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WO2019188192A1 - Émetteur optique - Google Patents

Émetteur optique Download PDF

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Publication number
WO2019188192A1
WO2019188192A1 PCT/JP2019/009706 JP2019009706W WO2019188192A1 WO 2019188192 A1 WO2019188192 A1 WO 2019188192A1 JP 2019009706 W JP2019009706 W JP 2019009706W WO 2019188192 A1 WO2019188192 A1 WO 2019188192A1
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WO
WIPO (PCT)
Prior art keywords
signal
optical
frequency
carrier
carrier wave
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Ceased
Application number
PCT/JP2019/009706
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English (en)
Japanese (ja)
Inventor
山崎　裕史
橋本　俊和
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NTT Inc
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Nippon Telegraph and Telephone Corp
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Filing date
Publication date
Application filed by Nippon Telegraph and Telephone Corp filed Critical Nippon Telegraph and Telephone Corp
Publication of WO2019188192A1 publication Critical patent/WO2019188192A1/fr
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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/516—Details of coding or modulation

Definitions

  • the present invention relates to an optical transmitter used for optical fiber communication. More specifically, the present invention relates to an optical SSB transmitter that performs optical SSB modulation.
  • the C band (wavelength 1.5 ⁇ m band) which is the lowest loss band of the optical fiber, but the influence of the wavelength dispersion of the optical fiber becomes a problem in the C band.
  • so-called fading in which the intensity of a specific frequency component of a signal spectrum is significantly attenuated in a baseband signal after intensity detection due to wavelength dispersion, is a serious problem.
  • Non-Patent Document 1 In order to generate an optical SSB signal, a method of using an optical IQ modulator (sometimes referred to as an SSB modulator) as in Non-Patent Document 1 and removing one sideband by interference between an I component and a Q component It has been known.
  • Optical SSB modulation based on the same principle can be performed by driving the arms of a Mach-Zehnder modulator (MZM) with drive signals whose phases are shifted from each other as in Non-Patent Document 2.
  • MZM Mach-Zehnder modulator
  • an optical IQ modulator is used to suppress the light source frequency component simultaneously with the modulation, and instead, an optical carrier is set up at one of the band edges of the modulated signal spectrum and transmitted.
  • a method for generating an optical SSB signal by effectively shifting the optical carrier frequency is also known.
  • Non-Patent Document 5 a method of attenuating one sideband with an optical filter after generating a normal optical DSB signal is called a VSB (Vestinal Sideband) method, which is also a kind of SSB, Signal degradation due to fading can be reduced.
  • VSB Vertical Sideband
  • the method for generating an optical SSB or VSB signal in a conventional optical SSB transmitter has the following problems.
  • FIG. 1 shows a configuration (a) of an optical SSB transmitter using an IQ modulator as an optical SSB transmitter of Conventional Example 1, and spectrums (b) and (c) of signals of each part.
  • the optical SSB signal (c) whose spectrum is shown at the right end is generated by optical modulation with the two systems of electrical signals shifted from each other.
  • FIG. 2 shows an optical VSB transmitter (a) using an optical filter as an optical SSB transmitter of Conventional Example 2, and spectrums (b) to (d) of signals of each part.
  • the optical intensity is modulated in (b) to generate a DSB optical signal (c) having a spectrum in the center.
  • the DSB optical signal shown in FIG. 2 (c) has a light spectrum with sidebands symmetrical spectral shape across the optical carrier of the central frequency f 0, the light of the lower sideband (LSB) It can be said that the signal S * ( ⁇ f + f 0 ) and the optical signal S (f ⁇ f 0 ) in the upper sideband (USB) are in a complex conjugate pair relationship, and one is the other complex conjugate signal.
  • this DSB optical signal is passed through an optical filter 23 having a transmission spectrum indicated by a dotted line in FIG. 2D, the lower sideband is partially suppressed to generate a VSB optical signal (d).
  • the conventional optical VSB transmitter 20 shown in FIG. 2 is simple because only one optical modulator drive system is required, but generally the transmission characteristics of the optical filter are not sufficiently sharp with respect to the signal bandwidth.
  • the sideband suppression becomes incomplete, and part of the LSB remains, fading suppression becomes incomplete, and there is a problem that fading cannot be suppressed.
  • the present invention has been made in view of such problems, and an object of the present invention is to provide an optical SSB transmitter that sufficiently suppresses fading due to chromatic dispersion while having a simple configuration. is there.
  • the present invention is characterized by having the following configuration.
  • an electric signal generating means for generating a driving electrical signal containing a component of the RF carrier and frequency f s following baseband modulation signal of frequency f s, A laser light source that oscillates at a frequency f 0 ;
  • a Mach-Zehnder modulator that is biased to a null point, is push-pull driven by the drive electrical signal, and modulates light output from the laser light source; Which is connected downstream of the Mach-Zehnder modulator, a transmission bandwidth f s or more, and either a transition region of the transmission band and blocking band from the frequency f 0 -f s from f 0 or frequency f 0 of f 0 + f s And an optical filter existing in the frequency range of the optical transmitter.
  • the electrical signal generating means includes A DSP that synthesizes and generates the RF carrier and the baseband modulated signal as a digital signal;
  • the electrical signal generating means includes RF carrier wave generating means for generating the RF carrier wave as an analog signal; A DSP for generating the baseband modulation signal as a digital signal; A DAC that converts the baseband modulation signal generated by the DSP into an analog signal;
  • the electrical signal generating means includes RF carrier wave generating means for generating an RF carrier wave of the frequency fs as an analog signal;
  • an optical SSB transmitter capable of sufficiently suppressing fading due to chromatic dispersion while having a simple configuration in which an MZM is driven by a single electric signal. Can do.
  • FIG. 2A is a diagram showing a configuration of a conventional optical VSB transmitter
  • FIGS. 2B to 2D are diagrams showing signal spectra of respective units.
  • FIG. 2A is a diagram illustrating a configuration of an optical SSB transmitter according to a first embodiment of the present invention
  • FIGS. 2B to 2D are diagrams illustrating signal spectra of respective units.
  • FIG. 4A is a diagram showing a configuration of an optical SSB transmitter according to a second embodiment of the present invention
  • FIG. 5B is a diagram showing a spectrum of a signal at each section.
  • FIG. 3 is a diagram schematically showing the configuration (a) of the optical SSB transmitter according to the first embodiment of the present invention and the spectrums (b) to (d) of the signals of each part.
  • the optical SSB transmitter 300 in FIG. 3A includes a drive signal generation unit 310, a laser light source 320, an MZM (Mach-Zehnder modulator) 330, and an optical filter 340.
  • MZM Machine-Zehnder modulator
  • the drive signal generation unit 310 is an electric signal generation unit that generates a drive electric signal for driving the MZM 330, and includes a DSP (digital signal processing circuit) 311 and a DAC (digital-analog converter) 312. An amplifier may be used after the DAC 312 as necessary. As shown in the spectrum of FIG. 3B, the drive signal output from the DAC 312 includes a baseband modulation signal 381 having a bandwidth B and an RF carrier 382 having a frequency f s ⁇ B.
  • the MZM 330 is a push-pull type (zero chirp type), and the DC bias is adjusted to a null point (a point at which the intensity of the light source frequency component is minimum).
  • a null point a point at which the intensity of the light source frequency component is minimum.
  • the transmission spectrum of the optical filter 340 is indicated by a dotted line in FIG. 3D, and the transmission spectrum is adjusted so as to suppress one of the shifted optical carriers.
  • the transmission spectrum of the optical filter 340 transmits the optical carrier of f 0 -f s on the LSB side and the optical signal component 384 in the range of f 0 -f s to f 0 , and f 0 + f s on the USB side. As long as the optical carrier is suppressed, it is sufficient.
  • an optical filter having a transmission bandwidth of f s or more and a transition region between the transmission band and the stop band in the range of frequencies f 0 to f 0 + f s may be used.
  • the difference in light transmittance between the transmission band and the blocking band is typically 20 dB or more.
  • optical filter 340 As shown in the spectrum of FIG. 3 (d), the results in the presence of positive only signal components viewed from f c on the frequency axis, this by f c An optical SSB signal 384 serving as an optical carrier wave is generated.
  • the optical filter 340 an optical carrier of f 0 + f s may be sufficient even be suppressed.
  • the penalty due to signal-signal beat interference (SSBI) increases as the optical carrier strength decreases with respect to the strength of other signal components.
  • the ratio with the intensity is +10 dB or more, but the specific setting of the intensity ratio depends on the required specifications of the system and the processing method on the receiving side. This is the same as the conventional optical SSB transmission.
  • the intensity of the optical carrier must be increased by an amount corresponding to the intensity of the image signal 385 compared to the conventional example.
  • the optical signal component 384 (see FIG. 3D) output in the first embodiment is obtained by shifting the negative frequency component of the baseband modulated signal 381 (see FIG. 3B) by + f 0. Equivalent to. Therefore, if the signal input to the DSP 311 is a signal whose positive frequency component of the spectrum is represented by S (f), simply converting this to DA and adding an RF carrier as it is will result in an output optical SSB signal. A signal equivalent to the conventional method cannot be obtained.
  • the driving electric signal generated by the electric signal generating means (310) is an RF carrier having a frequency f s and a complex conjugate signal S * ( ⁇ f) of the modulated electric signal S (f) only at the frequency f s of the RF carrier.
  • the shifted baseband modulated signal S * ( ⁇ f + f s ) is included.
  • the bandwidth B of the drive electrical signal is equal to or less than the frequency f s of the RF carrier.
  • the process of inverting the spectrum as described above to obtain the complex conjugate may be performed not on the transmission side but on the reception side. That is, if a signal whose spectrum positive frequency component is represented by S (f) is used as it is as the baseband modulation signal 381, the spectrum positive frequency component is represented by S * ( ⁇ f + f 0 ) as the optical signal component 384. As a result, the signal having the positive frequency component of the spectrum represented by S * ( ⁇ f + f s ) is obtained as an electrical signal on the receiving side.
  • reception-side processing can be realized, for example, by using a receiver including an analog-digital converter (ADC) and a DSP.
  • ADC analog-digital converter
  • the driving electric signal obtained by adding the RF carrier 382 to the baseband modulation signal 381 as described above is generated as a digital signal by the DSP 311 in FIG. 3A and converted into an electric waveform of an analog signal by the DAC 312 to be converted into an MZM 330. Used for driving.
  • the drive system is achieved by using the single-system drive push-pull MZM330.
  • the optical filter 340 is used, unlike the conventional VSB method, since the optical carrier wave is set at the band edge in the MZM 330, the residual component due to the “round” of the optical filter 340 does not cause fading. That is, according to the first embodiment of the present invention, the above-described problems of the conventional technology can be solved.
  • the time optical filter 340 the optical signal component of the range of the optical carrier and f 0 of f 0 + f s of the f 0 + f s is transmitted, and the optical carrier of f 0 -f s is used as such as to suppress That's fine.
  • the baseband modulation signal 381 does not need to be changed.
  • FIG. 4 is a diagram schematically showing the configuration (a) of the optical SSB transmitter according to the second embodiment of the present invention and the spectrums (b) to (e) of the signals of the respective parts.
  • the configuration of the optical SSB transmitter 400 in FIG. 4A is the same as that of the first embodiment shown in FIG. 3A except for the drive signal generator 410, and therefore only the drive signal generator 410 will be described. To do.
  • the drive signal generation unit 410 in FIG. 4A is an electric signal generation unit that generates a drive electric signal for driving the MZM 430, and includes a DSP 411, a DAC 412, an RF carrier wave generation unit 413, and an adder. 414.
  • the DSP 411 and the DAC 412 are used only for generating the baseband modulation signal 481 in FIG. 4B, and the RF carrier 482 in FIG. 4E is generated separately by the RF carrier generation unit 413.
  • the adder 414 adds the baseband modulation signal 481 (b).
  • the intensity of the optical carrier needs to be sufficiently larger than the other signal intensities, the intensity of the RF carrier 482 needs to be sufficiently greater than the intensity of the baseband modulation signal 481.
  • the DSP 411 and the DAC 412 are used only for the generation of the baseband modulation signal 481, and the RF carrier 482 is separately generated as an analog signal by the RF carrier generation unit 413, and is added by the adder 414 as an analog signal in the analog domain.
  • a clock signal source synchronized with the DAC 412 can be used.
  • an amplifier, a phase shifter, and the like may be disposed in front of the adder 414.
  • the DSP 411 (311) and the DAC 412 (312) positively correct the positive frequency component S (f ⁇ f c ) of the spectrum of the signal to be transmitted as the optical signal component 484 (384).
  • the method of generating a signal whose frequency component is represented by S * ( ⁇ f + f s ) and using it as the baseband modulation signal 481 (381) has been described.
  • the processing corresponding to this is performed on the receiving side, such as ADC and DSP. You may implement
  • the positive frequency component is X * ( ⁇ in the conventional SSB transmitter. Since a signal corresponding to a signal represented by f + f s ) is transmitted, the negative frequency component of the baseband received signal after intensity detection is shifted by + f s on the receiving side. After performing the processing to make the positive frequency component, necessary processing such as channel equalization may be performed.
  • a modulation method that can be realized without performing a spectrum operation on the receiving side and using a DAC such as NRZ as a baseband modulation method.
  • the DSP 411 and the DAC 412 can be replaced with an analog modulation signal generating unit that operates in an analog manner and generates a baseband modulation signal as an analog signal.
  • an optical SSB transmitter capable of sufficiently suppressing fading due to chromatic dispersion while having a simple configuration in which an MZM is driven by one electric signal.
  • Optical filter 10 10, 20, 300, 400 Optical SSB transmitter 11, 21, 320, 420 Laser light source 12 IQ modulator 22 Optical intensity modulator 23, 340, 440 Optical filter 310, 410 Drive signal generator 330, 430 MZM (Mach-Zehnder modulation) vessel) 311 and 411 DSP (digital signal processing circuit) 312 and 412 DAC (digital-analog converter) 381, 481 Baseband modulation signal 382, 482 RF carrier wave 384, 484 Optical signal component 385, 485 Image component 413 RF carrier wave generator 414 Adder

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Communication System (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)

Abstract

La présente invention concerne un émetteur SSB optique qui supprime suffisamment, par une configuration simple, une atténuation provoquée par une dispersion de longueur d'onde. L'émetteur optique comprend : un moyen de génération de signal électrique qui génère un signal électrique de commande comprenant une onde porteuse radiofréquence, RF, ayant une fréquence fs et une composante de signal de modulation en bande de base ayant une fréquence fs ou inférieure ; une source de lumière laser qui oscille à une fréquence f0 ; un modulateur de Mach-Zehnder qui est polarisé à un point nul et attaqué en push-pull par le signal électrique d'attaque et module une lumière délivrée en sortie par la source de lumière laser ; et un filtre optique qui est connecté à un étage ultérieur au modulateur de Mach-Zehnder, possède une bande passante de transmission de fs ou plus, et possède une région de transition entre une bande de transmission et une bande d'arrêt, la transition région étant présente à l'intérieur d'une plage fréquentielle de fréquences de f0-fs à f0 ou de fréquences de f0 à f0+fs.
PCT/JP2019/009706 2018-03-29 2019-03-11 Émetteur optique Ceased WO2019188192A1 (fr)

Applications Claiming Priority (2)

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JP2018065344A JP2019174747A (ja) 2018-03-29 2018-03-29 光送信器
JP2018-065344 2018-03-29

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009201099A (ja) * 2008-02-21 2009-09-03 Nec Lab America Inc １００Ｇｂｉｔ／ｓのＯＦＤＭ光信号生成方法及び装置
US20100104294A1 (en) * 2008-10-28 2010-04-29 Chen Jye Hong Optical modulation device
JP2015121796A (ja) * 2010-12-03 2015-07-02 レイセオン カンパニー 超広帯域の帯域幅を有する波形を合成する方法及び装置
US20170317760A1 (en) * 2016-04-29 2017-11-02 Zte Corporation Optical mm-wave signal generation using a single iq modulator

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009201099A (ja) * 2008-02-21 2009-09-03 Nec Lab America Inc １００Ｇｂｉｔ／ｓのＯＦＤＭ光信号生成方法及び装置
US20100104294A1 (en) * 2008-10-28 2010-04-29 Chen Jye Hong Optical modulation device
JP2015121796A (ja) * 2010-12-03 2015-07-02 レイセオン カンパニー 超広帯域の帯域幅を有する波形を合成する方法及び装置
US20170317760A1 (en) * 2016-04-29 2017-11-02 Zte Corporation Optical mm-wave signal generation using a single iq modulator

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
MENG, X. J.: "A SSB-Based frequency doubling optical transmitter using cascaded Mach-Zehnder modulators", CONFERENCE ON LASERS AND ELECTRO-OPTICS, 1 June 2003 (2003-06-01), pages 1644 - 1646, XP031952064 *
YAMAZAKI, HIROSHI ET AL.: "Discrete multitone transmission at net data rate of 250Gb/s using digital-preprocessed analog-multiplexed DAC with halved clock frequency and suppressed image", JOURNAL OF LIGHTWAVE TECHNOLOGY, vol. 35, no. 7, 1 April 2017 (2017-04-01), pages 1300 - 1306, XP011645659, doi:10.1109/JLT.2017.2650205 *

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