WO2019159891A1 - Light transmitter, light receiver, and optical communication method - Google Patents

Light transmitter, light receiver, and optical communication method Download PDF

Info

Publication number
WO2019159891A1
WO2019159891A1 PCT/JP2019/004849 JP2019004849W WO2019159891A1 WO 2019159891 A1 WO2019159891 A1 WO 2019159891A1 JP 2019004849 W JP2019004849 W JP 2019004849W WO 2019159891 A1 WO2019159891 A1 WO 2019159891A1
Authority
WO
WIPO (PCT)
Prior art keywords
signal
optical
modulation
path
intensity
Prior art date
Application number
PCT/JP2019/004849
Other languages
French (fr)
Japanese (ja)
Inventor
山本　浩史
Original Assignee
日本電気株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 日本電気株式会社 filed Critical 日本電気株式会社
Publication of WO2019159891A1 publication Critical patent/WO2019159891A1/en

Links

Images

Classifications

    • 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
    • H04B10/54—Intensity modulation
    • 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
    • H04B10/548—Phase or frequency modulation
    • H04B10/556—Digital modulation, e.g. differential phase shift keying [DPSK] or frequency shift keying [FSK]
    • 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
    • H04B10/60—Receivers
    • H04B10/66—Non-coherent receivers, e.g. using direct detection

Definitions

  • the present invention relates to an optical communication technology, and more particularly to an optical communication system using a direct detection method.
  • a transmission speed of about 25 Gbps is required not only for basic communication but also for client-side optical communication at the end.
  • Client products are required to be low cost and low power.
  • a direct modulation (direct modulated laser diode: DML) system in which an LD (Laser Diode) element is controlled is often employed.
  • the laser light source since the laser light source also functions as an optical modulator, the modulation characteristics of the optical output unit are easily affected by changes in the external environment and the laser driving state. For example, as the operating temperature increases, the output light intensity and modulation band decrease. Further, when the laser driving current is increased, the output light intensity is increased and the modulation band is improved. As described above, when the optical transmission waveform is affected by the operating temperature, the laser drive current, or the like, waveform distortion may occur, the eye opening may be closed, and reception sensitivity may be deteriorated or the transmission distance may be shortened.
  • Patent Document 1 relates to a direct detection optical transmission system.
  • the optical transmission system of Patent Document 1 transmits an optical signal subjected to multilevel phase modulation and intensity modulation using an external modulator through a transmission line, and a difference between signals received as two optical signals via a delay detection circuit.
  • the multi-level signal is determined by processing the dynamic phase component.
  • Patent Document 2 also discloses a phase modulator used for an optical transmission system.
  • Patent Document 1 is not sufficient in the following points. Since the technique of Patent Document 1 performs communication at an increased transmission speed by a multi-level modulation method, it is easily affected by signal degradation during transmission. For this reason, if the transmission quality is to be maintained, there is a possibility that the receiving apparatus becomes complicated and the receiving apparatus becomes large. Further, the technique of Patent Document 2 may not be able to maintain transmission quality when the transmission band is expanded. Therefore, the techniques of Patent Document 1 and Patent Document 2 are not sufficient as techniques for maintaining signal transmission quality even when the transmission band is expanded or the distance is extended without requiring a complicated configuration. .
  • the present invention provides an optical transmitter capable of maintaining signal transmission quality without requiring a complicated configuration even when the transmission band is extended or the distance is extended.
  • the purpose is that.
  • the optical transmitter of the present invention includes an optical output means, a control means, an intensity modulation means, and a phase modulation means.
  • the light output means generates continuous light having a wavelength assigned to the own device.
  • the control means includes a first control signal and intensity for controlling intensity modulation applied to the continuous light based on a combination of the phase difference of the optical signal corresponding to successive bits and the intensity of the optical signal and the correspondence with the code data to be transmitted. Controls the phase modulation applied to the modulated signal.
  • the intensity modulation means generates a signal obtained by applying intensity modulation to the continuous light based on the first control signal as an intensity modulation signal.
  • the phase modulation means performs phase modulation on the intensity modulation signal based on the second control signal, and outputs an optical signal subjected to phase modulation.
  • the optical receiver of the present invention includes a delay unit, a coupling unit, and a photoelectric conversion unit.
  • the delay means branches the optical signal subjected to phase modulation and intensity modulation based on a combination of the phase difference of the optical signal corresponding to consecutive bits and the intensity of the optical signal, and passes the branched optical signal. 1 path and a second path.
  • the second path causes a one-bit delay with respect to the first path.
  • the coupling means combines the optical signals that have passed through the first path and the second path, and outputs a component that has no phase difference among the combined optical signals, and the combined optical signal.
  • An optical signal is output to the fourth path for outputting a component having a predetermined phase difference.
  • the photoelectric conversion means receives the first light receiving element to which the optical signal output from the third path is input and the optical signal output from the fourth path and is connected in series with the first light receiving element.
  • the second light receiving element converts the optical signal into an electrical signal and outputs it.
  • the optical communication method of the present invention generates continuous light having a wavelength assigned to its own device.
  • the optical communication method of the present invention controls the intensity modulation applied to continuous light based on the combination of the phase difference of the optical signal corresponding to consecutive bits and the intensity of the optical signal, and the code data to be transmitted.
  • a second control signal for controlling phase modulation applied to the control signal and the intensity modulation signal is generated.
  • intensity modulation is performed on continuous light based on a first control signal to generate an intensity modulation signal
  • phase modulation is performed on the intensity modulation signal based on a second control signal
  • phase modulation is performed. Outputs the optical signal subjected to.
  • signal transmission quality can be maintained without requiring a complicated configuration even when the transmission band is expanded or the distance is extended.
  • FIG. 1 is a diagram showing an outline of the configuration of the optical transmitter 100 of the present embodiment.
  • FIG. 2 is a diagram showing an outline of the configuration of the optical receiver 200 of the present embodiment.
  • the optical transmitter 100 of this embodiment includes an optical output unit 101, a control unit 102, an intensity modulation unit 103, and a phase modulation unit 104.
  • the light output means 101 generates continuous light having a wavelength assigned to the device itself.
  • the control means 102 is a first control signal that controls intensity modulation applied to continuous light based on the correspondence between the phase difference of the optical signal corresponding to successive bits and the intensity of the optical signal and the code data to be transmitted. And phase modulation applied to the intensity-modulated signal.
  • the intensity modulation means 103 generates a signal obtained by applying intensity modulation to continuous light based on the first control signal as an intensity modulation signal.
  • the phase modulation means 104 performs phase modulation on the intensity modulation signal based on the second control signal, and outputs an optical signal subjected to phase modulation.
  • the optical receiver 200 of this embodiment includes a delay unit 201, a coupling unit 202, and a photoelectric conversion unit 203.
  • the delay means 201 branches the optical signal that has been subjected to phase modulation and intensity modulation based on the combination of the phase difference of the optical signal corresponding to successive bits and the intensity of the optical signal, and passes the branched optical signal A first route and a second route are provided.
  • the second path causes a one-bit delay with respect to the first path.
  • the combining unit 202 combines the optical signals that have passed through the first path and the second path, and outputs a combined third optical path that outputs a component having no phase difference among the combined optical signals, and the combined optical signal.
  • the optical signal is output to a fourth path for outputting a component having a predetermined phase difference.
  • the photoelectric conversion means 203 is connected in series with the first light receiving element to which the optical signal output from the third path is input and the optical signal output from the fourth path is input. In the second light receiving element, the optical signal is converted into an electric signal and output.
  • FIG. 3 shows an example of the configuration of an optical communication system using the optical transmitter 100 and the optical receiver 200 of the present embodiment.
  • An optical communication system can be configured by connecting the optical transmitter 100 and the optical receiver 200 of the present embodiment via a transmission line 300 using an optical fiber.
  • the optical signal output from the optical transmitter 100 is input to the optical receiver 200 via the transmission path 300.
  • the optical transmitter 100 performs composite modulation of intensity modulation and phase modulation on an optical signal to be transmitted, and transmits an optical signal in which code data is assigned to the phase difference and signal intensity of successive signals.
  • the optical receiver 200 on the receiving side acquires information on the phase difference and signal strength of successive signals by performing delay detection. Therefore, in the optical communication system using the optical transmitter 100 and the optical receiver 200 of the present embodiment, the transmission band can be expanded without increasing the transmission speed. Therefore, the optical receiver 200 according to the present embodiment can perform the decoding process in a state where the influence of signal degradation is suppressed even when the transmission distance of the signal increases. As a result, by using the optical transmitter 100 and the optical receiver 200 of the present embodiment, it is possible to maintain signal transmission quality without requiring a complicated configuration even when the transmission band is expanded or the distance is extended. Can do.
  • FIG. 4 shows an outline of the configuration of the optical transceiver 10 of the present embodiment.
  • the optical transceiver 10 of this embodiment is a communication module that transmits and receives optical signals when performing optical communication by the direct detection method.
  • the optical transceiver 10 of this embodiment includes a control unit 11, an optical transmission unit 12, an optical reception unit 13, a modulation control unit 14, a bias voltage control unit 15, an output control unit 16, an amplification unit 17, A connector portion 18 is provided.
  • the control unit 11 has a function of controlling the operation of each part of the optical transceiver 10.
  • the control unit 11 performs control of the signal amplification factor in the modulation control unit 14 and the amplification unit 17, control of the calibration operation of each part of the optical transceiver 10, and the like.
  • the optical transmitter 12 has a function of generating an optical signal that is modulated based on transmission code data.
  • the optical transmitter 12 further includes an optical output unit 21, an intensity modulator 22, and a phase modulator 23.
  • the light output unit 21 outputs continuous light having a predetermined wavelength.
  • the predetermined wavelength of the continuous light is set to a wavelength assigned to the optical transceiver 10 based on the wavelength design of the optical communication system in which the optical transceiver 10 is used.
  • the optical output unit 21 is configured by using, for example, a DFB-LD (Distributed Feedback Laser Diode). Further, the function of the light output unit 21 of the present embodiment corresponds to the light output means 101 of the first embodiment.
  • the intensity modulation unit 22 has a function of performing intensity modulation on continuous light having a predetermined wavelength input from the light output unit 21.
  • the intensity modulator 22 is configured as an intensity modulator using a Mach-Zehnder type modulator.
  • the intensity modulation unit 22 performs intensity modulation on the continuous light input from the light output unit 21 based on the high-frequency signal input from the modulation control unit 14 as the intensity modulation control signal S11, and intensity-modulates the phase modulation unit 23. Output as signal S13.
  • a bias voltage is applied to the modulation element of the intensity modulation unit 22 to correct the operating point.
  • the bias voltage is applied based on a signal input as a bias voltage control signal S15 from the bias voltage control unit 15.
  • the function of the intensity modulation unit 22 of this embodiment corresponds to the intensity modulation unit 103 of the first embodiment.
  • the phase modulation unit 23 has a function of further performing phase modulation on the intensity modulation signal S13 subjected to intensity modulation in the intensity modulation unit 22.
  • the phase modulation unit 23 is configured as a phase modulator using a Mach-Zehnder type modulator.
  • the phase modulation unit 23 performs phase modulation on the intensity modulation signal S13 based on the high-frequency signal input from the modulation control unit 14 as the phase modulation control signal S12.
  • the period of the intensity modulation performed in the intensity modulation unit 22 and the phase modulation performed in the phase modulation unit 23 are the same.
  • the intensity modulation in the intensity modulator 22 and the phase modulation speed in the phase modulator 23 are the same, and a 1-bit signal is subjected to composite modulation by intensity modulation and phase modulation.
  • the phase modulation unit 23 outputs an optical signal obtained by performing phase modulation on the intensity modulation signal S13 as the phase modulation signal S14.
  • the phase modulation signal S14 output from the phase modulation unit 23 is output from the optical transceiver 10 and transmitted to the transmission path.
  • the function of the phase modulation unit 23 of the present embodiment corresponds to the phase modulation unit 104 of the first embodiment.
  • the optical transmission unit 12 of this embodiment generates an optical signal subjected to both intensity modulation and phase modulation.
  • FIG. 5A shows a constellation on the phase plane for the intensity modulation signal S13.
  • FIG. 5B shows a constellation on the phase plane for the phase modulation signal S14.
  • the intensity modulation unit 22 performs intensity modulation based on a binary control signal indicating that the intensity is “High” or “Low”.
  • the signal after intensity modulation in the intensity modulation unit 22 corresponds to one of symbols indicated by “1” and “0” in FIG. 5A.
  • phase modulation unit 23 performs phase modulation based on a binary control signal indicating that the phase is “0” or “ ⁇ ”.
  • the optical signal that has been subjected to the phase modulation after the intensity modulation is performed corresponds to one of symbols indicated by “11”, “10”, “01”, and “00” in FIG. 5B.
  • FIG. 6 schematically shows an example of a modulation curve when modulation is performed in the intensity modulation unit 22 and the phase modulation unit 23 of the present embodiment.
  • a point of a predetermined bias voltage is set as an operating point indicated by an asterisk.
  • the intensity modulation unit 22 when the code data is “1”, a voltage corresponding to “High” is applied around the operating point, and the amplitude is larger than that of the “Low” signal.
  • the optical signal is output to the phase modulation unit 23.
  • the intensity modulation unit 22 applies a voltage corresponding to “Low” when the code data is “0”, and outputs an optical signal having a smaller amplitude than the “High” signal to the phase modulation unit 23.
  • the operating point is controlled by the bias voltage control unit 15.
  • phase modulation control signal S12 having the same speed as that of the intensity modulation control signal S11 is added to the modulator of the phase modulation unit 23 in the subsequent stage of the intensity modulation unit 22.
  • the phase modulation control signal S12 is “1”
  • the phase difference is 0,
  • the phase modulation control signal S12 is “0”
  • the phase difference ⁇ is obtained at each timing.
  • the phase of the optical signal itself is changing. That is, as illustrated on the right side of FIG. 6, the phase modulation unit 23 performs a signal having a phase of “0” or “ ⁇ ” with respect to an optical signal having an amplitude corresponding to “High” or “Low”. Phase modulation is performed so that
  • the optical transmission unit 12 of the present embodiment generates an optical signal in which double information is added to a 1-bit optical signal by combining intensity modulation and phase modulation. For example, intensity modulation is performed at a baud rate of 25 GBaud and phase modulation is simultaneously performed at the same speed, thereby obtaining a doubled transmission band of 56 Gbps.
  • the optical transmission unit 12 adds information based on code data as a phase difference between optical signals corresponding to consecutive bits when performing phase modulation. That is, the optical transmission unit 12 according to the present embodiment generates an optical signal based on transmission data by assigning code data to combinations of phase differences between consecutive bits and individual bit intensities. An example of the correspondence between the phase difference between consecutive bits and the intensity of each bit and the code data assigned to each combination will be described later.
  • the optical receiver 13 has a function of receiving an optical signal by a direct detection method.
  • FIG. 7 shows only the portion of the optical receiver 13 in the optical transceiver 10 of the present embodiment.
  • the optical receiver 13 further includes a delay circuit unit 31, a light receiver 32, and a current-voltage converter 33.
  • the delay circuit unit 31 branches the input optical signal into two different paths, multiplexes the optical signals that have passed through the respective paths interfere with each other, and then outputs them to the photodiode of the light receiving unit 32.
  • the delay circuit unit 31 is formed so that the optical path length of the other path is longer than the optical path length of one path by an amount corresponding to 1 bit. Further, the delay circuit unit 31 outputs a component having a phase difference of ⁇ and a component having a phase difference of 0 among the combined optical signals to different photodiodes. In the example of FIG.
  • the delay circuit unit 31 outputs a component having a phase difference of ⁇ among the combined optical signals to the photodiode of the upper light receiving unit 32, and outputs a component having a phase difference of 0 to the lower light receiving unit. It outputs to 32 photodiodes.
  • the function of the delay circuit unit 31 of the present embodiment corresponds to the delay unit 201 and the coupling unit 202 of the first embodiment.
  • the light receiving unit 32 converts the optical signal input from the delay circuit unit 31 into an electrical signal.
  • the light receiving unit 32 includes two photodiodes connected in series with each other. For example, PIN-PD (p-intrinsic-n Photodiode) is used as the photodiode.
  • PIN-PD p-intrinsic-n Photodiode
  • the light receiving unit 32 converts the optical signal input to each photodiode into a current signal, and outputs the difference between the current signals converted from the two photodiodes to the current-voltage conversion unit 33 at the subsequent stage. Further, the function of the light receiving unit 32 of the present embodiment corresponds to the photoelectric conversion unit 203 of the first embodiment.
  • the current-voltage conversion unit 33 converts the current signal input from the light receiving unit 32 into a voltage signal and outputs the voltage signal.
  • the current-voltage converter 33 is configured using a transimpedance amplifier.
  • the modulation control unit 14 controls intensity modulation and phase modulation applied to the light input from the light output unit 21 in the light transmission unit 12.
  • the modulation controller 14 is a driver IC (Integrated Circuit) that controls the voltage applied to the modulator in the intensity modulator 22 and the phase modulator 23.
  • the modulation control unit 14 generates an intensity modulation control signal S11 and a phase modulation control signal S12 based on signals input as differential electrical signals TD1 and TD2 from the current-voltage conversion unit to which the optical transceiver 10 is connected.
  • the modulation control unit 14 outputs the generated intensity modulation control signal S11 to the intensity modulation unit 22.
  • the modulation control unit 14 outputs the generated phase modulation control signal S12 to the phase modulation unit 23.
  • the function of the modulation control unit 14 of the present embodiment corresponds to the control means 102 of the first embodiment.
  • the bias voltage control unit 15 controls the bias voltage applied to the intensity modulation unit 22 of the optical transmission unit 12.
  • the bias voltage control unit 15 applies a bias voltage for correcting the operating point of the modulator of the intensity modulation unit 22 to the modulator of the intensity modulation unit 22.
  • the bias voltage is set by performing a calibration operation when the optical transceiver 10 is activated.
  • the set value of the bias voltage may be stored in the bias voltage control unit 15 in advance.
  • the output control unit 16 controls the wavelength and power of light output from the light output unit 21.
  • the amplifying unit 17 amplifies and outputs the signal input from the optical receiving unit 13.
  • a linear amplifier can be used for the amplifying unit 17.
  • the amplifying unit 17 amplifies the signal input from the current-voltage converting unit 33 to a signal level corresponding to the specification of the optical transmission apparatus to which the optical transceiver 10 is connected, and outputs the signal level.
  • the amplifying unit 17 outputs the amplified electrical signal as differential electrical signals RD1 and RD2 to the optical transmission apparatus to which the optical transceiver 10 is connected.
  • the connector unit 18 is a connector for connecting the optical transceiver 10 to the optical transmission device.
  • the optical transceiver 10 transmits and receives control signals and data communication signals to and from the optical transmission device via the connector unit 18.
  • the control unit 11, the modulation control unit 14, the bias voltage control unit 15 and the output control unit 16 of the present embodiment are configured using semiconductor devices. Each part may be constituted by an independent semiconductor device, and some parts may be constituted by the same semiconductor device. As the semiconductor device, for example, ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array) is used.
  • ASIC Application Specific Integrated Circuit
  • FPGA Field Programmable Gate Array
  • FIG. 8 shows an example of the configuration of an optical communication system using the optical transceiver 10 of the present embodiment.
  • the optical communication system in FIG. 8 includes an optical transmission device 40-1 and an optical transmission device 40-2.
  • the optical transmission device 40-1 and the optical transmission device 40-2 are connected via a transmission line 301 using an optical fiber.
  • Each of the optical transmission device 40-1 and the optical transmission device 40-2 includes an optical transceiver 10 and a signal processing circuit 41 that processes signals to be transmitted and received.
  • the signal processing circuit 41 performs transmission data encoding, redundancy processing, and the like to generate frame data for transmission. Further, the signal processing circuit 41 performs a demodulation process on the received signal.
  • the signal processing circuit 41 is configured by a semiconductor device such as FPGA or ASCI.
  • the transmission signal and the reception signal may be processed in different semiconductor devices. An operation of the optical transceiver 10 used in the optical communication system having such a configuration will be described as an example.
  • the optical output unit 21 of the optical transmission unit 12 When the optical transceiver 10 starts operating, the optical output unit 21 of the optical transmission unit 12 generates continuous light having a predetermined wavelength and outputs the continuous light to the intensity modulation unit 22. The light input from the optical output unit 21 to the optical transmission unit 12 is input to the intensity modulation unit 22.
  • high-frequency signals based on transmission data are input as differential electrical signals TD1 and TD2 from the optical transmission apparatus to which the optical transceiver 10 is connected to the modulation control unit 14.
  • the modulation control unit 14 applies a voltage to the modulator of the intensity modulation unit 22 based on the intensity modulation control signal S11.
  • the bias voltage controller 15 outputs a bias voltage control signal S15 to the intensity modulator 22, and applies a bias voltage for correcting the operating point to the modulator of the intensity modulator 22.
  • the intensity modulation unit 22 When light is input from the light output unit 21, the intensity modulation unit 22 performs intensity modulation on the input light based on the intensity modulation control signal S 11 input from the modulation control unit 14. The intensity modulator 22 outputs the intensity-modulated optical signal to the phase modulator 23 as an intensity modulation signal S13.
  • phase modulation unit 23 When an optical signal subjected to intensity modulation is input to the phase modulation unit 23, the phase modulation unit 23 performs phase modulation on the input optical signal based on the phase modulation control signal S12 input from the modulation control unit 14. Apply.
  • the phase modulation signal S14 subjected to phase modulation in the phase modulation unit 23 is output from the optical transceiver 10.
  • the optical signal output from the optical transceiver 10 is sent to the optical transmission device on the receiving side, that is, the opposite optical transmission device via the transmission path.
  • the optical transceiver 10 receives an optical signal in the optical transmission apparatus on the receiving side
  • the received optical signal is sent to the optical receiver 13.
  • the delay circuit unit 31 branches the input optical signal into two different paths, causes the optical signals that have passed through the respective paths to interfere with each other, and then the photodiode of the light receiving unit 32. Output to.
  • the optical signal is input to the photodiode below the light receiving unit 32.
  • the phase difference of the optical signal that has passed through the two paths of the delay circuit unit 31 is ⁇ , the optical signal is input to the photodiode on the upper side of the light receiving unit 32.
  • the light receiving unit 32 converts the input optical signal into an electrical signal.
  • the light receiving unit 32 includes two photodiodes in series, and outputs the difference between the current signals output from the two photodiodes to the subsequent current-voltage conversion unit 33.
  • the current-voltage conversion unit 33 converts the input electrical signal from a current signal to a voltage signal and outputs the voltage signal to the amplification unit 17.
  • the amplifying unit 17 amplifies the signal level to within the setting range of the optical transmission apparatus to which the optical transceiver 10 is connected, and optically transmits the differential electric signals RD1 and RD2. Output to the device.
  • the optical transceiver 10 of the present embodiment inputs the received optical signal to the 1-bit delay detection circuit configured as the delay circuit unit 31.
  • the 1-bit delay detection circuit 2-bit data transmission can be performed with one optical signal by assigning 1 bit each to the phase change based on the phase difference from the previous signal and the intensity of each signal. It becomes possible.
  • an optical signal with a baud rate of 28 GBaud can be received as 56 Gbps.
  • modulation is performed with 56 GBaud, it is possible to suppress the input conversion noise of the transimpedance amplifier of the optical receiver 13 and reduce the influence of dispersion, so that the reception quality can be maintained even if the transmission distance is increased. .
  • FIG. 9 shows a constellation on the phase plane of the optical signal input to the optical receiver 13.
  • FIG. 10 shows the relationship between the code signal and the intensity of the received signal and the phase difference of the optical signal after passing through the delay detection circuit when decoding the received signal subjected to intensity modulation and phase modulation. Is.
  • the phase difference between the signals before and after the 1-bit delayed detection is performed on the 2-bit code data of “00”, “11”, “01”, and “10”, the phase change direction, and the signal Combinations of strength are supported.
  • the case is assigned where the signal strengths of the bits subsequent to “00” are both “Low” and the phase difference is “0”. Further, “11” is assigned with the case where the signal strengths of consecutive bits are both “High” and the phase difference is “0”. Also, the case where the signal strength of consecutive bits is “Low” and “High”, the phase difference is “ ⁇ ”, and the phase change is 0 to ⁇ is assigned to “01”. Further, “10” is assigned the case where the signal strength of consecutive bits is “High” and “Low”, the phase difference is “ ⁇ ”, and the phase change is from ⁇ to 0.
  • the direction of phase change is determined by the received code change. Therefore, the signal can be decoded on the receiving side by performing modulation on the basis of the phase difference between the continuous signals on the transmitting side, the phase change direction, and the correspondence between the signal strength and the code data. Information indicating the correspondence between the phase difference between successive signals, the phase change direction, and the intensity of the signal and the code data is shared in advance between the transmission side and the reception side.
  • FIG. 11 schematically shows an optical transceiver that performs only intensity modulation as an example of a configuration to be compared with the optical transceiver 10 of the present embodiment.
  • the transmission waveform may be affected and waveform distortion or the like may occur.
  • the optical transceiver 10 according to the present embodiment is used for such a configuration, the quality of the signal is maintained while the transmission band is widened by transmitting an optical signal subjected to combined modulation of intensity modulation and phase modulation. be able to.
  • the optical transceiver 10 of the present embodiment performs combined modulation of intensity modulation and phase modulation on an optical signal to be transmitted.
  • the optical transceiver 10 of this embodiment adds data for transmission to an optical signal based on the phase difference between successive signals and the intensity of the signal. Further, the optical transceiver 10 on the receiving side acquires information on the phase difference and signal strength of successive signals by performing delay detection. Therefore, the optical transceiver 10 according to the present embodiment can expand the band without increasing the transmission speed, so that the influence of the signal can be suppressed and the demodulation process can be performed. As a result, by using the optical transceiver 10 of the present embodiment, signal transmission quality can be maintained without requiring a complicated configuration even when the transmission band is expanded or the distance is extended.
  • the optical transceiver 10 of the second embodiment performs intensity modulation of signal intensity in two stages of High and Low, but intensity modulation by multi-stage signal intensity setting such as PAM (Pulse Amplitude Modulation) 4 or PAM 8 is performed. You may go.
  • the transmission band can be further improved by performing determination on the receiving side in multiple stages.
  • an example of an optical communication system in which the transmission-side and reception-side optical transceivers 10 are one is shown.
  • the optical communication system uses a plurality of optical transceivers 10 to communicate wavelength multiplexed signals. The system which performs may be sufficient.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Communication System (AREA)

Abstract

[Problem] To provide a light transmitter that does not require a complicated configuration to maintain the transmission quality of a signal, even when widening the transmission bandwidth or extending the transmission distance. [Solution] This light transmitter comprises a light output means, a control means, an intensity modulation means, and a phase modulation means. The light output means generates continuous light of a wavelength assigned to a host device. On the basis of the correspondence between code data to be transmitted and a combination of the phase difference of a light signal equivalent to a series of bits and the intensities of the optical signals, the control means controls a phase modulation performed on: a first control signal that controls an intensity modulation performed on the continuous light; and a signal on which the intensity modulation has been performed. The intensity modulation means generates, as an intensity modulation signal, the signal obtained by performing the intensity modulation on the continuous light on the basis of the first control signal. Also, the phase modulation means performs the phase modulation on the intensity modulation signal on the basis of a second control signal, and outputs the light signal on which the phase modulation has been performed.

Description

光送信器、光受信器および光通信方法Optical transmitter, optical receiver, and optical communication method
　本発明は、光通信技術に関するものであり、特に、直接検波方式の光通信システムに関するものである。 The present invention relates to an optical communication technology, and more particularly to an optical communication system using a direct detection method.
　近年、動画コンテンツ利用などによる光通信の大容量化に伴い、基幹通信だけでなく、末端となるクライアント側光通信においても、２５Ｇｂｐｓ程度の伝送速度が求められるようになっている。クライアント向け製品は、低価格かつ低電力であることが求められる。そのため、クライアント向けの光送信モジュールでは、ＬＤ（Laser Diode）素子を制御した直接変調（Direct Modulated Laser diode：ＤＭＬ）方式が採用されていることが多かった。 In recent years, with the increase in capacity of optical communication due to the use of moving image content, a transmission speed of about 25 Gbps is required not only for basic communication but also for client-side optical communication at the end. Client products are required to be low cost and low power. For this reason, in an optical transmission module for a client, a direct modulation (direct modulated laser diode: DML) system in which an LD (Laser Diode) element is controlled is often employed.
　しかし、ＤＭＬ方式では光変調器の機能をレーザー光源が兼ねるため、光出力部の変調特性は、外部環境の変動やレーザーの駆動状態の影響を受けやすい。例えば、動作温度が高くなると出力光強度および変調帯域が低下する。また、レーザーの駆動電流を大きくすると、出力光強度が大きくなるとともに変調帯域が向上する。このように動作温度やレーザー駆動電流などにより光送信波形が影響を受けると、波形歪が発生し、アイ開口が閉じて、受信感度劣化や伝送距離が短くなる恐れがある。 However, in the DML method, since the laser light source also functions as an optical modulator, the modulation characteristics of the optical output unit are easily affected by changes in the external environment and the laser driving state. For example, as the operating temperature increases, the output light intensity and modulation band decrease. Further, when the laser driving current is increased, the output light intensity is increased and the modulation band is improved. As described above, when the optical transmission waveform is affected by the operating temperature, the laser drive current, or the like, waveform distortion may occur, the eye opening may be closed, and reception sensitivity may be deteriorated or the transmission distance may be shortened.
　２５Ｇｂｐｓ程度の速度での駆動では、ＬＤ素子の特性変動が製品としてのパフォーマンスに大きく影響を与え得る。そのため、伝送距離や伝送帯域を伸ばしたいという要求がある場合、ＥＭＬ（Electro-absorption Modulated Lasers）などの外部変調方式が用いられる。しかし、外部変調方式でも数１０ｋｍ程度が限界に近く、伝送帯域や距離を拡大するためには、デジタルコヒーレント方式など複雑かつ高価な部品構成を必要とする通信システムを用いる必要がある。そのため、複雑な構成を必要とすることなく、伝送帯域の拡大や距離の延伸を行っても信号の伝送品質を維持できる技術があることが望ましく関連する技術の開発が行われている。そのような、信号の伝送品質を維持するための技術としては、例えば、特許文献１のような技術が開示されている。 When driving at a speed of about 25 Gbps, characteristic variations of the LD element can greatly affect the performance of the product. Therefore, when there is a request for extending the transmission distance or transmission band, an external modulation method such as EML (Electro-absorption Modulated Lasers) is used. However, in the external modulation system, about several tens of kilometers is close to the limit, and in order to expand the transmission band and distance, it is necessary to use a communication system that requires a complicated and expensive component configuration such as a digital coherent system. Therefore, it is desirable that there is a technique capable of maintaining the signal transmission quality even when the transmission band is extended or the distance is extended without requiring a complicated configuration, and a related technique has been developed. As such a technique for maintaining the transmission quality of a signal, for example, a technique as disclosed in Patent Document 1 is disclosed.
　特許文献１は、直接検波方式の光伝送システムに関するものである。特許文献１の光伝送システムは、外部変調器を用いて多値位相変調と強度変調を施した光信号を伝送路で伝送し、遅延検波回路を介して２つの光信号として受信した信号の差動位相成分の処理を行うことで多値信号の判定を行っている。特許文献１は、そのような構成とすることで、伝送特性の劣化を防止することができるとしている。また、特許文献２にも、光伝送システムに用いる位相変調器が示されている。 Patent Document 1 relates to a direct detection optical transmission system. The optical transmission system of Patent Document 1 transmits an optical signal subjected to multilevel phase modulation and intensity modulation using an external modulator through a transmission line, and a difference between signals received as two optical signals via a delay detection circuit. The multi-level signal is determined by processing the dynamic phase component. Japanese Patent Application Laid-Open No. H10-228561 can prevent deterioration of transmission characteristics by adopting such a configuration. Patent Document 2 also discloses a phase modulator used for an optical transmission system.
国際公開第２０１１／０８３５７５号International Publication No. 2011/083575 国際公開第２０１０／０２１２８０号International Publication No. 2010/021280
　しかしながら、特許文献１の技術は次のような点で十分ではない。特許文献１の技術は、多値変調方式によって伝送速度を上げて通信を行うため、伝送時の信号の劣化の影響を受けやすい。そのため、伝送品質を維持しようとすると受信側の装置が複雑化し受信装置が大型化する恐れがある。また、特許文献２の技術も伝送帯域を拡げた場合に伝送品質を維持できない恐れがある。そのため、特許文献１および特許文献２の技術は、複雑な構成を必要とすることなく、伝送帯域の拡大や距離の延伸を行っても信号の伝送品質を維持するための技術としては十分ではない。 However, the technique of Patent Document 1 is not sufficient in the following points. Since the technique of Patent Document 1 performs communication at an increased transmission speed by a multi-level modulation method, it is easily affected by signal degradation during transmission. For this reason, if the transmission quality is to be maintained, there is a possibility that the receiving apparatus becomes complicated and the receiving apparatus becomes large. Further, the technique of Patent Document 2 may not be able to maintain transmission quality when the transmission band is expanded. Therefore, the techniques of Patent Document 1 and Patent Document 2 are not sufficient as techniques for maintaining signal transmission quality even when the transmission band is expanded or the distance is extended without requiring a complicated configuration. .
　本発明は、上記の課題を解決するため、伝送帯域の拡大や距離の延伸を行っても複雑な構成を必要とすることなく、信号の伝送品質を維持することができる光送信器を提供することを目的としている。 In order to solve the above-described problems, the present invention provides an optical transmitter capable of maintaining signal transmission quality without requiring a complicated configuration even when the transmission band is extended or the distance is extended. The purpose is that.
　上記の課題を解決するため、本発明の光送信器は、光出力手段と、制御手段と、強度変調手段と、位相変調手段を備えている。光出力手段は、自装置に割り当てられた波長の連続光を生成する。制御手段は、連続するビットに相当する光信号の位相差および光信号の強度の組み合わせと、伝送する符号データと対応を基に、連続光に施す強度変調を制御する第１の制御信号および強度変調に施した信号に施す位相変調を制御する。強度変調手段は、連続光に第１の制御信号に基づいて強度変調を施した信号を強度変調信号として生成する。また、位相変調手段は、強度変調信号に第２の制御信号に基づいて位相変調を施し、位相変調を施した光信号を出力する。 In order to solve the above problems, the optical transmitter of the present invention includes an optical output means, a control means, an intensity modulation means, and a phase modulation means. The light output means generates continuous light having a wavelength assigned to the own device. The control means includes a first control signal and intensity for controlling intensity modulation applied to the continuous light based on a combination of the phase difference of the optical signal corresponding to successive bits and the intensity of the optical signal and the correspondence with the code data to be transmitted. Controls the phase modulation applied to the modulated signal. The intensity modulation means generates a signal obtained by applying intensity modulation to the continuous light based on the first control signal as an intensity modulation signal. The phase modulation means performs phase modulation on the intensity modulation signal based on the second control signal, and outputs an optical signal subjected to phase modulation.
　本発明の光受信器は、光受信器は、遅延手段と、結合手段と、光電変換手段を備えている。遅延手段は、連続するビットに相当する光信号の位相差および前記光信号の強度の組み合わせに基づいて位相変調および強度変調が施された光信号を分岐し、分岐した前記光信号を通過させる第１の経路と、第２の経路とを備えている。第２の経路は、第１の経路に対して１ビット分の遅延を生じさせる。結合手段は、第１の経路と第２の経路を通過した光信号を合波し、合波した光信号のうち位相差が無い成分を出力する第３の経路と、合波した光信号のうち所定の位相差を有する成分を出力する第４の経路とに光信号を出力する。光電変換手段は、第３の経路から出力された光信号が入力される第１の受光素子と、第４の経路から出力された光信号が入力され、第１の受光素子と直列に接続された第２の受光素子において光信号を電気信号に変換して出力する。 The optical receiver of the present invention includes a delay unit, a coupling unit, and a photoelectric conversion unit. The delay means branches the optical signal subjected to phase modulation and intensity modulation based on a combination of the phase difference of the optical signal corresponding to consecutive bits and the intensity of the optical signal, and passes the branched optical signal. 1 path and a second path. The second path causes a one-bit delay with respect to the first path. The coupling means combines the optical signals that have passed through the first path and the second path, and outputs a component that has no phase difference among the combined optical signals, and the combined optical signal. An optical signal is output to the fourth path for outputting a component having a predetermined phase difference. The photoelectric conversion means receives the first light receiving element to which the optical signal output from the third path is input and the optical signal output from the fourth path and is connected in series with the first light receiving element. The second light receiving element converts the optical signal into an electrical signal and outputs it.
　本発明の光通信方法は、自装置に割り当てられた波長の連続光を生成する。本発明の光通信方法は、連続するビットに相当する光信号の位相差および光信号の強度の組み合わせと、伝送する符号データと対応を基に、連続光に施す強度変調を制御する第１の制御信号および強度変調信号に施す位相変調を制御する第２の制御信号を生成する。本発明の光通信方法は、連続光に第１の制御信号に基づいて強度変調を施して強度変調信号を生成し、強度変調信号に第２の制御信号に基づいて位相変調を施し、位相変調を施した光信号を出力する。 The optical communication method of the present invention generates continuous light having a wavelength assigned to its own device. The optical communication method of the present invention controls the intensity modulation applied to continuous light based on the combination of the phase difference of the optical signal corresponding to consecutive bits and the intensity of the optical signal, and the code data to be transmitted. A second control signal for controlling phase modulation applied to the control signal and the intensity modulation signal is generated. In the optical communication method of the present invention, intensity modulation is performed on continuous light based on a first control signal to generate an intensity modulation signal, phase modulation is performed on the intensity modulation signal based on a second control signal, and phase modulation is performed. Outputs the optical signal subjected to.
　本発明によると、伝送帯域の拡大や距離の延伸を行っても複雑な構成を必要とすることなく信号の伝送品質を維持することができる。 According to the present invention, signal transmission quality can be maintained without requiring a complicated configuration even when the transmission band is expanded or the distance is extended.
本発明の第１の実施形態の光送信器の構成の概要を示す図である。It is a figure which shows the outline | summary of a structure of the optical transmitter of the 1st Embodiment of this invention. 本発明の第１の実施形態の光受信器の構成の概要を示す図である。It is a figure which shows the outline | summary of a structure of the optical receiver of the 1st Embodiment of this invention. 本発明の第１の実施形態の光送信器と光受信器を用いた光通信システムの構成の例を示す図である。It is a figure which shows the example of a structure of the optical communication system using the optical transmitter and optical receiver of the 1st Embodiment of this invention. 本発明の第２の実施形態の光トランシーバの構成の概要を示す図である。It is a figure which shows the outline | summary of a structure of the optical transceiver of the 2nd Embodiment of this invention. 本発明の第２の実施形態における強度変調後のコンスタレーションを示す図である。It is a figure which shows the constellation after the intensity | strength modulation in the 2nd Embodiment of this invention. 本発明の第２の実施形態における位相変調後のコンスタレーションを示す図である。It is a figure which shows the constellation after the phase modulation in the 2nd Embodiment of this invention. 本発明の第２の実施形態の強度変調部と位相変調部で施される変調の例を模式的に示した図である。It is the figure which showed typically the example of the modulation | alteration performed with the intensity | strength modulation part and phase modulation part of the 2nd Embodiment of this invention. 本発明の第２の実施形態の光受信部の構成を示す図である。It is a figure which shows the structure of the optical receiver of the 2nd Embodiment of this invention. 本発明の第２の実施形態の光トランシーバを用いた光通信システムの構成の例を示す図である。It is a figure which shows the example of a structure of the optical communication system using the optical transceiver of the 2nd Embodiment of this invention. 本発明の第２の実施形態における受信信号のコンスタレーションを示す図である。It is a figure which shows the constellation of the received signal in the 2nd Embodiment of this invention. 本発明の第２の実施形態における受信信号の位相および強度と符号の関係を示した図である。It is the figure which showed the phase and intensity | strength of a received signal, and the relationship of a code | symbol in the 2nd Embodiment of this invention. 本発明と対比した構成の光トランシーバの例を示す図である。It is a figure which shows the example of the optical transceiver of a structure contrasted with this invention.
　（第１の実施形態）
　本発明の第１の実施形態について図を参照して詳細に説明する。図１は、本実施形態の光送信器１００の構成の概要を示した図である。また、図２は、本実施形態の光受信器２００の構成の概要を示した図である。 (First embodiment)
A first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an outline of the configuration of the optical transmitter 100 of the present embodiment. FIG. 2 is a diagram showing an outline of the configuration of the optical receiver 200 of the present embodiment.
　本実施形態の光送信器１００は、光出力手段１０１と、制御手段１０２と、強度変調手段１０３と、位相変調手段１０４を備えている。光出力手段１０１は、自装置に割り当てられた波長の連続光を生成する。制御手段１０２は、連続するビットに相当する光信号の位相差および光信号の強度の組み合わせと、伝送する符号データとの対応を基に、連続光に施す強度変調を制御する第１の制御信号および強度変調を施した信号に施す位相変調を制御する。強度変調手段１０３は、連続光に第１の制御信号に基づいて強度変調を施した信号を強度変調信号として生成する。また、位相変調手段１０４は、強度変調信号に第２の制御信号に基づいて位相変調を施し、位相変調を施した光信号を出力する。 The optical transmitter 100 of this embodiment includes an optical output unit 101, a control unit 102, an intensity modulation unit 103, and a phase modulation unit 104. The light output means 101 generates continuous light having a wavelength assigned to the device itself. The control means 102 is a first control signal that controls intensity modulation applied to continuous light based on the correspondence between the phase difference of the optical signal corresponding to successive bits and the intensity of the optical signal and the code data to be transmitted. And phase modulation applied to the intensity-modulated signal. The intensity modulation means 103 generates a signal obtained by applying intensity modulation to continuous light based on the first control signal as an intensity modulation signal. Further, the phase modulation means 104 performs phase modulation on the intensity modulation signal based on the second control signal, and outputs an optical signal subjected to phase modulation.
　また、本実施形態の光受信器２００は、遅延手段２０１と、結合手段２０２と、光電変換手段２０３を備えている。遅延手段２０１は、連続するビットに相当する光信号の位相差および前記光信号の強度の組み合わせに基づいて位相変調および強度変調が施された光信号を分岐し、分岐した前記光信号を通過させる第１の経路と、第２の経路とを備えている。第２の経路は、第１の経路に対して１ビット分の遅延を生じさせる。結合手段２０２は、第１の経路と第２の経路を通過した光信号を合波し、合波した光信号のうち位相差が無い成分を出力する第３の経路と、合波した光信号のうち所定の位相差を有する成分を出力する第４の経路とに光信号を出力する。光電変換手段２０３は、第３の経路から出力された光信号が入力される第１の受光素子と、第４の経路から出力された光信号が入力され、第１の受光素子と直列に接続された第２の受光素子において光信号を電気信号に変換して出力する。 Also, the optical receiver 200 of this embodiment includes a delay unit 201, a coupling unit 202, and a photoelectric conversion unit 203. The delay means 201 branches the optical signal that has been subjected to phase modulation and intensity modulation based on the combination of the phase difference of the optical signal corresponding to successive bits and the intensity of the optical signal, and passes the branched optical signal A first route and a second route are provided. The second path causes a one-bit delay with respect to the first path. The combining unit 202 combines the optical signals that have passed through the first path and the second path, and outputs a combined third optical path that outputs a component having no phase difference among the combined optical signals, and the combined optical signal. The optical signal is output to a fourth path for outputting a component having a predetermined phase difference. The photoelectric conversion means 203 is connected in series with the first light receiving element to which the optical signal output from the third path is input and the optical signal output from the fourth path is input. In the second light receiving element, the optical signal is converted into an electric signal and output.
　また、図３は、本実施形態の光送信器１００と光受信器２００を用いた光通信システムの構成の例を示している。本実施形態の光送信器１００と光受信器２００を、光ファイバを用いた伝送路３００を介して接続することで光通信システムを構成することができる。そのような構成の光通信システムでは、光送信器１００から出力された光信号が、伝送路３００を介して光受信器２００に入力される。 FIG. 3 shows an example of the configuration of an optical communication system using the optical transmitter 100 and the optical receiver 200 of the present embodiment. An optical communication system can be configured by connecting the optical transmitter 100 and the optical receiver 200 of the present embodiment via a transmission line 300 using an optical fiber. In the optical communication system having such a configuration, the optical signal output from the optical transmitter 100 is input to the optical receiver 200 via the transmission path 300.
　本実施形態の光送信器１００は、送信する光信号に強度変調と位相変調の複合変調を施し、連続する信号の位相差と信号の強度に符号データを割り当てた光信号を送信している。また、受信側の光受信器２００は、遅延検波を行うことで連続する信号の位相差と信号の強度の情報を取得している。よって、本実施形態の光送信器１００と光受信器２００を用いた光通信システムでは、伝送速度を上げなくても伝送帯域を広げることができる。そのため、本実施形態の光受信器２００は、信号の伝送距離が拡がった場合にも、信号の劣化影響が抑制された状態で復号処理を行うことができる。その結果、本実施形態の光送信器１００および光受信器２００を用いることで、伝送帯域の拡大や距離の延伸を行っても複雑な構成を必要とすることなく信号の伝送品質を維持することができる。 The optical transmitter 100 according to the present embodiment performs composite modulation of intensity modulation and phase modulation on an optical signal to be transmitted, and transmits an optical signal in which code data is assigned to the phase difference and signal intensity of successive signals. Also, the optical receiver 200 on the receiving side acquires information on the phase difference and signal strength of successive signals by performing delay detection. Therefore, in the optical communication system using the optical transmitter 100 and the optical receiver 200 of the present embodiment, the transmission band can be expanded without increasing the transmission speed. Therefore, the optical receiver 200 according to the present embodiment can perform the decoding process in a state where the influence of signal degradation is suppressed even when the transmission distance of the signal increases. As a result, by using the optical transmitter 100 and the optical receiver 200 of the present embodiment, it is possible to maintain signal transmission quality without requiring a complicated configuration even when the transmission band is expanded or the distance is extended. Can do.
　（第２の実施形態）
　本発明の第２の実施形態について図を参照して詳細に説明する。図４は、本実施形態の光トランシーバ１０の構成の概要を示したものである。本実施形態の光トランシーバ１０は、直接検波方式による光通信を行う際に光信号の送信および受信を行う通信モジュールである。 (Second Embodiment)
A second embodiment of the present invention will be described in detail with reference to the drawings. FIG. 4 shows an outline of the configuration of the optical transceiver 10 of the present embodiment. The optical transceiver 10 of this embodiment is a communication module that transmits and receives optical signals when performing optical communication by the direct detection method.
　本実施形態の光トランシーバ１０は、制御部１１と、光送信部１２と、光受信部１３と、変調制御部１４と、バイアス電圧制御部１５と、出力制御部１６と、増幅部１７と、コネクタ部１８を備えている。 The optical transceiver 10 of this embodiment includes a control unit 11, an optical transmission unit 12, an optical reception unit 13, a modulation control unit 14, a bias voltage control unit 15, an output control unit 16, an amplification unit 17, A connector portion 18 is provided.
　制御部１１は、光トランシーバ１０の各部位の動作を制御する機能を有する。制御部１１は、変調制御部１４および増幅部１７における信号の増幅率の制御や光トランシーバ１０の各部位のキャリブレーション動作の制御等を行う。 The control unit 11 has a function of controlling the operation of each part of the optical transceiver 10. The control unit 11 performs control of the signal amplification factor in the modulation control unit 14 and the amplification unit 17, control of the calibration operation of each part of the optical transceiver 10, and the like.
　光送信部１２は、送信用の符号データに基づいて変調が施された光信号を生成する機能を有する。光送信部１２は、光出力部２１と、強度変調部２２と、位相変調部２３をさらに備えている。 The optical transmitter 12 has a function of generating an optical signal that is modulated based on transmission code data. The optical transmitter 12 further includes an optical output unit 21, an intensity modulator 22, and a phase modulator 23.
　光出力部２１は、所定の波長の連続光を出力する。連続光の所定の波長は、光トランシーバ１０が用いられる光通信システムの波長設計に基づいて光トランシーバ１０に割り当てられた波長に設定されている。光出力部２１は、例えば、ＤＦＢ－ＬＤ（Distributed Feedback Laser Diode）を用いて構成されている。また、本実施形態の光出力部２１の機能は、第１の実施形態の光出力手段１０１に相当する。 The light output unit 21 outputs continuous light having a predetermined wavelength. The predetermined wavelength of the continuous light is set to a wavelength assigned to the optical transceiver 10 based on the wavelength design of the optical communication system in which the optical transceiver 10 is used. The optical output unit 21 is configured by using, for example, a DFB-LD (Distributed Feedback Laser Diode). Further, the function of the light output unit 21 of the present embodiment corresponds to the light output means 101 of the first embodiment.
　強度変調部２２は、光出力部２１から入力される所定の波長の連続光に強度変調を施す機能を有する。強度変調部２２は、マッハツェンダ型の変調器を用いた強度変調器として構成されている。強度変調部２２は、変調制御部１４から強度変調制御信号Ｓ１１として入力される高周波信号に基づいて、光出力部２１から入力される連続光に強度変調を施して、位相変調部２３に強度変調信号Ｓ１３として出力する。また、強度変調部２２の変調素子にはバイアス電圧が印加され動作点の補正が行われている。バイアス電圧は、バイアス電圧制御部１５からバイアス電圧制御信号Ｓ１５として入力される信号に基づいて印加させる。また、本実施形態の強度変調部２２の機能は、第１の実施形態の強度変調手段１０３に相当する。 The intensity modulation unit 22 has a function of performing intensity modulation on continuous light having a predetermined wavelength input from the light output unit 21. The intensity modulator 22 is configured as an intensity modulator using a Mach-Zehnder type modulator. The intensity modulation unit 22 performs intensity modulation on the continuous light input from the light output unit 21 based on the high-frequency signal input from the modulation control unit 14 as the intensity modulation control signal S11, and intensity-modulates the phase modulation unit 23. Output as signal S13. A bias voltage is applied to the modulation element of the intensity modulation unit 22 to correct the operating point. The bias voltage is applied based on a signal input as a bias voltage control signal S15 from the bias voltage control unit 15. The function of the intensity modulation unit 22 of this embodiment corresponds to the intensity modulation unit 103 of the first embodiment.
　位相変調部２３は、強度変調部２２において強度変調が施された強度変調信号Ｓ１３にさらに位相変調を施す機能を有する。位相変調部２３は、マッハツェンダ型の変調器を用いた位相変調器として構成されている。位相変調部２３は、変調制御部１４から位相変調制御信号Ｓ１２として入力される高周波信号に基づいて、強度変調信号Ｓ１３に位相変調を施す。強度変調部２２において施される強度変調と位相変調部２３において施される位相変調の周期は、同一である。すなわち、強度変調部２２における強度変調と位相変調部２３における位相変調の速度は、同一であり、１ビットの信号に強度変調および位相変調による複合変調が施される。位相変調部２３は、強度変調信号Ｓ１３に位相変調を施した光信号を位相変調信号Ｓ１４として出力する。位相変調部２３から出力された位相変調信号Ｓ１４は、光トランシーバ１０から出力され伝送路に送信される。また、本実施形態の位相変調部２３の機能は、第１の実施形態の位相変調手段１０４に相当する。 The phase modulation unit 23 has a function of further performing phase modulation on the intensity modulation signal S13 subjected to intensity modulation in the intensity modulation unit 22. The phase modulation unit 23 is configured as a phase modulator using a Mach-Zehnder type modulator. The phase modulation unit 23 performs phase modulation on the intensity modulation signal S13 based on the high-frequency signal input from the modulation control unit 14 as the phase modulation control signal S12. The period of the intensity modulation performed in the intensity modulation unit 22 and the phase modulation performed in the phase modulation unit 23 are the same. That is, the intensity modulation in the intensity modulator 22 and the phase modulation speed in the phase modulator 23 are the same, and a 1-bit signal is subjected to composite modulation by intensity modulation and phase modulation. The phase modulation unit 23 outputs an optical signal obtained by performing phase modulation on the intensity modulation signal S13 as the phase modulation signal S14. The phase modulation signal S14 output from the phase modulation unit 23 is output from the optical transceiver 10 and transmitted to the transmission path. The function of the phase modulation unit 23 of the present embodiment corresponds to the phase modulation unit 104 of the first embodiment.
　本実施形態の光送信部１２は、強度変調と位相変調の両方を施した光信号を生成する。図５Ａは、強度変調信号Ｓ１３についての位相平面上のコンスタレーションを示したものである。また、図５Ｂは、位相変調信号Ｓ１４についての位相平面上のコンスタレーションを示したものである。強度変調部２２は、強度が「Ｈｉｇｈ」と「Ｌｏｗ」のいずれであることを示す２値の制御信号に基づいて、強度変調を行う。強度変調部２２における強度変調後の信号は、図５Ａにおいて「１」、「０」で示したシンボルのいずれかに相当する。 The optical transmission unit 12 of this embodiment generates an optical signal subjected to both intensity modulation and phase modulation. FIG. 5A shows a constellation on the phase plane for the intensity modulation signal S13. FIG. 5B shows a constellation on the phase plane for the phase modulation signal S14. The intensity modulation unit 22 performs intensity modulation based on a binary control signal indicating that the intensity is “High” or “Low”. The signal after intensity modulation in the intensity modulation unit 22 corresponds to one of symbols indicated by “1” and “0” in FIG. 5A.
　また、位相変調部２３は、位相が「０」と「π」のいずれであることを示す２値の制御信号に基づいて、位相変調を行う。強度変調が施された後にさらに位相変調が施された光信号は、図５Ｂにおいて「１１」、「１０」、「０１」、「００」で示したシンボルのいずれかに相当する。 Further, the phase modulation unit 23 performs phase modulation based on a binary control signal indicating that the phase is “0” or “π”. The optical signal that has been subjected to the phase modulation after the intensity modulation is performed corresponds to one of symbols indicated by “11”, “10”, “01”, and “00” in FIG. 5B.
　また、図６は、本実施形態の強度変調部２２および位相変調部２３において変調が行われる際の変調曲線の例を模式的に示したものである。強度変調部２２の変調器が出力する光の強度と変調器に印加される電圧の関係を示したトランスファーカーブにおいて、所定のバイアス電圧の点を星印で示す動作点とする。動作点を中心にＮＲＺ（Non Return to Zero）の強度変調制御信号Ｓ１１を変調器に印加することで、図６の左側に示すような強度変調後の光出力信号が得られる。 FIG. 6 schematically shows an example of a modulation curve when modulation is performed in the intensity modulation unit 22 and the phase modulation unit 23 of the present embodiment. In the transfer curve showing the relationship between the intensity of light output from the modulator of the intensity modulator 22 and the voltage applied to the modulator, a point of a predetermined bias voltage is set as an operating point indicated by an asterisk. By applying the intensity modulation control signal S11 of NRZ (Non Return to Zero) around the operating point to the modulator, an optical output signal after intensity modulation as shown on the left side of FIG. 6 is obtained.
　図６の左側に示す通り、強度変調部２２では、符号データが「１」のときに動作点を中心として「Ｈｉｇｈ」に対応する電圧が印加され、「Ｌｏｗ」の信号に比べて振幅が大きい光信号が位相変調部２３に出力される。また、強度変調部２２では、符号データが「０」のときに「Ｌｏｗ」に対応する電圧が印加され、「Ｈｉｇｈ」の信号に比べて振幅が小さい光信号が位相変調部２３に出力される。動作点は、バイアス電圧制御部１５によって制御されている。 As shown on the left side of FIG. 6, in the intensity modulation unit 22, when the code data is “1”, a voltage corresponding to “High” is applied around the operating point, and the amplitude is larger than that of the “Low” signal. The optical signal is output to the phase modulation unit 23. The intensity modulation unit 22 applies a voltage corresponding to “Low” when the code data is “0”, and outputs an optical signal having a smaller amplitude than the “High” signal to the phase modulation unit 23. . The operating point is controlled by the bias voltage control unit 15.
　次に、強度変調部２２の後段にある位相変調部２３の変調器に強度変調制御信号Ｓ１１と同じ速度の位相変調制御信号Ｓ１２を加える。図６の右側に示すように、位相変調制御信号Ｓ１２が「１」の場合は、位相差０、位相変調制御信号Ｓ１２が「０」の場合は、位相差πとすると、それぞれのタイミングで得られる光信号自体の位相が変化している。すなわち、図６の右側に示すように、位相変調部２３は、「Ｈｉｇｈ」または「Ｌｏｗ」に対応する振幅の光信号に対して、「０」または「π」のいずれかの位相の信号となるように位相変調を施している。 Next, the phase modulation control signal S12 having the same speed as that of the intensity modulation control signal S11 is added to the modulator of the phase modulation unit 23 in the subsequent stage of the intensity modulation unit 22. As shown on the right side of FIG. 6, when the phase modulation control signal S12 is “1”, the phase difference is 0, and when the phase modulation control signal S12 is “0”, the phase difference π is obtained at each timing. The phase of the optical signal itself is changing. That is, as illustrated on the right side of FIG. 6, the phase modulation unit 23 performs a signal having a phase of “0” or “π” with respect to an optical signal having an amplitude corresponding to “High” or “Low”. Phase modulation is performed so that
　このように本実施形態の光送信部１２は、強度変調と位相変調を組み合わせることで１ビットの光信号に倍の情報を付加した光信号を生成する。例えば、２５ＧＢａｕｄのボーレートで強度変調した上で、同時に同じ速さで位相変調する事で、２倍の５６Ｇｂｐｓの伝送帯域が得られる。 As described above, the optical transmission unit 12 of the present embodiment generates an optical signal in which double information is added to a 1-bit optical signal by combining intensity modulation and phase modulation. For example, intensity modulation is performed at a baud rate of 25 GBaud and phase modulation is simultaneously performed at the same speed, thereby obtaining a doubled transmission band of 56 Gbps.
　本実施形態の光送信部１２は、位相変調を施す際に、連続するビットに対応する光信号の位相差として符号データに基づく情報を付加する。すなわち、本実施形態の光送信部１２は、連続するビットの位相差と個々のビットの強度の組み合わせに符号データを割り当てることで送信用のデータに基づいた光信号を生成する。連続するビットの位相差と個々のビットの強度の組み合わせと、それぞれの組み合わせに割り当てられる符号データとの対応の例は、後で説明する。 The optical transmission unit 12 according to the present embodiment adds information based on code data as a phase difference between optical signals corresponding to consecutive bits when performing phase modulation. That is, the optical transmission unit 12 according to the present embodiment generates an optical signal based on transmission data by assigning code data to combinations of phase differences between consecutive bits and individual bit intensities. An example of the correspondence between the phase difference between consecutive bits and the intensity of each bit and the code data assigned to each combination will be described later.
　光受信部１３は、直接検波方式によって光信号を受信する機能を有する。図７は、本実施形態の光トランシーバ１０のうち光受信部１３の部分のみを示したものである。光受信部１３は、遅延回路部３１と、受光部３２と、電流電圧変換部３３をさらに備えている。 The optical receiver 13 has a function of receiving an optical signal by a direct detection method. FIG. 7 shows only the portion of the optical receiver 13 in the optical transceiver 10 of the present embodiment. The optical receiver 13 further includes a delay circuit unit 31, a light receiver 32, and a current-voltage converter 33.
　遅延回路部３１は、入力された光信号を異なる２本の経路に分岐し、それぞれの経路を通過した光信号を互いに干渉させて合波した後、受光部３２のフォトダイオードに出力する。遅延回路部３１は、一方の経路の光路長に対してもう一方の経路の光路長が１ビットに相当する分だけ長くなるように形成されている。また、遅延回路部３１は、合波した光信号のうち位相差がπの成分と位相差が０の成分を互いに異なるフォトダイオードに出力する。図７の例では、遅延回路部３１は、合波した光信号のうち位相差がπの成分を上側の受光部３２のフォトダイオードに出力し、位相差が０の成分を下側の受光部３２のフォトダイオードに出力している。また、本実施形態の遅延回路部３１の機能は、第１の実施形態の遅延手段２０１および結合手段２０２に相当する。 The delay circuit unit 31 branches the input optical signal into two different paths, multiplexes the optical signals that have passed through the respective paths interfere with each other, and then outputs them to the photodiode of the light receiving unit 32. The delay circuit unit 31 is formed so that the optical path length of the other path is longer than the optical path length of one path by an amount corresponding to 1 bit. Further, the delay circuit unit 31 outputs a component having a phase difference of π and a component having a phase difference of 0 among the combined optical signals to different photodiodes. In the example of FIG. 7, the delay circuit unit 31 outputs a component having a phase difference of π among the combined optical signals to the photodiode of the upper light receiving unit 32, and outputs a component having a phase difference of 0 to the lower light receiving unit. It outputs to 32 photodiodes. The function of the delay circuit unit 31 of the present embodiment corresponds to the delay unit 201 and the coupling unit 202 of the first embodiment.
　受光部３２は、遅延回路部３１から入力される光信号を電気信号に変換する。受光部３２は、互いに直列に接続された２個のフォトダイオードを備えている。フォトダイオードには、例えば、ＰＩＮ－ＰＤ（p-intrinsic-n Photodiode）が用いられる。受光部３２は、それぞれのフォトダイオードに入力される光信号を電流信号に変換し、２個のフォトダイオードから変換された電流信号の差を後段の電流電圧変換部３３に出力する。また、本実施形態の受光部３２の機能は、第１の実施形態の光電変換手段２０３に相当する。 The light receiving unit 32 converts the optical signal input from the delay circuit unit 31 into an electrical signal. The light receiving unit 32 includes two photodiodes connected in series with each other. For example, PIN-PD (p-intrinsic-n Photodiode) is used as the photodiode. The light receiving unit 32 converts the optical signal input to each photodiode into a current signal, and outputs the difference between the current signals converted from the two photodiodes to the current-voltage conversion unit 33 at the subsequent stage. Further, the function of the light receiving unit 32 of the present embodiment corresponds to the photoelectric conversion unit 203 of the first embodiment.
　電流電圧変換部３３は、受光部３２から入力された電流信号を電圧信号に変換して出力する。電流電圧変換部３３は、トランスインピーダンスアンプを用いて構成されている。 The current-voltage conversion unit 33 converts the current signal input from the light receiving unit 32 into a voltage signal and outputs the voltage signal. The current-voltage converter 33 is configured using a transimpedance amplifier.
　変調制御部１４は、光送信部１２において光出力部２１から入力される光に施される強度変調および位相変調を制御する。変調制御部１４は、強度変調部２２および位相変調部２３において変調器に印加する電圧を制御するドライバＩＣ（Integrated Circuit）である。変調制御部１４は、光トランシーバ１０が接続されている電流電圧変換部から差動電気信号ＴＤ１およびＴＤ２として入力される信号に基づいて、強度変調制御信号Ｓ１１および位相変調制御信号Ｓ１２を生成する。変調制御部１４は、生成した強度変調制御信号Ｓ１１を強度変調部２２に出力する。また、変調制御部１４は、生成した位相変調制御信号Ｓ１２を位相変調部２３に出力する。また、本実施形態の変調制御部１４の機能は、第１の実施形態の制御手段１０２に相当する。 The modulation control unit 14 controls intensity modulation and phase modulation applied to the light input from the light output unit 21 in the light transmission unit 12. The modulation controller 14 is a driver IC (Integrated Circuit) that controls the voltage applied to the modulator in the intensity modulator 22 and the phase modulator 23. The modulation control unit 14 generates an intensity modulation control signal S11 and a phase modulation control signal S12 based on signals input as differential electrical signals TD1 and TD2 from the current-voltage conversion unit to which the optical transceiver 10 is connected. The modulation control unit 14 outputs the generated intensity modulation control signal S11 to the intensity modulation unit 22. Also, the modulation control unit 14 outputs the generated phase modulation control signal S12 to the phase modulation unit 23. Further, the function of the modulation control unit 14 of the present embodiment corresponds to the control means 102 of the first embodiment.
　バイアス電圧制御部１５は、光送信部１２の強度変調部２２に印加されるバイアス電圧を制御する。バイアス電圧制御部１５は、強度変調部２２の変調器の動作点を補正するバイアス電圧を強度変調部２２の変調器に印加する。バイアス電圧は、光トランシーバ１０の起動時等にキャリブレーション動作を行うことによって設定される。また、バイアス電圧の設定値は、バイアス電圧制御部１５にあらかじめ保存されていてもよい。 The bias voltage control unit 15 controls the bias voltage applied to the intensity modulation unit 22 of the optical transmission unit 12. The bias voltage control unit 15 applies a bias voltage for correcting the operating point of the modulator of the intensity modulation unit 22 to the modulator of the intensity modulation unit 22. The bias voltage is set by performing a calibration operation when the optical transceiver 10 is activated. The set value of the bias voltage may be stored in the bias voltage control unit 15 in advance.
　出力制御部１６は、光出力部２１から出力される光の波長およびパワーを制御する。 The output control unit 16 controls the wavelength and power of light output from the light output unit 21.
　増幅部１７は、光受信部１３から入力される信号を増幅して出力する。増幅部１７には、例えば、線形増幅器を用いることができる。増幅部１７は、電流電圧変換部３３から入力される信号を光トランシーバ１０が接続されている光伝送装置の仕様に応じた信号レベルに増幅して出力する。増幅部１７は、増幅した電気信号を差動電気信号ＲＤ１およびＲＤ２として光トランシーバ１０が接続されている光伝送装置に出力する。 The amplifying unit 17 amplifies and outputs the signal input from the optical receiving unit 13. For example, a linear amplifier can be used for the amplifying unit 17. The amplifying unit 17 amplifies the signal input from the current-voltage converting unit 33 to a signal level corresponding to the specification of the optical transmission apparatus to which the optical transceiver 10 is connected, and outputs the signal level. The amplifying unit 17 outputs the amplified electrical signal as differential electrical signals RD1 and RD2 to the optical transmission apparatus to which the optical transceiver 10 is connected.
　コネクタ部１８は、光トランシーバ１０を光伝送装置に接続する際のコネクタである。光トランシーバ１０は、コネクタ部１８を介して光伝送装置と制御信号およびデータ通信用の信号の送受信を行う。 The connector unit 18 is a connector for connecting the optical transceiver 10 to the optical transmission device. The optical transceiver 10 transmits and receives control signals and data communication signals to and from the optical transmission device via the connector unit 18.
　本実施形態の制御部１１、変調制御部１４、バイアス電圧制御部１５および出力制御部１６は、半導体装置を用いて構成されている。個々の部位が独立の半導体装置によって構成されていてもよく、また、いくつかの部位が同一の半導体装置によって構成されていてもよい。半導体装置としては、例えば、ＡＳＩＣ（Application Specific Integrated Circuit）やＦＰＧＡ（Field Programmable Gate Array）が用いられる。 The control unit 11, the modulation control unit 14, the bias voltage control unit 15 and the output control unit 16 of the present embodiment are configured using semiconductor devices. Each part may be constituted by an independent semiconductor device, and some parts may be constituted by the same semiconductor device. As the semiconductor device, for example, ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array) is used.
　本実施形態の光トランシーバ１０の動作について説明する。図８は、本実施形態の光トランシーバ１０を用いて光通信システムの構成の例を示したものである。図８の光通信システムは、光伝送装置４０－１と、光伝送装置４０－２を備えている。光伝送装置４０－１と、光伝送装置４０－２は、光ファイバを用いた伝送路３０１を介して接続されている。光伝送装置４０－１および光伝送装置４０－２は、光トランシーバ１０と、送受信する信号を処理する信号処理回路４１をそれぞれ備えている。 The operation of the optical transceiver 10 of this embodiment will be described. FIG. 8 shows an example of the configuration of an optical communication system using the optical transceiver 10 of the present embodiment. The optical communication system in FIG. 8 includes an optical transmission device 40-1 and an optical transmission device 40-2. The optical transmission device 40-1 and the optical transmission device 40-2 are connected via a transmission line 301 using an optical fiber. Each of the optical transmission device 40-1 and the optical transmission device 40-2 includes an optical transceiver 10 and a signal processing circuit 41 that processes signals to be transmitted and received.
　信号処理回路４１は、送信用のデータの符号化および冗長化処理等を行って送信用のフレームデータを生成する。また、信号処理回路４１は、受信信号の復調処理を行う。信号処理回路４１は、ＦＰＧＡやＡＳＣＩ等の半導体装置によって構成されている。送信信号と受信信号の処理は、それぞれ別の半導体装置において行われてもよい。このような構成の光通信システムに用いられた光トランシーバ１０の動作を例に説明する。 The signal processing circuit 41 performs transmission data encoding, redundancy processing, and the like to generate frame data for transmission. Further, the signal processing circuit 41 performs a demodulation process on the received signal. The signal processing circuit 41 is configured by a semiconductor device such as FPGA or ASCI. The transmission signal and the reception signal may be processed in different semiconductor devices. An operation of the optical transceiver 10 used in the optical communication system having such a configuration will be described as an example.
　送信側の光伝送装置の光トランシーバ１０において光信号を送信する際の動作について説明する。光トランシーバ１０が動作を開始すると、光送信部１２の光出力部２１は、所定の波長の連続光を生成し、強度変調部２２に出力する。光送信部１２に光出力部２１から入力された光は、強度変調部２２に入力される。 The operation when an optical signal is transmitted in the optical transceiver 10 of the optical transmission apparatus on the transmission side will be described. When the optical transceiver 10 starts operating, the optical output unit 21 of the optical transmission unit 12 generates continuous light having a predetermined wavelength and outputs the continuous light to the intensity modulation unit 22. The light input from the optical output unit 21 to the optical transmission unit 12 is input to the intensity modulation unit 22.
　また、光トランシーバ１０が接続されている光伝送装置から変調制御部１４に送信用のデータに基づいた高周波信号が差動電気信号ＴＤ１およびＴＤ２として入力される。差動電気信号ＴＤ１およびＴＤ２が入力されると、変調制御部１４は、強度変調制御信号Ｓ１１を基に強度変調部２２の変調器に電圧を印加する。また、このとき、バイアス電圧制御部１５は、強度変調部２２にバイアス電圧制御信号Ｓ１５を出力し、強度変調部２２の変調器に動作点を補正するためのバイアス電圧を印加している。 Further, high-frequency signals based on transmission data are input as differential electrical signals TD1 and TD2 from the optical transmission apparatus to which the optical transceiver 10 is connected to the modulation control unit 14. When the differential electrical signals TD1 and TD2 are input, the modulation control unit 14 applies a voltage to the modulator of the intensity modulation unit 22 based on the intensity modulation control signal S11. At this time, the bias voltage controller 15 outputs a bias voltage control signal S15 to the intensity modulator 22, and applies a bias voltage for correcting the operating point to the modulator of the intensity modulator 22.
　光出力部２１から光が入力されると、強度変調部２２は、変調制御部１４から入力される強度変調制御信号Ｓ１１に基づいて、入力された光に強度変調を施す。強度変調部２２は、強度変調を施した光信号を位相変調部２３に強度変調信号Ｓ１３として出力する。 When light is input from the light output unit 21, the intensity modulation unit 22 performs intensity modulation on the input light based on the intensity modulation control signal S 11 input from the modulation control unit 14. The intensity modulator 22 outputs the intensity-modulated optical signal to the phase modulator 23 as an intensity modulation signal S13.
　位相変調部２３に強度変調が施された光信号が入力されると、位相変調部２３は、変調制御部１４から入力される位相変調制御信号Ｓ１２を基に、入力された光信号に位相変調を施す。位相変調部２３において位相変調が施された位相変調信号Ｓ１４は、光トランシーバ１０から出力される。光トランシーバ１０から出力された光信号は、受信側の光伝送装置、すなわち、伝送路を介して対向する光伝送装置に送られる。 When an optical signal subjected to intensity modulation is input to the phase modulation unit 23, the phase modulation unit 23 performs phase modulation on the input optical signal based on the phase modulation control signal S12 input from the modulation control unit 14. Apply. The phase modulation signal S14 subjected to phase modulation in the phase modulation unit 23 is output from the optical transceiver 10. The optical signal output from the optical transceiver 10 is sent to the optical transmission device on the receiving side, that is, the opposite optical transmission device via the transmission path.
　次に受信側の光伝送装置において光トランシーバ１０において光信号を受信する際の動作について説明する。伝送路を介して光信号を光トランシーバ１０が受信すると、受信した光信号は、光受信部１３に送られる。光信号が入力されると、遅延回路部３１は、入力された光信号を異なる２本の経路に分岐し、それぞれの経路を通過した光信号を互いに干渉させた後、受光部３２のフォトダイオードに出力する。 Next, the operation when the optical transceiver 10 receives an optical signal in the optical transmission apparatus on the receiving side will be described. When the optical transceiver 10 receives an optical signal via the transmission path, the received optical signal is sent to the optical receiver 13. When an optical signal is input, the delay circuit unit 31 branches the input optical signal into two different paths, causes the optical signals that have passed through the respective paths to interfere with each other, and then the photodiode of the light receiving unit 32. Output to.
　遅延回路部３１の２本の経路を通った光信号の位相が一致するとき、光信号は、受光部３２の下側のフォトダイオードに入力される。また、遅延回路部３１の２本の経路を通った光信号の位相差がπのとき、光信号は、受光部３２の上側のフォトダイオードに入力される。 When the phase of the optical signal that has passed through the two paths of the delay circuit unit 31 matches, the optical signal is input to the photodiode below the light receiving unit 32. In addition, when the phase difference of the optical signal that has passed through the two paths of the delay circuit unit 31 is π, the optical signal is input to the photodiode on the upper side of the light receiving unit 32.
　フォトダイオードに光信号が入力されると、受光部３２は、入力された光信号を電気信号に変換する。受光部３２は、２個のフォトダイオードを直列に備え、２個のフォトダイオードから出力される電流信号の差を後段の電流電圧変換部３３に出力する。 When an optical signal is input to the photodiode, the light receiving unit 32 converts the input optical signal into an electrical signal. The light receiving unit 32 includes two photodiodes in series, and outputs the difference between the current signals output from the two photodiodes to the subsequent current-voltage conversion unit 33.
　受光部３２から電気信号が入力されると、電流電圧変換部３３は、入力された電気信号を、電流信号から電圧信号に変換して増幅部１７に出力する。増幅部１７に電気信号が入力されると、増幅部１７は、光トランシーバ１０が接続されている光伝送装置の設定範囲内まで信号レベルを増幅して、差動電気信号ＲＤ１およびＲＤ２として光伝送装置に出力する。 When an electrical signal is input from the light receiving unit 32, the current-voltage conversion unit 33 converts the input electrical signal from a current signal to a voltage signal and outputs the voltage signal to the amplification unit 17. When an electric signal is input to the amplifying unit 17, the amplifying unit 17 amplifies the signal level to within the setting range of the optical transmission apparatus to which the optical transceiver 10 is connected, and optically transmits the differential electric signals RD1 and RD2. Output to the device.
　上記の通り、本実施形態の光トランシーバ１０は、受信した光信号を遅延回路部３１として構成されている１ビット遅延検波回路に入力する。１ビット遅延検波回路では、１ビット前の信号との位相差を基にした位相の変化と、個々の信号の強度にそれぞれ１ビットずつ割り当てることで、１つの光信号で２ビットのデータ伝送が可能になる。例えば、２８ＧＢａｕｄのボーレートの光信号を５６Ｇｂｐｓとして受信することができる。５６ＧＢａｕｄで変調した場合に比べて、光受信部１３のトランスインピーダンスアンプの入力換算雑音の抑制や分散の影響の低減が可能であるため、伝送距離を大きくしても受信品質を維持することができる。 As described above, the optical transceiver 10 of the present embodiment inputs the received optical signal to the 1-bit delay detection circuit configured as the delay circuit unit 31. In the 1-bit delay detection circuit, 2-bit data transmission can be performed with one optical signal by assigning 1 bit each to the phase change based on the phase difference from the previous signal and the intensity of each signal. It becomes possible. For example, an optical signal with a baud rate of 28 GBaud can be received as 56 Gbps. Compared to the case where modulation is performed with 56 GBaud, it is possible to suppress the input conversion noise of the transimpedance amplifier of the optical receiver 13 and reduce the influence of dispersion, so that the reception quality can be maintained even if the transmission distance is increased. .
　図９は、光受信部１３に入力される光信号の位相平面上のコンスタレーションを示したものである。また、図１０は、強度変調と位相変調が施された受信信号を復号する際の、受信信号の強度および遅延検波回路を通過後の光信号の位相差と、符号データとの関係を示したものである。 FIG. 9 shows a constellation on the phase plane of the optical signal input to the optical receiver 13. FIG. 10 shows the relationship between the code signal and the intensity of the received signal and the phase difference of the optical signal after passing through the delay detection circuit when decoding the received signal subjected to intensity modulation and phase modulation. Is.
　図１０の例では「００」、「１１」、「０１」および「１０」の２ビットの符号データに、１ビット遅延検波をした際の前後の信号の位相差、位相の変化方向および信号の強度の組み合わせが対応している。 In the example of FIG. 10, the phase difference between the signals before and after the 1-bit delayed detection is performed on the 2-bit code data of “00”, “11”, “01”, and “10”, the phase change direction, and the signal Combinations of strength are supported.
　図１０の例では「００」に連続するビットの信号強度がともに「Ｌｏｗ」、位相差が「０」の場合を割り当てている。また、「１１」に、連続するビットの信号強度がともに「Ｈｉｇｈ」、位相差が「０」の場合を割り当てている。また、「０１」に、連続するビットの信号強度が「Ｌｏｗ」と「Ｈｉｇｈ」、位相差が「π」で位相の変化が０からπの場合を割り当てている。また、「１０」に、連続するビットの信号強度が「Ｈｉｇｈ」と「Ｌｏｗ」、位相差が「π」で位相の変化がπから０の場合を割り当てている。 In the example of FIG. 10, the case is assigned where the signal strengths of the bits subsequent to “00” are both “Low” and the phase difference is “0”. Further, “11” is assigned with the case where the signal strengths of consecutive bits are both “High” and the phase difference is “0”. Also, the case where the signal strength of consecutive bits is “Low” and “High”, the phase difference is “π”, and the phase change is 0 to π is assigned to “01”. Further, “10” is assigned the case where the signal strength of consecutive bits is “High” and “Low”, the phase difference is “π”, and the phase change is from π to 0.
　位相の変化の方向は、受信した符号の変化によって判断される。そのため、送信側において連続する信号の位相差、位相の変化方向および信号の強度と符号データとの対応を基に変調を施すことで、受信側において信号を復号することができる。連続する信号の位相差、位相の変化方向および信号の強度と符号データとの対応を示す情報は、送信側と受信側であらかじめ共有されている。 The direction of phase change is determined by the received code change. Therefore, the signal can be decoded on the receiving side by performing modulation on the basis of the phase difference between the continuous signals on the transmitting side, the phase change direction, and the correspondence between the signal strength and the code data. Information indicating the correspondence between the phase difference between successive signals, the phase change direction, and the intensity of the signal and the code data is shared in advance between the transmission side and the reception side.
　図１１は、本実施形態の光トランシーバ１０と対比する構成の例として、強度変調のみを行う光トランシーバを模式的に示したものである。このような強度変調のみの場合には、外部環境の変動によってレーザーの出力状態が変動するので、送信波形が影響を受けて波形歪み等が生じることがある。そのような構成に対し、本実施形態の光トランシーバ１０を用いると、強度変調と位相変調の複合変調が施された光信号を伝送することで、伝送帯域を広げつつ、信号の品質を維持することができる。 FIG. 11 schematically shows an optical transceiver that performs only intensity modulation as an example of a configuration to be compared with the optical transceiver 10 of the present embodiment. In the case of only such intensity modulation, since the output state of the laser fluctuates due to fluctuations in the external environment, the transmission waveform may be affected and waveform distortion or the like may occur. When the optical transceiver 10 according to the present embodiment is used for such a configuration, the quality of the signal is maintained while the transmission band is widened by transmitting an optical signal subjected to combined modulation of intensity modulation and phase modulation. be able to.
　本実施形態の光トランシーバ１０は、送信する光信号に強度変調と位相変調の複合変調を施している。本実施形態の光トランシーバ１０は、連続する信号の位相差と信号の強度によって光信号に送信用のデータを付加している。また、受信側の光トランシーバ１０は、遅延検波を行うことで連続する信号の位相差と信号の強度の情報を取得している。そのため、本実施形態の光トランシーバ１０は、伝送速度を上げずに帯域を拡大することが出来るので信号の影響を抑制して、復調処理を行うことができる。その結果、本実施形態の光トランシーバ１０を用いることで、伝送帯域の拡大や距離の延伸を行っても複雑な構成を必要とすることなく信号の伝送品質を維持することができる。 The optical transceiver 10 of the present embodiment performs combined modulation of intensity modulation and phase modulation on an optical signal to be transmitted. The optical transceiver 10 of this embodiment adds data for transmission to an optical signal based on the phase difference between successive signals and the intensity of the signal. Further, the optical transceiver 10 on the receiving side acquires information on the phase difference and signal strength of successive signals by performing delay detection. Therefore, the optical transceiver 10 according to the present embodiment can expand the band without increasing the transmission speed, so that the influence of the signal can be suppressed and the demodulation process can be performed. As a result, by using the optical transceiver 10 of the present embodiment, signal transmission quality can be maintained without requiring a complicated configuration even when the transmission band is expanded or the distance is extended.
　第２の実施形態の光トランシーバ１０は、ＨｉｇｈとＬｏｗの２段階の信号強度の強度変調を行っているが、ＰＡＭ（Pulse Amplitude Modulation）４やＰＡＭ８等の多段階の信号強度設定による強度変調を行ってもよい。そのような構成とする場合には、受信側での判定も多段階で行うことで伝送帯域をさらに向上することができる。また、第２の実施形態では、送信側と受信側の光トランシーバ１０が１台の光通信システムの例について示したが、光通信システムは、複数の光トランシーバ１０を用いた波長多重信号の通信を行うシステムであってもよい。 The optical transceiver 10 of the second embodiment performs intensity modulation of signal intensity in two stages of High and Low, but intensity modulation by multi-stage signal intensity setting such as PAM (Pulse Amplitude Modulation) 4 or PAM 8 is performed. You may go. In such a configuration, the transmission band can be further improved by performing determination on the receiving side in multiple stages. In the second embodiment, an example of an optical communication system in which the transmission-side and reception-side optical transceivers 10 are one is shown. However, the optical communication system uses a plurality of optical transceivers 10 to communicate wavelength multiplexed signals. The system which performs may be sufficient.
　以上、上述した実施形態を模範的な例として本発明を説明した。しかしながら、本発明は、上述した実施形態には限定されない。即ち、本発明は、本発明のスコープ内において、当業者が理解し得る様々な態様を適用することができる。 The present invention has been described above using the above-described embodiment as an exemplary example. However, the present invention is not limited to the above-described embodiment. That is, the present invention can apply various modes that can be understood by those skilled in the art within the scope of the present invention.
　この出願は、２０１８年２月１６日に出願された日本出願特願２０１８－２６１７４を基礎とする優先権を主張し、その開示の全てをここに取り込む。 This application claims priority based on Japanese Patent Application No. 2018-26174 filed on Feb. 16, 2018, the entire disclosure of which is incorporated herein.
　１０　　光トランシーバ
　１１　　制御部
　１２　　光送信部
　１３　　光受信部
　１４　　変調制御部
　１５　　バイアス電圧制御部
　１６　　出力制御部
　１７　　増幅部
　１８　　コネクタ部
　２１　　光出力部
　２２　　強度変調部
　２３　　位相変調部
　３１　　遅延回路部
　３２　　受光部
　３３　　電流電圧変換部
　４０－１　　光伝送装置
　４０－２　　光伝送装置
　４１　　信号処理回路
　１００　　光送信器
　１０１　　光出力手段
　１０２　　制御手段
　１０３　　強度変調手段
　１０４　　位相変調手段
　２００　　光受信器
　２０１　　遅延手段
　２０２　　結合手段
　２０３　　光電変換手段
　３００　　伝送路
　３０１　　伝送路
　Ｓ１１　　強度変調制御信号
　Ｓ１２　　位相変調制御信号
　Ｓ１３　　強度変調信号
　Ｓ１４　　位相変調信号
　Ｓ１５　　バイアス電圧制御信号 DESCRIPTION OF SYMBOLS 10 Optical transceiver 11 Control part 12 Optical transmission part 13 Optical reception part 14 Modulation control part 15 Bias voltage control part 16 Output control part 17 Amplification part 18 Connector part 21 Optical output part 22 Intensity modulation part 23 Phase modulation part 31 Delay circuit part 32 Light receiver 33 Current-voltage converter 40-1 Optical transmission device 40-2 Optical transmission device 41 Signal processing circuit 100 Optical transmitter 101 Optical output means 102 Control means 103 Intensity modulation means 104 Phase modulation means 200 Optical receiver 201 Delay means 202 Coupling means 203 Photoelectric conversion means 300 Transmission path 301 Transmission path S11 Intensity modulation control signal S12 Phase modulation control signal S13 Intensity modulation signal S14 Phase modulation signal S15 Bias voltage control signal

Claims (10)

  1. 　自装置に割り当てられた波長の連続光を生成する光出力手段と、
    　連続するビットに相当する光信号の位相差および前記光信号の強度の組み合わせと、伝送する符号データと対応を基に、前記連続光に施す強度変調を制御する第１の制御信号および強度変調後の信号にさらに施す位相変調を制御する第２の制御信号を生成する制御手段と、
    　前記連続光に第１の制御信号に基づいて強度変調を施した信号を強度変調信号として生成する強度変調手段と、
    　前記強度変調信号に第２の制御信号に基づいて位相変調を施し、位相変調を施した光信号を出力する位相変調手段と
    　を備えることを特徴とする光送信器。     Light output means for generating continuous light of the wavelength assigned to the device;
    A first control signal for controlling the intensity modulation applied to the continuous light based on the combination of the phase difference of the optical signal corresponding to consecutive bits and the intensity of the optical signal, and the corresponding code data to be transmitted, and after the intensity modulation Control means for generating a second control signal for controlling the phase modulation to be further applied to the signal;
    Intensity modulation means for generating, as an intensity modulation signal, a signal obtained by applying intensity modulation to the continuous light based on a first control signal;
    An optical transmitter comprising: phase modulation means for performing phase modulation on the intensity modulation signal based on a second control signal and outputting an optical signal subjected to phase modulation.
  2. 　前記第１の制御信号および前記第２の制御信号は、同一の周期の信号であることを特徴とする請求項１に記載の光送信器。 The optical transmitter according to claim 1, wherein the first control signal and the second control signal are signals having the same period.
  3. 　前記制御手段は、前記第１の制御信号および前記第２の制御信号をそれぞれ２値の信号として生成し、前記光信号に施される前記強度変調および前記位相変調を制御することを特徴とする請求項１または２に記載の光送信器。 The control means generates the first control signal and the second control signal as binary signals, respectively, and controls the intensity modulation and the phase modulation applied to the optical signal. The optical transmitter according to claim 1 or 2.
  4. 　連続するビットに相当する光信号の位相差および前記光信号の強度の組み合わせに基づいて位相変調および強度変調が施された光信号を分岐し、分岐した前記光信号を通過させる第１の経路と、前記第１の経路に対して１ビット分の遅延を生じさせる第２の経路とを遅延手段と、
    　前記第１の経路と前記第２の経路を通過した光信号を合波し、合波した前記光信号のうち位相差が無い成分を出力する第３の経路と、合波した前記光信号のうち所定の位相差を有する成分を出力する第４の経路とに前記光信号を出力する結合手段と、
    　前記第３の経路から出力された前記光信号が入力される第１の受光素子と、前記第４の経路から出力された前記光信号が入力され、前記第１の受光素子と直列に接続された第２の受光素子において前記光信号を電気信号に変換して出力する光電変換手段と
    　を備えることを特徴とする光受信器。     A first path for branching an optical signal that has been subjected to phase modulation and intensity modulation based on a combination of a phase difference of an optical signal corresponding to consecutive bits and the intensity of the optical signal, and passing the branched optical signal; A second path that causes a delay of 1 bit with respect to the first path, and delay means;
    The optical signal that has passed through the first path and the second path is multiplexed, and a third path that outputs a component having no phase difference in the combined optical signal, and the combined optical signal Coupling means for outputting the optical signal to a fourth path for outputting a component having a predetermined phase difference,
    The first light receiving element to which the optical signal output from the third path is input and the optical signal output from the fourth path are input and connected in series with the first light receiving element. An optical receiver comprising: photoelectric conversion means for converting the optical signal into an electrical signal and outputting the electrical signal in the second light receiving element.
  5. 　前記所定の位相差は、前記光信号の半波長に相当する位相差であることを特徴とする請求項４に記載の光受信器。 The optical receiver according to claim 4, wherein the predetermined phase difference is a phase difference corresponding to a half wavelength of the optical signal.
  6. 　前記光電変換手段から出力される前記電気信号を位相差および信号の強度を基に復調する復調手段をさらに備えることを特徴とする請求項４または５に記載の光受信器。 6. The optical receiver according to claim 4, further comprising demodulation means for demodulating the electric signal output from the photoelectric conversion means based on a phase difference and signal intensity.
  7. 　請求項１から３いずれかに記載の光送信器と、
    　請求項４から６いずれかに記載の光受信器と
    　を備え、
    　前記光送信器から出力された前記光信号が、伝送路を介して前記光受信器に入力されることを特徴とする光通信システム。     An optical transmitter according to any one of claims 1 to 3,
    An optical receiver according to any one of claims 4 to 6,
    An optical communication system, wherein the optical signal output from the optical transmitter is input to the optical receiver via a transmission path.
  8. 　自装置に割り当てられた波長の連続光を生成し、
    　連続するビットに相当する光信号の位相差および前記光信号の強度の組み合わせと、伝送する符号データと対応を基に、前記連続光に施す強度変調を制御する第１の制御信号および強度変調を施した信号に施す位相変調を制御する第２の制御信号を生成し、
    　前記連続光に第１の制御信号に基づいて強度変調を施した信号を強度変調信号として生成し、
    　前記強度変調信号に第２の制御信号に基づいて位相変調を施し、位相変調を施した光信号を出力することを特徴とする光通信方法。     Generates continuous light of the wavelength assigned to its own device,
    A first control signal and intensity modulation for controlling intensity modulation applied to the continuous light based on the combination of the phase difference of the optical signal corresponding to consecutive bits and the intensity of the optical signal and the code data to be transmitted. Generating a second control signal for controlling the phase modulation applied to the applied signal;
    A signal obtained by performing intensity modulation on the continuous light based on a first control signal is generated as an intensity modulated signal;
    An optical communication method comprising: phase-modulating the intensity-modulated signal based on a second control signal and outputting a phase-modulated optical signal.
  9. 　伝送路を介して受信した前記光信号を分岐し、分岐した前記光信号を第１の経路と、前記第１の経路に対して１ビット分の遅延を生じさせる第２の経路とを通過させ、
    　前記第１の経路と前記第２の経路を通過した光信号を合波し、合波した前記光信号のうち位相差が無い成分を出力する第３の経路と、合波した前記光信号のうち所定の位相差を有する成分を出力する第４の経路とに前記光信号を出力し、
    　前記第３の経路から出力された前記光信号が入力される第１の受光素子と、前記第４の経路から出力された前記光信号が入力され、前記第１の受光素子と直列に接続された第２の受光素子において前記光信号を電気信号に変換して出力することを特徴とする請求項８に記載の光通信方法。     The optical signal received via a transmission path is branched, and the branched optical signal is allowed to pass through a first path and a second path that causes a one-bit delay with respect to the first path. ,
    The optical signal that has passed through the first path and the second path is multiplexed, and a third path that outputs a component having no phase difference in the combined optical signal, and the combined optical signal The optical signal is output to a fourth path that outputs a component having a predetermined phase difference,
    The first light receiving element to which the optical signal output from the third path is input and the optical signal output from the fourth path are input and connected in series with the first light receiving element. 9. The optical communication method according to claim 8, wherein the second light receiving element converts the optical signal into an electrical signal and outputs the electrical signal.
  10. 　前記電気信号を位相差および信号の強度を基に復調することを特徴とする請求項９に記載の光通信方法。 The optical communication method according to claim 9, wherein the electrical signal is demodulated based on a phase difference and a signal strength.
PCT/JP2019/004849 2018-02-16 2019-02-12 Light transmitter, light receiver, and optical communication method WO2019159891A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2018026174 2018-02-16
JP2018-026174 2018-02-16

Publications (1)

Publication Number Publication Date
WO2019159891A1 true WO2019159891A1 (en) 2019-08-22

Family

ID=67618493

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2019/004849 WO2019159891A1 (en) 2018-02-16 2019-02-12 Light transmitter, light receiver, and optical communication method

Country Status (1)

Country Link
WO (1) WO2019159891A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3863198A1 (en) * 2020-02-07 2021-08-11 Nokia Solutions and Networks Oy Apparatus and method for signal modulation in a point-to-multipoint optical network

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030198478A1 (en) * 2002-04-23 2003-10-23 Quellan, Inc. Method and system for generating and decoding a bandwidth efficient multi-level signal
JP2005110256A (en) * 2003-09-29 2005-04-21 Lucent Technol Inc System and method for optical transmission
JP2010199638A (en) * 2009-02-20 2010-09-09 Nec Corp Optical transmitter, optical receiver, and optical communication system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030198478A1 (en) * 2002-04-23 2003-10-23 Quellan, Inc. Method and system for generating and decoding a bandwidth efficient multi-level signal
JP2005110256A (en) * 2003-09-29 2005-04-21 Lucent Technol Inc System and method for optical transmission
JP2010199638A (en) * 2009-02-20 2010-09-09 Nec Corp Optical transmitter, optical receiver, and optical communication system

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3863198A1 (en) * 2020-02-07 2021-08-11 Nokia Solutions and Networks Oy Apparatus and method for signal modulation in a point-to-multipoint optical network
US11265083B2 (en) 2020-02-07 2022-03-01 Nokia Solutions And Networks Oy Apparatus and method for signal modulation in a point-to-multipoint optical network

Similar Documents

Publication Publication Date Title
US9722722B2 (en) Dense wavelength division multiplexing and single-wavelength transmission systems
US10225017B2 (en) Optical transmitter and method for controlling the same
US10389449B2 (en) Hybrid direct-modulated/external modulation optical transceiver
US20060072924A1 (en) Duo-binary optical transmitter tolerant to chromatic dispersion
US20070003179A1 (en) QPSK light modulator
JP2013153259A (en) Communication device and communication method
US9215116B2 (en) Method, transmitter and receiver device for transmitting a binary digital transmit signal over an optical transmission link
EP1511195B1 (en) Duobinary optical transmission device using one semiconductor optical amplifier
US20120051756A1 (en) Dual polarization transceiver
US20100239264A1 (en) Optical transmission system, apparatus and method
US10469173B2 (en) High-speed low-power-consumption optical transceiver chip
US20090238568A1 (en) Optical Shaping for Amplification in a Semiconductor Optical Amplifier
JP2009171135A (en) Optical transmitter, optical transmission system, and modulation scheme selection method
EP1404036B1 (en) Duobinary optical transmission apparatus
WO2010035662A1 (en) Optical transmitter, optical receiver, and optical communication system
US20050078965A1 (en) RZ-AMI optical transmitter module
JP2000106543A (en) Optical transmitter
WO2019159891A1 (en) Light transmitter, light receiver, and optical communication method
Rafique et al. Digital pre-emphasis based system design trade-offs for 64 Gbaud coherent data center interconnects
KR20160096471A (en) Optical transmitter and receiver of flexible modulation formats
JP4053473B2 (en) Optical transmitter
US10305600B2 (en) Multilevel optical signal system
CN107852246B (en) Digital signal processing device and optical transceiver
WO2014141260A1 (en) Pre-compensation of chromatic dispersion using coherent-less dsp
EP1473856B1 (en) Duobinary optical transmission apparatus

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 19754114

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 19754114

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: JP