JP4889661B2 - Optical multicarrier generator and optical multicarrier transmitter using the same - Google Patents

Description

  The present invention relates to an optical multicarrier generator used as a light source of an optical communication system and an optical multicarrier transmitter using the same.

  Up to now, the speed of optical fiber transmission has been increased by time division multiplexing, but the problem that the transmission distance is limited by the chromatic dispersion of the optical fiber has become apparent. As one means for solving this problem, it is conceivable to use a dispersion compensation device such as a dispersion compensation fiber. However, it is desirable to avoid the use if possible from the viewpoint of the equipment size or equipment cost or additional loss.

  As one of the solutions, a method of developing a high-speed signal in parallel and transmitting it with a plurality of optical carriers is being studied. In the transmission system using a plurality of optical carriers, a system using a plurality of independent light sources is the most general, but from the viewpoint of the apparatus size and the apparatus cost, a multi-wavelength which uses a light modulator to increase the wavelength of continuous light from one light source. The carrier light source is attractive.

FIG. 17 shows a configuration example of a multicarrier light source that generates four optical carriers from a single wavelength light source (see Non-Patent Document 1). Continuous (CW) light generated from a laser diode (LD) as a continuous light oscillation light source 50 is input to two cascaded Mach-Zehnder (MZ) type optical modulators 51 and 52. The front stage Mach-Zehnder optical modulator 51 is driven by an RF (Radio Frequency) signal having a frequency f ₀ , and the rear stage Mach-Zehnder optical modulator 52 is driven by an RF signal having a frequency 2f ₀ . These RF signals are input to the Mach-Zehnder optical modulators 51 and 52 by the phase shifters 53 and 54 as two input lights having a phase difference, respectively.

As shown in FIG. 17, by driving the Mach-Zehnder optical modulators 51 and 52 by push-pull, the carrier component of CW light is suppressed at the output of the preceding Mach-Zehnder optical modulator 51, and the drive signal thereby generating two optical carriers spaced by twice the frequency 2f ₀ of the frequency f _0.

The spectrum of the output light from the preceding stage Mach-Zehnder optical modulator 51 is shown in FIG. This signal is further input to the Mach-Zehnder optical modulator 52 at the subsequent stage. The Mach-Zehnder optical modulator 52 in the subsequent stage generates two carriers separated from the two optical carriers by a frequency 4f _{0 which is} twice the drive signal frequency 2f ₀ .

In other words, the optical frequency omega _c -f ₀ is converted into light of the light and the frequency omega _c + f ₀ of the frequency omega _c -3f _0, the frequency omega _c + light f ₀ is light and the frequency of the frequency omega _c -f ₀ omega _c + 3f ₀ converted to light. As a result, four optical carriers are generated as shown in FIG.

A. Chowdy, Z .; Jia, G .; K. Chang, and R.C. Younce, "Novel 100Gbps Ethernet Systems for Next-generation Metro Transport and Wide-area Access Networks using Optical carrier suppression and separation Technique," Proceedings of LEOS Summer Topical Meeting 2007, Paper TuE1.2,2007.

  However, in the configuration in which Mach-Zehnder type optical modulators are connected in cascade, an increase in optical loss is inevitable, and it is difficult to ensure a high optical signal-to-noise ratio (OSNR). Furthermore, it is difficult to increase the number of optical carriers to 8 or 16 waves from the viewpoint of not only optical loss but also apparatus size and apparatus cost.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a low loss, small size, low cost optical multicarrier generator and an optical multicarrier transmitter using the same. For the purpose.

When the present invention is viewed from the viewpoint of an optical multicarrier generator, the optical multicarrier generator of the present invention includes continuous light generating means for generating continuous light, a Mach-Zehnder optical intensity modulator, a fundamental wave, third harmonic or al the (2n-1) th harmonic components (n is a natural number of 2 or more) generating an RF signal of the sum of n sine waves consisting of the n-1 odd order harmonics up And an RF signal generating means for driving the Mach-Zehnder type optical intensity modulator with a zero chirp by the RF signal around a point where the transmittance is minimized.

  As a result, the continuous light generating means as one single wavelength light source and the Mach-Zehnder light intensity modulator as one optical modulator can generate optical carriers of a plurality of wavelengths, A loss, small size, and low cost optical multicarrier generator can be realized.

  Furthermore, an amplitude ratio setting means for setting an amplitude ratio of the n sine waves can be provided. In general, the RF component has a higher loss as the frequency is higher, and the optical modulator has a lower modulation efficiency as the frequency is higher. Therefore, an optical multicarrier finally obtained by adding the fundamental wave and the third harmonic with the same power The spectral flatness of is reduced. Therefore, if the amplitude of the third harmonic is made larger than that of the fundamental wave in advance, it becomes possible to ensure the spectral flatness of the finally obtained optical multicarrier.

  Further, phase synchronization means for synchronizing the n sine waves with each other may be provided. For this purpose, for example, a phase setting means for setting the phase of the n sine waves is provided. Thereby, the freedom degree which controls the interference between multicarrier signals can be made high.

Further, as an example of the RF signal generating means, an RF oscillator that generates the fundamental wave and the fundamental wave generated by the RF oscillator are input, and the third harmonic to the (2n-1) th harmonic. A plurality of harmonic generators that generate n −1 odd harmonics in parallel up to the third harmonics generated by the plurality of harmonic generators to the (2n−1) th harmonics And an adder that adds the n- 1 odd harmonics up to the wave and the fundamental wave to generate a sum RF signal of n sine waves .

  In addition, an optical interleave filter having a free spectral range that is twice the frequency of the fundamental wave may be provided at the output of the Mach-Zehnder optical intensity modulator. Thereby, an unnecessary frequency component can be reduced.

  When the present invention is viewed from the viewpoint of an optical multicarrier transmission apparatus, the optical multicarrier transmission apparatus of the present invention includes the optical multicarrier generation apparatus of the present invention described above and a plurality of outputs from the optical multicarrier generation apparatus. And an optical multicarrier modulator for performing data modulation on an optical carrier having a wavelength of.

  As a result, the continuous light generating means as one single wavelength light source and the Mach-Zehnder light intensity modulator as one optical modulator can generate optical carriers of a plurality of wavelengths, A loss, small size, and low cost optical multicarrier transmission apparatus can be realized.

  Further, synchronization means for synchronizing the data signal input to the optical multicarrier modulator and the RF signal for driving the Mach-Zehnder optical intensity modulator constituting the optical multicarrier generator can be provided. . Thereby, the freedom degree which controls the interference between multicarrier signals can be made high.

  The optical multicarrier modulator may further include an optical phase control means for controlling the optical phase of each optical carrier. Alternatively, the optical multi-carrier modulator can include bit phase control means for controlling a bit phase of a data signal for modulating each optical carrier. Thereby, the freedom degree which controls the interference between multicarriers can be made high.

  According to the present invention, an optical carrier having a plurality of wavelengths can be generated by one single wavelength light source and one optical modulator, and thereby a low loss, small size, low cost optical multicarrier generator and It is possible to realize an optical multicarrier transmission apparatus using the same.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
1st embodiment of this invention is embodiment which concerns on an optical multicarrier generator. FIG. 1 shows a configuration example according to the first embodiment of the optical multicarrier generator of the present invention. In this configuration, four optical carriers are generated by using one continuous light oscillation light source 5 and one zero chirp Mach-Zehnder optical modulator 6. In the following, Mach-Zehnder is expressed as MZ. An RF signal for driving the zero chirp MZ type optical modulator 6 is constituted by an RF oscillator 1 that generates a single frequency RF signal, a third harmonic generator 2, and an adder 3.

The RF signal of frequency f ₀ generated by the RF oscillator 1 is branched into two, and one of the branched RF signals is converted into a harmonic signal of frequency 3f ₀ by the third harmonic generator 2 and branched. The other RF signal (frequency f ₀ ) is added by the adder 3. The added signal is amplified up to an amplitude capable of driving the modulator by the modulator driver 4 and input to the zero chirp MZ type optical modulator 6.

A configuration example of the third harmonic generator 2 is shown in FIG. In this configuration, the fundamental wave f ₀ and the second harmonic generated by the second harmonic generator 20 are input to the mixer 22, and the sum frequency component 3f ₀ and the difference frequency component f ₀ output from the mixer 22 are input. Can be generated by selecting the sum frequency component 3f ₀ by the band pass filter (BPF) 21. The second harmonic generator 20 is commercially available as a frequency doubler and is widely available.

  In addition, as the 3rd harmonic generator 2 shown in FIG. 1, you may use the frequency multiplication circuit (triple) which directly generates the 3rd harmonic from a fundamental wave.

The operation of the zero chirp MZ type optical modulator 6 will be described in detail with reference to FIGS. FIG. 3 shows the operation of the fundamental wave (frequency: f ₀ ) drive. For comparison, the operation of the third harmonic (frequency: 3f ₀ ) drive is shown by a broken line, but it will not be described here.

As shown in FIG. 3, the drive voltage and the transmittance of the zero chirp MZ type optical modulator 6 show a sine wave relationship. The zero chirp MZ type optical modulator 6 is driven by a drive signal having a frequency f ₀ around a point having the minimum transmittance. When the zero chirp MZ modulator 6 is driven with zero chirp, the optical phase of the output light is inverted at the point where the transmittance is minimum, so that the output optical signal alternates with the pulse repetition frequency being twice the drive signal frequency as shown in FIG. It becomes an optical pulse whose optical phase is reversed. “0” and “π” in the figure indicate the optical phase of the output optical signal. As a result, it is possible to generate two optical carrier frequency interval 2f ₀ in the driving signal of a frequency f _0.

FIG. 4 shows the operation of the third harmonic (frequency: 3f ₀ ) driving. Similar to FIG. 3, the operation of the fundamental wave (frequency: f ₀ ) drive is shown by a broken line for comparison. When the zero chirp MZ type optical modulator 6 is driven with a drive signal having a frequency of 3f ₀ based on the same operating principle as in FIG. 3, two optical carriers having a frequency interval of 6f ₀ are generated as shown in FIG. Can do.

In the region where the operation of the zero chirp MZ type optical modulator 6 can be regarded as linear, when the drive signal is linearly added, the output optical signal is also linearly added. Therefore, the fundamental wave (frequency: f ₀ ) and the third harmonic ( When the _zero chirp MZ optical modulator 6 is driven by a signal obtained by linearly adding (frequency: 3f ₀ ), the output optical signal is linearly added by two optical carriers having a frequency interval of 2f ₀ and two optical carriers having a frequency interval of 6f ₀ . A signal is obtained. This is shown in FIG. As a result, four optical carriers having a frequency interval of 2f ₀ can be generated.

  FIG. 6 shows an optical multicarrier generated by actually driving the zero chirp MZ type optical modulator 6 with a synthesized signal of a fundamental wave having a frequency of 12.5 GHz and a third harmonic wave having a frequency of 37.5 GHz. In FIG. 6, the horizontal axis represents wavelength and the vertical axis represents signal intensity. It can be seen that four optical carriers having a flat spectrum are generated.

Weak spectral components are seen at the original carrier frequency of the continuous wave oscillation light source 5 and at a frequency separated from that by an integer multiple of 25 GHz. This is due to the imperfection of the zero-chirp MZ type optical modulator 6 and the drive signal. This is due to the frequency 2f ₀ component included in the. These unnecessary frequency components can be effectively reduced by inserting an optical interleave filter into the output of the zero chirp MZ type optical modulator 6.

(Second embodiment)
The second embodiment of the present invention is an embodiment according to an optical multicarrier generator. FIG. 7 shows a configuration example according to the second embodiment of the optical multicarrier generator of the present invention. In this configuration example, in addition to the configuration example according to the first embodiment shown in FIG. 1, an optical interleave filter 7 is inserted in the optical output stage. The free spectral range (FSR) of the optical interleave filter 7 is set equal to the frequency interval 2f ₀ of the optical multicarrier.

  FIG. 8 schematically shows the relationship between the transmittance characteristics of the optical interleave filter 7 and the optical multicarrier frequency. In FIG. 8, the horizontal axis represents the optical frequency, and the vertical axis represents the transmittance. It can be seen that only the desired optical frequency component can be selectively extracted by the optical interleave filter 7. As the optical interleave filter 7, a simple Mach-Zehnder interferometer (MZI) may be used, or a so-called interleaver having a sharp cutoff characteristic may be used. In order to further improve the extinction ratio, interleave filters may be connected in multiple stages.

(Third embodiment)
The third embodiment of the present invention is an embodiment according to an optical multicarrier generator. FIG. 9 shows a configuration example according to the third embodiment of the optical multicarrier generator of the present invention. In the configuration example according to the first embodiment shown in FIG. 1, an example in which four optical carriers are generated is shown, but in this configuration example, a configuration example in which the number of optical carriers is generalized is shown. Here, a configuration in which 2n optical carriers are generated using a drive signal of the zero chirp MZ type optical modulator 6 configured by the sum of n sine waves is shown.

The fundamental wave (frequency: f ₀ ) generated by the RF oscillator 1 is branched into n pieces, one is left as it is, and the remaining (n−1) pieces are third harmonic generators 12-3 to (2n). -1) Using the harmonic generator 12- (2n-1), the third harmonic is converted to the (2n-1) th harmonic (n is a natural number of 2 or more), and the fundamental wave is converted to the ( 2n-1) The n sine waves up to the second harmonic are added by the adder 13. The added signal is amplified by the modulator driver 4 to an amplitude that can drive the zero chirp MZ type optical modulator 6.

The zero chirp MZ type optical modulator 6 operates in the same manner as described with reference to FIGS. 3 to 5, and as a result, 2n optical multicarriers having a frequency interval of 2f ₀ can be generated. Of course, the optical interleave filter 7 may be inserted in the output stage as in the configuration example according to the second embodiment shown in FIG.

A configuration example of the (2n-1) th order harmonic generator 12- (2n-1) is shown in FIG. In this configuration, the (2n-3) th harmonic and the second harmonic generated from the fundamental wave by the (2n-3) th harmonic generator 121 and the second harmonic generator 120 are mixed with each other. Fill in 122, a sum frequency component output from the mixer 122 (2n-1) f ₀ and difference frequency components (2n-5) f ₀ Kazu Tonouchi frequency component (2n-1) f ₀ of the bandpass filter ( It can be generated by selecting with (BPF) 123. For example, when n = 2, the configuration is the same as that of the third-order harmonic generator shown in FIG. Since the (2n-3) -order harmonic generator 121 can be realized by a combination of a lower-order harmonic generator and a second-order harmonic generator, finally, the second-order harmonic generator, That is, all harmonics can be generated using only the frequency doubler.

(Fourth embodiment)
The fourth embodiment of the present invention is an embodiment according to an optical multicarrier generator. FIG. 11 shows a configuration example according to the fourth embodiment of the optical multicarrier generator of the present invention. In this configuration example, amplitude adjustment means 8 and delay adjustment means 9 are added to the configuration example according to the first embodiment shown in FIG. The role of the amplitude adjusting means 8 is to ensure the spectral flatness of the finally generated optical multicarrier by adjusting the amplitude ratio between the fundamental wave and the third harmonic.

  In general, the RF component has a higher loss as the frequency is higher, and the optical modulator has a lower modulation efficiency as the frequency is higher. Therefore, an optical multicarrier finally obtained by adding the fundamental wave and the third harmonic with the same power The spectral flatness of is reduced. Therefore, if the amplitude of the third harmonic is made larger than that of the fundamental wave in advance, it becomes possible to ensure the spectral flatness of the finally obtained optical multicarrier.

  In FIG. 11, the amplitude adjusting means 8 is inserted in the fundamental wave path, but of course, it may be inserted in the third harmonic path, or it may be inserted in both the fundamental and third harmonic paths. May be. The same applies to the case of 2n optical multicarrier generators using up to the (2n-1) th harmonic as shown in FIG. 9, and the amplitudes of the fundamental and each harmonic are arbitrarily adjusted. Thus, it is possible to ensure the spectral flatness of the finally obtained optical multicarrier.

  On the other hand, the role of the delay adjusting means 9 is to adjust the optical phase between the carriers of the finally obtained optical multicarrier. By adjusting the optical phase, it is possible to control coherent interference between optical multicarriers when data modulation is performed, and at the same time, it is possible to control the optical signal waveform of the entire optical multicarrier signal.

  As a result, the degree of freedom regarding the optimization of the transmission characteristics of the optical multicarrier signal can be increased, and as a result, an optical multicarrier signal closer to the optimum can be generated. In FIG. 11, the delay adjusting means 9 is inserted in the fundamental wave path, but of course, it may be inserted in the third harmonic path or in both the fundamental wave and third harmonic paths. May be.

  The same applies to the case of 2n optical multicarrier generators using up to the (2n-1) th harmonic as shown in FIG. 9, and the delay between the fundamental wave and each harmonic is arbitrarily adjusted. This makes it possible to control the optical phase between finally obtained optical multicarriers.

(Fifth embodiment)
The fifth embodiment of the present invention is an embodiment according to an optical multicarrier generator. FIG. 12 shows a configuration example according to the fifth embodiment of the optical multicarrier generator of the present invention. In this configuration example, a specific configuration example of an MZ type optical modulator capable of realizing zero chirp is shown. In principle, a zero chirp operation can be realized by driving the two-electrode drive MZ type optical modulator 16 with signals having the same amplitude, the phases of which are inverted from each other by using the inverting circuit R.

In order to realize the present invention, not limited to this configuration example, a zero-chirp MZ optical modulator may be used in principle. For example, an MZ type using an x-cut lithium niobate (LiNbO ₃ : LN) substrate. It can also be realized by an optical modulator or an MZ type optical modulator using a z-cut LN substrate whose polarization is reversed.

(Sixth embodiment)
The sixth embodiment of the present invention is an embodiment according to an optical multicarrier transmission apparatus. FIG. 13 shows a configuration example according to the sixth embodiment of the optical multicarrier transmission apparatus of the present invention. In this configuration example, an optical multicarrier modulator 30 is further provided in the configuration example according to the first embodiment of the optical multicarrier generator 10 of the present invention shown in FIG. The optical multicarrier modulator 30 in this configuration example includes an optical demultiplexing filter (DEMUX) 31, four data modulators 32-1 to 32-4, and an optical multiplexing filter (MUX) or an optical coupler 33.

  The four optical carriers generated by the optical multicarrier generator 10 are demultiplexed into four by the optical demultiplexing filter 31, and data modulation is performed by the individual data modulators 32-1 to 32-4, respectively. Thereafter, it is output as an optical multicarrier modulation signal recombined by the optical multiplexing filter or optical coupler 33.

  An optical multiplexing filter realized by an arrayed waveguide grating (AWG) or the like generated on a planar lightwave circuit (PLC) substrate is limited in the band of the optical modulation signal, but can suppress the crosstalk from the adjacent carrier signal low. it can.

  On the other hand, the optical coupler receives almost no crosstalk from the adjacent carrier signal, although the optical signal band is hardly limited. Which is adopted is determined in consideration of various factors such as the frequency interval of the multicarrier, the optical modulation format, the symbol rate of the optical modulation signal, and the allowable crosstalk amount.

  The multicarrier frequency interval and the symbol rate of the optical modulation signal may be arbitrarily determined. However, if the symbol rate is higher than the multicarrier frequency interval, interference from adjacent carrier signals cannot be suppressed in principle. Is set below the multicarrier frequency interval.

  The optical modulation format may be any modulation format such as NRZ intensity modulation (OOK), optical differential phase modulation (DPSK), optical differential quadrature phase modulation (DQPSK), optical quadrature amplitude modulation (QAM), and optical duobinary modulation (ODB). Good. The data # 1, # 2, # 3, and # 4 that drive the optical multicarrier modulator 30 may or may not be synchronized in bit phase. In the case of synchronization, the degree of freedom for controlling interference between multicarrier signals is increased.

  Further, the data # 1, # 2, # 3, and # 4 for driving the optical multicarrier modulator 30 may be synchronized with the sine wave output from the RF oscillator 1 constituting the optical multicarrier generator 10. However, they do not have to be synchronized. When synchronized, the degree of freedom for controlling interference between multicarrier signals is increased as in the case where the bit phases are synchronized with each other.

  Further, the optical phases of the respective optical carriers demultiplexed into four in the optical multicarrier modulator 30 may be synchronized or may not be synchronized. In the case of synchronization, the degree of freedom for controlling interference between multicarrier signals is increased. FIG. 14 shows an optical multicarrier signal spectrum when ODB modulation is actually applied. In FIG. 14, the horizontal axis represents wavelength and the vertical axis represents signal intensity.

  The multicarrier frequency interval is 25 GHz, which is the same as that shown in FIG. 6, and the symbol rate of the ODB signal is 25 Gsymbol / s (bit rate: 25 Gbit / s).

  In this configuration example, the case of 4 carriers is shown, but an optical multicarrier transmission apparatus of 2n carriers is configured using the optical multicarrier generation apparatus 10 that can generate 2n carriers as shown in FIG. You can also.

(Seventh embodiment)
The seventh embodiment of the present invention is an embodiment according to an optical multicarrier transmission apparatus. FIG. 15 shows a configuration example according to the seventh embodiment of the optical multicarrier transmission apparatus of the present invention. This configuration is different from the configuration example according to the sixth embodiment shown in FIG. 13 in that it includes a deserializer 40 of 1: 4, and four output signals from the deserializer 40 are four data of the optical multicarrier modulator 30. The modulators 32-1 to 32-4 are being driven. When a data signal (input data) to be transmitted to the optical multicarrier transmission apparatus is input serially, it is necessary to adopt the configuration shown here.

  Here, since the deserializer 40 uses the sine wave output from the RF oscillator 1-1 constituting the optical multicarrier generator 10-1, as the synchronous clock, all four data signals # 1 to # 4 are used. It is synchronized with the sine wave output from the RF oscillator 1-1. The advantages of being synchronized are as described above, but of course they need not be synchronized.

  In this configuration example, the case of 4 carriers is shown, but an optical multicarrier transmission device of 2n carriers is configured using the optical multicarrier generation device 10-1 capable of generating 2n carriers as shown in FIG. You can also

(Eighth embodiment)
The eighth embodiment of the present invention is an embodiment according to an optical multicarrier transmission apparatus. FIG. 16 shows a configuration example according to the eighth embodiment of the optical multicarrier transmission apparatus of the present invention. This configuration example is different from the configuration example according to the seventh embodiment shown in FIG. 15 in that the four data modulators 32-1 to 32-4 constituting the optical multicarrier modulator 30-1 are driven. Four phase shifters 41-1 to 41-4 for controlling the bit phase of two data signals are inserted, and four optical phase shifters 34 for controlling the optical phase between optical multicarriers. -1 to 34-4 are inserted.

  Here, the four data signals # 1 to # 4 that drive the data modulators 32-1 to 32-4 are synchronized, and it is possible to control interference between multicarriers by controlling the bit phase. The degree can be increased. In addition, the optical phases of the four optical carriers demultiplexed in the optical multicarrier modulator 30-1 are synchronized, and the degree of freedom to control the interference between the multicarriers is made possible by controlling the optical phase. Can be increased.

  In this configuration example, the case of 4 carriers is shown, but an optical multicarrier transmission device of 2n carriers is configured using the optical multicarrier generation device 10-1 capable of generating 2n carriers as shown in FIG. You can also

  INDUSTRIAL APPLICABILITY The present invention can be used to realize a low loss, small size, low cost optical multicarrier generator and an optical multicarrier transmitter using the same.

It is a figure which shows the structural example which concerns on 1st embodiment of the optical multicarrier generator of this invention. It is a figure which shows the structural example of a 3rd harmonic generator. It is a figure for demonstrating the operation | movement of a _zero chirp MZ type | mold optical modulator in detail, and is a figure which shows the operation | movement of a fundamental wave (frequency: f0). Zero Chirp is a diagram for explaining in detail the operation of the MZ-type optical modulator, the third harmonic (frequency: 3f ₀₎ is a diagram showing the operation of the drive. Zero Chirp is a diagram for explaining in detail the operation of the MZ-type optical modulator, shows how the two two linear addition signal of the optical carrier of the optical carrier frequency spacing 6f ₀ frequency interval 2f ₀ is obtained It is. It is a figure which shows the optical multicarrier produced | generated by actually driving the zero chirp MZ type | mold optical modulator with the synthetic signal of the fundamental wave of frequency 12.5GHz, and the 3rd harmonic of frequency 37.5GHz. It is a figure which shows the structural example which concerns on 2nd embodiment of the optical multicarrier generator of this invention. It is a figure which shows typically the relationship between the transmittance | permeability characteristic of an optical interleave filter, and an optical multicarrier frequency. It is a figure which shows the structural example which concerns on 3rd embodiment of the optical multicarrier generator of this invention. It is a figure which shows the structural example of a (2n-1) th order harmonic generator. It is a figure which shows the structural example which concerns on 4th embodiment of the optical multicarrier generator of this invention. It is a figure which shows the structural example which concerns on 5th embodiment of the optical multicarrier generator of this invention. It is a figure which shows the structural example which concerns on 6th Embodiment of the optical multicarrier transmission apparatus of this invention. It is a figure which shows the optical multicarrier signal spectrum when actually applying ODB modulation. It is a figure which shows the structural example which concerns on 7th Embodiment of the optical multicarrier transmission apparatus of this invention. It is a figure which shows the structural example which concerns on 8th embodiment of the optical multicarrier transmission apparatus of this invention. It is a figure which shows the structural example of the multicarrier light source which generates four optical carriers from the single wavelength light source in a prior art. It is a figure which shows the spectrum of the output light of the Mach-Zehnder type optical modulator of the front | former stage in FIG. 17, and the output light spectrum of the Mach-Zehnder type | mold optical modulator of a back | latter stage.

Explanation of symbols

1, 1-1 RF oscillator 2, 12-3 Third harmonic generator (RF signal generating means)
3, 13 Adder (RF signal generating means)
4, 4-1, 4-2 Modulator driver (zero chirp driving means)
5, 50 Continuous light source (continuous light generator)
6 Zero chirp MZ type modulator 7 Optical interleave filter 8 Amplitude adjustment means (amplitude ratio setting means)
9 Delay adjustment means (phase synchronization means, phase setting means)
10, 10-1 Optical multicarrier generator 12-5 Fifth harmonic generator (RF signal generating means)
12- (2n-1) 2nd harmonic generator (RF signal generating means)
16 2-electrode drive MZ type modulator 20 Second harmonic generator (RF signal generating means)
21 Band pass filters 22, 122 Mixer (RF signal generating means)
30, 30-1 Optical multicarrier modulator 31 Optical demultiplexing filter 32-1 to 32-4 Data modulator 33 Optical multiplexing filter or optical coupler 34-1 to 34-4 Optical phase shifter (phase synchronization means, phase setting) Means, optical phase control means)
40 Deserializer (synchronization means)
41-1 to 41-4, 53, 54 Phase shifter (phase synchronization means, phase setting means, bit phase control means)
51, 52 Mach-Zehnder type optical modulator 120 Second harmonic generator 121 Second (2n-3) harmonic generator 123 Band pass filter (BPF)
R Inversion circuit

Claims (10)

Continuous light generating means for generating continuous light;
A Mach-Zehnder light intensity modulator,
The fundamental wave and the third harmonic or al (2n-1) th harmonic components (n is a natural number of 2 or more) n-1 pieces of up to the n consisting of odd-order harmonics of the sum of a sine wave RF signal generating means for generating an RF (Radio Frequency) signal;
An optical multicarrier generator comprising: the Mach-Zehnder type optical intensity modulator, and zero chirp driving means for driving the RF signal with zero chirp centering on a point where the transmittance is minimized.   2. The optical multicarrier generator according to claim 1, further comprising amplitude ratio setting means for setting a ratio of amplitudes of the n sine waves.   3. The optical multicarrier generator according to claim 1, further comprising phase synchronization means for synchronizing the n sine waves with each other.   4. The optical multicarrier generator according to claim 3, further comprising phase setting means for setting the phase of the n sine waves. The RF signal generating means includes
An RF oscillator for generating the fundamental wave;
Using the fundamental wave generated by the RF oscillator as an input, a plurality of harmonics that generate n- 1 odd harmonics from the 3rd harmonic to the (2n-1) th harmonic in parallel A generator,
By adding the n- 1 odd harmonics from the third harmonic to the (2n-1) th harmonic generated by the plurality of harmonic generators and the fundamental wave, n sine An optical multicarrier generator according to any one of claims 1 to 4, further comprising: an adder that generates an RF signal that is a sum of waves .   The optical multicarrier generator according to any one of claims 1 to 5, further comprising an optical interleave filter having a free spectral range that is twice the frequency of the fundamental wave at the output of the Mach-Zehnder optical intensity modulator. . The optical multicarrier generator according to any one of claims 1 to 6,
An optical multicarrier transmitter comprising: an optical multicarrier modulator that performs data modulation on optical carriers having a plurality of wavelengths output from the optical multicarrier generator.   8. A synchronizing means for synchronizing a data signal input to the optical multicarrier modulator and the RF signal for driving the Mach-Zehnder optical intensity modulator constituting the optical multicarrier generator. Optical multicarrier transmitter.   9. The optical multicarrier transmission apparatus according to claim 7, wherein the optical multicarrier modulator includes optical phase control means for controlling an optical phase of each optical carrier.   The optical multicarrier transmission apparatus according to claim 7 or 8, wherein the optical multicarrier modulator includes bit phase control means for controlling a bit phase of a data signal for modulating each optical carrier.

Images