JP2004287074A - Wavelength variable optical pulse generating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength variable optical pulse generating device which can be used especially in the field of super high speed optical communication and can be used as the light source of e.g. TDN-WDM of a terabit band or a light source as soliton communication, in the wavelength variable optical pulse generating device by which the wavelength of an optical pulse having a high repetition frequency is made variable in a wide wavelength band region. <P>SOLUTION: The wavelength variable optical pulse generating device is provided with an optical pulse source, a polarization regulator in which an optical pulse from the optical pulse source is made incident, an optical fiber in which the optical pulse from the polarization regulator is made incident and which shows a self-frequency shift effect to be an optical non-linear phenomenon, and an optical filter in which the optical pulse from the optical fiber is inputted and which can remove inputted light. The optical pulse source produces the optical pulse having intensity by which the self-frequency shift effect is caused by the optical fiber and the optical filter filters the spectrum of the optical pulse outputted from the optical fiber. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wavelength-variable optical pulse generator that can vary the wavelength of an optical pulse having a high repetition frequency in a wide band.
[0002]
[Prior art]
Such an optical pulse light source can be used for various purposes in the field of ultra-high-speed optical communication. For example, it can be used as a light source for OTDM-WDM in the terabit band, a light source for soliton communication, or a wavelength converter for received optical pulses. It is required to use it.
[0003]
In order to transmit a large amount of data over a long distance using an optical fiber, a wavelength region (1.55 μm) of a silica-based optical fiber having the lowest loss is mainly used at present. The low-loss area extends over 300 nm in the EU band, and low-loss data transmission can be performed in that wavelength band. Therefore, an optical pulse light source that covers this wavelength area is required.
[0004]
An active synchronous fiber laser using an erbium-doped fiber has the ability to generate a picosecond or less optical pulse at a repetition frequency of 10 GHz or more. However, according to Non-Patent Document 1, from the limit of the gain width of the erbium element, The wavelength range in which short light pulses can be generated is limited to a region of about 30 nm centering on 1.55 μm.
[0005]
In other regions, there are also optical pulse lasers based on semiconductor lasers, but similarly to the above, there is a limitation on the frequency bandwidth, which limits the wavelength tunable region. Further, it is also known that it is difficult to generate an optical pulse of picosecond or less necessary for generating a soliton optical pulse from a semiconductor laser.
[0006]
As means for solving this problem, a means for stably and efficiently performing sub-picosecond optical pulses by wavelength conversion using the nonlinear effect of an optical fiber, a tunable light source using the same, and applications thereof will be described.
[0007]
The principle that the wavelength tunable light source generates an optical pulse train is based on the effect of a soliton self-frequency shift (SSFS). This is because a light pulse with high luminance is propagated through an optical fiber having anomalous dispersion, and the light pulse is affected by self-phase modulation and anomalous dispersion. It is a thing that used that. As is well known, when an optical pulse soliton propagates through an optical fiber, the long wavelength side of the optical spectrum has a gain derived from the short wavelength side due to the Raman effect, and is amplified by this. Therefore, a phenomenon is seen in which the spectrum moves to the longer wavelength side as the light pulse propagates. Such a phenomenon is described in Non-Patent Document 2, for example, and is called soliton self-frequency shift.
[0008]
For example, Non-Patent Document 3 reports an example in which an optical pulse from a passive mode-locked laser having a wavelength of 1.56 μm and a repetition frequency of 50 MHz is propagated through an optical fiber of 70 meters and the wavelength is shifted to 2.16 μm. . Another example is that an optical pulse having a repetition frequency of 50 MHz, a wavelength of 1.3 μm, and a width of 200 fs from an optical parameter oscillator is extended to 1.65 μm using a fiber (Air-Silica Microstructure Fiber) having a special structure of 15 cm. Non-Patent Document 4.
[0009]
Until now, such wavelength conversion in the long wavelength band has been difficult to use in the communication field because the repetition frequency is in the band of 100 MHz or less. In general, when the repetition frequency is increased, the luminance (peak value) decreases in inverse proportion, so that there is a problem that a nonlinear effect required for soliton self-frequency shift (SSFS) cannot be obtained. In addition, if the optical fiber used for this purpose has a high nonlinearity and a high propagation loss, there is also a problem that necessary energy is lost and soliton cannot be formed.
[0010]
[Non-patent document 1]
E. FIG. Yoshida, N .; Shimizu, and M.S. Nakazawa, “A 40-GHz, 0.9 ps regeneratively mode-locked fiber laser with a tuning run of 1530-1560 nm,” Photonics Technology Letters, p. 1587-1589, 1999.
[Non-patent document 2]
F. M. Mitschke and L.M. F. Mollenauer, "Discovery of the solutionself-frequency shift," Optics Letters 11, pp. pp. 659-661 (1986).
[Non-Patent Document 3]
M. E. FIG. Fermann, A .; Galvanauskas, M .; L. Stock, and K. K. Wong, D.C. Harter and L. Goldberg, "Ultrawide tunable Ersoliton fiber laser amplified in Yb-dopedfiber", Optics Letters 24, pp. 1428-1430 (1999).
[Non-patent document 4]
X. Liu, C.I. Xu, W.C. H. Knox, J .; K. Chandalia, B.S. J. Eggleton, S.M. G. FIG. Kosinski and R. S. Windeler, “Soliton self-frequency shift in a short tapered air-silicamic microstructure fiber”, Optics Letters 26, pp. 147-64. 358-360 (2001).
[Non-Patent Document 5]
A. Suzuki, M .; Tanaka, M .; Fujita, H .; Kubota, K, Suzuki, and S.W. Kawanishi, "Nonlinear Coefficient of highly nonlinear photonic crystal fiber", The Institute of Electronics, Communications and Communications and Information and Communications and Information and Communications and Information and Communications. 148, Miyazaki, Japan 2002.
[0011]
[Problems to be solved by the invention]
Until now, such wavelength conversion in the long wavelength band has been difficult to use in the communication field because the repetition frequency is in the band of 100 MHz or less. In general, when the repetition frequency is increased, the luminance (peak value) decreases in inverse proportion, so that there is a problem that a nonlinear effect required for soliton self-frequency shift (SSFS) cannot be obtained.
[0012]
The present invention has been proposed in view of the above, and relates to a wavelength tunable optical pulse generator that tunables the wavelength of an optical pulse having a high repetition frequency in a wide wavelength band. It is an object of the present invention to provide a wavelength-variable optical pulse generator which can be used as a light source of OTDM-WDM in a terabit band or a light source for soliton communication.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, a first feature of the present invention is to convert a wavelength, an optical pulse source, a polarization adjuster that receives an optical pulse from the optical pulse source, and Inputting an optical pulse from the polarization adjuster, and inputting an optical fiber exhibiting a self-frequency shift effect, which is an optical nonlinear phenomenon of an optical nonlinear medium, and an optical pulse from the optical fiber, and removing the input light. An optical filter, wherein the optical pulse source generates an optical pulse having such an intensity that the optical fiber causes a self-frequency shift effect, and the optical filter includes the optical fiber. Filtering a part of the spectrum of the light pulse output from the light source.
[0014]
A second feature of the present invention is applicable to WDM, and includes an optical pulse source, a branching unit that branches an optical pulse from the optical pulse source into a plurality of branch components, and at least two of the branching components. Wavelength conversion means for converting the wavelength of the branch component, and a wavelength conversion means for converting the light pulse of at least two of the branch components, a modulation means for modulating, and a merging means for merging the modulated branch components, The wavelength converter is a wavelength converter using a self-frequency shift effect using an optical nonlinear medium exhibiting an optical nonlinear phenomenon.
[0015]
A third aspect of the present invention is applicable to OTDM, and includes an optical pulse source, wavelength conversion means for converting the wavelength of an optical pulse from the optical pulse source, and the wavelength-converted optical pulse. A branching unit that branches the plurality of branching components, a modulation unit that modulates at least two of the branching components, and a merging unit that merges the modulated branching components, and the wavelength conversion unit includes: The wavelength conversion means uses a self-frequency shift effect of an optical nonlinear medium exhibiting an optical nonlinear phenomenon.
[0016]
A fourth feature of the present invention is applicable to OTDM-WDM, and includes an optical pulse source, a first branching unit that branches an optical pulse from the optical pulse source into a plurality of branch components, Wavelength converting means for converting the wavelength of at least two of the branch components, second branch means for further splitting the wavelength-converted light into at least two branch components, and each of the branch components by the second branch means. Modulation changing means for modulating, second merging means for merging the modulated branch components again, and first merging means for merging the optical pulse merged by the second merging means with another wavelength branch component. Wherein the wavelength conversion means is a wavelength conversion means using a self-frequency shift effect of an optical nonlinear medium exhibiting an optical nonlinear phenomenon.
[0017]
A fifth feature of the present invention is that an optical pulse source, a branching unit that branches an optical pulse from the optical pulse source into a plurality of branching components, and a modulation unit that modulates at least two of the branching components, respectively. A wavelength converting means for converting the wavelength of the modulated light pulse, and a merging means for merging the modulated and wavelength-converted branch components, wherein the wavelength converting means is a light exhibiting an optical nonlinear phenomenon. The wavelength conversion means uses a self-frequency shift effect using a nonlinear medium.
[0018]
A sixth feature of the present invention is that first wavelength conversion means for converting the wavelength of the light pulse from the light pulse light source, and the light pulse whose wavelength has been converted by the wavelength conversion means is incident on an optical nonlinear material. And a second wavelength converting means for generating a second harmonic. The first wavelength converting means is a wavelength converting means made of an optical nonlinear medium which induces an optical nonlinear phenomenon. .
[0019]
A seventh feature of the present invention is that a branching unit that branches an optical pulse from an optical pulse light source into a plurality of branching components, and a first wavelength converting unit that converts the wavelength of the optical pulse that is one of the branching components And a multiplexing means for multiplexing with an optical pulse which is another branch component, and an optical pulse having a sum frequency or an optical pulse having a difference frequency between the wavelength-converted optical pulse and the wavelength-unconverted optical pulse. And a second wavelength converting means, wherein the first wavelength converting means uses an optical wavelength shifting means made of an optical nonlinear medium which induces an optical nonlinear phenomenon.
[0020]
An eighth feature of the present invention resides in that a branching means for branching an optical pulse from an optical pulse light source into a plurality of branching components, and a first wavelength converting means for converting the wavelength of the optical pulse which is one of the branching components. And a second wavelength converting means for converting the wavelength of the optical pulse, which is another one of the branch components, and a multiplexing means for multiplexing the output of the first wavelength converting means and the output of the second wavelength converting means. And third wavelength converting means for generating an optical pulse having a sum frequency or an optical pulse having a difference frequency between the output of the first wavelength converting means and the output of the second wavelength converting means, The first and second wavelength conversion means are wavelength conversion means using an optical wavelength shift means made of an optical nonlinear medium that induces an optical nonlinear phenomenon.
[0021]
A ninth feature of the present invention is that the wavelength conversion means is made of a photonic crystal fiber having nonlinear optical characteristics.
[0022]
A tenth feature of the present invention is that the photonic crystal fiber is a polarization maintaining type.
[0023]
An eleventh feature of the present invention is that the wavelength converter specifies the intensity of the incident light with respect to a predetermined wavelength of the incident light to the photonic crystal fiber, and determines the wavelength change amount. That is.
[0024]
A twelfth feature of the present invention is that the wavelength converter adjusts the amplitude of the incident light pulse with an amplifier or an attenuator and then causes the light pulse to be incident on the photonic crystal fiber. And means for adjusting the amplification degree of the amplifier or the attenuation degree of the attenuator so that negative feedback is obtained.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals will be used for the same device or a device having a similar function unless otherwise specified.
[0026]
First, the present invention is devised to repeatedly increase the frequency up to a region required for communication. As the means, a highly nonlinear photonic crystal fiber (PCF) having a narrow core (direct line 2 μm or less) doped with germanium to obtain high nonlinearity, a fiber with high anomalous dispersion, and a fiber with low loss are selected. The length of the optical fiber to send is increased.
[0027]
FIG. 1 shows a first embodiment. In FIG. 1, a pulse laser 2 such as a mode-locked laser and a fiber amplifier 3 are used as shown in FIG. 1A, or an optical pulse is inputted from outside as shown in FIG. 1B. , An optical pulse source 1 that supplies an optical pulse, a polarization adjuster 4, a wavelength converter 100 including an optical fiber 6 exhibiting a non-linear effect, and an optical filter 5 constitute a wavelength variable optical pulse generator. Here, as shown in FIG. 1B, when the polarization adjuster 4 is not used, the optical fiber 7 is a polarization-maintaining optical fiber. The optical fiber 6 causes a self-frequency shift effect due to the optical nonlinear phenomenon of the optical nonlinear medium. Such optical fibers are well known. For example, it is an optical fiber having anomalous dispersion, or a photonic crystal fiber (PCF: Photonic Crystal Fiber). Due to this self-frequency shift effect, the wavelength is converted to a longer wavelength. Generally, the spectrum of the output light of the optical fiber 6 is wider than that of the input light. The optical filter 5 removes input light from the spread spectrum due to the nonlinear effect of the optical fiber 6, and selects and outputs a spectrum having a desired width. As such means, a fiber Bragg grating (FBG) or a long wavelength transmission filter suitable for the input wavelength may be used. In the case where an FBG is used, if an optical isolator or a circulator is used before the FBG, reflected input light can be easily removed.
[0028]
With this configuration, wavelength conversion can be performed in a wide band, but the amount of wavelength shift depends on the output intensity of the optical pulse source 1 as described below. Therefore, it is desirable to use one having a stable output intensity. Further, as described below, the reason for using the polarization adjuster 4 is that the wavelength shift amount is sensitive to the state of polarization. For this reason, although it operates without using a polarization adjuster on the input side of the PCF, it is desirable to install a polarization adjuster for stable operation.
[0029]
For example, a case where a mode-locked fiber laser that generates an optical pulse train having a wavelength of 1.56 μm, a repetition frequency of 10 GHz, and a width of 1.3 ps is used as a light source, amplified by an optical fiber amplifier having an output of 2 W, input to a PCF, and the output is observed. This will be described below. The nonlinear count in this experimental system is 62 W ^-1 km ^-1 , (About 30 times the nonlinearity of a normal dispersion-shifted fiber), at a wavelength of 1.55 μm, the internal loss is 40 dB / km, and the chromatic dispersion is 119 ps / nm / km, a PCF equivalent to that described in Non-Patent Document 5. Was used. The length of the optical fiber used was 12 m, and the loss was 0.51 dB, which was a relatively low value.
[0030]
FIG. 11A shows an output light pulse spectrum of a 10 GHz repetition fiber laser, and FIG. 11B shows an output spectrum of a PCF. It can be seen that the wavelength of the light pulse has shifted. FIG. 12 shows the shape of the light pulse when the light centered at 1.61 μm is selected (however, the autocorrelation shape), and it can be seen that the light pulse is narrower than the input pulse.
[0031]
Further, as shown in FIG. 13, the output wavelength in the PCF shifts to the longer wavelength side as the input intensity from the light source increases. It can be seen that wavelength conversion in a wide band is possible, but the amount of wavelength shift is very sensitive to input power.
[0032]
FIG. 14 shows output waveforms depending on three states of the polarization adjuster when the input intensity to the PCF is kept constant. From this figure, it can be seen that the wavelength shift amount is very sensitive to the state of polarization.
[0033]
Even if adjustment is performed using a polarization adjuster, the polarization state changes in the PCF due to environmental temperature changes and local temperature fluctuations, so it is necessary to always adjust the polarization state of the input light. It is. In order to solve such a problem, it is desirable to use a polarization maintaining PCF for the optical fiber 6.
[0034]
Next, a second embodiment is shown in FIG. The configuration in FIG. 2A may be the same as the configuration in FIG. In this configuration, the optical pulse source 1 and the wavelength converter 100 constitute a variable wavelength optical pulse generator. Also here, the optical fiber 6 is an optical fiber having anomalous dispersion, and causes a self-frequency shift effect due to the optical nonlinear phenomenon of the optical nonlinear medium. A part of the optical pulse having the wavelength selected by the optical filter 5 is sent to the photodetection amplifier 8 by the splitter 10, converted into an electric signal, and fed back to the amplifier 3 by the feedback circuit 9. Will be returned to. By this feedback, for example, when the wavelength of the wavelength-converted light fluctuates from the determined wavelength to the shorter wavelength side, the amplification factor of the amplifier 3 is increased, and the wavelength is adjusted to the determined value. Although not shown in the figure, it is also possible to adjust the wavelength of the output light while adjusting the intensity of the input light using a variable optical attenuator instead of the amplifier. The wavelength converter 102 shown in FIG. 2B is an example including the optical amplifier 3 and the feedback circuit 9. The photodetector amplifier 8 is a circuit as shown in the block diagram of FIG. 16A, and has a transmission characteristic sandwiching a wavelength-converted waveform as shown in FIG. , 30b, the wavelength can be more effectively stabilized.
[0035]
Next, a third embodiment is shown in FIG. In this configuration, an optical pulse from the optical pulse source 1 is split by the splitter 14 into optical paths A and B. In the optical path A, the optical fiber 6 and the optical filter 5 exhibiting the non-linear effect constitute a wavelength variable optical pulse generator. Also here, the optical fiber 6 exhibiting the nonlinear effect causes a self-frequency shift effect due to the optical nonlinear phenomenon of the optical nonlinear medium. The optical pulse having the wavelength selected by the optical filter 5 is input to the multiplexer 12. An optical coupler, a wavelength multiplexing coupler, a lens, or the like can be used as the multiplexer. In the optical path B, the optical pulse is delayed by the low dispersion optical fiber 11. This is for the same timing as the light pulse traveling on the optical path A. If a delay device having a variable delay time is used as the optical fiber 11, the operation can be performed more accurately in a wide wavelength range. The optical pulses on the optical paths A and B are multiplexed by the multiplexer, and are incident on the nonlinear medium 13. The nonlinear medium 13 outputs an optical pulse including an optical pulse having a sum frequency and an optical pulse having a difference frequency. By selecting an optical pulse having a sum frequency from this output, it is possible to realize a wavelength-variable optical pulse generator capable of changing the frequency in the vicinity of approximately twice the frequency of the output of the pulse generator 1. Further, by selecting an optical pulse having a difference frequency, an optical pulse having a frequency corresponding to the change due to the self-frequency shift effect can be obtained. In general, a light pulse having a long wavelength can be easily obtained at the wavelength corresponding to the change.
[0036]
Next, a fourth embodiment is shown in FIG. The configuration in FIG. 4 may be the same as the configuration in FIG. 3 except for the use of an optical fiber of an optical nonlinear medium. In this configuration, the low dispersion optical fiber 11 and the optical fiber 6 exhibiting a nonlinear effect are used instead of the low dispersion optical fiber 11 of FIG. Also in this case, it is important that the optical fibers propagating in the optical paths A and B are multiplexed at the same timing. For example, the frequency shift of the optical path B can be made smaller than that of the optical path A by making the delay due to the optical fiber 6 exhibiting the nonlinear effect of the optical path B smaller than the delay of the optical path A. Naturally, the optical filter in optical path A and that in optical path B are matched to their respective frequency shifts and have different filtering characteristics. The advantage of this configuration is that the peak value is higher because the pulse width of both components to be non-linearly synthesized is narrower than that of the sum frequency or difference frequency in the third embodiment shown in FIG. Thus, wavelength conversion can be performed more efficiently.
[0037]
Next, a fifth embodiment is shown in FIG. The configuration of FIG. 5 is for generating modulated light pulses of different wavelengths. In this configuration, the optical pulse from the optical pulse source 1 is split by the splitter 14 into optical paths 1, 2,. In the optical path 1, the wavelength of the light pulse is converted by the wavelength converter 16 and modulated by the modulator 17. Here, any one of the wavelength converters in the first to fourth embodiments can be used as the wavelength converter 16. Further, as the modulator 17, an intensity modulator, a phase modulator, a frequency modulator, a polarization modulator, a simple optical shutter, or the like can be used. The optical pulses modulated in the optical paths 1, 2,..., N are multiplexed by the multiplexer 15 and output. The light pulses output here are separated as shown in FIG. 8A on the frequency axis, but overlap as shown in FIG. 8B on the time axis. From this figure, it can be seen that it can be used as wavelength division multiplexing (WDM).
[0038]
Next, a sixth embodiment is shown in FIG. The configuration of FIG. 6 is for generating modulated light pulses of different wavelengths at different timings. In this configuration, the optical pulse from the optical pulse source 1 is split by the splitter 14 into optical paths 1, 2,. In the optical path 1, the wavelength of the light pulse is converted by the wavelength converter 16 and modulated by the modulator group 18. Here, any one of the wavelength converters in the first to fourth embodiments can be used as the wavelength converter 16.
[0039]
Further, the configuration shown in FIG. 7 can be used as the modulator group 18. In this configuration, an optical pulse having a wavelength of λi is split by the splitter 24 into optical paths 1, 2,. In each of the branched optical paths, a delay time is given according to each of the optical paths, and is modulated by each of the modulators. Here, as the modulator 17, an intensity modulator, a phase modulator, a frequency modulator, a polarization modulator, a simple optical shutter, or the like can be used. The modulated optical pulses in each optical path are multiplexed by the multiplexer 25.
[0040]
The output of the multiplexer 25 is multiplexed and output by the multiplexer 15 of FIG. The light pulses output here are separated from each other as viewed in the frequency axis as shown in FIG. 8C, and are separated as shown in FIG. 8D from the time axis. From this figure, it can be seen that it can be used as optical time division-wavelength division multiplexing (OTDM-WDM).
[0041]
Next, a seventh embodiment is shown in FIG. The configuration of FIG. 9 is for generating wavelength-converted optical pulses at different timings. In this configuration, an optical pulse from the optical pulse source 1 is wavelength-converted by the wavelength converter 102, and is split by the splitter 14 into optical paths 1, 2,. In each of the branched optical paths, a delay time is given according to each of the optical paths, and is modulated by each of the modulators. Here, as the modulator 17, an intensity modulator, a phase modulator, a frequency modulator, a polarization modulator, a simple optical shutter, or the like can be used. The modulated optical pulses in each optical path are multiplexed by the multiplexer 15.
[0042]
Next, an eighth embodiment is shown in FIG. The configuration shown in FIG. 10 expands the variable wavelength range by generating harmonics of a wavelength-converted optical pulse. In this configuration, the wavelength of the light pulse from the light pulse source 1 is converted by the wavelength converter 100, and a harmonic is generated by the optical nonlinear material 20. The optical filter 21 selects an optical pulse having a desired frequency from the harmonics.
[0043]
Next, a ninth embodiment is shown in FIG. The configuration shown in FIG. 15 is a configuration in which the wavelength converter 16 and the modulator 17 of the fifth embodiment shown in FIG. 5 are replaced. When a modulator having no amplifying action is used for the modulator 17, the configuration of FIG. 5 has a higher intensity of the light pulse in the wavelength converter, and is more advantageous for wavelength conversion. Conversely, when a modulator having an amplifying action is used for the modulator 17, the configuration of FIG. 15 is more advantageous for wavelength conversion. In addition, in the case of a modulator having a small allowable value of the intensity of an optical pulse that can be input, the configuration of FIG. 5 is desirable. On the other hand, in the case of using a modulator having characteristics with large frequency dependence, the configuration of FIG. Is more desirable.
[0044]
As described above, the configuration based on the present invention can be used as a wavelength converter in a field that requires wavelength conversion of a high-speed data stream in a long wavelength band, for example, in an optical communication field. Further, it can be used as an optical pulse light source that is variable in wavelength over a wide band. In addition, it can be used as a tunable light source in a wavelength band that has not been easily obtained until now by using second harmonic generation of light, distributed feedback laser, light sum frequency generation, and the like.
[0045]
【The invention's effect】
Since the present invention has the above-described configuration, the following effects can be obtained.
[0046]
An optical pulse source, a polarization adjuster for inputting an output optical pulse, an optical fiber for inputting an optical pulse therefrom and exhibiting a self-frequency shift effect, and inputting the optical pulse to remove input light. An optical filter is used to generate an optical pulse from the optical pulse source, the intensity of which causes an optical fiber to cause a self-frequency shift effect, and to filter out part of the spectrum of the generated optical pulse. It is now possible to convert the wavelength of an optical pulse to a high repetition frequency, which was not possible until now. At present, wavelength conversion of a repetitive optical pulse (10 GHz) which is 100 times or more that of the conventional one can be realized by using this means.
[0047]
Further, the present invention can be used as a wavelength converter in a field that requires wavelength conversion of a high-speed data stream in a long wavelength band, for example, in an optical communication field. Further, it can be used as an optical pulse light source that is variable in wavelength over a wide band. In addition, it can be used as a tunable light source in a wavelength band that has not been easily obtained until now by using second harmonic generation of light, distributed feedback laser, light sum frequency generation, and the like.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a first embodiment.
FIG. 2 is a block diagram showing a second embodiment.
FIG. 3 is a block diagram showing a third embodiment.
FIG. 4 is a block diagram showing a fourth embodiment.
FIG. 5 is a block diagram showing a fifth embodiment.
FIG. 6 is a block diagram showing a sixth embodiment.
FIG. 7 is a block diagram illustrating a configuration of a modulator group.
FIG. 8 is a schematic diagram showing output on a time axis and a frequency axis.
FIG. 9 is a block diagram showing a seventh embodiment.
FIG. 10 is a block diagram showing an eighth embodiment.
FIG. 11 is a diagram showing a wavelength shift by a PCF.
FIG. 12 is a diagram showing an autocorrelation shape of output light.
FIG. 13 is a diagram showing the input intensity dependency of the wavelength shift by the PCF.
FIG. 14 is a diagram showing an output waveform depending on a polarization state.
FIG. 15 is a block diagram showing a ninth embodiment.
FIG. 16 is a diagram illustrating the photodetector amplifier of FIG. 2;
[Explanation of symbols]
1 Optical pulse source
2 pulse laser
3 Amplifier
4 Polarization adjuster
5 Optical filter
6 Optical fiber showing nonlinear effect
7 Optical fiber
8 Photodetector amplifier
9 Feedback circuit
10 Switch
11 Low dispersion optical fiber
12 multiplexer
13 Nonlinear medium
14 Switch
15 multiplexer
16 wavelength converter
17 Modulator
18 Modulator group
19 Optical filter
20 Nonlinear materials
21 Optical Filter
24 switch
25 combiner
30a, 30b filter
31 Photodetector
32 differential amplifier
100, 101, 102, 103, 104 wavelength converter

Claims (12)

An optical pulse source;
A polarization adjuster that receives an optical pulse from the optical pulse source,
An optical fiber that receives an optical pulse from the polarization adjuster and exhibits a self-frequency shift effect, which is an optical nonlinear phenomenon of an optical nonlinear medium,
An optical filter capable of inputting an optical pulse from the optical fiber and removing the input light,
The optical pulse source is configured to generate an optical pulse having such an intensity that the optical fiber causes a self-frequency shift effect,
The above-mentioned optical filter has a configuration of filtering a part of light of the spectrum of the optical pulse outputted from the above-mentioned optical fiber. An optical pulse source, and branching means for branching an optical pulse from the optical pulse source into a plurality of branch components,
Wavelength conversion means for converting the wavelength of at least two of the branch components;
Modulating means for modulating the wavelength of the optical pulse of at least two branch components, and modulating the light pulse;
Converging means for converging the modulated branch component,
A wavelength tunable optical pulse generator, wherein the wavelength converting means is a wavelength converting means using a self-frequency shift effect using an optical nonlinear medium exhibiting an optical nonlinear phenomenon. An optical pulse source;
Wavelength conversion means for converting the wavelength of the light pulse from the light pulse source;
Branching means for branching the wavelength-converted optical pulse into a plurality of branch components;
Modulating means for modulating at least two of the branch components;
Converging means for converging the modulated branch component,
The wavelength converting means is a wavelength converting means using a self-frequency shift effect of an optical nonlinear medium exhibiting an optical nonlinear phenomenon. An optical pulse source;
First branching means for branching the light pulse from the light pulse source into a plurality of branch components;
Wavelength conversion means for converting the wavelength of at least two of the branch components, and second branch means for further splitting the wavelength-converted light into at least two branch components;
Modulation conversion means for modulating each of the branch components by the second branch means;
Second merging means for merging the modulated branch components again;
A first converging unit for converging the optical pulse merged by the second merging unit with another wavelength branch component;
The wavelength converting means is a wavelength converting means using a self-frequency shift effect of an optical nonlinear medium exhibiting an optical nonlinear phenomenon. An optical pulse source, and branching means for branching an optical pulse from the optical pulse source into a plurality of branch components,
Modulating means for modulating at least two of the branch components, respectively;
Wavelength conversion means for converting the wavelength of the modulated light pulse,
Merging means for merging the modulated and wavelength-converted branch components,
A wavelength tunable optical pulse generator, wherein the wavelength converting means is a wavelength converting means using a self-frequency shift effect using an optical nonlinear medium exhibiting an optical nonlinear phenomenon. First wavelength conversion means for converting the wavelength of the light pulse from the light pulse light source;
A second wavelength converting means for generating a second harmonic by making the optical pulse wavelength-converted by the wavelength converting means incident on an optical nonlinear material;
The above-mentioned first wavelength conversion means is a wavelength conversion means comprising an optical non-linear medium which induces an optical non-linear phenomenon. Branching means for branching the light pulse from the light pulse light source into a plurality of branch components;
First wavelength conversion means for converting the wavelength of an optical pulse which is one of the branch components;
Multiplexing means for multiplexing with an optical pulse which is another branch component;
Second wavelength conversion means for generating an optical pulse having a sum frequency or an optical pulse having a difference frequency between the wavelength-converted optical pulse and the optical pulse not to be wavelength-converted,
The wavelength tunable optical pulse generator according to claim 1, wherein said first wavelength converting means uses an optical wavelength shifting means comprising an optical nonlinear medium for inducing an optical nonlinear phenomenon. Branching means for branching the light pulse from the light pulse light source into a plurality of branch components;
First wavelength conversion means for converting the wavelength of an optical pulse which is one of the branch components;
Second wavelength conversion means for converting the wavelength of the light pulse which is another one of the branch components;
The sum frequency of the multiplexing means for multiplexing the output of the first wavelength conversion means and the output of the second wavelength conversion means, and the sum frequency of the output of the first wavelength conversion means and the output of the second wavelength conversion means A third wavelength conversion means for generating an optical pulse having an optical pulse or an optical pulse having a difference frequency.
The tunable optical pulse generator according to claim 1, wherein said first and second wavelength converting means are wavelength converting means using an optical wavelength shifting means comprising an optical nonlinear medium for inducing an optical nonlinear phenomenon. 9. The tunable optical pulse generator according to claim 1, wherein said wavelength converting means is made of a photonic crystal fiber having nonlinear optical characteristics. The wavelength tunable optical pulse generator according to claim 9, wherein the photonic crystal fiber is a polarization maintaining type. 2. The method according to claim 1, wherein the wavelength converter specifies an intensity of the incident light and determines a wavelength change amount for a predetermined wavelength of the light incident on the photonic crystal fiber. 10. The wavelength-variable optical pulse generator according to any one of 10. The above wavelength converter adjusts the amplitude of the incident light pulse with an amplifier or an attenuator, and then causes the light pulse to be incident on the photonic crystal fiber. 11. The tunable optical pulse generator according to claim 1, further comprising means for adjusting the degree of amplification of the amplifier or the degree of attenuation of the attenuator.

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