JP4963462B2 - Multi-wavelength light source device - Google Patents

Description

  The present invention relates to a phase-locked carrier light source for wavelength division multiplexing transmission signals in optical communication and a multi-wavelength light source device for use as a reference frequency light source having high coherence in optical frequency measurement.

  A multi-wavelength light source that simultaneously generates multi-wavelength light with line spectra arranged at equal intervals on the optical frequency axis is expected to be applied as a carrier light source for wavelength division multiplexing (WDM) transmission signals in optical communications. Yes.

  Advantages of adopting such a multi-wavelength light source as the carrier light source include, for example, the following. That is, it is possible to reduce the size of the apparatus as compared with the case where light sources are individually prepared according to the required number of wavelengths, and by using a frequency stabilized light source as a seed light source, It is possible to stabilize the frequency, which is useful for the realization of a robust photonic network, and because the phase relationship between each carrier light is fixed, the nonlinear phenomenon in the transmission optical fiber in wavelength division multiplexing transmission. For example, it is possible to compensate for induced interchannel crosstalk.

  The application of a multi-wavelength light source as an optical frequency ruler, that is, a reference frequency source having high coherence in optical frequency measurement is also being actively studied.

  Conventionally, as one technique for realizing a multi-wavelength light source, a configuration using a pulse light source with a repetition frequency fm and a nonlinear optical fiber (see Non-Patent Document 1) has been proposed. By adopting such a configuration, it is possible to generate supercontinuum light in which line spectra are arranged at intervals of the frequency fm, and to simultaneously obtain light having a large number of wavelengths.

  However, the nonlinear optical fiber has a special structure, and its design and manufacture are not easy. In addition, it is difficult to accurately predict the spectrum waveform of the obtained multi-wavelength light from the dispersion characteristics and nonlinear characteristics of the nonlinear optical fiber.

  On the other hand, as another conventional technique for realizing a multi-wavelength light source, a configuration in which a CW laser light source 110, a Mach-Zehnder intensity modulator 120, and a phase modulator 130 are combined as shown in FIG. 7 (for example, Patent Document 1, Non-Patent Document 2) has been proposed.

  In the example shown in FIG. 7, a sine wave electric signal having a predetermined frequency fm generated by the oscillator 140 is applied to the Mach-Zehnder intensity modulator 120, and a sine wave electric signal having a frequency fm generated by the oscillator 140 is applied to the phase modulator 130. The time position is adjusted by the shifter 160 and the power is appropriately adjusted by the amplifier 170 to be applied.

  The operating principle of the multi-wavelength light source device shown in FIG. 7 will be briefly described. The CW light output from the CW laser light source 110 and incident on the Mach-Zehnder intensity modulator 120 is converted into a pulse train having a repetition frequency fm and a duty ratio of about 50% by the Mach-Zehnder intensity modulator 120 and output. This pulse train is incident on the phase modulator 130 and is further subjected to sinusoidal phase modulation of the frequency fm by the phase modulator 130, whereby multi-wavelength light is obtained. The Mach-Zehnder intensity modulator 120 is driven by a sine wave electric signal having a frequency fm generated by the oscillator 140.

  FIG. 8 shows the calculation result of the multi-wavelength optical spectrum when the modulation index Δθ of the phase modulation in the configuration shown in FIG. 7 is 10π. In FIG. 8, each black circle indicates the intensity of each line spectrum. It can be seen from FIG. 8 that multi-wavelength light having a flat optical spectrum waveform can be obtained by the configuration shown in FIG.

  As the voltage amplitude of the sinusoidal electric signal input to the phase modulator 130 is increased and the modulation index Δθ is increased, the spectrum width of the multi-wavelength light is expanded while keeping the optical spectrum flat. Further, even if the positions of the Mach-Zehnder intensity modulator 120 and the phase modulator 130 in FIG. 7 are interchanged, the optical spectrum of the obtained multi-wavelength light is the same. The timing of phase modulation and intensity modulation is adjusted by the phase shifter 160 so that the maximum optical spectrum spread is obtained.

  FIG. 9 shows the relationship between the number of wavelengths and the modulation index Δθ of phase modulation. The black circles shown in FIG. 9 are the calculation results of the relationship between the number of wavelengths and the modulation index Δθ, and the solid line is the approximate straight line. As can be seen from FIG. 9, the number of wavelengths of the multi-wavelength light increases almost in proportion to the modulation index Δθ of the phase modulation.

  Further, in a multi-wavelength light source device using a modulator as shown in FIG. 7, the intensity of each line spectrum of multi-wavelength light can be analytically obtained from the modulation index of the modulator, so that the spectrum waveform can be accurately determined. The advantage is that it is easy to predict.

JP 2006-195499 A E. Yamada et al., "106 channel x 10 Gbit / s, 640 km DWDM transmission with 25 GHz spacing with supercontinuum multi-carrier source", Electron. Lett., Vol.37, no.25, p.1534-1536 , 2001 M.Doi et al., "Advanced LiNbO3 optical modulators for broadband optical communications", IEEE J. Selected Topics in Quantum Electronics, vol.12, no.4, p.745-750, 2006

  When a multi-wavelength light source is used as a carrier light source for wavelength division multiplex transmission signals, it is desirable that the larger the number of wavelengths that can be generated at one time, the smaller the device size required to generate one carrier light. When a multi-wavelength light source is used as a reference frequency light source in optical frequency measurement, the greater the number of wavelengths that can be generated at one time, the wider the optical frequency measurement becomes possible.

  For example, in the conventional multiwavelength light source device in which the CW light source 110, the Mach-Zehnder intensity modulator 120, and the phase modulator 130 shown in FIG. 7 are combined, the number of wavelengths increases substantially in proportion to the modulation index Δθ of the phase modulator 130.

Here, the modulation index Δθ has a relationship as shown in the following formula (1) between the amplitude V _a of the voltage of the sinusoidal electric signal applied to the modulator and the half-wave voltage Vπ of the phase modulator.

Since the modulation index Δθ is proportional to the voltage amplitude V _a of the sine wave electric signal as shown in the equation (1), it is necessary to increase the intensity of the sine wave signal input to the phase modulator in order to increase the number of wavelengths. There is.

  That is, for example, in Non-Patent Document 2 described above, a modulation index of 15π is realized by inputting a 10 GHz sine wave signal having a peak-to-peak voltage of 40 V to a phase modulator having a half-wave voltage of 1.3 V, and approximately 90 waves. However, in order to further increase the number of wavelengths, it is necessary to increase the voltage amplitude of the electric signal input to the phase modulator.

  However, considering the possibility of dielectric breakdown of the phase modulator, there is an upper limit to the input electric signal strength that can be applied. Therefore, for example, it can be said that it is not practical to increase the number of wavelengths by 10 times by inputting an electric signal having a voltage amplitude of 10 times to the phase modulator.

  Further, as a technique for increasing the number of wavelengths of multi-wavelength light, in addition to the technique for increasing the voltage amplitude of the electric signal input to the phase modulator described above, FIG. 16 (eighth embodiment) of Patent Document 1 is shown. As described above, there is a method of using a plurality of phase modulators and inputting modulation signals having the same frequency to them. According to such a method, it is possible to obtain about X times the number of wavelengths by increasing the number of phase modulators to X with the voltage amplitude of the electric signal input to the phase modulator being the same.

  However, in this case, it is necessary to control all the modulation timings in the X phase modulators with a phase shifter or the like, which complicates the apparatus configuration. Further, the excess loss of the phase modulator is added by X units, which may lead to deterioration of the carrier-to-noise ratio of multiwavelength light. Therefore, it can be said that, for example, a method of increasing the number of wavelengths 10 times by using 10 phase modulators with X = 10 is not realistic.

  The present invention has been made in view of the above circumstances, and in a multi-wavelength light source device that combines a CW light source, a Mach-Zehnder intensity modulator, and a phase modulator, the input electric signal intensity to the phase modulator is input to the modulator. An object of the present invention is to provide a multi-wavelength light source device that can keep the number smaller than the limit and can increase the number of wavelengths much more efficiently than the number of modulators.

A multi-wavelength light source device according to a first invention for solving the above-described problems includes a laser light source that generates laser light as input light, phase modulation means that applies phase modulation to the input light, and the input F ₁ , f ₂ ,..., F _i satisfying the relationship of intensity modulation means for applying intensity modulation to light and f _i = n × f _{i + 1} (i is a natural number, n is a natural number of 2 or more). ,..., F _N multi-wavelength light source devices each including N electrical signal generating means for generating electrical signals having N types of frequencies (N is a natural number of 2 or more), wherein the phase modulation means and The intensity modulation means is connected in series to the laser light source in any order, and the phase modulation means changes the optical phase of the output light in proportion to the sum of the N types of electric signals generated by the electric signal generation means. Phase modulation is performed so that the intensity modulation means has a light intensity of the output light And performing intensity modulation so as to change in proportion to the product of the N types of electric signals generated by the electrical signal generating means.

A multi-wavelength light source device according to a second invention for solving the above-mentioned problems is the first invention, wherein the phase modulation means comprises N phase modulators, and the intensity modulation means comprises N intensity modulations. The N phase modulators and the N intensity modulators are connected in series in an arbitrary order, the i-th phase modulator of the N phase modulators, and the N number of phase modulators. the i-th intensity modulator of the intensity modulator, characterized in that the electrical signal of the frequency f _i from the electric signal generator is input as a modulation signal.

A multi-wavelength light source device according to a third aspect of the present invention for solving the above-described problems is the first aspect, wherein one phase modulator as the phase modulation means and N intensities as the intensity modulation means A modulator and multiplexing means for multiplexing the electrical signals of the N types of frequencies, wherein the phase modulator and the N intensity modulators are connected in series in an arbitrary order, and the phase modulator The N frequency electrical signals combined by the multiplexing means are input as modulation signals, and the i-th intensity modulator of the N intensity modulators is supplied from the electric signal generator. An electrical signal having a frequency f _i is input as a modulation signal.

A multi-wavelength light source device according to a fourth aspect of the present invention for solving the above-mentioned problems is the first aspect, wherein the N phase modulators as the phase modulation means and one intensity as the intensity modulation means A modulator and multiplication means for multiplying the electrical signals of N kinds of frequencies, wherein the N phase modulators and the intensity modulators are connected in series in an arbitrary order, the i th phase modulator of the phase modulator electrical signal having a frequency f _i from the electric signal generator is input as a modulation signal, wherein N is further said intensity modulator multiplied by said multiplication means It is characterized in that electrical signals of various frequencies are input as modulation signals.

  A multi-wavelength light source device according to a fifth aspect of the present invention for solving the above-mentioned problems is the first aspect, wherein one phase modulator as the phase modulating means and one intensity as the intensity modulating means. A modulator; a multiplexing unit that multiplexes the electrical signals of the N types of frequencies; and a multiplying unit that multiplies the electrical signals of the N types of frequencies, and the phase modulator and the intensity modulator Are connected in series in an arbitrary order, and the phase modulator receives the N kinds of electrical signals combined by the combining means as modulation signals, and the intensity modulator further includes the multiplying means. The electrical signals of the N kinds of frequencies multiplied by the above are input as modulation signals.

  6. The multi-wavelength light source device according to claim 4, wherein the multiplication means is configured using a double balanced mixer.

  According to the present invention, in a multi-wavelength light source device combining a CW laser light source, a Mach-Zehnder intensity modulation means, and a phase modulation means, a very large intensity modulation electric signal is not input to the phase modulation means, and a very large number The number of wavelengths can be remarkably increased without installing a phase modulation means.

  Conventionally, the maximum number of output wavelengths reported in a multi-wavelength light source device combining a CW laser light source, a Mach-Zehnder intensity modulation unit, and a phase modulation unit is about 90 waves reported in Non-Patent Document 2, The invention makes it possible to provide a multi-wavelength light source device that can significantly increase the number of wavelengths with excellent efficiency and can easily realize ten times the number of wavelengths of 900 waves or more.

The present invention relates to a laser light source that generates laser light as input light, phase modulation means that applies phase modulation to the input light, intensity modulation means that applies intensity modulation to the input light, and f _i = n × f _{i +} 1 _(i is a natural number, n represents a natural number of 2 or more) f _1, f ₂ satisfies the _{relationship, ···, f i, ···,} n types of f _n (n is a natural number of 2 or more) And N electrical signal generating means for generating electrical signals of the respective frequencies, the phase modulating means and the intensity modulating means are connected in series to the laser light source in an arbitrary order, and the phase modulating means is the optical phase of the output light. Is phase-modulated so as to change in proportion to the sum of the N types of electric signals generated by the electric signal generating means, and the intensity modulating means generates N types of electric lights whose output light intensity is generated by the electric signal generating means. The intensity modulation is performed so as to change in proportion to the product of the signals.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram illustrating an example of a multi-wavelength light source device according to the present embodiment. FIG. 2 is an explanatory diagram schematically illustrating a spectrum of multi-wavelength light obtained by the multi-wavelength light source device according to the present embodiment. These are graphs showing the relationship between the optical frequency of the spectrum of the multi-wavelength light obtained by the multi-wavelength light source device according to this embodiment and the light intensity.

The multi-wavelength light source device of this embodiment uses CW laser light output from a CW laser light source as seed light, Mach-Zehnder intensity modulators as N (N is a natural number of 2 or more) intensity modulation means, F ₁ , f satisfying the relationship of f _i = n × f _{i + 1} (i is a natural number satisfying 1 ≦ i ≦ N−1, and n is a natural number of 2 or more). ₂ ,..., F _i ,..., F _N using N types of electrical signals generated by synthesizers as N electrical signal generators that generate electrical signals of N types of frequencies, respectively, as modulation signals. The multi-wavelength light is generated by performing the intensity modulation by the Mach-Zehnder intensity modulator and the phase modulation by the phase modulator.

Specifically, two Mach-Zehnder intensity modulators, two phase modulators, and two units that generate electric signals of two types of frequencies f ₁ and f ₂ that satisfy the relationship of f ₁ = 30 × f ₂ , respectively. A configuration in which multi-wavelength light having a wavelength of about 900 waves is generated by using the synthesizer will be described. The first phase modulator of the two phase modulators and the first intensity modulator of the two intensity modulators modulate the electric signal of the frequency f ₁ from the electric signal generator. An electric signal having a frequency f ₂ from an electric signal generator is input as a modulation signal to the second phase modulator and the second intensity modulator.

  Describing in more detail using FIG. 1, two Mach-Zehnder intensity modulators 21 and 22 and two phase modulators 31 and 32 are alternately arranged in a CW laser light source 10 having a single central wavelength. And connected in series.

  A preceding Mach-Zehnder intensity modulator (hereinafter referred to as a first Mach-Zehnder intensity modulator) 21 is repeated at a predetermined cycle (30 GHz in this embodiment) generated by the first synthesizer 41 as an electric signal generator. The signal voltage is configured to be input via the first power distributor 51, the first phase shifter 61a, and the first amplifier 71a. Similarly, the signal voltage generated by the first synthesizer 41 is supplied to the preceding phase modulator (hereinafter referred to as the first phase modulator) 31 from the first power distributor 51 and the second phase shifter 61b. The signal is input via the second amplifier 71b.

  The subsequent Mach-Zehnder intensity modulator (hereinafter referred to as a second Mach-Zehnder intensity modulator) 22 is repeated at a predetermined cycle (1 GHz in this embodiment) generated by the second synthesizer 42 as an electric signal generator. The signal voltage is configured to be input via the second power distributor 52, the third phase shifter 62, and the third amplifier 72a. Similarly, the signal voltage generated by the second synthesizer 42 is supplied to the second power distributor 52 and the fourth amplifier 72b in the subsequent phase modulator (hereinafter referred to as the second phase modulator) 32. Input.

  The power distributors 51 and 52 perform power distribution of electrical signals from the synthesizers 41 and 42, the phase shifters 61a, 61b, and 62 are time positions, and the amplifiers 71a, 71b, 72a, and 72b are powers of signal voltages, respectively. Adjust as appropriate. Further, it is assumed that the first synthesizer 41 and the second synthesizer 42 are synchronized by a synchronization clock. The multi-wavelength light source device of the present embodiment includes a DC bias power source that applies an appropriate DC bias voltage to the Mach-Zehnder intensity modulators 21 and 22 (not shown).

  In the multi-wavelength light source device of the present embodiment, the light from the CW laser light source 10 enters the first Mach-Zehnder intensity modulator 21 and is intensity-modulated with a 30 GHz sine wave signal, and then further by the first phase modulator 31. By applying sine wave phase modulation of 30 GHz, multi-wavelength light having a frequency interval of 30 GHz is generated.

  Here, the intensity modulation of 30 GHz is performed by changing the DC bias and the modulated electric signal intensity input to the first Mach-Zehnder intensity modulator 21 so that the time waveform has a repetition frequency of the output pulse light of 30 GHz and a duty ratio of about 50%. This is done by setting. The modulation index of 30 GHz sine wave phase modulation is set to about 4.7π.

With this setting, as shown in FIG. 9, 31 multi-wavelength lights can be generated.
The multi-wavelength light having the frequency interval of 30 GHz and 31 waves is further subjected to 1 GHz intensity modulation by the second Mach-Zehnder intensity modulator 22 and 1 GHz phase modulation by the second phase modulator 32.

  Here, the intensity modulation of 1 GHz is such that when CW light having one wavelength is incident on the second Mach-Zehnder intensity modulator 22, a time waveform with a repetition frequency of the output pulse light of 1 GHz and a duty ratio of about 50% is obtained. In addition, the DC bias and the modulated electric signal intensity input to the second Mach-Zehnder intensity modulator 22 are set. The modulation index of 1 GHz sinusoidal phase modulation is set to about 4.7π.

  Note that the timing of each intensity modulation and phase modulation is adjusted by the phase shifters 61a, 61b, 62 so that the maximum optical spectrum spread is obtained.

  With such a setting, it is possible to newly generate multi-wavelength light of 1 GHz interval and 31 waves from each of 30-GHz space and 31 multi-wavelength light output from the first phase modulator 31.

  FIG. 2A shows the optical spectrum output from the first phase modulator 31 when CW light of one wavelength is input from the CW laser light source 10 to the first Mach-Zehnder intensity modulator 21 in this embodiment. FIG. 2B is a schematic diagram showing the optical spectrum output from the second phase modulator 32 when CW light having one wavelength is input to the second Mach-Zehnder intensity modulator 22 in this embodiment. FIG. 2C is a schematic diagram for the first Mach-Zehnder intensity modulator 21, the first phase modulator 31, the second Mach-Zehnder intensity modulator 22, and the second phase modulator 32 in this embodiment. When the CW light having one wavelength is input to the first Mach-Zehnder intensity modulator 21 with 30 GHz and 1 GHz modulation, the spectrum of the multiwavelength light finally output from the second phase modulator 32 is obtained. Show schematic To have.

  2A, when CW light having one wavelength is input from the CW laser light source 10 to the first Mach-Zehnder intensity modulator 21, 31 multi-wavelength light is emitted from the first phase modulator 31 at intervals of 30 GHz. It can be seen that it occurs.

  Further, from FIG. 2B, when CW light having one wavelength is input to the second Mach-Zehnder intensity modulator 22, 31 multi-wavelength light is generated from the second phase modulator 32 at intervals of 1 GHz. I understand that

  From FIG. 2 (c), the gap between the various spectra of the 31-wave multi-wavelength light generated by the first Mach-Zehnder intensity modulator 21 and the first phase modulator 31 is the second Mach-Zehnder intensity. It can be seen that it is filled with a line spectrum of 1 GHz intervals generated using the modulator 22 and the second phase modulator 32.

Here, the modulation frequency (hereinafter referred to as the previous modulation frequency) applied to the first Mach-Zehnder intensity modulator 21 and the first phase modulator 31 is f _F , and the first Mach-Zehnder intensity modulator 21 and the first phase. The number of wavelengths generated by the modulator 31 (hereinafter referred to as the number of wavelengths generated in the preceding stage) is N _F , and the modulation frequency applied to the second Mach-Zehnder intensity modulator 22 and the second phase modulator 32 (hereinafter referred to as the subsequent stage modulation). the) that the frequency f _L, the second Mach-Zehnder intensity modulator 22 and the number of wavelengths that occur when you enter a CW light of the second phase modulator 32 to one wavelength (hereinafter, referred to as the number of wavelengths generated at the later stage) Is N _L.

When the ratio f _F / f _L of the modulation frequency of the front stage and the rear stage is an even number, the gap on the optical frequency axis of the multi-wavelength light generated by the first Mach-Zehnder intensity modulator 21 and the first phase modulator 31 is determined. In order to fill with multi-wavelength light generated by the Mach-Zehnder intensity modulator and the phase modulator in the subsequent stage, it is desirable that the value of the number of wavelengths N _L generated in the subsequent stage is about f _F / f _L +1.

In this case, the total number of wavelengths _NT obtained by the Mach-Zehnder intensity modulator and the phase modulator at the front stage and the rear stage is expressed by the following equation (2).

N _T = N _F + (N _F −1) × (N _L −2) + (N _L −1) (2)

Further, when the ratio f _F / f _L of the modulation frequency at the front stage and the rear stage is an odd number, the multi-wavelength light generated by the first Mach-Zehnder intensity modulator 21 and the first phase modulator 31 on the optical frequency axis. In order to fill the gap with the multi-wavelength light generated by the second Mach-Zehnder intensity modulator 22 and the second phase modulator 32, the value of the number of wavelengths N _L generated in the subsequent stage is about f _F / f _L. It is desirable.

In this case, the total number of wavelengths _NT obtained by the Mach-Zehnder intensity modulator and the phase modulator in the former stage and the latter stage is expressed by the following equation (3).

N _T = N _F + (N _F −1) × (N _L −1) + (N _L −1) (3)

In this embodiment, the front stage of the modulation frequency f _F = 30 GHz, since a subsequent stage of the modulation frequency is at f _L = 1 GHz, the ratio f _F / f _L of front and rear stages of the modulation frequency is an even a 30. Further, the number of wavelengths generated in the front stage is N _F = 31 waves, and the number of wavelengths generated in the rear stage is N _L = 31 waves. Therefore, it can be seen that the total number of wavelengths _NT shown in FIG. 2 (c) is 931 waves from the equation (2).

FIG. 3 shows the spectrum of the multi-wavelength light obtained by the multi-wavelength light source device of the present embodiment by computer simulation. FIG. 3 (a) shows the entire optical spectrum, and FIG. The optical spectrum near the center is enlarged. The optical frequency of the CW light source is set to 193.4 THz (wavelength: 1550.116 nm), the modulation index of the first and second phase modulators 31 and 32 is both 4.7π, and the first Mach-Zehnder intensity modulator. The modulation frequency f _F of 21 and the first phase modulator 31 is set to 30 GHz, and the modulation frequency f _L of the second Mach-Zehnder intensity modulator 22 and the second phase modulator 32 is set to 1 GHz.

  From FIG. 3A, it can be seen that the spectrum spread of multi-wavelength light extends over 900 GHz. Further, it can be seen from FIG. 3B that multi-wavelength light is generated at a frequency interval of 1 GHz. As shown in these figures, it was confirmed by this computer simulation that multiwavelength light of 900 waves or more can be obtained.

  Further, assuming that the half-wave voltages of the phase modulators 31 and 32 used in this embodiment are the same as the value 1.3 V of the phase modulator used in Non-Patent Document 2, the modulation index of phase modulation is used. The voltage required to realize 4.7π is 12.2 V (+25.7 dBm), which is sufficiently smaller than the input limit of the phase modulator.

  Conventionally, the maximum number of output wavelengths reported in a multi-wavelength light source device combining a CW laser light source, a Mach-Zehnder intensity modulator, and a phase modulator is about 90 waves reported in Non-Patent Document 2, With the configuration shown in the embodiment, it is possible to increase the number of wavelengths in a state of extremely excellent efficiency, and it is possible to easily realize the number of wavelengths of 900 waves or more, which is ten times that of the prior art. That is, it is possible to generate light having a very large number of wavelengths without excessively increasing the electric signal input to the phase modulator.

In the present embodiment, the combination of [MZ intensity modulator + phase modulator] shows an example of connecting two stages, the number of connection stages N _S further increases and prepared the number of modulated signals corresponding thereto By doing so, it is possible to remarkably increase the total number of wavelengths _NT . Approximate relationship of the connection number N _S and the total number of wavelengths N _T is expressed by the following equation (4).

However, N _PS is the number of generated wavelengths per combination of [Mach-Zehnder intensity modulator + phase modulator].

Conventionally, as shown in FIG. 16 (eighth embodiment) of Patent Document 1, in a method in which a plurality of phase modulators are used and a modulation signal having the same frequency is input thereto, the number of wavelengths _NT is phase modulated. It is known that it increases in proportion to the number of stages of the vessel. On the other hand, in the configuration of the present embodiment, the total number of wavelengths _NT increases exponentially as the number of connection stages in the combination of [Mach-Zehnder intensity modulator + phase modulator] increases (4 ).

  In the present embodiment, the configuration in which the phase modulator is arranged in the subsequent stage of the Mach-Zehnder intensity modulator in the combination of [Mach-Zehnder intensity modulator + phase modulator] in each stage is shown. Light is obtained. Moreover, although the example which inserts a phase shifter in the Mach-Zehnder intensity | strength modulators 21 and 22 and the phase modulator 31 was shown in the present Example, the modulator which inserts a phase shifter is not restricted to what was shown in FIG. However, it is preferable to select a modulator that needs to give a large modulation signal as a modulator that does not insert a phase shifter.

  A second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a configuration diagram illustrating an example of the multi-wavelength light source device according to the present embodiment.

  As shown in FIG. 4, the present embodiment uses one phase modulator 30 instead of the two phase modulators 31 and 32 in the first embodiment, and provides a multiplexer 80 as a multiplexing means. In this example, a signal obtained by combining the 30 GHz modulation signal and the 1 GHz modulation signal by the multiplexer 80 is input to the phase modulator 30. Other configurations are substantially the same as those shown in FIG. 1 and described above, and members having the same functions are denoted by the same reference numerals, and redundant description is omitted.

  The multi-wavelength light spectrum obtained by the configuration of this embodiment shown in FIG. 4 is the same as the multi-wavelength light spectrum obtained by the configuration of Embodiment 1 shown in FIG.

  In the present embodiment, the configuration in which the phase modulator 30 is arranged in two stages, that is, after the first and second Mach-Zehnder intensity modulators 21 and 22, is shown. However, the phase modulator 30 has two stages of Mach-Zehnder. It may be inserted before the intensity modulators 21 and 22, or between the first Mach-Zehnder intensity modulator 21 and the second Mach-Zehnder intensity modulator 22, and in either case, it is the same as the output light obtained in this embodiment. Output light can be obtained.

  In this embodiment, the combination of two Mach-Zehnder intensity modulators and one phase modulator is used. However, the number of modulation signals, the number of connection stages of the Mach-Zehnder intensity modulators, and the combination of the modulation signals input to the phase modulators. By increasing the wave number in the same manner, the total number of wavelengths can be significantly increased.

  A third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a configuration diagram illustrating an example of the multi-wavelength light source device according to the present embodiment.

  As shown in FIG. 5, the present embodiment uses one Mach-Zehnder intensity modulator 20 instead of the two Mach-Zehnder intensity modulators 21 and 22 in the first embodiment, and also includes a multiplier 90 as multiplication means. In this example, a signal obtained by multiplying the 30 GHz modulation signal and the 1 GHz modulation signal by the multiplier 90 is input to the Mach-Zehnder intensity modulator 20. For example, a double balanced mixer can be used as a component for multiplying a plurality of modulation signals. Other configurations are substantially the same as those shown in FIG. 1 and described above, and members having the same functions are denoted by the same reference numerals, and redundant description is omitted.

  The multi-wavelength light spectrum obtained by the configuration of this embodiment shown in FIG. 5 is the same as the multi-wavelength light spectrum obtained by the configuration of Embodiment 1 shown in FIG.

  In this embodiment, the Mach-Zehnder intensity modulator 20 is arranged in two stages, that is, before the first and second phase modulators 31 and 32. However, the Mach-Zehnder intensity modulator 20 has two stages. It may be inserted after the phase modulators 31 and 32, or between the first phase modulator 31 and the second phase modulator 32. In either case, the output is the same as the output light obtained in this embodiment. Light can be obtained.

  In this embodiment, a combination of one Mach-Zehnder intensity modulator and two phase modulators is used. However, the number of modulation signals, the number of connection stages of the Mach-Zehnder intensity modulator, and the combination of the modulation signals input to the phase modulator are also described. By increasing the wave number in the same manner, the total number of wavelengths can be significantly increased.

  A fourth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a configuration diagram illustrating an example of the multi-wavelength light source device according to the present embodiment.

  As shown in FIG. 6, in this embodiment, instead of the two Mach-Zehnder intensity modulators 21 and 22 and the two phase modulators 31 and 32 in the first embodiment, one Mach-Zehnder intensity modulator 20 and A single phase modulator 30 is used, and a multiplier 90 and a multiplexer 80 are provided, and a signal obtained by multiplying the 30 GHz modulation signal by the 1 GHz modulation signal by the multiplier 90 is input to the Mach-Zehnder intensity modulator 20. In this example, a signal obtained by combining the 30 GHz modulation signal and the 1 GHz modulation signal by the multiplexer 80 is input to the phase modulator 30. For example, a double balanced mixer can be used as a component for multiplying a plurality of modulation signals. Other configurations are substantially the same as the configurations shown in FIG. 1 or FIG. 4, and members having the same functions are denoted by the same reference numerals, and redundant description is omitted.

  The multi-wavelength light spectrum obtained by the configuration of this embodiment shown in FIG. 6 is the same as the multi-wavelength light spectrum obtained by the configuration of Embodiment 1 shown in FIG.

  In the present embodiment, the configuration in which the phase modulator 30 is arranged after the Mach-Zehnder intensity modulator 20 is shown, but the same output light can be obtained even if this order is changed. Further, in this embodiment, two modulation signals generated by the first synthesizer 41 and the second synthesizer 42 are incident on each of the Mach-Zehnder intensity modulator 20 and the phase modulator 30. The number of wavelengths can be remarkably increased by increasing the number of.

(Other examples)
In the above description, the preferred embodiments of the present invention have been illustrated and described. However, the present invention is not limited to the above embodiments, and the constituent members and the like are within the scope of the claims. Various modifications such as replacement, change, addition, increase / decrease in number, shape design change, and setting parameter change are all included in the embodiments of the present invention.

  The present invention is applicable to a phase-locked carrier light source for wavelength division multiplexing transmission signals in optical communication and a multi-wavelength light source device for use as a reference frequency light source having high coherence in optical frequency measurement.

It is a figure which shows the 1st Example of the multiwavelength light source device of this invention. It is a figure which shows typically the multiwavelength light spectrum in the 1st Example of the multiwavelength light source device of this invention. It is a figure which shows the result of the computer simulation of the multiwavelength light spectrum in 1st Example of the multiwavelength light source device of this invention. It is a figure which shows the 2nd Example of the frequency stabilization light source of this invention. It is a figure which shows the 3rd Example of the frequency stabilization light source of this invention. It is a figure which shows the 4th Example of the frequency stabilization light source of this invention. It is a block diagram which shows the structural example of the prior art of a CW light source. It is a figure of the calculation result which shows the example of the output light spectrum in the multiwavelength light source device which combined the CW light source, the Mach-Zehnder intensity modulator, and the phase modulator. It is a figure which shows the calculation result of the relationship between the number of wavelengths and the modulation index of a phase modulation in the multiwavelength light source device which combined the CW light source, the Mach-Zehnder intensity modulator, and the phase modulator.

Explanation of symbols

10 CW laser light source 20, 21, 22 Mach-Zehnder intensity modulator 30, 31, 32 Phase modulator 41, 42 Synthesizer 51, 52 Power distributor 61a, 61b, 62 Phase shifter 71a, 71b, 72a, 72b Amplifier 80 Multiplexer 90 multiplier

Claims (6)

A laser light source that generates laser light as input light;
Phase modulation means for applying phase modulation to the input light;
Intensity modulation means for applying intensity modulation to the input light;
_{f i = n × f i +} 1 (i is a natural number, n represents a natural number of 2 or more) f _1, f ₂ satisfies the relationship, ···, f _i, ···, an N type (N of f _N A multi-wavelength light source device comprising N electrical signal generating means for generating electrical signals having a frequency of 2 or more natural numbers,
The phase modulation means and the intensity modulation means are connected in series to the laser light source in any order,
The phase modulation means performs phase modulation so that the optical phase of the output light changes in proportion to the sum of the N types of electric signals generated by the electric signal generation means,
The multi-wavelength light source apparatus characterized in that the intensity modulation means performs intensity modulation so that the light intensity of output light changes in proportion to the product of the N types of electric signals generated by the electric signal generation means. The phase modulation means comprises N phase modulators;
The intensity modulation means comprises N intensity modulators;
The N phase modulators and the N intensity modulators are connected in series in any order,
The i-th phase modulator of the N phase modulators and the i-th intensity modulator of the N intensity modulators _receive an electrical signal having a frequency fi from the electrical signal generator. The multiwavelength light source device according to claim 1, wherein the multiwavelength light source device is input as a modulation signal. One phase modulator as the phase modulation means;
N intensity modulators as the intensity modulation means;
Combining means for combining the electrical signals of the N types of frequencies,
The phase modulator and the N intensity modulators are connected in series in any order,
The phase modulator receives the N types of electric signals combined by the combining means as modulation signals,
Furthermore the N to i-th intensity modulator of the intensity modulator the electrical electrical signal of a frequency f _i from the signal generator to be input multiple of claim 1, wherein the modulated signal Wavelength light source device. N phase modulators as the phase modulation means;
One intensity modulator as the intensity modulating means;
Multiplying means for multiplying the electrical signals of the N types of frequencies,
The N phase modulators and the intensity modulator are connected in series in any order,
Wherein the i th phase modulator of the N phase modulators electrical signal having a frequency f _i from the electric signal generator is input as a modulation signal,
The multi-wavelength light source device according to claim 1, wherein the N-frequency electrical signals multiplied by the multiplication unit are input as modulation signals to the intensity modulator. One phase modulator as the phase modulation means;
One intensity modulator as the intensity modulating means;
A multiplexing means for multiplexing the electric signals of the N types of frequencies;
Multiplying means for multiplying the electrical signals of the N types of frequencies,
The phase modulator and the intensity modulator are connected in series in any order,
The phase modulator receives the N types of electric signals combined by the combining means as modulation signals,
The multi-wavelength light source device according to claim 1, wherein the N-frequency electrical signals multiplied by the multiplication unit are input as modulation signals to the intensity modulator.   6. The multi-wavelength light source device according to claim 4, wherein the multiplication means is configured using a double balanced mixer.

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