to the array waveguide grating (AWG) 51 and the optical spectrum analyzer (OSA) 50, respectively. The optical spectrum analyzer (OSA) 50 is a measuring instrument that performs frequency analysis on the optical sampling pulse train distributed from the optical distributor 49 at a ratio of 1 / 100.

[0032] The array waveguide grating (AWG) 51 wavelength-decouples the optical sampling pulse train, which is distributed from the optical distributor 49 at a 99 / 100 ratio, into two optical pulse trains with two wavelength components (short wavelength and long wavelength). The oscilloscope (OSC) 52 is a measuring instrument that observes the time waveforms of the two wavelength components (short wavelength and long wavelength) of the optical pulse trains wavelength-decoupled by the array waveguide grating (AWG) 51, using two input channels (Ch1 and Ch2), respectively.

[0033] Figure 5A shows the measurement results from the optical sampling pulse generator 10a related to the experimental example shown in Figure 4. More specifically, Figures 5A(a) to (e) are a reproduction of Figure 3, Figure 5A(f) shows the time waveform of the light pulse sequence shown in Figure 5A(d) (i.e., the time waveform before optical time compression), Figure 5A(g) shows the spectrum of the light pulse sequence shown in Figure 5A(d) (i.e., the spectrum before optical time compression observed by the optical spectrum analyzer (OSA) 50), and Figure 5A(h) shows the time waveform of the light sampling pulse sequence shown in Figure 5A(e) (i.e., the time waveform after optical time compression).

[0034] As shown in Figures 5A(f) and (g), the sequence of optical pulses output from the Mach Tender modulator (MZM) 46 has a repetition frequency of 30.025 MHz, and each optical pulse contains two wavelength components (short wavelength and long wavelength).

[0035] Furthermore, as can be seen by comparing (f) and (h) in Figure 5A, the frequency of the input optical pulse train is doubled by the highly dispersed compensation fiber (DCF) 48.

[0036] Figure 5B shows the measurement results before and after the array waveguide grating (AWG) 51 from the optical sampling pulse generator 10a related to the experimental example shown in Figure 4. More specifically, Figure 5B(a) is the same as Figure 5A(h), that is, it shows the time waveform of the optical sampling pulse train input to the array waveguide grating (AWG) 51, Figure 5B(b) shows the array waveguide grating (AWG) 51, Figure 5B(c) shows the time waveform of one of the two wavelength components of the optical pulse output from the array waveguide grating (AWG) 51 (the short-wavelength optical pulse input to Ch1 of the oscilloscope (OSC) 52), and Figure 5B(d) shows the time waveform of the other of the two wavelength components of the optical pulse output from the array waveguide grating (AWG) 51 (the long-wavelength optical pulse input to Ch2 of the oscilloscope (OSC) 52).

[0037] Figure 5B shows that the optical sampling pulse train output from the highly dispersion-compensated fiber (DCF) 48 (Figure 5B(a)) is interleaved by wavelength division multiplexing, consisting of a short-wavelength optical pulse train (Figure 5B(c)) and a long-wavelength optical pulse train (Figure 5B(d)).

[0038] As described above, the optical sampling pulse generation device 10 according to this embodiment includes a light source 20 that repeatedly emits broadband optical pulses 30 at a first frequency, and time-varying spectral light 32a~32d (chirped) whose wavelength increases or decreases over time for a period longer than the period corresponding to the first frequency by wavelength dispersion of the broadband optical pulses 30 emitted from the light source 20. The system comprises a disperser 22 that outputs a sequence of time-varying spectral light 32a to 32d in which n (n≧2) time-varying spectral light 32a to 32d overlap in time by generating light, a signal generator 24 that repeatedly outputs a sampling pulse 34 at a second frequency which is m (≧1) times the first frequency, a modulator 26 that modulates the intensity of the sequence of time-varying spectral light 32a to 32d output from the disperser 22 with the sampling pulse 34 output from the signal generator 24, thereby outputting optical pulses 36a to 36e for each sampling pulse 34, each containing n wavelength components included in the n time-varying spectral light 32a to 32d at the time the sampling pulse 34 was input, and a dispersion compensator 28 that generates an optical sampling pulse sequence 38 in which a sequence of optical pulses each containing n×m wavelength components is repeated at the first frequency (i.e., the first frequency has a frequency multiplied by n×m) by dispersion compensation on the optical pulses 36a to 36e output from the modulator 26.

[0039] This eliminates the need for expensive and restrictive wavelength-selective switches as in conventional technologies. Instead, time-varying spectral light generated from broadband optical pulses is superimposed in time by optical time extension through chromatic dispersion. After sampling by intensity modulation, optical time compression is performed by inverse dispersion, resulting in a sampling frequency multiplied by n for each time-varying spectral light that overlaps. This generates an interleaved optical sampling pulse train with a first frequency multiplied by n × m. In other words, it is possible to generate a high-frequency, high-precision interleaved optical sampling pulse train using wavelength division multiplexing with a simple low-frequency-to-high-frequency conversion technique, without using expensive wavelength-selective switches.

[0040] Furthermore, by changing the timing, waveform, frequency, and the number n of time-varying spectral light particles superimposed in time of the sampling pulse output from the signal generator 24, it is possible to change the frequency of the generated optical sampling pulse train, the interleaved wavelengths, the multiplicity of the interleaved wavelengths, and the wavelength components superimposed therein, thereby ensuring programmable variability on the order of microseconds.

[0041] Here, the sampling pulse 34 may have a waveform of the sinc function. This makes the sampling pulse a Nyquist pulse, allowing the sampling pulse to be approached in time (i.e., made higher frequency).

[0042] Furthermore, the sampling pulse 34 is an electrical signal, and the modulator 26 may be an electro-optic modulator. This makes it possible to generate sampling pulses with arbitrary waveforms using an inexpensive arbitrary waveform generator, or to perform sampling on a series of time-varying spectral light using an inexpensive electro-optic modulator.

[0043] Figure 6 is a flowchart showing the procedure for the optical sampling pulse generation method according to the embodiment. It shows the processing procedure by the optical sampling pulse generation device 10 according to the embodiment shown in Figure 2.

[0044] First, by using the light source 20 and the disperser 22, the broadband light pulse 30 repeatedly emitted from the light source 20 at a first frequency is wavelength-dispersed to generate time-varying spectral light 32a to 32d (chirped light) whose wavelength increases or decreases over time for a period longer than the period corresponding to the first frequency. This outputs a sequence of time-varying spectral light 32a to 32d in which n (n≧2) time-varying spectral light 32a to 32d overlap in time (dispersion step S10).

[0045] Next, using the signal generator 24 and the modulator 26, the sequence of time-varying spectral light 32a to 32d output from the disperser 22 is intensity-modulated with a sampling pulse 34 repeatedly output from the signal generator 24 at a second frequency that is m (≧1) times the first frequency. This results in the output of optical pulses 36a to 36e for each sampling pulse 34, each containing n wavelength components from the n time-varying spectral light 32a to 32d at the time the sampling pulse 34 was input (modulation step S11).

[0046] Finally, by using the dispersion compensator 28, dispersion compensation is performed on the optical pulses 36a to 36e output in the modulation step S11, thereby generating an optical sampling pulse train 38 in which a sequence of optical pulses, each having n × m wavelength components, is repeated at a first frequency (i.e., the first frequency has a frequency multiplied by n × m) (dispersion compensation step S12).

[0047] This allows for the generation of high-precision, high-frequency interleaved optical sampling pulse trains using wavelength division multiplexing, employing a simple low-frequency-to-high-frequency conversion technique, rather than relying on expensive and restrictive wavelength-selective switches as in conventional technologies. Furthermore, the generated optical sampling pulse trains are programmable and variable on the microsecond order.

[0048] In the above embodiments and experimental examples, an optical sampling pulse train with a frequency doubled was generated by temporally superimposing two consecutive time-varying spectral light signals. However, the multiplication is not limited to this number; an optical sampling pulse train with a frequency multiplied by three or more may be generated by temporally superimposing three or more consecutive time-varying spectral light signals.

[0049] Figure 7 illustrates a method for generating optical sampling pulses according to a first modified embodiment. This figure shows a method for generating an optical sampling pulse train 38 by multiplying the repetition frequency of the sampling pulse 34 by three or more (for example, 100 times, 1000 times) by superimposing three or more (for example, 100 times, 1000 times) consecutive time-varying spectral light 32 in time.

[0050] As shown in Figure 7, for example, when 100 time-varying spectral light pulses 32 overlap in time (i.e., when the optical time is extended to 1000 ns), the sampling pulse 34 produces a sequence of optical pulses 36, each having 100 wavelength components. This sequence of optical pulses 36 is input to the dispersion compensator 28, generating an interleaved optical sampling pulse train 38 by wavelength division multiplexing, with a frequency (here, 10 GHz) that is 100 times the repetition frequency (here, 100 MHz) of the sampling pulse 34.

[0051] Thus, when using the disperser 22 to superimpose n time-varying spectral light pulses generated from broadband optical pulses, n may be 100 or greater. This yields an optical sampling pulse train 38 with a frequency obtained by multiplying the repetition frequency of the sampling pulse 34 by 100 or more. For example, applying this to the sampling of analog / digital conversion enables a dramatic increase in the speed of analog / digital conversion.

[0052] Furthermore, in the above embodiments and experimental examples, sampling was performed using one sampling pulse for each location where n (or 2 in the embodiments) consecutive time-varying spectral light overlaps in time. However, sampling may be performed using two or more sampling pulses for each location where n consecutive time-varying spectral light overlaps in time.

[0053] Figure 8 illustrates a method for generating optical sampling pulses according to a second modified embodiment. Here, an example is shown in which, at each point where n (here, 2) consecutive time-varying spectral light 32 overlap in time, sampling is performed with m or more (here, 2) sampling pulses 34 to generate an interleaved optical sampling pulse train 38 having a frequency (here, 400 MHz) obtained by multiplying the repetition frequency (here, 100 MHz) of a broadband optical pulse 30 by n × m (here, 4).

[0054] Thus, the second frequency, which is the repetition frequency of the sampling pulse 34, may be twice or more (i.e., m≧2) the first frequency, which is the repetition frequency of the broadband optical pulse 30. This makes it possible to generate an optical sampling pulse train 38 in which the repetition frequency of the low-frequency broadband optical pulse 30 is increased to a much higher frequency.

[0055] The optical sampling pulse generation apparatus and optical sampling pulse generation method relating to this disclosure have been described above based on embodiments and modifications, but this disclosure is not limited to these embodiments and modifications. Within the scope of this disclosure, various modifications that a person skilled in the art can conceive of may be applied to these embodiments and modifications, as well as other forms constructed by combining some of the components of the embodiments and modifications, are also included without departing from the spirit of this disclosure. [Industrial applicability]

[0056] This disclosure can be used as an optical sampling pulse generator, and in particular as a device that generates high-frequency, high-precision optical sampling pulse trains interleaved by wavelength division multiplexing, for example, as an optical sampling pulse generator used in analog / digital converters. [Explanation of Symbols]

[0057] 10, 10a Optical sampling pulse generator 12 Optical Fibers 14 Conductor Cables 20 light source 22 Distributor 24 Signal Generator 26 Modulator 28 Dispersion compensator 30 Broadband optical pulses 32, 32a~32d Time-varying spectral light (chirped light) 34 sampling pulses 36, 36a~36e Light pulses 38 Optical sampling pulse train 40 Mode-Synchronized Fiber Laser (MLFL) 41 Wavelength Selective Switch (WSS) 42 Chirp Fiber Bragg Grating (CFBG) 43 Polarization Controller 44 Arbitrary Waveform Generator (AWG) 46. ​​Mach Tender Modulator (MZM) 47 Amplifier 48. High-Dispersion Compensated Fiber (DCF) 49 Optical distributor 50 Optical Spectrum Analyzer (OSA) 51 Array waveguide grating (AWG) 52 Oscilloscope (OSC)

Claims

1. A light source that repeatedly emits broadband light pulses at a first frequency, A disperser that outputs a sequence of time-varying spectral light in which n (n≧2) time-varying spectral light overlaps in time by wavelength-dispersing a broadband optical pulse emitted from the light source to generate time-varying spectral light (chirped light) whose wavelength increases or decreases over time for a period longer than the period corresponding to the first frequency, and by dispersing the broadband optical pulse emitted from the light source, A signal generator that repeatedly outputs a sampling pulse at a second frequency which is m (≧1) times the first frequency, A modulator that modulates the intensity of the time-varying spectral light sequence output from the disperser with a sampling pulse output from the signal generator, thereby outputting an optical pulse for each sampling pulse that has n wavelength components included in the n time-varying spectral light sequences at the time the sampling pulse was input. The system includes a dispersion compensator that performs dispersion compensation on the optical pulse output from the modulator to generate an optical sampling pulse train in which the sequence of optical pulses having n × m wavelength components is repeated at a first frequency. Optical sampling pulse generator.

2. The sampling pulse has a waveform of the sin function, The optical sampling pulse generation apparatus according to claim 1.

3. The second frequency is at least twice the first frequency. The optical sampling pulse generation apparatus according to claim 1.

4. The sampling pulse is an electrical signal, The modulator is an electro-optic modulator. The optical sampling pulse generation apparatus according to claim 1.

5. The aforementioned n is 100 or more. The optical sampling pulse generation apparatus according to any one of claims 1 to 4.

6. A dispersion step involves generating a sequence of time-varying spectral light in which n (n≧2) time-varying spectral light overlaps over time by wavelength-dispersing broadband optical pulses repeatedly emitted from a light source at a first frequency, thereby generating time-varying spectral light (chirped light) whose wavelength increases or decreases over time for a period longer than the period corresponding to the first frequency. A modulation step in which the sequence of time-varying spectral light output in the dispersion step is intensity-modulated with sampling pulses repeatedly output from a signal generator at a second frequency that is m (≧1) times the first frequency, thereby outputting an optical pulse for each sampling pulse that has n wavelength components included in the n time-varying spectral light at the time the sampling pulse was input, The modulation step includes a dispersion compensation step in which dispersion compensation is performed on the optical pulse output in the modulation step to generate an optical sampling pulse train in which the sequence of optical pulses having each of the n × m wavelength components is repeated at a first frequency. A method for generating optical sampling pulses.

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