JP3694638B2 - Coherent multiwavelength signal generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coherent multi-wavelength signal generator that spectrally slices coherent multi-wavelength light output from a multi-wavelength light source, modulates coherent light of each wavelength with a plurality of optical modulators, and multiplexes and outputs the result. In particular, the present invention relates to a coherent multi-wavelength signal generator that controls the optical spectrum shape of multi-wavelength light output from a multi-wavelength light source so that the input / output noise characteristics of the optical modulator become a design value.
[0002]
[Prior art]
FIG. 17 shows a configuration example of a conventional wavelength division multiplexing transmission system. In the figure, the optical transmitter 50 includes semiconductor lasers (for example, distributed feedback laser: DFB-LD) 51-1 to 51-n having different wavelengths defined by transmission specifications (for example, ITU-T G.692 recommendation). An optical modulator 52-1 to 52-n that modulates the output light of each semiconductor laser with a transmission signal, a multiplexer 53 that combines the modulated signal light and outputs wavelength multiplexed signal light, and an optical amplifier 54. An optical receiver 70 connected to the optical transmitter 50 via the transmission line optical fiber 60, an optical amplifier 71 that amplifies the transmitted wavelength multiplexed signal light, and demultiplexes the wavelength multiplexed signal light into signal light of each wavelength. And a receiver 73-1 to 73-n for receiving signal light of each wavelength.
[0003]
Here, the semiconductor laser has the property that the oscillation wavelength shifts due to changes in temperature and injection current, and the oscillation wavelength changes with time. Circuit is required. Since this wavelength stabilization needs to be performed for each semiconductor laser, the ratio of the wavelength stabilization circuit to the entire device increases as the number of wavelength multiplexing increases and the wavelength multiplexing interval increases in density. become.
[0004]
For such a configuration using a plurality of semiconductor lasers, there is a method of generating light of a plurality of wavelengths by filtering (spectral slicing) multi-wavelength light having a flat light spectrum with a demultiplexer. As a light source that generates this multi-wavelength light, there are a light source that uses amplified spontaneous emission light (ASE light) output from an optical fiber amplifier and a light source that repeatedly uses short light pulses. However, light obtained by spectrally slicing ASE light is incoherent light and is not suitable for high-density, multi-wavelength wavelength multiplex transmission.
[0005]
On the other hand, when using short optical pulses repeatedly, in order to eliminate the power level deviation of each wavelength channel after spectrum slicing, for example, optical spectrum flattening accompanying wideband spectrum generation by supercontinuum generation by nonlinear optical fiber transmission There have been proposed a method of performing optical spectrum flattening by suppressing power level deviation using an optical filter having an inverse characteristic.
[0006]
[Problems to be solved by the invention]
However, in the flattening associated with supercontinuum generation, the dispersion profile and the fiber length of the nonlinear optical fiber to be used are designed so that the spectrum of a given seed pulse becomes wide and flat. For this reason, the obtained optical spectrum shape is determined by the characteristics of the nonlinear optical fiber, and the power level deviation of each mode cannot be dynamically controlled. In addition, in flattening using an optical filter with reverse characteristics, the optical spectrum shape after transmission through the optical filter is determined by the transmission characteristics of the optical filter, and the power level deviation of each mode can be controlled dynamically as well. There wasn't.
[0007]
On the other hand, light having a single central wavelength can be modulated with an electrical signal having a specific repetition period to generate multiwavelength light with a flattened optical spectrum, and the shape of the optical spectrum (each mode). Multi-wavelength light source (optical spectrum flattening method and optical spectrum flattening device (Japanese Patent Application No. 2000-207475), multi-wavelength batch generation device (Japanese Patent Application No. 2000-207494)), which can be controlled "Application" is filed.
[0008]
The present invention generates performance of multi-wavelength light using a multi-wavelength light source of the prior application, and has a performance specification required for an optical transmitter using a conventional semiconductor laser in a configuration capable of controlling the optical spectrum shape of the multi-wavelength light. An object of the present invention is to provide a coherent multi-wavelength signal generator that can be designed to match the above.
[0009]
[Means for Solving the Problems]
The coherent multi-wavelength signal generator according to the present invention relates to the relative intensity noise RIN of the optical modulator input or the signal-to-noise ratio SNR of the optical modulator output that modulates the coherent light of each wavelength obtained by spectral slicing the multi-wavelength light. The optical spectrum shape of the multi-wavelength light is controlled so as to obtain a predetermined RIN or SNR required from the parameters of the transmission system (type of optical fiber, distance, number of relay stages) .
[0010]
The multi-wavelength light source includes a light source that generates light having a single center wavelength, and an optical modulator that generates multi-wavelength light by intensity-modulating or phase-modulating the output light with a predetermined periodic signal. adjust the voltage or bias voltage of the optical modulator, which is configured to control the optical spectral shape of the multi-wavelength light generated (claim 1).
[0011]
Moreover, multi-wavelength light source is configured to control the multi-wavelength light of the light spectrum shape which occurs by controlling the phase of the periodic signal (claim 2). Moreover, multi-wavelength light source is configured to control the multi-wavelength light of the light spectrum shape which occurs by controlling the multiplication number of the periodic signal frequency (Claim 3).
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a first embodiment of a coherent multi-wavelength signal generator according to the present invention. In the figure, a coherent multiwavelength signal generator includes a multiwavelength light source 11 of the prior application, a duplexer 12 that spectrally slices multiwavelength light into each wavelength, and an optical modulator 52 that modulates each spectral slice light with a transmission signal. -1 to 52-n, a multiplexer 53 that combines each modulated signal light and outputs a coherent multiwavelength signal, an optical amplifier 54, and a part of the multiwavelength light output from the multiwavelength light source 11. The optical spectrum of the multi-wavelength light source 11 is inputted so that the branched multi-wavelength light is inputted to the branched optical coupler 13 and the relative intensity noise RIN of the optical modulator input or the signal-to-noise ratio SNR of the optical modulator output becomes the design value. It is comprised by the control circuit 14 which performs shape control.
[0013]
FIG. 2 shows a second embodiment of the coherent multi-wavelength signal generator of the present invention. The coherent multi-wavelength signal generator of this embodiment includes an optical amplifier 15 that amplifies multi-wavelength light between the multi-wavelength light source 11 and the duplexer 12 in the configuration of the first embodiment. A part of the wavelength light is guided to the control circuit 14.
[0014]
FIG. 3 shows a configuration example of a wavelength division multiplexing transmission system using the coherent multi-wavelength signal generator of the present invention. In the figure, an optical receiver 70 connected to the coherent multi-wavelength signal generator 10 via a transmission line optical fiber 60 includes an optical amplifier 71 that amplifies the transmitted wavelength multiplexed signal light, and wavelength multiplexed signal light at each wavelength. Is composed of a demultiplexer 72 that demultiplexes the signal light and receivers 73-1 to 73-n that receive the signal light of each wavelength.
[0015]
FIG. 4 shows a first configuration example of the multi-wavelength light source 11. In the figure, a multi-wavelength light source 11 includes a light source 21 that generates light having a single center wavelength, and a plurality of light modulators 22-1 and 22-2 that perform amplitude modulation or phase modulation on output light of the light source 21. An optical modulation unit 23, a periodic signal generator 24 that generates a predetermined periodic signal, and a power adjustment unit 25-1 that adjusts a predetermined periodic signal voltage and applies the voltage to each of the optical modulators 22-1 to 22-2. ˜25-2 and power variable DC power sources 26-1 to 26-2 that apply bias voltages adjusted in power to the optical modulators 22-1 to 22-2. The optical modulation unit 23 may be configured to perform phase modulation by a path branched using, for example, a Mach-Zehnder intensity modulator and perform an amplitude modulation operation as a whole.
[0016]
In the optical modulator 22-1 of the optical modulator 23, the phase or amplitude of the time waveform of the output light (continuous light) of the light source 11 is modulated, so that the phase of each mode of the discrete light spectrum of the output light is constant. Correlation is given (FIG. 5 (a)). Further, the optical modulator 22-2 modulates the amplitude or phase of the modulated wave to shift the discrete light spectrum to the upper and lower sidebands on the frequency axis (FIG. 5 (b)). Here, by adjusting the frequency shift amount, the discrete light spectra can be overlapped to control the power level deviation of each mode to be constant (FIG. 5 (c)).
[0017]
FIG. 6 shows an example of optical spectrum shape control when an intensity modulator and a phase modulator are used as the optical modulator 23. FIGS. 6A, 6B and 6C are spectrum examples when the applied voltage (Vπ voltage conversion) of the LiNbO ₃ Mach-Zehnder intensity modulator is changed, and FIGS. (f) is a spectrum example when the applied voltage (converted to Vπ voltage) of the phase modulator is changed, and FIGS. 6 (g), (h), and (i) show the applied voltages of both modulators. It is an example of the optical spectrum of the multi-wavelength light when combining each. In the optical spectrum of this multi-wavelength light, there are a plurality of carriers 41 that are coherent light and spontaneous emission light 42 that spreads over a wide band.
[0018]
FIG. 7 schematically shows an optical spectrum of the multi-wavelength light amplified by the optical amplifier. In the optical spectrum of multi-wavelength light, there are a plurality of carriers 41 that are coherent light, spontaneous emission light 42 that spreads over a wide band, and spontaneous emission light (amplified spontaneous emission light: ASE light) 43 generated by an optical amplifier. Exists.
[0019]
The control parameters for changing the optical spectrum shape are the modulation index (periodic signal voltage) of the intensity modulator and the phase modulator and the bias voltage of the intensity modulator. That is, a predetermined optical spectrum shape is obtained by inputting a control signal to the power adjusting units 25-1 to 25-2 and the power variable DC power sources 26-1 to 26-2 and adjusting the periodic signal voltage and the bias voltage. Can be controlled.
[0020]
FIG. 8 shows a second configuration example of the multi-wavelength light source 11. In this configuration, a phase adjuster 27 and a multiplier 28 are arranged in front of the power adjustment units 25-1 to 25-2 of the first configuration example. The phase adjuster 27 adjusts the phase difference of the periodic signals applied to the optical modulators 22-1 and 22-2, and the multiplier 28 controls the multiplication number of the periodic signal frequency, whereby a predetermined optical spectrum shape is obtained. It can be controlled to obtain.
[0021]
FIG. 9 shows an example of controlling the optical spectrum shape by adjusting the phase of the periodic signal. FIGS. 9A, 9B, and 9C show optical spectrum shapes when the phase differences are set to 0, + X, and −X, respectively.
[0022]
FIG. 10 shows an example of control of the optical spectrum shape by frequency multiplication of the periodic signal. 10A, 10B, and 10C show the optical spectrum shapes when the multiplication numbers are set to 1, 2, and 3, respectively.
[0023]
FIG. 11 shows a third configuration example of the multi-wavelength light source 11. In this configuration, an electroabsorption-type intensity modulator 29 is used as the light modulation unit 23 of the first configuration example. Utilizing the exponential characteristics of the absorption coefficient (transmittance) with respect to the applied voltage of this electroabsorption-type intensity modulator, the output light intensity of a rectangle is shown with respect to the periodic signal voltage, and the duty is changed by changing the bias point. The ratio can be changed and the optical spectrum shape can be changed.
[0024]
FIG. 12 schematically shows an optical spectrum of multi-wavelength light when an electroabsorption intensity modulator is used. In the optical spectrum of multi-wavelength light, there are a plurality of carriers 41 that are coherent light and spontaneous emission light 42 that spreads over a wide band.
[0025]
FIG. 13 shows a fourth configuration example of the multi-wavelength light source 11. In the figure, the multi-wavelength light source 11 includes a pulse light source 31 and a spectrum shape control means 32 that controls the spectrum shape of the output pulse light of the pulse light source 31. The spectrum shape control means 32 controls the spectrum shape (related to the pulse width and chirp amount) in the frequency region of the pulsed light to a predetermined spectrum shape by pulse compression such as adiabatic compression using a dispersion reducing fiber, for example. As shown in FIG. 14, the control parameter in this case is a compression ratio determined by the dispersion value D ₀ on the input side and the dispersion value D ₁ on the output side of the dispersion reducing fiber.
[0026]
FIG. 15 shows the relationship between the optical spectrum of the coherent component of the multi-wavelength light and the transmission characteristics of the duplexer 12. In the figure, level 1 is a coherent component of multi-wavelength light, and twice the level 2 and level 3 is a noise component having a beat frequency equal to the wavelength channel interval. Therefore, by making the transmission bandwidth of the demultiplexer 12 sufficiently smaller than the wavelength channel spacing of multi-wavelength light, leakage from adjacent channels can be suppressed when a desired wavelength component is cut out. As a result, continuous light can be output even when the multi-wavelength light is pulsed light.
[0027]
Hereinafter, in the configuration for controlling the optical spectrum shape of multi-wavelength light, a design for matching with performance specifications required for an optical transmission unit using a conventional semiconductor laser will be described.
[0028]
(Example of designing the modulator input relative intensity noise RIN (i))
FIG. 16 shows the relationship between stimulated emission light and spontaneous emission light of a semiconductor laser. In the semiconductor laser, the light output intensity gradually changes as the injection current (pumping light intensity in the case of a solid-state laser or the like) increases until the threshold is lower than the threshold, and the light emission increases rapidly at the threshold. . Spontaneous emission light is incoherent light, provided as the optical output intensity P _SE at the threshold, stimulated emission light is coherent light, is provided in the optical output intensity P _LAS according to the injection current.
[0029]
Here, the stimulated emission probability ratio γ to the spontaneous emission is
γ = 10log ₁₀ (P _LAS / P _SE )
Defined by
[0030]
On the other hand, the spontaneous emission light band is BW _SE [Hz], the relative intensity noise RIN [dB / Hz] before the spectrum slice by the demultiplexer, and the light intensity of the i-th wavelength component spectrum-sliced by the demultiplexer is Pi. Then, the relative intensity noise RIN (i) is
RIN (i) = RIN + 10log ₁₀ (Pi / ΣPi)
RIN = -γ-10log ₁₀ BW _SE +3
It is expressed.
[0031]
The control circuit 14 in FIG. 1 measures the relative intensity noise RIN of the multi-wavelength light and estimates the i-th output light intensity spectrum-sliced by the demultiplexer 12 to give Pi, thereby comparing the i-th wavelength component relative. Intensity noise RIN (i) is calculated. Then, the power adjustment unit 25, the power variable DC power source 26, the phase adjuster 27, the multiplier 28, and the like of the multi-wavelength light source 11 are controlled so that the relative intensity noise RIN (i) of each wavelength component becomes a design value.
[0032]
The i-th output light intensity Pi of the branching filter 12 may be input to the control circuit 14 as measured by the input power monitoring function of the optical modulators 52-1 to 52-n. In addition, the control circuit 14 may directly measure the relative intensity noise RIN (i) of each wavelength component spectrally sliced by the duplexer 12.
[0033]
Further, the multi-wavelength light amplified by the optical amplifier 15 is input to the control circuit 14 of FIG. As shown in FIG. 7, the multi-wavelength light includes spontaneous emission light (amplified spontaneous emission light: ASE light) 43 generated by the optical amplifier 15.
[0034]
Here, when the gain of the optical amplifier 15 is g, the optical amplification band is BW _AMP [Hz], the total number of transverse modes is m, the inversion distribution parameter is nsp, and the center optical frequency of the multi-wavelength light source 11 is ν [Hz]. The stimulated emission probability ratio γ for spontaneous emission is
γ = ₁₀ log ₁₀ [gP _LAS / {gP _SE (BW _SE / BW _AMP ) + hν (g−1) nsp · m · BW _AMP }]
It is expressed.
[0035]
(Example 1 of designing signal-to-noise ratio SNR of modulator output)
In the coherent multiwavelength signal generator shown in FIG. 1 or FIG. 2, the band of the receiver 73 of the wavelength multiplexing transmission system shown in FIG. 3 is Be [Hz], the demultiplexing band of the demultiplexer 72 is Bo [Hz], and the signal , The signal light intensity of the i-th modulator output is P (i) [dBm], the stimulated emission light intensity of this modulator output is Pc (i) [dBm], and the spontaneous emission of this modulator output The light intensity is Ps (i) [dBm], the equivalent current at the receiver is Ieq [A], the shot noise of the signal component is Ns, the beat noise of the signal component and the spontaneous emission light is Ns-sp, and between the spontaneous emission light beat noise and Nsp-sp, the thermal noise of the receiver and N _th, the signal-to-noise ratio SNR of the modulator output,
SNR = S / (Ns + Ns -sp + Nsp-sp + N th)
Ps (i) = RIN (i) +10 log ₁₀ Be + Pc (i) +10 log ₁₀ M
S = ((eη / hν) Pc (i)) ²
Ns = 2e ((eη / hν) P (i)) Be
Ns-sp = 4 (eη / hν) ² Pc (i) Ps (i) Be / Bo
N _th = Ieq ² Be
It is expressed. However, P (i), Pc (i), and Ps (i) in S, Ns, and Ns-sp are linear notation and the unit is W.
[0036]
The control circuit 14 of the coherent multi-wavelength signal generator is configured such that the power adjustment unit 25, the power variable DC power supply 26, the phase adjuster 27, and the multiplication of the multi-wavelength light source 11 so that the signal-to-noise ratio SNR of the modulator output follows the above equation. The device 28 and the like are controlled.
[0037]
(Example 2 of designing signal-to-noise ratio SNR of modulator output)
In the coherent multiwavelength signal generator shown in FIG. 1 or FIG. 2, the band of the receiver 73 of the wavelength multiplexing transmission system shown in FIG. 3 is Be [Hz], the demultiplexing band of the demultiplexer 72 is Bo [Hz], and the signal , The signal light intensity of the i-th modulator output is P (i) [dBm], the stimulated emission light intensity of this modulator output is Pc (i) [dBm], and the spontaneous emission of this modulator output The optical intensity is Ps (i) [dBm], the equivalent current at the receiver is Ieq [A], the rate of leakage from the jth port to the ith port in the multiplexer is XT (j), Crosstalk signal light intensity is Px (i) [dBm], shot noise of signal component is Ns, beat noise of signal component and spontaneous emission light is Ns-sp, beat noise of signal component and crosstalk signal light is Ns-x , Beat noise between spontaneously emitted light, Nsp-sp, beat noise between crosstalk signal light and spontaneously emitted light, Nx-sp, receiver thermal noise When N _th, the signal-to-noise ratio SNR of the modulator output,
SNR = S / (Ns + Ns -sp + Nx-sp + Nsp-sp + Ns-x + N th)
Ps (i) = RIN (i) +10 log ₁₀ Be + Pc (i) +10 log ₁₀ M
Px (i) = ΣP (j) · XT (j)
S = ((eη / hν) Pc (i)) ²
Ns = 2e ((eη / hν) P (i)) Be
Ns-sp = 4 (eη / hν) ² Pc (i) Ps (i) Be / Bo
Nx-sp = 4 (eη / hν) ² Px (i) Ps (i) Be / Bo
Ns-x = (eη / hν) ² Pc (i) Px (i)
N _th = Ieq ² Be
It is expressed. However, P (i), Pc (i), and Ps (i) in S, Ns, Ns-sp, Nx-sp, and Ns-x are linear notations and the unit is W.
[0038]
The control circuit 14 of the coherent multi-wavelength signal generator is configured such that the power adjustment unit 25, the power variable DC power supply 26, the phase adjuster 27, and the multiplication of the multi-wavelength light source 11 so that the signal-to-noise ratio SNR of the modulator output follows the above equation. The device 28 and the like are controlled.
[0039]
【The invention's effect】
As described above, the coherent multi-wavelength signal generator of the present invention adjusts the voltage or bias voltage of the periodic signal applied to the optical modulator constituting the multi-wavelength light source, and changes the optical spectrum shape of the generated multi-wavelength light. Quantitatively design the relative intensity noise RIN of the optical modulator input or the signal-to-noise ratio SNR of the optical modulator output that modulates the coherent light of each wavelength obtained by spectrum slicing multi-wavelength light, depending on the configuration to be controlled Can do.
[0040]
The same applies to the configuration for controlling the optical spectrum shape of the multi-wavelength light generated by controlling the phase or frequency multiplication number of the periodic signal applied to the optical modulator constituting the multi-wavelength light source.
[0041]
Thereby, it is possible to design a coherent multi-wavelength signal generator capable of matching with performance specifications required for an optical transmitter using a conventional semiconductor laser.
[Brief description of the drawings]
FIG. 1 is a diagram showing a first embodiment of a coherent multi-wavelength signal generator according to the present invention.
FIG. 2 is a diagram showing a second embodiment of the coherent multi-wavelength signal generator according to the present invention.
FIG. 3 is a diagram showing a configuration example of a wavelength division multiplexing transmission system using the coherent multi-wavelength signal generator of the present invention.
4 is a diagram showing a first configuration example of a multi-wavelength light source 11. FIG.
FIG. 5 is a diagram for explaining the principle of multiwavelength light generation in the multiwavelength light source 11;
6 is a diagram showing an example of optical spectrum shape control in the case where an intensity modulator and a phase modulator are used as the optical modulation unit 23. FIG.
FIG. 7 is a diagram showing an optical spectrum of multi-wavelength light amplified by an optical amplifier.
FIG. 8 is a diagram showing a second configuration example of the multi-wavelength light source 11;
FIG. 9 is a diagram illustrating an example of controlling the shape of an optical spectrum by adjusting the phase of a periodic signal.
FIG. 10 is a diagram illustrating an example of control of an optical spectrum shape by frequency multiplication of a periodic signal.
11 is a diagram showing a third configuration example of the multi-wavelength light source 11. FIG.
FIG. 12 is a diagram showing an optical spectrum of multiwavelength light when an electroabsorption intensity modulator is used.
13 is a diagram showing a fourth configuration example of the multi-wavelength light source 11. FIG.
FIG. 14 is a diagram for explaining the principle of adiabatic compression using a dispersion-reducing fiber.
15 is a view for explaining the relationship between the optical spectrum of coherent components of multi-wavelength light and the transmission characteristics of the duplexer 12. FIG.
FIG. 16 is a diagram for explaining the relationship between stimulated emission light and spontaneous emission light of a semiconductor laser.
FIG. 17 is a diagram illustrating a configuration example of a conventional wavelength division multiplexing transmission system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Coherent multiwavelength signal generator 11 Multiwavelength light source 12 Demultiplexer 13 Optical coupler 14 Control circuit 15 Optical amplifier 21 Light source 22 Optical modulator 23 Optical modulator 24 Periodic signal generator 25 Power adjuster 26 Power variable direct-current power supply 27 Phase Adjuster 28 Multiplier 29 Electroabsorption-type intensity modulator 31 Pulse light source 32 Spectral shape control means 50 Optical transmitter 51 Semiconductor laser (DFB-LD)
52 optical modulator 53 multiplexer 54 optical amplifier 60 transmission line optical fiber 70 optical receiver 71 optical amplifier 72 duplexer 73 receiver

Claims (6)

A multi-wavelength light source for generating coherent multi-wavelength light having a plurality of wavelength components;
A duplexer that separates the multi-wavelength light into wavelengths;
An optical modulator that modulates the coherent light of each wavelength separated by the duplexer with a transmission signal;
A coherent multi-wavelength signal generator comprising: a multiplexer that multiplexes each modulated signal light modulated by the optical modulator and outputs a coherent multi-wavelength signal;
The multi-wavelength light source includes a light source that generates light having a single center wavelength, and an optical modulator that generates multi-wavelength light by intensity-modulating or phase-modulating the output light with a predetermined periodic signal,
RIN [dB / Hz] is measured for the relative intensity noise of the multi-wavelength light output from the multi-wavelength light source, and the light of the i-th wavelength component (i-th modulator input) spectrally sliced by the duplexer Intensity Pi is estimated or measured from the output of the duplexer, the stimulated emission probability ratio for spontaneous emission is γ [dB], the stimulated emission intensity is P _LAS [dBm], and the spontaneous emission intensity is P _SE [dBm]. If the spontaneous emission band is BW _SE [Hz], the relative intensity noise RIN (i) of the light intensity P i of the i-th wavelength component is RIN (i) = RIN + ₁₀ log ₁₀ (Pi / ΣPi)
RIN = -γ-10log ₁₀ BW _SE +3
γ = 10log ₁₀ (P _LAS / P _SE )
A control circuit that adjusts at least one of the voltage of the periodic signal or the bias voltage of the optical modulator to control the optical spectrum shape of the multi-wavelength light output from the multi-wavelength light source so that the design value shown in FIG. coherent WDM signal generating apparatus characterized by comprising a. A multi-wavelength light source for generating coherent multi-wavelength light having a plurality of wavelength components;
A duplexer that separates the multi-wavelength light into wavelengths;
An optical modulator that modulates the coherent light of each wavelength separated by the duplexer with a transmission signal;
A coherent multi-wavelength signal generator comprising: a multiplexer that multiplexes each modulated signal light modulated by the optical modulator and outputs a coherent multi-wavelength signal;
The multi-wavelength light source includes a light source that generates light having a single center wavelength, and an optical modulator that generates multi-wavelength light by intensity-modulating or phase-modulating the output light with a predetermined periodic signal,
RIN [dB / Hz] is measured for the relative intensity noise of the multi-wavelength light output from the multi-wavelength light source, and the light of the i-th wavelength component (i-th modulator input) spectrally sliced by the duplexer Intensity Pi is estimated or measured from the output of the duplexer, the stimulated emission probability ratio for spontaneous emission is γ [dB], the stimulated emission intensity is P _LAS [dBm], and the spontaneous emission intensity is P _SE [dBm]. If the spontaneous emission band is BW _SE [Hz], the relative intensity noise RIN (i) of the light intensity P i of the i-th wavelength component is RIN (i) = RIN + ₁₀ log ₁₀ (Pi / ΣPi)
RIN = -γ-10log ₁₀ BW _SE +3
γ = 10log ₁₀ (P _LAS / P _SE )
The wavelength of the periodic signal or the bias voltage of the optical modulator is adjusted to control the phase of the periodic signal so that the design value is represented by the multiple wavelength output from the multiple wavelength light source. A coherent multi-wavelength signal generator comprising a control circuit for controlling the shape of an optical spectrum of light. A multi-wavelength light source for generating coherent multi-wavelength light having a plurality of wavelength components;
A duplexer that separates the multi-wavelength light into wavelengths;
An optical modulator that modulates the coherent light of each wavelength separated by the duplexer with a transmission signal;
A coherent multi-wavelength signal generator comprising: a multiplexer that multiplexes each modulated signal light modulated by the optical modulator and outputs a coherent multi-wavelength signal;
The multi-wavelength light source includes a light source that generates light having a single center wavelength, and an optical modulator that generates multi-wavelength light by intensity-modulating or phase-modulating the output light with a predetermined periodic signal,
RIN [dB / Hz] is measured for the relative intensity noise of the multi-wavelength light output from the multi-wavelength light source, and the light of the i-th wavelength component (i-th modulator input) spectrally sliced by the duplexer Intensity Pi is estimated or measured from the output of the duplexer, the stimulated emission probability ratio for spontaneous emission is γ [dB], the stimulated emission intensity is P _LAS [dBm], and the spontaneous emission intensity is P _SE [dBm]. If the spontaneous emission band is BW _SE [Hz], the relative intensity noise RIN (i) of the light intensity P i of the i-th wavelength component is RIN (i) = RIN + ₁₀ log ₁₀ (Pi / ΣPi)
RIN = -γ-10log ₁₀ BW _SE +3
γ = 10log ₁₀ (P _LAS / P _SE )
And adjusting at least one of the voltage of the periodic signal or the bias voltage of the optical modulator so as to be a design value represented by the following, and controlling the multiplication number of the periodic signal frequency to output from the multi-wavelength light source A coherent multi-wavelength signal generator comprising a control circuit for controlling the optical spectrum shape of multi-wavelength light. The coherent multiwavelength signal generator according to any one of claims 1 to 3, further comprising an optical amplifier that amplifies the multiwavelength light output from the multiwavelength light source and inputs the amplified light to the duplexer.
The control circuit has a gain of the optical amplifier as g, an optical amplification band as BW _AMP [Hz], a total number of transverse modes as m, an inversion distribution parameter as n _sp , and a center optical frequency of the multi-wavelength light source as ν [Hz]. When the relative intensity noise RIN (i) of the i-th wavelength component (i-th modulator input) spectrally sliced by the duplexer is
RIN (i) = RIN + 10log ₁₀ (Pi / ΣPi)
RIN = -γ-10log ₁₀ BW _SE +3
γ = 10log ₁₀ [gP _LAS / {gP _SE (BW _SE / BW _AMP ) + hν
_{· (G-1) n sp} · m · BW AMP} ]
The coherent multi-wavelength signal generator is configured to control the optical spectrum shape of the multi-wavelength light output from the multi-wavelength light source so as to have a design value represented by the following . In the coherent multiwavelength signal generator according to any one of claims 1 to 4 ,
The control circuit sets the receiver band to Be [Hz], the demultiplexer band of the pre-receiver duplexer to Bo [Hz], the signal mark ratio to M, and the signal light intensity of the i-th modulator output. P (i) [dBm], the stimulated emission light intensity of this modulator output is Pc (i) [dBm], the spontaneous emission light intensity of this modulator output is Ps (i) [dBm], and the equivalent in the receiver The current is Ieq [A], the shot noise of the signal component is Ns, the beat noise of the signal component and the spontaneous emission light is Ns-sp, the beat noise between the spontaneous emission light is Nsp-sp, and the thermal noise of the receiver is N _th Then, the signal-to-noise ratio SNR of the modulator output is
SNR = S / (Ns + Ns -sp + Nsp-sp + N th)
Ps (i) = RIN (i) +10 log ₁₀ Be + Pc (i) +10 log ₁₀ M
S = ((eη / hν) Pc (i)) ²
Ns = 2e ((eη / hν) P (i)) Be
Ns-sp = 4 (eη / hν) ² Pc (i) Ps (i) Be / Bo
N _th = Ieq ² Be
(However, P (i), Pc (i), and Ps (i) in S, Ns, and Ns-sp are linear notation and the unit is W)
The coherent multi-wavelength signal generator is configured to control the optical spectrum shape of the multi-wavelength light output from the multi-wavelength light source so as to have a design value represented by the following . In the coherent multiwavelength signal generator according to any one of claims 1 to 4 ,
The control circuit sets the receiver band to Be [Hz], the demultiplexer band of the pre-receiver duplexer to Bo [Hz], the signal mark ratio to M, and the signal light intensity of the i-th modulator output. P (i) [dBm], the stimulated emission light intensity of this modulator output is Pc (i) [dBm], the spontaneous emission light intensity of this modulator output is Ps (i) [dBm], and the equivalent in the receiver The current is Ieq [A], the rate of leakage from the j-th port to the i-th port in the multiplexer is XT (j), the crosstalk signal light intensity in the multiplexer is Px (i) [dBm], Shot noise of signal component is Ns, beat noise of signal component and spontaneous emission light is Ns-sp, beat noise of signal component and crosstalk signal light is Ns-x, beat noise between spontaneous emission light is Nsp-sp, cross When the beat noise of the talk signal light and spontaneous emission light is Nx-sp and the thermal noise of the receiver is N _th , the signal-to-noise ratio SNR of the modulator output is
SNR = S / (Ns + Ns -sp + Nx-sp + Nsp-sp + Ns-x + N th)
Ps (i) = RIN (i) +10 log ₁₀ Be + Pc (i) +10 log ₁₀ M
Px (i) = ΣP (j) · XT (j)
S = ((eη / hν) Pc (i)) ²
Ns = 2e ((eη / hν) P (i)) Be
Ns-sp = 4 (eη / hν) ² Pc (i) Ps (i) Be / Bo
Nx-sp = 4 (eη / hν) ² Px (i) Ps (i) Be / Bo
Ns-x = (eη / hν) ² Pc (i) Px (i)
N _th = Ieq ² Be
(However, P (i), Pc (i) in S, Ns, Ns-sp, Nx-sp, Ns-x,
Ps (i) is linear notation, unit is W)
The coherent multi-wavelength signal generator is configured to control the optical spectrum shape of the multi-wavelength light output from the multi-wavelength light source so as to have a design value represented by the following .

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